04/25/23 1

Engineered Tungsten Surfaces for IFE Engineered Tungsten Surfaces for IFE Dry Chamber WallsDry Chamber Walls

Plasma Processes Inc.4914 Moores Mill Road

Huntsville, AL 35811

Scott O’Dell

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Plasma Processes, Inc.

IntroductionIntroduction

Tungsten is an ideal material for armoring IFE dry chamber walls. High melting temperature Low thermal erosion

Techniques for accommodating cyclic energy deposition are needed.

In addition, elimination of helium build-up is desired to prevent premature armor failure.

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Plasma Processes, Inc.

SolutionSolution

Use a functional gradient material to join the tungsten armor to low activation ferritic steel walls Minimize stress at the interface due to CTE mismatch

Provide short transport path for removal of helium Nanometer grain structure to promote grain boundary

diffusion (GB diffusion > Bulk diffusion) Interconnected nanometer size porosity

PPI and UCSD has been awarded a DOE STTR Grant to develop Engineered Tungsten Armor using advanced Vacuum Plasma Spray (VPS) forming techniques

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Plasma Processes, Inc.

Vacuum Plasma Spray Vacuum Plasma Spray Plasma Processes, Inc. is a small

business that specializes in the development and fabrication of refractory metals and advanced ceramic materials for High Heat Flux (HHF) applications.

Innovative Vacuum Plasma Spray (VPS) forming techniques are used to produced: Complex components to near net

shape Advanced high temperature

coatings and composite materials Join materials with dissimilar

CTEs Low ActivationFerritic Steel

Dense W Functionally Graded to Ferritic Steel

Nano-grained, porous W (1-2 microns thick)

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Plasma Processes, Inc.

VPS Formed Refractory Metal ComponentsVPS Formed Refractory Metal Components

Plasma facing component heat sinks with in-situ formed helical fins

Thin-walled closed end refractory metal cartridges with ceramic liners for processing samples in microgravity (leak rate of <1x10-8 sccs He)

Nozzle inserts to reduce/eliminate throat erosion solid rocket engines

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Plasma Processes, Inc. Joining of Materials with Dissimilar Joining of Materials with Dissimilar Coefficients of Thermal ExpansionCoefficients of Thermal Expansion

Gradual transition from one material to the other reduces stress as compared to a typical sharp interface.

Ability to use coatings that enhance bonding between the armor and the substrate.

Recently functional gradients have been used to join thick (3-5mm) VPS W deposits to actively cooled Cu alloy heat sinks for MFE PFCs.

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Plasma Processes, Inc.Medium Scale MFE PFC Armored Medium Scale MFE PFC Armored with VPS Tungstenwith VPS Tungsten

Deposition of VPS W Armor

Medium Scale after Armor Castellation (top view of 0.4m long PFC)

Close-up of Castellated Armor

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Plasma Processes, Inc.

Influence of Particle Size on VPS WInfluence of Particle Size on VPS W

A B C

• Average starting particle size: A) 26μm B) 13μm C) 3μm• Micrographs demonstrate by reducing the starting powder size the grain structure of the resulting deposit can be reduced.

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Plasma Processes, Inc.

Ultrafine Grained VPS WUltrafine Grained VPS W

Submicron W powder (0.5μm)

Transition metal carbides to pin the grain boundaries (HfC)

VPS formed W components with ultrafine grained structures have been produced.

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Plasma Processes, Inc.

Porous VPS TungstenPorous VPS Tungsten

By controlling the deposition parameters, porous deposits can be produced.

Porous W deposits between dense W layers have been produced for use as helium cooled heat sinks.

Helium flow tests have demonstrated the porosity is interconnected.

Size of porosity is highly dependent on the size of the starting powder.

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Plasma Processes, Inc.

He Cooled W Heat SinkHe Cooled W Heat Sink

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Plasma Processes, Inc. Engineered W Surfaces for IFE Dry Engineered W Surfaces for IFE Dry Chamber WallsChamber Walls

Develop a preliminary model to aid in the design and optimization of engineered W

Develop VPS fabrication techniques based on functional gradient materials for joining engineered W to low activation ferritic steel

Produce engineered W surfaces comprised of nanometer size grains and interconnected nanometer porosity to eliminate He entrapment

Demonstrate migration of helium through the engineered tungsten surface

Produce samples for thermal cycle testing and analysis

He LeakDetector

RubberStopper

Engineered Tungsten Cylinder

Container filledwith helium

Port to detector

Evacuated

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Plasma Processes, Inc.

Tungsten Brush Armor for MFE PFCsTungsten Brush Armor for MFE PFCs

PPI, SNLs and Boeing have worked to develop W brush armor for MFE PFCs PPI was the first to produce medium scale PFCs with W brush armor (PW-8 and

PW-14) 32mm x 100mm armor area comprised of 10mm tall W rods

Medium scale mockups have been thermal response tested to ~23 MW/m2

Survived 500 thermal cycles at ~20 MW/m2

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Plasma Processes, Inc. Insulator Coating for the University of Insulator Coating for the University of Washington’s HIT DeviceWashington’s HIT Device

In a recent effort for the University of Washington, PPI applied an alumina dielectric coating on plasma facing surfaces of the Helicity Injected Torous (HIT) device.

The Helicity Injected Torus with Steady Inductive Helicity Injection (HIT- SI) is a new spheromak under construction at the University of Washington. HIT- SI has several unique features, the most notable being the “bow tie” cross- section of the confinement region and the presence of two semi- toroidal helicity injectors at each end.

HIT-SI components before deposition of dielectric coating ..

Inner cone after deposition of dielectric alumina coating