High voltage in noble liquids for high energy physics

Noble liquid radiation detectors have long been afflicted by spurious electron emission from their cathodic electrodes. This phenomenon must be understood and mitigated in the next generation of liquid xenon (LXe) experiments searching for WIMP dark matter or neutrinoless double beta decay, and in the large liquid argon (LAr) detectors for the longbaseline neutrino programmes. We present a systematic study of this spurious emission involving a series of slow voltage-ramping tests on fine metal wires immersed in a two-phase xenon time projection chamber with single electron sensitivity. Emission currents as low as 10 −18 A can thus be detected by electron counting, a vast improvement over previous dedicated measurements. Emission episodes were recorded at surface fields as low as ∼10 kV/cm in some wires and observed to have complex emission patterns, with average rates of 10-200 counts per second (c/s) and outbreaks as high as ∼10 6 c/s. A fainter, less variable type of emission was also present in all untreated samples. There is evidence of a partial conditioning effect, with subsequent tests yielding on average fewer emitters occurring at different fields for the same wire. We find no evidence for an intrinsic threshold particular to the metal-LXe interface which might have limited previous experiments up to fields of at least 160 kV/cm. The general phenomenology is not consistent with enhanced field emission from microscopic filaments, but it appears instead to be related to the quality of the wire surface in terms of corrosion and the nature of its oxide layer. This study concludes that some surface treatments, in particular nitric acid cleaning applied to stainless steel wires, can bring about at least order-of-magnitude improvements in overall electron emission rates, and this should help the next generation of detectors achieve the required electrostatic performance.

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“…A review of the various high-voltage (HV) issues affecting these communities can be found in Ref. [4].…”

Section: Introductionmentioning

confidence: 99%

Study and mitigation of spurious electron emission from cathodic wires in noble liquid time projection chambers

Tomás

Araújo

Bailey

et al. 2018

Astroparticle Physics

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“…and a W-value of 23.6 eV, we expect the spectral contribution of39 Ar to be flat in the low-energy ("few electron events") region with an amplitude of ∼4.1 events•(e − ) −1 kg −1 day −1 , seeFigure 8. Efforts have been made to collect Ar from exhaust streams of underground mining facilities, which are depleted in39 Ar by ∼150× that of atmospheric Ar[36]. With an assumed depletion factor of 150, the background39 Ar rate drops to just 0.027 events•(e − ) −1 kg −1 day −1 , ∼ 100× lower than the predicted CENNS rates.…”

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confidence: 95%

“…Assuming the beta spectrum given in Ref [35]. and a W-value of 23.6 eV, we expect the spectral contribution of39 Ar to be flat in the low-energy ("few electron events") region with an amplitude of ∼4.1 events•(e − ) −1 kg −1 day −1 , seeFigure 8. Efforts have been made to collect Ar from exhaust streams of underground mining facilities, which are depleted in39 Ar by ∼150× that of atmospheric Ar[36].…”

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confidence: 97%

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Modeling ionization and recombination from low energy nuclear recoils in liquid argon

Foxe

Hagmann

Jovanovic

et al. 2015

Astroparticle Physics

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Coherent elastic neutrino-nucleus scattering (CENNS) is an as-yet undetected, flavor-independent neutrino interaction predicted by the Standard Model. Detection of CENNS could offer benefits for detection of supernova and solar neutrinos in astrophysics, or for detection of antineutrinos for nuclear reactor monitoring and nuclear nonproliferation. One challenge with detecting CENNS is the low energy deposition associated with a typical CENNS nuclear recoil. In addition, nuclear recoils result in lower ionization yields than those produced by electron recoils of the same energy. While a measurement of the nuclear recoil ionization yield in liquid argon in the keV energy range has been recently reported, a corresponding model for low-energy ionization yield in liquid argon does not exist. For this reason, a Monte Carlo simulation has been developed to predict the ionization yield at sub-10 keV energies. The model consists of two distinct components: (1) simulation of the atomic collision cascade with production of ionization, and (2) the thermalization and drift of ionization electrons in an applied electric field including local recombination. As an application of our results we report updated estimates of detectable ionization in liquid argon from CENNS at a nuclear reactor.

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“…The high voltage feedthroughs (HVFT) need to hold up to 20 kV in the gate and 50kV in the cathode. The design of both is based in the design shown by H. Wang in [6] PoS(ICHEP2016)497 F. Monrabal on behalf of the NEXT Collaboration (Fig. 3 right).…”

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confidence: 99%

The NEXT experiment to search for the neutrinoless double beta decay of Xe-136

Monrabal¹

2017

Proceedings of 38th International Conference on High Energy Physics — PoS(ICHEP2016)

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High voltage in noble liquids for high energy physics

Cited by 25 publications

References 71 publications

Study and mitigation of spurious electron emission from cathodic wires in noble liquid time projection chambers

Study and mitigation of spurious electron emission from cathodic wires in noble liquid time projection chambers

Modeling ionization and recombination from low energy nuclear recoils in liquid argon

The NEXT experiment to search for the neutrinoless double beta decay of Xe-136

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