ECAL quality assurance and construction
(Chris Booth, Tim Haycock, Rangeen Salih, Lee Thompson, Greg Ward, Mark Ward)
Following the successful completion of the so-called "downstream ECAL" or DsECAL in
2008 the attention of T2K-UK has, in 2009, now turned to the construction
and commissioning of a further 12 ECAL modules that will jointly
form the Barrel and P0D ECALs in the T2K ND280 detector.
Collectively these 12 ECAL modules will be constructed from a total of 16500 scintillator bars with lengths from 1.5m to 3.8m, the Sheffield T2K has overall responsibility for cutting all of these bars and performing both mechanical and optical quality assurance tests before they are distributed to T2K UK groups (including Sheffield) to be assembled into ECAL scintillator-lead layers. The picture shows the arrival of the first batch of 3000 scintillator bars in March 2009.
Mechanical Quality Assurance
Scintillator bars are cut to approx. 0.1mm accuracy in length and then a number of mechanical QA checks are made before the bar is accepted for assembly, these checks include:
- Horizontal and vertical dimensions via 'Go' and 'NoGo' gauges
- Extruded hole diameter measurements
- Overall bar integrity including TiO2 coating inspection
- Confirmation that the extruded hole is clear along the full length of the bar
Optical Quality Assurance
The light yield of a small fraction of all bars is carefully measured using a cosmic ray muon telescope. The light yield response to these MIPs (minimum ionizing particles) at a fixed point along the scintillating bar is determined. Typical results from these studies can be seen in the figure below.
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