Cryogenic Temperature Coaxial Probe
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
A 50-ohm characteristic impedance coaxial probe is needed for high frequency signals from wafers immersed in liquid nitrogen (N2), for example, GaAs integrated circuits. The probe must have minimal thermal conduction to room temperature, where electrical connection to instrumentation is made. A successful probe has been made using a stainless steel outer conductor, a tungsten inner conductor joined to a commercial connector. Using a standard two-piece connector a slotted TEFLON* tube and stainless steel outer conductor to tip are employed as shown in the figure. A loop is formed at this end in part 2. The outer conductor is slotted to a depth of approximately 3/8 in.; the center conductor is inserted using the TEFLON tube as a spacer to maintain characteristic impedance.