55857127
PROMISING PERFORMANCE OF THE Nb/Cu CLAD SEAMLESS SUPERCONDUCTING RF CAVITIES
For future large applications of superconducting RF cavities, one has to fabricate cost-effective cavities with high electric-field gradients. We have proposed the fabrication of L-band seamless cavities from Nb/Cu clad material in order to eliminate the electron beam welding process. A feasibility study on the fabrication of 1.3 GHz Nb/Cu Clad single cell cavities from the clad sheet material was done. Three single cell Nb/Cu clad seamless cavities were fabricated by the collaboration with INFNLNL in Italy. In this paper, cold test results of seamless type cavities obtained by the spinning method are presented. The best performance of the cavities was Eacc = 25.1 MV/m with Qo=2.5X10 10 at a temperature of 1.4 K, which is very promising.
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.
118654996
Analytic Formulae for the Off-Center CMB Anisotropy in a General Spherically Symmetric Universe
The local void model has recently attracted considerable attention because it can explain the apparent accelerated expansion of the present universe without introducing dark energy. However, in order to justify this model as an alternative to the standard ΛCDM cosmology, the model should be tested by various observations, such as the CMB temperature anisotropy, besides the distance-redshift relation of SNIa. For this purpose, we derive analytic formulae for the dipole and quadrupole moments of the CMB temperature anisotropy that hold for any spherically symmetric universe model and can be used to compare consequences of such a model with observations of the CMB temperature anisotropy rigorously. We check that our formulae are consistent with the numerical studies previously made for the CMB temperature anisotropy in the void model. We also update the constraints concerning the location of the observers in the void model by applying our analytic dipole formula with the latest WMAP data. Subject Index: 400, 401, 402, 403, 468
55909393
Quarks in finite nuclei
We describe the development of a theoretical description of the structure of finite nuclei based on a relativistic quark model of the structure of the bound nucleons which interact through the (self-consistent) exchange of scalar and vector mesons.
14114906
Clear anti-correlation between luminosity and high energy cutoff in the low/hard state of the black hole candidate GX339-4
We have analyzed the 171 RXTE data sets of the black hole candidate GX 339-4 in the low/hard state during its 1996--2005 outburst. All the broadband spectra were successfully modeled by a simple analytic model, power-law with an exponential cutoff. The obtained energy cutoff($E_{\rm{cut}}$) is distributed over 50--300 keV, and the photon index over 1.4-1.6. We found a clear correlation ($E_{\rm{cut}}$ is proportional to $L^{-0.75 \pm 0.04}$) between luminosity in 2-200 keV (L) and $E_{\rm{cut}}$ when L is larger than 5$\times 10^{37}$ erg $s^{-1}$, while $E_{\rm{cut}}$ is almost constant at 200 keV when L is smaller than 5$\times 10^{37}$ erg $s^{-1}$. This anti-correlation is unchanged by adopting the more physical model of thermal Comptonization by Sunyaev and Titarchuk, although a slightly different relation is obtained as the electron temperature is proportional to $L^{-0.23 \pm 0.02}$. These anti-correlations are qualitatively explained by a picture where the energy flow rate from protons to electrons balance with cooling due to inverse Compton scattering.
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.