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Experimental and Numerical Preparation for the Study of Metamaterial Structures

in an HPM Environment Tyler Wynkoop

Alan Lynn Mark Gilmore

University of New Mexico Department of Electrical and Computer Engineering

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Overview • Introduction • SINUS Accelerator • Modular Horn Antenna • Metamaterial samples to be tested • Diagnostics • Summary

Objective • Objective: Characterize failure mechanisms of

metamaterial structures in an HPM environment – Arcing – Corona – Melting – Multipactoring – Etc.

• Operational limits of MTM structures – E-field – Pulse width – Rise time – Etc.

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Introduction • Design and implement a test stand

– High fields – Versatile geometries

• Look for failure mechanisms via diagnostic tools – Fast Imaging Camera – PMT Camera – Spectroscopy – Thermal Characterization (infrared)

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SINUS-6 Accelerator

• Vbeam ≤ 700 kV • Pulse width ~

12 ns FWHM • Cathode current

typically ~ 6 kA (carbon field emission cathode)

• S-band Magnetron

Horn Antenna

Transformer

Capacitor Bank

Magnetron

Pulse Forming Line

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Metamaterial Test Environment • High fields • Adjustable fields • Supports multiple configurations • Maximum diagnostic access • Minimal power reflection

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Modular Horn Antenna

~19.5”

•Interchangeable metamaterial mounting plates in red

•Metamaterial sample in Blue

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Metamaterial Sample

• Simulation done with Metamaterial package in CST

• Split Ring Resonator designed for resonance in S-Band

• No dielectric substrate • Work in progress

Dimensions in mm

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Metamaterial Sample Resonance Characteristics

• Problems with simulation • Electrostatic vs.

Electromagnetic • Incorrect anisotropic

behavior

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Diagnostic Triggering Self-breaking Gas SwitchJitter ~ 1 µs

PFL

Thyristor

Voltage PulseFWHM ~ 15 ns

Self-breaking Gas SwitchJitter ~ 1 µs

PFL

Thyristor

Voltage PulseFWHM ~ 15 ns

D-dot probe

Trigger

Camera

Mirror

SINUS-6

• Problematic triggering • μs switch jitter • ns pulse length

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Fast Camera

• Stanford Computer Optics 4 Quick E

• 1.2 ns/frame, 300 – 800 nm wavelength range

• completely opto-isolated in screen box

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PMT Array •16 Channel PMT Array •0.6 ns rise time •Each channel is 0.8x16 mm •Power supply and amplifier shown below

Fast 1D photomultiplier array for continuous, time-resolved 1D imaging

PMT Array Schematic

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Front end Optics

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Spectroscopy and Other Diagnostics • McPherson 205f

– 350 – 850 nm – Species present (e.g. C+, Cu+, H, etc) – Ions vs. neutrals – Electron temperature (Te) and density (ne) – Ti = Te, if highly collisional

• McPherson 2062 – 4 meter – 2400 lines/mm grating – resolution: 0.006 nm – Ion temperature Ti (if Ti > 8 eV) – Ion drifts, Vi – Possibly: Surface Electric Field (via Stark splitting)

• Thermal Characterization (infrared) – Method to be determined

McPherson 205f

McPherson 2062DP

could yield additional information on the nature of breakdown

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Shielding • Isolated power

• Pneumatic remote disconnect

• Fiber optic trigger input • Fast Imaging Camera

• Fiber optic ethernet control

• PMT camera • Fiber optic input

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Summary • SINUS-6 Driver

– Triggering challenges being addressed • Metamaterial Test Environment

– Modular Horn Antenna • Fabrication to begin this month

• MTM Structures – Design in progress

• Diagnostics – Fast Imaging Camera

• Ready to be installed

– PMT Array • In fabrication

– Spectroscopy and Thermal Characterization • Under consideration

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Thank You!