Quantitative Long-Term Monitoring of the Circulating Gases in the KATRIN Experiment Using Raman Spectroscopy
Authors: Aker Max , Altenmüller Konrad , Beglarian Armen , Behrens Jan , Berlev Anatoly , Besserer Uwe , Bieringer Benedikt , Blaum Klaus , Block Fabian , Bornschein Beate , Bornschein Lutz , Böttcher Matthias , Brunst Tim , Caldwell Thomas C. , Chilingaryan Suren , Choi Wonqook , Díaz Barrero Deseada D. , Debowski Karol , Deffert Marco , Descher Martin , Doe Peter J. , Dragoun Otokar , Drexlin Guido , Dyba Stephan , Edzards Frank , Eitel Klaus , Ellinger Enrico , Engel Ralph , Enomoto Sanshiro , Fedkevych Mariia , Felden Arne , Formaggio Joseph F. , Fränkle Florian , Franklin Gregg B. , Friedel Fabian , Fulst Alexander , Gauda Kevin , Gil Woosik , Glück Ferenc , Größle Robin , Gumbsheimer Rainer , Hannen Volker , Haußmann Norman , Helbing Klaus , Hickford Stephanie , Hiller Roman , Hillesheimer David , Hinz Dominic , Höhn Thomas , Houdy Thibaut , Huber Anton , Jansen Alexander , Karl Christian , Kellerer Jonas , Kippenbrock Luke , Klein Manuel , Köhler Christoph , Köllenberger Leonard , Kopmann Andreas , Korzeczek Marc , Kovalík Alojz , Krasch Bennet , Krause Holger , La Cascio Luisa , Lasserre Thierry , Le Thanh-Long , Lebeda Ondřej , Lehnert Bjoern , Lokhov Alexey , Machatschek Moritz , Malcherek Emma , Marsteller Alexander , Martin Eric L. , Meier Matthias , Melzer Christin , Mertens Susanne , Müller Klaus , Niemes Simon , Oelpmann Patrick , Osipowicz Alexander , Parno Diana S. , Poon Alan W.P. , Lopez Poyato Jose M. , Priester Florian , Rest Oliver , Röllig Marco , Röttele Carsten , Robertson R.G. Hamish , Rodenbeck Caroline , Ryšavỳ Milos , Sack Rudolf , Saenz Alejandro , Schäfer Peter , Schaller (née Pollithy) Anna , Schimpf Lutz , Schlösser Klaus , Schlösser Magnus , Schlüter Lisa , Schrank Michael , Schulz Bruno , Sefčík Michal , Seitz-Moskaliuk Hendrik , Sibille Valérian , Siegmann Daniel , Slezák Martin , Spanier Felix , Steidl Markus , Sturm Michael , Sun Menglei , Telle Helmut H. , Thorne Larisa A. , Thümmler Thomas , Titov Nikita , Tkachev Igor , Vénos Drahoš , Valerius Kathrin , Vizcaya Hernández Ana P. , Weber Marc , Weinheimer Christian , Weiss Christiane , Welte Stefan , Wendel Jürgen , Wilkerson John F. , Wolf Joachim , Wüstling Sascha , Xu Weiran , Yen Yung-Ruey , Zadoroghny Sergey , Zeller Genrich 
Published: August 2020

The Karlsruhe Tritium Neutrino (KATRIN) experiment aims at measuring the effective electron neutrino mass with a sensitivity of 0.2 eV/c2, i.e., improving on previous measurements by an order of magnitude. Neutrino mass data taking with KATRIN commenced in early 2019, and after only a few weeks of data recording, analysis of these data showed the success of KATRIN, improving on the known neutrino mass limit by a factor of about two. This success very much could be ascribed to the fact that most of the system components met, or even surpassed, the required specifications during long-term operation. Here, we report on the performance of the laser Raman (LARA) monitoring system which provides continuous high-precision information on the gas composition injected into the experiment’s windowless gaseous tritium source (WGTS), specifically on its isotopic purity of tritium—one of the key parameters required in the derivation of the electron neutrino mass. The concentrations cx for all six hydrogen isotopologues were monitored simultaneously, with a measurement precision for individual components of the order 10−3 or better throughout the complete KATRIN data taking campaigns to date. From these, the tritium purity, εT, is derived with precision of <10−3 and trueness of <3 × 10−3, being within and surpassing the actual requirements for KATRIN, respectively.