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.
120870231
L-band superconducting cavities at KEK for TESLA
An attractive future application of superconducting cavities is a TeV energy superconducting linear collider (TESLA). The substantial merits of TESLA compared to a normal conducting linear collider are to loosening of alignment tolerance and less wake field due to the lower frequency (1.3 GHz). The final focus also is easier to obtain by having the electron/positron population in bunches. TESLA demands upgrading field gradients to over 25 MV/m. KEK has been carrying out R&D on 1.3 GHz niobium superconducting cavities since 1990. So far, seven single cell cavities and two 9-cell cavities have been fabricated and tested. In parallel, input coupler design and niobium material studies are being conducted. This paper reports the present status of KEK's efforts for TESLA.<<ETX>>
210986995
Cavity Performances in the 1.3 GHz Saclay / KEK Nb Cavities
Three single-cell cavities, which had been tested at KEK, were sent t o Saclay in order to compare the cavity performance. Two cavities made f r om Japanese niobium materials were fabricated and tested at Saclay. These cavities were prepared by the Saclay's standard surface treatment. Quench field, quench location and RRR in the cavity were measured in each cav i ty test. Their changes due to additional surface removal and heat t reatment were investigated. Qo degradation without electrons at high fields was observed in every cavity test.
135200451
Beam loading in JHF 50 GeV proton synchrotron
107821728
Characteristics of the results of measurement on 1.3 GHz high gradient superconducting cavities
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.
17407776
The quark-meson coupling model
We review the quark-meson coupling model, in which the quark degrees of freedom are explicitly involved to describe the properties of not only nuclear matter but also finite nuclei. Then, we present the electric and magnetic form factors for the proton bound in specific orbits for several closed-shell nuclei.
124728025
A microscopic understanding of the structure functions of finite nuclei
Abstract A number of relatively successful quark model descriptions of nuclear matter have recently been developed, based on a mean-field description of non-overlapping nucleon bags bound by the self-consistent exchange of scalar (σ) and vector (ω) mesons. The meson fields modify the internal quark motion in the nucleon bag in medium and this induces a saturation mechanism for nuclear matter. The model gives a nuclear compressibility around 220 MeV and provides a rather satisfactory interpretation of nuclear matter properties. Furthermore, it has recently been shown that the twist-2 valence quark distributions of the free nucleon calculated in the MIT bag model are in reasonable agreement with world data. By using a local density approximation we combine these developments to microscopically investigate the structure functions of finite nuclei. The effect of nuclear shadowing and antishadowing is taken into account phenomenologically. The model can quantitatively reproduce the existing experimental data - the so-called European Muon Collaboration (EMC) effect. We show that the quark degrees of freedom in nuclei and the final state interaction between the debris of the struck nucleon and the residual nucleus both play important roles in the nuclear structure functions. Thus the conventional treatment based on nucleon binding within the impulse approximation is quantitatively unreliable. We also study the effects of the self-coupling terms of the σ field and nucleon-nucleon correlations on some nuclear matter properties and the nuclear structure functions.
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.
118625081
Effects of Fock term, tensor coupling and baryon structure variation on a neutron star
Abstract The equation of state for neutron matter is calculated within relativistic Hartree–Fock approximation. The tensor couplings of vector mesons to baryons are included, and the change of baryon internal structure in matter is also considered using the quark–meson coupling model. We obtain the maximum neutron-star mass of ∼ 2.0 M ⊙ , which is consistent with the recently observed, precise mass, 1.97 ± 0.04 M ⊙ . The Fock contribution is very important and, in particular, the inclusion of tensor coupling is vital to obtain such large mass. The baryon structure variation in matter also enhances the mass of a neutron star.
118292595
Quarks in nuclear medium
Using the quark-meson coupling (QMC) model we study nuclear matter from the point of view of quark degrees of freedom. As the nucleon model we adopt the MIT bag model and the relativistic constituent quark model, where a square well and harmonic oscillator potentials are used to confine the quarks. We introduce the Lorentz-vector type confining potential as well as the Lorentz-scalar type one in order to examine how the vector confining potential contributes to the properties of the nucleon and nuclear matter. Next, we perform a re-definition of the scalar field in matter and transform the QMC model to a QHD-type model with a non-linear scalar potential. The result obtained from QMC is then compared with the potentials which are determined so as to fit various properties of finite nuclei and nuclear matter in relativistic mean-field models. The QMC model provides the parameters $\kappa \sim 20 - 40$ (fm$^{-1}$) and $\lambda \sim 80 - 400$ for the standard, non-linear scalar potential. We discuss a relationship between the QMC and QHD-type models in detail.