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Development of a chemical dosimeter for electron beam food irradiationRivadeneira, Ramiro Geovanny 16 August 2006 (has links)
A chemical solution composed of paraffin wax, chloroform, and methyl yellow
biological indicator was shaped into a solid 3-D apple phantom to determine absorbed
dose from e-beams and X-rays. The purpose of this research was to determine the most
uniform irradiation treatment on apple-phantoms (a complex shaped target) and
GAFCHROMIC® HD-810 films using electron beams from (1) a 2 MeV Van de Graaff
(VDG) accelerator, (2) a 10 MeV Linear Accelerator (LINAC), and (3) X-rays from a 5
MeV LINAC.
Irradiation with the VDG accelerator confirmed that tilting the apple-phantom yaxis
towards the e-beam source by 90 degrees, 45, and 22.5 degrees resulted in more
uniform treatment in both the methyl yellow apple phantom and HD-810 film. The
phantoms were over-exposed at the top and bottom regions when their y-axis was
oriented exactly parallel to the e-beam at 22.5-degrees. The 45-degree orientation
ensured uniformity throughout the whole apple surface without overexposing it at the
top and bottom. In contrast, the 90-degree orientation resulted in the least effective
treatment with the bottom and top region not receiving any radiation. A 10 MeV dual e-beam showed uniform penetration from top to bottom in the
HD-810 film and apple phantoms. The HD-810 film responded linearly with doses up to
1.5 kGy while the methyl yellow response was non-linear up to 0.5 kGy maximum. The
X-ray irradiation completely penetrated the apple phantoms from top to bottom showing
excellent lateral uniformity at different penetration depths.
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