53960485
TECHNIQUES OF SC CAVITY PREPARATION FOR HIGH GRADIENT
High gradient of sc cavities was much improved in the past one decade. Today the accelerating field gradient >30 MV/m is produced routinely in single cell niobium cavities by electropolishing (EP). Recently, such a gradient has been achieved in TTF 9-cavities. In this paper, essential preparation techniques for the high gradient are introduced. Especially, EP is a breakthrough technique and its superiority will be resolved from recent new phenomena. In the last, recent results of multi-cell cavities with both β=1 and medium β are reviewed.
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.
107821728
Characteristics of the results of measurement on 1.3 GHz high gradient superconducting cavities
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.
125432193
State-of-the-art and future prospects in rf superconductivity
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.
121309735
Casimir effect on quark-gluon plasma
We study the Casimir effect on baryon-free quark-gluon plasma confined in a slab region. The energy and entropy densities of confined QGP at the transition temperature are 2∼3 times as large as those of unconfined QGP when the width of the slab is about 1 fm.
119242705
Equation of State for Neutron Stars: Hyperon Mixing in SU(3) Flavor Symmetry
Using various kinds of relativistic mean-field models as well as the quark-meson coupling model, we study in detail the properties of neutron stars. We find that the equation of state in SU(3) flavor symmetry can support a neutron star with mass of $(1.8 \sim 2.1) M_{\odot}$ even if hyperons exist inside the core of a neutron star.
120893951
Effect of the Fermi motion on nuclear structure functions and the EMC effect
The effect of the Fermi motion on nuclear structure function at largeQ2 (the EMC effect) is discussed in detail. We especially study its dependences on the kinematics of interaction, the 4-momentum transferQ2, the nucleon momentum distribution inside nucleus and the nuclear mass number. Moreover the structure function of12C at very largex such asx>1 is evaluated by only the nuclear Fermi motion, and related problems are discussed. We also point out a new dynamical mechanism expected to produce the depletion of valence quark inside nucleus for intermediatex, which does not encroach upon the conventional nuclear physics, and discuss it along the line of scaling hypothesis proposed by Daté et al.
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.