Optically stimulated luminescence (OSL) is a method to measure radiation doses using certain crystalline materials like quartz and aluminum oxide. When these materials are irradiated, electrons become trapped in imperfections in the crystal lattice. During OSL, laser light stimulates the trapped electrons to emit visible light, and the light intensity is proportional to the radiation dose. OSL dosimeters provide sensitive measurements from 1 mrem to 1000 rem and have advantages over traditional thermoluminescent dosimeters like higher precision and no requirement for heating. OSL is used for dating ancient materials and measuring radiation exposure in occupational and medical settings.

1. Presentation starts in

8. INTRODUCTION TO OSL..
• IN PHYSICS, OPTICALLY STIMULATED LUMINESCENCE (OSL) IS A METHOD FOR MEASURING DOSES FROM
IONIZING RADIATION.
• THE METHOD MAKES USE OF ELECTRONS TRAPPED BETWEEN THE VALENCE AND CONDUCTION BANDS IN
THE CRYSTALLINE STRUCTURE OF CERTAIN TYPES OF MATTER (SUCH AS QUARTZ, FELDSPAR, AND
ALUMINIUM OXIDE). THE TRAPPING SITES ARE IMPERFECTIONS OF THE LATTICE - IMPURITIES OR
DEFECTS.

9. PRINCIPLE
• IRRADIATION OF THE MATERIAL, STIMULATES SOME ELECTRONS INTO AN EXCITING STATE.
• DURING PROCESSING, LASER LIGHT STIMULATES THESE ELECTRONS, CAUSING THEM TO RETURN TO
THERE GROUND STATE WITH THE EMISSION OF VISIBLE LIGHT.
• THE INTENSITY OF THE VISIBLE LIGHT EMISSION IS PROPORTIONAL TO THE RADIATION DOSE RECEIVED
BY IT.

10. INSIDE SIGHT..
• THE PHENOMENOLOGICAL DESCRIPTION OF THE OSL AND THERMOLUMINESCENCE PROCESS ARE THE SAME.
• PURE CRYSTALLINE DIELECTRIC MATERIALS EITHER CONTAIN OR HAVE ADDED TRACE AMOUNTS OF CONTAMINANTS THAT FORM CRYSTAL-LATTICE IMPERFECTIONS.
• THESE IMPERFECTIONS ACT AS TRAPS FOR ELECTRONS OR HOLES AND ALSO CAN ACT AS LUMINESCENCE CENTERS, WHICH EMIT LIGHT WHEN ELECTRONS OR HOLES RECOMBINE NEAR THEM.
• AFTER IRRADIATION, FREE ELECTRONS AND HOLES ARE GENERATED THAT CAN BE TRAPPED.
• THE RECOMBINATION CENTERS IN AL2O3:C ARE MAINLY CREATED BY OXYGEN VACANCIES AND ARE CALLED F CENTERS .
• RADIATION GENERATED HOLES CAN BE TRAPPED AT THE RECOMBINATION CENTER, CREATING F+ CENTERS.
• WHEN THE CRYSTAL IS HEATED OR OPTICALLY STIMULATED, ELECTRONS CAN BE EJECTED OUT OF TRAPS AND RECOMBINE WITH HOLES AT THE F+ CENTER.
• THE RECOMBINATION ENERGY IS TRANSFERRED TO A LUMINESCENCE CENTER WHERE LIGHT IS EMITTED;
F++ELECTRON→F +420 NM LIGHT.
• IF THIS RECOMBINATION CASCADE IS INITIATED BY HEAT THEN IT IS CALLED THERMOLUMINESCENCE; IF IT IS INITIATED BY LIGHT THEN IT IS CALLED OPTICALLY STIMULATED LUMINESCENCE.

12. OSL DOSIMETRY..
• THE OSL DOSIMETER PROVIDES A NEW DEGREE OF SENSITIVITY BY GIVINGAN ACCURATE READING AS
LOW AS 1 MREM FOR X-RAY AND GAMMA RAY PHOTONS WITH ENERGIES RANGING FROM 5 KEV TO
GREATER THAN 40 MEV.
• THE OSL DOSIMETER'S MAXIMUM EQUIVALENT DOSE MEASUREMENT FOR X-RAY AND GAMMA RAY
PHOTONS IS 1000 REM.
• IN DIAGNOSTIC IMAGING THE INCREASED SENSITIVITY OF THE OSL DOSIMETER MAKES IT IDEAL FOR
MONITORING EMPLOYEES WORKING IN LOW-RADIATION ENVIRONMENTS AND FOR PREGNANT WORKERS.

13. APPLICATION OF OSL..
• OSL IS USED IN AT LEAST TWO DIFFERENT APPLICATIONS:
• OPTICAL DATING OF ANCIENT MATERIALS
• RADIATION DOSIMETRY, WHICH IS THE MEASUREMENT OF ACCUMULATED RADIATION DOSE IN THE
TISSUES OF HEALTH CARE, NUCLEAR, RESEARCH AND OTHER WORKERS, AS WELL AS IN BUILDING
MATERIALS IN REGIONS OF NUCLEAR DISASTER

14. OSL VS TLD..
THE OSL PROCESS IS NOT UNLIKE TLD. BOTH ARE BASED ON STIMULATED
LUMINESCENCE. HOWEVER OSL HAS SEVERAL ADVANTAGES OVER TLD.
 WITH A MINIMUM REPORTABLE DOSE OF 1 MREM, OSL IS MORE SENSITIVE
THEN TLD.
OSL HAS PRECISION OF +-1 MREM, WHICH BEATS TLD.

15. OTHER FEATURES OF OSL INCLUDES..
NO HEATING CONTROLS FOR THE READER
NO NITROGEN REQUIRED
NO GLOW CURVE ANALYSIS REQUIRED
NO ANNEALING OVEN
SIMPLER AND MORE RELIABLE ANALYSIS INSTRUMENTATION
ROBUST AND DURABLE
MINIMAL FADE < 5% IN A YEAR.
INSENSITIVE TO ENVIRONMENTAL EFFECTS OF WATER, HEAT,
PRESSURE AND CHEMICAL CONTAMINANTS
VARY LIGHT OUTPUT TO OPTIMIZE LOW-DOSE, HIGH-DOSE, OR BOTH.
FLEXIBLE OPERATING PARAMETERS.
BEAM CROSS-OVER.
SIMPLE, LONG-LIVED LED ILLUMINATION.
SYSTEM PROVIDES IMMEDIATE DOSE RESULT.
LESS MAINTENANCE AND EASE OF OPERABILITY THAN TLD READERS.

18. CONCLUSION..
• OSLDS EXHIBIT HIGH PRECISION AND ACCURACY IN MEASURING DOSE, ARESMALL IN SIZE, HAVE NO
ENERGY DEPENDENCE, HAVE NO DEPENDENCE ON IRRADIATION ANGLE, AND CAN BE READ LONG AFTER
IRRADIATION. OSLD CAN SUBSTITUTE FOR TLD AND DIODES FOR IN VIVO DOSIMETRY AND ROUTINE
CLINICAL DOSE MEASUREMENTS. BECAUSE OF THEIR VERY LOW INTRINSIC BUILDUP OSLDS ARE IDEAL
FOR MEASURING SURFACE DOSE. WITH PROPER HANDLING OSLDS CAN BE A PERMANENT RECORD OF
MEASURED DOSE, THEY ARE REUSABLE, THE READOUT PROCESS IS LESS THAN 1 MIN, AND THE READOUT
IS BY OPTICAL STIMULATION VERSUS HIGH TEMPERATURE SO THE DOSIMETER CAN BE MADE OUT OF
INEXPENSIVE PLASTIC.

19. LINKS..
• RADIOLOGIC SCIENCE FOR TECHNOLOGIST, STEWART C.BUSHING, SEVENTH EDITION, PAGE NO.544
• HTTP://EN.WIKIPEDIA.ORG/WIKI/OPTICALLY_STIMULATED_LUMINESCENCE
• HTTP://WWW.LANDAUERAUSTRALASIA.COM/SHOPPINGCART/PRODUCTINFO.ASPX?PRODUCTID=1
• SCREEN SHOTS FROM
HTTPS://WWW.AAPM.ORG/MEETINGS/09SS/DOCUMENTS/25CYGLER-OSL.PDF