Relationships between absorbed dose to water rate and field size for electron beam

This paper describes the relationships between absorbed dose to water rate and field sizes for electron beams with nominal energies of 10, 12 and 15 MeV from an elektra S/N 15614 linear accelerator machine owned by Adam Malik hospital. Measurement of percentage depth doses for every electron beam energy was carried out inside a water phantom using a PTW Tandem dosemeter with a 0.125 cc ionization chamber at a constant source to surface distance of 100 cm. Measurement of ionization to determine absorbed dose to water rate and ion recombination correction factor has been carried out by using a 0.6 cc ionization chamber type of NE 2571 serial number 2491 connected to a Farmer electrometer type of 2570/1 B serial number 1182 at the source to the phantom surface distance of 100 cm with field sizes defined by 6 cm x 6 cm, 10 cm x 10 cm, 14 cm x 14 cm and 20 cm x 20 cm applicators. The measurement results were calculated based on the IAEA publication Technical Reports Series No. 277. The result obtained showed that the absorbed doses rate changed of 4% with the field sizes. (author)