150367726
THERMAL QUENCH PHENOMENA ON THE 1 . 3 GHZ HIGH GRADIENT SUPERCONDUCTING CAVITIES
The temperature dependence of the quench field was investigated between 1.8 K and 4.2 K using the 1.3 GHz single-cell niobium cavities. The location of the thermal quench was identified by the carbon thermometries, and the inner surface of the heating region was carefully inspected. In the cavities having high quench fields, a sharp drop of the quench field was clearly observed just at λ -point. The temperature rise on the seam of electron beam welding was observed in the cavities having low quench fields. A Q-switch phenomenon was observed in one cavity.
125432193
State-of-the-art and future prospects in rf superconductivity
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.
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.
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.
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.
14514129
BEAM LOADING EFFECTS IN JHF SYNCHROTRON
Beam loading effects on the rf system of JHF proton synchrotrons have been investigated by both computer simulation and experiment using a low energy electron beam. From the simulation results, it is found that even under the heavy beam loading the beam acceleration becomes stable if applying the beam loading compensation, and the compensation experiment is succeeded on proto-type Magnetic Alloy loaded cavity.
18878762
Nucleon structure effect on the longitudinal response function
Using the quark-meson coupling model, we study the longitudinal response function for quasielastic electron scattering from nuclear matter within relativistic RPA. In QMC the coupling constant between the scalar meson and the nucleon is expected to decrease with increasing nuclear density. Furthermore, since the electromagnetic form factors of the in-medium nucleon are modified at the same time, the longitudinal response function and the Coulomb sum are reduced by a total of about 20% in comparison with the Hartree contribution.
55610926
EVALUATION OF MAGNETIC ALLOYS FOR JHF RF CAVITY
A new type of rf accelerating cavity using a high permeability magnetic alloy (MA) has been developed for the high intensity JHF proton synchrotrons. Compared with ordinary ferrites, the MA cores are very stable at high rf magnetic field and thus very high accelerating gradient (=accelerating voltage per cavity length) is available. We have measured several magnetic alloys in order to find a proper material for the cavity. In this paper, the test results are summarized and the evaluation of these materials is presented.
122192107
Formation Zone and Correlation between Mesons and Recoiled Protons in Deep Inelastic Neutrino-Nucleus Interactions
In a recent experiment of deep inelastic neutrino-nucleus scattering, it was observed that there is almost no correlation between produced mesons and slow protons when the multiplicity of the former is small while a positive correlation emerges as it becomes larger. We show that this is a direct manifestation of nonvanishing formation time. The correlation is calculated using an appropriate parametrization of semi-inclusive quark fragmentation functions. Comparison with data indicates that the proper formation time is 0.4-0.6 fm/c
11540608
The Nolen-Schiffer anomaly and isospin symmetry breaking in nuclear matter
Abstract The quark-meson coupling model which we have developed previously is extended to incorporate the δ meson. It is then used to study the Nolen-Schiffer anomaly and isospin symmetry breaking in nuclear matter. We find that, in combination with the u - d mass difference, the difference between quark scalar densities in protons and neutrons generates an effective neutron-proton mass difference of the right magnitude. Finally we find that isospin symmetry breaking in the quark condensates can be directly related to the δ meson field.