Abstract
Voltages above a hundred kilo-volt will be required to generate the drift field of future very large liquid Argon Time Projection Chambers. One of the most delicate component is the feedthrough whose role is to safely deliver the very high voltage to the cathode through the thick insulating walls of the cryostat without compromising the purity of the argon inside. This requires a feedthrough that is typically meters long and carefully designed to be vacuum tight and have small heat input. Furthermore, all materials should be carefully chosen to allow operation in cryogenic conditions. In addition, electric fields in liquid argon should be kept below a threshold to reduce risks of discharges. The combination of all above requirements represents significant challenges from the design and manufacturing perspective. In this paper, we report on the successful operation of a feedthrough satisfying all the above requirements. The details of the feedthrough design and its manufacturing steps are provided. Very high voltages up to unprecedented voltages of −300 kV could be applied during long periods repeatedly. A source of instability was observed, which was specific to the setup configuration which was used for the test and not due to the feedthrough itself.
Highlights
Detector active LAr number of drift length high voltage at cathode [kV] volume [m3] drift regions [m]
We showed that a sustained stable electric field of -100 kV over one centimeter in liquid Argon was achievable at equilibrium [11]
In order to increase stability with respect to bubble formation which can never be totally excluded in large systems, electric fields in liquid argon should be kept below the threshold of 40 kV/cm
Summary
It has a female receptacle to accept the feedthrough cable plug on one end and a male threaded contact on the other for electrical connection to the detector Both inner and outer conductor tube thicknesses are. The diameter of the hole reduces from 43 to 32 mm to accept the feedthrough cable plug on one end and to allow the insertion of the inner conductor on the other. This step is quite critical mechanically, HMDPE is a rather soft material and it is not trivial to drill a precise and aligned hole in a 2 meter long rod.
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