Dosimeters are devices that are used to measure the exposure to ionizing radiation. They can be used in various applications such as healthcare, nuclear power plants, and industrial radiography. Dosimeters can be classified into two main groups, namely active and passive dosimeters. Active dosimeters continuously measure radiation exposure, while passive dosimeters accumulate the total amount of radiation over a period of time. In this article, we will focus on the energy dependence of integrating dosimeters.
The Dosimeter Response
The response of a dosimeter is defined as the ratio of the output from the dosimeter to the energy deposited in the dosimeter. The response of a dosimeter is influenced by various factors such as the energy of the incident radiation, the type of radiation, and the material used to make the dosimeter. The response of a dosimeter is typically presented in a graph, which shows the relative response of the dosimeter at different energies, normalized to a reference radiation field.
Curve A in the graph presented in the article shows the relative response of a dosimeter to different energies of radiation. The response is normalized to 1.25 MeV Co-60 gamma rays. The equation used to calculate the relative response is given by:
where r is the response of the dosimeter, X is the energy deposited in the dosimeter, and the subscript E refers to the energy of the incident radiation. The symbol μen/ρ represents the mass energy absorption coefficient, and the subscript g refers to the material in which the energy is deposited. The subscript air refers to the air, which is used as a reference material.
The Onset of Photoelectric Effect
As mentioned earlier, the response of a dosimeter is influenced by various factors, including the energy of the incident radiation. At energies below 100 keV, the photoelectric effect becomes predominant. The photoelectric effect is a process in which a photon collides with an atom, and an electron is ejected from the atom. The energy of the incoming photon is transferred to the ejected electron, and the remaining energy is absorbed by the atom. The ejected electron is known as a photoelectron.
The energy of the incident radiation is inversely proportional to the wavelength of the radiation. At energies below 100 keV, the wavelength of the radiation is long enough to cause the photoelectric effect. The photoelectric effect is more common for high atomic number materials such as lead and tungsten. The photoelectric effect results in an over-response of the dosimeter at energies below 100 keV. This is evident in curve A in the graph presented in the article.
The Drop in Dosimeter Response
Curve C in the graph presented in the article shows the relative response of a LiF thermoluminescent dosimeter (TLD) at different energies. The response is normalized to 1.25 MeV Co-60 gamma rays. The LiF thermoluminescent dosimeter is a type of passive dosimeter that is widely used in radiation dosimetry. The thermoluminescent dosimeter works on the principle of thermoluminescence. When a thermoluminescent dosimeter is exposed to ionizing radiation, the radiation interacts with the atoms in the dosimeter, causing them to become excited. When the dosimeter is heated, the excited atoms release the stored energy in the form of light. The amount of light emitted is proportional to the amount of radiation absorbed by the dosimeter.
Curve C in the graph shows that the relative response of the LiF thermoluminescent dosimeter drops to 80% at very low energies. This is a sharp drop in the dosimeter response compared to the pronounced peak observed at energies below 100 keV in curve A. The drop in the dosimeter response at low energies is unexpected, and it raises questions of what could have caused such a response.
Possible Causes of the Drop in Dosimeter Response
Several factors could contribute to the drop in the response of the LiF thermoluminescent dosimeter at very low energies. One possible cause is the energy absorption efficiency of the dosimeter. At low energies, the energy of the radiation is quickly absorbed by the material in the dosimeter. Therefore, the efficiency of energy absorption decreases at very low energies, resulting in a drop in the response of the dosimeter.
Another possible cause could be the sensitivity of the dosimeter. The sensitivity of the dosimeter decreases at very low energies, resulting in a drop in the response of the dosimeter. The sensitivity of the dosimeter depends on various factors such as the size of the detector, the type of material used to make the detector, and the energy of the incident radiation.
Another possible cause of the drop in the response of the dosimeter could be the saturation of the dosimeter. Saturation occurs when the dosimeter is exposed to a high dose of radiation, and the number of electrons released by the dosimeter reaches a maximum. The dosimeter cannot detect any additional radiation, resulting in a drop in the response of the dosimeter.
Conclusion
The energy dependence of integrating dosimeters is an essential factor that affects the accuracy and reliability of radiation dosimetry. The response of a dosimeter is influenced by various factors such as the energy of the incident radiation, the type of radiation, and the material used to make the dosimeter. The graph presented in the article shows the relative response of a dosimeter at different energies, normalized to a reference radiation field.
Curve A in the graph shows the over-response of the dosimeter at energies below 100 keV due to the onset of the photoelectric effect. Curve C in the graph shows the unexpected drop in the response of a thermoluminescent dosimeter at very low energies. Several possible causes of the drop in response of the dosimeter have been discussed, including energy absorption efficiency, sensitivity, and saturation of the dosimeter.
Understanding the energy dependence of integrating dosimeters is crucial in ensuring accurate and reliable radiation dosimetry. Further research is needed to investigate the causes of the drop in the response of the dosimeter at very low energies.
Energy Dependence of Integrating Dosimeters
Dosimeters are devices that are used to measure the exposure to ionizing radiation. They can be used in various applications such as healthcare, nuclear power plants, and industrial radiography. Dosimeters can be classified into two main groups, namely active and passive dosimeters. Active dosimeters continuously measure radiation exposure, while passive dosimeters accumulate the total amount of radiation over a period of time. In this article, we will focus on the energy dependence of integrating dosimeters.
The Dosimeter Response
The response of a dosimeter is defined as the ratio of the output from the dosimeter to the energy deposited in the dosimeter. The response of a dosimeter is influenced by various factors such as the energy of the incident radiation, the type of radiation, and the material used to make the dosimeter. The response of a dosimeter is typically presented in a graph, which shows the relative response of the dosimeter at different energies, normalized to a reference radiation field.
Curve A in the graph presented in the article shows the relative response of a dosimeter to different energies of radiation. The response is normalized to 1.25 MeV Co-60 gamma rays. The equation used to calculate the relative response is given by:
where r is the response of the dosimeter, X is the energy deposited in the dosimeter, and the subscript E refers to the energy of the incident radiation. The symbol μen/ρ represents the mass energy absorption coefficient, and the subscript g refers to the material in which the energy is deposited. The subscript air refers to the air, which is used as a reference material.
The Onset of Photoelectric Effect
As mentioned earlier, the response of a dosimeter is influenced by various factors, including the energy of the incident radiation. At energies below 100 keV, the photoelectric effect becomes predominant. The photoelectric effect is a process in which a photon collides with an atom, and an electron is ejected from the atom. The energy of the incoming photon is transferred to the ejected electron, and the remaining energy is absorbed by the atom. The ejected electron is known as a photoelectron.
The energy of the incident radiation is inversely proportional to the wavelength of the radiation. At energies below 100 keV, the wavelength of the radiation is long enough to cause the photoelectric effect. The photoelectric effect is more common for high atomic number materials such as lead and tungsten. The photoelectric effect results in an over-response of the dosimeter at energies below 100 keV. This is evident in curve A in the graph presented in the article.
The Drop in Dosimeter Response
Curve C in the graph presented in the article shows the relative response of a LiF thermoluminescent dosimeter (TLD) at different energies. The response is normalized to 1.25 MeV Co-60 gamma rays. The LiF thermoluminescent dosimeter is a type of passive dosimeter that is widely used in radiation dosimetry. The thermoluminescent dosimeter works on the principle of thermoluminescence. When a thermoluminescent dosimeter is exposed to ionizing radiation, the radiation interacts with the atoms in the dosimeter, causing them to become excited. When the dosimeter is heated, the excited atoms release the stored energy in the form of light. The amount of light emitted is proportional to the amount of radiation absorbed by the dosimeter.
Curve C in the graph shows that the relative response of the LiF thermoluminescent dosimeter drops to 80% at very low energies. This is a sharp drop in the dosimeter response compared to the pronounced peak observed at energies below 100 keV in curve A. The drop in the dosimeter response at low energies is unexpected, and it raises questions of what could have caused such a response.
Possible Causes of the Drop in Dosimeter Response
Several factors could contribute to the drop in the response of the LiF thermoluminescent dosimeter at very low energies. One possible cause is the energy absorption efficiency of the dosimeter. At low energies, the energy of the radiation is quickly absorbed by the material in the dosimeter. Therefore, the efficiency of energy absorption decreases at very low energies, resulting in a drop in the response of the dosimeter.
Another possible cause could be the sensitivity of the dosimeter. The sensitivity of the dosimeter decreases at very low energies, resulting in a drop in the response of the dosimeter. The sensitivity of the dosimeter depends on various factors such as the size of the detector, the type of material used to make the detector, and the energy of the incident radiation.
Another possible cause of the drop in the response of the dosimeter could be the saturation of the dosimeter. Saturation occurs when the dosimeter is exposed to a high dose of radiation, and the number of electrons released by the dosimeter reaches a maximum. The dosimeter cannot detect any additional radiation, resulting in a drop in the response of the dosimeter.
Conclusion
The energy dependence of integrating dosimeters is an essential factor that affects the accuracy and reliability of radiation dosimetry. The response of a dosimeter is influenced by various factors such as the energy of the incident radiation, the type of radiation, and the material used to make the dosimeter. The graph presented in the article shows the relative response of a dosimeter at different energies, normalized to a reference radiation field.
Curve A in the graph shows the over-response of the dosimeter at energies below 100 keV due to the onset of the photoelectric effect. Curve C in the graph shows the unexpected drop in the response of a thermoluminescent dosimeter at very low energies. Several possible causes of the drop in response of the dosimeter have been discussed, including energy absorption efficiency, sensitivity, and saturation of the dosimeter.
Understanding the energy dependence of integrating dosimeters is crucial in ensuring accurate and reliable radiation dosimetry. Further research is needed to investigate the causes of the drop in the response of the dosimeter at very low energies.