An Interesting Poster to look at from the Tri Alpha Energy Team in California

Fig. 1: 2D drawing of CTI with annotations.
Fig. 11: Detail of CT injectors on C-2W.
Preliminary Results of Multi-pulse Compact Toroid Refueling in the C-2W Field-Reversed Configuration
Abstract: One of the limiting factors in the lifetime of a field- reversed configuration (FRC) is particle loss. To refuel the long- lived FRC plasma in the C-2W experiment a multi-pulse compact toroid injector (CTI) has been developed. Refueling is accomplished with two radially oriented magnetized coaxial plasma guns(MCPG), diametrically opposed on the mid-plane of the confinement vessel. The MCPG consists of puff valves, a quasi-DC iron-core magnet providing the compact toroid’s (CT) stuffing flux, a pre-ionizer system to improve breakdown and decrease jitter, in addition to coaxial electrodes where the CT is formed and accelerated. These systems allow for the creation of a relatively hot spheromak-like CT, while limiting excess neutral gas. The multi-pulse capability is achieved with individual pulsed power supplies for each CT for a total of 5 CT’s from each of the two injectors at a repetition rate up to 1kHz. Initial results, including CT parameters and affects on FRC will be presented.
 Introduction:
 TAE has developed a multi-pulse CTI for refueling long-lived FRCs.
There are two radial injectors, each of which can inject 5 CTs with arbitrary timing up to 1kHz.
 The CTI system is a magnetized coaxial plasma gun, which consists of the the following sub-systems:
 Puff valves to inject neutral gas.
 Quasi-DC magnet providing the stuffing flux.
 Pre-ionization system delivers a seed plasma to assist gun breakdown.
 Main discharge circuitry, which provides the current to form and accelerate the spheromak-like plasma.
 Single Sided Injection
 Particle Introduction: the CTI is able to introduce particles into
the core of the FRC.
 Perturbations to the FRC
 Un-balanced CT injection leads to perturbations of the FRC.
 Results:
 From initial results the CTI system is able to, non-catastrophically,
introduce relatively hot particles into the FRC’s core for multiple refueling events. This helps to overcome one of the limits of FRC lifetime, namely particle loss.
 There is further need for optimization of both the CT and FRC for refueling.
Ceramic break
Pre-ionizer Center electrode
Fig. 10: C-2W overview cartoon.
 Future Work
 Complete commissioning and
optimizing the two multi-pulse
CTIs.
 Improvements to neutral gas
introduction  References:
Outer electrode
Puff valve
Fig. 2: Simplified circuit schematic showing a two pulse system.
Quasi-DC Magnet
Fig. 5: Double sided injection, East at 2ms, West at 3ms. Particle inventory.
 Density
 Line-integrated electron density increases at the central plane,
coinciding with the CT injection.
I. Allfrey1, T. Matsumoto1, T. Roche1, H. Gota1, T. Asai2, F. Tanaka2 and the TAE Team 1TAE Technologies, Inc., 19631 Pauling, Foothill Ranch, CA 92610
2Nihon University., Chiyoda-ku, Tokyo 101-8308, Japan
Fig. 3: Single-sided injection at 1ms. Particle count averaged over the FRC volume.
 Double Sided Injection at 2ms  Particle Inventory
 The CTI increases the particle inventory, which is calculated with volume from magnetics and density from interferometry.
Fig. 4: FRC perturbations from magnetics. The single-sided CT injection coincides with the onset of N = 2 instability.
 The Effects of Multiple CT Injection on the FRC Shape
 As particles are introduced and temperature should decrease and the
FRC shape change due to a decease in plasma pressure. However, from initial results there seems to minimal affect on the FRC shape with double-sided injection.
Fig. 9: Line-integrated density for a FRC with three CT injections: 2ms, 4ms and 6ms.
Fig. 6: Double sided injection, line-integrated density measured on the central plane. The CTs are injected at 2, 4 and 6ms, marked by the cyan lines.
Fig. 8: FRC length and elongation.
 See “Increased ionization efficiency for high performance CT injection” for details.
 T. Edo et al. Performance Improvement of a Magnetized Coaxial Plasma Gun by Adopting Iron-Core Bias and Pre-Ionization Systems, Plasma and Fusion Research
Presented at the 60th Annual APS DPP meeting in Portland, OR November 7, 2018
Fig. 7: Separatrix radius on the center plane, double sided injection.
 Machine Overview