Berlin 2005 – scientific programme

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P: Plasmaphysik

P 5: Niedertemperaturplasmen / Plasmatechnologie 2

P 5.4: Talk

Friday, March 4, 2005, 15:30–15:45, HU 3038

Space charge potential in the molecular gaseous tritium source plasma of the KATRIN experiment — •Ferenc Glück (for the KATRIN Collaboration) — Forschungszentrum Karlsruhe, Institut f. Kernphysik

The aim of the KATRIN experiment is to determine the absolute value of the neutrino mass down to 0.2 eV, by measuring the integral energy spectrum of the electrons created by beta decay of T₂ molecules. The gaseous tritium source is planned to have 27 K temperature in a 10 m long and 9 cm diameter tube, and in a 3.6 T axial magnetic field. About 2 × 10¹²/s positive ion — secondary electron pairs are created in the source due to beta decay and ionization processes. The charged particles can leave the source tube by gas flow and diffusion (in a time-scale of 1 s), and in addition they can be destroyed by electron-ion volume recombination. The plasma density is a few times 10⁶ e/cm³. The cooling of the secondary electrons is determined mainly by inelastic, elastic and superelastic collisions with the gas molecules. Our Monte Carlo calculations show that the electron distribution function has a large peak at 2.5 meV. The space charge potential is expected to be smaller than 20 mV, which corresponds to a negligible systematic effect for the neutrino mass determination.

Supported by BMBF Nr. 05CK1VK1/7, 05CK1UM1/5 and 05CK2PD1/5.