Andrew A. Egly

In this study, particle-in-cell (PIC) simulation was used to validate a conceptual design for a quasi-spherical, net power, hydrogen-plus-boron-11-fueled fusion reactor incorporating high-temperature superconducting (HTS) magnets. By burning a fully thermalized plasma, our proposed MET6 reactor uses the principles of the 1980 magneto-electrostatic trap design of Yushmanov to improve the classic Polywell design. Because the input power consumed by the reactor will barely balance the waste bremsstrahlung radiation, future research must focus on reducing the bremsstrahlung losses to reach practical net power levels. The first step to reducing bremsstrahlung, explored in this paper, is to tune the reactor parameters to reduce the energies of trapped electrons. We assume the quality factor Q can be approximated as the ratio of fusion power output divided by bremsstrahlung power loss. Thus, assuming the particles’ power loss is negligible compared to bremsstrahlung power loss, the resulting quality factor is estimated to be Q ≈ 1.3.

Particle in Cell (PIC) simulation has been used to validate a conceptual design for a quasi-spherical, net power, hydrogen plus boron-11 fueled, fusion reactor incorporating high temperature superconducting (HTS) magnets. By burning a fully thermalized plasma, our proposed MET6 reactor uses the principles of Magneto-Electrostatic Trap design of Yushmanov (1980) to improve the classic Polywell design, resulting in a predicted power-balance Q ≈ 1.3. Because the input power consumed by the reactor will barely balance the waste bremsstrahlung radiation, future research must focus on reducing the bremsstrahlung losses to reach practical net power levels. A first step to reducing bremsstrahlung, explored in this paper, is to tune the reactor parameters to reduce the trapped electrons energies.

Optical interferometers used for plasma-density measurements are often robustly mounted, two-arm, high-cost, high-maintenance installations. The Second- Harmonic Dispersion Interferometer (SHDI) is a greatly simplified approach, with a single, common-path optical axis. In this design the primary laser is frequency doubled before, and after, the plasma, in order to allow the dispersive-phase shift between the beams to be measured accurately. Overall the system design is low-cost and low-maintenance and provides superior performance compared to a standard microwave interferometer and second harmonic CO 2 interferometer.[1]

A second-harmonic, dispersion interferometer is used to image large-area (≃5 cm²) plasma-jet and gas-jet density profiles. Achromatic telescopes magnify the diameters of the primary-laser beam (1064 nm) and its second-harmonic (532 nm) before probing the sample and de-magnify the beam diameters after the sample, where the primary beam transfers its phase change to a second, second-harmonic beam, allowing the sample’s dispersive-phase change to be measured between two, orthogonally polarized second harmonic beams. The telescopes produce an azimuthally symmetric, dispersive-phase shift in the sample + background phase-change image and in the background phase-change image, which is removed by digital subtraction. The interferometer’s performance was verified using standard-optical components as dispersive elements (BK7 lenses and wedge plates), resolving a minimum, phase-change sensitivity of Δϕ_min ≳ 15 mrad and spatial resolution of Δx_res ≃ 100 μm. The phase change produced by unknown-density objects (a pulsed-plasma-jet and a pulsed-gas-jet) was measured, and their data were used to recover the original, 2D density profiles using an inverse Abel transform: peak-number density, N_gas ≃ 6 × 10²⁰ cm⁻³ and N_e ≃ 5 × 10¹⁶ cm⁻³; line-integrated density, ∫N_gasdl ∼ 2 × 10¹⁹cm⁻² and ∫N_edl ∼ 1 × 10¹⁶cm⁻². The techniques and methods developed here are scalable to even larger probe-beam diameters and frame-capture rates, leading to a diagnostic capability that is well-suited for applications involving the real-time measurement of density.