Optical Alignment System for the PHENIX Muon Tracker
description
Transcript of Optical Alignment System for the PHENIX Muon Tracker
Rikkyo University Murata.lab / RIKEN Master course 2nd Kentaro Watanbe
PHENIX Colaboration meeting 2012@ Rikkyo UniversityOptical Alignment System
for the PHENIX Muon Tracker
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In order to achieve better momentum resolution We should correct for these relative movement !! The purpose of the optical alignment system(OASYS) is the real-time monitoring of the relative alignment among the stations.
the muon is flyting 15 degrees
Alignment for MuTr W physics
W signal : 500μm 〜 1.0mmMuTr Chamber resolution : 100μm
During the experiment period Each chamber moves 50 to 300 μm by the magnetic field or temperature excursion !!!
Optical Alignment System ① The OASYS consists of a light source at station 1, a convex lens at station 2, and a CCD camera at station3. When an individual station moves, the image on the CCD camera moves reflecting the station movement. By observing the position of the light spot on the image of the CCD camera, we can monitor each station’s relative movement.
We use a halogen lamp and optical fiber as a light source for the OASYS. Optical fibers guide light from the halogen lamp It is attached on the edge of station1. Seven CCD cameras have been set up to each octant as in a diagram.
station1 station3station2
OASys CCD →
Optical Alignment System ②
56 OASYS cameras by each arm. total 112 cameras
The results of measurement are peak position distributions for 1000 samples obtained within 30 minutes. The typical sharp image and the typical broad image are displayed. The measured resolution is 1.4 μm for sharp image, and 3.1 μm for the broad image.
Resolution for the CCD camera
The typical sharp image The typical brod image
resolution is 1.4 μm resolution is 3.1 μm
capture raw data image
6.6mm
8.8mm
OASys determines the center position by Fitting. First, it makes two histograms which are projected image on the horizontal or vertical axis.….
Optical Alignment SystemNo
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n Normalize vertical (first day opsition) Range : -15[pixel] to 15[pixel], Horaizontal Range : 2010/1/10~2010/4/20
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12 camerabroken
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Movement of optics
X direction
Y directionRun9 first of March to end of June
4 month
one day
Daily fluctuation
10μm
Fourier transform
No Peak Spectrum !
This fluctuation is defined error of long term.
I’m focused the movement of the long term. So, I treat daily fluctuation as random noise. it means the error bar of OASys become about 10μm
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Linear Fit the Movement of optics
90μm
7 0μm
X direction
Y direction
I think this long term movement as the rotation or translational motion or Monotonic expansion of the chamber by the fixture degradation, land subsidence.
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Linear fit all camera: North Arm X direction 2009 3/1 〜 6/30 (120day)
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Linear fit : North Arm Y direction 20093/1 〜 6/30 (120day)
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Linear fit : South Arm X direction 20093/1 〜 6/30 (120day)
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Linear fit : South Arm Y direction 20093/1 〜 6/30 (120day)
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OASys Vector Map in Run9
It is real chamber movement ??
North Arm South Arm
What do you think this movement ??
collision
external point
stub point st3
sagittastub point st2
stub point st1
sagitta = stub point st3
stub point st3
external point
external point
ー※The external division is defined from 2 stub information (st1&st2).
How to define the sagitta
Zero Field Run Saggita AnalysisWe must confirm that OASys parameter can be tracing real chamber movement by another independent tool. It is “zero field run saggita analysis !!” Because, in the zero magnetic field, almost track became straight. It means the sagitta will disturibute around 0.0
Sagitta distribution & miss Alignment
2009 PHYSICS RUN
zero field cosmic 1st zero field 2nd zero field
pp500GeV pp200GeV
March MayJanuary
chamber moving ??
mean March
mean May
Miss Alignment = mean_March – mean_May > chamber resolution
Muon momentum study pp500GeV
momentum [GeV]
run condition
under 10GeV 97.3% of ALL !!
This spectrum is pp500GeV track associated muon momentum distribution (No track cut ).
500GeV (3104228/3187765) 97.3%
momentum [GeV]
High pt spectrum seems to decrease than pp500GeV. However under 10GeV muon is 98.3%, high pt muon is not sensitive for the residual distribution.
Muon momentum study pp200GeV
run condition
under 10GeV 98.3% of ALL !!
200GeV (961325/945105) 98.3%
Muon momentum study summary
pp200GeVpp500GeV
momentum [GeV]
The residual distribution is based on under 10 GeV muon. The spectrum is same in pp200GeV and pp500GeV. It means the residual from different beam can be compered. And the different of beam is not sensitive 2nd gaussian.
pp200GeVpp500GeV
1/momentum [/GeV]
Normalized ( 〜10GeV)
1/p
Normalized log
scale
1GeV
0.2GeV
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sample: south octant8 half2
simulation study From zero field cosmic study, we make sure second gaussian component is not based on hadron decay. So, we guess that component will be based on the effect of multiple scattering another momentum. After the last meeting, Oide-san gave me simple multiple scattering root macro. I modified that macro to near real condition.
Fist Step : Air volume contribution (fix muon momentum)
At first I assumed if 2.0 GeV muon go through between St1 to St3. Then muon is affected by the effect of multiple scattering from air volume. I want to know the final position (St3) is how much spread by that effect.
2GeV muon
st1
st3
calculation by handThe multiple scattering is roughly Gaussian for small deflection angles, the projected angular distribution, with a width given by
The projected y direction distribution is given by
@ South station2 〜 station3
moun momentum : 2GeVx : 160cmair radiation length : 37g ・cm^-2air density :
→σ = 469μm
the result of simulation
2GeV muon
The cause of fixed momentum 2Gev, it can be fit with single gaussian. This simulation consistent with hand calculation.
different momentum distribution1GeV fixedRMS: 939μm
2GeV fixedRMS: 470μm
5GeV fixedRMS: 188μm
10GeV fixedRMS: 94μm
different momentum contribution
The second gaussian component is appeared !!!
Generate muon distribution pp500GeV
Fit 2gaussian
simulation datamomentum 1 〜10GeV
RChiS= 1.1019
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South Arm Run9 March Zero field
oct 1 half 1
oct 1 half 2
oct 2 half 1
oct 2 half 2
oct 3 half 1
oct 3 half 2
North Arm Run9 March Zero field
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A few octant have asymmetry distribution. It is not first priority to find out this asymmetry source. However, I was able to find out that source by simple correlation study. So, today I would like to talk about this study.
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Run9 South March mean position direction ?
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Run9 North March mean position direction ?
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0 1 2 3 4 5 6 7 8 9
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Calculation alignment system (Millepede)
PHENIX Physics RUNzero field run 1st zero field run 2nd zero field run 3rdfew
monthsfew months
Meaning OASysIt is important to align relative positions among the three stations, because it affects the momentum measurement. We align position among the three stations using field off run at the beginning of the experiment. However, each station moved 100-300 μm during the experiment period. In order to monitor this real-time movement, an optical alignment system(OASYS) has been installed into muon tracking chamber.
Optical Alignment System (OASys)The zero field run data taking is less frequent.
However, OASys data taking can be 365days. It is meaningful OASYS.
OASys data taking
Making use of this advantage, OASys send the signal to taking zero field run for Millepede Alignment.
Re-Alignment
Re-Alignment
warning!! warning!!
The change of Second gaussian component上記の通り、2つのガウシアンと pol0 でフィッティングを行うと3月のデータと5月のデータで第2ガウシアンの ratio が変化しているように見受けられる。特に5月のデータでは、その量が総じて減っている。この理由を考察する事で今までハドロンの decay として扱っていた2つ目の component に対して正確に ID する事が今回の study の目的である。
Run9 March South Oct8 half1Rchis : 1.82
Run9 MaySouth Oct8 half1Rchis : 3.07
単純に Fit が上手く決まらないのが原因で第2ガウシアンの要素が死んだと考えるもののsample 。
Run9 MarchNorh Oct3 half1Rchis : 1.24
Run9 MayNorh Oct3 half1Rchis : 170
Fit は上手くいっていて本当に第2ガウシアンのスペクトルの形が変化したのかもしれない。と思うもの。
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