# Presentation: 264488

## Slide 1

## Short pulse X-ray generation by Compton Scattering	

**Short pulse X-ray generation ****by Compton Scattering**

_***Background***_
- *To measure defect of a high speed material
- *To study the dynamics in physics and chemical and biological fields
_***Generation of femtosecond X-ray***_
-   High energy X-ray photons are generated by the scattering between photons (low energy) and relativistic  electrons (Compton Scattering).
-   If the electron bunch length is in femtosecond or the femtosecond laser pulse interacts at 90 degree, femtosecond X-ray pulse is generated.
_***Advantages***_
- *monochromatic
- *low divergence
- *Be easy to change of X-ray energy
- *Small apparatus

- FESTA, SHI

## Generation of high brightness femtosecond X-ray pulses

- Femtosecond Laser
- (Ti:Sapphire, 100fs, 1J)

- Picosecond Laser

- Synchronization

- Femtosecond X-ray pulses

- Photocathode RF Gun

- 150 MeV Microtron

- FESTA,   SHI

## Stabilization of master oscillator

- O.C.

- Ti:sapphire Crystal

- SESAM

- PZT

- 532nm,3.5W

- Translation Stage

- Photo Diode

- 119MHz

**Stabilization of master oscillator**

## Jitter measurement : spectral side-band analysis and time domain demodulation method

- Amplitude noise + n2×phase noise L(f)

- n:order

- Power spectral density of phase noise *S****(f) = 2L(f)*

- RMS timing jitter ***j*

*t*

- Pulse Train

- Detector

- Vector Signal Analyzer

- Phase noise

- F. F. T.

- Power spectral density of phase noise *S****(f)*

**Spectral side-band analysis method**

**Time domain demodulation method**

**Jitter measurement : spectral side-band analysis and time domain demodulation method**

## Jitter reduction

- Power spectral density of phase noise

- Timing Jitter
-     Not stabilized    ~ 5 ps
-     Stabilized          ~ 100 fs

## Jitter and drift measurement of master oscillator

- 200th harmonics
- Jitter : < 100 fs

- Standard deviation : < 1 mHz

## BBO

- Laser 2

- PZT

- Laser 1

- Synthesizer

- Timing
- Stabilizer

- 119 MHz

- PZT

- PZT Driver

- Pulse
- Stretcher

- Photo Diode

- Photo multiplier

- CCD

- Oscilloscope

- Photo multiplier

- Measurement system

- Loop Gain

- AC

- DC

- Manual

**OPLL and the measurement system of the up-converted signal **

##  The feedback is disturbed and run off the stabilized condition by a little fluctuation.

-  The feedback is disturbed and run off the stabilized condition by a little fluctuation.

**The up-converted signal : OPLL is operating (Optimum loop gain )**

- Overlapping

- Up-converted signal

## Temporally stabilization of the amplified pulses by adaptive control

**Regenerative amplifier**

- Mode-locked Ti:sapphire laser

- Seed in

- Pumping

- Temperature Stabilized Pockels Cell

- PZT

- Translation Stage

- SHG
- Nd:YAG laser

**Pulse Stretcher and Pulse Compressor**

**Temporally stabilization of the amplified pulses by adaptive control**

## Timing fluctuation measurement scheme of the low repetition rate amplified pulse

- To multi-pass amplifier

**Timing fluctuation measurement scheme of the low repetition rate amplified pulse**

## Energy stability ~0.4% (rms)

-  All-solid-state pump source
-  Pockels cell temperature stabilized
- < 0.1°C (may be much less)
-  Room temperature stabilized
- < 0.1°C
-  Covered to avoid airflow
- Repetition: 1kHz

- Energy stability ~0.4% (rms)

**Energy stability of amplified pulse**

## Reduction of timing fluctuation of the amplified pulses

## Stable terawatt Ti:sapphire laser system

- Ti: SA : Ti: sapphire crystal, PC: Pockels cell, FR: Faraday rotator,
- TL: Telescope, PBS: Polarizing beam-splitter, G: Grating, AP: Aperture.

- AP

## Performance of the stable terawatt Ti:sapphire laser system operating at 50 Hz

- f = 50Hz
- 1.3TW
- p = 78 fs

- Power stability of the amplified and compressed pulses. Inset:autocorrelation of the pulse. The pulse width is 78 fs assuming sech2 pulse shape.

- Pointing stability of the amplified and compressed pulses.

## Beam profiles of amplified laser pulse from the multipass amplifier

- Near-field beam profile  of the amplified pulse before compression.

- ~100-**m

- Far-field beam profile  of the amplified pulse before compression. The beam spot size is almost equal to that for the diffraction-limited beam.

- ~5-mm

## Spatial stabilization for terawatt laser pulses

- TW laser pulse

- Adaptive optics

- Deformable mirror

- Corrected TW laser pulse

## FESTA

- Block diagram of the synchronization and RF system
- 		TG : trigger generator
- 		SG : signal generator
- 		Syn : synchronizer
- 		KLy : Klystron
- 		PS : phase shifter

## Electron Accelerating System for X-ray generation

**Electron Accelerating System for X-ray generation**

- FESTA, SHI

**Linac**

**Compton Chamber**

**M1 CT SC**

**CT SL SC**

**SC               SC**

**M2**

**Beam Dumper**

**(High Brightness Electron Source using a Photocathode RF Gun)**

## Electron Accelerating System

**Photocathode RF Gun**

**Linac**

**Bending Magnet**

**Electron Accelerating System**

- FESTA, SHI

## Synchronized system

**1/24**

**Klystron**

**Picosecond Laser**

**Photocathode RF Gun**

**2856 MHz RF**

**RF**
**Driver**

**RF Signal Generator**

**Femtosecond Laser**

**Electron pulse**

**Linac**

**Femtosecond Laser Pulse**

**Femtosecond X-ray**

**Trigger Generator**

**Synchronizer**

**Attenuator**

**Attenuator**

**Power**
**Source**

**10 MHz RF**

**10****~****50 Hz**

**10****~****50 Hz**

**Isolator**

**Circulator**

**Isolator**

**Picosecond Laser Pulse**

**119 MHz RF**

**D**

**D**

**D**

**D**

**D**

**Phase Shifter**

**Trigger signal**

**119 MHz RF**

**Power divider**

**Phase Shifter**

- FESTA, SHI

**Power divider(1:1)**

**Phase Shifter**

## Pointing stability of electron bunches

**4****ω**

**Picosecond Laser**

- FESTA, SHI

**CCD Camera**

**Phosphor Screen**

**Beam size****:**** ****σ:<150μm**

**Pointing stability**

**σ:<20μm**

**e****-**

**(Beam Center Fluctuation)**

**(After Linac)**

## High Quality Electron Beam 

- FESTA, SHI

- 20mm

**Phosphor screen**

**UV laser**

**Mask**

**Image**

**Electron**

## Energy of electron bunches after the linac

- FESTA, SHI

## FESTA

## FESTA

## Peak brilliance(B) :

- Ref. of paper: I. V. Pogorelsky, I. Ben-Zvi, et al. (BNL), “Demonstration of 8x1018 photons/second
-                        peaked at 1.8A in relativistic Thomson scattering experiment”

- Nx: total x-ray yield
- :    electron energy factor
- rb:   electron beam size
- x:   X-ray pulse width(= b :electron pulse width for 0-degree Thomson scattering)

- BNL:
-        Nx=7.6x106 photons/pulse
-  =120
-        rb=32m
- b=3.5ps
-        B=1018

## Specification of X-ray source in FESTA

-        Nx=107 photons/pulse(1nC, 1J@800nm)
-        Ex=270keV
-  =300
-        rb=50m
- x=280fs@b=1ps, L=100fs
-        B=8x1019

- Phase II:
-        Nx=106 photons/pulse(1nC, 1J@800nm)
-        Ex=15keV(30keV for head-on collision)
-  =60
-        rb=100m(50 m for laser beam size)
- x=400fs@b=5ps, L=100fs
-        B=1x1017

- Phase I:
-        Nx=105 photons/pulse(1nC, 100mJ@800nm)
-        Ex=1.9keV
-  =24
-        rb=100m
- x=600fs@b=5ps, L=100fs
-        B=6x1014

- _Specification of X-ray source in FESTA_

## Peak Brilliance  

- 124.0

- 12.4

- 1.24

- 0.124

- 0.0124

-    Wavelength of X-rays  [nm]

- 1015

- 1017

- 1019

- 1021

- 1023

- 1025

- 10-3

- 10-2

- 10-1

- 100

- 101

- 102

- 103

- Energy of X-rays  [keV]

- Peak Brilliance
- [photons/s/mm2/mrad2/0.1%BW]

- _Photon Factory_

*Wigglers*

- _X-ray Lasers_

*C*

*Ta*

*Ge*

*Se*

*B*

*Y*

*Fe*

*Mg*

- _Laser_
- _Harmonics_

- _200 eV_
- _Black Body_

- _Aurora_

- 1013

- 1011

*Bending*
*Magnet*

- _SPring8_

*Wigglers*

*Bending Magnet*

- _BNL Compton_

- _ALS Compton_
- _(LBNL)_

- _FESTA Compton_
- _(Phase I)_

- _FESTA Compton_
- _(Phase III)_

- _Laser-plasma_

- _FESTA Compton_
- _(Phase II)_

## Slide 30

## Summary

- Stabilized TW (100mJ, 100fs) laser at 50Hz
- Stabilized e-beam of 1nC, 12MeV, 3ps at 50Hz
- Sub-ps synchronization achieved
- X-ray generation in ps achieved
- Ready for femtosecond X-ray generation
- (1.9keV, 480fs, 1.8x105photons/pulse)