Development of NTD-Ge Cryogenic Sensors in LUMINEU

One of the goals of LUMINEU is to develop NTD-Ge sensors for various applications. The steps are to produce NTD-Ge sensors first, then to study the dependence of their performance on the production parameters, and finally to optimize their electric contacts. In this paper, we present the different possibilities for estimating and measuring the real neutron fluence received by each Ge wafer irradiated in a thermal neutron reactor. Measurements of their resistivity at 300 K indicate a fluence discrepancy from the expected value and confirm the homogeneity of the doping throughout the volume. In addition, we present a method allowing an improved estimation of the impedance below 30 mK just by measuring the ratio of the NTDs’ resistivity at 77 and 4 K.