Calibration of Analog
Sensors for the Alignment
of Muon Chambers in the
CMS experiment
Marion Ripert, Georgia Karagiorgi, Thomas Moschoutis
Dr. L. Caraway, Dr. M. Hohlmann
Department of Physics and Space Sciences
Florida Institute of technology
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
Large Hadron Collider
• pp machine (mainly)
s =14 TeV
7 Times higher than energy
in the Tevatron at Fermilab.
•Bunches of protons collide in CMS every 25 ns
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
The Muon Detector
Outer barrel rings
Endcap disks
Central barrel ring
The CMS solenoid will be 13m long with an inner
diameter of 6m – the largest superconducting
solenoid ever made!
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
Installation of muon
chambers on ME+2 endcap
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
R – Sensor
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
Z - Sensor
Linear motion potentiometer
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
Calibration of R , Z
sensors and clinometers
Z -sensor
R-sensors
Clinometer
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
Recent Activities
• Calibration Bench finished for R sensors, Z
sensors, and Clinometers
• Understanding & reducing uncertainties:
-Reference bar accuracies
-Mechanical Tolerance on dowel holes & pins
-Mounting procedures
• Calibrating production sensors for ME+3
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
Line Up Reference points
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
Results for R-sensors:
sensors
10
Plate ME+2/2/3-HV-OR with R-sensor R2TP1sens-22_03>OUT
Sensor Response vs. Distance
Sensor Response (V)
(5 out of 30 trials shown)
8
6
• remove plate from stand
• reestablish initial absolute distance with R-bar
• remount plate
• remeasure
4
Mean Fit line (30 measurements): y(x) = -51.3923 + 2.00482x
σ(slope) = rms = 0.00047
σ(Y-intercept) = rms = 0.0314
2
26
Marion Ripert
27
28
29
Distance (cm)
Florida Academy of Sciences,
30
Tampa, March 18, 2005
31
Measuring relative changes in
distances
14
Test1 : Histogram of 30 measurements of the slope (V/cm)
of the linear curve ( Sensor Resonse (V) vs distance (cm))
of the extension of the R sensors ( LX-PA-2 S/N 3310410;
PLATE me+2/2/8-AN-OR) with old holes.
12
mean: 2.04529 V/cm
rms : 0.00166V/cm
<slope> = 2.0453 ±0.0003 (stat) V/cm
10
<
<
FREQ
8
>
=
>
Corresponds to σ∆x = 8 µm
over full range (50 mm)
6
4
Æ 5 calibration measurements
per sensor will be sufficient to
achieve σ∆x = 20 µm over 50mm
2
0
2.040
2.041
Marion Ripert
2.042
2.043
2.044
2.045
2.046
2.047
SLOPE (V/cm)
Florida Academy of Sciences,
2.048
2.049
2.050
Tampa, March 18, 2005
2.051
2.052
Measuring absolute distances : need new
dowel holes.
σ (intcpt ) = 0.061 V
σ ( x ) = 300µm ⇒ problem with tolerance of dowel holes
10
Test1: Histogram of 30 measurements of the Y-intercept
(Volts) of the linear curve ( sensor response (Volts)
vs Distance (cm)) of the extension of the R-sensors
( LX-PA-2 S/N 3310410;plate ME+2/2/8-AN-OR)
with old holes.
8
Hist :
mean = -47.311V; rms = 0.0609 V
G-FIT:
mean = -47.278V;
sigma = 0.0682V;
Freq
6
4
2
0
-47.60
-47.55
Marion Ripert
-47.50
-47.45
-47.40
-47.35
-47.30
Y-intercept (V)
Florida Academy of Sciences,
-47.25
-47.20
Tampa, March 18, 2005
-47.15
-47.10
Checking the Calibration method :
No dismounting and remounting of
plates between measurement
10
σ(intcpt) = 0.0032 V corresponding to σ(x) = 16 µm
9
=> It’s the holes, not the calibration method !
8
Sensor Response ( V)
7
6
5
'scan1'
scan2
scan3
scan4
scan5
'Mean Fit Line'
4
3
2
1
0
23.0
23.5
Marion Ripert
24.0
24.5
25.0
25.5
26.0
Distance (cm)
Florida Academy of Sciences,
26.5
27.0
Tampa, March 18, 2005
27.5
28.0
Results with new holes
Histogram of 30 measurements of the Y intercept
(Volts of the Sensor Response vs Distance cm)
10
mean = -47.4861 V
σ Gaussrms
( intcpt
= 0.0276)V = 0 . 015 V ⇒ σ ( x ) = 75 µ m
G-Fit
mean = -47.4894 V
sdev = 0.00071 V
FREQ
8
6
4
2
0
-47.60
Marion Ripert
-47.58
-47.56
-47.54
-47.52
Y intercept V
Florida Academy of Sciences,
-47.50
-47.48
Tampa, March 18, 2005
-47.46
Current uncertainties in
absolute R calibration
• Random uncertainties: (Dowel hole/pin tolerances, Initial absolute
distance with reference bars) ± 75 µm
• Systematic uncertainties: (including
calibration of stepper motor.
Mechanical accuracy of reference bars. Non –parallel mover axis and line
connecting R -post and dowel hole
) ≤ ± 150 µm
Total ≤ ± 150 µm
Required: < ± 430 µm (from simulations)
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
Future Plan
• ME+2 : R and Z sensors ready for
shipping and installation.
• Start mass calibration for R sensors and Z
sensors, Inclinometers for ME+3,+4…
Marion Ripert
Florida Academy of Sciences,
Tampa, March 18, 2005
References
• CMS, The Muon Project Technical Design Report. The
CMS collaboration, CERN/LHCC 97-32
• Dick Loveless, EMU meeting at Carnegie Mellon, 2003
• http://bulletin.cern.ch/