54 research outputs found
Characterization of a medium size Xe/TMA TPC instrumented with microbulk Micromegas, using low-energy gamma-rays
NEXT-MM is a general-purpose high pressure (10 bar, ~ 25 l active volume) Xenon-based TPC, read out in charge mode with an 0.8 cm × 0.8 cm-segmented 700 cm2 plane (1152 ch) of the latest microbulk-Micromegas technology. It has been recently commissioned at University of Zaragoza as part of the R&D of the NEXT 0νββ experiment, although the experiment's first stage is currently being built based on a SiPM/PMT-readout concept relying on electroluminescence. Around 2 million events were collected during the last months, stemming from the low energy γ-rays emitted by a 241Am source when interacting with the Xenon gas (Eγ = 26, 30, 59.5 keV). The localized nature of such events around atmospheric pressure, the long drift times, as well as the possibility to determine their production time from the associated α particle in coincidence, allow the extraction of primordial properties of the TPC filling gas, namely the drift velocity, diffusion and attachment coefficients. In this work we focus on the little explored combination of Xe and trimethylamine (TMA) for which, in particular, such properties are largely unknown. This gas mixture offers potential advantages over pure Xenon when aimed at Rare Event Searches, mainly due to its Penning characteristics, wave-length shifting properties and reduced diffusion, and it is being actively investigated by our collaboration. The chamber is currently operated at 2.7 bar, as an intermediate step towards the envisaged 10 bar. We report here its performance as well as a first implementation of the calibration procedures that have allowed the extension of the previously reported energy resolution to the whole readout plane (10.6% FWHM@30 keV)
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Role of electron swarm studies in the development of gaseous dielectrics
Recent knowledge provided by swarm studies allowing control of the number densities and energies of free electrons in electrically stressed gases is highlighted. This knowledge aided the discovery of new gas dielectrics and the tailoring of gas dielectric mixtures. The role of electron attachment in the choice of unitary gas dielectrics or electronegative components in dielectric gas mixtures, and the role of electron scattering at low energies in the choice of buffer gases for mixtures is outlined
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Electron collisions in gas switches
Many technologies rely on the conduction/insulation properties of gaseous matter for their successful operation. Many others (e.g., pulsed power technologies) rely on the rapid change (switching or modulation) of the properties of gaseous matter from an insulator to a conductor and vice versa. Studies of electron collision processes in gases aided the development of pulsed power gas switches, and in this paper we shall briefly illustrate the kind of knowledge on electron collision processes which is needed to optimize the performance of such switching devices. To this end, we shall refer to three types of gas switches: spark gap closing, self-sustained diffuse discharge closing, and externally-sustained diffuse discharge opening. 24 refs., 15 figs., 2 tabs
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Intermediate Phase Studies for Understanding Radiation Interaction With Condensed Media: The Electron Attachment Process.
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Electronegative gases
Recent knowledge on electronegative gases essential for the effective control of the number densities of free electrons in electrically stressed gases is highlighted. This knowledge aided the discovery of new gas dielectrics and the tailoring of gas dielectric mixtures. The role of electron attachment in the choice of unitary gas dielectrics or electronegative components in dielectric gas mixtures, and the role of electron scattering at low energies in the choice of buffer gases for such mixtures is outlined
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Gaseous dielectrics
Thirty papers were presented at the meeting. A separate abstract was prepared for each of 10 papers. The remaining 20 papers were not in scope for the Energy Data Base. (LCL
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Calculation of electric field-induced detachment rate of electrons from mononegative ions; relevance to gaseous dielectrics
This model for the mononegative atomic or molecular ion in its effect on the most loosely bound electron is a spherical square well (constant positive inner potential within a sphere of radius r/sub 0/ and zero potential outside). From it we have calculated by quantum mechanics the emission rate w/sub ..nu..lm/ of electrons from the ..nu../sup th/ excited state (of orbital angular momentum and magnetic quantum numbers l and m and energy E/sub ..nu..l/ < 0) under the influence of a constant electric field F. The calculation is conceptionally simple (involving time-dependent perturbation theory) but technically complicated (requiring an eleven-fold integration), and leads to a surprisingly simple final expression. The relevance of our calculations to gaseous dielectrics is discussed
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A multiphoton ionization technique for the determination of the ionization threshold of molecules in fluid media
A new laser-induced multiphoton conductivity technique for the determination of the ionization threshold of molecules in fluids (liquids and dense gases) is described. Results are presented and discussed on aromatic molecules in nonpolar fluids. 2 refs., 1 fig., 1 tab
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Electron attachment as a probe of photoionization processes in liquid media
The effects of electron attaching additives on the photoionization threshold of pyrene in seven liquid media comprising a dielectric hydrocarbon liquid and an electron attaching additive, A, were studied. The photoionization threshold, I/sub L/, was found to be independent of the dielectric hydrocarbon liquid and the concentration of each A used. On the basis of these data it was concluded that in the presence of an efficient A at high concentrations, the photoejected electron is captured by A at times shorter than those required for electron solvation (or any possible trapping by the solvent) and that the photoionization process for a solute molecule in these dielectric liquids is probably completed at times less than or equal to 10/sup -14/ and greater than or equal to 10/sup -16/ s and its energetics are rather independent of the bulk properties of these liquids
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Isotope dependence of the breakdown strength of gases
It has been found that while the highly nonuniform direct current breakdown voltages, V/sub s/, of H/sub 2/ and NH/sub 3/ exceed, respectively, those of D/sub 2/ and ND/sub 3/, the V/sub s/ of CH/sub 4/ is substantially lower than that of CD/sub 4/. The former (direct) isotope effect may be attributed to the higher ionization coefficients for the deuterated species compared with the nondeuterated, and the latter (inverse) isotope effect may result from differences in the electron-impact-induced dissociation processes of the isotopic pairs of molecules
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