55567556
Single crystal niobium development
Tokyo Denkai, KEK and TKX have developed a new niobium ingot slicing technique that allows slicing 150 pieces of large grain niobium discs in two days. Tokyo Denkai installed the slicing machine in December 2009. We inspected the sliced discs by the ultrasonic imaging and understood niobium crystal growth mechanism in Electron Beam Melting, which gave us an idea to make a single crystal niobium ingot. This paper describes the new high-speed production process of niobium discs, an idea of single crystal niobium ingot production and its pilot study result.
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.
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.
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.
122693286
Nuclear effects in the semi-inclusive cross section of high energy neutrino-nucleus interactions
Abstract In high energy neutrino scattering off nuclei, the cross sections σ ( x ) show experimentally a remarkable dependence on the presence or the absence of slow recoil protons. It is found that the effect is explained by the kinematics of slow protons directly produced by diquark fragmentation and the rescattering of leptoproduced nucleons.
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.
15022310
A Deformable Bag Model of Hadrons. I
As a generalization of the MIT spherical bag model, we construct the spheroidal bag model of hadron with an arbitrary eccentricity. This generalization is made by slightly modifying the MIT linear boundary condition: The linear boundary condition is examined in detail. Our model always satisfies two necessary requirements of the MIT bag model --i. e., n-j=O, no quark colour flux leaves the bag, and ijq =0, the scalar density of quark should vanish on the bag surface-- and it reduces to the MIT spherical bag model in the limit of zero-eccentricity. Lagrangian formalism of our model is briefly described. The eigenfrequencies of a single massless quark confined in this spheroidal bag are numer­ ically calculated. We obtain the level-splitting of the excited quark orbits, which is just analogous to the well-known Nilsson's splitting of single particle orbits in deformed nuclei. By using the numerical results of the lowest orbit, the effect of the bag-deformation on the mass of low-lying hadrons is estimated. It is found that, although the spherical bag is stable, tbe quark bag is extremely soft against the quadrupole deformation. Brief discussions are added on the mechanisms which make the spherical bag more stable.
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.
123001860
NEW APPROACH FOR FEW-BODY SYSTEMS BASED ON JACOBI-COORDINATE BASIS ANTI-SYMMETRIZED MOLECULAR DYNAMICS FROM ATOMS TO QUARK-SYSTEMS
Proposed a new method which is suitable for systematic calculations in few-body systems, we call it the Jacobi-coordinate-basis antisymmetrized molecular dynamics (JAMD). We show good abilities of the method by demonstrating some examples in atoms, molecules, nuclei, and baryons systems.