1. The progress of Beam Instrumentation for BEPCII
Beam Instrumentation Group Accelerator Center, IHEP
2018/9/22
4th-IMAC meeting

2. Outline Introduction Linac BI progress Ring BI progress Summary
2018/9/22
4th-IMAC meeting

3. Introduction
After the 3rd IMAC meeting, we took full advantage of the great opportunity that the BEPC was operating. Most of the monitor prototypes for storage ring had been tested with beam, such as MX-BPM, DCCT, TFB and so on. We think these test results can certainly promote our work.
For the linac, we also did many experiments together with physics people. We measured the electron and positron emittance at different location, the beam energy and energy spread by using analyzing magnet of AM1 and AM3, beam current, two bunches acceleration and beam orbit along the linac by using BPM system.
2018/9/22
4th-IMAC meeting

4. Linac BI
The Linac Beam Instrumentation System consists of BPM, BCT, Emittance Measurement, Profile monitor and EPICS based DAQ system.
In the last year, The DAQ system based on EPICS had been built and we successfully completed the system commissioning. There are 5 monitor stations along the linac gallery. Each monitor station consists of a VME computer, a gated integrator for BCT, and a log-ratio BPM, a DG535 for triggering and a signal-switching box. Each monitoring station can control 6 BPMs and 6 BCTs at maximum.
2018/9/22
4th-IMAC meeting

5. Linac BPM
Total of 20 BPM’s
15 Stripline BPMs at each quadruple triplets
1 Stripline BPMs at linac end,
1 Stripline BPMs at pre-injector end,
1 Stripline BPMs near AM3
2 button BPMs at gun exit
A computer located in control room can acquire the beam position data through IOC and then to display the beam orbit in real time.
2018/9/22
4th-IMAC meeting

6. Linac BPM
Because of the budget, we have to adopt switching mode for the BPM system. In order to prolong the lifetime of the RF coaxial relay, the data-taking cycle speed at present is about 1Hz for one monitoring station. This data acquisition speed is enough for normal orbit measurement. But in some cases, the fast data-taking can help us to record the beam transverse position for every pulse.
We ever considered to adopt solid-state MUX switches to achieve higher switch rates.
But after the investigation, we find the solid-state switch has smaller signal dynamic range than coaxial relay and solid-state switch is easily to occur current leakage between different channels.
2018/9/22
4th-IMAC meeting

7. Linac BPM
The BPM data is used for the system resolution analysis. This figure shows a group of data of BPM5. The red line and blue line represent the BPM resolution (RMS values) in horizontal and vertical direction, respectively. This RMS values contain beam orbit oscillation and BPM system error. By comparing the horizontal and vertical direction, we think that the beam orbit oscillation is the main source to affect the system resolution of BPM.
For BPM01 and BPM02, the beam position resolution of less than 100 m can be easily obtained.
0.15mm RMS value
0.43mm RMS value
2018/9/22
4th-IMAC meeting

8. Linac BI
After BEPC shut down, the beam instrumentation system of linac was continually improved according to the operation situation. We improved the optical path of AM3 and positron target screen, a new alignment support for BPM01 and BPM02，a molybdenum mesh at the front of screen of PR1 and PR2 in order to avoid the static electron accumulating, and newly installed BPM and fluorescent screen monitor located at the downstream of AM3 and AM2, respectively. In order to measure the beam energy spread non-intrusively, a BPM with 8 stripline electrodes was installed in the large dispersion section of the transport line.
2018/9/22
4th-IMAC meeting

9. Linac BI the optics path of positron target screen AM3 optics path
2018/9/22
4th-IMAC meeting

10. newly installed BPM at downstream of AM3
Linac BI
8 stripline electrodes BPM
molybdenum mesh
newly installed BPM at downstream of AM3
2018/9/22
4th-IMAC meeting

11. Linac BI
BPM01 and BPM02 are located at the gun exit. Due to the tight space, there was no support for these two BPMs to keep the relative position between the BPM and adjacent magnetic unchanged. This time we try to install a alignment support.
Alignment support
2018/9/22
4th-IMAC meeting

12. Linac BI
11 BPMs and 12 Collimators had been installed in transportline. Collimator will be used for the control of beam emittance and beam energy spread. In order to monitoring the transportation efficiency of positron, two beam charge monitors were installed at the end of linac and positron transportline, respectively.
Beam Charge Monitor
Collimator
2018/9/22
4th-IMAC meeting

13. Summary of Linac BI
The BPM system and beam profile monitor for the positron target play an important role when the positron beam commissioning. The BPM’s sensitivity is enough for the weak positron beam.
The device of BCT, Emittance Measurement and Profile can work well. But for BPM system, sometimes the resolution (RMS value) is larger than 0.2mm. Maybe it is caused by the transverse wakefiled, beam energy fluctuation or others.
The EMI issue is still to be.
2018/9/22
4th-IMAC meeting

14. BI of Storage Ring Beam Position Monitor Bunch Current Monitor
Syn. Light monitor
DCCT
Transverse Feedbake System
Tune value measurement
Beam Loss Monitor
2018/9/22
4th-IMAC meeting

15. Beam Position Monitor
Almost all of BPM blocks have been manufactured by vendor. The cabling in the tunnel was finished. Near half of BPM blocks were calibrated in laboratory by using calibration antenna. The calibration results were double checked by physics group and our group. For the BPM DAQ system, an IOC for MX-BPM electronics had been developed and tested in laboratory. The prototype of digital BPM (Libera) was tested as well. It will be used for the turn-by-turn beam orbit measurement. As for the closed orbit feedback or IR feedback, the hardware is same with BPM system, but the control software will be developed by physics group and control group.
2018/9/22
4th-IMAC meeting

16. Beam Position Monitor Table： The type and quantity of BPM blocks
BPM type
BPM quantity
Feedthrough Type
Antechamber 1 76
15mm, stainless steel, USA
Antechamber 2 20
Racetrack type 16
Circular Type
100、150 6
316L-15mm, Japan
O-BPM1 2
I-BPM2 10
C-BPM8
CuNi-8mm, Japan
I-BPM1
IR Y-type 4
Small aperture
2018/9/22
4th-IMAC meeting

17. Beam Position Monitor
BPM
BPM
Cable
fixing
2018/9/22
4th-IMAC meeting

18. Beam Position Monitor BPM was being calibrated The curve-fitting
X ±10mm， Y ±5mm
BPM was being calibrated
The curve-fitting
Calibration results for antechamber type BPM:
Sensitivity: ( , )
Simulation results by using finite element method:
Sensitivity: (25.1, 24.9)
2018/9/22
4th-IMAC meeting

19. Beam Position Monitor MX-BPM tested results with beam COD mode
Resolution < 0.01mm ( I > 5.5mA )
MX-BPM tested results with beam
2018/9/22
4th-IMAC meeting

20. Beam Position Monitor Chassis Layout for BPM electronics 2018/9/22
4th-IMAC meeting

21. Beam Position Monitor DAQ structure OPI TCP/IP LAN Sync IOC e+ IOC e+
BPM Station 1
BPM Station 3
BPM Station 1
BPM Station 3
BPM Station 2
BPM Station 4
BPM Station 2
BPM Station 4
BPM Station 5
BPM Station 5
DAQ structure
2018/9/22
4th-IMAC meeting

22. Beam Position Monitor Development environment 2018/9/22
4th-IMAC meeting

23. Bunch Current Monitor
The bunch current system is consisted of front end circuits, data acquisition and shared memory system.
It is distributed in two places. one is in the beam instrumentation station. The other one is in the Central Control Room.
2018/9/22
4th-IMAC meeting

24. Bunch Current Monitor front end circuits Shared memory 2018/9/22
4th-IMAC meeting

25. Bunch Current Monitor FADC:ECAD2081500 Sampling clock : 1.5GHz
Internal FPGA for DSP programming
Schematic drawing of FADC structure
2018/9/22
4th-IMAC meeting

26. Some experiments done in lab
Bunch Current Monitor
Some experiments done in lab
Build the development environment
Install the FADC、shared memory card VMIVME-5565 and a CPU(MVME5100) in a VME computer.
Install the VMIPCI-5565 card in a PCI bus based computer.
Connect the VMIVME-5565 and VMIPCI-5565 with multimode optic fiber.
Download the application program into the CPU.
Test the shared memory cards
Test the FADC card
2018/9/22
4th-IMAC meeting

27. Development environment
Bunch Current Monitor
Development environment
2018/9/22
4th-IMAC meeting

28. Recovered signal by using sampling points
Bunch Current Monitor
AD test results
Recovered signal by using sampling points
Flow chart for AD test
2018/9/22
4th-IMAC meeting

29. Bunch Current Monitor
The front end circuit is same as the Transverse Feedback System of BEPCII.
For the FADC board, the AD part has been tested but the FPGA development is in progress.
The BCM system should work with the timing system of BEPCII. So we should discuss the data format and injection algorithm with the control group in further.
2018/9/22
4th-IMAC meeting

30. Synchrotron Light Monitor
SRM layout
First mirror
2018/9/22
4th-IMAC meeting

31. Synchrotron Light Monitor
The SRM detectors had been manufactured and assembled by vendor. After finished the vacuum checking, we started some experiments on alignment and calibration in our laboratory. The detector supports for the alignment and calibration had been modified according to the experiment results. This figure shows the detector was being aligned.
2018/9/22
4th-IMAC meeting

32. Synchrotron Light Monitor
The calibration of the transverse magnification of the imaging system is needed to obtain measurements of absolute dimensions. This is done in a very simple way by sliding the lens. Displacing the lens a precise value in horizontal plane or vertical plane represents a transverse source point displacement of the same value (but of the opposite sign) and a displacement of the beam spot on the CCD camera of that value multiplied by the system-magnification.
2018/9/22
4th-IMAC meeting

33. Magnification (simulation value)
Synchrotron Light Monitor
The calibration of the transverse magnification
Calibration results:
Laser wavelength: 650nm
Lens displacement = 0.150mm
Image displacement = mm
Magnification = 3765/150 =2.51
wavelength
Magnification (simulation value)
365nm
2.2
450nm
2.3422
550nm
2.4392
650nm
2.5
2018/9/22
4th-IMAC meeting

34. Synchrotron Light Monitor
Determine the SRM resolution: 10% of vertical beam size (~20 µm)
The beam size is about 0.2mm in vertical direction. The magnification of the imaging system is 2.2 for 365nm light. A selected camera with specifications as blow:
·Number of effective TV Lines Pixels 736 (H) x 568 (V)
·Pixel size 11 µm (H) x 11 µm (V)
·Optical size 1/2 type
So, the image size is 0.2mm x 2.2＝440µm.
Corresponding number of pixels is 440µm / 11µm = 40.
Resolution is 200µm / 40 = 5µm
So, if the beam orbit is stable, then the system resolution will be good than 10% of vertical beam size.
2018/9/22
4th-IMAC meeting

35. DCCT
The new DCCT had been tested in BEPC. According to the experiment results, we modified the structure of ceramic pipe. In the machining process of ceramic pipe, the vendor met some difficulties on the Kovar welding. Finally, they solved this issue.
New DCCT tested with beam
2018/9/22
4th-IMAC meeting

36. DCCT
New DCCT tested with beam
2018/9/22
4th-IMAC meeting

37. Consideration to noise rejection
DCCT
Consideration to noise rejection
The noise caused by EMI and RFI can be demodulated in the readout instrument due to it’s high-impedance input. These interference's can be significantly reduces or eliminated by the use of common-mode filters. Simple common-mode filters can be made by passing the signal cable through a ferrite core. The magnetic characteristics of the ferrite cores must correspond to the frequency spectrum of the noise to be rejected.
To reject differential mode noise, install a ceramic capacitor between signal wire and ground at the input of the readout instrument. Moreover, we hope the BEPCII new grounding system can make effects to reduce the noise in further.
2018/9/22
4th-IMAC meeting

38. DCCT
The Labview-Based DAQ system for DCCT is developed. This is the DAQ structure.
2018/9/22
4th-IMAC meeting

39. DCCT
The control system of BEPCII is based on EPICS, so the DAQ system as an EPICS IOC is developed by using the Channel Access VIs.
CA-Server in LabVIEW
CA-Client in LabVIEW
LabVIEW Interface to EPICS IOC
2018/9/22
4th-IMAC meeting

40. DCCT An example of software development of CA server and CA client
2018/9/22
4th-IMAC meeting

41. Transverse Feedback System
The prototype of TFB system was built and tested in BEPC. With the help of KEK expert, we were successful in the prototype experiments. This figures show the experiment results.
TFB turn-off TFB turn-on
The experiment results of TFB prototype
2018/9/22
4th-IMAC meeting

42. Signal from Kicker for monitoring
Transverse Feedback System
Single shot mode
Pickup signal
Beam orbit
ContinualAcq. mode
Experiment
data
Signal from Kicker for monitoring
TFB turn-off
TFB turn-on
2018/9/22
4th-IMAC meeting

43. Transverse Feedback System
The machining of one unit of kicker has been finished. The electrical performances were checked in laboratory.
2018/9/22
4th-IMAC meeting

44. Tune value measurement
According to the operation experience of BEPC and the requirements of BEPCII, the tune measurement system adopt both Fast Fourier Transform (FFT) method and swept-frequency method.
2018/9/22
4th-IMAC meeting

45. Tune value measurement
For the swept-frequency method, the betatron tune is measured by exciting the beam externally in the horizontal and vertical planes simultaneously through a stripline, similarly, picked up by another BPM and sending to the spectrum analyzer .
Tune system structure
2018/9/22
4th-IMAC meeting

46. Beam Loss Monitor
After the electronics design was finished, we signed a contract with the vendor through a public bidding for the electronics manufacture. Now, the electronics prototype had been manufactured. The DAQ system has been developed as well. The BLM detectors were bought from Bergoz company. We tested the BLM prototype by using radiation source in laboratory and residual activated dose in linac tunnel, respectively.
2018/9/22
4th-IMAC meeting

47. Beam Loss Monitor The electronics prototype DAQ sample 2018/9/22
4th-IMAC meeting

48. Summary System AP Requirements Test results BPM SRM COD accuracy：0.1mm
Resolution：<0.01mm
  BBA will be adopted
<0.01mm (I > 5.5mA)
Tune
Resolution：0.0001(0.1kHz)
 0.03kHz SWF mode
DCCT
Dynamic range：0.0~1.5A
Linearity：0.1 %
0.0~20.0A  
< 0.05% in lab.
BCM
Relatively precision：1/256
Bunch spacing：2ns
 8 bits AD & 256 cycles averaged
SRM
Beam size
Resolution:(10%)sy
  < (10%)sy simulation
Bunch length
Resolution：2 ps
  using streak camera
2018/9/22
4th-IMAC meeting

49. Summary
In general, the progress of the beam instrumentation system, especially hardware could keep the synchronous with the BEPCII CPM plan. Firstly, the mechanical machining of most devices had been finished. Secondly, most prototypes were tested with beam.
According to suggestion of IMAC experts, 5 Profile monitors for positron ring commissioning had been designed and the manufacture will be finished next month.
Next step, our work will focus on the software development.
The software interfaces between diagnostic system, control system and physics group has been determined.
2018/9/22
4th-IMAC meeting

50. Thanks!
Thank you for your attention!
2018/9/22
4th-IMAC meeting