Triaxial $μ$-PIC for resolving Multi-Hit Ambiguity

Abstract

The micro pixel chamber ($μ$-PIC), a type of micro-pattern gaseous detectors (MPGD), features pixel electrodes structured similarly to a sliced proportional counter. Conventionally, $μ$-PIC electrodes are connected to orthogonal strip electrodes to reduce the number of readout circuits; however, this configuration introduces multi-hit ambiguity when tracing winding tracks or during high-rate operations. A well-known solution to this problem is the adoption of an additional readout axis. To this end, we designed a new electrode structure using Garfield++ simulations and fabricated a triaxial $μ$-PIC based on through-glass-via (TGV) technology. This triaxial $μ$-PIC achieved a high gas gain of $1.1\times 10^4$ and the energy resolution of 22\% (FWHM) at 5.9~keV, Furthermore, the false-hit probability was less than 0.78\% at a 95\% confidence level for two clusters separated by a distance of over 3 mm, consistent with Garfield++ predictions. With this triaxial $μ$-PIC, single avalanche signals are collected from three independent readout strip electrodes (the anode and two cathodes). The charge ratio among these electrodes remains nearly constant at anode:U-cathode:V-cathode=3:2:1. In addition, we successfully achieved an enhanced gain of $3.2\times 10^4$ without increasing the discharge risk by employing an alternative operation mode.