Interaction of radiation with material, detection of radiation Flashcards
Write the formula describing the attenuation of gamma or X-ray radiation in an absorbing material.
J = J0 e -ux
where J0 denotes the incident intensity and J is the transmitted intensity after passing through an absorber of thickness x.
μ is the absorption/attenuation coefficient.
What is the definition of the attenuation coefficient of a material for gamma or X-ray and what is its SI unit?
The attenuation coefficient is the reciprocal of the distance at which the intensity of the radiation decreases to 1/e-times (37%) of the initial value. [μ]=1/m.
How does the intensity of alpha-radiation change as a function of the distance from the radiation source?
It is constant in the beginning then suddenly decreases to zero.
Why are alpha and beta(-) radiations called directly ionizing radiations?
Due to their charge, ionization is caused by the direct electrostatic interaction with atomic electrons. Their energy decreases in a series of ionizations along their path.
Why do we call gamma radiation and X-rays indirectly ionizing radiation?
Primary (direct) interactions between the photons and atomic electrons account for only 5% of ionizations. The majority (95%) of ionizations are caused by high-energy electrons emitted during the primary interactions.
Compare the path of alpha- and beta(-) particles passing through an absorbing material.
The path of the alpha particle is straight, whereas that of the beta(-) particle is zigzagged.
What kind of radioactive radiations can be detected by a GM-counter?
alpha-, beta- and gamma-particles can be detected.
What kind of radioactive radiations can be detected by a GM-counter?
alpha-, beta- and gamma-particles can be detected.
What is the basic principle of operation of a photomultiplier tube?
Electrons liberated from a light sensitive cathode by photons are accelerated in an electric field and collide into other electrodes (dynodes) whose potentials are increased in succession along the length of the tube. The energy of this collision is sufficient to free several secondary electrons. In this way the number of electrons increases at each dynode.
What is the basic operation principle of ionization detectors?
Electrons and positive ions produced by the ionization process are separated by the electric field of the detector. The charged particles are attracted towards the appropriate electrodes and generate electric impulses.
What is the basic operation principle of ionization detectors?
Electrons and positive ions produced by the ionization process are separated by the electric field of the detector. The charged particles are attracted towards the appropriate electrodes and generate electric impulses.
What is the principle of detection of radioactive radiation by a scintillation detector?
In certain organic and inorganic substances the energy of radioactive particles is converted to luminous energy, i.e. they generate visible light flashes.
What is the principle of detection of radioactive radiation by a scintillation detector?
In certain organic and inorganic substances the energy of radioactive particles is converted to luminous energy, i.e. they generate visible light flashes.
List the radioactive radiations in order of increasing penetrability!
alpha<betha<gamma
