PFC Operation Manual
1. Introduction
1.
Introduction
Description and Applications
WARNING
Do not attempt to perform any installation, operation, or maintenance
procedures on the PFC until you have thoroughly read and understood the
information in the Safety section of this Manual. Failure to heed this warning
can result in serious injury or death.
Primary Definitions:
Refrigeration Unit:
The enclosure that cools and pumps the refrigerant through the
refrigerant line
and cryosurface.
Refrigerant Line:
In this manual, this term refers to the insulated bundle that contains two
lines (supply and return) that conducts a refrigerant between the PFC refrigeration unit and the
cryosurface.
Cryosurface:
This is the cooling surface that is installed in the customer's vacuum chamber. It
is usually shaped either as a coil (for water vapor capture), or as a ring of baffles (for capturing
backstreaming oil).
In this manual, the Polycold Fast Cycle (PFC) water vapor cryopump is referred to as the “PFC.”
The PFC is a cryogenic refrigeration system that captures volatile molecules by freezing them
onto a cold surface. The PFC consists of a refrigeration unit, refrigerant lines (supply and return),
and a cryosurface with cryogenic feedthrough. The refrigeration unit can pump cold or hot
refrigerant (for defrost) in a continuous loop through the refrigerant lines and cryosurface. The
refrigerant is a proprietary mixture of refrigerants made by Brooks Polycold Systems Inc.
Within the refrigeration unit, heat absorbed by the refrigerant is transferred to water that is
supplied by the customer.
Primary application
: Capture water vapor in a vacuum chamber after opening the high vacuum
valve. Water vapor is usually the most reactive contaminant in a high-vacuum system, and
comprises 65% to 95% of the residual gas in such systems.
For this application, the cryosurface is normally a coil. The coil can be quickly cooled and
defrosted to correspond with vacuum chamber cycles. See Figure 1.
Secondary application:
The PFC can also be used to minimize backstreaming (see Figure 2).
Backstreaming is a phenomenon where oil diffusion pumps are used. Some of the hot oil from
the diffusion pump migrates into the vacuum chamber, where it condenses onto surfaces,
contaminating the system. For this application, the cryosurface is a baffle. “Fast Cycle” refers to
the fast interchange between the cold and defrost states. However, quick cooling and defrosting
is not normally required or desired for this application.
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825160-00, revision B
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