Targets for high repetition rate laser facilities:needs,challenges and perspectives

A number of laser facilities coming online all over the world promise the capability of high-power laser experiments with shot repetition rates between 1 and 10 Hz. Target availability and technical issues related to the interaction environment could become a bottleneck for the exploitation of such facilities. In this paper, we report on target needs for three different classes of experiments: dynamic compression physics, electron transport and isochoric heating, and laser-driven particle and radiation sources. We also review some of the most challenging issues in target fabrication and high repetition rate operation. Finally, we discuss current target supply strategies and future perspectives to establish a sustainable target provision infrastructure for advanced laser facilities.

Preparation of large,ultra-flexible and free-standing nanomembranes of metal oxide-polymer composite and their gas permeation properties

In this work,fabrication of free-standing nanomembranes of metal oxide(MO_(x))and polymers by simple spin-coating method is discussed.First,double-layer nanomembranes containing MO_(x) and epoxy resin of polyethyleneimine and poly[(o-cresyl glycidyl ether)-co-formaldehyde]were prepared.Free-standing nanomembranes were successfully prepared,but defects formed in the metal oxide nanolayer during sharp bending of the nanomembrane.To overcome fragility of MO_(x) nanolayer,poly(vinyl alcohol)nanolayers were introduced between MO_(x) nanolayers by layer-by-layer(LbL)assembly process.The LbL nanomembrane was also free-standing and was highly flexible during macroscopic membrane manipulations.Even after transfer of the LbL nanomembrane onto a porous support,it did not have apparent cracks,confirmed by scanning electron microscopy(SEM).The LbL nanomembrane sustained low gas permeance,confirming the absence of significant defects,although it shows excellent flexibility.We believe that the presented LbL nanomembrane could be a platform useful for the design of molecular nanochannels,which is the next challenge for efficient gas separation.

Precise Orientational Control of Electroactive Units Using a Tripodal Triptycene Scaffold to Direct Noncovalent Pairing at the Single Molecular Level

A break junction technique has been established to explore conductive behavior at the single molecular level,and recent interest has shifted toward the evaluation of bimolecular systems interacting through noncovalent intermolecular forces.This requires precise control over the orientation of the two molecules so that they can adapt an appropriate face-to-face arrangement between two electrodes.Herein,we present an approach using a tripodal triptycene scaffold that allows for accurate positioning of electroactive subunits with an upright configuration on substrate surfaces.We incorporated electron-donating tetrathiafulvalene or electron-accepting anthraquinone into the molecular scaffold and confirmed that the resulting molecules retain the electronic properties particular to their attached subunits.Self-assembled monolayers(SAMs)of these molecules were prepared on Au(111)and characterized by XPS and STM.STM break junction techniques were applied to the SAMs,revealing two electrical conduction regimes;one arises from single-molecules sandwiched between two electrodes,and the second from intermolecularly interacting homodimers that bridge between electrodes.This observation demonstrates the validity of the approach of using tripodal triptycene scaffolds to precisely direct electroactive subunits to undergo intermolecular pairing.We believe that the present work will provide a new avenue for evaluating the heterodimers at the single molecular level.