Characterizing Auger electron multiplicities and energies with the Auger Radioisotope Microscope (ARM)

The ARM has recently completed a successful proof-of-principle measurement using X-ray photoionization of stable krypton to characterize the correlated Auger electron multiplicity distribution and electron energy spectrum [1]. Using applied static fields and two sets of parallel MCP detectors, the ARM collects time-of-flight and spatial readout data from (multi)electron-ion coincidence events initiated by gas-phase Auger cascades.

In this talk I will cover plans to extend the ARM toward directly studying radioactive Auger emitters including medical isotope candidates through the introduction of a cryogenic buffer gas beam source. Radionuclide Auger emitters are ideal for targeted therapy as the low-energy, high multiplicity electron emission characteristic of Auger cascades can result in highly localized (< ~100 nm) damage in biological media and thereby minimizing damage to nearby healthy tissue.

Very limited experimental data is available for the lowest energy electrons (<500 eV), yet it is these electrons which are the most effective at DNA double strand breaks and also the most challenging to model. The ARM is expected to fill this crucial data gap and provide benchmark data needed to improve fundamental atomic relaxation models and inform oncological dosimetry models.

[1] Stollenwerk P.R., et al., New Journal of Physics 27, 053901 (2025)