D. E. Kim

Improvement of the pulsed wire method for undulator magnetic-field measurement

The U10 undulator for the Pohang Light Source was measured with a pulsed wire measurement (PWM) method. By adjusting the aperture of the slotted optical switch (SOS) for PWM, the sensitivity of SOS output to the wire displacement improved significantly. A calibration table, which translates the output voltage to the displacement of wire, was obtained and the linearity of the PWM was enhanced using this table. The magnetic-field profile of the U10 undulator measured with the PWM method agrees well with that measured with Hall probe mapping. The effect of the wire dispersion on PWM is also discussed.

Introduction of the high radiation resistance of undulator magnet

One of the neodymium‐iron‐boron (Nd2Fe14B) magnet with high coercivity was found to show very high resistance to irradiation. The sample was irradiated with 2.0 GeV electrons. The radiation‐induced demagnetization of this Nd2Fe14B magnet was as small as that of the samarium‐cobalt (Sm2Co17) magnets, known as to show high radiation resistance, irradiated under same experimental conditions for comparison.

Field Mapping System for Solenoid Magnet

A three‐dimensional Hall probe mapping system for measuring the solenoid magnet of PLS photo‐cathode RF e‐gun has been developed. It can map the solenoid field either in Cartesian or in cylindrical coordinate system with a measurement reproducibility better than 5 × 10−5 T. The system has three axis motors: one for the azimuthal direction and the other two for the x and z direction. This architecture makes the measuring system simple in fabrication. The magnetic center was calculated using the measured axial component of magnetic field Bz in Cartesian coordinate system because the accuracy of magnetic axis measurement could be improved significantly by using Bz, instead of the radial component of magnetic field Br. This paper describes the measurement system and summarizes the measurement results for the solenoid magnetic of PLS photo‐cathode RF e‐gun.

Improvement of radiation resistance of NdFeB magnets by thermal treatment

The effect of the thermal stabilization on the radiation sensitivity of neodymium‐iron‐boron (Nd2Fe14B) undulator magnets to high‐energy electron irradiation was investigated. The sample magnets were baked in an oven for 24 hours before irradiation, and the temperatures of this thermal treatment were varied from 142 °C to 240 °C. All of the thermally stabilized magnets showed higher resistance to irradiation with 2.0 GeV electrons than unbaked sample. Their demagnetization curves decreased linearly with respect to the number of electrons, and with a demagnetization rate remarkably smaller than that of the unbaked magnets. Though, when the stabilizing temperature exceeded some point, the resistance showed small decrease.

Developmental Status of Beam Position and Phase Monitor for PEFP Proton Linac

The PEFP (Proton Engineering Frontier Project) at the KAERI (Korea Atomic Energy Research Institute) is building a high‐power proton linear accelerator aiming to generate 100‐MeV proton beams with 20‐mA peak current. (Pulse width and max. repetition rate of 1 ms and 120 Hz respectively.) We have developed the Beam Position and Phase Monitor (BPPM) for the machine that features the button‐type PU, the full‐analog processing electronics, and the EPICS‐based control system. The beam responses of the button‐type PU have been obtained using the MAGIC (Particle‐In‐Cell) code. The processing electronics has been developed in collaboration with Bergoz Instrumentation. In this article, we report the present status of the system developments except the control system.

A new PLS-II in-vacuum undulator and characterization of undulator radiation

This paper describes the result of overall studies from development to characterization of undulator radiation. After three years of upgrading, PLS-II has been operating successfully since 21st March 2012. During the upgrade, we developed and installed an in-vacuum undulator (IVU) that generates brilliant X-ray beam. The IVU with a 3 GeV electron beam generates undulator radiation up to ~ 21 keV by using 11th higher harmonic. The characterizations of the undulator radiation at an X-ray beam line in PLS-II agreed well with the simulation. Based on this performance demonstration, the in-vacuum undulator is successfully operating at PLS-II.

Conceptual design of a 14 cm period multipole wiggler at PLS

Pohang Accelerator Laboratory (PAL) is developing a Multipole Wiggler (MPW14) to utilize high-energy (B30 keV) synchrotron radiation at Pohang Light Source (PLS). The MPW14 is a hybrid type device to achieve maximum peak flux density and wide beam fan that can serve two beamlines. PLS MPW14-features period of 14 cm, minimum gap of 14 mm, 20 full field periods, maximum flux density of 2.06 T, 3036 mm total magnetic structure length. The peak flux density is very high compared to the other wigglers of similar pole gap and the period. The high peak flux density was possible using advanced new magnetic material and optimized magnetic geometry. The MPW14 will be used in hard X-ray region of 10–30 keV at 2.5 GeV electron energy. The total photon power is 6.19kW and the peak power density is 5.27 kW/mrad 2 at 2.5 GeV, 150 mA. To withstand the big magnetic loads with minimum deflections, C-type support structure is designed with detailed FEM structural analysis. In this article, all the conceptual design efforts for the PLS MPW14 wiggler will be described. r 2001 Elsevier Science B.V. All rights reserved. PACS: 41.85.L

Effects of an elliptically polarizing undulator on the beam dynamics in PLS-II

The non-linear effects caused by the intrinsic field’s transverse roll-off in an elliptically polarizing undulator with a 72-mm period and a maximum peak field of 0.72 T (EPU72) on the dynamics aperture of the Pohang Light Source II (PLS-II) were investigated. A kick-map and a frequency map analysis both demonstrated that EPU72 will not reduce the lifetime or cause injection problems in PLS-II.

Physics Requirements of PAL‐XFEL Undulator

Pohang Accelerator Laboratory(PAL) is planning a 0.3 nm SASE (Self Amplification of Spontaneous Emission) XFEL based on 3.7 GeV linear accelerator. For short saturation length, application of SPring8 type in vacuum undulator is needed. This reflects the experiences from SPring8 SCSS project. The end structures were designed to be asymmetric along the beam direction to ensure systematic zero 1st field integral. The thickness of the last magnets were adjusted to minimize the transition distance to the fully developed periodic field. This approach is more convenient to control than adjusting the strength of the end magnets. The final design features 4 mm minimum pole gap, 15 mm period, peak effective field of 1.09 Tesla. In this article, the physical design of the undulator, the design of the end structure, and the physics requirements of the undulator system will be presented.

Design of High Field Multipole Wiggler at PLS

Pohang Accelerator Laboratory (PAL) is developing a high field multipole wiggler for new EXAFS beamline. The beamline is planning to utilize very high photon energy (∼40keV) synchrotron radiation at Pohang Light Source (PLS). To achieve higher critical photon energy, the wiggler field need to be maximized. A magnetic structure with wedged pole and blocks with additional side blocks which are similar to asymmetric wiggler of ESRF are designed to achieve higher flux density. The end structures were designed to be asymmetric along the beam direction to ensure systematic zero 1st field integral. The thickness of the last magnets were adjusted to minimize the transition sequence to the fully developed periodic field. This approach is more convenient to control than adjusting the strength of the end magnets. The final design features 140mm period, 2.5 Tesla peak flux density at 12mm pole gap, 1205mm magnetic structure length with 16 full field poles. In this article, all the design, engineering efforts for the ...