1. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 1 A Bunch Shape Monitor for high current LINACs B. Zwicker, P. Forck, P. Kowina, C. Dorn Gesellschaft für Schwerionenforschung GSI, Darmstadt Bunch Shape Workshop, Lund, February 11 th 2013

2. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 2 Overview High current LINACs at GSI and FAIR Motive for a BSM Non-intercepting Bunch Shape Monitor Performance and Problems Outlook

3. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 3 UNILAC Beam Transport SIS18 High Current LINACS UNILAC accelerates various ions (p - U) RF 36 MHz or 108 MHz E kin up to 11.4 MeV/u Rep. Rate 50 Hz Pulse length max. 5 ms Max. 20 mA current (pulsed) Low beta < 0.16

4. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 4 p-LINAC primary injector for SIS 100 RF 352 MHz E kin up to 70 MeV Rep. Rate 5 Hz Pules length 0.1 ms High currents up to 70 mA beta < 0.38 p-LINAC SIS18 SIS 100 SourceRFQCH-DTL 60 m 70 MeV 3 MeV95 keV to SIS18 Re-Buncher High Current LINACs

5. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 5 Motive for a BSM UNILAC For optimal matching of the different UNILAC sections the bunch profile should be known (partly KONUS) Experience how to reach high performance helps, too Several times non-gaussian profiles have been observed p-LINAC The p-LINAC operates up to 70 MeV with a compact not common design (KONUS) Due to KONUS beam dynamics, the logitudianal bunch profile is very crucial Simulation failures far less tolerable

6. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 6 Motive A tungsten wire will melt (3695 K) or even vaporize (11.4 MeV/u, U 73+, I = 2mA, f= 5Hz)

7. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 7 Motive A tungsten wire will melt (3695 K) or even vaporize A carbon (3750 K) wire shows similar behavior Work function determinates temperature (Thermionic Emission) (11.4 MeV/u, U 73+, I = 2mA, f= 5Hz)

8. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 8 Motive A tungsten wire will melt (3695 K) or even vaporize A carbon (3750 K) wire shows similar behavior Work function determinates temperature (Thermionic Emission) (11.4 MeV/u, U 73+, I = 2mA, f= 5Hz) Therefore the non-intercepting Bunch Shape Monitor with residual gas has been developed at GSI

9. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 9 Non-intercepting Bunch Shape Monitor BSM Schema Residual gas works as secondary electron source SE are extracted with 30 kV through a slit An energy sensitive analyser ensures usage of SE created by the bunch An rf-deflector transforms the time information (time of flight) in a spatial distribution Readout by MCP + Phosphor + CCD

10. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 10 The E-field box : E-field box E-field up to -30 kV Field forming side electrodes → 430 V/mm High field for fast extraction Non-intercepting Bunch Shape Monitor

11. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 11 The E-field and analyzer: Energy analyzer for source volume restriction: Radius ρ=30 mm, 90 0 bending, ±5.5 kV Remote controlled aperture: 0.1 to 2 mm point-to-point focusing for ±0.25mm and ±0.5mm aperture (remote cont.) ⇒ ±0.2 mm vert. prolongation, comparable to wire Non-intercepting Bunch Shape Monitor

12. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 12 f0f0 36 MHz108 MHz length800 mm P max 100 W30 W Q0Q0 290370 t max 6 ms α max 3030 3030 Common U Σ < 7 kV as einzel lens Different U Δ < 1 kV as steerer length 18 cm Non-intercepting Bunch Shape Monitor electron beam electron beam Rf-deflector The rf-deflector produced by INR Troitzk: Parallel wire λ/4-resonator:

13. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 13 Image devices Micro Channel Plate amplifies incoming electrons Picture taken by a CCD-Camera shows spatial distribution Pseudocolors give high contrast 200 mm Non-intercepting Bunch Shape Monitor MCP Ø70mm suppression grid MCP CCD- Camera 70 mm dV

14. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 14 Phase calibration In order to determ the time width of the profile a phase calibration has to be done At least two measurements have to be executed with a different phase of the rf-amplitude By knowing the exact delay and by measuring the displacement one obtains the span corresponding to one pixel Valid only in the strict linear range of the sine function 61 pixel Exp: A delay of 514.4 ps and a displacement of 61 points leads to 9.18 ps / pixel Non-intercepting Bunch Shape Monitor

15. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 15 Non-intercepting Bunch Shape Monitor CCD-Camera Beamtube rf-deflector MCP E-Fieldbox Analyser 1 m

16. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 16 Performance and Problems 16 pixel Profile Resolution Min electrostatic lens (rf-deflector) focus about 16 pixel Depending on the rf-deflector amplitude a resolution of 144 ps has been achieved ( 9.2 ps/pixel at 36 MHz, corresponding 2° phase resolution) Usage of new apertures control should further improve the resolution For higher frequencies resolution should increase in the absolute value

17. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 17 Performance and Problems Beam parameters: U 28+, I = 200 μA, T= 180 μs Projection of spatial distribution provides the bunch profile (averaged over 64 pulses) Through the given rf-deflector amplitude the picture resolution is up to 9.6 ps / pixel projection spatial distribution projection 780 ps

18. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 18 Performance and Problems Single gap resonator Proof of principle: To confirm the validity of the obtained profile it is recommended to change the bunch profile in a well- known manner By using the single gap resonators one can be pretty sure whether the bunch is stretched or focused If the BSM is working it should be sensitive for the bunch manipulations

19. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 19 1200 ps normal 440 ps bunched debunched 480 ps Performance and Problems Proof of principle: The BSM was able to measure profiles from normal to focus and finally stretched under equal conditions (parameters: U 36+, I = 100 μA, T= 180 μs, but non-constant rf-amplitude) W = 28 dBmW = 29 dBm W = 18 dBm

20. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 20 Performance and Problems Strong background, poor contrast for grey values Poor peak-to-noise ratio complicates data acquisition and limits resolution (where starts the actual signal?) low rf-power high rf-power

21. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 21 Performance and Problems Through subtracting a background-only picture from the pictures a detailed profile can be obtained time in ns High Background Low Background substracted original

22. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 22 Performance and Problems Signal quality behaves not as expected with the parameters Lower MCP voltage seems to improve the quality (saturation?) Higher difference between Phosphor and MCP also improves the quality original 4000 Peak-to-noise ratio Phosphor voltage ín V MCP in V 7 6 5 4 3750 3500 1800 16801740

23. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 23 Performance and Problems The E-field created by space charge causes signal distortion due to additional momentum of the SE (image distortion)

24. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 24 Emittance Determination from Bunch Shape Monitor Variation of buncher: Bunch shape was determined, modified by a buncher Pick-up: No measurable influence Emittance determination possible Beam parameters: Ni 14+ at 11.4 MeV/u I=2 emA, 200 μs macro pulse Average: 4 macro pulses Pressure p=10 -5 mbar (no significant beam influence)

25. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 25 Performance and Problems Small beam currents show only a moderate effect High currents strongly influence the obtained profile

26. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 26 Outlook Commissioning BSM at UNILAC (done) Gain experience to improve overall performance Understand and eliminate disturbance und background Improve resolution (new aperture control, higher contrast, less image distortion) Evaluate BSM and give a reference for the p-LINAC

27. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 27 Conclusion LINAC performance depends on the bunch profile High current LINACs need a non-destructive device Several different profiles with a phase resolution up to 2° has been obtained BSM has not well understood background and image distortion Simulations and further investigations will take place

28. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 28 Thank You!

29. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 29 Performance and Problems High current measurement (2 mA) for U 73+ Steering by different voltage of rf-plates Steering does not affect background MCP might be saturated

30. L. Groening, Sept. 15th, 2003 GSI-Palaver, Dec. 10 th, 2003, A dedicated proton accelerator for p-physics at the future GSI facilities B. Zwicker, Bunch Shape Workshop, Lund Feb. 11 th 2013 A longitudinal Bunch Shape Monitor for high current LINACs 30 Performance and Problems