# Presentation: 402154

## Ultrafast X-ray

**Ultrafast X-ray**
**Streak Camera**

**Zenghu Chang**
**University of Michigan**

##  W. Peng, B. Shan and J. Liu

** ****W. Peng, B. Shan and J. Liu**
*Xi’an Institute of Optics and Precision Mechanics*
**H. Wang, G. Mourou**
*University of Michigan*
**A. Lindenberg, S. Johnson, R. W. Falcone**
*University of California, Berkeley*
**P. A. Heimann, and H. A. Padmore**
*Lawrence Berkeley National Laboratory*
**R. W. Lee**
*Lawrence Livermore National Laboratory*
** **

## Streak Camera

**Streak Camera**

**Convert time into space **

- Mirror

- Film

- Slit

***t **=****x/v*

***x*

*v*

***t*

## X-ray Streak camera

**X-ray Streak camera**

- Deflection
- Plates

- Screen

- Photocathode

*h*

*e*

*h*

-  1975, first demonstration
-  1990, 2 ps resolution
-  1996, 0.5 ps resolution
-  1997, synchrotron application

- Edef

## Sub-ps X-ray Streak Camera

- CCD
- Camera

- MCP

- Phosphor

- Cathode

- Anode

- Magnetic lens

- Deflection
- plates

- X-ray

- Laser

- Photoconductive
- Switch

- HV Pulser

## Time-resolved Experiments

**X-ray**
**Pulse width: 100 ps**
**Repetition: 500 MHz**
**Spot size: 100 ********m**
**Photon: small**

**Laser**
**Pulse width: 100 fs**
**Repetition: 1-10 kHz**
**Fluctuation: 1%**

** ****Detector**

**Sample**

**X-ray**

**Laser**

## Detector Requirements 

**Temporal Specification**
**Resolution**: 100 fs
**Window**: 100 ps
**Synchronization: **100 fs @ 1-10 kHz
**S/N ratio**** **
** ****Quantum efficiency: **>5%
-  **Slit match spot size**: ~100 m
** ****Signal accumulation**: 1 minute
** ****X-ray pulse selection**: 1 kHz

## Factors AffectTemporal Resolution

**Scanning Speed**
**    *****t **s**= ****x/v*

## Scanning Speed

***x : *slit width & spatial resolution
* *
- For ***x *=60 m,to have* ****t *= 100 fs*, *
*	**	**V= 6**·**10**8** *m/s*=2c*

*********t******s ******= ************x/v***

## Sub-ps X-ray Streak Camera

- CCD
- Camera

- MCP

- Phosphor

- Cathode

- Anode

- Magnetic lens

- Deflection
- plates

- X-ray

- Laser

- Photoconductive
- Switch

- HV Pulser

## Traveling-Wave Deflection

-  High defection sensitivity:
-   10 cm/kV
-  Fast response time:
-   300 ps
-  High scanning speed:
-   ~*c *

## Factors AffectTemporal Resolution

**Scanning Speed**
**    *****t **s**= ****x/v*

** ****Transit Time Dispersion**
-     Velocity distribution

## Reducing transit time

-  Magnetic lens
-  Deflection before focusing
-  Small total dispersion

**Transit Time Dispersion**

## Temporal Dispersion 

- CsI

**E**

- Anode

- Cathode

## Single Shot Resolution

## Factors AffectTemporal Resolution

**Scanning Speed**
**    *****t **s**= ****x/v*

** ****Transit Time Dispersion**
-     Velocity distribution

** ****Timing Jitter**
-     Laser instability

## Photo-conductive Switch

- Defection
- plates

- RL

- VDC

- GaAs Switch

- Laser

- +300 V

- -300 V

- 300 ps

## Timing Jitter

**0**

**Time**

**Voltage**

**t****1**

**t****2**

**Va**

**0.5Va**

**V****1**

**V****2**

**Timing Jitter**

## Timing Jitter

******t****jitter**** = 0.5 T****rise**** ********V/V****a**

******t****jitter ****=1.5  ps**
- when Trise=300 ps,   V/Va = 1 %

## Jitter Limited Resolution

## Detector Requirements 

**Temporal Specification**
**S/N ratio**** **

## Absorption of Photocathode

## PhotocathodeOptimum Thickness

##  Improving S/N Ratio

- Match the slit width and the spot size
-    100 m
- Gating the MCP intensifier
-    1 kHz
- Signal Accumulation
-     ~1 minute

## Time-Resolved Diffraction 

**Time-Resolved**** ****Diffraction**** **

**Sample**
**  ****SbIn**

**X-ray**

**Laser**

**Streak**
**Camera**

## Summary

**Streak Tube:**
-      High resolution: 500 fs
-      High deflection sensitivity: 10 cm/kV
**Photo-conductive Switch:**
-      Small trigger energy: 20 J
-      Small jitter: 2 ps
**Gated Intensifier**
-      Narrow window: 10 ns

## Next Step: 100 fs Camera

**Streak Tube**
-     UHV design allowing higher extraction field
-      Better deflection plates for faster scan
**Synchronization**
-     Laser Energy Compensation