Scintillation Counter and Semiconductor Detector
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The document provides an overview of scintillation counters, including their historical invention and operational principles for detecting ionizing radiation. It details various types of scintillators and semiconductor detectors, explaining their compositions and mechanisms for radiation detection. Additionally, it discusses advantages of semiconductor detectors in detecting alpha and beta particles with high resolution and efficiency.
Scintillation Counter and Semiconductor Detector
- 1. SCINTILLATION COUNTER JEEVANANTHAM P I MSc Chemistry, SRMV College, Coimbatore. jeevananthamche@gmail.com
- 2. History The modern electronic scintillation counter was invented in 1944 by Sir Samuel Curran(UK) Previously scintillation events had to be laboriously detected by eye using a spinthariscope which was a simple microscope to observe light flashes in the scintillator
- 3. What is Scintillation? The emission of flouroscene in a phosphor by absorption of charged particle or high energy photons
- 4. Principle : Scintillation counter is an instrument that is used for detect and measuring ionising radiation It comprises of the scintillator that generates photons by excitation effect in response to incident radiation and detecting the resultant light pulses
- 5. Radiation strike the crystal Photoelectron emitted by scintillator the electron move cathode to anode through dynode Electric pulse delivered to PM tube Electric pulse amplified and delivered WORKING
- 8. Types of scintillator : Cesium iodide (CsI) detection of protons and alpha particles. Sodium iodide (NaI) containing a small amount of thalliumdetection of gamma waves zinc sulfide (ZnS) detector of alpha particles( Zinc sulfide is the material Rutherford used to perform his scattering experiment. ) Lithium iodide (LiI) is used in neutron detectors.
- 10. QUESTN...... Which is the correct representation for “SINGLET” & “TRIPLET” ? A) B) C) D) E) F) Ans: SINGLET =B TRIPLET =D,E
- 12. Semiconductor detector A detector which is used to detect the ionising radiation by using semiondutors (usually silicon or germanium) The detecting is a single crystal consisting of a sandwich of intrinsic silicon between a P-Type layer and N-Type layer forming p-i-n diode.
- 13. Semiconductor in pure form is known as intrinsic semiconductor Ex : pure Silion and pure Germanium at room temperature no of electron equal to number of holes
- 14. N- type P-type
- 15. When the radiation interact with silicon crystal they excite elelctron from the valence band into the condution band creating a eletron – hole pair. When a reverse bias potential is applied to the crystal,the eletrons and holes are separated and a charge pulse of electrons can be measured Detection mechanism
- 16. o Generally used for detection of alpha and beta particles o Very high resolution energy measurement o Doesnot depend upon the type of radiation that deposites the energy o Negligible absorption energy o Act as a solid state ionization chamber
- 17. Types 1) Silicon detectors 2)Diamond detectors 3)Germanium detectors 4)Cadmium telluride and 5) cadmium zinc telluride detectors 6)AIP – Aluminium Phosphide 7)AIAs – Aluminium Arsenide 8)GaP – Galium Phosphide 9)GaAs – Galium Arsenide 10)InP – Indium Phosphide
- 18. advantages Minimum energy needed to create an eletron – hole pair(3.6eV) for silicon.this leads to better detection resolution. Small charge collection time (<10) Very small recombination losses due to fast charge collection.
- 19. In the ciruit diagram, the direction of eletron moves ____________ direction to the current a) Same b)opposite c) +ve to –ve d) –ve to +ve QUESTN… Ans : B & C