1. LASER FRAME: Straightness monitor (Tentative results of resolution test) Third Mini-Workshop on Nano Project at ATF May 30-31,2005 KEK Nano BPM Group Y.Higashi, Y.Honda, T.Tauchi, H.Hayano, J.Urakawa, T.Kume, K.Kubo, H.Yamaoka

2. Outline Why we need Laser Frame as Straightness monitor Complete design of the Laser Frame Configuration Laser BPM Assembly Tentative results of resolution test Long distance(50-100m) straightness monitor base on the laser frame techniques Schedule for the summer installation

3. Why we need Laser Frame Initial alignment (10  m) of the cavity BPM OD of cavities will be used as reference Fine alignment using BPMs signals Needs Nano-Movers Needs stable position of base of movers, magnets etc. with nm order Needs reference lines Laser Frame as Straightness monitor

4. Concept of Laser Frame We use; @ Laser-BPM @ Interferometer @ Vacuum environment

5. Laser BPM Reference Bar L 2L dy  P1 dP1=2Lsin  +dy dP2=Lsin  +dy sin  dP1-dp2)/L dy= dP1+Lsin  D11 D12 D21 D22 P1=D11-D12 P2=D21-D22 Ref.1Ref.2 D1D2

6. Ground Motion Measurement Ground Surface Vacuum Chamber Plate O rings Laser BPM Mirror for Interferometer To reference Bar O rings Two Laser Beam

7. Measurement of intensity change of light due to nm position shift of laser light Tested by Y.Honda

8. Over view of KEK Nano BPM

9. Vertical Interferometer Extended Reference Bar Reference Bar Plane Mirror Leg Vacuum pipe, chamberB.S, Mirror, Detector Laser BPM Two Beam Optics Laser Beam from Fiber

10. Cross sectional drawing of a Laser BPM (including vacuum chamber) To detector Vacuum chamber Laser ray Ground

11. Resolution test setup conditions =>Laser: YAG Laser (CW,500mW, 532nm, Single mode, W 0 =0.9mm, Divergence 1mrad. Spot size 2900  m, Rayleigh length = πw0^2 /λ= 4.8 m ) =>Environment (not vacuum but transport in the pipe ) =>BPM location (2 m distance from the reference beam generator) =>Beam splitter ( PBS 50% transmission) =>Detector (diff. amp gain 100-10000) =>Base (Granite table 1x2m. 0.3m thick no apply vibration isolator) =>BPM movement ( measured by capacitance gauge(resolution: 3nm) =>Tilt measurement ( light lever ratio 1:2)

12. Measuring items Use a Single Laser BPM =>Vertical resolution =>Tilt resolution

13. Calibration setup of beam position measurment(1) 2 m Laser 4 th BPM Reference beam generator

14. YAG Laser 500mW Optical fiber Beam divider 1 st BPM 2 nd BPM 3 rd BPM Setup (2) Beam intensity of n th BPM= p * 0.5 n (n= BPM number, p=power)

15. Vacuum chamber Laser ray Resolution test of the 4 th BPM

16. Tentative results of resolution

17. Summary Vertical resolution => 10 nm Tilt resolution => 5x10 -6 rad. Need to Test => Long distance (10-2 0m) Interferometer test in 1m distance

18. Laser beam based alignment for JHF proton Linac

19. Long distance alignment test length about 100m

20. Laser position change at 50m away due to environmental change

21. Laser position change at 100m away due to environmental change

22. Reference Bar

23. Laser Input

24. Distance change between Reference Bar and cavity (Due to the environmental change) 7  m 1 hour

25. Deviation due to assembling and fabrication errors (2Kgf) dY +0.1  m-0.4  m -0.6  m+0.4  m -0.1  m

26. Schedule for summer installation