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

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

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

Concept

Beam Paths

Electron Bunch Patterns

Bunch Length Control

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

Coherent Emission from FEL

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

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

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

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

Peak Brightness

Average Brightness

Latest Layout

Cross-section

Building Internal View

Building External View

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