LHO Module Total Outgassing Outgas rate/unit area Hydrogen Date Outdoor Temps Post Bake(1998) H2 at 23C at 0C
torr- l/sec torr-l/s/cm^2 torr-l/s/cm^2 high/low C torr-l/s/cm^2
Y1 1.3 e-6 1.77 e-14 4.4 e-14 Mar 5 7.2/0 6.3 e-14 9.0 e-15
Y2 2.4 e-7 3.3 e-15 8.25 e-15 Mar 6 5/1.1 4.7 e-14 6.8 e-15
X1 5.4 e-7 7.3 e-15 1.83 e-14 Mar 7 12.2/3.3 5.2 e-14 7.4 e-15
X2 3.4 e-7 4.6 e-15 1.2 e-14 Mar 8 12.2/1.1 4.6 e-14 6.6 e-15
Volume of each module ~ 2.35 e6 liters
Area of each module ~ 7.35 e7 cm^2 (excludes baffles and port hardware)
Gauge factor for cold cathode and H2 = 2.5
Note that each module accumulation includes the 80k pumps at either end - a significant surface area of untreated SS with H2 outgassing of perhaps 100x that of the beam tube steel(per unit area).
A quick estimate of the SS surface in the long pump is 285,000 cm^2. If you assume 100 times the H2 outgassing this yields an equivalent 2.8 e7cm^2 or 1/3 of the beam tube. The internals of the pump are largely aluminum and likely do not contribute to the H2 outgassing.
80K pump contribution added, fixed degrees C.
Second accumulation on Y1 March 12 with 80K pump CP1 isolated:
We have two accumulations - one for the 80K pump and one for the Y1 module.
CP1 outgassing:
Estimated volume of CP1 including one gate valve interior = 22,800 liters
Estimated surface area of SS of CP1 plus valve = 285000 cm2
Pressure rise in 8700 seconds = 8.9 e-8 torr = 2.3 e-7 t-l/sec x gauge factor of 2.5 = H2 outgassing of 2.1 e-12 tl/s/cm^
Y1 Module:
Outgas rate without CP1 is now 2.63e-7 e-7 t l/s or 1/5 of what it was before. On the other hand summing the two yields ~5 e-7 tl/s rather than the 1.3 e-6 obtained a few days ago.
Perhaps this is an indication of our measurement error. Arithmetic error?