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Diode detector (PIN photo diode detector) Hyun Suk Kim 7 th of Jan, 2014.

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Presentation on theme: "Diode detector (PIN photo diode detector) Hyun Suk Kim 7 th of Jan, 2014."— Presentation transcript:

1 Diode detector (PIN photo diode detector) Hyun Suk Kim 7 th of Jan, 2014

2 Contents 1.Basic Physics of Diode as a Radiation Detector 2. Diode detector (P-type, N-type)3. Photodiode detector (PIN-Photodiode)

3 1. Basic Physics of Diode as a Radiation Detector

4 What is Diode

5 Use of Diode detector in SNUH EPID (Hydrogenated amorphous silicon (a-Si:H) PIN photodiode) SFD diode detector(P-type) Mapcheck2(N-type) ① Diode ② Photo-diode CT detector array

6 History of Diode detector in Radiation Oncology Silicon diode detectors have been used in high-energy photon and electron beam dosimetry for many years (from Jones 1963) Diodes have gained in popularity since the 1980s Now, one of the most useful dosimeters

7 What is semiconductor SemiconductorSemiconductor –Material which has electrical conductivity between conductor and insulator –Ability to change conductivity by the addition of impurities ("doping") –Require only a few eV to generate a charge carrier Radiation detection & measurement, 4/E, Knoll

8 ① N-type semiconductor

9 ② P-type semiconductor P-type semiconductor –doped with impurities of 3 valance electrons element B(boron) called an “acceptor” – “acceptor” contribute a free electron to the silicon –Holes(+) are the majority carriers –electrons(-) are the minority carriers

10 P-N junction Made of p-type and n-type semiconductor in direct contact Also called the “depletion region” Diode detector is made by P-N junction principle

11 2. Diode detector (P-type & N-type)

12 P-type & N-type diode detector N-type diode P-type diode SFD Mapcheck2 Diode detector is made by P-N junction principle

13 Need no bias voltage in diode detector TG-62, 2005 (DIODE IN VIVO DOSIMETRY FOR PATIENTS RECEIVING EXTERNAL BEAM RADIATION THERAPY)

14 How can we measure dose using diode? Incident ionizing radiation electron-hole pairs The minority carriers (electrons on the p-side and holes on the n-side) diffuse toward the opposite side Measured by the electrometer + - TG-62, 2005 (DIODE IN VIVO DOSIMETRY FOR PATIENTS RECEIVING EXTERNAL BEAM RADIATION THERAPY)

15 3. Photodiode detector (PIN-Photodiode)

16 What is PIN-Photodiode Made of a PIN structure Intrinsic semiconductor Intrinsic semiconductor –In concentration, hole = electron –Intrinsic semiconductor = pure semiconductor

17 Diode Operation(Bias) Forward biasForward bias : –As electrons and holes are pushed toward the junction –“Depletion region” is reduced –Act like “conductor” Reverse biasReverse bias : –As electrons and holes are pulled away from the junction –“Depletion region” widen –Act like “opened circuit” (no leakage current) → detect only photo-generated carrier

18 Physical Principles of PIN photo diode Fundamentals of Photonics, 2 nd Edition, Saleh

19 Use of Photodiode detector in Radiation oncology Hydrogenated amorphous silicon (a-Si:H) P-I-N photodiode Varian Image Acquisition System 3 Reference guide, 2011 CT detector array Courtesy of Prof. Kim J-H EPID(Electronic Potal Imaging Devices)

20 Advantage of PIN-photodiode Sensitive detectors susceptible to visible and infrared radiation(R. Nowotny et al, Nuc. instr. and meth. 147, 1977) Used with x- and gamma-ray spectroscopy with a high energy resolution(Takahiko Aoyama et al, Med. Phys 29(7), 2012) PIN improve response time and higher efficiency than PN structure Takahiko Aoyama et al, Med. Phys 29(7), 2012 Visible ray S , HAMAMATSU(760~1100 nm) linearity in low dose range.

21 What can we do?

22 Discussion & Question

23 Thank you for your attention


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