10-16 June 2018
Dalhousie University
America/Halifax timezone
Welcome to the 2018 CAP Congress Program website! / Bienvenue au siteweb du programme du Congrès de l'ACP 2018!

POS-55 Response of an Organic Photodiode to a Kilovoltage Photon Beam under Different Bias Conditions

12 Jun 2018, 18:00
1h 30m
SUB McInnes Hall (Dalhousie University)

SUB McInnes Hall

Dalhousie University

Poster Competition (Graduate Student) / Compétition affiche (Étudiant(e) 2e ou 3e cycle) Physics in Medicine and Biology / Physique en médecine et en biologie (DPMB-DPMB) DPMB Poster Session & Finals: Poster competition and Mingle session with Industrial partners/employers (9) | Session d'affiches DPMB et finales: Concours d'affiches et rencontres avec partenaires industriels et employeurs (9)

Speaker

Michael Hupman (Department of Physics & Atmospheric Science, Dalhousie University)

Description

The response of an organic photodiode to fields of 300 kVp photon beams was measured while varying the bias applied to the diode. A heterojunction photodiode was fabricated by spin coating a blend of P3HT and PCBM on a glass substrate. The bottom contact was ITO and the top contact aluminum. The photodiode was irradiated with an Xstrahl 300 orthovoltage x-ray unit (Xstrahl Ltd., Surrey, UK). All irradiations were performed with a 5 cm diameter, 30 cm length cone with the photodiode placed on top of 10 cm of solid water to allow for backscatter. The photodiode was irradiated in 100 MU increments. For each bias the measurement was repeated 3 times. The diode current was measured using a source measurement unit (Keithley 2614B). All machine outputs were measured with a calibrated ionization chamber. The total charge collected for an increment of dose was determined by integrating the area under the curve of the current as a function of time when the beam was on. The sensitivity of the diode was then calculated by dividing the total charge collected by the dose. The noise was measured by irradiating the setup without the photodiode, but all electrical connections in place and the current measured. With the beam off the measured current was 1 ± 1 pA. With the beam on, but no photodiode in the holder the current increased to 5 ± 1 pA. With a dose rate of 4.1 cGy/s the measured current was 110 ± 10, 330 ± 30, 460 ± 30, and 550 ± 50 pA for applied biases of 0, 1, 1.5, and 2 V, respectively. The calculated sensitivity was 26 ± 2, 86 ± 8, 110 ± 7, and 130 ± 10 pC/cGy for applied biases of 0, 1, 1.5, and 2 V, respectively.

Primary author

Michael Hupman (Department of Physics & Atmospheric Science, Dalhousie University)

Co-authors

Irina Valitova (Department of Physics & Atmospheric Science, Dalhousie University) Prof. Ian Hill (Department of Physics & Atmospheric Science, Dalhousie University) Prof. Alasdair Syme (Department of Radiation Oncology, Dalhousie University )

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