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An Investigation of Cerenkov Light Production in the Exradin W1 Scintillator Under Various Measurement Conditions

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E Simiele

E Simiele*, W Culberson , Univ of Wisc Madison, Madison, WI

Presentations

SU-E-T-108 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall


Purpose: To investigate the effects of depth, fiber-optic cable bends, and incident radiation angle on Cerenkov production in the Standard Imaging Exradin W1.

Methods: Measurements were completed using a Varian Clinac 21EX linear accelerator with an Exradin W1 scintillator as well as a cable-only scintillator (no scintillation material) to isolate the Cerenkov signal.
The effects of cable bend radius and location were investigated by bending the fiber-optic cable into a circle with radii ranging from 1.0 to 10.8 cm and positioning the center of the coil at distances ranging from 10.0 to 175.0 cm from the photodiode.
The effects of depth and incident radiation angle were investigated by performing measurements in water at depths ranging from 1.0 cm to 25.0 cm and angles ranging from 0° to 80°. Eclipse treatment-planning software was utilized to ensure a consistent dose was delivered to the W1 regardless of depth or angle.

Results: Measured signal in both channels of the cable-only scintillator decreased as the bend radius decreased and as the distance between the bend and photodiode increased. A fiber bend of 1.0 cm radius produced a 17.1% decrease in the green channel response in the cable-only scintillator. The effect of depth was less severe; a maximum increase of 6.6% in the green channel response was observed at a depth of 25.0 cm in the W1. In the angular dependence investigation, the signal in both channels of the W1 peaked at an angle of 40°; which is in agreement with the nominal Cerenkov emission angle of 45°.

Conclusion: The green channel response in the W1 (mainly Cerenkov signal) varied with depth, fiber-optic cable bends, and incident radiation angle. Fully characterizing Cerenkov production is essential to ensure it is properly accounted for in scintillator measurements.

Funding Support, Disclosures, and Conflict of Interest: Research funding and materials received by Standard Imaging, Inc. (Middleton WI)


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