After performing another accumulation on Y1 with CP1 isolated from the tube we think we have found our leak. It looks like the annulus of the gate seal has a leak into the system.

This was highlighted when we reopened GV6 after the accumulation.

So in summary the outgassing from Y1 appears to be in line with the 3 other modules, the CP1 outgassing rate is reasonable and we have a leak to follow up on.

SUMMARY:

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*                            5 e-7                              6.8 e-15                         1.7 e-14                   Mar 12       16/4                             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).

Y1 result is estimated from the sum of two accumulations(tube + CP1) performed on Mar 12.

NOTE: If you subtract the outgassing due to CP1 or CP2 from the Y1 and X1 results you will get numbers much closer to the Y2 and X2 modules. The measured outgassing from CP1 is 2.3 e-7 tl/s.