Silicon Strip Detector

For the detection of low-energy recoil particles such as protons, deuterons, or α-particles, multiple silicon strip detectors can be mounted inside the scattering chamber. A detector consists of the silicon substrate, a customized APV-based readout system and an additional cooling system. For particle identification, an additional scintillator telescope detector with SiPM readout is incorporated to provide information on energy losses.

The silicon substrate has the dimensions 50 x 50 mm2 and is divided into sixteen p-doped strips embedded in a n-doped substrate. Hitting the silicon, an ionizing recoil particle produces multiple electron-hole pairs. An external electric field forces the holes to drift towards the nearest strip with an horizontal resolution of σx ~ 0.9 mm. The vertical resolution is determined by measuring the charge asymmetry at both ends of the silicon strip.

At the same time electrons drift in the opposite direction to the substrate producing a signal at the rear of the detector. This signal is called 'sum signal'. It is not possible to trace the spatial information from the sum signal, but it also carries the timing information of the incident particle.

To amplify the collected charge of the silicon strips the signal processing is based on the APV25-S1 frontend chip. Since the APV requires a trigger signal to start the data readout, an additional board was developed to generate that trigger signal based on the sum signal. The final readout board also allows the monitoring of the detector temperature.

Since the signal-to-noise ratio is dominated by the strongly temperature-dependent leakage current, a cooling system is connected to the detector. Therefore, a cooling block is mounted on the backside of the detector. The circulating ethanol cools the detector system down to -20°C.