| 1. |
- Böhm, Sebastian, et al.
(författare)
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First results from the Stockholm Electron Beam Ion Trap
- 2007
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 58:303, s. 303-306
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Tidskriftsartikel (refereegranskat)abstract
- A new laboratory for highly charged ions is being built up at Stockholm university. An electron beam ion trap (EBIT) (3T magnet,≤30 keV electron beam) was installed. It is used for spectroscopic studies, precision mass measurements, electron ion collisions, and highlycharged ion surface studies. Here we report about a fast ion-extraction scheme from ebit and first results using a time-of-flight detection as well as a labview based operational system of ebit.
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| 2. |
- Khaplanov, Anton, et al.
(författare)
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A gamma-ray polarimeter based on a single segmented planar HPGe detector
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 593:3, s. 459-465
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Tidskriftsartikel (refereegranskat)abstract
- The polarization sensitivity of a segmented planar HPGe detector has been measured. For this purpose 662 keV photons from a Cs-137 source which were Compton scattered at approximate to 90 degrees in a coaxial germanium detector were utilized as a source of partially linearly polarized gamma radiation of the energy; approximate to 288 keV. The detector has a 50 x 50 x 21 mm sensitive volume and 5 x 5 electrical segmentation of the cathode contact. The degree of linear polarization is determined through the analysis of the directions of Compton scatterings inside the detector. The locations of the Compton scattering interactions and of the subsequent photo-absorption interactions have been determined with the help of pulse shape analysis (PSA), provided that these interactions are in two different segments of the planar detector. A comparison with a polarization analysis using the position resolution defined by the physical segmentation (without the use of PSA) was also performed. It is demonstrated that the use of PSA enables a much higher polarization sensitivity for events where the 288 keV photons scatter between adjacent pixels. Such events constitute 90% of the data for the 288 keV photons and are even more important for gamma-rays of lower energies.
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| 3. |
- Khaplanov, Anton, et al.
(författare)
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Position sensitivity of segmented planar HPGe detectors for the DESPEC project at FAIR
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 592, s. 325-333
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Tidskriftsartikel (refereegranskat)abstract
- One of the proposed germanium detector systems for the upcoming DESPEC array at the FAIR facility consists of triple modules of electrically segmented planar high-purity germanium detectors. In this work, the position sensitivity obtained by means of pulse shape analysis (PSA) for simulated gamma-ray interactions has been studied for the possible segmentation patterns for such detectors-the double-sided strip detector (DSSD) and the one-sided pixelated geometry. An over-all similar number of readout channels has been considered for each case, resulting in 8 + 8 strips and 16 pixels. It has been found that the higher physical granularity of the DSSD results in a significantly higher position resolution, as well as in a somewhat lower probability of merging multiple interaction points. A drawback of the DSSD geometry is the inability to assign the interactions to the correct voxels for certain complex multiple interaction patterns. This effect has been studied in detail. Finally, a comparison has been made with the existing 25-pixel planar detector at KTH [A. Khaplanov, et al., Nucl. Instr. and Meth. A 580 (2007) 1075; L. Milechina, B. Cederwall, Nucl. Instr. and Meth. A 550 (2005) 278)].
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| 4. |
- Khaplanov, Anton, et al.
(författare)
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Position sensitivity of the proposed segmented germanium detectors for the DESPEC project
- 2009
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 604:1/2, s. 56-59
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Tidskriftsartikel (refereegranskat)abstract
- The DESPEC HPGe array is a part of the NuSTAR project at FAIR, Germany. It is aimed at the spectroscopy of the stopped decaying exotic nuclei. Segmented gamma-ray tracking detectors are proposed for this array in order to maximize detection efficiency and background suppression when searching for very rare events. Two types of detector modules-stacks of three 16-fold segmented planar crystals and 12- and 16-fold segmented clover detectors-have been investigated and compared from the point of view of the achievable position resolution using pulse shape analysis (PSA). To this end, detector signals from realistic gamma-ray interactions have been calculated. These signals were treated by PSA in order to reconstruct the photon interaction locations. Comparing the initial interaction locations to the reconstructed ones, it was found that the double-sided strip planar detector yielded position reconstruction errors at least a factor 2 lower than the other detectors considered
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| 5. |
- Kojouharov, I., et al.
(författare)
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The GSI HPGe detector scanner - A sophisticated device based on PET technique
- 2007
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Ingår i: 2007 IEEE Nuclear Science Symposium Conference Record. - : IEEE. - 1424409233 - 9781424409235 ; , s. 2213-2215
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Konferensbidrag (refereegranskat)abstract
- A new 3D HPGe detector scanner based on PET technique has been proposed and implemented. The scanning technology utilizes a 2D position sensitive detector array made of fibre scintillation detectors ordered in cone geometry and read out by position sensitive photomultipliers. This allows simultaneous scanning of numerous coordinate points. The third coordinate of the interaction point in the germanium volume to be scanned is obtained by measuring y-rays Compton scattered by 90° using collimated scintillation detectors. The first results of the proposed scanning technology clearly demonstrate the feasibility to obtain high quality data from a germanium detector within a reasonable time employing a moderate 1 MBq activity y source.
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| 6. |
- Maiorova, A. V., et al.
(författare)
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Polarization studies on the two-step radiative recombination of highly charged, heavy ions
- 2009
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 42:12
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Tidskriftsartikel (refereegranskat)abstract
- Radiative recombination of a free electron into an excited state of a bare, high-Z ion is studied, together with its subsequent decay, within the framework of the density matrix theory and Dirac's relativistic equation. Special attention is paid to the polarization and angular correlations between the recombination and the decay photons. In order to perform a systematic analysis of these correlations the general expression for the double-differential recombination cross section is obtained by making use of the resonance approximation. Based on this expression, detailed computations for the linear polarization of x-ray photons emitted in the (e, 2 gamma) two-step recombination of uranium ions U92+ are carried out for a wide range of projectile energies.
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| 7. |
- Orban, Istvan, 1980-, et al.
(författare)
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Charge-state Selected Detection of Photons from Electron-Ion Interactions in an EBIT
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114.
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Tidskriftsartikel (refereegranskat)abstract
- A new approach provides charge-state selective recombination rate coefficients from TOF spectraof highly charged ions extracted from an EBIT. Experimentally derived dielectronic recombinationspectra are compared with results of relativistic many body perturbation theory calculations. Electronimpact excitation rate coefficients are also obtained from the experiment through the separationof the DR contribution in the X-ray spectra. The combination of TOF and X-ray measurementsoffers a powerful tool for the simultaneous extraction of atomic quantities for several charge states.
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| 8. |
- Tashenov, Stanislav, et al.
(författare)
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Gamma-ray tracking and background suppression in the planned germanium array of DESPEC : A comparative analysis
- 2009
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 604:1-2, s. 64-66
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Tidskriftsartikel (refereegranskat)abstract
- A new high efficiency gamma-ray spectrometer is being designed for the DESPEC project at FAIR. It should accomplish all types of decay studies with implanted radioactive ion beams. The gamma-ray tracking and imaging capabilities of the array will be its essential property allowing low background detection of the rare decay events. For this purpose two types of germanium detectors are considered, i.e. segmented planar and coaxial detectors. Several final array configurations based on these detectors, differently segmented, are evaluated and compared in this paper.
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| 9. |
- Tashenov, Stanislav, et al.
(författare)
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Hard X-ray polarimetry by means of Rayleigh scattering
- 2009
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 600:3, s. 599-603
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Tidskriftsartikel (refereegranskat)abstract
- A new linear polarimetry technique based on Rayleigh scattering is introduced. Its properties are compared to the Compton technique. Experimental verification was realized using a 5 x 5 segmented planar HPGe pixel detector. In the proof-of-principle experiment a measurement of Rayleigh scattering off lead atoms was performed for linearly polarized; approximate to 53.3 keV photons at two scattering angles.
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