1. LCLS-II Linac LLRF Control System – L2, L3 Zheqiao Geng Preliminary Design Review May 7, 2012

2. LCLS-II L2 and L3 L2 (11-3 to 14-6) and L3 (14-8 to 20-4) 14-1, 14-2 and 14-3 for BC2 beam energy feedback 14-1, 14-2 and 14-3 for BC2 beam energy feedback 14-8 for TCAV3 14-8 for TCAV3 Beam Phase Cavity PH03 Beam Phase Cavity PH03

3. Outline Introduction Requirements Scope Architecture and Design Safety Cost and Schedule Lessons Learnt from LCLS Summary Slide 3

4. Introduction This talk presents the design of LLRF system for the main Linac of L2 and L3 The design follows PAD/PAC/VME solution used at LCLS New features compared to LCLS LLRF System  A simplified phase reference line  Fast phase control for the entire sectors (8 klystrons per sector)  More diagnostics for Sub-boosters and energy feedback klystrons in Sector 14 Slide 4

5. Physics Requirements Slide 5 LCLS-II Linac Requirements - PRD

6. Scope of L2/L3 LLRF System Slide 6 A phase reference line providing 2856 MHz reference to all sectors in L2/L3, LCLS-II experiment and LCLS (for relative timing measurement) Fast phase control of the Sub-boosters of Sector 11 to Sector 20 with PACs and PADs Individual phase control of station 14-1, 14-2, 14-3 and 14-8 with PACs, PADs and SSSBs Measurement of Beam Phase Cavity 03 (PH03) installed in Sector 15 Control infrastructure (VME, EVR and so on) and EPICS software

7. Interface and Context Slide 7 LCLS-II Injector LLRF System: Provides 2856 MHz reference at RF HUT Sub-boosters: Controlled and measured by PACs and PADs Sector Phase Reference Line: Gets phase reference input power Station 14-1, 14-2, 14-3 and 14-8: Controlled and measured by PACs, SSSBs and PADs Beam Phase Cavity PH03: Measured by PADs LCLS-II Experiment and LCLS: Get phase reference Timing System: Provides EVG fibers to LLRF BCS: Provides gate signals to SSSBs of station 14-1, 14-2, 14-3 and 14-8 AC Power Supply System: Provides remotely controllable power switch to LLRF chassis Water Cooling System: Provides temperature stabilized cooling water to LLRF chassis Fast Feedback System: Provides phase set points to feedback stations (14-1, 14-2 and 14-3) and feedback sectors (Sector 18 and 19) Physics Applications: Gets LLRF data and sets LLRF parameters Details will be described in the LCLS-II ESD: LCLS-II Linac LLRF System Requirements Specification (SLAC-I-060-102-113-00)

8. Architecture of LLRF Phase Reference Line Slide 8 Single Main Phase Reference Line (MPRL) is used to distribute 2856 MHz reference Use 1-5/8 inch rigid coax cable as MPRL for low attenuation and acceptable drifts MPRL will be routed in the Linac tunnel for better temperature stabilities Reference signal is coupled out at each sector, amplified and fed into the existing Phase Reference Line of the sector. Sub-booster takes the reference and generates power to the Sub Drive Line All klystrons of the LCLS-II Linac will be synchronized by the same phase reference The design provides an easy way for phase changes of sectors

9. Design of LLRF Phase Reference Line Slide 9 Low Risk - 1-5/8 inch rigid coax cable has been used in sector PRL and the 2830.5 MHz distribution of LCLS, no failure observed from LCLS

10. Drifts of LCLS Phase Reference Line Slide 10 Cable drifts respect to beam from S20 to S24 (~ 400m) Temperature coefficient about 1.5 deg@2856 MHz / 100m / degF 1-5/8 inch rigid coax cable drift Attenuation: 0.033 dB/m @ 2856 MHz Linac tunnel temperature drifts at Sector 22 and 25

11. Drifts of LCLS Phase Reference Line (cont.) Slide 11 1-5/8 inch rigid coax cable drifts from S20 to S28 (~ 800m)

12. Drifts Estimation of LCLS-II Phase Reference Line Slide 12 Portions of cable in klystron gallery suppose to have ~5deg@2856 MHz drift with temperature change of 25 degF Maximum drift (RF station at the end of Linac) estimated > 20 deg @ 2856 MHz daily Rainy Days! Methods for drift measurement  Beam phase cavity signals  Beam induced signals from stand-by stations (spare RF stations)  Phasing sectors or klystrons periodically Methods for drift compensation  Software correction with the drift measurements  Beam based feedback

13. Architecture of Sector Phase Control Slide 13 Green boxes and lines are new from LLRF Local LO and Clock generation A PAC chassis is used to control the phase of entire sector Two PADs chassis are used to measure RF signals including replacing the head-tail phase monitor Will be implemented for Sector 11 to 20

14. Architecture of Control of Sector 14 and15 Slide 14 Green boxes and lines are new from LLRF Controls of station 14-1, 14-2 and 14-3 are combined with the Sector 14 control to share the LO and Clock generator Control of station 14-8 and measurement of PH03 are combined with the Sector 15 control Critical cables (ACCin and ACCout) are routed in the tunnel which has a temperature stability of about 1 degF. Phase drift < 0.5 deg@2856 MHz for the longest cables of 14-3 Diagnostic cables (Klystron Drive, Klystron Beam V and Klystron Out) routed in klystron gallery

15. Design of PAD (Phase & Amplitude Detector) Slide 15 Use the same PAD design for LCLS-II Injector LLRF System - Needs 28 chassis (20 for Sub-boosters and 8 for klystrons) Low Risk - LCLS has had 1 PAD chassis failure (infant mortality) since it began operations. NLCTA and KTL have also used similar PAD designs ADCs: 69dB SNR

16. Design of PAC (Phase & Amplitude Controller) Slide 16 Use the same PAC design for LCLS-II Injector LLRF System - Needs 14 chassis (10 for Sub-boosters and 4 for klystrons) Low Risk - LCLS has had 0 PAC chassis failures since it began operations. NLCTA and KTL have also used similar PAC designs Devices using the PAC achieve 0.03 degrees RMS jitter

17. Design of SSSB (Solid State Sub-booster) Slide 17 Use the same SSSB design for LCLS - Needs 4 chassis Low Risk - 9 of these units have been running since LCLS started operation without a failure

18. Design of LO and Clock Generator Slide 18 Use the same design for LCLS-II Injector LLRF System - Needs 10 chassis for all sectors Low Risk – Simplified LO generation scheme which will be more robust. The new LO generator has been successfully used in LLRF AIP and no failures observed up to now

19. Safety Slide 19 Hazards  Non Ionizing Radiation The NIRS system modifications for LCLS are included here –This is the Summing chassis that takes an input from the LCLS-II Vacuum PLC and gives an input to the MKSU. Up to the 5045 klystron the highest average power level in the RF system is 2W at the output of the main RF and LO distribution amplifiers. Get the system reviewed by the NIRSC.  Other electrical The LLRF chassis are powered by 110VAC and all chassis are EEIPed. Safety Systems  BCS The BCS interface will be a duplicate of LCLS 1 –This ties into the Solid State Sub-Boosters –A modification should be make to go from twinax to coax to reduce noise  PPS – covered in modulator presentation The PPS interface to modulators will allow access to the injector vault while running the linac This involves a PPS interface to be installed on the modulator and is discussed in the modulator presentation.  BCS and PPS reviews will be conducted by the BCS and PPS groups

20. Costs Slide 20 ItemM&S Cost ($K)Labor (hour) L3 (including L2) LLRF Systems (PAD, PAC, SSSB, Cabling and Components)307.182161 L3 (including L2) LLRF Installation51168 Note: The cost information is derived from P6. It only cost 14 PAD chassis and 7 PAC chassis (only half of the number needed in this design). A new cost model need to be developed!

21. Schedule Slide 21 FDR by July 2012 Hardware ready for rack installation by Feb. 2015 Rack installation finished by June 2015 Production software release by July 2015

22. Lessons Learnt from LCLS LCLS has a complex phase reference system which makes difficulties in machine operation  Problems with L2 phase adjustment. L2 phase is adjusted with the SPAC inserted in the reference line. The phase of the entire reference line will be changed when adjusting L2 phase. This brings phase uncertainties to the reference signal used to synchronize the LCLS experiments  Difficult to change L3 phase. The MDL SPAC must be adjusted to change the L3 phase. It will change the phase of the entire machine including L2 and Timing System reference, causing L2 phase requiring re-adjustment and timing jumps Poor diagnostics makes it difficult for trouble shootings  No fast phase measurement of phase reference line at each sector  No fast phase measurement of feedback klystrons for L2 energy feedback Slide 22

23. Summary The design of phase reference line is quite different from the design for LCLS. The new design addresses the lessons learnt from LCLS operation Sub-booster control improves the machine level operability  More actuation freedom for feedback control  Clean phase adjustment for L2 or L3 Diagnostics of Sector control and individual klystron control improves the measurability and visibility of the machine Slide 23

24. Thank you!