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We introduce a concept of laser-generated neutrons to transmute transuranic elements separated from spent nuclear fuel (SNF) and dissolved in a molten salt to form a subcritical core whose liquid s...

Efficiently heating a magnetically confined plasma to thermonuclear temperatures remains a central issue in fusion energy research. One well-established technique is to inject beams of neutral particles into the plasma, a process known as neutral beam injection. In the classical picture, fast ions generated from neutral beam injection predominantly heat electrons as they are slowed by friction. This electron heat is then collisionally coupled to the plasma ions, which comprise the fusion fuel. Fast ions can also drive plasma waves, which divert energy from the fuel and can degrade confinement. Here we present new observations from a field reversed configuration plasma in which a beam-driven wave in the open field line region couples directly to fuel ions, drawing a high-energy tail on subcollisional timescales that dramatically enhances the fusion rate. This mode therefore allows the beam energy to bypass the electron channel and does so without having a deleterious effect on global plasma confinement. Our results demonstrate a means of directly and non-destructively coupling energy from fast ions to plasma ions, which may pave the way for improved neutral beam injection heating efficiency or the prevention of ash accumulation with alpha channelling. A major challenge for achieving useful thermonuclear fusion regimes is heating plasma to reactive temperature conditions. It is demonstrated experimentally how energetic ions, generated via neutral beam injection, can be exploited for this process.

To simulate an early 20th century viral pneumonia radiotherapy treatment using modern fluoroscopy and evaluated it according to current dose guidelines. Monte Carlo was used to assess the dose distribution on an anthropomorphic phantom. Critical organs were: skin, breasts, esophagus, ribs, vertebrae, heart, thymus, and spinal cord. A 100 kVp beam with 3 mm Al HVL, 25 × 25 cm2 posterior-anterior (PA) field and 50 cm source-to-surface distance were simulated. Simulations had a resolution of 0.4 × 0.4 × 0.06 cm3 and a 6% uncertainty. Hundred percent dose was normalized to the skin surface and results were displayed in axial, coronal, and sagittal planes. Dose volume histograms were generated in MATLAB for further analysis. Prescription doses of 0.3, 0.5, and 1.0 Gy were applied to the 15% isodose for organ-dose comparison to current tolerances and potential risk of detriment. Ninety-five and ninety-seven percent of the right and left lung volumes, respectively, were well-covered by the 15% isodose line. For the 0.3, 0.5, and 1.0 Gy prescriptions, the maximum skin doses were 2.9, 4.8, and 9.6 Gy compared to a 2.0 Gy transient erythema dose threshold; left/right lung maximum doses were 1.44/1.46, 2.4/2.4, and 4.8/4.9 Gy compared to a 6.5 Gy pneumonitis and 30 Gy fibrosis thresholds; maximum heart doses were 0.5, 0.9, and 1.8 Gy compared to the 0.5 Gy ICRP-recommendation; maximum spinal cord doses were 1.4, 2.3, and 4.6 Gy compared to 7.0 Gy single fraction dose threshold. Maximum doses to other critical organs were below modern dose thresholds. A 100 kVp PA field could deliver a 0.3 Gy or 0.5 Gy dose without risk of complications. However, a 1.0 Gy dose treatment could be problematic. Critical organ doses could be further reduced if more than one treatment field is used.

The advanced beam-driven FRC is a Field Reversed Configuration (FRC) with the addition of neutral beam (NB) injection, electrode biasing, and magnetic expander divertors. The resulting configuration has novel features that make it necessary to revisit many key results in FRC theory. Three of these features include (i) a large energetic ion population, (ii) in-principle capability to adjust the electric field and rotation profiles, and (iii) a combination of magnetic and electrostatic confinement of electrons in the SOL. In some fueling scenarios the electron density profile may exhibit a significant peak outside of the separatrix. To explore these features a hybrid fluid/kinetic equilibrium model has been used to reconstruct typical experimental profiles of the C-2W experiment. Results indicate that the energetic ions provide at least 50% of the total plasma pressure. These equilibrium profiles have been used as initial conditions for global, cross-separatrix, turbulent transport simulations using the 3D electrostatic particle-in-cell code ANC. Electrostatic fluctuations were found to nonlinearly saturate at an amplitude which is an order magnitude lower than that observed previously. The tokamak turbulence code GTC code has also been extended to handle FRC physics in the new GTC-X version, which has been used to perform simulations of turbulent transport in the SOL relevant to electrode biasing. It is found that equilibrium × flow shear significantly decreases ion temperature gradient saturation amplitude and ion heat transport. Also in the SOL, a 1D2V continuum code has been developed and applied to parallel electron heat transport. Results show the formation of pre-sheath potential and reduction of parallel electron heat loss close to the ideal ambipolar limit, a result which has been validated by experimental diagnostics. These transport modifications caused by the three novel configuration features help to explain the remarkable plasma performance of the C-2W experiment.

International audience; Recent developments in fiber lasers and nanomaterials have allowed the possibility of using laser wakefield acceleration (LWFA) as the source of low-energy electron radiation for endoscopic and intraoperative brachytherapy, a technique in which sources of radiation for cancer treatment are brought directly to the affected tissues, avoiding collateral damage to intervening tissues. To this end, the electron dynamics of LWFA is examined in the high-density regime. In the near-critical density regime, electrons are accelerated by the ponderomotive force followed by an electron sheath formation, resulting in a flow of bulk electrons. These low-energy electrons penetrate tissue to depths typically less than 1 mm. First a typical resonant laser pulse is used, followed by lower-intensity, longer-pulse schemes, which are more amenable to a fiber-laser application.

C-2 is a unique, large compact-toroid (CT) device at Tri Alpha Energy that produces field-reversed configuration (FRC) plasmas by colliding and merging oppositely directed CTs. Significant progress has recently been made on C-2, achieving ~5 ms stable plasmas with a dramatic improvement in confinement, far beyond the prediction from the conventional FRC scaling. This stable, long-lived FRC plasma state is called the high-performance FRC (HPF) regime. The key approaches to achieve the HPF regime are as follows: (i) dynamic FRC formation by collision/merging of super-Alfvenic CTs, (ii) effective control of stability and transport by end-on plasma guns and neutral-beam (NB) injection, and (iii) active wall conditioning using titanium and lithium gettering systems. Moreover, further improvement in FRC confinement has been obtained with improved open-field-line plasma properties such as a lower fluctuation level, reduced transport rates in radial/axial directions, and lower background neutral density a...

TAE Technologies' research is devoted to producing high temperature, stable, long-lived field-reversed configuration (FRC) plasmas by neutral-beam injection (NBI) and edge biasing/control. The newly constructed C-2W experimental device (also called "Norman") is the world's largest compact-toroid (CT) device, which has several key upgrades from the preceding C-2U device such as higher input power and longer pulse duration of the NBI system as well as installation of inner divertors with upgraded electrode biasing systems. Initial C-2W experiments have successfully demonstrated a robust FRC formation and its translation into the confinement vessel through the newly installed inner divertor with adequate guide magnetic field. They also produced dramatically improved initial FRC states with higher plasma temperatures (Te ~250+ eV; total electron and ion temperature g1.5 keV, based on pressure balance) and more trapped flux (up to ~15 mWb, based on rigid-rotor model) inside the FRC immediately after the merger of collided two CTs in the confinement section. As for effective edge control on FRC stabilization, a number of edge biasing schemes have been tried via open field-lines, in which concentric electrodes located in both inner and outer divertors as well as end-on plasma guns are electrically biased independently. As a result of effective outer-divertor electrode biasing alone, FRC plasma diamagnetism duration has reached up to ~9 ms which is equivalent to C-2U plasma duration. Magnetic field flaring/expansion in both inner and outer divertors plays an important role in creating a thermal insulation on open field-lines to reduce a loss rate of electrons, which leads to improvement of the edge and core FRC confinement properties. Experimental campaign with inner-divertor magnetic-field flaring has just commenced and early result indicates that electron temperature of the merged FRC stays relatively high and increases for a short period of time, presumably by NBI and ExB heating.

Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095, USAA high temperature, stable, long-lived field-reversed configuration (FRC) plasma state has been produced in the C-2 device by dynamically colliding and merging two oppositely directed compact toroids, with combining effects of biasing edge plasma near the FRC separatrix from an end-plasma-gun with magnetic-mirror-plugs andof neutral-beam (NB) injection. The plasma-gun creates an inward radial electric field which mitigates the n = 2rotational instability. The gun also produces E×B velocity shear in the FRC edge layer, which may explain observations of improved transport properties. The FRCs are nearly axisymmetric which enables fast ion confinement, and increasing NB power input clearly extends the FRC lifetime. The combined effects of the plasma-gun with mirror-plugs and of NB injection yield anew High Performance FRC regime with confinement times improved by factors 2 to 4 and FRC lifetimes extended from 1 to 3 ms.

Conventional field-reversed configurations (FRC) face notable stability and confinement concerns, which can be ameliorated by introducing and maintaining a significant fast ion population in the system. This is the conjecture first introduced by Norman Rostoker multiple decades ago and adopted as the central design tenet in Tri Alpha Energy’s advanced beam driven FRC concept. In fact, studying the physics of such neutral beam (NB) driven FRCs over the past decade, considerable improvements were made in confinement and stability. Next to NB injection, the addition of axially streaming plasma guns, magnetic end plugs, as well as advanced surface conditioning lead to dramatic reductions in turbulence driven losses and greatly improved stability. In turn, fast ion confinement improved significantly and allowed for the build-up of a dominant fast particle population. This recently led to the breakthrough of sustaining an advanced beam driven FRC, thereby demonstrating successful maintenance of trapped magnetic flux, plasma dimensions and total pressure inventory for times much longer than all characteristic system time scales and only limited by hardware and electric supply constraints.

The Field Reversed Configuration (FRC) is a high-beta Compact Toroid that includes closed and open field line regions of poloidal magnetic field. Improving the transport properties of both regions ...

In modern field-reversed configuration (FRC) experiments (Binderbauer et al 2015 Phys. Plasmas 22 056110) at TAE Technologies, classical FRC instabilities are suppressed by advanced neutral beam injection and edge biasing methods, leading to high plasma confinement and fast ion pressure built-up which is comparable to the bulk plasma pressure. In some of these high performance FRC plasmas, a new macroscopically non-destructive fast ion driven micro-burst instability is observed as periodic small amplitude bursts with frequency down chirping in the diamagnetic drift frequency range, repeating about every 0.1 to 0.5 ms. The occurrence of these micro-bursts and burst-free operation can be controlled by changing the injected neutral beam energy. Major observed characteristics of this new instability are presented. Possible explanation of the phenomenon is suggested.

Developing a stable plasma state with high-beta (ratio of plasma to magnetic pressures) is of critical importance for an economic magnetic fusion reactor. At the forefront of this endeavour is the field-reversed configuration. Here we demonstrate the kinetic stabilizing effect of fast ions on a disruptive magneto-hydrodynamic instability, known as a tilt mode, which poses a central obstacle to further field-reversed configuration development, by energetic beam injection. This technique, combined with the synergistic effect of active plasma boundary control, enables a fully stable ultra-high-beta (approaching 100%) plasma with a long lifetime.

X-ray therapy was used to treat pneumonia during the first half of the 20th century. Fifteen studies report that approximately 700 cases of bacterial (lobar and bronchopneumonia), sulfanilamide non-responsive, interstitial, and atypical pneumonia were effectively treated by low doses of X-rays, leading to disease resolution, based on clinical symptoms, objective disease biomarkers, and mortality incidence. The capacity of the X-ray treatment to reduce mortality was similar to serum therapy and sulfonamide treatment during the same time period. Studies with four experimental animal models (i.e., mice, guinea pig, cat, and dog) with bacterial and viral pneumonia supported the clinical findings. The mechanism by which the X-ray treatment acts upon pneumonia involves the induction of an anti-inflammatory phenotype that leads to a rapid reversal of clinical symptoms, facilitating disease resolution. The capacity of low doses of X-rays to suppress inflammatory responses is a significant new concept with widespread biomedical and therapeutic applications.

Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The $n=2$ rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces $E\ifmmode\times\else\texttimes\fi{}B$ shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms.

A high temperature field reversed configuration (FRC) has been produced in the newly built, world’s largest compact toroid (CT) facility, C-2, by colliding and merging two high-β CTs produced using the advanced field-reversed θ-pinch technology. This long-lived, stable merged state exhibits the following key properties: (1) apparent increase in the poloidal flux from the first pass to the final merged state, (2) significantly improved confinement compared to conventional θ-pinch FRCs with flux decay rates approaching classical values in some cases, (3) strong conversion from kinetic energy into thermal energy with total temperature (Te + Ti) exceeding 0.5 keV, predominantly into the ion channel. Detailed modeling using a new 2-D resistive magnetohydrodynamic (MHD) code, LamyRidge, has demonstrated, for the first time, the formation, translation, and merging/reconnection dynamics of such extremely high-β plasmas.

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-β plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

Conventional field-reversed configurations (FRCs), high-beta, prolate compact toroids embedded in poloidal magnetic fields, face notable stability and confinement concerns. These can be ameliorated by various control techniques, such as introducing a significant fast ion population. Indeed, adding neutral beam injection into the FRC over the past half-decade has contributed to striking improvements in confinement and stability. Further, the addition of electrically biased plasma guns at the ends, magnetic end plugs, and advanced surface conditioning led to dramatic reductions in turbulence-driven losses and greatly improved stability. Together, these enabled the build-up of a well-confined and dominant fast-ion population. Under such conditions, highly reproducible, macroscopically stable hot FRCs (with total plasma temperature of ∼1 keV) with record lifetimes were achieved. These accomplishments point to the prospect of advanced, beam-driven FRCs as an intriguing path toward fusion reactors. This paper reviews key results and presents context for further interpretation.