107821728
Characteristics of the results of measurement on 1.3 GHz high gradient superconducting cavities
54939600
PROTON LINAC ACTIVITIES IN JAERI
204924797
Development of Superconducting Linac for the Kek/Jaeri Joint Project
The JAERI/KEK Joint Project for the high-intensity proton accelerator facility has been proposed with a superconducting (SC) linac option from 400 MeV to 600MeV. System design of the SC linac has been carried out based on the equipartitioning concept. The SC linac is planned to use as an injector to a 3GeV rapid cycling synchrotron (RCS) for spallation neutron source after it meets requirement to momentum spread less than +-0.1%. In the R&D work for SC cavities, vertical tests of single-cell and 5 cell cavities were performed. Experiments on multi-cell (5 cell) cavities of b=0.50 and b=0.89 at 2K were carried out with values of maximum electric surface peak fields of 23MV/m and 31MV/m, respectively. A model describing dynamic Lorentz detuning for SC cavities has been developed for pulse mode operation. Validity of the model was confirmed experimentally to simulate the performance.
117369687
COMPACT HE II COOLING SYSTEM FOR SUPERCONDUCTING CAVITIES
This paper describes a compact He II cooling system for superconducting cavities. The cooling system mainly comprises a vacuum vessel, an 80 K liquid nitrogen bath, a 4 K He I bath, a He II bath, an evacuation pump, a single-stage GM cryocooler for the 80 K bath, and a 4 K GM cryocooler for the 4 K He I bath. Superfluid helium is generated and refilled into the He II bath via a heat exchanger and a JT valve by operating the evacuation pump. The refrigeration capacity attained was more than 10 W at 1.8 K. The cooling system was connected with a single-cell cavity cryostat. A superconducting cavity was immersed in superfluid helium. He II was supplied to the cavity vessel from the cooling system and evaporated helium gas was returned to it. High electric fields were obtained during superconducting cavity operations.
59055417
A wideband RF cavity for JHF synchrotrons
Thirty kilo watt "wide band" cavity has been developed for a test cavity of Japanese Hadron Facility (JHF). A new material, "FINEMET" which has very broad band impedance for the RF frequency, high permeability and large shunt impedance is used for the magnetic core of the cavity. An acceleration voltage of 10.4 kV which is larger than the designed value has been obtained. The characteristics of the core are also suitable to generate isolated RF pulses for the barrier bucket. The results for the barrier bucket are described.
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>>
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
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.
13952308
Meson mixing amplitudes in asymmetric nuclear matter
Abstract Using a purely hadronic model, we study the charge-symmetry-breaking ρ – ω , σ – δ , σ – ρ and δ – ω mixing amplitudes in isospin asymmetric nuclear matter. The basic assumption of the model is that the mixing amplitude is generated by nucleon and antinucleon loops and hence driven entirely by the difference between proton and neutron Fermi momenta and the proton–neutron mass difference. We find that the behavior of the mixing amplitude is very complicated in the spacelike region and quite sensitive to the proton fraction of nuclear medium and nuclear density. In particular, in neutron rich nuclei (like Pb) and/or neutron stars the mixing amplitudes become about 10∼100 times as large as those in typical mirror nuclei.
135524505
A New type of RF cavity for high intensity proton synchrotron using high permeability magnetic alloy
A new type of rf accelerating cavity using a high-permeability magnetic alloy (MA) core is proposed for a highintensity hadron synchrotron. The prototype of a single-gap high gradient cavity whose total length is only 40cm is under development and a maximum rf voltage of 20kV has been obtained so far.
118287869
The challenge of the EMC effect
A number of relatively successful quark model descriptions of nuclear matter have recently been developed, based on a mean-field description of non~overlapping nucleons bound by the self-consistent exchange of (1' and w mesons. By combining one such model with a recently developed method of calculating structure functions for the free nucleon, we are able tc. make a microscopic calculation of the structure functions of finite nuclei (in the local density approximation). As well as providing a semi-quantitative understanding of existing data, the model suggests that the impulse approximation, used in many theoretical treatments of nucleon binding, may be quite unreliable.