Absolute dosimetry at ultra-high dose rate
In plain words
Standard dose meters saturate when the dose arrives in a single very intense pulse, because the charges they collect recombine before being counted. There is no accepted way to measure such doses absolutely.
Precise statement
Establish traceable absolute dosimetry for pulses delivering 100 to 1000 rad in 1 to 4 microseconds, with instantaneous dose rates up to $10^9\,\mathrm{rad}/\mathrm{s}$, where ion-chamber general recombination is severe and the Boag formalism (the standard correction for charge recombination in ion chambers) fails. Candidate standards: water and graphite calorimetry, Fricke and alanine chemical dosimeters, scintillator and Cherenkov detectors. An answer is a primary standard plus validated transfer detectors with uncertainty below 2 percent.
What would settle it
Agreement within 2 percent between calorimetric primary standards and transfer dosimeters across the pulse-structure range.
Status in the literature
Unverified note
Calorimeter-based ultra-high dose-rate standards were under development at several national laboratories as of 2025.