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Ronald Tosh (Fed)

Ron Tosh is a physicist in the Radiation Physics Division working in the Dosimetry Group on standards and instrumentation for absorbed dose. He joined NIST in 2004 after several years as a sales engineer for National Instruments (now NI). Prior to that, he did experimental research in molecular-beam scattering as a postdoc in the Department of Chemistry and Biochemistry at the University of Delaware. He received both M.S. and Ph.D. in physics from the Department of Physics and Astronomy at the University of Pittsburgh, with a research emphasis in atomic physics and gaseous electronics.

Current projects at NIST include development of calorimetry standards for absorbed dose in beams of gamma rays, x-rays, electrons and protons used in medicine and industry. Research activities are focused on dosimetry in radiation fields with large spatial gradients and high dose rates, with applications in radiotherapy, irradiation of surfaces, and radiosensitivity of semiconductor microdevices and biological systems.


Photonic Radiation Sensors Survive Huge Doses Undamaged
Calibrating Cancer Radiotherapy Beams Using Light and Sound
Using Calorimetry to Estimate Absorbed Dose from CT Scans

Projects and Research

Photonic Dosimetry
Remote Sensing Methods for Imaging Dose to Water
Electron and Proton Absorbed-Dose-to-Water Primary Standards


U.S. Department of Commerce Silver Medal – for contributions to standards for x-ray scanning systems used in transportation security screening.


Calorimetry in Computed Tomography Beams

Huaiyu H. Chen-Mayer, Ronald Tosh, Fred B. Bateman, Paul Bergstrom, Brian E. Zimmerman
A portable calorimeter for direct realization of absorbed dose in medical computed tomography (CT) procedures was constructed and tested in a positron emission


Ryan P. Fitzgerald, Zeeshan Ahmed, Denis E. Bergeron, Nikolai Klimov, Dan Schmidt, Ronald Tosh
With the recent redefinition of the SI base units in terms of constants of nature, the race is on to maximize achievable precision by developing primary

On-chip Silicon Photonics Radiation Sensors

Nikolai N. Klimov, Zeeshan Ahmed, Lonnie T. Cumberland, Ileana M. Pazos, Ronald E. Tosh, Ryan P. Fitzgerald
We have examined the impact of cobalt-60-ray radiation up to 1 megagray (MGy) absorbed dose on silicon photonic devices. We do not find any systematic impact

Assessing Radiation Hardness of Silicon Photonic Sensors.

Zeeshan Ahmed, Lonnie T. Cumberland, Ronald E. Tosh, Nikolai N. Klimov, Ileana M. Pazos, Ryan P. Fitzgerald
In recent years silicon photonic platforms have undergone rapid maturation enabling not only optical communication but complex scientific experiments ranging


Photonic Calorimeter and Process for Performing Calorimetry

NIST Inventors
Ronald Tosh , Zeeshan Ahmed , Ryan P. Fitzgerald and Nikolai Klimov
Patent Description The invention i s a photonic device whose resonance characteristics (such as, quality factor, peak position, and free spectral range) change in a predictable way in response to the interaction of radiation with the sensor and/or its surroundings. The invention can be used in an
A list of radiation-induced materials modifications that are NIST traceable

Photonic Dosimeter and Process for Performing Dosimetry

NIST Inventors
Ronald Tosh , Zeeshan Ahmed , Ryan P. Fitzgerald and Nikolai Klimov
Patent Description Radiation-induced materials modification is ubiquitous. These applications rely on dosimetry to reliably deliver the desired amount of radiation to the right place. Currently the dosimetry standard is based on calorimetry of a large water phantom irradiated exclusively by Co-60
Created September 24, 2019, Updated June 15, 2021