Annual Report of IHEP IV Accelerator Science and Technology BEPC

26 2002 Annual Report of IHEP IV. Accelerator Science and Technology 4.1 BEPC Operation Great achievement was made during the BEPC operation in 2002. The total operation time was 4908 hours, in which 1729.2 hours were for high energy physics experiments, 1425.2 hours for the synchrotron radiation application, 511.5 hours for the injection, 164.6 hours for the breakdown, 388.2 hours for hardware maintenance and regulation and 655.3 hours for the machine study. Compared with last year, the total operation time exceeded the operation plan by 348 hours on account of high operation efficiency. Table 1 and Figure 1 show the statistics of the BEPC operation in 2002. Table 4.1 BES Total (hour) Percentage (%) 1729.4 35.24 BSRF 1425.2 29.04 Statistics of BEPC performance in 2002 MD 655.3 13.35 Injection 511.5 10.42 Recovery 388.2 7.91 Breakdown 164.6 3.35 Other 33.8 0.69 Other Recovery Failure Injection 8% 3% 1% 10% MD 13% BSRF 29% BES 36% Figure4.1 Statistics of the BEPC performance in 2002 4.1.1 Operation for High Energy Physics Operation for high energy physics accounted for 35.24%. When BES operated at the resonance peak of Ψ (2S)、Ψ(3770), the maximum current reached 90mA. Due to the effort of the operation group, many records such as the peak luminosity were broken. 14.63 million hadron events were collected as against the planned 14 million. 350 hours were offered to the 10th Experiment Hall for the BES-III design. IV. Accelerator Science and Technology 27 The 2001/2002 operation of BEPC was finished on June15, 2002. When a beam was supplied to BES at the energies of ψ(2S) and ψ(3770), BEPC was operated stably and the collision beam current increased gradually. The maximum beam current was about 90 mA. Thanks to the hard work of the operation people, some operation records such as the peak current and luminosity and the hadron events per shift, per day and per week were frequently renewed. For example, on the night shift of March 12, 2002, the maximum luminosity reached 1.258× 1031 cm-2s-1, a new record of luminosity at ψ(2S) energy. Till March 13, 2002, BES has gained 14.62 M hadron events in total as against the scheduled 14 M ψ(2S) events. From April 23 to May 19, BES gained 0.2858 M ψ(3770) events. The integrated luminosity was -1 8.15 pb as against the scheduled 6~8 pb-1. As for the storage ring, the machine studies were focused on such issues as PEI experiment, BBA, the RF system three-cavity tuning and the BEPC coupling measurement and so on. As the BEPC injector, machine studies were also important for the linear accelerator. Many results were achieved on the energy gain research, positron beam, energy spread, buncher and pre-buncher adjustment, which was essential to keep greater beam and injection rate. The injection rate was more than 3 mA/s on the average. In 2002, the machine study was focused on the following fields: 1) Studies on the photoelectron effect; 2) Studies on the beam-based alignment system; 3) Studies on the beam lifetime reduction in the dedicated SR operation, i.e., observing the electron beam lifetime when the distributed ion pumps were swi- tched off; 4) Studies on the dedicated SR mode; 5) Studies on the GAP of 4W2 wiggler magnet; 6) Studies on the top off injection; 7) Measurement of the coupling in BEPC, etc. 4.1.2 Operation for Synchrotron Radiation Accounting for 29.04%, 1425.2 hours were offered to synchrotron radiation, which is the longest operation time up to now, in synchrotron radiation mode, the maximum current reached 120-130mA with a 20-30 hours’ lifetime. 293 BSRF experimental tasks were completed. On the whole, the beam quality and operation efficiency were satisfactory. The 2002/2003 operation of the storage ring started on November 8, 2002. After two weeks’ commissioning of the machine, the BEPC began supplying beam to SR by operating in a dedicated mode. During the commissioning, the beam was injected favorably, but the beam lifetime was very short, as the worst vacuum in the storage ring was only 3×10-8 Torr. Gradually, the beam lifetime was increased as the vacuum became better. Two new wiggler magnets, 1W1 and 4W2, worked normally, but fine adjustment of the beamline and more studies on the GAP of 4W2 are needed. The 4W1A beamline was very difficult to operate. Although the position and angle of the beam at 4W1 were adjusted with great efforts, no directed light could be observed. Thus the beamline had to be abandoned provisionally at last. 4.2 Beam Optics and Orbit Correction for the BEPCII Linac 4.2.1 Code Development for On-line Beam Optics and Orbit Correction The first version of the on-line beam optics and orbit correction code has been completed (emittance growth is not included). The results are consistent with TRANSPORT. This code includes optics matching and orbit correction code (including alignment errors). According to the LINAC lattice features, both “Stepwise” method and “Global” method can be adopted. Both are being optimized. Parameters of the current machine operation will be used to check the code and its ability to adjust the beam. If the new control system and database based on EPICS take a long time to construct, simple interface between the beam optics code and the existing LINAC control system must be prepared to meet the need of beam tuning. This issue is under consideration. Both the Chinese version and the English version of the preliminary design report on the beam optics and orbit correction have been completed. 4.1.3 Machine Studies The total time for machine studies was 655.3 hours in the last periods to ensure the operation of BES and synchrotron radiation. 28 2002 Annual Report of IHEP 4.2.2 Preliminary Study on Beam Optics and Orbit Correction The preliminary study on the beam optics and orbit correction (supported by the Accelerator Center) has been completed. A final report includes the beam optics and orbit correction scheme, the design, the construction and measurement of a BPM prototype and a corrector prototype. Evaluation has been made by the Accelerator Center. All materials have been placed on file. 4.2.3 Prototypes of BPM and Corrector A BPM prototype and a corrector prototype have been installed in the linac tunnel. Beam test is being prepared. Batch production of BPMs and Correctors will be conducted early next year after the beam test of the prototypes. 4.2.4 Linac Beam Modeling PARMELA code has been purchased from LANL. It has been installed and tested. A design on the new pre-injector system with sub-harmonic bunchers is being conducted. Simulation for BEPCII pre-injector has been completed. Before the SLAC review meeting, the scheme called BEPCII-A including linear lattice, nonlinear effects, the magnets errors effects on dynamic aperture and the misalignment effects on COD has been completed. From September, ten new schemes respectively called B, C, D, E, F, G, H, I, J, K were proposed with the help of other hardware groups. During the international mini-workshop, the criteria of the good lattice scheme were assumed. The working point of the lattice is .53/.55 for horizontal/vertical plane. The dynamic aperture should be larger than 10 sigma when 3 times’ design errors and 10 sigma of energy spread are included. The schemes of F, G, K were studied in detail especially on the dynamic aperture. After these studies, the BEPCII lattice was upgraded to become symmetric between the electron and positron ring and symmetric between parts of north and south arcs. The related synchrotron radiation modes were also computed. 2. Impedance and Beam Instabilities The impedance of the injection kickers and the crotch of IR have been computed. The HOM heating effects of the two parts have also been estimated. The fast ion instability has been estimated analytically. The photon electron yields and distribution inside the antechamber have been simulated. The ECI instability has also been simulated. The simulation results show that the antechamber can reduce the ECI instability effectively. 3. Injection and Transport Line Design The preliminary design for the injection and transport lines has been done. The injection parameters, the errors and physical aperture requirements on the injection elements have been proposed. The loss rate for different energy error has been estimated. The motion of the injected particles was tracked preliminarily. The upgrade requirements on the lattice and beam diagnostic system for the transport lines were proposed. 4. Others The Chinese and English preliminary design reports have been finished. In addition, the preliminary design of Chinese spallation neutron source has been made. Two kinds of rapid cycling synchrotron lattice have been computed. The computation produced 8 versions of lattice and their requirements on physical aperture of magnets. 4.3 Accelerator Physics Study 4.3.1 Beam Instability Study Four new detectors for photon electron were designed, made and installed in BEPC. Machine study has been done thrice as a preliminary observation of them. The machine studies will help understand the effects of the clean electrode on reducing the photon electron instability. The study on mode coupling instability including the damping effect has made great progress by cooperating with Tsinghua University. Several people participated in the study on the beam instability under the CAS/JSPS contract. The NSFS contract on bunch lengthening has been finished on time. The beam lifetime effects on shutting down the distribution ion pump have been observed for the BEPC synchrotron radiation mode. The observation shows that shutting down some ion pumps is helpful for reducing the times of the beam lifetime dramatic decrease. 4.3.2 Design of BEPC-II 1. Lattice IV. Accelerator Science and Technology 29 4.3.3 Academic Exchange and Papers One person went to Japan and one to Switzerland for long-term collaboration. One person took part in JLC and KEKB review meeting. One person went to Switzerland to attend E-Cloud'2002. Three people went to SLAC for BEPCII review meeting. One person went to Korea for LINAC2002. Three persons went to Singapore as teachers for OCPA Accelerator Physics School. 2 persons including one Ph.D student went to Singapore as students for OCPA Accelerator Physics School. One person went to Japan for beam dynamics seminar. Five persons went to Mianyang for the workshop of Chinese accelerator physics. 15 papers were submitted to the previous meetings or workshop. 4.5 Accelerator Technology 4.5.1 The Microwave Power Source and Electron Gun System 1. BEPC Operation In 2002, the microwave power source system has worked well, thus ensuring the smooth operation of BEPC. 4 HK-1 klystrons and 3 thyratrons have been replaced from BEPC. 2. Upgrading of the Klystron Test Stand According to the parameter of the microwave power source for BEPC-II, we have built the klystron test stand. It will be used to test the TH2128C klystron and other microwave components. 3. Upgrading of the BEPC-II Microwave Power Source The preliminary design of upgrading the microwave power source for BEPC-II has been finished. It passed the appraisal by both Chinese and foreign experts. Good result was obtained in upgrading the test stand and some experiments. 3 sets of TH2128C klystron and pulse-transformer–oil-tank were ordered and received. They will be used to run at M/K Unit 8 and Unit7 after acceptance test. 4. The Electron Gun System The electron gun runs well without any fault report. The design report of upgrading the electron gun system for BEPC-II has been finished. It passed the appraisal by both Chinese and foreign experts. Now it is being installed and debugged on the test stand. 4.4 Designing of the Interaction Region of BEPC-II Progress has been made in optimizing the design of the BEPCII interaction region (IR) optics. The main parameters such as length, field strength and requirement of the field qualities for the septum bending magnet ISPB, two-in-one quadrupole Q1a have been confirmed. After detailed discussion with BNL, the technical specifications of superconducting magnets for the BEPC-II interaction region have been finished and sent to BNL. The engineering design of the superconducting magnet has started at BNL. The physical and structural designs of the IR special magnets Q1a and ISPB have been finished primarily. The prototype magnets of Q1a and ISPB are being fabricated. Furthermore, the physical design of the IR special magnet Q2 has been accomplished. The preliminary design of the IR vacuum chamber system has been finished and the detailed procedures for assembling all the IR elements have been studied carefully. The preliminary design and the analysis of forces of IR supporting system have been finished. The calculations about the distributions of the synchrotron radiation power, which is produced with colliding and synchrotron radiation modes have been completed. The water- cooling system and the main design parameters of masks such as position, shape and material have been studied preliminarily. 4.5.2 The Beam Instrumentation 1. Operation and Maintenance To ensure a good running status and lower breakdown rate of the beam instrumentation (BI) equipment, efforts were made for the summer maintenance. Although a lot of things were handled for moving the office and return old devices in summer, the summer maintenance work was finished on time. In addition, according to the past experience, enough attention was paid to the spare parts’ order in advance. Generally speaking, the BI system runs well, but it still has some troubles as listed below: How to get a kind of camera that can endure large dose radiation? 30 2002 Annual Report of IHEP How to eliminate the DCCT’s interference? Some measures are considered and trials will be arranged. We expect to find the cause and solve them. 2. Beam Loss Monitor System for the Storage Ring The upgrade of the beam loss monitor system (BLM) has been finished. It was examined by the IHEP specialist group. This system runs well and achieves the design technique target. The work is being filed away. Certainly, the BLM system performance will be continuously improved. 3. Linac Beam Instrumentation System Upgrade The structural designing of Linac BI to be upgraded has been accomplished. The key task we are now concerned is the BPM electronics scheme evaluation. The major work finished this year is as follows: The BEPC-II Linac BI preliminary design both in Chinese and in English has been finished. We attended the SLAC International Review Meeting on the BEPCII Design Report. The linac BI system cost budget, the CPM plan and the devices list were submitted. The prototype BPM with stripline type was made and it calibrated. 4. Storage Ring Beam Instrumentation Upgrade The BEPC-II preliminary design was our major task in 2002. How to develop the design work with the shortage of manpower is a great challenge to us. According to our case, we decided to enhance the cooperation between SSRF, Tsinghua University and our Institute. Referring to the experience of KEKB and PEP-II, the key techniques were identified. The major work finished this year is as follows: Both the Chinese version and the English version of the BEPCII BI preliminary design were accomplished. Some accelerator physicists were sent to attend the SLAC International Review Meeting. The BI system cost budget, the CPM plan and the devices list were submitted. The BPM electronics schemes with Bergoz MX-BPM for COD measurement and DBPM for the first turn and turn-by-turn measurement were put forward. The main technical parameters of the storage ring beam instrumentation system and detectors quantities, detector sizes and locations were basically determined. 4.5.3 The Radio Frequency System 1. Operation of BEPC During the operation seasons of 2002, the beam current reached 130mA. From March 18 to April 19, 2002, the operation in synchrotron radiation mode lasted 720 hours, the RF system broke down for only two times, amounting to about 4hrs. To ensure the stable operation, two wind flux switches were added to avoid the overheating of the windows, two new capacitor sleeves changed and the resistor of the W1 transmitter repaired during the summer’s maintenance. The remote monitoring system of the RF system status parameters was put into test running. The network connection has been realized, but there remains some improvement work to do. In the synchrotron radiation mode operation of this year, the beam current was lower than 100mA, so the next run for synchrotron radiation mode operation is a challenge to us. 2. Preparations for BEPC-II The frequency-change design for the BEPCII superconducting cavity based on the KEKB SC cavity was accomplished. KEKB 508MHz superconducting cavity technologies will be used in the BEPC-II 500MHz system, but we face the following problems: Change of the frequency from 508.887 MHz to 499.80 MHz, The space for installation and maintenance, synchrotron irradiation, HOM and multi-bunch instability, the multipacting, Length of the coupler, Choice of the transition part’s angle, heat loss, State regulation for pressure vessel in China, etc. IV. Accelerator Science and Technology 31 After finishing the calculations of the BEPC-II SC cavity, some measurements were made of the model cavity at KEK with a good result achieved. Work on the BEPC-II RF power source has begun. It includes the BEPC-II RF power source layout, the CPM plan, the technical requirements of klystrons, and the power supplies and circulators, the signal list for low level controls, the construction work of the transmitter halls, the cooling systems, the price for each part and guarantee as well as service. 3. Academic Activities Supported by the Institute of Chinese Physics, our Institute sponsored the Second Countrywide Accelerator Radiofrequency Microwave Technology seminar in summer. 30 deputies from 11 institutions attended the seminar. With the development of the BEPC-II design, 4 people were sent to visit Newman laboratory, Cornell University in May and KEK in September, respectively. Extensive discussions were focused on the technologies about superconducting cavity with the RF experts in these laboratories. KEK experts visited IHEP 4 times for the collaboration. They rendered us a lot of assistance. According to the requirement of the BEPCII general layout, the vacuum chamber for the electron ring was studied and designed. The temperature and internal stress of the mask for the synchrotron radiation light were calculated and analyzed and the water-cooling mask was finally determined. A three-dimension model of the standard vacuum chamber for the outer ring was designed and its support was considered. The preliminary design of a standard girder of the outer ring for the BEPC-II storage has been completed. The result of the calculated internal stress and distortion has met the demand of the BEPC-II girder. At the same time, deliberations were given to the adjustment and the fixation at pre-alignment and renewed orientation after disassembly for every magnet and vacuum chamber and so on. The preliminary design of the survey and alignment for the BEPC-II storage has been completed. The control network was determined. It is composed of the horizontal network and the elevation network. The survey modes of the control network were chosen. The design of the control network in the BEPC-II tunnel has been completed. To perform the precision alignment, five-step procedures will be applied during the pre-installation and pre-alignment. 2. The BEPC Maintenance and Improvement The laser tracker measurement is the focal point of survey and alignment of BEPC in 2002. We studied the abnormal change when the actual values from magnet measurement fit the normal values from network measurement and found a method to solve the problem. Then we worked out “the Operating Program of Tracker Survey and Alignment in BEPC” before the measurement was carried on in the tunnel. During the measurement in tunnel, we draw out a new plan to measure the horizontal network on the basis of the experience of last year. The plan turned out to be a success. We used the lap and level-measuring method in a creative way to measure the elevation network, accomplished the closure of the elevation network measurement by means of tracker for the first time (closing error is 0.1mm), and solved preliminarily the problem of large errors and no closure when the elevation network was measured with the aid of tracker in the world. In this year, we finished mainly the lofting of 1W1, 4W2 and 3B3 front-end regions, the survey and alignment of the linac and ring, the adjustment of all Q magnets of the 4.5.4 The Mechanical System 1. The BEPC-II Project According to the data of the BEPC-II lattice, the arrangement of equipment for BEPC-II was studied. The maximum restricted dimensions of equipment along the beam center and the positions between each other were determined. The design of the BEPC-II general layout provides a lot of information on all equipment. Thus the beam effective aperture of the BEPC-II vacuum chambers can be examined and their impedance and ECI estimated. Based on the demand of the BEPC-II general layout, the vacuum chamber for the positron ring was studied and designed. Considering the synchrotron radiation light, ECI and the cut-off frequency of TE mode, the design of the antechamber vacuum chambers was optimized with their temperature and internal stress reaching a reasonable range. A three-dimension model of the standard antechamber vacuum chamber for the outer ring was designed and its support considered. 32 2002 Annual Report of IHEP ring, and the survey and alignment of 3W1, 4W1, 4W2 and 4B9 front-end regions. We completed the improvement of R1W1, R3B3 and R4W2 vacuum chambers for the synchrotron radiation. Their leak was less than 2 x 10-10 Torr⋅l/s. At one time, the bend fixtures for the aluminum vacuum chambers were completed. The output current read back linearity of 60 sets of corrector power supplies measured and calculated and a set of new and more accurate coefficient data provided for the BEPC operation; The temperature difference between the original position of the detector for the dipole magnet coil and the middle of the dipole magnet coil in the BEPC transport line tested, and a thermo-detector in the middle of coil added to increase the reliability of the magnet protection system and All cooling water flow relays of magnet power supply tested and some of them replaced. 2. R & D of BEPC-II (1) The Storage Ring Injection System The preliminary design of the storage ring injection system both in Chinese and English was accomplished. It was reviewed by American experts at SLAC. The scheme of kicker received affirmative comment. Conditions in the experimental hall were prepared for R&D of the injector devices. The manufacturer of the ceramic plates, which are the key part of the kicker was selected. The investigation of manufacturer for other parts and equipment was almost completed. The design and machining of the test set-up for kicker magnet power supply were finished and the devices for experimental study prepared. (2) The Magnet Power Supply System The preliminary design of the storage ring magnet power supply system both in Chinese and English was accomplished. It was reviewed by American experts at SLAC. Both the system scheme and machine design received affirmative comment from the experts. The investigation of power supply manufactory is under way. The experimental study on the chopper type power supply was finished and the topology of power circuit fixed. The programmable power supply controller with operation software was designed. The contract 4.5.5 The Power Supply System 1. Operation and Maintenance of BEPC The operation and maintenance involved about 200 equipment of 4 sub-systems including the storage ring magnet power supply, the transport line magnet power supply, the storage ring injection system and the interlock of magnet winding protection. Since most of these equipment have been operating for 15 years, the equipment failure caused by aging parts, especially the power supplies of B, Q, SKQ and 4W1, has become more serious. In contrast to the number of equipment, only two persons are deputed for the whole maintenance positions. Apparently, this is a very hard job. However, we overcame the shortage of manpower by organizing very often most of the BEPC-II staffers of the PS Group into the maintenance and repair. As a result, the failure rate accounted for only 6% of the BEPC total failure. The main items of maintenance and repair done in 2002 are as follows: Most of the cooling water pipes in the magnet power supply cabinet replaced; 4 sets of kicker power supplies improved; the power transistors for capacitor charging replaced by IGBT and over-temperature protection interlock set up in IGBT. This improvement can help avoid operation failure; The maintenance and repair of electrostatic separators: replacing the insulation grease and fixing high voltage switch; Repair of 5 sets of input lines switch of power supply; All the input lines’ switches of the magnet power supply cleaned and tested (replaced); The maintenance and repair of the storage ring water-cooling control system; IV. Accelerator Science and Technology 33 was signed with the manufacturer on the fabrication of the prototype of a chopper type Q PS. Investigation of the power supply controller was made. Investigation of DC current transducer (DCCT) was made. A few different DCCT products were tested to check and compare their performances. R&D of the power supply local controller was carried on, the product types of main devices were chosen. Investigation of the coil protection system of the I.R. magnets has started. The preliminary design of the power supply installation-engineering requirement has been accomplished. It involves the power supply cabinet dimension, the location and arrangement of the power supply equipment, the power supply system operation parameters such as the capacitance of the power supply input lines, the cooling water and the air conditioning requirement, the magnet cable parameter and the EMC requirement. 4.5.6 The Microwave System 1. Operation and Maintenance The microwave system operated normally in 2002. Due to careful maintenance and check, the failure time was short and the failure ratio was low. 2. The Upgrade and Study of BEPC-II (1) Development of the New Positron Target and Focusing System The design and related technical documents of a new type of positron target have been finished. The physics computation and structural design of the positron uniform field solenoid focusing system have been done. 8 sets of big quadruple magnet power supply were developed, and they all passed the test and met the requirements. We are ready to put them into trial operation to obtain technical support for big batch development. Figure 4.5.6-1 shows the assemblage diagram of positron convert target chamber. Figure 4.5.6-1 Assemblage diagram of the positron convert target chamber (2) Upgrade of the High Power RF Transmission System 11 new 65 MW wave-guide valves and new directional couplers have been developed. The microwave, vacuum and mechanical performances met our design requirement. 4 sets of valves and directional couplers were installed to sections of 6th, 7th, 8th and 10th of the linac respectively this summer. Up to now, its operating status is good as shown in Figure 4.5.6-2. 34 2002 Annual Report of IHEP Figure 4.5.6-2 (3) SLED Upgrade The 65MW wave-guide valve A prototype of the new SLED detuning system has been developed and tested. It was installed to the 7th section of the linac for high power test this summer. Figure 4.5.6-3 (4) The Accelerating Structure Upgrade A prototype of the new SLED detuning system The design, manufacture and measurement of the experimental cavity have been done. The final dimensions of the accelerating structure were determined according to our testing data and computation. (5) The Buncher and Driver System Upgrade The prototype of a new IφA control unit has been finished. It is in the trial run. Experimental analysis of the driver system has been done and the upgrade scheme determined. (6) The Phasing System The systematic analysis and the scheme of the phasing system have been finished. IV. Accelerator Science and Technology 43 (7) Development of Accelerator Parts for International Collaborators Three S-band accelerating structures and two sets of SLED have been exported to ANL in USA and KHI in Japan. One 1.6 meter-long accelerating structure for ANL has also been finished recently. 4.5.7 The Control System 1. System Maintenance During the maintenance this summer, 11 CAMAC power supply fans, 2 sets of CAMAC power supplies and 5 pieces of 400V pulse amplifiers were replaced with new ones. The server application for BEPC status display has been improved to support multi-user’s access. 2. System Improvement The temperature measurement system for vacuum chambers on the storage ring has been completed. The system includes RS-485 links, 30 temperature sensors, 5 remote I/O units and a set of industrial PC. The linac control system has been improved. The control of Focusing Power Supplies for Slow Electron Experimental Beam has been done. The system consists of CANbus, 28 sets of power supplies, 3 sets of vacuum gauges, 8 remote I/O modules, and a PC. The power supply controls for magnets of linac focus, quadrupoles, some large aperture quadrupoles have been improved. The system includes CANbus, 71 power supplies. By the end of September the applications for linac commissioning were put into use, which has a special file system support, adjustable connecting of tracing-ball, Web diagnosing, and remote interface to commissioning. The control of microwave phase-shifter has been finished, including CANbus, drive for pulse counting, and corresponding man-machine interfaces. 3. The BEPC-II Project The design of the BEPC-II control system has been approved at the domestic review meeting held in January 2002 and the international review meeting held at SLAC in May 2002. After the review meeting, the control group made great efforts for the detailed design of the sub-system controls. Many discussions were conducted with the accelerator physics group and the magnet power supply group on the control precision, resolution for the magnet power supply on the storage ring. After the discussions, the design of the control interface for magnet power supplies has been selected. R&D of the BEPC-II control system started at the end of October. In the R&D stage different kinds of interfaces will be installed and tested and major key technologies studied. The project called “the Establishment of the Realtime Developing Environment for the Spectrometer Data Acquisition and Accelerator Control Systems” has been finished. In this task, the control group built the real-time developing environment based on EPICS. The system consists of a SUN workstation and MVME2431 board, Solaris8, vxWork5.4, EPICS Base 3.13.4 & Extensions and a lot of third-party software supporting EPICS system. The IOC database has been created and tested. Driver supports for VME I/O boards based on VxWorks have been developed. At the same time, the EPICS system has been opened for some users of accelerator center. The work has made good preparations for the construction of the BEPC-II control system. The Third Asian EPICS Seminar hosted by IHEP and KEK was held at IHEP from August 20th to 22nd, 2002. More than 30 specialists from Japan, USA, Germany and China (IHEP and SSRF) attended the seminar. The participants and specialists discussed about the technologies of the BEPC-II control system development. The BEPC-II project and the EPICS progress at IHEP were reported and the experience of using EPICS on different lads exchanged. The proposed goal of this seminar was reached. The EPICS web pages at the Accelerator Center were set up, including EPICS training, seminars and user’s manuals. The papers and inner reports on the EPICS research and experience of the control group were also put in this web site. 36 2002 Annual Report of IHEP 4.5.8 The Magnet System 1. BEPC operation and maintenance The upgrading item of the Energy Monitor System of the reference magnet after the first stage work was finished at the end of last year. The all works have been finished basically before the BEPC on new run. This system will be operation and provided precise energy calibration for the high energy physics experiment. The 3W1 Control System was maintained when the work down period. It not only make the system operation normally and run in good status for the dedicated synchrotron radiation mode experiment. 2. Two permanent wigglers The installation of two multipole permanent magnet wigglers in the BEPC storage ring is one of the upgrading items of BSRF. After the performances were tested, the two wigglers were commissioned and installed in September and October 2002, respectively, as shown in Figure 4.5.8-1 Figure 4.5.8-1 The two newly-installed 1W1 and 4W2 wigglers (left: 1W1, right: 4W2) 3. 1W1 Permanent Magnetic Wiggler 1W1 is a kind of out-of-vacuum wiggler, which was completed by the Beijing Turbine Electrical Machinery Company Ltd. before the end of 2001. It was transported to the 5th Hall at IHEP. It was tuned together with the control system. Then its magnetic field was measured and its shim done, as shown in Figure 4.5.8-2. Owing to various reasons, 1W1 wiggler has some problems. The time scale limited a right choice of high quality Vanadium Permendur materials, so the peak field did not reach the designed 1.4 Tesla. However, it still met the requirements of photon flux and energy for the synchrotron radiation. Besides, a few poles and blocks were split open because of the glue quality. It has been sent back to the Company for repair. There might be some defects in the prescription of the epoxy and its glue process. 1W1 permanent wiggler was checked and accepted after the magnetic field and the mechanical precision were measured in July 2002. IV. Accelerator Science and Technology 43 Figure 4.5.8-2 The control system and magnet field measurement for 1W1 wiggler 4. Acceptance Test of the Point-by-Point Measurement Device The new point-by-point measurement device was manufactured by the Beijing Turbine Electrical Machinery Company Ltd. Its control system was completed by our Institute. Both its hardware and software had been tested for half a year. Using bi-frequency laser interferometer, the Lathe Research Institute approved by the state tested this system. The tested results met the design requirements. It was used to measure the magnetic field of 1W1 wiggler, as shown in Figure 7. 5. 4W2 Permanent Magnetic Wiggler 4W2 is an in-vacuum wiggler, whose poles are all in the vacuum chamber. This project is not only an entirely new subject at home, but also a new one abroad. We aim at developing a new technology in the world for the insertion device. We have signed a contract with Shanghai Jiaotong University in November 2001 on cooperative development of such a wiggler. Distribution of magnet field for various gap of 1W1 B0(T) 1.5 1 0.5 0 -0.5 -1 -1.5 0 500 1000 1500 2000 Z(mm) Figure 4.5.8-3 Distribution of the magnetic field of 1W1 measured with point-by-point device 38 2002 Annual Report of IHEP The 4W2 in-vacuum wiggler involves a wide range of subjects and technologies, including magnetic field, precision machine, super high vacuum automatic control and other multi-subject items. The gap of the 4W2 is large, ranging from 12mm to 120mm. Particularly in the synchrotron radiation mode, the peak magnetic field is up to 1.8 Tesla and the attraction force reaches 14000kN. But in the collision mode, the required central peak magnetic field is less than 1000 Gs. The vacuum chamber has 0.58 cubic meter of volume. Inside this chamber there are magnetic units made of Nd-Fe-B blocks and Fe-Co-V poles with Tin film coated, beryllium bronze spring, the low-Q strip of OFHC with Ni-plating, about thousands of screws coated with Ag, the O-dust and back beam in it. The weight of all these parts is nearly 1000 kg. So its development needs complex and advanced techniques. The general assembly of the 4W2 in-vacuum wiggler was completed in the second half of August 2002. After the magnetic field and mechanical precision were examined, the 4W2 was tested and accepted on September 12, 2002. The tested reports indicate that all of the design performances and indexes of the 4W2 in-vacuum wiggler have been reached and exceeded. This is the first in-vacuum wiggler that has been commissioned in China. 4W2 in-vacuum wiggler was transported to IHEP on 21October, 2002. Then the packing box was opened. After the devices were checked, the leakage of the vacuum systems detected and then put in place in the storage ring. Figure 4.5.8-4 The magnetic field measurement for the small gap of 4W2 and the vacuum measurement 6. Modification of the magnet on the path of SR extraction from 4W2 In order to extract the synchrotron radiation light from 4W2, the downstream magnets R4Q7, R4S3 and R4BV3 need to be modified. The current spare magnets were used for the designing and fabrication carried out early than have been planned. Before being modified, all these three kinds of magnets were measured carefully, and after their modification, the magnetic fields were measured again under the same conditions as before just to ensure the performances of the magnets remain unchanged. 7. Design of the BEPC-II magnets The BEPC-II double-ring is designed to contain many kinds of magnets. Besides the existing magnets and the injection systems, the interaction region system containing the superconducting magnets in the IR and the special magnets in the beam separation region was added. The design of the BEPC-II magnets includes dipoles, quadrupoles and sextupoles, except the magnets of the interaction region. Work on the normal magnet system for the storage ring consists of two parts. One is the design and fabrication of magnets for the new ring and the other is the improvement of the quadrupoles’ coils for the old ring. The magnets for the new ring contain di- IV. Accelerator Science and Technology 39 poles, quadrupoles and combined sextupoles. According to the requirement of the accelerator and the layout of the tunnel, the preliminary design and the main parameters in Chinese/English versions and the three dimensional structure drawings of three magnets have been given. The report in English was presented at the International Review Meeting held at SLAC. It received favorable comments by foreign exports. The magnets for the interaction region will not be described in this system. Figure 4.5.8-5 The 3-D view of the BEPC-II dipole magnet Figure 4.5.8-6 The 3-D views of the BEPC-II quadrupole and corrector-combined sextupole 8. International Collaboration A total of 296 SPEAR3 production magnets plus their prototypes which have four types and nine different effective magnetic lengths and a total of 9799 measurement files in 14 batches have been completed and shipped to SLAC successfully by the end of April 2002. The Inter-laboratory Collaborative Agreement between SLAC and IHEP including the design, fabrication and measurement of the magnets for the SPEAR3 project, a third generation synchrotron light source at SLAC, was discussed in March and approved in October, 1999. It took about three years to complete. Four individual magnet measurement systems with the aim to perform precise, fast and reliable measurement were developed and updated at IHEP for Spear3 magnet measurements. In addition, all measurement results and measurement systems for SPEAR3 magnets have been filed in hardcopy and on CD disks and archived at IHEP. The field optimization measurements of the second prototype of linac H/V corrector for BEPC also have been completed by the end of September 2002. 4.5.9 The Vacuum System The vacuum group took charge of the operation, maintenance and upgrade of the BEPC storage ring ultra-high vacuum system, the transport lines’ highvacuum system and the linac high-vacuum system 40 2002 Annual Report of IHEP as well as the preliminary design for the BEPC-II vacuum system. The main work completed during the year of 2002 is as follows: 1. Operation The performance of the BEPC vacuum system has been excellent in 2002. It provided the dynamic pressure of less than 2×10-9 Torr in the presence of the circulating beams. The beam lifetime is longer than 8 hours. The occurrence of leaks is rare in spite of very large number of individual components. Most of the leaks can be eliminated during the first pump down and global leak check of a vacuum sector. 2. Maintenance All the vacuum equipment was overhauled during the summer shutdown. More than 200 ion pumps were checked and repaired, and about 10 ion pumps and 20 high –voltage feed-through replaced. The polluted high-voltage feed-through was scrubbed. More than 60 ion pump powers were repaired and the turbomolecular pump groups and the vacuum gauges fixed. 3. Improvement To meet the demand of upgrading the synchrotron radiation devices, three bending aluminum chambers in the storage ring were machined and welded in order to add the synchrotron radiation front-ends. The Vacuum Group has finished the leak detection, baking and pre-evacuating of the vacuum chambers. When the three changed vacuum chambers (3B3, 1W1 and 4W2) were installed in the storage ring, we carried out the leak detection and bake-out for the sectors and obtained the ultra-high vacuum. 4W2 is an in-vacuum wiggler manufactured for the first time in China. One of the main issues for fabricating this in-vacuum wiggler is how to achieve ultra-high vacuum in the situation of the large outgassing rates. The 4W2 static pressure of 3.8×10-10Torr has been reached using reasonable pump-down techniques. Figure 4.5.9 illustrates the 4W2 pump-down process. 1.00E-03 （ Pressure Torr） 1.00E-04 1.00E-05 1.00E-06 1.00E-07 1.00E-08 1.00E-09 1.00E-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 Time（Hour） Figure4.5.9 The 4W2 pump-down process 4. The preliminary design of the BEPC-II vacuum system The preliminary design report of the BEPC-II storage ring vacuum system has been finished and reviewed at SLAC. The experimental equipment of ultra-high vacuum has been set up and used to measure the pumping speed and the ultimate vacuum for all kinds of vacuum pumps. In addition, we carried out a great deal of R& D for TiN coating technique inside the vacuum chamber, and shall start practical research. IV. Accelerator Science and Technology 41 4.5.10 Radiation Protection 1. The BEPC-II Radiation Protection “The BEPC-II Radiation Protection Appraisement Report” and “the BEPC-II Environmental Effect Appraisal Report” passed the evaluation of the Ministry of Health, China and the State Generation Administration of Environmental Protection, respectively. The preliminary design of the BEPC-II radiation protection was completed. 2. Systematic Operation and Improvement for the BEPC Environmental and Area Radiation Inspection (1) Systematic Operation The operation of the BEPC environmental and area radiation inspection system is stable. 40 existing radiation monitors in all are distributed in each BEPC area, from the 4 local data acquisition stations gathering data to the central monitor system. For the BEPC environmental and area radiation inspection dosage statistics of 2002, please refer to Table 4.5.10-1. Table 4.5.10-1 Environmental and Area Radiation Inspection Dosage Statistics of 2002 Area West of 2nd collision point East of 2nd collision point West of annulus entry East of annulus entry Control room of BES Outer wall of BES shield Inner wall of BES shield North end of linac corridor Entry of linac corridor South end of linac corridor Port of 4Wb Port of 4B9 Southeast gate of the 12th Experimental Hall Port of 3w1 beamline, east Port of 3w1 beamline, west Port of 3w1 beamline, north 19th Environmental Station 20th Environmental Station Dose from 7-12, 2001 1.4979 15.4641 8.8527 6.4377 1.1249 2.3914 1.1178 24.1032 4.2225 1.3604 10.1067 3.0945 0.4876 0.6214 5.1159 3.8408 0.4905 0.4798 Dose from 1-6, 2002 1.9541 24.0387 7.64 12.8477 0.6842 4.072 2.7405 9.2919 8.3023 3.4228 14.6313 8.8746 0.6891 0.9091 14.8447 11.4001 0.4171 0.6031 Total (mSv) 3.452 39.5028 16.4927 19.2854 1.8091 6.4834 3.8583 33.3942 12.5248 4.7832 24.738 11.9691 1.1767 1.5305 19.9606 15.2409 0.9076 1.0829 (2) System Expansion 42 2002 Annual Report of IHEP According to the requirement of the Nuclear Analysis Division, three areas of radiation protection and 6 radiation monitors were added in the slow positron source hall. And one data acquisition card at the 4th local station was expanded. The software of the central control was upgraded and its function expanded. (3) System Repair 9 monitors were repaired in summer time and annual graduation of all monitors carried out. 3. Personal Dosage Inspection For personal dosage inspection result in 2002, please see Table 4.5.10-2. Table 4.5.10-2 Unit Experimental Physics Center Accelerator Center Proton Linac Division Synchrotron Radiation Division Division in Charge of Running Conventional Facilities Office in Charge of Day to Day Affairs of BEPC National Lab. Security Office Laser Division Nuclear Analysis Division Total Percentage Neutron treatment of cancer Personal Dosage Inspection Result in 2002 Total Dose 6.93 5 1 14.63 5.38 5.68 4 13.85 0.02 4 12 20 172 33.86% 18 10 1.97% 1 1 0.19% 5.96 0.33 1.5 2.41 6.09 56.49 Average Dose 0.06 0.09 0.17 0.09 0.33 0 0.17 0.15 0.12 1.18 Frequency distribution of dose equivalent (people) <0.1 103 115 12 43 3 12 5 4 28 325 63.98% <0.5 23 38 19 21 35 >0.5~1 >1~5.0 4. Measurement of the Radiation Level at Specific Areas In 2002, the dosage level at the following specific locations was measured: the instrument control room in synchronous mode; the top hole of the first target room in the 10th Hall during bombardment (the extraction port of the beamline of the slow positron source); the radioactive chemical building of the Application Department in Zhongguancun; the rare valuable metals recovered; the office building and the basement of the east wing and the control room of BES during muiti-bunch injection. IV. Accelerator Science and Technology 43 5. The Personal Safety Interlock System Following 3 months’ hard work, transformation has been accomplished regarding the doors of the LINAC, the transportation lines, the tunnel of the transportation line, the tunnel of the experimental hall of nuclear physics, the experimental hall of nuclear physics and the BES hall. And most of the work on the software and hardware of the system of entrance guard was also completed. The system was put in operation in the second half of 2002. Operation shows that it works well. According to the requirement of the Experimental Physics Center, the protection door of the BES hall was thoroughly transformed in summer. The transformed protection door is interlocked with the accelerator. It is opened and closed by the entrance guard. The transformation led to the improvement not only in appearance but also to safety and reliability. The major characteristics of this system are: Card is to be read when getting in and out; Work site is to be patrolled and cleared; Reconfirmation of leaving the site; Zero count Measurement of the radiation level in ns in case of emergency; Warning signal of a speech sound, light, etc. 6. The Fire Alarm System In 2002, the condition of fire appeared twice in BEPC, which was detected and warned by the automatic fire alarm system. In addition to the repair of the equipment outside in summer, the detector was changed and 253 detectors were cleaned. The second phased task was completed in terms of installation of all detectors in the library, the nuclear analysis laboratory and the 12th Hall. Debugging work is on. The preliminary design of the BEPC-II fire alarm system has been accomplished. And it is the same case with the preliminary designs of the automatic fire alarm systems in the hall of the positron injector and the superconducting experimental hall. 7. The Flood Alarm System This system maintains stable operation this year. 8. Investigation of High Energy Neutron Detector High energy neutron detector was investigated with reference and experimental method collected. The feasibility study report on developing high energy neutron detector was accomplished. 4.5.11 Study of Superconductivity 1. Establishment of the Superconducting Cavity Laboratory The newly constructed Superconducting Cavity Laboratory with a total floor space of 230m2 as shown in Figure 4.5.11-1, passed the check according to the requirement of fire prevention and control at the end of November. Figure 4.5.11-1 The newly-constructed superconducting testing hall 44 2002 Annual Report of IHEP The chemical polishing device（shown in Figure 4.5.11-2）, the barrel polishing machine（shown in Figure 4.5.11-3）, the high-pressure ultra-pure water rinsing system (shown in Figures4.5.11-4 & Fig.4.5. 11-5), the Class 100 clean room（shown in Fig.4.5. 11-6）, the vacuum system, the helium gas pumping system and the stand for cavity assembling, etc. have been made, and they are being installed in the this laboratory one by one. Some microwave instruments and components for vertical measurement have been ordered. It is expected that the Superconducting Cavity Laboratory will be completed and come in use next September. Figure 4.5.11-2 The chemical polishing device Figure 4.5.11-3 The barrel polishing machine Figure 4.5.11-4 The high pressure water rinsing system IV. Accelerator Science and Technology 45 Figure 4.5.11-5 The ultra-pure water system Figure 4.5.11-6 The Class 100 clean room 2. Early Study on High Gradient Medium-β Superconducting Cavity for High Intensity Proton Linac β (1) The 1.3GHz β=0.45 test HCOF cavity was fabricated and measured (shown in Figure 4.5.11-7): Freq.=1294MHz; Q=9000. Figure 4.5.11-7 The 1.3GHz β =0.45 test HCOF cavity (2) The die and jags for fabricating the 1.3GHz SC cavity are ready. (3) All the niobium sheets and blocks with the RRR value of 300 for 1.3GHz SC cavity have been ordered from Tokyo Denkai Co., Ltd. (4) The initial permeability at different temperatures (273K, 77K, 4.2K) of another 3 kinds of Chinese magnetic shield materials (permalloy 1J79, grain oriented silicon steel 30QG110 and pure iron for shielding) has been measured. The performance of permalloy 1J79 at low temperature is the best: µr=14833@77K. (5) The magnetic shield coefficient of a barrel shape with a bottom cover was measured. Based on it, the dimensions of the magnetic shield barrel with a bottom cover for the 1.3GHz cavity has been determined：350×2000, using two layers of permalloy 1J79 with a thickness 1.3∼1.5mm. The required earth magnetic field in it should be ≤2mGs at room temperature. It will be completed soon. 46 2002 Annual Report of IHEP (6) The dimensions of the cryostat with multi-shield and multi-layer adiabatic structure for 1.3GHz cavity have changed to Ø 358×2800. It will be finished next May. (7) The 300W(CW) 1.3GHz solid-state amplifier will be delivered soon. 3. Key Technology Study on Rapid Cycling Synchrotron (Radio Frequency Sub-system) Based on the CSNS/RCS lattice version 3.0, the frequency swing of the RF system is 0.959∼2.435 MHz, and a total of about 160 kV RF accelerating voltage will be needed. But the straight sections are limited by 2×6.5m. So it means that a high gradient RF accelerating structure will be needed for the CSNS/RCS. Some investigations in it have been done. It is now clear that the gradient of a ferrite-loaded cavity is about ≤10kV/m, limited by Brf ≤100Gauss. But the gradient of a loaded cavity with magnetic alloy can be >25kV/m. The magnetic alloy cavities have successfully operated at other laboratories. So magnetic alloy cavity is the only way for CSNS/ RCS unless a new kind of ferrite can operate at high field (Brf >350 Gs). This project started in October this year. is needed to optimize the system flow, these work was finished through external assistance. In order to find collaborators during the engineering design and construction stages, a initial design contract was signed through long time discussions with the Institute of Physics and Chemistry, the Chinese Academy of Sciences on January 8, 2002 and the Institute of Cryogenics and Superconductivity Technology, HARBIN Institute of Technology on January 15, 2002 respectively. And these contracts had been executed before June 30, 2002. Based on the initial designs of these two collaborators, we finished the BEPC-II cryogenic system report to get funded and the design report. At present, the BEPC-II cryogenic system has entered the engineering design and manufacturing stage. 3. Investigation in Helium Refrigerator It has been decided that BEPC-II will adopt the two 500W/4.5K helium-refrigerator scheme. However, no mature product of this type of refrigerators is available in domestic market. So the main investigation was focused on the standard products of foreign companies, such as TCF50 of Linde AG and Helial 2000 of Air Liquide. We shall modify the standard product to meet the requirement of BEPC-II. 4.5.12 The BEPC-II Cryogenics System 1. Preparations of the Cryogenic System The BEPC-II cryogenic system was set up on November 16, 2001. As it was set up much later than any other systems, it lagged behind other systems in many respects. Only the initial work has been finished, including the CPM plan, cost estimation, recruiting some new members. At the same time, we accomplished a report named the initial consideration about the BEPC-II cryogenic system as the working base of cryogenic system. 2. The Conceptual and Preliminary Design of the BEPC-II Cryogenic System The conceptual design report was made on December 14, 2001 with the scheme of adopting one or two refrigerators described and every heat load of cryogenic system as well as every operation mode estimated, respectively. As the cryogenic system is a very complex system, some large software package 4.6 Beijing Proton Linear Accelerator & Its Applications 4.6.1 R&D of Intense-Beam RFQ The ADS group continues with the R&D work on the intense-beam RFQ accelerator with the support from “the 973 Program”. We are going to build the first intense-beam proton RFQ accelerator in China, with the output energy of 3.5MeV and the peak current of 50mA at the duty factor of 6%. Our major research activities this year involve the optimization of the RFQ physics design, the technology design of the subsystems, the manufacture of the copper cold model for technology development and the setup of the RF power system. In the RFQ design, with the combined advantages of PARMTEQM code and LIDOS.RFQ code, we obtained the optimized RFQ physics design with the best dividing position for the two coupled-segments. A variety of error effects were modeled and then the machining and assembling allowances clarified. 3D RF field modeling of the RFQ cavity reached high IV. Accelerator Science and Technology 47 accuracy with a better simulation code. Comparison of the modeling with the measurement of a cold-model cavity is under way. The subsystem for the RFQ accelerator was designed. The physical and mechanical designing of the vacuum system was accomplished. And machining work on it already started. The physical and mechanical designing of the water-cooling system was near completion. The mechanical designing of the alignment-supporting frame was accomplished. It is the same case with the active tuner designing and the physics design of the beamline downstream the RFQ for beam diagnostics. Technology used in manufacturing the RFQ cavity is a key issue in building our RFQ accelerator. To develop such a technology together with our cooperative company and university, a series of vertical brazing tests with test pieces were conducted in a hydrogen furnace. Various designs were tried of the contacting surface and filler's grooves， well as the as variation of brazing temperature. Consequently a possible option was determined. To master the machining technology, a short RFQ cavity with vane modulation and a long RFQ cavity without modulation were fabricated. Owing to the cooperative relationship between IHEP and CERN, a high power RF system decommissioned from LEPII, including a CW klystron of 1.2MW, a high power supply, a circulator, the control deck and some other equipment, was moved to IHEP. Installation of the system was finished and connection of the system is now under way. A pair of down-step transformers of 10kV/1kV designed by our institute and developed in our country was installed to match the power supply from CERN. The water-cooling system for the RF power system was developed and installed. In addition to the ADS research, we also started the preliminary study on the design of the China Spallation Neutron Source. CAS supported our research on CSNS proton linear accelerator. new system includes a duo-plasma ion source, a beam transformer, a low energy beam transport line, a four-rod type RFQ, a RF power source, a vacuum and water-cooling system, etc. In addition, on the test stand, there are still another beam transformer and a Faraday Cup for the beam current measurement. Due to the hard work of our researchers, a maximum pulsed-beam current of 8mA has been obtained at the exit of RFQ. The researches include: 1. The Mechanical Assemblage of Four Electrodes After the completion of welding between the 14 supports and the substrate, the assemblage of the four electrodes was finally finished in April because of the overtime work of our staff member’s workers. Except several places on the rods, the alignment and assemblage precision is within ±50µm. 2. RF Measurements of RFQ After the mechanical assemblage of the 4-rods, supports and substrate and their installation inside the cavity, the RF measurements of RFQ were carried out. By slightly adjusting the two tuners installed on the cavity, we could get the operation frequency (its value is 201.25MHz) of RFQ and its corresponding Q value 2800, which was almost the same as that of the 4-rods RFQ (measured in 2000) in ISIS. Due to the small beam hole and the modulation of the electrodes, it is comparatively difficult to accurately measure the field distribution. The measured results show that the field distribution in RFQ after welding is basically the same as that before welding. The flatness of the filed distribution along the longitudinal direction is about ±3.8%, and the azimuthally symmetry of the field distribution is within ± 5.8%. 3. Experiments of Power-input Coupling Loop The shape and size of the coupling loop were finally determined after extensive experimental investigations. The first measured result of SWR was about 1.1 by the network analyzer, and this SWR value changed to 1.27 in the later measurement by the directional coupler under high power condition. 4. Experimental Results of Ion Source and LEBT 4.6.2 Status of Researches on Four-rod Type RFQ The four-rod type RFQ was designed and constructed as a substitute for the present BPL 750keV electrostatic accelerator (the injector of BPL). This 48 2002 Annual Report of IHEP The maximum measured pulsed-beam current at the exit of the ion source was about 150mA, but a beam bombardment trace was found at the entrance of the first solenoid. The maximum pulsed-beam current was about 50-70mA at the entrance of RFQ after the beam went through LEBT, the normalized remittance was about 2 π mm*mad. Both the beam quality from the ion source and the focusing of LEBT still need further improvement. 5. The Equipment on the Test Stand The ion source, LEBT, RFQ, beam transformer 2 and the Faraday cup were all installed on the stand after alignment. After the vacuum leakage check, the static vacuum of the RFQ cavity was up to 1×10-4 Pa, and this value was increased to 8×10-4Pa after the beam was on. The pressure of cooling water at the exit of the pump was set to 0.3MPa. 6. RF Conditioning The RF power to RFQ was fed in August this year from smaller power higher pulse repetition rate to larger power and lower pulse repetition rate. In the process of the RF conditioning, it was found that the system with a 250kW RF output pulsed power, a 350µs pulse width and a 10Hz pulse repetition rate could operate only 15 minutes before the appearance of the whole reflection of the RF power and that the system could work normally over a long period of time when the pulse repetition rate was set to 5Hz and the temperature of cooling water lowed from 18.10C to 15.70C. 7. Measurements of Inter-electrode Voltage At the exit of RFQ, the beam current measured at first was almost zero. The beam dynamic simulation showed that when the real inter-electrode voltage was much lower than the designed value, the beam could not pass through RFQ. So, in order to judge whether the inter-electrode voltage had reached the designed value, the inter-electrode voltage under the RF power feeding condition was measured using the way of X-γ ray spectrum. With the present RF output power limit, the maximum inter-electrode voltage measured was 120kV (the designed value is 130kV). Through this experiment, the effective shunt impedance of RFQ obtained was about 35kΩ. 8. Experiments of Water-cooling System Some experiments were done on the water-cooling system in order to ascertain its maximum cooling capability. The experiments showed that with the RF output pulsed power of 250kW, the pulse width of 350µs and the cooling water temperature of 15.70C, the whole system could work normally more than two hours. It was confirmed in later experiments. 9. Beam-tuning Experiments In the present beam-tuning experiments, a maximum pulsed-beam current of 8mA had been measured with both the beam transformer and the Faraday cup at the exit of RFQ. The inter-rod voltage was about 103 keV when the data were acquired. 4.6.3 Fast Neutron Radiotherapy Research The study of fast neutron radiotherapy made progress in 2002. The major contents are as follows: 1. Research of Fast Neutron Therapy Clinical Treatment A fast neutron radiotherapy facility was developed at our Institute for research on cancerous tumor management. This is the only one in China up to date. The clinical treatment was successfully made under the guidance of an expert group, whose members are from IHEP and some famous medical institutions and hospitals. The total number of patients is 682 since November 1991. 47 patients were treated by neutron beam therapy during this year. It is concluded that neutrons are efficacious for certain specific tumor types, such as parotidoscirrhus, prostate sarcoma, salivary gland sarcoma, pancreas cancer, melanocarcinoma, osteosarcoma, chondrosarcoma, synoviosarcoma, cystadenocarcinoma, nasopharynx carcinoma, soft tissue sarcoma, fibrosarcoma, liposarcoma, chordoma, metastasis cancer of head and neck, lung-metastasis, malignant neoplasm of gum, submaxillary gland, malignant neoplasm of rectum, malignant neoplasm of retroperitoneum and peritoneum, malignant neoplasm of pleura, malignant neoplasm of orbital, malignant neoplasm of buttock and perineum, lymphangiosarcoma, etc. To retrospectively analyze the clinical results of soft tissue sarcoma with P(35MeV)→Be fast neutron, and neutron and photon mixed radiotherapy, the following conclusions can be drawn: Fast neutron radiotherapy is effective for soft tissue sarcoma, and IV. Accelerator Science and Technology 49 fast neutron and photon mixed beam can improve the treatment as compared with fast neutron alone. Unresectable or residue G1/G2 tumors after resection are fit for neutron therapy. The side effects of the treatment can be moderate. 2. Research of Neutron Radiophysics The physical characteristics of the P (35Mev) Be neutron therapy beam were measured. The physical characteristics of the P (35MeV) Be neutron beam were compared with other modern fast neutron radiotherapy facilities. A lot of experiments and tests of neutron radiophysics were done on the IHEP neutron radiotherapy facility: (1) Research on methods of measurement of neutron energy spectra Comparisons of several methods to measure neutron energy spectra were done. The comparison of neutron energy spectrum with the spectrum of dose deposition by the neutron beam in the depth is to be done. (2) Neutron dose distribution measurements; Measurements of the Central Axis Depth Dose (CADD); Off-Axis Ratios (OAR) in air for differential fields. Acquired data are good enough for neutron clinical treatment. (3) Calibration of the neutron dose measurement instruments The ionization chambers and the neutron dose measurement instruments are sent to NIM (National Institute of Metrology) for calibration in their 60Co-γ ray. The NBS furnished an Annual Calibration Certificate. (4) The neutron therapy beam calibration is to be done on every treatment day. There are two calibration programs for daily therapy: ionization chamber calibration in terms of 60Co-γray in a 137Cs source, and neutron beam transmission chamber calibration. (5) Research of microdosimetry and nanodosimetry. (6) Research of three-dimensional neutron treatment plan and conformal techniques. 3. Research of Neutron Radiobiology The research of fast neutron radiobiology was car- ried out. Two tumor cell lines were used during the fast neutron radiobiology test: the human nasopharyngeal cancer cell line (CNE-1) and the human fibrosarcoma cell line (HT1080). The research contents are as follows: (1) To determine the cell killing effects and relative biological effectiveness (RBE) on two human tumor cell lines by P (35Mev) Be fast neutron and 6MV-X ray, and to analyze the influencing factors. The conclusion is that fast neutron can kill tumor cell more effectively than X-ray as tumor cell lines with different radiosensitivity to X-ray show close sensitivity to fast neutron. The RBE of fast neutron to photon can vary significantly with different endpoints. (2) To study the radiobiological effects of the mixed beam of neutron and photon on human tumor cell lines and discuss about the mechanism. The conclusions are the mixed beam of neutron and X-ray show a synergic effect in vitro in CNE-1 cell killing effects and that cell cycle arrest and apoptosis may play some roles in the radiation damage repair of mixed beam. 4. The computer programs for data of patient are more perfect. 5. The neutron therapy facility was maintained during the summer-maintenance period. 6. Three seminars on neutron radiotherapy were held this year. Discussions were focused on fast neutron therapy clinical data, neutron radiation physics, neutron radiobiology and technical aspects in neutron radiotherapy. It is concluded that the fast neutron radiotherapy is one of the most significant radiotherapies. Differing from low-LET radiation in the radiobiological effects, neutron has higher relative biological effectiveness (RBE), less repair of radiation injury to cell, less variation of radioresistance through the phase of the cell cycle and less radioresistance of hypoxic cells, i.e. a lower oxygen enhancement ratio (OER) than low-LET radiation. Neutrons are efficacious for certain specific tumor types. A professional meeting (2002.10.29.) was held at our Institute with representatives from “People To People Ambassador Programs RADIATION ONCOLOGY DELEGATION TO CHINA” and from the Chinese Fast Neutron Radiotherapy Group taking part. Dis- 50 2002 Annual Report of IHEP cussions were focused on the use of neutron therapy in the treatment of cancer patients, the study of neutron therapy and international collaboration in this field and a comparison of fast neutron radiotherapy in the U.S.A. and China. The presentations are: (a) “Present Status of Radiation Oncology in China” by Professor Weibo Yin, China. (b) “Role of Particle Radiation in Cancer Treatment” by Professor George Laramore, U.S.A. (c) “Fast Neutron Radiation for Inoperable Non-Small Cell Lung Cancer, a follow up of 5 years” by Professor Ma Lin, China. (d) “Fast Neutron Therapy of Inverted Papilloma” by Professor Qinfu Feng, China. 7. There are four papers about fast neutron radiation therapy: “Neutron Radiotherapy” (24th chapter from a new work “Accelerator for Medical Applications”), “ Fast Neutron Radiotherapy Soft Tissue Sarcoma”, “The Neutron Spectrum Measurement on Fast Neutron Radiotherapy” and “Fast Neutron Radiotherapy for Patients with Soft Tissue Sarcoma-A Retrospective Analysis of 52 Cases”, the 4th Shanghai International Conference on Radiation Oncology held in Shanghai in May 2002. China is a densely populated country. The incidence of cancer increases year after year. It is necessary to develop neutron radiation therapy. magnet power sources, examined and considered to improve the control board for the magnet power source. Now the PCB has been drawn, the sample of it will be made and some experiments of it will also be done. The RF system group has fixed the factory that manufactures high power electronic tube 820 used for the 5MW RF system while it was maintaining the RF system. The assistant group examined and repaired the vacuum system, the water-cooling system, the air condition system and the electric apparatus in the hall to ensure the normal operation of BPL. In the second half of this year, the operation of BPL was suspended, but had to be kept in a good state according to the decision made by our Institute. An average target beam current of 16µA was obtained in the test operation. 4.6.5 Study of the Medium-Energy Proton Linac with Intense Beam Current This subject is an important one belonging to National Natural Science Foundation of China. It is jointly undertaken by China Institute of Atomic Energy, Peking University and our Institute. It started in 1999. Our institute is mainly responsible for theoretical research. Based on extensive investigation in the development of proton linac with intense current in the world, studies were made on many structures of intense current proton linac (including RFQ，DTL, SDTL, CCDTL)，the choice of the work frequency, the accelerating gradient and the focus structure of accelerator, the match between RFQ and DTL, the design method of “equipartition of temperature” for the quasi-period structure, the transport characteristics and the formation of beam halo of the intense beam in the periodic field, etc. A preliminary plan of the intense current proton linac used for clean nuclear energy system and that of the principle demonstration facility for the intense current linac were put forward. The preliminary plan of H- linac used for spallation neutron source was discussed. The optimization design of RFQ and the physical design of low energy beam transport line were finished. In addition, On the basis of the international development of superconducting accelerator structures and intense current cyclotrons, a theoretical research was carried out on the properties of the elliptical 4.6.4 Operation of BPL During the first half of this year, BPL was well maintained and operated. In the routine operation, the average target beam current was always kept above 18µA. The overall operation time of BPL in the first operation turn of this year was about 2100 hours. BPL provided a good test stand for the researches of fast neutron therapy clinical treatment and neutron radiobiology as well as for the physical experiments such as proton radiation, etc. During the summer maintenance of BPL, all sub-systems of the accelerator were carefully maintained and in the meantime, experiments of 4-rods RFQ were done. The pre-injector group examined and repaired carefully the gas-providing system, fixed the factory producing oxide cathodes, and improved the wet-removing system in the pre-injector hall. The general tuning group maintained carefully the sub-system AD, DA modules of CAMAC, examined and replaced some inserts of CAMAC and NIM in the control system, repaired carefully the bad IV. Accelerator Science and Technology 51 superconducting cavity, the properties of ISCL superconducting cavity, the properties of spoke superconducting cavity, the effect of space charge and the beam halo in an intense current cyclotron. Now, the subject has been successfully completed. Thanks to the hard work, we have got the basic knowledge of the theoretical problem about intense current proton linac, obtained some achievements on the intense current accelerator theory, published more than twenty articles and design reports and laid the foundation for the research of medium-energy proton linac with intense beam current in our country. 4.6.6 Study of Proton Treatment Technology The subject “Study on the Proton Treatment Technology” is an item under the National Climb Program, which started in 1995 and ended in 1999. Part of this research was continued with self-raised fund and finished completely in 2002. This subject has involved the researches of proton treatment accelerator, beam distribution and transport system, dose measurement and biological effectiveness. It has played an important role in promoting the development of domestic proton treatment.