Schlemme, Steffen Erich (2019)
Nucleon-knockout Reactions from Neutron-deficient Carbon Isotopes and Characterization of a Particle Detector Combination for the Super-FRS at FAIR.
Technische Universität Darmstadt
Ph.D. Thesis, Primary publication
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Item Type: | Ph.D. Thesis | ||||
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Type of entry: | Primary publication | ||||
Title: | Nucleon-knockout Reactions from Neutron-deficient Carbon Isotopes and Characterization of a Particle Detector Combination for the Super-FRS at FAIR | ||||
Language: | English | ||||
Referees: | Enders, Prof. Dr. Joachim ; Kröll, Prof. Dr. Thorsten | ||||
Date: | 2019 | ||||
Place of Publication: | Darmstadt | ||||
Date of oral examination: | 28 January 2019 | ||||
Abstract: | Nuclear structure far from stability show unpredicted and very interesting effects, like deformation and halos. A thorough and unified understanding of these observations is needed to comprehend the nuclear many-body problem and the force between the nuclear constituents. Since the middle of the 20th century the nuclear shell model is used to describe nuclear structure. Single-nucleon removal cross sections depend on the state in which the removed nucleon resided. Thus, the quality of a model prediction can be probed by comparing theoretical cross sections with experimental results. Previous measurements indicate that the reduction factor between theoretical and experimental cross sections decreases for an increasing asymmetry between proton and neutron number. Cross sections of one-neutron removal from 10C, 11C, 12C and one-proton removal from 9C were determined in inverse kinematics. At the fragment separator FRS at GSI Helmholtzzentrum für Schwerionenforschung at about 1670 MeV/nucl. reaction residues were separated and identified The removal reactions yielded the cross sections sigma_exp of sigma_exp(12C-n) = 49.44 +/- 0.88 mb, sigma_exp(11C-n) = 24.44 +/- 0.21 mb, sigma_exp(10C-n) = 20.21 +/- 0.28 mb, sigma_exp(9C-p) = 51.10 +/- 1.35 mb and reduction factors R_s = sigma_exp/sigma_th, when compared to theoretical values obtained using the eikonal approximation, of R_s(12C) = 0.51 +/- 0.01, R_s(11C) = 0.47 +/- 0.01, R_s(10C) = 0.46 +/- 0.03, R_s(9C) = 1.00 +/- 0.03. With the exception of the proton removal, R_s is almost independent from the neutron-to-proton ratio. Beyond the reduction factor, shell model eikonal approximation describe the data well. While a decreasing trend for increasing neutron deficiency was found, the evolution is still flat. Comparisons of the theoretical momentum transfer from the removed nucleon to the reaction residue showed a consistency when compared to the experimentally measured momentum distribution of the residues, proving the eikonal approximation to be correct for modeling the knock out process. At GSI a new accelerator facility, the facility for antiproton and ion research (FAIR), is under construction aiming at the delivery of higher beam energies and intensities. That will allow to investigate more exotic ions, hitherto not accessible in experiments or only at low statistics. Higher intensities lead to higher demands on the future detectors, placed along the beam line near the production target in front of the Super-FRS. Particle detector combinations (PDC) consisting of different detectors for different ion-intensity levels are used to monitor the ion flux. In the framework of this dissertation, prototypes of an ionization chamber (IC) and a secondary-electron monitor (SEM) constructed for FAIR, as well as different designs of single- and polycrystalline diamond detectors were studied. Functionality and performance of all detectors were investigated with a quasi-continuous 12C beam at 62 MeV/nucl. at intensities in the order of 10^5 - 10^7 particles per second. A spilled 124Xe beam at 200 MeV/nucl. with intensities in the order of 10^3 - 10^6 ions per spill was used to investigate the lowest reachable uncertainty when calibrating the IC-prototype. All investigated detectors showed full functionality and a linear response with respect to different beam intensities. A calibration of the IC-prototype within an uncertainty of below 1% was possible. The SEM shows a linear response when compared to intensities of the carbon beam down to 150kHz. A direct calibration of the SEM, using a single-crystal diamond detector as reference, yielded an uncertainty of about 5.1%. The single-crystal diamond detector features a count efficiency of 100% versus a plastic scintillator. No signs of radiation damage were visible before absorbing a dose of about 25 kGy. The polycrystalline diamond detectors exhibits a counting efficiency of 95 +/- 2 % at intensities up to 700 kHz and a rate-dependent decrease of counting efficiency at higher intensities. On the other hand no significant signs of radiation damage were found after depositing a dose of above 4 MGy. Thus, all of the investigated detectors are suitable to be used as part of a FAIR-PDC. Using a polycrystalline diamond detector as reference detector for the calibration process will reduce the frequency of physical access of the beam line for maintenance. Periodic efficiency checks of the polycrystalline diamond detector, using a single-crystal diamond detector, will guarantee a low uncertainty of the obtained count rates. A calibration of the IC to high accuracy has been demonstrated. The accuracy of the rate determined from the SEM was limited due to the low charge of the beam used in the tests and is expected to improve with the high-Z beams at FAIR. |
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URN: | urn:nbn:de:tuda-tuprints-88439 | ||||
Classification DDC: | 500 Science and mathematics > 530 Physics | ||||
Divisions: | 05 Department of Physics > Institute of Nuclear Physics > Experimentelle Kernphysik > Atom- und Kernphysik radioaktiver Nuklide 05 Department of Physics > Institute of Nuclear Physics > Experimentelle Kernphysik > Experimental Nuclear Structure Physics with Exotic Ion Beams 05 Department of Physics > Institute of Nuclear Physics > Experimentelle Kernphysik > Technische Kernphysik und Beschleunigerphysik |
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Date Deposited: | 19 Aug 2019 13:51 | ||||
Last Modified: | 09 Jul 2020 02:39 | ||||
URI: | https://tuprints.ulb.tu-darmstadt.de/id/eprint/8843 | ||||
PPN: | 452906504 | ||||
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