Search results for "Neutron temperature"
showing 10 items of 103 documents
Production of neutron-rich surface-ionized nuclides at PARRNe
2002
Yields of neutron-rich isotopes produced by fast neutron induced fission of 238 U were measured at the ISOL set-up Production dAtomes Radioactifs Riches en Neutrons. A surface ion source was used to ionize selectively elements with low ionization potentials. In order to observe also the most n-rich isotopes, the identification was achieved by a combined measurement of b- and c-rays and b-delayed neutrons. The flux of fast neutrons inducing fission was generated by a 1 lA beam of 26 MeV deuterons stopped in a graphite converter. The target was a standard ISOLDE type 238 UC
Optical absorption and Raman studies of neutron-irradiated Gd3Ga5O12 single crystals
2018
Abstract In this work we have performed a comparative analysis of optical absorption and micro-Raman spectra for series of Gd3Ga5O12 (GGG) single crystals irradiated by fast neutrons with fluences from 1016 n/cm2 to 1018 n/cm2. It was found that the optical absorption spectra of non-irradiated Czochralski grown GGG consist of the relatively narrow lines in the UV spectral range related to the 4f–4f transitions in Gd3+. Transitions from the 6S7/2 ground state to the 6P, 6J and 6D states in a Gd3+ cation are clearly detected. For a GGG crystal containing Ca impurity ions, additional absorption band at 350 nm is observed, and it is tentatively ascribed to oxygen vacancies associated with Ca im…
Thermoluminescence response of sodalime glass irradiated with proton and neutron beams
2012
In the research field of emergency dosimeters to be used in case of accidental radiation exposure of the population, watch glass has been considered as a possible fortuitous dosimetric material. This paper reports on results obtained by thermoluminescence of glass samples exposed to neutron and proton beams. Thermoluminescent glow curves have been analyzed for each irradiation studying the modifications induced by the irradiation as a function of proton dose or neutron fluence. The glow curve in a specific temperature range has been used as dosimetric parameter. The thermoluminescence response of samples exposed to protons has been found to be linear in the dose range between 2 and 20 Gy an…
Measurements of the 90,91,92,94,96 Zr n, gamma cross-sections at n_TOF
2005
Neutron capture cross sections of the 90,91,92,94,96Zr have been measured over the energy range from 1 eV to 1 MeV at the spallation neutron facility n TOF at CERN in 2003. The innovative features of the neutron beam, in particular the high instantaneous flux, the high energy resolution and low background, together with improvements of the neutron sensitivity of the capture detectors make this facility unique for neutron-induced reaction cross section measurements with much improved accuracy. The preliminary results of the Zr measurements show capture resonance strengths generally smaller than in previous measurements. Peer Reviewed
Characterization of a neutron-beta counting system with beta-delayed neutron emitters
2016
Abstract A new detection system for the measurement of beta-delayed neutron emission probabilities has been characterized using fission products with well known β-delayed neutron emission properties. The setup consists of BELEN-20, a 4π neutron counter with twenty 3He proportional tubes arranged inside a large polyethylene neutron moderator, a thin Si detector for β counting and a self-triggering digital data acquisition system. The use of delayed-neutron precursors with different neutron emission windows allowed the study of the effect of energy dependency on neutron, β and β–neutron rates. The observed effect is well reproduced by Monte Carlo simulations. The impact of this dependency on …
Transient and stable color centers in neutron irradiated MgO
2008
Abstract The transient absorption and luminescence induced by the pulsed electron beam have been investigated in the MgO single crystal containing transition metal ion (Cr, Mn, Fe) impurities and preliminary irradiated by the fast neutrons. It is supposed that the different behavior of the absorption spectra of the MgO samples preliminary irradiated by the different fast neutron fluence is connected with the destruction of the hole centers and with the creation of interstitial protons and the formation of the microphase Mg(OH)2. We assume that the luminescence band at ∼3.2 eV is connected with F+ color centers.
A neutron spectrometer for studying giant resonances with (p, n) reactions in inverse kinematics
2014
A neutron spectrometer, the European Low-Energy Neutron Spectrometer (ELENS), has been constructed to study exotic nuclei in inverse-kinematics experiments. The spectrometer, which consists of plastic scintillator bars, can be operated in the neutron energy range of 100 keV to 10 MeV. The neutron energy is determined using the time-of-flight technique, while the position of the neutron detection is deduced from the time-difference information from photomultipliers attached to both ends of each bar. A novel wrapping method has been developed for the plastic scintillators. The array has a larger than 25% detection efficiency for neutrons of approximately 500 keV in kinetic energy and an angul…
Mitigation of backgrounds from cosmogenic 137 Xe in xenon gas experiments using 3 He neutron capture
2020
[EN] Xe-136 is used as the target medium for many experiments searching for 0 nu beta beta. Despite underground operation, cosmic muons that reach the laboratory can produce spallation neutrons causing activation of detector materials. A potential background that is difficult to veto using muon tagging comes in the form of Xe-137 created by the capture of neutrons on Xe-136. This isotope decays via beta decay with a half-life of 3.8 min and a Q(beta) of similar to 4.16 MeV. This work proposes and explores the concept of adding a small percentage of He-3 to xenon as a means to capture thermal neutrons and reduce the number of activations in the detector volume. When using this technique we f…
Experimental neutron capture data of 58Ni from the CERN n_TOF facility
2014
The $^{58}$Ni $(n,\gamma)$ cross section has been measured at the neutron time of flight facility n_TOF at CERN, in the energy range from 27 meV up to 400 keV. In total, 51 resonances have been analyzed up to 122 keV. Maxwellian averaged cross sections (MACS) have been calculated for stellar temperatures of kT$=$5-100 keV with uncertainties of less than 6%, showing fair agreement with recent experimental and evaluated data up to kT = 50 keV. The MACS extracted in the present work at 30 keV is 34.2$\pm$0.6$_\mathrm{stat}\pm$1.8$_\mathrm{sys}$ mb, in agreement with latest results and evaluations, but 12% lower relative to the recent KADoNIS compilation of astrophysical cross sections. When in…
Experimental Assessment of a Flat Sandwich-Like Self-Powered Detector for Nuclear Measurements in ITER Test Blanket Modules
2018
Neutron and gamma flux measurements in designated positions in the test blanket modules (TBMs) of ITER will be important tasks during its campaigns. Investigations on self-powered detectors (SPDs), a class of reactor flux monitors are undertaken in the framework of an ongoing project on development of nuclear instrumentation for European ITER TBMs. This paper reports the findings of experiments performed with an SPD in flat sandwich-like geometry. A detector with vanadium emitter is chosen for preliminary studies. Its irradiation in a thermal neutron field gives a proof of the principle of flat SPDs. It is further irradiated in the mixed neutron-gamma field of a 14-MeV neutron generator and…