Hartig, Anna-Lena (2022)
Evolution of CALIFA: From single detector modules to benchmark reactions.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00020884
Dissertation, Erstveröffentlichung, Verlagsversion

Kurzbeschreibung (Abstract)

As one of the key detectors of the R3B setup (Reactions with Radioactive Relativistic Beams) at FAIR (Facility for Antiproton and Ion Research), the CALIFA (CALorimeter for the In Flight detection of γ rays and light charged pArticles) detector array surrounds the reaction target and measures γ rays with energies of 100keV < E_γ < 30MeV as well as light charged particles up to E particle = 700MeV. The entire array will consist of 1952 CsI(Tl) scintillating crystals in the Barrel and 460 crystals in the Endcap part. Each crystal is read-out by a Large Area Avalanche Photo Diode. To match the requirements, several steps, tests and quality assurance procedures have to be fulfilled in order to provide the basic components of the CALIFA array. This work gives a detailed description of the assembly of 120 Endcap detector-units and the equipment of two Endcap segments. Furthermore, a gain-matching procedure is performed on the two Endcap segments and their energy resolution is compared to additional test results on the same crystals and to test data stemming from Barrel detectors. A benchmark experiment was performed at the Bronowice Cyclotron Center in Kraków using the quasi-free scattering reaction 208Pb(p,2p)207 Tl in direct kinematics. Within the scope of the experiment, a monoenergetic proton beam of E beam = 200 MeV impinged on a 208 Pb target and the outgoing protons and γ rays were detected by 3 CALIFA petals, containing 64 crystals each. Additionally, two DSSSDs (Double Sided Silicon Strip Detectors) were used to enable vertex reconstruction. The entire setup was read-out by the CALIFA DAQ and operated in air. As proof of concept, two known γ transitions in 207Tl could be identified studying the reaction 208Pb(p,2p)207Tl. In coincidence with one proton, the transition from the 11/2− state, with a lifetime of 1.33s, could be observed. Furthermore, it could be shown in this work that the coincident measurement of the two outgoing protons together with the γ ray, stemming from the transition of the 5/2+ state to the 3/2+ state in 207Tl, is feasible. For use at FAIR, the performance of the CsI(Tl) detectors matches the requirements of CALIFA. The conducted experiment is the first successful measurement of a (p,2pγ) reaction for such heavy nuclei and therefore was a good test case for experiments planned at FAIR that will investigate nuclei in the third r-process peak.

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