Development of a new in-water-phantom graphite calorimeter for the measurement of absorbed dose to water in medium energy x-ray beams

¹ Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti dell’ENEA (ENEA-INMRI), Via Anguillarese, 301, 00123, Santa Maria di Galeria (RM), Italy
² ‘Al I. Cuza’ Iasi University, Faculty of Physics, Carpath Center, 11 Carol I Blvd, RO-700506, Iasi, Romania

^a Corresponding author: massimo.pinto@enea.it

Abstract

This paper summarizes the progress on the construction of a graphite calorimeter for the measurement of absorbed dose to water D_w in medium-energy filtered x-ray qualities, as part of the EMRP funded project “Metrology for radiotherapy using complex radiation fields” (MetrExtRT, http://radiotherapyemrp.eu/). The design and the construction of a new primary standard for absorbed dose to water (D_w) is shown, together with a presentation of the preliminary estimates of conversion factors, calculated by Monte Carlo using the EGSnrc code, and heat-transport calculations resulting from COMSOL simulations. The vacuum-gap-insulated calorimeter core has a thickness of 2 mm and a diameter of 20 mm. The graphite calorimeter is embedded in a PMMA waterproof sleeve and can be positioned at the desired measurement depth in a water phantom. Once completed, the new calorimeter will participate in an international comparison with other existing standards of absorbed dose to water for medium energy x-rays.