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 Complete design of the Laser Frame Configuration Laser BPM Assembly Tentative results of resolution test Summary

Why we need Laser Frame Initial alignment (10  m) 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

Concept of Laser Frame We Vacuum environment * Eliminate the residual errors in Laser interferometry from air turbulence and nonlinearity

Over view of KEK Nano BPM

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

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

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

Resolution test setup conditions => Laser: YAG Laser (CW,500mW, 532nm, Single mode, W 0 =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 ) =>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)

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

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

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)

Vacuum chamber Laser ray Resolution test of the 4 th BPM

Resolution test Results Laser power: 500 mW, 532 nm micrometer stage １ um ~ １ V (Amp. gain 2000) ⇒ 1nm~1mV Spot size = 2900 um (1-sigma,at 2m from source point) w 0 = 900 um (divergence 1mrad.) Rayleigh length = πw 0 ^2 /λ= 4.8 m

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

Elevation View

Reference Bar

Laser Input

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

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