| Accelerating V | — kV |
| Working Dist. | — mm |
| Magnification | ×— |
| Pixel Size | — nm |
| Detector | SE |
| Scan Mode | NORMAL |
| Dwell Time | — µs |
| Resolution | 1024×768 |
| Date / Time |
Would you like to run the guided tutorial?
It walks you through every control — beam parameters, focus, alignment, wobble, and more — and ends with you having built a properly-tuned SEM image.
SEM Trainer is a browser-based simulator that mimics the controls and image behavior of a Scanning Electron Microscope. The sample is a tin-particle preparation on a carbon substrate, rendered procedurally in world-space so it stays sharp at every zoom level. Every control changes the image the way it would on a real instrument: beam energy, focus, stigmation, aperture alignment, scan speed, and so on.
The interface is laid out like a real SEM:
The right-sidebar Vacuum cell is a three-state selector. Pick the mode using the three small buttons (VENT / LV / HV) under the icon. The current chamber pressure shows beneath them and the SVG status box mirrors the active mode.
Chamber is open to atmosphere — the sample-exchange state. The E-Gun shuts down immediately, the viewport blacks out with a red VENTED — CHAMBER OPEN overlay, and the beam cannot be re-enabled. Selecting LV or HV from vented triggers the 10-second STARTING VACUUM pump-down screen.
Residual gas in the chamber neutralises surface charge on insulating samples — the primary advantage of LV. The image is blurred and slightly de-saturated to simulate beam-skirting through gas. The SE detector is automatically forced to BSE in LV (SE would arc in residual gas), and the trainer will refuse to switch back to SE until you return to HV. kV is clamped to ≥ 10 kV. Insulating samples (Alumina, biological insects, the unknown contamination sample) image cleanly here with no charging artefacts.
Standard SEM operating mode. Full resolution, full kV range, both detectors available. Insulating samples viewed in HV with the SE detector active trigger a flashing ⚠ CHARGING DETECTED warning in the top-right corner — the typical real-SEM symptom of trying to image an uncoated insulator. Switching to LV or to the BSE detector clears the warning.
The semi-transparent bar at the bottom of the image is the live read-out, just like the data strip burned into a real SEM micrograph. Left to right: kV (accelerating voltage), SP (spot size), WD (working distance, mm), x-mag, HV (E-Gun on/off), SE (detector type).
Hover the bar to bring its opacity up. Scroll the mouse wheel on any value to adjust it. Arrow keys work too if you click to focus a value. Clicking HV toggles the E-Gun (subject to the vacuum interlock).
While your cursor is over the imprint, the viewport's zoom-on-scroll is suppressed so you can adjust values without zooming.
The energy of the electron beam. Higher kV (20–30) penetrates further into the sample and improves resolution, but can damage sensitive specimens and reduces surface contrast. Lower kV (1–5) is gentler and surface-sensitive. Trainer default: 10 kV.
The diameter of the beam at the sample. Smaller spot = sharper image with less signal (noisier). Larger spot = more current and stronger signal but blurrier. Trainer default: 7.
The distance from the objective lens pole-piece to the sample's focal plane. On a real SEM the focus knob shifts the focal plane up or down, and the WD display reads where that plane currently sits — same model used here. The sample's true WD is randomized between 7.0 and 13.0 mm each session, and you have to focus to bring the focal plane onto it. Each unit of Coarse Focus shifts the WD readout by 0.15 mm; each unit of Fine Focus by 0.015 mm (10× smaller, for the last bit of trim). Scrolling the WD value on the imprint bar moves the coarse focus slider directly.
The amber Sample dropdown in the top toolbar (right of User Manual) picks the loaded specimen. Changing the sample re-paints the SE/BSE view and synchronously updates the matching preset in the EDS and EBSD panels.
Each sample carries a conductivity property (conductor / semiconductor / insulator) that drives the HV-mode charging warning and is used by the EDS / EBSD modules.
Opens from the gear icon. The e-gun fine-tuning controls live here.
Type any value 0–30 kV, or click one of the four preset buttons (10, 15, 20, 25 kV). A red-X icon appears while the value is invalid.
Beam diameter setting, integer values.
Voltage that heats the cathode wire to release electrons. Recommended range 2.0–2.15 V. Above 2.2 V shortens filament life — the simulator notifies you when you cross that threshold. The red marker on the slider track is the recommended zone.
The voltage that pulls electrons from the filament toward the sample. Bias and filament together drive the emission current.
Live read-out. Target is 80 ± 5 µA. The display turns amber when you're inside the 75–85 µA window. At the trainer's defaults (filament 2.10 V, bias 300 V) you should be right at 79 µA.
Opens from the spoke-gear icon. Two image post-processing controls:
Opens from the magnifier icon. Direct entry field at the top accepts 1,500×–50,000× (red-X marks out-of-range values). Six amber preset buttons jump to common magnifications (1.5k / 5k / 10k / 20k / 30k / 50k). The Continuous MAG Save checkbox tells the snapshot tool to embed the current mag in the saved filename.
You can also change magnification by scrolling on the x-mag value in the imprint bar (≈8% per tick) or by scrolling anywhere on the viewport (zoom-to-cursor 15% per tick), both clamped to the 1.5k–50k window.
Opens from the focus reticle icon. The slider position you need to reach for a sharp image is the position where the focal plane sits exactly on the sample — randomized each session (the sample is at a different WD every reload). kV, spot, and any column-alignment error also shift the optimum.
Large-step focal-plane adjustment — 0.15 mm of WD change per slider unit. Use this to bracket the sample.
Small-step trim — 0.015 mm of WD change per slider unit (10× smaller than coarse). Use it for the last bit of sharpness after coarse is dialled in.
Drives the focal plane directly to the sample's randomized true WD. Sets coarse to the calculated optimum and fine back to 50; the notification confirms the resulting WD (e.g. "Auto-focus complete — WD 11.3 mm"). Equivalent to a real SEM's auto-focus button — useful for recovery after a Shuffle.
Astigmatism is when the focused beam is not perfectly round — it's elliptical. Causes: contamination, magnetic fields, dirty apertures. Visually: a strong directional smear (horizontal when Stig X is off, vertical when Stig Y is off). The trainer uses a GPU SVG directional-blur filter so the effect is instant and smooth as you drag. Centering both sliders at 50 removes the filter entirely.
Opens from the crosshair-target icon.
The wheel icon (to the left of RED) toggles wobble. Wobble modulates the objective-lens current at about 1 Hz. A 540×440 ROI box appears in the center of the viewport showing a live image; if the aperture is mis-aligned, the image inside the ROI visibly swings back and forth. The further off-axis the aperture, the bigger the swing.
The right sidebar now has two detector buttons. The active one glows amber.
Combining HV + SE + an insulating sample (alumina, biological insect specimens, the unknown contamination preset) lights the red ⚠ CHARGING DETECTED badge in the top-right of the viewport. Switch to LV (residual gas neutralises charge) or to BSE (no acceleration of secondary electrons) to clear the warning.
The RED button opens a 540×440 ROI in the center of the viewport that refreshes at 2× the current scan-mode speed. While RED is on, the main image is frozen and every adjustment you make (focus, alignment, brightness, kV, etc.) previews only inside the ROI. When you turn RED off, the full image updates to reflect all the changes you made.
Use RED for rapid focus/alignment tuning when full-frame scans are too slow. Wobble and RED are mutually exclusive — turning on either one automatically disables the other.
30 fps refresh with heavy detector noise (the image looks like TV static dancing on top of the sample). Use for live tuning — you see every adjustment instantly, but quality is low.
7 fps refresh with moderate noise. Middle ground.
Zero noise, no auto-refresh. A bright amber scan line sweeps top-to-bottom over 9 seconds, committing the clean image row by row as it passes. This is the SEM equivalent of a slow, high-quality acquisition. If you zoom or change settings during SLOW, only the rows the line has touched since the change reflect the new state — exactly like a real long-integration capture.
Small status light to the right of the Reset button. Color reflects the worst of the eight tunable parameters (coarse focus, fine focus, stig X/Y, tilt X/Y, aperture X/Y):
Hover the LED for the exact percentage.
The bottom-right of the viewport shows an opacity-faded overlay (matches the imprint bar — ~50 % at rest, ~92 % on hover) with three quick-access auto controls, each paired with a fine-trim slider:
Each auto button resets its companion trim slider to zero so pressing the button brings you back to the calibrated optimum, with the trim available for off-optimum nudges from there. The trims write directly to the underlying state (and to the matching panel sliders), so the Focus / Brightness / Alignment panels stay in lock-step.
The right-sidebar EDS button opens the Energy Dispersive X-Ray Spectroscopy panel — a draggable industrial UI with a real-time spectrum graph, status indicators, and sample preset matched to the loaded specimen.
Peak intensities scale with what is currently visible in the viewport, not the bulk preset ratio. Particle-bearing samples (Tin-on-Carbon, Gold-on-Carbon, NMC) interpolate between a particleElements composition and a substrateElements composition by counting bright pixels inside the viewport. Zoom into a single tin sphere and the spectrum is nearly pure Sn; pan to a bare carbon patch and you read mostly C. Single-phase samples (Si, Cu, ceramics, biologicals) use their bulk composition unchanged.
Searches a bremsstrahlung-subtracted "net" spectrum for peaks above a noise floor, then matches each preset element's characteristic lines (within ±2.5 bins) to find which ones actually fired. Only elements that are in the loaded preset are considered — so a Tin-on-Carbon scan can never accidentally report Boron. Lines whose energy exceeds 95 % of the current beam kV are also skipped (the beam can't excite them). The chip readout sorts by net peak height and shows estimated weight-%.
Clicking anywhere on the spectrum identifies the closest characteristic line and pops a notification with the element / line / energy.
The right-sidebar EBSD button opens the Electron Backscatter Diffraction panel — a draggable dual-pane workspace showing a live Kikuchi pattern viewer and an Inverse Pole Figure orientation map. Sample preset stays synchronised with the toolbar selection.
A color-coded LED (Ready / Acquiring / Indexing / Calibrating / Done / Error) plus live Pattern Quality, Confidence Index, FPS, indexed-percentage, and timer readouts.
Pattern bands are procedurally generated per material with deterministic seeding (so the same sample always shows the same band pattern). Subtle per-frame drift simulates a live camera; per-frame speckle noise scales with the Gain slider and is attenuated by Exposure and Binning — exactly how a real EBSD camera responds. Pattern Quality is derived from the gain/exposure balance.
Voronoi-seeded grains painted with vivid IPF-style hues. As the scan runs, pixels fill in left-to-right top-to-bottom at a rate that completes within the configured time. Grain boundaries render near-black, un-indexed pixels render dark grey. Frequency of un-indexed pixels is driven by per-material indexability: 0.98 for silicon, ~0.92 stainless, down to ~0.04 for biological / amorphous samples. Single-crystal samples (Si) paint as one uniform IPF color; amorphous samples (insect cuticle, tin/gold-on-carbon) produce mostly noisy non-indexed greyness with rare random hits.
Click any grain after the scan completes to get fake Euler angles (φ₁, Φ, φ₂) and a per-grain CI. Calibrate runs a 2.2 s pattern-scrambling animation. Export PNG saves the orientation map.
The top-toolbar icons (after the cursor) draw on the viewport overlay:
The multicolor orb opens a 10-color palette popup. Pick a color to use for any new annotation; the orb's bottom edge tints to the current color.
The camera icon in the left sidebar saves a PNG of the visible viewport with the current CSS filter baked in (focus blur, brightness/emission). The filename uses the product name and the current date, e.g. JH Technologies SEM Trainer 2026-05-11.png.
The Tutorial button (right of the alignment LED) launches a 30-step contextual walkthrough. It starts by deliberately disturbing every parameter, then walks you through every control in order, gated by an action at each step. By the time you reach the final step, every parameter is back to its optimum / default and you've built a properly-tuned image. You can replay it any time — the button stays in the toolbar for a refresher.