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- ItemKinematics of femtosecond laser-generated plasma expansion: Determination of sub-micron density gradient and collisionality evolution of over-critical laser plasmas([S.l.] : American Institute of Physics, 2021) Scott, G.G.; Indorf, G.F.H.; Ennen, M.A.; Forestier-Colleoni, P.; Hawkes, S.J.; Scaife, L.; Sedov, M.; Symes, D.R.; Thornton, C.; Beg, F.; Ma, T.; McKenna, P.; Andreev, A.A.; Teubner, U.; Neely, D.An optical diagnostic based on resonant absorption of laser light in a plasma is introduced and is used for the determination of density scale lengths in the range of 10 nm to >1 μm at the critical surface of an overdense plasma. This diagnostic is also used to extract the plasma collisional frequency, allowing inference of the temporally evolving plasma composition on the tens of femtosecond timescale. This is found to be characterized by two eras: the early time and short scale length expansion (L < 0.1λ), where the interaction is highly collisional and target material dependent, followed by a period of material independent plasma expansion for longer scale lengths (L > 0.1λ); this is consistent with a hydrogen plasma decoupling from the bulk target material. Density gradients and plasma parameters on this scale are of importance to plasma mirror optical performance and comment is made on this theme.
- ItemImpact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids([S.l.] : American Institute of Physics, 2015) Jablonowski, H.; Bussiahn, R.; Hammer, M.U.; Weltmann, K.-D.; von Woedtke, T.; Reuter, S.Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100–400 nm) and, in particular, vacuum ultraviolet (VUV, 10–200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•−) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.
- ItemAn ion trap built with photonic crystal fibre technology([S.l.] : American Institute of Physics, 2015) Lindenfelser, F.; Keitch, B.; Kienzler, D.; Bykov, D.; Uebel, P.; Schmidt, M.A.; Russell, P.St.J.; Home, J.P.We demonstrate a surface-electrode ion trap fabricated using techniques transferred from the manufacture of photonic-crystal fibres. This provides a relatively straightforward route for realizing traps with an electrode structure on the 100 micron scale with high optical access. We demonstrate the basic functionality of the trap by cooling a single ion to the quantum ground state, allowing us to measure a heating rate from the ground state of 787 ± 24 quanta/s. Variation of the fabrication procedure used here may provide access to traps in this geometry with trap scales between 100 μm and 10 μm
- ItemPhoton-electron coincidence experiments at synchrotron radiation facilities with arbitrary bunch modes([S.l.] : American Institute of Physics, 2021) Ozga, C.; Honisch, C.; Schmidt, P.; Holzapfel, X.; Zindel, C.; Küstner-Wetekam, C.; Richter, C.; Hergenhahn, U.; Ehresmann, A.; Knie, A.; Hans, A.We report the adaptation of an electron–photon coincidence detection scheme to the multibunch hybrid mode of the synchrotron radiation source BESSY II (Helmholtz-Zentrum Berlin). Single-event-based data acquisition and evaluation, combined with the use of relative detection times between the coincident particles, enable the acquisition of proper coincidence signals from a quasi-continuous excitation pattern. The background signal produced by accidental coincidences in the time difference representation is modeled using the non-coincident electron and photon spectra. We validate the method by reproducing previously published results, which were obtained in the single bunch mode, and illustrate its usability for the multibunch hybrid mode by investigating the photoionization of CO2 into CO+2 B satellite states, followed by subsequent photon emission. The radiative lifetime obtained and the electron binding energy are in good agreement with earlier publications. We expect this method to be a useful tool to extend the versatility of coincident particle detection to arbitrary operation modes of synchrotron radiation facilities and other excitation sources without the need for additional experimental adjustments.
- ItemImproved accuracy in high-frequency AC transport measurements in pulsed high magnetic fields([S.l.] : American Institute of Physics, 2020) Mitamura, Hiroyuki; Watanuki, Ryuta; Kampert, Erik; Förster, Tobias; Matsuo, Akira; Onimaru, Takahiro; Onozaki, Norimichi; Amou, Yuta; Wakiya, Kazuhei; Yamamoto, Isao; Matsumoto, Keisuke T.; Suzuki, Kazuya; Zherlitsyn, Sergei; Wosnitza, Joachim; Tokunaga, Masashi; Kindo, Koichi; Sakakibara, ToshiroWe show theoretically and experimentally that accurate transport measurements are possible even within the short time provided by pulsed magnetic fields. For this purpose, a new method has been devised, which removes the noise component of a specific frequency from the signal by taking a linear combination of the results of numerical phase detection using multiple integer periods. We also established a method to unambiguously determine the phase rotation angle in AC transport measurements using a frequency range of tens of kilohertz. We revealed that the dominant noise in low-frequency transport measurements in pulsed magnetic fields is the electromagnetic induction caused by mechanical vibrations of wire loops in inhomogeneous magnetic fields. These results strongly suggest that accurate transport measurements in short-pulsed magnets are possible when mechanical vibrations are well suppressed. © 2020 Author(s).
- ItemPiezoelectric-driven uniaxial pressure cell for muon spin relaxation and neutron scattering experiments([S.l.] : American Institute of Physics, 2020) Ghosh, Shreenanda; Brückner, Felix; Nikitin, Artem; Grinenko, Vadim; Elender, Matthias; Mackenzie, Andrew P.; Luetkens, Hubertus; Klauss, Hans-Henning; Hicks, Clifford W.We present a piezoelectric-driven uniaxial pressure cell that is optimized for muon spin relaxation and neutron scattering experiments and that is operable over a wide temperature range including cryogenic temperatures. To accommodate the large samples required for these measurement techniques, the cell is designed to generate forces up to ∼1000 N. To minimize the background signal, the space around the sample is kept as open as possible. We demonstrate here that by mounting plate-like samples with epoxy, a uniaxial stress exceeding 1 GPa can be achieved in an active volume of at least 5 mm3. We show that for practical operation, it is important to monitor both the force and displacement applied to the sample. In addition, because time is critical during facility experiments, samples are mounted in detachable holders that can be rapidly exchanged. The piezoelectric actuators are likewise contained in an exchangeable cartridge. © 2020 Author(s).