120566869
The TOPAZ inner drift chamber
We have constructed a cylindrical drift chamber with anode and cathode delay-line readouts, which is the innermost tracking device of the TOPAZ detector. This inner drift chamber (IDC) is used for the tracking of charged particles in both rφ and rz planes. Fast track-finding logics have been developed for the event triggering. We describe the design, the construction and the performances of the IDC in the first beam run.
125636037
TEST OF THE DELAY LINE FOR Z READOUT OF THE TOPAZ INNER DRIFT CHAMBER
123873319
Experimental observations of the ion-related coupled bunch instability in a bunch train in TRISTAN AR
An experiment was carried out in TRISTAN AR for the search of the fast beam-ion instability (FBII). A train of 100 bunches with 2 ns spacing was stored with the help of the transverse bunch feedback system. The nitrogen gas was intentionally leaked into the inside of the vacuum duct to enhance the ion effect. The oscillation patterns were recorded by the beam position monitor system which is capable of storing the transverse position of every bunch up to 1600 turns. The spectra of the bunch oscillations were also measured by a spectrum analyzer. This paper describes the results of the experiment and also discusses the possible explanation of them in terms of the FBII.
523124
Development of a 56 mm aperture superconducting dipole model magnet for LHC
A 56 mm single aperture superconducting dipole model magnet, which is one of the frameworks of the LHC collaboration between KEK and CERN, has been developed. A central field of 8.65 T is provided at a load line ratio of 90% with a 5 block coil wound with NbTi superconducting cables. The magnet has a straight section of 0.8 m and a total length of 1.2 m. The distinctive features of the magnet are a magnetically symmetrical configuration being applicable to the twin aperture magnet and mechanical consideration sharing the magnetic forces with a high manganese steel collar and a horizontally split iron yoke. The magnet showed almost no training at 4.4 K. The first quench current at 1.8 K was 91% of the short sample I/sub c/ and the magnet reached a central magnetic field of 8.8 T. Finally it could be excited with the current of more than 99% of the short sample limit which corresponds to a central field of 9.63 T.
116197080
Test results of TRISTAN insertion quadrupole magnet in superfluid Helium
125921586
Experiment on the fast beam-ion instability at the TRISTAN AR
86865953
Present Status of KEKB Vacuum System
The commissioning of KEKB (KEK B-factory) started in December 1998. The vacuum system has been working almost satisfactorily. The photon stimulated gas desorption coefficient of copper beam chamber is decreasing steadily and reached to about 2 - 4 × 10 -6
113855195
Studies of Fabrication Procedure of 9-cell SRF Cavity for ILC Mass-production at KEK.
We had been constructing a new facility for the fabrication of superconducting RF cavity at KEK from 2009 to 2011. In the facility, we have installed a deepdrawing machine, a half-cup trimming machine, an electron-beam welding machine, and a chemical etching room in one place. We started the studies on the fabrication of 9-cell cavity for International Linear Collier (ILC) using this facility. The studies are focusing on the cost reduction with keeping high performance of cavity, and the goal is the establishment of mass-production procedure for ILC. We already finished the fabrication of two 9-cell cavities in this facility. This article reports the current status of the studies.
120683961
Narrow Spacing Drift Chamber
Linearity and efficiency of a 3-mm spacing drift chamber was examined with an electron beam. A spatial coordinate is measurable with an accuracy of 0.2 mm.
96731395
Graphitization of inner surface of copper beam duct of KEKB positron ring
In order to evaluate the best technique to reduce electron cloud instability, we measured the electron cloud density in copper ducts coated with titanium nitride and non-evaporable getter used in the KEK B-factory (KEKB) positron ring. In this study, we developed a new system for the graphitization of copper beam ducts. The graphitization of a copper surface by intense electron bombardment resulted in the reduction in the secondary electron yield (SEY) to 1.0 in a laboratory experiment and to 1.1 in a real beam duct. The electron cloud density in the graphitized duct is 30% lower than that in an uncoated copper duct. Thus, it has been confirmed that the graphitization of a beam duct leads to a reduction in the electron cloud density in the duct.
119688485
EVIDENCE FOR THE EXISTENCE OF A Z