RF power coupling for the CSNS DTL

The China Spallation Neutron Source(CSNS)drift tube linac(DTL)consists of four tanks and each tank is fed by a 2.5 MW klystron.Accurate predication of RF coupling between the RF cavity and ports is very important for DTL RF coupler design.An iris-type coupler is chosen to couple the RF power to the DTL accelerating cavity.The physical design of the DTL coupler and the calculations of RF coupling between the cavity and coupler are carried out.The results from the numerical simulations are in excellent agreement with the analytical results.     

RF power coupling for the CSNS DTL

The China Spallation Neutron Source (CSNS) drift tube linac (DTL) consists of four tanks and each tank is fed by a 2.5 MW klystron. Accurate predication of RF coupling between the RF cavity and ports is very important for DTL RF coupler design. An iris-type coupler is chosen to couple the RF power to the DTL accelerating cavity. The physical design of the DTL coupler and the calculations of RF coupling between the cavity and coupler are carried out. The results from the numerical simulations are in excellent agreement with the analytical results.     

医用质子加速器注入器7 MeV漂移管直线加速器的设计

 针对质子治癌直线加速器功耗少、长度短的要求,设计了一台工作频率为324 MHz的漂移管型质子直线加速器(DTL)。该DTL把粒子从2.5 MeV加速到7 MeV,功耗为265 kW, 总长1.9 m。横向聚焦采用FODO结构,漂移管内放置永磁铁。提出一种新的束流匹配方案,在射频四极场加速器(RFQ)与DTL之间不设束运线,而是以 DTL入口处的4个单元为匹配段,把RFQ出口处相椭圆匹配到DTL周期结构入口处的相椭圆。 用PARMILA程序对该DTL进行了动力学模拟,结果表明该方案的束流发射度增长很小。     

Design optimization of the APF DTL in the SSC-linac

A linear accelerator as a new injector for the SSC(Separated Sector Cyclotron)of the HIRFL(Heavy Ion Research Facility Lanzhou)is being designed.The DTL(Drift-Tube-Linac)has been designed to accelerate 23Su34+from 0.140 MeV/u to 0.97 MeV/u.To the first accelerating tank which accelerates23SU34+to 0.54 MeV/u,the approach of Alternating-Phase-Focusing(APF)is applied.The phase array isobtained by coupling optimization software Dakota and beam optics code LINREV.With the hybrid of Multiobjective Genetic Algorithm(MOGA)and a pattern search method,an optimum array of asynchronous phases is determined.The final growth,both transversely and longitudinally,can meet the design requirements.In this paper,the deign optimization of the APF DTL is presented.     

Three-dimensional simulation studies of 10 MeV, 352.2 MHz drift tube Linac

It is proposed to build a drift tube Linac (DTL) at Raja Ramanna Centre for Advanced Technology, Indore, India, that will form a part of the future Spallation Neutron Source. This DTL will accelerate 30 mA H-ion beam from 3 MeV to 10 MeV. The DTL is designed to operate at 352.2 MHz with a maximum duty cycle of 3%. The DTL tank will consist of three sections, each about 1.2 m in length having 60 cells. The DTL has a ramped accelerating field, which is ramped in the first section of DTL from 1.8 to 2.2 MV/m and remains constant over the rest of the length of DTL. The field in DTL will be stabilized using post-couplers. The three-dimensional (3D) design of the DTL is done using CST microwave studio (CST MWS) incorporating the various non-axisymmetric components such as tuners, post-couplers and vacuum ports. The frequency shifts due to these components have been evaluated. This paper presents the details of the studies and analysis of 3D simulations of post-couplers, tuners and vacuum ports.     

中国散裂中子源直线射频功率源系统的研制

中国散裂中子源加速器质子束流加速能量为1.6 GeV,重复频率为25 Hz,撞击固体金属靶产生散射中子,一期工程的打靶束流功率为100 kW。直线加速器的设计束流流强为15 mA,输出能量为81 MeV。射频加速和聚束系统包括一台射频四极场加速器、中能束流传输线的两个聚束器、四节漂移管直线加速器加速腔和直线-环束流传输线的一个散束器,与之相对应,共有8个单元在线运行的射频功率源为其提供所需的射频功率。目前,直线射频功率源系统预研项目已全部完成,各项性能参数均已达到设计指标,当前正处在批产安装调试阶段。151013     

CRRFA-30L波段射频加速器

 主要介绍CRRFA-30L波段射频加速器结构和性能，论述了热阴极射频腔注入器、束流加速系统、微波功率源和控制等结构中主要技术及其研究进展，给出了加速器输出束流参数测量与测量结果分析，达到设计应用要求。     

The R&D status of DTL for CSNS

The China Spallation Neutron Source (CSNS) is a spallation neutron research facility being built at Dongguan in Guangdong Province. The 324 MHz Alvarez-type Drift Tube Linac will be used to accelerate the H⁻ ion beam from 3 to 80.0 MeV with peak current 15 mA. The R&D of a prototype structure at the low energy section of DTL is taking place at IHEP. The first unit tank ∼2.8 m in length and 28 drift tubes containing electromagnetic quadrupoles are developed. The SAKAE coils are applied in the fabrication of the electromagnetic quadrupoles. This paper introduces the R&D status of the tank and 28 drift tubes. The fabrication process and measurement results of the electromagnetic quadrupoles of special interest are also presented.

     

Dosimetric comparison of water phantoms,ion chambers,and data acquisition modes for LINAC characterization

PurposeIn this study a dosimetric comparison utilizing continuous data acquisition and discrete data acquisition is examined using IBA Blue Phantom (IBA Dosimetry, Schwarzenbruck, Germany) and PTW (PTW, Freiberg, Germany) MP3-M water tanks. The tanks were compared according to several factors including set up time, ease of use, and data acquisition times. A tertiary objective is to study the response of several ionization chambers in the two tanks examined.MethodsMeasurements made using a Varian 23EX LINAC (Varian Medical Systems, Palo Alto, CA) include PDDs and beam profiles for various field sizes with IBA CC13, PTW Semiflex 31010, PTW Pinpoint N31016, and PTW 31013 ion chambers for photons (6, 18 MV) and electrons (6, 9, 12, 15, and 18 MeV). Radial and transverse profile scans were done at depths of maximum dose, 5 cm, 10 cm, and 20 cm using the same set of tanks and detectors for the photon beams. Radial and transverse profile scans were done at depth of maximum dose for the electron beams on the same tanks and chambers. Data processing and analysis was performed using PTW's MEPHYSTO Navigator software and IBA's OmniPro Accept version 6.6 for the respective water tank systems.ResultsPDD values agree to within 1% and dmax to within 1 mm for the PTW MP3-M tank using PTW 31010 and Blue Phantom using IBA CC13 chamber, respectively and larger discrepancy with the PTW PinPoint N31016 chamber at 6 MV. With respect to setup time the PTW MP3-M and IBA Blue phantom tank took about 20 and 40 min, respectively. Scan times were longer by 5–15 min per field size in the PTW MP3-M tank for the square field sizes from 1 cm to 40 cm as compared to the IBA Blue phantom. However, data processing times were higher by 7 min per field size with the IBA system.ConclusionsTank measurements showed little deviation with the higher energy photons as compared to the lower energy photons with regards to the PDD measurements. Chamber construction as well as tank set up may be causing the slight deviation in data. It is important to identify the exact source of the potential errors to ensure that proper tank usage is performed when making such measurements to ensure that patient safety is in compliance. Beam profiles done with different chambers and tanks showed little to no deviation from one to another. With regards to continuous versus discrete data measurements the main difference was in the data processing technique used. Discrete data obtained required less data processing as compared to the continuous data acquired.     

Preliminary design studies of a 100 MeV H−/H+ LINAC as injector for SNS synchrotron/ADS LINAC

It is proposed to construct a spallation neutron source (SNS) at Centre for Advanced Technology (CAT) based on a 1 GeV proton synchrotron with 100 MeV H⁻ LINAC as injector. Additionally, the LINAC can form the first 100 MeV part of a 1 GeV proton LINAC to be built in future for accelerator driven system (ADS) applications. We are exploring a configuration of the 100 MeV LINAC which will consist of an H⁻ ion source, a 4–6 MeV RFQ followed either by a 20 MeV drift tube LINAC (DTL) and 100 MeV separated function drift tube LINAC (SDTL) or a coupled cavity drift tube LINAC (CCDTL) structure. In this paper, we present the results of our preliminary physics design studies of the RFQ-SDTL, RFQ-CCDTL and RFQ-DTL-SDTL configurations. The design of the 4.5 MeV RFQ is discussed along with the matching sections between the RFQ-SDTL/DTL and RFQ-CCDTL. The choice of the accelerator configuration and that of various parameters of the individual accelerator structures under consideration are discussed. The design objectives are to arrive at a configuration which eases heat removal for CW operation and which is less prone to halo formation in order to reduce the beam loss at higher energies.     

强流直线感应加速器束流智能调谐系统设计

 介绍了正在研究设计的调谐强流电子束束心轨迹的计算机智能系统。根据目前正在设计建造的 “神龙一号”加速器束流输运环境，为抑制束心螺旋运动，适应束输运磁场元件无散热装置，调谐过程中应尽量减少实验次数，智能调谐方法主要采用数值模拟和计算机克隆调谐和人工调谐相结合。以束心轨迹的数值模拟为基础，对束心位置调谐过程中的核心部分二极场调谐磁元件的调谐特性曲线进行了数值模拟，并与实验获得的调谐特性曲线进行了比较。获得了数值模拟和实验的初步结果。     

运行VOF法模拟LNG液舱的晃荡特性

液舱晃荡引起的载荷己成为航行中载液船舶安全性评估的重要内容之一、以及船舶结构动力学的一个热点.文中首先运用VOF法建立LNG晃荡液舱模型,给出对LNG液舱晃荡特性数值模拟方法,运用模拟结果讨论不同工况(如装载率、频率、横摇角度幅值)下晃荡动压特性,在此基础上给出了LNG液舱的晃荡载荷特性与抑制晃荡的措施.     

Current and frequency modulation characteristics for continuous-wave quantum cascade lasers at 9.06 μm

We report the characteristics of current induced frequency modulation (FM) for two continuous-wave quantum cascade lasers (QCLs) at 9.06 μm. Both the frequency tuning rate and the phase shift between intensity modulation and FM are measured at different modulation frequencies from 10 Hz to 200 kHz. The frequency tuning rate of the QCLs depends on both the modulation frequency and amplitude. The tested QCL has been used to detect ambient water vapor with wavelength modulation spectroscopy for validation with a numerical model.     

Accelerator development in India for ADS programme

At BARC, development of a Low Energy High Intensity Proton Accelerator (LEHIPA), as front-end injector of the 1 GeV accelerator for the ADS programme, has been initiated. The major components of LEHIPA (20 MeV, 30 mA) are a 50 keV ECR ion source, a 3 MeV Radio Frequency Quadrupole (RFQ) and a 20 meV drift tube linac (DTL). The Low Energy Beam Transport (LEBT) and Medium Energy Beam Transport (MEBT) lines match the beam from the ion source to RFQ and from RFQ to DTL respectively. Design of these systems has been completed and fabrication of their prototypes has started. Physics studies of the 20–1000 MeV part of the Linac are also in progress. In this paper, the present status of this project is presented.      

The radio-frequency design of an iris-type coupler for the CPHS radio-frequency quadrupole

The Compact Pulsed Hadron Source (CPHS) project is a university-based proton accelerator platform (13 MeV, 16 kW, 50 mA peak current, 0.5 ms pulse width at 50 Hz) for multi-disciplinary neutron and proton applications. The CPHS linac consists of a 3 MeV radio-frequency quadrupole (RFQ) linac and a 13 MeV drift tube linac (DTL). Both the RFQ and DTL share a 325 MHz, 2.1 MW klystron source. A single iris-type radio-frequency (RF) coupler is used to feed 537 kW of RF power to the RFQ cavity. Three-dimensional electromagnetic models of the ridge-loaded tapered waveguide (RLWG) and the coupler-cavity system are presented, and the design process and results of the RLWG and iris plate are described in detail.     

IH型漂移管直线加速器的束流动力学研究（英文）

为了提高兰州重离子加速器冷却储存环（HIRFL-CSR）的运行效率、改善加速器输出束流品质,并实现几个加速装置分时供束,提高整个重离子加速装置的利用率,特为（HIRFL-CSR）增建一台新的注入器--CSRLINAC。在108.48 MHz的RFQ之后的CSR-LINAC主加速段,主要由一台108.48 MHz和两台216.96 MHz的IH型漂移管直线加速器组成,用于加速荷质比为1/8.5~1/3之间的重离子,其最大的束流流强为3 mA,并将粒子从0.3 MeV/u加速到3.71 MeV/u。运用KONUS动力学原理,在满足设计指标的情况下,首先利用TraceWin程序进行中能束线MEBT设计,后针对高频腔体设计和束流匹配的基本参数的系列讨论,特别是对CSR-LINAC的中能束流匹配线、参数选择和IH型KONUS结构的漂移管直线加速器进行设计模拟优化。最终得出,在保证腔体设计指标和95.3%的传输效率的情况下,该紧凑型直线加速结构经过三个腔体的加速后,束流的纵向归一化均方根发射度增长仅有25%;同时发现,当流强达到3 mA时,存在空间电荷效应,导致其纵向相宽增长约25%,最大横向包络也存在16.5%的涨落。In order to improve the operation efficiency of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou (HIRFL-CSR), a heavy ion linac (linear accelerator) was proposed and designed as a new injector for HIRFL-CSR. Following the 108.48 MHz Radio-Frequency Quadrupole (RFQ), three tanks in total with Interdigital H-mode drift tube linac (IH-DTL) structure are installed to boost the beam energy from 0.3 to 3.71 MeV/u, and the beam current of ions with charge-to-mass ratio from 1/8.5 to 1/3 can reach to 3 mA. The first tank operatesat the same frequency as the RFQ, and the rest two operate at 216.96 MHz. The “Combined Zero-Degree Synchronous Particle Structure” (KONUS) beam dynamics was used in the beam dynamics design. The overview of the physics design on the main accelerating components, including RF design and beam dynamics design are introduced in this paper. The optimized structure design, fabrication status and simulation results are presented in this contribution. It shows that under the condition of assurance of 95.3% transmission efficiency, the normalized rms emittance is about 25%. When the beam current is up to 3 mA, owing to the space charge effect, the increase of longitudinal phase spread and transverse envelope are about 25% and 16.3%, respectively.     

Thermal analysis and water-cooling design of the CSNS MEBT 324 MHz buncher cavity

At least two bunchers are needed in the 3MeV H^－ Medium Energy Beam Transport (MEBT) line located between RFQ and DTL for the CSNS (China Spallation Neutron Source). A nose-cone geometry has been adopted as the type of buncher cavity for its simplicity, higher impedance and lower risk of multipacting. By making use of the results got from the simulations on the buncher with two-dimension code SUPERFISH, the thermal and structural analyses have been carried out, the process and results to determine the resulting frequency shift due to thermal and structural distortion of the cavity are presented, the water-cooling channel position and the optimum cooling water temperature as well as the tuning method by adjusting the cooling water temperature when the cavity is out of resonance are also determined through the analyses.     

Thermal analysis and water-cooling design of the CSNS MEBT 324 MHz buncher cavity

At least two bunchers are needed in the 3 MeV H- Medium Energy Beam Transport(MEBT)line located between RFQ and DTL for the CSNS(China Spallation Neutron Source).A nose-cone geometry has been adopted as the type of buncher cavity for its simplicity,higher impedance and lower risk of multipacting.By making use of the results got from the simulations on the buncher with two-dimension code SUPERFISH,the thermal and structural analyses have been carried out,the process and results to determine the resulting frequency shift due to thermal and structural distortion of the cavity are presented,the water-cooling channel position and the optimum cooling water temperature as well as the tuning method by adjusting the cooling water temperature when the cavity is out of resonance are also determined through the analyses.     

基于光纤色散相位补偿的高分辨率激光频率扫描干涉测量研究

为了实现更高分辨率的激光频率扫描干涉测量, 增大光源的扫频范围以及减小扫描频率的非线性成为关键. 采用外腔式大带宽扫频光源结合光纤辅助干涉仪构建的外部时钟频率采样非线性校正是目前较为常用的方法. 本研究发现随着扫频带宽和测量范围的增加, 光纤辅助干涉仪与测量光路中存在的色散失配导致频谱出现严重展宽, 极大的降低了测量的分辨率. 本文建立了辅助干涉仪和测量干涉仪色散失配影响的理论模型, 利用该模型分析了扫频带宽和测量范围与测量分辨率的变化关系, 与实验结果相一致, 并进而提出了基于峰值演化消畸变的色散相位补偿方法, 有效地提高了测量的分辨率, 在2.53 m 处实现了接近理论值的64.5 μm的测量分辨率. 该色散失配模型及补偿方法为提高大尺寸激光频率扫描干涉仪的测量分辨率及测距范围提供了参考.     

Voltage calculations for annular tanks partly-filled with charged liquid

A Bessel function expression is developed for the voltages produced when annular tanks (vertical axis cylindrical tanks with central conductors) are filled with liquids of uniform charge density. The expression is used to calculate the maximum surface voltage and this is compared with the maximum voltage predicted for tanks without a central conductor. Previous estimates of the percentage voltage reduction produced by a central conductor during tank filling have indicated a reduction of about 42% for practical tank dimensions. The new results, which are obtained with a more realistic model geometry, suggest a reduction of only about 29%.