[Dsg-rich] decrease Nitrogen flow to see how RICH humidity is affected

[Marco Contalbrigo]

Hi Tyler,
today we set up a cosmic run that will run the whole night. The
electronics is ON, the cooling air is at maximum flow and is not
fully dry. We did not reduce the nitrogen flow to be able to keep
a steady humidity state, although at values larger than the ones
obtained with the only N2 flow.

We can not run the nominal 20+20 nitrogen slm, except at the
beginning of a new dewar, when it develops high pressure. At the
same time, a sizeable (not quantified but apparently significant)
fraction of the liquid N2 is exhausted directly into the air,
likely due to the pressure and flow limitations in the distribution
line. This is a reason of concern as it may impact the N2 reserve
more than a higher but controlled RICH flow.

Last night, the RICH humidity kept decreasing with N2 flow
reducing from ~38 to ~34 slm and NO air cooling. Thus we
definetely do not need 40 slm flow to keep dry the RICH,
when electronics and cooling are OFF.

Ciao, Marco.

On Thu, 21 Dec 2017, Tyler Lemon wrote:

> Hello Marco Contalbrigo,
> 
> Today, it would be good to do a test overnight to see how RICH's internal humidity
> is maintained if its nitrogen flow is decreased.
> 
> RICH is now in a steady state with its internal humidity at or below ~3%. We could
> lower the nitrogen flow from ~35 L/min to ~25 L/min to see how, if at all, the
> internal humidity changes overnight.
> 
> If we are able to maintain an acceptable humidity with a lower flow, it would
> lessen the chances that we will run out of nitrogen over the shutdown.
> 
> Best regards,
> Tyler
> 
>