Abstract
We present a new technology for the shaping of the electric field in Time Projection Chambers (TPCs) using a carbon-loaded polyimide foil. This technology allows for the minimisation of passive material near the active volume of the TPC and, thus, is capable to reduce background events originating from radioactive decays or scattering on the material itself. Furthermore, the high and continuous electric resistivity of the foil limits the power dissipation per unit area and minimizes the risks of damages in the case of an electric field breakdown. Replacing the conventional field cage with a resistive plastic film structure called “shell” decreases the number of components within the TPC and, therefore, reduces the potential points of failure when operating the detector. A prototype liquid argon (LAr) TPC with such a resistive shell and with a cathode made of the same material was successfully tested for long-term operation with electric field values up to 1.6 k V cm − 1 . The experiment shows that it is feasible to successfully produce and shape the electric field in liquefied noble-gas detectors with this new technology.
Highlights
The high tracking accuracy and the calorimetric features have made Time Projection Chambers (TPCs) based on liquefied noble gases an established detector type for many experiments running or planned on neutrino physics [1,2,3] and direct dark matter searches [4,5,6].The basic working principle of a TPC is illustrated in Figure 1: Charged particles travelling through a medium lose their energy by ionising its atoms
We propose as an alternative to the conventional field cage, a continuous resistive plane forming a so-called “resistive shell”
The resistive shell TPC was continuously operated for 80 hours at electric field intensities up to
Summary
The high tracking accuracy and the calorimetric features have made Time Projection Chambers (TPCs) based on liquefied noble gases an established detector type for many experiments running or planned on neutrino physics [1,2,3] and direct dark matter searches [4,5,6]. Conventional TPC designs [5,7,8] employ metallic field cage structures to produce a uniform electric field between the anode and the cathode; these consist of a sequence of conductive elements surrounding the TPC drift region. Modularisation reduces the stored energy, simplifies electric-field stability and lowers the requirements for LAr purity. It brings the benefit of a reduced track multiplicity per TPC unit which simplifies the event reconstruction. We propose as an alternative to the conventional field cage, a continuous resistive plane forming a so-called “resistive shell” This will provide a continuous linear potential distribution along the drift direction, paired with a rather simple mechanical design. The results of a data taking period of 5 days carried out in July 2018 are presented in Section 3, followed by Section 4 with the conclusion and outlook
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