Radioactive isotopes produced through cosmic muon spallation are a background for rare-event detection in nu detectors, double-beta-decay experiments, and dark-matter searches. Understanding the ...nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of {sup 11}C. Data from the Kamioka liquid-scintillator antineutrino detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillators, and for checking estimates from current simulations based upon MUSIC, FLUKA, and GEANT4. Using the time correlation between detected muons and neutron captures, the neutron production yield in the KamLAND liquid scintillator is measured to be Y{sub n}=(2.8+-0.3)x10{sup -4} mu{sup -1} g{sup -1} cm{sup 2}. For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.
Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector ...for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4mrad from the measured profile center. The normalized event rate is measured with 4% precision.
Superconducting combined function magnets for the J-PARC (Japan Proton Accelerator Research Complex) neutrino experiment have been successfully developed at High Energy Accelerator Research ...Organization, KEK. The first prototype magnet reassembled for the quench protection studies, and the cold test result indicated that the eight quench protection heaters are effective for the safe protection of the magnet. Three production magnets have been fabricated and tested at 4.5 K, 1 atm, in a vertical cryostat, and the excellent excitation and quench performances are observed. In the field measurement during cold tests, all the magnets indicated the field qualities good enough to fulfill the specification. The field measurement at room temperature has been also performed with the three production magnets for checking the dipole field component. The results are consistent with the computation.
In the development of RHQT-processed Nb 3 Al wires for high-field accelerator magnet applications, one of the major objectives is to increase the non-copper critical current density in the field ...range of 12-15 T. To pursue this goal, a low-matrix- ratio wire was fabricated, and the effects of the RHQ conditions and the area reduction after the RHQ treatment on the properties of the wire were investigated. This paper describes the details and results of this study.
The first full-scale prototype magnet system assembled with the cryostat for the J-PARC proton beam line of neutrino experiment was successfully developed and tested. Two superconducting combined ...function magnets have been installed into the cryostat. The magnets were successfully cooled down to 4.5 K by forced flow supercritical helium and excited up to the current of 7345 A which is the nominal current of 50 GeV proton beam. The spot heater quench test showed that the quench characteristics in the supercritical helium were very similar to that in the liquid helium at 4.2 K, 1 atm. The quench protection scheme with both cold diodes and quench protection heaters was tested, and it has been verified that the magnet can be protected with safe margin.
We have developed Nb3Al wires with a low Nb matrix ratio in order to attain a high critical current density. Test wires were prepared with different fabrication parameters, mainly the Nb matrix ...ratio, RHQ current, and the area reduction ratio of the wire after an RHQ heat treatment. The critical current and n-values of these wires were measured. Our newly developed wire with a Nb matrix ratio of 0.6 was almost the same RHQ heat-treatment effect and area reduction effect as those of samples with different Nb matrix ratios. However, the critical current density of our wire was lower than that of these samples. In order to determine the reason for this low critical current density, Tc measurements and tensile strain tests were also performed. In this paper, we report the characteristics of the sample with a Nb matrix ratio of 0.6 and compare them with those of the other samples.
The inner triplet quadrupole magnets (MQXA) for the LHC low-beta insertion have been developed. The quadrupoles provide a field gradient of 215 T/m at 1.9 K in a coil aperture of 70 mm diameter and ...with an effective magnetic length of 6.37 m. The series of 20 magnets have been produced in industry, and full testing has been done at KEK. We present an overview of the production and the results from mechanical and magnetic measurements.
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