122734835
Simultaneous measurements of absolute numbers of electrons and scintillation photons produced by 5.49 MeV alpha particles in rare gases
The absolute numbers of scintillation photons and electrons produced by 5.49 MeV alpha particles were measured simultaneously in argon, krypton and xenon in the gas pressure range from 1.01/spl times/10/sup 5/ Pa to 1.01/spl times/10/sup 6/ Pa. The ratio of the number of excited atoms to the number of electron-ion pairs is an important quantity for understanding the energy pathway of the absorbed radiation energy and was found to be 0.52, 0.55, and 0.60 in argon, krypton and xenon, respectively. The ratios were determined by measuring the number of scintillation photons originating from the excited atoms and the number of electrons. The value of W/sub s/, which is defined as the average energy to produce one photon, in the case that all of the electron-ion pairs recombine was estimated to be 17.5, 15.4, and 13.0 eV in argon, krypton and xenon, respectively. From the relation between the numbers of electrons escaping from the recombination with ions and the numbers of scintillation photons, it is confirmed experimentally that one scintillation photon is emitted from one recombination process. This means that an excited molecule caused by three-body collisions is not de-excited without emitting a scintillation photon in the vacuum ultraviolet region.
137182571
A New Material Evaluation Method on Niobium by Magnetization Measurement
As a new evaluation method for the material defects or surface contamination of niobium, we have tried magnetization measurement using very small niobium samples. We could see the hyst~resis curve varied depending on the sample's history. This method has a high sensitivity. Th~ m.f1uence ?y surface treatments was observed on the hysteresis curve; annealing, chemical p~hshmg, Q-dlsease due to hydrogen etc .. In this paper we will report several study results by this method.
125432193
State-of-the-art and future prospects in rf superconductivity
94312812
High Field Studies on L-band Superconducting Cavities at KEK
Several 1.3 GHz single-cell and nine-cell niobium cavities were fabricated to attain a higher maximum accelerating gradient and to understand the phenomena limiting it. Vertical cold tests at {approx}1.8 K for the 4 single-cell cavities prepared by various surface treatments have been conducted 15 times. In eight of the tests, maximum accelerating gradients (E{sub acc}, max) of more than 14 MV/m were obtained with no field emission. Furthermore, E{sub acc}, max values of higher than 20 MV/m with a high Q{sub 0} value of {approx}10{sup 10} were achieved repeatedly after heat treatment at 1400 degrees C. Once quenching was observed at E{sub acc}, max (14 {approx} 20 MV/m), however, a common phenomenon resulting in Q{sub 0}-deterioration occurred in every test. The cavity performances and the phenomenon at high fields are reported in this paper.
6846765
HIGHER HARMONICS BEAM LOADING COMPENSATION FOR A BROAD BAND MA-LOADED RF CAVITY
A broad band RF cavity loaded with magnetic alloy cores has been developed for the Japanese Hadron Facility synchrotrons. Its Q-value can be chosen at between 0.5 and 5. To reduce transient beam loading effects, a small Qvalue (< 3) is preferable to shorten the transient period. However, the circulating beam current of up to 7 A will induce a spurious voltage at the accelerating gap, which deforms the gap voltage due to higher harmonics components, if the Q-value is less than 3. The resulting RFbucket distortion may cause the beam loss. Therefore we have designed a beam loading compensation system to suppress the higher harmonics components.
55249742
Activities on Superconducting Cavities at TOSHIBA
Abstructs R&D activities on superconducting cavities at TOSHIBA are presented. Two L-band single-cell niobium cavities and an L-band three-cell structure were fabricated in our company and measured at KEK. The maximum field gradient of Eacc,max>30MV/m in both single-cell cavities and Eacc,max =18MV/m in the three-cell structure were attained respectively. An optimization study on the annealing temperature for the hydrogen Q-disease is reported. R&D of hydroforming to fabricate seamless cavities is also presented.
119821537
The in-medium effects on the neutrino reaction in dense matter
The nucleon form factors in free space are usually thought to be modified when a nucleon is bound in a nucleus or immersed in a nuclear medium. We investigated effects of the density-dependent axial and weak-vector form factors on the electro-neutrino (νe) and anti-electro-neutrino (νe) reactions with incident energy Ev ≤ 80 MeV via neutral current (NC) and charged current (CC) for a nucleon in a nuclear medium or 12C. For the density-dependent form factors, we exploited the quark-meson-coupling (QMC) model, and apply them to the νe and νe induced reactions by NC and CC. In CC reaction, about 5 % decrease of the electro neutrino (νe) reaction cross section on the nucleon is shown to be occurred in normal density, ρ = ρ0∼0.15fm−3, and also about 5 % reduction of total νe cross section on 12C is obtained by the modification of the weak form factors for bound nucleons. Density effects for both cases are relatively small, but they are as large as the effect by the Coulomb distortion of outgoing leptons in t...
14114906
Clear anti-correlation between luminosity and high energy cutoff in the low/hard state of the black hole candidate GX339-4
We have analyzed the 171 RXTE data sets of the black hole candidate GX 339-4 in the low/hard state during its 1996--2005 outburst. All the broadband spectra were successfully modeled by a simple analytic model, power-law with an exponential cutoff. The obtained energy cutoff($E_{\rm{cut}}$) is distributed over 50--300 keV, and the photon index over 1.4-1.6. We found a clear correlation ($E_{\rm{cut}}$ is proportional to $L^{-0.75 \pm 0.04}$) between luminosity in 2-200 keV (L) and $E_{\rm{cut}}$ when L is larger than 5$\times 10^{37}$ erg $s^{-1}$, while $E_{\rm{cut}}$ is almost constant at 200 keV when L is smaller than 5$\times 10^{37}$ erg $s^{-1}$. This anti-correlation is unchanged by adopting the more physical model of thermal Comptonization by Sunyaev and Titarchuk, although a slightly different relation is obtained as the electron temperature is proportional to $L^{-0.23 \pm 0.02}$. These anti-correlations are qualitatively explained by a picture where the energy flow rate from protons to electrons balance with cooling due to inverse Compton scattering.
122693286
Nuclear effects in the semi-inclusive cross section of high energy neutrino-nucleus interactions
Abstract In high energy neutrino scattering off nuclei, the cross sections σ ( x ) show experimentally a remarkable dependence on the presence or the absence of slow recoil protons. It is found that the effect is explained by the kinematics of slow protons directly produced by diquark fragmentation and the rescattering of leptoproduced nucleons.
118377380
Neutron Star Properties in the Chiral Quark–Meson Coupling Model
We study the properties of neutron stars using the chiral quark–meson coupling model, in which the quark–quark hyperfine interaction due to the exchanges of gluon and pion based on chiral symmetry is considered. We also examine the effects of hyperons and Δ-isobars in a neutron star. Extending the SU(6) spin-flavor symmetry to more general SU(3) flavor symmetry in the vector–meson couplings to baryons, the maximum mass of neutron star can reach the recently observed massive pulsar mass, $${1.97 \pm 0.04 M_{\odot}}$$. In this calculation, Λ and Ξ are generated in a neutron star, while Σ and Δ-isobars do not appear.
119178074
Fermi matrix element with isospin breaking
Abstract Prompted by the level of accuracy now being achieved in tests of the unitarity of the CKM matrix, we consider the possible modification of the Fermi matrix element for the β -decay of a neutron, including possible in-medium and isospin violating corrections. While the nuclear modifications lead to very small corrections once the Behrends–Sirlin–Ademollo–Gatto theorem is respected, the effect of the u − d mass difference on the conclusion concerning V u d is no longer insignificant. Indeed, we suggest that the correction to the value of | V u d | 2 + | V u s | 2 + | V u b | 2 is at the level of 10 − 4 .