Precision electromagnetic lenses

Inside every electron microscope in India — the ones that characterise alloys, hunt failure modes in metals, image semiconductor devices — sits a column of precision electromagnetic lenses. India buys almost all of them from abroad. One working prototype exists, built by a government laboratory. No Indian company manufactures these lens columns commercially.

An electromagnetic lens is not glass. It is a solenoid magnet whose field converges a beam of electrons; changing the current through the coil changes the focal length and magnification. Stack these lenses in a precisely arranged column, pair them with an electron gun that generates the beam, and the instrument can resolve structures a transmission electron microscope pushes to better than 50 picometres, at magnifications up to about 10,000,000x.

That performance is why the lens column is hard. A magnetic field that focuses electrons cleanly needs pole pieces machined to micron-level dimensional accuracy, made from soft magnetic alloys chosen for stable, aberration-free focusing. The excitation coils demand current supplies stable to parts per million, or the focal length drifts. The whole column must sit under ultra-high vacuum so electron trajectories are not distorted. The physics has been understood since Ernst Ruska and Max Knoll built the first prototype in 1931, and Siemens sold the first commercial transmission electron microscope in 1939 — but reproducing that reliably, instrument after instrument, is a manufacturing discipline only a handful of firms hold.

Today that market is held largely by Japanese and German majors. JEOL describes itself as a global leader in transmission and scanning electron microscopes and mass spectrometers; both JEOL and Hitachi High-Tech market their electron microscope lines directly into India, selling their own electron optics as the source of the imaging performance on offer. Indian trade directories listing "electron microscope manufacturers" are populated mostly by suppliers and traders of imported systems and consumables, not builders of the lens columns themselves. India's broader precision-instruments import category — which includes these analytical instruments — was worth about USD 4.09 billion in 2023, down from about USD 11.67 billion in 2022.

Against that, one genuine indigenous milestone stands out. The Bhabha Atomic Research Centre has developed a tungsten-filament scanning electron microscope with 20 nanometre imaging resolution, using its own electromagnetic coils to demagnify and focus the beam onto the specimen. BARC positions it as cost-effective import-substitution for higher-education institutions, research labs and industry, spanning material and alloy characterisation, failure-mode analysis, mineral characterisation, powder metallurgy, pharmaceuticals, the semiconductor industry and R&D organisations. It is listed as a technology available for transfer. But it remains a prototype: there is no evidence yet of an industrial partner manufacturing or selling it at scale.

The gap persists because commercial manufacture rests on several foundational capabilities that are still emerging in India, not yet mature. High-purity soft magnetic core alloys, ultra-stable ppm-level current supplies, bright field-emission electron sources and electron-optics simulation software are all listed as emerging; ultra-high-vacuum systems, precision machining and coil winding are demonstrated. A prototype can be assembled from what a national lab has on hand. A product line requires all of these to be reliable, repeatable and sourced at volume.

The direction is already articulated by the community that uses these instruments. The Electron Microscope Society of India, organised since December 1961, has through its leadership called for indigenising the various configurations of electron microscopes under the country's self-reliance programme, and asked industry to partner with academia and R&D institutions to develop Make-in-India scanning and transmission electron microscopes. The physics is settled and a working column exists. What remains is turning a demonstrated prototype, and its emerging foundations, into a manufacturer.