High-energy Heavy Ion Microbeam

Centre for Accelerator Science

Overview

The high-energy heavy ion microprobe is a unique scientific instrument in Australia, which is coupled to an accelerator system to produce a highly focused beam of accelerated ions with a spot size down to the sub-micrometre dimensions – ion microbeam.

The (heavy) ion beam produced by a tandem accelerator is focused by a system of electromagnetic lenses similarly to focusing the light using a system of optical lenses like in a camera. The object is a beam passing through a tiny rectangular aperture that is far away from the lens system compared to the aperture size. The microprobe is essentially an inverted microscope that uses a focused beam of accelerated ions with energy in the MeV range as an imaging probe.

The ion microbeam is defined by the ion type, energy, and charge, as well as the microbeam current in a given spot size area (the current density or the ion flux).

The microprobe is a tool for bulk, the direct opposite to the electron or low-energy (keV) ion microscope that is a surface imaging (probing) tool. It is used for the characterisation or modification of material properties at depths from approximately 1 micrometre to maximum depths of up to 500 micrometres from the material surface. The selection of ion type and energy is guided by the required probing depth in material/sample/target.

Current capability: ANSTO microprobes (ion micro-beamlines) primary use is to perform precision irradiations for radiation effects testing in electronics and devices, solar cells, radiation damage studies of advanced materials for space, defence and nuclear applications, as well as radiation effects on living biological samples.

ANSTO Heavy Ion Microprobes

The Centre for Accelerator Science houses 2 heavy ion microprobe beamlines on the 10MV ANTARES and 6MV SIRIUS accelerator, designed to focus ions of the most elements from the hydrogen up to lead. The main parameter defining the focusing capability of a microprobe is the magnetic rigidity (the product of the ion mass and energy divided by the square of ion charge).

The ANTARES heavy ion microprobe is a unique instrument, among only a few microprobes in the world that can generate the focusing magnetic field of 1 Tesla and higher in each lens, reaching a maximum rigidity of about 120 amu*MeV/e² , compared to the SIRIUS microprobe capable of maximum rigidity of 38 amu*MeV/e².

Technical Specification:

ANTARES Heavy Ion Microprobe
Maximum Rigidity	120 amu*MeV/e2
Focusing system:	Oxford Microbeams triplet lens
Beam spot size:	1-6 µm (depending on ion beam brightness)
Magnetic beam scanning:	~ 50 - 3000 µm (X, Y)
Positioning or scanning accuracy:	~1 µm (X, Y, Z, R)
Automated object and collimating slits accuracy:	~100 nm aperture
Optical microscope for imaging:	40X

Ion Microbeam Delivery

The modern computer-controlled microprobe allows:

Scanning resolution	32 - 1024 pixels (X, Y)
Pixel dwell time	200 µs – 1 s
Beam spot:
in vacuum	0.5 - 1 µm
in-ambient air	1 - 50 µm
Scanning Modalities:
Beam Fast Raster-Scanning	10 x 10 µm² - 3 x 3 mm²
Stage Scanning (stationary beam + sample translation)	Up to 50 x 50 mm² (upgrade in December 2026 - up to 150 x 150 mm²)
Hybrid Fast Scanning (monodirectional fast beam-scanning + sample translation)	Customised shape and size
Grey-Scale Scanning	Customised shape and size, and gradient of fluence/dose in a single irradiation
Rates Regimes:
Single-ion regime	100 - 10,000 particle/s
Intermediate regime	10 - 100 fA
High-current regime	pA - µA
Flux	10 ⁴- 10 ⁹ particle/cm²/s
Fluence	10 ⁴- 10 ¹² particle/cm²

Microprobe Capabilities

Irradiations

The ion microprobes on the ANTARES and SIRIUS accelerators provide highly controlled, spatially resolved irradiation capabilities for studying radiation effects in electronics, materials and biological systems. By focusing ion beams to micrometre-scale spot sizes, they enable precision irradiation of selected regions within devices, materials or cells, allowing investigations of localized radiation responses and damage mechanisms.

The microbeam irradiation capability supports radiation effects testing of microelectronic devices and integrated circuits, including single-event effects (SEE) studies, fault localization, and the characterization of radiation-induced failure mechanisms. Precise beam positioning, ion counting and single-ion detection capabilities enable deterministic single-ion and low-fluence irradiations, supporting advanced investigations of device sensitivity and the development of radiation-hardened technologies.

For materials research, the microprobes are used to investigate radiation damage processes relevant to space, defence and nuclear applications. The capability to deliver well-defined ion species, energies and fluences enables displacement damage dose (DDD) studies and accelerated testing of materials exposed to harsh radiation environments. These capabilities are particularly valuable for assessing radiation-induced degradation in structural materials, semiconductor devices and space photovoltaic technologies, including solar cells, where ion irradiations can reproduce the particle damage accumulated during long-term mission operation. A key strength of the ANSTO microprobes is the versatility provided by advanced scanning and irradiation modalities developed in-house, enabling customised irradiation patterns, targeted exposure of selected regions, high-precision dose delivery, and complex irradiation protocols tailored to specific research and testing requirements.

In radiobiology, the microbeam enables targeted irradiation of individual cells, cellular components or defined cell populations, providing unique opportunities to study DNA damage, cellular response pathways, bystander effects and other fundamental biological processes. Combined with high spatial accuracy and precise dose delivery, these capabilities support mechanistic investigations that are not possible with conventional broad-beam irradiation techniques.

Depending on the application, irradiations can be performed using either low-current single-ion delivery for deterministic targeting studies or higher-current beams for accelerated damage accumulation, DDD testing and statistically significant radiation effects experiments.

Ion Beam Analysis (IBA)

The ion microprobe is particularly useful for analysing materials with complex microstructures. Its high-resolution scanning ion beam enables the investigation of variations in elemental composition, electronic properties and material structure on the micrometre scale. By combining the two-dimensional (2D) spatial resolution of the microbeam with the depth sensitivity of ion beam analysis (IBA) techniques, three-dimensional (3D) compositional and structural characterisation can be achieved.

The ANSTO microprobes support a comprehensive suite of microbeam IBA techniques. Low-current operation enables scanning transmission ion microscopy (STIM), secondary electron microscopy (SEM) and ion beam induced current (IBIC) microscopy, providing information on material structure, surface morphology and device performance. High-current operation supports particle-induced X-ray emission (PIXE), Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA), elastic recoil detection analysis (ERDA) and forward scattering, enabling elemental mapping, compositional analysis and depth profiling.

The temporal dimension can be added through pulsed ion beams and single-ion detection, allowing deterministic single-ion implantation and studies of dynamic processes following individual ion impacts. Microbeam capabilities are broadly divided into low-current operation for single-ion studies and high-resolution imaging, and high-current operation for rapid, high-sensitivity elemental and structural characterisation. The achievable beam current depends on the required spatial resolution, with smaller beam spot sizes requiring lower currents and longer acquisition times.

External ion microbeam

ANSTO operates Australia's only heavy-ion external microbeam capability, providing a unique platform for precision irradiation studies that cannot be performed under conventional vacuum conditions. In this configuration, the ion microbeam is extracted from the accelerator vacuum through an ultra-thin membrane (typically 500-1000 nm thick) into an ambient environment, while maintaining excellent beam focus, positional accuracy and intensity. Although ions experience a small energy loss when traversing the extraction window and air gap, this is readily compensated through beam energy adjustment, enabling accurate and reproducible irradiation conditions.

The external microbeam greatly expands the range of samples and experiments that can be investigated, particularly in radiobiology, medical research and applied physics. Unlike conventional vacuum-based irradiation systems, biological samples can be maintained under physiological conditions at atmospheric pressure, room temperature and in their native liquid medium. This capability enables irradiation of living cells, microorganisms, tissues, seeds, plants, and complex biological models while preserving normal cellular function and biological relevance.

A key strength of the ANSTO facility is its ability to deliver highly localised beams of energetic ions with precise control of ion species, energy, flux and dose rate. This allows investigations of radiation-induced DNA damage, cellular response mechanisms, bystander effects and relative biological effectiveness (RBE), as well as studies supporting particle and radiation therapy, radiation protection and space radiobiology research. The capability is equally valuable for applied physics applications requiring irradiation of large, delicate or non-vacuum-compatible samples.

The heavy-ion external microbeam can deliver a wide range of radiological dose rates by selecting the appropriate ion species and beam parameters and by optimising microprobe operating conditions. Combined with ANSTO's advanced beam-scanning and targeting modalities, this enables highly flexible irradiation protocols ranging from single-cell and sub-cellular targeting studies to uniform irradiation of larger biological samples and tissues. This combination of precision, versatility and operation under ambient conditions makes the ANSTO external microbeam a unique national capability supporting world-leading research in radiobiology, radiation effects and advanced materials science.