Woonha Hwang

Commissioning of the PLS-II

After 14 years of successful operation, the Pohang Light Source (PLS) has completed PLS-II upgrade to meet the increasing demand from the growing user community. The PLS-II upgrade has increased the beam energy from 2.5 GeV to 3 GeV; the number of insertion devices has been increased by a factor of two (20 IDs); and the beam current has been increased to 400 mA from 200 mA. The beam emittance has been reduced to below 10 nm while retaining the existing PLS tunnel as well as the existing injection system. During the six months of commissioning in the latter half of 2011, we have successfully achieved 14 insertion device operations and top-up operations with 100 mA beam current and 5.8 nm beam emittance. In this paper, we report the experimental results obtained from the PLS-II commissioning.

Development of new S-band RF window for S-band RF system of Pohang Light Source-II linear accelerator

The RF windows have been used in the Pohang Accelerator Laboratory, Pohang Light Source-II (PLS-II) must meet the conditions for operating at a peak power of 80 MW and a repetition rate of 10 Hz. In these operational conditions of the PLS-II, the original RF window that was designed for a peak power of 60 MW is more likely to inflict damages that cause vacuum leaks. Therefore, for the new RF window, the circular cavity of TE012 mode with two coupling irises design is employed to reduce the peak electric field on the ceramic surface, while the circular cavity of TE111 mode is used for the original RF window. The finite-difference time-domain (FDTD) simulation was used for the design. For this paper, we present the result of the prototype and its high power test.

Status of the PLS-II Synchrotron Light Source

Pohang light source (PLS) had been operated for 14 years successfully. The number of beamlines of PLS was two at the beginning stage. The number of beam-lines has been increased two or three every year. And the total beam-lines in operation became 28 in 2010 and 3199 users had visited PAL for their experiments [1]. The user community gradually extended and they became to require brighter beam to see small signal from a sample. To meet this requirement of the user community, the PLS machine was upgraded as PLS-II. The main goals of the PLS-II machine are to increase the beam energy from 2.5 to 3 GeV, and to increase the number of insertion device (ID) by the factor of two (20 IDs). This PLS-II upgrade project had been completed in 2011 and user service has been started in 2012. We will report the current status of PLS-II machine in this paper.

Beam diagnostic system for high intensity proton linac at KAERI

A 100-MeV high-intensity (20 mA CW) proton linac is being built in the KAERI (Korea Atomic Energy Research Institute), Korea. Beam diagnostic system for the machine require to include BCMs (Beam Current Monitors), BPPMs (Beam Position and Phase Monitors), and other devices. BCMs are of special importance for high-intensity proton linacs, since the control of beam loss is critical. They should have high stability and resolution better than 5E-4. BPPMs are for measuring beam position and phase (w.r.t RF) simultaneously, that are crucial for the successful commissioning and operation of the accelerator. All diagnostic devices are required to operate both in CW and pulsed (several ms) modes. Pulsed mode operation is useful when machine tuning and commissioning. In this article, we report the developmental status of beam diagnostic devices for the KOMAC accelerator, with detailed description on the BPPM PU design.

Development of a new waveguide valve using RF choke flange for PLS linac

Waveguide valves capable of handling a peak power of 80 MW are required at the time of klystron replacement in PLS Linac. We designed a U-shaped waveguide valve and made two prototypes. However, they have some problems caused by RF power leak from the waveguide to the vacuum enclosure. This caused an increase of vacuum pressure and arcing in the vacuum chamber at the power level of 60 MW. A new choke flange has been designed with MAFIA code to solve problems caused by the RF power leak. A model choke flange has been fabricated and tested with a Network Analyzer and a 600 W solid state amplifier. It was observed that the RF leak at the choke flange can be reduced more than 20 dB in comparison with no choke case. High power RF test for the new waveguide valve with RF choke flange was performed in S-band resonant ring. The RF transmission through the valve was achieved up to 125 MW peak power level at the pulse width of 4 /spl mu/s and the repetition rate of 30 Hz.