Operating Principles of the CCT Series
Horizontally Mounted Traps
Vertically Mounted Traps
Upgrading Unvalved CCTs with Valves
The diffusion pump was one of the earliest pumps to be used in the UHV industry, its attractive feature being its ability to pump both active and inert gases without a memory effect. With the addition of a CCT trap it becomes a true UHV pump. On-going chemical developments have constantly improved the range and quality of pump oils, which has ensured that diffusion pumps have retained their importance in the market. The diffusion pump is popular with customers requiring reliability, high pumping speeds, low maintenance and inexpensive running costs.
There are two historical arguments against using a diffusion pump: namely the damage resistance of the pump when accidentally exposed to air whilst running, and oil contamination of the vacuum system. However, the performance and design of modern diffusion pump oils minimises the problems encountered by accidental exposure of the pump to air.
With the combination of VG Scienta's CCT traps and good UHV operating practice, we have been able to reduce oil contamination to a minimum. The combination of liquid nitrogen cooling and a specially designed chevron array allows a large surface area to be kept at nearly -196° C for a long period.
This long term improvement of performance has permitted the diffusion pump to continue to be operated in the UHV industry, especially where high pumping throughput at a low price is required.