Accelerator Physics and Engineering Seminars: Archive

Below is a list of past seminars related to the Accelerator Science and Engineering Traineeship (ASET) program.

The ASET program at MSU leverages unique campus-based equipment, systems, and experts at FRIB, extensive ASET faculty and research support in several MSU academic programs, and resources at U.S. Department of Energy national laboratories. 

2024

1 November 2024
Recent Advances in Compact Normal-Conducting Radiofrequency Linacs
Dr. Xueying Lu, Northern Illinois University

High-energy particle accelerators continue to play a pivotal role in advancing particle physics. Normal-conducting radiofrequency (NCRF) technology is essential in the development of compact and cost-effective accelerators with increased energy reach and intensity. NCRF linacs have seen remarkable progress in the accelerating gradient and RF-to-beam efficiency, and these advances are driven by new understanding of RF breakdown physics, innovative structure topologies and coupling schemes, advanced materials and fabrication techniques, and new operation regimes including operation at cryogenic temperatures, at various frequencies, and with nanosecond-long RF pulses. In this talk, I will review some recent progress in NCRF linac structures and discuss their synergies with advanced accelerator concepts. These recent advances have directly inspired several current linear collider options and compact light sources, which I will also introduce.

18 October 2024
Radio-Frequency Superconductivity R&D at Fermilab for Accelerators and Quantum Applications
Dr. Daniel Bafia, Fermilab

This presentation will highlight recent R&D efforts at Fermilab focused on niobium superconducting radio-frequency (SRF) cavities for both particle accelerator and quantum information science applications. It will present new insights into how various surface processing techniques have enhanced Nb SRF cavity performance, resulting in higher quality factors and accelerating gradients by integrating cryogenic RF measurements with advanced materials science. Additionally, these resonant structures provide a deeper understanding of the mechanisms limiting quantum coherence times in 2D and 3D quantum computing architectures. By simplifying complex multi-layer devices into single-interface systems, Fermilab has identified key sources of loss, such as amorphous native niobium oxide and dielectric substrates. These findings have aided in the development of quantum bits with record-breaking coherence times and thus advancing the field of quantum information science.

7 October 2024
AI-ML Tools for Heavy-Ion Linac Operations* 
Brahim Mustapha, Argonne National Laboratory

At a heavy ion linac facility, such as ATLAS at Argonne National Laboratory, a new ion beam is tuned once or twice a week. The use of machine learning can be leveraged to streamline the tuning process, reducing the time needed to tune a given beam and allowing more beam time for the experimental program. After establishing automatic data collection and two-way communication with the control system, we have developed and deployed machine learning models to tune and control the machine. We have successfully trained online different Bayesian Optimization (BO)-based models for different sections of the linac, including the commissioning of a new beamline. We have demonstrated transfer learning from one ion beam to another allowing fast switching between different ion beams. We have also demonstrated transfer learning from a simulation-based model to an online machine model and using Neural Networks as prior-mean for BO optimization. Following a first failed attempt to deploy Reinforcement Learning (RL), we have succeeded in training multiple RL models online. More recently, these models are being generalized to other sections of the ATLAS linac and can, in principle, be adapted to control other ion linacs and accelerators with modern control systems.

* This work was supported by the U.S. Department of Energy, under Contract No. DE-AC02-06CH11357. This research used the ATLAS facility, which is a DOE Office of Nuclear Physics User Facility. Project funded through a “Data, Artificial Intelligence, and Machine Learning at DOE Scientific User Facilities” Grant from the DOE’s Office of Nuclear Physics.

4 October 2024
High gradient SRF Travelling-Wave Acceleration Structure for Linear Colliders
Vyacheslav P. Yakovlev, Fermi National Accelerator Laboratory

A niobium-based superconducting standing-wave RF structure has an acceleration gradient limited to about 50 MV/m by the critical RF magnetic field. To overcome this barrier, we investigate a variant of niobium-based traveling-wave (TW) structures. It is shown that the TW structure can have an acceleration gradient above 70 MV/m, which is about 40% higher than that of state-of-the-art standing-wave structures with the same critical magnetic field. The implementation of this work opens the way to upgrade the energy of the International Linear Collider well beyond 1 TeV. The challenges and progress in the development of the TW SRF are presented, as well as the first experimental results for a prototype TW SRF cavity with a feedback waveguide. A traveling wave is demonstrated for the first time in an SRF cavity at 2K.

20 September 2024
SRF Technology for Quantum Computing and Dark Matter Searches
David van Zanten, FermiLab

Quantum information science is no longer a field of uniquely theoretical endeavors. Current state-of-the-art quantum hardware is capable of processing shallow algorithms and nearly reaches the domain where classical computing will struggle. In addition to the increase in performance, the last decade has shown a broadening of applications well beyond the typical mantra of the programmable quantum processor. A telling example is the use of quantum states for the detection of particles and Dark Matter searches. Despite the advancements of the last decade, there is still ample room for new experiments and a pressing need for improvements. Adopting elements from Superconducting Radiofrequency technologies will help to push the frontier of this field. In this talk I will introduce the concepts of Quantum Information science and discuss why the field would benefit from SRF technologies and how the combination of SRF technologies and Quantum Information science leads to new enabling technologies for example for Dark Matter searches.

6 September 2024
Optimization Studies of Radiation Shielding for PIP-II Project at Fermilab
Dr. Alajos Makovec, FermiLab

The Proton Improvement Plan-II (PIP-II) at Fermilab represents a significant advancement in the quest to answer some of the most profound questions about our universe using the world's most intense high-energy neutrino beam. The project requires the construction of a new addition to the Fermilab accelerator complex – an 800-MeV high-intensity superconducting linear accelerator. Ensuring the safety and regulatory compliance of this ambitious project is paramount, necessitating thorough dose rate assessments under both normal operational and accidental scenarios to align with the Fermilab Radiological Control Manual (FRCM) standards.

Our approach included a comprehensive update of the geometry model to incorporate new magnet and collimator designs, essential for reflecting the current state of PIP-II infrastructure. The implementation of high-resolution detector planes, despite their computational demands, enabled us to gather detailed radiation field data crucial for optimizing shielding configurations. To overcome the significant computational demands, we developed a branching code that drastically reduced simulation runtimes while maintaining statistical integrity. This was achieved through geometry splitting and the application of Russian Roulette techniques, tailored to prioritize regions of interest based on predefined importances and weight limits.

To complement these efforts, we are developing a new, more user-friendly graphical user interface (GUI) for the Monte Carlo code MARS. This GUI includes tools like the MTUPLE Grid Visualizer, which simplifies the visualization of simulation results. Together with other features under development, it aims to streamline the input creation and post-processing workflows.

19 April 2024
High-field superconductors and superconducting magnets for ECRIS and frontier nuclear physics
Dr. Tengming Shen, Lawrence Berkeley National Laboratory

FRIB and LBNL have been collaborating to build high-field superconducting ECR ion source (ECRIS). Out of this collaboration, the first 28 GHz all superconducting Nb-Ti based ECRIS magnet has been in operation at FRIB since 2022 and the designing and prototyping efforts in using a higher-field Nb3Sn conductor are ongoing. This talk will discuss performance, design, design and simulation tools, fabrication methods used for these magnets, and their limits. This talk will also discuss characteristics of practical high field superconductors (Nb-Ti, Nb3Sn, and high-temperature superconductors), a new MARS-ECRIS magnet concept being prototyped at LBNL, the possibility of utilizing high-temperature superconductors for building ECRIS and frontier nuclear physics.

12 April 2024
Hadron Storage Ring of Electron-Ion Collider
Dr. Vadim Ptitsyn, Brookhaven National Laboratory

The Electron Ion Collider (EIC) is a new collider that will carry out experiments to study in great detail the structure of nucleons and nuclei, as well as the role of gluons in the matter around us. The collider is presently in the design and early construction stages at the Brookhaven National Laboratory. One of the major components of the EIC is the Hadron Storage Ring (HSR), which will provide for collisions in a wide energy range beams of different species, from protons to heavy ions. A large part of the experimental program of the EIC requires polarized beams; thus, the HSR will be capable of providing highly polarized beams of protons and helions. The HSR will reuse most of the existing hardware from the RHIC accelerator ring; however, extensive modifications will have to be performed to prepare for the new accelerator parameters and performance required by the EIC. This includes upgrades of the beam vacuum chamber, beam instrumentation, RF system, and the injection system. A hadron cooler must be constructed to create the hadron beam quality required for high luminosity experiments. We will overview the main design features of the HSR, as well as the most important upgrades required to transform RHIC into the EIC HSR.

9 April 2024
Beam diagnostics of the J-PARC accelerator and its applications 
Dr. Takeshi Toyama, J-PARC

First, I will present an overview of J-PARC's project status and plans (J-PARC stays for Japan Proton Accelerator Research Complex). Next, I will review the beam diagnostic instruments of the J-PARC accelerators. The talk will focus on high-intensity H-minus and proton beam measurements and discuss our experience with "non-invasive" diagnostics. Application to the machine protection system (MPS) will show how the MPS has been progressing by responding to actual incidents caused by increasing beam intensity.

22 March 2024
SRF Cavities Resonance Control
Dr. Yuriy Pischalnikov, Fermilab

SRF cavities, that are central elements of the modern accelerator complexes, required accurate frequency control, which is achieved using cavity tuners. Review of the sources of the SRF cavity detuning and brief discussion of the mitigation techniques will be presented. Talk will summarize the result of 20 years of international activities into development of different types of SRF cavity tuners.  The solutions of the many technical problems to deliver tuners that could reliably operate for 30+ years (lifetime of the accelerator) will be discussed

8 March 2024
Strong Hadron Cooling for the Electron-Ion Collider
Erdong Wang, Brookhaven National Laboratory

The anticipated peak and average luminosity of L = 10³⁴ cm^-2s^-1 at the Electron Ion Collider (EIC) can be attained with strong cooling of the hadron beam, as the emittance of the highly luminous beams is prone to rapid growth due to Intrabeam Scattering and other diffusion mechanisms. A novel cooling method, coherent electron cooling (CeC), has been considered as the baseline strong hadron cooling approach. CeC involves utilizing an electron beam to detect the positions of protons within the bunch and then applying energy kicks to reduce their longitudinal and transverse actions. In this presentation, we will first introduce the heating mechanism and provide an overview of the basic principles of hadron cooling. Subsequently, we will delve into the underlying physics of the CeC process. We will then discuss the current progress in design. Finally, we will discuss the challenges encountered and outline mitigation strategies, emphasizing the importance of a high-quality electron beam, high current energy recovery Linac, and the precise sub-micron alignment of electrons and protons.

23 February 2024
Electron Synchrotron for EIC
Vahid Ranjbar, Brookhaven National Laboratory
 

Two new Electron Synchrotron’s will be built for the Electron Ion Collider (EIC). These include the Rapid Cycling Synchrotron (RCS) which is used for injection into the Electron Storage Ring (ESR).  Both machines will transport and store polarized electrons at energies as high as 18 GeV and be built in the existing RHIC tunnel. We will review the physic requirements and novel design of these machines, focusing on the RCS.

9 February 2024
Beam-Beam Effects in Future EIC 
Yun Luo, Brookhaven National Laboratory
 

The Electron-Ion Collider (EIC), to be constructed at Brookhaven National Laboratory, will collide polarized high-energy electron beams with hadron beams, achieving luminosities up to 10^34 cm^-2s^-1 in the center-mass energy range of 20-140 GeV. To attain such high luminosity, we adopt high bunch intensities for both beams, employ flat beams at the interaction point, and implement a crossing angle collision with crab cavities in both rings. Beam-beam interaction poses a significant challenge in the design of the EIC. In this talk, the speaker will first introduce the basics of beam-beam interaction in circular colliders and the ongoing Electron-Ion Collider project. The speaker will then present the optimization of beam-beam related design parameters, selected simulation results, optics and machine imperfections, and the impacts of noises on beam-beam performances.

26 January 2024
Advancing SRF cryomodules performance for modern particle accelerators
Donato Passarelli, Fermi National Accelerator Laboratory
 

Superconducting Radio Frequency (SRF) technology plays a key role in modern particle accelerators. Starting from an overview on main accelerator types and SRF cryomodule structures, we then delve into the detailed design and development approaches employed for the PIP-II SRF LINAC, an ongoing major upgrade of the Fermilab accelerator complex. Specifically the presentation focuses on the engineering  approaches and innovative solutions that are playing a fundamental role in shaping the future of particle accelerator technology.

12 January 2024
AI/ML applications at SLAC National Accelerator Laboratory
Daniel Fried Ratner, SLAC National Accelerator Laboratory
 

Across the DOE, the wealth of data, robust automation, and stringent requirements for control, simulation, and data acquisition, make “Big Science” experiments — telescopes, particle accelerators, etc. — ideal targets for AI/ML. At the same time, the flavor of AI/ML techniques differ from those found in industry. In this talk, I will show some example AI projects at SLAC, including autonomous optimization of an x-ray laser, anomaly detection for a particle accelerator, and single-particle imaging of biomolecules (an example of an inverse problem). I will also highlight how these same methods can find use in other science domains.

2023

15 December 2023
A New Regime of High-Gradient Acceleration: Exploring Short-Pulse Two-Beam Acceleration
Chunguang Jing, Argonne National Laboratory
 

The quest for high-gradient acceleration technologies is essential for the advancement of linear colliders, free-electron lasers, and compact accelerator-based applications. Pioneered by the AWA (Argonne wakefield accelerator) group, the utilization of short-pulse SWFA (structure wakefield accelerator) technology has shown remarkable promise in surpassing the long-standing barrier of ~100 MV/m in X-band normal conducting structures. Recent experiments have demonstrated the feasibility of this approach, with gradient exceeding 300 MV/m in various X-band structures, including accelerating structures and an X-band photogun. Furthermore, a breakthrough was made with the discovery of a breakdown-insensitive acceleration regime in pulse durations below 10 ns.

1 December 2023
Nb₃Sn cavities for high-energy physics applications using magnet conductor methods and copper cavity bodies
Lance Cooley, Florida State University
 

For the past 6 years, our team has been developing methods to create high-quality coatings of Nb₃Sn by methods compatible with copper cavity bodies for astrophysics detectors and high-power electron beam applications. Since the melting point of copper is 1,085 °C, binary synthesis by reaction of Nb with Sn is impractical due to the need to react above 910 °C to suppress formation of unwanted Nb-Sn intermetallic phases. We take advantage of art used in the manufacturing of superconducting Nb₃Sn wires, such as the conductors for the recent High-Luminosity Upgrade of the Large Hadron Collider at CERN. In wires, ductile Cu and Sn components are combined during a staged heat treatment to form α- and ε- bronze phases, which then react with Nb to produce Nb₃Sn at temperatures between 600 and 800 °C. For cavities, we pioneered a novel approach where a bronze phase is made first, then heated into the Nb₃Sn reaction temperature zone during the deposition of Nb. This results in a rapidly growing film with microstructure unlike what is produced by solid-state reaction, and this conveys certain advantages for superconducting properties. As with magnet conductors, high tin activity is crucial for growth of films with stoichiometric composition and best properties. On the other hand, deposition and post-reaction approaches using a copper base facilitate incorporation of diffusion barriers to prevent contamination of copper and addition of interface layers to offset thermal contraction strain. We outline several approaches for copper substrates with different combinations of Nb, Cu-Sn, diffusion barrier, and thermal contraction mismatch materials. In the broader context, our work is a central component of global efforts to achieve Nb₃Sn cavities, including tin-vapor methods at Fermilab and Cornell University, direct deposition from Nb₃Sn targets at CERN, and alternative Cu-Sn methods at the University of Pisa in Italy, IHEP in China, and NIMS in Japan.

Lance Cooley (1,2), Andre Juliao (1), and Wenura Withanage (1,3)
1 – Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, Tallahassee FL USA
2 – Department of Mechanical Engineering, Florida A&M University – Florida State University College of Engineering
3 – Intel Corporation, Hiillsboro OR USA

17 November 2023
Magnets for the Mu2e experiment at Fermilab
Karie Badgley, Fermi National Accelerator Laboratory
 

The Mu2e experiment will measure the charged-lepton flavor violating (CLFV) neutrino-less conversion of a muon into an electron (Mu2e) in the field of a nucleus. The conversion results in a mono-energetic electron of ~105 MeV that recoils from the nucleus. The goal is to achieve a single-event sensitivity of 3x10^-17 on the conversion rate, which would improve the sensitivity by four orders of magnitude over previous experiments. The Mu2e experiment is entering an exciting phase with the first magnet planned to arrive at the experiment late this year. We will use the recent progress on the transport solenoids for Mu2e to look at the design, fabrication, testing, and assembly of magnets. We will start with a brief physics motivation and introduction to the Mu2e experiment, with a focus on the superconducting solenoid systems. We will also cover other magnetic measurement systems, magnet test stands, and future test facilities at Fermilab.

3 November 2023
Advanced Materials for Accelerator Technologies in Euclid’s R&D Program
Alexei Kanareykin,  CEO of Euclid Techlabs

With the talk, we present recent developments of the high-power microwave components with their applications for SRF accelerators. The first example is the Ferroelectric Fast Reactive Tuner (F-FRT) developed by Euclid in collaboration with FNAL and BNL, and successfully tested at CERN. This technique has now become practically feasible due to the recent development of a new extremely low loss and fast (10 ns-100 ns time range) ferroelectric material, which has been tested, and fast frequency tuning has been demonstrated. F-FRTs can be used for a wide variety of SRF related technologies including microphonics suppression for ERLs and heavy ion accelerators (FRIB), transient beam loading compensation for HE-LHC and EIC, and fast RF switching too. We will also present a MW level RF window based on the new conductive low-loss ceramic especially designed for this type of high-power component. At the recent high-power tests at Fermilab and Jlab, this new composite material overperformed the standard alumina window currently used for SRF power couplers. At the end, we will talk about Euclid’s program on synthetic diamond growth for light source X-ray optics and other accelerator applications.

3 November 2023
Modeling of Material Degradation Under Irradiation
Tomoaki Suzudo, Japan Atomic Energy Agency

It is critical to know how the material properties evolve under irradiation in order to ensure their integrity when they are applied, for example, to nuclear reactors and accelerators. However, the radiation effects on materials are often complex and hard to predict. It is important to know what occurs in the atomic scale. In this seminar, the computational approach to these problems is discussed. Especially, I would like to share the information on how atomistic modeling methods, such as the first principles method and molecular dynamics, can be useful in many situations.

20 October 2023
Modern cathode materials for LCLS-II HE
John Smedley, SLAC National Accelerator Laboratory 

LCLS-II has just started operations this month, and extended X-FEL operation to MHz repetition rates, at least for soft x-rays. LCLS-II HE is an upgrade which will extend the x-ray reach of LCLS-II into the hard x-ray. The performance of this machine will be determined largely by the performance of it's electron source - this talk will focus explore two ongoing development efforts to improve the electron source for LCLS-II HE, one focused on gun development and one focused on cathode development. We will also explore the materials science of modern cathodes, and a few related applications.

11 October 2023
The global effect towards making a Muon Collider
Diktys Stratakis, Fermilab 

6 October 2023
Advanced Light Sources R&D program at RadiaBeam
Alex Murokh, RadiaBeam CEO

In this presentation we review RadiaBeam programs to develop Inverse Compton Scattering (ICS) gamma ray source and compact XFEL light source. We also present recent progress on development and commissioning of the novel C-band hybrid photoinjector. The hybrid allows simultaneously enabling high brightness e-beam generation, acceleration, and longitudinal compression with only 80 cm of space, between the photocathode surface and the linac entrance plane. The commissioning results illuminate unique hybrid dynamics. The near-term plans for the ongoing 100 MeV beam energy upgrade, and ICS source commissioning are also presented. We also provide a brief overview of RadiaBeam capabilities, product line and other R&D programs. 

22 September 2023
High power operation, Upgrade and R&D at Spallation Neutron Source
Sang-ho Kim, Oak Ridge National Laboratory

The Spallation Neutron Source (SNS) provides the most intense proton beams for scientific research and industrial development. SNS has acquired extensive operational experience and numerous lessons and achieved stable and reliable operation. Currently the proton power upgrade (PPU) project is in progress with a goal of increasing the proton beam power capability from 1.4 MW to 2.8 MW. The PPU scope is optimized between built-in upgrade provisions, cost effectiveness and technical aspects based on SNS experiences. The SNS accelerator contains both the highest power proton Linac and the highest-intensity ring on a per-pulse basis. Accelerator research program at SNS capitalizes on these unique machine capabilities to address barriers to achieving next-generation beam powers beyond the current beam power record. The presentation will cover status of SNS, PPU project progress and current/planned topics of research and development at SNS.

8 September 2023
Combining fiber lasers for accelerators and broad applications
Tong Zhou, Lawrence Berkeley National Laboratory

Talk abstract: Laser-plasma accelerators (LPA) have demonstrated ultra-high accelerating gradients, with the potential to make future accelerators and colliders more compact and lower-cost. Next generation LPAs require ultrafast laser drivers with multi-J-class energies and up to tens of kHz rep-rates, i.e. hundred-kW-class average power. Current ultrashort laser technologies, e.g. Ti:S, operating at tens of J-class energies and rep-rates up to a few Hz, are limited by thermal handling and efficiency and do not scale to tens of kHz rep-rates and hundred-kW-class average power. Fiber lasers are the most efficient high-average power laser technology demonstrated to date, and coherently combined (in space, time, and spectrum) fiber lasers are considered one of the most promising solutions to achieve the laser needs of future LPAs and colliders. Tremendous progress has been made on demonstrating the principles of the scalable, coherently-combined, ultrafast fiber lasers. In the near- to mid-term, tens of kW systems will be available to drive LPAs, and an R&D path has been identified to achieve hundreds of kW laser systems.

31 May 2023
Title: Plasma Processing for SRF cavities: Past, Present and Future
Paolo Berrutti, Fermilab

Talk abstract: Plasma processing has been used reliably to recover SRF cavity performance for a decade, starting from the very first successful application at ORNL for SNS multicell cavities. Recently HOMs plasma ignition has allowed plasma processing of LCLS-II and CEBAF cavities, overcoming coupling limitations at room temperature imposed by the fundamental passband. The reason that sparked the interest in plasma cleaning is its capability of recovering cavities performance in-situ, in the accelerator tunnel, without requiring a lot of man-hours for cryomodule disassembly and cavity re-processing. In this talk past and present experiences of plasma cleaning will be presented, along with some potential future developments for this technique.

24 April 2023
High-Brightness Electron Injectors for High-Duty-Cycle X-Ray Free Electron Lasers (Part II)
Fernando Sannibale, Lawrence Berkeley National Laboratory

Talk abstract: The successful development in the last two decades of X-ray free electron lasers (FELs) with their revolutionary brightness performance has been tightly dependent on the parallel development of electron guns and injectors capable of providing the high-brightness electron beams required for FEL lasing at these short wavelengths. The ultimate brightness delivered by a linear accelerator (linac) is already set at its injector and the remaining part of the accelerator can be only designed to preserve the injector performance. The technology to be used for the accelerator part of an X-Ray FEL strongly depends on the duty-cycle at which the FEL operates. Normal-conducting, room-temperature, copper based radiofrequency (RF) technology is typically used for low duty-cycles of up to approximately 10^-3.  For higher duty-cycles and up to continuous wave (CW) operation, the linac must rely on superconductive RF technology because, with the higher duty-cycle, the increasingly higher power dissipated in normal conducting RF structures becomes excessive for the technology. The situation changes in the lower energy part of the accelerator, where injector schemes, based on direct current, normal conducting and superconducting RF electron guns, are demonstrating the beam quality performance required by high-duty-cycle X-ray FELs. In this talk, we start with a quick recap of FEL physics fundamentals, followed by a description of the requirements for high duty-cycle injectors, by an overview of the pursued technologies and schemes, and by a discussion on the main differences in terms of beam dynamics between low and high duty-cycle injectors.

21 April 2023
RF and Challenges in Fermilab’s Proton Synchrotrons
Paul Derwent, Fermi National Accelerator Laboratory

Talk abstract: As America's particle physics laboratory, Fermilab operates and builds powerful particle accelerators for investigating the smallest things human beings have ever observed.  The focus of Fermilab's long term research program is the physics of neutrino oscillations. Currently the laboratory supports both long baseline and short baseline programs.  Looking towards the future, the Deep Underground Neutrino Experiment (DUNE), located at the Sanford Underground Research Facility in Lead, South Dakota, will study neutrino oscillations with a baseline of 1300 km.  The physics goals of DUNE require an intense proton beam.  I will describe some of the synchrotron RF challenges associated with these intense proton beams.

7 April 2023
High-Brightness Electron Injectors for High-Duty-Cycle X-Ray Free Electron Lasers (Part I)
Fernando Sannibale, Lawrence Berkeley National Laboratory

Talk abstract: The successful development in the last two decades of X-ray free electron lasers (FELs) with their revolutionary brightness performance has been tightly dependent on the parallel development of electron guns and injectors capable of providing the high-brightness electron beams required for FEL lasing at these short wavelengths. The ultimate brightness delivered by a linear accelerator (linac) is already set at its injector and the remaining part of the accelerator can be only designed to preserve the injector performance. The technology to be used for the accelerator part of an X-Ray FEL strongly depends on the duty-cycle at which the FEL operates. Normal-conducting, room-temperature, copper based radiofrequency (RF) technology is typically used for low duty-cycles of up to approximately 10^-3.  For higher duty-cycles and up to continuous wave (CW) operation, the linac must rely on superconductive RF technology because, with the higher duty-cycle, the increasingly higher power dissipated in normal conducting RF structures becomes excessive for the technology. The situation changes in the lower energy part of the accelerator, where injector schemes, based on direct current, normal conducting and superconducting RF electron guns, are demonstrating the beam quality performance required by high-duty-cycle X-ray FELs. In this talk, we start with a quick recap of FEL physics fundamentals, followed by a description of the requirements for high duty-cycle injectors, by an overview of the pursued technologies and schemes, and by a discussion on the main differences in terms of beam dynamics between low and high duty-cycle injectors.

24 March 2023
Machine-Assisted Discovery of Integrable Symplectic Mappings
Timofey V. Zolkin, Fermi National Accelerator Laboratory

Talk abstract: Integrable systems possess a hidden symmetry associated with the existence of conserved quantities known as integrals of motion. These systems play an important role in understanding general dynamics in accelerators and have potential for future designs. This presentation will cover two automated methods for finding integrable symplectic maps of the plane. The first algorithm is based on the observation that the evolution of an integrable system in phase space is confined to a lower-dimensional submanifold of a specific type. The second algorithm relies on an analysis of dynamical variables. Both methods rediscover some of the famous McMillan-Suris integrable mappings and ultra-discrete Painlevé equations. Over 100 new integrable families are presented and analyzed, some of which are isolated in the space of parameters, while others are families with one parameter (or the ratio of parameters) being either continuous or discrete. In addition, the newly discovered maps are related to a general 2D symplectic map through the use of discrete perturbation theory. A method is proposed for constructing smooth near-integrable dynamical systems based on mappings with polygon invariants.

24 February 2023
Road to High Charge in the Advanced Photon Source Injector
Katherine Harkay, Argonne National Laboratory

Talk abstract: Next-generation, high-performance storage ring (SR) light sources based on multibend achromat optics will require on-axis injection because of the extremely small dynamic aperture. Injectors will need to supply full-current bunch replacement in the SR with high single-bunch charge for what is known as swap-out injection. For upgrades of existing light sources, such as the Advanced Photon Source Upgrade (APS-U), it is economical to retain the existing injector infrastructure and make appropriate improvements. The challenges include achieving high single-bunch charge in the presence of instabilities, beam loading, charge stability and reliability. In this talk, I discuss the rationale for the injector upgrades chosen for APS-U, progress, and future plans. To date, we have achieved single-bunch charge from the injectors that doubles the original design value, and have a goal to achieve about three times the original design value.

10 February 2023
Ion Instabilities in Low Emittance Storage Rings
Joseph Calvey, Argonne National Laboratory

Talk abstract: Ion trapping occurs when a negatively charged beam ionizes residual gas inside an accelerator vacuum chamber, and the resulting ions become trapped in the beam’s potential. These ions can cause a variety of undesirable effects, including coherent instability and emittance growth. Ion trapping is of particular concern for next-generation electron storage rings, such as the upcoming Advanced Photon Source Upgrade (APS-U), because of their challenging emittance and stability requirements. Ion instability has been studied experimentally in the present APS using a gas injection system. This system was designed to create a controlled pressure bump of Nitrogen gas, so that the resulting instability could be studied in detail. In particular, the growth of individual unstable modes has been measured using a bunch-by-bunch feedback system. In addition, the particle tracking code ELEGANT was enhanced to permit modeling both the coherent and incoherent aspects of the ion instability. This code has been used to better understand the results of the gas injection experiments, and to develop a plan for mitigating the ion instability in the APS-U.

27 January 2023
Fixed Field Alternating Gradient for Multi-turn Superconducting Energy Recovery Linac (ERL) and Medical Applications
Dejan Trbojevic, Brookhaven National Laboratory

Talk abstract: An introduction to the Fixed Field Alternating (FFA) Gradient accelerators will be provided with pros and cons for accelerating particle beams. A design, installation, and commissioning of the Cornell University Brookhaven National Laboratory ERL Test Accelerator (CBETA) is shown. A new and an existing FFA approach for the FLASH proton cancer therapy accelerator and the proton delivery gantry with permanent magnets will be presented. A single beam line ERL LHeC lattice for the future Electron Ion Collider at LHC is shown.

13 January 2023
Non-Invasive Laser-Based Particle Counter Development for Continuous Electron Beam Accelerator Facility (CEBAF)
Amy Sy from Jefferson Laboratory

Talk abstract: Field emission is one of the most important issues limiting performance of superconducting radio frequency (SRF) systems and leads to SRF cavity trips at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. Studies have confirmed that particulates are the dominant source of field emitters and the particulates are transported into cavities from elsewhere in the accelerator. Non-invasive monitoring of particulate movement will help to inform mitigation methods towards reduced trip rate and gradient loss. A novel, non-invasive laser-based particle counter is under development at Jefferson Lab. The system is built by OmniSensing Photonics, LLC and is based on the optical interference of two coherent laser beams generated by splitting a single laser beam. Phase modulation is applied to the reference beam, while the detector beam traverses the active area to reflect off of an internal reflective surface before recombination with the reference beam in the detector unit. Disturbances in the intensity and phase of the beam interference can indicate particulate passage through the detector beam. In this talk, progress in system development and characterization at Jefferson Lab will be discussed.  

2022

16 December 2022
Brookhaven National Laboratory's 200 MeV Proton Linac 52 Years Young
Vincent LoDestro, Brookhaven National Laboratory

Talk outline:
-Introduction
-Why build a particle accelerator?
-A brief history of linac construction
-How it works (original operation and design)
-Systems upgrades improves performance
-Brief video tour
-Summary and questions

2 December 2022
Design of 3 GeV High-Gradient Booster for Upgraded Proton Radiography at Los Alamos Neutron Science Center 
Yuri Batygin and Sergey Kurennoy, Los Alamos National Laboratory

Talk abstract: Proton radiography was developed at the Los Alamos National Laboratory in the mid-1990s as a multi-pulse flash technique for deep-penetrated hydro test objects study. Currently, it utilizes an 800-MeV proton beam from the Los Alamos linear accelerator with a beamline for beam imaging. Increasing the proton beam energy from the present 800 MeV to 3 GeV will improve the resolution of the proton radiography by a factor of 10. It will bridge the gap between the existing facilities, which cover large length scales for thick objects, and future high-brightness light sources, which can provide the finest resolution. Proton radiography operates with a sequence of short beam pulses (~20 x 80 ns) separated by intervals of variable duration, from about 200 ns to 1-2 μs. To achieve the required beam parameters, and to accommodate the accelerator within the existing Los Alamos Neutron Science Center (LANSCE) facility, a high-gradient 3-GeV booster is designed. The accelerator consists of 1.4 GHz buncher, two accelerators based on 2.8 GHz and 5.6 GHz high-gradient accelerating structures, and 1.4 GHz debuncher. Utilization of buncher-accelerator-debuncher scheme allows us to combine high-gradient acceleration with the reduction of beam momentum spread by a factor of 3. The paper discusses details of linac design and expected beam parameters.

18 November 2022
Interdisciplinary Challenges of Superconducting Radio-Frequency (SRF) Cryomodules 
Jeremiah Holzbauer, Fermilab

Talk abstract: Accelerator physics is a strongly-applied discipline, with SRF cryomodules being a extreme example. Delivery and successful operation of cryomodules requires simultaneous performance of dozens of specialized systems and disciplines. Unexpected issues are inevitable during a large SRF project, and it is critical to have a strong, cross-discipline team to meet these challenges. This talk will highlight several examples of these challenges based on experience at Fermilab on the LCLS-II and PIP-II projects, including failures and lessons learned from transportation, testing, and operations.

4 November 2022
Tracking of a single electron in IOTA
Aleksandr L. Romanov, Fermilab

Talk abstract: This seminar will cover completed and planned experiments on single electron tracking at the Integrable Optics Test Accelerator (IOTA, Fermilab). Conducted experiments have proven the feasibility of the complete 6-dimensional tracking of an electron. As the next step, we plan to demonstrate it experimentally. Direct 6-dimensional tracking of a single electron in a storage ring will enable a new class of beam diagnostic technologies. It will allow a high-precision characterization of single-particle dynamics. To track a charged particle we detect single photons randomly emitted over many turns. State-of-the-art technologies of photon detection have temporal and spatial resolution sufficient for high-precision tracking if coupled with advanced analysis algorithms. Complete tracking of a point-like object will enable the first measurements of single-particle dynamical properties, including dynamical invariants, amplitude-dependent oscillation frequencies, and chaotic behavior. These single-particle measurements will be employed for long-term tracking simulations, training of AI/ML algorithms, and ultimately for precise predictions of dynamics in the present and future accelerators.

21 October 2022
Transverse Beam Dynamics an Extreme Space Charge at the Fermilab Booster
Jeffrey S. Eldred, Fermilab

Talk abstract: The Fermilab Booster is an operational proton synchrotron which features the world's most extreme space-charge forces. With the upcoming PIP-II linac project for the ambitious DUNE/LBNF program, the Booster will need to cut uncontrolled particle losses by half while simultaneously accelerating 50-percent more charge. Several areas of transverse beam dynamics in the Booster are discussed. The vertical half-integer resonance leads to rapid emittance growth and early beam loss in the Booster, but my recent work in correcting the resonance has also revealed an unexpected benefit. Electron cloud effects in the gradient dipole magnets are also being investigated. Advanced ML algorithms are proposed for robust operations with the Booster's idiosyncratic optics. Lastly, I discuss how critical design questions for future intense rings can be informed by the empirical study of space-charge and machine resonances.

7 October 2022
Advances in Superconducting Magnet Technology for Future Colliders
Soren Prestemon, Lawrence Berkeley National Laboratory

Talk abstract: Superconducting accelerator magnets are the driving technology for the science reach of future colliders, dictating the energy reach of a collider and dominating a facility's cost. As the international community prepares to implement the relatively high-field superconductor Nb3Sn into a collider for the first time with the LHC Luminosity Upgrade project, the research community is working hard to prepare the next generation of magnet technology, targeting ever higher fields, larger apertures, and the use of next-generation high temperature superconductors. We will review the state of the art in high field magnets, with particular attention to the needs of the accelerator community. We will then describe the primary research directions being pursued, and highlight specific advances in modeling, diagnostics, materials and magnet testing. Important distinctions between the magnet technology associated with each of the primary commercial superconductors, namely NbTi, Nb3Sn, Bi2212, and REBCO, will be explored. Finally we will summarize the directions being considered by the collider community, and summarize the magnet research roadmap we have developed to advance our field and address the physics community needs. 

23 September 2022
Online Optimization Methods and Application
Xiaobiao Huang, SLAC National Accelerator Laboratory 

Talk abstract: Experience of developing online optimization methods, such as robust conjugate direction search (RCDS) and multi-generation Gaussian process optimizer (MG-GPO), and applying them to real-life accelerator problems will be presented. The applications include minimization of vertical emittance, optimization of storage ring dynamic aperture and lifetime, and optimization of linac transmission. Challenges of online optimization application and methods to address them will be discussed.

9 September 2022
Superconducting Radiofrequency Photoinjectors: A Quest for High-Brightness CW Electron Beams
Irina Petrushina, Stony Brook University

Talk abstract: High-current low-emittance CW electron beams are of great importance for the existing and future DOE facilities, medical, industrial and security applications. The CW superconducting radiofrequency (SRF) electron photoinjector is one of the most advanced, but also one of the most challenging, technologies promising to deliver such beams. While SRF technology is paving the way for future accelerators, the compatibility of the SRF environment with complex photocathodes remains on the forefront of modern accelerator science, and many important questions remain unanswered. In this seminar we will discuss the major components of an SRF photoinjector and review the existing designs and their specifics. We will dive into the details of the design and operation of the BNL 113 MHz SRF gun that has demonstrated exceptional performance delivering high charge electron bunches (up to 20 nC/bunch) and low transverse emittances, while operating for months with a single photocathode.

22 April 2022
Overview of the Electron-Ion Collider (EIC)
Christoph Montag, Brookhaven National Laboratory

The EIC currently being designed by a partnership between Brookhaven National Laboratory and Jefferson Lab will open exciting new frontiers for research in nuclear physics and quantum chromodynamics. The potential and the associated design requirements of the facility are laid out in detail in a comprehensive White Paper that has been compiled by the U.S. nuclear physics community with world-wide support. An overview of the facility will be given, and latest design advances will be presented.

8 April 2022
Machine Learning to Improve the Operation of the Spallation Neutron Source
Willem Blokland, Oak Ridge National Laboratory

At the Spallation Neutron Source at Oak Ridge National Laboratory, research in collaboration with Jefferson Laboratory is ongoing to improve the accelerator and target operations using Machine Learning (ML). ML has the capability to see correlations in the data where other methods cannot and, through surrogate models, provide much faster simulation. After a short introduction to ML, the talk will discuss four use-cases: Predicting upcoming errant beam pulses by analyzing data from a beam current monitor, improve the mercury filled high power target using surrogate modeling, use time-series ML methods to model the High Voltage Converter Modulator to estimate hardware components’ remaining lifetimes, and use data-driven ML methods to improve the Cryogenic Moderator System response to beam on-off events. Initial results will be discussed, as well as the infra-structure that was set up to collect data and the tools to work with a remote team.

25 March 2022
In Pursuit of Next Generation Particle Accelerators
Emilio Nanni, SLAC National Accelerator Laboratory

Accelerators ranging from midscale radio frequency photo injectors for femtosecond electron-diffraction experiments, to kilometer-long free electron lasers that produce femtosecond x-ray pulses are utilized to resolve materials with atomic precision on femtosecond timescales. While the performance and recent results of these facilities are extraordinary, ensuring their continued vitality requires us to explore new accelerator physics and innovate the next generation of technology. One approach to achieving performance and accelerating gradients orders of magnitude above present capabilities is to dramatically increase the operational frequency into the Terahertz (THz) range. We are exploring accelerating structures designed to withstand high gradients and able to manipulate high-charge beams on femtosecond timescales, developing novel electronic and photonic THz sources, and laying the foundation for THz accelerator technology. Results from recent experiments on high-gradient THz accelerators and their application to time stamping and electron bunch compression for ultrafast electron diffraction will be presented, along with a future outlook for the field.

25 February 2022
Application of Lasers for Diagnostics of Negative Hydrogen Beams
Alexander (Sasha) Aleksandrov, Oak Ridge National Laboratory

Talk abstract: Beam diagnostics for resolving internal structure of a beam in an accelerator use interaction of the beam particles with a probe that can be inserted in the beam. Many types of probes can be used for this purpose, from a simple wire to a beam of different particles. Negative ions of hydrogen (H-) are widely used in initial stages of high-intensity circular proton acceleration. These particles interact efficiently with photons, therefore, a laser beam makes an ideal probe for diagnostics of H- beams. Lasers can be used to measure many important beam parameters: transverse and longitudinal beam size, transverse and longitudinal emittances, beam energy and intensity. A review of the laser-based beam diagnostics will be given in this talk. Most of the material is based on the experience from the Spallation Neutron Source, the world highest power H- accelerator.      

11 February 2022
The Upgraded Injector Test Facility at Jefferson Lab
Matthew Poelker, Jefferson Lab

The Upgraded Injector Test Facility at Jefferson Lab is a compact superconducting radio frequency (SRF) linac that can provide spin polarized electron beam at energy up to 10 MeV. In this talk, I describe the facility and the performance of the novel SRF cryomodule used to accelerate the beam. I will present brief descriptions of two inaugural studies performed at the facility, and discuss possible future applications.   

28 January 2022
DC Photoemission Guns and a Quest for Higher Operating Voltage
Carlos Hernandez-Garcia, Thomas Jefferson National Accelerator Facility

Talk abstract: High voltage DC photoemission electron guns have demonstrated high performance for a variety of meaningful accelerator applications, including:

• Ultra-high vacuum required for obtaining long-photocathode lifetime from high polarization GaAs photocathodes for nuclear physics
• Generating tens of mA for electron coolers, energy recovery linacs, and free-electron lasers
• Bright electron beams for electron microscopy and for ultra-fast electron diffraction

The photocathode accelerating field must be sufficiently high (often > 10 MV/m) to compensate for high bunch charge and improve injector transmission, imposing challenging requirements to reliably apply high voltage to the electrodes and HV feedthroughs without breakdown. Further, the electrodes must be free of field emission to preserve the vacuum conditions necessary for long photocathode lifetime. At Jefferson Lab, we have developed compact DC high voltage photoguns based on an inverted-geometry ceramic insulator concept. Our design is based on achieving exceptional vacuum, being free of field emission and operating with reliable approaches to applying high voltage to the photogun. I will provide an overview of DC photogun designs in operational accelerators, practical considerations to reliably apply high voltage, and summarize both successes and failures learned over the two past decades in building these photoguns.

14 January 2022
EDM Measurement in Small Rings
Vasiliy Morozov, Oak Ridge National Laboratory

Talk abstract: V.S. Morozov¹, R. Suleiman², and Ya.S. Derbenev² present a new design of highly-specialized small storage rings for low-energy polarized electron beams. The new design is based on the transparent spin methodology that cancels the spin precession due to the magnetic dipole moment at any energy while allowing for spin precession induced by the fundamental physics of interest to accumulate. The buildup of the vertical component of beam polarization can be measured using standard Mott polarimetry that is optimal at low electron energy. These rings can be used to measure the permanent electric dipole moment of the electron, relevant to CP violation and matter-antimatter asymmetry in the universe, and to search for dark energy and ultra-light dark matter.

¹Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
²Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA

2021

17 December 2021
Making Molecular Movies with MeV Electrons
Xiaozhe Shen, SLAC National Accelerator Laboratory

Talk abstract:Visualization of structural changes of materials with atomic spatial (Angstrom) and temporal resolutions (femtosecond) is of crucial importance to the understanding of the relation between structure and functionality, and the ultimate goal of controlling energy and matter^[1]. In the past decades, ultrafast electron diffraction/microscopy (UED/UEM) has been rapidly developing, aiming to provide the relevant length and time scales for ultrafast science^[2-3]. With the advent of high accelerating gradient radiofrequency photoinjector, high brightness electron beam at mega-electron-volt (MeV) energy has become accessible for UED to reach ~1 Å spatial resolution and ~100 femtosecond temporal resolution. In 2014, SLAC National Accelerator Laboratory launched a UED/UEM initiative, aiming to provide the world’s leading ultrafast electron scattering instrument using MeV electron beams. A prototypical MeV UED beamline was built and has been evolving over the years^[4-6] for the goal that has long been envisioned—making space-and-time resolved molecular movies. A great number of successful ultrafast scientific results have been achieved at SLAC MeV UED in the regions of condense matter physics, warm-dense matter physics, as well as chemical science^[7-9]. Since 2019, SLAC MeV UED has become an official user facility as part of Linac Coherent Light Source to serve the ultrafast science community^[10]. In this talk, the experimental set up of SLAC MeV UED and selected ultrafast scientific results will be presented. Research and development efforts to further expand the capabilities of SLAC MeV UED will also be discussed.

^[1] "Directing matter and energy: Five challenges for science and the imagination,” A Report from the Basic Energy Sciences Advisory Committee, 2007
^[2] R. J. D. Miller, Science 343, 1108 (2014)
^[3] Ahmed H. Zewail, Science 328, 187 (2010)
^[4] S. P. Weathersby, et al., Review of Scientific Instruments 86, 073702 (2015)
^[5] X. Shen, et al., Ultramicroscopy 2018, 184, 172-176
^[6] X. Shen, et al., Struct. Dyn. 6, 054305 (2019)
^[7] E. J. Sie, et al., Nature 565, 61 (2019)
^[8] M. Z. Mo, et al., Science 360, 1451 (2018)
^[9] J. Yang, et al., Science 361, 64 (2018)
^[10] SLAC MeV UED user facility webpage

3 December 2021
Superconducting Radio Frequency Cavity Fault Classification Using Machine Learning at Jefferson Lab
Chris Tennant, Jefferson Lab

Talk abstract: We report on the development of machine learning models for classifying C100 superconducting radio frequency (SRF) cavity faults in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. Of the 418 SRF cavities in CEBAF, 96 are designed with a digital low-level rf system configured such that a cavity fault triggers recordings of rf signals for each of the eight cavities in the cryomodule. Subject matter experts analyze the collected time-series data and identify which of the eight cavities faulted first and classify the type of fault. This information is used to find trends and strategically deploy mitigations to problematic cryomodules. However, manually labeling the data is laborious and time consuming. By leveraging machine learning, near real-time—rather than postmortem—identification of the offending cavity and classification of the fault type has been implemented. We discuss performance of the machine learning models during a recent physics run. We also discuss efforts for further insights into fault types through unsupervised learning techniques, and present preliminary work on cavity and fault prediction using data collected prior to a failure event.

19 November 2021
Accelerator Research at Fermilab's IOTA/FAST Facility
Alexander A. Valishev, Fermi National Accelerator Laboratory

Talk abstract: The Fermilab Accelerator Science Facility (FAST), is a research machine to conduct accelerator proof-of-principle experiments as well as technology development to enable future particle physics accelerator facilities. The centerpiece of the facility is the Integrable Optics Test Accelerator (IOTA), a small storage ring designed to satisfy the requirements of a diverse beam physics research program using either electron or proton beams. This talk will discuss some of the challenges of accelerator physics and how the IOTA/FAST experimental program addresses them. The covered topics include nonlinear beam dynamics, beam instabilities, beam cooling, and photon science.

5 November 2021
Particle-Matter Interaction Simulations in Accelerator Applications
Dali Georgobiani, Fermi National Accelerator Laboratory

Talk abstract: An overview of underling physics in high-energy or/and high-power particle beam interactions with matter in accelerator applications and its implementation in the Monte Carlo simulations is presented and discussed. Effects in materials under irradiation, materials response related to component lifetime and performance are considered with a focus on existing and future accelerator complex needs. The implementation of this multi-faceted physics and adequate state-of-the art computing techniques in the modern Monte Carlo codes, code main features, results of the code benchmarking, validation, and intercomparison are described.

22 October 2021
Plasma Processing Boosts the Energy of the Spallation Neutron Source Superconducting Linac
Marc Doleans, Oak Ridge National Laboratory
 

Talk abstract: The Spallation Neutron Source (SNS) has been in operation for neutron science since 2006 at the Oak Ridge National Laboratory. The SNS provides the most intense, pulsed accelerator-based neutron beams in the world. It uses 1.4 MW of average proton beam power on its liquid mercury target to generate neutrons for research. Most of the proton beam energy is imparted by the superconducting linac portion of the accelerator. In its early years of operation, the superconducting accelerating cavities suffered from excessive parasitic electron activity leading to thermal instability and reduced accelerating gradients. As the result, the proton beam energy remained at 940 MeV, below the SNS design beam energy of 1000 MeV. To remediate this issue, a new in-situ processing technique was proposed and developed. The technique centered on using a plasma inside the resonant cavities to further process their inner RF surfaces and allow increased accelerating gradients. The presentation will cover the successful development and deployment of this new technique leading to a proton beam energy of 1 GeV for neutron production.

8 October 2021
Cathode R&D for High Intensity Electron Source at Brookhaven National Laboratory
Mengjia Gaowei, Brookhaven National Laboratory

Talk abstract: Attaining high quantum yield, low emittance, and long lifetime from an alkali antimonide photocathode has remained a sustained focus in recent years, due especially to the need for electron beams of high average current for strong hadron cooling. The ongoing development of photocathodes is motivated by the unprecedented needs of this application, namely simultaneous optimization among photoemission metrics that tend to be linked by the underlying physics. The challenge of optimizing these processes and their linked photoemission metrics has driven improvements in cathode material characterization and new fabrication techniques. At BNL, a new suite of materials science tools is now available to address the poor crystallinity and lack of surface and bulk engineering that has previously limited the performance of these materials. In situ and real time x-ray characterization study has been performed to reveal the compositional, structural and surface evolution of the alkali-based photocathodes prepared using different growth techniques and recipes, as well as their correlation with quantum efficiency and degradation mechanisms. The structural, stoichiometric and surface information revealed by these measurements are essential for optimizing the cathode quantum efficiency, emittance and operational lifetime for applications in future light sources.

24 September 2021
Advances in Recirculating Superconducting Proton Linac Study 
Ji Qiang, Lawrence Berkeley National Laboratory

Talk abstract: Superconducting proton linacs can be used as a driver for a wide range of applications including spallation neutron source, accelerator driven nuclear energy production, neutrino physics study, and medical application. However, the construction and operation of such a superconducting proton linac is expensive. In this talk, we will discuss a new type of proton linac, recirculating superconducting proton linac, and its recent advances. This accelerator has the potential to substantially reduce the cost of a superconducting proton linac by using much less number of superconducting cavities.

10 September 2021
Injection Technologies for High Power Proton Rings: Present and Future
Sarah Cousineau, Oak Ridge National Laboratory

Talk abstract: High power, pulsed proton rings rely on charge exchange injection to control the phase space density while the charge density of the beam is increased. Traditional charge exchange injection from an H-linac into a ring relies on very thin carbon foils to strip the electrons from the hydride. The presence of the foil material in the path of the beam introduces complications such as scattering of beam resulting in high radiation in the vicinity of injection. Additionally, while foil technology has advanced considerably over the decades with latest foils able to sustain megawatt beam cycles for months, there is still a fundamental beam power density limitation on the foils. Next generation machines will need to rely on alternative methods for charge exchange. One such method under development is the laser assisted charge exchange method (LACE), which utilizes magnets and lasers in place of the foil to remove the electrons. This talk will discuss the successes and limitations of foil technology, and the development of the LACE technique as a candidate for replacing the foils in future high power accelerators.

23 April 2021
The Argonne Tandem Linac Accelerator System (ATLAS) Multi-User Upgrade and New Applications (PDF)
Brahim Mustapha, Argonne National Laboratory

Talk abstract: The recently approved multi-user upgrade of the ATLAS facility at Argonne will enable simultaneous acceleration and delivery of two different ion beams to different experimental areas. In the initial phase, one stable, nearly continuous-wave beam from the Electron Cyclotron Resonance ion source, and one pulsed radioactive beam from the Electron Beam Ion Source charge breeder of the Californium Rare Isotope Beam Upgrade (CARIBU-EBIS) will be interleaved in time via a pulsed electrostatic deflector at injection, and accelerated through the first two sections of the linac. At that point, one of the beams is deflected via a pulsed switching magnet to a lower energy experimental area while the other is further accelerated through the third linac stage of ATLAS and delivered to a higher energy experimental area. Details of the proposed implementation and the expected gains from this upgrade will be presented. In addition to enhancing the ATLAS nuclear physics program, this upgrade will also increase the availability of beam time for applications such as material irradiation, isotope-production research and development, and radiobiology studies with ion beams. A brief overview and typical results from these applications will be presented.

9 April 2021
Fusion Sciences & Ion Beam Technology
Qing Ji and Arun Persaud, Lawrence Berkeley National Laboratory

Talk abstract: We report on two different accelerator technologies being developed at Lawrence Berkeley National Laboratory (LBNL). First, we will describe the Neutralized Drift Compression Experiment-II (NDCX-II) at Berkeley Lab. NDCX-II is a 1 MeV induction LINAC delivering high peak ion current (~ 1 A) of ultrashort pulse length (a few ns FWHM) with a beam spot of 1 mm radius on target. We will discuss its design, control system, and recent experiments. NDCX-II has been in operation for several years. The hot-plate surface lithium ion source has been replaced with a plasma source that can generate proton and helium ions in a large area (~ 6 cm in diameter). Recently, NDCX-II has been used to study radiation effects induced by ions with high fluences and high dose rate in diodes and transistors. Second, we will discuss the development of a multi-beamlet, compact RF accelerator that is fabricated using a stack of inexpensive PCBoard wafers. This is a new implementation of an accelerator design from the 1980’s, but with an order of magnitude reduction in size. We have demonstrated working implementations of the basic components (focusing and acceleration elements) and recently achieved beam energies of 50 keV. The technology can be scaled up to higher currents and MeV beam energies.

26 March 2021
High Gradient C-band Research at Los Alamos (PDF)
Evgenya Simakov and John Lewellen, Los Alamos National Laboratory

Talk abstract: Our talk will report on the design, assembly, and high-power conditioning of the new high-gradient C-band Engineering Research Facility (CERF-NM) at Los Alamos National Laboratory (LANL). At LANL, we commissioned the CERF-NM that is a test stand powered by a 50 MW, 5.712 GHz Canon klystron. The test stand is capable of conditioning single-cell accelerating cavities for operation at surface electric fields up to 300 MV/m. The RF field is coupled into the cavity from a WR187 waveguide through a mode launcher that converts the fundamental mode of the rectangular waveguide into the TM01 mode of the circular waveguide for coupling into the cavity. The test stand is currently fully conditioned to operate at the power of 50 MW, 100 Hz repetition rate, and RF pulse length up to 1 microsecond. The first cavity to be tested for high gradient operation will be a beta=0.5 proton accelerating cavity fabricated at SLAC National Accelerator Laboratory.

It is well-known that a notable bottleneck in achieving high-gradient in RF structures is the onset of RF breakdown. While bulk mechanical properties are known to significantly affect breakdown propensity, the underlying mechanisms coupling RF fields to bulk plastic deformation in experimentally relevant thermo-electrical loading conditions remain to be identified at the atomic scale. In this talk, we will also present results of large-scale molecular dynamics simulations (MD) to investigate possible modes of coupling. We consider the activation of Frank-Read (FR) sources, which leads to dislocation multiplication, under the action of bi-axial thermal stresses and surface electric-field. With a charge-equilibration formalism incorporated in a classical MD model, we show that a surface electric field acting on an either pre-existing or dislocation-induced surface step, can generate a long-range resolved shear stress field inside the bulk of the sample. We investigate the feedback between step growth following dislocation emission and subsequent activations of RF sources and discuss the regimes of critical length-scales and densities of dislocations, where such a mechanism could promote RF breakdown precursors. Some interesting simulation results will be presented and discussed.

12 March 2021
Recent Advances and Breakthrough for Superconducting Radio Frequency Cavities at Fermi National Accelerator Laboratory (PDF)
Martina Martinello, Fermi National Accelerator Laboratory

Talk abstract: The talk will discuss the state-of-the-art surface treatments for superconducting radio frequency cavities, stressing how to obtain both high Q-factor and high-accelerating gradients. The physics underneath performance improvement will be discussed and correlated with material analysis results. The talk will also discuss the technology advances in correlation with LCLS-II HE and PIP-II projects.

26 February 2021
Superconducting Accelerator Magnet Design and Applications
GianLuca Sabbi, Lawrence Berkeley National Laboratory

Talk abstract: This presentation will review the fundamentals of superconducting accelerator magnet design, including material properties, magnetic, mechanical and quench protection analysis. Two specific applications will be discussed in some detail: IR quadrupoles for HL-LHC, and magnets for ECR ion sources. Broader applications of high field magnet technology will also be mentioned in areas ranging from NMR/MRI, radiation therapy and fusion energy devices.

12 February 2021
Adaptive Feedback and Machine Learning for Time-Varying Particle Accelerator Systems (PDF)
Alexander Scheinker, Los Alamos National Laboratory

Talk abstract (PDF)

29 January 2021
Spin Manipulation Experiment in the Relativistic Heavy Ion Collider
Haixin Huang, Brookhaven National Laboratory (BNL)

Talk abstract: The BNL nuclear physics program requires polarized hadron beams in the Relativistic Heavy Ion Collider (RHIC) and Electron-Ion Collider. Frequent reversals of the beam polarization direction in a storage ring can significantly reduce the systematic errors in an experiment’s spin asymmetry measurements. At high energy colliders with Siberian snakes, a more sophisticated spin flipper constructed of nine dipole magnets, was used to flip the spin in the BNL RHIC. A special optics choice was also used to make the spin tune spread very small. The same device was used to drive coherent spin motion to measure the important quantity, spin tune. The principle and experiment results are discussed.

15 January 2021
Electron Cooling in a Collider* (PDF)
Alexei Fedotov, Brookhaven National Laboratory

Talk abstract: High-energy electron cooling is being considered for several accelerator physics projects worldwide, including for the Electron Ion Collider under design at Brookhaven National Laboratory (BNL). Since accelerating DC electron beams above few MeV is technologically challenging, rf-acceleration of electron bunches becomes a practical approach for high-energy applications. A world's first electron cooling of ion beams employing such RF-accelerated electron bunches was recently demonstrated at BNL using the Low Energy Relativistic Heavy Ion Collider (RHIC) electron Cooler (LEReC) ^[1]. Many challenges associated with such an approach were successfully overcome. The cooling task becomes even more challenging when one attempts to cool ion beams in collisions, requiring careful optimization between the electron cooling process and the ion beam lifetime due to various effects, including the beam-beam interactions. In this presentation, we discuss first successful application of electron cooling technique for colliding ion beams in RHIC. 

^[1] A.V. Fedotov et al., “Experimental demonstration of hadron beam cooling using radio-frequency accelerated electron bunches”, Phys. Rev. Letters 124, 084801 (2020)
*Work supported by the U.S. Department of Energy

2020

11 December 2020
Optical Stochastic Cooling at Fermilab’s IOTA Ring
Jonathan D. Jarvis, Fermi National Accelerator Laboratory

Talk abstract: In modern accelerators, the ability to increase or maintain beam density and lifetime is essential. Historically, this has required the development and application of a variety of beam-cooling concepts and technologies to facilitate particle accumulation, higher luminosity and to counteract diffusive (heating) effects, such as intrabeam scattering (IBS), Touschek scattering, and residual-gas scattering. One of the greatest conceptual and technological triumphs in this area was van der Meer’s Nobel-Prize-winning Stochastic Cooling (SC), which was vital in the accumulation of antiprotons and in the delivery of the beam quality required for the discovery of the W and Z bosons. Extension of the SC principle to optical frequencies and bandwidths (Df~10¹³ Hz) was first suggested in the early 1990s by Zolotorev, Zholents and Mikhailichenko and could increase achievable cooling rates by three to four orders of magnitude. In this talk, we will review the basic concepts of Optical Stochastic Cooling (OSC) and describe the experimental OSC program underway at Fermilab’s Integrable Optics Test Accelerator (IOTA) ring. We will also discuss development efforts focused on high-gain optical amplification for OSC and the use of OSC concepts and technology as a more general tool for phase-space control and measurement.

13 November 2020
Electron Ion Collider and Superconducting Radio Frequency Device Development at Brookhaven (PDF)
Zachary Conway, Brookhaven National Laboratory

Talk abstract: This presentation will overview the superconducting radio frequency devices required for the future Electron Ion Collider and ongoing work at Brookhaven National Laboratory addressing related technical challenges. One of the challenges of operating superconducting resonant cavities in hadron synchrotrons is the need to operate with large frequency sweeps, greater than one percent in some cases during beam acceleration. A physical example of these challenges is found in the refurbished 56 MHz superconducting accelerator system to be installed in the Relativistic Heavy Ion Collider in 2022. The 56 MHz superconducting system addresses synchrotron acceleration via a novel coupler and tuner which damp and detune the resonator during beam acceleration. A full review of the 56 MHz system upgrades and conclusions on how these results may impact plans for the Electron Ion Collider will be discussed.

30 October 2020
National Synchrotron Light Source II: Present Status and Upgrade Plans (PDF)
Guimei Wang, Brookhaven National Laboratory

Talk abstract: The National Synchrotron Light Source II (NSLS-II) is a 3 GeV, low-emittance (H:1 nm-rad and V:8 pm-rad), high-brightness third-generation synchrotron light source at Brookhaven National Laboratory. It is to deliver a broad range of light to 60-70 beamlines at full build-out. The storage ring was commissioned in 2014 and began its routine operations in December of the same year. Since then, we have been continuously installing and commissioning new insertion devices and beamlines. At this point, the facility hosts 28 beamlines to deliver light from infrared to hard x-ray. Over the past five years, the storage ring performance continuously improved, including 500 mA demonstration and 400 mA routine top off operation. In fiscal year 2020, we delivered 5,400 hrs beam time with 97-percent operation reliability. 

Towards the future, a program to explore upgrade paths for the NSLS-II was initiated in 2019, with the goal of dramatically increasing its brightness and flux, which requires significantly lower emittance. Instead of following the Multi-Bend Achromat (MBA) lattice approach, recently we proposed an alternative way to reach low emittance by use of a lattice element that we call "Complex Bend." The Complex Bend is a new concept of bending magnet consisting of a number of dipole poles with strong alternate focusing to maintain the beta-function and dispersion oscillating at very low values, thus reach low emittance. Candidate lattices have achieved ~30 pm-rad emittance with 5 mm on-momentum dynamic aperture to allow off-axis injection.  

16 October 2020
The Recycler and Main Injector in the Megawatt Era (PDF)
Robert Ainsworth, Fermi National Accelerator Laboratory
 

Talk abstract: As part of the Nova upgrades in 2012, the recycler was repurposed as a proton stacker for the main injector with the aim to deliver 700 kW. Since January 2017, this design power has been run routinely. Looking towards PIP-II, the recycler and main injector will be required to stack and accelerate 50% more beam in order to deliver 1.2 megawatt beam power for LBNF/DUNE. This intensity increase poses serious challenges of which some will be discussed, such as space charge tune shifts during slip-stacking, transition crossing in the main injector and instabilities in both machines. Different schemes to mitigate these issues, such as resonance compensation and a gamma-t jump system will be discussed.

2 October 2020
Accelerator R&D Activities at Argonne National Laboratory (PDF)
John Byrd, Argonne National Laboratory

Talk abstract: I will talk about the wide range of accelerator R&D going on at Argonne National Laboratory. The main activity is the design and construction of a new 6 GeV electron storage ring that will replace the existing Advanced Photon Source (APS) storage ring. When commissioning finishes, planned for 2023, the APS Upgrade will be the world’s  brightest storage ring light source. We are currently engaged in several studies to understand the challenges of very low emittance electron beams. Argonne is also deeply engaged in physics and technology of future light sources. I will touch on activities such as superconducting undulators, low emittance electron sources, x-ray free electron laser oscillators as well a future beam wakefield driven accelerators. 

18 September 2020
Nb₃Sn Superconductors for Accelerator Magnets (PDF)
Xingchen Xu, Fermi National Accelerator Laboratory

Talk abstract: Nb₃Sn, currently the second most-widely used superconductor (second only to NbTi), has important applications in the building of high-field magnets (typically above 10 T) for nuclear magnetic resonance (NMR) devices, particle accelerators, experimental thermonuclear fusion reactors, and other research-use magnets. Nb₃Sn is the superconductor of choice to build accelerator magnets for the planned Future Circular Collider (FCC), as the successor to the Large Hadron Collider (LHC). However, the critical current density (Jc - the most important performance index of superconductors - of the state-of-the-art Nb₃Sn, which has been at a plateau for nearly two decades, is significantly below that required by the FCC specification at 16 T. On the other hand, a new type of Nb₃Sn superconductor we are developing based on the internal oxidation technology, which introduces oxide nanoprecipitates as artificial pinning centers (APC) to Nb₃Sn, has demonstrated significantly superior performance to state-of-the-art Nb₃Sn, including doubling the Jc at high fields (16 T and above) while significantly reducing the undesirable magnetization at low fields (3 T and below). This talk will discuss the applications of Nb₃Sn superconductors in accelerator magnets, their current status, the prospect for a new generation of Nb₃Sn superconductors based on the APC technology, and why such conductors, if successful, can be a game changer for future energy-frontier circular colliders.

29 January 2020
Fusion, Beams and Qubits (PDF)
Thomas Schenkel, Lawrence Berkeley National Laboratory

2019

5 December 2019
Accelerator and Beam Physics Research Opportunities at Fermilab (PDF)
Vladimir Shiltsev, Fermi National Accelerator Laboratory

21 November 2019
Particle Accelerators at Los Alamos National Laboratory (LANL) (PDF)
Stephen Milton, LANL

18 September 2019
Physics of Multi-Bend Achromat Lattice (PDF)
Ryan Lindberg, Argonne National Laboratory
 

20 May 2019
Plasma Spectroscopy Techniques for Diagnosing Plasmas in High Energy Density, Pulsed-Power Accelerators (PDF)
Mark D. Johnston, Sandia National Laboratories
 

2018

29 November 2018
Los Alamos Accelerator Science and Technology (PDF)
Robert Garnett, LANL
 

12 September 2018
Nb₃Sn SRF Cavity Development at Fermilab (PDF)
Sam Posen, Fermi National Accelerator Laboratory
 

31 August 2018
High Level Control Room Applications Software at SNS (PDF)
Andrei Shishlo, Oak Ridge National Laboratory
 

14 March 2018
R&D at JLAB Towards High Performance Superconducting RF Cavities (PDF)
Speaker: Pashupati Dhakal, Thomas Jefferson National Accelerator Facility
 

2017

10 April 2017
Perspectives on Ultra-Compact High Gradient RF Accelerator Technology and its Application (PDF)
Sami Tantawi, Stanford Linear Accelerator Center