ASP STERRAD 100, Service Manual

Page: 24 / 309

Diffusion Pump-Down
Duration Parameter Limit
2 Minutes Pressure 500 mTorr or greater
If the chamber pressure has stayed within the limits, the last 2 minutes
of the diffusion stage are used to evacuate enough of the vapor from the
chamber to establish the 500 mTorr pressure for the plasma stage. The
vacuum pump is turned on and the throttle valve is opened until the 500
mTorr threshold is reached. The process controller then modulates the
throttle valve position to maintain 500 ±25 mTorr. This phase is
completed at two minutes regardless of the chamber pressure.
Plasma Stage
Duration Parameter Limit
3 Minutes Time Maximum pump down
time to reach 525 mTorr
15 Minutes Time Plasma stage with RF
turned ON
5 Minutes Debounce for initial
pressure surge
1 min. debounce after 5
minutes debounce
Delivered power 365 Watts min.
400 Watts nominal
Pressure 525 mTorr max.
475 mTorr min.0
If the pressure in the chamber has not reached the 500 mTorr threshold
when the plasma stage begins, an additional 3 minutes is allowed to
reach 500 mTorr. If the pressure still has not reached 500 mTorr at the
end of that period, the cycle is canceled with the message “Vacuum
Insufficient for Plasma.”
When the pressure has reached 500 mTorr, radio frequency (RF) energy
is radiated within the process chamber for 15 minutes. This RF energy
results in the formation of a plasma from the hydrogen peroxide. In the
plasma state, the hydrogen peroxide vapor breaks apart into reactive
species that include free radicals.
The combined use of hydrogen peroxide vapor and plasma, safely and
rapidly sterilizes most medical instruments and materials without
leaving toxic residues.
System Operation Theory of Operation-Overview
2-8 STERRAD® 100 Sterilizer ASP Service Guide rev. D