Lab Activities: Chamber Baking & Mixing Station Flushing Claudio Curtis Dan PPS meeting 22 June, 2011

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 2 System Overview Three heating coils: one per flange plus a central with two power lines controlled by a temperature sensor in the bottom flange Chamber gas input line Chamber gas output line Vacuum pump

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 3 The First Run The temperature sensor controlling the power to the heating coils is located in the bottom flange close to the connectors, around two inches from the edge. The power absorbed by the central heater (attached to the thin body) is reduced respect to the ones on the flanges (massive) Curtis made a first baking (and pumping) with a limit temperature set to 70°C Claudio started a second baking up to 100°C, but the coils went well over that threshold, especially the central heater which is in contact with less material, going over 200°C. The T-sensor inside the chamber (previously not read out) showed 137°C!

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 4 The Problem The location of the sensor –it does not reflect the temperature of the central coil –it is too far even from the flange heater: long delay between the coil reaching the target T and the sensor detecting it, causing the power to be applied for too long The central part of the heating system is the one really responsible for the internal overshoot: its temperature swings by over 50°C between when the power is on and off To avoid to go above the target temperature for the weekend the threshold was set to 75°C, corresponding to an internal T~100°C

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 5 Sensor Position BEFORE  AFTER

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 6 The Solution T-sensor moved: still on the bottom flange, bit closer much to the edge. Curtis was machining the new hole (with two additional holes+screws to help separating the flange from the body) Claudio dismounted the chamber and inspected for eventual damages: many components and cables were assured up to 125°C. At the opening no smell of burned parts, eventually solvent smell (form cable outgassing, Peter). Everything tested OK: –Cable connectors could lose their spring ability at high T –The motor stage cables –The RO and HV PC board connectors

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 7 New Protocol Heating in steps (it takes ~3h): –with the whole system on set the target to T final -10°C –wait for thermal equilibrium –unplug the 2 power lines for the central heater –set T final The difference from the temperatures inside and at the sensor in the new location is less than 3°C: set to T~100°C, inside measured T~97°C (and the flange heater are below 106°C) The control is now so much reliable that we could leave the central part on: to be tested

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 8 Flushing the Mixing Station Procedure used to flush with Ar only the mixing station 1)If the chamber is connected (after baking) closed the (cooling off) chamber valves + the vacuum valve (#29) 2)the Ar bottle mounted with a gas heater element plus a a gas flow meter is attached to a tube with a quick Swedgelock connector going to the front panel valve #57 (input without MCF)

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 9 Flushing the Mixing Station (2) 3)Turn on the gas heater by plugging the power cord 4)Attached a (plastic) pipe to the Exhaust valve (back of the pane) going out of the window 5)The gas flow controls (#41 for the exhaust and 59 for the input line) are fully opened and the flow is regulated by the valve at the bottle (this is simply one way to operate). For a R-2-15-AAA Brooks Flow Meters with V tube and stainless steel ball the full flow is 1/8 liter/min. The volume of the gas piping on the gas panel is estimated (to be verified) ~ 1/8 liter, so the full flow is around one volume per minute 6)Wait for the Ar to get to at least atmospheric pressure before opening the exhaust valves #39 (Exhaust) and #41 (Control flow) 7)Fully open valves 39 and 41 and regulate the pressure at the bottle. Be sure to remain above atmospheric pressure (avoiding air back flow)

22 Jun 2011 UoM Lab Activities - Claudio & Dan & Curtis 10Plans Small gas leak ~1 mTorr/sec close to 3 T’s (hard to know which one) spraying He around while the He leak detector was running Once the mixing station is ready (now), re-connect the vacuum pump and open the valves to evacuate the gas used to purge the gas mixing system (mixing station and chamber input gas line) Finally attach the ArCO 2 93:7 to the input valve #57 (without MCF) and fill the chamber at 500 Torr, getting ready to start looking at the signal with scope or DRS4