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IV. Accelerator Science and Technology 47
IV. Accelerator Science and Technology
4.1 The BEPC Operation
The BEPC operation in 2001 included data taking at the energies of 1.55 GeV
and 1.84 GeV, the supply of beam to synchrotron radiation (SR) users for about 3
months, and some necessary machine studies for the BEPC upgrading and the BEPC
II design. During the whole year of 2001, the BEPC obtained 16.5 M J/ψ events and
4.8 M ψ(2s) events.
With the efforts made by all people in charge of the BEPC operation and
maintenance, the linac provided beams stably to the storage ring during the
operation in spite of such difficulties as the aging problems of instruments and the
shortage of manpower. Many records of operation were broken, thus greatly
improving the efficiency of the BEPC performance. The average injection rate of
positron was 2~3 mA/min and the maximum value reached above 6 mA/min. The
shortest time interval between two injections was only 12 minutes. Up to April 3, the
mission on providing beam for the BES data taking was fulfilled ahead of time.
Beams were provided solely for the SR users in three segments of time, totaling 84
days. All the goals of the operation were reached successfully.
During the summer shutdown, the power supplies of the positron source and
the AM3 analyzer were updated. The control system was improved with the new
display of remote control data. The whole environment for operation was
ameliorated.
In the first half of 2001, the storage ring ran mainly at the J/ψ energy. Some
operation records, such as the peak current and luminosity and the hadron events per
48 2001 Annual Report of IHEP
shift, per day and per week were frequently renewed. People on point duty helped
the hardware people find problems in operation with the help of the BEPC database,
thus greatly decreasing the time for solving problems. In the SR operation, the
maximum beam current reached 100～120 mA at the energy of 2.2 GeV with a
beam lifetime of 20～30 hours. Occasionally, the beam lifetime was reduced. In
February, the time-fixed injection was adopted for the SR operation which produced
a very good result.
During the second half of 2001, the dedicated operation group was founded in
the Accelerator Center. Though the operation work was very tough, academic
exchanges were conducted among people of the operation group and some
professional training of them was carried out. With the support of the maintenance
people, the operation team optimized the machine at the end of 2001.
The 2001/2002 operation of the storage ring started on Sept. 17, 2001. After
one-week commissioning of the machine, the BEPC began to provide beam to SR
by operating in a dedicated mode. During the dedicated operation, the normal
injected beam current reached 120～135 mA with 50～60 unequal population
bunches around the ring. The beam lifetime kept more than 18 hours. The energy for
the injection was 1.1 GeV, due to the faults of the modulators in the linac. The
efficiency of injection did not decrease due to the lower energy. The normal
injection process took only 20 minutes. The beam lifetime reduction still existed
during the SR operation. This was caused by the dust effect. Though we did some
special machine studies on that and proposed some measures, only few methods
were effective. The data taking for high energy physics in this run began just after
the first period of SR operation. During the conversion from the SR mode to the
collision mode, some machine studies like the beam lifetime under the dedicated SR
mode and the beam-based alignment were carried out.
In 2001, the BEPC had been operated for about 6,645 hours with 39.07% for
the BES, 27.57% for the SR operation, 10.81% for the dedicated machine studies,
IV. Accelerator Science and Technology 49
5.47% for the faults, 5.79% for the machine warm-up and 0.23% for the others. The
statistics was shown in Table 4.1-1 and Fig. 4.1-1.
Table 4.1-1 Statistics of BEPC Operation in 2001
BES BSRF MD Inj. Startup Failure Others
Total 2596.1 1831.9 718.2 735.5 384.8 363.5 15.4
Percentage (%) 39.07 27.57 10.81 11.07 5.79 5.47 0.23
5.8% 5.5% 0.2% BES
39.1% BSRF
11.1%
MD
Injection
Startup
10.8% Failure
Others
27.6%
Figure 4.1-1 Statistics of BEPC operation in 2001
In 2001, the machine study was focused on the following fields:
1) Studies on the beam lifetime reduction in the dedicated SR operation, i.e.,
observing the electron beam lifetime when the distributed ion pumps were switched
off and the positron beam lifetime in normal beam and machine conditions; 2)
Observation of the vacuum pressure under high beam current; 3) Measurement of the
synchrotron phase angle with streak camera; 4) Studies on the beam-based alignment
system and 5) Studies on the photoelectron effect.
The BEPC has been running for more than 13 years. The aging problem of
many components of the linac and the storage ring is so serious that the rate of
failures of hardware is very high. After some main parameters of the storage ring
such as the tunes, the beam orbit and status of the RF cavities were optimized, the
50 2001 Annual Report of IHEP
BEPC gradually got to a stable stage for operation. Till the end of 2001, the peak
luminosity at the energy of 1.84GeV reached 1.133×1031cm-2s-1 and the peak
collision beam current 86mA. These values reached a record high in the history of
the BEPC operation.
4.2 The Linac
4.2.1 The Microwave System
1. Operation and Maintenance
Thanks to the careful maintenance and timely dealing with failures, the
microwave system operated well in 2001. Very few faults were directly caused by
the microwave system itself.
Due to the high failure rate and the short lifetime of the old microwave
amplifier, the new 1kW RF solid state amplifier was developed in 2001 and used in
the linac in April. It had an excellent performance that met the requirement of the
machine after being commissioned and smoothly fit to the BEPC linac. Up to now, it
has been operating well.
2. Upgrades and Studies of BEPC II
There were three subprojects regarding upgrades and studies of the BEPC II.
They all progressed well.
For the microwave system, the new high power load model was made and
measured. The development and measurement of the prototype of the 65 MW
wave-guide valve, the improvement and measurement of the old 65 MW wave-guide
valve and the principle experiment on the new SLED detuning system were all
accomplished. The maintenance and re-measurement of the 6 backup accelerator
tubes were done and the design of the upgraded tubes was carried out. The focusing
and exciting lines were tested. The principle test of the new type of IΦA control
system was accomplished too.
IV. Accelerator Science and Technology 51
Concerning the focusing system upgrade, the design, the computer simulation
and the optimization of different types of magnet shimming were done.
As to the positron target upgrade, the physics design of a new positron target
was done, and it passed the review in November 2001. The engineering design was
basically finished. The development of the 12kA pulse power supply for positron is
under way.
3. International Collaboration and Development
The development of two SLEDs and two S-band accelerator tubes to be
exported to ANL, USA and one S-band tube to Kawazaki Co., Japan is well on the
way. Hopefully the development of these components and the microwave
measurement will be accomplished at the beginning of 2002.
4.2.2 The RF Power Source System
1. Equipment Operation and Maintenance
Three Hk-1 klystrons with the average lifetime of about 25,000 hours were
replaced. One 5054 model 65 MW klystron was set up in the klystron gallery. Seven
hydrogen thyratrons with the average lifetime of around 21,000 hours were replaced.
No. 14 and 15 modulators and the M/K control system network were improved. 16
sets of the power source systems, such as EOLC, the focusing power supply of
klystron, etc., were maintained in the summer shutdown, thus ensuring the startup of
the BEPC. Thanks to the aforesaid efforts together with sufficient spare parts
available, the rate of failure was lowered and the stability of the whole system
operation increased.
2. BEPC II Design Work
The RF power source system of the BEPC II was preliminarily designed. The
new BEPC II klystron, the modulator system and the flux concentrator pulse power
supply were proposed. The TH2128C klystron was chosen for the BEPC II project.
52 2001 Annual Report of IHEP
4.2.3 The Electron Gun System
1. Routine Operation and Maintenance
Except for two failures caused by the heater power supply, which led to the
shutdown of the machine for repair, the electron gun system ran very well. In the
summer shutdown, the maintenance of the electron gun system was accomplished in
time, thus guaranteeing the operation of the whole system.
2. Design of the Electron Gun System for BEPC II
Simulation was done for the BEPC II electron gun. The test bench was
upgraded continuously.
4.2.4 Beam Modeling and Orbit Correction for BEPC II Linac
1. Optics Correction
Based on the non-periodic features of the existing linac lattice, some feasible
and effective correction schemes have been studied for the e- beam to the linac end,
the primary e- beam from the buncher to the e+ yield target and the e+ beam to the
linac end. For the e+ beam with a very large emittance and a large transverse
momentum, the re-arranged 24 big quadrupole systems (installed on the accelerating
structures) will be used to focus the beam, together with the existing 15 triplet
quadrupole systems. A preliminary design of the above correction schemes has been
proposed and positively reviewed.
2. Improvement of the Emittance Measurement
The emittance measurement device has been newly designed and installed at the
buncher exit. It is used for the beam matching from the buncher’s solenoid focusing
system to the downstream quad system. The emittance measurement device at the
linac end has been improved. It is used for the beam matching from the linac to the
beam transport line. The above emittance measurement devices (each consisting of a
profile monitor, a drift and a single quad) have been technically upgraded to
IV. Accelerator Science and Technology 53
significantly improve the measurement accuracy and reliability with such measures
as: 1) putting the profile monitor at a distance, which equals to the focus length of
the single quad (correctly that corresponds to the middle current of its power supply),
having a sensitive profile change rate to the focus strength; 2) taking multi-pair
values (>10) of measured σ (profile) ~ k (focusing strength), then fitting a σ (k)
parabolic curve to get the emittance parameters of ε, α and β. The quad’s length is
chosen to meet a thin lens approximation condition to simplify the transport matrix
(from quad to the profile monitor) and 3) with MATLAB 3.3 as the software for data
acquisition and procession, the illumination of the profile monitor was improved.
The measurement system was re-installed and aligned. The readout of the bunch
sizes was clear enough with accurate and reliable data processing.
With the above improvements, the emittance measurements were done
successfully with good repetition and reliable results. Furthermore, a great amount
of normalized emittance growth through the linac was found, and its possible
reasons were studied. It is meaningful for ensuring the emittance of the BEPC II
linac.
3. Studies of e－ Beam’s Spot Size on e＋ Target
＋
To get a most effective e yield by minimizing the e－ beam spot size on the
target, a preliminary study on this issue was carried out first on the existing e＋
source by using a profile monitor PR2. The PR2 was located about 56 cm away from
the e＋ target. The dilutions of the measured spot size, due to the e－ beam’s initial
energy spread (causing chromatic/dispersive effects) and its initial beam offset
－
(causing wake effect), were studied. A further beam simulation to minimize the e
beam spot size for the BEPC II e＋ source (with a primary e－ beam of higher energy,
larger emittance and higher beam current) was studied. As a result, the tolerance for
the initial e－ beam offset and the linac misalignment was proposed.
54 2001 Annual Report of IHEP
4. Preliminary Design of the Orbit Correction
The orbit correction system with a “one-to-one” scheme was preliminarily
designed to partially cure the emittance dilution and the orbit offset due to the initial
beam offset and the linac misalignments. The influences on the emittance dilution
and the orbit offset by many kinds of machine errors were studied with beam
simulation. The efficiency to cure these dilutions with the proposed orbit correction
was studied too. The prototype of the strip-line BPM and the prototype of the
corrector were developed.
4.3 The Storage Ring
4.3.1 Accelerator Physics Study
1. Design Study of BEPC II
The Accelerator Physics Group was mainly involved in the design study of the
BEPC II in 2001. It covered the single-ring scheme and the double-ring scheme. For
the single-ring scheme, it involved the optimization of the linear lattice, the
correction of the chromaticity, the tracking study on the dynamic aperture and the
detailed design of the injection channel for the 6×3 bunches in the βy* = 1cm
scheme. From March 2001, study on the double-ring scheme began and a very
preliminary design was accomplished. It was reported on the International Review
Meeting on the Preliminary Design of the BEPC II held in April, thus making it
possible to convert the single-ring scheme to the double-ring scheme. After the
review meeting, the group was devoted to the study of the double-ring scheme. In
June, the preliminary parameters of the hardware system were submitted to
corresponding groups. In July, IHEP made a preliminary review on the lattice design.
From August, the study on the dynamic aperture, the injection, the Green function of
the wake field, the beam instability and beam-beam interaction went into detail. In
the meantime, a preliminary study showed that the 2.5 GeV dedicated synchrotron
radiation scheme was feasible, and the 2.8 GeV scheme seemed very difficult. In
October, the hardware parameters were formally issued.
IV. Accelerator Science and Technology 55
In December, IHEP made a second review on the designs of the accelerator
physics such as the lattice design, the dynamic aperture study, the beam instability,
the injection, the beam-beam simulation and the study on the dedicated synchrotron
radiation scheme.
2. Research of Beam Physics
The studies on the interaction between beam and photoelectron were carried out.
Two photoelectron collectors were designed and manufactured and will be installed
on the storage ring soon. With the existing photoelectron detector, some experiments
such as the studies on the relations between the collector current and the bunch
spacing, the bunch number, etc., were carried out.
3. Academic Activity
Three people were sent to KEK, Japan and one to CERN, Switzerland for
academic collaboration in 2001. Four people were sent to KEK for short-term
collaboration on the electron cloud study and attending the international Two-Stream
Instability Workshop. One person attended PAC’01 in Chicago, USA and 5 attended
APAC’01 in Beijing. About 13 papers were submitted to the above conferences.
4.3.2 The Magnet Power Supply System
1. BEPC Upgrade and Maintenance
All members of the Power Supply Group did their best for the operation in
2001 by recovering the equipment in time when they were at fault. The failure rate
accounted for only 4.3% of the total.
Although the BT power converters on the storage ring were used for only 6 to 7
years, due to the quality, a lot of faults occurred. Some of them had affected the
operation. So they were rebuilt in six months. The chassis, the cabinets and some
main components were still used to save money. After this renovation, the power
converters of BT were more stable with few faults occurring in the operation of the
BEPC.
56 2001 Annual Report of IHEP
The control system for the storage ring cooling water often went wrong. It
sometimes read wrong temperature or even went to shutdown and caused the
temperature of the RF cavities out of control or even beam loss. It was due to no
shake hands signal between the hardware and the software. As the whole system
would be renovated, what we could do was to adjust the delay time of the software
to make it work well for a long time. At the same time, the interface was changed to
be friendlier.
Seven sets of QT power converters were repaired to meet the requirement of
the machine commissioning. They have been used for more than ten years. Since
there were no spare parts of the main components, nor could they be bought in
market, we had to replace them with other types of components. Two sets of DCCTs
were mounted on RSQ1 and RSQ2, respectively. In the last operation of RSQ1 and
RSQ2 it was found that there were some differences between the reference value and
the read-back in the control room and that the read-back was always shifted. It was
because only one DCCT was used on each power converter and this DCCT was for
both the feedback and the read-back. So first we mounted a DCCT on RSQ1 for the
read-back and RSQ1 became stable. Then we mounted two DCCTs on RSQ1 and
RSQ2 in the summer shutdown of the BEPC.
In the later period of shutdown, a magnet temperature protection system was
designed for the Physics Division.
2. Academic Activities
In 2001, there was a shortage of manpower for the injection system. So some
experts were invited to give lecturers on specific topics beginning from the basic
knowledge on injection system combined with their practical experience. After the
talks, members of the Power Supply Group knew some details about the transport
line and the control technology for the pulse waveform. As there were a lot of young
people in this group who have never worked on the power converter system design,
experts of the power converter system from SSRF were invited to give talks on their
IV. Accelerator Science and Technology 57
R&D of the power converter system. From these talks, they knew what kind of
problems of the whole system should be paid more attention to. Some inner-group
talks for the BEPC II design were given. The leaders of all subsystems gave talks
about their R&D for the BEPC II, and the young people were encouraged to do
some R&D with their new ideas. Some engineers from related companies were also
invited to give talks about the new technology on the control system, PLC, etc..
People from the Power Supply Group took part in the Annual Meeting of the
Chinese Power Converter Association. During the meeting, they discussed with their
colleagues working in the same field and also let them know what this group has
done as well as some of its special problems. They attended the Seminar of EPICS,
from which they learnt the development of the accelerator control technology in the
world. This will be helpful to them when they design the interface of power
converter for the BEPC II.
3. R&D of BEPC II
In the conceptual design of the BEPC II, people of the Power Supply Group
first reviewed the designs of the power converter systems in other accelerator labs
and studied the structures and technologies used there. Then they decided to do the
R&D study by themselves and manufacture the converter by industries. They
studied the reference materials brought from other labs abroad by their colleagues.
Some key technologies for the BEPC II were investigated. The technology of full
bridge phase shift soft switch was adopted on the 500A/30V power converter. The
EMC control technology was designed and tested. They also separated the power
converter into two modules, the control box and the power converter box.
Considering the resistor of the output cable, they calculated the output of the
chopper, designed the family of the chopper and the DC power converter, simulated
the output filter with PSPICE and optimized the parameters. After these calculations,
they supplied the requirement for the AC networks. The 16 bits DAC and 20 bits
ADC were designed. In the BEPC power converter system, the DAC 1136K was
used for the D/A converter, which was good enough for our requirement. But since it
58 2001 Annual Report of IHEP
is no longer manufactured, a new type of DAC has to be found. For the BEPC,
DVM and multi-plexer were used as the read-back A/D converter. Now the
distributed system for the power converter control will be used. The ADC was
designed to change the analog signal of current to digital signal. The concept design
of the chopper system was finished, and some detailed design was done. Some
simulations were done with the PSPICE. The power supply people discussed the
interface of the P.S. with the control people.
4.3.3 The Vacuum System
1. BEPC Operation
Work for the routine operation of the BEPC was done in terms of ensuring the
stable operation of the vacuum system, maintenance of the vacuum system in the
summer shutdown and some basic experiments.
During the period of the BEPC running, only one leakage of the UHV angle
valve happened in the vacuum system and affected the BEPC operation. The
problem was solved in four hours and the machine’s normal operation resumed. In
addition, the Vacuum Group cooperated with other groups in changing 5 klystrons, 2
wave-guide valves and other equipment. Besides these, this group did some other
experiments, one of which was to adhere six temperature monitors (thermocouple)
outside the vacuum tube. It was found that the temperature at some places was
higher after the measurement. The experiment of outgassing rate was done. The high
power load was processed in vacuum. Leakage test for two klystrons was done. The
vacuum system for the test bench of klystron was improved.
The maintenance of the vacuum system in summer shutdown influenced
directly the efficiency of the BEPC new run. In the shutdown, they changed three
VAT all-metal gate valves and replaced the old rubber seal or the damaged valves.
They overhauled the high-voltage ceramic elements of the sputter ion pumps, which
were apt to break, and high-voltage cables. About 200 sputter ion pumps were dealt
with. The vacuum recovery in 6 sections that were exposed to air was fulfilled. With
IV. Accelerator Science and Technology 59
the cooperation of other groups, they finished the maintenance during the shutdown
with a premise of quality guarantee.
2. Design Study of the BEPC II Vacuum System
The main work completed for the BEPC II vacuum system during the year of
2001 is as follows:
The feasibility design report of BEPC II vacuum system was finished and
passed the international review. The material and shape of the BEPC II vacuum
chamber were decided. The vacuum people evaluated a number of possible vacuum
materials, based on the engineering requirements (stress, photon desorption, fatigue
strength, etc.) and fabrication methods. They finalized their choices. The arc
chambers for the electron ring will be made of Al-alloy (Al-6061) and extruded into
a racetrack shape (120×54mm) chamber; and for the positron ring the Al-alloy
(Al-5083) will be adopted as an antechamber with a cross section of 120×54mm in
octagon.
The preliminary structural analysis of the antechamber was finished. The cross
sections of antechamber in different magnets were also decided. The gas loads due
to photon desorption and thermal sources were calculated. The pumping system in
the arcs was specified, which contains ion pumps, distributed ion pumps (DIP),
titanium sublimation pumps (TSP) and non-evaporable getters (NEG). The pressure
distribution in the arc was calculated. Some vacuum techniques such as coating TiN
on the inner side of the vacuum chamber, the vacuum chamber cleaning and baking,
etc. were investigated.
4.3.4 The RF System
1. The BEPC Operation
The operation and maintenance of the BEPC RF system were accomplished
though there were many difficulties in the RF System Group. No long shutdown of
the BEPC was caused by the fault of the RF system. The stable performance of the
60 2001 Annual Report of IHEP
RF system contributed a lot in the time-fixed injection, which was realized for the
first time in the BEPC in the dedicated synchrotron radiation operation. No failures
happened in the three-week long SR operation.
The startup of the 2001/02 BEPC running was moved up to Sept. 17, 2001. The
RF people thoroughly cleaned and inspected 8 RF sources and other equipment, and
conditioned 4 RF cavities, thus guaranteeing the startup of the BEPC. In addition, it
was the first time for the RF system to realize non-person on watch.
2. Preliminary Design of the BEPC II Superconducting RF System
In the designs of the single-ring and double-ring schemes for the BEPC II,
which were reviewed in April 2001, the features and feasibilities of the cavities on
KEKB and CESR were compared. Some issues on the superconducting RF cavities
to be placed in the tunnel were studied. The double-ring scheme with two
superconducting RF cavities was decided and the working frequency of 499.800
MHz for the BEPC II RF system fixed at the review meeting at the end of July.
In the second half of 2001, the studies were concentrated on the introduction of
the KEKB superconducting RF cavity against the background of collaboration with
KEK, and the effect of synchrotron radiation as well as the height of the tunnel in
particular. In addition, the region for conditioning the superconducting RF cavity
and the improvement of the RF power source were also considered in the general
system layout.
3. Academic Exchange and Collaboration
The hardware of RF low level interlock for SSRF was developed. Some key
professional experts attended the review of the RF system. The RF people joined the
tuning of the low level system and the test of high power in SSRF, etc.. They drew
the engineering experience of the 500 MHz RF system and promoted the R & D
work of the RF system for SSRF. Besides, the work on guiding the manufacture of
the RF cavity for the Hefei NSRL, USTC still continues.
IV. Accelerator Science and Technology 61
In the meantime, they strengthened the international collaboration by actively
conducting academic exchanges from which they learned the new development in
the superconducting field all over the world. Some technical discussions with Linde
Co. and Air Liquid Co were carried out for future bid of the RF system. The
collaborative relation was set up between our RF group and the related KEK/PF
group.
After entering the “Knowledge Innovation Project” in July 2001, the RF Group
was reorganized. Though the job for each individual is different, everyone can
support each other, join the BEPC operation and maintenance and do his best for the
BEPC II design work. The close cooperation has solved the problem of manpower
shortage.
4.3.5 The Magnet System
1. The BEPC Operation and Maintenance
The energy monitor system of the reference magnet and the control system for
the 3W1, which were related with the operation of the BEPC, were maintained
routinely and overhauled in the summer shutdown. The normal operation of these
two systems guaranteed the experiments of high energy physics and dedicated
synchrotron radiation.
The energy monitor system of the reference magnet has been running for more
than 10 years. Now, some equipments of this system have become aged and some of
its elements have been washed out. The corresponding spare parts are no longer
manufactured. So, this system has to be thoroughly upgraded. Upgrading of the first
stage was finished at the end of 2001. And upgrading of the second stage is hoped to
finish in the summer of 2002.
2. The Inner IHEP Cooperative Subject
The Magnet Group undertook the design, manufacture and magnetic
measurement of the magnet in the bifurcation of beam line for the subject of test
62 2001 Annual Report of IHEP
beam of the Experimental Physics Center. In addition, this group also finished the
measurement of the 3 dipoles and 4 quadrupoles from DESY and a spare TQ50
quadrupole in the BEPC transport line, and the machining, manufacturing and
magnetic measurement of a new quadruple as shown in Fig. 4.3.5-1.
Figure 4.3.5-1 Newly Manufactured TQ50 Quadrupole
－
3. Upgrading Item of BEPC/BSRF－the Permanent Insertion Device
Two multipolar permanent magnetic wigglers will be installed in the BEPC
storage ring. This is one of the upgrading items for the BSRF. According to the
arrangement of IHEP, the Magnet Group undertook the design and manufacture of
the permanent magnetic wigglers. The progresses of these two wigglers are as
follows:
(1) 1W1 Permanent Magnetic Wiggler
1W1 is a kind of out-of-vacuum wiggler, which means the poles are outside the
vacuum chamber. According to the requirements of the accelerator aperture and
BSRF, on the basis of the conceptual design, the detailed design of physics,
mechanical structure and control system was finished before the end of February.
The corresponding inviting public bidding and its explanation were also finished. At
the beginning of March, the public bidding for 1W1 wiggler was carried out. The
Beijing Turbine Electrical Machinery Company Ltd. got the bid among 6 companies
IV. Accelerator Science and Technology 63
for bidding. The manufacture of 1W1 was accomplished before the end of 2001
according to the CPM schedule. The control system was also finished. It will be
tuned together with the magnet in the near future. The magnetic measurement and
shimming will also be done soon. Figure 4.3.5-2 shows the shape of the 1W1
wiggler after assembly.
Figure 4.3.5-2 Shape of 1W1 Wiggler after Assembly
(2) 4W2 Permanent Magnetic Wiggler
The 4W2 permanent wiggler is an in-vacuum wiggler, whose poles are all in
the vacuum chamber. This project is not only a totally new subject at home, but also
a new one abroad. Therefore it has some technical difficulties.
The special manpower was concentrated on the feasibility study of the 4W2
wiggler. Based on this, the general design report of the mechanical and control
system for the 4W2 wiggler was finished, and it passed the review by experts. With
the approval of the Upgrades Leading Group of IHEP, Shanghai Jiaotong University
and the Shanghai Kelin Co. were selected in September for joint manufacture of it
through bid discussion. Now, according to the CPM schedule, this project is
progressing well with the whole set of the engineering construction drawings
finished.
4. Development of New Point-by-Point Measurement Device
The limitation of the scale of the current point-by-point measurement machine
64 2001 Annual Report of IHEP
inconveniences the measurement of the newly produced wiggler and the long
magnets to be developed for BEPC II. A new device， 3-meter long and 2.5-meter in
scale， was proposed. The mechanical part and the control system of the device were
manufactured by the Beijing Turbine Electrical Machinery Company Ltd. And the
group in charge of this project at IHEP， respectively， shown in Fig.4.3.5-3. Next，
the device will be tuned together with the control system to fit the requirement of
design.
Figure 4.3.5-3 New Device of Point-by-Point Measurement
5. Design of the BEPC II Magnets
(1) Conceptual Design of the Magnets in the BEPC II Single-ring
Scheme
The Design and manufacture of three new kinds of magnets, namely, the
superconducting quadrupole magnet, the kicker magnet and the electrostatic
separator, are involved in the BEPC II single ring scheme. The conceptual design
reports both in English and Chinese on the fast kicker system, the high voltage
electrostatic separator and the superconducting quadrupole magnet were completed.
All these designs were reported and discussed at the international review meeting in
April.
IV. Accelerator Science and Technology 65
(2) Conceptual Design of the Magnets in the BEPC II Double-ring
Scheme
The BEPC II double-ring scheme was proposed at the international review
meeting held in April. Compared with the single ring scheme, the magnet system of
the double-ring scheme has changed a lot. A new ring needs to be designed and
constructed. It contains many kinds of magnets. Besides the existing magnet and the
injection systems, the interaction region (IR) system containing the superconducting
magnets in the IR and the special magnets in the beam separation region was added.
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 magnets’ coils for the old ring.
The magnets for the new ring contain dipoles, quadrupoles and combined
sextupoles. According to the requirement of the accelerator and the layout of the
tunnel, the feasibility designs of some major kinds of magnets for the new ring and
the optimization of different designs have been done. The preliminary design and the
main parameters of the magnets for the new ring and the general structure drawings
have been given.
The power converter system requires that the future power supply should be the
sort of low current and high voltage. Thus, the magnets’ coils for the old ring should
be improved according to the magnet design for the new ring. Considering the
differences of the design and manufacture between the sextupoles of the old and new
rings, and the operation current of the sextupoles in the old ring, which is not high,
the coils of the sextupoles for the old ring will not be changed.
6. International Collaboration
The storage ring of SPEAR3 in USA consists of 292 magnets, which fall into 4
sorts and 8 series with different effective lengths. Except that the quadrupole has
only QMS tuning trim, the other three kinds of magnets are all combined magnets,
which complicate their production and measurement.
66 2001 Annual Report of IHEP
The magnetic measurements of 242 magnets fabricated for SPEAR3 including
40 gradient dipoles, 102 quadrupoles with QMS tuning coils, 76 sextupoles with
skew quadrupole trim coils and 24 dipole correctors combined H/V function as well
as a H/V prototype corrector and their measurement system have been completed by
the SPEAR3 Magnet Measurement Group at IHEP and verified at SLAC by the end
of December 2001. Review of the above measurement results from SLAC indicated
that all the received magnets have either met or exceeded the required magnetic
performance specifications. Especially, the H/V corrector measurements have been
reviewed favorably that "The IHEP field error distribution computations using the
rotating coil multipole error spectrum and phases indicated that the field error
distribution achieved the required tolerances. The SLAC wire measurements verified
that the field error distribution was satisfactory."
In addition, more than 5,000 raw data and reduced data files stored in the
magnetic media and 2,500 reduced data files in hard copy were shipped to SLAC in
11 batches in a timely fashion.
The successful completion of 83% of the production magnets for SPEAR3
project has not only enabled IHEP to win a great international prestige but also
brought about a considerable economic benefit to it. Fig. 4.3.5-4 shows the dipole of
SPEAR3 fabricated at IHEP.
Figure 4.3.5-4 SPEAR3 Dipole (Designed and Fabricated at IHEP)
IV. Accelerator Science and Technology 67
4.3.6 The Control System
1. The BEPC Operation
The Control Group solved the problems of abnormal switching of the vacuum
valves and the RF voltage down due to the cooling water together with other groups.
The Control Group helped the Power Supply Group to replace the power supplies
for the correctors and the electrostatic separators in the ring. The aging parts in the
control system were gradually upgraded and repaired. The window of the BEPC
status display was changed to the multi-user mode from the single-user mode.
In 2001, the control people improved the concentrated control mode to the
distributed mode according to the development of the control system. The
intellectualization of vacuum local control system in the storage ring has been
finished. Meanwhile, the fast read-back of the main BQ power supplies in the
storage ring was realized with the improvement of the read-back accuracy. The BBA
system was set up and operated smoothly with the experimental result achieved. The
control system of the correctors on the transport lines, including the change of the
interface and some software, was upgraded. Two UPS power supplies were added
for the linac control system, thus increasing the stability of the linac. To solve the
problems in the running of the BEPC, they finished the development of the
application codes which could give a protection prompt under the compact mode.
Now the improvement of the control system for the transport line is being
carried on, with the application of PC-CCU2. On the basis of the investigation on
the control system of accelerators, the development of the control cell, which
focuses on the features and requirements of the BEPC control equipments, is under
way.
As to the linac control system, it was thoroughly renovated using the on-line
bus, as demonstrated in the fulfillment of the project of the digitalization for the 16
klystrons’ interlock protection on the basis of bus RS-485, the improvement of the
68 2001 Annual Report of IHEP
control for the power supply of the energy analysis dipole based on the CAN bus,
the improvement of the control system for the 24 steering magnets’ power supplies,
the upgrade of the power supply control system for the transport line and the
improvement of the linac electricity crate. All these systems now work normally.
The amount of the signals processed by the control system is about 107 AO, 155 AI,
124 BO and 126 BI. After the upgrade in 2001, the control system of the linac as a
whole has increased to a new level, especially with the introduction of the coding
method of Internet/Intranet in the design. The responsible person of the system can
learn the current status of the equipments and their parameters in his office or some
other places via the Internet/Intranet. The remote inspection of the control system
itself is also realized.
The other parts of the control system were maintained well with a low fault rate.
The BEPC was smoothly operated.
2. The BEPC II Control System
The conceptual design of the control system for the BEPC II was completed
and then reported at the Review Meeting on the Feasibility Study of BEPC II held at
IHEP in April 2001. It was decided by the project leaders that the BEPC II control
system will be developed with EPICS (the Experimental Physics and Industrial
Control System). Now the EPICS prototype has been built which consists of a SUN
Unix workstation and a PowerPC microprocessor running VxWorks operating
system. And a PC based Linux EPICS/IOC works well with the PCI I/O modules. In
addition, the control people discussed the control issues with experts both at home
and abroad and learned their system structure and corresponding technologies. Our
control people also contacted relevant companies to look into their products for our
control system.
In September 2001, the Control Group of the BEPC II was organized.
Following the principle of software engineering, they have investigated and
analyzed users’ requirements. Now the detailed design of the control system for the
IV. Accelerator Science and Technology 69
BEPC II is in progress.
The collaboration agreement between the control groups of SSRF and BEPC II
has been signed for developing the vacuum control system for the storage ring.
“The Asian EPICS Seminar and Collaboration Meeting” was held at IHEP,
Beijing on August 22-31, 2001. It was jointly hosted by IHEP and KEK and
sponsored by the Chinese Particle Accelerator Society. 78 participants from China,
Japan, USA and Korea attended the meeting. During the meeting, these participants
who took great interest in EPICS exchanged experiences on how to use it and learnt
how to develop a system with it. The meeting was a great success.
4.3.7 The Beam Instrumentation System
The BEPC Beam Instrumentation (BI) Group is responsible for the operation of
the BEPC, the maintenance of the BEPC beam diagnostic instrumentation system
and the upgrades of the BEPC II beam diagnostic instrumentation system. At present,
there are altogether 15 kinds of BI systems (mainly including BPM, DCCT, timing,
BCT, PR, SR light monitor, tune, beam finder, log database of the BEPC, and so on)
on the BEPC distributed in the linac, the transport line and the storage ring. While
maintaining the BI system for the BEPC, it also undertakes the upgrades of the
BEPC II BI system. Although the manpower is in shortage, all members of the BI
Group have been making their efforts to keep the BI system in a good condition.
Besides the regular maintenance during the BEPC summer shutdown in 2001, their
main efforts were concentrated on the improvement of the hardware of the
emmitance measurement system in order to increase the measurement accuracy. A
study was conducted on the streak camera used for the fixed beam finder (FF)
against the radiation dose.
4.3.8 The Mechanical System
1. Alignment of the BEPC
Under the guidance of the principle of low investment, the mechanical people
70 2001 Annual Report of IHEP
have studied how to dovetail in principle the alignments with the previous BEPC
optical instrument and the laser tracker and also the way for the transition. Then they
rebuilt all the fixtures and benchmarks to make them suitable to the method of laser
tracker measurement. With these improvements, they completed for the first time the
alignment of the storage ring and the linac by using only the laser tracker in 2001.
Following the examination of the tracker, the magnets and the electrostatic
separators on each side of the detector were tuned accurately to their positions. In
the meantime, together with SSRF, they finished the “Comparison Research on the
Measurement Precision in Elevation between Laser Tracker SMX4500 and N3 Spirit
Level”, from which they obtained the basic and necessary data for the future various
alignment schemes with the laser tracker.
2. Installation & Alignment of the Shenlong-I Accelerator in CIEP
The mechanical people joined the review of the alignment of the accelerator
and the design of the girder for the Shenlong-I accelerator in CIEP in the first half of
2001. In the middle of 2001, they went to CIEP to guide the calibration,
pre-alignment and installation of the accelerating cell. At the end of 2001, three of
them went to CIEP for a period of about 2 months for the overall alignment of the
accelerator. During this period, they finished the examination of the pre-alignment
result, the setup and the measurement of the control net, the calibration of the
theoretical coordinates, the coarse location and fine adjustment of the five-cell.
During this process, they further carried out the study on “Error Analysis of
Coordinate in Multistation Measurement with Laser Tracker and A Modified Method
of Control Network Coordinates” and increased the accuracy of measurement with
the laser tracker, thus meeting the requirement of the alignment accuracy.
3. The BEPC II Mechanical System
According to the BEPC II lattice data, the layout of the BEPC II has been
drawn. Since the space of the drift in the BEPC II arc is limited to arrange various
elements, the positions of quadrupoles and sextupoles have to be adjusted to fit the
IV. Accelerator Science and Technology 71
different requirements of various systems. On the basis of the overall requirements,
they put forward the limits of all components’ dimensions for relevant systems with
the principle of the smaller the dimensions, the better. Without considering the effect
of synchrotron radiation, under the premise that the lattice of the BEPC II should
satisfy all the requirements of every system, the elements are arranged in four arcs as
uniformly as possible, with a symmetric arrangement of components in arc I and IV,
II and III. After considering the requirement of the beam effective aperture and
preventing the synchrotron radiation light from hitting the bellows, the flanges and
the welding seam, the dipoles in arc II and I of the BEPC have to be inter-changed.
Thus, the layout of the dipoles in the positron ring or in the electron ring is the same
along the beam direction in the four arcs, i.e., the distance from the exit of the dipole
to the quadrupole is 563.05mm, the distance from the quadrupole to the sextupole is
150mm, and the distance from the sextupole to the entrance of the dipole is
289.5mm. In the electron ring, the distance from the exit of the dipole to the
quadrupole is 350mm, the distance from the quadrupole to the sextupole is 150mm,
and the distance from the sextupole to the entrance of the dipole is 502.55mm.
4. Alignment of the BEPC II
The CPM plan for the alignment measurement system up to March 2002 was
fixed. Having investigated and studied the alignment measurements of foreign
colliders, the alignment requirements of the new BEPC II were put forward and then
discussed with the Accelerator Physics Group for modifications.
After learning the BEPC II design, the mechanical people tried to design the
control network for the alignment. The design of the horizontal network will be
optimized. The horizontal network is divided into two levels: the ground and the
tunnel network. The ground network will use 6 old permanent monuments. The code
SURVEY was used, with the coordinates of network points S7, S65E, S65P, S23,
S101, S102, and the temporary point S000. The program for simulating measured
values according to the old scheme has been coded with the preliminary results as:
the accuracy of point position could be 1mm, when Ms=0.7mm, Mα=2.0”. The
72 2001 Annual Report of IHEP
tunnel network consists of 108 points, among which three network points S9, S27
and S36 are the original BEPC network points R7, R23 and R31. S9 and S27 are
also the ground network points. The tunnel network is measured with a laser tracker
SMX4500. The measurements will be performed in 36 stations nearby each floor
point. There are at least 6 common points between two stations. The input file of
code SURVEY will be directly created by the program of simulating measurement.
The preliminary result is that the radial accuracy of adjacent points is smaller than
0.05mm when Ms=0.05mm.
5. Scheme of the Special Magnets in IR Region of BEPC II
From September 12, 2001, the mechanical people studied the scheme of the
special magnets in the IR region of the BEPC II. The preliminary design of the
magnet ISPB has been finished together with the Group of IR Region. 7 versions of
the plain drawings for designing the dual-aperture magnet IQ1 and finally the study
report were completed. Now the designing of the 3-dimension drawing that was
preliminarily decided is under way.
6.
International Collaboration ProjectSPEAR3 Magnets
The production drawings for the dipoles, quadrupoles and sextupoles of
SPEAR3 were modified and reviewed. The drawings of correctors were designed.
To guarantee the quality of the SPEAR3 magnets, the tracking cards for the
production of dipoles, quadrupoles, sextupoles and correctors were made. The
problems encountered in the magnets’ fabrication were solved in the workshop. The
modifications and notices of fabrication proposed by SLAC were also made known.
Thanks to the efforts of all people undertaking the SPEAR3 magnet project,
altogether 218 magnets including the dipoles, the quadrupoles and the sextupoles of
8 different lengths and 19 styles were finished in time and with very good quality.
7. The 1W1 Permanent Wiggler Magnet
IV. Accelerator Science and Technology 73
The mechanical production of the 1W1 permanent wiggler was finished in time
according to the contract between IHEP and the Beijing Heavy Machinery Factory.
Owing to the electric machine and the way of inspection, both IHEP and the factory
agreed to install the wiggler first in the factory. The preliminary check and
measurement of the wiggler were done before it was delivered to IHEP. The
accuracy requirement was reached. The electric parts were installed at IHEP with a
successful test.
The mechanical structure of the 1W1 permanent wiggler is “C” style. It is
different from the “H” style 3W1 permanent wiggler magnet. The “C” style frame is
a compact one. The force that acts on it is complicated. Consideration has been
given in the design on how to solve the deformation and how to adjust the accuracy.
The fabrication proved that the methods were rationally used and were instrumental
to the mechanical accuracy. In addition, some new structures were also adopted to
weaken the magnetic attraction and for the supports of aligning adjustment.
4.3.9 Design of the BEPC II Interaction Region
1. Layout Optimization for the IR
In order to get enough beam separation, the position of the septum bending
magnet was adjusted on the basis of the original design. As to the definition of beam
stay clear (BSC) in the interaction region, it was suggested to be calculated as 14σ. A
two-in-one dual-aperture quadrupole was designed to take the place of two
quadrupoles OQ1 and IQ1 to increase the free space in this region for installing
other important magnets and instruments and to keep the symmetry of lattice.
2. Design Study on the Special Magnets in the IR
(1) The Septum Bending Magnet
The basic design requirements of the septum bending magnet are 0.6m in
length with a field of 4,000Gs and the septum thickness less than 10mm. The studies
of the elementary structure design and the field simulation were completed, but the
74 2001 Annual Report of IHEP
cooling system was not yet confirmed because of some key technical difficulties.
Some special experiments will be carried out as the next step.
(2) The Dual-aperture Quadrupole
The basic design requirements of the dual-aperture quadrupole are 0.6m in
length and no less than 210mm between the two holes. The studies of the
preliminary structure design and the field simulation have been completed.
(3) The Superconducting Quadrupole
The force calculation between the BES III solenoid field and the coils of the
superconducting quadrupole was finished. Investigations were made on the design
techniques of the KEKB superconducting quadrupole and discussions conducted
about the possibility of cooperating with KEK. In order to reduce the background
due to synchrotron radiation, some design requirements such as the compensation
coils, eccentric installation, enlarging the aperture of Be pipe, etc. should be studied
carefully.
3. The Girder System for the IR Quadrupoles
The 3-dimension structure drawings of the girder system for the IR quadrupole
were completed. The mechanical calculation of the stability of the girder system was
considered. Some problems related to the girder system and the door-opened
maintenance of the BES III were discussed.
4. The Connection of the Vacuum Chamber at IR
The IR Group suggested that the Be pipe near the IP be designed together with
the central drift chamber as a whole system. The system connected with the flange
of the vacuum chamber at the superconducting magnet can be moved out from the
main drift chamber. This consideration may simplify the installation technique,
avoid the use of special flange and increase the reliability of the vacuum system.
5. Study on the Collision Background
IV. Accelerator Science and Technology 75
The distribution of the synchrotron radiation fan in the IR magnets and the
positions of masks were studied preliminarily.
4.3.10 The BEPC II Injection System
On the basis of the investigation on the electrostatic separator and the kicker,
the feasibility studies on the ±110kV low-impedance horizontal electrostatic
separator and low-impedance fast pulse kicker for the injection system in the BEPC
II single-ring scheme were finished in March 2001. The preliminary design of some
important parts such as the power supply structure drawings of the coaxial
lump-parameter PFN, the design of the terminal resistor and the compensating
capacitor, the system assembling drawing and the EMI design, the design of the
transition curve for separator’s ground potential, the theoretical calculation and the
structure design of the HOM absorber and the high voltage coaxial vacuum
feedthrough, were all finished. The injection system was reviewed at the
international review meeting held at IHEP on April 2. Then, the Chinese version of
the BEPC II injection system was completed.
After May, the preliminary design of the kicker system for the BEPC II
double-ring scheme began. Due to the change of the general scheme, the design of
the kicker system has been changed several times. First, the design of the ferrite
ceramic chamber kicker was finished. Since the space of the straight section for the
kicker was lessened from 2.5m to 1.5m, the high mask for synchrotron light widened
the aperture of kicker and the ferrite magnet and its power supply were very difficult
to design and install, the safety and reliability of the system were much affected.
Therefore the design of the kicker changed to the slot pipe magnet system with strip
lines on the chamber from December. Now, the physics designs for this kind of
magnet and its power supply have been finished. Their preliminary design is in
progress.
The investigation of the kicker for the beam abort system was done.
76 2001 Annual Report of IHEP
4.3.11 The Superconducting Group
1. The Establishment of the Superconducting Cavity Laboratory
The preliminary design of the Superconducting Cavity Laboratory was finished
in February, and it passed the examination in March. It has been decided to build a
new experimental hall (about 230m2) near the west side of the BEPC rather than a
reconstruction of No. 6 Experimental Hall. The new experimental hall construction
is on the way and is expected to complete around May 1, 2002.
Some investigations have been made on the class 100 clean room, the
high-pressure ultra-pure water rinsing system, the vacuum system, the high-pressure
pump, the chemical polishing system, the helium gas pumping system and the stand
for cavity assembly, etc.. Orders have been placed for 16 kinds in total, amounting to
88 pieces of microwave components for the vertical measurement. Some microwave
instruments for the vertical measurement have been investigated too. They await
orders.
On October 18, the Beijing Research Center for the RF Superconductivity was
founded by IHEP and Peking University according to the instruction of Professor Lu
Yongxiang, president of the Chinese Academy of Sciences.
2. Preliminary Study on the High Gradient Middle β Superconduc-
ting Cavity for High Intensity Proton Linac
(1) Optimization of 1.3 GHz Scaled Superconducting Cavity Shape
The optimal design of the 1.3GHz β=0.45 single cell scaled SC cavity shape
has been done based on the research on the effects of any cavity geometry variable
over the cavity characteristics. The final results published at APAC’01 are as
follows:
The geometrical parameters of the cavity shape:
Gap length 49.86mm
Iris ellipse a = 1cm, b = 3cm
Iris Bore radius 3.8cm
IV. Accelerator Science and Technology 77
Dome ellipse A = 1.083cm, B = 2.166cm
Wall angle 5°
Beam tube length 13cm
Equation flat 0.4cm
Cavity Diameter 215.82mm
Cavity Length 309.86mm
The electromagnetic characteristics of the cavity are:
Frequency 1296.07MHz
β 0.45
Q0 4.41E+09 @2K
G 117.8
Esp/Eacc 4.62
R/Q 7.284Ω
Hsp/Eacc 125Gs/(MV/m)
(2) The Niobium Bar Stock Rolling and Its RRR Value Measurement
Some niobium bar stocks (Φ85×740) made in China have been rolled into the
niobium sheets (thickness 2.5mm), which will be used for the forming tests and the
electric beam welding tests. The RRR value of those niobium materials is only 35.
This is the reason why those materials cannot be used to fabricate a cavity body.
(3) The Physical and Mechanical Design of the Cryostat for 1.3 GHz
SC Cavity
The preliminary physical design of the cryostat for 1.3GHz scaled SCC was
done with the following results:
Maximum cavity dissipation power 35 W @Q0=1×109, Eacc=10MV/m
Maximum liquid helium vaporization 40 L/h @ 1.8K
Maximum helium gas product rate 630 L/h.
Based on these data, a multi-shielded and multi-layer adiabatic structure was
chosen for the cryostat. (Ø 320×2200). The vacuum in the adiabatic structure is
1×10-3Pa with the total heat leak ≤ 2W.
(4) Investigations on the Magnetic Shield Materials and Their Initial
78 2001 Annual Report of IHEP
Permeability Measurements at Low Temperature
Some investigations on the magnetic shield materials have been made. And the
initial permeability of five kinds of magnetic shield materials (the Permalloy 1J85,
Grain oriented silicon steel 27QG122, 27QG110, 30QG120 and non-oriented silicon
steel J23-50) at different temperatures (273K, 77K, 4.2K) has been measured. All of
those data have filled the gaps in the ferromagnetic material characteristics in China.
(5) Fabrication and Vertical Measurement of the 1.3GHz Supercon-
ducting Cavity
The first 1.3GHz, β=0.45 single cell niobium superconducting cavity in China
was fabricated and measured by using KEK’s facilities. A very good result was
achieved: Esp=37MV/m, Q0=6×109 at 1.3K (See “IHEP SC-01 low β Cavity 1st
measurement”), as shown in Figure 4.3.11-1 and 4.3.11-2.
Figure 4.3.11-1 The 1.3GHz Middle β High Gradient Superconducting Cavity
IV. Accelerator Science and Technology 79
Figure 4.3.11-2 Measurement Result of the 1.3 GHz Middle β High Gradient
Superconducting Cavity.
4.3.12 Radiation Protection
1. The Operation and Improvement of the BEPC Environmental and
Site Radiation Inspection System
(1) Operation of the System
After two stages’ improvement, the BEPC environmental and site radiation
inspection system runs stably. Now, there are altogether 36 radiation monitors
distributed in the area of the BEPC, taking data from 4 local data acquisition stations
and sending these data to the central control inspection system.
Table 4.3.12-1 lists the detailed data of the BEPC environmental and site
radiation inspection dosage statistics in 2001.
80 2001 Annual Report of IHEP
Table 4.3.12-1 Statistics of the Inspected Dosage at the BEPC Area
Area Dose on Dose on Total(mSv)
1-6month 7-12month
West of 2nd colliding point 1.6439 1.4979 3.1418
East of 2nd colliding point 0.7442 15.4641 16.2083
West of annulus entryway 3.0598 8.8527 11.9125
East of annulus entryway 7.1166 6.4377 13.5544
Control room of BES 0.3768 1.1249 1.5017
Outside wall of shield BES 2.8971 2.3914 5.2885
Inside wall of shield BES 0.7478 1.1178 1.8656
Northern end of Linac 21.7165 24.1032 45.8188
Entryway of Linac 2.4061 4.2225 6.6286
Southern end of Linac 0.6644 1.3604 2.0248
East hall of Synchrotron No. 1 7.9405 10.1067 18.0473
East hall of Synchrotron No. 2 4.7632 3.0945 7.8577
Entryway of east hall of Synchrotron 0.4499 0.4876 0.9357
West hall of Synchrotron No. 1 0.4499 0.6214 1.0713
West hall of Synchrotron No. 2 0.4499 5.1159 5.5658
West hall of Synchrotron No. 3 0.4499 3.8408 4.2907
No. 19 station 0.4669 0.4905 0.9574
No. 20 station 0.4582 0.4798 0.938
Note: The data of the northern end of the linac gallery are not accurate since the monitors are
affected by the strong electricity perturbation there.
(2) Upgrades of the System
According to the items specified in the second stage of upgrade, one inspection
monitor was newly added in the SR east hall and 3 monitors in the SR west hall.
Two monitors in the SR east hall were upgraded. The software for the central control
was updated and developed. The system ran well in the past six months after the
IV. Accelerator Science and Technology 81
acceptance test in May 2001.
2. Monitoring on Personal Dosage
(1) Monitoring on Personal Dosage for Radiation Workers in 2001
(See Table 4.3.12-2)
Table 4.3.12-2 Report on the Monitoring Personal Dosage in 2001
Div. Personnel Measure <0.1 <0.5 >0.5~ >1~5 Total Average
count count mSv mSv 1mSv mSv Dose Dose
Div. 1 90 73 49 24 6.68 0.091
Div. 2 5 5 5 m m
Div. 3
Div. 6 41 30 23 7 1.64 0.055
Linac 37 37 9 18 9 1 14.3 0.387
StorageRing 79 73 51 18 3 1 9.00 0.123
Automatic 22 19 8 11 2.82 0.148
Control
Proton Linac 41 39 18 20 1 5.85 0.15
Syn.Rad Div. 62 61 20 41 10.1 0.166
Protection 8 8 1 6 1 2.72 0.34
group
General 43 43 2 25 16 18.0 0.419
operation
Office of 14 14 5 9 1.78 0.127
National Lab
Security 12 12 8 4 1 1.29 0.108
Office
FEL Div. 23 20 9 9 1 5.23 0.261
Nucl.Anal. 56 53 24 28 1 6.34 0.12
Div.
Radiation 10 10 3 7 1.60 0.16
center
Cancer Cure 20 20 20 4.41 0.22
Percentage 47.6 45.2 6.57 0.61
(%)
Total 533 487 232 220 32 3 85.8 0.176
(2) Monitoring for Synchrotron Light Users during SR Operation
82 2001 Annual Report of IHEP
300 persons were monitored for their dosage each time.
(3) Radiation Badges Supplied
10 Sets of radiation badges were prepared respectively for the temporary users
in No. 3 and No. 9 halls.
3. The Measurements of Radiation Level in Specific Areas
The radiation dosage levels of the following specific areas were measured in
2001:
1) The top cover of the BES hall
2) The areas of dosage interlock
3) The induced radiation of the linac gallery
4) The environmental radiation level of #2 Tower Building
5) The Nuclear Physics Hall and the newly built No. 3 Target Chamber
6) The sensitive and important areas in the SR halls
7) The guardroom at the BEPC gate
8) The radiative source and sample placed in Nuclear Analysis Division.
4. Preliminary Design of the Radiation Protection System for
BEPC II
The preliminary design of the radiation protection system for the BEPC II has
been finished. “The Assessment Report on the BEPC II Radiation Protection” and
“The Assessment Report on the BEPC II Environmental Influence” have been
written. They are expected to pass the reviews by some state authorities concerned
in February 2002.
5. The Personal Safety Interlock System
The system has been performing well all over the year due to the thorough
inspection and maintenance in the summer shutdown.
According to the requirement specified in the assessment report of the BEPC II
radiation protection, the design of the personnel safety interlock system was fulfilled.
IV. Accelerator Science and Technology 83
Some investigations on the interlocks of entrance guard and dosage interlocks were
made. Experiments on the control software, the entrance guard controller and the
dosage detector were carried out on the BEPC with a lot of experimental data
achieved. In addition, “The Technical Report on the Synchrotron Radiation
Personnel Safety Interlock System” and “The Technical Report on the Personnel
Safety Interlock System of Nuclear Experimental Hall” were completed.
6. The Fire Alarm System
Fire (smoke) broke out five times on the BEPC in 2001. Due to the automatic
fire alarm system, big economic losses were avoided and safe operation of the BEPC
was guaranteed.
During the maintenance in the summer shutdown, the main machine of the
alarm system and its outside equipment as well as 300 smoking experimental
detectors were inspected. 28 detectors and one UPS power supply were changed.
The parameters of the system and the bus were measured in an all round way, thus
ensuing the system to perform well. The second stage of the project for the BEPC
automatic fire alarm system, including the 3rd construction design approved by the
Beijing Fire Extinguishment Bureau that has issued to us the construction certificate,
the contracts on equipment and acceptance test of some equipment, the project
construction bidding and the contract of construction were completed too. Now, the
project is in the construction stage. 80% of the outdoor cable project, 65% of the
indoor project including the Nuclear Analysis Application Hall, the Library and the
building of the Theoretical Physics Division were finished. The investigation and
study of the automatic fire alarm system for the BEPC II are being made.
4.4 Beijing Proton Linear Accelerator & Its Applications
84 2001 Annual Report of IHEP
4.4.1 The Operation and Improvement of BPL
During the operation of this year, the 35 MeV Beijing Proton Linear
Accelerator (BPL) worked well without any big trouble encountered. The total
operation time of the BPL was about 1,900 hours with about 1,500 hours being for
the fast neutron radiotherapy and neutron radiobiology experiments and about 400
hours for its examination, maintenance and operation preparation. In the routine
operation, a stable average target beam current (about 18-20µA) could be obtained.
With such an intense beam current, the production of neutron was ensured.
Therefore, a good experimental platform for the fast neutron radiotherapy study and
neutron radiobiology research was provided.
Concerning the application of the proton beam, it was found that the users were
still not fully aware of the radioactivity of the sample bombarded by the 35 MeV
proton beam, so the treatment and analyses of the sample were affected to some
extent. In order to extend the range of applications of the proton beam in scientific
research, the problem brought by the radioactivity of the sample must be correctly
dealt with.
During the summer maintenance, careful examinations and repairs were
conducted of all sub-systems of the accelerator. The pre-injector group paid much
attention to the examination and replacement of some control inserts of the
audio-frequency power source and the pre-injector. Examinations and repairs were
also made of the discharge power source of the ion source. The Radio Frequency
Group made a thorough examination of the radio frequency system and tested the
dynamic properties of all the repaired TH116 electronic tubes. The General Tuning
Group thoroughly maintained the power sources of the magnets of the drift tubes,
examined and replaced some inserts of the CAMAC and NIM in the control system.
At the same time, the indicator of the water-cooling system for the magnets of the
drift tubes on the control panel was also recovered. The Assistant Group made a
careful examination and repair of the assistant system. In addition, in order to satisfy
the requirement of the vacuum of the tank by the BPL, three 1000l/s ion-pumps used
IV. Accelerator Science and Technology 85
for the tank of the accelerator were replaced. The Neutron Group carefully examined
and repaired all systems related to the study of fast neutron radiotherapy and sorted
out the researching materials.
Up to now, we have tuned the BPL many times. An average target current of
18~20µA necessary for the study on fast neutron therapy has reached. The
calibration of the neutron dose measurement instruments was attested by the
National Institute of Metrology (NIM).
All the above-mentioned work was done through the hard work of the staffers
of Division 11 who have overcome the difficulties of insufficient manpower,
irrational age structure of staffers and shortage of fresh blood.
4.4.2. Research Activities on the Accelerator Driven Clean
Nuclear Power System
The focal points of this subject were centered on the physics study of the
medium energy high current accelerator and the accelerating structure research of
the lower energy intense beam linac. Some progresses have been made in such
respects as the RFQ physics design, the RF study of the RFQ structure, the RFQ
cold model measurement, the thermal analysis of RFQ cavity, the design of the RF
power system, the mechanical design of the RFQ and the preliminary design of
medium energy high current proton linac. They are described briefly as follows：
1. The RFQ beam dynamics design was conducted with the codes of
PARMTEQ and LIDOS.RFQ. The design parameters of a 5 MeV and a 3.5 MeV
RFQ have been obtained.
2. The 2D and 3D RF cavity designs for the 5MeV RFQ have been made with
the codes of SUPERFISH and MAFIA. In the 3D modeling, the effects of the tuners,
the vacuum port, the undercuts and the coupling disk were studied.
3. It was decided to omit the R&D procedure of RFQ during the construction of
its cold model in order to save time and money. To set up the correct RF
86 2001 Annual Report of IHEP
measurement method and tuning procedure, the cooperation with LNL, Italy was
carried out.
4. The thermal features of the RFQ cavity were analyzed with ANSYS code.
The distribution and size of the cooling channels have been determined.
5. The mechanical design drawings for the RFQ technology module have been
finished. At present, we are performing the machining test of the module to
investigate some key technologies, including the deep-hole drilling, control of the
error allowance, brazing and material property.
6. The preliminary design of the RF power system has been outlined. The major
components of the system will be sent to IHEP from CERN soon. The preparation
for the installation of the RF power system is almost finished.
7. The preliminary beam dynamics design of a linac of 300 MeV/3mA has been
proposed. We also made a proposal for the linac of the China Spallation Neutron
Source with the beam energy of 70 MeV and the average current of 200 µA, as the
injector to a 1GeV RCS.
4.4.3 Fast Neutron Radiotherapy Research
In 2001 progress was made in the studies of fast neutron radiotherapy in the
following respects: (1) The physical characteristics of the P(35 Mev)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 test of neutron radiophysics have been done on the IHEP
neutron radiotherapy facility; (2) Research on the methods of measurement of the
neutron energy spectra: The comparison of several methods of measurement of
neutron energy spectra has been done. The comparison of neutron energy spectrum
with the spectrum of dose deposition by the neutron beam in the depth has been
done; (3) Neutron dose distribution measurements: Measurements of the Central
Axis Depth Dose (CADD) and Off-Axis Ratios (OAR) in air for differential fields.
Acquired data are good enough for neutron clinical treatment; (4) Calibration of the
IV. Accelerator Science and Technology 87
neutron dose measurement instruments: The ionization chambers and the neutron
dose measurement instruments were sent to NIM (the National Institute of
Metrology) for calibration in their 60Co- γ ray. The NBS furnished a Calibration
certificate. The calibration is done once a year; (5) The neutron therapy beam
calibration was done every treatment day. There were two calibration programs for
daily therapy: the ionization chamber calibration in terms of 60Co- γ ray in a 137Cs
source and the neutron beam transmission chamber calibration; (6) Research of
micro-dosimetry and nano-dosimetry and (7) Research of 3 dimensional neutron
treatment plan and conformal techniques.
The research of fast neutron radiobiology has been carried out. In the fast
neutron radiobiology test, two tumor cell lines were used: the human
nasopharyngeal cancer cell line (CNE-1) and the human fibrosarcoma cell line
(HT1080). The research contents were: (1) The biological effects of the P(35Mev)Be
fast neutron and the 60Co- γ ray for single irradiation have been compared. The
comparison with RBE values for radiation of P(35Mev)Be fast neutron and the
60Co- γ ray has been done; (2) The research of fast neutron radiation-induced DNA
double-strand breaks. Research of dose effect-relationships for induction of
chromosome aberrations and (3) The research of neutron radiation sensitivity of two
tumor cells (CNE-1 and HT1080).
Concerning the research of fast neutron therapy clinical treatment, a fast
neutron radiotherapy facility has been developed at IHEP for research on cancerous
tumor management. This is the only one in China up to now. The clinical treatment
has been successfully made under the guidance of an expert group, whose members
are from IHEP and some famous medical institutions and hospitals. 63 patients were
treated by neutron beam therapy during this year. More than 600 patients have been
treated since November 1991. 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,
88 2001 Annual Report of IHEP
fibrosarcoma, liposarcoma, chordoma, metastasis cancer of the head and neck,
lung-metastasis, etc..
The computer programs for the data of patients were perfected.
Three seminars on neutron radiotherapy were held in 2001. In the seminars, fast
neutron therapy clinical data, neutron radiation physics, neutron radiobiology and
technical aspects in neutron radiotherapy were widely discussed. It was 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.
China is a densely populated country where the incidence of cancer increases
year after year. Thus it is necessary to develop neutron radiation therapy.
4.4.4 Other Basic and Applied Research
1. Beam Transport & Scanning System of the 1.2 MeV Accelerator
This is a research subject carried out in collaboration with the Institute of
Modern Physics, CAS. Division 11 of IHEP was in charge of the design and
construction of the beam transport system and the beam scanning system. Now the
task has been successfully finished.
2. The Experimental Study on the Structure of CCDTL
With the help of our machine shop, the manufacture and welding of the
oxygen-free copper model cavity of CCDTL (coupled cavity drift tube linac) have
been finished. In order to tune the model cavity successfully, first we got a good
field distribution and dispersion curve by tuning the cavity series without changing
the shape of the cavity. Then, by following the process of tuning a real cavity series,
we obtained the designed work frequency, the dispersion curve, the coupling
IV. Accelerator Science and Technology 89
coefficient and the field distribution profile by deforming the cavity.
3. Development of the Key Components of Electrostatic Electron
Accelerator Used for the Flue Dust Cleaning System
Our efforts were involved in the development of two components: 1) The
electronic gun system. Based on the original laboratory facilities, the power source
for the filament, the high voltage system and the beam measurement system were
improved. An indirectly heating plane type of LaB6 cathode was designed. Under
the conditions of different heating current, heating voltage and extracting voltage,
the extracting beam currents were measured. Now the designing requirement of
60-80mA current has been met and 2) The high voltage generator. The accelerator is
a kind of direct-current high-voltage one. The electrons are accelerated by the
electric fields produced by the inductance-coupling cascade generator. The
inductance of the second coil and the capacitance between the second coil and the
steel cylinder wall forms an oscillating circuit. Now we have grasped the design and
measurement of the second coil, and basically grasped the layout of the capacitors,
the resistors, the silicon stacks and the diodes.
