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End date: 2024 × Start date: 2020 × DDC: 530 × DDC: 620 × Version: publishedVersion × Publisher: [S.l.] : American Institute of Physics ×

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    Photon-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.
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    Improved 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, Toshiro
    We 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).
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    Piezoelectric-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).