51814291
Design study on standing-wave linear accelerator
A compact standing-wave linac has been designed using S-band microwaves for medical and industrial applications. It uses a bi-periodic structure with constant impedance. It consists of a buncher section with three-cells and on-axis coupled cavities with nine-cells. The total length is 740.0 mm including the electron gun. Using SUPERFISH, HFSS and PARMELA codes, it is capable to deliver 4.5 MeV electron beams with pulsed microwaves of 4.8 MW at 2,856 MHz. In this paper, we present the detailed design studies on a compact S-band standing-wave linac.
26940755
Ultra-low noise single-photon detector based on Si avalanche photodiode.
We report operation and characterization of a lab-assembled single-photon detector based on commercial silicon avalanche photodiodes (PerkinElmer C30902SH, C30921SH). Dark count rate as low as 5 Hz was achieved by cooling the photodiodes down to -80 °C. While afterpulsing increased as the photodiode temperature was decreased, total afterpulse probability did not become significant due to detector's relatively long deadtime in a passively-quenched scheme. We measured photon detection efficiency >50% at 806 nm.
56441588
RF noise driven dipole mode parametric resonance
In the Pohang Light Source (PLS) storage ring, we have occasionally experienced the abnormal spontaneous beam. lifetime reduction and strong longitudinal damping. Due to the abnormal beam lifetime reduction, available beam time is reduced substantially. From the recent data analysis of the PLS longitudinal feedback system (LFS) and the streak camera, we have found that the abnormal phenomena can be generated by the RF noise via the dipole mode parametric resonance of the RF phase modulation. We describe the observation of the dipole mode parametric resonance driven by the RF noise and compare it with a simulation result in the PLS storage ring.
67819097
Fast beam-ion instability driven longitudinal damping
In the Pohang Light Source storage ring, we empty 68 buckets of total 468 buckets to cure the conventional ion trapping. However, the fast beam-ion instability is occasionally generated at higher beam current. Immediately after the strong vertical beam shaking due to the fast beam-ion instability, the longitudinal coupled bunch mode instabilities are substantially damped down without any active feedback system. We have described the fast beam-ion instability driven longitudinal damping and its mechanism in the Pohang Light Source storage ring.
54856298
Low frequency longitudinal relaxation oscillation
From the recent data analysis of the longitudinal feedback system and the streak camera, we have found a longitudinal relaxation beam oscillation whose frequency is a multiple of 36 Hz. When the relaxation oscillation is generated, horizontally oscillating wide beams are observed at the diagnostic beamline, and the beam lifetime is fluctuated. The strength of the longitudinal coupled bunch mode instabilities is also modulated sinusoidally. We have described the observed longitudinal relaxation oscillation in the Pohang Light Source storage ring.
122988282
A method of closed orbit correction under constraint conditions
We have developed the correction algorithm of the closed orbit distortion (COD) under the constraint condition where beam positions at particular points are not changed. The new algorithm is based on the modified PSINOM algorithm including the regularization process in order to avoid the inversion problem of the ill-posed response matrices. We have confirmed that the COD is well corrected with no orbit leak in the simulation and is in good agreement with the experiment.
122338380
COSMIC RAY MUONS FROM LOW GALACTIC LATITUDE
Occasional spurious tracks are found on photographs taken during routine observations with the 40-inch heavy-liquid bubble chamber (HLBC) at the Argonne National Laboratory (Roe, Sinclair, and Vander Vilde 1964). These tracks are caused by cosmic ray muons, and are rather similar to streaks caused by meteors on photographs of the sky. The HLBC is located at Ν 41°42'03" latitude and W 87°59'24" longitude, and at an altitude of 227.38 meters above sea level. It has a field of view in the form of a strip 50° wide centered on the north-zenith-south meridian. The strip extends from horizon to horizon. As the earth turns, 87 percent of the celestial sphere passes through the field of view. The product of the cross-sectional capture area of the HLBC times its field of view is 1.7 meter2 steradian. Each picture covers the entire field of view and has a sensitive time of six milliseconds. The chamber is ex-
5119942
Measuring superparticle masses at hadron collider using the transverse mass kink
We present a detailed study of the collider observable mT2 applied for pair-produced superparticles decaying to visible particles and a pair of invisible lightest supersymmetric particles (LSPs). Analytic expressions of the maximum of mT2 over all events (mT2max) are derived. It is noticed that if the decay product of each superparticle involves more than one visible particle, mT2max being a function of the trial LSP mass mχ has a kink structure at mχ = true LSP mass, which can be used to determine the mother superparticle mass and the LSP mass simultaneously. To see how well mT2max can be constructed from collider data, a Monte-Carlo analysis of the gluino mT2 is performed for some superparticle spectra.
668406
Quantization of electromagnetic fields in a circular cylindrical cavity
We present a quantization procedure for the electromagnetic field in a circular cylindrical cavity with perfectly conducting walls, which is based on the decomposition of the field. A new decomposition procedure is proposed; all vector mode functions satisfying the boundary conditions are obtained with the help of this decomposition. After expanding the quantized field in terms of the vector mode functions, it is possible to derive the Hamiltonian for this quantized system.
55217395
DESIGN OF INJECTION AND EXTRACTION BEAMLINES FOR THE ALPHA PROJECT
The ALPHA facility consists of an electron linac and an electron storage ring to provide uniform intense beams for radiation test, and it has a potential to be a future X-Ray source. The ring uses four dipoles from the Cooler Injection Synchrotron (CIS) [1], which was constructed for proton acceleration from 7 MeV to 240 MeV. The circumference of the ALPHA storage ring is 20 m, and its lattice has an adjustible momentum compaction factor by changing the field strength of a pair of gradient damping wigglers [2]. For the proof of working principles, we use a refurbished 20 MeV CLINAC as the injector. The CLINAC will be upgraded to a 50 MeV linac by the end of 2011. Two operation modes (debunching and accumulation modes) [3] are currently planned for the ALPHA facility. For the debunching mode, two magnetic kickers are located at symmetric positions with respect to the Lambertson magnet. When the magnetic kickers are turned at 24 mrad, the closed orbit of the storage ring passes through the Lambertson magnet, and thus the injected beam is extracted in a single pass. In this case, the storage ring can be considered as a big α– magnet for debunching. For the beam accumulation mode, the magnetic kicker’s power supply is designed to have 500 ns decay time (beam revolution time in ring is 66 ns). The closed orbit is gradually moved back to designed orbit during injection so that multi-turn accumulation can be achieved in this way. In this paper, we describe the design concepts of the injection and extraction beamlines to maximize beam transport and to satisfy desired beam properties.
119804529
Model for relativistic bound-state perturbation theory
A model for relativistic bound-state perturbation theory is presented. For the bound-state wave function needed in the perturbation formula, the covariant-harmonic-oscillator wave function is used. As for the perturbing potential, the Feynman propagator corresponding to one-meson exchange is used. This model produces a relativistic derivation of the Breit--Fermi formula, which was recently used by De Rujula, Georgi, and Glashow in their study of hadronic masses. (AIP)