 QCS Industries designed
this system under contract to Computing Devices
International for the EONS lab at McClellan AFB. This
system will attain a vacuum of 1.0E-06 torr within a
period of less than 2 hours. The canister is milled from
an Aluminum block. The block was first inspected using
ultrasonics then milled. The end of the chamber consists
of a copper plate that is fused from two halves. Each
half has a slot milled in it which when the two halves
are fused together, form a tube embedded inside the
copper plate. This tube is for bringing liquid nitrogen
into the copper plate for cooling purposes. On the
backside of the copper plate is a hollowed out section
that accepts an electric heater made from a flexible
circuit coated in silicon rubber. The heater thickness is
less than 0.025". Over the heater another thinner
copper plate is attached to give the heater a backing
plate to keep it pressed against the main copper plate
and to prevent the heater itself from getting too hot. In the
center of the copper end plate is a three (3) inch
diameter hole that has a stainless ring welded to it. To
this ring is attached a ceramic tube with chromal
flanges. The flanges are welded to the ring on one end
and to a three inch diameter tube on the other end. External
to the chamber is a three inch 90° stainless steel elbow.
This constitutes the high vacuum chamber and exhaust
tube. Inside the chamber and mounted on the copper end plate is a stand for attaching devices under test (DUT). The devices can be attached at any distance from 0.5" to 10" from the end plate end. The position of the part determines the level of Cobalt 60 irradiation that the part will get. This chamber along with its outer chamber, which is also under vacuum, can be inserted into the Cobalt 60 irradiator at McClellan AFB. The chamber walls are also thin enough that they can be positioned in front of the Proton Particle Beam accelerator/generator at UC Davis so that parts can be simultaneously heated/cooled, evacuated and bombarded with Protons. The wall thickness is such that the Proton beam is only attenuated by about 10dB. A lead shield can be attached creating a standard dose enhancement chamber for the Gamma irradiation tests. This chamber can also be used for humidity tests at varying temperatures, though not simultaneously with vacuum. For humidity the vacuum attachments are removed and the humidity attachments are put in place. The humidity system is a closed system, that is, water in a heated and/or cooled bubbler is purged with recirculating air which travels through tubes to the chamber and the DUT, then returns from the chamber back to the bubbler. The humidity is monitored in the chamber and the temperature of the bubbler is changed to maintain the humidity at the prescribed level. |
