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.
43997367
New generation digital longitudinal feedback system for Duke FEL and HIγS facilities
To cure harmful longitudinal coupled-bunch mode beam instabilities during high-current and multi-bunch beam operations at the Duke free electron laser (FEL) and high intensity gamma-ray source (HIgammaS) facilities, we have been developing a new generation digital bunch-by-bunch longitudinal feedback (LFB) system which is based on an Integrated gigasample processor (iGp-64F). In this paper, we describe the new generation digital longitudinal feedback system for the Duke FEL and HIgammaS facilities.
11157984
Growth time of the longitudinal coupled bunch mode beam instability at the Duke FEL facility
To determine the required power of an amplifier for the longitudinal feedback (LFB) system, the growth time of the strongest longitudinal coupled bunch mode instability (CBMI) in the Duke storage ring should be measured in advance. In 2005, we measured strength of the strongest longitudinal beam instability in the Duke storage ring with four and eight symmetrically filled buckets. By analyzing measured data, the growth time of the strongest dipole mode of the longitudinal CBMI in the Duke storage ring can be estimated. At a beam energy of 274 MeV, the growth time is about 0.365 ms for a total stored beam current of 160 mA. From the measured growth time, we estimated the required power of the amplifier for the LFB system. To damp all harmful longitudinal CBMIs with an energy deviation of 0.1 % (rms) within its growth time of 0.365 ms, we have to supply about HOW (rms) to an LFB kicker whose a central frequency is 937.3875 MHz. In this paper, we describe the growth time of the longitudinal CBMI at the Duke storage ring and the estimation of the required power for the LFB system to damp all CBMIs within 0.365 ms.
119689322
Internal Space-time Symmetries according to Einstein, Wigner, Dirac, and Feynman
When Einstein formulated his special relativity in 1905, he established the law of Lorentz transformations for point particles. It is now known that particles have internal space-time structures. Particles, such as photons and electrons, have spin variables. Protons and other hadrons are regarded as bound states of more fundamental particles called quarks which have their internal variables. It is still one of the most outstanding problems whether these internal spacetime variables are transformed according to Einstein’s law of Lorentz transformations. It is noted that Wigner, Dirac, and Feynman made important contributions to this problem. By integrating their efforts, it is then shown possible to construct a picture of the internal spacetime symmetry consistent with Einstein’s Lorentz covariance. email: yskim@physics.umd.edu email: marilyne.noz@gmail.com 1
23657326
AC Power Supply for Wobbler Magnet of the MC-50 Cyclotron
A wobbler magnet and an AC power supply for the MC-50 cyclotron (k=50) at Korea Institute of Radiological and Medical Sciences (KIRAMS) were designed and constructed to increase the area of beam irradiation. The power supply has two independently operating channels for the vertical and horizontal coils of the wobbler magnet. The frequency of the AC power supply for both coils is programmable from 1 to 20 Hz in a step of 1 Hz, and the maximum output current is 12 A rms. With the wobbler magnet, the uniform irradiation area of the proton beam increased ∼ 4 times larger than the one without the magnet, and various properties of the magnet and power supply system indicate that the system is well suited for many ion beam experiments.
121660054
Present status of the Pohang Light Source
The Pohang Light Source (PLS) Project is now in its final year of the construction phase. The machine consists of a full energy (2 GeV) linear accelerator injector, a storage ring with a 12‐period TBA structure, and 32 eventual beamlines from insertion devices and bending magnets. The commissioning of the injector linac was completed in June 1994. The overall commissioning of the PLS is expected to be completed by the end of 1994. The facility will provide high brightness, tunable radiation in a wide spectral range up to 30 keV of photon energy, and will serve national and international users starting in mid‐1995.
119099546
Quark number susceptibility with finite chemical potential in holographic QCD
We study the quark number susceptibility in holographic QCD with a finite chemical potential or under an external magnetic field at finite temperature. We first consider the quark number susceptibility with the chemical potential. We observe that approaching Tc from high temperature regime, χq/T2 develops a peak as we increase the chemical potential, which confirms recent lattice QCD results. We discuss this behavior in connection with the existence of the critical end point in the QCD phase diagram. We also consider the quark number susceptibility under the external magnetic field. We predict that the quark number susceptibility exhibits a blow-up behavior at low temperature as we raise the value of the magnetic field. We finally spell out some limitations of our study.
122652147
A quark way to asymptopia