| 1. |
- Al-Adili, Ali, et al.
(författare)
-
Neutron-multiplicity experiments for enhanced fission modelling
- 2017
-
Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 9782759890200
-
Konferensbidrag (refereegranskat)abstract
- The nuclear de-excitation process of fission fragments (FF) provides fundamental information for the understanding of nuclear fission and nuclear structure in neutron-rich isotopes. The variation of the prompt-neutron multiplicity, ν(A), as a function of the incident neutron energy (En) is one of many open questions. It leads to significantly different treatments in various fission models and implies that experimental data are analyzed based on contradicting assumptions. One critical question is whether the additional excitation energy (Eexc) is manifested through an increase of ν(A) for all fragments or for the heavy ones only. A systematic investigation of ν(A) as a function of En has been initiated. Correlations between prompt-fission neutrons and fission fragments are obtained by using liquid scintillators in conjunction with a Frisch-grid ionization chamber. The proof-of-principle has been achieved on the reaction 235U(nth,f) at the Van De Graff (VdG) accelerator of the JRC-Geel using a fully digital data acquisition system. Neutrons from 252Cf(sf) were measured separately to quantify the neutron-scattering component due to surrounding shielding material and to determine the intrinsic detector efficiency. Prelimenary results on ν(A) and spectrum in correlation with FF properties are presented.
|
|
| 2. |
- Al-Adili, Ali, et al.
(författare)
-
Studying fission neutrons with 2E-2v and 2E
- 2018
-
Ingår i: SCIENTIFIC WORKSHOP ON NUCLEAR FISSION DYNAMICS AND THE EMISSION OF PROMPT NEUTRONS AND GAMMA RAYS (THEORY-4). - : EDP Sciences. - 9782759890316
-
Konferensbidrag (refereegranskat)abstract
- This work aims at measuring prompt-fission neutrons at different excitation energies of the nucleus. Two independent techniques, the 2E-2v and the 2E techniques, are used to map the characteristics of the mass-dependent prompt fission neutron multiplicity, 7(A), when the excitation energy is increased. The VERDI 2E-2v spectrometer is being developed at JRC-GEEL. The Fission Fragment (FF) energies are measured using two arrays of 16 silicon (Si) detectors each. The FFs velocities are obtained by time-of-flight, measured between micro-channel plates (MCP) and Si detectors. With MCPs placed on both sides of the fission source, VERDI allows for independent timing measurements for both fragments. Cf-252(sf) was measured and the present results revealed particular features of the 2E-2v technique. Dedicated simulations were also performed using the GEF code to study important aspects of the 2E-2v technique. Our simulations show that prompt neutron emission has a non-negligible impact on the deduced fragment data and affects also the shape of 17(A). Geometrical constraints lead to a total-kinetic energy-dependent detection efficiency. The 2E technique utilizes an ionization chamber together with two liquid scintillator detectors. Two measurements have been performed, one of Cf-252(sf) and another one of thermal-neutron induced fission in U-235(n,f). Results from Cf-252(sf) are reported here.
|
|
| 3. |
- Andreou, Charalambos M., et al.
(författare)
-
Low-Power, Subthreshold Reference Circuits for the Space Environment : Evaluated with -rays, X-rays, Protons and Heavy Ions
- 2019
-
Ingår i: Electronics. - : MDPI. - 2079-9292. ; 8:5
-
Tidskriftsartikel (refereegranskat)abstract
- The radiation tolerance of subthreshold reference circuits for space microelectronics is presented. The assessment is supported by measured results of total ionization dose and single event transient radiation-induced effects under -rays, X-rays, protons and heavy ions (silicon, krypton and xenon). A high total irradiation dose with different radiation sources was used to evaluate the proposed topologies for a wide range of applications operating in harsh environments similar to the space environment. The proposed custom designed integrated circuits (IC) circuits utilize only CMOS transistors, operating in the subthreshold regime, and poly-silicon resistors without using any external components such as compensation capacitors. The circuits are radiation hardened by design (RHBD) and they were fabricated using TowerJazz Semiconductor's 0.18 m standard CMOS technology. The proposed voltage references are shown to be suitable for high-precision and low-power space applications. It is demonstrated that radiation hardened microelectronics operating in subthreshold regime are promising candidates for significantly reducing the size and cost of space missions due to reduced energy requirements.
|
|
| 4. |
- Bielewicz, M., et al.
(författare)
-
(n,xn) cross section measurements for Y-89 foils used as detectors for high energy neutron measurements in the deeply subcritical assembly “QUINTA”
- 2017
-
Ingår i: ND 2016: INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY. - Les Ulis : EDP Sciences. - 9782759890200
-
Konferensbidrag (refereegranskat)abstract
- Study of the deep subcritical systems (QUINTA) using relativistic beams is performed within the project “Energy and Transmutation of Radioactive Wastes” (E&T – RAW). The experiment assembly was irradiated by deuteron/proton beam (Dubna NUCLOTRON). We calculated the neutron energy spectrum inside the whole assembly by using threshold energy (n,xn) reactions in yttrium (Y-89) foils. There are almost no experimental cross section data for those reactions. New Y-89(n,xn) cross section measurements were carried out at The Svedberg laboratory (TSL) in Uppsala, Sweden in 2015. In this paper we present preliminary results of those experiments.
|
|
| 5. |
- Ledoux, X., et al.
(författare)
-
The Neutrons for Science Facility at SPIRAL-2
- 2018
-
Ingår i: Radiation Protection Dosimetry. - : OXFORD UNIV PRESS. - 0144-8420 .- 1742-3406. ; 180:1-4, s. 115-119
-
Tidskriftsartikel (refereegranskat)abstract
- The neutrons for science (NFS) facility is a component of SPIRAL-2, the new superconducting linear accelerator built at GANIL in Caen (France). The proton and deuteron beams delivered by the accelerator will allow producing intense neutron fields in the 100 keV-40 MeV energy range. Continuous and quasi-mono-kinetic energy spectra, respectively, will be available at NFS, produced by the interaction of a deuteron beam on a thick Be converter and by the Li-7(p, n) reaction on thin converter. The pulsed neutron beam, with a flux up to two orders of magnitude higher than those of other existing time-of-flight facilities, will open new opportunities of experiments in fundamental research as well as in nuclear data measurements. In addition to the neutron beam, irradiation stations for neutron-, proton- and deuteron-induced reactions will be available for cross-sections measurements and for the irradiation of electronic devices or biological cells. NFS, whose first experiment is foreseen in 2018, will be a very powerful tool for physics, fundamental research as well as applications like the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors.
|
|
| 6. |
- Ledoux, X., et al.
(författare)
-
The neutrons for science facility at SPIRAL-2
- 2017
-
Ingår i: ND 2016. - Les Ulis : EDP Sciences.
-
Konferensbidrag (refereegranskat)abstract
- Numerous domains, in fundamental research as well as in applications, require the study of reactions induced by neutrons with energies from few MeV up to few tens of MeV. Reliable measurements also are necessary to improve the evaluated databases used by nuclear transport codes. This energy range covers a large number of topics like transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors. A new facility called Neutrons For Science (NFS) is being built for this purpose on the GANIL site at Caen (France). NFS is composed of a pulsed neutron beam for time-of-flight facility as well as irradiation stations for cross-section measurements. Neutrons will be produced by the interaction of deuteron and proton beams, delivered by the SPIRAL-2 linear accelerator, with thick or thin converters made of beryllium or lithium. Continuous and quasi-mono-energetic spectra will be available at NFS up to 40 MeV. In this fast energy region, the neutron flux is expected to be up to 2 orders of magnitude higher than at other existing time-of-flight facilities. In addition, irradiation stations for neutron-, proton- and deuteron-induced reactions will allow performing cross-section measurements by the activation technique. After a description of the facility and its characteristics, the experiments to be performed in the short and medium term will be presented.
|
|
| 7. |
- Majerle, Mitja, et al.
(författare)
-
Peak neutron production from the 7Li(p,n) reaction in the 20-35 MeV range
- 2020
-
Ingår i: ND 2019. - : E D P SCIENCES. - 9782759891061
-
Konferensbidrag (refereegranskat)abstract
- New experimental data on the peak neutron production in the Li-7(p,n) reaction were collected during several irradiation campaigns at the NPI CAS. Time-of-flight method was used to measure the number of the peak neutrons in the forward direction, and the number of produced Be-7 nuclei was determined using gamma-spectrometry. The new measurement results are compared with experimental data from the literature and used for the validation of several different systematics and nuclear data libraries developed over the years.
|
|
| 8. |
- Pomp, Stephan, 1968-, et al.
(författare)
-
Measurement of fission yields and isomeric yield ratios at IGISOL
- 2018
-
Ingår i: Scientific Workshop on Nuclear Fission Dynamics And The Emission of Prompt Neutrons and Gamma Rays (Theory-4). - : EDP Sciences. - 9782759890316
-
Konferensbidrag (refereegranskat)abstract
- Data on fission yields and isomeric yield ratios (IYR) are tools to study the fission process, in particular the generation of angular momentum. We use the IGISOL facility with the Penning trap JYFLTRAP in Jyvaskyla, Finland, for such measurements on Th-232 and U-nat targets. Previously published fission yield data from IGISOL concern the Th-232(p,f) and U-238(p,f) reactions at 25 and 50 MeV. Recently, a neutron source, using the Be(p,n) reaction, has been developed, installed and tested. We summarize the results for (p,f) focusing on the first measurement of IYR by direct ion counting. We also present first results for IYR and relative yields for Sn and Sb isotopes in the 128-133 mass range from U-nat(n,f) based on gamma-spectrometry. We find a staggering behaviour in the cumulative yields for Sn and a shift in the independent fission yields for Sb as compared to current evaluations. Plans for the future experimental program on fission yields and IYR measurements are discussed.
|
|
| 9. |
- Prokofiev, Alexander V., 1963-, et al.
(författare)
-
CUP–A New High-Flux Irradiation Position at the ANITA Neutron Facility at TSL
- 2014
-
Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 61:4, s. 1929-1936
-
Tidskriftsartikel (refereegranskat)abstract
- A new irradiation position has been constructed,characterized, and put into operation at the ANITA facility in The Svedberg Laboratory (TSL) for accelerated testing of components and systems for single event effects. Results of beam characterization measurements are reported. The energy-integrated neutron flux above 10 MeV, amounting to more than 10^7 cm^-2 s^-1 , is the highest among the facilities with atmospheric-like spectra. The employed characterization and simulation techniques are applicable for a broad class of neutron facilities.
|
|
| 10. |
- Solders, Andreas, 1976-, et al.
(författare)
-
Simulations of the stopping efficiencies of fission ion guides
- 2017
-
Ingår i: Nd 2016. - Les Ulis : EDP Sciences. - 9782759890200
-
Konferensbidrag (refereegranskat)abstract
- With the Ion Guide Isotope Separator On-Line (IGISOL) facility, located at the University of Jyväskylä, products of nuclear reactions are separated by mass. The high resolving power of the JYFLTRAP Penning trap, with full separation of individual nuclides, capacitates the study of nuclides far from the line of stability. For the production of neutron-rich medium-heavy nuclides, fissioning of actinides is a feasible reaction. This can be achieved with protons from an in-house accelerator or, alternatively, with neutrons through the addition of a newly developed Be(p,xn)-converter. The hereby-obtained fission products are used in nuclear data measurements, for example fission yields, nuclear masses, Q-values and decay spectroscopy. Prior to separation, the ionized reaction products are stopped in a helium-filled gas cell, referred to as the ion-guide. In this work we present simulations of the stopping of fission products in an ion guide developed for neutron-induced fission. The production and extraction rates are evaluated and compared against experimental values.
|
|
