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Current Status of LASER FRAME for KEK-Nano BPM (Tentative results of resolution test)

Current Status of LASER FRAME for KEK-Nano BPM (Tentative results of resolution test). Second Mini-Workshop on Nano Project at ATF December 11-12, 2004 KEK-Nano BPM Group Y.Higashi, Y.Honda, T.Tauchi, H.Hayano, J.Urakawa, T.Kume,K.Kubo, H.Yamaoka…. Outline. Why we need Laser Frame

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Current Status of LASER FRAME for KEK-Nano BPM (Tentative results of resolution test)

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  1. Current Status of LASER FRAMEforKEK-Nano BPM(Tentative results of resolution test) Second Mini-Workshop on Nano Project at ATF December 11-12, 2004 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 • Complete design of the Laser Frame Configuration • Laser BPM Assembly • Tentative results of resolution test • Summary

  3. Why we need Laser Frame Initial alignment (10 mm) OD of cavities will be used as reference Fine alignment using BPMs signals Needs Nano-Movers Needs stable positioning with nm order Needs reference lines Laser Frame

  4. Concept of Laser Frame We use; @ Laser-BPM @ Interferometer @ Vacuum environment * Eliminate the residual errors in Laser interferometry from air turbulence and nonlinearity

  5. Over view of KEK Nano BPM

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

  7. Laser BPM Reference Bar P1 P1=D11-D12 P2=D21-D22 dP1=2Lsin q +dy dP2=Lsin q +dy sin q= (dP1-dp2)/L dy= dP1+Lsin q D12 D11 q 2L dy L D21 D22

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

  9. Resolution test setup conditions =>Laser: YAG Laser (CW,500mW, 532nm, Single mode, W0=0.9mm, Divergence 1mrad.) =>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 racio 1:2)

  10. Test items Use a Single Laser BPM =>Vertical resolution =>Tilt resolution

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

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

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

  14. Resolution test Results Laser power:500 mW , 532 nm micrometer stage １um ~ １V(Amp. gain 2000) ⇒1nm~1mV Spot size = 2900 um (1-sigma,at 2m from source point) w0 = 900 um(divergence 1mrad.) Rayleigh length = πw0^2 /λ= 4.8 m

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

  16. Elevation View

  17. Reference Bar

  18. Laser Input

  19. Distance change between Ref. Bar and cavity(Due to the environmental change) 7 mm 1 hour

  20. Deviation due to assembling and fabrication errors (2Kgf) -0.4mm -0.6mm +0.4mm dY -0.4mm +0.1mm -0.1mm

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