Development of a low energy particle detector using a superconducting transition edge sensor

It is possible for a superconductive transition edge sensor (TES) to detect directly the low energy proton generated in the neutron beta decay. The precision measurement of the proton spectrum is important to test the prediction of the Standard Model of electroweak interaction. Therefore, we are developing a TES microcalorimeter with a large effective area for a proton detector. Our first TES device consists of four-pixels using a Ti/Au bilayer. All pixels are parallel biased and X-rays from a 55Fe source are detected successfully.