Results
Data & Findings
Primary erosion campaign, electron-backstreaming lifetime analysis, and Fowler–Nordheim breakdown risk assessment. All 36 runs fully reproducible from VIOT3/campaign_results.json.
Inside the work
The impact behind the numbers.
A conceptual CEX-ion impact sequence at the accelerator grid. The measured simulation results appear in the charts below.
Track
Follow charge-exchange ions that can be accelerated back toward the downstream accelerator-grid face.
Count
Compare the atoms lost from the substrate and coating across campaign runs.
Interpret
Read erosion alongside lifetime and field-emission risk; each tells a different part of the story.
Erosion Campaign
36 runs
3 materials
4 throttles
3 seeds
N=1e5
DX=10 µm
5,000 steps
Comparative erosion — atoms sputtered per run
| Throttle | I_b (A) | Mo (atoms) | GNP (atoms) | Graphene (atoms) | GNP LEF | Graphene LEF |
|---|---|---|---|---|---|---|
| TH0 | 0.51 | 6.827e10 | 1.740e10 | 1.841e11 | 3.92× | 0.37× |
| TH5 | 0.84 | 1.124e12 | 2.657e11 | 1.988e12 | 4.23× | 0.57× |
| TH10 | 1.10 | 4.435e12 | 1.579e12 | 6.293e12 | 2.81× | 0.70× |
| TH15 | 1.76 | 3.730e13 | 2.679e13 | 4.404e13 | 1.39× | 0.85× |
GNP LEF = Mo erosion / GNP erosion. Values >1 mean GNP reduces erosion. Values <1 for Graphene mean graphene worsens erosion. CV < 0.57% across all 12 cases.
Lifetime-extension factor vs. throttle — GNP reduces erosion, graphene worsens it
EBS Lifetime
10 seeds
N=2e5
TH10
NX=117
Barrier depth
1091.15 V
Electron-backstreaming lifetime factor (LEF_EBS)
| Coating | φ_m (V) | dφ_m/dr (V/m) | dr/dt (m/s) | dφ_m/dt (V/s) | LEF_EBS |
|---|---|---|---|---|---|
| Mo (baseline) | 8.95 | 7.367e5 | 4.309e-8 | 3.148e-2 | 1.0× |
| GNP | 8.95 | 7.367e5 | 3.270e-9 | 2.389e-3 | 13.18× |
| Graphene | 8.85 | 7.367e5 | 6.382e-8 | 4.702e-2 | 0.669× |
Internal cross-check: dφ_m/dr = 736,719.386 V/m identical to machine precision across all three coatings — validates that LEF_EBS differences come purely from erosion rates. 95% CI widths: ~0.5% of mean.
Breakdown Risk
Fowler–Nordheim
Weibull model
NSTAR nominal
≈1.9 MV/m
Fowler–Nordheim vacuum breakdown — Weibull parameters
| Material | φ (eV) | Weibull λ | Weibull k | Onset (P>1e-4) | P_BD @ 15 MV/m |
|---|---|---|---|---|---|
| Mo | 4.6 | 100 | 2.0 | 7.27 MV/m | 0.15 |
| Graphene | 4.5 | 150 | 1.8 | 4.01 MV/m | 0.44 |
| GNP | 4.5 | 200 | 1.5 | 2.26 MV/m | 0.58 |
NSTAR nominal inter-grid field ≈ 1.9 MV/m. Rim field enhancement β ~2–10 for machined edges, ~70 for sharp nanostructures — can push local field into the 2.3–7.3 MV/m divergence band.
Vacuum-breakdown onset field by material — lower is riskier
Summary
GNP wins on erosion. GNP is risky on breakdown.
GNP reduces erosion 1.39–4.23× and extends EBS-limited life up to 13.18×. Its edge-rich morphology drops breakdown onset from 7.3 to 2.3 MV/m — partially negating the benefit. Graphene is actively harmful at all throttles: it adds an erosion channel and shortens EBS life to 0.669×.