1. Injector Commissioning Masanori Satoh (Accelerator Laboratory, KEK) for the Injector Linac Commissioning Group The 20th KEKB Accelerator Review Committee, Feb. 23-25, 2015

2. Injector Commissioning Contents 1.Injector upgrade overview 2.Energy spread/low emittance preservation 3.Simultaneous top-up for 4-rings 4.Progress of electron commissioning 5.Issues and Schedule 6.Summary 2

3. Injector Commissioning Injector upgrade overview Injector linac –Provide e-/e+ for 4 independent storage rings –600-m-long, 50 Hz, two bunch operation (96 ns interval) Collider rings (top-up): –KEKB (shut down in 30 Jun. 2010) HER(e-): 8 GeV, 1 nC LER(e+): 3.5 GeV, 1 nC –SuperKEKB HER: 7 GeV, 5 nC LER: 4 GeV, 4 nC (w/ damping ring) Two light Sources: –PF: e-, 2.5 GeV, 0.3 nC (top-up) –PF-AR: e-, 3 GeV, 0.3 nC (twice daily injection) 3

4. Injector Commissioning Injector upgrade items 4 Low emittance photo-cathode rf gun –e-: 1 nC, 100 mm  mrad => 5 nC, 20/50 mm  mrad (Ver./Hor.) –e+: 1 nC, 2100 mm  mrad => 4 nC, 20/100 mm  mrad (Ver./Hor.) –Component alignment and fine beam control for low emittance preservation New positron capture system (Flux concentrator, Large aperture S- band structure), and damping ring New timing system (bucket selection for DR/MR) Fast RF monitor, high precision BPM readout and other new subsystems Simultaneous top-up injection –Including PF-AR via new beam transport. Pulsed Quads, steering magnets (Sector3- Sector5) Main ring commissioning: Jan. of 2016

5. Injector Commissioning low emittance RF gun A B C12345 1.5 GeV e- e+ target e-:Chicane 10 nC x 2 bunches x 50 Hz (for LER) 5 nC x 2 bunches x 50 Hz (for HER) 5 nC x 1 bunch x 5 Hz (for PF-AR) 0.3 nC x 1 bunch x 25 Hz (for PF) 1.1 GeV DR Decelerate e+ target 54321C e- e+ 1.1 GeV 4.219 GeV 1.5 GeV same energy e-/e+ beams are delivered to 4-rings with different bunch charge and energy. Beam acceleration modes must be switched by 50 Hz pulse-by-pulse for top-up injection. HER: 7 GeV e- PF-AR: 6.5 GeV e- PF: 2.5 GeV e- LER: 2.5 GeV e+ 5 nC x2 5 nC x1 0.3 nC x1 4 nC x2 Energy profiles and beam properties Pulsed Quad (Doublet) for pulse- by-pulse switching Compatible settings for e-/e+ beams (DC Quads)

6. Injector Commissioning Energy spread requirement Energy spread should be less than 0.1%. Uniform beam distribution is necessary for mitigation longitudinal wakefield and reduce energy spread. Temporal manipulation of laser system Gaussian Uniform 0.1% Gaussian w/ S-band Uniform w/ S-band Uniform w/ X-band

7. Injector Commissioning Emittance growth due to component misalignment Sector Cto5: -10 deg rf phase R56 =-0.20 Simulation results from 100 different seeds. Misalignment of Quadrupole magnets and Accelerating structure:  < 0.1 mm:  20 mm·mrad is almost satisfied.  0.1 mm: emittance preservation is required by some methods. 20 mm·mrad ・ quadratic curve as a function of misalignment ・ strongly depend on error seeds Norm. projected rms emittance (mm  mrad) Misalignment  (mm) Simulation SAD code, Elegant Initial bunch charge: 5 nC Initial emittance: 6 mm  mrad Initial bunch length: 10 ps (FWHM) Initial energy spread : 0.4% Initial beam energy: 20 MeV Uniform longitudinal beam distribution

8. Injector Commissioning Offset injection for emittance preservation Low emittance electron beam should be delivered to MR w/o damping ring. Emittance preservation is key issue for e- beam. Low emittance rf gun Offset injection: intentional change of misalignment seed. Control the steering magnet at the beginning of Sector C Bunch compression Offset injection

9. Injector Commissioning Offset injection (simulation) Sector Cto5: -10 deg rf phase R56 =-0.20 Kick angle is relatively small. Need a high-precision and stable orbit control.

10. Injector Commissioning 風間スライド挿入 10

11. Injector Commissioning Low emittance electron issue Component alignment is important  < 0.1 mm: enough for emittance (alignment is very difficult)  mm  beam manipulation is necessary. Simulation w/ misalignment  ～  mm (100 error seeds) Emittance can be preserved by J-ARC: Bunch compression Sector C: Offset injection Alignment requirement:  mm for global (whole Linac)  mm for local (one Sector ̴ 100 m)

12. Injector Commissioning e-/e+ beam fast switching (SuperKEKB) 12 Fixed positron target with a hole (e- beam pass through inside a hole) A hole is at the center of beam line for low emittance e- beam. Same scheme was successful in KEKB operation.

13. Injector Commissioning Simultaneous top-up injection for three rings Stored beam current stability in 2000. - KEKB: 300 mA (~ 50 %) - PF: 240 mA (~ 53 %) 13 Stored beam current stability in Apr. 2010. - KEKB: 1 mA (~ 0.05%) : e-: 12.5 Hz, e+: 25 Hz - PF: 0.05 mA (~ 0.01%) : 0.5 Hz KEKB e- KEKB e+ Luminosity PF PF-AR injection (twice daily) interrupt KEKB injection. Big issue for SuperKEKB operation. Beam lifetime ~ 6 min.)

14. Injector Commissioning Simultaneous top-up including PF-AR injection PF-AR and KEKB share the long part of beam transport line. Existing tunnel space is very tight. New tunnel has been constructed in Mar. of 2014. Pulsed bend will be installed at #3 switch yard of Linac. New BT will be available in Jan. of 2017. H. Takaki (KEKB review 2013)

15. Injector Commissioning Injector commissioning - Our goal - Beam charge/emittance –e- 5 nC: 20/50 mm  mrad w/o DR (Ver./Hor.) –e+ 4nC : 20/100 mm  mrad w/ DR (Ver./Hor.) Emittance preservation at end of Linac –Bunch compression at A1 unit/J-ARC –Offset injection/wakefield bump (High precision orbit measurement/control) Beam stability –Charge –Position –Energy –Energy spread –Emittance Simultaneous top-up for 4 rings 15

16. Injector Commissioning Injector commissioning Injector commissioning has been started in Oct. of 2013. 16

17. Injector Commissioning Beam orbit example 17

18. Injector Commissioning Charge history 0.58 nC 5.6 nC

19. Injector Commissioning Beam diagnostics Beam position measurement –BPMs x 90 (strip-line type electrodes) Beam profile/Emittance measurement –Fluorescent screen monitors x100 –Single wire scanner x1 –Multiple wire scanner x5 Bunch length measurement –Streak camera x3 19

20. Injector Commissioning Typical beam charge stability 20 1 hour  I : 10% ~ 20% ~ 2.5% (KEKB operation)

21. Injector Commissioning Shot-by-shot beam profile stability 21

22. Injector Commissioning Two bunch operation example 22

23. Injector Commissioning Emittance measurement example (A1 unit) 23 Quadrupole scan Screen monitor at chicane Horizontal   nx : 15.43 mm·mrad Vertical   ny  9.42 mm·mrad Chicane

24. Injector Commissioning Emittance measurement example (Sector B) 24 Multiple wire scanner at the end of Sector B Typical result (1 nC): –  n,x : 66.006 ± 10.755 mm  mrad –  n,y : 77.309 ± 14.522 mm  mrad Charge stability is not so small. Software is under development for subtracting shot-by-shot beam fluctuation.

25. Injector Commissioning Emittance history 25 Emittance at Gun and Sector B were measured by Quad scan and multiple wire scanner. In Nov. and Dec. of 2014

26. Injector Commissioning Emittance 26 Emittance plot as function of bunch charge

27. Injector Commissioning Offset Injection (experiment) 27 Feasibility of offset injection was studied w/ bunch charge of 0.3 nC.

28. Injector Commissioning Bunch compression at A1 unit 28 A1 RF  -30°: 10 ～ 15 ps A1 RF  0°: 30 ～ 40 ps w/o bunch compression w/ bunch compression 10 ps 40 ps First Accelerating structure Chicane

29. Injector Commissioning Bunch compression @ J-ARC 29 Isochronous, R56 = -0.3 m w/ different RF  in SectorA/B Isochronous R56 = -0.3 m

30. Injector Commissioning Preliminary result of bunch compression @ J-ARC 30 Isochronous (w/o bunch compression), R 56 = -0.3 m (w/ bunch compression) w/ different RF  in SectorA/B Clear bunch compression has not yet been measured. Emittance measurement by multiple wire scanner at Sector2 w/ and w/o J-ARC bunch compression. Streak camera at SectorC

31. Injector Commissioning e+ beam measurement First e+ beam was measured by current system at Jun. 9 th 2014. Primary e- beam charge: 0.5 nC e+ charge: 0.02 nC @ SP_28_4 31 e- beame+ beam x (mm) y (mm) I (nC) target

32. Injector Commissioning Beam injection study (new timing system) 32 Beam orbit for PF injection (new system) Beam orbit for PF injection (current system) Beam injection to PF/PF-AR w/ new EVG

33. Injector Commissioning R 16, R 36 elements at J-ARC 33 Design value w/ fudge factors R 16, R 36 values were measured at J-ARC and SectorC. w/ and w/o fudge factors (B’ = A fudge x B’ model ) Find suitable fudge factors –Typical fudge factors used for KEKB operation are 1% ~ 5%.

34. Injector Commissioning Chicane at Unit-A1 34

35. Injector Commissioning Unit A1 (remodeling) 35 Previous thermionic e- gun will be temporarily back in end of this Apr. for radiation facility test. –Left the beam line for rf gun in current position. –Beam line level of beam line will be changed from 1200 mm to 1950 mm. –Spare magnets will be used for new beam line. Commissioning will be started in early May. RF e- gun beam line Thermionic e- gun 1950 mm 1200 mm Merger line

36. Injector Commissioning Design drawing of A1 beam line 36

37. Injector Commissioning Optics design 37 Quadrupole triplets will be installed in merger line. Ver. beam size (mm) Hor. beam size (mm) Beam energy (MeV) Merger line

38. Injector Commissioning Summary of e- commissioning 38 ItemRequirementCurrent status Beam charge (nC) 5 (10 for e+ primary) 5.6 (first BPM) 0.58 (Linac end) Beam energy (GeV)77 Normalized emittance  mm  mrad  50/20 (Hor./Ver.) (at the end of Linac) 20/7 (Hor./Ver.) (from RF gun) Bunch charge stability2.5% (KEKB)10% ~ 20% Bunch compression @ A1 unit30 ps => 10 ps30 ~ 40 ps ~ 10 ~ 15 ps Bunch compression @ J-ARC10 ps => 5 psn/a Temporal manipulation of laserUniform shapen/a Emittance preservation 20 mm  mrad (Linac end) n/a Max. beam repetition5025 # of bunches22 OperationSimultaneous top-upn/a

39. Injector Commissioning Issues Injector commissioning –Oct. ~ Dec. of 2013/ Apr. ~ Jun. of 2014/ Oct. ~ Dec. of 2014 –Not enough time for injector commissioning –e+ commissioning: Installation of flux concentrator has delayed from Dec. of 2013 to May of 2014. First e+ beam was measured in Jun. of 2014. Progress in LAS RF conditioning (x10) is slow. Twice accidents in Dec. of 2013 and Dec. 2014 (cable burned) Not yet enough primary e- bunch charge –e- commissioning: Beam stability (charge, position) is not yet enough. 39

40. Injector Commissioning Summary 40 Commissioning stage 1: (Oct. 2013  Mar. 2014) –New RF gun commissioning (laser tuning and cavity conditioning) –High intensity charge –Prepare beam diagnostics and commissioning tools –New Photo-cathode RF gun has successfully manufactured and installed. (Summer 2014) 5.6 nC from New RF n5.6 nC from New RF Gun 0.58 nC at end of Linac0.58 nC at end of Linac Stage 2: (Apr. 11  Jul. 1, 2014) –Emittance preservation of e- at the end of Sector B, Sector 5 Bunch compression at J-ARC, offset injection, wake field bump,….. –Positron beam commissioning (May 2014  ) –Beam stability Charge, Position, Energy, Energy spread, Emittance