laser frame: straightness monitor (tentative results of resolution test) third mini-workshop on nano...
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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
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