• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.442-444
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• 1998

We made the beam crosssectional monitor system which was possible to display the ion beam crosssection extracted from accelerator on personal computer monitor. Previous beam profile monitor system could detect the central beam position with limited low beam current, but this developed beam crosssectional monitor system could operate at the relatively higher beam current. In addition we realized the real time data taking system by adopting the VXI system for beam size, central position and crosssection.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.527-527
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• 2012

In the Pohang Light Source (PLS), a major upgrade (PLS-II) of existing machine had been performed in last 3 years. Big improvements in beam parameters are expected from this major upgrade and various diagnostic instruments were installed to measure them. These include beam position monitor, beam current monitor, tune monitor, scraper, beam loss monitor, photon beam monitor, beam size monitor, streak camera, and so on. In this work, we would like to briefly introduce diagnostic instruments of the PLS-II and present measurement results in the commissioning process of the PLS-II.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.325-325
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• 2010

The beam position monitor (BPM) in the storage ring measures the position of electron beam with pickup electrodes which are coupled in capacitive way to the electron beam. However, some of the BPM in the PLS storage ring suffer the vertical noise signal at the operation frequency of about 500 MHz, so the pick-up frequency of these BPM is change to 375 MHz. In this study, it is experimentally proved in the PLS beam chamber that the BPM noise is caused by the TE mode excited in the beam chamber.

• Nuclear Engineering and Technology
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• v.45 no.4
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• pp.523-528
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• 2013

The beam position monitor (BPM) is an essential component for the PEFP 100-MeV linac's commissioning. A prototype stripline-type linac BPM was designedfor this purpose. The electrode aperture is 20 mm in diameter, and the electrode is 25 mm long, so it can be installed between Drift Tube Linac (DTL)101 and DTL102, which is the shortest distance. One end of the electrode is connected to the Sub Miniature Type A (SMA) feed through for signal measurement, and the other end is terminated as a short. The signal amplitude of the fundamental component was calculated and compared with that of the second harmonic component. The designed BPM was fabricated and a low-power RF test was conducted. In this paper, the design, fabrication and low power test of the BPM for the PEFP linac are presented.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.138-145
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• 1999

By varying the beam current of a color CRT(cathode ray tube) monitor, the misconvergence, spot size, display luminance, and chromaticity coordinate of a white pattern were measured at 4 screen positions. The misconvergence was measured with a linear CCD (charge coupled-device). The resolution was obtained by using SQRI (square root integral) method. The misconvergence of a color monitor was not influenced by the beam current but by the screen position. The misconvergence on a screen perimeter caused the resolution to decrease.

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.1-6
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• 2011

A sudden step change is observed in the vertical position readings from beam position monitors (BPMs) mounted at the several sector vacuum chambers of Pohang Light Source. To study the source of this sudden step change, we measured the RF transmission scattering matrix (S21) through the pickup electrodes of BPMs mounted at the both ends of the sector vacuum chamber. The measured $S_{21}$ graph of the sector vacuum chambers suffering sudden step change has a peak in the BPM operation frequency bandwidth. Otherwise that of the other sector vacuum chambers doesn't have a peak. It is shown by the numerical simulation that the peak found in the BPM operation frequency bandwidth corresponds to the longitudinal harmonic of transverse electric resonance mode.

• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.331-337
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• 2006

Cavity-type beam position monitors were developed in collaboration with KEK to use for the future accelerators such as international linear collider (ILC) or x-ray free electron laser (XFEL) in PAL. BPM components such as BPM cavity, beam tubes, waveguides and feedthroughs were assembled by brazing at the same time to reduce mechanical errors during the fabrication. There are four screwed pins around outer rim of the cavity for the tuning of cavity frequency and x-y isolation. The resonance frequency of BPM is 6.422 GHz, the inner diameter of cavity is 53.822 mm, and the range of mechanical adjusting is $+ / - 250{\mu}m$. The x-y isolation was measured better than -40 dB after tuned. Test results of signal forms, x-y isolations, sensitivities are satisfied within requirements for the KEK ATF2 beam line.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1954-1956
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• 1996

In this paper, we measured the reflectance of the $100{\mu}m{\times}100{\mu}m$ micromirror. In order to reduce the size of the HeNe laser beam, an eyepiece and an objective lens were used. CCD camera was used to the monitor the position and focusing. It was found that the diameter of the focused laser beam was about $3{\mu}m$. The reflectance of the reflectance of the micromirror was over the surface and 87% of the commercial mirror.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.229-229
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• 2012

It is significant issue to control the unwanted transverse electric (TE) modes in the vacuum chamber for preventing the position reading noise from the beam position monitor (BPM) of storage ring. We introduce shunt structure to control the frequency distribution of TE resonance modes excited in the vacuum chambers of the Pohang Light Source II (PLS-II). The design of shunt structure is performed using the full three dimensional finite-difference time-domain (FDTD) simulation. It is verified that the sympton of the BPM noise is not oberved up to the beam current of 190 mA in the commmissioning of PLS-II.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2249-2251
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• 1997

Total 144 quadrupole magnets are installed in PLS. The magnets are connected in series with groups of two or 24. Each group is powered by a high-precision constant-current DC power supply. For the purpose of the beam based alignment of beam position monitors in the PLS, it is necessary to adjust the current of each quadrupole independently. To achieve this, a high current shunt regulator is designed. It can shunt a maximum 50 A of the quadrupole magnet current. The shunt regulator is programmable and the current amplitude can be varied linearly with a 12-bit resolution. Power transistors are used in the current shunt regulator. The operation of transistors is in linear region. The RS232C protocol is used for remote control and status report of the shunt regulator to the main control centre of the PLS. Preliminary result indicates that the calibration accuracy of the beam position monitor can be achievable in less than $10{\mu}m$.