Ronald Petzoldt, Dan Goodin, Brian Vermillion, Neil Alexander, Tom Drake, Bob Stemke, Lane Carlson, Landon Carlson Presented by Daniel Frey High Average.

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 WorkshopPrinceton University Oct 27-28, 2004

Target Injection Update

Gas-Gun Status Update

Goals AchievedImprove 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

Interference Slug

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Grooved Slug

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Vibration model

Teflon Seal and Wave Spring have improved accuracy

• Wave springs to improve symmetry of “push” during separation.

Coil Spring Wave 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 sabotAttachment 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

IssueElectromagnetic

InjectionGas-gun

Injector Wear No barrel to wear outBarrel and sabot wear would

require replacement

Reliability Non-contacting one piece sabot

Mechanical sabot separation and deflection reduce

reliability

Gas Mitigation No propellant gasRequires 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 Coil Sabot Coil

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Sabot traveling into the slide

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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 10-12 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.