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ERLP / ALICE: a bit of history

ERLP / ALICE: a bit of history. Yuri Saveliev. ... how all this started. ERLP. SRS. .... Oh yes ! We get there. .... Hmmmm Not quite. ... to greener p astures. DIAMOND. 4GLS. ERLP: test bed and a learning tool. New accelerator technologies for the UK

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ERLP / ALICE: a bit of history

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  1. ERLP / ALICE: a bit of history Yuri Saveliev

  2. ... how all this started ERLP SRS .... Oh yes ! We get there ... .... Hmmmm Not quite .... ... to greener pastures DIAMOND 4GLS

  3. ERLP: test bed and a learning tool New accelerator technologies for the UK First SCRF linac operating in the UK First DC photoinjector gun in the UK First ERL in Europe First IR-FEL driven by energy recovery accelerator in Europe ... lots of help from all around the world ... BIG THANKS to all and , especially, to colleagues from JLab !!

  4. The ALICE (ERLP) Facility @ Daresbury Laboratory Tower or lab picture

  5. The ALICE Facility @ Daresbury Laboratory Accelerators and Lasers InCombined Experiments An accelerator R&D facility based on a superconducting energy recovery linac photoinjector laser Free Electron Laser EMMA superconducting linac DC gun superconducting booster

  6. ALICE Machine Description RF System Superconducting booster + linac 9-cell cavities. 1.3 GHz, ~10 MV/m. Pulsed up to 10 Hz, 100 μS bunch trains Beam transport system. Triple bend achromatic arcs. First arc isochronous Bunch compression chicane R56 = 28 cm Undulator Oscillator type FEL. Variable gap Diagnostics YAG/OTR screens + stripline BPMs Electro-optic bunch profile monitor TW laser For Compton Backscattering and EO ~70 fS duration, 10 Hz Ti Sapphire DC Gun + Photo Injector Laser 230 kV GaAs cathode Up to 100 pC bunch charge Up to 81.25 MHz rep rate

  7. ERLP : infancy 2003 - Project conceived and funded - calls for tenders; placing orders started 2004 - PI laser system (commissioning at RAL) - machine specification completed - magnets, IOTs, gun, SF6 vessels, DC HV ... 2005 - Gun HV PS assembled - ... problems (gun ceramic, buncher etc) - NWSF project starts (TW laser and CBS project)

  8. 2006: Gun commissioning & first beam • conditioning resistor failure • - gun instability in 260-310kV range of voltages • - low and rapidly deteriorating QE (~0.5% max and ~0.1% most of the time) • - gun vacuum/current leakage problems after one of the cathode activations August 16th 2006 FIRST BEAM ... and 2K cryogenic system commissioned !

  9. 2007: fighting gun problems - strong field emission from the new cathode - rapidly deteriorating QE (from initially >1%) - highly non-uniform QE map (due to wafer heating problems) - mechanical failure inside the cathode ball (flap) New cathode installed - rapid QE deterioration - strong gun contamination after each cathode activation - gun disassembled for wafer change then ... vacuum leak discovered • Eventually (end of 2007) : • The beam from PI gun fully • characterised at 350keV • > 100pC achieved (QE>3%)

  10. Meanwhile ... ERLP continues to take its shape

  11. 2008: Energy recovery ! • Booster cryo modules repair at ACCEL (January-March) • Stanford ceramic installed in the PI gun (June)  230kV only • First beam through the booster (October) • First beam through the linac (December) • ... And finally • ... Just before Christmas • Full energy recovery • (20.8MeV; at a few pC of bunch charge only)

  12. 2009: continuous improvements • Starting conditions: • strong beam loading limitations in SC linacs • and strong field emission in main linac  ~20pC and ~20MeV • pitiful photoelectron cathode lifetime • (20pC was a blessing rather than norm ) • strong field emitters on cathode and cathode ball (hence 200kV only) • Progress: • full cathode re-activation and elimination of a minute vacuum leak •  QE ~ 4% ; >80pC ; long lifetime • Kr based “plasma cleaning” of the gun •  removed the most annoying FE on cathode ball • LLRF optimisation to alleviate beam loading •  40pC; 81MHz; 100us • RF cavities conditioning and RF pulse optimisation •  operation at up to 30MeV possible !

  13. 2009: further milestones : THz Coherently enhanced broadband THz radiation generated (Feb)

  14. 2009: further milestones : CBS exp. X-rays Compton backscattering demonstrated on ALICE: November 2009 ... Just two days before the start of the shutdown !!! Scintillator Be window Laser beam Interaction region Camera: Pixelfly QE Electron beam

  15. 2010: “accelerating” • Helium processing of linac cavities • (March) • PI laser burst generator • allows < 81MHz operation • enables Q=60pC as standard • THz cells exposures started in April • (in an incubator located in • the accelerator hall) • EMMA ring completed and commissioned • ... many-many turns (August) • IR FEL : first lasing !! (October) He processing by ASTeC RF + cryogenic groups with assistance from T. Powers (Jlab)

  16. 23rd October 2010: ALICE FEL First Lasing Lasing 100-40 pC@ 16.25 MHz The peak power ~3 MW Single pass gain ~20 % First Lasing Data: 23/10/10 Continuous tuning 5.7-8.0 µm, varying undulator gap.

  17. 2011: EMMA • First extraction of beam from the ring (March) • First acceleration in EMMA (March) • Acceleration by EMMA : 12  21MeV (April) • Proof-of-principle demonstrated • Paper to Nature Physics submitted (and accepted ?) • ... to be continued First NS FFAG “EMMA”: Successful International Collaboration

  18. 2011: FEL and FELIS • FEL beam transported to the Diagnostic room (March) • Scanning Near-field Optical Microscope (SNOM) installed • received from Vanderbuilt Uni. • Free Electron Laser integration with • Scanning Near-field Optical Microscope FELIS • First SNOM image (September) • Short e-bunch characterisation with EO diagnostic Electro-optic bunch profile measurement (ZnTe crystal probed by Ti Sapphire laser)

  19. 2011: THz for biology ALICE : a source of high power broadband coherently enhanced THz radiation • THz beam transported to the TCL (Tissue Culture Lab) • that’s ~ 30m away from chicane • Biological experiments in TCL started (June) Estimate > 10 KW in single THz pulse with ~ 20% transport efficiency to TCL Research program to determine safe limits of exposure of human cells to THz and effect of THz on differentiation of stem cells

  20. sample fs UV pulse 2011: Other developments • Quantum dots studies for novel solar cells (with Manchester Uni.) • - employs high power THz from ALICE • Timing and synchronisation experiments • - fibre-ring-laser-based system; • - aims for sub-10fs timing distribution for future light sources • Digital LLRF development • Experiments on interaction of short electron bunches with high power • electromagnetic radiation • Photocathode research • DICC: International collaboration on SC cryomodule development

  21. ALICE Milestones: still growing .... exponentially

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