Search results for "Spallation"
showing 10 items of 41 documents
The new neutron-rich isotope228Rn
1989
2 pages, 1 table, 2 figures.-- PACS nrs.: 23.90.+w; 27.90.+b.-- Section: Short Notes.
<title>Studies of the activation background in CsI(Tl) detectors</title>
1993
CsI scintillation crystals are widely used as detection in (gamma) -ray astronomy observations. In the MeV energy region, one of the most important background sources in CsI is the (beta) decays induced in the crystal by cosmic ray protons and their secondaries. One recent idea for reducing this background is to use discrete detector arrays to reject the large amount of localized (beta) decay events. Two experiments were carried out with 1 cm3 CsI crystals bombarded with energetic proton beams and fast/thermal neutrons, with the aim of evaluating the effectiveness of this method in pixelated (1 cm3) CsI detectors. The ratio of the number of decays resulting in single site and multiple site …
He-3 spin filter for neutrons
2005
The strongly spin-dependent absorption of neutrons in nuclear spin-polarized (3)He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable (3)He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A sh…
Gamma Ray Spectrum from Thermal Neutron Capture on Gadolinium-157
2018
International audience; We have measured the |$\gamma$|-ray energy spectrum from the thermal neutron capture, |${}^{157}$|Gd|$(n,\gamma)$|, on an enriched |$^{157}$|Gd target (Gd|$_{2}$|O|$_{3}$|) in the energy range from 0.11 MeV up to about 8 MeV. The target was placed inside the germanium spectrometer of the ANNRI detector at J-PARC and exposed to a neutron beam from the Japan Spallation Neutron Source (JSNS). Radioactive sources (|$^{60}$|Co, |$^{137}$|Cs, and |$^{152}$|Eu) and the |$^{35}$|Cl(|$n$|,|$\gamma$|) reaction were used to determine the spectrometer‘s detection efficiency for |$\gamma$| rays at energies from 0.3 to 8.5 MeV. Using a Geant4-based Monte Carlo simulation of …
Internal geometry and coolant choices for solid high power neutron spallation targets
2014
Abstract The next generation of neutron spallation sources envisages high power proton beam interaction with a heavy metal target. Solid targets have potentially higher spallation efficiency due to the possibility to use metals with higher density than used in liquid metal targets, but to realize this potential the solid fraction must be high enough. As the power released in the form of heat can reach several MW in the target volume of typically 10 l, target cooling can be a serious challenge. Heat evacuation efficiency for different solid fraction geometries at high power is analyzed for different coolant options (helium, water and gallium) using empirical correlations for friction factors…
Frontiers of Heavy - Ion Physics and Superheavy Elements
2003
This contribution will focus on three topics of GSI nuclear structure research: super heavy elements, direct mass measurements in the storage ring, and the measurement of spallation cross section in reversed kinematics. The GSI project for an extended synchrotron facility will be outlined.
Reactor antineutrino detection in Double Chooz experiment: Techniques for background reduction
2014
Abstract A crucial task for the Double Chooz reactor antineutrino experiment is the thorough study of the different backgrounds in the detector. Newly developed background reduction techniques minimize the impact of the backgrounds on our sensitivity. Moreover, only a precision and accuracy measurement of the residual background would allow to measure the mixing angle θ 13 with high precision. Neutrino coincidence signals are imitated by signals produced in several others physics processes: accidental coincidences of single events (accidental background), as well as correlated events induced by cosmic muons, including stopping muons, fast neutrons and spallation isotopes Li 9 /He 8 . The Do…
β-decay half-life of70Kr: A bridge nuclide for therpprocess beyondA=70
2000
The -decay half-life of 70 Kr has been measured for the first time at the ISOLDE PSB Facility at CERN. Mass separated 70 Kr ions were produced by 1 GeV proton induced spallation reactions in a Nb foil. The measured half-life is 57(21) ms. This value is consistent with the half-life calculated assuming a pure Fermi decay, but is clearly lower than the value used in a recent rp-process reaction flow calculation. The result shows that the reaction flow via two-proton-capture of 68 Se is 2.5 times faster than previously calculated assuming an astrophysical temperature of 1.5 GK and a density of 10 6 g/cm 3 .
New neutron-rich isotopes of astatine and bismuth
1989
Neutron-rich isotopes of astatine have been produced through spallation reactions with 600 MeV protons on a232Th target and identified by spectroscopic techniques combined with one-line mass separation at the ISOLDE facility. The half-lives of218At and219At have been remeasured to be 1.5(3) s and 57(4) s, respectively. Four new isotopes of astatine,220−223At, have been observed for the first time, and their half-lives were found to be 3.73(13) min, 2.3(2) min, 54(10) s, and 50(7) s, respectively. Another nuclide,216Bi, has been observed for the first time as the daughter product of the220At alpha decay, and its half-life has been measured to be 6.6(21) min.
Probing neutrino magnetic moments at the Spallation Neutron Source facility
2015
24 pages.- 8 figures