Validation of Enhanced Electron Yield Measurements of Low-Conduct

Utah State University DigitalCommons@USU Spring 2016 Validation of Enhanced Electron Yield Measurements of Low-Conductivity, High-Yield Materials Justin Christensen Utah State Unive

Utah State University

DigitalCommons@USU

Spring 2016

Validation of Enhanced Electron Yield Measurements of

Low-Conductivity, High-Yield Materials

Justin Christensen

Utah State University

Gregory Wilson

Utah State University

JR Dennison

Utah State Univesity

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Part of the Condensed Matter Physics Commons

Recommended Citation

Christensen, Justin; Wilson, Gregory; and Dennison, JR, "Validation of Enhanced Electron Yield

Measurements of Low-Conductivity, High-Yield Materials" (2016) Utah State University Student Research Symposium Presentations Paper 131

https://digitalcommons.usu.edu/mp_presentations/131

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Validation of Improvements to Electron

Yield Measurement of Low-Conductivity, High-Yield Materials

Justin Christensen

JR Dennison

What is Yield?

(@EQ σ (/ (@ID charge (@SUB emit)) (@ID charge (@SUB inc))))

-Primary Electron

Secondary Electron

Backscattered

Electron

-+

Spacecraft Charging

Simulating Space

Yield of conductors

(@EQ σ (/ (@ID charge (@SUB emit)) (@ID charge (@SUB inc))))

DC Beam

A A A A

Emitted

V Bias +50 V

Collector Bias Grid

Inner Grid

Sample Stage

Charging

- +++++++++

Electron Microscopy

How do we fix it?

Pulsed Electron Beam

Charge Neutralization Fast Low-Current Measurement

It worked, kind of

Problems

• Tungsten

filament

• Grounded inner

grid

• Flood gun,

UVLED ground

loops

• UVLED ~290 nm,

low intensity.

Changes

• Tantalum disk

filament

• Biased inner

grid

• Isolated Flood

gun, and UVLED

• UVLED ~250nm

high intensity.

Improvements

HOPG Graphite

Symbol Facility Refs Measured Values

σ max E max (eV) E 1 (eV) E 2 (eV)

● CSIC SEY Facility 1-3 1.38±0.02 215±5 68±1 629±10

■ LaSeine—TEY Facility 4-5 1.48±0.05 270±20 60±2 610±40

▲ Onera—DEESSE Facility 6-7 1.28±0.05 190±10 69±1 552±20

♦ USU—SEEM Facility (clean) 8,9,15 1.4±0.1 200±30 40±2 895±20 Round Robin Average Values 1.39±0.08 220±36 59±13 670±150

● Standard 1: Whetten 12 1.01±0.01 300±20 250±30 350±20

● Standard 2: Wintucky 13 NA NA NA 330±20

Symbol Facility Refs Measured Values

σ max E max (eV) E 1 (eV) E 2 (eV)

● CSIC SEY Facility (contin.) 1-3 2.06±0.02 600±20 24±1 NA

■ Onera—DEESSE Facility 4-5 1.81±0.03 360±20 28±1 ~6000

□ Onera—DEESSE (Etched) 4-5 1.46±0.03 1250±50 NA ~6000

▲ LaSeine—TEY Facility (March 2) 6-7 2.48±0.03 200±20 NA NA

∆ LaSeine—TEY Facility (March 6) 6-7 2.3±0.1 240±30 12±2 NA

♦ USU—SEEM Facility (pulsed) 8-9 1.54±0.08 700±30 55±3 4000±200

◊ USU—SEEM Facility (contin.) 8,15 2.24±0.02 650±50 NA NA Round Robin Average Values 2.0±0.4 600±460 24±9 5000±1000

● Standard: Thomas & Pattinson 11 2.21±0.02 900±30 50±10 NA

Collaborative Standard Tests

Future Work

• Current analysis program

could show how yield changes

over the course of a pulse

(~1% of total pulse charge)

• Gold data should show no

charging effects

• Zero charge plateau.

improve calibration standards

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• What is Yield

• Measuring Yield

• Conductors

• Insulators

Improvements

• Measurement

• Neutralization

• Analysis

Future Work

• Verify Model

• Various Insulators

Outline

Problems

• Tungsten filament

• Grounded inner

grid

• Flood gun, UVLED

ground loops

• UVLED ~290 nm,

low intensity

• Emitted charge

A

Problems

• Tungsten filament

• Grounded inner

grid

• Flood gun, UVLED

ground loops

• UVLED ~290 nm,

low intensity

• Emitted charge

calculation