1. Keyence reproducibility study D. Lawrence P. O’Connor 2/2/09

2. Setup Optical flat on 3-ball stage spanning cutout in optical table Softwall cleanroom fans may be turned on or off Temperature measurement from Netbotz appliance on W wall of lab Alternate temperature measurement from Cryo-con PtRTDs on optical bench near CCD test Dewar Keyence averaging parameter 128 to keep noise < 0.1um Log time, temperature, Keyence reading, gantry XY-position for 3 motion conditions: 1.Gantry centered over optical flat 2.Gantry repeatedly move to 5 widely-spaced reference points on flat 3.Gantry perform dense (2x2mm) scan of flat, interrupt dense scan every ~ 60s to measure 5 reference points

3. Keyence noise vs. averaging choose 128-point averaging to keep noise below 0.1um

4. Condition 1: no gantry motion log z-displacement, temp every 20s for 65 hours starting 1/9/09 17:10 fan ON continuously raw data:

5. Cond. 1, 43 minute moving average full dataset 33 minute section

6. Cond. 1, correlation (moving average Disp – Temp over 65 hrs)

7. Cond. 1, 11 min moving average

8. Cond. 1, 160s moving average

9. Cond. 1, 88hr run started 1/29/09, fan off temp vs. time z vs. time correlation

10. Condition 1, long run started 1/29/09, 88 hrs., fan off temp. vs. timez vs time evidence of oscillation

11. Condition 1, 88hr scan started 1/29/09 Rate of change of temperature and time during scan

12. Condition 2: gantry scan of 5 reference points Reference points located at N,S,E,W, and center of flat 12 3 4 5

13. Plane fit to the 5 points vs. time Z-intercept X-slopeY-slope

14. z (rel) vs. timetemperature vs. time z-intercept vs. temperature

15. Condition 2, longer scan slopes intercept z-height of 5 refpoints temperature

17. Cond. 2, 1/29/09, fan off 3.5um/deg C

18. Cond. 2, fans off

19. Condition 3: dense scan with periodic re-measurement of reference points scan entire surface of 8” diameter optical flat at 2mm grid –approx 4300 points –scan at ~ 1.02s/point  about 1.6 hrs to scan, serious temperature drift error likely to compensate temperature drift: –assume SHAPE of flat doesn’t change –track rigid body motion (tip,tilt,piston) –choose 5 reference points (N,S,E,W,Center) –return to reference points every ~ 1 minute to track common-mode motion due to temperature choose diagonal scan pattern to distribute x- and y-gantry motion equally in time repeat scan 16 times over Jan. 17 – 18 2009

20. scan patternz-height of 5 reference points vs time 16 repeat scans Condition 3: z-height vs. time

21. z vs. x and y (first scan)

22. first pass residuals, uncorrected

23. residuals before and after correction for drift blue – no drift correction green – drift corrected