Detector Installation and Alignment

Arrangement of modules

Position (ordered by increasing z) Module ID Near Bottom Passage 08-4L Near Bottom QRL 07-4L Near Top QRL 10-4L Near Top Passage 09-4L Far Bottom Passage 02 Far Bottom QRL 03 Far Top QRL 01 Far Top Passage 05

Alignment

Overview

• Initial definition of steps and requirements (Massi, BGV meeting #33)
• More drawings and consideration available in the detector installation procedure described by Nicolas and Paolo, see this page
• All BGV elements (chambers, detector support and modules) will be installed in the LHC plane, i.e. inclined with respect to the local horizontal plane. More details can be found here (Plamen, BGV meeting #47)
• In separate sections below are discussed:
  • Metrology measurements of single SciFi modules
  • Assembly and metrology of 2MAs
  • Survey alignment in the tunnel
• A draft document considering the various alignment steps: SciFi Alignment v2r7

Metrology of single SciFi modules

Metrology measurements were performed on each BGV SciFi module (10 in total). The primary goal was to determine the relative position of the alignment targets on the module and the module edges. This also allowed to compare with the design and to check for damage parts and fibres.

Mechanical drawing indicating the nominal BGV module dimensions and distances to the alignment targets. (Florian, Oct 2014) pdf version available here

The metrology measurements were performed by Dominique Pugnat (CERN Metrology). Details can be found in the following presentations:

• First metrology of one SciFi module, definition of procedure (BGV meeting #42)
• Results from measurements of 5 modules (BGV meeting #45)

Metrology reports and data

• The original reports produced by Dominique Pugnat (EN-MME-MM) can be found here: https://edms.cern.ch/document/1432936/1. This EDMS document is restricted, access rights can be provided by Dominique
• There are major flaws in the original metrology reports: missing all data for module 05, missing ~half of the points for module 07, many instances of repeating/wrong measured points
• After some additional actions by Dominique, Valdir and Plamen, the complete set of measurements was produced
• The final measurement data used in the 2MA alignment studies is attached to this TWiki page in XLS and TXT format
• Module with re-glued stud: module 04
  • After the metrology the stud of this module was detached by accident and then re-glued. It was decided to keep this module as spare

Assembly and metrology of 2MAs

Procedure

Document by Paolo and Massi:

• final version (v2, 2015-04-08): docx

Document by Plamen:

• SciFi Alignment v2r7
• Goals and lab measurement procedure: see Section 3
• Sequence for the 2MA metrology ("protocol"): see Section 3.2
• Method based on FreeCAD to calculate the needed module sphere positions: see Section 5

Calculated position of spheres

2MAs position in BGV, module IDs, and sphere positions for metrology (using as input the single module metrology data).
Both Plamen's and Valdir's results can be used for the 2MA metrology (diff of positions of all corners and spheres is < 0.1 mm).
The files AlignSummary contain information about the modules alignment, e.g. angles of the modules faces and DOCA to the beam pipe.

2MA ID - Location	Module below	Module above	SW Aligned modules position			Files for Metrology
			Plamen	Valdir	Compare
1 - Far Bottom	02	03	Module02, Module03 AlignSummary	Module02, Module03	Module02, Module03	TMA #1
2 - Far Top	01	05	Module01, Module05 AlignSummary			TMA #2
3 - Near Top	09-4L	10-4L	Module09, Module10 AlignSummary			TMA #3
4 - Near Bottom	07-4L	08-4L	Module07, Module08 AlignSummary	Module07, Module08	Module07, Module08	TMA #4

2MA Metrology Reports

Measurements and module position adjustment

• Performed by Cyril Haerinck, with the support of Ahmed Cherif (CERN Metrology)
• 2MAs with ID=1 and ID=4: performed in week 35 2015
• 2MAs with ID=2 and ID=3: performed in week 45 2015
• About 2 days per 2MA (a bit more time needed initially to prepare tools and gain experience with the procedure)

Metrology reports

• EDMS (restricted access): https://edms.cern.ch/document/1537263
• The relevant files are attached to this TWiki page (see table below)

2MA ID - Location	Metrology Report
1 - Far Bottom	File
2 - Far Top	File
3 - Near Top	File
4 - Near Bottom	File

Comments

• The 2MA IDs correspond to the 2MA installation sequence given in the BGV detector installation procedure (P. Magagnin)
• A quick check showed that the distances between the 3 spheres in each module is slightly larger (~0.1 mm) than the values measured in the single module metrology
  • The suspicion is that the sphere holders were not fully inserted, although a push-in with a moderate force was attempted during the 2MA metrology. A possible (speculative) explanation is expansion of the modules' plastic part due to higher humidity
  • The modules were positioned such that the additional length between the two side spheres is equal (reminder: the reference position for each sphere was calculated from the single module metrology data)
  • A study is needed to evaluate the potential impact on the modules position

Survey alignment in the tunnel

Installation and alignment of the Intermediate Plates

• Nominal position of the alignment targets: LHCBGVDA0080
• Performed in Jan 2015. Photos can be found here
• Survey report provided by J-F Fuchs and P. Bestmann:
  • Original report
  • Annotated report -- provides additional info and comments on the results (text in red)
  • The Intermediate plates have tilt, but no slope. Do we want to install the modules with slope? (3.6 mrad)
  • The deviations nominal - measured are:
    • Smaller than 0.3 mm in the y (along beam) and z (vertical) directions. Therefore, we don't expect interference between Top and Bottom 2MAs (the nominal distance in the longitudinal direction is 2 mm)
    • Up to 8.5 mm in the x (horizontal) direction (the plate fixation includes one fixed point which does not allow perfect alignment in all directions). It should be possible to correct this when installing the 2MAs

Longitudinal position of modules

• Summarized in these slides (08/09/2014)