1. What’s already existing?What’s already existing? Laser system & impacts on Optics TransportLaser system & impacts on Optics Transport –Laser power –Focusing optics –Lens tolerances & system alignment –Scanning range SummarySummary chafik@pp.rhul.ac.uk 3 rd Mini-Workshop on Nano Project at ATF/KEK 30 th May 2005 Optics Transport for the Laser-wire at the ATF Extraction Line Laser-wire Team

2. 2 What’s already existing? A tiny change is needed in order to bring the laser beam to the focusing optics: - Breadboard underneath the pipe - Pick-up the beam at MS1 Present setup for the e+ polarisation experiment MS1 M2

3. 3 Laser Power Laser Damage Threshold (LDT): Best Coating  20 Joules/cm 2 @ 532 nm, 8 ns. E = 300 - 600 mJoules Pulse length = 200 - 300 ps Beam diameter 2.R = 6 mm Power density = 600 mJoules . R 2 = 2.1 Joules/cm 2  13.3 Joules/cm 2 LDT (8 ns) = 2.1 Joules/cm 2. 8 ns 0.2 ns ½  Safety factor is not enough ! Attenuate the beam to a couple of 10’s MW  several 1000’s of photons.

4. 4 Goal = Achieve a 1  m spot size:  f =.  /1  /1 aspheric lens Simulation Input waist ≥ 20mm  3” optics post- BE @45 °  2” optics is appropriate. Focusing Optics Tight tolerance on the lens:  < 0.3 degrees tilt  < 0.5 mm decenter CCD1 CCD2 MS1 MS2 MS1 = Steering mirror 1 Setup is being developed at RHUL

5. 5 Scanning range σ = e-beam size N= number of sigma scans Scanning range is:  = N x σ /f Example: f = 60 mm & N = ± 5  (  m)1 6  (mrad) 0.080.5 Scan angle over exaggerated Scanning is done with a Piezo driven Scanner: PI S330:  = ± 2.5 mrad, f=1KHz, good repeatability. Other options (A.O & E.O) are being investigated.

6. 6 e-beam z x 3000 1000 Breadboard e-beam z x IP Pick-up Beam Expander Shutter MS1 Scanning Mirror 2650 100 200 1200 400 1290 700 960 EM ZEMAX screenshot of the beam path CCD1 Green red Iris CCD’2 CCD3 MS2 EM MS_F1 MS_F2 -Beam dumps are not shown -Fast photodiode is not shown -Some of the equipment are movable and multi-task: CCDs  alignment, waist monitor, collimation)

7. 7 Zemax Simulation Waist at IP Aberrations Encircled energy

8. 8 Summary & Plan - KEK agreed to prepare the breadboard for us, its support, and its enclosure as well. Many thanks ! - Thanks to our colleagues from the e+ Polarization experiment, the beam is delivered to the breadboard in the tunnel. - The UK-group will take responsibility of getting all items needed on the breadboard (focusing, alignment, diagnostics, …) A shopping list is prepared will start ordering the items starting from next week. - The setup will be tested in the UK before being shipped to KEK in September