Beam Profile Monitor for Intense, Negative, Hydrogen-Ion Beams in the J-PARC Linac

Akihiko Miura,Kazuo Hasegawa,Tomoaki Miyao,Tomofumi Maruta,Yong Liu,Kazuhiko Horioka 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.6

Tracking the beam halo and its growth are essential to mitigate the beam dynamics problem in high-current accelerators. In the J-PARC linac, a beam halo has been reported to appear at the place of a mismatched magnet and/or an inaccurately set cavity. The beam loss becomes more significant as the beam’s output power increases. We developed a sensitive wire scanner monitor (WSM) to measure the transverse root-mean-squared (RMS) size of a negative hydrogen-ion beam for the transverse matching between quadrupole magnets. Although the dynamic range of 10+2 is sufficient to evaluate the RMS beam size, we set a dynamic range goal of 10+4 because we intend to observe the beam halo at the same time. We achieved a dynamic range over 10+4 by selecting a proper combination of wire material and diameter by considering the interactions between the beam and the wires. This enabled a measurement of the beam halo evolution in the linac. We discuss the mechanism that enabled the wider dynamic range compared with proton-beam WSMs. In addition, we propose a new chopper-phase-tuning method, which is realized because of the wide dynamic range of the WSM. This method may provide an accurate tuning scheme for not only the present operation but also the high-peak beam-current operation of the linac.

Beam Loading Effect and Its Compensation in the PEFP Proton Linac

Han-Sung Kim,Hyeok-Jung Kwon,Kyung-Tae Seol,Yong-Sub Cho 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3

The front part of the PEFP proton linac mainly consists of a 3-MeV radio-frequency quadrupole (RFQ) and a 20-MeV drift tube linac (DTL). The design beam current in the RFQ and DTL is 20 mA, which results in a beam loading effect. The additional RF power required to compensate for the reduced RF field amplitude in the cavity due to the beam loading effect under nominal conditions is about 15% and 60% of cavity wall power loss in the RFQ and in each DTL tank, respectively. In addition to the reduced RF field amplitude, beam loading causes an RF phase shift in the accelerating cavity, which has an adverse effect on the beam stability. In this paper, the measurement results for a beam-induced RF field reduction and phase change are presented along with discussions on a beam loading compensation method by using feedback, as well as feedforward control, in a low level RF system. The front part of the PEFP proton linac mainly consists of a 3-MeV radio-frequency quadrupole (RFQ) and a 20-MeV drift tube linac (DTL). The design beam current in the RFQ and DTL is 20 mA, which results in a beam loading effect. The additional RF power required to compensate for the reduced RF field amplitude in the cavity due to the beam loading effect under nominal conditions is about 15% and 60% of cavity wall power loss in the RFQ and in each DTL tank, respectively. In addition to the reduced RF field amplitude, beam loading causes an RF phase shift in the accelerating cavity, which has an adverse effect on the beam stability. In this paper, the measurement results for a beam-induced RF field reduction and phase change are presented along with discussions on a beam loading compensation method by using feedback, as well as feedforward control, in a low level RF system.

Estimations of beam tails and beam lifetimes in PLS-II

Elsevier 2011 Current Applied Physics Vol.11 No.5

Recent light sources are characterized by beams with a small emittance, high beam current and small vertical gap in insertion devices. We investigated beam tail distributions and beam lifetimes for a light source at PLS-II by using a fast simulation method. The simulations were performed to obtain transverse and longitudinal tail distributions due to beam-residual gas bremsstrahlung, beam-residual gas scattering and intra-beam scattering. The simulation results on the tail distributions were compared with a solvable model and showed good agreements. The simulated beam lifetime was estimated as a function of vacuum pressure and vertical aperture in the ring. The simulated beam lifetime at PLS-II was estimated to be around 7 h for a beam current of 400 mA in a half vertical gap of 3 mm and a vacuum pressure of 1 nTorr. It was shown that the beam lifetimes, due to the beam-residual gas bremsstrahlung and beam-residual gas scattering, were greatly affected by the vacuum pressures and vertical aperture, and their contributions to the beam lifetime were larger than the intra-beam scattering. Our results show that a control of the vacuum pressure is important in the recent light sources with a small emittance, high beam current and small vertical gap.

Estimations of beam tails and beam lifetimes in PLS-II

김은산 한국물리학회 2011 Current Applied Physics Vol.11 No.5

Recent light sources are characterized by beams with a small emittance, high beam current and small vertical gap in insertion devices. We investigated beam tail distributions and beam lifetimes for a light source at PLS-II by using a fast simulation method. The simulations were performed to obtain transverse and longitudinal tail distributions due to beam-residual gas bremsstrahlung, beam-residual gas scattering and intra-beam scattering. The simulation results on the tail distributions were compared with a solvable model and showed good agreements. The simulated beam lifetime was estimated as a function of vacuum pressure and vertical aperture in the ring. The simulated beam lifetime at PLS-II was estimated to be around 7 h for a beam current of 400 mA in a half vertical gap of 3 mm and a vacuum pressure of 1 nTorr. It was shown that the beam lifetimes, due to the beam-residual gas bremsstrahlung and beam-residual gas scattering, were greatly affected by the vacuum pressures and vertical aperture, and their contributions to the beam lifetime were larger than the intra-beam scattering. Our results show that a control of the vacuum pressure is important in the recent light sources with a small emittance, high beam current and small vertical gap.

깊이 1200mm급 변단면보의 중간모멘트골조용 내진접합부 개발

정시화,알미아이유 로벨 원디므,박만우,주영규 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.4

Deep beam has high section modules compared with shallow beam of the same weight. However, deep beam has low rotational capacity and high possibility of brittle failure so it is not possible to apply deep beams with a long span to intermediate moment frames, which should exhibit a ductility of 0.02rad of a story drift angle of steel moment frames. Accordingly, KBC and AISC limit the beam depth for intermediate and special moment frame to 750mm and 920mm respectively. The purpose of this paper is to improve the seismic performance of intermediate moment frame with 1200mm depth beam. In order to enhance vulnerability of plastic deformation capacity of deeper beam, Multi-Reduced Taper Beam(MRTB) shape that thickness of beam flange is reinforced and at the same time some part of the beam flange width is weakened are proposed. Based on concept of multiple plastic hinge, MRTB is intended to satisfy the rotation requirement for intermediate moment frame by dividing total story drift into each hinge and to prevent the collapse of the main members by inducing local buckling and fracture at the plastic hinge location far away from connection. The seismic performance of MRTB is evaluated by cyclic load test with conventional connections type WUF-W, RBS and Haunch. Some of the proposed MRTB connection satisfies connection requirements for intermediate moment frame and shows improved the seismic performance compared to conventional connections. 본 연구에서는 보 깊이 1200mm의 중간모멘트골조 접합부를 개발하여 기존 철골 중간모멘트골조의 회전 성능을 향상시키고자 하였다. 깊은 보가 가지는 취약한 소성변형능력을 향상시키고자 보의 휨거동에 기반한 MRTB 접합부를 제안하였고, 제안된 접합부들의 내진 성능은 기존 접합부들과 함께 반복가력실험을 수행하여 평가하였다. MRTB 접합부는 중간모멘트골조 요구 성능을 만족하며 기존 접합부들 보다 향상된 회전 성능을 나타내었고, MRTB 형상별 거동 특성 차이를 나타내었다.

Experimental study of the behavior of beam-column connections with expanded beam flanges

Hongwei Ma,Jiwei Wang,Eric M. Lui,Zeqing Wan,Kun Wang 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.3

This paper describes an experimental study of steel beam-column connections with or without expanded beam flanges with different geometries. The objectives of this study are to elucidate the cyclic behavior of these connections, identify the location of the plastic hinge zone, and provide useful test data for future numerical simulations. Five connection specimens are designed and tested under cyclic load. The test setup consists of a beam and a column connected together by a connection with or without expanded beam flanges. A constant axial force is applied to the column and a time varying point load is applied to the free end of the beam, inducing shear and moment in the connection. Because the only effect to be studied in the present work is the expanded beam flange, the sizes of the beam and column as well as the magnitude of the axial force in the column are kept constant. However, the length, width and shape of the expanded beam flanges are varied. The responses of these connections in terms of their hysteretic behavior, failure modes, stiffness degradation and strain variations are experimentally obtained and discussed. The test results show that while the influence of the expanded beam flanges on hysteretic behavior, stiffness degradation and energy dissipation capacity of the connection is relatively minor, the size of the expanded beam flanges does affect the location of the plastic hinge zone and strain variations in these beam-column joints. Furthermore, in terms of ductility, moment and rotational capacities, all five connections behave well. No weld fracture or premature failure occurs before the formation of a plastic hinge in the beam.

Personal Computer를 이용한 Beam 解析 Program 開發

김종관 조선대학교 생산기술연구소 1991 生産技術硏究 Vol.13 No.2

Beam analysis personnel computer programs was developed using GW-BASIC language which is executed under Hercules graphics card and Hangul MS-DOS Version 3.2. The kinds of beam analyzed is Cantilever beam, Simple beam, Both ends fixed beam, Overhangs beam. Deflection curves was executed under Hercules graphics card in Cantilever beam and Overhangs beam and emphasized the visualization effects. It was supposed to be helpful for the education of analyses of computer application in mechanics of materials.

Analytic solution of Timoshenko beam excited by real seismic support motions

김용우 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.2

Beam-like structures such as bridge, high building and tower, pipes, flexible connecting rods and some robotic manipulators are often excited by support motions. These structures are important in machines and structures. So, this study proposes an analytic method to accurately predict the dynamic behaviors of the structures during support motions or an earthquake. Using Timoshenko beam theory which is valid even for non-slender beams and for high-frequency responses, the analytic responses of fixed-fixed beams subjected to a real seismic motions at supports are illustrated to show the principled approach to the proposed method. The responses of a slender beam obtained by using Timoshenko beam theory are compared with the solutions based on Euler-Bernoulli beam theory to validate the correctness of the proposed method. The dynamic analysis for the fixed-fixed beam subjected to support motions gives useful information to develop an understanding of the structural behavior of the beam. The bending moment and the shear force of a slender beam are governed by dynamic components while those of a stocky beam are governed by static components. Especially, the maximal magnitudes of the bending moment and the shear force of the thick beam are proportional to the difference of support displacements and they are influenced by the seismic wave velocity.

Possibility of Interchanging Patients for Beam-Matched Linear Accelerators from the Same Vendor

강성희,정진범,엄근용,송창훈,김인아,김재성,김연래,강상원,김경현,서태석 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.8

The purpose of this study is to investigate the possibility of interchanging patients on beam-matched linear accelerators (linacs), by evaluating the dosimetric variation and the dose delivery accuracy of volumetric modulated arc therapy (VMAT). Two VitalBeam linacs installed recently in our center were included in this study. For dosimetric data comparison, beam data, such as percentage depth doses (PDDs), beam profiles, output factors, multi-leaf collimator (MLC) leaf transmission factors, and the dosimetric leaf gap (DLG), for 6-MV and 10-MV beams were measured on both linacs. Sixty patients (20 head and neck, 20 lung, and 20 prostate cancers) were selected to evaluate the dosimetric parameters and the delivery accuracy of the VMAT plans created for various treatment sites. All the VMAT plans were generated using the Eclipse treatment planning system (TPS) with the same optimizer algorithm. The dose differences between two beam-matched linacs for planning target volumes (PTVs) and organs at risk (OARs) were recorded and analyzed. Patient-specific dosimetric quality assurance (DQA) using the Electronic Portal Image Device (EPID) were performed, and the measured planar doses were compared with those calculated by using the TPS though absolute dose gamma evaluation using 2%/2 mm and 2%/3 mm criteria. The differences in all dosimetric beam data between the two beam-matched linacs were all within 1% for the 6-MV and the 10-MV beams. For all 60 cases of three treatment sites, no notable differences were observed in the dosimetric comparison and the DVH variation between the beam-matched linacs. The average differences in dosimetric parameters of PTV and OARs were all within 1%. Furthermore, all passing rates of measured doses on the beam-matched linacs were higher than 93% and 97% for the 2%/2 mm and the 2%/3 mm criteria, respectively. Our overall dosimetric variation in beam data and VMAT plans remains within the tolerance of clinical acceptability. Pretreatment verification results were also clinically acceptable, showing good agreement with the calculated doses. Therefore, this study demonstrated the possibility of swapping patients in a VMAT plan without any modification and re-planning between two beam-matched linacs.

Development of the Proton Beam Monitoring System at the 45-MeV Proton Irradiation Test Facility

Sang-Pil Yun,In-Seok Hong,Yong-Sub Cho 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3

A proton beam monitoring system has been developed to measure the intensity and the profile of an external proton beam. The beam monitoring system, which consists of a beam intensity monitor and a beam profile monitor (BPM), can provide the intensity and the profile of a proton beam. As a beam monitor for the intensity measurement, a parallel plate ionization chamber (PPIC) is chosen because of its stable operation and wide dynamic range for the detection of a proton beam. To maintain the beam quality, the PPIC electrodes were fabricated with a very thin aluminized polyester film (25 μm). The structure of the BPM is similar to that of the PPIC, except that the BPM is equipped with a position-sensitive electrode. This position-sensitive electrode allows the BPM to measure the profile of a proton beam. The signals from the beam intensity monitor and the BPM are recorded by using a Lab-view-based PXI system (National Instruments Co.), which displays information on both the intensity and the profile by using a proton beam analysis program supported by Lab-view. As a result, we can monitor information on the proton beam during irradiation tests by using a remote control. A proton beam monitoring system has been developed to measure the intensity and the profile of an external proton beam. The beam monitoring system, which consists of a beam intensity monitor and a beam profile monitor (BPM), can provide the intensity and the profile of a proton beam. As a beam monitor for the intensity measurement, a parallel plate ionization chamber (PPIC) is chosen because of its stable operation and wide dynamic range for the detection of a proton beam. To maintain the beam quality, the PPIC electrodes were fabricated with a very thin aluminized polyester film (25 μm). The structure of the BPM is similar to that of the PPIC, except that the BPM is equipped with a position-sensitive electrode. This position-sensitive electrode allows the BPM to measure the profile of a proton beam. The signals from the beam intensity monitor and the BPM are recorded by using a Lab-view-based PXI system (National Instruments Co.), which displays information on both the intensity and the profile by using a proton beam analysis program supported by Lab-view. As a result, we can monitor information on the proton beam during irradiation tests by using a remote control.