Digital signal analysis for CsI(Tl) detectors and the active-target at R 3 B
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Abstract
Modern experimental setups tend to replace analogue front-end electronics with fully digital systems. The detector signals are sampled in early stages and most of the signal processing is performed digitally. The presented work is divided into two major subjects involving digital signal analysis: firstly employed to correct temperature dependent gain variations and perform particle identification of CsI(Tl) based detectors and secondly to test the unctionality of an active-target prototype (AcTar) for the Reactions with Relativistic Radioactive Beams (R3B) setup.
In the first part of this work a pulse shape based method for monitoring the interior temperature of the CsI(Tl) crystal is proposed. The method uses the correlation between the gain and defined pulse shape parameters to correct the effect of temperature variations in the energy calibration of the corresponding detector system. The suitability of the method was tested using both, a photomultiplier tube (PMT) and an avalanche photodiode (APD) readout photosensor. The analysis shows that the gain changes due to temperature variations can be corrected to a precision better than 1% with both the PMT and APD photosensors, well below the CsI(Tl) intrinsic resolution for ∼1 MeV γ-rays.
For particle identification, the fuzzy clustering algorithm is used to compute the principle pulse shape associated with the different particle species in an unsupervised fashion. The results show good discrimination between protons and γ-rays. In the second part of this work the functionality of the AcTar prototype for the R3B setup has been tested. The objective was to prove the feasibility and performance of such kind of detector with the use of heavy ion beams. As a proof of concept, a 58Ni beam at 700 MeV/u was impinging on a He-H2 (3%) gaseous target mixture. The presented results show the principle unctionalities of the detector and suggest that pulse shape analysis can indeed be used to track the recoil particles and reconstruct the kinematics. It is the first time that an active-target of such kind has been successfully tested with beams heavier than carbon.