Neutral bremsstrahlung and excimer electroluminescence in noble gases and its relevance to two-phase dark matter detectors

Proportional electroluminescence (EL) is the physical effect used in two-phase detectors for dark matter searches, to optically record (in the gas phase) the ionization signal produced by particle scattering in the liquid phase. In our previous work the presence of a new EL mechanism, namely that of neutral bremsstrahlung (NBrS), was demonstrated in two-phase argon detectors both theoretically and experimentally, in addition to the ordinary EL mechanism due to excimer emission. In this work the similar theoretical approach is applied to all noble gases, i.e. overall to helium, neon, argon, krypton and xenon, to calculate the EL yields and spectra both for NBrS and excimer EL. The relevance of the results obtained to the development of two-phase dark matter detectors is discussed.

Horizontal position reconstruction in PandaX-II

Dual-phase noble-gas time projection chambers (TPCs) have improved the sensitivities for dark matter direct search in past decades. The capability of TPCs to reconstruct 3-D vertexes of keV scale recoilings is one of the most advantageous features. In this work, we develop two horizontal position reconstruction algorithms for the PandaX-II dark matter search experiment using the dual-phase liquid xenon TPC. Both algorithms are optimized by the 83mKr calibration events and use photon distribution of ionization signals among photomultiplier tubes to infer the positions. According to the events coming from the gate electrode, the uncertainties in the horizontal positions are 3.4 mm (3.9 mm) in the analytical (simulation-based) algorithm for an ionization signal with several thousand photon electrons in the center of the TPC.

Electroluminescence and Electron Avalanching in Two-Phase Detectors

Electroluminescence and electron avalanching are the physical effects used in two-phase argon and xenon detectors for dark matter searches and neutrino detection, to amplify the primary ionization signal directly in cryogenic noble-gas media. We review the concepts of such light and charge signal amplification, including a combination thereof, both in the gas and in the liquid phase. Puzzling aspects of the physics of electroluminescence and electron avalanching in two-phase detectors are explained, and detection techniques based on these effects are described.

Selection of ion sensor operating parameters in quasi-static conditions

Evaluating combustion quality using sensors that allow continuous assessment of the process is one of the modern methods of engine sensory diagnostics. The proper calibration of such systems is a task that requires many studies to determine the conditions and quantities affecting the process. The analysis of significance of quantities related to the ionization signal was carried out in the article. The magnitude of the voltage generating the electric field, the type of spark plug used, the distance of the spark plug electrodes and the dynamic factor – spark plug operating temperature – were all tested. The tests were carried out using a CNG burner (with an excess air ratio of lambda = 1) and four spark plugs. As a result of the ionization signal research, the following relationships were obtained: regarding the impact of the sensor position on the amount of generated voltage (the smaller the distance the greater the value of the signal), the effect of temperature on the sensor resistance (non-linear relationship: increase in temperature decreases resistance, with R2 = 0.9997) effect of system voltage on the ionization signal (linear relationship: voltage increase increases the ionization current signal with a determination coefficient of R2 = 0.9803). In addition, it was found that using an iridium electrode candle had the best effects on the ionization current, regardless of the electrode’s geometrical parameters.

Relations between ion signal and flame propagation in cylinder of a rapid compression machine

Internal combustion engine diagnostics using traditional methods of cylinder pressure signal processing limits the amount of information available about the combustion process. It is necessary to conduct research in order to obtain more precise information – increasing the combustion process diagnosis potential. One such suggestion is the use of an ionization signal and an attempt to link it to the flame development during combustion of gaseous fuels. The article attempts to identify such a relationship using a rapid compression machine due to optical access it provides to the combustion chamber. As a result of the research, the relationships between the ionization voltage (chemical and thermal) of the first combustion phase and the corresponding flame development rates were determined. A relatively high coefficient of determination value was obtained for both relations, which indicates the possibility of obtaining diagnostic information about the combustion process from the ionization signal.

Proposal for Two-Phase Cryogenic Avalanche Detector for Dark Matter Search and Low-Energy Neutrino Detection

The proposal for the detector of ultimate sensitivity for Dark Matter search and low-energy neutrino detection, including that of coherent neutrino-nucleus scattering, is presented, based on the technique of two-phase Cryogenic Avalanche Detectors (CRADs) in Ar. Such a detector, with a 160 l cryogenic chamber, will be able to operate in single electron counting mode with superior (~ 1 mm) spatial resolution. To obtain such characteristics, a novel technique to detect ionization signal is applied, namely an optical readout using combined multiplier comprising of Gas Electron Multipliers (GEMs) and a matrix of Geiger-mode APDs (GAPDs)

Measurement of the Transverse Diffusion Coefficient of Charge in Liquid Xenon

Liquid xenon (LXe) is a very attractive material as a detection medium for ionization detectors due to its high density, high atomic number, and low energy required to produce electron-ion pairs. Therefore it has been used in several applications, like γ detection or direct detection of dark matter. Now Subatech is working on the R & D of LXe Compton telescope for 3γ medical imaging, which can make precise tridimensional localization of a (β+, γ) radioisotope emitter. The diffusion of charge carriers will directly affect the spatial resolution of LXe ionization signal. We will report how we measure the transverse diffusion coefficient for different electric field (0.5 ~ 1.2 kV/cm) by observing the spray of charge carriers on drift length varying until 12 cm. With very-low-noise front-end electronics and complete Monte-Carlo simulation of the experiment, the values ​​of transverse diffusion coefficient are measured precisely.