- Email: [email protected]
Upgrade of a kicker control system for the HIRFL
Nuclear Instruments and Methods in Physics Research A 738 (2014) 50–53
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Upgrade of a kicker control system for the HIRFL Yan-Yu Wang a, Wen-Xiong Zhou a,b, Jin-Fu Luo a,b, De-Tai Zhou a, Jian-Chuan Zhang a,b, Xiao-Li Ma a, Da-Qing Gao a, Jing-Bin Shang-Guan a a b
Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China University of the Chinese Academy of Sciences, Beijing 100039, China
art ic l e i nf o
a b s t r a c t
Article history: Received 13 November 2013 Received in revised form 3 December 2013 Accepted 3 December 2013 Available online 10 December 2013
A kicker system plays an important role in beam extraction and injection for a ring-like accelerator. The kicker system in the Heavy Ion Research Facility in Lanzhou (HIRFL) is used for beam extraction and injection between two cooling storage rings (CSRs). The system consists of two parts: one part is used for beam extraction from the CSR/main (CSRm), and the other is used for beam injection into the CSR/ experimental (CSRe). To meet the requirements of special physics experiments, we upgraded the kicker control system. In this upgraded system, the position of the beam bunches can be determined by measuring the phase of the radio frequency (RF) signal in real time because each beam bunch is synchronized with the RF signal. The digital timing control and delay regulatory function, which are based on a new design using ARM þ DSPþ FPGA technology, achieved a precision of 2.5 ns, which is a significant improvement over old system's precision of 5 ns. In addition, this system exhibits a better anti-interference capability. Moreover, the efficiency of beam extraction can be enhanced, and the accuracy of the reference voltage setting can reach as low as 0.1%, compared to 2% for the old system. & 2013 Elsevier B.V. All rights reserved.
Keywords: HIRFL Kicker control system Timing FPGA
1. Introduction The HIRFL consists of an injector, a beam transport line, a main ring (CSRm), an experimental ring (CSRe) and the radioactive ion beam line in Lanzhou (RIBLL2), which connects the CSRm and the CSRe. The total length of the HIRFL is approximately 500 m [1]. A schematic layout of the system is shown in Fig. 1. In the HIRFL system, the beam is first accumulated in the CSRm, then cooled along with the electron beam and finally accelerated. After the beam reaches the required energy, the kicker system is used to extract the beam bunches from the CSRm and inject these beam bunches over the RIBLL2 into CSRe or the external target experimental terminal for physics experiments. Two sets of kicker systems are required to ensure normal operation of the HIRFL: one set of kicker systems (six channels) is used to extract the beam bunches from the CSRm, whereas the other (four channels) is used to inject the beam bunches into the CSRe. When the accelerator is operated, the precision of the kicker power supplies must reach a pulse length on the order of nanoseconds; otherwise, the beam bunch cannot be extracted. Thus, a high-precision kicker control system was designed and implemented in 2007. A high-precision sequential trigger mechanism was incorporated into the control system to ensure a precision of 5 ns [2]. Due to the requirements of new physics experiments and the 5 years over which the system has been operated, the old kicker
E-mail address: [email protected] (Y.-Y. Wang). 0168-9002/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nima.2013.12.007
control system cannot satisfy the requirements of current special physics experiments. There are several reasons for this inadequacy. First, the precision of 5 ns restricts the improvement of the precision for the phase detection of the beam bunches. Second, the delayer is a monostable circuit on the kicker power supply side, which is easily disturbed by ambient temperature fluctuations. As a result, the control signal cannot be synchronized with the beam bunches due to time drift and jitter [3].Third, the precision of the reference voltage is only 2% in the old system, making it difficult to finely adjust the kick currents; as a result, the energy of the power supply cannot sufficiently match the energy of the beam bunch. Fourth, many physics experiments require a trigger signal from the kicker control system to act as the event trigger. Such a trigger cannot be flexibly offered in the old system. Finally, the fine delay time between the kicker power supplies cannot be adjusted in the old system. To address these issues, we upgraded the beam kicker control system to improve the control precision and to increase the flexibility of the system. In the hardware design process, we used a monolithic circuit architecture that incorporates advanced RISC machine (ARM) technology, digital signal processing technology (DSP) and field programmable gate array (FPGA) technology; the new control system has a time precision of 2.5 ns, which can meet all of the requirements of those special physics experiments.
2. Operating principles As shown in Fig. 2, the control of the CSRm consists of seven steps: preparation, beam injection (from the RIBLL1 to CSRm
Y.-Y. Wang et al. / Nuclear Instruments and Methods in Physics Research A 738 (2014) 50–53
51
Fig. 3. The relationship between the power supplies and the magnets. Fig. 1. A schematic layout of the system.
Table 1 The characteristics of the kicker power supplies.
Fig. 2. Control steps of the CSRm (SF is the sweep frequency, and PF is the point frequency).
through an electrostatic separator), beam accumulation, beam acceleration, beam storage, beam extraction and state recovery. Every step is assigned an event code, which is used to trigger the control of the corresponding devices at different steps. The kicker control system is triggered when it receives the event code for beam extraction. The entire process can be completed within 20–35 s. The kicker system consists of kicker magnets (ferrite) and HV pulse power supplies. The kicker control system can execute functions such as sequential control, trigger logic, reference voltage setting and waveform detection. During the control process, to efficiently inject the beam bunches into the CSRe or the external target experimental terminal, there are two types of timing points that must be accurately determined. One timing point is the kicker critical time of the CSRm (kick the particle beam bunches out) and CSRe (kick the particle beam bunches in) and the other timing point is known as the delay time, i.e., the signal transmission time required for the CSRm to send a signal to notify the CSRe when to kick the beam bunches in. However, because there is no beam phase probe system at the CSRm [4], it is not possible to directly determine the positions of the beam bunches; thus, we infer the position through the measurement of the phase of the RF signal, which is a point frequency signal during the extraction stage. Doing so enables the indirect determination of the beam bunch position because the phase of the RF signal and the bunch are synchronized. Thus, the timing of the beam extraction must be accurately synchronized with the phase of the RF signal. The kicker system of the HIRFL consists of 10 kicker HV power supplies, which are used to drive two sets of kicker magnets (ferrite); all kicker magnets and power supplies are homemade.
Parameter
Value
Rising time Falling time Cycle Maximum current Maximum voltage
150 ns 150 ns 10–15 s 2700 A 78 kV
The relationship between the power supplies and the kicker magnets is shown in Fig. 3. Six power supplies are used to drive a kicker magnet for the extraction of beam bunches on the CSRm side, where the other four power supplies are used to drive another kicker magnet for the injection of beam bunches on the CSRe side. The distance between the two sets of kicker power supplies is approximately 200 m, and the distance between the two sets of kicker magnets is approximately 120 m (which is equal to the length of the RIBLL2). The characteristics of the kicker power supply and the kicker magnet are presented in Tables 1 and 2, respectively [5,6]. The kicker system has five workflows: 1. 2. 3. 4. 5.
receive the corresponding event code; charge 10 power supplies; determine the phase of the RF signal; produce the trigger and the synchronous signal; recover and start the next cycle.
3. Old kicker control system architecture The old kicker control system consists of four PCB boards: a communication board, a control board, a signal delaying board and a reference voltage setting board. Backplane buses are used to connect the four circuit boards to each other. The functions of each of the circuit boards are as follows. First, the communication board is used to implement remote control and configure the relevant parameters, such as the frequency of the RF signal, the trigger point of the phase and the delay time between the charging and the discharging of the HV power supplies. Second, the control board is used to receive the event signal, measure the phase of the RF signal and synchronously control the kicker power supplies and other devices. In the hardware design process, we used an FPGA (ACEX1K50; Altera Corporation). After following special procedures for this type of
52
Y.-Y. Wang et al. / Nuclear Instruments and Methods in Physics Research A 738 (2014) 50–53
Table 2 The characteristics of the kicker magnets. Parameter
Value
Maximum field Maximum current Maximum voltage
0.038 T 2500 A 7 20.4 kV
Kicker event
FPGA+DSP+ARM
Intranet
Kicker Controller
RF signal
(CSRm) CSRm_Charge
CSRe_Discharge
CSRm_DisCharge0 . . . CSRm_DisCharge5
FPGA+DSP+ARM
CSRe_Charge
Kicker Controller (CSRe)
CSRm_DisCharge0 . . CSRm_DisCharge3 . Fig. 4. Control scheme.
FPGA, the control precision of the kicker power supply can reach 5 ns. Third, the signal delaying board is used to adjust the delay time of the signal from the kicker controllers of the CSRm to the kicker controllers of the CSRe. Finally, the reference voltage setting board is used to set the reference voltage for the power supplies, with a precision of 2%.
4. New kicker control system architecture 4.1. Control scheme design The upgraded controllers use a monolithic circuit architecture. One control board can complete all functions except for the reference voltage setting function. To ensure normal operation of the entire system, it is necessary to use only two respective kicker controllers for the CSRm and the CSRe. Fig. 4 shows the control scheme design. The controller of the CSRm is used to receive the kicker event code, measure the phase of the RF signal and control six kicker power supplies. At the same time, this controller can synchronously send a signal to the CSRe to trigger the injection function. The control of the kicker power supply consists of charging and discharging steps. First, the kicker power supplies have to share only one control signal to be charged because the maximum permissible error of the charging is a pulse length on the scale of milliseconds. Second, the discharging of the kicker power supplies is completed on the scale of microseconds. The interval precision of discharging for every two power supplies can reach 2.5 ns. 4.2. Controller architecture The controller incorporates ARM (S3C6410), DSP (DSPC6713B) and FPGA (CycloneIII) technologies. The functions of each module are described as follows.
The operating frequency of the ARM is 667 MHz. The ARM has two functions. First, in the Linux operating system environment, the ARM is used to acquire the configuration information and the control information of the background computer, after which the control information is sent to the FPGA to control or configure the FPGA and the DSP through a serial peripheral interface (SPI) bus. Second, the RS485 interface of the ARM is used as the interface of the controller. The controller can communicate with a self-developed module ICP400 to control the reference voltage setting through the RS485 interface. The maximal operating frequency of the FPGA is 503 MHz. In the architecture of this controller, the FPGA is designed to receive the event code and the RF signal. At the same time, this FPGA is also used to control the kicker power supply and synchronize with other control systems through a glass fiber. In this system, we retain the old plastic fiber interface to ensure the compatibility of the entire system. In addition, to reduce the delay time of the signal transmission between the CSRm and the CSRe, we replace the old plastic fiber with a glass fiber and add the glass fiber interface. Compared with the plastic fiber, the glass fiber can complete long-distance transmission without a repeater. For this kicker control system, using a glass fiber can reduce the delay time caused by the repeater, which improves the synchronous control function of the two kicker systems of the CSRm and the CSRe. The FPGA we used features rich logic cells. Thus, many delayers with a precision of 2.5 ns can be implemented in the controllers. The monostable circuit delayers used on the side of the power supplies are replaced with full-digital delayers in a new controller to avoid time drift and jitter, and the interval delayer time that can be achieved in the digital delayer is 2.5 ns. The reference voltage setting function of the kicker power supplies is improved by using the ICP400, a controller developed completely in-house. This model provides a digital–analog converter (DAC) with a maximum precision of 16 bits, which improves the precision of the reference voltage setting from 2% to 0.1% under harsh conditions. The DSP is used for complex calculations. In the beam transport process, once the controller receives the event code for the control process, the DSP will detect the frequency of the RF signal, locate the frequency point of the RF signal according to frequency points preset in the controller to measure the phase and, finally, indirectly locate the beam bunches. Fig. 5 shows the controller architecture of the upgraded control system. 4.3. Anti-interference measures The kicker control system always operates in an extremely harsh environment of high voltage and enormous current. These conditions may seriously damage the controllers. When the HV power supply is activated, the system is instantaneously discharged and an extremely strong interference pulse is emitted from the ground wire of the power supply, which can damage the devices and perhaps even disrupt the entire system. We have taken many measures in this upgraded control system to solve this problem of interference [7]. 1. To reduce the interference from the ground wires, the ground of the controller power supplies is completely separated from the ground of the kicker power supplies. At the same time, when installing the controllers, we isolated the circuit board of the controllers from the outer covering to prevent the entire system from grounding through the outer covering. 2. Double-layer shielded twisted pairs (double-layer STPs) are used for the analog signal wires to reduce the effects of electromagnetic interference.
Y.-Y. Wang et al. / Nuclear Instruments and Methods in Physics Research A 738 (2014) 50–53
53
Old fiber MSCSRe
HVCSRe
MSCSRm
Event
HVCSRm
RF
Intranet IPC
EMIF ARM
DSP
FPGA
SPI
RS485 ICP400 MS6
HV6
MS0
HV0
Kicker Power
Event New/ CSRe Charge
CSRe Discharge
Supply New fiber Fig. 5. Controller architecture.
kicker control system are shown in Table 3 (the time period of the RF signal is 1 μs).
Table 3 Comparison of the old and new systems. Parameter
Old system
New system
Phase (deg) Minimum delay time (ns) Position (m)
1.8 5 0.805
0.9 2.5 0.4025
3. Ferrite beads are fixed around the signal wires (both ends) and the power wires to reduce the effects of electromagnetic interference. 4. In the process of designing the controller, all of the I/O ports were designed using transient voltage suppressor (TVS) diodes, which can prevent damage to the controllers from the interference pulse signal. 5. Isolators are used to eliminate various types of signal interference. 5. Improvement of the new kicker control system The most important improvement made to the old kicker control system is its precision. The new system can accurately measure the position of the beam bunches and send the control signals. We can determine the precision of the position of the beam bunches by using the following formula: L¼
3601 P T
L is the precision of the position, P is the precision of the control system and T is the time period of the high-frequency signal. The minimum delay time of the synchronous signal and the control signal for the power supplies is the same as the precision of the kicker control system. The improvements made to the old
6. Conclusions The upgraded beam kicker control system was demonstrated to be more reliable and more stable than the old control system. The upgraded system has five specific advantages. First, because of the monolithic circuit architecture and the newly designed ARMþDSP þ FPGA technology, the control precision of the kicker system is improved from 5 ns to 2.5 ns. In addition, digital timing control and delay regulatory functions are also achieved. Second, the reference voltage setting precision of the kicker power supply is improved from 2% to 0.1%. Third, the discharging of every kicker power supply can be independently controlled, which can satisfy the requirements of different experiments. Fourth, the system eliminates various types of interference, protects the devices from harsh conditions and reduces costs. Finally, the new system improves the efficiency of beam injection and beam injection of the HIRFL. References [1] Jiawen Xia, Wenlong Zhan, Baowen Wei, et al., High Power Laser and Particle Beams 20 (11) (2008) 1787. [2] Yanyu Wang, Yuhui Guo, Feiyu Lin, et al., High Power Laser and Particle Beams 20 (8) (2008) 1353. [3] Jinhui Chen, Chinese Physics C 32 (2008) 4. [4] R. Koyama, N. Sakamoto, M. Fujimaki, et al., Nuclear Instruments and Methods in Physics Research A 729 (2013) 788. [5] Lizhen Ma, Shaofei Han, Yuan He, et al., High Power Laser and Particle Beams. 18 (2006) 147. [6] Qunyao Wang, Daqing Gao, Jingbin ShangGuan, et al., Power Supply Technologies and Applications 9 (1) (2006) 36. [7] Wenxiong Zhou, Yanyu Wang, Detai Zhou, et al., Nuclear Instruments and Methods in Physics Research A 728 (2013) 112.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Upgrade of a kicker control system for the HIRFL Yan-Yu Wang a, Wen-Xiong Zhou a,b, Jin-Fu Luo a,b, De-Tai Zhou a, Jian-Chuan Zhang a,b, Xiao-Li Ma a, Da-Qing Gao a, Jing-Bin Shang-Guan a a b
Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China University of the Chinese Academy of Sciences, Beijing 100039, China
art ic l e i nf o
a b s t r a c t
Article history: Received 13 November 2013 Received in revised form 3 December 2013 Accepted 3 December 2013 Available online 10 December 2013
A kicker system plays an important role in beam extraction and injection for a ring-like accelerator. The kicker system in the Heavy Ion Research Facility in Lanzhou (HIRFL) is used for beam extraction and injection between two cooling storage rings (CSRs). The system consists of two parts: one part is used for beam extraction from the CSR/main (CSRm), and the other is used for beam injection into the CSR/ experimental (CSRe). To meet the requirements of special physics experiments, we upgraded the kicker control system. In this upgraded system, the position of the beam bunches can be determined by measuring the phase of the radio frequency (RF) signal in real time because each beam bunch is synchronized with the RF signal. The digital timing control and delay regulatory function, which are based on a new design using ARM þ DSPþ FPGA technology, achieved a precision of 2.5 ns, which is a significant improvement over old system's precision of 5 ns. In addition, this system exhibits a better anti-interference capability. Moreover, the efficiency of beam extraction can be enhanced, and the accuracy of the reference voltage setting can reach as low as 0.1%, compared to 2% for the old system. & 2013 Elsevier B.V. All rights reserved.
Keywords: HIRFL Kicker control system Timing FPGA
1. Introduction The HIRFL consists of an injector, a beam transport line, a main ring (CSRm), an experimental ring (CSRe) and the radioactive ion beam line in Lanzhou (RIBLL2), which connects the CSRm and the CSRe. The total length of the HIRFL is approximately 500 m [1]. A schematic layout of the system is shown in Fig. 1. In the HIRFL system, the beam is first accumulated in the CSRm, then cooled along with the electron beam and finally accelerated. After the beam reaches the required energy, the kicker system is used to extract the beam bunches from the CSRm and inject these beam bunches over the RIBLL2 into CSRe or the external target experimental terminal for physics experiments. Two sets of kicker systems are required to ensure normal operation of the HIRFL: one set of kicker systems (six channels) is used to extract the beam bunches from the CSRm, whereas the other (four channels) is used to inject the beam bunches into the CSRe. When the accelerator is operated, the precision of the kicker power supplies must reach a pulse length on the order of nanoseconds; otherwise, the beam bunch cannot be extracted. Thus, a high-precision kicker control system was designed and implemented in 2007. A high-precision sequential trigger mechanism was incorporated into the control system to ensure a precision of 5 ns [2]. Due to the requirements of new physics experiments and the 5 years over which the system has been operated, the old kicker
E-mail address: [email protected] (Y.-Y. Wang). 0168-9002/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nima.2013.12.007
control system cannot satisfy the requirements of current special physics experiments. There are several reasons for this inadequacy. First, the precision of 5 ns restricts the improvement of the precision for the phase detection of the beam bunches. Second, the delayer is a monostable circuit on the kicker power supply side, which is easily disturbed by ambient temperature fluctuations. As a result, the control signal cannot be synchronized with the beam bunches due to time drift and jitter [3].Third, the precision of the reference voltage is only 2% in the old system, making it difficult to finely adjust the kick currents; as a result, the energy of the power supply cannot sufficiently match the energy of the beam bunch. Fourth, many physics experiments require a trigger signal from the kicker control system to act as the event trigger. Such a trigger cannot be flexibly offered in the old system. Finally, the fine delay time between the kicker power supplies cannot be adjusted in the old system. To address these issues, we upgraded the beam kicker control system to improve the control precision and to increase the flexibility of the system. In the hardware design process, we used a monolithic circuit architecture that incorporates advanced RISC machine (ARM) technology, digital signal processing technology (DSP) and field programmable gate array (FPGA) technology; the new control system has a time precision of 2.5 ns, which can meet all of the requirements of those special physics experiments.
2. Operating principles As shown in Fig. 2, the control of the CSRm consists of seven steps: preparation, beam injection (from the RIBLL1 to CSRm
Y.-Y. Wang et al. / Nuclear Instruments and Methods in Physics Research A 738 (2014) 50–53
51
Fig. 3. The relationship between the power supplies and the magnets. Fig. 1. A schematic layout of the system.
Table 1 The characteristics of the kicker power supplies.
Fig. 2. Control steps of the CSRm (SF is the sweep frequency, and PF is the point frequency).
through an electrostatic separator), beam accumulation, beam acceleration, beam storage, beam extraction and state recovery. Every step is assigned an event code, which is used to trigger the control of the corresponding devices at different steps. The kicker control system is triggered when it receives the event code for beam extraction. The entire process can be completed within 20–35 s. The kicker system consists of kicker magnets (ferrite) and HV pulse power supplies. The kicker control system can execute functions such as sequential control, trigger logic, reference voltage setting and waveform detection. During the control process, to efficiently inject the beam bunches into the CSRe or the external target experimental terminal, there are two types of timing points that must be accurately determined. One timing point is the kicker critical time of the CSRm (kick the particle beam bunches out) and CSRe (kick the particle beam bunches in) and the other timing point is known as the delay time, i.e., the signal transmission time required for the CSRm to send a signal to notify the CSRe when to kick the beam bunches in. However, because there is no beam phase probe system at the CSRm [4], it is not possible to directly determine the positions of the beam bunches; thus, we infer the position through the measurement of the phase of the RF signal, which is a point frequency signal during the extraction stage. Doing so enables the indirect determination of the beam bunch position because the phase of the RF signal and the bunch are synchronized. Thus, the timing of the beam extraction must be accurately synchronized with the phase of the RF signal. The kicker system of the HIRFL consists of 10 kicker HV power supplies, which are used to drive two sets of kicker magnets (ferrite); all kicker magnets and power supplies are homemade.
Parameter
Value
Rising time Falling time Cycle Maximum current Maximum voltage
150 ns 150 ns 10–15 s 2700 A 78 kV
The relationship between the power supplies and the kicker magnets is shown in Fig. 3. Six power supplies are used to drive a kicker magnet for the extraction of beam bunches on the CSRm side, where the other four power supplies are used to drive another kicker magnet for the injection of beam bunches on the CSRe side. The distance between the two sets of kicker power supplies is approximately 200 m, and the distance between the two sets of kicker magnets is approximately 120 m (which is equal to the length of the RIBLL2). The characteristics of the kicker power supply and the kicker magnet are presented in Tables 1 and 2, respectively [5,6]. The kicker system has five workflows: 1. 2. 3. 4. 5.
receive the corresponding event code; charge 10 power supplies; determine the phase of the RF signal; produce the trigger and the synchronous signal; recover and start the next cycle.
3. Old kicker control system architecture The old kicker control system consists of four PCB boards: a communication board, a control board, a signal delaying board and a reference voltage setting board. Backplane buses are used to connect the four circuit boards to each other. The functions of each of the circuit boards are as follows. First, the communication board is used to implement remote control and configure the relevant parameters, such as the frequency of the RF signal, the trigger point of the phase and the delay time between the charging and the discharging of the HV power supplies. Second, the control board is used to receive the event signal, measure the phase of the RF signal and synchronously control the kicker power supplies and other devices. In the hardware design process, we used an FPGA (ACEX1K50; Altera Corporation). After following special procedures for this type of
52
Y.-Y. Wang et al. / Nuclear Instruments and Methods in Physics Research A 738 (2014) 50–53
Table 2 The characteristics of the kicker magnets. Parameter
Value
Maximum field Maximum current Maximum voltage
0.038 T 2500 A 7 20.4 kV
Kicker event
FPGA+DSP+ARM
Intranet
Kicker Controller
RF signal
(CSRm) CSRm_Charge
CSRe_Discharge
CSRm_DisCharge0 . . . CSRm_DisCharge5
FPGA+DSP+ARM
CSRe_Charge
Kicker Controller (CSRe)
CSRm_DisCharge0 . . CSRm_DisCharge3 . Fig. 4. Control scheme.
FPGA, the control precision of the kicker power supply can reach 5 ns. Third, the signal delaying board is used to adjust the delay time of the signal from the kicker controllers of the CSRm to the kicker controllers of the CSRe. Finally, the reference voltage setting board is used to set the reference voltage for the power supplies, with a precision of 2%.
4. New kicker control system architecture 4.1. Control scheme design The upgraded controllers use a monolithic circuit architecture. One control board can complete all functions except for the reference voltage setting function. To ensure normal operation of the entire system, it is necessary to use only two respective kicker controllers for the CSRm and the CSRe. Fig. 4 shows the control scheme design. The controller of the CSRm is used to receive the kicker event code, measure the phase of the RF signal and control six kicker power supplies. At the same time, this controller can synchronously send a signal to the CSRe to trigger the injection function. The control of the kicker power supply consists of charging and discharging steps. First, the kicker power supplies have to share only one control signal to be charged because the maximum permissible error of the charging is a pulse length on the scale of milliseconds. Second, the discharging of the kicker power supplies is completed on the scale of microseconds. The interval precision of discharging for every two power supplies can reach 2.5 ns. 4.2. Controller architecture The controller incorporates ARM (S3C6410), DSP (DSPC6713B) and FPGA (CycloneIII) technologies. The functions of each module are described as follows.
The operating frequency of the ARM is 667 MHz. The ARM has two functions. First, in the Linux operating system environment, the ARM is used to acquire the configuration information and the control information of the background computer, after which the control information is sent to the FPGA to control or configure the FPGA and the DSP through a serial peripheral interface (SPI) bus. Second, the RS485 interface of the ARM is used as the interface of the controller. The controller can communicate with a self-developed module ICP400 to control the reference voltage setting through the RS485 interface. The maximal operating frequency of the FPGA is 503 MHz. In the architecture of this controller, the FPGA is designed to receive the event code and the RF signal. At the same time, this FPGA is also used to control the kicker power supply and synchronize with other control systems through a glass fiber. In this system, we retain the old plastic fiber interface to ensure the compatibility of the entire system. In addition, to reduce the delay time of the signal transmission between the CSRm and the CSRe, we replace the old plastic fiber with a glass fiber and add the glass fiber interface. Compared with the plastic fiber, the glass fiber can complete long-distance transmission without a repeater. For this kicker control system, using a glass fiber can reduce the delay time caused by the repeater, which improves the synchronous control function of the two kicker systems of the CSRm and the CSRe. The FPGA we used features rich logic cells. Thus, many delayers with a precision of 2.5 ns can be implemented in the controllers. The monostable circuit delayers used on the side of the power supplies are replaced with full-digital delayers in a new controller to avoid time drift and jitter, and the interval delayer time that can be achieved in the digital delayer is 2.5 ns. The reference voltage setting function of the kicker power supplies is improved by using the ICP400, a controller developed completely in-house. This model provides a digital–analog converter (DAC) with a maximum precision of 16 bits, which improves the precision of the reference voltage setting from 2% to 0.1% under harsh conditions. The DSP is used for complex calculations. In the beam transport process, once the controller receives the event code for the control process, the DSP will detect the frequency of the RF signal, locate the frequency point of the RF signal according to frequency points preset in the controller to measure the phase and, finally, indirectly locate the beam bunches. Fig. 5 shows the controller architecture of the upgraded control system. 4.3. Anti-interference measures The kicker control system always operates in an extremely harsh environment of high voltage and enormous current. These conditions may seriously damage the controllers. When the HV power supply is activated, the system is instantaneously discharged and an extremely strong interference pulse is emitted from the ground wire of the power supply, which can damage the devices and perhaps even disrupt the entire system. We have taken many measures in this upgraded control system to solve this problem of interference [7]. 1. To reduce the interference from the ground wires, the ground of the controller power supplies is completely separated from the ground of the kicker power supplies. At the same time, when installing the controllers, we isolated the circuit board of the controllers from the outer covering to prevent the entire system from grounding through the outer covering. 2. Double-layer shielded twisted pairs (double-layer STPs) are used for the analog signal wires to reduce the effects of electromagnetic interference.
Y.-Y. Wang et al. / Nuclear Instruments and Methods in Physics Research A 738 (2014) 50–53
53
Old fiber MSCSRe
HVCSRe
MSCSRm
Event
HVCSRm
RF
Intranet IPC
EMIF ARM
DSP
FPGA
SPI
RS485 ICP400 MS6
HV6
MS0
HV0
Kicker Power
Event New/ CSRe Charge
CSRe Discharge
Supply New fiber Fig. 5. Controller architecture.
kicker control system are shown in Table 3 (the time period of the RF signal is 1 μs).
Table 3 Comparison of the old and new systems. Parameter
Old system
New system
Phase (deg) Minimum delay time (ns) Position (m)
1.8 5 0.805
0.9 2.5 0.4025
3. Ferrite beads are fixed around the signal wires (both ends) and the power wires to reduce the effects of electromagnetic interference. 4. In the process of designing the controller, all of the I/O ports were designed using transient voltage suppressor (TVS) diodes, which can prevent damage to the controllers from the interference pulse signal. 5. Isolators are used to eliminate various types of signal interference. 5. Improvement of the new kicker control system The most important improvement made to the old kicker control system is its precision. The new system can accurately measure the position of the beam bunches and send the control signals. We can determine the precision of the position of the beam bunches by using the following formula: L¼
3601 P T
L is the precision of the position, P is the precision of the control system and T is the time period of the high-frequency signal. The minimum delay time of the synchronous signal and the control signal for the power supplies is the same as the precision of the kicker control system. The improvements made to the old
6. Conclusions The upgraded beam kicker control system was demonstrated to be more reliable and more stable than the old control system. The upgraded system has five specific advantages. First, because of the monolithic circuit architecture and the newly designed ARMþDSP þ FPGA technology, the control precision of the kicker system is improved from 5 ns to 2.5 ns. In addition, digital timing control and delay regulatory functions are also achieved. Second, the reference voltage setting precision of the kicker power supply is improved from 2% to 0.1%. Third, the discharging of every kicker power supply can be independently controlled, which can satisfy the requirements of different experiments. Fourth, the system eliminates various types of interference, protects the devices from harsh conditions and reduces costs. Finally, the new system improves the efficiency of beam injection and beam injection of the HIRFL. References [1] Jiawen Xia, Wenlong Zhan, Baowen Wei, et al., High Power Laser and Particle Beams 20 (11) (2008) 1787. [2] Yanyu Wang, Yuhui Guo, Feiyu Lin, et al., High Power Laser and Particle Beams 20 (8) (2008) 1353. [3] Jinhui Chen, Chinese Physics C 32 (2008) 4. [4] R. Koyama, N. Sakamoto, M. Fujimaki, et al., Nuclear Instruments and Methods in Physics Research A 729 (2013) 788. [5] Lizhen Ma, Shaofei Han, Yuan He, et al., High Power Laser and Particle Beams. 18 (2006) 147. [6] Qunyao Wang, Daqing Gao, Jingbin ShangGuan, et al., Power Supply Technologies and Applications 9 (1) (2006) 36. [7] Wenxiong Zhou, Yanyu Wang, Detai Zhou, et al., Nuclear Instruments and Methods in Physics Research A 728 (2013) 112.