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By employing THz time-domain spectroscopy, far infrared optical properties of TmFeO3 single crystal are investigated schematically in temperature range from 5 to 300 K. The temperature dependence of resonances due to iron ions and Tm ions absorption due to crystal field are clarified. The experimental results demonstrate that the temperature induced spin reorientation transition (SRT) as well as crystal...
We developed photothermoelectric devices based on graphene transistors with tunable p-n junctions achieved through partial polymer gating. This approach presents the advantage of combining broadband photoresponse with transparent gates. After demonstrating that the photocurrent mechanism is consistent with photothermoelectric effects, we studied different device designs in order to determine the best...
We demonstrate that collective Thomson scattering of millimeter wave electron cyclotron resonance heating radiation can be used for measurements of the main-ion temperature in the ASDEX Upgrade tokamak.
We present contact-free THz near-field measurements at large-area graphene covered by an ion gel top-gate. In dependence of the gate-voltage, we map the THz near-field transmission amplitude and the resulting sheet resistance distribution across the graphene layer. High-resolution access to the local charge carrier properties of the buried graphene enables the visualization of inhomogeneity and defects...
We investigated the soft desorption mechanism of organic molecules under irradiation of intense THz free electron laser pulses resonant for intermolecular motions in the solids by time-of-flight mass spectrometry and time-resolved luminescence measurements.
Microwave diagnostics will play an increasingly important role in burning plasma fusion energy experiments like ITER and beyond. The Collective Thomson Scattering (CTS) diagnostic to be installed at ITER is an example of such a diagnostic with great potential in present and future experiments. The ITER CTS diagnostic will inject a 1 MW 60 GHz gyrotron beam into the ITER plasma and observe the scattering...
We studied adsorption state of water molecules in a porous coordination polymer (PCP) using infrared spectroscopy. We observed two absorbance peaks below 4% relative humidity (RH) that originate from OH stretch modes of adsorbed water molecules. Their peak frequencies and areas indicate that one of the OH is free, and the other is hydrogen bonded. We also found that Free-OH plays a role of water attraction...
We propose a diagnostic capable of measuring 2D fast-ion velocity distribution functions f2Dv in the MeV-range in magnetized fusion plasmas. Today velocity-space tomography based on fast-ion Dα spectroscopy is regularly used to measure f2Dv for ion energies below 100 keV. Unfortunately, the signal-to-noise ratio becomes fairly low for MeV-range ions. Ions at any energy can be detected well by collective...
Mixed perovskites Sr1−xBaxMnO3 were lately indicated as possible multiferroics with a strong magnetoelectric coupling. However, THz spectroscopy with varying temperature and magnetic field revealed no magnetodielectric effect. Our study brings new information on the ferroelectric phase transition.
When studying magnetic excitations, neutron spectroscopy is typically the method of choice. The low-energy and electromagnetic nature of terahertz radiation presents a new and complementary technique to probe exotic magnetic states. Here we perform terahertz spectroscopy on the quantum spin-ice candidate Tb2Ti2O7 using standard and coherent synchrotron radiation. These novel measurements show fine...
The upgrade of the electron cyclotron (EC) system of the TCV tokamak has entered in its realization phase. The MW-class dual-frequency gyrotron design (84 or 126GHz/2s), based on the 140GHz W7-X gyrotron, is finalized and a contract for the manufacturing of two units has been placed with Thales Electron Devices (TED). For maintaining a high level of operational flexibility of the EC-system the integration...
Salt-induced change in water dynamics inside multi-lamellar vesicles (MLV) is experimentally studied with terahertz (THz) time-domain spectroscopy (TDS). The dielectric constants of lipids dispersed in NaCl solutions with different salt concentrations are measured. We find that the water molecules with fast relaxation time (∼100 fs) significantly increase with NaCl concentrations. Furthermore, by...
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