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