Microbeam

A microbeam is a beam of particles or photons whose cross-sectional diameter is on the micrometer scale, used to examine or modify a localized region of a sample. Microbeams may be produced from charged particle beams such as protons, helium or carbon ions, focused by magnetic or electrostatic optics, or from X-ray sources using advanced focusing crystals or lenses. The term encompasses both ion microbeams and X-ray microbeams.

In radiobiology, targeted microbeam irradiation enables delivery of radiation to single cells or subcellular regions while sparing neighboring tissue. This supports studies of DNA damage, repair, signaling, and bystander effects. A related field is microbeam radiation therapy (MRT), which uses arrays of micrometer-wide X-ray beams from synchrotron sources to create high-dose thin peaks with intervening low-dose valleys, aiming to improve tumor control and reduce normal tissue toxicity.

In materials science and analytical chemistry, microbeams underpin techniques such as micro X-ray fluorescence (μXRF) and microbeam electron diffraction, offering spatially resolved compositional and structural data. Focused ion beams are also used for micromachining and sample preparation (FIB), enabling detailed imaging and analysis at the microscale.

Generation and delivery require precise beam optics and stable sources, high-precision positioning, and adequate shielding. Facilities include ion accelerators and synchrotrons or laboratory-scale microbeam setups with compact optics. Dose control, beam uniformity, and thermal management are important considerations.

Limitations include instrumentation complexity, potential sample damage from high local doses, and the need for meticulous calibration. The field relies on specialized facilities and skilled operators.