121918158
Recent Progress at KEKB
We summarize the machine operation of KEKB during past one year focusing on progress for this period.
8862999
Recent progress of KEKB
We summarize the machine operation of KEKB during past one year focusing on progress for this period.
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
122032423
Experiences at the KEK B-factory vacuum system
24439340
Direct electron acceleration by stochastic laser fields in the presence of self-generated magnetic fields.
A simple direct acceleration model is proposed, taking into account the stochastic phase disturbance of the coherent driving laser fields. A relativistic single particle simulation shows that plasma electrons are efficiently accelerated far above the ponderomotive energy. The energy and momentum distributions of the accelerated electrons are derived to examine the effects of the self-generated magnetic field on the characteristics of the electron beams. In addition to the beam collimation effect, the magnetic field is found to further enhance the electron acceleration, resulting in the generation of ultrahigh energy electrons.
121897579
Study of timing degradation and light attenuation in long plastic scintillation rods for time-of-flight counters in relativistic heavy ion experiments
Abstract We have studied the timing and light yield characteristics of long and thin scintillator samples of various sizes. Both the light yield and the time resolution degrade exponentially with respect to the distance from one end; the inverse slope parameters for the time resolutions are found to be twice those of the light yield. This is interpreted in terms of a photoelectron statistics picture, which can also explain the observed position dependence of time resolution for time-of-flight counters.
125636037
TEST OF THE DELAY LINE FOR Z READOUT OF THE TOPAZ INNER DRIFT CHAMBER
121673805
Polarimeter System for High-Energy Protons Using Carbon Plate and Liquid Hydrogen
In order to measure recoil proton polarization for the reaction γ+p→π°+p in a wide energy range, a polarimeter system has been constructed using carbon plate and liquid hydrogen as the scatterer. It consists of multi-wire proportional chambers, wire spark chambers, scintillation counter hodoscopes, and scatterers. Carbon plates for lower energy protons and liquid hydrogen for higher-energy protons were used as scatterers. The liquid-hydrogen polarimeter has worked reliably in continuous operation for a long time. The performance of the system in the experiment is described.
119848927
A new type of liquid-3He target system using small mechanical refrigerators
Abstract A new type of liquid- 3 He target has been developed for photoabsorption experiments at intermediate energies. Using the cooling power of liquid 4 He at reduced vapour pressure, 3 He gas is liquefied into a cylindrical target cell of 180 ml and is maintained at 2.0 K during the experiment. Evaporated 4 He gas is evacuated by a rotary pump and returned into the 4 He bath in the cryostat, where two small mechanical refrigerators with cooling capacities of 3 W at 4.3 K and 10 W at 20 K are operated for the purpose of 4 He recondensation. A maintenance-free operation of more than 1000 hours has become possible by adopting the 4 He circulation system.
121021517
A honeycomb sandwich structure vacuum jacket for cryogenic targets
Abstract Cryogenic targets (H 2 , D 2 and 4 He) have been built for use in the study of photonuclear reactions with a π sr spectrometer, TAGX, at the 1.3 GeV Tokyo electron synchrotron. A new type of vacuum jacket, fabricated from plastic honeycomb core and Mylar skins, has been used in the target system for more than 5000 hours. The average radiation thickness and the average density of this jacket are measured to be 3.3 × 10 −3 X 0 and 0.15 g/cm 3 , respectively.
2080857
A Resonance Model of Quasi-Periodic Oscillations of Low-Mass X-Ray Binaries
We try to understand the quasi-periodic oscillations (QPOs) in low-mass neutron-star and black-hole X-ray binaries by a resonance model in warped disks with precession. Our main concern is high-frequency QPOs, hectohertz QPOs, and horizontal-branch QPOs in the z sources and the atoll sources, and the corresponding QPOs in black-hole X-ray binaries. Our resonance model can qualitatively, but systematically, explain these QPOs by regarding hectohertz QPOs as a precession of warp.