Geometry Monitoring System

1
Geometry Monitoring System

• Present status (TDR) and difficulties
• The RELCAM sensor (TDR)
• The RASNIK alternative
• A realistic RASNIK segment
• Equations to be solved
• Ongoing work
• Project plan

2
Present difficulties

• In TDR, the set-up of laser lines is
• 4 lines in two vertical planes and one step
• 4 lines in 45o planes in azimuth and two steps
• Problems of this set-up are
• No projectivity
• Two supports to be monitored
• induce lost of precision
• Effect of temperature gradient expected important
  in this case of long light lines
• question about realistic shielding

3
The RELCAM sensor

• In TDR, was presented the RELCAM sensor
• Semi-reflecting mirror
• CMOS camera (628 x 582 pixels)
• Test on bench
• Laser (785 nm), Granit table (2.5 x 0.5 m2)
• Motorized stage (x, y) 0.5 µm
• Results
• Resolution sx sy 0.5 µm
• Stability ?x, ?y lt 0.8 µm per oC
• Linearity lt 1 µm within 2 x 2 cm2
• Problem a 2 dimension sensor in the transverse
  directions (x, y)
• z direction not monitored

4
One step laser lines

• We cannot adopt such a set-up
• Due to the constraints imposed by the coil
• More than 24 slats of the stations 3, 4, 5 would
• be on the path of the lines
• No realistic change in their design is possible
• without triggering a crisis with Manoel and
  others
• Need of new system for monitoring

5
Alternative proposal

• Based on the RASNIK sensor
• Each element is set on a chamber frame/support to
  be monitored
• Resolution sx sy 1 µm, sz 100 µm
• Well adapted to our problem
• Used by L3, adopted by (GEM) and ATLAS
• Advantages it is a 3 dimension sensor
• and no laser beam is used (safety)

6
A realistic RASNIK segment

• Initial positions of the Mask and Camera not on
  the Lens axis
• Initial recorded Mask image is not centered on
  the Mask
• x M,L,C, yM,L,C, zM,L,C shifts can be extracted
  from the analysis of the final Mask image

7
The recorded images
y
16 pads
x
M
25 pads
25 pads
8
Equations to be solved

• x0 (y0) initial distance between the camera and
  the plane xOz (yOz) containing the optical axis
• of the lens
• d (d) initial Mask-Lens distance (Camera-Lens)
  along the optical axis
• The displacements of the RASNIK elements (Mask,
  Lens, Camera) in their coordinate systems are
• xM, yM, zM, xL, yL, zL, xC, yC, zC
• Few RASNIK lines are necessary for the monotoring
  of three planes
• if these planes are rigid planes

x
y
M
(Philippe Pillot)

• x, y shifts of the image
• M magnification

9
Proposal for a new set-up
Reference plane

• We propose to study the performance of a
  monitoring system with
• 8 RASNIK segments on
• the muon filter (C), the chamber
  10 (L), the chamber 9 (M)
• Then, 8 RASNIK segments on
• the chamber 10 (C), the chamber 8
  (L), the chamber 6 (M),
• the chamber 6 (C), the chamber 4
  (L), the chamber 2 (M),
• the chamber 9 (C), the chamber 7
  (L), the chamber 5 (M),
• and the chamber 5 (C), the chamber 3
  (L), the chamber 1 (M)
• And, to increase the constraints between the two
  groups of chambers,
• 8 RASNIK segments on
• the chambers 2 (C), the chamber 1
  (L and M),
• and the chamber 4 (C), the chamber 3 (L
  and M)

10
Present work

• Evaluation of the performances of the proposed
  setup
• Resolution in position of each chamber
• Resolution in mass at the ? mass
• Localization of the monitoring lines through the
  spectrometer
• Position of the elements on the chamber
  frames/supports
• in collaboration with the Engineers
• Decision (?) for a monitoring of the
  chamber/support flatness
• Choice of the system, position of the elements
• in collaboration with the Engineers
• Alternative to RASNIK (?)
• System baseline design to be decided by June 2002
  (?)

11
Project plan

• Development of the system starting as soon as
  possible in 2002
• Measure of the performances
• Study of the temperature gradient effects
  (neutralization)
• Technical support demanded, answer expected soon
• Realisation of the system starting in 2004
• Design study
• Fabrication of sensors and supports
• Calibrations
• Installation
• Lyon and Erevan
• Budget (MOU)
• 140 KFS to be re-estimated