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ABSTRACT: Pohang Accelerator Laboratory has prepared to SRF 3<sup>rd</sup> harmonic cavity to increase beam lifetime and to damp orbit instability by lengthening electron bunch in PLS. The SRF cavity was developed and its vertical test was done already with success. Higher order modes were analyzed to optimize its performance in beam orbit. Most of them are not effective to electron beam, while the others have possibility to impact orbit stability. These harmful HOMs can be removed by HOM absorber installed in beam pipe.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: The sequence control system of 1-MW CW klystron for the PEFP (Proton Engineering Frontier Project) has been developed in order to drive the 1-MW klystron amplifier. The system is able to control several power supplies and many environment conditions. The system was developed using the simulator which was made similar to real conditions. We had to solve problems to manage well in real site experiments. The hardware of sequence control and the interlock system are based on the Allen-Bradley's SLC500 Programmable Logic Controller (PLC). Also the system can be controlled by a touch screen at local mode or Ethernet network with high level HMI at remote mode
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: The timing system for the Pohang Light Source (PLS) storage ring consists of a trigger synchronize module, a fine delay module, a repetition rate pulse generator module, and so on. All the timing modules are installed in the VXI crate and controlled by the 32 bit microprocessors with the host computer. Although the timing system has been operated without any serious problems since commissioning in 1994, there were some minor troubles, and the performances were not so excellent. Therefore, upgrade of the timing system is progressing with a synchronous universal counter and other commercial modules of NIM type for increasing of a reliability, easy maintenance, low timing jitters, and all types of beam filling pattern.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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I.H. Yu,
D.T. Kim,
J.S. Yang,
H.S. Kang,
W.H. Hwang, M.H. Chun,
K.M. Ha,
Y.J. Han,
S.C. Kim,
S.H. Nam,
J.M. Han,
H.J. Kwon,
Y.S. Cho,
K.T. Seol
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ABSTRACT: At the 100 MeV proton linac of the KOMAC (Korea Multi-Purpose Accelerator Complex), the low level RF system provides field control for the entire KOMAC proton linac, including an RFQ and a DTL1 at 350 MHz as well as 7 DTL cavities at 700 MHz. In addition to field control, it provides cavity resonance control, and incorporates the personnel and machine protection functions. An accelerator electric field stability of ± 1% in amplitude and ± 1° in phase is required for the RF system. In order to accomplish these requirements, a digital feedback control technique is adopted for flexibility of the feedback and feed forward algorithm implementation. In this paper, the detailed description of the low level RF system is given.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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E.-S. Kim, M.-H. Chun,
J.-Y. Huang,
U.-H. Huang,
H.-S. Kang,
D.-T. Kim,
S.-H. Nam,
H.-J. Park,
J.-S. Yang,
M. Yoon,
I.-H. Yu
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ABSTRACT: We present investigations on beam instabilities that have been
observed at 2.0 GeV and 2.5 GeV in the PLS storage ring. Stored beam
currents of 2.0 GeV in the ring has been mainly limited by coupled-bunch
instabilities. We have investigated dependences of the coupled-bunch
instabilities on betatron tune, chromaticity and RF cavity temperatures
at 2.0 GeV. 450 mA beam could be stored at 2.0 GeV. Bunch filling
patterns and betatron tune are investigated to suppress the beam
instabilities at 2.5 GeV. At 2.5 GeV, we do not observe any beam
instabilities up to 200 mA. Higher beam currents than 200 mA are limited
by total RF power
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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Yujong Kim,
C. Kim,
K.H. Kim,
C.D. Park, M.H. Chun,
J.S. Yang,
I.H. Yu,
M. Kwon,
J.Y. Huang,
S.H. Nam,
M.H. Cho,
W. Namkung,
I.S. Ko
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ABSTRACT: 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
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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Yujong Kim,
C. Kim,
K.H. Kim,
J.S. Yang, M.H. Chun,
I.H. Yu,
M. Kwon,
J.Y. Huang,
S.H. Nam,
M.H. Cho,
W. Namkung,
I.S. Ko
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ABSTRACT: 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
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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Yujong Kim,
C. Kim,
K.H. Kim, M.H. Chun,
J.S. Yang,
I.H. Yu,
M. Kwon,
J.Y. Huang,
S.H. Nam,
M.H. Cho,
W. Namkung,
I.S. Ko
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ABSTRACT: 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
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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Yujong Kim,
C. Kim,
K.H. Kim,
I.H. Yu,
J.S. Yang, M.H. Chun,
M. Kwon,
J.Y. Huang,
S.H. Nam,
M.H. Cho,
W. Namkung,
I.S. Ko
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ABSTRACT: 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
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: Pohang Accelerator Laboratory, PAL, has been preparing the PLS-II project with 3 GeV Linac by upgrading the present 2.5 GeV Linac. The specification of the beam energy spread and rf phase should be much tighter than that of PLS Linac. In the present 2.5 GeV Linac of PAL, the specifications of the beam energy spread and rf phase are 0.6 % p-p and 3.5 degrees p-p respectively. The output power of the linac klystron is 80 MW at the pulse width 4 micro-seconds and the repetition rate of 10 Hz. The PxFEL for 10 GeV that is the future project plan requires 0.1 % rms and 0.1 degrees rms as specifications of the beam energy spread and rf phase respectively. We developed the Deqing system to keep modulator beam voltage stable less than 0.01 % rms for 3 GeV Linac and PxFEL. And the phase amplitude detection system (PAD) and phase amplitude control (PAC) system is also needed to improve the rf stability. This paper describes the microwave system for the PxFEL, PAD, and PAC system.
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Sun An,
Y U Sohn,
H S Kang, M H Chun,
I S Park,
I H Yu,
K H Park,
H G Kim,
M H Jung,
Y D Joo,
C D Park,
K R Kim,
S H Nam
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ABSTRACT: Pohang Accelerator Laboratory has obtained a full funding to upgrade Pohang Light Source. In the PLS-II storage ring, three elliptical superconducting RF cavities of 500 MHz will be used for accelerating an electron beam with energy of 3.0 GeV, and working at temperature of 4.4 K. Each cavity is powered by one set of high power source, and controlled by one set of digital LLRF and control system. The cryomodules are cooled by a cryogenic plant of 700 W.
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ABSTRACT: The RF system for the Pohang Light Source (PLS) storage ring consists of four independent RF stations. We have been gradually upgraded up to total maximum RF power of 270kW so far, and can operate the stored currents of 180mA at 2.5GeV. Because of adding the insertion devices and increasing the storage current up to 250mA, more RF power is required. Therefore, two more 60kW klystrons will be replaced with 75kW klystrons this year, and one more RF station with fifth RF cavity will be installed in the next year. This paper describes the progress and plan about the upgrade of the RF system.
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J Y Huang,
H S Kang,
S J Park,
C B Kim,
S H Jeong,
S H Kim,
Y J Park,
S C Kim, M H Chun,
Y J Han,
I S Park,
H J Park,
D T Kim,
S Rah,
J H Hong,
Y S Bae,
I S Ko
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ABSTRACT: Beam diagnostics for self amplification of spontaneous emission(SASE) x-ray free electron laser(XFEL) calls for precision of femto-second in time structure and sub-micrometer in beam position measurement. In the Pohang Accelerator Laboratory x-ray free electron laser (PAL-XFEL), thus, major development efforts should be performed on the measurement of femto-second bunch structure and sub-micrometer transverse beam position measurement techniques. The existing instruments can be used for standard diagnostics such as single bunch charge measurement, wire scanner or optical transition radiator for beam size measurement. Femto-second bunch length measurement can be realized using coherent transition radiation, and transverse deflecting cavity. Nanometer beam position measurement technique under developement in collaboration with the linear collider group will be utilized for PAL-XFEL sub-micrometer beam position measurement. Overall plan and the ongoing development activities will be presented.
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ABSTRACT: The rf system for the Pohang Light Source (PLS) storage ring is operating at total maximum rf power of 300kW with four 75kW klystron amplifiers and four KEK PF-type normal conducting (NC) rf cavities for 190mA at 2.5GeV [1]. The PLS will be upgraded from 2.5GeV to 3.0GeV called the PLS-II [2]. Therefore the rf system should be greatly upgraded to supply total 670kW beam power. We are investigating the some upgrade ways with adding NC cavities or new super conducting (SC) rf cavities. According to the cavity type, the high power rf system will be adjusted the total rf power, and source type and quantity such as klystron or IOT. This paper describes the present operation status and several optional ways of high power rf system for the upgrade project of PLS storage ring.
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Yujong Kim,
H Kitamura,
C Kim,
K H Kim,
I H Yu,
J S Yang, M H Chun,
J Y Huang,
S H Nam,
M H Cho,
W Namkung,
I S Ko
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ABSTRACT: In the Pohang Light Source (PLS) storage ring, there are various RF noises coming from the RF low level systems. In order to investigate the nonlinear effects of RF noise on the various beam properties such as the bunch length, the beam lifetime, and the longitudinal coupled bunch mode instabilities (CBMI's), we have studied the RF noise driven phase modulation in the PLS storage ring.
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ABSTRACT: A formula for the determination of higher-order mode (HOM) frequency in an active storage ring RF cavity is derived, which utilizes the frequency tuning mechanism of the low-level RF feedback system. It helps us to understand the behavior of coupled bunch instabilities in a storage ring whenever we change the operating beam current, the cavity gap voltage, and the ring RF frequency as well. This analysis includes the fundamental mode frequency detuning for beam loading and Robinson damping. At any operating conditions of the RF cavity, the HOM frequencies can be precisely calculated with the low-power measurement data of the frequency shift as a function of the tuner position. The formula shows a good agreement with the measurement results.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 483(3):629-640. · 1.21 Impact Factor
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ABSTRACT: The RF system for the Pohang Light Source (PLS) storage ring consists of four independent RF stations and its total power of 255kW can support the stored currents of about 400mA at 2.0GeV and 220mA at 2.5GeV with three insertion devices operation. The RF system has been operated for a large number of hours with relatively good efficiency since 1995. Major improvements such as the RF cavity cooling, low level RF system, and the stable operation of the high power RF system have been completed since the start of commissioning in 1994. This paper reports status of the major RF system of the storage ring such as klystron amplifiers, RF cavities, low level RF system, and so on.
