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

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

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

Concept of Laser Frame We Vacuum environment

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

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

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

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

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. 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 ) =>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)

Measuring 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

Tentative results of resolution

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

Laser beam based alignment for JHF proton Linac

Long distance alignment test length about 100m

Laser position change at 50m away due to environmental change

Laser position change at 100m away due to environmental change

Reference Bar

Laser Input

Distance change between Reference 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

Schedule for summer installation