| 1. |
- Billnert, Robert, 1981, et al.
(författare)
-
New information on the characteristics of 1 in. x 1 in. cerium bromide scintillation detectors
- 2011
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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 .- 1872-9576. ; 647:1, s. 94-99
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Tidskriftsartikel (refereegranskat)abstract
- In view of highly demanded new and accurate data on prompt gamma-ray emission in nuclear fission a major part of investigations is directed towards the selection of suitable detector systems. Here we have studied a new type of crystal scintillation detectors made from cerium bromide (CeBr(3)). For the first time a full characterization of such a detector is presented in terms of energy resolution, pulse-height linearity, intrinsic activity and intrinsic timing resolution. In particular the latter one is very important for prompt fission gamma-ray studies, because the presence of fast neutrons, emitted in fission too, requires the time-of-flight method for their discrimination. The energy resolution has been found to be comparable to that of cerium-doped LaCl(3):Ce detectors at an efficiency comparable to the one of a LaBr(3):Ce detector of the same size. The intrinsic activity of the CeBr(3) crystal was observed to be much lower compared to lanthanum halide crystals. The intrinsic timing resolution of a coaxial 1 in. x 1 in. sized detector was measured relative to that of a previously characterized LaCl(3):Ce detector and found to be (326 +/- 7) Ps at (60)Co energies, which is in between those of a LaBr(3):Ce and a LaCl(3):Ce detector of same size.
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| 2. |
- Billnert, Robert, 1981, et al.
(författare)
-
New prompt spectral gamma-ray data from the reaction Cf-252(sf) and its implication on present evaluated nuclear data files
- 2013
-
Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 87:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present results from new spectral prompt gamma-ray measurements from the spontaneous fission of Cf-252. Apart from one recent experiment, about four decades have passed since the last dedicated experiments were reported in the literature. Hence, there was a need for a revision. We have measured prompt fission. rays with both cerium-doped LaBr3 and CeBr3 scintillation detectors, both of which exhibit excellent timing and good energy resolution. The emission yield was determined to be nu(gamma) = (8.30 +/- 0.08)/fission and nu(gamma) = (8.31 +/- 0.10)/fission, with the average energy of is an element of(gamma) = (0.80 +/- 0.01) MeV and is an element of(gamma) = (0.80 +/- 0.01) MeV and total energy of E-gamma,E-tot = (6.64 +/- 0.08) MeV and E-gamma,E-tot = (6.65 +/- 0.12) MeV, with the LaBr3 and CeBr3 detectors, respectively. Since the results from the two detectors are in excellent agreement and confirm the historical data, but not those in the present evaluated nuclear data files, we strongly recommend an update.
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| 3. |
- Billnert, Robert, 1981, et al.
(författare)
-
Novel Scintillation Detectors for Prompt Fission γ-Ray Measurements
- 2012
-
Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 31, s. 29-34
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Konferensbidrag (refereegranskat)abstract
- In this work we present first results from measurements of prompt fission γ-rays from the spontaneous fission in 252Cf. New and accurate data on corresponding γ-rays from the reactions 235U(nth,f) and 239Pu(nth,f) are highly demanded for the modeling of new Generation-IV nuclear reactor systems. For these experiments we employed scintillation detectors made out of new materials (LaBr3, LaCl3 and CeBr3), whose properties were necessary to know in order to obtain reliable results. Hence, we have characterized these detectors. In all the important properties these detectors outshine sodium-iodine detectors that where used in the 1970s, when the existing data had been acquired. Our finding is that the new generation of scintillation detectors is indeed promising, as far as an improved precision of the demanded data is concerned.
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| 4. |
- Billnert, R., et al.
(författare)
-
Prompt γ-ray spectral data from 252Cf(SF), 235U(nth, f) and 241Pu(nth,f)
- 2014
-
Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 59:C, s. 17-23
-
Konferensbidrag (refereegranskat)abstract
- In this paper we talk about our work in developing a method to measure and analyze prompt fission γ-rays, as well as our results from the measurement of three different reactions, namely 252Cf(SF), 235U(nth,f) and 241Pu(nth,f). The first two had, at the beginning of our measurements, not been examined since the early 1970s, and the last reaction had never been measured. Our results show a slight improvement over evaluated data-tables in comparison with benchmark experiments, but can still not explain all of the underestimation witnessed. Our results also show that new evaluations is needed, especially for 252Cf(SF) and 241Pu(nth,f).
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| 5. |
- Dragić, A.L., et al.
(författare)
-
Shape-isomer studies with resonance neutron capture
- 2014
-
Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 59:C, s. 125-131
-
Konferensbidrag (refereegranskat)abstract
- An experiment searching for formation of super-deformed shape isomers in odd uranium isotopes following neutron capture is designed at the GELINA neutron source of IRMM. We focus on neutron energies around the so-called intermediate structure in the fission cross-section, where the coupling between compound states above the first and the second minimum is largest. The experimental arrangement is described. The results of a feasibility study on the population of the shape isomer in 235U, using a 234U target, together with the results from first run with a 238U target are presented.
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| 6. |
- Eckardt, C., et al.
(författare)
-
Development of an Active 238UF6 Gas Target
- 2012
-
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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| 7. |
- Enders, J., et al.
(författare)
-
Reactions with polarized electrons and photons at low momentum transfers at the superconducting Darmstadt electron linear accelerator S-DALINAC
- 2011
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 295:1, s. Art. no. 012152-
-
Konferensbidrag (refereegranskat)abstract
- A source of polarized electrons has been installed at the superconducting Darmstadt electron linear accelerator S-DALINAC. Experiments with polarized electrons from 100 keV to about 80 MeV are expected to commence in early 2011. This contribution summarizes the status of the polarized source as well as ongoing preparations for the experimental program with polarized beams. In particular, we present results on unpolarized test experiments of the, 234,238U(γ,f) reactions and considerations for the 2D(e→,e′p) and reactions.
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| 8. |
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| 9. |
- Göök, A., et al.
(författare)
-
Application of the ShockleyRamo theorem on the grid inefficiency of Frisch grid ionization chambers
- 2012
-
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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| 10. |
- Göök, A., et al.
(författare)
-
Fragment characteristics from fission of U-238 and U-234 induced by 6.5-9.0 MeV bremsstrahlung
- 2011
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 851:1, s. 1-16
-
Tidskriftsartikel (refereegranskat)abstract
- Fission of U-238 and U-234 induced by bremsstrahlung of 6.5-9.0 MeV endpoint energy has been investigated at the superconducting Darmstadt electron linear accelerator S-DALINAC. Using a twin Frisch grid ionization chamber, fission-fragment energy and mass distributions have been determined by means of the double kinetic-energy technique. Results on the fission-fragment characteristics from U-238(gamma, f) are in agreement with results from the literature. In addition fission-fragment mass and energy distributions from U-234(gamma, f) are presented for the first time in this energy region. An analysis of fission modes within the Brosa model has been performed. The relative yield of the S 1 mode was found to be (13 +/- 3)% in U-234 and (35 +/- 2)% in U-238.
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| 11. |
- Göök, A., et al.
(författare)
-
Particle emission angle determination in Frisch grid ionization chambers by electron drift-time measurements
- 2010
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 621:1-3, s. 401-405
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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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| 12. |
- Hambsch, F. -J, et al.
(författare)
-
Fission Fragment Yield, Cross Section and Prompt Neutron and Gamma Emission Data from Actinide Isotopes
- 2014
-
Ingår i: Nuclear Data Sheets. - : Elsevier BV. - 0090-3752 .- 1095-9904. ; 119, s. E38-E41
-
Tidskriftsartikel (refereegranskat)abstract
- Recent experimental investigations on major and minor actinides at the JRC-IRMM are presented. Fission-fragment distributions of isotopes with vibrational resonances in the sub-threshold fission cross section, i. e. U-234,U-238, have been measured. For U-234, the impact of an increased neutron multiplicity for the heavy fragments with higher incident neutron energies has been studied as observed in experiment and also recently theoretically predicted. The impact is found to be noticeable on post-neutron mass yields, which are the relevant quantities for a-priori waste assessments. The fission cross sections for Pu-240,Pu-242 at threshold and in the plateau region are being investigated within the ANDES project. The results show some discrepancies to the ENDF/B-VII. 1 evaluation mainly for Pu-242 around 1 MeV, where the evaluation exhibits a resonance-like structure not observed so clearly in the present work. The requested target accuracy in design studies of innovative reactor concepts like Gen-IV is in the range of a few percent. In order to be able to respond to requests for measurements of prompt neutron and gamma-ray emission in fission JRC-IRMM has also invested in setting up a neutron and gamma-ray detector array. The neutron array is called SCINTIA and has so far been tested with Cf-252(SF). For gamma-ray multiplicity and spectrum measurements of Cf-252(SF) and U-235(n(th), f) lanthanum- and cerium-halide detectors were successfully used.
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| 13. |
- Hambsch, F. -J, et al.
(författare)
-
Investigation of the Fission Process at IRMM
- 2011
-
Ingår i: Journal of the Korean Physical Society. - : Korean Physical Society. - 0374-4884 .- 1976-8524. ; 59:2, s. 1654-1659
-
Tidskriftsartikel (refereegranskat)abstract
- The investigation of the fission process is and has been a major undertaking at IRMM. The most recent investigations concerned the reaction (234)U(n,f) and (238)U(n,f) around vibrational resonances at the barrier of the fission cross-section. Furthermore prompt neutron emission of (252)Cf(SF) has been investigated understanding for the first time the prompt neutron multiplicity as a function of total kinetic energy (TKE). Theoretical modelling of reaction cross sections as well as prompt neutron multiplicity and spectra has been performed using the experimental data as input parameters. Also instrument developments for correlation measurements of fission fragment properties has been pursued in recent years with the time-of-flight spectrometer VERDI and detectors for prompt fission gamma-ray.
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| 14. |
- Ledoux, X., et al.
(författare)
-
The Neutrons for Science Facility at SPIRAL-2
- 2014
-
Ingår i: Nuclear Data Sheets. - : Elsevier BV. - 0090-3752 .- 1095-9904. ; 119, s. 353-356
-
Tidskriftsartikel (refereegranskat)abstract
- The Neutrons For Science (NFS) facility is a component of SPIRAL-2 laboratory under construction at Caen (France). SPIRAL-2 is dedicated to the production of high intensity Radioactive Ions Beams (RIB). It is based on a high-power linear accelerator (LINAG) to accelerate deuterons beams in order to produce neutrons by breakup reactions on a C converter. These neutrons will induce fission in U-238 for production of radioactive isotopes. Additionally to the RIB production, the proton and deuteron beams delivered by the accelerator will be used in the NFS facility. NFS is composed of a pulsed neutron beam and irradiation stations for cross-section measurements and material studies. The beams delivered by the LINAG will allow producing intense neutron beams in the 100 keV-40 MeV energy range with either a continuous or quasi-mono-energetic spectrum. At NFS available average fluxes will be up to 2 orders of magnitude higher than those of other existing time-of-flight facilities in the 1 MeV - 40 MeV range. NFS will be a very powerful tool for fundamental physics and application related research in support of the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors. The facility and its characteristics are described, and several examples of the first potential experiments are presented.
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| 15. |
- Lutter, G., et al.
(författare)
-
Radiopurity of a CeBr3 crystal used as scintillation detector
- 2013
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 703, s. 158-162
-
Tidskriftsartikel (refereegranskat)abstract
- Cerium bromide (CeBr3) has recently been shown to exhibit several properties making it a suitable material as a scintillation detector in nuclear physics applications. The intrinsic activity of gamma-ray emitting radionuclides in a 38.1 mm x 38.1 mm (diameter x height) crystal of CeBr3 was investigated. The measurements were carried out in the HADES underground laboratory located 225 m underground. Two primordial radionuclides were detected; Ac-227 (and its daughters) with massic activity of 0.30 +/- 0.02 Bq/kg and La-138 with massic activity of 7.4 +/- 1.0 mBq/kg. Two activation products were also detected; Ce-139 and Br-82. Their massic activities (assuming a homogeneous distribution in the crystal) just before taking the CeBr3 crystal underground were 4.3 +/- 0.3 mBq/kg and 18 +/- 4 mBq/kg correspondingly. None of the other common primordial radionuclides (K-49, Ra-226, Ra-228, Th-228, and U-235) were detected and their detection limits were below 2 mBq/kg except for U-238 for which the upper limit was 135 mBq/kg and Pb-210 with an upper limit of 600 mBq/kg.
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| 16. |
- Oberstedt, Andreas, 1961, et al.
(författare)
-
Gamma-ray Measurements with LaBr3: Ce Detectors – thinking Outside the Box
- 2012
-
Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 31, s. 21-28
-
Konferensbidrag (refereegranskat)abstract
- Recently developed cerium-doped lanthanum bromide (LaBr3: Ce) scintillation detectors have shown to possess promising properties with respect to the detection of γ-rays compared to previously known materials. In this work however, we demonstrate how these detectors may be used to obtain information not only about γ-rays, but also about neutrons, i.e. thinking "inside" and "outside" the box, respectively. For this purpose γ-rays were detected in coincidence with fission fragments and both their energy and their time-of-flight relative to the instant of a fission event is recorded. By evaluating the time-of-flight distributions of γ-rays, identified as decays of excited states after population by inelastically scattered neutrons inside the scintillation crystal as well as other surrounding materials, we show that it is possible to acquire knowledge from and about the spectrum of incident neutrons. We give three examples for conceivable applications, used to determine geometrical profiles, cross sections and neutron spectra, respectively.
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| 17. |
- Oberstedt, Andreas, 1960-, et al.
(författare)
-
Identification of prompt fission gamma-rays with lanthanum-chloride scintillation detectors
- 2012
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 668, s. 14-20
-
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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| 18. |
- Oberstedt, Andreas, 1961, et al.
(författare)
-
Identification of prompt fission γ-rays with lanthanum-chloride scintillation detectors
- 2012
-
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
-
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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| 19. |
- Oberstedt, Andreas, et al.
(författare)
-
Improved values for the characteristics of prompt-fission gamma-ray spectra from the reaction U-235(n(th), f)
- 2013
-
Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X .- 2469-9985 .- 2469-9993. ; 87:5, s. 051602-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present results from measurements of prompt gamma rays from the thermal neutron induced fission of U-235. Photons were measured in coincidence with fission fragments with cerium-doped LaCl3 and LaBr3 as well as CeBr3 scintillation detectors, which offer an intriguing combination of excellent timing resolution and good resolving power. The spectra measured with all employed detectors are in excellent agreement with respect to their shapes. Characteristic parameters were extracted for a gamma-energy range from 0.1 to 6.0 MeV and the results obtained with several detectors were averaged. From that, the average emission yield of prompt-fission gamma rays was determined to be (nu) over bar (gamma) = (8.19 +/- 0.11) per fission, the average energy per photon to be epsilon(gamma) = (0.85 +/- 0.02) MeV, and the total energy to be E-gamma,E-tot = (6.92 +/- 0.09) MeV. The uncertainties are much lower than the 7.5% requested for the modeling of advanced nuclear reactor cores. Estimating the influence of gamma rays with energies between 6 and 10 MeV on the values determined in this work revealed a negligible deviation of the order of the found uncertainties.
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| 20. |
- Oberstedt, Andreas, et al.
(författare)
-
Neutron measurements with lanthanum-bromide scintillation detectors : a first approach
- 2013
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 708, s. 7-14
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we report on the measurement of gamma-rays using a 2 in. x 2 in. LaBr3:Ce scintillation detector. The gamma-rays were emitted in the spontaneous fission of Cf-252 and detected in coincidence with fission fragments. After presenting some of the properties of the detector, we show how well gamma-rays produced in different reactions may easily be distinguished by their characteristic time-of-flight. Then we focus on the analysis of gamma-rays from inelastically scattered neutrons in the scintillation crystal and demonstrate how this information may be used for neutron spectroscopy. We determine the neutron detection efficiency and compare it to the result of calculations based on existing reaction cross-sections. Finally, we discuss the detection performance in relation to other detector systems commonly used for neutron monitoring.
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| 21. |
- Oberstedt, Andreas, 1960-, et al.
(författare)
-
New prompt fission gamma-ray spectral data and its implication on present evaluated nuclear data files
- 2013
-
Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3892 .- 1875-3884. ; 47, s. 156-165
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we report on new spectral prompt gamma-ray measurements from the spontaneous fission of Cf-252 and thermal neutron-induced fission of U-236*. In both experiments, fission of U-236*. In both experiments, gamma-ray multiplicities, average and total gamma-energies were extracted. gamma-ray multiplicities, average and total.-energies were extracted. Apart from one recent measurement on Cf-252, about four decades have passed since the last dedicated experiments were reported in literature. Hence, there was a need for a revision, not only with respect to high priority nuclear data requests by the Nuclear Energy Agency (NEA). In the first mentioned experiment we have measured prompt fission gamma-rays with both cerium-doped LaBr3 and CeBr3 scintillation detectors, which both exhibit excellent timing and good energy resolution. The results from both detectors are in excellent agreement with each other and confirm the historical data. In the experiment on U-235(n(th), f) we employed cerium-doped LaCl3 detectors, together with the lanthanum bromide detectors mentioned above. Even here the first results indicate a good agreement with data from the early 1970' s. They are also in accordance with data in evaluated libraries like ENDF/B-VII.0, while this is not the case for Cf-252(SF). Hence, here an update is strongly recommended.
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| 22. |
- Oberstedt, Andreas, 1961, et al.
(författare)
-
Systematics of prompt fission γ-ray spectra characteristics
- 2014
-
Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 59:C, s. 24-30
-
Konferensbidrag (refereegranskat)abstract
- Systematics from 2001, describing prompt fission γ-ray spectra (PFGS) characteristics as function of mass and atomic number of the fissioning system, has been revisited and parameters have been revised, based on recent experimental results. Although originally expressed for spontaneous and thermal neutron induced fission, validity for fast neutrons was assumed and applied to predict PFGS characteristics for the reaction n + 238U up to incident neutron energies of En = 20 MeV. The results from this work are compared with preliminary experimental results.
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| 23. |
- Oberstedt, S., et al.
(författare)
-
Artificial diamonds as radiation-hard detectors for ultra-fast fission-fragment timing
- 2013
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 714, s. 31-37
-
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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| 24. |
- Oberstedt, S., et al.
(författare)
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First results on the neutron-induced fission cross-section of Pa-231 for incident neutron energies E-n > 17 MeV
- 2012
-
Ingår i: Annals of Nuclear Energy. - : Elsevier. - 0306-4549 .- 1873-2100. ; 43, s. 26-30
-
Tidskriftsartikel (refereegranskat)abstract
- First results on the neutron-induced fission cross-section of Pa-231 for incident neutron energies E-n > 17 MeV are presented. The experiments were carried out with quasi mono-energetic neutrons produced in the reaction T(d, n)He-4. Corrections for low-energy neutron background produced in this reaction at incident deuteron energies E-d > 2 MeV are taken into account and based on experimental data obtained by two different techniques. Despite the relatively large error bars at the higher neutron energies, the new cross-section values meet the accuracy requirements set by the IAEA and will allow to remove the hitherto existing large spread between different previously published data. Recent cross-section calculations describe well the new experimental results, which are in consistency with cross-section values obtained in a particle-transfer reaction at excitation energies corresponding to neutron energies E-n < 10 MeV.
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| 25. |
- Oberstedt, S., et al.
(författare)
-
High-precision prompt-gamma-ray spectral data from the reaction Pu-241(n(th), f)
- 2014
-
Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 90:2, s. Art. no. 024618-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present results from the first high-precision prompt-gamma-ray spectral measurements from the reaction Pu-241(n(th), f). Apart from one recent experiment, no data are reported in the literature for this fissioning system, which motivated a new dedicated experiment. We have measured prompt-fission gamma rays with three cerium-doped LaBr3 (two 5.08 cm x 5.08 cm and one 7.62 cm x 7.62 cm) and one CeBr3 (5.08 cm x 5.08 cm) scintillation detectors, which all exhibit excellent timing and good energy resolution. The average gamma-ray multiplicity was determined to be (nu) over bar (gamma) = (8.21 +/- 0.09) per fission, the average energy to be epsilon(gamma) = (0.78 +/- 0.01) MeV, and the total energy to be E-gamma,E-tot = (6.41 +/- 0.06) MeV as the weighted average from all detectors. Since the results from all detectors are in excellent agreement, and the total released gamma energy is modestly higher than the one in the present evaluated nuclear data files, we suspect that the underestimation of the prompt-gamma heating in nuclear reactors is due to fast-neutron-induced fission on U-238 or rather from fission induced by gamma rays from neutron capture in the construction material.
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| 26. |
- Oberstedt, S., et al.
(författare)
-
New Prompt Fission gamma-ray Data in Response to the OECD/NEA High Priority Request
- 2014
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Ingår i: Nuclear Data Sheets. - : Elsevier BV. - 0090-3752 .- 1095-9904. ; 119, s. E225-E228
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report about new prompt fission gamma-ray measurements, which we have performed with highly efficient gamma-ray detectors based on lanthanide-halide crystals, aiming at very fast timing in conjunction with a good energy resolution. About four decades after the experiments were performed, whose results are still used for current evaluations, we present new spectral prompt fission gamma-ray data from the reactions Cf-252(SF) and U-235(n(th),f). Based on our new findings we recommend to replace the current ENDF/B-VII. 1 evaluation for Cf-252(SF) and U-235(n(th),f) as well as to perform new measurements for U-238(n,f) and Pu-241(n,f).
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| 27. |
- Oberstedt, S., et al.
(författare)
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Prompt fission γ -rays from the reactions 252Cf(SF) and 235U(nth, f) - New data
- 2013
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 62, s. Art. no. 02003-
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Konferensbidrag (refereegranskat)abstract
- We present new spectral data of prompt γ-ray emission from the spontaneous fission of 252Cf. This work was performed in direct response to an OECD/NEA high priority data request. We discuss the impact of our new data on evaluated nuclear data tables not only for this nuclide, but also for 238U and 241Pu, which are always produced in a reactor. Furthermore, we will show results from our investigation of prompt γ-ray emission from the reaction 235 U(nth, f), measured in at the Centre for Energy Research of the Hungarian Academy of Sciences in Budapest, Hungary. Spectral data obtained with three different detectors are consistent and led to an uncertainty on total energy and multiplicity considerably smaller than requested by the OECD/NEA.
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| 28. |
- Wilson, J.N., et al.
(författare)
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LICORNE: A new and unique facility for producing intense, kinematically focused neutron beams at the IPN Orsay
- 2013
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 62, s. Art. no. 05006-
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Konferensbidrag (refereegranskat)abstract
- LICORNE is a new neutron source recently installed at the tandem accelerator of the Institut de Physique Nucléaire d'Orsay, where a Li7-beam is used to bombard a hydrogen-containing target to produce an intense forward-directed neutron beam. The directionality of the beam, which is the unique characteristic of LICORNE, will permit the installation of γ-ray detectors dedicated to the investigation of fission fragment de-excitation which are unimpeded by neutrons from the source. A first experimental program will focus on the measurement of prompt γ-ray emission in the neutron-induced fission of fertile and fissile isotopes at incident neutron energies relevant for the core design of Generation-IV nuclear reactors. Other potential uses of the LICORNE facility for both fundamental and applied physics research are also presented.
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| 29. |
- Sardet, A., et al.
(författare)
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Experimental studies of prompt fission neutron energy spectra
- 2013
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Ingår i: Physics Procedia: Scientific Workshop on Nuclear Fission Dynamics and the Emission of Prompt Neutrons and Gamma Rays, THEORY-2 2012; Biarritz; France; 28 November 2012 through 30 November 2012. - : Elsevier BV. ; 47, s. 144-149
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Konferensbidrag (refereegranskat)abstract
- Prompt fission neutron spectra were measured in the reactions 238U(n, f), 235U(n, f) and 237Np(n, f) at different incident neutron energies. The neutrons were detected using a coaxial doped p-terphenyl scintillation detector in coincidence with fission fragments and their time-of-flight was recorded. The properties of the neutron detector were determined and the results are presented in this work. A preliminary neutron detection efficiency was applied to data from the neutron-induced fission of 238U at En = 5.2 MeV, leading to encouraging results.
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