Charger–1: A Pulsed Fusion Propulsion Testbed Dr. Robert B. Adams, NASA-MSFC Dr. Jason Cassibry, UAHuntsville Ross Cortez, UAHuntsville What We’re Building • A test facility for high power and thermonuclear fusion propulsion concepts, astrophysics modeling, radiation physics • Located in the UAH Aerophysics Lab at Redstone (Decade Module 2) What We’re Building • The highest instantaneous pulsed power facility in academia – 572 kJ (1 TW at 100 ns) • Main equipment donated by DTRA to UAHuntsville • MSFC loaning experiment side equipment, expertise, other equipment Operation of a Z Pinch • Components: Cathode, Anode, Hypersonic Nozzle, Gas Cylinder, Evacuated Chamber, Current (I) Operation of a Z Pinch • Current (I) generates azimuthal magnetic flux (B) • Lorentz force drives Ion Motion inward (pinch compression), producing intense X-rays and plasma conditions. How It Works • Successive systems compress and intensify pulse: 1.2 MV @ 1 MA over 100 ns • Pulse Compression Stages: Marx Bank (Oil Insulated) -> Transfer Capacitor (Water Insulated) -> Triggered Output Switches -> Output Line (Water Insulated) -> Opening Switch -> Vacuum Insulator / Inductive Energy Storage -> Bremsstrahlung Diode / Plasma Opening Switch. Marx Bank • Full power: charged to ±85 kV • Aerovox capacitors, C = 2.2 μF, rated at 100 kV • Once triggered, erected Marx looks more or less like a single capacitor with value 1.1 μF, charged to 1.02 MV • Total stored energy: 572 kJ Transfer Capacitor • Collection of 32 coaxial lines bussed together on either end • Water filled • Urethane diaphragm that separates oil in Marx tank from water in the TC • Total capacitance C = 0.43 μF • Divertor switches located on both upstream and downstream ends of TC • Designed to remove 320 kJ immediately after forward pulse has passed Output Line: Switches • 6 switches control output from TC: these switches are fired simultaneously and are in parallel to share the output current equally - Pressurized with SF6 to ~90 psig (variable depending on test) - Last triggered stage in pulsed power system - Peak voltage on switches: 1.2-1.4 MV - Total current carried: 1.6-1.8 MA • Jitter in the firing of output switches is ~2-3 ns leading to an overall jitter in the arrival time of the current at the front end of 4-5 ns Output Line • Single line has impedance Z ~ 0.5 Ω and is 100 ns long • Total insulator stack height is 35 cm - This design requires cleaning of the insulator surface after 20-30 full power discharges • At the end of the water OL is an oil section isolated on the upstream side from water by a 1 inch thick polyurethane diaphragm and isolated on the downstream side from the vacuum components by a 16 gradient ring, polyurethane and Dendresist, high voltage insulator Test Stand • Formerly GDM experiment in PRC – loaned to Aerojet • 48” dia x 5 ft long vacuum chamber - 15 ports, large sight glass - Hinged end door • Alcatel Pascal Series roughing pumps • Alcatel turbopumps • Miscellaneous valves, controllers, isolation gate, cables, etc. • Larger roughing pumps acquired Planned Experiments (Slide 13) • Pulsed Fission-Fusion (PuFF) (Subscale Thermonuclear Test) - Leverages legacy nuclear experience - Potential for nearer term thermonuclear fusion - Addresses plasma instability issues • Magnetic Nozzle Experiment (Pulsed Plasma Propulsion) - Seed field propagation - Field line freezing - Scaling laws relating solar and laboratory scales - Test bed for space weather codes Planned Experiments (Slide 14) • LiD Wire Array Diode (Subscale Thermonuclear Test) - Measure x-ray and neutron output - Estimate fusion energy output - Code validation - Optimization of diode design - Scaling for break even design - Diode options: Basic (Al, Cu Wire Arrays), Option 1 (Li Wire Array / D-Li Axial Core), Option 2 (Liquid Injection) • Simulation of Coronal Mass Ejection (Space Weather Experiment) - Measure jet velocity - Magnetic reconnection physics - Scaling laws relating solar and laboratory scales - Test bed for space weather codes - Stages: 1. Two wire loops in series, 2. Wires ablate and magnetic reconnection begins at center, 3. Plasma jet formed and accelerated Planned Experiments (Slide 15) • Solar Wind Interaction with Lunar Regolith (Space Weather) - Tests possible depth of H2O on Moon - Measures shielding capabilities of regolith - Improves understanding of plasma impingement physics • Other Experiments - Ablative Z-pinch - Radiation shielding Propulsion Technologies Trade Space • Specific Power α (W/kg) vs. Specific Impulse Isp (sec) map: - Primary Research Area (TRL 1-3 unproven technology): Inertial Confinement Fusion, Magnetic Inertial Fusion, Antimatter Initiated Fusion, Magnetic Confinement Fusion. - Secondary Research Area / Other Systems: Nuclear Pulse, Advanced NEP, Nuclear Thermal, Solar Thermal, Chemical, Plasma Sails, Solar Sails, Solar Electric, Nuclear Electric. Propulsion Technologies Vehicle Architecture • Vehicle configuration including Stacked Capacitor Modules (2) (10 m long x 3.6 m x 7.2 m, 8 plcs), Z-Pinch Nozzle, Lithium Hydride Radiation Shield, SMES Envelope, Deuterium-Tritium Tank, SP-100 Reactor, Lithium-6 Tanks, Radiators, RCS Thrusters, Lander, Surface Habitat, ISRU, and Transhab. Status - Facility • Layout detailing MDAS, EDAS, Screen Room, Water (H2O), Oil, and SF6 storage subsystems and current operational / processing status. Fluence • Decade Quad designed to: - Produce 20 krad over 2,500 cm2 in a 45 sec pulse - Generate hot x-rays (30 keV to 2 MeV) using Bremsstrahlung Radiation Source (BRS) • Charger – 1: - Only stores 572 kJ - Does not include BRS - Could create multiple fluences by z-pinch of various fuels • Target: - 100-140 mrad outside wall per year Shielding Concepts • Currently two major design concepts: - Polycarbonate/Acrylic shell with sand filler - Concrete Conclusions • Target Date for low power testing is Spring 2013 • Other experimenters are welcome! • Charger – 1 will enable research into multiple propulsion concepts, astrophysics and radiation protection.