55112672
Improvement of cavity performance by electropolishing in the 1.3 GHz Nb superconducting cavities
A steep drop of the cavity quality factor (Q/sub 0/) at high electric field has been observed frequently in chemically-polished and high-pressure-rinsed Saclay cavities, even in the absence of field emission. Three single-cell cavities from Saclay were tested at KEK following electropolishing and high pressure rinsing. This treatment eliminated the steep Q/sub 0/ drop, the quench field increased to an accelerating gradient of more than 30 MV/m with a quality factor above 2/spl times/10/sup 10/. No dependence of the quench field on the niobium RRR was observed between RRR=200 and 320 in electropolished cavities.
125432193
State-of-the-art and future prospects in rf superconductivity
107821728
Characteristics of the results of measurement on 1.3 GHz high gradient superconducting cavities
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>>
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.
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.
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.
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.
119159473
Equation of state for neutron stars in SU(3) flavor symmetry
Using several relativistic mean field models (such as GM1, GM3, NL3, TM1, FSUGold and IU-FSU) as well as the quark-meson coupling model, we calculate the particle fractions, the equation of state, the maximum mass and radius of a neutron star within relativistic Hartree approximation. In determining the couplings of the isoscalar, vector mesons to the octet baryons, we examine the extension of SU(6) spin-flavor symmetry to SU(3) flavor symmetry. Furthermore, we consider the strange ($\sigma^{\ast}$ and $\phi$) mesons, and study how they affect the equation of state. We find that the equation of state in SU(3) symmetry can sustain a neutron star with mass of $(1.8 \sim 2.1) M_{\odot}$ even if hyperons exist inside the core. In addition, the strange vector ($\phi$) meson and the variation of baryon structure in matter also play important roles in supporting a massive neutron star.
17428438
Stability analysis using EMTP for JHF systems
The Stability analysis for JHF (Japan Hadron Facility) synchrotron has been performed by using a code for the stability analysis, EMTP(Electronic Magnetic Transient Program). We have examined two cases; a MA (Magnetic Alloy) loaded cavity and ordinary ferrite one. The MA loaded cavity has low Q value and does not require the tuning system for a frequency sweep. The result shows that the MA loaded cavity has larger stable area than the ordinary ferrite loaded cavity. The JHF RF system using the MA loaded cavity can be operated stably. Another simulation has been performed with a code, MC(Micro Cap). The results were consistent with the EMTP analysis.
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.