Experimentelle Physik 5 21Nov2013 Experimentelle Physik 5 (Timing - - PowerPoint PPT Presentation

Experimentelle Physik 5

21Nov2013

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(Timing of) light propagation in fibre

• 2011
• First simple simulation of scifi in Geant4 to evaluate time distribution of photons

arriving at fibre end

• 2012
• Measurement of timing in 2.5 m fibre with and without mirrored end
• 2012 and 2013
• More sophisticated simulation of fibre in Geant4
• more information used and stored, higher flexibility, …
• studies beside timing possible
• Simulation results used by electronics development group (→ choice of

integration time window, spill-over)

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SiPM Studies

• 2010
• Irradiation of SiPM arrays with protons in Nice and Munich
• 2011 and 2012
• In situ irradiation in LHCb cavern (arrays and single channel SiPM, 2012 cooled

and non-cooled)

• 2013
• Further measurements with irradiated sensors (annealing test) and data

evaluation

• Measured quantities and parameters
• LED and dark spectra → gain, relative pde, cross-talk, pedestal position and

width

• Dark current, dark count rate, dark count rate distribution → after-pulse

probability (only possible with small dark count rates)

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Fibre Quality Control

21Nov2013

Light guidance test Diameter check Loose spools for speed control of fibre spools

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Fibre Quality Control

21Nov2013

• 3 Spools tested, so far only diameter
• About one big blob (>300 mu) per km
• Several small blobs (between 270 mu and 300 mu)
• Next steps:
• Optimize Quality Control with SiPM
• Compare the data with standard light

attenuation measurements

• Therefor build a dark box
• Simplify the handling

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• Winding on threaded wheel „Aachen style“, but
• Wheel is fixed, positioning spool moves
• Tension and feeding spool speed controled by loose spool
• Glue is placed by hand after each layer
• Produced three good 7-9cm mats
• Quality and amount of human influence necessary depends on „blobiness“ of

fibre

• Winding speed: 10s/3m = 0.3m/s
• One is in Heidelberg, one was cut in pieces for quality analysis, one is left
• Produced one 14cm wide mat
• Winding speed: 5s/3m = 0.6m/s
• Several different problems due to different reasons

Winding

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• Gained some experience with glueing broke fibre in a layer -> might be

possible

• Online fibre laying check with video

Winding

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• Stone table with rail and milling

head installed

• Trying different parameters for best

cut

• Parallel cut to fibres will not be

possible until alignment is implemented

Cutting

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Fibre Mat Quality Control

• Finished:
• check the initial straigtness of the mat with an

alignment wire -> mat to flexible

• Ongoing:
• optical check of crosssection (fit circles)
• See next slides
• Planned:
• check light guidance (compare layers)
• Test with radioactiv source (long term)

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Fibre Mat Quality Control

• Cut a mat in 2.5cm long pieces (30 pieces)
• Take a picture with high resolution (scanner, 9600 dpi)
• C++ code for finding circles in picture (OpenCV)
• As result you (will) get the radii and the centers of the detected circles in

the picture

• Check the uniformity and straigtness of the mat

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Fibre Mat Quality Control

• Planned for the Futute: analysis with a microscope
• Detectes circles automatically and is able to give you different parameters
• For example: radius, position, circularity, ...

21Nov2013