Cirrus SP101013.111 – 10 October 2012
MKS Instruments UK Ltd., Spectra Products
26
The total pressure should gradually start to rise as the system outgases and you should bake the
system at least until the pressure starts to fall. In normal operation an initial bake of at least 24 hours
is required, although in general the longer the system is baked the better.
To improve the background further, it is recommended that you run and degas both filaments. The
amount of time spent in reducing the background peaks depends entirely on the application and is left
to the discretion of the customer. If the Cirrus is switched off, it will vent to atmosphere introducing
water vapour and should be baked again.
6.5 Temperature Settings
The Heat/Bake option should be set to Bake for the initial bake out to reduce the water background.
After this period, running at the lower temperature of Heat is adequate in preventing the condensation
of vapours in the vacuum chamber which could lead to memory effects.
Often it is not necessary to have the system heater on at all, but this will depend on the application.
The Cirrus is designed to allow continuous operation using the Faraday detector, with the system
heater on Bake or Heat.
6.6 Capillary Heater
Use the Capillary Heater to lessen the chance of vapour condensing in the capillary leading to memory
effects, or even blockage. Whether you need to heat the capillary or not depends on the application
and the nature of the gases being sampled.
The Cirrus is designed to allow the capillary heater to be run continuously.
