Beam Optimization for Throughput Measurements of the Gas Operated Large Ion-bunch Atomic Trap for He6-CRES*

The He6-CRES experiment aims to accurately measure beta decay spectra by observing the cyclotron frequency of emitted beta particles as they Larmor precess within a strong magnetic field. Ultimately, the experiment hopes to measure the Fierz parameter, a standard model variable, to within 0.1%. The Gas Operated Large Ion-bunch Atomic Trap for He6-CRES (GOLIATH) radiofrequency quadrupole (RFQ), a planned upgrade to the experiment, enables confining a continuous beam of ions into bunches during measurement, allowing for a wider range of isotopes to be used in CRES experiments. Furthermore, GOLIATH was designed to surpass expected limitations of bunch size caused by the space-charge effect by up to a factor of 50; maximizing the throughput of this trap is therefore essential to reaching our desired precision.

Testing the GOLIATH RFQ requires a precisely aligned, well calibrated ion beam to gauge transmission through the device. Performing a non-destructive current measurement near the beginning of the beamline enables calculation of injected beam strength. Pairing this measurement with another rate measurement allows us to normalize our throughput measurements to source activity. Using a microchannel plate detector, we can also image the beam with single particle detection, aiding in calibrating beam steerers and lenses and providing transmission information at low intensities.