First accelerated beam from reaccelerator identified

The first accelerated beam through the ReA3 reaccelerator was identified today during commissioning of the radio frequency quadrupole accelerator (RFQ).

ReA3 is designed to accelerate rare isotope beams produced by NSCL's Coupled Cyclotron Facility and will be part of FRIB. Once completed, ReA3 will serve the nuclear science community by delivering a wide variety of exotic isotopes for nuclear science experiments at variable energies with high beam quality.

The RFQ is a cavity structure designed to create an electromagnetic field which focuses and accelerates a bunched beam at the same time.  A photograph is shown in Figure 1.

A silicon foil detector was used to determine the kinetic energy of the accelerated beam particles. Figure 2 shows the energy spectrum from the accelerated beam together with the peak from the calibration alpha source. As expected, a peak at about half the energy of the calibration source was found giving clear evidence of the accelerated beam. The peak disappears when the beam is blocked before the RFQ or when the RFQ voltage is below the acceleration gradient.  Commissioning will continue to determine the absolute energy and the energy spread of the beam.

Beam commissioning through the first part of the superconducting radio frequency (SRF) linac is the next step in commissioning the reaccelerator.