# Presentation: 014204

## Optical properties of the output of a high-gain, self-amplified free-electron laser 

- _Yuelin Li__1_, Sam Krinsky2, John Lewellen1, Vadim Sajaev1
- 1Advanced Photon Source, Argonne National Laboratory
- 2Brookhaven National Laboratory

## Acknowledgements

**K.-J. Kim, S. V. Milton, K. Harkay, O. Makarov, R. Dejus (ANL)**
**Z. Huang (SLAC)**
**Work supported by the U. S. Department of Energy, Office of Basic Energy Sciences, **

**Acknowledgements**

## Layout

**SASE and SASE experiments**
**The LEUTL system and the FROG experiment**
**The system**
**Statistics in the time domain**
**Statistics in the frequency domain**
**Correlation between the two domains**
**Near term plan**
**Conclusion**
**Acknowledgement**

## Layout

**SASE and SASE experiments**
**The LEUTL system and the FROG experiment**
**The system**
**Statistics in the time domain**
**Statistics in the frequency domain**
**Correlation between the two domains**
**Near term plan**
**Conclusion**
**Acknowledgement**

## SASE FELs

**SASE FELs**

**Demonstrated, existing, and future projects**

**LEUTL @ APS**
**TTF @ DESY**
**HGHG, VISA & DUV @ BNL**

**LCLS @ SLAC**
**TESLA @ DESY**
**BATES @ MIT**
**4GLS @ Rutherford**
**...............**

**Yu et al, PRL 91, 074801 (2003)**

**Ayvazyan et al, PRL 88 104802 (2002)**

## Some results on optical properties of SASE FEL

**Some results on optical properties of SASE FEL**

**DESY: energy statistics**

**LEUTL: spectra**

**Time Integrated Results:**

## DESY: Spatial coherence

**DESY: Spatial coherence**

**Ischebeck, NIM 507, 175 (2003).**

**Any information about the temporal structure?**

## Layout

**SASE and SASE experiments**
**The LEUTL system and the time-resolved  experiment**
**The system**
**Statistics in the time domain**
**Statistics in the frequency domain**
**Correlation between the two domains**
**Near term plan**
**Conclusion**
**Acknowledgement**

## The low-energy undulator test line FEL: future ALFF

**The low-energy undulator test line FEL: future ALFF**

**6 Hz, 0.5 ps, 50 **********J @ 120-530 nm**
**Milton *****et al*****., *****Science***** 292, 2037 (2001)**

## The facility and application experiment

**The facility and application experiment**

**S****ingle ****P****hoton ****I****onization or ****R****esonant ****I****onization at ****T****hreshold**

**FEL undulator hall**

## The FROG experiment at 530 nm

**The FROG experiment at 530 nm**

## Layout

**SASE and SASE experiments**
**The LEUTL system and the FROG experiment**
**The system **
**Statistics in the time domain**
**Statistics in the frequency domain**
**Correlation between the two domains**
**Near term plan**
**Conclusion**
**Acknowledgement**

## Temporal structure: Analysis

- The field of a SASE FEL (by solving Green’s function) is** **
**[S. Krinsky and Z. Huang, Phys. Rev. ST Accel. Beams ****6****, 050702 (2003).]**

**Temporal structure: Analysis**

**Goodman, Statistical Optics, (John Wiley & Sons, New York, 1985), p. 35.**
**S. Krinsky, PRSTAB 6, 050701 (2003).**

**Summing of random phasors:**
**Chaotic light**

## Interest in temporal structure

**Interest in temporal structure**

**Experimental data**
**Simulation**
**Analytical theory**** **

## Temporal structure: spike width and spacing

**Li et al., PRL 91 243602 (2003).**

**Temporal structure: spike width and spacing**

-  ** = 52 fs

**Follow statistics for chaotic light exactly.**

## Derivative of phase (frequency)

**Li et al., PRL 91 243602 (2003).**

**Derivative of phase (frequency)**

**********=0.0094 rad/fs**

**Each intensity spike is a coherence mode.**

## Layout

**SASE and SASE experiments**
**The LEUTL system and the FROG experiment**
**The system**
**Statistics in the time domain**
**Statistics in the frequency domain**
**Correlation between the two domains**
**Near term plan**
**Conclusion**
**Acknowledgement**

## Frequency domain statistics

**Frequency domain statistics**

**The frequency domain follows the same statistical behavior**** **
**Intensity spikes are coherence modes in the frequency domain**

## Layout

**SASE and SASE experiments**
**The LEUTL system and the FROG experiment**
**The system**
**Statistics in the time domain**
**Statistics in the frequency domain**
**Correlation between the two domains**
**Near term plan**
**Conclusion**
**Acknowledgement**

## Correlation between the time and frequency domains

**Correlation between the time and frequency domains**

**The two domains should have about the same number of intensity spikes**** **

## Number of spikes in the two domains

**Number of spikes in the two domains**

**Experiment A**

**Experiment B**

## Time-bandwidth product.......

**Time-bandwidth product.......**

**Number of modes=(W/**********W****)****2**** =<tbwp>/0.5 **

## Conclusion

**SASE FEL output is chaotic: fully coherent transversely (****to be measured****), but only partially coherent longitudinally **
**Time and frequency domain statistics determined.**
**Explicitly determined the correlation between the two domains. **
**Also the first time a chaotic light source is fully characterized. **

**Conclusion**

## Self Amplified free electron laser

**Self Amplified free electron laser**

**Grow from noise**
**Microbunching->amplification**
**Slippage->coherence buildup**
**Continuously tunable**
**X-ray capability**

## Layout

**SASE and SASE experiments**
**The LEUTL system and the FROG experiment**
**The system**
**Statistics in the time domain**
**Statistics in the frequency domain**
**Correlation between the two domains**
**Near term plan**
**Conclusion**
**Acknowledgement**

## Future experiment: growth of spatial coherence

**Future experiment: growth of spatial coherence**

**And the coherence grows along the undulators**

**Courtesy of V. Kumar**

## Future experiment: growth of spatial coherence

**Future experiment: growth of spatial coherence**

**Ischebeck, NIM 507, 175 (2003).**

**Our Plan**

## Layout

**SASE and SASE experiments**
**The LEUTL system and the FROG experiment**
**The system**
**Statistics in the time domain**
**Statistics in the frequency domain**
**Correlation between the two domains**
**Near term plan**
**Conclusion**
**Acknowledgement**