Studies of back-streaming white neutrons at CSNS Jing, H.T.; Tang, J.Y.; Tang, H.Q. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2010, Letnik:
621, Številka:
1
Journal Article
Recenzirano
Back-streaming neutrons through the incoming proton channel at the spallation target station of China Spallation Neutron Source (CSNS) are harmful to the proton beam line and should be dealt with ...carefully. On the other hand, those back-streaming neutrons may be useful for other applications. This paper presents preliminary studies on the characteristics of the neutrons, which have a very wide energy spectrum (white neutrons) and are very suitable for nuclear data measurements. The corresponding yields and time structures of the neutrons in the energy range of 1
eV to 1
MeV from a tungsten target for a proton beam of 1.6
GeV in energy and 63
μA in average current have been simulated. From the simulation results, one can obtain an uncollimated neutron flux of around 2.0×10
5
n/cm
2/pulse within the given energy range at 80
m away from the target, which accounts for about 53% of the total neutrons. The time resolution of 0.3–0.9%, which is important for the time-of-flight method, is obtained for both the parasite operation mode with two proton bunches and the dedicated operation mode with a single proton bunch.
We report the results of searches for solar axions and galactic dark matter axions or axionlike particles with the CDEX-1 experiment at the China Jinping Underground Laboratory, using 335.6 kg days ...of data from a p-type point-contact germanium detector. The data are compatible with the background model, and no excess signals are observed. Limits of solar axions on the model-independent coupling gAe<2.5×10−11 from Compton, bremsstrahlung, atomic-recombination, and deexcitation channels and gANeff×gAe<6.4×10−17 from a Fe57 M1 transition at 90% confidence level are derived. Within the framework of the Dine-Fischler-Srednicki-Zhitnitskiy and Kim-Shifman-Vainshtein-Zakharov models, our results exclude the axion mass heavier than 0.9 and 177 eV/c2, respectively. The derived constraints for dark matter axions below 1 keV improve over the previous results.
Previous research has found heroin addicts to be impulsive. This study employed functional magnetic resonance imaging technology to investigate the differences between heroin addicts and normal ...controls in neural activity associated with cognitive regulation of behavior. Twenty-one Chinese men participated in this study, 11 of whom were newly admitted heroin-addicted patients and 10 of whom were healthy volunteers. In the experimental task, the subjects were required to first identify the correct directions of arrowheads and then give the opposite answers. Behaviorally, the heroin-dependent patients took a much shorter time to complete the more demanding second part of the task but committed more errors than the normal controls. This pattern of behavior, characteristic of people who are disinhibited and who tend to be impulsive, was consistent with previous reports of impulsivity observed in people who have abused heroin. The neural activity of the patients that was associated with performing the experimental task of cognitive regulation was different to that of the normal controls in terms of the pattern of prefrontal activation, the attenuation of activity in the anterior cingulate, and the additional recruitment of the right inferior parietal region. This study is the first that seeks to understand the neural activity associated with impulsive behavior in people who abuse heroin. The pattern of imaging data obtained resembled the pattern of data observed in immature brains attempting to exercise cognitive control of behavior. Further theoretical and clinical implications of the findings are discussed.
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