1. Optical Cavity construction at LAL  2000 : polarimeter at HERA 2-mirror cavity cw ND:YAG laser, F=30000 (  ~10 -11 )  2005 : Ti:sapph pulsed laser locking to a F=30000 cavity (  ~10 -11 )  2010 : 4-mirror non planar cavity installed at KEK, pulsed laser (Yb fiber) F=3000  2010 : 4 mirror planar cavity foir ThomX (design  construction end 2012) (  ~10 -12 )

2. 2-mirror cavity at HERA (polarimetry) Finesse =30000, cw ND:YAG laser Tube protons In 2000

3. HERMES à 100m ZEUS 1km

4. From 2006 Still used From 2006 Still used At LAL we have a Ti:sapph oscillator / 2 mirror cavity Finesse = 30000 (MIRA : 800nm, 2ps@76MHz, pumped with a green laser beam)

5. 5 ATF e - beam Injection laser 2 flat mirrors 2 spherical mirrors laser/beam Interaction point Angle laser / e - beam= 8° Non planar 4-mirror at ATF (circularely polarised eigen modes) Non planar 4-mirror at ATF (circularely polarised eigen modes) ATF beam pipe: 5mm slit…

6. 6 2 flat mirrors 2 spherical mirrors e-e- laser Mirror positioning system Invar base to ensure length stability Mounting in class 10 room 12 encapsulated Motors R. Cizeron

7. Gimbal  θx θy Actuator Piezo Mounting Z Translation on 3 balls θx θy Ring Piezo Spring ring Mirror

8. 8 Vacuum inside ~3x10 -8 mbar without baking (in situ) Vacuum inside ~3x10 -8 mbar without baking (in situ) Vacuum vessel for ATF

9. 9 Implementation at ATF Pulse Motor Port for Up-Down Move Pulse Motor Port for Horizontal Move From Hirotaka-san Assumed ATF Beam Line ATF table mount system (~1µm precision) used for spatial laser and e - beam matching Electron beam pipe Class 100 air flow KEK 2-mirror cavity Cavity Finesse=3000

10. 10 Numerical Pound-Drever-Hall feedback Rétroaction on laser frequency 10 Clk = 100 MHz 8x ADC 14 bits 8x DAC 14 bits => Filtering => 18 bits / 400 kHz FPGA Virtex II Clk = 100 MHz 8x ADC 14 bits 8x DAC 14 bits => Filtering => 18 bits / 400 kHz FPGA Virtex II We are developing our own card for ThomX optimised for ‘fast’ feedback

11. 36mm 24mm Prototype of nonlanar 4 mirrors resonator (low finesse) Check the general astigmatism mode shape/propagation ( Arnaud, Bell Syst. Tech. ( 1970)2311 )  Ok but strong abherations:non-parxiale corrections In the strong divergent regime 50cm