Even for equal doses when effect of heating rate for given TL glow curve on different identical samples of same TL material, the results on the effect of heating rate on TL glow curves lead to misconception on
1. Variation of glow peak height with changing heating rate
2. Area under glow curve
3. Thermal quenching phenomena.
4. Even TL glow curve generally known not to exhibit thermal quenching exhibits same when measurement is made on Risoe reader system.
Please note that in the original work of Gorbics, Nash and Attix on glow curves of 6 standard TL materials, results different from those recorded using RISOE reader were observed and predicted.
Please provide your experience as the feedback will be of great use and help for TL community.
I also had the same observation when working with aluminium oxide. In my thinking, the secret is in how the Reader was coded. So yes one can conclude that the effect is an inherent feature of the reader and not the samples themselves.
@Angel. Thanks. In view of inherent Commond the results for any glow curve of a given phosphor will exhibit same trend. Making difficult to predict or test theory and to study thermal quenching as well.
@Angel; Typical theoretical behaviour of TL glow curve is given by
https://www.researchgate.net/publication/253500369_Dependence_of_peak_height_of_glow_curves_on_heating_rate_in_thermoluminescence
So we observed contradictions to interpretation some/many times.
Article Dependence of peak height of glow curves on heating rate in ...
Risø TL data is automatically plotted against ramp temperature, which is equivalent to plotting against time. Thomsen et al. (2007) examined the difference between the ramp temperature and the heater plate thermocouple temperature over the temperature range of 100 to 700 °C and found that the “systematic deviations are all within 0.25°C of the Set temperature”. Thus, heater plate temperature and temperature derived from the ramp rate and time are essentially indistinguishable. The relationship between sample temperature and heater plate temperature will be specific to each experiment and depend, inter alia, on thermal conductivity of the sample substrate. For the Risø Reader this potential thermal lag is discussed in Jain et al. (2007).
Thomsen, K.J., 2007. Temperature calibration and MiniSys temperature upgrade for the Risø TL/OSL-DA-15 reader. Ancient TL Vol. 25 No.1, 25-27
Jain et al., 2007. A peak structure in isothermal luminescence signals in quartz: Origin and implications. Journal of Luminescence, Vol 127, 678-688
@Thompson, thanks for explanation and references (I will surely refer). Sir even if the temperature gradients are neglected in crude approximation, the features of the tl glow curves as predicted by theory prevail as mentioned. The presence of temperature gradient due to planchet, thickness of sample and thermal conductivity will further distort the glow curves but features predicted by theory are likely to hold. Presence of thermal quenching will further worsen the issue as is generally interpreted by many users of RISO due to lack of tuning of reader with predictions of theory.
The two paper of S.G.Gorbics. A.E.Nash. and .F.H.Attix
1. Thermal quenching of luminescence in six thermoluminescent dosimetry phosphors—I: Quenching of X-ray-excited radioluminescence, The International Journal of Applied Radiation and Isotopes, Volume 20, Issue 12, December 1969, Pages 829-841.
2. Thermal quenching of luminescence in six thermoluminescent dosimetry phosphors—II: Quenching of Thermoluminescence,
The International Journal of Applied Radiation and Isotopes
Volume 20, Issue 12, December 1969, Pages 843-846, IN5-IN6, 847-852.
Same results are included in the book of Attix, Introduction of Radiological Physics and radiation Dosimetry, Chapter 14.
is of great help on the issue.
I feel results of effect of heating rate on TL glow curves recorded on RISO reader are erroneous. Second it gives huge Temp. gradients as readouts are not performed directly on planchet; This problem further increases especially at higher heating rates.
What Attix's book say on this effect:
Introduction of Radiological Physics and radiation Dosimetry , Page 398, old Edition, 1986
.
"Aside from this effect, varying the heating rate leaves total
light output constant, preserving the area of glow curves in terms of brightness vs.
time (but not brightness vs. temperature), given the same dose to the phosphor".
This needs to be highlighted to many TL researchers as there is gross error by various users.
Not sure i understand your question.
If you want to investigate the heating rate effect, you can plot the data per Kelvin (instead of count rate) as a function of temperature.
@Jain-As I understand, Y-axis as displayed in RISO reader is counts/channel or else. If we study any standard well studied phosphor (glow curve) and well established previously, RISO will show something new against the expectations like increase heating rate, glow peak height increases but this does not happen in RISO, it shows decrease. Even in alumina which has very high thermal quenching, there also glow peak height increases with increase of heating rate, but in RISO its reverse. Now a days, all studies on dependence of response on heating rate performed on RISO only lead to one conclusion in general i.e. : The glow curve exhibits thermal quenching.
@Jain-I only feel some inherent normalization in software or some limitation of electronics causes deviation from expected results. If we refer to previous experimental studies of (given below) Attix et al., we get precise and actual results as predicted in theory at least for main glow glow curves of some standard phosphors; but the RISO results are adding/leading to misconception onlt that also globally and contradict even the basic/classic paper of Randall-Wilkins.
S.G.Gorbics. A.E.Nash. and .F.H.Attix
1. Thermal quenching of luminescence in six thermoluminescent dosimetry phosphors—I: Quenching of X-ray-excited radioluminescence, The International Journal of Applied Radiation and Isotopes, Volume 20, Issue 12, December 1969, Pages 829-841.
2. Thermal quenching of luminescence in six thermoluminescent dosimetry phosphors—II: Quenching of Thermoluminescence,
The International Journal of Applied Radiation and Isotopes
Volume 20, Issue 12, December 1969, Pages 843-846, IN5-IN6, 847-852.
inherently there will be some peak shift and smaller change in shape due to change in heating rate. Remembering heating rate change (assuming increase) will lead to the depletion of stored charge and will increase their recombination at the recombination center, thereby increasing rate of observed intensity. which is likely to lead the shift in the peak position and slight change in the shape ( inclined towards y axis).
i think if you want to compare or analyze the properties of different samples then use same TD and same heating rate for comparison as well as physics studies. This normalization will help to bring down all the variability to minimal level. you can decide the heating rate based on the correlation of TL and OSL of the samples. I mean one can try to find the OSL signal associated with TL peak and then use the heating rate so as the peak position does not change.
@tyagi....the real issue is not the comparision of different samples but it affects in understanding the different effects of change in heating rate on the same sample. In order to understand the effect of change in heating rate we need to understand exactly which type of normalization is used in the program of the riso software that is given in the result.
Yes ritesh you are right. That is why i said use the heating rate which does not alter the peak position and peak position is to be identified by TL OSL correlation.
Am i right.
To all the fellow researcher before considering quenching and the peak shift recorded in riso machine we must be aware of how the instrument works. So in this regard I would like to share some points:
1. The photon counter used in Riso has linearity of 1.5*10^6 Hz i.e any measurement beyond this will be non linear. (source https://www.hamamatsu.com/resources/pdf/etd/m-h7421e.pdf)
2. The linearity of nucleonix TL reader is 10^5 Hz (source Luminescence
Basic Concepts, Applications and Instrumentation Edited by
Hardev Singh Virk)
3. Both of them use the kanthal heater which is controlled by changing the firing angle of the AC using Triac which make it prone to heating error.
4. Nucleonix provides Intensity, Temp and time as output whereas Riso gives only intensity and temp which makes it difficult to see any temperature lag due to filter algorithm or circuits during signal conditioning.
Agreed to @singh sir, but these are all under instrumental error and in the present limit we probably will not be able to eliminate. Besides these will be added to the sample inherent properties at any point of measurement, and by statistical comparison we can minimize them.
@Tyagi:Please refer to
Article Dependence of peak height of glow curves on heating rate in ...
for further clarity.
and
Article Effect of heating rate on TL glow curves - Theoretical and e...
as well.
@Tyagi-I strongly suspect/feel some inherent erroneous normalization in RISOE reader?
@Tyagi you got the wrong notion. My point was to record within the limit so as avoid error. Again using statistical correction will dilute the analysis.
By keeping the channel number same for all heating rates we can make sure that the PMT will record the counts for every degree of rise in temp. By this way we can get the counts/Kelvin as suggested by Dr Mayank. Worth a try for known phosphors which doesn't show thermal quenching to test this
@Menon: Did same long back, even then dosimetry peak of CaSO4:Dy showed TL quenching, but we know it does not.
@Ritesh: Looking at literature shows that this has become wider problem globally in contrast to theoretical predictions, surely there is some inherent fatal error introduced by programmers/electronic issues. Here in India, no such issue for locally made TL readers. See Fig. 8 of following publication of Kulkarni et al.
Article A versatile integrated system for thermoluminescence and opt...
As expected, alumina which exhibits huge thermal quenching, even there peak height increases with increasing heating rate and same is predicted by theory. No such normalization issues.
@Ritesh in the absence of thermal quenching , the peak height would have increased by a approximate factor with which heating rate increases, if heating rate doubles the height would have increased by 1.9 times or so ideally .
@Singh-Had also discussed the issue indirectly in 2007: Refer to Chapter 8 of the:Book STUDY OF LOCALISED TRANSITIONS IN THERMALLY STIMULATED LUMIN...
Book STUDY OF LOCALISED TRANSITIONS IN THERMALLY STIMULATED LUMIN...
Refer to Book: by Dr. L. Lovedy Singh
Book Theoretical aspects of TL and OSL: a preliminary approach
Page nos 44-47.
Its difficult to understand why many researchers generally publish "peak height decreases with increasing heating rate". There are almost 30-40 such international papers in various international Journals for last 5 years or so.
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