AEML / RESEARCH TOOLS / 01

Gas TEM timing & dose planner

See when the gas arrives, when you record, and how many electrons reach the specimen.

Illustrative defaults · Delayed mixing model · Replace with your measured response

90% of composition change28.4 sMeasured from the valve command

Complete frames12 framesPartial final frames are excluded

Planned incident fluence149.8 e⁻/Å²From acquisition start to window end

Less beam-on time90 %Versus continuous beam, same window

View charts ↓Adjust inputs ↓

01 Gas response

Initial gas fraction mol%Switched gas fraction mol%Transport delay sMixing time constant τ s

Return to initial gas after a pulse

Valve pulse duration sTime window s

Estimate from measured t10 / t90

Use an independent step response representative of the specimen position, measured from the valve command. Fractions refer to the total composition change.

t10 st90 s

02 Imaging & beam

Incident current pAAcquisition start sIlluminated width nmIlluminated height nmExposure per frame sFrame start interval s

Blank the beam between frames

Stopping camera recording does not stop specimen irradiation. With blanking off, the beam stays on from acquisition start to the end of the time window.

At the specimen

t = 45 s

VALVE20%

→10 s

Mixed observation region

MODELED GAS19.7%○ Beam off

Gas change & image acquisition

mol%

Modeled at specimenValve commandExposure

Cumulative incident fluence

e⁻/Å²

This planContinuous beam

At cursor 62.4 e⁻/Å²Beam-on rate 12.48 e⁻/Å²/s

Time cursor45 s

Playback compresses the time window into 15 seconds. Slide the cursor to inspect any time.

CSV includes complete-frame start/end times, exposure-averaged modeled gas fraction, cumulative fluence and all inputs. Calculations run in your browser.

MODEL / VERSION 1

What this model can tell you

One delayed, well-mixed volume

A valve step reaches an effective observation volume after a delay. Its composition then relaxes with time constant τ. A finite pulse is the difference of two step responses. Gas consumption, adsorption, temperature changes and spatial gradients are excluded.

τ dc/dt = cᵢₙ(t − tᵈ) − ct₉₀ = tᵈ + ln(10)τ

For a step: τ = (t90 − t10) / ln(9); td = t10 + τ ln(0.9). The two-point estimate is a starting point; check the full response trace. An outlet MS delay is not automatically the specimen delay. Recalibrate when flow, pressure or temperature changes.

Incident electrons, not a damage threshold

The fluence calculation assumes a constant incident current over a uniformly illuminated rectangle and ideal beam blanking. Enter the illuminated area, which may differ from the camera field of view. STEM scan-area averages do not describe instantaneous probe-peak exposure.

J = I / (e A) · D = J × tᵇᵉᵃᵐ

Focusing, searching, spectroscopy and prior irradiation are excluded. Lower cumulative fluence does not by itself prove lower beam-induced chemistry: dose rate, gas and specimen matter. Compare fresh areas and beam-off controls. This planner predicts neither reaction rate nor beam damage.

Research context & constants

These sources motivate delay calibration and beam controls; they do not validate this simplified planner for a particular holder.

Inspired by the interactive teaching approach of Jehyun Lee’s snowflake and iron-oxidation simulators. This tool uses an independent model and implementation. Snowflake ↗ · Iron oxidation ↗