He6-CRES ExB Sweeper: a new decay cell for emptying trapped CRES events*

The He6-CRES experiment aims to precisely measure the beta spectra of ¹⁹Ne and ⁶He to set limits on the Fierz interference term (b) using Cyclotron Radiation Emission Spectroscopy (CRES). First results of broadband CRES have been reported \footnote{https://doi.org/10.48550/arXiv.2209.02870}, but to reach the goal of a b≤10^-3 measurement, improvements to the CRES event rate are needed. Over the past year we have worked to increase the event rate by improving the vacuum, doubling the frequency bandwidth, and most recently implementing ExB electrodes that empty the magnetic trap of electrons by creating an electric field perpendicular to the main magnetic field which causes ExB drift towards the detector walls.

This talk will describe the updated design of the ExB decay cell and present CRES data analyzing the effectiveness of ExB trap emptying compared to simply turning off the magnetic trap. We will also discuss how trap emptying is complicated by the complexities of cyclotron trajectories in a CRES experiment.