Detector Installation and Alignment

Arrangement of modules

(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



  • 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:

Metrology reports and data

  • The original reports produced by Dominique Pugnat (EN-MME-MM) can be found here: 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


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
Module02, Module03 Module02, Module03 TMA #1
2 - Far Top 01 05 Module01, Module05
    TMA #2
3 - Near Top 09-4L 10-4L Module09, Module10
    TMA #3
4 - Near Bottom 07-4L 08-4L Module07, Module08
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

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


  • 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)
Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf 2014_09_08-SciFi_Modules_Absolute_Position.pdf r1 manage 522.5 K 2015-03-24 - 11:20 PlamenHopchev  
PNGpng 2MA_Paolo_ID.png r1 manage 82.0 K 2015-09-22 - 15:30 PlamenHopchev  
Texttxt 2MA_modules_02_03_data_of_module02.txt r1 manage 1.5 K 2015-08-18 - 13:38 PlamenHopchev  
Texttxt 2MA_modules_02_03_data_of_module03.txt r1 manage 1.4 K 2015-08-18 - 13:38 PlamenHopchev  
Texttxt 2MA_modules_07_08_data_of_module07.txt r1 manage 1.5 K 2015-08-18 - 13:38 PlamenHopchev  
Texttxt 2MA_modules_07_08_data_of_module08.txt r1 manage 1.4 K 2015-08-18 - 13:38 PlamenHopchev  
PDFpdf BGV_MODULE_911100_METROLOGIE_01--Rotated.pdf r1 manage 85.5 K 2015-04-13 - 17:44 PlamenHopchev  
PNGpng BGV_MODULE_911100_METROLOGIE_01--Rotated.png r1 manage 329.1 K 2015-04-13 - 17:44 PlamenHopchev  
PDFpdf BGV_SciFi_Aligment_v2r7.pdf r1 manage 2661.2 K 2015-08-24 - 09:26 PlamenHopchev  
PDFpdf BGV_TMA1_FarBot_02_03.pdf r1 manage 90.1 K 2015-10-25 - 09:14 PlamenHopchev  
PDFpdf BGV_TMA2_FarTop_01_05.pdf r1 manage 89.9 K 2015-10-25 - 09:14 PlamenHopchev  
PDFpdf BGV_TMA3_NearTop_09_10.pdf r1 manage 90.0 K 2015-10-25 - 09:14 PlamenHopchev  
PDFpdf BGV_TMA4_NearBot_07_08.pdf r1 manage 90.5 K 2015-10-25 - 09:14 PlamenHopchev  
Unknown file formatdocx Detector_alignment_in_metrology_FINAL_VERSION.docx r1 manage 710.6 K 2015-08-19 - 14:15 UnknownUser  
PDFpdf EDMS_1537263_-_DECTECTEUR_BGV2MA-1_avec_spheres_ref.pdf r1 manage 184.1 K 2015-09-22 - 14:57 PlamenHopchev  
PDFpdf EDMS_1537263_-_DECTECTEUR_BGV2MA-2.pdf r1 manage 186.2 K 2015-11-06 - 10:05 PlamenHopchev  
PDFpdf EDMS_1537263_-_DECTECTEUR_BGV2MA-3.pdf r1 manage 186.2 K 2015-11-06 - 10:05 PlamenHopchev  
PDFpdf EDMS_1537263_-_DECTECTEUR_BGV2MA-4_avec_spheres_ref.pdf r1 manage 184.4 K 2015-09-22 - 14:57 PlamenHopchev  
PDFpdf LHCBGVDA0080.pdf r1 manage 1460.6 K 2015-07-15 - 10:10 PlamenHopchev  
Compressed Zip archivezip r1 manage 16.4 K 2015-07-15 - 09:29 PlamenHopchev  
Compressed Zip archivezip r1 manage 536.4 K 2015-07-15 - 09:29 PlamenHopchev  
PDFpdf SURVEY--Report_BGV_alignement_plaques-TERRAIN_Fini.pdf r1 manage 226.7 K 2015-07-15 - 09:51 PlamenHopchev  
PDFpdf SURVEY--Report_BGV_alignement_plaques-TERRAIN_Fini_Annotated.pdf r1 manage 245.1 K 2015-07-17 - 11:19 PlamenHopchev  
Texttxt SWAligned_Bot_2MA_01_05_0.txt r1 manage 2.0 K 2015-10-25 - 09:08 PlamenHopchev  
Texttxt SWAligned_Bot_2MA_02_03_0.txt r1 manage 2.0 K 2015-08-18 - 13:46 PlamenHopchev  
Texttxt SWAligned_Bot_2MA_07-4L_08-4L_0.txt r1 manage 2.0 K 2015-08-18 - 13:46 PlamenHopchev  
Texttxt SWAligned_Bot_2MA_09-4L_10-4L_0.txt r1 manage 2.0 K 2015-10-25 - 09:08 PlamenHopchev  
Texttxt SWAligned_Top_2MA_01_05_0.txt r1 manage 2.0 K 2015-10-25 - 09:08 PlamenHopchev  
Texttxt SWAligned_Top_2MA_02_03_0.txt r1 manage 2.0 K 2015-08-18 - 13:46 PlamenHopchev  
Texttxt SWAligned_Top_2MA_07-4L_08-4L_0.txt r1 manage 2.0 K 2015-08-18 - 13:46 PlamenHopchev  
Texttxt SWAligned_Top_2MA_09-4L_10-4L_0.txt r1 manage 2.0 K 2015-10-25 - 09:08 PlamenHopchev  
Texttxt TMA_ALIGNMENT_DATA_01_05.txt r1 manage 2.9 K 2015-10-25 - 09:26 PlamenHopchev  
Texttxt TMA_ALIGNMENT_DATA_02_03.txt r1 manage 2.9 K 2015-10-25 - 09:26 PlamenHopchev  
Texttxt TMA_ALIGNMENT_DATA_07-4L_08-4L.txt r1 manage 2.9 K 2015-10-25 - 09:26 PlamenHopchev  
Texttxt TMA_ALIGNMENT_DATA_09-4L_10-4L.txt r1 manage 2.9 K 2015-10-25 - 09:26 PlamenHopchev  
Texttxt mod_02_03_data_of_02.txt r1 manage 6.1 K 2015-08-18 - 13:53 PlamenHopchev  
Texttxt mod_02_03_data_of_03.txt r1 manage 6.1 K 2015-08-18 - 13:53 PlamenHopchev  
Texttxt mod_07_08_data_of_07.txt r1 manage 6.1 K 2015-08-18 - 13:53 PlamenHopchev  
Texttxt mod_07_08_data_of_08.txt r1 manage 6.1 K 2015-08-18 - 13:53 PlamenHopchev  
PNGpng modules_id_arrangement_v3b.png r1 manage 1570.9 K 2015-11-06 - 11:35 PlamenHopchev  
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