1. Controls CBETA controls will extend existing EPICS control system
EPICS include standard components:
data acquisition and control
operator interface
save/restore settings
data archiving
alarm state notification
interfaces to Matlab, Python, C++, …
Leverages a proven, scalable platform supported by a large, open, active community

3. Two important additions to be made to existing controls infrastructure:
Accelerator configuration repository – provide a central repository for component details, make these details available to controls, simulation, and user
Implement an interface between Bmad and EPICS, allowing Bmad to read/write current machine settings

4. Diagnostics

5. Diagnostics
The principal challenge for CBETA diagnostics is the presence of multiple beams which must be individually diagnosed and controlled.
Additionally must cope with limited longitudinal space and
large horizontal offsets in FFAG-arcs

6. BPMs – dealing with multiple beams: separation in time
Diagnostics - BPMs
BPMs – dealing with multiple beams: separation in time
Probe bunches separated by 9.5 RF cycles (7.3 nS)

7. Diagnostics - BPMs

8. Reflection from first beam pulse
Diagnostics - BPMs
Injector 8 mm buttons in 35 mm diameter beam-pipe
First beam pulse
Reflection from first beam pulse

9. Diagnostics - BPMs
‘Oscilloscope trace’ for injector button trace acquired with V301 (Dec. 2016)
ADC clocked from injector RF master oscillator
read out EPICS
Need to address the ringing

10. Diagnostics - BPMs EPICS user interface screen from beam test
4 bunches shown in this raw ADC data
~40dB gain in V301, no external amplifiers
timing seemed remarkably stable – but in CBETA will need to automate timing adjustment to machine state
1 second average position

11. Diagnostics - BPMs
Current plans are for 70 mm ID pipe with 18 mm buttons oriented as shown.
For different arrangements of buttons we evaluate the average sensitivity over a region of interest. The ROI is show here is for the FFAG arc.
The arrangement shown on top favors horizontal resolution over vertical in the ROI. The reverse is true for the bottom arrangement.

12. Synchrotron Radiation for 40 mA beam, 5 m bend radius
Diagnostics - BPMs
Synchrotron Radiation for 40 mA beam, 5 m bend radius
4 eV

13. 4-Button BPM (for Halbach Cell)
Diagnostics - BPMs
4-Button BPM (for Halbach Cell)

14. Bunch Arrival Monitors
Diagnostics - BAMs
Bunch Arrival Monitors
CBETA operation requires precise control of the timing/phase of the bunch entering the linac.
BAM
BAMs
Control Arrival Time here

15. Diagnostics - BAMs Injector RF BPM electronics 1300 MHz RF
Laser at 1300 or subharmonic
LO at 1300 – 12.5 MHz
ADC clock at 50 MHz
are all phase locked.
The phase of the IF signal relative to the ADC clock is a direct measure of bunch phase relative to 1300 MHz reference.
Typically achieve 0.1° or 0.2 pS
Note: no adjustment required for changing machine conditions

16. Diagnostics - BAMs
The existing RF BPM electronics don’t work in the presence of multiple beams.
However in the splitters there are only two beams. Measurement of amplitude and phase at two harmonics does work – amplitude and phase of two beams can be reconstructed. (e.g. the signal from two equal amplitude beams 180° out of phase cancel at 1.3 GHz but add at 2.6 GHz)

17. Diagnostics – Viewscreens
Viewscreens are destructive diagnostics – all subsequent beam is lost. Their value is for first pass commissioning, especially before BPMs are working, and for beam transverse profile measurements.
We plan to include:
FFAG section – one per girder initially
2 viewscreens per splitter
10 additional screens in injector, linac, mirror merger, and transport to dump
BeO screens are planned (low cost vs. YAG:Ce or diamond). During the upcoming MLC test run period we will quantify resolution, linear range, and damage threshold.

18. Machine Protection Machine Protection
Melting time for 100 mA, 50 MeV electron beam incident on aluminum beam-pipe.

19. Machine Protection
Machine Protection System: Beam Loss Monitors and subsystem specific circuitry feed Fast Laser Shutter
Beam loss monitors will be implemented as a combination of
PMT + scintillator (possibly fiber)
Offers easy gain adjust
Requires base, HV supply, HV cables
Photodiodes
Beam current monitors (injector – dump)

20. Machine Protection Number and location of BLMs to be informed by
Identification of loss scenarios (Bmad)
Modeling of radiation pattern (Geant4)
Thermal modeling of deposited power (Ansys)
We would like to identify a ‘safe’ current for commissioning as well a loss threshold for the monitors.
Related issues: activation of beam-line components, radiation damage

21. Summary –
Controls: existing EPICS controls provide a solid foundation for CBETA
Diagnostics: we have identified a set of hardware approaches requiring modest development that will allow us to commission CBETA