· . · . . + . . . i .. 1 . + . . ; 'C ' , . . | OF L ORNLP 2516 . .. • i . . . . - . . - - . 11 . . . . . . EL . - . - -- - . . . MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS -1963 . : onw for 25.16 ORML - AEC - OFFICIAL . 20NOV 2 9 1966.. .CONF-661005-23 ucs +.00; mm-50 . . .." ... MASTER ... . - . :.:..: - OF .. .. . SCINTILLATION EXTRAPOLATION DOSIMETRY SMALL BETA-EMITTING SOURCES W. H. Wilkie and B. R. Fish Health Physics Division Oak Ridge National Laboratory - Oak Ridge, Tennessee miri. . . . . . *** CSS i - RELEASED 'FOR AKKOUECEMENT IN KÜCLEAR: SCIENCS ABSTRACTS ... . . -, min, minimo · He: . - - ii .! 1 i .. ... mm . LEGAL NOTICE . sv . L 1 This report was prepared as an account of Government sponsored work. Neither the United States, por the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, expressed or implied, with respect to the accu- racy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not Infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, person acting on behalf of the Commission" includes any em- ployee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor. Limia 1 3 CAEC -0 1 . 7:.. SCINTILLATION EXTRAPOLATION DOSIMETRY OF SMALL BETA-EMITTING SOURCES* :* ORNL - AEC - OFFICIAL . . - ' 1 · W.. H. Wilkie and B. R. Fish Health Physics, Division' Oak Ridge National Laboratory Oak Ridge, Tennessee - *... - ABSTRACT 11 .. ... . . .. ... . . ..: .. A technique is described which may be utilized for obtaining values of :: absorbed dose to tissue -equivalent volumes approaching the volume of individual tissue cells. The method incorporates a series of scintillators (anthracene or NE-102-A. plastic) with dimensions ranging from 11-mm diameter x 0.5-mm thick to I.-mm diameter x .032-mm thick mounted on lucite light pipes. 'Pulse-height spectra are obtained using each scintillation assembly with absorber thicknesses from zero to several hundred mg cm . These are converted to energy spectra using a computer program to apply : appropriate corrections, and the absorbed dose is calculated. Individual dose measure- ments are then assembled into extrapolation curves which relate dose to tissue volumes : at specified absorber thicknesses. This technique is useful for measurements with sources of activity in the range of 0.05 to 500 MCI, which is below the range for which an ionization extrapolation chamber can be used. A comparison is made between the anthracene and plastic scintillation : assemblies, and the corrections necessary to convert pulse height data to absorbed. dose are discussed. The advantages and difficulties of this method are evaluated and si compared with similar measurements using an air ionization extrapolation chamber of the Loevinger design. :: Mic-inde : : hina -:: - . - - .." - - ----- . *... ... · : · · ... . ** . .: ***... ! W Research sponsored by the United States Atomic Energy Commission under contract with the Union Carbide Corporation. 1 76 : . .. . .. .. ...: Paper to be presented at the Symposium on Solid-State and Chemical Radiation Dosimetry in Medicine and Biology, Vienna, Austria, October 3-7, 1966. .. .. .. *** . ....... .. . - .. .. .... •; OINE - AEC - OFFICIAL A • ORNL - AEC - OFFICIAL . - INTRODUCTION The continuing development of theoretical models and experimental techniques for tissue -equivalent dosimetry is of great importance in medicine and biology. The field of bota dosimetry has receivod considerable attention particularly since 1950, and much progress has been made in the basic understanding of both the physical processes involved in electron slowing-down and in the biological damage resulting to tissue from energetic electrons. L. V. Spencert'has discussed calculation of the dose due to negatons, incorpo- rating the Bethe -Bloch stopping power formula for the determination of the slowing- - ........ .: .. .. . .. - , . ... scattering. This method has a sound theoretleal basis for dose calculations. Another approach has been proposed by Loevinger?" bd This method, based on experimental measurements, describes a point -source function which, with the proper parameters, may be integrated over a distributed source area or volume to arrive at estimates of absorbed energy at points inside a medium. Both of these upproaches require the medium to be of infinite extent and homogeneous in composition, although the betapa sources need not be uniformiy distributed. The Loevinger method is applicable only to media of low atomic number. There remain physically important areas of investigation for which there are no : applicable theories and for which adequare,experimental techniques have not been .. . .. :;;" a.. .....7 .. .. - >.". ..... . .. :.. ...... . and nonuniform systems. The purpose of this paper is to describe a technique for determining the absorbed dose to vanishingly small volumes of tissue. This technique : may be applied to physical situations such as a radioactive particle on the surface of the skin. : . The scintillation method has been applied to determining beta dose by several authors. Brannen and Oldes have used an optical lens and a photomultiplier tube to view a small volume of plastic scintillator sheet imbedded in the center of a 2 in. * 2 in. * 2 in. lucite phantom to obtain depth-dose estimates relative to the ORNL - AEC - OFFICIAL :.. ORNL - AEC - OFFICIAL - . . - .'." . ' surface dose delivered by a 1.5 Mev beam of electrons. The effective volume from which scintillations were observed was l. mm? Other authors lomo have used thin anthracene and piastic scintillators mounted on lucite light pipes.to measure depth- dose relative to surface dose from plane sources of beto emitters. Nentwing has used thin plastic scintillators for the development of a portable scintillation detector for the purposes of rudiation protection. In all of these investigations the dose measurements were relative, and the output incorporated current measuring devices. The currents observed were assumed directly proportional to dose, and this. assumption can result in serious error. More accurate dosimetry is possible using an ionization extrapolation chamber such as described by Loevinger. mira : Coro .... .... ... . ...... ............ .. . . . . . ini.. . .:; . orien . -.--:: • ne .... .... inom .......... . .....no www.rod i tam .... in . ce . · APPARATUS AND EXPERIMENTAL METHOD In order to use scintillators for the determination of the energy deposited by the absorption of beta particles, it is necessary to know the fluorescence response of each detec' or in terms of light output per unit energy absorbed. It is well known : that organic scintillators exhibit a characteristic nonlinear response to surface- incident regatons of low energy. Birks") has discussed the scintillation process in detail and laas proposed a theoretical relation describing the response function of scintillators which adequately follows experimental data. In a previous work Wilkie and Birkhoffl' explain its use with reference to the response of anthracene to surface- incident beta particles. Thin scintillators of anthracene and NE-102 were used in the present work. These scintillators were joined to polished lucite light pipes I-inch diameter by 1/2-inch thick. Scintillator-light pipe assemblies were optically coupled with clear silicone oil to an end-window photomultiplier tube (a selected, low noise Amperex, Type XP-1010). Pulse outpur from the photomultiplier was recorded using a multi- --. channel analyzer (Nuclear Data Model ND-110) the linearity of which was adjusted : using a précision pulse generator (ORNL Model Q1212-C). Response characteristics of enim- . .re;-. . na. . . mon. part . ...min ma . . .. ., ..: . . . · on ...or ---mori - - . PNL - AEC - OFFICIAL . ". - * 6 . more on h. 1 : these scintillator assemblies were studied with the aid of a linear accelerator designed and built for this purpose. The accelerator provided a beam of monoenergetic electrons with energies variable between zero and 60 keV. A schematic of this apparatus is... shown in Fig. l.' An alpha source of Americium-241 provided a reference peak which : was used to normalize the data from different scintillation assemblies. A point calibration of beta particles was not practical since the scintillator thicknesses (3 to 50 mg cm ) were not sufficient to provide a total absorption peak whereas the .., alpha particles were completely absorbed by 3 mg cm-211 giving a relatively sharp peak equivalent to 473 keV betas absorbed in NE-102 or 520 to 560 keV batas absorbed in anthracene depending on the condition of the surface of the particular : crystal. Figure 2 shows a typical alpha spectrum for anthracene. Figure 3 shows a comparison of the response of plastic and anthracene to surface-incident negatons. The response curve of the plastic exhibited considerably less curvature at the low energies, and the straight line fitted to the data points below: 60 keV extrapolated to the response at 624 keV within experimental error.... All of the. assemblies exhibited essentially the same response curve except in the case of several* obviously inferior anthracene crystals. The pulse height distributions for the mono- energetic negatons were distinguishable from the eles.tronic noise down to 5 keV for both types of scintillators. No corrections were made for the difference between the mean and the mode of the distribution caused by the asymmetry due to statistical fluctuations in the number of photoelectrons emitied by the photocathode when low- energy negatons were absorbed by the scintillotors. Figure 4 shows the response curve with additional points obtained using internal conversion electrons from 13/mBa, 20% Hg, and 14m, 14in. Figures 5 and 6 show the pulse-height distributions of 1:7 30 and 60 keV negatons on the two types of scintillators. : Two types of radioactive particles have been used in the development of this ** dosimetric method. Sulfur spheres were formed by dropping molten sulfur into a column 1 1/2-inches diameter by 36-inches long containing glycerol. The sulfur . r . ORNI - AEC - OFFICIAL - zli ORNL - AEC - OFFICIAL 11 . THE ti i was purified by four distillations in a nitrogen atmosphere. "The upper third of the glycerol was maintained at a temperature abot 120° C. The sulfur formed spheres. which solidified as they sank into the cooler portion of the glycerol. These spheres : were then activated in a neutron flux to produce 355 and 32p. Figure 7 shows the relative abundance of these two radionuclides after 20 minutes irradiation and the subsequent change in fractional activities with decay time. Sulfur-35 has a half- life of 87.1 days with a maximum beta energy of 167 keV while Phosphorus -32 has a half-life of 14.3 days with a maximum beta energy of 1.7 Mev. Consequently, the shift to lower energy of the emission spectrum will be reflected in dose measurements. The other type of radioactive particulate for which dose measurements were made was spherical uranium-dicarbide fuel beads activated in a neutron flux for 10 minutes to ., produce a mixed fission spectrum. A schematic of the apparatus used to obtain the data for determining the absorbed dose is shown in Fig. 8. The instrumentation was calibrated prior to each i dose measurement by positioning an alpha source of *'An 15 cm. from the scintillator ; face, evacuating the chamber to a pressure of less than 100 w Hg, and adjusting the amplifier gain so that the alpha peak was appearing in the proper channel of the analyzer. Whenever an absorber was to be used to obtain a depth-dose measurement 1 it was found necessary to place a similar absorber having a 1-mm aperture in the center over the scintillator face in order to approximate the light collection geometry for the dose measurement. Without this technique a calibration error of approximately 10% would occur. After calibration air was readmitted to the chamber, and the radioactive particie for which dose information was to be obtained was placed on the scintillatori axis with the appropriate absorber of mylar (polyethylene terephthalate) or polystyrene. The gross pulse -height spectrum was then recorded at a total counting rate of less than ; 104 per sec in order to minimize difficulties due to accidental.coincidences, phototube drift, and errors in the determination of total live time of the count. After the gross i pulse-height spectrum was recorded the scintillator assembly was removed, and a ....... iii. . : .-. . - re- : RNL - AEC - OFFICIAL .. . . - lucite cylinder with the same dimensions as the light pipe of the scintillator assembly was coupled to the phototuba. The source and absorbers were placed on the lucite cylinder in the same configuration as before, and a background was subtracted from the previously recorded grass spectrum. The background spectrum was quite significant for the scintillators with thicknesses below 75 microns. It included contributions from the fluorescence of the lucite, Cerenkov radiation, and electronic noise from the phototube and the analyzer. Of these the least significant was the electronic noise. Failure to subtract the composite background from the gross spectrum could result in errors of as much as 50% in the dose estimates for the thinnest scintillators.. ." DOSIMETRY CALCULATIONS After a net pulse-height spectrum was obtained the absorbed dose rate in rads per hour per millicurie was calculated using the relation BŠ Nc E . De Pexpl-10? - En el - - **" ...- . --..- --.---.... .ii. .. . . : B = conversion factor P = count period *exp(-7 1] = decay correction : No = number of counts in channel c. . Ec = energy associated with channel Fc = nonlinear correction factor . . :. . ...--. = ratio of stopping-power of tissue to scintillator Come siin...::... The nonlinear corrector factor, Fc, should be used whenever. a nonlinearity is observed in the pulse height versus energy response which results in a changing energy band width per channel, A computer program was written to perform the required mathe-' matical manipulations for the dose calculation. .com . .., indian ... . .. .. :"....io -..... INL - AEC - OFFICIAL * " ..... . ORNI - AEC - OFFICIAL . . , v m RESULTS orvo 7' 4 , Iiiii " . . . --..-ora....ma 1 .,-- . -- · ..- - Much information may be obtained from the scintillation method described. ..13 Every dose estimate. is derived from an energy spectrum which is plotted in graphical form by the computer pragram. Typical spectra are shown in Fig. 9 for a sulfur sphere using three Il-mm diameter scintillators of NE-102 with thicknesses of 405, 93, and 32 microns. If dose estimates for a radioactive particulate are obtained using a series of scintillators of the same diameter but different thicknesses an extrapolation interpre- : tation may be applied which yields a dose estimate for that diameter and zero thickness. In addition, if the dose estimates for zero thickness are plotted as a function of dia - meter the resulting curve may be extrapolated to zero diameter to give an estimate of the zere volume dose. Figures 10 and Il illustrate this procedure for two sulfur spheros of different diameters. Depth dose curves and data for the determination of dose change az a function of time for decaying sources may be obtained as previously described. The dose values if not extrapolated by the use of additional scintillation assemblies may be interpreted directly as the absorbed dose (or dose rate) averaged over the volume of the scintillator used for the measurement. Figure 12 shows a typical depth dose curve for a sulfur sphere obtained using a plastic scintillator 10-mm diameter and 93 microns thick. . Figure 13 shows a dose data obtained for a neutron-activated UC, sphere using an air ionization extrapolation chamber 123 with an 11-mm diameter electrode compared with the data from an anthracene dosimeter Il-mm diameter by 105 microns thick. The dose measurements for the anthracene were corrected to zero thickness by extrapolation using a series of Il-mm diameter scintillators with thickness ranging from 405 microns to 32 microns. The magnitude of this correction was +24%. V ITY ... . . .... ; :: To * 2- . . - - . 're minene. A { ir . .. . . - 4 .. . Il . 11 .....: intimida - 1 . - - -. , ORNIAEC - OFFICIAL .. - --..*... :-*.. con ... 11 . ORNL - AEC - OFFICIAL - - ..---- - - ..... - .. - ... ..-...--. :... - ... . .. -. • " ii . . - DISCUSSION It is evident that the dosimetric method described in this paper is feasible. It has high sensitivity and is useful for estimating the absorbed dose to small volumes of Houe using sources with activities in the range of 0.05 to 500 NCI. The largar activities are restricted to geometries which result in counting rates of less than 104 per second, however. This is a factor of 100 more sensitive than an air ionization extrapolation chamber of the Loevinger design. Careful measurements with the con- ventional extrapolation chamber may be more precise, but electrical field distortion limits the electrode spacing to about 500 p when one of the electrodes is a flexible mylar film. The scintillation method may be used with thicknesses to 30 u when using the total energy peak of a 5 Mev alpha source and as thin as 5 u If the alpha peak observed is recognized as corresponding to a fraction of the total energy absorbed. An accurate determination of the sensitive volumes of the scintillators is imperative be- cause this figure enters directly into the dose calculation. The thickness was measured with a Leitz microscope having a fine focus adjustment calibrated in microns. Another advantage of the scintillation method is the yield of spectral information associated with each dose determination. It is obvious that care must be used when evaluating a scintillation dosimeter when the output is in the form of anode current. Such a dosimeter may have limited use in determining relative dose values when the spectrum ; of the energy absorbed in the scintillator is qualitatively the same but could lead to erroneous conclusions if the spectrum changes and the low energy portion contributes. significantly to the dose. If anthracene is the scintillator being used then assuming a linear response can result in an error in the dose estimate of approximately 15% for a typical beta spectrum. There are limitations in this approach to experimeníai dosimetry. The primary : disadvantage involved with the use of NE-102 is the lesser amount of light collected ? r by the photocathode. Besides a lower inherent fluorescent efficiency than anthracene more light is lost at the interface of the scintillator and the lucite pipe. This is due - - - - .. .. ' within o .. ... - .. . i AU . . .. + . mm ORNL - AEC - OFFICIAL . 224 - . TA fo . - - 15 LAN min . a ":*.. - . . . . i! . . .. . ... ... ... . .. .. . ... ... to critical angle considerations resulting when the refractive index of the scintillator is greater than that of the light pipe. The refractive indices for NE-102 and lucite are 1.58 and 1.50, respectively. Polystyrene, u = 1.59, would be a better choice of light pipe were it not for the much higher fluorescence to ionizing particles. Anthracene has a higher specific fluorescence to ionizing particies and hence better : energy resolution, but the disadvantages outweigh the advantages for this type of dosimetry. The quality of the crystals is variable, and the edges tend to crumble upon machining. The crystals musi be joined to the lucite light pipes by an optical cement such as Canada balsam dissolved in a solvent. This makes the accurate determination of the sensitive volume of the scintillator quite difficult. The surface is subject to : deterioration in an oxygen atmosphere, and sublimation in a vacuum changes the response characteristics and reduces the volume of the scintillator. Plastic scintillators do not have these disadvantages, and may be successfully used in a dosimetric experie ment of this type provided care is taken in the construction of the assemblies, and a high quality photo tube is incorporated. There is room for improvement in the techniques described in this paper, and our efforts are being directed toward this end. Closer tolerance is needed for machins. ing the diameter of the scintillators, and more thicknesses are needed for each diameter in order to increase the reliability of the extrapolation curves and remove subjective judgments. We are investigating the difficulties involved in reducing the dimensiuns of the scintillators. These include calibration for thicknesses less than the range of the alpha particle and assessing the significance of the fraction of events resulting in an energy absorption of less thari 1000 ev per incident-negaton. This is the approximate amount of energy which on the average results in the emission of one photoelectron from the photocathode of the phototube." The determination of this fraction of incident-negatons whose energy loss within the scintillator is not detected is a function of the err ission spectrum, the dimensions of the scintillator and the source and the composition of the surrounding media. In the absence of an applicable theory perhaps the problem is amenable to a computer solution using Monte Carlo calculations... ... . .... .... . . '.. ---.,-.. - * -; . .. . . 7 . " . rever i .. : Podi 2 om ORNL - AEC - OFFICIAL - ; ? I! : . .' ." ri • 10 10 . .. . : OiNL - AEC - OFFICIAL .'' . ..-- - . . -- . - --' in.me REFERENCES 1. 1 Spencer, L. V., Phys. Rev., 98 (1955) 1959. ? : Hino, O. Jon Brownell, G. bon Radiation Desimesty, Academic Press, In New York (1956). 3. Loevinger, R., Radiology, 66 (1956) 55. . ::. 4 Olde, G. L., Brannen, E., Rev. Sci. Instr., 30 11(1959) 1014. 5 Brannen, E., Olde, G. L., Phys. Med. Biol., 5 (1960) 37. 16 Ittner, III, W. B., Ter-Progossian M., Nucleonics, 12 5(1954) 56. 7 Goodwin, P. N., Nucleonics, 14 9(1956) 120. ' :: 8. Sinclair, W. K., Grott, N. G., British J. Rad., 29 (1956) 29. 9 Nentwig, G., Kernenergie, 8 8(1965) 481. 10 Loevinger, R., Rev. Sci. Instr., 24 10(1953) 907. ::.".11 Birks, J. B., The Theory and Practice of Scintillation Counting, Pergamon Press, New York (1964). * 12 Wilkie, W. H., Birkhoff, R. D., "Measurement of Spectral Distribution of Positron Flux in an Infinite Copper Medium Containing CuO4, ORNL-3469 (1963). 913 Wright, G. T., J. Sci. Instr., 31 (1954) 462..! 14 Boyett, R. H., (Personal communication), Oak Ridge National Laboratory, Oak Ridge, Tennessee. ". -'--'- . - .. . . .. ... .. ....... . ... *.- --' .... - . -. . - . ..: :: i ; --.-. . : : ai.. ... . : .. . : ... . . ..wr.. ni .. .. ... .. ...-. . : -. - . ..- - :-:::-"??.... - . ORNL - AEC - OFFICIAL isso . ";!;:,:::!!:, .. NEUVENWI U thy . . 11 ... . LI .4. --. . .: . ; - . " - . - .. : . * . . . . . . ' . - - - .. . . .. ... . PHOTOTUBE - SCINTILLATOR :: MANIPULATOR SOURCE . - SECTIONS ACCELERATING - . 241Am a SOURCE TARGET CHAMBER . ELECTRON GUN - 1 . - - - . .. Lume - : : . . -. - vi... . -. :: 1 11 VACUUM PUMPS FIG. I SCHEMATIC OF APPARATUS .. . ·lid. . . 2 . - . - - .. 11 . . .. . 11" . . . . .. ... . . .. 1 . .. ...... + 7 'L. ... SUPPLY HIGH VOLTAGE TYPEWRITER ANALYZER MULTICHANNEL ..! - DISPLAY OSCILLOS COPE . SUPPLY MIGH VOLTAGE GUN SUPPLY ELECTRON . 4 . 2 ":" 1 5 . 1 . . . . . . " - - th: . Ut ORNL - DWG 86-7754 . .. 17* xm :.:. ::..:. :. : .3 -7 1 1- - .-. . --. ..--.- ;14-.4. rimetronn e - m a .. .. .. -.** :::;.:. - om I 2 :...: :: .: . - . . -.1- m .. . concom 13,- Srine w inne en vir nominis *... --- ORNL - AEC - OFFICIAL **. .* .. - Hi - OFFICIAL .-. . ? " comment - immirocinic.com .. . -- ...- . .. -*... Y: i. - ?..ni • . .' : :•:-,-,- . . . .. . . . .. . .. .. . ..." . NUMBER PER CHANNEL . . . . - . : .inn , det . : , ** . ia .. ... ... . . ' . ' ..:.:. : .: :.:.:.:. . .ri. .. .:. .. . . . .... 'i'... . . 50 .... . CHANNEL NUMBER . ALPHA SPECTRUM OF AMERICIUM-241 * 12.2 %. RESOLUTION . 7 7 • . ANTHRACENE i :.. .. ORNL-DWG. 66-7749 --, .:; **.. . . . '. - -, ...' ii . . . : . .-. - ... .s' . - .* nee - . . . . .-,. .....na . . . . . . . RNL - AEC - OFFICIAL . wwwmum '. .. -- . -., * , ; -, ...' - meni. ... •.• . ' - VN . . - .. - .:--- .-- . .. -O. .,. . ..... I ..... .. ... .. -- - - - - - . . I -0..". :... . ..... ...'- . -.. . . . PULSE HEIGHT (ARBITRARY UNITS ) :.: ... 7 70% .. . ini . .. : ... - - ... --... - - :-::--- 1 -- . . 9. - . .. ? . 2 ... ni .: ? :. . syin, 20. - . 1 SURFACE - INCIDENT NEGATONS FIG. 3 RESPONSE OF ANTHRACENE AND NE-102 TO ENERGY ( Ke V) O ANTHRACENE • NE-102 NORMALIZED AT E« 624 kev. 30. e-coracion - 40 --30 '' ' ' . EXTRAPOLATION FROM 624.k@V : :- :... ..... ......... ::'in : ... .. in • ORNL DWG 66-9746 .. :: . . .::: . - ..:* ... propose - r a - . .... . ........ ... ..". .. er... -- - ... - - . Di **** --. .. ..--. . ORNL-AEC - OFFICIAL . :ORNL - AEC - OFFICIAL ORNL, DWG 66-7744 ORNL - AEC - OFFICIAL : 80 - 137 m Dr 80- .. ģ . i - ..!!! . . & . . . PULSE HEIGHT (ARBITRARY UNITS ) & & H9-203 & Orgin-114m-114 K+L ..:.. LINE AR ACCELERATOR .. -. o 200000 ... . : 100 500 600 . 200 . 300 400 : ENERGY (KOV) :: FIG 4 RESPONSE OF ANTHRACENE TO SURFACE INCIDENT NEGATONS ÖRNL - AEC - OFFICIAL ORNL - AEC - OFFICIAL " .. . . . . ORNL - AEC - OFFICIAL # 2 *#* . .. - - ...... .:- - . ***** __ORNL DWG 66-7748 34.2% RESOLUTION 22.3% RESOLUTION . - . 60S ANTHRACENE . I. "... r . . 50 - . . . - - - - . - FREQUENCY - . , - ! . --In. .. .".. .. ::' 11 • ' L ... . . 30 keV 60 key .... nie . incons: 1 . . + . . . : 10 -70 ::: 20 30 40 50 60 PULSE HEIGHT ( ARBITRARY UNITS) .. 1 st no...".. ... - ...: . - ..... .. .... . int FIG.5 PULSE-HEIGHT DISTRIBUTIONS USING - ANTHRACENE, 7se - . *, UKRL - All - OFFICIAL ! :- - i 2 + L am . .. hod.or... ... . .... .. n . . . . - - - *** " . ' . i ORNL DWG 66-7747 52.5 % RESOLUTION 32.5 % RESOLUTION. .... - NE 102 . .. FREQUENCY **** .. 20+ : .. . .. - 1ot 30 kev [ ] 60 keV p. : ".. ::. ...... . . . 60 20 30 40 50 PULSE HEIGHT (ARBITRARY UNITS) : .: .:. . -- - . . TA SA . 1.OK ORNL DWG 66-7745 - . -- . ...... . - - - : : : ... i .8% . TOTAL .. .65 ACTIVITY :.:.. - 32p - - i. 10 20 50 60: . :,., 30 40 DECAY TIME (DAYS ) ... S ... ... . . . . . ., . 1. ..n . ': . . .. . . . . -. . FIG. 7 FRACTIONAL ACTIVITIES IN NEUTRON- ACTIVATED SULPHUR. . . .... im i .. ... ... . oni in .. : - . .. :: ani ipi. * ? - det ....... ... .. .r - AEC - Officie ? 1.. . . . . "': ORNL - AEC - OFFICIAL TV101330 - JIV-INDO -..... . ..." .. .... ...... . animo momen ...remonitor . ... .... . . inicio - - - - .. -.. -!" . - : .:.:. ~ :.com ::.. : on! .'--mvi .. .... - ore. ..... -.- ... ' . . .. .: : : : ORNL DWG. 66-1405 in criantini .. VACUUM CHAMBER :. A , . . . . '.. -SOURCE HOLDER . VACUUM PUMP OSCILLOSCOPE DISPLAY ->COLLIMATORS SCINTILLATION ASSEMBLY AMPLIFIER AND MULTICHANNEL ANALYZER PHOTOTUBE .. - .. . VACUUM GAGE :.:.. - ..: :. TYPEWRITER AND PUNCH READOUT - ... '. ; : :.. .. . . :: . . ... :, ..:::', i n : ... . 2 . For . ...... .... i HIGH VOLTAGE SUPPLY . 1 in FIG. 8 .... iii - SCHEMAT!C OF APPARATUS FOR DOSIMETRY !, 1 . .. . .. .. . . DRNI - AEC ONN-M2C-UHHILIAL . . 17 ... ... ..... . .." . . : . NUMBER / SECOND PER MILLICURIE FIG. 9 . ... . ....... ., T : . . -- $21 ... 250 THICKNESSES A-405, B-93,C-32 MICRONS BETA SPECTRA: USING NE-102, 11 mm DIAMETER BY ENERGY (keV) 375 i . . 1 500 . " į . . .... .a : 625 . .. . 5 --- ; ? ORNL-DWG_66-7970 -. - I . -.. .* :: f .. *.;.. - -- insan -...... : 750 i....iving , ... .. ...... . .......... , ist rm.:-::- ... . ... .:.p . - . ' -. : mar, armen i *.Si..; .." *'.*** . . .. ..... ... m - - .. ' • :* . Mwen var pa mo i o .'" . .. ... . .-.a i-. :. . . --- .. .. ORNL-AEC - OFFICIAL . OPICIAL .. . . .. .. .. ori.... :: ; : ;? : - . : mo.nw.consommeren, maar . ...:::: ORNL-DWG. 66-7756 :..- .in - . . U- . A " SULFUR SPHERE :.620 MICRONS DIAMETER 0.27 H CI 32p .. 0.27 Ci s |_ 7.2 mg/cm2 ABSORBER wo - wao na si ::*.! ja 1 mm DIA. .,"27" ." . . . .' . . .. .: ., ...:: . 2 mm DIA . A . ... ".1 :. .,: . . : - . . 3 MM DIA . : * RADS / HOUR PER MILLICURIE ic.co.rs . . . . . . 1 .. . . .. .. . . - ...-' 6 mm .- - -* wiem .: .. .. ... . : . 'll mm DIA. . ..i . - lavad . !! ..- ! ine 10 . ? 100 4 : 200 - DIAMETER (mm) 5 6 ? § 9 10 300 400 500 0. THICKNESS ( MICRONS) . . : . . jaremo . . . ... ...*** Login ---FIG. 10 EXTRAPOLATION CURVES FOR SULFUR SPHERE ::. 1-AEC - OFFICIAL . . - -- .. .... i .. Wah ONI - AC - ORNL-DWG. 66-7969 Ant . . . . . ... . 4 . . . . . . .. mm DIA :: SULFUR SPHERE 1.56 mm DIAMETER 0.59 H CH 32p. 1.0 y Ci sos 2 mm DIA 10.8 mg/cm2 ABSORBER . . 1. ................. :: .. V * .„ - . W *';' LIR *;** r ......... -0-3 mm DIA .. .. *. - - -... 6 mm DIA . . . . - . ., ,:: -- -. . - . ..' limm DIÀ... . . ... --- . . n . . i : 9 6- DIAMETER ( MILLIMETERS) 3 4 5 6 7 8 100 200 300 O-THICKNESS ( MICRONS ) 100 . : FIG. II. EXTRAPOLATION CURVES FOR SULFUR SPHERE ir, ORNI MAEC - OFFICIAL . ::- - - ORMI - AEC - OFFICIAL ..... . . . . . ORNL - AEC - OFFICIAL sic. . . .. .. ... - - - - - ..--.--.. --- RADS / HOUR PER MILLICURIE . . . TTTTTT TTTTTTTT . . . . . .:.:. ::. :*:. : :: . -.- 100. - ::::. ... ' '. .......p . . ... ; -...,:. ... 200 1 . . - FIG. 12. DEPTH-DOSE FOR SULPHUR SPHERE ABSORBER(mg/cm, ' : 4.2 Ci 355 1.5 H CI 32p . i 300 DEPTH DOSE SULFUR SPHERE 1.71.mm DIAMETER ..... :: H.. - 1 . ORNL DWG 66-7753 ' , . ..- -. . . . i . .. :. -...... . . - " - • ORNL - AEC - OFFICIAL : : :" - 2,, . ....... .. .. . .. . .. .. . .. . .. .. .. . . .. . . - - - .. . .. .. 1 . ." - - - . . Q.NL - AEC - OFFICIAL . . - : --.- -- 3 :?. : : .. :..::: : : - : --.-. . ..... .. . ; -.... ... . .. .:: . . .... RADS / HOUR PER FISSION .. ...?..:' 10 TTT met : . . . .. ......: Finis, *?". 11 !.. . . 2 . 1 ooilanden 2......... .. in ter FIG.13 ... CHAMBER AND A SCINTILLATION DOSIMETER. COMPARISON OF DOSE DATA FROM AN AIR IONIZATION h DECAY TIME IN MINUTES لللللللللللللللللللللللل 1 . 103. • IONIZATION EXTRAPOLATION CHAMBER : O ANTHRACENE SCINTILLATION DOSIMETER : - iu ORNL-DWG 66-7755R minazione -.. vn. Hon . . . ..-: .. . ... . --:-...-.. -- *** -- ... ::; -.-'.i. 2 -i. . .. - - .. .. -.... . .. '. ' . .. . :. - -messo iemand como: motim.cnndamento inti pis, me ringankan p : -*. . . .. .. ... . . ORNL - AEC - OFFICIAL ORNL - AEC - OFFICIAL END ...3 : DATE FILMED 12/ 21 / 66 ... -- . ... .... ni L .. we 19 * : . : . . . che 2017 r VE .