Z. Szillasi On behalf of GEM Alignment group November 15, 2017

The general concept of GEM alignment The aim of the GE-alignment: to locate the strips of the read-out boards in the CMS coordinate system and monitor their movements. The general alignment concept: The strips are sealed during the production and not observable. Therefore the strip positions have to be transferred to the observable (outer) part of the chambers during the construction The chamber bodies have to be equipped with the necessary elements for position monitoring. The alignment readout+control should provide the operation of the system. The opto-geometrical data analysis provides the position data. Track-analysis can improve the final accuracy. 9/12/2018 GEM Alignment

Must be aligned to precision ~ spatial resolution Phase II Muon Detector Must be aligned to precision ~ spatial resolution 9/12/2018 GEM Alignment

Alignment elements on the chamber - recap Survey target holder (S) R φ S Z R-measurement Also sensors between the chambers and the base-plate are considered (z-measurement) φ-measurement The total number of align. elements per chamber and their locations are still under discussion 9/12/2018 GEM Alignment

Study with simplified model Survey targets Distance sensors A s the first step a simplified arrangement (see on the picture) has been studied to gin experience with such a system. The „chambers” contain survey targets and a pair of distance sensors on both edges. The model seems to work and converge to correct results. The next step is to describe the real system and substitute the survey measurement by the R and Z measurements. The opto-geometrical modelling will give the final answer to the question of the achievable alignment precision and helps to optimize the configurtion of the alignment elements on the chambers (super-chambers). 9/12/2018 GEM Alignment

Calibration of the readout boards - 1 Readout board of the long chamber (strips on the back side) R-sensors Phi-sensors Sensors on the readout board of the long chamber

Fiber Bragg Grating (FBG) Concept TEMPERATURE CHANGE Thermal expansion for Termo-optic effect for STRESS Where: neff is the effective refractive index of the fiber, Λ is the grating pitch and λB is the reflected Bragg wavelength. Elasto-optic effect for Direct Strain for 9/12/2018 GEM Alignment

Fiber Bragg Grating (FBG) Concept STRAIN AND TEMPERATURE Sensitivity : FBG Spectral Response (Temperature) T FBG SPECTRAL RESPONSE: Temperature Shift Temperature Sensitivity ≈10pm/°K @ λB=1550nm 9/12/2018 GEM Alignment

Fiber Bragg Grating (FBG) Concept STRAIN AND TEMPERATURE Sensitivity: FBG Spectral Response (Axial Strain) ε FBG SPECTRAL RESPONSE: Axial Strain Shift Strain Sensitivity ≈1pm/με @ λB=1550nm 9/12/2018 GEM Alignment

Temperature (T) sensor The sensor Two FBGs in a sensor: Strain (S) sensor Temperature (T) sensor Glued under tension Glued under tension Optical fiber Glued with no tension

Sensor on the readout board 17mm x 50mm cutout requested on the GEB for long chambers The sensor holder (bracket) glued on the readout board The sensor fixed to the bracket after the GEB installation 9/12/2018 GEM Alignment

Mechanical design 9/12/2018 GEM Alignment

LINEAR MOTOR DRIVES & RAILS CAMERA LINEAR MAGNETIC ENCODER GEM-PLATE INTERCHANGEABLE BASE-PLATE LINEAR GUIDE OPTICAL TABLE 9/12/2018 GEM Alignment

POSITIONONG BRACKET 9/12/2018 GEM Alignment

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Positioning Bracket Reference point 9/12/2018 GEM Alignment

Reference point of Sensor Reference Edge Bracket 9/12/2018 GEM Alignment

3 4 2 1 Measuring and technological order Determination of the inner reference points from the outers with coordinate measuring system. (Calibration of the base plate) Optometric check of the base plate with the designed measuring and bonding system. Fixation of sensor brackets onto the base plate GEM plate bonding to brackets Determination of the position of strips from the outer references with optometric method. Calculation of the positions of strips from the bracket’s references 3 4 2 1 9/12/2018 GEM Alignment

Scanning table in the lab 9/12/2018 GEM Alignment

Displacement Sensor dY dX Force(N) Fiber sensor Fixed side 9/12/2018 GEM Alignment

Displacement Sensors 9/12/2018 GEM Alignment

Displacement sensor Force Spring Sensor Head 9/12/2018 GEM Alignment

Displacement Sensor 9/12/2018 GEM Alignment

Displacement Sensor 9/12/2018 GEM Alignment

Displacement Sensor 9/12/2018 GEM Alignment

Slice test chamber 9/12/2018 GEM Alignment

Sensor – finite element analysis 5mm here 20 micrometer here 9/12/2018 GEM Alignment

Slice test chamber with Alignment sensors Alignment sensor body without spring (for reference measurement) ST2 ST1 Alignment sensor bracket for R sensor Alignment sensor body with spring ST3 ST4 9/12/2018 GEM Alignment

Slice test chamber in CMS Chamber name where the alignment sensor is installed: SCL-01 super chamber Barcode on patch panel: GE1/1-SCL-001 / 3063000110011000001 Name on chimney: GEII-VII-L-CERN 0002 (Top chamber) This chamber is installed on position YE-1 GE1/1/28 Continuous data taking and monitoring of the peaks during sensor installation on chamber and also before and after the installation of the chamber in P5. As soon as the final optical cable installed the chamber connected to the FOS readout optical system. Since then it is included in the FOS DCS system. Each peak on this spectrum represents either a strain (distance) sensor or a temperature compensator sensor 9/12/2018 GEM Alignment

sensors are not calibrated! Sensor behaviors during the first magnet ramp up 2017.05.05-07 sensor response vs. magnetic field sensors are not calibrated! ST3S and ST4S are the strain sensor part and they equipped with spring and the temperature change is compensated 2017.05.05. 2017.05.06. 2017.05.07. 2017.05.08. ST3S sensor show correlation with magnetic field while ST4S not very much ST3S and ST4S show correlation something witch is induced by a temperature change (see next slides) 9/12/2018 GEM Alignment

sensors are not calibrated! Sensor behaviors during the first magnet ramp up 2017.05.05. sensor response vs. magnetic field sensors are not calibrated! ST3S and ST4S are the strain sensor part and they equipped with spring and the temperature change is compensated 2017.05.05. 2017.05.06. Magnified view, clear correlation of ST3S with magnetic field 9/12/2018 GEM Alignment

sensors are not calibrated! Sensor behaviors during the first magnet ramp up 2017.05.05-07 sensor response vs. LV VFAT status sensors are not calibrated! ST3S and ST4S are the strain sensor part and they equipped with spring and the temperature change is compensated LV VFAT ON ~0.1nm Magnetic field is stable in this period LV VFAT OFF 2017.05.05. 2017.05.06. 2017.05.07. 2017.05.07. ST3S and ST4S sensors show correlation with the LV switch on of the chamber  heat dilatational movement between chambers This is Δλ = ~0.1nm  9/12/2018 GEM Alignment

ST3S sensor delta 0T vs 3.8T (LV ON) comparison sensors are not calibrated! ST3S and ST4S are the strain sensor part and they equipped with spring and the temperature change is compensated ~0.1nm 2017.05.05. 2017.05.06. 2017.05.07. 2017.05.08. ST3S sensor response to magnetic field: Δλ = ~0.1nm  9/12/2018 GEM Alignment

Observed movements of the chambers ST3 ST4 X magnetic field response heat dilatation of the chambers Chambers fixed with screw in outer R Chambers fixation is a pin in a rail in inner R 9/12/2018 GEM Alignment