[Dsg-rich] Supplemental N2 supply for RICH

[Travel User]

Dear Marc and DSG,

Thank you very much for sending this e-mail out. 
As you have correctly written, an uninterrupted N2 supply is mandatory for the RICH thus I am sure that Denny and Bob will take as soon as possible the necessary actions in order to implement the secondary N2 supply.

Best regards

Patrizia

> On Sep 21, 2018, at 2:02 PM, Marc McMullen <mcmullen at jlab.org> wrote:
> 
> Hi Denny, Bob, Marco C. and Marco M.
> 
> As you are aware, the RICH detector requires an uninterrupted gas supply. The moisture content of the detector shell volume, which houses the Aerogel tiles, increases rapidly with the cessation of N2, as shown by the observations presented by Tyler Lemon (DSG RICH contact). The maintenance outage, to install the isolation valves (9/21), has presented us with information on just how much the humidity in the detector volume can change in just 27 minutes. Unfortunately, what cannot be measured is the amount of absorption into the tiles, or the efficiency degradation due to moisture.
> 
> What can be done is taking preventative measures to ensure the safety of the detector for future events. To that end, DSG has discussed the design and implementation of a secondary N2 supply. In previous discussions DSG and Hall B planned to use high pressure LN2 dewars to supply the detector during a planned outage. This would still be a viable solution for an outage lasting many hours or longer.
> 
> For unplanned outages or very short planned outages, a supplementary N2 circuit (see attached) developed by G. Jacobs and the DSG could use multiple high pressure N2 bottles in parallel. Gas flow can be triggered using a pressure controlled switch, and check valves will ensure the gas flows to the detector instead of back towards the standard N2 source.  DSG has already procured eight 255cf bottles of N2, which are currently located on the gas pad outside of the gas shed.  We have calculated 2 to 3 hours of gas per cylinder at the current flow rate (40Lpm).
> 
> Once this plan is approved, DSG can source all necessary components and provide diagrams. Hall B Engineering should evaluate the system for integration/installation with the current Hall B N2 system, and provide all required safety documentation/inspections (including Jlab pressure systems compliance). DSG can assist with installation, at the direction of the Hall work coordinator to ensure all Hall B/Physics work governance procedures are observed.
> 
>  With pre-assembly, planning, and coordination between Hall B and the DSG, work in the hall can be minimized so that installation can be completed in a short amount of time.
> 
> Regards,
> 
> 
> -- 
> Marc McMullen
> Detector Support Group
> 757-269-7738
> <RICH-N2-valve panel-REV2-AUTOCHANGE.pdf>_______________________________________________
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