Experimental study of electric breakdowns in liquid argon at centimeter scale

Abstract

In this paper we present results on measurements of the dielectric strength of liquid argon near its boiling point and cathode-anode distances in the range of 0.1 mm to 40 mm with spherical cathode and plane anode. We show that at such distances the applied electric field at which breakdowns occur is as low as 40 kV/cm. Flash-overs across the ribbed dielectric of the high voltage feed-through are observed for a length of 300 mm starting from a voltage of 55 kV. These results contribute to set reference for the breakdown-free design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

Direct comparison of high voltage breakdown measurements in liquid argon and liquid xenon

“…The purity monitor measured the lifetime of electrons as they drift through the noble liquid, which directly relates to the liquid purity level. A purity measurement was desired since prior work in LAr suggests that breakdown strength depends on the presence of impurities in the liquid, with HV breakdown occurring at higher fields with higher levels of electronegative contaminants [7,23]. Very low impurity levels are desired in XeBrA because the results are intended to inform direct dark matter and neutrino experiments, which typically operate with very long electron lifetimes of O(1 ms).…”

“…• Purity: Impurities lowered breakdown fields in transformer oil [22] and LHe [14,20]. Conversely, in LAr, the presence of impurities increased breakdown fields [6,7,23].…”

“…• Polarity: In LAr [7,23], LN [12], and LHe [14,24], research has shown that sparks during dielectric breakdown are initialized on the cathode surface and are affected by spacecharge effects on the cathode surface and in the stressed volume. However, the formation of filamentary discharges, known as streamers, has been shown to be preferentially initiated at the anode in a wide range of other liquids [25].…”

First Demonstration of a Pixelated Charge Readout for Single-Phase Liquid Argon Time Projection Chambers

“…LAr is filtered first on filling through a pair of Oxysorb-Hydrosorb filters, and then recirculated through a single custom-made filter containing both activated copper and silica gel. The cryostat and filtering method were previously used for LAr purity measurements [24], and High-Voltage (HV) breakdown studies [25]. Based on these previous studies, an impurity concentration O(1 ppb) of oxygen-equivalent is estimated, which corresponds to a charge lifetime of (290 ± 30) µs.…”

Cryogenic CMOS cameras for high voltage monitoring in liquid argon

“…The work presented here concerns the use of Complementary Metal-Oxide Semiconductor (CMOS) cameras at cryogenic temperature within LAr, with a view to using this technology for optical readout in LAr and LXe detectors. Charge-coupled device (CCD) and CMOS cameras have previously been used to monitor LAr detectors [3][4][5][6][7]. However, this has been either from outside the cryostat, through a view port, or by incorporation of an enclosure with raised temperature.…”