MDI alignment progressThe pre-alignment of the QD0’s

Niels van Bakel, Bram Bouwens, Hubert Gerwig, Lau Gatignon,Harry van der Graaf, Henk Groenstege, Joris van Heijningen, Jan Koopstra,Helene Mainaud Durand,, Richard Rosing, Vivien Rude CERN, Nikhef

IWAA 2012Fermilab,

Sept 13, 2012

X

Y

X

Y

X

Y

Alignment of two objects:- omit Z- omit rotZ

Measure:- translation X- translation Y- rotX-rotY

-Equivalent to-4 points (X,Y)

Momentum Measurement of chargedparticles in the L3 experiment:Chamber Position Monitoring

• Lorentz Force:• Track Curvature measurement

Detector

Muon Particle Track

Detector

Detector

Direct measurement: two anti // Rasniks:

light source + image sensor

lens

… would only require path of sight of 20 mm2….…. along beampipe…..!

Monitor X,Y of (both) QD0 end ref’s with respect to RR(with Rasniks)

to be calibratedon 3D measuring machine

Rasnik Lines-of Sight

spokes

Reference Ring RR

Spoke

- length 3.5 m;- has only one function: to transfer radial position better than 1 μm

Material: Zerodur: thermal expansion coefficient < 0.2 x 10-6

Alignment is NOT influented by:

- (common) deformation of RRs (sag, spoke load)- temperature of individual RR- (common) deformation of spoke wheel (spoke weight compression)- temperature of individual spoke wheel

Spoke tip on RR side: contact definition < 0.1 μm

Steelball Zerodur rod (6 mm x 6 mm x 3500 mm

spoke support tube: flexo suspension

Inner spoke detailOuter spoke detail

Precision ringQD0 support tube

Volume reserved for support plate of Rasnik/Rasdif

Radial retraction for endcap opening

1983: 4QD Red Alignment System Nikhef (Rasnik)

1993: CCD Rasnik

2003: RasDif: long distance

Comparison Stretched Wire Systemversus RasDif (TT1)

RasChain: interconnected Rasnik systemsfor basic CLIC units of 2010 mm

MDI/QD0 alignment: vibrations

- new (green) semiconductor lasers- shielding- image analysis software

diffraction plate simulated measured

Thermal shielding of light path