- Project: Research involvement in the context of the Technical Physics master course at TU Wien, Austria
- Collaboration / Institute: CBM-STS (GSI Centre for Heavy-Ion Research / FAIR, Darmstadt, Germany)
- Date: January 2017
- Time Invested: 7 months
- Keywords: semiconductor physics, high-energy particle physics, heavy-ion collisions, data analysis, quality assurance
Abstract
Silicon Microstrip Sensors as used in the Silicon Tracking System (STS) of the Compressed Baryonic Matter (CBM) experiment at FAIR/GSI, Darmstadt, Germany, have to provide a high track reconstruction efficiency as well as a low material budget. They are undergoing extensive quality assurance measures and are studied for their potential use in future CBM-STS. In this work, we describe the measurement and data acquisition processes for a sensor prototype using the Alibava System readout electronics. We refine the gain and offset determination procedure for the readout channels by implementing a nonlinear fitting method, which compensates for non-physical preamplifier outputs at small induced charges. Further, a cluster reconstruction algorithm was developed and applied to the measurement data, which dynamically searches for strip clusters of variable sizes in order to reconstruct signal spectra. In the reconstruction process, the background event distribution is estimated and subtracted by assuming symmetric noise and using information about clusters having the least significant amplitudes. The obtained signal distribution can be well fitted with a Landau–Gauss convolution function having its most probable value of the Landau density at Δp=20.08 ± 0.16 (stat.) ± 0.54 (syst.) kiloelectrons~(ke). In order to study the signal spread caused by charge diffusion in the sensor bulk material, we also investigate interstrip crosstalk effects in two-strip-cluster events, where we find a charge-sharing rate between strips of 16.3%. Additionally, two cross-check analyses are performed: 1) Cuts on the signal-to-noise ratios of the clusters (SNR ≥ 4) are set, which yields results compatible with prior analyses. 2) A different approach of generating two-strip-cluster data is pursued which is able to reproduce the general features of the charge distribution between strip pairs. This method, however, also shows deviations from preceding results, e.g., a charge-sharing rate of 5.6% (7.3%) towards strips to the left (right). Ultimately, we hope that our results will prove themselves useful in choosing analysis methods and code implementations for future CBM-STS precision measurements.