Background information

Monitoring R&D issues for the relative gain calibration and monitoring system for the calorimeters and possibly other detector systems.
Calibration Specifications Table for BCAL, FCAL, TOF and START
Oct 26, 2010 Calibration/Monitoring minutes
Nov 23, 2010 Calibration/Monitoring minutes

Tentative Agenda

Attendees: Christina, George V., Pavlos (Athens), George L., Zisis (Regina)

Linearity: Elton mentioned possible tests for the SiPM linearity.
1. Each array has around 50,000 pixels which at 25% QE correspond to 200,000 photons. A significant loss of linearity will undoubtedly be associate with a serious degradation of the unit that should clearly manifest itself in its overall operation.
2. Linearity should be tested on the bench, prior to installing SiPMs on the modules. After that, there is no need to monitor it, however, the LEDs can be driven at different biases if we so desire. Linearity checks will probably not be done well with only 3x or 4x the light anyway. Much more would be needed.
3. Also, breadth of fibre spectrum would complicate extraction of linearity.
4. We need to decide whether online monitoring of linearity is needed.
Mechanical: Mechanical issues of the fibre concept are a serious concern in many areas:
1. Mounting/installing. Careful calculations of fibre lengths are required. The radius of curvature of each fibre must stay fixed once installed or the light losses vary.
2. Maintenance. Any breaks will be hard to replace. The light guide will need to be drilled in situ, hole cleaned and fibre epoxied. All in situ once the BCAL is installed.
3. Cost is significant for either single fibres or fused ones with a single/common input and many (16) outputs.