1 June 2002 1 June 2002 Workshop on b/tau Physics at LHC, Workshop on b/tau Physics at LHC, Helsinki Helsinki 1 CMS Tracker CMS Tracker Hardware Alignment Hardware Alignment Goals of TK hardware alignment Concept General layout Internal TK alignment External TK alignment (LINK) Hardware Conclusions A.Ostaptchouk, RWTH-Aachen A.Ostaptchouk, RWTH-Aachen
CMS Tracker Hardware Alignment. A.Ostaptchouk, RWTH-Aachen. Goals of TK hardware alignment Concept General layout Internal TK alignment External TK alignment (LINK) Hardware Conclusions. Goals of Hardware Alignment. External alignment: 100 m measurement of - PowerPoint PPT Presentation
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1 June 20021 June 2002 Workshop on b/tau Physics at LHC, HelsinkiWorkshop on b/tau Physics at LHC, Helsinki 1
1 June 20021 June 2002 Workshop on b/tau Physics at LHC, HelsinkiWorkshop on b/tau Physics at LHC, Helsinki 2
Goals of Hardware Alignment Goals of Hardware Alignment
Internal alignment: 100 m measurement of Si-module relative positions for track pattern recognition (recent H.Voss and B.Schwering results: 1000 m ! t.b.c.) 10 m monitoring of Si-module positions stability for track parameter reconstruction
External alignment:
100 m measurement of TK position w.r.t. MS 20 rad measurement of TK orientation w.r.t. gravity both for joint TK+MS track fit
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Concept of Hardware Alignment Concept of Hardware Alignment
1. No dedicated optical sensors Collimated laser beams with ~ 1060 nm produce signals directly in the TK Si-modules
2. No external reference structures All the elements of the alignment system are mounted directly on the TK parts
3. No precise positioning or aiming of beam collimators Number of measurements redundant enough to reconstruct detector positions without knowledge of laser beam initial parameters
4. Minimal impact on the TK layout and production technology The effected tracker parts are as uniform as possible
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General Layout of Alignment System General Layout of Alignment System
Internal alignment:
eight Ray 2 and eight Ray 3 beams per TEC align forward wheels, monitor 50% of petals
eight Ray 4 beams align end-caps and barrels w.r.t. each other
External alignment:
six Ray 1 beams per TEC align TK w.r.t. MS
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Track residuals in End-CapsTEC: before applying alignment corrections RMS = 1.1 mm TEC: after applying alignment corrections RMS = 27 m
Track residuals in BarrelsTOB: after applying alignment corrections RMS = 49 m TIB: after applying alignment corrections RMS = 85 m
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orientation of TK w.r.t. gravity is determined by precise measurement of TEC back-disc orientation w.r.t. TEC wheels and gravity It requires back-disc instrumentation with Si-modules at radius of ray 2 and tiltmeters
Concept of External Alignment System
position of TK w.r.t. MS is determined by precise measurement of continuous laser beam positions inside TK and MS (LINK)
On TK side it requires: 2D-sensors on TEC petalsperiscopes inside TEC back-disc
is defined by measurements of 6 laser beams (ray #1) inside the TK volume:
• r-positions of laser beams w.r.t. TKr 20 m• -orientations of laser beams w.r.t. TK 20 rad (characteristic distance between TK and MS L 5 m )
TK-Gori - precision of TK orientation w.r.t. gravity
is determined by two independent factors:• back-disc orientation w.r.t. TEC (measured by 8 laser beams, ray #2)BD-TEC 10 rad • back-disc orientation w.r.t. gravity (measured by 4 tiltmeters, requires their calibration w.r.t. back-disc fiducials)BD-G 10 rad
TK-G
ori = BD-TEC BD-G 20 rad
TK-MS
pos = r L 100 m
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Hardware:Hardware:Experience from AMS-1 Experience from AMS-1
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Hardware:Hardware:Experience from AMS-1 Experience from AMS-1
Si-module transparency (@ = 1064 nm) is about 20 – 25 %Beam spot position resolution is better than 10 m
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