1. ALICE-TRD gas system 1/4/2015R. Guida PH-DT-DI1

2. TRD gas system Few numbers:  Total number of modules/racks: 20 (max leak rate certified at construction 0.1 l/h per rack)  Total pipe length: 2.5 km  ~ 400 welds  Gas connections/connectors: ~1200  Safety release valves: 22 (gas system) + 2 (gas supply) Budget considerations:  Gas “value” in the detector & gas system: ~ 500 kCHF  Gas “value” just in the gas system high pressure: ~ 40 kCHF  Gas “value” in the Xe gas supply (1 cylinder): ~ 100 kCHF 1/4/2015R. Guida PH-DT-DI2

3. TRD gas system 1/4/2015R. Guida PH-DT-DI3 X i.e.: 80 kCHF/h i.e.: 30 kCHF/h X A different perspective:

4. Failure risk evaluation 1/4/2015R. Guida PH-DT-DI4

5. Actions 1/4/2015R. Guida PH-DT-DI5  Standard maintenance (as for all LHC gas systems)  Upgrades/Consolidations are needed. Example: ▫New Xe recuperation module (2012): ∙30 kCHF (i.e. 2 m 3 Xe) paid by PH-DT-Gas Service using M&O ∙Improved Xe recuperation  Follow-up after last incident: ▫Investigate the possibility to remove the safety valves ∙in the input of the gas distribution racks (200-300 mbar set value, indeed chambers already break at 2 mbar) ∙in the purifier module by reducing the purge gas pressure and adding the safety on purge and regeneration gases ∙in the exhaust module  discussion ongoing (timescale: ~ months including implementation)

6. Actions 1/4/2015R. Guida PH-DT-DI6  Follow-up after last incident: ▫Reduce mixture loss due to the purifier changeover ∙New moisture analyser to be validated with respect to potential ageing effects ∙Pump to be used in the purifier to be validated with respect to potential ageing effects ∙Modification in the purifier operation sequence  Work ongoing (timescale: ~ months depending on results) ▫Install weighting scale for Xe  Discussed with EN-MEF (waiting for timescale and cost estimate) ▫Different procedure for Xe supply ∙Connect only cylinder with Xe gas (max 1 m 3 )  To be discussed with detector experts  Monitoring tools available since beginning (gas flow + all parameters available through pvss and DIP exchange)

7. Conclusions 1/4/2015R. Guida PH-DT-DI7  Follow-up of all action proposed  General consideration: ▫The amount of Xe can justify investment (beyond standard M&O) to secure the Xe-capital