VELO2 Full Metrology Girish Patel University of Liverpool 16/11/12.
-
Upload
magnus-mason -
Category
Documents
-
view
216 -
download
0
Transcript of VELO2 Full Metrology Girish Patel University of Liverpool 16/11/12.
VELO2 Full Metrology
Girish PatelUniversity of Liverpool
16/11/12
G. D. Patel, University of Liverpool 2
Each fiducial made of 4 circles, centre of each was measured
Measure 5x4 = 20 fiducial points, plus 8 more over surface of silicon. Measure all upstream sensors on all modules, then all downstream.This means that R and Phi sensors are alternately measured
VELO2 Full Metrology
G. D. Patel, University of Liverpool 3
Take all measured points (almost 1300) and plot the Z value versus measurement number for ALL measurements.
Measurements on a single silicon plane should all have same Z, then jump by separation between modules to next silicon plane. All upstream planes followed by all downstream planes explains the overall structure of the plot.
However, quite a few anomalies, from single rogue points in a group of 28 to several points, differing by fractions of mm to 30mm!
Executive Summary – Data as it stands is not useable
VELO2 Full Metrology
G. D. Patel, University of Liverpool 4
VELO A-side
Points with incorrect z
Missing sensor at z=-36
LHCb
Z-v
alue Point Measurement
Number
-767
-717
-667
-617
-467
-37
-734
-684-634
-584
-277
-434
Sensor pairs on a module are separatedby ~2mm. Measurements do not matchcf -767 and -734, are co-ordinate systems changed during measurements?
VELO2 Full Metrology
G. D. Patel, University of Liverpool 5
VELO C-side
Points with incorrect z
Missing sensor at z=139
VELO2 Full Metrology
G. D. Patel, University of Liverpool 6VELO2 Full Metrology
G. D. Patel, University of Liverpool 7
I then ordered the measurement by the mean Z per plane and calculated dZ between adjacent planes. This should be the z-separation between silicon planes on a module (~2mm)alternating with the separation between modules nominally 30, 50, 150 and 160mm.
In other words this mixes up the upstream and downstream measurements. This should not matter if the co-ordinate reference frame is unchanged over all measurements.
VELO2 Full Metrology
G. D. Patel, University of Liverpool 8
VELO2-C
Expected separation on a module
Missing plane OR Z mismatch
Separation between modules ~30, 50, 150, 160
VELO2 Full Metrology
G. D. Patel, University of Liverpool 9
VELO2-A
Expected separation on a module
Missing plane OR Z mismatch Odd separation on a
module
Separation between modules ~30, where are others
VELO2 Full Metrology
G. D. Patel, University of Liverpool 10
I calculate a mean x,y,z for each of the five fiducials on each sensor from the four centres
I then calculate the mean x,y,z of the five fiducials and arrive at a set of numbers for each sensor. The nominal expected values are given in table above.
With the VELO1 metrology the coordinate system of the metrology was very close to the LHCb system with x=y=0 at the centre of the silicon. The mean fiducial position could therefore be compared with the nominal designed average fiducial position and this is shown in the next slide and matched reasonably well.
<x> <y>R 0.0 -20.90
Phi 0.6 -20.85
Each fiducial made of 4 circles, centre of each was measured
R fids symmetric
VELO2 Full Metrology
G. D. Patel, University of Liverpool 11
VELO1 C-side
Expect -20.90
Expect -20.85
Expect 0.6
Expect 0.0
Expect -0.6
VELO2 Full Metrology
G. D. Patel, University of Liverpool 12VELO2 Full Metrology
G. D. Patel, University of Liverpool 13VELO2 Full Metrology
G. D. Patel, University of Liverpool 14VELO2 Full Metrology
G. D. Patel, University of Liverpool 15VELO2 Full Metrology
G. D. Patel, University of Liverpool 16
Calculate STDEV of all Z measurements on a silicon plane. Zero if silicon flat AND vertical.
A-side mean = 0.063
C-side mean = 0.036
Outliers have points that differ in z by ~0.5mm!
VELO1 Mean RMS 0.044 below.
Z planarity
VELO2 Full Metrology