The Jandel cylindrical probe head has been successfully used in vacuum that was at 1 x 10^-10m bar. The application was described in the "Journal of Physics: Condens. Matter 3 (1991) S291-S296"

It is basically the Jandel cylindrical probe with certain modifications viz:

All the connections are crimped, and instead of the usual wire lead, the brass terminal pins are replaced by hypodermic tube and extended through the top of the probe head and vacuum wire crimped into each separately. Thus there are four insulated conductors to be connected to the measuring equipment.

The four conductor wires from the probe can be supplied to Jandel by the purchaser, or Jandel will supply the probe with wire that is Teflon coated with 20 silver plated copper conductors 0.1 mm diameter, which is reasonably flexible.

The probe head is supplied with all of the usual components except the insulating pad is ruby, the tension adjusting screw is Teflon, and the connecting wires are crimped into hypodermic tube material instead of being soldered internally into brass pins. Non-anodized aluminum alloy is used for the body, nose-piece, and top, instead of the usual anodized material.

Material involved are:

• 6262 Al alloy
• Virgin Teflon
• Tungsten carbide needles
• Steel piano wire springs
• Anstenitic stainless steel screws
• Ruby (single crystal alumina) jewel guides
• Hypodermic needle tubing about dia. 1.5 mm
• Phospohor bronze connecting ligaments (to enable the needle connections to flex)
• No blind holes

The characteristics for the probe need to be defined, i.e., spring load, needle tip radii, spacing, and whether a linear or square probe pattern is preferred.

Regarding the four pins (shown in the photo above) on the back of the probe, those are 'terminal pins' for connecting to the 4 conductor cable. At the other end the terminal pins they are extended inside the probe by the use of hypodermic needle tubing and the ligament is crimped at that end also - there is no use of solder.