Performance of ultra-thin silicon detectors in a 5 MeV antiproton beam

The performance of ultra-thin silicon detectors (6, 55 and 67 μm) was tested in order to provide beam position information, intensity monitoring and a fast trigger signal for the ATHENA experiment. The aim of this experiment is to produce cold antihydrogen using a low energetic (5 MeV) bunched (≈500 ns) antiproton beam from the CERN Antiproton Decelerator (AD). The detector has to be operated in vacuum at ≈10 K and inside a 3 T superconducting magnet. To avoid absorption in the low energetic beam it is imperative to use a thin detector, produced by special lapping and etching techniques. Several detectors were tested in one of the extraction lines of the AD. Additional tests were performed using a laser setup at 660 and 1060 nm to prove the functionality of the complete system. One detector was finally installed in the ATHENA experiment for the August 2000 run where currents of up to 1 A were observed in the detector with simple 50 Ω resistive readout. Results are presented from this detector showing beam profiles, intensities and time structure.