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

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

Diagnostics

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

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)

Diagnostics - BPMs

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

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

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

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.

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

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

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

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

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)

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.

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

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)

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

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