Investigation of rear wall candidates for keV sterile neutrino search at KATRIN

The search for keV sterile neutrinos at the KArlsruhe TRItium Neutrino (KATRIN) experiment is set to start in 2026, measuring the full energy range of the tritium beta-decay spectrum. This novel approach introduces additional systematic uncertainties that must be addressed to ensure reliable results. A key challenge is mitigating the major systematics associated with electron backscattering and radioactive contamination of the rear wall. This talk introduces current concepts for rear wall optimization and discusses experimental efforts to validate these designs. Specifically, the (de)contamination behavior of potential rear wall materials such as beryllium and micro-structured silicon tested with the TRACE experiment is presented. This work is supported by the Helmholtz Association and by the Ministry for Education and Research BMBF (grant numbers 05A23PMA, 05A23PX2, 05A23VK2 and 05A23WO6)