Calibration of Carestream Image Plates for Broad-Spectrum Photon Diagnostics at DARHT

The Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility consists of a pair of linear induction accelerators operating electron beams at about 1.6kA and 16-20MeV. The x-ray emission from DARHT consists of fluorescence x-rays up to 66keV and broad-band bremsstrahlung emission up to the end-point energy of the accelerator. Image plates are a widely utilized diagnostic tool for ionizing radiation, yet comprehensive calibrations available in the literature have largely focused on Fujifilm image plates. Carestream images plates have been found to be advantageous on the DARHT because they lack a magnetic backing material that can interfere with low energy electrons. However, Carestream image plates differ from Fujifilm in active-layer composition which necessitates an independent calibration.

We present a detailed calibration of Carestream image plate sensitivity to x-ray and gamma-ray photons over an energy range of 17 keV to 88 keV and from 3 MeV to 13 MeV. To span these broad spectra, a combination of photon sources was used. From 17 keV to 88 keV x-ray fluorescence (XRF) generated by exposing metal foils to a continuous Bremsstrahlung source was utilized. From 3 MeV to 13 MeV the image plates were placed in the path of a quasi-mono-energetic gamma-ray beam generated via inverse Compton scattering at the High Intensity Gamma-ray Source (HIγS) [1]. The resulting data provide a comprehensive response curve, but we report data diverging from the most obvious trend line at 3 MeV.

[1] H. Weller et al., Research opportunities at the upgraded HIγS facility, Progress in Particle and Nuclear Physics, Vol. 62, Issue 1 (2009)