In order to bring the background spectrum of the RGA to a minimum, the RGA
was baked for two hours before obtaining the measurements. The turbo pump
was continuously running during the measurements, making the Wenzel pressure
gauge located next to the RGA indicate a pressure below 
mBar.
A spectrum of the RGA background was recorded, and then the valve to the
LN2 cooled NOTCam dewar was opened. After a pause of 10 minutes to let the
environment stabilize, a spectrum of the NOTCam vacuum was obtained.
The two spectra are displayed in figure 7.
As the cold vessel was cryo-pumping the RGA, the RGA background is scaled
by a factor of 0.22 to provide a good fit to the cold spectrum.
Even when scaled to each other, the spectra show significant differences:
The background has stronger lines at 17 and 18 AMU. This is water from the
room temperature environment. In the cold vessel, water is effectively frozen.
The cold pressure is dominated by the 
signature at 2 AMU, with a
partial pressure of 
mBar.
Also seen are 
at 28 and 14 AMU, 
at 32 and 16 AMU, and the
noble gases He (4 AMU), Ne (22 and 20 AMU) and Ar (40 AMU).
A cold spectrum made earlier under the same conditions also showed a NO
peak at 30 AMU.
Many other components are ambiguous or unidentified. A peak at 149 AMU is
suspected to be related to plastisizers.
