Beam Jitter Measurement Emittance Calculation Jong Min Yoon

Beam Jitter Measurement & Emittance Calculation Jong Min Yoon Cornell University A 0 Photoinjector Mentor : Victor Scarpine & Jinhao Ruan

Outline n n A 0 Photoinjector Beam Jitter Measurement Definition of jitter ¨ Significance of the jitter measurement ¨ Principles of measurement ¨ Experimental Setup ¨ n Emittance Calculation of Multi-Slit Method Definition of emittance ¨ Multi-Slit method ¨ Program demonstration ¨

A 0 Photoinjector

Electron Beam Parameters n n n n n Typically 10 bunches/RF pulse(81. 25 MHz) 1 Hz repetition rate Laser energy 16 m. J/pulse @ 263 nm <5 n. C/bunch (have had >12 n. C in the past) 4 Me. V gun output energy 16 Me. V total energy Dp/p ≈ 0. 3%@ 16 Me. V (1 n. C) Bunch length ≈ 2 mm (1 n. C) gez ≈ 120 mm-mrad (RMS @ 1 n. C) gex, gey≈4 mm-mrad 1 (RMS @ 1 n. C) sec

Beam Jitter Measurement

What is Jitter? Ideal Situation 81. 25 MHz or 1/81. 25 µs All electron bunches travels at a uniform interval

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

Why Measuring the Jitter? n The stability of experiments carried out with A 0 photoinjector depends sensitively on precise synchronization between the electron beam and other components in A 0 photoinjector. n Jitter measurement is the first step to build a precise arrival-time monitor of electron bunches.

Principle of the Beam Phase Monitor Oscilloscope 81. 25 MHz Compact ultra-high precision beam phase monitor system, Florian Löhl, FLS 2006, May 16 th, 2006

Schematic Diagram of Experimental Setup

Schematic Diagram of Experimental Setup

Beam Pick-up Courtesy of MDI, DESY

Schematic Diagram of Experimental Setup

Nanoseconds Delay Line 3. 4 ns

Nanoseconds Delay Line 3. 5 ns

Nanoseconds Delay Line 3. 6 ns

Amplitude Change along with the Delay Time Amplitude (m. V) 1200 1000 800 600 400 200 0 2. 8 3. 3 3. 8 Delay Time (ns) 4. 3 4. 8

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 16 th, 2006

Amplitude Change along with the Delay Time Amplitude (m. V) 1200 1000 800 600 400 200 0 2. 8 3. 3 3. 8 Delay Time (ns) 4. 3 4. 8

Amplitude Change along with the Delay Time Amplitude (m. V) 1200 1000 At 3. 57 ns, sigma of amplitude fluctuation = 51. 8 m. V 800 - Corresponding jitter = 2. 924 ps The 600 precision of our setup is not good enough Slope : -17. 715 m. V/ps – we want sub 1 ps 400 200 0 3. 43 3. 48 3. 53 Delay Time (ns) 3. 58 3. 63 3. 68

Emittance Calculation of Multi-Slit method

Electron Beam Line

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

Emittance Along a beamline, the shape of beam ellipse in x, x’ plane changes, But the area πɛ remains constant

Why measuring it? n n 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

Multi-Slit Method

Program Demonstration

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

References n n n Ray Fliller III, “Advanced Accelerator R&D at the A 0 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

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