Determination of the sticking probability of a Zr–V–Fe nonevaporable getter strip

Abstract

The Karlsruhe Tritium Neutrino experiment is an ambitious experiment to determine the electron neutrino mass with a sensitivity of 0.2eV. To achieve this extremely high precision, stringent UHV pressures below 10−11mbar in two large spectrometer vessels are requested. This will be achieved by several kilometers of nonevaporable Zr–V–Fe alloy getter (NEG) strips (type St707, manufactured by SAES Getters) which are to be integrated into robust cylindrical cartridges. The knowledge of the sticking probability is essential because the interference between the strips has to be taken into account in order to optimize the interior NEG pump geometry. In this article, the authors will use the Monte Carlo simulation approach to derive the sticking probability of the St707 NEG strip from the experimental data. The derived sticking probability is 0.0290(4), which is about 25% higher than the value estimated by the one-dimensional approximation, used by the standard procedure of the analytical method. Based on this value, different geometrical configurations of the pump setup are discussed. It is shown that the pumping speed of the resulting NEG pump with 1km St707 NEG strips is about 337m3∕s for H2 at 15°C.