Ronald Petzoldt, Dan Goodin, Brian Vermillion, Neil Alexander, Tom Drake, Bob Stemke, Lane Carlson, Landon Carlson Presented by Daniel Frey High Average Power Laser Program Workshop Princeton University Oct 27-28, 2004 Target Injection Update

Gas-Gun Status Update GoalsAchieved Improve shot placement accuracy from previous testing. Placement accuracy, targets: 10 mm (1  ) Rotational tilt at deflector: 8 ° (1  ) System has responded to improvements Placement accuracy, targets: 7.5 mm (1  ) Rotational tilt at deflector: 4 ° (1  ) Convert to rep-rated (6 Hz) operation and measure time jitter. (< ± 1 ms) Operational at 6 Hz with up to 5 shot bursts Placement time jitter of 0.5 ms (1  ) Develop a membrane support to eliminate point loading effects on the target Performed shots with membrane support at 400 m/s

Angular rotation Separation effects A simple plastic sabot was tested first and achieved a 10 mm (1  ) placement accuracy We have added a Teflon seal to provide an interference fit. Reduced angular rotation from a 8 ° to 4 ° (1  ) at deflector Observed an order of magnitude reduction in barrel vibration signal. Two Mech’s Teflon Seal Sabots have reduced angular rotation Teflon Seal Vibration model

Teflon Seal and Wave Spring have improved accuracy Wave springs to improve symmetry of “push” during separation. Coil SpringWave Spring Target placement accuracy went from 10 mm to 7.5 mm (1  ) (without deflection) Target separation from the sabot still remains an issue for placement accuracy. Sabot separation at TCC (18 m) Target

Rep-rated (6 Hz) operation and Time Jitter We have demonstrated 6 Hz operation of revolver with bursts of up to 5 shots Revolver assembly holds timing of 0.2 ms (1  ) using photo-sensor cam timing Actual target placement 0.5 ms (1  ) (extrapolated to TCC) Revolver assembly

Membrane support is required for cryogenic operation Modified our sabot (all plastic) with a thin thermoplastic (Para-film) membrane Target successfully separated at ~400 m/s Membrane sabot separation at 400 m/s Membrane installed in sabot Attachment point Target Sphere

Evaluating an Electromagnetic Injector The current gas-gun has been useful for initial testing of target injection, rep-rated operation, and tracking demonstrations An “advanced” electromagnetic injector has a number of advantages and is desirable for a prototypical power plant design Issue Electromagnetic Injection Gas-gun Injector Wear No barrel to wear out Barrel and sabot wear would require replacement Reliability Non-contacting one piece sabot Mechanical sabot separation and deflection reduce reliability Gas Mitigation No propellant gas Requires differential gas pumping equipment Sabot Design Reusable one piece sabot Recyclable two-piece sabot

Non-contacting Electromagnetic Injector Bertie Robson has devised a unique levitating coil gun that we are evaluating –Provides for a self-centering projectile, eliminating the need for a guide tube (barrel). –The accelerator in principle can be both tilt and laterally stable. Restoring torque exists for coil tilt. At larger distances, restoring force exists for lateral stability. Phase stability possible because sabot current increases if sabot moves farther from acceleration coil. –Sabot coil conductivity is a concern  P-O-P experiment to measure ring down time -With an attractively accelerated sabot, the field coil and the sabot coil have currents flowing in the same direction Accelerating CoilSabot Coil Fr Sabot traveling into the slide Fz

Proof-of Principle Experiment The experiment consists of a cryostat and four separate coils Constant field coil Induction Field coil Sabot coil Pickup coil The first step is to generate a current that can exist for ~ 600 ms at cryogenic temperatures. We will be conducting a P-O-P experiment to determine the ring down time of a carefully produced coil. –The coil will have to be made of high purity aluminum or copper wire –The experiment will be conducted at cryogenic temperatures –The coil will be wound, annealed and joined to produce ultra low resistivity (6 X Ω-m) at the required cryogenic temperatures (~15k) –We will also address magneto-resistivity effects on the coils Cryostat Robson’s design has been reviewed by GA EM aircraft launch group who agree concept is unique and feasible for a stable cryogenic accelerator

Summary of Recent Injector Testing Since last time: Gas-gun has demonstrated membrane separation, rep-rated operation (6 Hz for up to five shot bursts) and provided for tracking demonstrations. Added “interference fit” Teflon seals to address in-barrel oscillation mechanism Added wave springs (uniform push) - Reduction of rotational tilt to 4 ° (1  ) - Increased placement accuracy 7.5 mm (1  ) Future EM work: We are conducting a proof-of-principle experiment to verify sabot coil performance for a future EM injector.