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 BPMOD of cavities will be used as reference

Fine alignment using BPMs signalsNeeds 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 use; @ Laser-BPM @ Interferometer @ Vacuum environment

Laser BPM

Reference Bar

L

2Ldy

P1 dP1=2Lsin +dy

dP2=Lsin +dy

sin dP1-dp2)/L

dy= dP1+Lsin

D11D12

D21D22

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 BPMOver view of KEK Nano BPM

Vertical Interferometer Extended Reference Bar

Reference Bar

Plane Mirror

Leg

Vacuum pipe, chamber B.S, Mirror, Detector

Laser BPM

Two Beam Optics

Laser Beam from Fiber

Cross sectional drawing of a Laser BPMCross sectional drawing of a Laser BPM(including vacuum chamber)(including vacuum chamber)

To detector

Vacuum chamber

Laser ray

Ground

Resolution test setup conditions

=>Laser: YAG Laser (CW,500mW, 532nm, Single mode, W0=0.9mm, Divergence 1mrad. Spot size 2900m, 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)

Measuring items

Use a Single Laser BPM

=>Vertical resolution =>Tilt resolution

Calibration setup of beam position measurment(1)

2 m

Laser

4th BPM

Reference beam generator

YAG Laser

500mW

Optical fiber

Beam divider

1st BPM

2nd BPM

3rd BPM

Setup (2)

Beam intensity of nth BPM= p* 0.5n

(n= BPM number, p=power)

Vacuum chamber

Laser ray

Resolution test of the 4th BPM

0

20

40

60

80

100

120

0 2 10-6 4 10-6 6 10-6 8 10-6 1 10-5 1.2 10-5

Tilt resolution

volt(T)

Tilt(rad)

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120

Vertical resolution

volt(V)

position(nm)

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

+0.1m-0.4m

-0.4m -0.6m +0.4m

-0.1m

Schedule for summer installation