DG系列大功率工业辐照电子加速器

中国科学院近代物理研究所成功研制了DG系列中频变压器型工业电子加速器,其中DG-2.5型加速器能量范围1.0-2.5 MeV,最大束流功率90 kw,束流扫描有效宽度1000 mm,适用于各种辐照领域;DG-1.2型能量范围0.8-1.2 MeV,最大功率50 kw;这两种型号加速器均通过了长时间测试,工作稳定、故障率低,采用计算机自动控制,并可与束下传动系统连锁,完全达到了工业应用的标准.     

Heavy-current accelerator based on a transformer

The operating principles of a direct-action accelerator designed to acceIerate electrons to an energy of 1.5 MeV with a mean beam power of tens of kilowatts and an efficiency of around 90% are described. The electron-current pulse length can be varied from 0 to g msec, and the repetition frequency up to 50 times per sec. The mean current im may reach 1/6 of the maximum current in the pulse. Magnetic lenses are installed in order to focus electron currents of up to 100 mA into a beam a few mm in diameter in the accelerating tube. Heavy-metal screens are placed close to the axis of the tube in order to protect the gas gaps and other electrically-stressed parts of the accelerator from radiation arising inside the tube.The construction of a system for producing an electron beam with an energy of 1.5 MeV and a mean power of 25 kW (i_m = 17 mA) is described.Translated from Atomnaya Énergiya, Vol. 20, No. 5, pp. 385–392, May, 1966.     

Experimental Results of Ion Beam Extraction of High-Current Ion Source for EAST Neutral Beam Injector

The first campaign of ion beam extraction tests are completed for EAST NBI high current ion source. The hydrogen ion beam with beam voltage of 80 keV is extracted from tetrode accelerator system. During the experiment, the characteristics of arc discharge and ion beam extraction are studied. The arc power reaches 120 kW and the extracted ion beam power reaches 3 MW. The relationship of some key parameters of arc and beam are investigated, and the details are described in this paper.     

12MeV、4.2kW电子直线加速器的辐照应用

研究了能量为６～１２ＭｅＶ、平均束功率为４．２ｋＷ的工业辐照用电子直线加速器的应用。结果表明，它在对改装半导体器件（二极管、三极管、可控硅）参数特性，大蒜辐照抑制发芽和食品辐照杀菌保鲜综合辐照加工方面更为合适。     

Measurement of the Beam Position in the Extraction System of the ILU-10 Linear Electron Accelerator

A system for measuring beam position for a ILU-10 pulsed linear electron accelerator is described. The accelerator generates an electron beam with energy up to 5 MeV. The rf generator operates at 115 MHz in the pulsed mode with pulse duration of about 500 sec and pulse repetition frequency up to 50 Hz. The average beam power can reach 60 kW. Two electrostatic sensors (pickups) are used to measure the position of the beam. The principle of operation of the measurement apparatus is based on homodyne detection of the signals from the pickups. The second harmonic of the frequency of the accelerating voltage of the accelerator power supply (230 MHz) is chosen as the working frequency. The detected signal is fed from each pickup plate into an integrator and then a ADC. The beam position is calculated on a computer. The resulting error in the beam coordinates is about 0.5 mm with a 110 mm in diameter position sensor.     

工业电子辐照加工及加速器性能检测

本文简要介绍了电子辐射加工技术的主要特点以及中国科学院高能物理研究所10MeV/15kW辐照加速器的主要性能。给出了能量、流强、扫描均匀性、扫描长度以及束斑形状等5个重要参数的测量方法及结果。      

Design and Development of a Power Supply System for NBI Test Stand of EAST

A neutral beam injector (NBI) test stand was constructed to develop a multi-megawatt prototype ion source as an auxiliary heating system on experimental advanced superconducting tokamak. A power supply system for the NBI test stand components such as a set of dc power supplies for plasma generator, a dc high voltage power supply of a tetrode accelerator, a transmission line and a surge energy suppressor. Stable arc discharges of the plasma generator with hydrogen gases for 100 s long pulse have been produced by six Langmuir probes feedback loop regulation mode to control the arc power supply. The 4 MW hydrogen ion beam of 1 s is extracted with beam energy of 80 keV and the beam current of 52 A. The dc high voltage power supply for the plasma grid of the prototype ion source was designed to contribute maximum voltage of 100 kV and current of 100 A. The high voltage power output is continuously adjustable to satisfy with plasma physics experiment in operation frequency of 10 Hz. To prevent damage of the beam source at high voltage breakdown, core snubber using deltamax soft magnetic materials have been adopted to satisfy the input energy into the accelerator from the power supply can be reduced to about 5 J in the case of breakdown at 80 kV. For the transmission line, a disc shape multi cable coaxial configuration was adopted and which the dimension of the diameter is 140 mm at the core snubber. The major issues of discharge characteristics with long pulse and beam extraction with high power for the prototype ion source were investigated on the NBI test stand.     

Studies on the Matching Network of the High Power Radio Frequency Transmitter for the NBI RF Ion Source

A radio frequency (RF) driven ion source has been developed at ASIPP (Institute of Plasma Physics, CAS) for the neutral beam injector with a 1 MHz, 25 kW RF power supply system. The paper describes the studies performed with emphasis on the RF matching network system design based on the dedicated Smith chart analyses to improve and simplify the optimized solution. Also the future RF matching network design was analyzed with the matching transformers which were set between the high-power RF transmitter and the RF driven ion source to isolate the high voltage from the accelerator of the ion source.     

高平均束流功率辐照加速器加速结构的研究

本文介绍了10 MeV/100 kW的高平均束流功率工业辐照加速器束流动力学模拟结果及其加速结构的优化设计结果。加速器采用驻波双周期轴耦合结构,1个加速腔和1个耦合腔构成1个加速单元,其工作频率为325 MHz,工作模式为π/2,加速腔和耦合腔之间通过耦合狭缝在轴向以磁耦合的方式耦合在一起。使用SUPERFISH优化加速腔的有效分路阻抗、Kilp系数等关键参数。束流动力学方面,使用PARMELA模拟论证在粒子源提供2.5 keV、500 mA的电子束后,通过6个加速腔可得到10 MeV/100 kW的平均束流功率。加速腔优化完成后使用CST对耦合腔进行了设计,此时由6个加速单元组成的加速结构有效分路阻抗为23.9 MΩ/m、无载品质因数为29 347,各加速腔与相邻的耦合腔耦合系数为4.7%,工作模式与其相邻模式的最小频率间隔为2 MHz,每个加速单元功耗为290 kW。     

Induced Activity of a Tungsten Target in a 10 MeV Electron Accelerator

Experiments are performed to determine the isotopic composition of the induced activity of a tungsten target for a 10 MeV electron beam. The measurement results are used to calculate the dose rate from the induced activity of the target for an accelerator with 100 kW beam power. It is established that ¹⁸⁷W radiation makes a substantial contribution to the dose rate. The neutron yield from the target and the flux density of neutrons scattered in the accelerator room are estimated.     

基于电子直线加速器的空间电子环境地面模拟用电子源设计与实现

空间电子环境地面模拟装置由1台电子直线加速器提供能量1~5 MeV范围内的电子,后续束流传输系统将电子束进行扩束处理。较大的能量范围对加速器的设计与运行条件提出了较高要求。本文主要阐述了该加速器的设计与实现过程,综合考虑了能量开关技术和束流负载效应,通过研究不同条件下的耦合度参数特性确定了加速管耦合度,分析提出了磁控管输出参数并进行了实验研究。加速器实验测试结果表明,电子束能量参数达到指标要求,为模拟装置提供了有效可靠的电子源。     

Stopping power of Mylar for heavy ions up to copper

The stopping powers of Mylar for several heavy ions covering Z=11 to 29 in the energy range 0.3 to 2.3 MeV/n have been measured using the elastic recoil detection technique and twin detector system. The technique provided a unique method to generate a variety of variable energy ion species utilizing a fixed energy 140 MeV Ag¹³⁺ primary beam from the Pelletron accelerator facility at Nuclear Science Center, New Delhi, India. Most of these measurements are new. The experimentally measured stopping power values have been compared with those calculated using LSS theory, Ziegler et al. formulation and Northcliffe and Schilling tabulations. Merits and demerits of these formulations are highlighted. Stopping power calculations using the Hubert et al. formulation have been extended successfully beyond its recommended range of validity, i.e. 2.5–500 MeV/n down to energies as low as 0.5 MeV/n.     

Design study on an accelerator-based facility for BNCT and low energy neutron source

We have challenged to reduce an accelerator beam power for an accelerator-based BNCT facility. The required neutron source strength at the target has been estimated so as to make the epithermal neutron flux in the patient irradiation field exceed 1.7 × 10⁹ n/cm²s. The energy of the incident proton and the arrangement of the moderator assemblies are optimized. The beam current and the accelerating voltage are determined so that the accelerator power becomes minimum. The beam power required for the treatment in one hour is 62.5 kW. The proposed facility is equipped with a 2.5 MeV proton accelerator of 25 mA. a lithium target, and a heavy water moderator contained in an aluminum tank.     

中国散裂中子源快循环同步加速器束团长度研究

束团长度是中国散裂中子源（CSNS）快循环同步加速器（RCS）束流动力学的关键参数,通过对束团长度的研究,可了解RCS的机器性能并进一步指导机器优化研究。本文对RCS 100 kW时的束团长度进行精确测量,100 kW引出时的束团长度为105 ns。RCS 500 kW时束团长度可能超过无损引出允许值,需压缩束团长度。理论上提高腔压可压缩束团长度,本文模拟研究500 kW时束团长度随腔压曲线的变化规律,模拟结果表明提高加速后半阶段的腔压可压缩束团长度,给出了500 kW时无束流损失引出的腔压曲线。基于100 kW束流条件实验验证了通过提高加速后半阶段腔压来压缩束团长度的有效性和可行性,实验测量结果与模拟结果一致。因此,提高加速后半阶段腔压是500 kW时无损引出束流的有效方法。     

Design of High Power Electron Linac at PNC

Abstract

A high power CW (Continuous Wave) test electron linac was designed to develop a higher power linac to transmute radioactive wastes. The test linac is energized by two 1.2 MW CW L-band klystrons to produce an electron beam with the energy of 10 MeV and current of 100 mA. The average beam power is 200kW–1MW for the duty factor 20–100.%.

In designing such a high power linac, authors selected a traveling-wave accelerator with TWRR (Traveling Wave Resonant Ring). This is to enhance the threshold current of BBU (Beam Break-Up) and to get high accelerator efficiency that results from the low value of attenuation constant τ and high field multiplication factor M which are permitted only with TWRR.

A kind of efficient cooling structure is adopted to an accelerator structure in order to disperse the generated heat by RF (Radio Frequency). The variational method is used to calculate the sizes and parameters of the disk-loaded accelerator structure employed. There is a discrepancy of the order of a few hundredth of one percent between the calculated sizes and the experimental ones. The M determined in the design agreed well with those measured in low and high power tests.     

Linear Accelerator for Multiply-Charged Ions at 8 MeV/nucleon – Injector in the TWA Accelerator Complex

The terawatt accumulator at the Institute of Theoretical and Experimental Physics is in the physical startup phase. A new high-current linear accelerator-injector must be developed to achieve design parameters 10¹¹ particles/sec on target; this injector should give at the entrance of the accelerator ring a heavy-ion beam with current 15–20 mA and energy ~7–8 MeV/nucleon with the required charge-to-mass ratio. To this end, a linear accelerator with rf quadrupole focusing at the working frequency 81 MHz was developed; it will accelerate Al¹¹⁺ or Co²⁵⁺ from a laser source before the synchrotron. The accelerator will consist of two sections. The first section with spatially uniform quadrupole focusing will accelerate the beam up to 1.6 MeV/nucleon. A new structure with rf quadrupole focusing and period length 2 is proposed for the second accelerating section. Preliminary numerical simulation of this structure showed that 7 MeV/nucleon with minimum beam losses and accelerating gradients 3.5 MV/m will be achieved on it. Construction of the first section with spatially uniform quadrupole focusing has begun.     

Technological Electron Accelerator with Beam Power up to 25 kW

A technological electron accelerator with beam power up to 25 kW is described. Cost and reliability criteria are used to justify the choice of microwave power supply and accelerator structure. The high average beam power and low cost of the setup put it on par with best foreign analogues. The high readiness factor and large decrease of the scheduled preventative maintenance time make it possible to use the accelerator as a multipurpose source of ionizing radiation in industrial radiation-technological processes and in scientific research.     

The development of a time of flight spectrometer for LARN

An elastic recoil detection time of flight system to depth profile light elements has been developed on ALTAÏS, the new Tandetron accelerator at LARN. The detector mounted at 45° from the beam axis consists of two isochronous electron detectors for the timing signal (START and STOP) and a 450 mm² heavy ion PIPS detector that detects the energy of the recoil atoms. The 2MV Tandem accelerator provides heavy ion beams with a maximum energy of 16 MeV depending on the charge transfer efficiency of the gas exchange canal located in the middle of the machine. A large variety of primary ion beams like ²⁸Si, ³⁵Cl, ⁶³Cu, ¹²⁷I or ¹⁹⁷Au can be produced with the SINIX heavy ion source and accelerated on the target. Typical current around 1 nA can be obtained. The energy transfer to the recoil atoms is typically in the MeV range and depends on the mass and the energy of the projectile. Some secondary effects like the energy loss in the carbon foils of the timing detector but also in the entrance window of the energy detector should not be neglected if we try to depth profile light elements with this technique. Time resolution of about 1 ns for the electrons detectors is suitable to obtain 1 amu mass resolution. Some examples of applications will be developed in this paper.     

Preliminary evaluation of beam dump for high current electron beam at JNC

A high current electron beam is required for transmuting fission products using gamma rays. Elemental technology for a linac that generates a high current beam in an efficient and stable manner is being developed at Japan Nuclear Cycle Development Institute (JNC). A beam dump for the high current, low energy electron beam (20 mA, 10 MeV) from this accelerator has been constructed and tested at JNC. A Ring and Disk (RD) structure was adopted to absorb the beam safely and to analyze the beam condition in real time. The thermal and stress analysis showed that a 200 kW electron beam could be securely stopped. The performance of the beam dump was evaluated using a beam of 7.0 MeV and an average current of 0.84 mA. The measured results showed that the electrons transported from the accelerator were completely absorbed. The temperature rise of the plates and the 1 cm dose equivalent rate of bremsstrahlung photons were consistent with the simulation data. In addition, the beam dump was found to be capable of monitoring the beam condition directly from the temperature distributions and peak current.     

10 MeV/50 kW脊型加速器输入耦合器的研制

10 MeV/50 kW脊型加速器是一种新型大功率电子辐照加速器,其加速腔中所需射频功率高达100 kW,为此专门研制了高功率输入耦合器。该耦合器主要由陶瓷窗、内外导体及耦合环组成,通过等效电路分析以及仿真计算确定了最终结构。设计采用了可独立拆卸的平板型陶瓷窗和可旋转调节的耦合环,以便于进行脊型加速器调试,并在内外导体和耦合环中设计了水冷回路带走功率传输产生的热量。经过测试,该输入耦合器可在0～2.2范围内调节耦合度,并成功向脊型谐振腔中注入了100 kW的脉冲峰值功率。