| 1. |
- Bevilacqua, Riccardo, et al.
(författare)
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A procedure for the characterization of electron transmission through Frisch grids
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 770, s. 64-67
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Tidskriftsartikel (refereegranskat)abstract
- In Frisch grid ionization chambers special attention must be paid to the operating voltages in order to avoid unwanted collection of electrons on the Frisch grid. Collection of electrons on the grid will lead to a decreased signal to noise ratio and consequently a deteriorated energy resolution. Furthermore, systematic errors in the determination of the angular distribution will be introduced. Theoretical formulas for minimized collection of electrons on the grid were derived by Bunemann et al. [3] in the special case of a Frisch grid consisting of a plane of parallel wires. No such formulas exist for other grid geometries and a careful calibration procedure is needed. We describe here a procedure for characterizing the Frisch grid in terms of its transparency to electrons for a grid consisting of a mesh of crossed wires.
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| 2. |
- Göök, Alf, et al.
(författare)
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A position-sensitive twin ionization chamber for fission fragment and prompt neutron correlation experiments
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier B.V.. - 0168-9002 .- 1872-9576. ; 830, s. 366-374
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Tidskriftsartikel (refereegranskat)abstract
- A twin position-sensitive Frisch grid ionization chamber, intended as a fission fragment detector in experiments to study prompt fission neutron correlations with fission fragment properties, is presented. Fission fragment mass and energies are determined by means of the double kinetic energy technique, based on conservation of mass and linear momentum. The position sensitivity is achieved by replacing each anode plate in the standard twin ionization chamber by a wire plane and a strip anode, both readout by means of resistive charge division. This provides information about the fission axis orientation, which is necessary to reconstruct the neutron emission process in the fully accelerated fragment rest-frame. The energy resolution compared to the standard twin ionization chamber is found not to be affected by the modification. The angular resolution of the detector relative to an arbitrarily oriented axis is better than 7° FWHM. Results on prompt fission neutron angular distributions in 235U(n,f) obtained with the detector in combination with an array of neutron scintillation detectors is presented as a proof of principle.
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| 3. |
- 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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| 4. |
- Oberstedt, Andreas, 1960-, et al.
(författare)
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Identification of prompt fission gamma-rays with lanthanum-chloride scintillation detectors
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 668, s. 14-20
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we demonstrate the employment of LaCl3 : Ce scintillation detectors for the identification of prompt fission gamma-rays from gamma-radiation in contrast to other reactions. We present the properties of cylindrical 1.5 in. x 1.5 in. detectors in terms of intrinsic activity, energy resolution, intrinsic full peak efficiency and intrinsic timing resolution. In addition, we show results from the measurement of gamma-rays emitted in coincidence with the spontaneous fission of Cf-252, which lead us to the conclusion that the properties of the detectors used in this work, in particular the good timing resolution and a reasonably good energy resolution, are more than just sufficient for the assessment of prompt gamma-heat in future nuclear reactors as requested by the OECD. Hence, in our opinion, LaCl3 : Ce detectors, compared to those made out of LaBr3 : Ce crystals, represent an appropriate and quasi low-cost choice for the above mentioned applications.
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| 5. |
- Oberstedt, S., et al.
(författare)
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Artificial diamonds as radiation-hard detectors for ultra-fast fission-fragment timing
- 2013
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 714, s. 31-37
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Tidskriftsartikel (refereegranskat)abstract
- In the framework of the construction of the double time-of-flight spectrometer VERDI, where we aim at measuring pre- and post-neutron masses directly and simultaneously, ultra-fast time pick-up detectors based on artificial diamond material were investigated for the first time with fission fragments from Cf-252 (0.5 MeV/u < E/A < 2 MeV/u). Signal stability under a high radiation fluence was determined up to at least 10(9) fission-fragments/cm(2) together with more than 3.5 x 10(9) neutrons/cm(2) and 3 x 10(10) alpha-particles/cm(2). This fluence is characteristic for fission experiments. The pre-requisite for the observed signal stability is the application of priming of the diamond material with a strong beta-source for about 48 h. The intrinsic timing resolution of a 100 mu m thick polycrystalline CVD diamond detector with a size of 1 x 1 cm(2) was determined to sigma(int) = (283 +/- 41) ps by comparison with Monte-Carlo simulations. Using broadband pre-amplifiers, 4-fold segmented detectors of same total size and with a thickness of 180 mu m show an intrinsic timing resolution of sigma(int) = (106 +/- 21) ps. This is highly competitive with the best micro-channel plate detectors. Due to the limited and batch-dependent charge collection efficiency of poly-crystalline diamond material, the detection efficiency for fission fragments may be smaller than 100%.
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| 6. |
- Peck, M., et al.
(författare)
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Pulse-height defect of Ar+CF4 mixtures as a counting gas for fission-fragment detectors
- 2019
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier B.V.. - 0168-9002 .- 1872-9576. ; 919, s. 105-112
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Tidskriftsartikel (refereegranskat)abstract
- For the detection of energetic charged particles, gaseous ionization detectors use a variety of counting gases. We studied the properties of non-flammable, high stopping-power Ar+CF4 as counting gas. We assess the usability of different mixtures for compact, high-luminosity fast ionization chambers for future applications in nuclear photonics. The pulse-height defect (PHD) of Ar+CF4 mixtures at different pressures has been extracted in comparison to P-10 gas (90%Ar+10%CH4) for fragments from 252Cf spontaneous fission in a twin Frisch-grid ionization chamber. For the different mixtures of Ar+CF4 (P-10), a PHD of 4.5–11MeV (4MeV) and 6–12MeV (5.5MeV) for light and heavy fragments, respectively, have been measured. Based on these findings, reconstructed 252Cf mass and total kinetic energy distributions are consistent with literature, which demonstrates success in the PHD correction procedure.
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| 7. |
- Oberstedt, Andreas, 1961, et al.
(författare)
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Identification of prompt fission γ-rays with lanthanum-chloride scintillation detectors
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 668:0, s. 14--20-20
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we demonstrate the employment of LaCl3:Ce scintillation detectors for the identification of prompt fission γ-rays from γ-radiation in contrast to other reactions. We present the properties of cylindrical 1.5 in.×1.5 in. detectors in terms of intrinsic activity, energy resolution, intrinsic full peak efficiency and intrinsic timing resolution. In addition, we show results from the measurement of γ-rays emitted in coincidence with the spontaneous fission of 252Cf, which lead us to the conclusion that the properties of the detectors used in this work, in particular the good timing resolution and a reasonably good energy resolution, are more than just sufficient for the assessment of prompt γ-heat in future nuclear reactors as requested by the OECD. Hence, in our opinion, LaCl3:Ce detectors, compared to those made out of LaBr3:Ce crystals, represent an appropriate and quasi low-cost choice for the above mentioned applications.
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