Experimental and Numerical Preparation for the Study of...

1

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

2

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.

3

4

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)

5

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

6

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

7

Modular Horn Antenna

~19.5”

•Interchangeable metamaterial mounting plates in red

•Metamaterial sample in Blue

8

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

9

Metamaterial Sample Resonance Characteristics

• Problems with simulation • Electrostatic vs.

Electromagnetic • Incorrect anisotropic

behavior

10

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

11

Fast Camera

• Stanford Computer Optics 4 Quick E

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

• completely opto-isolated in screen box

12

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

13

Front end Optics

14

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

15

Shielding • Isolated power

• Pneumatic remote disconnect

• Fiber optic trigger input • Fast Imaging Camera

• Fiber optic ethernet control

• PMT camera • Fiber optic input

16

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

17

Thank You!