Why Micromegas ?

1. Why Micromegas? Jörg Wotschack

2. In short Single device for trigger, precision & 2ndcoordinate • Best performance • Simplest and most elegant trigger scheme • Safest for high rates • Most ‘friendly’ operating parameters (gas, HV) • Easiest to build, commission, install, and maintain • Lowest costs for production, operation, and maintenance Jörg Wotschack

3. Performance • Best space resolution • Only detector(of those proposed) that achieves a double track resolution of O(mm) • Finest granularity, therefore superior track reconstruction • Track vectors in single plane, a very powerful tool for pattern recognition and track reconstruction • Lowest sensitivity to cavern background (1/3 x MDT), another factor in favour of MMs Jörg Wotschack

4. Trigger • Trigger granularity is a single strip, i.e. 0.5 mm (out of 64 strips or 32 mm) • Four strip addresses per chamber plane are transmitted to USA15 every bunch crossing (25 ns) • Trigger decision by track matching algorithm in look-up table or FPGA • Proposed scheme avoids processing on SW other than in front-end chip • the trigger info is routed through the same fibre that is used for the data transmission to USA15 • trigger processing electronics is accessible during running (in contrast, the TGC and RPC concepts need an on-chamber majority decision; electronics not accessible during a full year) • Look-up memories or FPGAs can be reprogrammed if required Jörg Wotschack

5. Safe a high rates • Far from critical rates, even at 15kHz/cm2 • Large safety margin if LHC luminosity would go up further or background rate increases • MMs are still operating fine at MHz/cm2 and above (trigger concept would need to be adapted, e.g. more fibres/plane in high rate regions) • No ageing observed in high-rate X-ray and neutron exposures (10-20 years of sLHC) • Long-time behaviour of resistive strips needs to be demonstrated; same holds for RPCs and TGCs for resistive coatings Jörg Wotschack

6. Operation and maintenance • MMs require only half of the services that are needed by the other proposals • No on-chamber trigger processing electronics • Most ‘friendly’ operating parameters • Low HV (500 V) • Inert and cheap gas, Ar:CO2 (93:7), at atmospheric pressure • Lowest costs for operation and maintenance Jörg Wotschack

7. Construction & commissioning • Industrial production of MMs (employing commercial equipment) using PCB technology • Assembly, commissioning, and testing in/by collaborating institutes. • Simple mechanics & assembly • No glueing of components, easy opening and replacement of detectors if required • Most cost effective of the three proposals • half the number of chambers, half of the electronics • half of the manpower and infrastructure for testing and commissioning Jörg Wotschack

8. In conclusion Single device for trigger, precision & 2ndcoordinate • Best performance • Simplest and most elegant trigger scheme • Safest for high rates • Most ‘friendly’ operating parameters (gas, HV) • Easiest to build, commission, install, and maintain • Lowest costs Why would one not choose micromegas ??? Jörg Wotschack