95672151
Studies of neutron emission from relativistic nuclear interactions
Abstract Studies were carried out on the yields and spatial distributions of secondary neutrons produced in the relativistic nuclear interactions of 1.5 GeV to 14.4 GeV projectiles p, d and α-particles with targets Pb and U/Pb. CR-39 track detectors were used to measure the neutrons. It shows that: (1) Secondary neutrons are produced in the whole length of Pb or U targets having a thickness of 20 cm. The neutron intensities produced by proton bombardments are reduced along the proton beam direction in the targets. The higher the energy of protons, the lower the reduction rate of the neutrons. The reduction rate of neutrons in U target is higher than in Pb target for the same energy of protons. (2) The radial intensities of neutrons decrease as the distance increases from the target central line. (3) The neutron yield in U target by proton bombardments is ∼55% higher than in Pb target. (4) The ratio of neutron yield by 14.4 GeV α to 7.3 GeV d bombardment in Pb target is 1.74 ± 0.20.
97825201
Investigation of neutron spectrum emitted from 44 GeV 12C+Cu interactions with nuclear emulsion
Abstract The Energy Spectrum of fast neutrons produced in 44 GeV 12 C+Cu interactions has been measured and analysed with nuclear emulsion of 8 cm in length, 2.2 cm in width and 400 μm in thickness made in China Institute of Atomic Energy, Beijing, China. The irradiation of the emulsion was carried out at the accelerator SYNCHROPHASOTRON of the Joint Institute for Nuclear Research, Dubna, Russia. The neutron spectrum was obtained through measuring the recoil protons in emulsion and the track parameters of α particles from interactions of 12 C(n,n′)3α in emulsion. The experimental neutron spectrum was compared with the results of a Monte-Carlo calculation, which shows that the shapes of both neutron spectra are identical within the limits of their statistical accuracy.
1531622
A Monitor Having Lots of Functions for a Linac with Feedback
In our 20 Mev electron linear accelerator with feedback we use a detector in the feedback loop to observe a microwave envelope which includes a lot of information. Under the accelerator operating condition from the micro wave envelope we can monitor the frequency, power, phase and beam loading and calculate the attenuation constant, group velocity, filling time and the field multiplication factor. We can also observe some unstable phenomena.
91211418
Further evidences for enhanced nuclear cross-sections observed in 44 GeV carbon ion interactions with copper
97547510
Study of neutron generation from relativistic heavy ion interactions
Abstract Study has been carried out on neutron generation in the interactions of 44 and 18 GeV 12 C with Cu-and Pb-targets. The properties studied include, (1) Relative yields of secondary neutrons generated in 44 GeV versus in 18 GeV 12 C bombardment to Cu target and also to Pb target. The ratios of these are 2.12±0.19 and 2.04±0.15, respectively, which is nearly in consistence with but somewhat larger than the values of theoretical calculations for Cu target. (2) Relative yields of secondary neutrons produced in Pb target versus in Cu target. The ratios obtained are 2.54±0.20 and 2.56±0.20 for 44 GeV and 18 GeV, respectively. More neutrons are generated in Pb target than in Cu target.
110807481
Development of a high power 1.2 MW CW L-band klystron
The high power CW L-band klystron has been developed as the RF source of the PNC high power CW electron linac (10 MeV, 100 mA). CW power of 1.2 MW at 1.249135 GHz and efficiencies over 65% were the design goals. RF analysis of the windows using high-frequency simulation codes provided information about power loss distribution in the ceramic and optimizing properties of the RF structure. The prototype klystron window was replaced with a long pill-box type beryllia window as a result of the simulation and hardware tests. The klystron has reached CW power of 885 kW with efficiency above 45%. This paper describes key points of the designs and results of the high power RF tests.
119274120
THE FIRST LIMITS ON THE ULTRA-HIGH ENERGY NEUTRINO FLUENCE FROM GAMMA-RAY BURSTS
We set the first limits on the ultra-high energy (UHE) neutrino fluence at energies greater than 10{sup 9} GeV from gamma-ray bursts (GRBs) based on data from the second flight of the Antarctic Impulsive Transient Antenna (ANITA). During the 31 day flight of ANITA-II, 26 GRBs were recorded by Swift or Fermi. Of these, we analyzed the 12 GRBs which occurred during quiet periods when the payload was away from anthropogenic activity. In a blind analysis, we observe 0 events on a total background of 0.0044 events in the combined prompt window for all 12 low-background bursts. We also observe 0 events from the remaining 14 bursts. We place a 90% confidence level limit on the E{sup -4} prompt neutrino fluence between 10{sup 8} GeV < E < 10{sup 12} GeV of E{sup 4}{Phi} = 2.5 x 10{sup 17} GeV{sup 3} cm{sup -2} from GRB090107A. This is the first reported limit on the UHE neutrino fluence from GRBs above 10{sup 9} GeV, and the strongest limit above 10{sup 8} GeV.
122576647
On muon production and other leakage aspects of pion absorption in a lead/scintillating-fiber calorimeter
Abstract We report on an experimental study of longitudinal leakage phenomena in hadronic shower development. Pions in the energy range of 10–150 GeV were sent into a lead/scintillating-fiber calorimeter with a thickness of 9.6 nuclear interaction lengths. The average fraction of the energy leaking out at the back of this calorimeter ranges from 0.04% at 10 GeV to 0.4% at 150 GeV. This leakage has a very small effect on the hadronic energy resolution. We measured the probability of the creation of escaping muons in the shower development process. This probability ranges from 0.2% at 10 GeV to 2.1% at 150 GeV. Assuming that these muons are produced from π- or K-decay, we find an exponentially decaying muon spectrum with a typical momentum of 2.8 GeV/ c , at 80 GeV incident energy. Also the rates at which hadrons and soft neutrons escape from the calorimeter are measured. Within the acceptance of the leakage calorimeter, neutrons are observed about 10 times as often as muons. Escaping hadrons dominate muons for shower energies above 20 GeV. The experiments were performed at CERN in the framework of the LAA project.
12346298
THE NATURE OF RED DWARF GALAXIES
Using dark matter halos traced by galaxy groups selected from the Sloan Digital Sky Survey Data Release 4, we find that about 1/4 of the faint galaxies ({sup 0.1} M{sub r} - 5log h> - 17.05, hereafter dwarfs) that are the central galaxies in their own halo are not blue and star forming, as expected in standard models of galaxy formation, but are red. In contrast, this fraction is about 1/2 for dwarf satellite galaxies. Many red dwarf galaxies are physically associated with more massive halos. In total, about {approx}45% of red dwarf galaxies reside in massive halos as satellites, while another {approx}25% have a spatial distribution that is much more concentrated toward their nearest massive halos than other dwarf galaxies. We use mock catalogs to show that the reddest population of nonsatellite dwarf galaxies is distributed within about three times the virial radii of their nearest massive halos. We suggest that this population of dwarf galaxies is hosted by low-mass halos that have passed through their massive neighbors, and that the same environmental effects that cause satellite galaxies to become red are also responsible for the red colors of this population of galaxies. We do not find any significantmore » radial dependence of the population of dwarf galaxies with the highest concentrations, suggesting that the mechanisms operating on these galaxies affect color more than structure. However, over 30% of dwarf galaxies are red and isolated and their origin remains unknown.« less
7047502
Neutron production by cosmic-ray muons at shallow depth
The yield of neutrons produced by cosmic ray muons at a shallow depth of 32 meters of water equivalent has been measured. The Palo Verde neutrino detector, containing 11.3 tons of Gd loaded liquid scintillator and 3.5 tons of acrylic, served as a target. The rate of one and two neutron captures was determined. Modeling the neutron capture efficiency allowed us to deduce the total yield of neutrons, Ytot=(3.60±0.09±0.31)×10^-5 neutrons per muon and g/cm^2. This yield is consistent with previous measurements at similar depths.
119107513
Non-Gaussianity from false vacuum inflation: old curvaton scenario
We calculate the three-point correlation function of the comoving curvature perturbation generated during an inflationary epoch driven by false vacuum energy. We get a novel false vacuum shape bispectrum, which peaks in the equilateral limit. Using this result, we propose a scenario which we call ``old curvaton''. The shape of the resulting bispectrum lies between the local and the false vacuum shapes. In addition we have a large running of the spectral index.