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Beam Jitter Measurement & Emittance Calculation. Jong Min Yoon Cornell University A0 Photoinjector Mentor : Victor Scarpine & Jinhao Ruan. Outline. A0 Photoinjector Beam Jitter Measurement Definition of jitter Significance of the jitter measurement Principles of measurement - PowerPoint PPT Presentation
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Beam Jitter Measurement& Emittance Calculation
Jong Min Yoon
Cornell University
A0 Photoinjector
Mentor : Victor Scarpine & Jinhao Ruan
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
A0 Photoinjector
Electron Beam Parameters
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) z ≈ 120 mm-mrad (RMS @ 1nC) x,y≈4 mm-mrad (RMS @ 1nC)
1 sec
10μs
81.25
Beam Jitter Measurement
What is Jitter?Ideal Situation
All electron bunches travels at a uniform interval
81.25 MHz or 1/81.25 µs
What is Jitter?Real Situation
The interval is somewhat irregularThis irregularity is called Jitter – in time domain
or Phase Noise – in frequency domain
81.25 MHz or 1/81.25 µs
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.
Principle of the Beam Phase Monitor
81.25 MHz
Compact ultra-high precision beam phase monitor system, Florian Löhl, FLS 2006, May 16th, 2006
Oscilloscope
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
3.4ns
Nanoseconds Delay Line
3.5ns
Nanoseconds Delay Line
3.6ns
Amplitude Change along with the Delay Time
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
Amplitude Change along with the Delay Time
Amplitude Change along with the Delay Time
Slope : -17.715mV/ps
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
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?
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
'xx L
Program Demonstration
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
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
Special Thanks to…
Victor Scarpine Jinhao Ruan Roger, Erik, and Jean Fermilab IPM program All other interns