A large, 64-pixel PIN-diode detector for low-energy beta-electrons

The Karlsruhe Tritium Neutrino Experiment (KATRIN) neutrino mass experiment is based on a precise energy measurement ( Δ E / E = 5 × 1 0 - 5 ) of electrons emerging from tritium beta decay ( E max = 18.6 keV ) . This is done by a large electrostatic retarding spectrometer, which is followed by an electron detector. Key requirements for this detector are a large sensitive area (∼80 cm2), a certain energy resolution ( Δ E = 600 eV at 18.6 keV) but also a certain spatial resolution (∼3 mm) which leads to a multi-pixel design. We present as a tentative design a detector system with a reduced size (16 cm2) and a reduced pixel number (64), making use of a monolithic segmented silicon PIN diode. Apart from a description of the electronic design, very first results are presented showing the capability of this detector technology to detect electrons from Tritium β-decay on a large entry window.