Fast electron transport dynamics and energy deposition in magnetized, imploded cylindrical plasma.

Inertial confinement fusion approaches involve the creation of high-energy-density states through compression. High gain scenarios may be enabled by the beneficial heating from fast electrons produced with an intense laser and by energy containment with a high-strength magnetic field. Here, we report experimental measurements from a configuration integrating a magnetized, imploded cylindrical plasma and intense laser-driven electrons as well as multi-stage simulations that show fast electrons transport pathways at different times during the implosion and quantify their energy deposition contribution. The experiment consisted of a CH foam cylinder, inside an external coaxial magnetic field of 5 T, that was imploded using 36 OMEGA laser beams. Two-dimensional (2D) hydrodynamic modelling predicts the CH density reaches [Formula: see text], the temperature reaches 920 eV and the external B-field is amplified at maximum compression to 580 T. At pre-determined times during the compression, the intense OMEGA EP laser irradiated one end of the cylinder to accelerate relativistic electrons into the dense imploded plasma providing additional heating. The relativistic electron beam generation was simulated using a 2D particle-in-cell (PIC) code. Finally, three-dimensional hybrid-PIC simulations calculated the electron propagation and energy deposition inside the target and revealed the roles the compressed and self-generated B-fields play in transport. During a time window before the maximum compression time, the self-generated B-field on the compression front confines the injected electrons inside the target, increasing the temperature through Joule heating. For a stronger B-field seed of 20 T, the electrons are predicted to be guided into the compressed target and provide additional collisional heating. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 2)'.

Collimated Propagation of Fast Electron Beams Accelerated by High-Contrast Laser Pulses in Highly Resistive Shocked Carbon.

Collimated transport of ultrahigh intensity electron current was observed in cold and in laser-shocked vitreous carbon, in agreement with simulation predictions. The fast electron beams were created by coupling high-intensity and high-contrast laser pulses onto copper-coated cones drilled into the carbon samples. The guiding mechanism-observed only for times before the shock breakout at the inner cone tip-is due to self-generated resistive magnetic fields of ∼0.5-1 kT arising from the intense currents of fast electrons in vitreous carbon, by virtue of its specific high resistivity over the range of explored background temperatures. The spatial distribution of the electron beams, injected through the samples at different stages of compression, was characterized by side-on imaging of hard x-ray fluorescence.

A multi-stage scintillation counter for GeV-scale multi-species ion spectroscopy in laser-driven particle acceleration experiments.

Particle counting analysis (PCA) with a multi-stage scintillation detector shows a new perspective on angularly resolved spectral characterization of GeV-scale, multi-species ion beams produced by high-power lasers. The diagnosis provides a mass-dependent ion energy spectrum based on time-of-flight and pulse-height analysis of single particle events detected through repetitive experiments. With a novel arrangement of multiple scintillators with different ions stopping powers, PCA offers potential advantages over commonly used diagnostic instruments (CR-39, radiochromic films, Thomson parabola, etc.) in terms of coverage solid angle, detection efficiency for GeV-ions, and real-time analysis during the experiment. The basic detector unit was tested using 230-MeV proton beam from a synchrotron facility, where we demonstrated its potential ability to discriminate major ion species accelerated in laser-plasma experiments (i.e., protons, deuterons, carbon, and oxygen ions) with excellent energy and mass resolution. The proposed diagnostic concept would be essential for a better understanding of laser-driven particle acceleration, which paves the way toward all-optical compact accelerators for a range of applications.

Development of an experimental platform for the investigation of laser-plasma interaction in conditions relevant to shock ignition regime.

The shock ignition (SI) approach to inertial confinement fusion is a promising scheme for achieving energy production by nuclear fusion. SI relies on using a high intensity laser pulse (≈1016 W/cm2, with a duration of several hundred ps) at the end of the fuel compression stage. However, during laser-plasma interaction (LPI), several parametric instabilities, such as stimulated Raman scattering and two plasmon decay, nonlinearly generate hot electrons (HEs). The whole behavior of HE under SI conditions, including their generation, transport, and final absorption, is still unclear and needs further experimental investigation. This paper focuses on the development of an experimental platform for SI-related experiments, which simultaneously makes use of multiple diagnostics to characterize LPI and HE generation, transport, and energy deposition. Such diagnostics include optical spectrometers, streaked optical shadowgraph, an x-ray pinhole camera, a two-dimensional x-ray imager, a Cu Kα line spectrometer, two hot-electron spectrometers, a hard x-ray (bremsstrahlung) detector, and a streaked optical pyrometer. Diagnostics successfully operated simultaneously in single-shot mode, revealing the features of HEs under SI-relevant conditions.

Kilotesla plasmoid formation by a trapped relativistic laser beam.

A strong quasistationary magnetic field is generated in hollow targets with curved internal surface under the action of a relativistically intense picosecond laser pulse. Experimental data evidence the formation of quasistationary strongly magnetized plasma structures decaying on a hundred picoseconds timescale, with the magnetic field strength of the kilotesla scale. Numerical simulations unravel the importance of transient processes during the magnetic field generation and suggest the existence of fast and slow regimes of plasmoid evolution depending on the interaction parameters. The proposed setup is suited for perspective highly magnetized plasma application and fundamental studies.

Neural network analysis of quasistationary magnetic fields in microcoils driven by short laser pulses.

Optical generation of kilo-tesla scale magnetic fields enables prospective technologies and fundamental studies with unprecedentedly high magnetic field energy density. A question is the optimal configuration of proposed setups, where plenty of physical phenomena accompany the generation and complicate both theoretical studies and experimental realizations. Short laser drivers seem more suitable in many applications, though the process is tangled by an intrinsic transient nature. In this work, an artificial neural network is engaged for unravelling main features of the magnetic field excited with a picosecond laser pulse. The trained neural network acquires an ability to read the magnetic field values from experimental data, extremely facilitating interpretation of the experimental results. The conclusion is that the short sub-picosecond laser pulse may generate a quasi-stationary magnetic field structure living on a hundred picosecond time scale, when the induced current forms a closed circuit.

Predictive capability of material screening by fast neutron activation analysis using laser-driven neutron sources.

Bright, short-pulsed neutron beams from laser-driven neutron sources (LANSs) provide a new perspective on material screening via fast neutron activation analysis (FNAA). FNAA is a nondestructive technique for determining material elemental composition based on nuclear excitation by fast neutron bombardment and subsequent spectral analysis of prompt γ-rays emitted by the active nuclei. Our recent experiments and simulations have shown that activation analysis can be used in practice with modest neutron fluences on the order of 105 n/cm2, which is available with current laser technology. In addition, time-resolved γ-ray measurements combined with picosecond neutron probes from LANSs are effective in mitigating the issue of spectral interference between elements, enabling highly accurate screening of complex samples containing many elements. This paper describes the predictive capability of LANS-based activation analysis based on experimental demonstrations and spectral calculations with Monte Carlo simulations.

Super-strong magnetic field-dominated ion beam dynamics in focusing plasma devices.

High energy density physics is the field of physics dedicated to the study of matter and plasmas in extreme conditions of temperature, densities and pressures. It encompasses multiple disciplines such as material science, planetary science, laboratory and astrophysical plasma science. For the latter, high energy density states can be accompanied by extreme radiation environments and super-strong magnetic fields. The creation of high energy density states in the laboratory consists in concentrating/depositing large amounts of energy in a reduced mass, typically solid material sample or dense plasma, over a time shorter than the typical timescales of heat conduction and hydrodynamic expansion. Laser-generated, high current-density ion beams constitute an important tool for the creation of high energy density states in the laboratory. Focusing plasma devices, such as cone-targets are necessary in order to focus and direct these intense beams towards the heating sample or dense plasma, while protecting the proton generation foil from the harsh environments typical of an integrated high-power laser experiment. A full understanding of the ion beam dynamics in focusing devices is therefore necessary in order to properly design and interpret the numerous experiments in the field. In this work, we report a detailed investigation of large-scale, kilojoule-class laser-generated ion beam dynamics in focusing devices and we demonstrate that high-brilliance ion beams compress magnetic fields to amplitudes exceeding tens of kilo-Tesla, which in turn play a dominant role in the focusing process, resulting either in a worsening or enhancement of focusing capabilities depending on the target geometry.

Efficient multi-keV x-ray generation from a high-Z target irradiated with a clean ultra-short laser pulse.

Kα line emissions from Mo and Ag plates were experimentally studied using clean, ultrahigh-intensity femtosecond laser pulses. The absolute yields of Kα x-rays at 17 keV from Mo and 22 keV from Ag were measured as a function of the laser pulse contrast ratio and irradiation intensity. Significantly enhanced Kα yields were obtained for both Mo and Ag by employing high contrast ratios and irradiances. Conversion efficiencies of 4.28×10⁻5/sr for Mo and 4.84×10⁻5/sr for Ag, the highest values obtained to date, were demonstrated with contrast ratios in the range 10⁻¹° to 10⁻¹¹.

Comparison of the surgical outcomes of thoracoscopic lobectomy, segmentectomy, and wedge resection for clinical stage I non-small cell lung cancer.

BACKGROUND: Video-assisted thoracoscopic surgery (VATS) for clinical stage I non-small cell lung cancer (NSCLC) has been widely used as a less invasive surgical procedure, but the resection method is still controversial. We retrospectively compared the surgical outcomes of lobectomy, segmentectomy and wedge resection. PATIENTS AND METHODS: A total of 411 patients with clinical stage I NSCLC who underwent VATS (218 males and 193 females, aged 69.3 years; 345 adenocarcinomas, 57 squamous cell carcinomas, and 9 others) were investigated. The surgical procedure was lobectomy in 289, segmentectomy in 38, and wedge resection in 84. Surgical outcomes were compared among these 3 groups. RESULTS: Demographic characteristics showed that the rate of elderly and male patients was higher in the wedge resection group. The 5-year survival rates for the lobectomy, segmentectomy, and wedge resection groups were 82.1, 87.2, and 55.4%, respectively. In the wedge resection group, the 5-year survival rate was 83.3% in patients undergoing intentional low-risk operations for small tumors with ground glass opacity, and 41.1% in those undergoing conservative high-risk operations because of comorbidities. Using Cox's proportional multivariate analysis and sex differences, histology, and tumor size as co-influential factors, the surgical procedure was found to be a significantly poor prognostic factor, and the hazard ratio of wedge resection relative to lobectomy was 4.30. CONCLUSION: The outcomes of VATS lobectomy and segmentectomy procedures for clinical stage I NSCLC were equivalent, while the outcome for VATS wedge resection was inferior. VATS wedge resection for clinical stage I NSCLC should be carefully indicated and requires adequate patient selection.

Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) following carboplatin-paclitaxel administration in a patient with lung cancer.

A 60-year-old female underwent right upper lobectomy of the lung and lymph node dissection under a diagnosis of cancer in the upper lobe of the right lung. Pathological examination showed stage IIIA adenocarcinoma with mediastinal lymph node metastasis. One month after the operation, adjuvant chemotherapy with carboplatin (CBDCA) and paclitaxel (PTX) was initiated. Four days after the chemotherapy, hyponatremia progressed, and central nervous system disorder developed. A diagnosis of syndrome of inappropriate secretion of antidiuretic hormone (SIADH) was made. She recovered after fluid intake restriction and electrolyte correction. SIADH was considered to be due to the adverse effects of anticancer drugs. In postoperative adjuvant chemotherapy, attention should be paid to the serum Na level.

Dosimetric calibration of GafChromic HD-V2, MD-V3, and EBT3 films for dose ranges up to 100 kGy.

A dosimetric calibration of three types of radiochromic films (GafChromicTM HD-V2, MD-V3, and EBT3) was carried out for absorbed doses (D) ranging up to 100 kGy using a 130 TBq Co60 γ-ray source. The optical densities (ODs) of the irradiated films were acquired with the transmission-mode flatbed film scanner EPSON GT-X980. The calibration data were cross-checked using the 20-MeV proton beam from the azimuthally varying field cyclotron at the Research Center for Nuclear Physics in Osaka University. These experimental results not only present the measurable dose ranges of the films depending on the readout wavelength, but also show consistency with our hypothesis that the OD response curve [log(OD)-log(D) curve] is determined by the volumetric average of the absorption dose and does not strongly depend on the type of radiation for the excitation.

Energetic α-particle sources produced through proton-boron reactions by high-energy high-intensity laser beams.

In an experiment performed with a high-intensity and high-energy laser system, α-particle production in proton-boron reaction by using a laser-driven proton beam was measured. α particles were observed from the front and also from the rear side, even after a 2-mm-thick boron target. The data obtained in this experiment have been analyzed using a sequence of numerical simulations. The simulations clarify the mechanisms of α-particle production and transport through the boron targets. α-particle energies observed in the experiment and in the simulation reach 10-20 MeV through energy transfer from 20-30 MeV energy incident protons. Despite the lower cross sections for protons with energy above the sub-MeV resonances in the proton-boron reactions, 10^{8}-10^{9}α particles per steradian have been detected.

A case of G-CSF-producing invasive apical cancer resected following preoperative adjuvant therapy.

The patient was a 47-year-old male with the chief complaints of right shoulder pain and fever. A 10-cm mass was found to be present in the right pulmonary apical region on chest X-ray examination. The mass was diagnosed as a G-CSF-producing invasive apical cancer and the patient underwent chemoradiotherapy followed by right upper lobectomy with combined resection of the chest wall, and lymph node dissection. A very small nodule was noted in the right frontal lobe on brain MRI before surgery, and the final diagnosis was pT3N0M1, stage IV lung adenocarcinoma. For the brain metastasis, gamma knife treatment and chemotherapy were performed after surgery, and there was no recurrence during 16 months after surgery. The prognosis for G-CSF-producing lung cancer and invasive apical cancer is poor. This was a rare and difficult case of lung cancer showing both characteristics of lung cancer.

Mediastinal tuberculous lymphadenitis with intractable fistula to the neck.

A 62-year-old female consulted our hospital due to an ulceration on the skin of her neck and a mediastinal tumor. Chest CT scan and MRI revealed a mediastinal tumor-like lesion with direct progression to the neck skin lesion. En bloc resection of the tumor including the neck skin ulcer was performed under a median sternotomy. Mediastinal tuberculous lymphadenitis was diagnosed histologically. This is a case of a very rare type of mediastinal tuberculous lymphadenitis that progressed to the neck with an intractable fistula.

Generation of focusing ion beams by magnetized electron sheath acceleration.

We present the first 3D fully kinetic simulations of laser driven sheath-based ion acceleration with a kilotesla-level applied magnetic field. The application of a strong magnetic field significantly and beneficially alters sheath based ion acceleration and creates two distinct stages in the acceleration process associated with the time-evolving magnetization of the hot electron sheath. The first stage delivers dramatically enhanced acceleration, and the second reverses the typical outward-directed topology of the sheath electric field into a focusing configuration. The net result is a focusing, magnetic field-directed ion source of multiple species with strongly enhanced energy and number. The predicted improvements in ion source characteristics are desirable for applications and suggest a route to experimentally confirm magnetization-related effects in the high energy density regime. We additionally perform a comparison between 2D and 3D simulation geometry, on which basis we predict the feasibility of observing magnetic field effects under experimentally relevant conditions.

Proof-of-principle experiment for laser-driven cold neutron source.

The scientific and technical advances continue to support novel discoveries by allowing scientists to acquire new insights into the structure and properties of matter using new tools and sources. Notably, neutrons are among the most valuable sources in providing such a capability. At the Institute of Laser Engineering, Osaka, the first steps are taken towards the development of a table-top laser-driven neutron source, capable of producing a wide range of energies with high brightness and temporal resolution. By employing a pure hydrogen moderator, maintained at cryogenic temperature, a cold neutron ([Formula: see text]) flux of [Formula: see text]/pulse was measured at the proximity of the moderator exit surface. The beam duration of hundreds of ns to tens of [Formula: see text] is evaluated for neutron energies ranging from 100s keV down to meV via Monte-Carlo techniques. Presently, with the upcoming J-EPoCH high repetition rate laser at Osaka University, a cold neutron flux in orders of [Formula: see text] is expected to be delivered at the moderator in a compact beamline.

Relativistic magnetic reconnection in laser laboratory for testing an emission mechanism of hard-state black hole system.

Magnetic reconnection in a relativistic electron magnetization regime was observed in a laboratory plasma produced by a high-intensity, large energy, picoseconds laser pulse. Magnetic reconnection conditions realized with a laser-driven several kilotesla magnetic field is comparable to that in the accretion disk corona of black hole systems, i.e., Cygnus X-1. We observed particle energy distributions of reconnection outflow jets, which possess a power-law component in a high-energy range. The hardness of the observed spectra could explain the hard-state x-ray emission from accreting black hole systems.

Biosynthesis of agr and beta-Ecdysones from Cholesterol outside the Prothoracic Gland in Bombyx mori.

Labeling experiments have established that cholesterol is converted into alpha-and beta-ecdysones in isolated abdomens of silkworm larvae. Since the isolated abdomens do not contain the prothoracic glands, a doubt is cast on the long-standing principle in insect endocrinology that the prothoracic glands are the source of ecdysone secretion.