Comments on 'Investigation of the chamber correction factor (kch) for the UK secondary standard ionization chamber (NE2561/NE2611) using medium energy x-rays'

Full text: In a recent paper, Rosser (1998) investigated a number of ionization chambers using medium energy x-rays. Some of the chambers investigated in this paper were for use in electron and low energy x-ray beams and not intended for use in the energy range investigated. However, these chambers were very useful as the intention of the paper was to investigate which aspects of the chamber design and construction resulted in a chamber with as flat an energy response in-air as possible, and to derive values for the chamber correction factor (kch). I would like to stress that the paper only used medium energy x-rays and did not attempt to investigate other energy ranges or modalities, and as a consequence the conclusions of the paper should not be taken to reflect the performance of the chamber in any other energy region. At the National Physical Laboratory we have been calibrating PTW Grenz chambers (Type 23344) in-air from 8 to 50 kV generating potential for many years and have found that the quality response is satisfactory. (author)