Dresden 2011 – wissenschaftliches Programm

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VA: Fachverband Vakuumphysik und Vakuumtechnik

VA 3: KATRIN Vacuum Systems

VA 3.3: Vortrag

Montag, 14. März 2011, 14:40–15:00, HSZ 101

Rotor temperature of turbo-molecular pumps in magnetic fields — •Joachim Wolf, Robin Größle, Norbert Kernert, and Sebastian Riegel — KIT - IK/IEKP, Postfach 3640, 76021 Karlsruhe

The KATRIN neutrino experiment operates about 20 turbo-molecular pumps (TMP) in the vicinity of super-conducting magnets, pumping out tritium gas from the electron beam-line of the experiment. In a dedicated test setup with Helmholtz coils systematic studies have been conducted, investigating the rotor temperature and stability of operation of TMPs (Leybold MAG-W 2800 and MAG-W 2200) at full speed as a function of gas load, magnetic field strength and direction of the field. The temperature of the magnetically levitated moving rotor was measured in vacuum with an infra-red pyrometer. An empirical model has been developed, describing quantitatively the temporal progression of the rotor temperature as a function of gas flow and field strength of an external static magnetic field. The model requires 5 pump-specific parameters, characterising the heating effects of eddy currents and gas friction as well as cooling by radiation loss and convection. When designing a vacuum system with TMPs in a critical environment (e.g. magnetic beam-line, fusion reactor), the model can be used to predict the maximum temperature of the rotor, to ensure a save operation of the pump. The model has been applied for simulating strong, pulsed magnetic fields as they occur at nuclear fusion experiments (JET) and for TMPs in the tritium loop of the KATRIN experiment. KATRIN is supported by the German BMBF project 05A08VK2, DFG TR27 and HGF.