| 61. |
- del Rio, J. S., et al.
(författare)
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CEPA: A LaBr 3 (Ce)/LaCl 3 (Ce) phoswich array for simultaneous detection of protons and gamma radiation emitted in reactions at relativistic energies
- 2014
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 66
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Konferensbidrag (refereegranskat)abstract
- A prototype CEPA4, made of four optically isolated phoswich-crystals of LaBr3(Ce)+LaCl3(Ce) packed together in one can of Al, was tested with high energy protons (70-230 MeV) at the cyclotron of Krakow. Further, the response to different gamma radiation standard sources and cosmic muons was determined. Shape analysis of the pulses derived from the four individually coupled PM-tubes was performed and were used as input functions for Monte Carlo simulations in order to simulate the efficiencies and resolutions of a final detector design consisting of 750 such phoswich crystals arranged in a cylindrical disc. © Owned by the authors, published by EDP Sciences, 2014.
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| 62. |
- del Rio, J. S., et al.
(författare)
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CEPA: A LaBr3(Ce)/LaCl3(Ce) Phoswich array for simultaneous detection of protons and gamma radiation emitted in reactions at relativistic energies
- 2014
-
Ingår i: International Journal of Modern Physics: Conference Series. Applications of Nuclear Techniques (CRETE13). - 2010-1945. ; 27, s. 1460143-
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Konferensbidrag (refereegranskat)abstract
- A sophisticated design of 750 LaBr3(Ce):LaCl3(Ce) phoswich crystals (CEPA10) with a segmentation determined by the Doppler correction and an energy resolution of 5% at 1 MeV is presented. Monte Carlo simulations have been performed for high energy protons (50–500 MeV) and gamma radiation (0.5–30 MeV) to determine the length and shape of the crystals for optimum performance of the detector. In the case of protons, the two-layer detector can be used as a ΔELaBr3 − ETot telescope or, for very high energies, as a double energy loss detector (ΔELaBr3 + ΔELaCl3), in order to determine the initial energy. In addition, an experimental test with high energy protons (70–230 MeV) was performed at the cyclotron center in Krakow, Poland with a first prototype of 2 x 2 phoswich rectangular crystals (CEPA4) packed in an aluminum can (0.5 mm case). To simulate CEPA10 efficiencies and resolutions, optical pulses detected in CEPA4 by photomultiplier tubes with a DAQ system were used as energy input functions in Monte Carlo simulations.
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| 63. |
- Diaz Fernandez, Paloma, 1983, et al.
(författare)
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Quasifree (p, pN) scattering of light neutron-rich nuclei near N=14
- 2018
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 97:2
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Tidskriftsartikel (refereegranskat)abstract
- Background: For many years, quasifree scattering reactions in direct kinematics have been extensively used to study the structure of stable nuclei, demonstrating the potential of this approach. The (RB)-B-3 collaboration has performed a pilot experiment to study quasifree scattering reactions in inverse kinematics for a stable C-12 beam. The results from that experiment constitute the first quasifree scattering results in inverse and complete kinematics. This technique has lately been extended to exotic beams to investigate the evolution of shell structure, which has attracted much interest due to changes in shell structure if the number of protons or neutrons is varied. Purpose: In this work we investigate for the first time the quasifree scattering reactions (p, pn) and (p, 2p) simultaneously for the same projectile in inverse and complete kinematics for radioactive beams with the aim to study the evolution of single-particle properties from N = 14 to N = 15. Method: The structure of the projectiles O-23, O-22, and N-21 has been studied simultaneously via (p, pn) and (p, 2p) quasifree knockout reactions in complete inverse kinematics, allowing the investigation of proton and neutron structure at the same time. The experimental data were collected at the (RB)-B-3-LAND setup at GSI at beam energies of around 400 MeV/u. Two key observables have been studied to shed light on the structure of those nuclei: the inclusive cross sections and the corresponding momentum distributions. Conclusions: The knockout reactions (p, pn) and (p, 2p) with radioactive beams in inverse kinematics have provided important and complementary information for the study of shell evolution and structure. For the (p, pn) channels, indications of a change in the structure of these nuclei moving from N = 14 to N = 15 have been observed, i.e., from the 0d(5/2) shell to the 1s(1/2). This supports previous observations of a subshell closure at N = 14 for neutron-rich oxygen isotopes and its weakening for the nitrogen isotopes.
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| 64. |
- Eckardt, C., et al.
(författare)
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Development of an Active 238UF6 Gas Target
- 2012
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 31, s. 141-146
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Konferensbidrag (refereegranskat)abstract
- At the superconducting 130 MeV Darmstadt electron linac S-DALINAC a new source of spin-polarized electrons using a GaAs cathode has been installed, opening the path for experiments with polarized electron and photon beams for nuclear structure studies at low momentum transfers, e.g., the search for forward-backward asymmetries originating from parity non-conservation (PNC) in the photon-induced fission process of 238U.Detailed studies of different properties, e.g., the energy dependence of fission modes, the population of fission isomers, or the search for (PNC) effects in the photon-induced fission process of 238U, depends on high quality data, therefore needing high luminosities. An active gas target containing uranium may overcome the problem that large solid target thicknesses cause poor energy and angular resolution.A single Frisch-grid ionization chamber has been built to test a mixture of standard counting gases (e.g., argon) with depleted uraniumhexafiliguoride (238UF6) using a triple alpha source, evaluating signal quality and drift velocity. For mass fractions up to 2 percent of 238U in the counting gas. The drift velocity increases with rising UF6 content, while a good signal quality and energy resolution is preserved.
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| 65. |
- Fritioff, T., et al.
(författare)
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Purification of radioactive neutron-rich argon beams using an ion source in charge breeding mode
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 556:1, s. 31-37
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of nuclear properties of some neutron-rich asymmetric fission isotopes at an ISOL laboratory present a severe problem when a plasma ion source is used as the primary ion-source. The problem is associated with intense multi-charged symmetric fission contaminants that cannot be mass-separated from asymmetric fission products. In this work we demonstrate how this problem can be overcome on-line by using an electron cyclotron resonance ion source (ECRIS) as a charge-breeding secondary ion-source. Mixed Ar+/Kr2+/Xe3+ radioactive beams from an plasma ion-source were injected into the PHOENIX ECRIS that currently is installed at the ISOLDE facility at CERN in order to improve the ratio of Ar to the background contaminants of Kr and Xe. The signal to noise ratio was improved by more than two orders of magnitude after charge-breeding and mass-separation of the Ar8+, Ar9+ beams. The information on the decay of the Ar-48 nucleus obtained in these tests is useful for a better understanding of the origin of the Ca-48/Ca-46 meteorite isotopic anomaly. Potential applications of the method are discussed.
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| 66. |
- G., Aad, et al.
(författare)
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Electron and photon performance measurements with the ATLAS detector using the 2015-2017 LHC proton-proton collision data
- 2019
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Ingår i: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the reconstruction of electrons and photons with the ATLAS detector, employed for measurements and searches exploiting the complete LHC Run 2 dataset. An improved energy clustering algorithm is introduced, and its implications for the measurement and identification of prompt electrons and photons are discussed in detail. Corrections and calibrations that affect performance, including energy calibration, identification and isolation efficiencies, and the measurement of the charge of reconstructed electron candidates are determined using up to 81 fb-1 of proton-proton collision data collected at √s = 13 TeV between 2015 and 2017. © 2019 CERN for the benefit of the ATLAS collaboration. Published by IOP Publishing Ltd on behalf of Sissa Medialab.
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| 67. |
- Göök, A., et al.
(författare)
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Application of the ShockleyRamo theorem on the grid inefficiency of Frisch grid ionization chambers
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 664:1, s. 289-293
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Tidskriftsartikel (refereegranskat)abstract
- The concept of grid inefficiency in Frisch grid ionization chambers and its influence on the anode pulse shape is explained in terms of the ShockleyRamo theorem for induced charges. The grid inefficiency correction is deduced from numerically calculated weighting potentials. A method to determine the correction factor experimentally is also presented. Experimental and calculated values of the correction factor are shown to be in good agreement.
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| 68. |
- Göök, A., et al.
(författare)
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Particle emission angle determination in Frisch grid ionization chambers by electron drift-time measurements
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 621:1-3, s. 401-405
-
Tidskriftsartikel (refereegranskat)abstract
- The double kinetic energy measurement of fission fragments with a double-sided Frisch grid ionization chamber allows a careful determination of the emission angle, which is essential in order to apply appropriate energy-loss corrections. We present a drift-time method, which uses the time that free electrons need to drift from the location of their creation, e.g. by a fission fragment in the counting gas, to the grid, before inducing a signal on the anode. Such a measurement leaves energy and angular information fully decoupled. We demonstrate the applicability of the drift-time method for the example of the 234,238U (γ,f) reactions performed at the superconducting Darmstadt electron linear accelerator. The angular resolutions achieved with this method are comparable to those obtained with other methods.
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| 69. |
- Korten, W., et al.
(författare)
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Physics opportunities with the Advanced Gamma Tracking Array : AGATA
- 2020
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 56:5
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Forskningsöversikt (refereegranskat)abstract
- New physics opportunities are opening up by the Advanced Gamma Tracking Array, AGATA, as it evolves to the full 4 pi instrument. AGATA is a high-resolution gamma -ray spectrometer, solely built from highly segmented high-purity Ge detectors, capable of measuring gamma rays from a few tens of keV to beyond 10 MeV, with unprecedented efficiency, excellent position resolution for individual gamma -ray interactions, and very high count-rate capability. As a travelling detector AGATA will be employed at all major current and near-future European research facilities delivering stable and radioactive ion beams.
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| 70. |
- Larsson, Irina, 1975
(författare)
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Helium measuring system for on-line fuel and control rod integrity surveillance in BWRs
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Accurate supervision of fuel and control rod integrity in a nuclear reactor core is very important for maintaining a safe and reliable operation of the reactor. Fuel rod failures can cause increased doses to personnel in the power plant, increased backend costs, limitations of the reactor operation and unplanned shut downs, which can lead to large economic losses. Control rod failures are normally not as severe as fuel rod failures, but can lower the reactor efficiency, cause operational restrictions and increase a need for control rod inspections during outage. Additional inspections can cause a prolonged outage, leading to economic losses.A project with the main objective to improve the detection of fuel and control rod failures in boiling water reactors (BWRs) by implementing continuous helium measurements in the off-gas system was initiated in 2007. The work was performed in collaboration between Chalmers University of Technology in Sweden, Forsmarks Kraftgrupp AB in Sweden and Kernkraftwerk Leibstadt (KKL) in Switzerland. During the project, helium detector systems have been installed in the reactor’s off-gas systems at both of the nuclear power plants (NPPs). The helium measuring system is a part of a combined on-line system which also includes nuclide specific measurements of gamma emitting noble gases. This combined system provides continuous information of both the fuel and control rod integrity. The work described in this thesis can be divided into two parts. One part includes evaluation of helium measurements for detection of control rod failures at KKL, which was the main purpose for the installation of the system at KKL in 2008. The helium measuring system at KKL has shown to be able to identify and follow control rod failures on-line. Since 2012 the helium measurement system is part of the process control and is included in the KKL core supervision system, which monitors the thermal operational parameter of the reactor core and all the relevant chemical parameters of the reactor water. The second part of the work was to investigate the ability of the helium measuring system to detect the small amount of helium that is expected to leak out in case of a fuel failure. This was also the main objective for the installation of the system at Forsmark 3 (F3) in 2010. Some helium releases from fuel failures at Forsmark 3 have been detected with the current system, however, further measurements might be needed to optimize the technique. Several factors, including operational parameters, which are influencing the helium measurements, have been identified and implemented in the developed equation for calculation of the helium background level in the off-gases. When being programmed in the core supervision system, such an automatic calculation of the helium background level, will give an immediate estimation of the released amount of helium if the helium concentration increase relative to the background level was detected.
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