[Bteam] Action items from yesterday's pathlength meeting

[Jay Benesch]

http://opweb.acc.jlab.org/CSUEApps/elog02/elog_item.php?elog_id=1539610
figure 5 shows two of the tunnel temperatures for the last two years and 
the NL energy most of that time.  The other two temperature sensors are 
broken (S) or not archived (W).  The largest excursion sustained is 
~15F.  Assume the tunnel ceiling is 9'; I forget exact height.  If the 
concrete doesn't change size the thermal expansion of the stands, bowing 
outward due to bolting top and bottom, would provide ~16 degrees of 
phase shift for the middle arc on the stack and less as one goes up or 
down on the stand.  Radial excursion ~2.8mm.

Thermal expansion of a concrete structure, per
http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
is about 75% of steel so the phase difference for 15F temperature change 
might be as low as 4 degrees.  Since the concrete is in contact with 
ground water I don't think it will change temperature as much as the 
stands.  It might be good to embed a thermocouple in the wall, making 
sure the leads are in thermal contact with the concrete for at least 3" 
so the leads don't distort the reading by conduction of "air 
temperature" to the measurement point.

The question then becomes how much hotter the tunnel will get.  I'm sure 
ME did the analysis but I can't find the in the public documents 12 GeV 
makes available.

Jay