1. Jim Clarke ASTeC Daresbury Laboratory March 2006
4GLS
Jim Clarke
ASTeC
Daresbury Laboratory
March 2006

2. Key Features
THz to soft X-Ray (<1keV) light source
Very short photon pulses (<< 1ps)
Combination of pulses for pump-probe experiments
Multiple experiments
Electrons not stored – continually refreshed
Very small emittance
Pulse timing flexibility
Energy recovery linac system
Three distinct types of Free Electron Laser
Conventional undulators
Coherent SR

3. Storage Ring vs Energy Recovery Linac
All previous light source generations are based upon storage rings
Electrons are stored for many hours and continually emit SR
Beam currents of many 100s mA easy to achieve because electrons continuosly circulating
Electron bunch properties fixed by ring design and SR emission – transverse and longitudinal
ERL does not store electrons, properties of injected electrons are maintained – no degredation due to instabilities
100mA beam current in ERL is enormous number of electrons cf storage ring

4. Concept

5. Beam Paths

6. Electron Bunch Patterns

7. Bunch Length Control

8. Superconducting RF
Key enabling technology
Makes energy recovery a practical system
1.3GHz solution – builds upon ILC technology
ERLP needs two cavities, 4GLS design based upon 7 cavity modules
HOM dampers needed between cavities

9. Coherent Emission from FEL

10. XUV-FEL
10 to 100 eV
Amplifier of seed pulse derived from conventional laser
Ensures high quality output since mimics input pulse
other devices such as X-FEL have no seed and suffer from poor pulse to pulse repeatability
~30 m long undulator system

12. Pulse Amplification Exit of FEL Entrance to FEL >2 GW, 100eV, 50fs
30 kW seed, 100eV, 30fs
Electron bunch length much longer than seed pulse – makes synchronisation much easier

13. VUV-FEL
3 to 10 eV
Similar principle as XUV-FEL but uses mirrors to self-seed
Economical since shorter undulator but also gives higher rep rate (no laser used)
4.33 MHz cf 1 kHz
Very tolerant to mirror degredation
Reflectivity 40 to 60% needed

15. IR-FEL
2.5 to 200 mm
More traditional FEL
Excellent mirrors available
Store light for many passes
Very stable output

16. Peak Brightness

17. Average Brightness

18. Latest Layout

19. Cross-section

20. Building Internal View

21. Building External View

22. Tremendous global interest in ERLs
Status & Future Plans
Tremendous global interest in ERLs
Many projects aiming to take advantage
4GLS remains the premier worldwide light source proposal – most ambitious combination of sources
Conceptual Design Report presently being written
will be published very soon
Next phase is Technical Design Report
Should be complete by March 07