Bhushan P. Kore,a N. S. Dhoble,b S. P. Lochabc and S. J. Dhoble*a
Dy3+-doped CaMg3(SO4)4 (CMS) phosphor was prepared by the acid distillation method and examined in
detail with a thermoluminescence (TL) study whereby the phosphor was irradiated with g-rays and a
carbon ion beam. A good dosimetric glow curve was observed that is stable against both types of
radiation. The CMS doped with 0.2 mol% of Dy3+ showed 3.5 times more sensitivity than commercially
available CaSO4:Dy3+ TLD phosphor when irradiated with a carbon ion beam. The observed glow curve
variation and resultant variation in the values of trapping parameters with a change in ion beam energy
suggest more complex interactions of ion beam within the phosphor at higher energies.
1. Introduction
The demand for the dosimetry of charged particle beams hastaken a decisive lead because of its utility in cancer diagnosisand therapy.1–3 Ion beam therapy has been found to be a crucialtool in clinical practice for curing tumors in comparison toconventional radiation beams.4,5 Using ion beams in cancertherapy is based on the phenomenon of dose deposition atBragg's peak. In comparison to conventional radiation therapysuch as g-rays and high energy photon beams, heavy charge iontherapy is superior. The heavy charge particles (HCP) such asC5+ ions are heavier than the constituent particles in conven-tional radiation, which ensures penetration into the naltreatment locations deep inside the body with minimum scat-tering and stiffer particle trajectories, low straggling effects, andsharper eld edges.4 Ion beam therapy appears to be a morefavorable option with several advantages when compared toconventional photon therapy. Ion beams have a well-denedrange and small angular scattering compared with conven-tional photon or electron beam radiotherapy. Conventionalphoton beams have a limited depth of penetration proportionalto the energy of the accelerator.
Beams of protons and carbon ions have a much morefavorable dose-depth distribution than photons and are the newfrontiers of cancer radiation therapy.5 Heavy ion beams deliver alarger mean energy per unit length of their trajectory in the bodythan proton and photon beams.6 Bone and so-tissue tumorsare usually surgically removed because they are generally radio-resistant, and the effect of photon radiation is not sufficient for
iversity, Nagpur-440033, India. E-mail:
Mahavidyalaya, Nagpur-440009, India
saf Ali Marg, New Delhi-110067, India
tion (ESI) available. See DOI:
hemistry 2014
long-term control. However, when surgery is difficult toperform, radiotherapy is oen employed as a sole treatment. Inthis sense, carbon ion radiotherapy exhibits more signicantbiological effects than other types of therapy.7 These factors arecrucial for tumors located close to critical organs such as the eyeor ear. Tumors that are to be treated with higher doses requirespecial care so that healthy tissues are not inuenced by theincident ion beam. This opens up a promising potential fortheir highly effective use in the treatment of intractable cancers.For this, the dose delivered to the tumor requires an accuratecalibration of radiotherapy sources and their proper dosimetry.These ideas encourage us to nd a suitable TLD phosphor forcarbon ion dosimetry.
For the high energies of heavy charged particles in theentrance region, low ionization density commonly producerepairable damages. However, with increased energy, energyloss towards the Bragg's peak is more signicant, whichproduce irreparable damages and results in a higher relativebiological efficiency (RBE). The biological effectiveness refersto the difference in rate at which cells are killed with the sameradiation dose. We have selected the carbon ion for studybecause heavier and lighter ions possess their own draw-backs. The limitation of using heavier ions such as neon orargon is that they cause irreparable damages in the entrancechannel (surface), and thus signicantly damage the healthytissues in front of the tumor.8 For very light ions such asprotons, the scattering effect is large, and therefore, nodamage potentiation (the increase in strength of nerveimpulses along pathways that have been used previously)can be observed in the target volume.8 Hence, carbon ionbeams represent a most favorable option in heavy iontherapy and for enhancing the biological efficiency in tumortherapy.9
Sulphate-based thermoluminescence (TL) materials areknown for their high sensitive TL response. It has been found
that mixed sulfates form a class of TL phosphors with good TLcharacteristics when doped with the appropriate activa-tors.10–13 This family includes several materials such asCaSO4:Dy
3+, and K3Na(SO4)2:Eu, which are studied due to theirexcellent thermoluminescent properties such as high TLsensitivity, high TL efficiency, linear dose response over a widerange of doses, and reproducibility. But all these phosphorssuffer from one or the other problem. More work is going oneither to improve TL properties of these existing materials orto develop new high sensitive TL phosphors with ideal TLcharacteristic. Therefore, there is a great demand for highlyefficient dosimetry materials for radiation dose assessmentand to meet technological challenges. Such efforts are alsocrucial in a number of other areas such as human explorationin outer space.14 Several methods and treatments have beenadopted (1) to improve TL sensitivity, (2) to know the respon-sible defects in these materials, and (3) to understand thephenomenon of TL in more detail.
To the best of our knowledge, the literature describingthe effect of carbon ion beams on phosphor materialsespecially with reference to dosimetry is very limited. Thisstudy is an attempt to obtain useful data regarding the TLresponse of carbon beam-irradiated highly sensitive phos-phor, which would be helpful in the dosimetry of carbon ionbeams.
2. Experimental2.1. Synthesis method
The phosphor studied in the present work was synthesizedusing the method described by Yamashita et al.15 For thepreparation of the Dy3+-doped CaMg3(SO4)4 (CMS) phosphor, allof the starting materials used were of analytical grade. CMSdoped with different concentrations of Dy3+ was prepared bydissolving CaSO4, MgSO4, and a stoichiometric amount Dy2O3
15 ml of hot sulfuric acid (the excess acid used). The mixturewas allowed to heat at approximately 300 �C for 20 h, and duringheating, the highly active acid vapors were condensed using awater-cooled condenser assembly so as to prevent any sponta-neous reactivity. Aer cooling the mixture to room temperature,excess acid in the sample was repeatedly washed out withdistilled water, and a water-insoluble compound was obtainedin the form of small crystals. Aer washing the sample 4 to 5times with distilled water, the remaining sample was dried in anoven at 80 �C. No further heat treatment was given to thesamples.
2.2. Experimental details
5 mg of CMS phosphor was exposed to g-rays from 60Co and137Cs sources for various doses to see the glow curve structurevariation with dose and the linearity of the phosphor. Thesamples in the form of pellets were irradiated at roomtemperature by a C5+ ion beam at energies of 50 MeV and 75MeV for different ion uences in the range of 15 � 1010 to 30 �1012 ions per cm2, using a 16 MV tandem Van de Graaff type
49980 | RSC Adv., 2014, 4, 49979–49986
electrostatic accelerator (15 UD pelletron) at the Inter-UniversityAccelerator Center, New Delhi, India. The full details of thissetup are given by Kanjilal et al.16 For irradiation, the samplepellets were mounted on a copper target ladder, as shown inFig. 1(a) and (b). The copper ladder prevents heating of thesample during swi heavy ion (SHI) irradiation. For irradiation,the ladder was kept inside the evacuated irradiation chamber,as shown in Fig. 1(c). The ion beams were magnetically scannedon a 10 mm � 10 mm area of sample surfaces for uniformirradiation. The beam spot size used was 2.5 mm2. The pressureof the vacuum chamber during ion beam irradiation was 5 �10�4 mbar.
The diffraction pattern of the CMS phosphor was exam-ined using synchrotron XRD (SXRD) measurements at theADXRD beamline (BL-12) of the Indus-2 synchrotron sourceat the Raja Ramanna Center for Advanced Technology(RRCAT), Indore, India.17,18 An image plate area detector (Mar345 Dtb) was used to record the diffraction pattern.Lanthanum hexaborate (LaB6) was used as a standard mate-rial for calibration of the beam energy and the sample todetector distance. The wave-length used was 0.77774 A. TheTL glow curves were recorded using a Harshaw TLD reader(Model 3500) tted with a 931B photomultiplier tube (PMT).The heating rate used was 5 �C s�1. The photoluminescence(PL) emission spectra of the samples were recorded using aRF-5301 PC Shimadzu spectrouorophotometer. Emissionand excitation spectra were recorded using a spectral slitwidth of 1.5 nm.
3. Results and discussion3.1. X-ray diffraction
The X-ray diffraction pattern of the CMS phosphor was recor-ded using the beam energy of 15.94 keV with a sample-to-image plate distance of 151.2 mm. These rened values wereobtained using the FIT2D program, and the image plate datales were also integrated using FIT2D, incorporating polari-zation correction.19 Fig. 2 shows more detail regarding thephase of this phosphor by presenting the high resolutionsynchrotron X-ray diffraction data collected at room temper-ature. The angle dispersive synchrotron XRD patterns arenearly pure phase and in good agreement with the standardICDD le no. 19-0241. The different Dy3+ concentration-dopedXRD patterns of the CMS phosphor are shown in Fig. S1.†,20 Allfour XRD patterns are almost identical, which suggests thatthe incorporation of Dy3+ into the CMS lattice does not inu-ence the crystal structure. Fig. S2† shows the modication ofthe XRD pattern of the CMS phosphor aer C5+ ion beamirradiation. A video illustrating the ion beam irradiation onsample pellets is also given in the ESI (le M1†). No new peakswere observed aer ion beam irradiation, indicating nochange in phase of the phosphor. Due to ion beam irradiation,the relative intensities of some dominant peaks change, andsome minor peaks are diminished. This alteration is small,and indicates that there was a small reduction in the crystal-linity of the phosphor aer ion beam irradiation. Therefore,
Fig. 1 (a) and (b) Copper ladder with pellets of CMS sample mounted on it; (c) inner view of the C5+ ion irradiation chamber.
Fig. 2 (a) High-resolution synchrotron X-ray diffraction patterns of the CMS phosphor; (b) the raw image plate X-ray diffraction data.
Paper RSC Advances
we can say that this phosphor is stable against C5+ ion beamirradiation.
3.2. SEM study
The SEM images of the as-synthesized samples are shown inFig. 3. The large particles were formed when the acid distillationmethod was used, and some grains have a disk shape whileothers are irregularly shaped with ne surfaces. The gureshows the microstructures consisting of large particles in the 5–
Fig. 3 SEM images of the CMS phosphor prepared by the acid distillatio
15 mm range, which would enable the phosphor to be useful indosimetry application.21
3.3. TL study
3.3.1. Effect of irradiation. Thermoluminescence iscommonly used for dose estimation of high-energy ionizingradiation absorbed by materials. In this work, the TL study ofthis phosphor was carried out to propose its use in monitoringnot only conventional radiation beams but also heavy ionbeams such as carbon. The TL glow curves were recorded with
n method.
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the help of the Harshaw TLD reader. For the TL readout, thexed mass (5 mg) of the irradiated sample was placed on aheating planchet, which was then allowed to heat at the rate of5 �C s�1. The light released from the sample was detected with aphotomultiplier tube, which was placed perpendicular to thesample. Fig. 4(a) shows typical TL glow curves of the CMSphosphor, irradiated with g-rays from a 60Co source at a 15 Gydose. The glow curve consists of a good dosimetric peak at260 �C with a small low-temperature peak at 150 �C. Among thefour different concentrations of Dy3+, the maximum TL sensi-tivity was observed for 0.2 mol% concentration.
To compare the TL sensitivity, we also measured the TL ofthe standard TLD (CaSO4:Dy
3+) phosphor. It was observed thatthe sensitivity of the CMS phosphor is approximately 50%compared to the sensitivity of CaSO4:Dy
3+. Fig. 4(b) shows theTL glow curve of the CMS phosphor for g-ray irradiation fromthe 137Cs source at 2300 mRad. The glow curve shape of the137Cs-irradiated samples was found to be similar to 60Co-irradiated samples, but there is a shi in the glow peak posi-tion towards lower temperatures when irradiated with the 137Cssource. The observed shi was approximately 3 �C for peak 1and 28 �C for peak 2. This shi may be due to the alteration inthe position of trapping levels inside the forbidden band gap. Ascan be seen from Fig. 4(c), the glow curve structures of CMSexposed to carbon ions (50 and 75 MeV) are similar to that of g-irradiated samples. The glow curves of CMS exposed to twodifferent energies of carbon ion beams are qualitatively similar,but quantitatively, there is a difference in the temperature andrelative intensities of the glow peaks, which leads to the modi-cations in the trapping parameters. Various authors havereported signicant variations in the glow curve structures andthe positions when samples were irradiated with differentsources.22–24 The CMS phosphor was found to possess a glowcurve that is stable with variation in irradiation species, as the
Fig. 4 TL glow curves of the CMS phosphor irradiated with (a) g-rays frommRad dose, (c) C5+ ion beam at 75 MeV with a 216 kGy dose, and (d) comC5+ ion beam at 50 and 75 MeV energies, and g-rays from a 60Co sourc
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carbon ion- and g-ray-irradiated samples show 11 and 8%fading, respectively, over 16 days of storage (see Section 3.6). Incomparison to our phosphors, the standard TLD phosphorCaSO4:Dy
3+ showed signicant change in the shape of the glowcurve when exposed to the carbon ion beam.
As can be seen in Fig. 4, the glow curve structure of CMSexposed to carbon ions at two different energies (i.e., 50 and 75MeV) is similar to that of the 137Cs and 60Co g-irradiated sample.There is a small difference between the TL glow peak tempera-ture for the 60Co and 137Cs g-irradiated sample. In the case of g-irradiated samples using the 60Co source, the second peak at260 �C is more prominent than the lower temperature peak at146 �C when compared with TL glow curves of g-irradiatedsamples using the 137Cs source. The lower temperature peakshows signicant growth compared to the high temperaturepeak. This clearly indicates that the number of traps responsiblefor these peaks is not in the same proportion in the two cases.For the 75 MeV C5+ ion-irradiated samples, additional trappinglevels form, which yield two more glow peaks compared to g-ray-irradiated samples. The occurrence of additional glow peaks at185 �C and 232 �C suggests the formation of intermediatetrapping levels in-between the trapping levels responsible for theoccurrence of glow peaks at 143 �C and 242 �C.Moreover, the C5+
ion-irradiated samples (50 MeV) show signicant change in theposition as well as intensity of the glow curve compared to glowcurves of C5+ ion-irradiated samples at 75 MeV. The C5+ ionirradiation at 50 MeV not only alters the positions of trappinglevels, causing a shi in the glow peak temperatures, but it alsocreates one additional trapping level that results in an additionalglow peak. Upon irradiating the samples with C5+ ions, theremay be the formation of new trapping and luminescent centersthat are responsible for this anomalous behavior. Similar effectsin the TL response of the CaSO4:Dy
3+ phosphor upon C6+ ionbeam irradiation have been reported by some authors.25
a 60Co source at a 15 Gy dose, (b) g-rays from a 137Cs source at a 2300parison between TL glow curves of the CMS phosphor irradiated with ae at a 15 Gy dose and a 137Cs source at a 2300 mRad dose.
It is expected that upon irradiating samples with a highlyenergetic ion beam such as that of 50 and 75MeV C5+ ions, therewill be changes in the TL glow curve structure because the TLtrapping and recombination mechanisms are very sensitive toany perturbation. The variation is more when atomic displace-ments occur due to non-elastic collisions, and ionization due tosecondary particles takes place.26 The obtained results showthat there is not much variation in the structure of the glowcurve, but there are minor changes in glow peak temperature,number of glow peaks, and TL intensity, which are responsiblefor the variation in trapping parameters. These variations intrapping parameters are due to the disorganization of the initiallocalized energy levels in themixed sulfate host as a result of thehigh energy ion irradiation.
3.3.2. Dose response. The TL response curves of the CMSphosphor irradiated by g-rays from 60Co and 137Cs sources anda carbon ion beam are shown in Fig. 5 (a)–(c), respectively. TheTL response curve of the materials irradiated by g-rays within adose range 10 Gy–10 kGy shows a linear response up to 1000 Gy;above 1000 Gy, slight saturation is observed. The phosphorirradiated with g-rays from the 137Cs source also shows a linearresponse from 100 mRad to 5 Rad. Unlike g-rays, the TLresponse of the CMS phosphor towards the carbon ion beamshows early saturation when irradiated within a dose range of22 kGy to 4 MGy. The saturation in the TL response of the CMSphosphor can be explained by the track interaction model(TIM).27,28 The intensity of the TL signal increases in proportionto the number of ion tracks. At higher uences (due to a largeux), the distance between nearest neighboring tracksdecreases and the probability of electrons escaping from thehost track ion and reaching neighboring tracks increases. Thisresults in increased luminescence recombination and ulti-mately increases the TL intensity. As the uence increases,further saturation effects occur where the distances betweennearby tracks decrease and the tracks begin to interact andoverlap. These overlapping regions do not give additional TLbecause they do not form additional trapping charge carriersdue to the full occupancy of the available trap and luminescencecenters. As the energetic ions are implanted in the matrix, they
Fig. 5 The TL response curves of the CMS phosphor irradiated by g-rays from (a) 60Co, (b) 137Cs, and (c) C5+ ion beams.
may be creating new kinds of defects, which make the processmore complicated.
The inuence of 50 and 75 MeV carbon ion beams is de-nitely more than that of g-rays, and therefore, the correspond-ing cross section of C5+ ion tracks inside the CMS phosphor ishigher. Low linear energy transfer (LET) radiation such as g-raysand electrons confers higher luminescence efficiency ascompared to high LET radiation consisting of heavily chargedparticles. However, high LET radiation may induce additionaldefects in the host material as compared to low LET radiation,and with increase in the radiation exposure, the density ofdefects inside the host increases, which leads to an increase inpeak intensity.
The dose delivered by carbon beam was calculated usingeqn (1):
D�Gy
� ¼ 1:602� 10�10 � dE=dX
r
�MeV cm2 g�1
�
� f�particles per cm�2
�(1)
where dE/dX is the mean energy loss, r is the density of thetarget material, and f is the ion uence. The energy loss (linearenergy transfer) was calculated using a Monte Carlo simulationbased on TRIM code given by Ziegler et al.29 The maximumpenetration depth inside the material was calculated to be 89mm, which is less than the thickness of the pellet i.e., 0.075 cm.The energy loss values for 50 MeV and 75 MeV are 2330 and1760 (MeV cm2 g�1), respectively. These values are an indicationof the amount of ionization caused by ions inside the targetmaterial, and the values suggest that the ionization caused bythe 50 MeV ion beam is higher than that produced by the 75MeV beam. This is also reected in the TL, where a highersensitivity was observed for the 50 MeV irradiated sample.Moreover, the penetration depth for 50 MeV and 75 MeV ener-gies was calculated to be 48 and 89 mm, respectively. The presentphosphor shows a decrease in TL sensitivity aer a 23 kGy doseof the C5+ ion beam. This remarkable result is extremelyimportant for CMS to be used as a dosimeter in such high dosesof ion beam irradiation.
3.4. PL study
The photoluminescence (PL) excitation and emission spectrafor different mol% concentrations of Dy3+-doped CMS pristinephosphor are shown in Fig. 6(a). The excitation spectrum ofpristine CMS phosphor shows a number of excitation peakswith a prominent peak at approximately 349 nm. The emissionspectrum that was recorded at this excitation wavelength showscharacteristic emission peaks of Dy3+ at approximately 484 nmand 574 nm, which were assigned to the transitions 4F9/2 /6H15/2 and
4F9/2 /6H13/2, respectively.30 Fig. 6(b) shows the PL
excitation and emission spectrum of 1 mol% Dy3+-doped CMSphosphor irradiated with 50 and 75 MeV carbon ion along withthat of pristine phosphor. From the excitation and emissionspectra, it was observed that phosphor exposed with a carbonion beam exhibited a decrease in PL emission intensity, andwith a further increase in the energy of the carbon ion beam, theemission intensity continued to decrease. There are several
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Fig. 6 (a) PL of the CMS phosphor for different concentrations of Dy3+; (b) PL of carbon ion-irradiated CMS (Dy3+ ¼ 0.2 mol%) phosphor at 50and 75 MeV and pristine sample.
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possible reasons for this decrease: (1) destruction of lumines-cence centers that are responsible for emission, (2) residualabsorption of both the excitation light as well as emission lightdue to the irradiation, and (3) damage to the microstructure ofthe phosphor due to ion-induced defects.31
At high ion uences, structural changes occur inside thesample that may reduce its PL output. This effect is directlyinuenced by the energy loss of the ions and thus by the sizeand the damage concentration. The observed saturation in theTL glow curves and Dy3+ PL emission of the samples exposed tothe 75 MeV C5+ ion beam might be due to the increased pene-tration depth of the ion beam. However, for the 50 MeV ionbeam, the penetration is less and the backscattering could bemore, resulting in a smaller number of implanted ions; there-fore, it still exhibits a higher TL and PL efficiency.
3.5. Glow curve analysis
To further verify the energy levels and other kinetic parametersof the glow peaks in all three cases, the glow curve deconvolu-tion was performed using glow curve deconvolution (GCD)functions as previously reported by Kitis et al.32
For general order,
I ¼ Imb
�b
b�1
�exp
�E
kT
T � Tm
Tm
�
��ðb� 1Þ
�1� 2kT
E
�T2
Tm2exp
�E
kT
T � Tm
Tm
�
þ1þ ðb� 1Þ 2kTm
E
��ðb=ðb�1ÞÞ(2)
where I (T) is the TL intensity at temperature T (K), Im is themaximum peak intensity, E is the activation energy (eV), and k isthe Boltzmann constant.
These parameters were applied to the experimentallyobtained glow curves to isolate each peak. Firstly, the order ofkinetics and activation energy of one of the peaks was foundusing Chen's set of empirical formulae.33
The trap depth is calculated using the following equation,which is independent of order of kinetics:
49984 | RSC Adv., 2014, 4, 49979–49986
E ¼ cg(kTm2/g) � bg(2kTm) (3)
where g is s, d or u are the constants cg and bg for the threeequations (s, d, or u), k is the Boltzmann constant, and Tm is themaximum peak temperature.
The frequency factor (s) is:
bE
kTm2¼ s exp
��E
kTm
�½1þ ðb� 1ÞDm� (4)
where Dm ¼ 2kTm/E, b is the order of kinetics, k is theBoltzmann constant, and b is the linear heating rate (5� C s�1).
To determine the order of kinetics (b), the form factormg (mg ¼ (T2 � Tm)/(T2 � T1)), which involves T1 and T2(temperatures corresponding to half of the intensities on eitherside of the maximum), was calculated. This form factor mg isindependent of the activation energy (E) and strongly dependson the order of kinetics (b). Finally, the peak was theoreticallygenerated using these parameters and separated from the mainexperimental glow curve. The benet of using the GCD methodis that most of the parameters used for generating a theoreticalcurve are easily derived from the experimentally recorded glowcurve. The thermal activation energy (E) was again calculatedusing the same set of equations. This procedure was repeatedfor each TL peak until a good t between the experimental andtheoretical glow curve was obtained.
The deconvolution of experimentally obtained glow peakswas carried out using the glow curve deconvolution program.The deconvolution of experimental glow curves was carried outin order to reveal the number of individual glow peaks presentin a complex glow curve, as shown in Fig. 7. The isolated glowpeaks were then examined to obtain data regarding trappingparameters. The generation of new absorption peaks with theincreasing energy of the carbon ion beam also illustrates thechanging position of the trapping levels (see Table 1).
3.6. Fading study
For the fading study, the g-ray- and carbon ion-irradiatedsamples were stored for a few days without taking any precau-tions to shield them from light or moisture. The glow curveswere then recorded for a period of approximately 16 days, as
Fig. 7 Comparison between the experimental (—), theoretically fitted(�), and deconvoluted (—) TL glow curves of the CMS phosphorexposed to (a) 15 Gy of g-rays from 60Co, (b) 2300 mR of g-rays from137Cs, (c) 216 kGy from the 75 MeV C5+ ion beam, and (d) 108 kGy fromthe 50 MeV C5+ ion beam.
Table 1 Trapping parameters of the CMS phosphor for different typesof irradiation calculated by Chen's method
Type of irradiation Peak number Tm (�C) mg E (eV) S (s�1)
shown in Fig. 8, which illustrates the fading plot of the g-ray-and carbon ion-irradiated phosphor. It was observed that thehigher temperature glow peak is quite stable over the storagetime. The carbon ion- and g-ray-irradiated samples exhibited 11and 8% fading, respectively, over 16 days of storage.
3.7. Absorption spectra
Fig. 9 shows the absorption spectra of the CMS phosphor for 0.2mol% Dy3+ doping. The calculated band gap energy of thepristine sample is 5.34 eV. It was observed that the absorption ofthe phosphor increases with increasing energy of the ion beam,
which is due to the generation of a large number of defects. Theabsorption was found to be shied towards a higher wavelengthwith increases in beam energy. The difference between the bandgap energy and the energy of the absorption peak represents theactivation energy of trapped charge carriers. The sample irra-diated by the 50MeV ion beam demonstrated absorption at 219,258, and 317 nm corresponding to 5.66, 4.80, and 3.911 eVenergies, respectively; the 75 MeV ion beam resulted inabsorption at 204, 243, 254, 313, and 459 nm corresponding to6.07, 5.10, 4.88, 3.96, and 2.70 eV energies, respectively. Theactivation energies calculated from the absorption spectra arenearly same as those calculated by Chen's peak shape method.
4. Conclusion
In conclusion, we provide insight for synthesizing a CMSphosphor by the acid distillation method with remarkable TLproperties. The phosphor was found to be 3.5 times more
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sensitive than a standard CaSO4:Dy3+ phosphor with a stable
dosimetric peak for C5+ ion irradiation. The TL response wasnearly identical for different types of irradiation. The irradiationresulted in a slight variation in glow peak position, and ionbeam irradiation caused additional glow peaks, which inu-ences the trapping parameters. The obtained results can beeasily correlated with the physical phenomenon, suggestingthat this phosphor can be used for carbon ion beam dosimetryalong with g-ray dosimetry over a wide range of exposures.
Acknowledgements
Authors are grateful to Inter University Accelerator Center(IUAC) New Delhi, India for providing nancial assistance tocarry out this work under research project UFR-56301. Theauthors would like to thank the Director of the Inter-UniversityAccelerator Centre (IUAC), New Delhi, for providing beam time.The authors are also grateful to the Director of the Center forAdvanced Technology, Indore, for providing access to theADXRD measurement facility and Dr A. K. Sinha and Dr M. N.Singh for their support during the ADXRD measurement.
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