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Four Hall Operation and Injector Updates

Four Hall Operation and Injector Updates. Reza Kazimi, JLAB HALL C C ollaboration M eeting August 15, 2013. Topic 1: Simultaneous Four-Hall Operation for 12 GeV CEBAF. Separating One Beam Out (500 MHz).

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Four Hall Operation and Injector Updates

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  1. Four Hall Operation and Injector Updates Reza Kazimi, JLAB HALL C Collaboration Meeting August 15, 2013

  2. Topic 1:Simultaneous Four-Hall Operation for 12 GeV CEBAF

  3. Separating One Beam Out (500 MHz) Kick one out and recirculate two. This is the configuration for the first four passes.

  4. Three Way Separation Three way split to the three halls. This is the configuration for the fifth passes.

  5. 12 GeV CEBAF Upgrade

  6. 750 MHz Hall D Separation into Splits 500 MHz Beams Two 250 MHz Left and Right Beams To Halls ABC A A • AL • AR AR AL • BR • BL • BL • BR B B • CL C • CR • CL C • CR To Hall D BunchTrain

  7. Four Hall Operation (D+3)

  8. Generating 250 MHz Beams • 250 MHz beams are required for D+3 to work. 500 MHz beams can also be used depending on the configuration. • Some experiments like to run at lower repetition rates.

  9. Pulse Picker • A new CEBAF injector low-level laser drive system has been proposed that uses electro-optic modulators (a telecom standard) to produce 250 MHz beams. • Only affects front-end laser seed drivers. No changes to laser table components. • Gives any hall a “pushbutton” selectable running frequency of 500 MHz or lower divisions of 250, 125, 62.5, or 31.25 MHz, without affecting other halls. • Will permit introduction of a 4th laser for Hall D.

  10. Upgrade to the Existing Lasers System, Selecting 1 Out of N Pulses.

  11. Frequency Divider

  12. Electro-optic Modulator

  13. 500 MHz Structure Laser (Green Trace)

  14. 250 MHz Structure Laser (Green Trace)

  15. 32 MHz Structure Laser (Green Trace)

  16. CEBAF 12GeV Beam Operations • Test the SubharmonicRepetition Rate • Subharmonic Repetition Rate • 5th pass 750 MHz Separator

  17. Topic 2:Injector Upgrade for 12 GeV CEBAF Why do we need to upgrade the injector?

  18. One Reason Is: Injector Energy Injector 11.25% of Linac Energy

  19. Another Reason: Beam Quality • In CEBAF many of critical beam parameters are set in the injector and some remain unchanged through the accelerator. Therefore, the injector plays a significant role in setting the final beam qualities such as bunch structure, energy spread, current stability, etc. • Parity quality of the beam is an important parameter for many of the experiments at CEBAF and it is achieved when the two helicity states are created and treated similarly particularly in the injector’s low energy region. Also, if the symmetry is maintained, the beam motion can be damped through the initial acceleration in the injector, further reducing the position asymmetry.

  20. Parity Quality Beams at CEBAF 1.158 1.158

  21. Brief Description of the 6 GeV CEBAF Injector Synchrotron Light Monitor 5 MeV Mott Polarimeter Chopper Cryounit Cryomodules Buncher Capture Gun#2 Injection Chicane Bunchlength FC#1 FC#2 Cavity PreBuncher Gun#3 100/500 keV Mott Polarimeter 45 MeV Dump/ Spectrometer Polarized Electron Source (130 kV) SRF Acceleration (<68 MeV) Synchronous Injection B C A Apertures V-Wien Filter H-Wien Filter Spin Solenoids Bunching & Acceleration 500 keV Electron Spin Manipulation SRF Acceleration (<10 MeV) Injection Chicane

  22. Synchrotron Light Monitor 5 MeV Dump Chopper Cryounit Cryomodules Buncher Capture Gun#2 Injection Chicane Bunchlength FC#1 FC#2 Cavity PCup Prebuncher Gun#3 500 keV Dump Spectrometer Breaking Down the Problem Acceleration Space Charge Apertures H-Wien Filter V-Wien Filter Bunching Process

  23. The CEBAF Injector Upgrade 5 MeV Dump Superconducting Booster Chopper Cryo-modules Buncher Capture Gun#2 Injection Chicane Faraday Cup Prebuncher Gun#3 500 keV Dump Spectrometer/Beam Dump Increase Gun Voltage from 130 kV to 200 kV Lowers the space charge effect and reduces difference between high and low bunch charge. Apertures Faraday Cup Faraday Cup H-Wien Filter V-Wien Filter

  24. The CEBAF Injector Upgrade 5 MeV Dump Superconducting Booster Chopper Cryo-modules Buncher Capture Gun#2 Injection Chicane Faraday Cup Prebuncher Gun#3 500 keV Dump Spectrometer/Beam Dump Increase Gun Voltage from 130 kV to 200 kV Lowers the space charge effect and reduces difference between high and low bunch charge. Apertures Faraday Cup Faraday Cup H-Wien Filter V-Wien Filter Upgrade the Wien Filters for higher energy beam Enables electron spin setting and 180 deg spin flip as required by Parity Quality experiments

  25. The CEBAF Injector Upgrade 5 MeV Dump Superconducting Booster Chopper Cryo-modules Buncher Capture Gun#2 Injection Chicane Faraday Cup Prebuncher Gun#3 500 keV Dump Spectrometer/Beam Dump Increase Gun Voltage from 130 kV to 200 kV Lowers the space charge effect and reduces difference between high and low bunch charge. Apertures Faraday Cup Faraday Cup H-Wien Filter V-Wien Filter Integrate Capture into the Booster Accommodates higher energy beam, simplifies beam setup, and increases reliability Upgrade the Wien Filters for higher energy beam Enables electron spin setting and 180 deg spin flip as required by Parity Quality experiments

  26. The CEBAF Injector Upgrade 5 MeV Dump Superconducting Booster Chopper Cryo-modules Buncher Capture Gun#2 Injection Chicane Faraday Cup Prebuncher Gun#3 500 keV Dump Spectrometer/Beam Dump New Booster with new SRF design Eliminates the x/y coupling and improves and simplifies the Parity Quality beam setup. Increase Gun Voltage from 130 kV to 200 kV Lowers the space charge effect and reduces difference between high and low bunch charge. Apertures Faraday Cup Faraday Cup H-Wien Filter V-Wien Filter Integrate Capture into the Booster Accommodates higher energy beam, simplifies beam setup, and increases reliability Upgrade the Wien Filters Enables 180 deg electron spin flip as required by Parity Quality experiments

  27. Modeling the New Booster • The challenge for the new system is to accelerate and bunch while keeping the energy spread and emittance growth low for all beam currents! • Different booster designs considered in an injector without a capture cavity: • 5+5 Existing booster, two 5-cell cavities • 1+7, 1-cell cavity and new CEBAF 7-cell cavity • 1+1+7 • 2+5 • 2+7 • 7+7

  28. The New Booster Design 5+5 2+7

  29. Bunch Length for Different Currents

  30. New Booster with 2 Cell + 7 cell Cavities Significantly reduced RFkick and x/y coupling and easier operation

  31. The CEBAF Injector Upgrade 5 MeV Dump Superconducting Booster Chopper Cryo-modules Buncher Capture Gun#2 Injection Chicane Faraday Cup Prebuncher Gun#3 500 keV Dump Spectrometer/Beam Dump Increase Gun Voltage from 130 kV to 200 kV Lowers the space charge effect and reduces difference between high and low bunch charge. New Booster with new SRF design Eliminates the x/y coupling and improves and simplifies the Parity Quality beam setup. Upgrade the Cryo-modules to increase the injector energy from 45 MeV to 123 MeV To achieve the 12 GeV injector energy requirement Apertures Faraday Cup Faraday Cup H-Wien Filter V-Wien Filter Integrate Capture into the Booster Accommodates higher energy beam, simplifies beam setup, and increases reliability Upgrade the Wien Filters Enables 180 deg electron spin flip as required by Parity Quality experiments

  32. Upgrade of the Accelerating modules C25 R100 Up to 30 MeV + Up to 100 MeV

  33. Order of Cryomodules Horizontal rmsbeam size (top) and beam energy (bottom) along the two modules. Red curve is high gradient module first. Blue curve is low gradient first.

  34. CEBAF 12GeV Beam Operations • Increase the Injector Energy from 45 MeV to 123 MeV • Increase Gun Voltage130 kV to 200 kV • Upgrade the Two Wien Filters • Integrate Capture into the Booster with new SRF design

  35. Other Improvement to the Injector • Add 2 BPMsjust after the gun (one before solenoid, one after solenoid). Provides ability for PQB measurements of position (all the time) and angle (with solenoid off); also, will provide Region 1 auto-steering, thus completing auto-steering from Gun to chopper. • We ask for a PSS system which does not turn off the gun HV for accesses (only for PSS faults); we will ask PSS to instead use an interlock with an insertable element. Benefit is avoiding instances where QE may be degraded. • Mott polarimeter is receiving an upgrade in order to test precision at 1% level and to characterize any systematics which affect measuring/setting spin direction.

  36. Conclusion • Injector energy will be nearly doubled to meet CEBAF requirement. • Approved Parity Violation experiments are more demanding and require upgrading some of the existing injector components and beam dynamics. • The injector upgrade will be done in phases and is planned to be completed by the end of FY2015 if budgetary and other limitations do not interfere. • The plan is to test the new injector components and optics before implementation in the CEBAF injector. • An upgrade to the electron gun laser system will not only allow 4-hall operation but also provide an independently changeable low rep rate beam to each hall.

  37. Thank You!

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