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Revived interest in proton-boron fusion has been fuelled by new laser matter interaction schemes with several possible applications. The authors report on a tabletop laser experiment that observes proton-boron fusion with an emphasis on the secondary cross-section peak around 150 keV.

Laser-driven proton-boron (pB) fusion has been gaining significant interest for energetic alpha particles production because of its neutron-less nature. This approach requires the use of B- and H-rich materials as targets, and common practice is the use of BN and conventional polymers. In this work, we chose plasma-assisted vapour phase deposition to prepare films of oligoethylenes (plasma polymers) on Boron Nitride BN substrates as an advanced alternative. The r.f. power delivered to the plasma was varied between 0 and 50 W to produce coatings with different crosslink density and hydrogen content, while maintaining the constant thickness of 1 μm. The chemical composition, including the hydrogen concentration, was investigated using XPS and RBS/ERDA, whereas the surface topography was analyzed using SEM and AFM. We triggered the pB nuclear fusion reaction focusing laser pulses from two different systems (i.e., the TARANIS multi-TW laser at the Queen’s University Belfast (United Kingdom) and the PERLA B 10-GW laser system at the HiLASE center in Prague (Czech Republic)) directly onto these targets. We achieved a yield up to 108 and 104 alpha particles/sr using the TARANIS and PERLA B lasers, respectively. Radiative-hydrodynamic and particle-in-cell PIC simulations were performed to understand the laser-target interaction and retrieve the energy spectra of the protons. The nuclear collisional algorithm implemented in the WarpX PIC code was used to identify the region where pB fusion occurs. Taken together, the results suggest a complex relationship between the hydrogen content, target morphology, and structure of the plasma polymer, which play a crucial role in laser absorption, target expansion, proton acceleration and ultimately nuclear fusion reactions in the plasma.

Injuries to the posterolateral corner (PLC) of the knee are uncommon, and usually associated with other ligamentous injuries. A combined posterior cruciate ligament (PCL) and PLC tear is the most frequent combination. Several studies describe anatomic reconstructive techniques using an open approach with large incisions and extensive exploration of the posterolateral structures. This Technical Note describes an all-arthroscopic technique as a safe and efficient treatment of combined PCL and PLC instability using the trans-septal approach.

Background: The arthroscopic approach to the posterior compartment of the knee is always challenging. This easy arthroscopic transseptal approach allows safe access to the posterior compartment of the knee, avoiding any potential neurovascular injury. Indications: Indications include arthroscopic posterior cruciate ligament (PCL) reconstruction, fixation of avulsion fractures of the tibial attachment of the PCL, arthroscopic posterolateral corner reconstruction, removal of loose bodies from the posterior compartment, PCL cyst removal, ramp repair, and arthroscopic arthrolysis of the posterior compartment. Technique Description: Using a posteromedial portal, a shaver is introduced with the tip in direct contact with the medial side of the septum facing anteriorly, away from the popliteal neurovascular bundle. The scope is then inserted into the posterolateral compartment to visualize the lateral side of the septum while the shaver remains in the posteromedial compartment. The septum is then released until the tip of the shaver is visible. The shaver is then removed and the scope can now be inserted from the posteromedial portal to the posterolateral compartment through the released septum. Results: The transseptal approach can be performed without any additional risk if the shaver remains centrally on the inferior aspect of the septum. Therefore, the risk of iatrogenic injury of the middle genicular artery is minimized. Likewise, with the knee flexed to 90°, there is no risk of damaging the popliteal neurovascular bundle. Having a precise knowledge of the anatomy of the posterior compartment of the knee minimizes any risks of the transseptal approach, avoiding any additional surgical time whilst facilitating the indicated operation. Conclusion: This easy arthroscopic transseptal approach allows safe access to the posterior compartment of the knee, avoiding any potential neurovascular injury.

The generation, detection, and quantification of high-energy proton spectra that are produced from laser-target interaction methodologies is a field of increasingly growing popularity over the last 20 years. Generation methods such as target normal sheath acceleration or similar allow for collimated laminar ion beams to be produced in a compact environment through the use of short-burst terawatt lasers and are a growing field of investment. This project details the development and refinement of a python-based code to analyze time-of-flight ion spectroscopy data, with the intent to pinpoint the maximum proton energy within the incident beam to as reliable and accurate a value as possible within a feasible processing time. TOF data for 2.2 × 1016 W/cm2 intensity laser shots incident on a 2 mm Cu target that were gathered from the PERLA 1 kHz laser at the HiLASE center were used as training and testing data with the implementation of basic machine learning techniques to train these methods to the data being used. These datasets were used to ensure more widely applicable functionality, and accurate calculation to within 1% accuracy of an assumed correct value was seen to be consistently achievable for these datasets. This wider functionality indicates a high level of accuracy for previously unseen TOF datasets, regardless of signal/noise levels or dataset size, allowing for free use of the code in the wider field.

Abstract Highly regular laser-induced periodic surface structures (HR-LIPSS) have been fabricated on surfaces of Mo, steel alloy and Ti at a record processing speed on large areas and with a record regularity in the obtained sub-wavelength structures. The physical mechanisms governing LIPSS regularity are identified and linked with the decay length (i.e. the mean free path) of the excited surface electromagnetic waves (SEWs). The dispersion of the LIPSS orientation angle well correlates with the SEWs decay length: the shorter this length, the more regular are the LIPSS. A material dependent criterion for obtaining HR-LIPSS is proposed for a large variety of metallic materials. It has been found that decreasing the spot size close to the SEW decay length is a key for covering several cm2 of material surface by HR-LIPSS in a few seconds. Theoretical predictions suggest that reducing the laser wavelength can provide the possibility of HR-LIPSS production on principally any metal. This new achievement in the unprecedented level of control over the laser-induced periodic structure formation makes this laser-writing technology to be flexible, robust and, hence, highly competitive for advanced industrial applications based on surface nanostructuring.

Two different scenarios are usually invoked in the formation of femtosecond Laser-Induced Periodic Surface Structures (LIPSS), either “self-organization” mechanisms or a purely “plasmonic” approach. In this paper, a three-step model of formation of single-laser-shot LIPSS is summarized. It is based on the periodic perturbation of the electronic temperature followed by an amplification, for given spatial periods, of the modulation in the lattice temperature and a final possible relocation by hydrodynamic instabilities. An analytical theory of the evolution of the temperature inhomogeneities is reported and supported by numerical calculations on the examples of three different metals: Al, Au, and Mo. The criteria of the possibility of hydrodynamic instabilities are also discussed.