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.
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.
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.
54512122
Bunch length beating in PLS storage ring
During the normal operation period in the Pohang Light Source (PLS) storage ring, the spontaneous bunch length oscillation or beating is generated by the nonlinear effects of the RF noise whose frequency is much lower than the bifurcation frequency. Due to the bunch length beating, we can not supply the uniform intensity beams to users. We have described the observed bunch length beating and its mechanism in the PLS storage ring with a simulation.
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.
120367938
Normalizable Wave Functions for Bound States and Resonances in S -Matrix Theory
Normalizable wave functions are constructed for bound states and resonances from the $S$-matrix quantities. The bound-state wave function is of the Schr\"odinger type. The Schr\"odinger equation does not give normalizable wave functions for resonances. Thus the resonance wave function is of the non-Schr\"odinger type. An $S$-matrix model is constructed to generate the desired resonance wave function. The manner in which this model departs from the conventional Schr\"odinger picture is discussed in detail. This $S$-matrix model is then applied to the $P$-wave two-pion system with a satisfactory numerical result for the $\ensuremath{\rho}$-meson radius.
59372197
BEAM SIMULATION OF SQQ INJECTION SYSTEM IN KIRAMS-30 CYCLOTRON ∗
The injection system of KIRAMS-30 cyclotron consists of a doublegap buncher,an SQQ, and a spiral inflector. Initial beam with 100 mmmrad has been generated by random Gaussian function in the transverse plane and random uniform function in the longitudinal direction. Using the 3D electric and magnetic fields of a buncher, SQQ, inflector, and return-yoke bore, the characteristics of the beam injected into the KIRAMS-30 cyclotron’s central region has been obtained. This paper presents the results of its beam characteristics and parameters of each beam element.
122652147
A quark way to asymptopia
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.