# Presentation: 447618

## The BESSY Soft X-Ray SASE  FEL (Free Electron Laser)

- Roland Müller

**EPICS Meeting Spring `02, BESSY, Berlin**

## Slide 2

## Slide 3

## SASE-FEL Setup

## 1980	First proposal
1996	First experimental observation
	UCLA:  = 16 m
Dec. 1999	APS:	lasing at  = 523 nm
Feb. 2000	DESY:	lasing at  = 80 nm
Sep. 2000	APS:	saturation at  = 523 nm
Feb. 2001	VISA/BNL: saturation at  = 800 nm
Apr. 2001	APS:	saturation at  = 385 and  = 265 nm
Sep. 2001	DESY:	saturation at  = 100 nm
Oct. 2001	First user experiments @ DESY-TTF

- 1996	First experimental observation
- 	UCLA:  = 16 m
- Dec. 1999	APS:	lasing at  = 523 nm
- Feb. 2000	DESY:	lasing at  = 80 nm
- Sep. 2000	APS:	saturation at  = 523 nm
- Feb. 2001	VISA/BNL: saturation at  = 800 nm
- Apr. 2001	APS:	saturation at  = 385 and  = 265 nm
- Sep. 2001	DESY:	saturation at  = 100 nm
- Oct. 2001	First user experiments @ DESY-TTF

**History of SASE**

- Development steps towards VUV and X-ray FELs

## SASE FEL User Facilities

_**Under construction and/or operational**_
- TTF / DESY* 	 > 6 nm 	(80 nm)
- LEUTL / APS* 	 > 120 nm 	(265 nm)
_**Proposed**_
- BESSY	   1.2 nm	(1 keV)
- SLAC	   1.5 Å 	(8 keV)
- SPring8	   15 nm 	 3.6 nm 	 0.1 nm
- TESLA	   0.85 Å 	(14 keV)
- ELETTRA, ENEA, Daresbury ......
- * Hybrid between FEL development & user facility

## TESLA X-ray FEL

**linear collider**

-  > 0.85 Å (14 keV): X-rays

## TTF FEL: 

**TTF FEL: **
**T****ESLA ****T****est ****F****acility**

-  > 6 nm (200 eV): VUV & XUV

## User Feedback

_**Proposal**_**:** FEL user-facility that becomes operational after 2007

**Important issues:**
- Photon energy:..............................	20 eV - 1.0 keV
-  		(60  1.2 nm)
- Micro-pulse duration:..............................	   20 fs
- Narrow spectral width:...........................	  10-4
- Synchronization with fs lasers
- As many as possible photons per pulse
- High average brilliance

## The BESSY FEL

**The BESSY FEL**

- drift for monochromators and beam-blowup

## The BESSY FEL

- Separate focussing undulator
- (control of the -function)

## The BESSY FEL

- Linac Tunnel

- Cryogenic Hall

- Injector Hall

- Experimental Hall

- BESSY II

-  > 1.2 nm (1 keV): VUV & soft X-rays

## Performance

## The BESSY Soft X-Ray SASE FEL

**The BESSY Soft X-Ray SASE FEL**

**X-RAYS**
**TESLA X-FEL**

**VUV and SOFT X-RAYS**
**BESSY  FEL**

**COMPLEMENTARITY of the**
**VUV and X-RAY FEL**

- 20 eV to 1 keV          	**PHOTON ENERGY**       500 eV  to 15 keV
- 	1 mJ		**PULSE ENERGY****	****	**1 mJ
- 200 fs to 20 fs		**PULSE LENGTH**		100 fs
- 1 kHz (1-25 pulses)	**REPETITION RATE** 	  5 Hz (7200 pulses)

## Critical Issues

**For any SASE-FEL Project:**
- Stability of the electron beam
- Diagnostics
- Spiking nature of the SASE-FEL radiation
- Synchronization with other laser sources
**Specific for the BESSY SASE-FEL:**
- Cryogenic requirements (15 MV/m, cw)
- Optimization of the photo-injector
- Beamlines

## Summary (1) Building of a “basic” FEL user facility

**Summary (1)**** ****Building of a “basic” FEL user facility**

**(based on super-conducting linac technology from DESY)**

_**Goal**_**:**
- construction of a SASE-FEL for the UV to soft X-ray spectral range
- construction of three parallel SASE-FEL beamlines
- Synchronization with conventional fs laser-sources: jitter  200 fs (rms)

_**Major cost factors**_**:**
- Civil engineering
- Cryogenic plant
- Accelerators
- Undulators
- Beamlines

_**Critical tasks**_**:**
- Injector system
- Bunch compressors
- Diagnostics
- Feedback  (Microphonics, Timing ...)
- Beamlines

## Summary (2)Implementing FEL enhancements*

- Enhancing the spectral resolution:
- / = 10-3  <10-4  (Seeding)
- Shortening the micro-pulse duration:
-  ***t* = 160 fs  20 fs  ? fs
- Flexible FEL output (fast scanning, chirping, etc.)
- Increasing the average brilliance

*******Not all enhancements can be obtained simultaneously**