|Message: Questions about scintillation phenomenon?||Not Logged In (login)|
Click on the Forum title, e.g. on the "Forums by Category" page, to read a sequence of postings to the Forum and its threads all in one page. If you are only interested in one thread or the thread following a specific posting, click the thread or the posting, which takes you to a smaller page, which contains only the part you are interested in and may be easier to navigate.
Messages are "chained" if there are only replies at the first level, i.e. 1/1.html, 1/1/1.html etc. In case of "chained" messages the message number is replaced by the icon and there is no indentation.
Inline: Display the subject line only or also the text of the posting(s); for the choice "All" the "Outline" choices are switched off.
|1||0||1||no text / full text of posting|
|2||1||All||text for level 1 only / text for All postings|
Outline: Choose the depth of the posting thread, successive toggle controls provide increasing detail.
|1||2||1||2 levels / 1 level (original posting)|
|2||3||2||3 levels / 2 levels|
|3||3||All||3 levels / all levels (all postings)|
Hi, I have some questions regarding scintillation phenomenon. I want to simulate NaI(Tl) scintillation detector. For this purpose, I refer to an example of the scintillation effect given in /novice/N06 example in Geant4 toolkit. At this application, I notice that the scintillation material is water. The optical and scintillation properties of water, that include refractive index, absorption length, light photon emission spectrum, decay time and fast and slow scintillation components, are stored in a G4MaterialPropertiesTable pointer. About these empirical properties, I have some questions as following: 1. Spectral distribution: - What does photonEnery matrix consisted of? - In other words, do the elements of photonEnery matrix include light photons energy emitted by water? - Can I conclude that the water emits 32 light photons with the energies given in this matrix? - If it is true, I need to have the details of NaI(Tl) emission spectrum light produced by gamma interaction in NaI(Tl). Although I find this spectrum curve of NaI(Tl) in the textbooks related to radiation detection titled “Radiation detection and measurement” by Glenn F. Knoll, but this curve does not include the details of each NaI(Tl) line spectrum such as the wavelengths of light emission and its intensities as are needed. Additionally, I have come the following sentence in a across book titled “The Theory and Practice of Scintillation Counting” by J. B. Birks, 1964: “The scintillation emission spectrum is mainly characteristics of the luminescence centre, i.e. Tl+ ion in the case of the thallium-activated crystal.” Based on the above phrase, I would like to raise the following questions: - Is it correct to use scintillation emission spectrum of Tl+ ion for photonEnergy matrix? - I get the 65 lines of Tl I from NIST atomic spectra database site. Although I know that the wavelength of maximum emission NaI(Tl) is 415 nm as it is mentioned in the radiation detection textbooks, so I expect to see this wavelength through 65 lines of Tl I, but I do not find this wavelength mentioned anywhere through 65 lines of Tl I. Can anyone explain it to me? In addition, I think that the intensity of the spectral lines emitted by a crystal (e.g. NaI(Tl)) is related to the energy of gamma ray excitation. If it is true, then I need to have the emission spectrum as a function of gamma ray energy. Do you agree with me? 2. Refractive index: I need to have the refractive index of NaI(Tl) crystal. For this purpose, refractive index data of pure NaI crystal are available in the following article: “Refractive Index of Alkali Halides and Its Wavelength and Temperature Derivatives” published J. Phys. Chem. Ref. Data, vol. 5, No. 2, 1976 p329-429.Since this data are related to pure NaI crystal, can I use it for Thallium-activated NaI crystal? 3. Absorption length: For the implementation of optical photon bulk absorption, I need to have the absorption length data for the spectral lines emitted by NaI(Tl) crystal. Where can I get this data? 4. Fast and slow scintillation components: In the N06 example, I notice that the scintillation water must consist of two components: a fast component with decay time of 1.0 ns and a slow component with 10.0 ns as it is shown in the following lines: myMPT->AddProperty(“FASTTIMECONSTANT”,1.*ns); myMPT->AddProperty(“SLOWIMECONSTANT”,10.*ns); … Water->SetMaterialPropertiesTable(myMPT); - Although I see two matrixes including 32 elements with the name of ScintilFast  and ScintilSlow , but I do not exactly know what these matrixes consist of. Please explain to me. - Are the emission spectrum lines of slow scintillation component similar to that of the fast component? - If it is the case, are the relative intensities of the fast and slow emission spectra different from each other? - Again if that is case, can I conclude that photonEnery matrix consists of the emission spectrum lines of slow and fast scintillation components and additionally ScintilFast  and ScintilSlow  matrixes include the relative intensities of the emission spectrum lines of slow and fast scintillation components? - Is it correctly defined? About NaI(Tl) crystal, I notice that this crystal exhibits a fast component with the decay time of 250 ns and a slow component of 620 ns. Are these parameters constant in NaI(Tl) crystal produced in the world? Also I do not have the information about the emission spectrum lines of slow and fast scintillation components from NaI(Tl) and also their relative intensities. Please guide me. 5. Resolution scale: Is the resolution a function of radiation source? In other words, is the resolution of NaI(Tl) crystal for Co-60 gamma radiation similar to that of Cs-137? I think that the NaI(Tl) crystal resolution is a function of gamma ray energy. Therefore, I need to set this parameter (RESOLUTIONSCALE) for each gamma ray source. Is it true? 6. Reflection mechanisms: In the NaI(Tl)that I have used, the material of crystal housing is Aluminum . I do not know the constant values of the following parameters: SPECULARLOBECONSTANT, SPECULARSPIKECONSTANT, BACKSCATTERCONSTANT, DIFFUSELOBECONSTANT, REFLECTIVITY and EFFICIEINCY. In addition, I do not find any explanations about the meaning of the reflectivity and efficiency parameters. . Where can I get this data? Please help me for understanding these subjects. Your sincerely Shahrokh
|Inline Depth:||Outline Depth:||Add message:|