Bochum 2009 – wissenschaftliches Programm
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HK: Fachverband Hadronen und Kerne
HK 67: Poster Session
HK 67.82: Poster
Donnerstag, 19. März 2009, 14:00–16:00, Audi-Max
Study of transmission and light yield of an n=1.07 silica aerogel — •L. Debenjak1, S. Sirca1, and P. Achenbach2 — 1Jožef Stefan Institute, Ljubljana, Slovenia — 2Institut für Kernphysik, Johannes Gutenberg-Universität, Mainz
The large momentum acceptance of the Kaos spectrometer at the Mainz Microtron MAMI requires the discrimination between kaons and pions for momenta ≥ 1 GeV/c. Silica aerogel with refractive index n∼ 1.07 has been chosen as a Čerenkov radiator for pion suppression. The area to be covered by the aerogel (H × W ∼ 40 × 200 cm2) is governed by the focal plane of the magnetic spectrometer.
A prototype detector with two aerogel tiles of d=2 cm thickness and 20 × 10 cm2 total area was designed, built and tested. Modifications to the basic geometry of the prototype were tried, e.g. different kinds of polished aluminum faces were used in the interior in order to improve the reflection of photons towards the PMTs.
The behaviour of the prototype has been simulated by using Litrani, a C++/ROOT-based program. Different parameters of the aerogel (absorption and scattering) have been measured and used as input data to the simulation code. The characteristic lengths were of the order of 10 cm in the wavelength range of the produced Čerenkov photons.
During two beam-times in Oct. and Nov. 2008 at MAMI the performance of the prototype was measured with electrons, pions, and protons. The absorption and scattering losses in the aerogel tiles lead to a very low number of deteced photons. Detection efficiencies were determined at different threshold settings and particle momenta.