Overview
ISO 24639:2022 - Microbeam analysis - Analytical electron microscopy - Calibration procedure of energy scale for elemental analysis by electron energy loss spectroscopy (EELS) - specifies a repeatable calibration procedure for the energy step and energy scale of EEL spectrometers used in transmission electron microscopes (TEM) and scanning TEM (STEM). The standard targets EELS work on electron‑transparent samples (e.g., thin foils) and is intended to achieve an energy‑scale uncertainty of ±3 % across the 0 eV to 3 000 eV range. It is not designed for backscattered electrons from bulk samples.
Key technical topics and requirements
- Scope and applicability: Calibration for in‑column, post‑column and equivalent EEL spectrometers operating with transmitted electrons in TEM/STEM.
- Energy step and energy scale: Procedures require calibrating the energy step (eV per channel) first, then the absolute energy scale for each EELS run.
- Accuracy requirement: Absolute energy scale accuracy of ±3 % (0–3 000 eV) to support reliable elemental identification via core‑loss edges.
- Peak definitions: Clear definitions for zero‑loss peak, plasmon‑loss, core‑loss edge onset, and core‑loss peak maximum; guidance on how to determine peak positions in practical spectra.
- Calibration methods:
- Method 1.1 - Two core‑loss edges dispersion using reference materials (two known core‑loss energies).
- Method 1.2 - Zero‑loss drift method: deducing energy step from shifts of the zero‑loss peak after changing the drift‑tube voltage.
- Instrument elements covered: entrance aperture, magnetic prism, drift tube, parallel or serial detector (photodiode arrays, CCD/CMOS), and related acceptance/collection/convergence angles.
- Supporting material: Annex A (informative) - calibration of drift tube voltage in the magnetic prism; Annex B - estimation of linearity of the energy step; Clause 6 - test report content.
Practical applications and users
- Who uses it:
- TEM/STEM operators and EELS specialists
- Materials scientists and microanalysis labs conducting elemental mapping and chemical-state analysis
- Quality managers ensuring traceable EELS measurements
- Instrument manufacturers and service engineers implementing or verifying spectrometer calibration
- Why it matters:
- Ensures consistent, traceable energy calibration for elemental identification from hydrogen to uranium.
- Reduces misidentification risk by standardizing how core‑loss onsets and peaks are measured.
- Supports inter‑laboratory comparability and conformity to technical quality requirements in microbeam analysis.
Related standards
- ISO 15932 (Microbeam analysis - Analytical electron microscopy - Vocabulary) is referenced for terminology used throughout ISO 24639:2022.
Keywords: ISO 24639:2022, EELS calibration, electron energy loss spectroscopy, energy scale calibration, energy step, TEM, STEM, magnetic prism, drift tube, zero-loss peak, core-loss edge, ±3% uncertainty.