The energy deposition of ions in dense plasmas is a key process in inertial confinement fusion that determines the α-particle heating expected to trigger a burn wave in the hydrogen pellet and resulting in high thermonuclear gain. However, measurements of ion stopping in plasmas are scarce and mostly restricted to high ion velocities where theory agrees with the data. Here, we report experimental data at low projectile velocities near the Bragg peak, where the stopping force reaches its maximum. This parameter range features the largest theoretical uncertainties and conclusive data are missing until today. The precision of our measurements, combined with a reliable knowledge of the plasma parameters, allows to disprove several standard models for the stopping power for beam velocities typically encountered in inertial fusion. On the other hand, our data support theories that include a detailed treatment of strong ion-electron collisions.

The structure and dynamics of ionic liquids (ILs) are unusual due to the strong associations of the ions and counter ions. These microscopic properties determine the bulk transport properties critical to applications of ILs such as advanced fuel cells. Here the terahertz dynamics and slower 10 relaxations of simple alkylammonium nitrate protic ionic liquids (PILs) are studied using femtosecond optical Kerr-effect spectroscopy, dielectric relaxation spectroscopy, and terahertz time-domain spectroscopy. The observed dynamics are remarkably simple and give insight into more general behaviour. Comparison with glass-forming liquids reveals an 15 underlying power-law decay while relaxation rates suggest supramolecular structure and nanoscale segregation.

Over the past decade, terahertz spectroscopy has evolved into a versatile tool for chemically selective sensing and imaging applications. In particular, the potential to coherently generate and detect short, and hence, broadband terahertz pulses led to the development of efficient and compact spectrometers for this interesting part of the electromagnetic spectrum, where common packaging materials are transparent and many chemical compounds show characteristic absorptions. Although early proof-of-principle demonstrations have shown the great potential of terahertz spectroscopy for sensing and imaging, the technology still often lacks the required sensitivity and suffers from its intrinsically poor spatial resolution. In this review we discuss the current potential of terahertz pulse spectroscopy and highlight recent technological advances geared towards both enhancing spectral sensitivity and increasing spatial resolution.

Metamaterial layers designed for gigahertz to terahertz (THz)-frequencies have been fabricated by inkjet printing. The spectral response of the structures consisting of periodically arranged metallic split-ring resonators is characterized by THz-time-domain spectroscopy and compared with identical structures produced by conventional photolithography and etching techniques. The broader linewidth of their resonances is shown to originate mainly from structural inhomogeneities. Our study shows that inkjet printing is a viable route for producing metamaterial structures, allowing for rapid processing and flexibility in the choice of substrates.

Using terahertz near-field imaging we experimentally investigate the resonant electromagnetic field distributions behind a split-ring resonator and its complementary structure with sub-wavelength spatial resolution. For the out-of-plane components we experimentally verify complementarity of electric and magnetic fields as predicted by Babinet's principle. This duality of near-fields can be used to indirectly map resonant magnetic fields close to metallic microstructures by measuring the electric fields close to their complementary analogues which is particularly useful since magnetic near-fields are still extremely difficult to access in the THz regime. We find excellent agreement between the results from theory, simulation and two different experimental near-field techniques.

We present the first direct experimental test of the complex ion structure in liquid carbon at pressures around 100 GPa, using spectrally resolved x-ray scattering from shock-compressed graphite samples. Our results confirm the structure predicted by ab initio quantum simulations and demonstrate the importance of chemical bonds at extreme conditions similar to those found in the interiors of giant planets. The evidence presented here thus provides a firmer ground for modeling the evolution and current structure of carbon-bearing icy giants like Neptune, Uranus, and a number of extrasolar planets.

This Letter reports on the measurement of the energy loss and the projectile charge states of argon ions at an energy of 4  MeV/u penetrating a fully ionized carbon plasma. The plasma of n(e)≈10(20)  cm(-3) and T(e)≈180  eV is created by two laser beams at λ(Las)=532  nm incident from opposite sides on a thin carbon foil. The resulting plasma is spatially homogenous and allows us to record precise experimental data. The data show an increase of a factor of 2 in the stopping power which is in very good agreement with a specifically developed Monte Carlo code, that allows the calculation of the heavy ion beam's charge state distribution and its energy loss in the plasma.

Imaging and sensing applications based on pulsed terahertz radiation have opened new possibilities for scientific and industrial applications. Many exploit the unique features of the terahertz (THz) spectral region, where common packaging materials are transparent and many chemical compounds show characteristic absorptions. Because of their diffraction limit, THz far-field imaging techniques lack microscopic resolution and, if subwavelength features have to be resolved, near-field techniques are required. Here, we present a THz near-field microscopy approach based on photoconductive antennas as the THz emitter and as a near-field probe. Our system allows us to measure amplitude, phase, and polarization of the electric fields in the vicinity of a sample with a spatial resolution on the micrometer scale (approximately lambda/20). Using a dielectric (plant leaf) and a metallic structure (microwire) as examples, we demonstrate the capabilities of our approach.