Design of an Electromagnetic Filter for Relic Neutrino Detection

Abstract

Standard cosmological models generically predict a relic sea of neutrinos known as the cosmic neutrino background. Despite the strong theoretical basis for their existence, relic neutrinos have never been directly detected due to the immense difficulty of detecting low-energy neutrinos. PTOLEMY will measure the tritium beta-decay spectrum near the endpoint energy to search for a small peak of counts due to inverse beta-decay induced by relic neutrinos. The extreme precision required to resolve a peak in the spectrum due to relic neutrinos necessitates an innovative detector design which pushes the limits of current experimental techniques at several frontiers. In this thesis, we present design and analysis work using electromagnetic simulations related to two components of the PTOLEMY detector: the radio frequency (RF) tracker and the transverse drift filter. The highlight of our work on the RF tracker is a novel antenna configuration which makes use of a cylindrical cavity resonator to enhance an order 1 femtowatt electron cyclotron radiation signal. This is the first design to demonstrate the feasibility of discriminating signals from electrons with different parallel momenta. We also summarize the performance of other tested antenna configurations and geometries. For the transverse filter, we conducted electromagnetic simulations to optimize the geometry of a full-scale prototype of the iron magnet designed for the transverse drift filter. We demonstrate using particle trajectory simulations that the geometry-optimized magnet can achieve balanced electron drift while reducing the electron kinetic energy to the desired threshold. Finally, we summarize our hardware work characterizing the response of an avalanche photodiode for use as part of a proof-of-concept electron drift demonstrator.