Laser generated electron transport experiment in a novel wire nail target

The transport of high intensity (2x1020 W/cm2) laser generated relativistic electrons with a solid target has been studied in a novel geometry. The targets were 20 um diameter solid copper wires, coated with ~ 2um of titanium, with an 80 um diameter hemispherical termination. They were illuminated by an ~500fs, ~200J pulse of 1.053um laser light focused to a ~ 20um diameter spot centered on the flat face of the hemisphere. K-alpha fluorescence from the Cu and Ti regions was imaged together with extreme ultraviolet (X-UV) emission at 68 and 256eV. Results showed a quasi exponential decline in K-alpha emission along the wire over a distance of a few hundred microns from the laser focus, consistent with bulk Ohmic inhibition of the relativistic electron transport. Weaker Ka and X-UV emission on a longer scale length showed limb brightening suggesting a transition to enhanced transport at the surface of the wire

Electron Generation and Transport using Second Harmonic Laser Pulses for Fast Ignition Laser Fusion Energy

A team of University of Alberta researchers, in collaboration with an international team of investigators, has spearheaded an experiment to study the generation and transport of MeV electrons produced by ultra-high intensity second harmonic Nd:Glass laser pulses. Intensities of up to 5 x I O’ 9 W cm2 have been used to irradiate a variety of targets to investigate the conversion efficiency into MeV energy electrons, as well as the energy spectrum and angular divergence of such electrons. Their transport through a cone tip simulating the generation of an energetic electron beam for the fast ignition of a laser-compressed fuel core was also measured. The experiments were carried out at the Titan high intensity 1aser facility located at the Lawrence Livermore National Laboratory. The experiment is the first step towards evaluating the potential effectiveness of using prepulse-free shorter wavelength second harmonic laser pulses as ignition sources for Fast Ignition Fusion Energy

Energy Injection for Fast Ignition

In the fast ignition concept, assembled fuel is ignited through a separate high intensity laser pulse. Fast Ignition targets facilitate this ignition using a reentrant cone. It provides clear access through the overlaying coronal plasma, and controls the laser plasma interaction to optimize hot-electron production and transport into the compressed plasma. Recent results suggest that the cone does not play any role in guiding light or electrons to its tip, and coupling to electrons can be reduced by a small amount of preplasma. This puts stringent requirements on the ignition laser focusing, pointing, and prepulse

Nationwide randomised trial evaluating elective neck dissection for early stage oral cancer (SEND study) with meta-analysis and concurrent real-world cohort.

BACKGROUND Guidelines remain unclear over whether patients with early stage oral cancer without overt neck disease benefit from upfront elective neck dissection (END), particularly those with the smallest tumours. METHODS We conducted a randomised trial of patients with stage T1/T2 N0 disease, who had their mouth tumour resected either with or without END. Data were also collected from a concurrent cohort of patients who had their preferred surgery. Endpoints included overall survival (OS) and disease-free survival (DFS). We conducted a meta-analysis of all six randomised trials. RESULTS Two hundred fifty randomised and 346 observational cohort patients were studied (27 hospitals). Occult neck disease was found in 19.1% (T1) and 34.7% (T2) patients respectively. Five-year intention-to-treat hazard ratios (HR) were: OS HR = 0.71 (p = 0.18), and DFS HR = 0.66 (p = 0.04). Corresponding per-protocol results were: OS HR = 0.59 (p = 0.054), and DFS HR = 0.56 (p = 0.007). END was effective for small tumours. END patients experienced more facial/neck nerve damage; QoL was largely unaffected. The observational cohort supported the randomised findings. The meta-analysis produced HR OS 0.64 and DFS 0.54 (p < 0.001). CONCLUSION SEND and the cumulative evidence show that within a generalisable setting oral cancer patients who have an upfront END have a lower risk of death/recurrence, even with small tumours. CLINICAL TRIAL REGISTRATION NIHR UK Clinical Research Network database ID number: UKCRN 2069 (registered on 17/02/2006), ISCRTN number: 65018995, ClinicalTrials.gov Identifier: NCT00571883