Patent ID: 12247151

DETAILED DESCRIPTION OF THE EMBODIMENTS

Synthesis of BeO Doped with Sodium, Dysporsium, Erbium

BeO samples were synthesized by a known synthesis method using Beryllium sulfate tetrahydrate (BeSO4.4H2O, ≥99.0%), Poly(ethyleneimine) solution (50% (w/v) in H2O) and Ammonium hydroxide solution (H5NO, ACS reagent, 28.0-30.0% NH3basis). Doping of the BeO samples were performed using Sodium nitrate (NaNO3≥99.0%), Dysprosium (III) nitrate hydrate (Dy(NO3)3·xH2O≥99.9%) and Erbium (II) nitrate pentahydrate (Er(NO3)3·5H2O≥99.9%).

Beryllium Oxide was doped with different concentrations of Sodium, Dysprosium and Erbium using precipitation method. Firstly, beryllium sulfate was mixed with distilled water using magnetic stirrer and wait until completely dissolved. Then, nitrate base doping material was added to this solution at different concentrations. On the other hand, a certain amount of polyethyleneimine solution was dissolved in distilled water on the stirrer until it becomes transparent. Dissolved polyethyleneimine solution was added to beryllium sulfate solution under vigorous stirring. Afterwards, a sufficient amount of ammonia was slowly added to the solution by controlling pH and consequently the white precipitate formation was observed. The precipitate was dried on the heater. In order to burn formed organics and to obtain BeO particles, the dried sample was calcinated at 800° C. with 5° C./min heating rate for 4 hours in an oxygen atmosphere. Finally, doped BeO white powders were achieved.

Achieved white BeO:Na,Dy,Er powders were studied in pellet forms for easy handling and having more settled OSL signals. BeO:Na,Er,Dy pellets were prepared using a hydraulic press with evacuable pellet dies under 250 kg force/cm2pressure for 1 min. In order to impart strength and integrity, prepared pellets were sintered at 1600° C., for 4 h in an oxygen atmosphere.

OSL and TL measurements were carried out using Risø, DA-20 model TL/OSL reader system. With the aim of checking the possibility of using TL and OSL signals of BeO:Na,Dy,Er pellets for dosimetric purposes, luminescence signals were obtained from BeO:Na,Dy,Er pellets which were irradiated with 0.1 Gy beta dose. The measurements of samples were started after half an hour of waiting at the room temperature after the sintering of the samples for stabilization of traps. TL and OSL measurements carried out and the results obtained are presented below.

OSL Signals of BeO:Na,Dy,Er Pellets (Irradiated with 0.1 Gy β-Doses)

In order to investigate the effect of dopant concentration on OSL signals of BeO, OSL measurements of BeO with various dopant concentrations for example, various Na, Dy, and Er concentrations were performed using blue light stimulation (stimulation time=200 s) after the irradiation with 0.1 Gy β-dose. First, we fixed Na and Dy concentrations as 0.1% and 0.005%, respectively and changed the Er concentration.FIG.1shows OSL signals of BeO:Na(0.1%), Dy(0.005%), Er(x %), with respect to various Er concentrations. As is seen from theFIG.1, the highest OSL intensity of BeO:Na,Dy,Er was obtained with the Er concentration of 0.05%. Then, OSL signals of BeO:Na(x %), Dy(0.005%), Er(0.05%), were illustrated according to various Na concentrations (seeFIG.2). As is seen from theFIG.2, doping percentage of Na 5% which gave the maximum OSL intensity was chosen for the Na concentration of the material. Finally, OSL signals of BeO:Na(5%), Dy(x %), Er(0.05%), were examined according to various Dy concentrations (see inFIG.3). As is seen from theFIG.3, the OSL signals with the maximum intensities were obtained from the combination of BeO:Na(5%), Dy(0.1%), Er(0.05%). For this reason, doping percentage of Dy was chosen as 0.1%.

Changes of maximum OSL intensities for the triple combinations of all dopant concentrations were illustrated inFIG.4.

XL Signals of BeO:Na,Dy,Er Pellets

Investigation of radioluminescence (X-ray luminescence, XL) characteristics is a good starting point for knowledge of the positions and general appearance of the luminescence bands. In this work, XL spectra of BeO with various Na, Dy, and Er concentrations were obtained using a resolution of 1 nm at room temperature and presented inFIGS.33A-C. The XL spectra of all BeO:Na,Dy,Er pellets showed the same broad peak located between 200 and ˜500 nm with a peak maximum at 250 nm with photon energies of ˜4.9 eV. On the other hand, the effect of dopant concentration on X-ray luminescence signals were also investigated and illustrated as a function of wavelength inFIGS.33A-C. While Er concentration increasing, an emission peak with increasing intensity was appeared at ˜570 nm (seeFIG.33A). The observed emission peak represents the main characteristic emission line from the trivalent Dy. With the increasing of Na concentration, the characteristic emission lines of Dy+3 were observed from 650 to 750 nm for only 10% Na doped sample between the samples (seeFIG.33B). As a surprising result, the increase in Dy concentration resulted in a significant reduction in main BeO emission (seeFIG.33C) and the characteristic emission of Er at 407 nm could not be observed because it remained under the main emission peak of BeO. For this purpose, the most suitable material selection for personal dosimetry was performed by taking into consideration the results of CW-OSL measurement.

A New Method Carried Out

BeO dosimetric phosphors doped with Sodium, Dysprosium and Erbium were produced by a new method followed by heat treatment. In this method, citric acid (C6H8O7) and ethylene glycol (C2H6O2) solution were chosen for polymer construction in the solution and to create organic complex/fuel agent, respectively. Firstly, stoichiometric quantities of beryllium sulfate as starting material were solved in ethylene glycol solution using magnetic stirrer and waited until it was completely dissolved. Nitrate base doping materials was added to this solution at different concentrations. Then citric acid was added in this solution. Ammonium hydroxide solution as agents for pH adjustment was slowly dropped into ethylene glycol solution. The solution was obtained which the pH value ˜7 after stirring for 10 min. On the other hand, a certain amount of polyethyleneimine solution was dissolved in distilled water on the stirrer. Dissolved polyethyleneimine solution was added to beryllium sulfate solution under vigorous stirring. After dried on the heater, the solution became dark brown gel. In order to burn formed organics, the dried sample was burned at 500° C. with 2° C./min heating rate for 1 hours in an oxygen atmosphere. Finally, the charred powder was calcinated at 800° C. with 5° C./min after it was thoroughly crushed in an agate mortar.

This method has the advantage of obtaining big grain diameters of phosphor along with their homogeneous size distribution for having better structure characteristics and better dosimetric properties. For example,FIG.5depicts OSL signals using blue light stimulation (stimulation time=200 s) after the irradiation with 0.1 Gy β-dose, from the BeO:Na(5%), Dy(0.1%), Er(0.05%) pellet synthesized using the new method.

Preheating Measurement

Pre-heating measurement was performed with the aim of determination appropriate pre-heating procedure of BeO. This procedure which allows removing the contribution of the unstable traps (low energy level traps) from OSL signals were examined in detail. The pre-heating duration time was kept constant for 10 seconds. BeO pellets were exposed to 0.5 Gy test dose, after then the pellets were pre-heated between 50-500° C. OSL signals were obtained from the pre-heated BeO pellets. After each irradiation, the same process was applied by increasing the temperature at 10° C. for each step. The integrated OSL signals of BeO pellets were plotted versus to pre-heating temperature for 1° C./s heating rate inFIG.6.

Reusability of BeO:Na(5%), Dy(0.1%), Er(0.05%)

Irradiation: 0.5 Gy beta dosePre-heating: 100° C. for 60sOSL reading: 200 sec. with 2000 data (time per data point: 0.1s)

To test the reusability, the OSL signals from annealed three pellets of BeO were recorded after 0.5 Gy β-radiation exposure and the same procedure was repeated 30 times. The samples were pre-heated at 100° C. for 60 s to remove the unstable signals and then the OSL read-outs were performed by blue light stimulation for 200 seconds at room temperature (with the time per data point 0.1). Normalized integrated OSL signals were plotted according to experimental cycles for BeO, as it is given inFIG.7. BeO OSL signals showed very regular repeatability for 30 cycles. Therefore, it was observed that the reproducibility of the previous-radiation sensitivity appeared with the maximum deviation of ±2%.

Correlation Between TL and OSL Signals

In order to investigate the effect of the blue light stimulation on TL measurements, TL signals of glow curve from BeO pellets were obtained and compared with: Na,Dy,Er ceramic pellet, the TL signals glow curve (direct TL) and the TL glow curve obtained after OSL measurements of the same BeO:Na(5%), Dy(0.1%), Er(0.05%) pellets. Measurement (residual TL) were recorded up to 650° C. at a heating rate of 1° C./s, after being irradiated with 0.5 Gy beta dose. The TL measurements were performed up to 650° C. with heating rate of 1° C./s. Obtained TLFIG.8Ashows direct TL, residual TL and bleached TL glow curves for each pellet. Bleached TL curves were obtained by subtracting the residual TL from the direct TL. The bleached TL curve for each studied sample represents the optically active parts of the TL glow curves. As is seen fromFIG.8A, the 1st peak of the TL glow curve of BeO:Na,Dy,Er pellet were affected by optical stimulation whereas the 2nd and 3rd peaks were not. This effect of light exposure on TL glow curve provides us to say that the source of the OSL signal might be associated with the 170° C. TL peak. Inset ofFIG.8A, only for 2nd and 3rd better viewing due to low TL signals.

In order to investigate the correlation between this affected TL peak and the source of the OSL signals for the studied pellet, the step-annealing experiments (thermal-stability experiments) were performed in the temperature range from 50 to 500° C. with 10° C. increments, 5° C./s heating rates. For this purpose, the pellets repeatedly heated to an annealing temperature after irradiation with 0.5 Gy, and the remaining OSL signals were given inFIG.8B. It can be reported that recorded using 200 s blue-light stimulation each time. The samples were depleted using TL measurements (up to 650° C.) following the OSL measurements. The changing of the integrated OSL signals (the sum of the counts obtained from 0 to 200 s) against the annealing temperatures were illustrated together with the TL curve for BeO:Na,Dy,Er pellet in BeO:Na(5%), Dy(0.1%), Er(0.05%) the TL peak ˜175° C. wasFIG.8B. It is clearly seen from the step-annealing curve inFIG.8B, the first decrease in OSL signals started after annealing temperature of 130° C. The decrease in OSL signals correlates with emptying of the 170° C. TL peak after the OSL stimulation. After the first decrease in the step-annealing curve, the OSL signals were very sensitive to blue light and faded very quickly. As seen fromFIG.8A, in the glow curves measured after OSL measurement the 175° C. peak nearly disappeared while the high temperature peaks seemed to be little affected stable up to 350° C. and started to the second decrease after this temperature. Following the complete discharging of the TL traps responsible for the 350° C. TL peak, the OSL signals reach the zero level. It shows that the source of the OSL signals is perhaps associated with both the 170 and 350° C. TL peaks and the OSL, most probably, employ the same recombination centers as the 170 and 350° C. TL peaks. As a result, optically active traps are correlating with the TL traps responsible from the TL peak observed at ˜175° C. for the BeO pellets.

Dark Fading

Irradiation: 0.5 Gy beta dosePre-heating: 120° C. (with heating rate 5° C./s for 60 s)TL reading: 650° C. (with heating rate 1° C./s)OSL reading: 200 s with 2000 data (time per data point: 0.1s)

As a desirable property for all dosimetry application, trapped charge population must be stable at room temperature. In order to investigate whether charge population in traps are stable or not, fading characteristics of BeO:Na,Dy,Er ceramic pellets were checked by keeping three calibrated samples in dark at room temperature after irradiation with 0.5 Gy beta dose. The fading of the samples was observed for various time intervals during three months; starting after half an hour from the exposure (seeFIG.9). The decrease of integrated OSL signal was observed as ˜7% at the end of 1 h. While the initial fall of the OSL signals at the end of the 6 h could be considered as a result of the escaping of electrons from the shallow traps at room temperature, the unexpected increase of the OSL signals with storage time during 12 h period could be related with the tunneling of escaped electrons from the shallow traps to deep traps at room temperature. Additionally, the OSL signals from the BeO pellets were first observed as very stable up to 1 week and slightly decreased (˜10%) up to two weeks when compared with the first readout OSL signals. At the end of the three months, the material decreased to almost same level as the second week.

Dose Response

Irradiation: (0.1-50) Gy beta dosePre-heating: 120° C. (with heating rate 5° C./s for 60 s)TL reading: 650° C. (with heating rate 1° C./s)OSL reading: 200 sec. with 2000 data (time per data point: 0.1s)

Dose dependence of the OSL signals of BeO:Na(5%), Dy(0.1%), Er(0.05%) pellets and Thermalox995 BeO chips were checked between 0.1 Gy and 50 Gy beta doses. The exposed doses were 0.1, 0.2, 0.5, 1, 2, 5, 10, 20 and 50 Gy. The OSL signals were obtained from irradiated three samples of BeO:Na(5%), Dy(0.1%), Er(0.05%) pellets and Thermalox995 BeO chips by a 200 seconds blue light stimulation at room temperature, after preheating the samples at 100° C. for 10 s to remove the unstable signals (SeeFIG.10). After each experimental cycle with the determined dose value, the residual signals of samples were depleted performing TL measurements from 50° C. up to 650° C. with the heating rate of 1° C./s.

As is seen from theFIG.10, the integrated total OSL signals of the samples were fitted very well to a linear function (y=a*x+b). For BeO:Na(5%), Dy(0.1%), Er(0.05%) pellets and Thermalox995 BeO chips, the slope values of the fitted curves were found as 1.07 and 0.97, respectively. As a result, one may say that while BeO:Na(5%), Dy(0.1%), Er(0.05%) pellets shows sublinear characteristic; Thermalox995 BeO chips shows supralinear characteristic in the range of 0.1 Gy and 50 Gy.

In order to investigate linear characteristic region of BeO:Na(5%), Dy(0.1%), Er(0.05%) pellets, dose response curve was plotted from 0.1 Gy up to 10 Gy and fitted with a linear function (see inFIG.11). According to this fitting, slope value was found as 1.01, and this result shows that OSL signals of BeO:Na(5%), Dy(0.1%), Er(0.05%) pellets have very good linear property up to 10 Gy.

On the other hand, the minimum detectable dose (MDD) of an OSL system is an important parameter to describe the ability of the system to measure low doses. The MDD is dependent on both the sensitivity of the reader and of the detector and can be estimated as the dose corresponding to three times the experimental standard deviation of the background.

The expression used in this work to calculate the MDD of a system was

MDD=[3·s⁡(B⁢G)a](1)where s(BG) is the experimental standard deviation of the background measured using bleached detectors and, a, is the sensitivity (counts/mGy). In this case, a is the angular coefficient of the linear calibration curve obtained using detectors irradiated with known doses. As a result, MDD values were calculated and given in Table 1.

TABLE 1Minimum detectable doses of BeO:Na(5%), Er(0.05%),Dy(0.1%) pellets and Thermalox995 BeO chipsaccording to the total area and maximum intensity ofthe OSL signal with apparatus.MDD (with Apparatus)#Using total areaUsing max intensityBeO:Na, Dy, Er116.8 ± 2.3 μGy121.6 ± 6.6 μGyThermalox995 chip10.9 ± 2.9 μGy12.6 ± 1 μGy

TABLE 2Minimum detectable doses of BeO:Na(5%), Er(0.05%),Dy(0.1%) pellets and Thermalox995 BeO chipsaccording to the total area and maximum intensityof the OSL signal without apparatus.MDD (without Apparatus)#Using total areaUsing max intensityBeO:Na, Dy, Er8.2 ± 0.8 μGy5.7 ± 0.2 μGyThermalox995 chip0.9 ± 0.2 μGy0.6 ± 0.1 μGy
Energy Response

The BeO:Na(5%), Er(0.05%), Dy(0.1%) pellets were irradiated with electrons and photons having various energies. The absorbed dose amount was performed as 0.2 Gy for each irradiation. The electron energies used were 4, 6, 9, 12, 15 and 18 MeV from a linear accelerator. X-ray irradiations were performed with photons from a 6, 10 and 18 MV linear accelerator and a 0.385 MeV192IR source. InFIG.12A, the distribution of data points is depicted as OSL sensitivity of samples versus photon and electron energies at the high energies. The upper and lower experimental standard deviation bar values of each data point for each energy value are overlapping with the other data's standard deviation bar. The results indicate that the OSL data of the energy response of BeO:Na(5%), Er(0.05%), Dy(0.1%) pellets did not change with different energy values except 18 MeV. Additionally, the photon response with the lower energy were plotted inFIG.12B. According to the plot, BeO:Na(5%), Er(0.05%), Dy(0.1%) pellets were found to be more sensitive at low energy exposure.

Thermal Quenching

With the reduction in luminescence efficiency at temperatures higher than room temperature, thermal quenching is observed in many materials. In order to investigate the presence of thermal quenching which gives information about the increase in probability of non-radiative transitions from the excited to the ground state of the luminescence centers (the Mott-Seitz model) 1, the study of temperature dependence of OSL signals from the studied BeO:Na,Dy,Er ceramic pellet was checked after the irradiation with 0.5 Gy beta dose and preheating at 110° C. for 60 s. The temperature dependence of the OSL signal can be expressed by a function of the type
IOSL(T)=η(T)IOSL=IOSL/(1+Cexp(−EQ/kT))where IOSLis OSL signal; η(T) is luminescence efficiency as a function of temperature; C is a constant; EQis the thermal activation energy for the non radiative process; k is the Boltzmann constant and T is the absolute temperature. In this work, OSL signals were obtained at various reading temperatures ranging from 50 to 150° C. with 10° C. increments as seen inFIG.32A. After each OSL measurement, residual luminescent signals were deleted by performing TL readouts up to 650° C. and the samples were irradiated again with the same dose for the next measurement. As is seen fromFIG.32A, the reduction in luminescence intensity with increasing readout temperature demonstrates the presence of the strong thermal quenching. The integrated OSL signals obtained at 110° C. decreased by ˜25% and at 150° C. decreased by ˜40% when compared with that of OSL signals obtained at 50° C.

On the other hand, in order to get information about thermal quenching mechanism, TOSL curves can be used as an alternative method. A TOSL curve indicates the temperature dependence of the OSL signal which is obtained by subtracting the TL curve from the TL curve obtained with OSL stimulation. Here we used 0.1 s pulsed stimulation with 0.9 s time interval between the pulses while TL readout. The signals measured during the light stimulations are the combinations of the OSL as a function of temperature and the TL (i.e. TL+OSL). The measurements performed during the time interval between the pulses give the TL signals (TL). The difference between the TL+OSL and TL curves gives the TOSL curve providing information about the temperature dependence of the OSL process.FIG.32Bshows TL+OSL, TL and TOSL curve for the BeO:Na,Dy,Er with TL readout up to 650° C. at a rate of 5° C./s having blue-light stimulation at the same period. InFIG.32B, from the TOSL curve, the OSL outputs have two decreased curves. First decrease is from 50° C. up to 150° C. and second one begins with 150° C. and reach to zero level at 250° C. It can be inferred that the first sharp decrease may be associated with the strong thermal quenching and the second decrease may be responsible for emptying the 170° C. dosimetric peak. The thermal quenching energies of the materials were evaluated using the data collected in OSL readouts (seeFIG.32A) and by fitting them into the Equation (2). We also used the reduction data in the initial parts of TOSL curves to evaluate the thermal quenching energies (seeFIG.32B). The obtained data were fitted to the curve given by Equation (2). The fitting curves and the estimated E_Q values (0.43 and 0.42 eV) using both methods were presented in the graphs of the insets ofFIG.32B, which plot the OSL signal intensity as a function of temperature.

Description of Invention for OSL Reader

There is provided herein an Optically Stimulated Luminescence (OSL) reader for obtaining the measurements of radiation exposure for BeO based compounds including BeO doped with Na, Dy, Er using OSL and for obtaining improved accurate OSL measurements over a great range of radiation exposures. This invention is a part of a dosimetry system which consists of BeO based novel OSL dosimetric materials including BeO doped with Na, Dy, Er and an OSL reader measures OSL versus time response from the pre-determined materials obtained during blue light stimulation. In more particular, this invention provides a reliable dose value over a wide range of radiation doses exposed to OSL dosimetric materials including BeO doped with Na, Dy, and Er.

OSL Reader

Design and Construction of Portable OSL Reader

An OSL measurement system should meet some essential criteria such as a stimulation light source with proper wavelength and power density, a luminescence detection system with high sensitivity and reliable sample positioning for automated multi-sample measurements. The system and its properties are shortly summarized below. The design consists of three main parts: ‘measurement chamber’, ‘motorized sample changer unit’ and ‘measurement electronics and software’. General overview of the system can be seen inFIG.13.

Measurement Chamber. Generally, commercial OSL dosimetry materials are stimulated using visible light whereas emission occurs at near ultraviolet (UV) region. BeO chips produced by C̨ukurova University group work in the same manner. Our portable OSL reader's measurement chamber designed for measuring these types of detectors. On the other hand, it is possible to change detection system for non-conventional dose detectors (such as TLD-400 and YAP:Mn, emitting in the visible region of the spectrum). A simplified view of the measurement chamber and a photo of the constructed reader is shown inFIG.14.

The measurement chamber consists of a high power blue LED (λpeak ˜475 nm, Cree XQEBLU-SB-0000-000000Y01), photomultiplier tube (PMT) module, and associated optics for collimating and collecting stimulation and emitted light. It is placed on top of the measurement chamber and the. The emission was collimated using acrylic non-imaging optics. Optical properties of the measurement chamber including the LED emission spectra and filter characteristics are presented inFIG.15.

The short wavelength emission from the LED was filtered using a glass long pass filter (Schott, GG420). Between the LED and the sample holder a dichroic mirror (which passes the visible and reflects the UV light) is placed at an angle of 45 degrees. After passing the dichroic mirror, the stimulation light is conveyed to the sample through a focusing optics (a UV grade biconvex lens) and illuminates the sample holder uniformly. The collimated luminescence light is reflected (with the help of the dichroic mirror) to the photo detector, which is located on the side of the measurement chamber. After passing a UV band pass filter (Hoya U-340+Schott DUG11combination with a pass band of 280-380 nm) the luminescence light reaches the PMT module.

Motorized Sample Changer Unit. The OSL reader was designed for measuring the OSL from 8 samples. For this purpose, a sample wheel is rotate using a stepper motor and can bring the sample of interest to the focal plane of the focusing optics of the measurement chamber. A side view of the measurement chamber and the sample tray can be seen inFIG.16. The sample tray is placed on a drawer mechanism so that it can go out for loading samples to the reader. It can be taken in and out using a switch placed on the front face of the reader unless there is an ongoing measurement process. Both sample wheel and drawer mechanisms are running with the help of stepper motors.

Measurement Electronics and User Interface Software. The core control system of the OSL reader is an Arduino DUE single-board microcontroller, which operates an Atmel SAM3X8E ARM Cortex-M3 CPU running at 84 MHz. This microcontroller is responsible for control of sample tray motors, control of stimulation light, counting pulses coming from PMT module and any other electronic switches and indicators. The firmware that controls the mentioned tasks were developed with a modified C language using the Arduino's integrated development environment (IDE). In order to control the measurement system, collect and store measured data, a user interface software is written Python language. The software enables the user to create a measurement sequence for each individual dosimeter; runs these sequences and handles data coming from Arduino DUE microcontroller board. The measurement data is presented graphically and can be stored for further analysis. A screenshot of the designed PC software is given inFIG.17.

The main objective of the user interface software is to allow users to define measurement sequences, to handle the order of measurements by sending appropriate commands to Arduino, to obtain measurement data from the microcontroller and to save as a tab separated text file to the computer. Users also can observe ongoing measurement using ‘Live Plot’ tab section. For every measurement step, the PC software and the microcontroller need to communicate with each other. Every time the device is powered on, it moves tray inside and find sample position 1. After initialization process is complete, the microcontroller informs PC software that the device is ready for measurement. Once samples are loaded into the instrument and the parameters for the measurement sequence are entered by the user, the PC software stores them and waits for ‘Start’ button on the software screen to be pressed. A simplified block diagram of the system showing the main parts of the measurement system can be seen inFIG.18.

After that, the user interface software sends the parameters of the measurement sequence to the microcontroller for every step of sequence. Then, the microcontroller first sets the desired sample position and initializes timers and counters for data collection timing and photon counting. Recorded data is sent to computer and saved as a tab separated text file. The data is then displayed on a plot and saved for further analysis for dose evaluation.

Operation Testing. After having completed the system its lab tests for electronic and mechanical validation. The functionality of the OSL measurement system was tested using luminescence materials relevant for radiation dosimetry. For this purpose, BeO (Thermalox 995, BrushWellman Inc.), Al2O3:C (Landauer Inc.) chips are used. InFIG.19, decay curves of BeO chips with different doses is given together with background level (signal measured using non-irradiated chips). This background level is around 350 counts per second. Inset toFIG.19, dose response of the OSL signal BeO in the interval 0.05 Gy to 1.00 Gy is also shown. LED intensity for these measurements are set to 10%.

Thus, the fulfilled development of OSL reader and performed operation tests with using of produced in frames of the studied dosimeters shows the feasibility of concept put as an approach of invention.

Fiber Optic OSL Probes

DESCRIPTION OF INVENTION

In-vivo measurement of irradiation dose in radiology and radiotherapy requires refined and sensitive remote irradiation dose measurement techniques. Optical fiber dosimetry using OSL probes has been studied as an alternative method of monitoring real time patient dose by different researchers. Being light weight and nonintrusive, optical fibers based dosimeters provide several advantages in in-vivo medical applications.

The fiber optic coupled radiation dosimeters used have been described in detail previously. This invention suggests that a prototype fiber optic dosimetry system coupled to BeO based dosimeters for example beryllium oxide doped with sodium, dysprosium and erbium, could be designed and developed using optically stimulated luminescence (OSL) technique. The first investigation in to the use of BeO based ceramic dosimeters for example beryllium oxide doped with sodium, dysprosium and erbium as the OSL probe for a fiber coupled luminescence dosimeter can be presented in future work related with BeO. Its feasibility for potential use in radiotherapy dosimetry can be demonstrated in future works.

The fiber optic dosimetry system uses OSL materials like a BeO based ceramic dosimeter for example beryllium oxide doped with sodium, dysprosium and erbium to detect radiation and a bifurcated optical cable to illuminate the sensor with the suitable light source and also to guide the light from the sensor to the detector.

In this invention we suggest a new fiber optic coupled novel OSL dosimeter that is based on the detection of luminescence from a BeO based ceramic dosimeter for example beryllium oxide doped with sodium, dysprosium and erbium. The unique physical and luminescence properties of BeO based ceramic dosimeter for example beryllium oxide doped with sodium, dysprosium and erbium fiber dosimeter as a near tissue equivalent material will permit novel solutions to accurate and reproducible in-vivo dose measurements with a linear dose rate and dose response. It will meet the needs of current radiotherapy with characteristics including real-time, small volume, highly sensitive and reproducible dosimetry.

Description of Method

Currently, in-vivo patient monitoring has mainly been performed using one of four available detector systems; thermoluminescence (TL)/optically stimulated luminescence (OSL) dosimeters, Si-diode detectors, MOSFET, or diamond detectors. Commonly used conventional electronic dosimeter systems have several shortcomings like use of external power supply with a high voltage (HV), degradation, sensitivity changes and no provision for real time dose under irradiation and no tissue equivalence. Fiber optic probes based on OSL are capable of measuring radiation for medical in-vivo applications. Being light weight and nonintrusive, optical fibers provide several advantages in the field of dosimetry. In fiber optic probes based on OSL, the radiation-sensing component is coupled to an optical fiber. Here, the fiber acts only as a wave guiding component to carry an optical signal from the sensing component to a detector.(Razvan Gaza, Stillwater, Okla. (US); Mark S. Akselrod, Stillwater, Okla.; McKeever, S. W. Stillwater, Okla. (US), Optically stimulated luminescence irradiation dosimetry method to determine dose rates during radiotherapy procedures, United States Patent, Aug. 30, 2005, U.S. Pat. No. 6,936,830 B2)(Jerimy C. Polf, Razvan Gaza, Stephen W. S. McKeever, Optically stimulated luminescence radiation dosimetry method to determine integrated doses and dose rates and a method to extend the upper limit of measureable absorbed radiation doses during irradiation; United States Patent, February 2006; U.S. Pat. No. 7,002,163 B2)

Two examples of materials used as the radiation-sensing component are Cut-doped silica (Huston et al., 2002) and Al2O3:C (Polf et al., 2002). Recent work with these materials demonstrates the ability of this sensor architecture to perform nonintrusive, in-vivo monitoring during radiotherapy. If OSL material attached to the end of a multimode fiber optic cable, it emits light when it is stimulated by means of laser. In applications where heating of the tip of the fiber is unacceptable, such as monitoring of dose to tumor during radiotherapeutic treatment of cancer patients, OSL dosimeter has importance where the dose can be read by stimulating with light (Magne and Ferdinand, 2004). Single channel BeO ceramic sensor based fiber optic dosimeter of small sensitive volume has a potential for use a reliable dosimeter in radiotherapy applications (Alaxsandre et al., 2013).

Fiber Optic OSL Probes

In OSL, since the stimulation wavelength is different from that of the emitted luminescence, such measurements can be carried out using a single optical fiber in connection with a suitable detection filter placed in front of a photomultiplier (PM) detector. Thus, the main advantages of an optical fiber dosimeter over the currently available radiation detectors used in clinical applications are a small-size sensor, and the capability to measure both real tune dose rate and absorbed dose. Furthermore ultrathin fiber dosimeters can be placed either on the body surface or in cavities near the organs of interest. A schematic diagram of a newly developed remote optical fiber dosimetry system for radiotherapy is shown inFIG.20. To produce OSL a green laser beam is focused through a dicronic color beam-splitter positioned in a 45° angle relative to the incident beam, and via the light fiber into the Al2O3:C dosimeter. The stimulated OSL signal, which mainly consists of blue light, is sent back from the dosimeter in the same fiber and reflected by the beam splitter into a miniature PM detector. In the current work the fiber dosimeter probe consists of a small single crystal of Al2O3:C (produced by Landauer Inc.) coupled to the end of a thin fiber made of plastic.

Further Investigations on Fiber Optic OSL Probes

In the last decade, there exits more information available on the fiber optic OSL probes. Unlike Al2O3:C crystals, BeO ceramics are near water equivalent (Zeff=7.13) and hence have the potential to be a near water equivalent alternative to Al2O3:C although its potential use as a BeO-coupled fiber optic dosimeter (FOD) has not yet been investigated. BeO may prove to be a more versatile FOD, which can bridge the gap between the near tissue equivalent plastic scintillators and OSL based Al2O3:C crystals.

A common concern with the use of BeO ceramics has been the toxicity. Inhalation of beryllium has been known to cause a chronic disease called Chronic Beryllium Disease (CBD) (NRC, 2008). BeO in solid form has not been shown to present any health risk. Only in its powder form where inhalation is possible does proper handling need to be considered (Walsh and Vidal, 2009).

Recent studies of Santos et al. at the University of Royal Hospital Adelaide suggest use of BeO as a radioluminescence (RL) and OSL material for fiber optical luminescence dosimetry (Santos et al., 2013; Santos et al., 2014; Santos et al., 2015). Techmann et al. from TU Dresden, Germany, determined the fundamental dosimetric and temporal properties of fiber optic probes based on the RL and OSL of BeO and evaluate its suitability for dose rate measurements in brachytherapy and other applications using non-pulsed radiation fields (Teichmann et al., 2016).

A Mm-Scale Dosimetry System Based on Optically Stimulated Luminescence of Beryllium Oxide

Because of their small dimension, almost no active dosimetry systems are able to measure inside the radiation field existing thermoelement pipes. New mm-scale luminescence dosimeters in combination with a packing and transport technique are presented. The dosimeters could measure doses from 0.1 mGy up to more than 100 Gy. Hence, over the possible exposure time durations, dose rates from μGyh−1 up to 1000 Gyh−1 are ascertainable. For potential users the system opens the opportunity for investigation of dose rates inside of shielding and in contaminated environments. Particularly in constricted environments the technique is a unique solution for dose and dose rate measurement tasks.

For more than ten years a valuable dosimetric method employing optically stimulated luminescence (OSL) of the material beryllium oxide (BeO) has been developed at Technical University Dresden (TU Dresden). Since 2006, with the BeOmax reader, a semi-commercial dosimetry system has been available for scientific as well as industrial users. The system has been continuously upgraded and adapted based on the requirements of the users. As a result, several forms of encapsulated dosimeters and handling techniques for bare BeO detectors are now available for dosimetric use. One detector form is a cylindric BeO substrate with a diameter and a height of 1 mm each, which is very useful for dosimetry within small or restricted spaces.

The BeO detector material is offered as Thermalox 995® by Materion Ceramics, Tucson, Ariz. (former known as Brush Wellmann Inc.). According to the intensive use of BeO in electronic industries, the BeO-chips are clearly cheaper than standard luminescence materials.

REFERENCES

Huston A L, Justus B L, Falkenstein P L, Miller R W, Ning H, Altemus R. Optically stimulated luminescent glass optical fibre dosemeter. Radiat Prot Dosimetry 2002; 101:23-6.Polf J C, McKeever S W, Akselrod M S, Holmstrom S. A real-time, fibre optic dosimetry system using Al2O3fibres. Radiat Prot Dosimetry 2002; 100:301-4.Magne S, Ferdinand P. Fiber optic remote gamma dosimeters based on optically stimulated luminescence: State-of-the-art at CEA. Paper Presented at 11th International Congress of the International Radiation Protection Association, Madrid, Spain; 2004.Alaxandre M, Santos C, Mohammadi M, Asp J, Monro M T, Afshar VS. Characterization of a real-time fiber-coupled beryllium oxide (BeO) luminescence dosimeter in X-ray beams. Radiat Meas 2013; 53:1-7.National Research Council, 2008, Managing Health Effects of Beryllium Exposure. Washington, D.C.: The National Academies Press. https://doi.org/10.17226/12464.Kenneth A. Walsh, Editor: David L. Olson, Edgar E. Vidal, Edward Dalder, Alfred Goldberg, and Brajendra Mishra, Beryllium Chemistry and Processing, ASM International, ISBN: 978-0-87170-721-5.A. M. C. Santos, Mohammad Mohammadi, Shahraam Afshar, Energy dependency of a water-equivalent fibre-coupled beryllium oxide (BeO) dosimetry system, February 2015 Radiation Measurements 73:1-6, DOI10.1016/j.radmeas.2014.12.0060-87170-721-5.A. M. C. Santos, M. Mohammadi, and S. Afshar V., “Investigation of a fibre-coupled beryllium oxide (BeO) ceramic luminescence dosimetry system”, Radiat. Meas., vol. 70, pp. 52-58, November 2014.A. M. C. Santos, M. Mohammadi, and S. Afshar V., “Evaluation of a real-time BeO ceramic fiber-coupled luminescence dosimetry system for dose verification of high dose rate brachytherapy”, Med. Phys., vol. 42, no. 11, pp. 6349-6356, October 2015.E. G. Yukihara, “Luminescence properties of BeO optically stimulated luminescence (OSL) detectors”, Radiat. Meas., vol. 46, no. 6-7, pp. 580-587, June 2011.A. Jahn et al., “The BeOmax system—Dosimetry using OSL of BeO for several applications”, Radiat. Meas., vol. 56, pp. 324-327, September 2013.T. Teichmann et al., “Real time dose rate measurements with fiber optic probes based on the RL and OSL of beryllium oxide”, Radiat. Meas., vol. 90, pp. 201-204, July 2016.Marian Sommer, Axel Jahn, Reiner M. Praetorius, Dora Sommer, Juergen Henniger, A mm-Scale Dosimetry System Based on Optically Stimulated Luminescence of Beryllium Oxide for Investigation of Dose Rate Profiles in Constricted Environments, WM2012 Conference, Feb. 26-Mar. 1, 2012, Phoenix, Ariz.Sommer, M., Freudenberg, R. and Henniger, J. (2007). New aspects of a BeO-based optically stimulated luminescence dosimeter. Radiation Measurements, 42, 617-620.Sommer, M., Jahn, A. and Henniger, J. (2008). Beryllium oxide as optically stimulated luminescence dosimeter. Radiation Measurements, 43, 353-356.Sommer, M., Jahn, A. and Henniger, J. (2011). A new personal dosimetry system for HP(10) and HP(0.07) photon dose based on OSL dosimetry of beryllium oxide, Radiation Measurements, 46, 1818-1821.

EXAMPLES

The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof.

Example 1—Synthesis of BeO:Na(x % Molar)

Beryllium oxide phosphors were prepared using precipitation method. During the production process, sodium (Na) which is the alkali metal group was used with different concentrations as a dopant ion.

A small amount of pure water was added to the beaker and stirred vigorously. Beryllium sulfate as a starting material was added into pure water and mixed up to the dissolved. Then, sodium nitrate as a dopant was added at different concentration into a resulting solution. When the sodium nitrate is dissolved Alkaline Poly(ethyleneimine) solution which is a precipitator was drop by drop under vigorously stirring. During this step, precipitated material was observed slowly. The pH of the resulting mixture was checked and found to be an acidic solution. Since the medium must be balanced by the acidic-basic level, we can say that the solution has non-precipitated material. If the medium is acidic, we add Ammonium hydroxide solution and balance the pH between 6-7. Obtained mixture was poured into porcelain crucible and dried at 370° C. (this is hot plate temperature) on the hot-plate about 2 hours. Dried precipitate was calcined at 800° C. for 4 hours in air furnace for the burning of organics. Calcined powder was ground in agate mortar and prepared in pellet form by evacuable pellet die. Prepared BeO:Na pellets were measured 6.15 mm in diameter by 0.82 mm in thickness. In order to impart strength and integrity, prepared BeO pellets were sintered using a box furnace at 1600° C. for 4 hours (with 5° C./s heating rate) in the middle of two alumina boat crucibles. OSL signals of Na doped beryllium oxide pellets are shown inFIGS.21A and21B.

Example 2—Synthesis of BeO:Dy(x %), Er(x %)

Beryllium oxide phosphors were prepared with double combinations of different concentrations of dysprosium (Dy) and erbium (Er) ions which are the lanthanide group as a dopant ion according to the same procedures in Example 1.

To increase the impurity of the crystal structure new doping were made. Er and Dy lanthanide ions were used as a dopant. Nitrate based Dy and Er ions as a dopant were added at different concentrations into a resulting solution. Keeping constant the concentration of Er as 0.1% molar and changing the concentrations of Dy as 0.005, 0.01, 0.1, 0.5% molar, doping treatments were performed. With the aim of checking the possibility of using OSL signals of BeO:Dy,Er pellets for dosimetric purposes, Luminescence signals were obtained from BeO:Dy,Er pellets which were irradiated with 0.1 Gy dose. Before the OSL measurements, BeO:Dy,Er pellets were annealed at 650° C. for 20 min and the measurements started after half an hour of waiting at the room temperature for stabilization of traps. The maximum intensities of OSL decay curves from Dy and Er doped beryllium oxide pellets were showed inFIG.22Cand the concentration of Dy ion was determined as 0.005%. After the determination of the Dy concentration, Er and Dy dopants were doped keeping constant the concentration of Dy and changing Er concentrations as 0.001, 0.01, 0.05, and 0.5% molar. The highest OSL signals were obtained from BeO:Dy(0.005%), Er(0.05%) (seeFIGS.22A,22B and22C).

Example 3—Synthesis of BeO:Na(x %), Dy(x %), Er(x %)

Beryllium oxide phosphors were prepared with triple combinations of different concentrations of Dy, Er and Na ions according to the same procedures as in Example 1.

Na, Dy and Er were used as a dopant for BeO. Firstly, Na and Dy concentrations were keeping constant 0.1% and 0.005% mole, respectively. Er concentrations were changed about 0.001, 0.01, 0.05, 0.5% mole. With the aim of checking the possibility of using OSL signals of BeO:Na,Dy,Er pellets for dosimetric purposes, Luminescence signals were obtained from BeO:Na,Dy,Er pellets which were irradiated with 0.1 Gy dose. Before the OSL measurements, BeO:Na,Dy,Er pellets were annealed at 650° C. for 20 min and the measurements started after half an hour of waiting at the room temperature for stabilization of traps. The OSL decay curves from Na, Dy and Er doped beryllium oxide pellets were showed inFIG.23Aand the concentration of Er ion was determined as 0.05% molar.

After the determination of the Er concentration, Na, Dy and Er ions were used as a dopant in the same way, but in this case, keeping constant Er (0.05%) and Dy (0.005%) concentrations, changing Na concentrations as 0.05, 0.1, 0.3, 0.5, 1, 3, 5 and 10% molar, doping treatments were performed. Wherein the reason for the use of high concentrations is thought that it will not change the crystallography, due to Na element with lower atomic radius than lanthanide. After the producing the materials, the OSL signals of each pellets were obtained and given inFIG.23Band the concentration of Na ion was determined as 5% molar.

Finally, keeping constant the determined concentrations of Er (0.05%) and Na (5%), Dy ion were doped at concentrations of 0.01, 0.05, 0.1, 0.5, 1, 2% molar. In the same way, the OSL signals of each produced pellets were obtained and given inFIG.23C. The highest luminescence signals were observed from BeO:Na(5%), Dy(0.1%), Er(0.05%) samples. Maximum intensities of OSL signals for 0.1 Gy beta irradiation from the triple combination of all Na, Dy and Er doped BeO pellets was illustrated inFIG.23D.

Example 4—Synthesis of BeO:Mg(x % Molar)

Beryllium oxide phosphors were prepared with different concentrations of magnesium (Mg) ion as a dopant according to the same procedures as in Example 1.

Firstly, magnesium was used as a dopant with different concentrations (0.005, 0.01, 0.03, 0.05, 0.3, 0.5, 1, 3, 5, 10, 15, 20% mole) OSL measurements were carried out using Risø, DA-20 model TL/OSL reader system (seeFIG.24A). With the aim of checking the possibility of using OSL signals of BeO:Mg pellets for dosimetric purposes, Luminescence signals were obtained from BeO:Mg pellets which were irradiated with 0.1 Gy dose. Before the OSL measurements, BeO:Mg pellets were annealed at 650° C. for 20 min and the measurements started after half an hour of waiting at the room temperature for stabilization of traps. According to obtained OSL signals, concentration of magnesium was determined as 0.05 and 0.3% mole (seeFIG.24B).

Synthesis of BeO:Mg(x %), Al(x %), BeO:Mg(x %), Ca(x %) and BeO:Na(x %), Mg(x %), Ca(x %)

Beryllium oxide phosphors were prepared in the same way with different concentrations of the double combinations of Mg—Al and Mg—Ca and the triple combinations of Na—Mg—Ca ions according to the same procedures as in Example 1.

When Al (Al(NO3)3.9H2O) and Ca (Ca(NO3)2.4H2O) ions in different concentrations (0.005, 0.01% molar) were doped separately and together to the BeO:Mg(0.05 and 0.3%), the highest OSL signals were obtained from BeO:Mg(0.05%), Ca(0.01%). Whereupon, to improve the trap structure, create different energy levels and increase the OSL signals, Al (Al(NO3)3.9H2O) ion was doped keeping constant the concentration of Mg and Ca ions as 0.05% and 0.01% molar, respectively (FIGS.25Aand B). In this process, the concentrations of the Al ions were chosen as 0.001, 0.005, 0.01, 0.05% molar. The highest OSL signals were obtained from the BeO:Mg(0.05%), Ca(0.01%), Al(0.05%) (seeFIG.25C).

Synthesis of BeO:Mg(x %), Er(x %), Dy(x %)

In addition, beryllium oxide phosphors were also prepared with different concentrations of the triple combinations of Mg—Er—Dy ions according to the same procedures as in Example 1.

In order to improve the OSL signals obtained from BeO:Mg(0.05%) samples, lanthanide ions Erbium and Dysprosium were doped to BeO:Mg(0.05%) compound keeping constant Er concentration as 0.1% and changing Dy concentrations as 0.005, 0.05, 0.01 and 0.1%) (FIG.26A). After applying this procedure, OSL signals were obtained for each doped BeO samples and according to OSL results, the suitable OSL signals were achieved when Dy concentration was chosen as 0.01% molar. After the determination of the suitable Dy concentration, Er with the concentrations of 0.001, 0.005, 0.01, 0.05% molar was doped keeping constant Dy concentration as 0.01% molar (FIG.26B). Finally, OSL signals were recorded from the pellets and the highest OSL signal was recorded from BeO:Mg(0.05%), Dy(0.01%), Er(0.001) pellets.

Synthesis of BeO:Mg(x %), Ca(x %), Al(x%), Dy(x %), Er(x %), Co(x %), Cu(x %)

After the determination of the Mg, Al, Ca, Er and Dy ion concentrations, Cobalt and Copper ions were doped to BeO:Mg(0.05%),Ca(0.01%),Al(0.05%),Dy(0.01%),Er(0.001%) compound using the concentration of Cobalt as 0.001% molar and changing the concentrations of Copper as 0.001, 0.005, 0.01, 0.05% molar. In order to understand the effect of doping Co and Cu ions on BeO:Mg,Ca,Al,Dy,Er samples, OSL signals were obtained from the each pellets and the highest luminescence signals were observed in BeO:Mg(0.05%),Ca(0.01%),Al(0.05%),Dy(0.01%),Er(0.001%),Co(0.001%),Cu(0.001%). Comparing the results of the OSL signals from BeO:Mg(0.05%),Dy(0.01%),Er(0.001), a decline of 60% in signals was observed (seeFIG.37).

Synthesis of BeO:Mg(x %),Ce(x %) and BeO:Mg(x %),Ce(x %),Li(x %)

On the other hand, beryllium oxide phosphors were also prepared with different concentrations of the double combinations of Mg—Ce and the triple combinations of Mg—Ce—Li ions according to the same procedures as in Example 1.

In addition to use of Mg as an additive at determined concentration, Cerium (Ce(NO3)3.6H2O) was added with different concentrations (0.01, 0.1, 0.5, 1% molar) into each of BeO doped with the concentrations of magnesium with 0.3 and 0.05% molar (FIGS.28A and28B). After this synthesized and preparation process as mentioned example 1, OSL signals were obtained from product pellets. As a result, the highest OSL signal was observed from BeO:Mg(0.3%),Ce(0.01%) and BeO:Mg(0.05%),Ce(0.01%). After the determination of the suitable Mg and Ce concentrations, Lithium (LiNO3) ion was doped keeping constant the concentration of Mg and Ce ions as 0.05% and 0.01% molar, respectively. In this process, the concentrations of the Li ions were chosen as 0.005, 0.01, 0.05, and 0.1% molar. The highest OSL signals were obtained from the BeO:Mg(0.05%),Ce(0.01%), Li(0.01%) (FIG.28C).

Example 5—Synthesis of BeO:Tb(x %),Gd(x %)

Another doping to the BeO material is the terbium (Tb)-gadolinium (Gd) combinations. BeO phosphors doped with this combination were prepared according to the same procedures as in Example 1. Tb concentrations was kept constant as 0.01% molar and Gd concentrations were chosen as 0.01, 0.05, 0.1, 0.5, 1 and 2% molar. The highest OSL signal was observed from the BeO:Tb(0.01%),Gd(0.01%), as seen inFIG.29.

Example 6—Synthesis of BeO:Al(x %),Ca(x %), (Lanthanides) Using Another Technique

BeO phosphors were obtained with another technique which is the Sol-Gel method and the lanthanides were used as a dopant ion during the production method. The ions doped by the sol-gel method were performed in triple combination with constant concentration of Al (1% molar) and Ca (0.1% molar) dopants and nitrate-based lanthanides La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy.

In this technique, the starting material was Beryllium sulfate tetra-hydrate as the precursor for the inorganic component, and Ethylene glycol solution and citric acid salts was chosen as an organic complexing/fuel agent. A certain amount of BeSO4was dissolved in ethylene glycol on the magnetic stirrer, then the hot plate of magnetic stirrer was turned on and a certain amount of citric acid was added. Hot-plate temperature was increased slowly up to about 300° C. through 2 hours. At this stage the amount of water in the environment gradually evaporated and it became a gel form. When the all medium was converted to gel form, the magnetic stirrer was taken, and the gel solution was fired in furnace at 500° C. for 1-2 hours. Since the gel form cannot be separated easily from the beaker, this burning process was carried out. Obtained material was in charred form after the burning treatment. Therefore, the charred material was exposed a second heat treatment to ensure the crystal structure and burn the material to obtain a white powder. Finally, a white soft BeO powder was obtained by calcination treatment at 800° C. for 4 hours. This production method and dopants show a relatively lower brightness than the precipitation method.

Preparation of luminescent phosphor pellets is applied heat treatment to material after pressing it by cold pressing. This process is convenient for shaping the phosphorus, and at the same time it is a process in which the crystallographic structure is arranged, and the phosphor is made brighter. Heat treatment depends on both the basic material BeO and the small amount of doped ions. After the pelletization process, BeO:Al(1%),Ca(0.1%), (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy 1%) sintered at 1600° C. for 4 hours. OSL measurements were carried out using Risø, DA-20 model TL/OSL reader system. With the aim of checking the possibility of using OSL signals of BeO:Al(1%),Ca(0.1%), (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy 1%) pellets for dosimetric purposes, Luminescence signals were obtained from doped BeO pellets which were irradiated with 0.1 Gy dose. Before the OSL measurements, doped BeO pellets were annealed at 650° C. for 20 min and the measurements started after half an hour of waiting at the room temperature for stabilization of traps. According to obtained OSL signals, the brightest samples were determined as BeO:Al(1%),Ca(0.1%),La(1%) pellets (seeFIG.30).

Example 7—Synthesis of BeO:Na(x %),Er(x %),Dy(x %) Using a New Technique

BeO phosphors doped with Na, Er and Dy were produced by a new method followed by heat treatment.

In this method, citric acid (C6H8O7, ACS reagent, ≥99.5%) and ethylene glycol (C2H6O2, Anhydrous, 99.8%) solution was chosen to construct the polymer in the solution and create organic complex/fuel agent, respectively. Firstly, stoichiometric quantities of Beryllium sulfate tetra hydrate (BeSO4.4H2O, ≥99.0%) as starting material was solved in ethylene glycol solution using magnetic stirrer and nitrate based doping materials (Sodium nitrate (NaNO3≥99.0%), Erbium (II) nitrate pentahydrate (Er(NO3)3·5H2O≥99.9%) and Dysprosium (III) nitrate hydrate (Dy(NO3)3·xH2O≥99.9%)) were added to this solution at certain concentrations. Then, citric acid was added in this beryllium sulfate-ethylene glycol solution. Ammonium hydroxide solution (H5NO, ACS reagent, 28.0-30.0% NH3basis) was added to this solution, which had a pH value of about 2-3. It was obtained the solution which the pH value ˜7 after stirring for 10 min. At the same time, a certain amount of Poly(ethyleneimine) solution (50% (w/v) in H2O) was diluted with water in another beaker. And now we have 2 solutions. One of them is beryllium sulfate-ethylene glycol-citric acid solution (including dopant ions) and the other is diluted poly solution. Now we add the two mixtures together to obtain the material as a precipitate. Diluted poly(ethyleneimine) solution was added to beryllium sulfate solution under vigorous stirring and precipitate particles were observed homogeneously.

Obtained final solution become the dark brown gel after dried on the heater about 3 hours. In order to burn formed organics, the dried sample was burned at 500° C. with 2° C./min heating rate for 1 hours in an oxygen atmosphere. Dried sample was obtained as charred powder after heat treatment and it was calcined at 800° C. with 5° C./min. Calcined powder was ground in agate mortar and prepared in pellet form by evacuable pellet die. In order to impart strength and integrity, prepared BeO pellets were sintered using a box furnace at 1600° C. for 4 hours (with 5° C./s heating rate) in the middle of two alumina boat crucibles. In the same way, after β-irradiation with 0.1 Gy, the OSL decay curve of the produced pellets was obtained using Risø, DA-20 model TL/OSL reader system and given inFIG.31.