An electron transparent proton detector for neutron decay studies

Abstract

We have developed an ultrathin (<100 nm), very strong polyimide foil which can span more than 6×6 cm2 and is ideal for the fabrication of low energy proton detectors. We have produced a proton detector geometry in which protons incident on the foil with kinetic energies greater than about 25 keV produce, on average, more than ten secondary electrons in a conversion crystal evaporated on the back face of the foil. These secondary electrons can be "postaccelerated" and counted in a variety of detectors. The polyimide foils are much more durable than carbon foils previously used in similar detection geometries. LiF was chosen as the conversion crystal, which is relatively insensitive to exposure to air, improving their secondary electron yield under typical operating conditions. In addition, we describe the operation of a very simple, small scale proton accelerator and detector testing chamber capable of providing up to 10 kHz of beam with energies between 10 and 50 keV onto a biased target with a maximum ion contamination of 0.5%. © 2006 American Institute of Physics.