Commissioning of the vacuum system of the KATRIN Main Spectrometer

TL;DR

The paper details the commissioning and performance evaluation of the vacuum system for the KATRIN Main Spectrometer, crucial for neutrino mass measurement, demonstrating it meets the ultra-high vacuum requirements.

Contribution

It presents the design, commissioning process, and performance results of the vacuum system for the KATRIN Main Spectrometer, a novel ultra-high vacuum setup for neutrino research.

Findings

Vacuum system achieved pressures close to 10^{-11} mbar.

System successfully underwent bake-out at 300°C.

Performance meets the experimental requirements for neutrino mass measurement.

Abstract

The KATRIN experiment will probe the neutrino mass by measuring the beta-electron energy spectrum near the endpoint of tritium beta-decay. An integral energy analysis will be performed by an electro-static spectrometer (Main Spectrometer), an ultra-high vacuum vessel with a length of 23.2 m, a volume of 1240 m^3, and a complex inner electrode system with about 120000 individual parts. The strong magnetic field that guides the beta-electrons is provided by super-conducting solenoids at both ends of the spectrometer. Its influence on turbo-molecular pumps and vacuum gauges had to be considered. A system consisting of 6 turbo-molecular pumps and 3 km of non-evaporable getter strips has been deployed and was tested during the commissioning of the spectrometer. In this paper the configuration, the commissioning with bake-out at 300{\deg}C, and the performance of this system are presented in detail. The vacuum system has to maintain a pressure in the 10^{-11} mbar range. It is demonstrated that the performance of the system is already close to these stringent functional requirements for the KATRIN experiment, which will start at the end of 2016.