Beam Jitter Measurement & Emittance Calculation

1. Beam Jitter Measurement& Emittance Calculation Jong Min Yoon Cornell University A0 Photoinjector Mentor : Victor Scarpine & Jinhao Ruan

2. Outline • A0 Photoinjector • Beam Jitter Measurement • Definition of jitter • Significance of the jitter measurement • Principles of measurement • Experimental Setup • Emittance Calculation of Multi-Slit Method • Definition of emittance • Multi-Slit method • Program demonstration

3. A0 Photoinjector

4. Electron Beam Parameters 1 sec Typically 10 bunches/RF pulse(81.25 MHz) 1 Hz repetition rate Laser energy 16 mJ/pulse @ 263nm <5nC/bunch (have had >12 nC in the past) 4 MeV gun output energy 16 MeV total energy Dp/p ≈ 0.3%@ 16MeV (1nC) Bunch length ≈ 2 mm (1nC) gez ≈ 120 mm-mrad (RMS @ 1nC) gex,gey≈4 mm-mrad (RMS @ 1nC)

5. Beam Jitter Measurement

6. What is Jitter? Ideal Situation 81.25 MHz or 1/81.25 µs All electron bunches travels at a uniform interval

7. What is Jitter? Real Situation 81.25 MHz or 1/81.25 µs The interval is somewhat irregular This irregularity is called Jitter – in time domain or Phase Noise – in frequency domain

8. Why Measuring the Jitter? The stability of experiments carried out with A0 photoinjector depends sensitively on precise synchronization between the electron beam and other components in A0 photoinjector. Jitter measurement is the first step to build a precise arrival-time monitor of electron bunches.

9. Principle of the Beam Phase Monitor Oscilloscope 81.25 MHz Compact ultra-high precision beam phase monitor system, Florian Löhl, FLS 2006, May 16th, 2006

10. Schematic Diagram of Experimental Setup

11. Schematic Diagram of Experimental Setup

12. Beam Pick-up Courtesy of MDI, DESY

13. Schematic Diagram of Experimental Setup

14. Nanoseconds Delay Line 3.4ns

15. Nanoseconds Delay Line 3.5ns

16. Nanoseconds Delay Line 3.6ns

17. Amplitude Change along with the Delay Time

18. Time-of-Arrival to Modulation Voltage Change in bunch time-of-arrival have difference voltages when laser pulse arrives  time mapped into laser modulation. Compact ultra-high precision beam phase monitor system, Florian Löhl, FLS 2006, May 16th, 2006

19. Amplitude Change along with the Delay Time

20. Amplitude Change along with the Delay Time At 3.57ns, sigma of amplitude fluctuation = 51.8mV - Corresponding jitter = 2.924ps The precision of our setup is not good enough – we want sub 1 ps Slope : -17.715mV/ps

21. Emittance Calculation of Multi-Slit method

22. Electron Beam Line

23. What is Emittance? ɛ = Area in x, x’ plane occupied by beam particles divided by π

24. Emittance Along a beamline, the shape of beam ellipse in x, x’ plane changes, But the area πɛ remainsconstant

25. Why measuring it? • We can know beam half width, beam half divergence, and whether beam is converging or diverging. • Emittance is one of key parameters for overall performance of an accelerator • Luminosity of colliders for particle physics • Brightness of synchrotron radiation sources • Wavelength range of free electron lasers • Resolution of fixed target experiments

26. Multi-Slit Method

28. Program Demonstration

29. Conclusion • Jitter measurement • First step to build a precise arrival-time monitor of electron bunches. • Principle and setup of measurement are explained. • Right now ~2ps precision • Emittance Calculation • One of the important beam parameters • Multi-slit method • Semi-automatic program

30. References Ray Fliller III, “Advanced Accelerator R&D at the A0 Photoinjector,” FNAL, February 5, 2008 F. Loehl, et al., “A sub-100 fs electron bunch arrival time monitor system for FLASH,” PAC 2006, Edinburgh, Scotland, 26-30 June, 2006 H. Braun, “Emittance Diagnostics,” CAS Beam diagnostic, Dourdan, 2 June 2008

31. Special Thanks to… Victor Scarpine Jinhao Ruan Roger, Erik, and Jean Fermilab IPM program All other interns