The high performance microstrip silicon detector tracking system for an innovative crystal based collimation experiment

In order to increase the LHC luminosity, an innovative crystal based collimation system is being developed in the UA9 experiment: exploiting the well-known effect of channeling and the recently discovered volume reflection phenomenon, a short silicon bent crystal will be used to replace the traditional multi-stage collimation system to remove the beam halo particles. This idea will be tested with a 120 GeV/c proton beam on the LSS5 straight section at the SPS accelerator ring (CERN) using several crystal technologies and a high performance tracking system based on high resolution (5 pm) double-side microstrip silicon detectors. The first silicon detector will be positioned in a roman pot at about 50 m from the crystal, where the phase difference of 90 maximizes the distance of the steered particles (due to the crystal) from the beam core; after around 20 m a second tracking station will be able to measure the steering angle. Each detector side is readout by three 128 channel VA1TA self-triggering ASICs, which contain a preamplifier, two shapers and a sample and hold circuit; the analog signals are digitized by one 10 MHz ADC (per ASIC) and are carried to the DAQ system (which is located on ground) by a series of fiber links (GOH). The DAQ will be completed by a Slow Controls system which will check the power supply voltages and currents and the roman pot pressures and temperatures. This paper gives an insight of the UA9 experiment, underlining the tracking system features and the first results of a silicon detector prototype in the SPS.