B014425 - IONIZING RADIATION DETECTORS

Italian

Ionizing radiation sources. Passage of radiation through matter. Gas detectors. Semiconductor detectors (Silicon and Germanium detectors). Scintillator detectors. Detector electronics.

G.F.Knoll – Radiation Detection and Measurements – Wiley 2000
W.R.Leo – Techniques for Nuclear and Particle Physics Experiments – Springer 1987

Knowledge acquired: : Basic knowledge on the main detector types for ionizing radiation detection (gas, scintillator and semiconductor detectors). Students acquire knowledge on detection principles and main characteristics of those detectors. For each detector type, a short visit to a lab (though with limited hands-on experience) is provided. Some knowledge is also acquired about the electronic chain usually coupled to radiation detectors. Knowledge about the most common radiation sources (alpha, beta, gamma) employed in research labs.
Competence acquired
Choice of the best suited detector for a given application. Setup of the detector and of the electronic chain with NIM modules.

Courses to be used as requirements (required and/or recommended)
Second year courses of the laurea degree in Physics and Astrophysics.

6 CFU,

Total hours of the course (including the time spent in attending lectures, seminars, private study, examinations, etc...): 150

Contact hours for: Lectures (hours): 48

Meeting with prof.: on request (email: pasquali@fi.infn.it)

Website
e-l.unifi.it

Oral exam. Usually at least one question is asked about radiation-matter interaction and one about some type of radiation detector. The exam aims at verifying the basic comprehension of the main physical phenomena connected with radiation detection, together with the use of a proper language and the correct terminology.

Introduction.

Ionizing radiation sources
Radiactive decay. Decay schemes. Activity, mean life, half life. Radioactive chains. Statistical fluctuations in nuclear decay.

Passage of radiation through matter
Charge particles: stopping power, Bohr formula, Bethe-Bloch formula. Bragg curve. Energy and range straggling. Scaling laws.
Electromagnetic radiation: cross section, mean free path. Compton scattering, photoelectric effect, pair production. Linear and mass attenuation coefficients.

General detector properties
Current and pulse mode. Pulse height spectrum. Resolution. Efficiency.


Gas detectors
Ionization chamber: charge production and collection. Recombination, attachment, diffusion. Charge transport. Induced signal. Frisch grid.
Proportional counters. Townsend avalanche. Fill gas. Diethorn law. Other detectors exploiting multiplication in gas.


Semiconductor Detectors
Intrinsic semiconductors. Doping. Extrinsic semiconductors.
Semiconductors as radiation detectors. Electron-hole pair production. Average energy per pair. Statistical fluctuations and Fano factor.
P-N junction detectors. Diffusion junction, surface barrier, ion implantation. Leakage currents. Pulse shape due to an electron-hole pair.
Si(Li) detectors. Signal shape.
HPGe detectors for gamma spectroscopy.
HPGe true coaxial, close-ended and bulletized.
Electric field in coaxial HPGe. Dead layers. Cooling system. Energy resolution. Pulse shape.

Scintillation detectors
Scintillator properties. Organic scintillators: scintillation process in organics. Properties of commonly used organic scintillators.
Inorganic scintillators: band structure of energy levels, doping with impurities, scintillation process. Properties of commonly used inorganic scintillators.
Photomultiplier (PMT): how it works, main properties.
Collecting scintillation light: self-absorption, losses at the surfaces, photocathode quantum efficiency.
Gamma spectroscopy with scintillators: pulse height spectrum (full energy peak, Compton edge, backscattering peak etc).


Electronics for radiation detection
Logic and linear pulses
A typical electronic chain: charge preamplifier+shaper amplifier+ADC. Electronic noise.