The first single-phase TPC
83mKr signals measued in the single-phase TPC and in the same detector operated in dual-phase mode.
The largest direct dark matter search experiments to date employ dual-phase time projection chambers (TPCs) with liquid noble gas targets. These detect both the primary photons generated by particle interactions in the liquid target, as well as proportional secondary scintillation light created by the ionization electrons in a strong electric field in the gas phase between the liquid-gas interface and the anode.
In this project, conducted within the ERC CoG project ULTIMATE,, we studied the detection of charge signals in a small-scale single-phase liquid-xenon-only TPC, that features the well-established TPC geometry with light readout above and below a cylindrical target. In the single-phase TPC, the proportional scintillation light (S2) is generated in liquid xenon in close proximity to 10 µm diameter anode wires. These thin wires establish the high electric fields (>400 kV/cm) that are required to enable this process.
The detector was characterized and the proportional scintillation process was studied using the 32.1 keV and 9.4 keV signals from 83mKr decays. A charge gain factor g2 of up to (1.9 ± 0.3) PE/electron was reached at an anode voltage 4.4 kV higher than the gate electrode, corresponding to (29 ±6) photons emitted per ionization electron. The duration of S2 signals is dominated by electron diffusion and approaches the xenon de-excitation timescale for very short electron drift times. The electron drift velocity and the longitudinal diffusion constant were measured at a drift field of 470 V/cm. The results agree with the literature and demonstrate that a single-phase TPC can be operated successfully.
- Publication:
Proportional scintillation in liquid xenon: demonstration in a single-phase liquid-only time projection chamber
Florian Tönnies, Adam Brown, Baris Kiyim, Fabian Kuger, Sebastian Lindemann, Patrick Meinhardt, Marc Schumann, Andrew Stevens
arXiv:2405.10687
