1. R&D description Schedule
4 mirrors high finesse optical cavity to produce high gamma ray flux at ATF
Japanese Labs. : KEK, ATF group, Hiroshima University
French Labs. : LAL (Orsay) in Collaboration with CELIA (Laser lab., Bordeaux) and LMA (mirror coatings Lab., Lyon)
R&D description
Schedule

2. New R&D : start february 2008 after 6th PCRD contract 2005-2008
1. Setup the following system at Bordeaux/Orsay
CELIA
>100W-200W
LAL/KEK/LMA
Oscillator
=1W, 1030nm
Dt~5ps frep=178.5MHz
From Onefive compagny
Amplifier
Rod type photonic fiber Yb Doped
Fabry-Perot cavity
Gain~10000
LAL
Numerical feedback
Goal : Laser average power >1MW inside the cavity…
2. Installation of the system at ATF/KEK

3. R&D at KEK : Cavity installation on the Accelerator Test Facility (ATF).
～ 54 m
Beam Energy
→ 1.28GeV
Beam Size
　→ 100μm×10μm
Emittance　→
1.0x10-9 rad.m
1.0x10-11 rad.m
(Ultra Low !!)
cavity
～ 30 m
(H. Shimizu)

4. The laser amplification R&D E. Cormier (CELIA)
Max published
OneFive laser
Dt=2-5ps, MHz, 1W
F. Röser et al. Optics letters, 30, p2754, 2005
Laser Diode
No compressor needed
Possible average power
100W-300W (simulation)
Doped rod type photonic fibre:
Large core diameter & monomode developed for CELIA
Gold grating-based strectcher gives negative chirp for spectral compression

5. Choice of the cavity geometry Interaction plane must be horizontal2D
2 choices 3D
Main constraint: 5mm vertical slit width
Optical path length = c/178.5MHz~1.6m
4 mirrors needed to reduce the laser spot size
Power/polarisation stabilisation with 3D configuration

6. Implementation studies at ATF has started
Cavity drawing has started

7. Rough schedule
Year 2008 :
Mechanical Design and installation plan studies in closed Collaboration with KEK-group
Meetings
LAL group visited KEK in Nov. 2007
KEK visited LAL in Feb. 2008
Next LAL visit at KEK: June 2008 to finalise mechanical drawings & participation to POSIPOL workshop at Hiroshima
Webex meetings
Laser Amplification studies at CELIA
Feedback studies & mechanical drawing/construction at LAL
Year 2009 (mid 2009 hopfully, end 2009 probably)
Transport of the system to KEK and installation on ATF