HELIUM LEVEL METER
To speed up the insertion of the target, the level meter probe originally positioned on the target stick has been fixed inside the banjo. The probe consists of a 40 cm superconductive wire which measures the level of the liquid helium from the bottom of the banjo: a value of ~60% corresponds to half banjo filled while ~80% to standard running conditions (full banjo).
The resistance of the probe is monitored through the four wires technique.The connection to the ILM-Oxford level meter consists of a hermetic 4 pin feed-through positioned on the upper flange of the stick. The level probe can be removed from the fixed position thanks to a 15 pin connector placed between the probe and the hermetic feed-through, close to the bellow on the top of the banjo.
The values of the resistance at room temperature as measured at the four pin Fisher connector are the following: