科研之友
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摘要
The tritium source in the Karlsruhe Tritium Neutrino Experiment (KATRIN) will deliver 1011 p decay electrons per second, in order to determine the mass of the electron antineutrino through analysing the tritium 3 spectrum. The source is built of a 10 m long beam tube of 90 mm inner diameter, which is operated at 30 K. Gaseous tritium is injected through a central injection chamber and diffuses towards the tube ends, where it is pumped by large turbomolecular pumps and further processed in a closed tritium loop. In order to achieve the KATRIN sensitivity of 0.2 eV/c(2), the decay rate in the source (and hence the tritium density profile) must be stable to a level of +/- 0.1%. As the density profile is influenced by the beam tube conductance, both the temperature stability and the temperature homogeneity must be within a range of +/- 0.03 K at 30 K. A thermosiphon with saturated neon was developed for this purpose, with horizontal evaporator tubes connected all along the 10 m beam tube. The system behaviour was tested in a 12 m long test cryostat, containing the original beam tube with the adjacent pumping chambers, as well as the cooling circuits and the thermal shields. The so-called %26quot;Demonstrator%26quot; was operated in the Tritium Laboratory Karlsruhe (TLK) being connected to the cryogenic infrastructure of KATRIN. The temperature stability was found a factor 20 better than specified, achieving a standard deviation of only 1.5 mK/h, which corresponds to Delta T/T = 5 x 10(-5) h(-1) relative stability at 30 K. The +/- 0.03 K temperature homogeneity along the 10 m beam tube was not yet reached, because of an increased heat load through the pump ports. The repeatability of the temperature measurement with vapour pressure sensors was within +/- 0.004 K.
- 出版日期2013-6
