Development of compact MWPC detectors for TRINAT experiment

To improve our beta asymmetry measurement using TRIUMF's neutral atom trap for beta decay (TRINAT), we are preparing for the next correlation measurement of polarized ³⁷K at TRIUMF. One of our limiting systematics is the performance of our current β detectors, which are made up of 300 um-thick double-sided Si-strip (DSSSD) ΔE-detector backed by a BC408 plastic scintillator E-detector. We are upgrading these telescopes to reduce the effect related with Landau tail of ΔE β spectra, the backscattering, and the struggling in the DSSSD by replacing it with a multiwire proportional counter (MWPC). We will also replace the magnetic-field-sensitive PMT readout of the scintillator with Si photomultipliers (SiPMs). The same re-entrant flanges will be used to house the new β telescopes, which limits the size of the new detector design. This talk will describe the development of two compact, small-area, position-sensitive MWPC detectors for TRINAT, particularly the spin-polarized β⁺ decay experiment. The detectors will help to reconstruct momentum vector of β particles on event-by-event basis, with higher precision than DSSSD detectors.