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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 - PowerPoint PPT Presentation
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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