137483084
Magnetization measurement of niobium for superconducting cavity material evaluation
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.
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.
209358824
THE CHARACTERISTICS OF DIFFERENT MAGNETIC MATERIAL FOR RF CAVITY UNDER PERPENDICULAR MAGNETIZATION
In recent years, a technology of perpendicular magnetization for ferrite loaded cavities is developed. Yttrium Garnet ferrite is generally used for that case with higher frequency range from 30-60 MHz. An attempt is taken to measure the characteristics of different new materials such as FINEMET,METGLAS and NiZn ferrite under the condition of perpendicular magnetization. The results are summarized in this paper.
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.
119441340
Relationship between the Quark-Meson Coupling Model and Quantum Hadrodynamics
Using the quark-meson coupling (QMC) model, we study nuclear matter from the point of view of quark degrees of freedom. Carrying out a re-definition of the scalar field in matter, we transform the QMC into a QHD-type model with a non-linear scalar potential. The potentials obtained from the QMC are compared with those of relativistic mean-field models. Since at present, rigorous studies of quantum chromodynamics (QCD) are limited to matter systems with high temperature and zero baryon density, it is important to build models that help to bridge the discrepancy between nuclear phenomenology and QCD. We have proposed a relativistic quark model for nuclear matter and finite nuclei that consists of non-overlapping nucleon bags bound by the self-consistent exchange of isoscalar, scalar (σ) and vector (ω) mesons in the mean-field approximation (MFA). This model is called the quark-meson coupling (QMC) model. 1) It has also been found in recent theoretical studies that various properties of finite nuclei can be described very well by relativistic mean-field (RMF) models, i.e., quantum hadrodynamics (QHD). 2) In this Letter, we consider the relationship between the QMC and the QHD and study howthe internal structure of the nucleon plays a role in effective nuclear models. In our previous works, 1) the MIT bag model has been used to describe the quark structure of the nucleon. Because the confined quarks interact with the scalar field σ in matter, the effective nucleon mass M � N in the QMC is given by a function of σ through the quark model of the nucleon. (Although the quarks also interact with the ω meson, it has no effect on the nucleon structure, except for a shift in the nucleon energy. 1) ) The (relativistic) constituent quark model (CQM) is an alternative model for the nucleon. Recently, Shen and Toki 3) have proposed a newversion of the QMC — the quark mean-field (QMF) model, in which the CQM is used to describe the nucleon. In the present study, in addition to the bag model (BM), we use the relativistic CQM with confining potentials V (r) of a square well (SW) and harmonic oscillator (HO) type to see the dependence of the matter properties on the quark model. It is assumed that the light (u or d) quark mass mq is 300 MeV in the CQM and 0 MeV in the BM. Furthermore, we introduce a Lorentz vector-type confining potential that is proportional to γ0, in addition to one of the scalar type, as
122485732
Axal Polarizability in the System of Two Chiral Nucleon Bags
17047743
Charge Symmetry Violation in Nuclear Physics
The study of charge symmetry violation in nuclear physics is a potentially enormous subject. Through a few topical examples we aim to show that it is not a subject of peripheral interest but rather goes to the heart of our understanding of hadronic systems.