The measured x,y co-ordinates of 5 fiducials are mapped to the nominal
positions by minimising the differences in x,y of measured and nominal
points using three free parameters, x0, y0 and rotation angle Zrot:
Xm - ( Xn*cos(Zrot) - Yn*sin(Zrot) - x0 )
Ym - ( Xn*sin(Zrot) + Yn*cos(Zrot) - y0)
| CERN (Fit Summary) | LHCb
x (mm) | LHCb
y (mm) | Vz
(mrad) |
|---|
| R si offset relative to nominal | -0.004 |
-0.031 | -0.068 |
| P si offset relative to nominal | -0.018 |
-0.040 | 0.017 |
| Mean offset | -0.011 |
-0.036 | |
|
| P si offset relative to R si | -0.014 |
-0.009 | 0.085 |
| Liverpool (Fit Summary) | LHCb
x (mm) | LHCb
y (mm) | Vz
(mrad) |
|---|
| R si offset relative to nominal | -0.001 |
-0.013 | -0.052 |
| P si offset relative to nominal | -0.009 |
-0.014 | 0.094 |
| Mean offset | -0.005 |
-0.014 | |
|
| P si offset relative to R si | -0.008 |
-0.001 | 0.146 |
|
The measured x,y co-ordinates of 5 fiducials and 8 extra points are fitted to
a plane Z - Vy*X - Vx*Y - Z0 = 0 by minimising deviations in Z
Free parameters are Vx, Vy and z-displacement Z0:
Min dz / Max dz / RMS mean / are about the mean of the Z measurements (μm)
RMS plane is the rms variation in z about the fitted plane (μm)
CERN (Fit Summary)
| Module | Glued | Type |
Min dz | Max dz | RMS
mean |
Vx
(mrad) | Vy
(mrad) | LHCb
Z0 (mm) | RMS
plane |
|---|
| 42 | R | R |
-78 | 79 | 50 |
-0.491 | 3.141 | -10.785 | 12 |
| 42 | R | Phi |
-65 | 55 | 37 |
-0.362 | 2.180 | -8.679 | 16 |
Liverpool (Fit Summary)
| Module | Glued | Type |
Min dz | Max dz | RMS
mean |
Vx
(mrad) | Vy
(mrad) | Module
Z0 (mm) | RMS
plane |
|---|
| 42 | R | R |
-76 | 99 | 50 |
1.405 | 1.857 | -0.924 | 13 |
| 42 | R | Phi |
-60 | 136 | 57 |
1.731 | 1.147 | 1.219 | 25 |
|