2008 Vol. 32, No. S1
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A 100MeV compact high intensity H-cyclotron is under design and construction at CIAE which will provide a 75MeV—100MeV, 200μA proton beam. The main magnet of this cyclotron adopts an integrally compact structure with a fixed field and four sectors, while the hill gap is constantly changeable. This paper reviews
the design features of the magnet, numerical simulation results, the inner defects of the magnet including the carbon content segregation and shrinkage porosity, factors related to mechanical design including the tolerance and deformation. The latest progress will also be reported in this paper.
High time-stability performance of the injection kicker system is important for the Beijing Electron Positron Collider Upgrade Project (BEPCⅡ), with jitter and drift less than ±5ns. In order to compensate the delay time drift of thyratron on the kicker pulsed power supply, a drift stabilizer is developed. The test results meet the demand of design by regulation resolution=1ns, jitter+drift <2ns in 8 hours. The detailed design of the time-drift stabilizer will be described in this paper.
The BEPCⅡ is the upgrade project of the Beijing Electron Positron Collider (BEPC). According to the BEPCⅡ double ring design scheme, a new ring will be added in the existing BEPC tunnel. The machine will provide electron and positron beams with an energy range from 1.0GeV to 2.1GeV for high energy physics research, and an electron beam of 2.5GeV, 250mA for synchrotron radiation. So actually there are three storage rings for the BEPCⅡ machine. Due to the limited space of the existing BEPC tunnel and the requirement of high luminosity, the antechamber type vacuum chamber is used, that makes the BEPCⅡ magnets' design and fabrication very difficult. In the paper the general features of the design and fabrication of several kinds of main magnets for the BEPCⅡ storage ring and its interaction region are introduced. And the magnetic field measurement results are presented.
Finite Element Method is used in this article to analyze the stress of CR superferric magnet. Magnetic force and the stress caused by this force are calculated. The thermal stress and strain of the coil caused by cooling down is also analyzed. The result will be taken as a check for the design of the coil and coilcase, and also as a reference for the optimization of further design and quench protection.
The CR superconducting magnet is a dipole of the FAIR project of GSI in Germany. The quench of the strand is simulated using FEM software ANSYS. From the simulation, the quench propagation can be visualized. Programming with APDL, the value of propagation velocity of normal zone is calculated. Also the voltage increasing over time of the strand is computed and pictured. Furthermore, the Minimum Propagation Zone (MPZ) is studied. At last, the relation between the current and the propagation velocity of normal zone,
and the influence of initial temperature on quench propagation are studied.
High homogeneity of the CR (collector ring) dipole magnet for FAIR (Facility for Antiproton and Ion Research) project at GSI is essential. The two optimized and analysis methods are introduced in detail. In order to obtain an ideal integral magnetic field distribution, the complicated end chamfer has been designed. By chamfering the removable pole, the distribution tolerance of high magnetic field is optimized to ±2×10－4. The method of adding a mirror plane is suitable for
the high magnetic field and it doesn't fit the low one. The OPERA is used to optimize the dipole magnetic field.
The China Spallation Neutron Source (CSNS) Rapid Cycling Synchrotron (RCS) is a high beam power proton accelerator. The task of RCS injection system is to inject the negative hydrogen ions coming from linac into RCS by stripping method. This power supply demands that its output pulse current falling edge be controlled by the program. The power supply uses the IGBT power amplifying method to generate the pulse current and makes it follow the setting waveform by the power supply's feedback control system. The tracking error is one of the important specifications of the power supply. To satisfy the tracking error less than 2%, the frequency of the IGBT topology requested is more than 400kHz. The IGBT topology is connected by the IGBT H bridges in series and parallel, and works in the phase shifted method to divide the current, the voltage and improve the equivalent frequency. High power, high frequency, fast speed response and optimal feedback control strategy are the key to the good performance of painting bumper magnets pulsed power supply.
A 40kV/6kA pulsed power supply was designed for the Rapid Cycling Synchrotron (RCS) extraction kicker magnet of the China Spallation Neutron Source. The calculation of the pulsed power supply's parameters, the design of power supply's system, the optimization of pulse forming network (PFN) are introduced in this paper. The magnet current pulse waveform is simulated by PSpice program in the situation of 36.5kV charging voltage. The simulation explains the influence of the PFN section number and the transmission cable
length on the magnet current pulse.
This paper concentrates on investigating the mechanical stability of a Beam Position Monitor (BMP) support prototype of the Shanghai Synchrotron Radiation Facility (SSRF) project. Both finite element analysis and vibration measurements have been performed. Inconsistent results between the simulations and experiments motivate us to study three connections between the support and the ground: ground bolt (used in the initial design), part grout and full grout (proposed in the later research). After changing the connection,
the first eigenfrequency is increased from 20.2Hz to 50.2Hz, and the ratio of the integrated RMS displacement (4—50Hz) is decreased from 4.36 to 1.23 in the lateral direction. The mechanical stability is improved greatly.
A novel high voltage switching circuit with parallel resonant topology is analyzed. Without adding other resonant components, this circuit makes full use of the transformer leakage inductance and winding capacitance so as to reduce the influence of the transformer parasitic parameter. Using device CD4046 to realize the switching control of MOS, this circuit can realize the constant-current charging to capacitor by operating the above resonance. The operating process of the circuit is analyzed, and the power calculation and some practical waveforms are given.
PSD yield is a key criterion to evaluate the vacuum chamber material and its surface pretreatment in an electron storage ring. In this paper, a stainless steel vacuum chamber of 1500 mm in diameter has been tested before and after TiN film coating on PSD experiment station of Machine Study Beamline of NSRL. Test results show that TiN film coating is an effective method to reduce photon
stimulated desorption for the stainless steel material.
The 3rd generation synchrotron light source requires high level of electron beam orbit stability. Shanghai Synchrotron Radiation Facility (SSRF) is a 3rd generation light source under construction; its orbit stability requirement is up to micro or sub-micro range. The storage ring mechanical components vibration caused by the ground motion would influence the orbit stability. The ground motion of SSRF is severe. It is essential to control the vibration of the mechanical components. Vibration damping is an effective method to control the vibration. The author designed a vibration damping structure for the SSRF mechanical components. The test results show that it can effectively control the mechanical vibration.
The cell circuit design and test of inductive adder pulse generator for kicker magnet are presented in the paper. The 3.3kV IGBT, a large dimension nanocrystalline core and a 2.5kV 50uF energy storage capacitor are used. The multi-channel trigger IGBT driver board is designed. IGBT failures under short circuit condition and protection scheme are explored. The multi-cell
prototype is designed. The waveforms of experiments are presented. It turns out that the rise and fall time of the output pulse is fast and the pulse width is adjustable. The maximum current of pulse reaches 2kA. It satisfies the higher requirement of beam injection technology.
In the BEPCⅡ, a great deal of DCCTs, with current output, are used as the measuring and feed-back units in power supplies. High Precision Standard Testing System for DCCT is designed and developed in order to detect and adjust the capability of DCCT. This testing system mainly consists of a PC computer, a 7.5 Digit Multimeter, a high precision DC current measuring system, and a high precision and stability power supply. The function and the structure of the testing system are simply analysed, and the test data are presented.
Recent vacuum system development with an XHV condition for the particle accelerators is briefly described. The progress of selecting and treatment of the materials used in XHV systems is introduced, and the choice of the main pump for an XHV system and some new pumping method are presented. Some leak detection experiences both for the superconducting and warm vacuum systems are recommended and the status of XHV measurement and the gauge calibration are introduced.
The optimized design of magnetic field for a cold yoke superconducting solenoid is introduced in this paper. Using some kinds of optimization designs and OPERA, we optimize the main solenoid, cold yoke and compensated winding. Through this design, the requests of the superconducting solenoid are realized.
The central region model (CRM) cyclotron is the experimental platform for the key technology study of a high intensity beam cyclotron. In this paper we introduce the spiral inflector and central region designed for the CRM cyclotron, including the physical design, the numerical control machining and the installation precision control techniques. The shape of electrodes is complex, and machining with a strict tolerance must be done by a numerical control machine tool with the number of its axles no less than 4. The electrodes of central region were finished by using 3-axle machine tools. The size of gaps between the ground and Dee tip is very important, a special device was made to guarantee the installation precision, and the error of gaps was controlled
The Central Region Model (CRM) is a compact H－ cyclotron. Because of the intrinsic asymmetry of the magnet, its machining and assembly are very complicated. To guarantee the magnet field distribution, it is necessary to measure and shim the magnetic field. This paper presents a study on the design and use of the mapping system based on the Hall Effect and the re-machining of
shimming bars after analyzing the magnetic field measurement data to achieve the isochronous field and good vertical focusing frequency. The method to effectively reduce the amplitude of the 1st harmonic by shimming bars 1s also introduced.
The research is to design a differential pumping system not only to achieve the pressure transition with a large throughput, but also to achieve a clean system without back-oil. In the paper, the pressure in differential stages is calculated; the differential pumping system design and equipment choice are introduced; the tests of Molecular/Booster Pump (MBP), a new kind of molecular-drag pump with large throughout and clean vacuum are described and the system experimental result and analysis are presented.
The place change of the key inserts, different kinds of magnets for instance, in an accelerator caused by the uneven earth subside will affect the accelerator commission. All accelerator laboratories, at home and abroad have taken the influences more and more seriously. The Shanghai Synchrotron Radiation
Facility (SSRF) under construction is located at Pudong, Shanhai, where geological condition is complicated. It is necessary to establish a monitoring system to monitor the uneven subside of foundation and key parts of the accelerator. The Hydrostatic Leveling System (HLS) is used to real time monitor the vertical displacement of the foundation and the supports of the key inserts in accelerator. This paper discusses the HLS's design plan, the principal parameters and the theoretical calculation. By discussion we can comprehend the importance and necessity to establish HLS in an accelerator in an all-round way.
With the calculation and measuring experiment methods, the effect of vacuum chamber materials' magnetic permeability on field distribution in a dipole magnet is discussed. The results show that when the relative magnetic permeability of chamber material μr≠1, it will affect the field uniformity. Once the high field uniformity is required, the material property and size of vacuum chamber in a dipole magnet have to be taken into account carefully.
A secondary electron yield test device for vacuum material study is set up, and its detailed design described in this paper. The test results for a few common vacuum materials with and without TiN film coating are presented, and the influential factors on secondary electron yield are analyzed. All the work will be helpful to the surface pretreatment of vacuum materials.
The 1.6GeV synchrotron of China Spallation Neutron Source (CSNS) project is a Rapid Cycling Synchrotron (RCS), which accelerates a high-intensity proton beam from 80MeV to 1.6GeV at a repetition rate of 25Hz. The RCS magnet system consists of 24 dipole magnets (main dipoles), 48 quadrupole magnets (main quadrupoles), 16 sextupole magnets, some tune shift quadrupoles and corrector magnets. All the magnets are of large aperture for a high beam power
of 0.1MW, one design issue is the fringe field at pole end. And the main dipoles and main quadrupoles work at 25Hz repetition rate, the eddy current is an additional issue. In this paper the magnet design of the two kinds of main magnets will be described.
The beam must be extracted into the air through the vacuum window to irradiate the living cell. In the window design, the material and thickness must be chosen to compromise the beam spot size broadening and the window safety. The structure-static analysis on the window of different structures and materials is done with the finite element analysis method, and the deformation and the equivalent stress are simulated. The safety of these candidates is investigated using the intensity theory. In addition, the small angle scattering and the transverse range of ions are simulated using SRIM code, including all the effects on the beam spot size broadening, such as the incident ion energy, the material and the thickness of the window and the air composing. At last, the appropriate vacuum windows are presented, including the structure, material and thickness.
The first medical high intensity cyclotron CYCIAE-30 and its beam line for the isotope production were built in 1994 at China Institute of Atomic Energy. Now, an upgrading beam line system is designed based on the existing beam line of CYCIAE-30 to transport the beam extracted from the cyclotron to a gas target for the new isotope production, including elements location design, optics simulation and magnet design. The machining and installation of all the elements are accomplished based on the design. The beam tuning is finished and the transmission of 96.5% is obtained.
The beam lifetime is an important parameter and it can affect the operation of the storage ring. By using the beam loss monitoring system, it can provide some explanation for the beam loss, to optimize the machine parameters and to further increase the beam lifetime. In this article, a beam loss detecting system for BEPCⅡ is introduced. The system is composed of the front-end electronics, the CAN bus and DAQ. Finally, the first application of the beam loss detection system for BEPCⅡ is presented too.
The superconducting cryogenic system has been designed and deployed in the Beijing Electron-Positron Collider Upgrade Project (BEPCⅡ). Process variables, including the pressure, level, flow and so on, are manipulated to get the liquid helium, two-phase helium flow and supercritical helium flow, which are used to cool down the three kinds of superconducting devices respectively. The system fully automates the superconducting cryogenic control with the structure of EPICS+PLC. EPICS is used to take charge of the process control, the logical control and the PID control loops whereas the low level interlocks of the pivotal equipments are run in PLCs to protect the superconducting device from damage.
Further studies on beam emittance measurement have been made to improve the emittance measurement precision at BEPCⅡ linac. Some problems in the measurement are solved and a code for beam emittance calculation is developed. With these improvements, the emittance measurement precision was upgraded.
The Shanghai Synchrotron Radiation Facility (SSRF) is a third-generation synchrotron radiation light source with 3.5GeV in energy, which is composed of the linear accelerator, the booster and the storage ring. The storage ring provides 16 standard straight sections of 6.5m and 4 long straight sections of 12 meters. Gas Bremsstrahlung (GB) produced by the interaction of the stored beam with the residual gas molecules in straight section, which is so intense and has a very small angular that the GB spectra, the GB power and the GB power distribution should be known. The characters of GB are studied by means of Fluka Monte Carlo code. Our result shows agreement with those obtained by the experiential formulae.
The upgrading of HI-13 tandem accelerator radioactivity protection interlock system will extend and optimize the original protection logical as well as the involved PLC control technology. A new reasonable displayed interface and convenient operation system will be designed.
In this paper, we introduce the most key points during the implementation of Bunch-by-Bunch transverse feedback system of HLS (Hefei Light Soure), such as the vector computation, the notch filter development, the data processing,
the phase space reconstruction method based on Hilbert transform, the mode analysis, and the development of feedback kicker cavity.
In this paper, the slow orbit feedback system of HLS, including the feedback principle, the hardware, the software and the main operation results, is briefly introduced. With the help of slow orbit feedback system, the vertical orbit stability of HLS is better than 30 microns, which meets the requirement of synchrotron radiation users and is comparable with the international advanced level of orbit stability in the same kind of machines.
With the developments of software radio technique, it not only revolutionizes
the technique in modern communication field, but also brings about technical innovation on the beam instrumentation for accelerators. The digital BPM based on software radio and digital receiver, has gained first successful application in accelerator at SLS. The company of Instrumentation Technologies made many efforts to update this device and finally the family devices-Libera were formed. It integrates the analog RF front end electronics, A/D converter, digital signal processing and synchrony trigger into an all in one measurement system with wideband. The Libera can be used at different types of accelerators and it has the functions of first turn, turn by turn and COD measurement. It plays an important role in the BEPCⅡ early commissioning, especially in the beam circulating and stacking of BER and BPR, and also in the residual orbit oscillation
measurement. In this paper, we introduce some measurement results by using the multifarious function of Libera, such as first turn, tune, residual orbit oscillation and optimum delay time of injection kicker.
This study investigated the characteristics of bremsstrahlung and induced neutrons from the electron storage ring in the Shanghai Synchrotron Radiation Facility (SSRF). The EGSnrc and MCNP Monte Carlo code has been used to perform the assess neutron and photon dose profiles for a variety of shield materials ranging from 5 to 115cm thick. The Monte Carlo simulations show that single material such as lead, iron and polyethylene have been found to be ineffective biological shield materials, while the mixed materials serve as effective shields for shielding high energy neutron. Mixed materials such as lead or iron combined with polyethylene or with concrete are good materials combination for high energy neutron radiation shield. And high-Z materials such as lead or iron combine with low-Z material containing some hydrogen such polyethylene are effective for shielding high energy neutrons as well as bremsstrahlung.
SSRF is a third generation, 3.5GeV synchrotron light source currently being constructed in Shanghai. The conceptual consideration of its timing system is described in this paper. Different storage ring filling patterns such as single
bunch pattern, multi-bunch filling pattern, mixed filling pattern and top-up pattern, demand a highly stable, low jitter timing system with the flexibility to recnfigure on programmable event driven basis. Based on the EPICS control system, the timing system provides digitally programmable sequencing and delay for the electron gun, the linac modulator, the booster and storage ring RF, the pulsed magnets, the instrumentation systems according to different operation pattern requirements.
In this paper, the average dose level is introduced in an environment and area when BEPCⅡ is debugged. The typical dose graphs are offered when the electronic storage ring is debugged and works in the synchrotron radiation mode. At the same time, some suggestions about radiation protection are presented. All the data indicate that the main and local part shielding satisfy the need and attain the design target.
A remote control system for the ECR ion source and LEBT device based on Siemens S7-300 PLC is introduced in the paper. A PROFIBUS-DP is used to exchange message between the host-computer and PLC. Human Machine Interface (HMI) is developed by Siemens WinCC software, with the functions of interlock, control, and data acquisition. Some detail problems such as structure, reconstructing incontrollable equipment, hardware and software designing are presented.
There exists strong electromagnetic radiation in inductive energy storage accelerators. It can destroy a measuring device at a distance.By repeated experiments, we found that it is a wide-spectrum electromagnetic wave with a main frequency of 75MHz. The effector such as coaxial transmission line is effected strongly in short distance.The current in the coaxial transmission line can be measured in Rogowski coils. The strength of field in it is about 500V/m and the peak current is 217mA. The radiation source may be LC oscillating or electric exploding opening switch. Through the experimental research, we think it probably may be caused by the LC oscillating in the circuit when the switches
conduct. And its strength is correlated to current change ratio. The change rate in secondary circuit is stronger than in primary circuit. So the radiation generated in secondary circuit is stronger than in primary circuit. It may be a reference for further research in inductive energy storage accelerators and
shielding electromagnetic disturbing.
For the development of high energy physics, it is needed to improve the performance of the relativistic electron bunch. The measurement of the ultrashort relativistic electron pulse becomes one of the key technologies. The electro-optic sampling measurement of relativistic electron pulses is a promising method. This method is nondestructive, non-intrusive, and real-time monitoring. Distance and angles of the reference frames will cause system deviations. In this paper these system deviations are analyzed by simulation. It provides a reference for the experiment.
The SSRF (Shanghai Synchrotron Radiation Facility) home-made digital power supply controller adopts advanced DSP and FPGA as core and precision ADC as data acquisition unit. The controller which is inlaid in the power supply case is composed of two cards of ADC and DSP. The controller can communicate with IOC by optical fiber through the UART port. The controller can easily change the parameter of the power supply to achieve high stability and repetition. As a
replacement of the imported PSI controller, the controller is mainly used in the SSRF media power supply (stability less than 100ppm), and can match all of the specifications.
The beam horizontal orbit at Hefei Light Source (HLS) was drifting all along while the storage ring was operating. To study this phenomenon, the displacement and the temperature variation of the BPM chamber were measured. By analyzing the measurement results, the main reason that explained the drifting phenomenon was found. The vacuum chamber following the dipole magnets was heated by the synchrotron light, which caused the increasing of the chamber surface temperature. The variation of the chamber temperature was
the main reason why the BPM chamber held the horizontal displacement. To suppress the orbit drifting, a compensation method of BPM movement was proposed and its experimental results were given.
The temperature is an important factor affecting the stability of electron beam orbits. For almost all accelerators, a well-working cooling system and the monitoring system are needed to keep the temperature constant. In this paper, the temperature monitor system for HLS based on EPICS, including its hardware, software and history database, is briefly introduced. It has been
indicated that the system satisfies the requirement of machine study and operation.
The paper introduces the synchrotron radiation system for Hefei Light Source (HLS), which includes the streak camera system, the bunch length system using photoelectric method, the beam profile measurement system, and the photon beam position measurement system. The bunch length and bunch lengthening were measured using the streak camera system and the photoelectric method. The beam profile measurement system was used to observe the suppression
effects of sextupole on beam transverse instability and the feedback effects of the transverse bunch-by-bunch feedback system. The photon beam position measurement system used two wire-type monitors and the logarithmic signal processor, which was used to detect the beam motions.
To bulid the set-up for energy calibration of electron beam by the method of resonant depolarization in HLS, physics calculation is finished, and the beam loss monitor system to measure the relative change of Touscheck lifetime made. With this system, the beam loss of Touscheck lifetime is measured. The change of Touscheck lifetime is expected to be measured due to depolarization.
Currently accelerator control systems adopt distribution architecture and are developed with integration tools, such as EPICS, TANGO and SCADA. The digital controller based on FPGA, DSP is widely used in accelerator controls and embedded EPICS IOC is a hot point. On the software side, laboratories have built their software development environments and the open sources Eclips, Abeans serve software development too. The high availability research is a challenge in the control world. The paper describes accelerator controls and progress of correlative technologies.
Recently many accelerator parameters are measured by using the digital technology. A data acquisition circuit board adopting software radio technology has been developed. With this circuit board and RF front-end produced i-tech company one can comprise the BPM system. A bunch length monitor composed of the circuit board, power splitter, mix, and band filter has been examined for the bunch length measurement of HLS. The data acquisition circuit board can be further improved, for example, the Ethernet can substitute VME; direct high frequency sampling can substitute medium frequency sampling; using large FPGA. Those will further improve the performance of the data acquisition system, and be the goal of developing this system in the future.
The paper introduces some of the recent developments in beam diagnostics, which include the beam position measurement techniques with sub-micrometer resolution, the beam size measurement techniques with sub-micrometer resolution, and the bunch length measurement techniques with sub-picosecond resolution. The cavity beam position monitor and the digital BPM signal processing technique are introduced for the beam position measurement techniques. The laser wire beam profile monitor, and the optical transition
radiation/optical diffraction radiation beam size monitor are introduced for the beam size measurement techniques. The spectral techniques of coherent radiation, the transverse deflecting cavity, the rf zero-phasing technique, and the electro-optic techniques are introduced for the bunch length measurement techniques.
One should pay attention to quite a lot of factors when the emittance of high-current ion beam is measured. The background subtraction and threshold setting, the measuring method of pulsed beam emittance, as well as the error sources in the emittance measurements and its elimination or correction are discussed based on the experience during the R&D of three emittance measurement units for high-current ion beams at Peking University.
The variation of the radiation field around accelerator is complex. Only by real-time monitoring can one learn them in detail. The traditional measurement methods have been out of date. The mini-DDL is a specific device designed for such radiation field real-time monitoring. It has huge flash memories and is small in size. It can communicate with the control PC via intranet or RS232 port.So it is suitable to be applied not only in area monitoring but also in temporary monitoring. The radiation field measurements results obtained using the Mini-DDL are introduced in this paper.
Correct Dumb-bells are very important to make sure the right field flatness, frequency of TM010 mode and length of 9-cell TESLA cavity. The shape of the dumb-bells will be wrong due to deep drawing, machining and EB welding. Then, the dumb-bells should be adjusted after iris and stiffness welding according to the mechanical and microwave measurement. Peking University has set up facilities for measuring and correcting the dumb-bells. This paper discusses the method of measuring and correcting the dumb-bells.
A test beam line for pulsed beam generation for 10 MeV central region model (CRM) of a compact cyclotron is under construction at China Institute of Atomic Energy (CIAE). A 70MHz continuous H－ beam with the energy of dosens of keV or a hundred keV will be pulsed to a pulse length of less than 10ns with the repetition rate of 1—8MHz. A 70.487MHz buncher will be used to compress the DC beam into the RF phase acceptance of ±30° of the CRM cyclotron. The 2.2MHz sine waveform will be used for the chopper. A pulse with the repetition rate of 4.4MHz and pulse length less than 10ns is expected after CRM cyclotron.
In a cyclotron, the RF cavity is the key device to accelerate ions. The RF cavity design for the 100MeV H－ cyclotron is very complex since the space is narrow and the Dee voltage is 60kV at the center and 120kV at the extraction region. CST MICROWAVE STUDIO is used in the design, and a real model has been made. The test result on the model is in good agreement with the simulation
The tolerances of the manufacture and installation errors and Dees deformation caused by gravity in RF cavity of CYCIAE-100 are investigated. Both the analytic treatment and numerical simulation are carried out to give the tolerance of the manufacture and installation errors which disturb the radial and vertical motion of the beam. The Dees deformation caused by gravity leads to axial misalignment of the Dees and then induces the build-up of coherent axial oscillations. However, the calculated results show that the deformation of our Dees is acceptable.
The static heat loss and unloaded Q0 are the most important values for both the cryogenic and the RF systems. The BEPCⅡ SRF cavity operates in a liquid helium bath contained in a vacuum insulated, liquid nitrogen cooled radiation shielded vessel. During the horizontal test at the test station, thermodynamic method is used to measure and calculate the static loss and Q0 value of the SRF cavity. This paper has briefly introduced the method and process to measure the static loss and Q0 value of the SRF cavity. The results under different experimental conditions are presented as important data for acceptance test of the SRF cavity.
The RF system for the Beijing Electron Positron Collider Upgrade (BEPCⅡ) Project had been working since Nov, 2006. It consists of 3 subsystems including the superconducting cavity, the klystron and the low level RF system. Compared with the former RF system, the operating frequency has been changed from 200MHz to 499.8MHz, and the superconducting cavity has been used to replace the normal cavity. Up to now, the RF system performance is good and achieves the designed target.
The application of the 3dB directional coupler is very extensive, such as the phase shifter, the attenuator and the RF pulse compressor etc. The performance of the 3dB directional coupler is very important for these components. Optimization design has been done using the HFSS code. The new phase shifter prototype using the new optimization results has been tested. The tested results are in agreement with the measured ones.
This paper presents the model cavity tune and cold test of an S-band 2MeV on-axis coupling SW accelerator. The measurement of the model cavity's frequency, degree of coupling, Q value and on-axis field distribution are described in detail. In addition, the results of cavity tune and cold test of the accelerating tube are given. The frequency consistency of the accelerator is within ±0.3MHz, the coupling degree in the supersaturation state 1.14, the quality factor of the accelerator 12000±200, and the field distribution ratio 1:2.2:2. All the results observed show that the accelerator satisfies the physics design with microwave
Cold-test experiment of an S-band broadband high power coupled-cavity traveling-wave tube (CCTWT) is introduced in this paper. The dispersion characteristic, the synchronous voltage and the interaction impedance of this S-band CCTWT are measured. The experimental results are in agreement with the numerical simulation values.
Researches on large grain superconducting cavities are carried out at SRF laboratory of Peking University. A 1.3GHz TESLA type single cell cavity and a 1.3GHz 2-cell cavity made of large grain niobium were fabricated by Peking University. With the collaboration of Jlab, the measured Eacc of the single-cell cavity reached 43.5MV/m after BCP, baking and high temperature heat treatment.
A simple theoretical model based on plasma physics is presented to analyze the microwave plasma effects on the electronic circuits. Results show that under certain parameter conditions the threshold for damaging the electronic circuits decreases with the decrease of the frequency of the high-power microwave. In addition, the oscillation amplitudes of the plasma electrons increase dramatically when the plasma frequency is near the high-power microwave frequency, which can easily damage the electronic circuits.
The application of the homemade 1K101 amorphous core in induction module is reported in this paper. The properties of magnetic, insulation and stability are studied with the cores. A pulse with pulse width of 120ns (FWFM), flattop of 72ns (±1%) and rise time of 17ns can be obtained with single-pulse induction module. Triple-pulse with the rise time of 35ns, flat-top of 60ns (±1%) and pulse width of 120ns (FWFM) was obtained when tested with a formal linear induction module at MHz repetition burst mode. The effective average flux swing of the amorphous core is about 1.41T. The cores work well with triple-pulse of 282kV. The properties of the cores are stable and suitable for induction module.
The BEPC RF system has been changed to superconducting cavities during the last four years. In the Summer of 2006, the high power test had been successfully carried. In November, the East RF was put into commissioning. The SRF system above 1.0MV voltage has been reached with the e+e－ collision beam over 100mA, and the beam current improved to 2.5GeV/250mA with 100kW beam power. The beam test shows the good matching of the RF parameters with measuring value and theoretic calculation. The commissioning and the high power test will be presented in this paper.
The superconducting RF cavity and superconducting magnet are the key devices in modern accelerators. With the development of accelerator technology and requirement of higher beam energy and luminosity, the cryogenic and superconducting technologies are applied widely in the accelerator construction. Based on the study of several typical accelerators which adopted cryogenic and superconducting technology, this paper introduces the recent activities of cryogenic system in overseas and domestic accelerators.
3 sets of 500MHz 300kW RF amplifiers to be used at the main ring of the Shanghai Synchrotron Radiation Facility (SSRF) have been installed on site. The Site Acceptance Test (SAT) of the first RF power source was completed in last March. The second and third RF power sources are going well and will be finished in October. The type choice, the layout of the RF power sources and the comparison between the SAT conclusion and the design goals are presented.
RF superconducting cavities can work in CW mode or long pulse mode. RF superconducting technology is widely used in particle accelerators. The development of RF superconductivity is limited by the material, surface treatment and installation. SRF technology is improved greatly after dozens of years' researches. Lots of techniques and experiences have been accumulated by running superconducting accelerators. In recent years, researches and developments have been carried out for future large scientific project. New cavity shape and superconducting cavities made of large grain niobium are the hot frontiers in SRF field. Energy Recovery Linacs have been developed in recent years. ERLs has many advantages such as high efficiency, energy saving, good stability, low radiation level, etc. ERLs are more and more used in advanced light sources and free electron laser facilities.
In this paper, the finite-difference time-domain (FDTD) algorithm is employed to simulate microwave pulse coupling into the dielectric slot on a rectangular cavity. We investigate the factors that influence the coupling resonant peak and resonant frequency of the dielectric slot, including the slot length, slot width, and relative dielectric constant. Numerical results show that the equation of resonant frequency for microwave coupling into the dielectric slot is modified.
Finally, the resonant condition of rectangular cavity with a dielectric slot is provided.
In this paper, the finite-difference time-domain (FDTD) algorithm is employed to simulate microwave pulse coupling into the rectangular cavity with aperture arrays. In the case in which the long-side of the slot in aperture arrays is perpendicular to the incident electrical field, and the electrical distribution of each center of slot in the aperture arrays in the process of microwave pulse coupling into the rectangular cavity with aperture arrays is analyzed in detail. We find that the effect of field enhancement of the slot in the middle of all the slots which distribute in the direction parallel to the incident electrical field is minimum and increases in turn from the middle to both sides symmetrically. We
also find that the effect of field enhancement of the slot in the middle of all the slots which distribute in the direction perpendicular to the incident electrical field is maximum and decreases in turn from the middle to both sides symmetrically. In the same time, we investigate the factors that influence the effect of field enhancement of the center of each slot and the coupling electrical distribution in the cavity, including the number of slots and the spacing between slots.
The resonant frequency of the ferrite-loaded cavities used in the future China Spallation Neutron Source (CSNS) sweeps from 1.02MHz to 2.42~MHz. The ferrite property is very important to the accelerator structure in the CSNS ring. A primary experiment was set up to measure the μrQf value and the power density of different ferrite materials. According to the comparison results, 4M2 ferrite rings were chosen to meet the requirement of CSNS.
The BEPCⅡ injector linac upgrade goal aims at higher beam energy with smaller beam emittance and energy spread to meet the colliding luminosity upgrade by two orders of magnitude. This paper describes the beam commissioning and operation. The beam energy, energy spread, current, transmission and emittance have met the design goal. The beam orbit and energy instabilities have been studied and a steady beam operation has been realized.
Bunch compressor is widely used in free electron laser facility. The normalized emittance dilution comes from the high order magnet components and the misalignment of dipole. This paper describes the tolerance study for the CTF first bunch compressor.
To meet the requirements of developing SFRFQ and upgrading the 1MeV ISR RFQ accelerator, an ECR O+ ion source and LEBT system have been developed. Using two Einzel Lenses to focus the beam, more than 3mA O+ beam with the energy of 22keV can be obtained at the end of LEBT. Its normalized root-mean-square emittance is about 0.12πmm﹒mrad.
The beam matching status between the two isochronous cyclotrons in the Heavy Ion Research Facility at the Lanzhou-Cooling Storage Ring (HIRFL-CSR) is described. Several methods which can be used to accomplish 100% matching are proposed. By comparing of them, the best method is determined. The advantage due to this method is discussed.
The design of 10MeV/20kW high power irradiating accelerator is presented. The Backward-Traveling-Wave (BTW) accelerating structure is adopted. This structure combines the advantage of traveling-wave accelerator structure with low power reflection and high stability and standing-wave accelerator structure with high shunt impedance. The work frequency of this accelerator is 2856MHz. Designed by Code AccDesign which is coded by ourselves, the output electron beam with final energy 10MeV and peak current 300mA was reached. The length of the accelerating tube is 1.5m, and the power efficiency from microwave to electron beam is 66%. The temperature and stress distribution were simulated. And the frequency shift by microwave loss was calculated.
An exact solution is derived for the equation of motion of a charged particle driven by an electrostatic wave. The explicit expression of particle velocity is obtained, and the trapping condition of the charged particle in the electrostatic wave is also derived exactly. The interaction between the charged particle and the electrostatic wave is discussed, which is a supplement to the existing textbook of plasma physics. The results are of interest to particle accelerators, microwave tubes, and basic plasma processes.
A new linear accelerating structure SFRFQ was proposed to transfer the RFQ inter-vane voltage to the inter-longitudinal accelerating gap voltage so as to improve the acceleration efficiency. A SFRFQ prototype is being constructed to explore its feasibilities, which will be installed behind the 1MeV ISR RFQ and accelerates the O+ beam from 1MeV to 1.6MeV. A high power SFRFQ model cavity was designed and tested, which has proved that an accelerating voltage higher than 70kV could be applied. A magnetic triplet matching section was designed to realize the beam matching between 1MeV ISR RFQ and SFRFQ. The upgrading of 1MeV ISR RFQ has been carried out smoothly, and its output beam current has reached 2mA.
As a novel technique in engineering, Virtual Prototyping (VP) was applied to the design of cyclotrons with the purpose of shortening the development period and reducing the costs for physical prototypes. The advances in VP techniques for compact cyclotron design in HUST are introduced. The idea of multi-domain collaborative design was proposed. This paper describes the pythonic mixed language programming approach to develop the VP integrate platform. Under this platform, the optimization design of main magnet, RF cavity and central region of cyclotrons is to be achieved.
In order to study the technology on cyclotron design, and to carry out researches on the crucial parts including the main magnet, beam diagnostics and engineering technology to accomplish the experimental verification of the 100MeV high intensity cyclotron and to pave the way for further increasing the current of the proton beam, a series of work has been done in succession since 2004, which highlights the research, design and fabrication of some of the critical parts. The technical requirement for each part has been reached consecutively. At present, all the work has been integrated into a set of comprehensive device, CRM Cyclotron, which is actually a test stand for high intensity cyclotron development. This report will lay emphasis on the following: the CRM Cyclotron design and fabrication of relevant equipment, magnetic field mapping and shimming, 10—15mA H- ion source, experimental research on RF cavity and injection system, beam commissioning on the internal target system, etc.
The intense dc beam transport in the solenoid lenses is analyzed with the Lie algebraic method, and the transfer matrix with space charge effects is obtained. Two cases are considered: one of them is that the external focusing force is greater than the space charge force; another is that the external force is less than the space charge force. The theoretical results are coded and used in the calculations of a low energy beam transport after the ECR ion source.
A 150MeV injector electron linac for the SSRF is under construction at SINAP. This linac has been installed, commissioned and handed over to the SSRF during the period of 2006—2007. This paper describes the special needs of an injector for a third generation synchrotron light source and the two specific modes of operation for this linac. The design results and the commissioning results for this linac are given in this paper.
This paper describes the subsystems commissioning process of Dragon-Ⅰ which include the injector, the pulsed power system, the transport system and the Bremsstrahlung target. The experimental results and further work are presented.
This paper describes the structure and work principle of a miniature and self-shielding electron-beam radiation processing system. Centering on the miniaturization and self-shielding, this system has been manufactured. Test results show that the energy of the electron beam is 2.5MeV, the average power of the beam is 1.2kW, the width of scanning is 300mm, and the radiation emission from this equipment to the environment is under 2uSv/h. This system is reliable, safe, easy to operate and suitable for online radiation processing for manufacture or setting on a vehicle.
The undulator is the key component in the compact THz radiation source based on FEL. By matching the adjustable period magnetic field of the undulator with the optical resonance cavity, the passing electron beam will generate coherent radiation with gain, and the radiation power required by THz source can be achieved finally. Compared with the pure permanent magnet type, the hybrid type undulator can decrease the field errors caused by non-homogeneous magnetization of magnetic blocks, and provide higher magnetic field. The conceptual design of a hybrid undulator used for THz radiation source is introduced. We use the FEM code OPERA/TOSCA to simulate 3D magnetic field of the undulator. After optimizing the end structure of the hybrid undulator, the first field integrals is controlled within 0.01Gs﹒m, and the deviation of the electron beam is less than 0.02mm.
Injection and extraction are usually the key systems in circular accelerators. They play important roles in transferring the beam from one stage acceleration to the other or to experimental stations. It is also in the injection and extraction regions where beam losses happen mostly. Due to the tight space and to reduce the perturbation to the circulating orbit, the devices are usually designed to meet special requirements such as compactness, small stray field, fast rise time or fall time, etc. Usual injection and extraction devices include septum magnets, kicker magnets, electrostatic deflectors, slow bump magnets and strippers. In spite of different accelerators and specification for the injection and extraction devices, many techniques are shared in the design and anufacturing. This paper gives a general review on the techniques employed in the major
circular accelerators in China.
The micro-beam irradiation system, which focuses the beam down to micron order and precisely delivers a predefined number of ions to a predefined spot of micron order, is a powerful tool for radio-biology, radio-biomedicine and micromachining. The Institute of Modern Physics of Chinese Academy of Sciences is developing a heavy-ion micro-beam irradiation system up to intermediate energy. Based on the intermediate and low energy beam provided by Heavy Ion Research Facility of Lanzhou, the micro-beam system takes the form of the magnetic focusing. The heavy-ion beam is conducted to the basement by a symmetrical achromatic system consisting of two vertical bending magnets and a quadrupole in between. Then a beam spot of micron order is formed by a magnetic triplet quadrupole of very high
gradient. The sample can be irradiated either in vacuum or in the air. This system will be the first opening platform capable of providing heavy ion micro-beam, ranging from low (10MeV/u) to intermediate energy (100MeV/u), for irradiation experiment with positioning and counting accuracy. Target material may be biology cell, tissue or other non-biological materials. It will be a help for unveiling the essence of heavy-ion interaction with matter and also a new means for exploring the application of heavy-ion irradiation.
This paper presents new beam test results for O+ beam on a high current Integral Split Ring Radio Frequency Quadruple (ISR RFQ) accelerator. After the upgrading, a new designed 2.45GHz O+ ECR Ion Source can provide a beam with macro-pulse peak current of 4mA at the injection point behind a 15mm diaphragm, whose O+ factor is 60%—80% varied with gas flow rate and the normalized rms emittance is less than 0.15πmm﹒mrad. The accelerated O+ beam current goes up to 2mA with the transmission of about 80% at 45kW RF power with duty factor 1/6 (pulse duration of 1ms and repetition frequency of 166Hz). The upgraded RF power system includes low level RF pulse modulation amplifier, AGC, 3W and 20W preamplifiers, 1kW driver and 30kW final amplifier, which can output nearly 50kW in pulsed mode. The vacuum has been improved, too. The upgraded 1MeV ISR RFQ can be used as the beam injector of a new designed SFRFQ accelerating system, which is under the construction at Peking University.
Cusp source is one of the essential elements in high density cyclotron, whose properties have a great impact on the extracted beam of the cyclotron. The article introduces the design and machining of the H- cusp source applied to the high intensity proton beam cyclotron. By investigating deeply the technology of high intensity plasma production, long life DC filament emission of electrons, magnetic confinement, electron filtering, residual gas and electron extraction control, we designed a new cusp source with an average beam density of 15—20mA based on the 10mA H- cusp source at CIAE.
The dispersion relation of a conventional 6-vane relativistic magnetron is derived and numerically calculated, which is employed to analyze the operating frequency of the device. Initial results of three-dimensional particle-in-cell simulation show that an average output microwave power of about 0.96GW at 4.5GHz is obtained at the beam energy of 437keV and current of 12.2kA when the externally applied magnetic field is about 0.6T. The efficiency is about 18%. An average output power of microwave about 4.4GW at 4.37GHz is also obtained at the beam energy of 1.05MeV and the current of 20.7kA when the structure parameters are improved. The efficiency is about 20%.
An ion source for HL-2A Neutral Beam Injection (NBI) was operated successfully in March 2007, in Southwestern Institute of Physics. A bucket source type and three-grid-system are used in this new ion source design. The filament current of 1100A, filament voltage of 12V, arc current of 1050A, arc voltage of 120V, highest plasmas density of 2.5×1012/cm3, extracted ion beam density of 0.44A/cm2, plasma density uniformity better than 5% in the area close to the first grid, duration of 2s, for this new source, have been achieved. The conceptual design, mechanical design and experiment result for the ion source are presented briefly in this paper.
The principle of Marx- pulse forming networks (PFN) is introduced in this paper. The PSpice simulation result of the Marx-PFN is presented and a smooth waveform is obtained in the condition of equal capacitance. Through optimizing the parameters of the networks, a 4-stage Marx-PFN has been built, a 40kV output with a FWHM of 3μs and a flat-top of 2μs is obtained on the marched resistance of 18Ω when the Marx-PFN is changed to 20kV.
Pulsed power technology has an important trend in the world, which has high power, long pulse, high operating frequency and miniaturization. Thus all-solid-state pulsed power technologies based on semiconductor devices have drawn more attention and widely used. This article introduces several kinds of semiconductor switches, such as SCR, IGBT, and SOS. The charging system based on SCR, the Marx generator, and pulsed transformer topology using IGBTs, and the system using SOS are described in detail. Some experimental results are also given. The use of semiconductor switches technology in solid state Marx generate can solve the disappointments such as short life time, low operating frequency, low reliability of conventional pulsed power equipments and has extensive perspective.
A permanent magnet microwave ion source with adjustable magnetic field is developed at China Institute of Atomic Energy. The magnetic field in the region of ionization chamber is generated by permanent magnets. Outside the magnet, an iron yoke is installed to adjust the magnetic field, and the yoke can be adjusted easily by hands. With adjustable magnetic field, the ion source can be tuned into the optimized operational condition. From an aperture of 3mm in diameter, 17mA hydrogen beam has been extracted.
To match the large power long pulse neutral beam injectors for HL-2A Tokamak, a circular magnetic multipole line-cusp ion source (namely a bucket ion source) has been designed. The arc chamber of this ion source is a water-cooled, stainless-steel cylinder 26cm in diameter, 4mm thick, and 24cm long. So far, many arc discharge experiments on this ion source have demonstrated that the plasma density has been 0.24A/cm2, for 3 seconds duration, within 5%—7% plasma uniformity, and 3 seconds maximum pulse. Arc discharge characteristics, such as the gas pressure dependence and filaments arrangements dependence have been studied experimentally and theoretically in this paper.
A 2MeV thermionic cathode test stand was established to meet the requirement of the large area thermionic cathode system. A 100mm in diameter type ``B''thermionic dispenser cathode was developed. A 1000A emission current was produced at the voltage of the diode about 1.8MV, the pulse width about 90ns(FWHM), and the cathode temperature about 1350℃. The emission current density is 12A/cm2. The results indicate that a large area thermionic cathode which produces high quality and high current electron beams is visible. The results also indicate that the ability of cathode emission relies on the diode-vacuum and cathode-temperature.
BBU (Beam breakup) instability once appeared in the early stage of ``Dragon-I'' LIA, which was excited by TM110 mode stimulated when the eccentric beam passed through the multi-functional cavity(MFC). The radio frequency characteristics of MFC were analyzed with three methods such as analytic calculation, numerical computation, and measurement. The frequency of the TM110 mode from these methods agreed with the experimental results, while the transverse coupling impedance was different from the experimental results by some times. The main BBU exciter was the big transverse coupling impedance of the MFC which could be concluded. A grid was designed to shield the gap of the MFC. The experiments show that the BBU was compressed and the high frequency oscillation disappeared.
The common characteristics of most capacitive energy storage systems are the use of gas switch, while the limitation of the recovery of gas switch and ablation of electrode lead to low repetition rates and short life. The widely researched technology of magnetic pulse compression has great perspective in long life, high average power and high repetition rates in the pulsed power system. Through the theoretical analysis and simulation of the parameters of the BOOST circuit, the LC circuit and magnetic compression circuit, the pulse generator circuit based on the BOOST circuit, the LC circuit, the pulsed transformer and the magnetic switch is designed, simulated and optimized by Pspice. The output pulse has 55kV voltage and 500ns pulse-width.
In this paper, the primary energy source of high current electron beam accelerator based on spiral pulse forming line is investigated. It consists of the constant-current power supply, the high voltage pulse capacitor, the field distortion switch, and the protection system. The primary energy source can discharge to the primary winding of the transformer with high voltage pulses whose amplitude of voltage is 40kV, current is 80kA, pulse width is 8μs and repetition frequency is less than 5Hz. The primary energy source is applied to a high current electron beam accelerator, and is featured by its compactness, stability and reliability.
It is an important research subject for the spaceflight countries to conduct equivalent simulation of 5eV atomic oxygen effects for the spaceflight material in low earth orbit. This paper introduces an apparatus used for producing atomic oxygen, which consists of a PIG ion source with permanent magnet, two electrodes extraction system, an electron deflector, an einzel lens, an ion decelerating electrode and a sample bracket. At present it has been used on the small debris accelerator in the Center for Space Science and Applied Research, Chinese Academy of Sciences, and the producing experiments of O－ are carried out. 200—300μA of O－ ions are extracted at the extraction voltage of 2—3kV. The experiments for decelerating of O－ ions and erosion of kapton foil are carried out also. Because of the target room used for both the atomic oxygen device and the small debris accelerator, the facility can be used for small debris impinging and atomic erosion for spaceflight materials simultaneouslly.
A new type of compact terahertz (THz) radiation source using free electron laser (FEL) is discussed in this paper. The concept machine consists of an independently tunable cell thermionic RF gun (ITC-RF Gun), an accelerating structure with symmetry RF-incoupler and a coaxial load RF-outcoupler, an undulator combined with an optical resonance cavity of hole-coupling mode. Without α-magnet and other bunch compressors, the size of this machine is decreased. The conceptual design and numerical simulation are presented.
In order to extract parallel beam from ion sources, it's necessary to design suitable electrode configurations in extraction zone. Taking the effect of the space-charge into account, the electrode configurations should vary with beam current density. A means of calculating extraction configuration of parallel beam with certain current density has been evolved from the space-charge limited current. By solving Poisson equation and Laplace equation, the potential distribution close to the strip beam has been gotten.
In order to reduce the gain of a receiving antenna in HPM power measurement, especially in lower frequency, a low gain dipole antenna of L band is designed. By theoretical analysis and numerical simulation, the optimized results of the antenn are obtained: its central frequency is 1.75GHz, the variety of gain is less than 1.1dB in frequency band 1.70—1.80GHz, the estimated value of the power capacity of the antenna is 0.1MW, which can satisfy the demand of corresponding measurement.
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