1. Bunch Length Measurements Mahmoud Ahmad 1 Stay treat, July 16, 2015

2. Outline Locations for bunch length measurements Slit - scan measurements Brock’s cavity measurements Back-phasing measurements SLM measurements Results summary 2

3. Brock’s Cavity SLM Chopper – slit 3 SLM Back-phasing Bunch length locations

4. 1- Slit – scan 4 Central plug C slit aperture B slit aperture Master slit A slit aperture FROM TECHNOTE: BEAM BASED DIAGNOSTIC TESTS THAT INDICATE A POSSIBLE CHOPPING APERTURE MISALIGNMENT J. Grames, M. Baylac, M. Poelker, M. Stutzman. Sample bunch with this narrow slit

5. 5 360(degree) : 2004(ps)unit of length (m) = ps x 3*10 8

6. Brock’s Cavity Chopper – slit 6

7. 2- Brock’s Cavity Cavity in the 1D line, aka “500keV spectrometer line ” It works! Fast oscilloscope trace of 500kV beam through cavity. But what are the “wiggles”? 7

8. 8

9. Brock’s Cavity Chopper – slit 9 Back-phasing

10. 10 3- Back-phasing Dipole

11. 11 Harp scan when bunch is on crest Harp scan when bunch is +90 off crest

12. Results 12 Sigma X (cm)Sigma Y (cm)Bdl (T.cm) On crest0.026 ± 0.0010.025 ± 0.001148873.875 +90 off crest0.444 ± 0.0140.025 ± 0.00193523.875 X 0 : Horizontal displacement at crest X + : Horizontal displacement at +90 off crest B 0 : Magnetic field at crest B + : Magnetic field at +90 off crest D : Dispersion Bunch length (rms) = 86.5 ± 2.9 um

13. Brock’s Cavity SLM Chopper – slit 13 SLM Back-phasing

14. 4- Synchrotron Light Monitor 14

15. Image processing 15 Spot at SLM1 for NL gang phase = -67.9 before and after frame removing Gaussian fitting for the same spot after subtracting the back ground and applying a horizontal projection

16. Results 16 B.L = ( 91.4 ± 6.5 ) umB.L = ( 112.8 ± 5.8 ) um B.L = ( 42.5 ± 5.1 ) um B.L = ( 46.1 ± 3.5 ) um

17. B.L evolution summary 17 TechniqueLocation Beam Energy Measured B.L (rms) Estimated B.L (rms) Slit - ScanChopper chamber 130 KeV16.2 ± 0.1 mm17.1 mm (GPT) Brock1D dump130 KeV24.5 ± 0.1 mm19.1 mm (GPT) Back- phasing 4D dump102 MeV86.5 ± 2.9 um60 um (Krafft et al.)* SLM 1 compress ARC 11052 MeV 91.4 ± 6.5 um 46.1 ± 3.5 um56 um ** SLM2 compress ARC 22002 MeV 112.8 ± 5.8 42.5 ± 5.1 um56 um ** * Measuring and controlling energy spread in CEBAF ** Optimization of M56 in the CEBAF injector

18. Which one is the best ? 18 Technique Beam Energy Estimated operation time ReliabilityAccuracy Slit - Scan130 KeV45 – 90 minVery GoodExcellent Brock130 KeV1 minExcellentGood Back- phasing 102 MeV60 - 90 minVery GoodExcellent SLM 11052 MeV15 – 30 minVery Good SLM 22002 MeV15 - 30 minVery Good

19. Special Thanks 19 Michael Tiefenback Matthew Poelker Arne Freyberger Geoff Krafft Alicia Hofler

20. Thank you 20