1. Xe leak status C. Garabatos

2. Leak story The maximum allowable leak rate corresponds to a loss of 10% of the total volume in one year – 0.3 l/h for the full system (0.5 l/h quoted in TDR) There has been a continuous effort to detect, quantify, find and fix leaks since the beginning of RUN1 – Several incidents lead to large losses (detector viscous leaks, leaky pressure regulator, back-up siphon effect, leaky pipe, leaky safety valves, recovery procedure) – RUN1: leak rate 1 l/h (2012-2013), including incidents – Found and fixed more leaks during LS1 1.04.2015I live in a world of... leaks2

3. Last incident: leaky safety valves 2 out of 14 safety valves in Distribution racks in CR5; leaks possibly related to manipulations for Kr calibration No pressure in this area when system stopped; 60 mbar in run Could be removed: ~1 bar vs. 0.2 bar; up to 3 interlocks plus the safety bubbler protect the chambers 1.04.20153I live in a world of... leaks

4. Current status Leak rate of order 0.1 l/h – more integration time is needed to better evaluate the current small leak rate – estimated contribution from detector: 0.08 l/h – similar contribution from purifier swapping 1.04.2015I live in a world of... leaks4

5. Next main leak: purifiers Due to H 2 O intake, purifier cartridges must be swapped every ~2 days Currently, each time the cartridge volume is vented out Plan: to pump volume back into system before regeneration –in progress 1.04.20155I live in a world of... leaks

6. Leak detection The gas system is closed; no gas is vented away except for leaks (and GC analysis) When the system needs gas, it injects from the mixer – if there is a new leak, the mixer injects more than usual Mixer data was manually exported from GCS and integrated locally –tedious and unreliable Action: import mixer data points into the TRD DCS and evaluate the leak rate; implement suitable alarms – in progress Action: monitor the pressure of the supply bottle (Van der Waals gas) Action: consider to install weighing scales in supply panel 1.04.20156I live in a world of... leaks

7. More action items Compress and inject remaining Xe from old cylinders -done Weigh each new Xe cylinder Revisit the necessity of several safety valves Install a new, non-ageing H 2 O sensor – possibility to optimise purifier cycle Note: every recovery and filling leads to gas losses of about 1 m 3 Xe each – this must be included in the budget 1.04.20157I live in a world of... leaks