DMEA231-004 - Modular Cryogenic Dewar for Radiation Testing

Failure of satellite electronics and other components exposed to natural space environment has been a concern since the early 1960s due to the radiation effects. The radiation effects can be divided into three mechanisms: total ionizing dose (TID), displacement damage (DD), and single event effect (SEE). These failure mechanisms are usually enhanced nonlinearly by other environmental conditions, such as temperature, pressure, and humidity, etc. Thus, the radiation testing, which is designed to understand failure mechanisms, characterize the radiation response of specific devices and to provide data for lot acceptance, should be performed in an environment with wide range of temperature and pressure, and as close as possible to the ones encountered in space. We propose a modular cryogenic Dewar for radiation testing for electronics and other devices. This modular Dewar, with finely controlled temperature, pressure, and humidity, would fit in current popular irradiation chambers in an easy way that it can be exchanged within 10 minutes by trained personnel. Human machine interface is also included so that the system can be controlled through a front panel. The proposed cryogenic Dewar consists of three subsystems: temperature control, humidity control, and vacuum system. The temperature control system can be further divided into cooling loop and heating loop. The cooling loop is designed to use non-reactive fluid to cool the device under test (DUT) down to -150 °C, while the heating loop can heat the DUT up to 200 °C. Both cooling and heating rates are designed to be > 1 °C per minute and could be controlled. The heating loop also maintains the temperature of all components exposed to humidity 3 °C higher than the dew point. The humidity control system is designed to reach a wide range of relative humidity 5% to 80% over a temperature range of 20 to 85 °C and pressure range from 0 to 200 psig in short time. The vacuum system is designed to evacuate the Dewar to 1E-6 Torr from ambient within 90 minutes. The Dewar is designed to be maintained at the desired vacuum level with accuracy of ±1%, and a leakage < 1E-8 scc/sec of helium. The Dewar is designed with a burst maximum operating pressure factor of safety of 4. With proper selection of the materials that can endure 2.0E7 rad during two-hour exposure (without using any chlorofluorocarbon compounds or polytetrafluoroethylene), the weight of the Dewar to be inserted into irradiation chamber is < 50 lbs. Multiple ports are included for feed-through installation of test interfaces and sensor interfaces.