Handbook of thermoluminescence download

Douglas, in Applied Thermoluminescence Dosimetry, op. Jacob Klein, Science , — Download references. Stern, J. Price, D. Simons, D. Land, V. Mathur, C. You can also search for this author in PubMed Google Scholar.

Reprints and Permissions. Stern, S. Journal of Materials Research 6, — Download citation. Received : 04 April Accepted : 12 March Published : 31 January Issue Date : July Anyone you share the following link with will be able to read this content:.

Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative. In the following discussion the case of Sj l is omitted to avoid a heavy formalism. Considering the net TL response, Eq. Figure 1 shows the plots of both Eqs. In this way Eq. Figure 2 shows, schematically, the behavior of the TL vs. The dotted line represents the proportionality as indicated by Eq. An unfortunate use of terminology has crept into the literature on thermoluminescence dosimetry which may easily mislead the uninitiated.

Plots of Eq. I I lrf Fig. TL response as a function of dose for three different types of TLDs. Calibration data for various dosimeter materials are usually presented, as already stated, as a plot of the logarithm of thermoluminescence response vs. Other straight lines imply some power relationship between the variables.

Then remember that a straight line on full log paper is not necessary linear. Scharmann, Adam Hilger Publ. For each detector one must know the individual background and the intrinsic sensitivity factor.

In any case it is good to give increasing doses following a logarithm scale i. Each experimental point is the average of the readings of five TLDs. The data are corrected by subtraction of the individual background and by the intrinsic sensitivity factor. For simplicity, Table 1 reports only the average values and the corresponding standard deviations.

The plot is shown in Fig. Dose Average reading foGy aAL 25 0. Example of TL response vs. Linearity plot for TLD Reference Furetta C. ICeJUc 1. Schulman J. Moreno y Moreno A. Botter-Jensen L. Takenaga M. Its effective atomic number 8. Thus it can be considered as tissue equivalent. Ti This phosphor is produced commercially by the Harshaw Chemical Co.

Harshaw patent [1] describes two preparation methods for LiF:Mg,Ti TL phosphor powders: the solidification method and the single crystal method. Once the material is cooled, it is crushed and sieved between 60 and um. To obtain them, the LiF powder mixture is placed in a neutral atmosphere and pressed at 3. The bar obtained is cut into sections to prepare pellets of uniform thickness and finally the faces of the pellets are polished.

The extruded dosimeters have identical TL characteristics as the TL phosphor powder. The powder mixture is homogenized, put in an aluminum oxide crucible, and held at the CHAPTER L crystallization temperature for about 3 h in a nitrogen flow oven. The product is finely pulverized and the treatment repeated.

Finally the product is repulverized and sieved between 60 and lira. The crystals are quenched by pouring them on a cold metal plate. A few ml of a solution 0. Once LiF is precipitated, the sample is centrifuged and washed repeatedly. Then the material is cooled to room temperature adding a few ml of LiCl solution.

Pellets thus obtained 5 mm diameter and 0. These compressed pellets undergo a thermal treatment in a nitrogen oven at a temperature slightly lower than that of LiF fusion to be sintered. The low temperature peaks 1, 2, and 3 are relatively unstable and must be suppressed by a thermal treatment. The linearity is maintained from mGy up to about 6 Gy, beyond which superlinearity appears.

LiF containing 6Li is sensitive to thermal neutrons. Peak 5 shows a response which deceases with increasing LET of ionizing particles protons, a-particles, etc. Peak 6 is particularly sensitive to a-particles. This difference in behavior is useful to measure thermal neutrons in a mixed radiation field. P LiF : Mg, Cu, P has been developed as a phosphor of low effective atomic number which exhibits a simple glow curve, low fading rate, and high sensitivity.

The resulting polycrystalline material is crushed and sieved selecting powder with grain sizes between and nm.

The final product is the TL phosphor powder. Patent Harshaw Chemical Co. Portal G. CEA-R 3. Azorin J. Nakajima T. Mexico 6. Furetta C , Mendozzi V. Scacco A. B Localized energy levels Trapping levels within the material's forbidden energy gap. The light emitted, when the electron comes back to its ground energy level, can be classified according to a characteristic time, T , between the absorption of the exciting energy and the emission of light.

The light is emitted with a wavelength larger than the wavelength of the absorbed light owing to dispersion of energy by the molecule. The process of phosphorescence is explained with the presence of a metastable level, between the fundamental and the excited levels, which acts as a trap for the electron. If the transition arrives at a temperature T and the energy difference E, between the excited and the metastable levels, is much larger than kT , the electron has a high probability to remain trapped for a very long time.

Assuming a Maxwellian distribution of the energy, the probability of escaping by the trap is given by As a consequence, the period of time between the excitation and the transition back to the ground state is delayed for the time the electron spends in the metastable state. In the previous equation, the probability p is a function of the stimulation method, which can be thermal or optical and will assume a different form according to the type of stimulation. Bube R. Mahesh K. In other words, a luminescent center is a quantum state in the band gap of an insulator which acts as a center of recombination of charge carriers when it captures a carrier and holds it for a period of time until another carrier of opposite sign is also trapped and both combine.

The recombination causes the release of the energy in excess as photons or phonons. Luminescence dosimetric techniques The main luminescence dosimetric techniques are: radio-thermoluminescence RTL or thermoluminescence TL which consists in a transient emission of light from an irradiated solid when heated; ii radio-photoluminescence RPL which consists of the emission of light from an irradiated solid by excitation with ultra-violet light; iii radio-lyoluminescence RLL which consists of a transient emission of light from an irradiated solid upon dissolving it in water or some other solvent i CHAPTER L Luminescence dosimetry Luminescence dosimetry is an important part of solid state dosimetry and incorporates processes whereby energy absorbed from ionizing radiation is later released as light.

Experiments have shown that 7] is strongly temperature dependent: the efficiency remains quite constant up to a critical temperature beyond which it decreases rapidly. Equation 2 can also be written as follows: 3 because the radiative probability Pr is not affected by temperature, while the nonradiative probability Pm depends on temperature through the Boltzmann factor. In the above Eq. From this higher state the electron can transfer to the ground state without emission of radiation.

Luminescence phenomena Luminescence is the emission of light from certain solids called phosphors. This emission, which does not include black body radiation, is the release of energy stored within the solid through certain types of prior excitation of the electronic system of the solid. This ability to store is important in luminescence dosimetry and is generally associated with the presence of activators. The following table lists the luminescence phenomena and the methods of excitation.

Furthermore, the wavelength of the emitted light is characteristic of the material. M Magnesium borate MgO x nB2O3 This phosphor is a near tissue equivalent material with an effective atomic number for photoelectron absorption equal to 8.

The preparation of polycrystalline magnesium borate activated by dysprosium has been reported at first in [1]. After that the material is annealed in a furnace, then cooled, ground, and screened.

The most sensitive material is obtained at the proportion of boric anhydride and magnesium oxide 2. The sensitivity is reported to be 10 to 20 times larger than that of LiF. The TL response Vs dose is linear from 10"5 to 10 Gy. A development of the preparation method of magnesium borate activated by Dy and Tm and other unknown impurities added as co-activators, was presented in [2]. The sensitivity has been reported to be about seven times greater than that of LiF; other investigators reported a factor of four [3].

Further investigations [3,4] reported high variability of the TL features within a batch as well as among different batches. This suggested the necessity of improving the material preparation in order to use such a phosphor widely in personnel and environmental dosimetry without problems of individual detector calibration. A new production of MgB. Kazanskaya V. Prokic M, Nucl. Barbina V. And Padovani R. Letters 67 55 Driscoll C. The molten mass is then cooled to room temperature. The atomic number of the obtained phosphor is about The dopants enhance the thermoluminescence emission.

The highest sensitive phosphor is obtained with Mn. The TL response is linear up to about 40 R []. Paun J. Jipa S. Nagpal J. TL properties of this system, whose effective atomic number is about 11, are reported since [] and are strongly dependent on the preparation procedure. The weight of dosimeter samples is typically 5 mg of powder. Solid discs are also available. The sensitivity of this material is 50 to 80 times higher than that of LiF TLD, depending on the sample quality. The exposure response is linear in the range from about 20 mR to R.

This sensitivity to biologically active UV light typical of germicidal lamps can be very useful for UV dosimetry. Hashizume T. IAEA, Vienna 2. Jun J. Bhasin B. May-Partridge wrote an empirical expression for taking into account experimental situations which indicated intermediate kinetics processes.

They started with the assumption that the energy level of traps is single, as already assumed for the first and second orders. Let's assume that the number n of charge carriers present in a single energy level is proportional to nb.

Then, the probability rate of escape is: 1 where s" is the pre-exponential factor. Equation 1 is the so-called general order kinetics relation, and usually b is ranging in the interval between 1 and 2. The pre-exponential factor s" is now expressed in cm3 b"1 sec"1. It has to be stressed that the dimensions of s" change with the order b.

Rearranging Eq. With this definition the difficulty with respect to the variation of dimensions has been bypassed. Anyway, the frequency factor s is constant for a given dose and would vary when the dose is varied. So we have again the explanation of the bell shape of the glow-curve as experimentally observed. To conclude, Eq. It must be stressed that Eq. Figure 1 shows the variation of the half-life as a function of the activation energy for given values of the frequency factor.

Figure 2 shows the same plot for given values of the activation energy. V 1 Variation of the half-life, Eq. The mean life concept cannot be applied to a second or general order kinetics because the isothermal decay is not exponential any more. Indeed, the half-life in the case of the first order kinetics is independent of the initial concentration of the trapped charges, which means to be independent of the dose.

In the case of the second order kinetics, the situation is totally different because the half-life is dose dependent i. So that, as the period of time from the initial irradiation increases, the same does the half life. The same happens for a general order case. Furetta C. This level is associated to a trapping level. Randall and Wilkins did not solve Eq. The value in double brackets corresponds to the slope of the straight line and -ln j to the intercept.

They showed from Eq. Reference Randall J. London, Ser. Reference Urbach F. An interpolation with a straight line having a slope equal to one.

The authors have suggested a slightly modified definition of the old dose response function. In this case Mo is negative but is still valid since it has no physical meaning. M D values above the extrapolated linear region produce f D to be larger than 1, and the supralinearity appears in the TL response. TLnet a. TL vs. TLnet corresponds to the reading minus background.

Some points of the curve can now be considered. Plot of TL vs. The above two values indicate superlinearity and supralinearity in the region preceding the linear part of the curve. A further example is the one given in Fig.

The data calculated using the previous equation are given in the following Table 2. Data calculated from Eq. Table 3 gives a summary of the various configurations which can be found in case of nonlinearity TL response. Inabe K. The most popular is the contact way realized using a planchet heating.

Because the temperature control is usually achieved by means a thermocouple mounted on the back of the planchet, this method gives only a control of the planchet's temperature and not of the sample. The temperature lag between planchet and sample, as well as the temperature gradient across the TLD, can strongly influence the analysis of the glow curve, specially in the calculation of the kinetic parameters, where an accurate temperature determination is absolutely necessary.

The problem of non-ideal heat transfer has been studied by various authors and corrections have also been proposed [] References 1. Taylor G. Gotlib V. Betts D. Piters T. Facey R. Comparison between experimental and theoretical glow-peaks. The procedure is now as follows: an experimental glow-curve is measured and an E value is estimated by using one of the experimental methods reported.

Then a theoretical glow-curve is plotted using Eq. The fitting of the remaining curve is then checked. If the chosen value of E is too small or too high the theoretical curve will lie above or below the experimental curve except for the maximum as shown in Fig. In these cases a new value of E is chosen and the procedure is repeated until the desired fit is obtained. Reference Mohan N. However, a better fit may be expected if only points below the maximum temperature are taken, since the main difference between first- and second-order peaks is in the region above the maximum.

The solution of Eq. Equation 2 can be normalized by dividing 1 T by I TjJ. The frequency factor s is found using the condition at the maximum and then some points I T! Reference Shenker D. The charge carriers released may recombine with opposite sign carriers, emitting light during the illumination bleaching light , or may be retrapped in other trapping centers. Observing then the changes occurring in the glow-curve resulting after the optical stimulation, relationships between thermoluminescence traps and optically activated centers can be obtained.

The term "beaching" is taken from the vocabulary of color centers: a crystal is colored by high dose of ionizing radiation and a subsequent illumination produces the color fading, i.

Optical fading The effect of light on an irradiated thermoluminescent sample consists of a reduction of the TL signal, depending on the light intensity, its wavelength and duration of exposure. For practical applications personel, environmental and clinical dosimetry , the sensitivity to the light of different TL materials can be avoided by wrapping the dosimeters in light-tight envelopes. If this procedure is not applied, fading correction factors have to be determined carrying out experiments in dark and light conditions.

Oven quality control The oven used for annealing should be able to keep predetermined temperature oscillations within well specified margins. However, it must be noted that the reproducibility of the annealing procedure, concerning both heating up and cooling down processes, is much more important than the accuracy of the temperature setting.

Temperature overshoots due to the high thermal capacity of the oven walls can be minimized using ovens with circulating hot air. In this way the problem related to a non-ideal thermal conductivity of the annealing trays is also solved. This facility could also reduce any possible contamination. It would be better to use different annealing ovens depending on the various needs: one of them should be suitable for high temperature annealing, another one for low temperature annealing and a third for any pre-readout thermal cycles.

Ceramic is preferable for its chemical inertia and good thermal conductivity. A quality control program concerning the ovens has been suggested by Scarpa and takes into account the various quantities which have to be checked, displayed graphically in Fig. The accuracy is related to the difference between the CHAPTER O temperature set and the temperature monitored; the instability of the oven concerns the oscillations of the temperature monitored.

Figure 2 shows an example concerning the heating up profile of a muffle oven. Because the heating time is a characteristic of each oven, it must be checked accurately. It is convenient to switch on the oven several hours before use. Quantities to be checked for the quality control of the ovens. During the steady phase of the oven the temperature, normally, is not stable. The oscillations around the temperature set depend on the quality of the oven.

This parameter has to be reported in the list of the characteristics of any new oven. As an example, Fig. Another effect to be taken into account is that one which arises when the door of a preheated oven is opened to put the tray inside; the temperature drops to a lower value and then increases above the pre-set value. Of course, it is not a good procedure to open the oven during the annealing treatment.

According to the previous effects, it is convenient to use at least two different ovens when the TL dosimeters need a complex annealing procedure, as in the case of LiF :Mg,Ti which needs a high temperature annealing followed by a low temperature treatment.

Figure 7 shows the space distribution of temperatures inside an oven. Because the temperature gradients are always present inside an oven, the TLD tray must always be positioned at the same place. Soc: Solid State Science, 2.

Balarin M. The expression N — n can be transformed using Eqs. Let us indicate with Tg the peak maximum temperature of a peak received with temperature lag, with TM the real value if there is no temperature lag, and with KT -Tg-TM the difference.

Solving Eq. Therefore, Eq. Reference Kitis G and Tuyn J. Some quality tests can be carried out, each giving a different precision. The simplest method is the following. The user screens all the samples by irradiating them with a known dose from a calibrated radiation source showing a good beam uniformity and making sure that all the samples have been inside the irradiation field.

Any TL sample outside the specified tolerance limits should be rejected. The TL dosimeters can also be screened at periodic time intervals. It must be noted that screening can only be used to determine acceptance or rejection of the samples. Indeed, there are two negative aspects of this procedure.

Firstly, accepting a large range of responses i. This is very dangerous when the dosimeters are used in clinical applications. Secondly, the replacement of the rejected TLDs is difficult when the replacement dosimeters come from a different batch: a bias error can be introduced into the whole procedure for the dose assessment. However, this test remains valid as a first step to know the characteristics of a new TLDs batch. A quality control concerning the batch homogeneity for TLDs used in personnel dosimetry is suggested in the technical recommendations of the International Electrotechnical Commission IEC document.

The procedure is given below with some examples. Procedure for batch homogeneity. All the N dosimeters of the same batch have to be annealed according to the annealing procedure used for the type of TL material under test.

At the end of the annealing procedure, all the dosimeters have to be irradiated using a calibrated gamma source under the appropriate electron equilibrium conditions. The given dose depends on the future use of the dosimeters; i. Immediately after irradiation the TLDs are read to measure the TL emission the readout cycle will be chosen as the best for the particular type of phosphor - see the section concerning the readout cycles of each dosimeter.

This value should be the same as that already determined during the initialization procedure. In case the background levels are higher, the characteristics of the annealing oven must be checked temperature uniformity inside the oven, correspondence between the temperature set and the actual temperature, etc.

If such expression is not verified, namely the Amax of the batch is larger than 30, then some TLDs have to be rejected. Figure 1 shows, as an example, a histogram obtained from the readings of a batch of TL dosimeters. Histogram of TLDs readings. Another procedure can be used for this test not included in the official recommendations. All dosimeters which exhibit a net TL readings outside the previous range are rejected.

I TL I Dos. Example of data for the homogeneity test. The superscripts M and m indicate the maximum and minimum values, respectively. It can be noted here that it is not always possible or convenient to reject some dosimeters, i.

In these cases all the samples are kept and their responses are corrected using the relative intrinsic sensitivity factor also called individual correction factor. Any way, it has to be stressed that either some or more samples are rejected or all of the batch samples are considered, the correction factor must be calculated and used to achieve the best uniformity of the batch response.

Another example is reported here. The test has been carried out for a sample of 80 TLDs and the results show its usefulness in some particular cases. It must be noted that the background signal was obtained as an average value and subtracted from each reading. Table 1 lists the net values and the corresponding histogram is given in Fig. Histogram of 80 readings. When the peaks are not too much overlapped, it is possible to use a thermal technique, called thermal cleaning, for getting a well defined and clearly separated peaks.

This technique has been introduced and described by Nicholas and Woods Let us imagine a phosphor showing a glow-curve with two, or more, overlapped peaks, each one having the maximum temperatures at T]2 phosphor is its very high intrinsic sensitivity to UV radiation.

The TL response is linear from 2 to 60 Gy; the reproducibility, over several repeated cycles of annealing, irradiation and readout, is better than 1.

Peters T. G and Hunt R. Shionoya, in Luminescence of Solids, edited by D. Vij Plenum Press, New York, 3. Bettinali C , Ferraresso G.

McKeever SW Thermoluminescence of solids. Cambridge University Press, Cambridge. Furetta C Handbook of thermoluminescence. World Sci. Download references. You can also search for this author in PubMed Google Scholar. Correspondence to W. The manuscript has not been published elsewhere and has not been submitted simultaneously for publication elsewhere. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Reprints and Permissions. Alazab, H. Thermoluminescence Properties of Bioglass for Radiation Dosimetry. Silicon Download citation. Received : 06 June Accepted : 30 August