In this paper we report on a first part of a study on the mechanisms leading to brittle fracture in neutron guides made of glass as structural element. Such devices are widely used to deliver thermal ...and cold neutron beams to experimental lines in most large neutron research facilities. We present results on macroscopic properties of samples of guide glass substrates which are subjected to neutron irradiation at relatively large fluences. The results show a striking dependence of some of the macroscopic properties such as density, shape or surface curvature upon the specific chemical composition of a given glass. The relevance of the present findings for the installation of either replacement guides at the existing facilities or for the deployment of instruments for ongoing projects such as the European Spallation Source is briefly discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper describes the production and chemical separation of the .sup.163 Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the ...neutron cross section of the .sup.163 Ho isotope. For this purpose, several batches of enriched .sup.162 Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired .sup.163 Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed.
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The three main requirements to the ion source of an ISOL facility are efficiency, selectivity and rapidity. For many metallic elements these requirements are ideally fulfilled by a resonance ...ionization laser ion source (RILIS). Presently such ion sources are used at the RIB facilities IRIS (Gatchina), ISOLDE (CERN), LISOL (Leuven), TIARA (Takasaki) and IMP (Lanzhou) to provide beams with low isobaric contamination. The isotopically pure beams enabled to make spectacular progress, for instance in nuclear spectroscopy of very rare isotopes. The scanning of the hyperfine structure with a small bandwidth laser allows moreover to separate individual isomers. The RILIS has also been used as a sensitive tool for atomic spectroscopy (measurement of the isotope shift and of nuclear moments) of exotic isotopes.
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The shape of exotic even-mass (182-190)Pb isotopes was probed by measurement of optical isotope shifts providing mean square charge radii (delta(r(2))). The experiment was carried out at the isolde ...(cern) on-line mass separator, using in-source laser spectroscopy. Small deviations from the spherical droplet model are observed, but when compared to model calculations, those are explained by high sensitivity of delta(r(2)) to beyond mean-field correlations and small admixtures of intruder configurations in the ground state. The data support the predominantly spherical shape of the ground state of the proton-magic Z=82 lead isotopes near neutron midshell (N=104).
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Nuclear fission yields are key parameters to evaluate reactor physics observables, such as fuel inventory, decay heat, spent fuel radiotoxicity, criticality but also for understanding the fission ...process. Despite a significant effort allocated to measure fission yields during the last decades, the recent evaluated libraries still need improvements in particular in the description of the uncertainties with the associated correlations. Additional kinds of measurements provide complementary information in order to test the models used in the nuclear data evaluation. Moreover, some discrepancies between these libraries must be explained. A common effort by the CEA, the LPSC and the ILL aims at tackling these issues by providing precise measurement of isotopic and isobaric fission yields with the related variance-covariance matrices. Nevertheless, the experimental program represents itself a large range of observables requested by the evaluations: isotopic yields, nuclear charge polarization, odd-even effect, isomeric ratio and their dependency with fission fragment kinetic energy as a probe of the nuclear de-excitation path in the (E
*
, J
π
) representation. Measurements for thermal neutron induced fission of
241
Pu have been carried out at the Institut Laue Langevin using the LOHENGRIN mass spectrometer. Experimental program, observables reachable, results and comparison to model calculations are shown.
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The gamma-ray decay of excited states of the one-valence-proton nucleus 133Sb has been studied using cold-neutron induced fission of 235U and 241Pu targets, during the EXILL campaign at the ILL ...reactor in Grenoble. By using a highly efficient HPGe array, coincidences between gamma-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to observe, for the first time, high-spin excited states above the 16.6 micros isomer. Lifetimes analysis, performed by fast-timing techniques with LaBr3(Ce) scintillators, reveals a difference of almost two orders of magnitude in B(M1) strength for transitions between positive-parity medium-spin yrast states. The data are interpreted by a newly developed microscopic model which takes into account couplings between core excitations (both collective and non-collective) of the doubly magic nucleus 132Sn and the valence proton, using the Skyrme effective interaction in a consistent way. The results point to a fast change in the nature of particle-core excitations with increasing spin.
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Nuclear fission yields are key data for reactor studies, such as spent fuel inventory or decay heat, and for understanding fission process. Despite a significant effort allocated to measure fission ...yields during the last decades, the recent evaluated libraries still need improvements in particular in the reduction of the uncertainties. Moreover, some discrepancies between these libraries must be explained.
Additional measurements provide complementary information and estimations of experimental correlations, and new kinds of measurements enable to test the models used during the nuclear data evaluation process. A common effort by the CEA, the LPSC and the ILL aims at tackling these issues by providing precise measurements of isotopic and isobaric fission yields with the related variance-covariance matrices. Additionally, the experimental program involves a large range of observables requested by the evaluations, such as kinetic energy dependency of isotopic yields and odd-even effect in order to test the sharing of total excitation energy and the spin generation mechanism. Another example is the complete range of isotopic distribution per mass that allows the determination of the charge polarization, which has to be consistent for complementary masses (pre-neutron emission). For instance, this information is the key observable for the evaluation of isotopic yields. Finally, ionic charge distributions are indirect measurements of nanosecond isomeric ratios as a probe of the nuclear de-excitation path in the
(E*, J
,
π
) representation.
Measurements for thermal neutron induced fission of
241
Pu have been carried out at the ILL in Grenoble, using the LOHENGRIN mass spectrometer. Methods, results and comparison to models calculations will be presented corresponding to a status on fission fragments observables reachable with this facility.
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Recent Results for the ECHo Experiment Hassel, C.; Blaum, K.; Goodacre, T. Day ...
Journal of low temperature physics,
08/2016, Volume:
184, Issue:
3-4
Journal Article
Peer reviewed
Open access
The Electron Capture in
163
Ho experiment, ECHo, is designed to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured spectrum following ...the electron capture (EC) in
163
Ho. Arrays of low-temperature metallic magnetic calorimeters (MMCs), read-out by microwave SQUID multiplexing, will be used in this experiment. With a first MMC prototype having the
163
Ho source ion-implanted into the absorber, we performed the first high energy resolution measurement of the EC spectrum, which demonstrated the feasibility of such an experiment. In addition to the technological challenges for the development of MMC arrays, which preserve the single pixel performance in terms of energy resolution and bandwidth, the success of the experiment relies on the availability of large ultra-pure
163
Ho samples, on the precise description of the expected spectrum, and on the identification and reduction of background. We present preliminary results obtained with standard MMCs developed for soft X-ray spectroscopy, maXs-20, where the
163
Ho ion-implantation was performed using a high-purity
163
Ho source produced by advanced chemical and mass separation. With these measurements, we aim at determining an upper limit for the background level due to source contamination and provide a refined description of the calorimetrically measured spectrum. We discuss the plan for a medium scale experiment, ECHo-1k, in which about
1000
Bq
of high-purity
163
Ho will be ion-implanted into detector arrays. With one year of measuring time, we will be able to achieve a sensitivity on the electron neutrino mass below 20 eV/c
2
(90
%
C.L.), improving the present limit by more than one order of magnitude. This experiment will guide the necessary developments to reach the sub-eV sensitivity.
The 41Ar(n,y)42Ar reaction Sahoo, R N; Paul, M; Köster, U ...
EPJ Web of Conferences,
01/2023, Volume:
284
Conference Proceeding, Journal Article
Peer reviewed
Open access
The cross-section of the thermal neutron capture 41Ar(n,γ)42Ar(t1/2=32.9 y) reaction was measured by irradiating a 40Ar sample at the high-flux reactor of Institut Laue-Langevin (ILL) Grenoble, ...France. The signature of the two-neutron capture has been observed by measuring the growth curve and identifying the 1524.6 keV γ-lines of the shorter-lived 42K(12.4 h) β− daughter of 42Ar. Our preliminary value of the 41Ar(n,γ)42Ar thermal cross section is 240(80) mb at 25.3 meV. For the first time, direct counting of 42Ar was performed using the ultra-high sensitivity technique of noble gas accelerator mass spectrometry (NOGAMS) at Argonne National Laboratory, USA.
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