DETECTOR ENGINEERING / S11141-10

Electrons in.
A measured voltage out.

A silicon backscattered-electron detector for your 3 kV and above microscope. Direct charge detection removes the optical path and its separate acceleration supply.

Explore the live circuit ↗Full electrical reference ↗

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1–30 keVCharacterized electron energy

10 × 10 mmActive silicon · Ø 2 mm hole

0–5 VReverse bias explored in this model

20 VAbsolute maximum reverse voltage

Device specifications: Hamamatsu S11141-10 / S11142-10 datasheet, pp. 1–4. Circuit component values below are proposed engineering assumptions. They have not been validated on a physical assembly.

SIDE-MOUNT DESIGN / RECORDED BOM GEOMETRY

Inside vacuum, beside the beam.

The detector, holder and short internal leads stay inside the evacuated specimen chamber. Backscattered electrons travel through an unobstructed vacuum path from the specimen to the exposed silicon face. Both A and K cross sealed electrical feedthroughs; the bias supply, amplifier, ADC conditioning and ESP32 remain outside in this design.

The new starting arrangement places the centre 16 mm sideways and 14 mm above the specimen, with the face tilted 48.8° from horizontal. The primary beam bypasses the sensor and holder. Position and tilt remain adjustable in the visualizer; previous centred setups are preserved.

Mechanical arrangement, dimensions, clearance derivation and commissioning ↗

This panel reads the recorded BOM geometry, not unsaved simulation controls. The bracket, chamber fit and cable routing remain proposals.

Clear the beam. Face the specimen.

MOUNT GEOMETRY

Inside specimen-chamber vacuum · metric side section · height above specimen · tilt from horizontal

Swipe the diagram sideways to inspect the dimensions.

Line of sight—

Side clearance estimate—

Face pointing error—

Package envelope 25 × 11 × 1 mm, plus your mounting allowance. This checks separation from the final-drift beam envelope and specimen plane; chamber, lens and cable collisions are not solved. Mounting and wiring procedure ↗

01 / POLARITY AND RETURN PATHS

Follow the complete circuit.

For a positive signal voltage, hold the cathode K near 0 V through the amplifier and bias the anode A negative. A 5 V reverse bias means V_K − V_A = +5 V.

The feedthroughs preserve the vacuum seal while carrying A and K to the external circuit. Electrons remain inside the chamber. Functional A/K connections are shown. Physical terminal orientation must come from the delivered detector drawing. The feedback values do not establish a stable OPA140 design by themselves; detector capacitance, wiring and op-amp dynamics must be included.

FROM	TO	PURPOSE
Detector A	Quiet −Vᴿ output	Through a sealed electrical feedthrough. Reverse bias; reference its supply return to signal 0 V.
Detector K	TIA inverting input	Short, shielded current path through a sealed electrical feedthrough to the external TIA.
TIA output	Rf ∥ Cf → inverting input	Negative feedback converts detector current to positive voltage.
TIA noninverting input	Signal 0 V	Defines the virtual reference at K.
Quiet +5 V / −5 V rails	Op-amp supply terminals	Decouple locally using the op-amp datasheet. Rails are distinct from its signal input.
TIA output	Conditioner → ESP32 GPIO34	Proposed unity-gain buffer with +0.15 V offset, filtering and protection fits the signal to the ADC input. Never connect the diode directly to GPIO34.
Analog and ADC references	Defined signal 0 V	Control return currents; keep pump, lens and digital switching currents away from the detector input.

References: OPA140 datasheet · Hamamatsu photodiode amplifier guidance · ESP32 pin and ADC specifications.

02 / WHAT THE MODEL CAN TELL YOU

Known device. Explicit assumptions.

Measured manufacturer anchors

At 5 V reverse bias: typical detector capacitance 450 pF and dark current 5 nA. At 1.5 keV incident energy, typical charge gain is 300. The simulator interpolates bias behavior and approximates energy response; it does not reproduce a calibrated device.

Specimen and collection

BSE yield, mean energy fraction and angular acceptance are adjustable assumptions. The tilted square sensor minus its central hole gives a geometric solid angle from its position and orientation. Real backscatter directions and energy spectra depend on material and geometry; directional surface shading is not simulated.

Gain and timing

The live circuit shows clipping and the approximate Rf × Cf response. Actual op-amp stability and scan-driver settling must be measured. Longer dwell reduces random noise, but cannot recover clipped information.

The image changes

The BSE view uses synthetic material contrast, without the earlier secondary-electron edge glow. Detector noise, gain clipping and scan-direction lag respond to the controls. It is an illustration, not a predicted micrograph.

JEOL: detector placement and BSE collection · JEOL: BSE image contrast and resolution.

03 / BRING-UP SEQUENCE

Build confidence one measurement at a time.

Confirm the delivered detector.Check its A/K orientation, mounting, vacuum and cleaning limits. Install the sensor and holder inside the evacuated chamber, with a clear vacuum path to the specimen and sealed A/K feedthroughs. For a side mount, keep the sensor, bracket and internal cable clear of the full scanned beam envelope. In centred comparison mode, check passage through the hole separately.
Bench-check the readout.Verify analog rails, polarity and output range. Use a known injected current to measure amplifier gain and settling before connecting the detector.
Measure the dark baseline.With beam blanked, record drift and noise at the intended bias. Verify the ADC conditioning and protective limits independently.
Establish the primary beam.Follow the gun, pumps and interlock procedure. Confirm beam current separately with a suitable Faraday cup. Begin at 3 kV with a conductive reference specimen.
Acquire slowly, then tune.Begin with 500 µs dwell as a model preset, not a device guarantee. Adjust collection and gain until the useful signal clears the noise without clipping.
Validate scan timing and shutdown.Measure driver and TIA settling before shortening dwell. Blank the beam, reduce gun HV/heating, and follow the selected equipment’s discharge, pump and vent instructions.

Electrons in.A measured voltage out.