Heidelberg 2007 – scientific programme
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T: Fachverband Teilchenphysik
T 604: Exp. Methoden der Astroteilchenphysik II
T 604.3: Talk
Friday, March 9, 2007, 17:15–17:30, KIP Kl. HS
Investigation of liquid argon scintillation properties for the GERDA DBD-experiment — •Peter Peiffer1, Tina Pollmann1, Stefan Schönert1, Anatoly Smolnikov2,3, and Sergei Vasiliev3 for the GERDA collaboration — 1MPI-K, Heidelberg, Germany — 2INR, Moscow, Russia — 3JINR, Dubna, Russia
The next generation DBD-experiment GERDA will operate HP-Ge-diodes in liquid argon (LAr). LAr scintillates at a wavelength of 128 nm. LArGe(Liquid ARgon GErmanium) is a R&D project, researching the properties of the scintillation and its use as anti-coincidence signal for the HP-Ge detectors operated in the LAr. The scintillation light is shifted by a wavelength-shifter (WLS) and detected by a cryogenic photo-multiplier-tube (PMT) immersed in the LAr. By optimization of the WLS the photo-electron yield has been improved from 400 pe/MeV to 1100 pe/Mev and has been stable for more than 6 months.
LAr scintillation light is emitted from two different excited molecular states, a singlet and a triplet state. The decay time constants are 6 ns for the singlet and 1.6 s for the triplet state [1] and the population of the states depends on the ionization density of the incident particle. This allows for a powerful discrimination between particles of different ionization densities, i.e. between gammas, alphas and neutrons.
The addition of Xe to the LAr can increase the light yield and has a significant impact on the pulse shape. First results from this ongoing research are presented.
[1]: Hitachi et al., Phys.Rev.B, Vol.27, No9, (1983) 5279