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Optimization of Bimetallic Mirrors Under Radial Temperature Distributions
IL MOON 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.3
The optical surface deformation of bimetallic mirror with various mirror shapes due to radial temperature distributions was investigated using the finite element analysis program SDRC-IDEAS. In this study, bimetallic bending effects with two different plating materials (nickel and aluminum) were considered for aluminum mirror and beryllium mirror substrates. Radial temperature distributions used in this thermo-elastic analysis, are cases of linear, quadratic or cubic variations. The optical surface deformations were reduced in terms of optical aberrations by the program PCFRINGE. Additionally, corrected surface errors after piston, tilts, and focus removed were calculated and compared. It was found that the optical performances of bimetallic mirrors strongly depend on the plating material, plating thickness, and the mirror substrate shapes. A detailed analysis as presented herein is generally required to adequately predict the bimetallic effects.
Dynamic Response Analyses of a Beam Launching Telescope
IL MOON 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.4
An image motion analysis is an essential for estimating the optical and the structural performance of a beam launching telescope (BLT) optical system under dynamic loads. As a test bed, a BLT system with a primary mirror of 700 mm was optimized for a spot size of 100 mm at 1 km from the telescope. In this design and development study, the telescope structure should be optimized with a minimal image motion of less than ±1 mm during operation environment of acoustic excitation load. To fulfill this design requirement, we calculated the dynamic response for the image motion based on line of sight (LOS) sensitivity equations integrated in finite element models by using EDS-IDEAS.ge=
유승훈,석희용,Hyojae Jang,Ilmoon Hwang,Jae Hoon Kim,허민섭,한상준 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.I
If GeV electron energies are to be achieved in the laser wakefield accelerator (LWFA), it is necessary to propagate an intense laser pulse over a long distance in a plasma without disruption. Many LWFA experiments have been done in the high-power, long-pulse, self-modulated regions, where self-guiding due to relativistic focusing appears to play a role in extending the acceleration length. However, there are strong instabilities and an electron dephasing problem due to the velocity difference between the electron beam and the wake wave. Our study shows that the upward density gradient scheme can be used to avoid the dephasing problem. In the study, particle-in-cell simulations were performed to search for the optimal conditions of the density gradient for the ongoing experiment. The simulation results show that the maximum energy of the accelerated electrons can be increased by about 50 \% in the upward density gradient case. Moreover, we present a brief plan of ongoing experimental research using the laser system at the Korea Electrotechnology Research Institute (KERI).
Simulations of the Raman Backward Amplifier Using the Parallelized Averaged-Particle-In-Cell Model
Min Sub Hur,Ilmoon Hwang,Hyyong Suk 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.4
A new version of the averaged particle-in-cell (aPIC) code has been developed to simulate the Raman backscatter (RBS) and the Raman backward laser amplification in plasmas. We observe in the aPIC simulations that the RBS coupling is weakened by the electron trapping, that is generated by wave-breaking. As a result, the amplification level is significantly reduced. In this paper, a physical interpretation of the trapping-induced RBS weakening is presented. In the numerical point of view, the new aPIC, which is a completely parallelized code, shows a parallelization efficiency that is notably improved from that of the semi-parallelized old aPIC.
이중순(Joongsoon Lee),손일문(Ilmoon Son),강병무(Byungmu Kang),박원호(Wonho Park) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_3
This paper describes the development of the engine electronic control system simulator such as intake & exhaust system, Ignition system, injection system for engine electronic control parts, hybrid vehicle system simulator, chassis electronic control system and common rail direct injection system for high technology vehicle part. Each system simulator is composed of hardware simulator including of teaching materials and it will be providers the special solution of education system that most teachers, learners and research-development engineer.
Beam Emittance Measurement for the PLS-II Linac
Byung-Joon Lee,Ilmoon Hwang,Chong do Park,Changbum Kim,SomJai Chunjarean 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.6
The second-generation Pohang Light Source (PLS-II) has a 100-MeV pre-injector for the 3-GeV linac. A thermionic gun produces an electron charge of 200 pC with a bunch duration of 500 ps by using a 250-ps triggering pulser. At the pre-injector, one of the most important beam parameters for identifying the beam quality is the transverse emittance of electron bunches. Therefore, we measure the beam emittance and the Twiss functions at 100 MeV in order to match the beam optics to the beam transport line and go through it to the storage ring. To measure the transverse emittance, we used a well-known technique, the quadrupole scan, at the pre-injector. The emittances were 0.591 mm-mrad in the horizontal direction and 0.774 mm-mrad in the vertical direction.
Youngdo Joo(주영도),Changbum Kim(김창범),Ilmoon Hwang(황일문),Chongdo Park(박종도) 한국진공학회(ASCT) 2011 Applied Science and Convergence Technology Vol.20 No.1
포항광가속기의 섹터 진공용기에 부착된 빔위치측정기의 수직방향 위치 읽음 값이 갑자기 변하는 오류가 관찰되었다. 이 오류의 원인을 알기 위해서 섹터 진공용기의 양 끝단에 있는 빔위치측정기의 전극을 통한 고주파전달 산란계수를 측정하였다. 급한 변화를 보이는 섹터 진공용기에서는 측정한 산란계수의 첨단 값이 빔위치측정기의 작동 주파수 내에 존재함을 확인하였고, 전산시늉을 통해 빔위치측정기의 작동 주파수내 첨단 주파수가 가로 전장 모드의 공진모드와 일치함을 확인하였다. 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 S₂₁ 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.