116378524
Experience with a zero impedance vacuum flange at He super-leak temperatures for the ILC
A new zero impedance vacuum flange has been developed for the accelerators in the ILC. We choose a unisex type with a 90-degree sharp edge forming the vacuum seal and giving a continuous smooth connection providing zero impedance as seen from the bunched beam and rf power. The variation in flatness between the flange and gasket along the inside wall is less than 50-μm. An He super-fluid leak rate of below 10 [atm/cm3/sec] was measured using the "build up method", i.e. the test measured the pressure built up over a three hour period while held at below 2-oK. We tested the several potential gasket materials: OFC (Oxygen Free Copper) alone, Nb (niobium) plated with 10-μm of OFC, and bulk Nb, all at temperatures below 2-oK. The same unisex type flange has also been used for the input power coupler for coaxial waveguide and for a cold side demountable type rf window. A long test run was carried out at an rf power of 1-MW, and a 1.5-msec pulse width, 5-pps repetition rate. Further, suitability was confirmed by operation at a maximum power of up to 2-MW, and a 1.5-msec pulse width, 3-pps repetition rate for 6 hours.
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.
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.
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.
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.
125432193
State-of-the-art and future prospects in rf superconductivity
119162077
The quark-meson coupling model and chiral symmetry
We extend the quark‐meson coupling (QMC) model to incorporate chiral symmetry. The relationship between the QMC model and chiral perturbation theory is also discussed. The nuclear central potential is modified by the effect of internal structure of the nucleon.
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.
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.
122485732
Axal Polarizability in the System of Two Chiral Nucleon Bags
16595187
Luminosity Dependence of the Electron Temperature in the Bright Hard State of the Black Hole Candidate GX 339–4
We have analyzed 200 Rossi X-ray Timing Explorer observations of the black hole candidate GX 339� 4, all from bright hard state periods between 1996 and 2005. The purpose of our study is to investigate the radiation mechanisms in the hard state of GX 339� 4. The broadband 3–200 keV spectra were successfully modeled by as imple analytic model, power-law with an exponential cut-off modified with a smeared edge. The obtained energy cut-off (Ecut )w as distributed over 50–200 keV, and the photon index over 1.4–1.7. We found a clear anti-correlation (Ecut / L � 0:70˙0:06 )b etween the X-ray luminosity (L )i n2–200 keV and Ecut ,w henL is larger than 7 � 10 37 erg s � 1 (assuming a distance of 8 kpc), while Ecut is roughly constant at around 200 keV when L is smaller than 7 � 10 37 erg s � 1 .T his anti-correlation remained unchanged by adopting a more physical thermal Comptonization model, which resulted in an anti-correlation that can be expressed as kTe / L � 0:24˙0:06 .T hese anti-correlations can be quantitatively explained by a picture in which the energy-flow rate from protons to electrons balances with inverse Compton cooling.