Large prototype goals Endplate design P. Colas

General ideas We have to agree first on the goals to understand how to build the endplate We have to agree first on the goals to understand how to build the endplate The design should be as close as possible for GEM and Micromegas (requires regular common meetings), but no mix possible The design should be as close as possible for GEM and Micromegas (requires regular common meetings), but no mix possible A (small) space should be kept for digital pixel readout (EUDET contract) A (small) space should be kept for digital pixel readout (EUDET contract) The endplate should be a support for several pannels or tiles. The endplate should be a support for several pannels or tiles.

Goals (open for discussion) What it is: What it is: –Demonstrate feasability and performances of the real detector, in particular possibility to cover by modules and to obtain the target resolution and feedback –Study various solutions for amplification, pad geometry, electronics –Gain a long-term experience of running in real conditions –Study distortions (their effect and how to correct them) What it is not: What it is not:

Goals (open for discussion) What it is not: What it is not: –An apparatus to study in detail gas properties (smaller devices do better for this) –An apparatus for detailed aging studies (special devices will allow testing of various materials and gases in high radiation, already started at Saclay and NIKHEF)

Ion feedback in the LP Possibility to test the effect of the ‘ion sheet’ (at each beam crossing a fraction of the positive ions flows back to the cathode Possibility to test the effect of the ‘ion sheet’ (at each beam crossing a fraction of the positive ions flows back to the cathode What is the effect of such an ion sheet on the electrons drifting from a track? What is the effect of such an ion sheet on the electrons drifting from a track? This can be studied using an UV lamp (as NIKHEF’s Xe lamp) to produce photoelectrons on the foil. This can be studied using an UV lamp (as NIKHEF’s Xe lamp) to produce photoelectrons on the foil. How to do this in practice? UV window? Lamp in the gas volume? How to do this in practice? UV window? Lamp in the gas volume?

Optimization of the configuration With David Attié, we studied the possible configurations to have With David Attié, we studied the possible configurations to have –Identical (interchangeable) modules –Enough boundary configurations (some modules can be dummy, just carrying the right potential) Each ‘tile’ must have its own seal-ring (see Dan Peterson’s drawing)

Options for the Micromegas endplates Should try the latest kind of ‘bulk’ available at that time Most likely resistive foils have to be included