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

Current Status of LASER FRAMECurrent Status of LASER FRAMEforfor

KEK-Nano BPMKEK-Nano BPM(Tentative results of resolution test)(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…..

OutlineOutline

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 FrameWhy we need Laser Frame

Initial alignment (10 m)OD of cavities will be used as reference

Fine alignment using BPMs signalsNeeds Nano-Movers

Needs stable positioning with nm orderNeeds reference lines

Laser Frame

Concept of Laser FrameConcept of Laser Frame

We use; @ Laser-BPM @ Interferometer @ Vacuum environment* Eliminate the residual errors in Laser int

erferometry from air turbulence and nonlinearity

Over view of KEK Nano BPOver view of KEK Nano BPMM

Vertical InterferometerVertical Interferometer

Extended Reference BarReference Bar

Plane Mirror

Leg

Vacuum pipe, chamber B.S, Mirror, Detector

Laser BPM

Two Beam Optics

Laser Beam from Fiber

Laser BPMLaser BPM

Reference Bar

L

2L

dy

P1 dP1=2Lsin +dy

dP2=Lsin +dy

sin dP1-dp2)/L

dy= dP1+Lsin

D11D12

D21D22

P1=D11-D12

P2=D21-D22

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 Resolution test setup conditions 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 generato

r)=>Beam splitter ( PBS 50% transmission)=>Detector (diff. amp gain 100-10000)=>Base (Granite table 1x2m. 0.3m thick no apply vibration isolat

or)=>BPM movement ( measured by capacitance gauge(resolution:

3nm)=>Tilt measurement ( light lever racio 1:2)

Test itemsTest 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

Resolution test ResultsLaser 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)

w0 = 900 um (divergence 1mrad.)

Rayleigh length = πw0^2 /λ= 4.8 m

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)

SummarySummary

Vertical resolution => 10 nmTilt resolution => 5x10-6 rad.

Need to Test => Long distance (1-2 m)

Interferometer

Elevation ViewElevation View

Reference BarReference Bar

Laser InputLaser Input

Distance change between Distance change between Ref. Bar and cavityRef. Bar and cavity

(Due to the environmental change)(Due to the environmental change)

7 m

1 hour

Deviation due to assembling Deviation due to assembling and fabrication errors (2Kgf)and fabrication errors (2Kgf)

dY

+0.1m-0.4m

-0.4m -0.6m +0.4m

-0.1m