Collected Charge and Lorentz Angle Measurement on Non-irradiated and Irradiated ATLAS Silicon Micro-Strip Sensors for the HL-LHC

In this thesis, the collected charge and the Lorentz angle on non-irradiated and the irradiatedminiature of the current test silicon micro-strip sensors (ATLAS12) of the future ATLAS innertracker are measured. The samples are irradiated up to 51015 1MeV neq=cm2 and some of themalso measured after short-term annealing (80 min at 60 C). The measurements are performedat the DESY II test beam, which provides the advantage of tracking to suppress noise hits.The collected charge is measured at various bias voltages for each sample. The results arecompared with the measurements performed using a Sr90 radioactive source. It is shown thatthe measurements with beam and radioactive source are consistent with each other, and theadvantage of tracking at the beam measurements provides the measurement of collected chargeon highly irradiated sensors at lower bias voltages.The Lorentz angle is measured for each sample at dierent magnetic eld strengths between0T and 1 T, the results are extrapolated to 2 T, which is the magnetic eld in the inner trackerof the ATLAS detector. Most of the measurements are performed at --500V bias voltage,which is the planned operation bias voltage of the future strip tracker. Some samples are alsomeasured at dierent bias voltages to observe the eect of bias voltage on the Lorentz angle. Thesignal reconstruction of the strip sensors are performed using the lowest possible signal-to-noisethresholds. For non-irradiated samples, the measured Lorentz angle agrees with the prediction ofthe BFK model. On the irradiated samples, the results suggest that the Lorentz angle decreaseswith increasing bias voltage due to the increasing electric eld in the sensor. The Lorentz angledecreases with increasing irradiation level; however, if the sample is under-depleted, the eectof electric eld dominates and the Lorentz angle increases. Once the irradiation level becomestoo high, hence the collected charge is small due to increasing trapping, the visible eect ofthe Lorentz force in the detector decreases, therefore the measured Lorentz angle decreases.Short-term annealing increases the Lorentz angle, due to the decrease in full depletion voltage.However, on the highly irradiated samples the annealing further decreases the Lorentz angle.The analysis is also re-performed using the signal threshold that will be used in the digitalreadout of strip sensors at the future ATLAS inner tracker. It is seen that the visible eect ofthe Lorentz force decreases at lower uences due to the higher threshold.