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Sample records for albedo dosimeter dvgn-01

  1. An investigation into the accuracy of the albedo dosimeter DVGN-01 in measuring personnel irradiation doses in the fields of neutron radiation at nuclear power installations of the joint institute for nuclear research

    NASA Astrophysics Data System (ADS)

    Beskrovnaya, L. G.; Goroshkova, E. A.; Mokrov, Yu. V.

    2010-05-01

    The calculated results of research into the accuracy of an individual albedo dosimeter DVGN-01 as it corresponds to the personal equivalent dose for neutrons H p (10) and to the effective dose for neutrons E eff in the neutron fields at Joint Institute for Nuclear Research Nuclear Power Installations (JNPI) upon different geometries of irradiations are presented. It has been shown that correction coefficients are required for the specific estimation of doses by the dosimeter. These coefficients were calculated using the energy sensitivity curve of the dosimeter and the known neutron spectra at JNPI. By using the correction factors, the uncertainties of both doses will not exceed the limits given to the personnel according to the standards.

  2. Use of a spherical albedo system for correcting the readings of albedo dosimeters in JINR phasotron neutron radiation fields

    NASA Astrophysics Data System (ADS)

    Mokrov, Yu. V.; Morozova, S. V.

    2014-03-01

    Results of calibrating a spherical albedo system in the radiation fields of a Pu-Be radionuclide neutron source are presented. It is shown that it can be used for correcting the readings of the DVGN-01 albedo dosimeter. The results of measurements with the system in JINR phasotron neutron fields for the purpose of correcting the DVGN-01 readings in these fields are given. The values of the correction factors for DVGN-01 albedo dosimeters when used in personnel neutron dosimetry (PD) on the JINR phasotron are determined.

  3. Comparative sensitivity study and reading correction of various albedo dosimeters in neutron fields on the U-400M accelerator

    NASA Astrophysics Data System (ADS)

    Mokrov, Yu. V.; Morozov, S. V.; Shchegolev, V. Yu.

    2013-03-01

    The sensitivities of three types of albedo dosimeters are experimentally studied in U-400M accelerator radiation fields in the experimental hall (one point) and behind its shielding (three points). It is shown that the ratios of the sensitivity of the albedo dosimeter (AD) and the combined personal dosimeter (CPD) used earlier at the Joint Institute for Nuclear Research (JINR) to the sensitivity of the DVGN-01 dosimeter are constant within 25%. This allows the AD and CPD sensitivities obtained earlier at the JINR facilities to be used for correcting readings of the DVGN-01 now used at JINR for personal radiation monitoring. Correction coefficients are found for DVGN-01 readings behind the U-400M shielding. This has allowed a more reliable correction coefficient to be established for the Flerov Laboratory of Nuclear Reactions (FLNR).

  4. An investigation into the sensitivity of various albedo neutron dosimeters aimed at correcting the readings

    NASA Astrophysics Data System (ADS)

    Alekseev, A. G.; Mokrov, Yu. V.; Morozova, S. V.

    2012-03-01

    The results of an experimental determination of the sensitivity of three types of individual neutron albedo dosimeters in neutron reference fields on the basis of radionuclide sources and at the top concrete shielding of the U-70 accelerator are presented. The results show that the ratios between the responses of the albedo dosimeters designed earlier at the Joint Institute for Nuclear Research (the albedo dosimeter (AD) and the multicomponent dosimeter (MD)) and the currently used DVGN-01 dosimeter are constant within 25% in a wide range of neutron energy. This fact makes it possible to use the results of measuring the AD and MD responses obtained earlier in neutron fields of nuclear-physical installations at the Joint Institute for Nuclear Research (JINR) for the correction of DVGN-01 dosimeter measurement results to apply it to personal radiation monitoring (PRM) at these installations. The correction factors for DVGN-01 measurement results are found and recommended to be used in PRM for most JINR installations.

  5. New technique to improve the accuracy of albedo neutron dosimeter evaluations

    NASA Astrophysics Data System (ADS)

    Hankins, D. E.

    The calibration factor for albedo neutron dosimeters varies greatly depending upon the energy of the neutrons in the exposure. Calibration results obtained over an eight-year period at each Lawrence Livermore National Laboratory facility where neutron exposure may occur were reviewed. A stronger relationship than expected was found between the ratio of the readings of the 9-in. to 3-in. spheres and the percent thermal. Readings from personnel and albedo badges were reviewed. The readings were consistent with the use of a calibration factor for the albedo dosimeter which varies with changes in the ratio of the personnel and albedo dosimeter TLD readings.

  6. Response of TLD-albedo and nuclear track dosimeters exposed to plutonium sources

    SciTech Connect

    Brackenbush, L.W.; Baumgartner, W.V.; Fix, J.J.

    1991-12-01

    Neutron dosimetry has been extensively studied at Hanford since the mid-1940s. At the present time, Hanford contractors use thermoluminescent dosimeter (TLD)-albedo dosimeters to record the neutron dose equivalent received by workers. The energy dependence of the TLD-albedo dosimeter has been recognized and documented since introduced at Hanford in 1964 and numerous studies have helped assure the accuracy of dosimeters. With the recent change in Hanford`s mission, there has been a significant decrease in the handling of plutonium tetrafluoride, and an increase in the handling of plutonium metal and plutonium oxide sources. This study was initiated to document the performance of the current Hanford TLD-albedo dosimeter under the low scatter conditions of the calibration laboratory and under the high scatter conditions in the work place under carefully controlled conditions at the Plutonium Finishing Plant (PFP). The neutron fields at the PFP facility were measured using a variety of instruments, including a multisphere spectrometer, tissue equivalent proportional counters, and specially calibrated rem meters. Various algorithms were used to evaluate the TLD-albedo dosimeters, and the results are given in this report. Using current algorithms, the dose equivalents evaluated for bare sources and sources with less than 2.5 cm (1 in.) of acrylic plastic shielding in high scatter conditions typical of glove box operations are reasonably accurate. Recently developed CR-39 track etch dosimeters (TEDs) were also exposed in the calibration laboratory and at the PFP. The results indicate that the TED dosimeters are quite accurate for both bare and moderated neutron sources. Until personnel dosimeter is available that incorporates a direct measure of the neutron dose to a person, technical uncertainties in the accuracy of the recorded data will continue.

  7. Response of TLD-albedo and nuclear track dosimeters exposed to plutonium sources

    SciTech Connect

    Brackenbush, L.W.; Baumgartner, W.V.; Fix, J.J.

    1991-12-01

    Neutron dosimetry has been extensively studied at Hanford since the mid-1940s. At the present time, Hanford contractors use thermoluminescent dosimeter (TLD)-albedo dosimeters to record the neutron dose equivalent received by workers. The energy dependence of the TLD-albedo dosimeter has been recognized and documented since introduced at Hanford in 1964 and numerous studies have helped assure the accuracy of dosimeters. With the recent change in Hanford's mission, there has been a significant decrease in the handling of plutonium tetrafluoride, and an increase in the handling of plutonium metal and plutonium oxide sources. This study was initiated to document the performance of the current Hanford TLD-albedo dosimeter under the low scatter conditions of the calibration laboratory and under the high scatter conditions in the work place under carefully controlled conditions at the Plutonium Finishing Plant (PFP). The neutron fields at the PFP facility were measured using a variety of instruments, including a multisphere spectrometer, tissue equivalent proportional counters, and specially calibrated rem meters. Various algorithms were used to evaluate the TLD-albedo dosimeters, and the results are given in this report. Using current algorithms, the dose equivalents evaluated for bare sources and sources with less than 2.5 cm (1 in.) of acrylic plastic shielding in high scatter conditions typical of glove box operations are reasonably accurate. Recently developed CR-39 track etch dosimeters (TEDs) were also exposed in the calibration laboratory and at the PFP. The results indicate that the TED dosimeters are quite accurate for both bare and moderated neutron sources. Until personnel dosimeter is available that incorporates a direct measure of the neutron dose to a person, technical uncertainties in the accuracy of the recorded data will continue.

  8. Simulation and test of a new albedo personal dosimeter for neutrons

    NASA Astrophysics Data System (ADS)

    Manfredotti, C.; Zanini, A.; Rollet, S.; Arman, G.

    1989-12-01

    A new personal dosimeter for neutrons, using three TLD 600s and one TLD 700 in a cadmium housing and detecting both incoming and albedo neutrons, has been designed, developed, tested and simulated by the code MORSE. Its response in the energy region between 10 -8 and 10 MeV is more similar to ICRP fluence-dose equivalent calibration factor behaviour with respect to previous albedo dosimeters, and particularly fast neutron tissue dose equivalents are less underestimated. Present data confirm that both accuracy and precision fulfil the International Commissions requests (NCR, NCRP, ANSI). Theory, simulation and experimental results obtained with a laboratory prototype are presented and discussed.

  9. Factors Affecting the Application of a Simple Ratio Technique for Spectral Correction of a Neutron Personnel Albedo Dosimeter.

    NASA Astrophysics Data System (ADS)

    Nelson, Robert Clifton

    To accurately assess the dose equivalent indicated by the albedo response of a neutron personnel dosimeter, additional knowledge is generally required in order to apply the needed spectral specific correction factors. This work was designed to evaluate the capability of the USAF Personnel Neutron Dosimeter to "self-calibrate" for moderated fission neutron spectra. The boron/bare ratio technique is compared with a simple theoretical model of the dosimeter and with the 23 cm (9 in) to 7.6 cm (3 in) Hankins' remmeter calibration technique. The overall goal was to provide dose-equivalent estimates comparable to those provided by the remmeter technique without the necessity of special on-site measurements. Although the boron/bare technique with the present dosimeter design fails to provide calibration factors needed for moderated fission neutron spectra, theoretical predictions based upon the model and the measured dosimeter responses are used to propose a dosimeter design which might fulfill the desired goal. Ancillary data gathered during the study are also presented.

  10. The Response of an Albedo Neutron Dosimeter to Moderated AmBe and 252(Cf) Neutron Sources.

    DTIC Science & Technology

    2014-09-26

    thermoluminescence detectors (TLD) are situated on each side of a cad- mium disc as illustrated in Fig. 1 (a). Since the Navy uses detectors held in dental...exposure, or loss or gain of stored thermoluminescence signal after exposure, were necessary. RESULTS AND DISCUSSION ii The results of the experiments to...Falk, "A Personnel Neutron Dosimeter Using Lithium Fluoride Thermoluminescent Dosim- eters," Report No. RFP-1581, Dow Chemical Co., Golden CO (1971

  11. Radiation dosimeters

    DOEpatents

    Hoelsher, James W.; Hegland, Joel E.; Braunlich, Peter F.; Tetzlaff, Wolfgang

    1992-01-01

    Radiation dosimeters and dosimeter badges. The dosimeter badges include first and second parts which are connected to join using a securement to produce a sealed area in which at least one dosimeter is held and protected. The badge parts are separated to expose the dosimeters to a stimulating laser beam used to read dose exposure information therefrom. The badge is constructed to allow automated disassembly and reassembly in a uniquely fitting relationship. An electronic memory is included to provide calibration and identification information used during reading of the dosimeter. Dosimeter mounts which reduce thermal heating requirements are shown. Dosimeter constructions and production methods using thin substrates and phosphor binder-layers applied thereto are also taught.

  12. Wristwatch dosimeter

    DOEpatents

    Wolf, M.A.; Waechter, D.A.; Umbarger, C.J.

    1986-08-26

    The disclosure is directed to a wristwatch dosimeter utilizing a CdTe detector, a microprocessor and an audio and/or visual alarm. The dosimeter is entirely housable with a conventional digital watch case having an additional aperture enabling the detector to receive radiation. 10 figs.

  13. Wristwatch dosimeter

    DOEpatents

    Wolf, Michael A.; Waechter, David A.; Umbarger, C. John

    1986-01-01

    The disclosure is directed to a wristwatch dosimeter utilizing a CdTe detector, a microprocessor and an audio and/or visual alarm. The dosimeter is entirely housable with a conventional digital watch case having an additional aperture enabling the detector to receive radiation.

  14. PERSONNEL DOSIMETER

    DOEpatents

    Birkhoff, R.D.; Hubbell, H.H. Jr.; Johnson, R.M.

    1959-02-24

    A personnel dosimeter sensitive to both gamma and beta radiation is described. The dosimeter consists of an electrical conductive cylinder having a wall thickness of substantially 7 milligrams per square centimeter and an electrode disposed axially within the cylinder and insulated therefrom to maintain a potential impressed between the electrode and the cylinder. A cylindrical perforated shield provided with a known percentage of void area is disposed concentrically about the cylinder. The shield is formed of a material which does not contain more than 15 percent of an element higher than atomic weight 13. The dose actually received is at most the gamma dose plus the beta dose indicated by discharge of the dosimeter divided by the known percentage.

  15. RADIATION DOSIMETER

    DOEpatents

    Balkwell, W.R. Jr.; Adams, G.D. Jr.

    1960-05-10

    An improvement was made in the determination of amounts of ionizing radiation, particularly low-energy beta particles of less than 1000 rad total dose by means of fluid-phase dosimeter employing a stabilized-- sensitized ferrous-ferric colorimetric system in a sulphuric acid medium. The improvement in the dosimeter consists of adding to the ferrous-ferric system in concentrations of 10/sub -2/ to 10/sup -4/M an organic compound having one or more carboxylic or equivalent groups, such compounds being capable of chelating or complexing the iron ions in the solution. Suitable sensitizing and stabilizing agents are benzoic, phthalic, salicylic, malonic, lactic, maleic, oxalic, citric, succinic, phenolic tartaric, acetic, and adipic acid, as well as other compounds which are added to the solution alone or in certain combinations. As in conventional fluid-phase dosimeters, the absorbed dosage is correlated with a corresponding change in optical density at particular wavelengths of the solution.

  16. Global Albedo

    Atmospheric Science Data Center

    2013-04-19

    ... the albedo. Bright surfaces have albedo near unity, and dark surfaces have albedo near zero. The DHR refers to the amount of spectral ... Atmospheric Science Data Center's  MISR Level 3 Imagery web site . The Multi-angle Imaging SpectroRadiometer observes the daylit ...

  17. Thermoluminescence dosimeter

    DOEpatents

    Zendle, Robert

    1985-01-01

    A thermoluminescence dosimeter having a very small rate of decline of sensitivity during subsequent uses after heating is disclosed. The dosimeter includes a detector crystal and a glass enclosure in which the detector crystal is located. The glass enclosure is air tight and is filled with a super dry inert fill gas. The inert fill gas is nonreactive with the detector crystal when the detector crystal is heated to thermoluminescence. The fill gas is selected from the group consisting of air, nitrogen, and argon, suitable admixed with 5 to 25 percent helium. The detector crystal consists essentially of calcium fluoride. The fill gas is preferably contained at a subatmospheric pressure in the glass enclosure.

  18. Thermoluminescence dosimeter

    DOEpatents

    Zendle, R.

    1983-11-03

    A thermoluminescence dosimeter having a very small rate of decline of sensitivity during subsequent uses after heating is disclosed. The dosimeter includes a detector crystal and a glass enclosure in which the detector crystal is located. The glass enclosure is air tight and is filled with a super dry inert fill gas. The inert fill gas is nonreactive with the detector crystal when the detector crystal is heated to thermoluminescence. The fill gas is selected from the group consisting of air, nitrogen, and argon, suitable admixed with 5 to 25 percent helium. The detector crystal consists essentially of calcium fluoride. The fill gas is preferably contained at a subatmospheric pressure in the glass enclosure.

  19. Composite material dosimeters

    DOEpatents

    Miller, Steven D.

    1996-01-01

    The present invention is a composite material containing a mix of dosimeter material powder and a polymer powder wherein the polymer is transparent to the photon emission of the dosimeter material powder. By mixing dosimeter material powder with polymer powder, less dosimeter material is needed compared to a monolithic dosimeter material chip. Interrogation is done with excitation by visible light.

  20. Intercomparison of high energy neutron personnel dosimeters

    SciTech Connect

    McDonald, J.C.; Akabani, G.; Loesch, R.M.

    1993-03-01

    An intercomparison of high-energy neutron personnel dosimeters was performed to evaluate the uniformity of the response characteristics of typical neutron dosimeters presently in use at US Department of Energy (DOE) accelerator facilities. It was necessary to perform an intercomparison because there are no national or international standards for high-energy neutron dosimetry. The testing that is presently under way for the Department of Energy Laboratory Accreditation Program (DOELAP) is limited to the use of neutron sources that range in energy from about 1 keV to 2 MeV. Therefore, the high-energy neutron dosimeters presently in use at DOE accelerator facilities are not being tested effectively. This intercomparison employed neutrons produced by the {sup 9}Be(p,n){sup 9}B interaction at the University of Washington cyclotron, using 50-MeV protons. The resulting neutron energy spectrum extended to a maximum of approximately 50-MeV, with a mean energy of about 20-MeV. Intercomparison results for currently used dosimeters, including Nuclear Type A (NTA) film, thermoluminescent dosimeter (TLD)-albedo, and track-etch dosimeters (TEDs), indicated a wide variation in response to identical doses of high-energy neutrons. Results of this study will be discussed along with a description of plans for future work.

  1. Operational comparison of bubble (super heated drop) dosimetry with routine albedo TLD for a selected group of Pu-238 workers at Los Alamos National Laboratory

    SciTech Connect

    Romero, L.L.; Hoffman, J.M.; Foltyn, E.M.; Buhl, T.E.

    1998-09-01

    Personnel neutron dosimetry continues to be a difficult science due to the lack of availability of robust passive dosimeters that exhibit tissue- or near-tissue- equivalent response. This paper is an operational study that compares the use of albedo thermoluminescent dosimeters with bubble dosimeters to determine whether bubble dosimeters do provide a useful daily ALARA tool that can yield measurements close to the dose-of-record. A group of workers at Los Alamos National Laboratory (LANL) working on the Radioisotopic Thermoelectric Generators (RTG) for the NASA Cassini space mission wore both bubble dosimeters and albedo dosimeters over a period from 1993 through 1996. The personal albedo dosimeter was processed on a monthly basis and used as the dose-of-record. The results of this study indicated that cumulative daily bubble dosimetry results agreed with whole-body albedo dosimetry results within about 37% on average.

  2. Global Albedo

    Atmospheric Science Data Center

    2013-04-19

    ... to one in the visible region of the solar spectrum whereas deep clean ocean water has an albedo that is close to zero. Five years of ... Atmospheric Science Data Center's  MISR Level 3 Imagery  web site. The Multi-angle Imaging SpectroRadiometer observes the daylit ...

  3. Fundamentals of gel dosimeters

    NASA Astrophysics Data System (ADS)

    McAuley, K. B.; Nasr, A. T.

    2013-06-01

    Fundamental chemical and physical phenomena that occur in Fricke gel dosimeters, polymer gel dosimeters, micelle gel dosimeters and genipin gel dosimeters are discussed. Fricke gel dosimeters are effective even though their radiation sensitivity depends on oxygen concentration. Oxygen contamination can cause severe problems in polymer gel dosimeters, even when THPC is used. Oxygen leakage must be prevented between manufacturing and irradiation of polymer gels, and internal calibration methods should be used so that contamination problems can be detected. Micelle gel dosimeters are promising due to their favourable diffusion properties. The introduction of micelles to gel dosimetry may open up new areas of dosimetry research wherein a range of water-insoluble radiochromic materials can be explored as reporter molecules.

  4. Pocket radiation dosimeter--dosimeter charger assembly

    DOEpatents

    Manning, Frank W.

    1984-01-01

    This invention is a novel pocket-type radiation dosimeter comprising an electrometric radiation dosimeter and a charging circuit therefor. The instrument is especially designed to be amenable to mass production, to have a long shelf life, and to be compact, lightweight, and usable by the layman. The dosimeter proper may be of conventional design. The charging circuit includes a shake-type electrostatic generator, a voltage doubler for integrating generator output voltages of one polarity, and a switch operated by an external permanent magnet.

  5. Pocket radiation dosimeter: dosimeter charger assembly

    DOEpatents

    Manning, F.W.

    1982-03-17

    This invention is a novel pocket-type radiation dosimeter comprising an electrometric radiation dosimeter and a charging circuit therefor. The instrument is especially designed to be amenable to mass production, to have a long shelf life, and to be compact, lightweight, and usable by the layman. The dosimeter proper may be of conventional design. The charging circuit includes a shake-type electrostatic generator, a voltage doubler for integrating generator output voltages of one polarity, and a switch operated by an external permanent magnet.

  6. Applicability of the polysulphone horizontal calibration to differently inclined dosimeters.

    PubMed

    Casale, Giuseppe R; Siani, Anna Maria; Diémoz, Henri; Kimlin, Michael G; Colosimo, Alfredo

    2012-01-01

    Polysulphone (PS) dosimetry has been a widely used technique for more than 30 years to quantify the erythemally effective UV dose received by anatomic sites (personal exposure). The calibration of PS dosimeters is an important issue as their spectral response is different from the erythemal action spectrum. It is performed exposing a set of PS dosimeters on a horizontal plane and measuring the UV doses received by dosimeters using calibrated spectroradiometers or radiometers. In this study, data collected during PS field campaigns (from 2004 to 2006), using horizontal and differently inclined dosimeters, were analyzed to provide some considerations on the transfer of the horizontal calibration to differently inclined dosimeters, as anatomic sites usually are. The role of sky conditions, of the angle of incidence between the sun and the normal to the slope, and of the type of surrounding surface on the calibration were investigated. It was concluded that PS horizontal calibrations apply to differently inclined dosimeters for incidence angles up to approximately 70° and for surfaces excluding ones with high albedo. Caution should be used in the application of horizontal calibrations for cases of high-incidence angle and/or high albedo surfaces.

  7. Wrist-watch dosimeter

    DOEpatents

    Wolf, M.A.; Waechter, D.A.; Umbarger, C.J.

    1982-04-16

    The disclosure is directed to a wristwatch dosimeter utilizing a CdTe detector, a microprocessor and an audio and/or visual alarm. The dosimeter is entirely housable within a conventional digital watch case having an additional aperture enabling the detector to receive radiation.

  8. DNA UVB dosimeters.

    PubMed

    Regan, J D; Yoshida, H

    1995-11-01

    DNA can be used to establish and monitor solar UVB dose. Since the principal molecular site of UVB damage in living organisms is DNA, it is logical to quantitate biologically effective solar UVB in DNA dosimeters. In addition to their particular sensitivity to UVB, DNA dosimeters have the advantage of a 2 pi geometry for collecting diffuse UVB radiation from all vectors, low cost, small size and portability, and no moving parts. Both molecular (cyclobutane pyrimidine dimers) and biological (bacteriophage plaques) dosimeters can be quantitated as endpoints to yield the total dose. DNA dosimeters integrate the absorbed energy of all UVB wavelengths (290-320 nm), are highly sensitive to the differential biological effectiveness of these wavelengths, and also integrate over time in hours, days or weeks of exposure. Our experiments have focused on the demonstration of DNA solar dosimeters in the ocean at various depths, the application of the dosimeters to the terrestrial monitoring of solar UVB under various conditions, and the development of a mini-dosimeter which uses nanograms of DNA and is assayed by polymerase chain reaction.

  9. Temporal dosimeter and method

    DOEpatents

    Warner, Benjamin P.; Lopez, Thomas A.

    2003-09-30

    The invention includes a temporal dosimeter. One dosimeter embodiment includes a housing that is opaque to visible light but transparent to ionizing radiation. The dosimeter also includes a sensor for recording dosages of ionizing radiation, a drive mechanism, a power source, and rotatable shields that work together to produce a compound aperture to unveil different portions of the sensor at different times to ionizing radiation. Another dosimeter embodiment includes a housing, a sensor, a shield with an aperture portion, and a linear actuator drive mechanism coupled to the sensor for moving the sensor past the aperture portion. The sensor turns as it moves past the aperture, tracing a timeline record of exposure to ionizing radiation along a helical path on the sensor.

  10. ULTRASONIC NEUTRON DOSIMETER

    DOEpatents

    Truell, R.; de Klerk, J.; Levy, P.W.

    1960-02-23

    A neutron dosimeter is described which utilizes ultrasonic waves in the megacycle region for determination of the extent of neutron damage in a borosilicate glass through ultrasonic wave velocity and attenuation measurements before and after damage.

  11. Dosimeter Design Program

    DTIC Science & Technology

    2015-01-05

    Mexico’s COSMIAC Center created a series of two different dosimeters for space flight. The first dosimeter was for low earth orbit and as such...to measure the radiation at various altitudes and orbital inclinations. By understanding the actual levels, this allows developers of large (and...unlimited    2    Low Earth Orbit (LEO). Satellites flown in LEO are often provided with natural protection from harmful effects normally found in the

  12. Magnetic field dosimeter development

    SciTech Connect

    Lemon, D.K.; Skorpik, J.R.; Eick, J.L.

    1980-09-01

    In recent years there has been increased concern over potential health hazards related to exposure of personnel to magnetic fields. If exposure standards are to be established, then a means for measuring magnetic field dose must be available. To meet this need, the Department of Energy has funded development of prototype dosimeters at the Battelle Pacific Northwest Laboratory. This manual reviews the principle of operation of the dosimeter and also contains step-by-step instructions for its operation.

  13. Response of the Hanford Combination Neutron Dosimeter in plutonium environments

    SciTech Connect

    Endres, A.W.; Brackenbush, L.W.; Baumgartner, W.V.

    1996-02-01

    This report documents response characteristics and the development of dose algorithms for the Hanford Combination Neutron Dosimeter (HCNO) implemented on January 1, 1995. The HCND was accredited under the U.S. Department of Energy (DOE) Laboratory Accreditation Program (DOELAP) during 1994. The HCND employs two neutron dose components consisting of (1) an albedo thermoluminescent dosimeter (TLD), and (2) a track-etch dosimeter (TED). Response characteristics of these two dosimeter components were measured under the low-scatter conditions of the Hanford 318 Building Calibration Laboratory, and under the high-scatter conditions in the workplace at the Plutonium Finishing Plant (PFP). The majority of personnel neutron dose at Hanford (currently and historically) occurs at the PFP. National Institute of Standards and Technology (NIST) traceable sources were used to characterize dosimeter response in the laboratory. At the PFP, neutron spectra and dose-measuring instruments, including a multisphere spectrometer, tissue equivalent proportional counters, and specially calibrated rem meters, were used to determine the neutron dose under several configurations from three different plutonium sources: (1) plutonium tetrafluoride, (2) plutonium metal, and (3) plutonium oxide. In addition, measurements were performed at many selected work locations. The HCNDs were included in all measurements. Comparison of dosimeter- and instrument-measured dose equivalents provided the data necessary to develop HCND dose algorithms and to assess the accuracy of estimated neutron dose under actual work conditions.

  14. Correcting the Response of an Albedo Neutron Dosimeter for Energy

    DTIC Science & Technology

    2007-01-01

    detectors; thermoluminescent dosemeters (TLDs), neutron, energy 16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON Dr. Gordon K. Riel a... Thermoluminescent Dosemeters (TLD).......................................................................................... 1 Detectors for Energy...SSBN ballistic missile submarine TLD thermoluminescent dosemeter USNA United States Naval Academy NSWCCD-63-TR–2006/36 1 Introduction The

  15. Length of stain dosimeter

    NASA Technical Reports Server (NTRS)

    Lueck, Dale E. (Inventor)

    1994-01-01

    Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

  16. Areal Average Albedo (AREALAVEALB)

    DOE Data Explorer

    Riihimaki, Laura; Marinovici, Cristina; Kassianov, Evgueni

    2008-01-01

    he Areal Averaged Albedo VAP yields areal averaged surface spectral albedo estimates from MFRSR measurements collected under fully overcast conditions via a simple one-line equation (Barnard et al., 2008), which links cloud optical depth, normalized cloud transmittance, asymmetry parameter, and areal averaged surface albedo under fully overcast conditions.

  17. Dose equivalent neutron dosimeter

    DOEpatents

    Griffith, Richard V.; Hankins, Dale E.; Tomasino, Luigi; Gomaa, Mohamed A. M.

    1983-01-01

    A neutron dosimeter is disclosed which provides a single measurements indicating the amount of potential biological damage resulting from the neutron exposure of the wearer, for a wide range of neutron energies. The dosimeter includes a detecting sheet of track etch detecting material such as a carbonate plastic, for detecting higher energy neutrons, and a radiator layer containing conversion material such as .sup.6 Li and .sup.10 B lying adjacent to the detecting sheet for converting moderate energy neutrons to alpha particles that produce tracks in the adjacent detecting sheet. The density of conversion material in the radiator layer is of an amount which is chosen so that the density of tracks produced in the detecting sheet is proportional to the biological damage done by neutrons, regardless of whether the tracks are produced as the result of moderate energy neutrons striking the radiator layer or as the result of higher energy neutrons striking the sheet of track etch material.

  18. Dosimeter Badge Detects Hydrazines

    NASA Technical Reports Server (NTRS)

    Young, Rebecca C.; Travis, Joshua C.; Moore, Gerald; Rose-Pehrsson, Susan; Carver, Patricia; Brenner, Karen

    1993-01-01

    Disposable dosimeter badge indicates approximate cumulative exposure to hydrazine or monomethyl hydrazine in air. Indication is change in colors of both paper tapes; one coated with para-N, N-dimethylaminobenzaldehyde. Colors of exposed tapes compared with colors on two preprinted color wheels to obtain estimate of exposure. Badges help minimize risks associated with exposure of personnel to hydrazine or monomethyl hydrazine, or suspected carcinogens. Also used as stationary monitors by taping them on walls or equipment at strategic locations.

  19. Earth's Reflection: Albedo

    ERIC Educational Resources Information Center

    Gillette, Brandon; Hamilton, Cheri

    2011-01-01

    When viewing objects of different colors, you might notice that some appear brighter than others. This is because light is reflected differently from various surfaces, depending on their physical properties. The word "albedo" is used to describe how reflective a surface is. The Earth-atmosphere has a combined albedo of about 30%, a number that is…

  20. Albedos. Final report

    SciTech Connect

    Hansen, F.V.

    1993-07-01

    The albedo of the earth's surface varies dramatically from values of about 3 to 4 percent for calm bodies of water up to about 55 percent for gypsum sands. This rather broad range of reflected incoming solar radiation presents difficulties when attempting to define an average albedo for terrain over a large region from locally determined values. The patchwork, or checkerboard, appearance of the earth's surface as viewed from above is the result of various human activities, such as agriculture, the proliferation of urban sprawl, and road building. Each of these variable appearing surfaces will have individual albedos, rendering any attempt to determine an a real albedo almost an impossibility on the mesoscale. However, a vast data base exists for microscale applications for individual acreages, for example. A compilation of these data is presented.... Albedo, Solar radiation, Crops, Urban areas, Land uses.

  1. Hanford personnel dosimeter supporting studies FY-1981

    SciTech Connect

    Not Available

    1982-08-01

    This report examined specific functional components of the routine external personnel dosimeter program at Hanford. Components studied included: dosimeter readout; dosimeter calibration; dosimeter field response; dose calibration algorithm; dosimeter design; and TLD chip acceptance procedures. Additional information is also presented regarding the dosimeter response to light- and medium-filtered x-rays, high energy photons and neutrons. This study was conducted to clarify certain data obtained during the FY-1980 studies.

  2. Observations of Surfzone Albedo

    NASA Astrophysics Data System (ADS)

    Sinnett, G.; Feddersen, F.

    2014-12-01

    The surfzone environment (where waves break) contains several unique and previously unconsidered processes that affect the heat budget. Entering short-wave radiation is a dominant term in both shelf and surfzone heat budgets. In contrast to the shelf, however, depth limited wave breaking in the surfzone generates spray, whitewater and suspended sediments, elevating the surface albedo (ratio of reflected to incident short-wave radiation). Elevated albedo reduces the level of solar short-wave radiation entering the water, potentially resulting in less heating. Additionally, surfzone water quality is often impacted by fecal bacteria contamination. As bacteria mortality is related to short-wave solar radiation, elevated surfzone albedo could reduce pathogen mortality, impacting human health. Albedo in the open ocean has been frequently studied and parameterizations often consider solar zenith angle, wind speed and ocean chlorophyll concentration, producing albedo values typically near 0.06. However, surfzone albedo observations have been extremely sparse, yet show depth limited wave breaking may increase the albedo by nearly a factor of 10 up to 0.5. Here, we present findings from a field study at the Scripps Institution of Oceanography pier to observe the affect of waves on surfzone albedo. Concurrent measurements were taken with a four-way radiometer (to measure both downwelling and upwelling short-wave and long wave radiation) mounted above the surfzone. A co-located GoPro camera was used to relate visual aspects of the surfzone to measured reflectance, and wave height and period were observed with a bottom mounted pressure sensor in 5 m water depth just outside the surfzone. Wind speed and direction were observed on the pier 10 m above the water surface. Here, we will examine the surfzone albedo dependence on surfzone parameters, such as wave height.

  3. Ionization chamber dosimeter

    DOEpatents

    Renner, Tim R.; Nyman, Mark A.; Stradtner, Ronald

    1991-01-01

    A method for fabricating an ion chamber dosimeter collecting array of the type utilizing plural discrete elements formed on a uniform collecting surface which includes forming a thin insulating layer over an aperture in a frame having surfaces, forming a predetermined pattern of through holes in the layer, plating both surfaces of the layer and simultaneously tilting and rotating the frame for uniform plate-through of the holes between surfaces. Aligned masking and patterned etching of the surfaces provides interconnects between the through holes and copper leads provided to external circuitry.

  4. PERSONNEL NEUTRON DOSIMETER

    DOEpatents

    Fitzgerald, J.J.; Detwiler, C.G. Jr.

    1960-05-24

    A description is given of a personnel neutron dosimeter capable of indicating the complete spectrum of the neutron dose received as well as the dose for each neutron energy range therein. The device consists of three sets of indium foils supported in an aluminum case. The first set consists of three foils of indium, the second set consists of a similar set of indium foils sandwiched between layers of cadmium, whereas the third set is similar to the second set but is sandwiched between layers of polyethylene. By analysis of all the foils the neutron spectrum and the total dose from neutrons of all energy levels can be ascertained.

  5. Pistol-shaped dosimeter charger

    DOEpatents

    Maples, Robert A.

    1985-01-01

    A pistol-shaped charger assembly clamps a cylindrical radiation dosimeter against one edge thereof. A triggerlike lever on the handgrip of the assembly is manually pivoted to actuate a piezoelectric current generator held in the handgrip and thereby charge the dosimeter.

  6. Pistol-shaped dosimeter charger

    DOEpatents

    Maples, R.A.

    A pistol-shaped charger assembly clamps a cylindrical radiation dosimeter against one edge thereof. A triggerlike lever on the handgrip of the assembly is manually pivoted to actuate a piezoelectric current generator held in the handgrip and thereby charge the dosimeter.

  7. A new radiochromic dosimeter film

    NASA Astrophysics Data System (ADS)

    Sidney, L. N.; Lynch, D. C.; Willet, P. S.

    By employing acid-sensitive leuco dyes in a chlorine-containing polymer matrix, a new radiochromic dosimeter film has been developed for gamma, electron beam, and ultraviolet radiation. These dosimeter films undergo a color change from colorless to royal blue, red fuchsia, or black, depending on dye selection, and have been characterized using a visible spectrophotometer over an absorbed dose range of 1 to 100 kGy. The primary features of the film are improved color stability before and after irradiation, whether stored in the dark or under artificial lights, and improved moisture resistance. The effects of absorbed dose, dose rate, and storage conditions on dosimeter performance are discussed. The dosimeter material may be produced as a free film or coated onto a transparent substrate and optionally backed with adhesive. Potential applications for these materials include gamma sterilization indicator films for food and medical products, electron beam dosimeters, and in-line radiation monitors for electron beam and ultraviolet processing.

  8. Asteroid sizes and albedos

    NASA Technical Reports Server (NTRS)

    Morrison, D.

    1977-01-01

    The radiometric method of determining asteroid diameters is described, and a synthesis of radiometric and polarimetric measurements of the diameters and geometric albedos of a total of 187 asteroids is presented. An analysis is offered of the size distributions of different albedo classes down to 80-km diameter for the entire main asteroid belt (2.0-3.5 AU). The distribution of albedos is found to be strongly bimodal, with mean albedos for the C and S group of 0.035 and 0.15, respectively. The C asteroids outnumber the S asteroids at all sizes and all values of semimajor axis, with the proportion of C asteroids increasing from a little over half inside 2.5 AU to more than 95% beyond 3.0 AU. Other aspects of the distribution of C, S, and M asteroids are discussed, and the total mass of main-belt asteroids larger than 70 km is estimated.

  9. The albedo of Titan

    NASA Technical Reports Server (NTRS)

    Lockwood, G. W.; Lutz, B. L.; Thompson, D. T.; Bus, E. S.

    1986-01-01

    Photometric observations of Titan since 1972 show a cyclical variation of about 10 percent. A minimum value of brightness and albedo apparently occurred in 1984. Spectrophotometric observations, made annualy since 1980 at 8 A resolution, 3295-8880 A, were used to derive the value p-asterisk = 0.156 + or - 0.010 for the integrated geometric albedo in 1984. Variations of the equivalent widths of spectral features were not seen.

  10. Greenland Glacier Albedo Variability

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The program for Arctic Regional Climate Assessment (PARCA) is a NASA-funded project with the prime goal of addressing the mass balance of the Greenland ice sheet. Since the formal initiation of the program in 1995, there has been a significant improvement in the estimates of the mass balance of the ice sheet. Results from this program reveal that the high-elevation regions of the ice sheet are approximately in balance, but the margins are thinning. Laser surveys reveal significant thinning along 70 percent of the ice sheet periphery below 2000 m elevations, and in at least one outlet glacier, Kangerdlugssuaq in southeast Greenland, thinning has been as much as 10 m/yr. This study examines the albedo variability in four outlet glaciers to help separate out the relative contributions of surface melting versus ice dynamics to the recent mass balance changes. Analysis of AVHRR Polar Pathfinder albedo shows that at the Petermann and Jakobshavn glaciers, there has been a negative trend in albedo at the glacier terminus from 1981 to 2000, whereas the Stor+strommen and Kangerdlugssuaq glaciers show slightly positive trends in albedo. These findings are consistent with recent observations of melt extent from passive microwave data which show more melt on the western side of Greenland and slightly less on the eastern side. Significance of albedo trends will depend on where and when the albedo changes occur. Since the majority of surface melt occurs in the shallow sloping western margin of the ice sheet where the shortwave radiation dominates the energy balance in summer (e.g. Jakobshavn region) this region will be more sensitive to changes in albedo than in regions where this is not the case. Near the Jakobshavn glacier, even larger changes in albedo have been observed, with decreases as much as 20 percent per decade.

  11. Albedo estimates for debris

    NASA Technical Reports Server (NTRS)

    Potter, A. E.; Henize, Karl G.; Talent, D. L.

    1989-01-01

    The albedo of upper-stage breakup debris is proposed as an accurate discriminator among the various possible causes of breakup, which encompass residual fuel explosions and hypervelocity particle impacts. The fragments from an impact are covered with a thin layer of soot deposited from the destruction of polymeric circuit boards, while pressure vessel explosion fragments can be expected to remain soot-free. Albedo also facilitates the interpretation of small-debris optical telescope measurements.

  12. Personnel electronic neutron dosimeter

    DOEpatents

    Falk, R.B.; Tyree, W.H.

    1982-03-03

    A personnel electronic dosimeter includes a neutron-proton and neutron-alpha converter for providing an electrical signal having a magnitude proportional to the energy of a detected proton or alpha particle produced from the converter, a pulse generator circuit for generating a pulse having a duration controlled by the weighed effect of the amplitude of the electrical signal, an oscillator enabled by the pulse for generating a train of clock pulses for a time dependent upon the pulse length, a counter for counting the clock pulses, and an indicator for providing a direct reading and aural alarm when the count indicates that the wearer has been exposed to a selected level of neutron dose equivalent.

  13. Personnel electronic neutron dosimeter

    DOEpatents

    Falk, Roger B.; Tyree, William H.

    1984-12-18

    A personnel electronic dosimeter includes a neutron-proton and neutron-alpha converter for providing an electrical signal having a magnitude proportional to the energy of a detected proton or alpha particle produced from the converter, a pulse generator circuit for generating a pulse having a duration controlled by the weighed effect of the amplitude of the electrical signal, an oscillator enabled by the pulse for generating a train of clock pulses for a time dependent upon the pulse length, a counter for counting the clock pulses, and an indicator for providing a direct reading and aural alarm when the count indicates that the wearer has been exposed to a selected level of neutron dose equivalent.

  14. Miniature spectrally selective dosimeter

    NASA Astrophysics Data System (ADS)

    Adams, R. R.; MacConochie, I. O.; Poole, B. D., Jr.

    1980-10-01

    A miniature spectrally selective dosimeter capable of measuring selected bandwidths of radiation exposure on small mobile areas is described. This is achieved by the combination of photovoltaic detectors, electrochemical integrators (E-cells) and filters in a small compact case which can be easily attached in close proximity to and substantially parallel to the surface being measured. In one embodiment two photovoltaic detectors, two E-cells, and three filters are packaged in a small case with attaching means consisting of a safety pin. In another embodiment, two detectors, one E-cell, three filters are packaged in a small case with attaching means consisting of a clip to clip over a side piece of an eye glass frame.

  15. Miniature spectrally selective dosimeter

    NASA Technical Reports Server (NTRS)

    Adams, R. R.; Macconochie, I. O.; Poole, B. D., Jr. (Inventor)

    1980-01-01

    A miniature spectrally selective dosimeter capable of measuring selected bandwidths of radiation exposure on small mobile areas is described. This is achieved by the combination of photovoltaic detectors, electrochemical integrators (E-cells) and filters in a small compact case which can be easily attached in close proximity to and substantially parallel to the surface being measured. In one embodiment two photovoltaic detectors, two E-cells, and three filters are packaged in a small case with attaching means consisting of a safety pin. In another embodiment, two detectors, one E-cell, three filters are packaged in a small case with attaching means consisting of a clip to clip over a side piece of an eye glass frame.

  16. The albedo of Earth

    NASA Astrophysics Data System (ADS)

    Stephens, Graeme L.; O'Brien, Denis; Webster, Peter J.; Pilewski, Peter; Kato, Seiji; Li, Jui-lin

    2015-03-01

    The fraction of the incoming solar energy scattered by Earth back to space is referred to as the planetary albedo. This reflected energy is a fundamental component of the Earth's energy balance, and the processes that govern its magnitude, distribution, and variability shape Earth's climate and climate change. We review our understanding of Earth's albedo as it has progressed to the current time and provide a global perspective of our understanding of the processes that define it. Joint analyses of surface solar flux data that are a complicated mix of measurements and model calculations with top-of-atmosphere (TOA) flux measurements from current orbiting satellites yield a number of surprising results including (i) the Northern and Southern Hemispheres (NH, SH) reflect the same amount of sunlight within ~ 0.2 W m-2. This symmetry is achieved by increased reflection from SH clouds offsetting precisely the greater reflection from the NH land masses. (ii) The albedo of Earth appears to be highly buffered on hemispheric and global scales as highlighted by both the hemispheric symmetry and a remarkably small interannual variability of reflected solar flux (~0.2% of the annual mean flux). We show how clouds provide the necessary degrees of freedom to modulate the Earth's albedo setting the hemispheric symmetry. We also show that current climate models lack this same degree of hemispheric symmetry and regulation by clouds. The relevance of this hemispheric symmetry to the heat transport across the equator is discussed.

  17. Brachytherapy dosimeter with silicon photomultipliers

    NASA Astrophysics Data System (ADS)

    Moutinho, L. M.; Castro, I. F. C.; Peralta, L.; Abreu, M. C.; Veloso, J. F. C. A.

    2015-07-01

    In-vivo and in-situ measurement of the radiation dose administered during brachytherapy faces several technical challenges, requiring a very compact, tissue-equivalent, linear and highly sensitive dosimeter, particularly in low-dose rate brachytherapy procedures, which use radioactive seeds with low energy and low dose deposition rate. In this work we present a scintillating optical fiber dosimeter composed of a flexible sensitive probe and a dedicated electronic readout system based on silicon photomultiplier photodetection, capable of operating both in pulse and current modes. The performance of the scintillating fiber optic dosimeter was evaluated in low energy regimes, using an X-ray tube operating at voltages of 40-50 kV and currents below 1 mA, to assess minimum dose response of the scintillating fiber. The dosimeter shows a linear response with dose and is capable of detecting mGy dose variations like an ionization chamber. Besides fulfilling all the requirements for a dosimeter in brachytherapy, the high sensitivity of this device makes it a suitable candidate for application in low-dose rate brachytherapy. According to Peralta and Rego [1], the BCF-10 and BCF-60 scintillating optical fibers used in dosimetry exhibit high variations in their sensitivity for photon beams in the 25-100 kVp energy range. Energy linearity for energies below 50 keV needs to be further investigated, using monochromatic X-ray photons.

  18. Spectrophotometry of PRESAGETM polyurethane dosimeters

    NASA Astrophysics Data System (ADS)

    Krstajic, N.; Wai, P.; Adamovics, J.; Doran, S.

    2004-01-01

    Preliminary optical density results on irradiated PRESAGE dosimeter are outlined in this article. PRESAGE is a solid dosimeter, based on a clear polyurethane combined with the leuco-dye leuco-malachite green. The purpose of these measurements was a) to obtain spectra for optimizing the wavelength of a new light source for the equipment and b) to obtain a dose-response relation. 10 PRESAGE cuvettes were given uniform doses from 0.1 to 40 Gy and later read out by spectrophotometer. The instrument used was CAMSPEC M350 Double Beam Spectrophotometer.

  19. Dose-equivalent neutron dosimeter

    DOEpatents

    Griffith, R.V.; Hankins, D.E.; Tomasino, L.; Gomaa, M.A.M.

    1981-01-07

    A neutron dosimeter is disclosed which provides a single measurement indicating the amount of potential biological damage resulting from the neutron exposure of the wearer, for a wide range of neutron energies. The dosimeter includes a detecting sheet of track etch detecting material such as a carbonate plastic, for detecting higher energy neutrons, and a radiator layer contaning conversion material such as /sup 6/Li and /sup 10/B lying adjacent to the detecting sheet for converting moderate energy neutrons to alpha particles that produce tracks in the adjacent detecting sheet.

  20. Application of the TLD albedo technique for monitoring and interpretation of neutron stray radiation fields

    NASA Astrophysics Data System (ADS)

    Piesch, E.; Burgkhardt, B.

    1980-09-01

    A single sphere albedo technique with TLD 600/TLD 700 detectors has been applied in neutron monitoring to calibrate albedo dosimeters and to interpret neutron stray radiation fields in terms of neutron dose equivalent separated for the energy groups below 0.4 eV, 0.4-10 keV and 10 keV-10 MeV, and Eeff for fast neutrons. The paper describes the technique for field and personnel monitoring under the aspect of an on-line computer program for data recording and processing.

  1. Miniature personal UV solar dosimeter

    NASA Technical Reports Server (NTRS)

    Adams, R. R.; Macconochie, I. O.; Poole, B. D., Jr.

    1981-01-01

    Small light-powered meter measures accumulated radiation in ultraviolet or other selected regions. Practical advantages are device's low cost, small size, accuracy, and adaptability to specific wave-band measurements. Medical applications include detection of skin cancer, vitamin D production, and jaundice. Dosimeter also measures sunlight for solar energy designs, agriculture and meteorology, and monitors stability of materials and environmental and occupational lighting.

  2. Surface albedo of cometary nucleus

    NASA Astrophysics Data System (ADS)

    Mukai, T.; Mukai, S.

    A variation of the albedo on the illuminated disk of a comet nucleus is estimated, taking into account the multiple reflection of incident light due to small scale roughness. The dependences of the average albedo over the illuminated disk on the degree of roughness and on the complex refractive index of the surface materials are examined. The variation estimates are compared with measurements of the nucleus albedo of Comet Halley (Reitsema et al., 1987).

  3. RADIATION DOSIMETER AND DOSIMETRIC METHODS

    DOEpatents

    Taplin, G.V.

    1958-10-28

    The determination of ionizing radiation by means of single fluid phase chemical dosimeters of the colorimetric type is presented. A single fluid composition is used consisting of a chlorinated hydrocarbon, an acidimetric dye, a normalizer and water. Suitable chlorinated hydrocarbons are carbon tetrachloride, chloroform, trichloroethylene, trichlorethane, ethylene dichioride and tetracbloroethylene. Suitable acidimetric indicator dyes are phenol red, bromcresol purple, and creosol red. Suitable normallzers are resorcinol, geraniol, meta cresol, alpha -tocopberol, and alpha -naphthol.

  4. Fast-neutron solid-state dosimeter

    DOEpatents

    Kecker, K.H.; Haywood, F.F.; Perdue, P.T.; Thorngate, J.H.

    1975-07-22

    This patent relates to an improved fast-neutron solid-state dosimeter that does not require separation of materials before it can be read out, that utilizes materials that do not melt or otherwise degrade at about 300$sup 0$C readout temperature, that provides a more efficient dosimeter, and that can be reused. The dosimeters are fabricated by intimately mixing a TL material, such as CaSO$sub 4$:Dy, with a powdered polyphenyl, such as p-sexiphenyl, and hot- pressing the mixture to form pellets, followed by out-gassing in a vacuum furnace at 150$sup 0$C prior to first use dosimeters. (auth)

  5. BETA-GAMMA PERSONNEL DOSIMETER

    DOEpatents

    Davis, D.M.; Gupton, E.D.; Hart, J.C.; Hull, A.P.

    1961-01-17

    A personnel dosimeter is offered which is sensitive to both gamma and soft beta radiations from all directions within a hemisphere. The device is in the shape of a small pill box which is worn on a worker-s wrist. The top and sides of the device are provided with 50 per cent void areas to give 50 per cent response to the beta rays and complete response to the gamma rays. The device is so constructed as to have a response which will approximate the dose received by the basal layer of the human epidermis.

  6. Portable neutron spectrometer and dosimeter

    DOEpatents

    Waechter, D.A.; Erkkila, B.H.; Vasilik, D.G.

    The disclosure relates to a battery operated neutron spectrometer/dosimeter utilizing a microprocessor, a built-in tissue equivalent LET neutron detector, and a 128-channel pulse height analyzer with integral liquid crystal display. The apparatus calculates doses and dose rates from neutrons incident on the detector and displays a spectrum of rad or rem as a function of keV per micron of equivalent tissue and also calculates and displays accumulated dose in millirads and millirem as well as neutron dose rates in millirads per hour and millirem per hour.

  7. Portable neutron spectrometer and dosimeter

    DOEpatents

    Waechter, David A.; Erkkila, Bruce H.; Vasilik, Dennis G.

    1985-01-01

    The disclosure relates to a battery operated neutron spectrometer/dosimeter utilizing a microprocessor, a built-in tissue equivalent LET neutron detector, and a 128-channel pulse height analyzer with integral liquid crystal display. The apparatus calculates doses and dose rates from neutrons incident on the detector and displays a spectrum of rad or rem as a function of keV per micron of equivalent tissue and also calculates and displays accumulated dose in millirads and millirem as well as neutron dose rates in millirads per hour and millirem per hour.

  8. The Ultraviolet Albedo of Ganymede

    NASA Technical Reports Server (NTRS)

    McGrath, Melissa; Hendrix, Amanda

    2013-01-01

    A large set of ultraviolet images of Ganymede have been acquired with the Hubble Space Telescope over the last 15 years. These images have been used almost exclusively to study Ganymede's stunning auroral emissions (Feldman et al. 2000; Eviatar et al. 2001; McGrath et al. 2004; Saur et al. 2011; McGrath et al. 2013), and even the most basic information about Ganymede's UV albedo has yet to be gleaned from these data. We will present a first-cut analysis of both disk-averaged and spatially-resolved UV albedos of Ganymede, with focus on the spatially-resolved Lyman-alpha albedo, which has never been considered previously for this satellite. Ganymede's visibly bright regions are known to be rich in water ice, while the visibly dark regions seem to be more carbonaceous (Carlson et al., 1996). At Lyman-alpha, these two species should also have very different albedo values.

  9. Snowmelt Increase Through Albedo Reduction

    DTIC Science & Technology

    1988-12-01

    Studies of Snow and Ice in Hyvarinen, T. and J. Lammasnieme (1987) Mountain Regions, International Association of Infrared measurement of free-water...snow-climate feedback, and the reduction in albedo by darkening agents has been studied and practiced extensively. Although much is known about albedo...sometimes CHARACTERISTICS gets in the way of man’s activities and must be removed as quickly as possible. When snow is Many studies of crystal growth in snow

  10. MISR Level 3 Albedo and Cloud Versioning

    Atmospheric Science Data Center

    2016-11-04

      MISR Level 3 Albedo and Cloud Versioning Component Global Albedo Product (CGAL) and Component Global Cloud Product (CGCL) - Daily, ...  CLOUD - Wind Vectors, Height Histogram Stage 1:  ALBEDO - Expansive, Restrictive and Local Albedo (except over snow and ice) ...

  11. Dosimeter and method for using the same

    DOEpatents

    Warner, Benjamin P.; Johns, Deidre M.

    2003-06-24

    A very sensitive dosimeter that detects ionizing radiation is described. The dosimeter includes a breakable sealed container. A solution of a reducing agent is inside the container. The dosimeter has an air-tight dosimeter body with a transparent portion and an opaque portion. The transparent portion includes a transparent chamber that holds the breakable container with the reducing agent. The opaque portion includes an opaque chamber that holds an emulsion of silver salt (AgX) selected from silver chloride, silver bromide, silver iodide, and combinations of them. A passageway in the dosimeter provides fluid communication between the transparent chamber and the opaque chamber. The dosimeter may also include a chemical pH indicator in the breakable container that provides a detectable color change to the solution for a pH of about 3-10. The invention also includes a method of detecting ionizing radiation that involves producing the dosimeter, breaking the breakable container, allowing the solution to flow through the passageway and contact the emulsion, detecting any color change in the solution and using the color change to determine a radiation dosage.

  12. Radiation Monitoring Equipment Dosimeter Experiment

    NASA Technical Reports Server (NTRS)

    Hardy, Kenneth A.; Golightly, Michael J.; Quam, William

    1992-01-01

    Spacecraft crews risk exposure to relatively high levels of ionizing radiation. This radiation may come from charged particles trapped in the Earth's magnetic fields, charged particles released by solar flare activity, galactic cosmic radiation, energetic photons and neutrons generated by interaction of these primary radiations with spacecraft and crew, and man-made sources (e.g., nuclear power generators). As missions are directed to higher radiation level orbits, viz., higher altitudes and inclinations, longer durations, and increased flight frequency, radiation exposure could well become a major factor for crew stay time and career lengths. To more accurately define the radiological exposure and risk to the crew, real-time radiation monitoring instrumentation, which is capable of identifying and measuring the various radiation components, must be flown. This presentation describes a radiation dosimeter instrument which was successfully flown on the Space Shuttle, the RME-3.

  13. Diffusion properties of a radiochromic hydrogel dosimeter

    NASA Astrophysics Data System (ADS)

    Skyt, P. S.; Kinnari, T. S.; Wahlstedt, I.; Yates, E. S.; Muren, L. P.; Petersen, J. B. B.; Balling, P.

    2013-06-01

    The aim of this study was to investigate the diffusion properties of a radiochromic hydrogel dosimeter based on leuco malachite green dye in a gelatine matrix. One half of each dosimeter was irradiated while the other half was left un-irradiated creating dose gradients over which diffusion could be investigated. Read-out of the optical response was performed with a high-resolution optical scanner. The dosimeters were found to exhibit a low diffusion rate but a high auto-oxidation level leading to a fading of the contrast in the dose response with time.

  14. Fiber-type dosimeter with improved illuminator

    DOEpatents

    Fox, Richard J.

    1987-01-01

    A single-piece, molded plastic, Cassigrainian-type condenser arrangement is incorporated in a tubular-shaped personal pocket dosimeter of the type which combines an ionization chamber with an optically-read fiber electrometer to provide improved illumination of the electrometer fiber. The condenser routes incoming light from one end of the dosimeter tubular housing around a central axis charging pin assembly and focuses the light at low angles to the axis so that it falls within the acceptance angle of the electrometer fiber objective lens viewed through an eyepiece lens disposed in the opposite end of the dosimeter. This results in improved fiber illumination and fiber image contrast.

  15. Fiber-type dosimeter with improved illuminator

    DOEpatents

    Fox, R.J.

    1985-12-23

    A single-piece, molded plastic, Cassigrainian-type condenser arrangement is incorporated in a tubular-shaped personal pocket dosimeter of the type which combines an ionization chamber with an optically-read fiber electrometer to provide improved illumination of the electrometer fiber. The condenser routes incoming light from one end of the dosimeter tubular housing around a central axis charging pin assembly and focuses the light at low angles to the axis so that it falls within the acceptance angle of the electrometer fiber objective lens viewed through an eyepiece lens disposed in the opposite end of the dosimeter. This results in improved fiber illumination and fiber image contrast.

  16. Performance criteria for dosimeter angular response

    SciTech Connect

    Roberson, P.L.; Fox, R. A.; Cummings, F. M.; McDonald, J. C.; Jones, K.L.

    1988-06-01

    This report provides criteria for evaluating the response of personnel dosimeters to radiation at nonperpendicular incidence. The US Department of Energy Laboratory Accreditation Program (DOELAP) ensures that dosimetry systems at DOE facilities meet acceptable standards for precision and accuracy. In the past, these standards were limited to tests for system variability, energy dependence, and level of detection. The proposed criteria will broaden the scope of DOELAP to include the angular response of personnel dosimeters. Because occupational exposures in the workplace are rarely due to radiation from only one direction, dosimeters must accurately assign individual dose equivalent from irradiation at any forward angle of incidence. Including an angular response criterion in DOELAP would improve the quality of personnel monitoring provided that the criterion is developed from appropriate dose quantities. This report provides guidance for assigning individual dose equivalents for radiation fields at nonperpendicular incidence to the dosimeter. 21 refs., 10 figs., 10 tabs.

  17. The shelf life of dyed polymethylmethacrylate dosimeters

    NASA Astrophysics Data System (ADS)

    Bett, R.; Watts, M. F.; Plested, M. E.

    2002-03-01

    The long-term stability of the radiation response of Harwell Red 4034 and Amber 3042 Perspex Dosimeters has been monitored for more than 15 years, and the resulting data used in the justification of their shelf-life specifications.

  18. Polymer gel dosimeter based on itaconic acid.

    PubMed

    Mattea, Facundo; Chacón, David; Vedelago, José; Valente, Mauro; Strumia, Miriam C

    2015-11-01

    A new polymeric dosimeter based on itaconic acid and N, N'-methylenebisacrylamide was studied. The preparation method, compositions of monomer and crosslinking agent and the presence of oxygen in the dosimetric system were analyzed. The resulting materials were irradiated with an X-ray tube at 158cGy/min, 226cGymin and 298cGy/min with doses up to 1000Gy. The dosimeters presented a linear response in the dose range 75-1000Gy, sensitivities of 0.037 1/Gyat 298cGy/min and an increase in the sensitivity with lower dose rates. One of the most relevant outcomes in this study was obtaining different monomer to crosslinker inclusion in the formed gel for the dosimeters where oxygen was purged during the preparation method. This effect has not been reported in other typical dosimeters and could be attributed to the large differences in the reactivity among these species.

  19. Albedo over rough snow and ice surfaces

    NASA Astrophysics Data System (ADS)

    Lhermitte, Stef; Abermann, Jakob; Kinnard, Christophe

    2014-05-01

    Surface albedo determines the shortwave radiation balance, arguably the largest energy balance component of snow and ice surfaces. Consequently, incorporation of the spatio-temporal variability of albedo is essential when assessing the surface energy balance of snow and ice surfaces. This can be done by using ground-based measurements or albedo data derived from remote sensing, or by modelling albedo based on radiative transfer models or empirically based parameterizations. One decisive factor when incorporating albedo data is the representativeness of surface albedo, certainly over rough surfaces where albedo measurements at a specific location (i.e., apparent albedo) can differ strongly from the material albedo or the true albedo (i.e., effective albedo) depending on the position of the sun/sensor and the surface roughness. This stresses the need for a comprehensive understanding of the effect of surface roughness on albedo and its impact when using albedo data for validation of remote sensing imagery, interpretation of automated weather station (AWS) radiation data or incorporation in energy balance models. To assess the effect of surface roughness on albedo an intra-surface radiative transfer (ISRT) model was combined with albedo measurements on a penitente field on Glaciar Tapado in the semi-arid Andes of Northern Chile. The ISRT model shows albedo reductions between 0.06 and 0.35 relative to flat surfaces with a uniform material albedo. The magnitude of these reductions primarily depends on the penitente geometry, but the shape and spatial variability of the material albedo also play a major role. Secondly, the ISRT model was used to reveal the effect of using apparent albedo to infer the effective albedo over a rough surface. This effect is especially strong for narrow penitentes, resulting in sampling biases up to ±0.05. The sampling biases are more pronounced when the sensor is low above the surface, but remain relatively constant throughout the day

  20. Albedo in the ATIC Experiment

    NASA Technical Reports Server (NTRS)

    Sokolskaya, N. V.; Adams, J. H., Jr.; Ahn, H. S.; Bashindzhagyan, G. L.; Batkov, K. E.; Case, G.; Christl, M.; Chang, J.; Fazely, A. R.; Ganel, O.; Six, N. Frank (Technical Monitor)

    2002-01-01

    ATIC(Advanced Thin Ionization Calorimeter) is a balloon borne experiment designed to measure the cosmic ray composition for elements from hydrogen to iron and their energy spectra from approx.50 GeV to near 100 TeV. It consists of a Si-matrix detector to determine the charge of a CR particle, a scintillator hodoscope for tracking, carbon interaction targets and a fully active BGO calorimeter. ATIC had its first 16-day flight from McMurdo, Antarctica from 28/12/2000 to 13/01/2000. The ATIC flight collected approximately 25 million events. To measure charge of primary particle in presence of radiation scattered back from the interaction and subsequent shower development in the calorimeter a charge detector must be a mosaic of small detector pads so that the pad containing the signal from the incident particle has no additional signal from albedo particles. Therefore the silicon matrix was built of 4480 individual silicon pads each 2 cm x 1.5 cm. The matrix consists of four planes of detectors and the active detector area, in these planes are partially overlapped to completely cover the aperture. The lateral and amplitude distributions of albedo signals in Si-matrix are analyzed for different primary nuclei and different energy deposits in BGO calorimeter. The greater part of albedo signals has Q near 1, where Q = square root of Amplitude(MIP). The albedo distribution exponentially decreases up to Q near 8. These high values are produced by slow protons and plans. There are also a small number of signals of Q > 8, mainly for heavy nucleus primaries. These signals are apparently generated by neutrons. The comparison of the experimental data and simulations with GEANT 3-21 code using QGSM generator for nucleus-nucleus interactions is presented.

  1. PNNL Results from 2009 Silene Criticality Accident Dosimeter Intercomparison Exercise

    SciTech Connect

    Hill, Robin L.; Conrady, Matthew M.

    2010-06-30

    This document reports the results of testing of the Hanford Personnel Nuclear Accident Dosimeter (PNAD) during a criticality accident dosimeter intercomparison exercise at the CEA Valduc Center on October 13, 14, and 15, 2009.

  2. Environmental dosimeter of the thermoluminescent type

    DOEpatents

    Eichner, F.N.; Kocher, L.F.

    1974-01-29

    A dosimeter for accurately monitoring normally low-energy radiation including a thermoluminescent CaF phosphor enclosed within a tantalum capsule is described. The tantalum acts as a filter to weaken the measured dose due to photons having energies below about 0.2 MeV. Tantalum end caps are maintained on the capsule body by a polyolefin sheath formed from heat-contractable tubing. After exposing the dosimeter to environmental radiation, it is placed in a shielded chamber for about 24 h and subsequently annealed at about 80 deg C to release radiation energy accumulated in low-temperature traps. The dosimeter is then disassembled and the phosphors photometrically read at temperatures about 50 deg C to determine the absorbed radiation dose. (Official Gazette)

  3. System for use with solid state dosimeter

    DOEpatents

    Miller, S.D.; McDonald, J.C.; Eichner, F.N.; Tomeraasen, P.L.

    1990-09-04

    The present invention constitutes a system for determining the amounts of ionizing radiation to which dosimeters using thermoluminescent materials have been exposed. In accordance with this system, the thermoluminescent materials which comprise the dosimeters are first cooled by contact with a cryogenic substance such as liquefied nitrogen. The thermoluminescent materials are then optically stimulated by exposure to ultraviolet light. Thereafter, the amounts of visible light emitted by the thermoluminescent materials are detected and counted as the materials are allowed to warm up to room temperature. The amounts of luminescence exhibited by the materials are related to radiation exposure and provide a sensitive measure of radiation dosage. It has been discovered that the above procedure is most effective when heavily doped thermoluminescent materials are used and that the procedure allows many useful plastic materials to now be employed in dosimeter constructions. 3 figs.

  4. System for use with solid state dosimeter

    DOEpatents

    Miller, Steven D.; McDonald, Joseph C.; Eichner, Fred N.; Tomeraasen, Paul L.

    1990-01-01

    The present invention constitutes a system for determining the amounts of ionizing radiation to which dosimeters using thermoluminescent materials have been exposed. In accordance with this system, the thermoluminescent materials which comprise the dosimeters are first cooled by contact with a cryogenic substance such as liquified nitrogen. The thermoluminescent materials are then optically stimulated by exposure to ultraviolet light. Thereafter, the amounts of visible light emitted by the thermoluminescent materials are detected and counted as the materials are allowed to warm up to room temperature. The amounts of luminescence exhibited by the materials are related to radiation exposure and provide a sensitive measure of radiation dosage. It has been discovered that the above procedure is most effective when heavily doped thermoluminescent materials are used and that the procedure allows many useful plastic materials to now be employed in dosimeter constructions.

  5. Solid state neutron dosimeter for space applications

    SciTech Connect

    Nagarkar, V.; Entine, G.; Stoppel, P.; Cirignano, L. ); Swinehart, P. )

    1992-08-01

    One of the most important contributions to the radiation exposure of astronauts engaged in space flight is the significant flux of high energy neutrons arising from both primary and secondary sources of ionizing radiation. Under NASA sponsorship, the authors are developing a solid state neutron sensor capable of being incorporated into a very compact, flight instrument to provide high quality real time measurement of this important radiation flux. The dosimeter uses a special, high neutron sensitivity, PIN diode that is insensitive t the other forms of ionizing radiation. The dosimeter will have the ability to measure and record neutron dose over a range of 50 microgray to tens of milligrays (5 millirads to several rads) over a flight of up to 30 days. the performance characteristics of the PIN diode with a detailed description of the overall dosimeter is presented. in this paper.

  6. Chemical Dosimeter Tube With Coaxial Sensing Rod

    NASA Technical Reports Server (NTRS)

    Lueck, Dale E.

    1993-01-01

    Improved length-of-stain (LOS) chemical dosimeter indicates total dose of chemical vapor in air. Made with rods and tubes of various diameters to obtain various sensitivities and dynamic ranges. Sensitivity larger and dose range smaller when more room for diffusion in gap between tube and rod. Offers greater resistance to changing of color of exposed dye back to color of unexposed condition, greater sensitivity, and higher degree of repeatability. Developed to measure doses of gaseous HCI, dosimeter modified by use of other dyes to indicate doses of other chemical vapors.

  7. Fiber optic dosimeter with silicon photomultipliers

    NASA Astrophysics Data System (ADS)

    Moutinho, L. M.; Castro, I. F.; Peralta, L.; Abreu, M. C.; Veloso, J. F. C. A.

    2014-08-01

    A small dimension, real-time readout dosimeter is desirable for specific applications in medical physics as for example, dose measurement in prostate brachytherapy. This particular radiotherapy procedure consists in the permanent deposition of low energy, low-dose and low-dose rate small sized radioactive seeds. We developed a scintillating fiber optic based dosimeter suitable for in-vivo, real-time low dose and low dose rate measurements. Due to the low scintillation light produced in the scintillating fiber, a high sensitive and high gain light detector is required. The Silicon Photomultipliers are an interesting option that allowed us to obtain good results in our studies.

  8. DEPRON dosimeter for ``Lomonosov'' satellite

    NASA Astrophysics Data System (ADS)

    Brilkov, Ivan; Vedenkin, Nikolay; Panasyuk, Mikhail; Amelyushkin, Aleksandr; Petrov, Vasily; Nechayev, Oleg; Benghin, Victor

    appearance of the instrument DEPRON (Dosimeter of Electrons, PROtons and Neutrons) was determined. DEPRON is intended for registration of the absorbed doses and linear energy transfer spectra for high-energy electrons, protons and nuclei of space radiation, as well as registration of thermal and slow neutrons. The experiment based on DEPRON instrument is aimed at the studies of the distribution of space radiation dose rate at high latitude paths in order to study the flight paths of perspective manned spacecraft. Present work provides a brief description of the DEPRON instrument, its calibration results and the structure of the output data.

  9. The Ultraviolet Albedo of Ganymede

    NASA Astrophysics Data System (ADS)

    McGrath, Melissa; Hendrix, A.

    2013-10-01

    A large set of ultraviolet images of Ganymede have been acquired with the Hubble Space Telescope over the last 15 years. These images have been used almost exclusively to study Ganymede’s stunning auroral emissions (Feldman et al. 2000; Eviatar et al. 2001; McGrath et al. 2004; Saur et al. 2011; McGrath et al. 2013), and even the most basic information about Ganymede’s UV albedo has yet to be gleaned from these data. We will present a first-cut analysis of both disk-averaged and spatially-resolved UV albedos of Ganymede, with focus on the spatially-resolved Lyman-alpha albedo, which has never been considered previously for this satellite. Ganymede's visibly bright regions are known to be rich in water ice, while the visibly dark regions seem to be more carbonaceous (Carlson et al., 1996). At Lyman-alpha, these two species should also have very different albedo values. References Carlson, R. and 39 co-authors, Near-infrared spectroscopy and spectral mapping of Jupiter and the Galilean satellites: Results from Galileo’s initial orbit, Science, 274, 385-388, 1996. Eviatar, A., D. F. Strobel, B. C. Wolven, P. D. Feldman, M. A. McGrath, and D. J. Williams, Excitation of the Ganymede ultraviolet aurora, Astrophys. J, 555, 1013-1019, 2001. Feldman, P. D., M. A. McGrath, D. F. Strobel, H. W. Moos, K. D. Retherford, and B. C. Wolven, HST/STIS imaging of ultraviolet aurora on Ganymede, Astrophys. J, 535, 1085-1090, 2000. McGrath M. A., Lellouch E., Strobel D. F., Feldman P. D., Johnson R. E., Satellite Atmospheres, Chapter 19 in Jupiter: The Planet, Satellites and Magnetosphere, ed. F. Bagenal, T. Dowling, W. McKinnon, Cambridge University Press, 2004. McGrath M. A., Jia, Xianzhe; Retherford, Kurt; Feldman, Paul D.; Strobel, Darrell F.; Saur, Joachim, Aurora on Ganymede, J. Geophys. Res., doi: 10.1002/jgra.50122, 2013. Saur, J., S. Duling, S., L. Roth, P. D. Feldman, D. F. Strobel, K. D. Retherford, M. A. McGrath, A. Wennmacher, American Geophysical Union, Fall Meeting

  10. Changes in Earth's albedo measured by satellite.

    PubMed

    Wielicki, Bruce A; Wong, Takmeng; Loeb, Norman; Minnis, Patrick; Priestley, Kory; Kandel, Robert

    2005-05-06

    NASA global satellite data provide observations of Earth's albedo, i.e., the fraction of incident solar radiation that is reflected back to space. The satellite data show that the last four years are within natural variability and fail to confirm the 6% relative increase in albedo inferred from observations of earthshine from the moon. Longer global satellite records will be required to discern climate trends in Earth's albedo.

  11. NOTE: Cell-phone interference with pocket dosimeters

    NASA Astrophysics Data System (ADS)

    Djajaputra, David; Nehru, Ramasamy; Bruch, Philip M.; Ayyangar, Komanduri M.; Raman, Natarajan V.; Enke, Charles A.

    2005-05-01

    Accurate reporting of personal dose is required by regulation for hospital personnel that work with radioactive material. Pocket dosimeters are commonly used for monitoring this personal dose. We show that operating a cell phone in the vicinity of a pocket dosimeter can introduce large and erroneous readings of the dosimeter. This note reports a systematic study of this electromagnetic interference. We found that simple practical measures are enough to mitigate this problem, such as increasing the distance between the cell phone and the dosimeter or shielding the dosimeter, while maintaining its sensitivity to ionizing radiation, by placing it inside a common anti-static bag.

  12. Compton effect thermally activated depolarization dosimeter

    DOEpatents

    Moran, Paul R.

    1978-01-01

    A dosimetry technique for high-energy gamma radiation or X-radiation employs the Compton effect in conjunction with radiation-induced thermally activated depolarization phenomena. A dielectric material is disposed between two electrodes which are electrically short circuited to produce a dosimeter which is then exposed to the gamma or X radiation. The gamma or X-radiation impinging on the dosimeter interacts with the dielectric material directly or with the metal composing the electrode to produce Compton electrons which are emitted preferentially in the direction in which the radiation was traveling. A portion of these electrons becomes trapped in the dielectric material, consequently inducing a stable electrical polarization in the dielectric material. Subsequent heating of the exposed dosimeter to the point of onset of ionic conductivity with the electrodes still shorted through an ammeter causes the dielectric material to depolarize, and the depolarization signal so emitted can be measured and is proportional to the dose of radiation received by the dosimeter.

  13. Response characteristics of selected personnel neutron dosimeters

    SciTech Connect

    McDonald, J.C.; Fix, J.J.; Hadley, R.T.; Holbrook, K.L.; Yoder, R.C.; Roberson, P.L.; Endres, G.W.R.; Nichols, L.L.; Schwartz, R.B.

    1983-09-01

    Performance characteristics of selected personnel neutron dosimeters in current use at Department of Energy (DOE) facilities were determined from their evaluation of neutron dose equivalent received after irradiations with specific neutron sources at either the National Bureau of Standards (NBS) or the Pacific Northwest Laboratory (PNL). The characteristics assessed included: lower detection level, energy response, precision and accuracy. It was found that when all of the laboratories employed a common set of calibrations, the overall accuracy was approximately +-20%, which is within uncertainty expected for these dosimeters. For doses above 80 mrem, the accuracy improved to better than 10% when a common calibration was used. Individual differences found in this study may reflect differences in calibration technique rather than differences in the dose rates of actual calibration standards. Second, at dose rates above 100 mrem, the precision for the best participants was generally below +-10% which is also within expected limits for these types of dosimeters. The poorest results had a standard deviation of about +-25%. At the lowest doses, which were sometimes below the lower detection limit, the precision often approached or exceeded +-100%. Third, the lower level of detection for free field /sup 252/Cf neutrons generally ranged between 20 and 50 mrem. Fourth, the energy dependence study provided a characterization of the response of the dosimeters to neutron energies far from the calibration energy. 11 references, 22 figures, 26 tables.

  14. Pen Ink as an Ultraviolet Dosimeter

    ERIC Educational Resources Information Center

    Downs, Nathan; Turner, Joanna; Parisi, Alfio; Spence, Jenny

    2008-01-01

    A technique for using highlighter ink as an ultraviolet dosimeter has been developed for use by secondary school students. The technique requires the students to measure the percentage of colour fading in ink drawn onto strips of paper that have been exposed to sunlight, which can be calibrated to measurements of the ultraviolet irradiance using…

  15. Analysis of nonstandard noise dosimeter microphone positions.

    PubMed

    Byrne, David C; Reeves, Efrem R

    2008-03-01

    This study was conducted as part of a project involving the evaluation of a new type of noise exposure monitoring paradigm. Laboratory tests were conducted to assess how "nonstandard" dosimeter microphones and microphone positions measured noise levels under different acoustical conditions (i.e., diffuse field and direct field). The data presented in this article reflect measurement differences due to microphone position and mounting/supporting structure only and are not an evaluation of any particular complete dosimeter system. To varying degrees, the results obtained with the dosimeter microphones used in this study differed from the reference results obtained in the unperturbed (subject absent) sound field with a precision (suitable for use in an ANSI Type 1 sound level meter) (1)/(2)-inch (12.7 mm) measurement microphone. Effects of dosimeter microphone placement in a diffuse field were found to be minor for most of the test microphones/locations, while direct field microphone placement effects were found to be quite large depending on the microphone position and supporting structure, sound source location, and noise spectrum.

  16. Underwater remote-reading dosimeter evaluation

    SciTech Connect

    Clow, H.E.; Emmons, G. )

    1985-01-01

    This paper reports on problems inherent in attempting to measure underwater dose rates and monitor and control diver exposures. At Connecticut Yankee, the authors had a specific procedure in effect to cover diving evolutions; however, the authors were not satisfied with the methods available to us for monitoring a diver's dose during a dive. The authors looked around and discovered that the ideal monitoring method was already at hand. In the past, the authors had successfully used the Xetex 503A Teledose system for high dose rate jobs under are variety of circumstances, but not underwater. The basic Teledose system consists of a base station and five individual electronic dosimeter/transmitters that can be worn by workers. The dosimeters are GM-tube types packaged in high-impact plastic or metal cases, each powered by a single 9-volt battery. The dosimeters do not have their own read-outs - instead, they transmit a coded pulse for each mR detected via a loop antenna to the base station, where the accumulated exposure for each of the five dosimeter units is displayed.

  17. Investigating hydrogel dosimeter decomposition by chemical methods

    NASA Astrophysics Data System (ADS)

    Jordan, Kevin

    2015-01-01

    The chemical oxidative decomposition of leucocrystal violet micelle hydrogel dosimeters was investigated using the reaction of ferrous ions with hydrogen peroxide or sodium bicarbonate with hydrogen peroxide. The second reaction is more effective at dye decomposition in gelatin hydrogels. Additional chemical analysis is required to determine the decomposition products.

  18. Calculation of albedos for neutrons and photons

    NASA Astrophysics Data System (ADS)

    Brockhoff, Ronald Carl

    2003-07-01

    The albedo concept is used to describe radiation that appears to be reflected from a surface, although in reality this reflected radiation is comprised of radiation that has entered the medium, and is subsequently scattered back through the surface. The albedo often offers a computationally simple alternative to estimate doses from radiation reflected from surfaces surrounding a streaming region. However, albedo data available prior to this study, are limited to relatively few source energies and reflecting media, and are based on obsolete and incomplete cross sections and response functions. The Monte Carlo code MCNP is applied in this study to calculate the differential photon and neutron dose albedos, along with the differential secondary-photon dose albedo, based on modern response functions and cross section data. Differential photon dose albedo data were calculated for source energies ranging from 0.1 to 10 MeV incident on slabs of concrete, iron, lead, and water. Differential neutron dose albedo data, and the associated differential secondary-photon dose albedo data, were calculated for source energy bands ranging from 0.1 to 10 MeV, and for thermal, Californium, and 14 MeV source spectra, incident on the same four reflecting media. The results indicate that (1) the approximation of the differential photon dose albedo proposed by Chilton and Huddleston usually deviates from the raw albedo data by less than 10% for source energies between 0.1 and 10.0 MeV, (2) the new 24-parameter approximation of the differential neutron dose albedo deviates from the raw albedo data by less than 10% for source energy bands between 0.1 and 10 MeV, and (3) the five-parameter approximation of the secondary-photon dose albedo deviates from the raw albedo data by less than 25% for source energies between 0.1 and 10 MeV. The differential dose albedo approximations obtained in this study are used to solve several example radiation transport problems, where the dose from reflected

  19. The temporal scale research of MODIS albedo product authenticity verification

    NASA Astrophysics Data System (ADS)

    Cao, Yongxing; Xue, Zhihang; Cheng, Hui; Xiong, Yajv; Chen, Yunping; Tong, Ling

    2016-06-01

    This study introduces a method that normalizes the inversed ETM+ albedo to the local solar noon albedo for the temporal scale of the MODIS albedo validation. Firstly, the statistical relation model between the surface albedo and the solar elevation angle was set up, and then deducing relationship between ETM+ albedo and the solar elevation angle, so the ETM+ albedo at local solar noon could be got. Secondly, the ground measurement albedo at the local solar noon was used to assess the inversed ETM+ albedo and the normalized albedo. The experiment results show that the method can effectively improve the accuracy of product certification.

  20. Exploring the dose response of radiochromic dosimeters

    NASA Astrophysics Data System (ADS)

    Skyt, P. S.; Wahlstedt, I.; Yates, E. S.; Muren, L. P.; Petersen, J. B. B.; Balling, P.

    2013-06-01

    The aim of this study was to explore the dose response of a newly developed radio-chromic hydrogel dosimeter based on leuco malachite green dye in a gelatine matrix. The original dosimeter composition was first investigated in terms of dose response and dose-rate dependence. In addition, the initiating compounds producing chlorine radicals were substituted with compounds producing fluorine radicals, oxygen-centered radicals, carbon-centered radicals and bromine radicals. Also the surfactant was substituted by other compounds of different molecular size and charge. The original composition gave a dose response of 3.5·10-3 Gy-1cm-1 at 6 Gy/min with a dose rate dependence giving a 27 % increase when decreasing the dose rate to 1 Gy/min. None of the substituted initiating components contributed to an increase in dose response while only one surfactant increased the dose response slightly.

  1. Performance Evaluation of a Colorimetric Hydrazine Dosimeter

    DTIC Science & Technology

    1994-06-16

    air has been developed. The passive badge consists of a dosimeter card containing a vanillin solution coated on a thin paper substrate. The active...patch consists of a thick cellulose substrate coated with a vanillin solution. When placed in a plastic sample holder attached to a personnel pump, up to...5 L/min can be drawn through the active badge substrate. Through a condensation reaction, vanillin reacts with hydrazine to form a colored product

  2. Radiological properties of normoxic polymer gel dosimeters

    SciTech Connect

    Venning, A.J.; Nitschke, K.N.; Keall, P.J.; Baldock, C.

    2005-04-01

    The radiological properties of the normoxic polymer gel dosimeters MAGIC, MAGAS, and MAGAT [methacrylic and ascorbic acid in gelatin initiated by copper; methacrylic acid gelatine gel with ascorbic acid; and methacrylic acid gelatine and tetrakis (hydroxymethyl) phosphonium chloride, respectively] have been investigated. The radiological water equivalence was determined by comparing the polymer gel macroscopic photon and electron interaction cross sections over the energy range from 10 keV to 20 MeV and by Monte Carlo modeling of depth doses. Normoxic polymer gel dosimeters have a high gelatine and monomer concentration and therefore mass density (kg m{sup -3}) up to 3.8% higher than water. This results in differences between the cross-section ratios of the normoxic polymer gels and water of up to 3% for the attenuation, energy absorption, and collision stopping power coefficient ratios through the Compton dominant energy range. The mass cross-section ratios were within 2% of water except for the mass attenuation and energy absorption coefficients ratios, which showed differences with water of up to 6% for energies less than 100 keV. Monte Carlo modeling was undertaken for the polymer gel dosimeters to model the electron and photon transport resulting from a 6 MV photon beam. The absolute percentage differences between gel and water were within 1% and the relative percentage differences were within 3.5%. The results show that the MAGAT gel formulation is the most radiological water equivalent of the normoxic polymer gel dosimeters investigated due to its lower mass density measurement compared with MAGAS and MAGIC gels.

  3. Hanford beta-gamma personnel dosimeter prototypes and evaluation

    SciTech Connect

    Fix, J.J.; Holbrook, K.L.; Soldat, K.L.

    1983-04-01

    Upgraded and modified Hanford dosimeter prototypes were evaluated for possible use at Hanford as a primary beta-gamma dosimeter. All prototypes were compatible with the current dosimeter card and holder design, as well as processing with the automated Hanford readers. Shallow- and deep-dose response was determined for selected prototypes using several beta sources, K-fluorescent x rays and filtered x-ray techniques. All prototypes included a neutron sensitive chip. A progressive evaluation of the performance of each of the upgrades to the current dosimeter is described. In general, the performance of the current dosimeter can be upgraded using individual chip sensitivity factors to improve precision and an improved algorithm to minimize bias. The performance of this dosimeter would be adequate to pass all categories of the ANSI N13.11 performance criteria for dosimeter procesors, provided calibration techniques compatible with irradiations adopted in the standard were conducted. The existing neutron capability of the dosimeter could be retained. Better dosimeter performance to beta-gamma radiation can be achieved by modifying the Hanford dosimeter so that four of the five chip positions are devoted to calculating these doses instead of the currently used two chip positions. A neutron sensitive chip was used in the 5th chip position, but all modified dosimeter prototypes would be incapable of discriminating between thermal and epithermal neutrons. An improved low energy beta response can be achieved for the current dosimeter and all prototypes considered by eliminating the security credential. Further improvement can be obtained by incorporating the 15-mil thick TLD-700 chips.

  4. Standard Procedure for Calibrating an Areal Calorimetry Based Dosimeter

    DTIC Science & Technology

    2015-05-01

    provided to assist in calibrating other dosimeters. 15. SUBJECT TERMS Millimeter waves, dosimeter, calorimeter, CLT, Carbon-loaded Teflon 16. SECURITY...Bioeffects Branch CL Center Left CLT Carbon-loaded Teflon CR Center Right GPIB General Purpose Interface Bus IR Infrared LC Lower Center...used carbon-loaded Teflon ® (CLT) as the radio frequency (RF) absorber for the dosimeter. The methodology presented will use CLT for the calibration

  5. Variability of albedo and utility of the MODIS albedo product in forested wetlands

    USGS Publications Warehouse

    Sumner, David M.; Wu, Qinglong; Pathak, Chandra S.

    2011-01-01

    Albedo was monitored over a two-year period (beginning April 2008) at three forested wetland sites in Florida, USA using up- and down-ward facing pyranometers. Water level, above and below land surface, is the primary control on the temporal variability of daily albedo. Relatively low reflectivity of water accounts for the observed reductions in albedo with increased inundation of the forest floor. Enhanced canopy shading of the forest floor was responsible for lower sensitivity of albedo to water level at the most dense forest site. At one site, the most dramatic reduction in daily albedo was observed during the inundation of a highly-reflective, calcareous periphyton-covered land surface. Satellite-based Moderate-Resolution Imaging Spectroradiometer (MODIS) estimates of albedo compare favorably with measured albedo. Use of MODIS albedo values in net radiation computations introduced a root mean squared error of less than 4.7 W/m2 and a mean, annual bias of less than 2.3 W/m2 (1.7%). These results suggest that MODIS-estimated albedo values can reliably be used to capture areal and temporal variations in albedo that are important to the surface energy balance.

  6. Radiation Dose from Lunar Neutron Albedo

    NASA Technical Reports Server (NTRS)

    Adams, J. H., Jr.; Bhattacharya, M.; Lin, Zi-Wei; Pendleton, G.

    2006-01-01

    The lunar neutron albedo from thermal energies to 8 MeV was measured on the Lunar Prospector Mission in 1998-1999. Using GEANT4 we have calculated the neutron albedo due to cosmic ray bombardment of the moon and found a good-agreement with the measured fast neutron spectra. We then calculated the total effective dose from neutron albedo of all energies, and made comparisons with the effective dose contributions from both galactic cosmic rays and solar particle events to be expected on the lunar surface.

  7. GAMMA AND X-RAY DOSIMETER AND DOSIMETRIC METHOD

    DOEpatents

    Taplin, G.V.; Douglas, C.H.; Sigoloff, S.C.

    1958-08-19

    An improvement in colorimetric gamma and x-ray dosimeter systems and a self-contained. hand carried dostmeter of the afore-mentioned type ts described. A novel point of the invention ltes in the addition of specific quantities of certain normalizing agents to the two phase chlorinated hydro-carbon-aqueous dyc colortmetric dosimeter to eliminate the after reaction and thereby extend the utility of such systein. The structure of the two phase colorimetric dosimeter tubes and the carrying case for the tubes of the portable dosimeter are unique features.

  8. The radius and albedo of Hyperion

    NASA Technical Reports Server (NTRS)

    Cruikshank, D. P.

    1979-01-01

    A measurement of the 20-micron thermal flux from Hyperion is reported, and the radius and surface geometric albedo of this outer satellite of Saturn are computed by the photometric/radiometric method. A corrected and normalized 20-micron thermal flux of 0.033 + or - 0.012 Jy is determined. A radius of 112 + or - 15 km and a surface geometric albedo of 0.47 + or - 0.11 are obtained by assuming values of unity for the phase integral, emissivity, and bolometric/visual geometric-albedo ratio. The sensitivity of the photometric/radiometric method to the assumed values of the parameters involved is discussed, and the results are compared with similar studies of Triton. It is concluded that neither Hyperion nor Triton appears to have a geometric albedo in the lower end of the distribution of small bodies in the solar system.

  9. Algebraic method for calculating a neutron albedo

    NASA Astrophysics Data System (ADS)

    Ignatovich, V. K.; Shabalin, E. P.

    2007-02-01

    A neutron albedo from arbitrary homogeneous and finely grained substances is examined on the basis of a new, algebraic, method. In the approximation of an isotropic distribution of incident and reflected neutrons, it is shown that, in the case of thermal neutrons, coherent scattering on individual particles of finely grained media increases only slightly the transport cross section, but, at a given wall thickness, it reduces the albedo because of a decrease in the density of the substance. A significant increase in the albedo is possible only for neutrons of wavelength on the order of dimensions of a powder grain. The angular distribution of reflected neutrons is discussed, and it is proven that a deviation of this distribution from an isotropic one does not lead to a change in the magnitude of the albedo.

  10. Angular dependence of a simple accident dosimeter

    SciTech Connect

    Devine, R. T.; Romero, L. L.; Olsher, R. H.

    2004-01-01

    A simple dosimeter made of a sulfur tablet, bare and cadmium covered indium foils and a cadmium covered copper foil has been modeled using MCNP5. Studies of the model without phantom or other confounding factors have shown that the cross sections and fluence-to-dose factors generated by the Monte Carlo method agree with those generated by analytic expressions for the high energy component. The threshold cross sections for the detectors on a phantom were calculated. The resulting doses assigned agree well with exposures made to three critical assemblies. In this study the angular dependence on a phantom is studied and compared with measurements taken on the GODIVA reactor. The dosimeter positions on the phantom are facing the source, on the back and the side. In previous papers the modeling of a simple dosimeter made of a sulfur tablet, bare and cadmium covered indium foils and a cadmium covered copper foil has been modeled using MCNP5. The conclusion made was that most of the neutron dose from criticality assemblies results from the high energy neutron fluences determined by the sulfur and indium detectors. The results using doses measured from the GODIVA, SHEBA, and bare and lead shielded SILENE reactors confirmed this. The angular dependence of an accident dosemeter is of interest in evaluating the exposure of personnel. To investigate this effect accident dosemeters were placed on a phantom and exposed to the GODIVA reactor at phantom orientations of 0{sup o}, 45{sup o}, 90{sup o}, 135{sup o}, and 180{sup o} to the assembly center line.

  11. Preliminary investigation and application of a novel deformable PRESAGE® dosimeter

    PubMed Central

    Juang, T; Newton, J; Das, S; Adamovics, J; Oldham, M

    2013-01-01

    Deformable 3D dosimeters have potential applications in validating deformable dose mapping algorithms. This study evaluates a novel deformable PRESAGE® dosimeter and its application toward validating the deformable algorithm employed by VelocityAI. The deformable PRESAGE® dosimeter exhibited a linear dose response with a sensitivity of 0.0032 ΔOD/(Gy/cm). Comparison of an experimental dosimeter irradiated with an MLC pencilbeam checkerboard pattern under lateral compression up to 27% to a non-deformed control dosimeter irradiated with the same pattern verified dose tracking under deformation. CTs of the experimental dosimeter prior to and during compression were exported into VelocityAI and used to map an Eclipse dose distribution calculated on the compressed dosimeter to its original shape. A comparison between the VelocityAI dose distribution and the distribution from the dosimeter showed field displacements up to 7.3 mm and up to a 175% difference in field dimensions. These results highlight the need for validating deformable dose mapping algorithms to ensure patient safety and quality of care. PMID:24454522

  12. Evaluation of a Colorimetric Personal Dosimeter for Nitrogen Oxide.

    ERIC Educational Resources Information Center

    Diamond, Philip

    A personal colorimetric dosimeter for nitrogen dioxide was developed. Tests were performed to determine the response of these strips to various concentrations of NO2. The dosimeter strips were satisfactory for approximate determinations of total exposure (concentration + time) of nitrogen dioxide. The total exposure was calculated in terms of time…

  13. A novel structure optical fiber radiation dosimeter for radiotherapy applications

    NASA Astrophysics Data System (ADS)

    Sun, Weimin; Qin, Zhuang; Ma, Yu; Zhao, Wenhui; Hu, Yaosheng; Zhang, Daxin; Chen, Ziyin; Lewis, Elfed

    2016-04-01

    An investigation into a novel in-vivo PMMA (polymethyl methacrylate) fiber-optic dosimeter to monitor the dose of ionizing radiation, both for instantaneous and integrating measurements, for radiotherapy applications is proposed. This fiber sensor is designed as an intracorporal X-ray ionizing sensor to enhance the curative effect of radiotherapy. The fiber-optic dosimeter is made in a PMMA fiber, whose core is micromachined to create a small diameter (0.25 to 0.5 mm) hole at one fiber end. An inorganic scintillating material, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) is chosen as the sensing material, because it can fluoresce on immediately under exposure of ionizing radiation (X-Rays or electron beam). This sensing material is filled and packaged in the small hole by epoxy resin adhesive. This kind of novel structure dosimeter shows high light coupling efficiency compared with other kind of inorganic scintillation dosimeter. This fiber-optic dosimeter shows good repeatability with a maximum deviation of 0.16%. The testing results of the fiber-optic dosimeter are perfectly proportional to the data of IC with R2 as 0.9999. In addition, the fiber sensor shows excellent isotropic in its radial angular dependence. All the experiments indicate that the fiber-optic dosimeter is properly used for patient in-vivo dosimeter such as brachytherapy applications or intraoperative radiation therapy.

  14. Laser readable thermoluminescent radiation dosimeters and methods for producing thereof

    DOEpatents

    Braunlich, P.F.; Tetzlaff, W.

    1989-04-25

    Thin layer thermoluminescent radiation dosimeters for use in laser readable dosimetry systems, and methods of fabricating such thin layer dosimeters are disclosed. The thin layer thermoluminescent radiation dosimeters include a thin substrate made from glass or other inorganic materials capable of withstanding high temperatures and high heating rates. A thin layer of a thermoluminescent phosphor material is heat bonded to the substrate using an inorganic binder such as glass. The dosimeters can be mounted in frames and cases for ease in handling. Methods of the invention include mixing a suitable phosphor composition and binder, both being in particulate or granular form. The mixture is then deposited onto a substrate such as by using mask printing techniques. The dosimeters are thereafter heated to fuse and bond the binder and phosphor to the substrate. 34 figs.

  15. Laser readable thermoluminescent radiation dosimeters and methods for producing thereof

    DOEpatents

    Braunlich, Peter F.; Tetzlaff, Wolfgang

    1989-01-01

    Thin layer thermoluminescent radiation dosimeters for use in laser readable dosimetry systems, and methods of fabricating such thin layer dosimeters. The thin layer thermoluminescent radiation dosimeters include a thin substrate made from glass or other inorganic materials capable of withstanding high temperatures and high heating rates. A thin layer of a thermoluminescent phoshphor material is heat bonded to the substrate using an inorganic binder such as glass. The dosimeters can be mounted in frames and cases for ease in handling. Methods of the invention include mixing a suitable phosphor composition and binder, both being in particulate or granular form. The mixture is then deposited onto a substrate such as by using mask printing techniques. The dosimeters are thereafter heated to fuse and bond the binder and phosphor to the substrate.

  16. SURFACE ALBEDO AND SPECTRAL VARIABILITY OF CERES

    SciTech Connect

    Li, Jian-Yang; Reddy, Vishnu; Corre, Lucille Le; Sykes, Mark V.; Prettyman, Thomas H.; Nathues, Andreas; Hoffmann, Martin; Schaefer, Michael; Izawa, Matthew R. M.; Cloutis, Edward A.; Carsenty, Uri; Jaumann, Ralf; Krohn, Katrin; Mottola, Stefano; Schröder, Stefan E.; Castillo-Rogez, Julie C.; Schenk, Paul; Williams, David A.; Smith, David E.; Zuber, Maria T.; and others

    2016-02-01

    Previous observations suggested that Ceres has active, but possibly sporadic, water outgassing as well as possibly varying spectral characteristics over a timescale of months. We used all available data of Ceres collected in the past three decades from the ground and the Hubble Space Telescope, as well as the newly acquired images by the Dawn  Framing Camera, to search for spectral and albedo variability on Ceres, on both a global scale and in local regions, particularly the bright spots inside the Occator crater, over timescales of a few months to decades. Our analysis has placed an upper limit on the possible temporal albedo variation on Ceres. Sporadic water vapor venting, or any possibly ongoing activity on Ceres, is not significant enough to change the albedo or the area of the bright features in the Occator crater by >15%, or the global albedo by >3% over the various timescales that we searched. Recently reported spectral slope variations can be explained by changing Sun–Ceres–Earth geometry. The active area on Ceres is less than 1 km{sup 2}, too small to cause global albedo and spectral variations detectable in our data. Impact ejecta due to impacting projectiles of tens of meters in size like those known to cause observable changes to the surface albedo on Asteroid Scheila cannot cause detectable albedo change on Ceres due to its relatively large size and strong gravity. The water vapor activity on Ceres is independent of Ceres’ heliocentric distance, ruling out the possibility of the comet-like sublimation process as a possible mechanism driving the activity.

  17. Gamma-ray Albedo of the Moon

    SciTech Connect

    Moskalenko, Igor V.; Porter, Troy A.

    2007-06-14

    We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma-rays from the Moon is very steep with an effective cutoff around 3 GeV (600 MeV for the inner part of the Moon disc). Since it is the only (almost) black spot in the gamma-ray sky, it provides a unique opportunity for calibration of gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The albedo flux depends on the incident CR spectrum which changes over the solar cycle. Therefore, it is possible to monitor the CR spectrum using the albedo gamma-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo -rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the GLAST LAT to monitor the CR spectrum near the Earth beyond the lifetime of PAMELA.

  18. 1987 Neutron and gamma personnel dosimeter intercomparison study using a D/sub 2/O-moderated /sup 252/Cf source

    SciTech Connect

    Swaja, R.E.; West, L.E.; Sims, C.S.; Welty, T.J.

    1989-05-01

    The thirteenth Personnel Dosimetry Intercomparison Study (i.e., PDIS 13) was conducted during April 1987 as a joint effort by Oak Ridge National Laboratory's (ORNL) Dosimetry Applications Research Group and the Southwest Radiation Calibration Center at the University of Arkansas. A total of 48 organizations (34 from the US and 14 from abroad) participated in PDIS 13. Participants submitted a total of 1,113 neutron and gamma dosimeters for this mixed field study. The dosimeters were transferred by mail and were handled by experimental personnel at ORNL and the University of Arkansas. The type of neutron dosimeter and the percentage of participants submitting that type are as follows: TLD-albedo (49%), direct interaction TLD (31%), CR-39 (17%), film (3%). The type of gamma dosimeter and the percentage of participants submitting that type are as follows: Li/sub 2/B/sub 4/O/sub 7/, alone or in combination with CaSO/sub 4/, (69%), /sup 7/LiF (28%), natural LiF (3%). Radiation exposures in PDIS 13 were limited to 0.5 and 1.5 mSv from /sup 252/Cf moderated by 15-cm of D/sub 2/O. Traditional exposures using the Health Physics Research Reactor (HPRR) were not possible due to the fact that all reactors at ORNL, including the HPRR, were shutdown by order of the Department of Energy at the time the intercomparison was performed. Planned exposures using a /sup 238/PuBe source were negated by a faulty timing mechanism. Based on accuracy and precision, direct interaction TLD dosimeters exhibited the best performance in PDIS 13 neutron measurements. They were followed, in order of best performance, by CR-39, TLD albedo, and film. The Li/sub 2/B/sub 4/O/sub 7/ type TLD dosimeters exhibited the best performance in PDIS 13 gamma measurements. They were followed by natural LiF, /sup 7/LiF, and film. 12 refs., 1 fig., 5 tabs.

  19. System albedo as sensed by satellites - Its definition and variability

    NASA Technical Reports Server (NTRS)

    Hughes, N. A.; Henderson-Sellers, A.

    1982-01-01

    System albedo, an important climatological and environmental parameter, is considered. Some of the problems and assumptions involved in evaluating albedo from satellite data are discussed. Clear-sky and cloud albedos over the United Kingdom and parts of northwest Europe are treated. Consideration is given to the spectral, temporal, and spatial variations and the effect of averaging. The implications of these results for those using and archiving albedo values and for future monitoring of system albedo are discussed. Normalization is of especial importance since this correction alters many albedo values. The pronounced difference in spectral albedo of the two visible channels reemphasizes the problem of attempting to calculate integrated albedo values from meteorological satellite data. The assumption of isotropic reflection is seen to be invalid, hindering the computation of accurate albedo values.

  20. SU-E-T-265: Presage Thin Sheet Dosimeter Characterization

    SciTech Connect

    Dumas, M; Rakowski, J

    2014-06-01

    Purpose: To quantify the sensitivity and stability of the Presage dosimeter in sheet form for different concentrations of chemicals and for a diverse range of clinical photon energies. Methods: Presage polymer dosimeters are formulated to investigate and optimize their sensitivity and stability. The dosimeter is composed of clear polyurethane base, leucomalachite green reporting dye, and bromoform radical initiator in 1mm thick sheets. The chemicals are well mixed together, cast in an aluminum mold, and left to cure at 60 psi for a minimum of 2 days. Dosimeter response will be characterized at multiple energies including Co-60, 6 MV, 15 MV, 50 kVp, and 250 kVp. The dosimeters are read by an Epson 10000 XL scanner at 800 dpi, 2{sup 16} bit depth. Red component images are analyzed with ImageJ. Results: Analysis of optical density verse dose for Co-60 energies indicates that the bromoform containing Presage was able to quantify dose from 0 to 300 Gy, with saturation beyond 300 Gy. Initial results show two regions of linear response, 0–100 Gy and 150–300 Gy. The 150–300 Gy region has a sensitivity of 0.0024 net OD/Gy. Further results on other energies are still in progress. Conclusions: This work shows the potential for use of thin sheets of Presage dosimeter as a dosimeter capable of being analyzed with a flatbed scanner.

  1. Light scattering in optical CT scanning of Presage dosimeters

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Adamovics, J.; Cheeseborough, J. C.; Chao, K. S.; Wuu, C. S.

    2010-11-01

    The intensity of the scattered light from the Presage dosimeters was measured using a Thorlabs PM100D optical power meter (Thorlabs Inc, Newton, NJ) with an optical sensor of 1 mm diameter sensitive area. Five Presage dosimeters were made as cylinders of 15.2 cm, 10 cm, 4 cm diameters and irradiated with 6 MV photons using a Varian Clinac 2100EX. Each dosimeter was put into the scanning tank of an OCTOPUS" optical CT scanner (MGS Research Inc, Madison, CT) filled with a refractive index matching liquid. A laser diode was positioned at one side of the water tank to generate a stationary laser beam of 0.8 mm width. On the other side of the tank, an in-house manufactured positioning system was used to move the optical sensor in the direction perpendicular to the outgoing laser beam from the dosimeters at an increment of 1 mm. The amount of scattered photons was found to be more than 1% of the primary light signal within 2 mm from the laser beam but decreases sharply with increasing off-axis distance. The intensity of the scattered light increases with increasing light attenuations and/or absorptions in the dosimeters. The scattered light at the same off-axis distance was weaker for dosimeters of larger diameters and for larger detector-to-dosimeter distances. Methods for minimizing the effect of the light scattering in different types of optical CT scanners are discussed.

  2. SU-E-T-749: Thorough Calibration of MOSFET Dosimeters

    SciTech Connect

    Plenkovich, D; Thomas, J

    2015-06-15

    Purpose: To improve the accuracy of the MOSFET calibration procedure by performing the measurement several times and calculating the average value of the calibration factor for various photon and electron energies. Methods: The output of three photon and six electron beams of Varian Trilogy linear accelerator SN 5878 was calibrated. Five reinforced standard sensitivity MOSFET dosimeters were placed in the calibration jig and connected to the Reader Module. As the backscatter material was used 7 cm of Virtual Water. The MOSFET dosimeters were covered with 1.5 cm thick bolus for the regular and SRS 6 MV beams, 3 cm bolus for 15 MV beam, 1.5 cm bolus for 6 MeV electron beam, and 2 cm bolus for the electron energies of 9, 12, 15, 18, and 22 MeV. The dosimeters were exposed to 100 MU, and the calibration factor was determined using the mobileMOSFET software. To improve the accuracy of calibration, this procedure was repeated ten times and the calibration factors were averaged. Results: As the number of calibrations was increasing the variability of calibration factors of different dosimeters was decreasing. After ten calibrations, the calibration factors for all five dosimeters were within 1% of one another for all energies, except 6 MV SRS photons and 6 MeV electrons, for which the variability was 2%. Conclusions: The described process results in calibration factors which are almost independent of modality or energy. Once calibrated, the dosimeters may be used for in-vivo dosimetry or for daily verification of the beam output. Measurement of the radiation dose under bolus and scatter to the eye are examples of frequent use of calibrated MOSFET dosimeters. The calibration factor determined for full build-up is used under these circumstances. To the best of our knowledge, such thorough procedure for calibrating MOSFET dosimeters has not been reported previously. Best Medical Canada provided MOSFET dosimeters for this project.

  3. The ultraviolet continuum albedo of Uranus

    SciTech Connect

    Cochran, W.D.; Wagener, R.; Caldwell, J.; Fricke, K.H. New York State Univ., Stony Brook York Univ., Toronto Bonn Universitaet )

    1990-01-01

    A radiative transfer code explicitly treating the Raman scattering of solar protons by H{sub 2} is presently used to analyze the Uranus geometric albedo in the 2000-5000 A range. The Baines and Bergstralh (1986) baseline model used reproduces the geometric albedo peak produced by Raman scattering filling of solar absorption line cores, but is found to be excessively bright for wavelengths below 2400 A. This discrepancy is resolvable through inclusion of an absorbing stratospheric haze layer, and results are thereby obtained which are consistent with the Pollack et al. (1987) model, in which aerosols are generated stratospherically through photochemical effects on hydrocarbons. 20 refs.

  4. The diameter and albedo of 1943 Anteros

    NASA Technical Reports Server (NTRS)

    Veeder, G. J.; Tedesco, E. F.; Tholen, D. J.; Tokunaga, A.; Matthews, K.; Neugebauer, G.; Soifer, B. T.; Kowal, C.

    1981-01-01

    The results of broadband visual and infrared photometry of the Apollo-Amor asteroid 1943 Anteros during its 1980 apparition are reported. By means of a radiometric model, a diameter of 2.3 + or - 0.2 km and a visual geometric albedo of 0.13 + or - 0.03 is calculated. The albedo and reflectance spectrum of Anteros imply that it is a type S asteroid. Thus, Anteros may have a silicate surface similar to other Apollo-Amor asteroids as well as some stony-iron meteorites.

  5. Ground albedo neutrons produced by cosmic radiations

    NASA Astrophysics Data System (ADS)

    Kodama, M.

    1983-05-01

    Day-to-day variations of cosmic-ray-produced neutron fluxes near the earth's ground surface are measured by using three sets of paraffin-moderated BF3 counters, which are installed in different locations, 3 m above ground, ground level, and 20 cm under ground. Neutron flux decreases observed by these counters when snowcover exists show that there are upward-moving neutrons, that is, ground albedo neutron near the ground surface. The amount of albedo neutrons is estimated to be about 40 percent of total neutron flux in the energy range 1-10 to the 6th eV.

  6. The determination of surface albedo from meteorological satellites

    NASA Technical Reports Server (NTRS)

    Johnson, W. T.

    1977-01-01

    A surface albedo was determined from visible data collected by the NOAA-4 polar orbiting meteorological satellite. To filter out the major cause of atmospheric reflectivity, namely clouds, techniques were developed and applied to the data resulting in a map of global surface albedo. Neglecting spurious surface albedos for regions with persistent cloud cover, sun glint effects, insufficient reflected light and, at this time, some unresolved influences, the surface albedos retrieved from satellite data closely matched those of a global surface albedo map produced from surface and aircraft measurements and from characteristic albedos for land type and land use.

  7. Guidelines for the calibration of personnel dosimeters

    SciTech Connect

    Roberson, P.L.; Holbrook, K.L.

    1984-01-01

    This guide describes minimum acceptable performance levels for personnel dosimetry systems used at Department of Energy (DOE) facilities. The goal is to improve both the quality of radiological calibrations and the methods of comparing reported occupational doses between DOE facilities. Reference calibration techniques are defined. A standard for evaluation of personnel dosimetry systems and recommended design parameters for personnel dosimeters are also included. Approximate intervals for the radiation energies for which these guidelines are appropriate are 15 keV to 2 MeV for photons; above 0.3 MeV for beta particles; and 1 keV to 2 MeV for neutrons. An analysis of ANSI N13.11 was completed using performance evaluations of selected personnel dosimetry systems in use at DOE facilities. The results of this analysis are incorporated in the guidelines.

  8. Dosimeter for monitoring vapors and aerosols of organic compounds

    DOEpatents

    Vo-Dinh, Tuan

    1987-01-01

    A dosimeter is provided for collecting and detecting vapors and aerosols of organic compounds. The dosimeter comprises a lightweight, passive device that can be conveniently worn by a person as a badge or placed at a stationary location. The dosimeter includes a sample collector comprising a porous web treated with a chemical for inducing molecular displacement and enhancing phosphorescence. Compounds are collected onto the web by molecular diffusion. The web also serves as the sample medium for detecting the compounds by a room temperature phosphorescence technique.

  9. Dosimeter for monitoring vapors and aerosols of organic compounds

    DOEpatents

    Vo-Dinh, T.

    1987-07-14

    A dosimeter is provided for collecting and detecting vapors and aerosols of organic compounds. The dosimeter comprises a lightweight, passive device that can be conveniently worn by a person as a badge or placed at a stationary location. The dosimeter includes a sample collector comprising a porous web treated with a chemical for inducing molecular displacement and enhancing phosphorescence. Compounds are collected onto the web by molecular diffusion. The web also serves as the sample medium for detecting the compounds by a room temperature phosphorescence technique. 7 figs.

  10. A new dosimeter formulation for deformable 3D dose verification

    NASA Astrophysics Data System (ADS)

    Høye, E. M.; Skyt, P. S.; Yates, E. S.; Muren, L. P.; Petersen, J. B. B.; Balling, P.

    2015-01-01

    We present the characteristics of a new silicone-based radiochromic dosimeter containing the leuco-malachite green (LMG) dye. The dose response as well as the dose-rate and photon-energy dependence of the dosimeter were characterized. To optimise the dose response, different concentrations of the chemical components were investigated. The dose response was found to decrease exponentially as a function of time after irradiation. A cylindrical dosimeter was produced and irradiated with a volumetric modulated arc therapy plan; the standard deviation between measured and calculated dose was 5% of the total dose.

  11. Personal noise dosimeters: accuracy and reliability in varied settings.

    PubMed

    Cook-Cunningham, Sheri Lynn

    2014-01-01

    This study investigated the accuracy, reliability, and characteristics of three brands of personal noise dosimeters (N = 7 units) in both pink noise (PN) environments and natural environments (NEs) through the acquisition of decibel readings, Leq readings and noise doses. Acquisition periods included repeated PN conditions, choir room rehearsals and participant (N = 3) Leq and noise dosages procured during a day in the life of a music student. Among primary results: (a) All dosimeters exhibited very strong positive correlations for PN measurements across all instruments; (b) all dosimeters were within the recommended American National Standard Institute (ANSI) SI.25-1991 standard of ±2 dB (A) of a reference measurement; and (c) all dosimeters were within the recommended ANSI SI.25-1991 standard of ±2 dB (A) when compared with each other. Results were discussed in terms of using personal noise dosimeters within hearing conservation and research contexts and recommendations for future research. Personal noise dosimeters were studied within the contexts of PN environments and NEs (choral classroom and the day in the life of collegiate music students). This quantitative study was a non-experimental correlation design. Three brands of personal noise dosimeters (Cirrus doseBadge, Quest Edge Eg5 and Etymotic ER200D) were tested in two environments, a PN setting and a natural setting. There were two conditions within each environment. In the PN environment condition one, each dosimeter was tested individually in comparison with two reference measuring devices (Ivie and Easera) while PN was generated by a Whites Instrument PN Tube. In condition two, the PN procedures were replicated for longer periods while all dosimeters measured the sound levels simultaneously. In the NE condition one, all dosimeters were placed side by side on a music stand and recorded sound levels of choir rehearsals over a 7-h rehearsal period. In NE, condition two noise levels were measured during

  12. Albedo of a Dissipating Snow Cover.

    NASA Astrophysics Data System (ADS)

    Robinson, David A.; Kukla, George

    1984-12-01

    Albedos of surfaces covered with 50 cm of fresh dry snow following a major U.S. East Coast storm on 11-12 February 1983 ranged from 0.20 over a mixed coniferous forest to 0.80 over open farmland. As the snow cover dissipated, albedo decreased in a quasi-linear fashion over forests. It dropped rapidly at first, then slowly, over shrubland; while the opposite was observed over farmland.Following the melt, the albedo of snowfree surfaces ranged from 0.07 over a predominantly wet peat field to 0.20 over a field covered with corn stubble and yellow grass. The difference between snow-covered and snowfree albedo was 0.72 over the peaty field and 0.10 over the mixed forest.Visible band (0.28-0.69 m) reflectivities of snow-covered fields and shrubland were higher than those in the near-infrared (0.69-2.80 m), whereas the opposite was true over mixed coniferous forests. Visible and near-infrared reflectivities were approximately equal over deciduous forests.Data were collected in a series of low-altitude flights between 10 February and 24 March 1984 in northern New Jersey and southeastern New York with Eppley hemispheric pyranometers mounted on the wingtip of a Cessna 172 aircraft.

  13. Albedo Accuracy Impact On Evapotranspiration Estimation

    NASA Astrophysics Data System (ADS)

    Mattar, C.; Franch, B.; Sobrino, J. A.; Corbari, C.; Jimenez-Munoz, J. C.; Olivera, L.; Skerbaba, D.; Soria, G.; Oltra-Carrio, R.; Julien, Y.; Manchini, M.

    2013-12-01

    In this work, we analyze the influence of estimating the land surface albedo directly from the surface reflectance or through the BRDF integration in the estimation of energy balance components such as the net radiation, latent and heat flux and consequently in the land surface evapotranspiration. To this end, we processed remote sensing and in-situ meteorological data measured at the agricultural test site of Barrax in the framework of Earth Observation: optical Data calibration and Information eXtraction (EODIX) project. Remote sensing images were acquisitioned for different View Zenith Angles (VZA) by the Airborne Hyperspectral Images (AHS). Results have shown that albedo estimations derived from BRDF model present stability through every image while albedo estimations using single reflectance presented high variation depending on the VZA. The highest difference was observed in the backward scattering direction along the hot spot region obtaining a RMSE of 0.11 through the AHS image which implied a relative error of 65%. This work has analyzed the error committed by many evapotranspiration studies that assume the surface as Lambertian and estimate the albedo from a surface reflectance weighted average.

  14. Albedos of Centaurs, Jovian Trojans and Hildas

    NASA Astrophysics Data System (ADS)

    Romanishin, William

    2017-01-01

    I present optical V band albedo distributions for samples of outer solar system minor bodies including Centaurs, Jovian Trojans and Hildas. Diameters come almost entirely from the NEOWISE catalog (Mainzer etal 2016- Planetary Data System). Optical photometry (H values) for about 2/3 of the approximately 2700 objects studied are from PanStarrrs (Veres et al 2015 Icarus 261, 34). The PanStarrs optical photometry is supplemented by H values from JPL Horizons (corrected to be on the same photometric system as the PanStarrs data) for the objects in the NEOWISE catalog that are not in the PanStarrs catalog. I compare the albedo distributions of various pairs of subsamples using the nonparametric Wilcoxon rank sum test. Examples of potentially interesting comparisons include: (1) the median L5 Trojan cloud albedo is about 10% darker than that of the L4 cloud at a high level of statistical significance and (2) the median albedo of the gray Centaurs lies between that of the L4 and L5 Trojan groups.

  15. Neutron albedo imager for land mine detection

    NASA Astrophysics Data System (ADS)

    McFee, John E.; Andrews, H. Robert; Ing, Harry; Cousins, Thomas; Faust, Anthony A.; Haslip, Dean S.

    2002-08-01

    Neutron albedo land mine detection involves irradiating the ground with fast neutrons and subsequently detecting the thermalized neutrons which return. This technique has been studied since the 1950's, but only using non-imaging detectors. Without imaging, natural variations in hydrogen content in the soil, chiefly due to moisture, and surface irregularities, produce enough false alarms to render the method impractical in all but the driest conditions. This paper describes research to design and build a prototype landmine detector based on neutron albedo imaging. Realistic Monte Carlo simulations were performed to assess the signal-to-noise ratio for various soil types and moisture contents, assuming a perfect two dimensional neutron imaging system. The study showed that a neutron albedo imager was feasible for mine detection and that image quality could be good enough to significantly improve detector performance and reduce false alarm rates compared to non-imaging albedo detection, particularly in moist soils and where surface irregularities exist. After reviewing various neutron detector technologies, a design concept was developed. It consisted of a novel thermal neutron imaging system, a unique neutron source to uniformly irradiate the underlying ground and hardware and software for image generation and enhancement. Performance capability, including spatial resolution and detection times, were estimated by modeling. A proof-of-principle imager is now being constructed with an expected completion date of Spring 2002. The detector design is described and preliminary results are discussed.

  16. Antioxidant effect of green tea on polymer gel dosimeter

    NASA Astrophysics Data System (ADS)

    Samuel, E. J. J.; Sathiyaraj, P.; Deena, T.; Kumar, D. S.

    2015-01-01

    Extract from Green Tea (GTE) acts as an antioxidant in acrylamide based polymer gel dosimeter. In this work, PAGAT gel was used for investigation of antioxidant effect of GTE.PAGAT was called PAGTEG (Polyacrylamide green tea extract gel dosimeter) after adding GTE. Free radicals in water cause pre polymerization of polymer gel before irradiation. Polyphenols from GTE are highly effective to absorb the free radicals in water. THPC is used as an antioxidant in polymer gel dosimeter but here we were replaced it by GTE and investigated its effect by spectrophotometer. GTE added PAGAT samples response was lower compared to THPC added sample. To increase the sensitivity of the PAGTEG, sugar was added. This study confirmed that THPC was a good antioxidant for polymer gel dosimeter. However, GTE also can be used as an antioxidant in polymer gel if use less quantity (GTE) and add sugar as sensitivity enhancer.

  17. Method and apparatus for reading free falling dosimeter punchcodes

    DOEpatents

    Langsted, James M.

    1992-12-22

    A punchcode reader is provided for reading data encoded in a punchcode hole array on a dosimeter. The dosimeter falls through a passage in the reader containing photosensor detectors disposed along the passage which provide output signals to a microprocessor. The signals are processed to determine the orientation of the dosimeter in the reader, the location and state of punchcode holes in a two row array thereby decoding the encoded data. Multiple rate of fall calculations are made, and if appropriate matching of the punchcode array is not obtained in three tries, an error signal is outputted to the operator. The punchcode reader also provides for storage of data from multiple dosimeters passed through the reader, and for the output of decoded data to an external display or a computer for further processing.

  18. Method and apparatus for reading free falling dosimeter punchcodes

    DOEpatents

    Langsted, J.M.

    1992-12-22

    A punchcode reader is provided for reading data encoded in a punchcode hole array on a dosimeter. The dosimeter falls through a passage in the reader containing photosensor detectors disposed along the passage which provide output signals to a microprocessor. The signals are processed to determine the orientation of the dosimeter in the reader, the location and state of punchcode holes in a two row array thereby decoding the encoded data. Multiple rate of fall calculations are made, and if appropriate matching of the punchcode array is not obtained in three tries, an error signal is output to the operator. The punchcode reader also provides for storage of data from multiple dosimeters passed through the reader, and for the output of decoded data to an external display or a computer for further processing. 8 figs.

  19. Investigating potential physicochemical errors in polymer gel dosimeters

    NASA Astrophysics Data System (ADS)

    Sedaghat, Mahbod; Bujold, Rachel; Lepage, Martin

    2011-09-01

    Measurement errors in polymer gel dosimetry can originate either during irradiation or scanning. One concern related to the exothermic nature of polymerization reaction was that the heat released in polymer gel dosimeters during irradiation modifies their dose response. In this paper, the effect of heat released from the exothermal polymerization reaction on the dose response of a number of dosimeters was studied. In addition, we investigated whether heat-generated geometric distortion existed in newly proposed gel dosimeters that contain highly thermoresponsive polymers. Our results suggest that despite a significant internal temperature increase in some gel compositions, their dose responses are not affected when oxygen is well expelled mechanically from the gel mixture. We also report on significant pre-irradiation instability in some recently developed polymer gel dosimeters but that geometric distortions were not observed. Data obtained by a set of small calibration vials are compared to those obtained from larger phantoms, and potential physicochemical causes of deviations between them are identified.

  20. The albedo of fractal stratocumulus clouds

    NASA Technical Reports Server (NTRS)

    Cahalan, Robert F.; Ridgway, William; Wiscombe, Warren J.; Bell, Thomas L.; Snider, Jack B.

    1994-01-01

    An increase in the planetary albedo of the earth-atmosphere system by only 10% can decrease the equilibrium surface temperature to that of the last ice age. Nevertheless, albedo biases of 10% or greater would be introduced into large regions of current climate models if clouds were given their observed liquid water amounts, because of the treatment of clouds as plane parallel. The focus on marine stratocumulus clouds is due to their important role in cloud radiative forcing and also that, of the wide variety of earth's cloud types, they are most nearly plane parallel, so that they have the least albedo bias. The fractal model employed here reproduces both the probability distribution and the wavenumber spectrum of the stratocumulus liquid water path, as observed during the First ISCCP Regional Experiment (FIRE). A single new fractal parameter 0 less than or equal to f less than or equal to 1, is introduced and determined empirically by the variance of the logarithm of the vertically integrated liquid water. The reduced reflectivity of fractal stratocumulus clouds is approximately given by the plane-parallel reflectivity evaluated at a reduced 'effective optical thickness,' which when f = 0.5 is tau(sub eff) approximately equal to 10. Study of the diurnal cycle of stratocumulus liquid water during FIRE leads to a key unexpected result: the plane-parallel albedo bias is largest when the cloud fraction reaches 100%, that is, when any bias associated with the cloud fraction vanishes. This is primarily due to the variability increase with cloud fraction. Thus, the within-cloud fractal structure of stratocumulus has a more significant impact on estimates of its mesoscale-average albedo than does the cloud fraction.

  1. Radiation measured during ISS-Expedition 13 with different dosimeters

    NASA Astrophysics Data System (ADS)

    Zhou, Dazhuang; Semones, Edward; Gaza, Ramona; Johnson, Steve; Zapp, Neal; Lee, Kerry; George, Tamra

    Radiation measured during ISS-Expedition 13 with different dosimeters D. Zhou1,2,*, E. Semones1, R. Gaza1,2, S. Johnson1, N. Zapp1, K. Lee1, T. George1 1Johnson Space Center - NASA, 2101 Nasa Parkway, Houston 77058, USA 2Universities Space Research Association, 3600 Bay Area Blvd, Houston 77058, USA *Corresponding author. E-mail address: dazhuang.zhou-1@nasa.gov (D. Zhou). Abstract Radiation in low Earth orbit (LEO) is mainly composed of Galactic Cosmic Rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). The biological impact of space radiation to astronauts depends strongly on the particles' linear energy transfer (LET) and is dominated by high LET radiation. It is important to measure the LET spectrum for the space radiation field and to investigate the influence of radiation on astronauts. At present, the preferred active dosimeters sensitive to all LET are the tissue equivalent proportional counter (TEPC) and silicon detectors in various configurations; the preferred passive dosimeters are thermoluminescence dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET as well as CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET. The TEPC, CR-39 PNTDs, TLDs and OSLDs were used to investigate the radiation exposure for the ISS mission Expedition 13 (ISS-12S) in LEO. LET spectra and radiation quantities (fluence, absorbed dose, dose equivalent and quality factor) were measured for the space mission with different dosimeters. This paper introduces the operational principles for the dosimeters, describes the method to combine the results measured by TLDs/OSLDs and CR-39 PNTDs, and presents the LET spectra and the radiation quantities measured. Keywords: space radiation; cosmic rays; active and passive dosimeters; LET spectra

  2. Methods and means of checking thermoluminescent and radiophotoluminescent dosimeters

    SciTech Connect

    Fominykh, V.I.; Oborin, A.V.; Sebekin, A.P.; Uryaev, I.A.

    1987-06-01

    The authors discuss methods of checking thermoluminescent and radiophotoluminescent dosimeters which are used often in monitoring radiation safety in various areas including nuclear power stations. When the dosimeters are checked in the fields of standard beta-ray sources, it is recommended that the standard absorbed-dose or equivalent-dose measures for beta radiation should be sources of /sup 90/Sr + /sup 90/Y, /sup 204/Tl, and /sup 147/Pm. Various safety guidelines are discussed.

  3. Surface-enhanced Raman scattering (SERS) dosimeter and probe

    DOEpatents

    Vo-Dinh, Tuan

    1995-01-01

    A dosimeter and probe for measuring exposure to chemical and biological compounds is disclosed. The dosimeter or probe includes a collector which may be analyzed by surface-enhanced Raman spectroscopy. The collector comprises a surface-enhanced Raman scattering-active material having a coating applied thereto to improve the adsorption properties of the collector. The collector may also be used in automated sequential devises, in probe array devices.

  4. Surface-enhanced Raman scattering (SERS) dosimeter and probe

    DOEpatents

    Vo-Dinh, T.

    1995-03-21

    A dosimeter and probe for measuring exposure to chemical and biological compounds is disclosed. The dosimeter or probe includes a collector which may be analyzed by surface-enhanced Raman spectroscopy. The collector comprises a surface-enhanced Raman scattering-active material having a coating applied thereto to improve the adsorption properties of the collector. The collector may also be used in automated sequential devices, in probe array devices. 10 figures.

  5. Radiation measured for ISS-Expedition 12 with different dosimeters

    NASA Astrophysics Data System (ADS)

    Zhou, D.; Semones, E.; Gaza, R.; Johnson, S.; Zapp, N.; Weyland, M.

    2007-10-01

    Radiation in low Earth orbit (LEO) is mainly from Galactic Cosmic Rays (GCR), solar energetic particles and particles in South Atlantic Anomaly (SAA). These particles' radiation impact to astronauts depends strongly on the particles' linear energy transfer (LET) and is dominated by high LET radiation. It is important to investigate the LET spectrum for the radiation field and the influence of radiation on astronauts. At present, the best active dosimeters used for all LET are the tissue equivalent proportional counter (TEPC) and silicon detectors; the best passive dosimeters are thermoluminescence dosimeters (TLDs) or optically stimulated luminescence dosimeters (OSLDs) for low LET and CR-39 plastic nuclear track detectors (PNTDs) for high LET. TEPC, CR-39 PNTDs, TLDs and OSLDs were used to investigate the radiation for space mission Expedition 12 (ISS-11S) in LEO. LET spectra and radiation quantities (fluence, absorbed dose, dose equivalent and quality factor) were measured for the mission with these different dosimeters. This paper introduces the operation principles for these dosimeters, describes the method to combine the results measured by CR-39 PNTDs and TLDs/OSLDs, presents the experimental LET spectra and the radiation quantities.

  6. Potential High Resolution Dosimeters For MRT

    NASA Astrophysics Data System (ADS)

    Bräuer-Krisch, E.; Rosenfeld, A.; Lerch, M.; Petasecca, M.; Akselrod, M.; Sykora, J.; Bartz, J.; Ptaszkiewicz, M.; Olko, P.; Berg, A.; Wieland, M.; Doran, S.; Brochard, T.; Kamlowski, A.; Cellere, G.; Paccagnella, A.; Siegbahn, E. A.; Prezado, Y.; Martinez-Rovira, I.; Bravin, A.; Dusseau, L.; Berkvens, P.

    2010-07-01

    resolution and a dose range over several orders of magnitude. This paper will give an overview of all dosimeters tested in the past at the ESRF with their advantages and drawbacks. These detectors comprise: Ionization chambers, Alanine Dosimeters, MOSFET detectors, Gafchromic® films, Radiochromic polymers, TLDs, Polymer gels, Fluorescent Nuclear Track Detectors (Al2O3:C, Mg single crystal detectors), OSL detectors and Floating Gate-based dosimetry system. The aim of such a comparison shall help with a decision on which of these approaches is most suitable for high resolution dose measurements in MRT. The principle of these detectors will be presented including a comparison for some dosimeters exposed with the same irradiation geometry, namely a 1×1 cm5 field size with microbeam exposures at the surface, 0.1 cm and 1 cm in depth of a PMMA phantom. For these test exposures, the most relevant irradiation parameters for future clinical trials have been chosen: 50 micron FWHM and 400 micron c-t-c distance. The experimental data are compared with Monte Carlo calculations.

  7. Potential High Resolution Dosimeters For MRT

    SciTech Connect

    Braeuer-Krisch, E.; Brochard, T.; Prezado, Y.; Bravin, A.; Berkvens, P.; Rosenfeld, A.; Lerch, M.; Petasecca, M.; Akselrod, M.; Sykora, J.; Bartz, J.; Ptaszkiewicz, M.; Olko, P.; Berg, A.; Wieland, M.; Doran, S.; Kamlowski, A.; Cellere, G.

    2010-07-23

    /s, micron resolution and a dose range over several orders of magnitude. This paper will give an overview of all dosimeters tested in the past at the ESRF with their advantages and drawbacks. These detectors comprise: Ionization chambers, Alanine Dosimeters, MOSFET detectors, Gafchromic registered films, Radiochromic polymers, TLDs, Polymer gels, Fluorescent Nuclear Track Detectors (Al{sub 2}O{sub 3}:C, Mg single crystal detectors), OSL detectors and Floating Gate-based dosimetry system. The aim of such a comparison shall help with a decision on which of these approaches is most suitable for high resolution dose measurements in MRT. The principle of these detectors will be presented including a comparison for some dosimeters exposed with the same irradiation geometry, namely a 1x1 cm{sup 5} field size with microbeam exposures at the surface, 0.1 cm and 1 cm in depth of a PMMA phantom. For these test exposures, the most relevant irradiation parameters for future clinical trials have been chosen: 50 micron FWHM and 400 micron c-t-c distance. The experimental data are compared with Monte Carlo calculations.

  8. Albedo boundaries on Mars in 1972: Results from Mariner 9

    USGS Publications Warehouse

    Batson, R.M.; Inge, J.L.

    1976-01-01

    A map of "albedo" boundaries (light and dark markings) on Mars was prepared from Mariner 9 images. After special digital processing, these pictures provide detailed locations of albedo boundaries, which is significant in interpreting recent eolian activity. Derivation of absolute albedo values from the spacecraft data was not attempted. The map correlates well with telescopic observations of Mars after the 1971 dust storm. ?? 1976.

  9. Factors Affecting the Application of a Simple Ratio Technique for Spectral Correction of a Neutron Personnel Albedo Dosimeter.

    DTIC Science & Technology

    1983-11-01

    nY reaction (Ha79). The effect pof the Boron-lO pouch can be theoretically calculated for known spectra by using the Boron-lO neutron absorption cross section curve...14 MeV the 6LiF response curve can be appropriately approximated by utilizing the Lithium-6 neutron absorption cross section curve (Ga76,GI83

  10. Preliminary evaluation of implantable MOSFET radiation dosimeters.

    PubMed

    Beddar, A S; Salehpour, M; Briere, T M; Hamidian, H; Gillin, M T

    2005-01-07

    In this paper, we report on measurements performed on a new prototype implantable radiation detector that uses metal-oxide semiconductor field effect transistors (MOSFETs) designed for in vivo dosimetry. The dosimeters, which are encapsulated in hermetically sealed glass cylinders, are used in an unbiased mode during irradiation, unlike other MOSFET detectors previously used in radiotherapy applications. They are powered by radio frequency telemetry for dose measurements, obviating the need for a power supply within each capsule. We have studied the dosimetric characteristics of these MOSFET detectors in vitro under irradiation from a 60Co source. The detectors show a dose reproducibility generally within 5% or better, with the main sources of error being temperature fluctuations occurring between the pre- and post-irradiation measurements as well as detector orientation. A better temperature-controlled environment leads to a reproducibility within 2%. Our preliminary in vitro results show clearly that true non-invasive in vivo dosimetry measurements are feasible and can be performed remotely using telemetric technology.

  11. A liquid fluorescence dosimeter for proton dosimetry

    NASA Astrophysics Data System (ADS)

    Nadrowitz, Roger; Coray, Adolf; Boehringer, Terence; Dunst, Jürgen; Rades, Dirk

    2012-03-01

    The pyromellitic acid (benzene-1,2,4,5-tetracrboxylic acid) dosimeter is a liquid, nearly tissue equivalent detector (the density of the solution is 1.000 56 g cm-3). This acid fluoresces after exposure to proton radiation, if excited with light. The detector was exposed to proton doses of 1.0-10.0 Gy (energies: 138 and 160 MeV). The correlation between fluorescence intensity and delivered energy dose is one to one and linear, whereby the deviation from the linear behavior for all measured values is less than 1%. Variations of the dose rate between 2.4 and 6.0 Gy s-1 had no influence on the correlation between dose and fluorescence. The quenching of the pyromellitic acid detector amounts to about 22% for 138 MeV protons in the Bragg peak. For the period of 1-26 days after exposure, an increase in fluorescence intensity of the exposed solutions (5.0 Gy) was noticed, which corresponds to a daily data drift averaging 0.91% if the solution is stored in the dark at 4 °C. Non-exposed solutions showed no change of the control value.

  12. A liquid fluorescence dosimeter for proton dosimetry.

    PubMed

    Nadrowitz, Roger; Coray, Adolf; Boehringer, Terence; Dunst, Jürgen; Rades, Dirk

    2012-03-07

    The pyromellitic acid (benzene-1,2,4,5-tetracrboxylic acid) dosimeter is a liquid, nearly tissue equivalent detector (the density of the solution is 1.000 56 g cm⁻³). This acid fluoresces after exposure to proton radiation, if excited with light. The detector was exposed to proton doses of 1.0-10.0 Gy (energies: 138 and 160 MeV). The correlation between fluorescence intensity and delivered energy dose is one to one and linear, whereby the deviation from the linear behavior for all measured values is less than 1%. Variations of the dose rate between 2.4 and 6.0 Gy s⁻¹ had no influence on the correlation between dose and fluorescence. The quenching of the pyromellitic acid detector amounts to about 22% for 138 MeV protons in the Bragg peak. For the period of 1-26 days after exposure, an increase in fluorescence intensity of the exposed solutions (5.0 Gy) was noticed, which corresponds to a daily data drift averaging 0.91% if the solution is stored in the dark at 4 °C. Non-exposed solutions showed no change of the control value.

  13. PDT Dose Dosimeter for Pleural Photodynamic Therapy

    PubMed Central

    Kim, Michele M.; Darafsheh, Arash; Ahmad, Mahmoud; Finlay, Jarod C.; Zhu, Timothy C.

    2016-01-01

    PDT dose is the product of the photosensitizer concentration and the light fluence in the target tissue. For improved dosimetry during plural photodynamic therapy (PDT), a PDT dose dosimeter was developed to measure both the light fluence and the photosensitizer concentration simultaneously in the same treatment location. Light fluence and spectral data were rigorously compared to other methods of measurement (e.g. photodiode, multi-fiber spectroscopy contact probe) to assess the accuracy of the measurements as well as their uncertainty. Photosensitizer concentration was obtained by measuring the fluorescence of the sensitizer excited by the treatment light. Fluence rate based on the intensity of the laser spectrum was compared to the data obtained by direct measurement of fluence rate by a fiber-coupled photodiode. Phantom studies were done to obtain an optical property correction for the fluorescence signal. Measurements were performed in patients treated Photofrin for different locations in the pleural cavity. Multiple sites were measured to investigate the heterogeneity of the cavity and to provide cross-validation via relative dosimetry. This novel method will allow for accurate real-time determination of delivered PDT dose and improved PDT dosimetry. PMID:27053825

  14. Solid state neutron dosimeter for space applications

    NASA Technical Reports Server (NTRS)

    Entine, Gerald; Nagargar, Vivek; Sharif, Daud

    1990-01-01

    Personnel engaged in space flight are exposed to significant flux of high energy neutrons arising from both primary and secondary sources of ionizing radiation. Presently, there exist no compact neutron sensor capable of being integrated in a flight instrument to provide real time measurement of this radiation flux. A proposal was made to construct such an instrument using special PIN silicon diode which has the property of being insensitive to the other forms of ionizing radiation. Studies were performed to determine the design and construction of a better reading system to allow the PIN diode to be read with high precision. The physics of the device was studied, especially with respect to those factors which affect the sensitivity and reproducibility of the neutron response. This information was then used to develop methods to achieve high sensitivity at low neutron doses. The feasibility was shown of enhancing the PIN diode sensitivity to make possible the measurement of the low doses of neutrons encountered in space flights. The new PIN diode will make possible the development of a very compact, accurate, personal neutron dosimeter.

  15. Worms in space? A model biological dosimeter.

    PubMed

    Zhao, Yang; Johnsen, Robert; Baillie, David; Rose, Ann

    2005-06-01

    Although it is well known that radiation causes mutational damage, little is known about the biological effects of long-term exposure to radiation in space. Exposure to radiation can result in serious heritable defects in experimental animals, and in humans, susceptibility to cancer, radiation-sickness, and death at high dosages. It is possible to do ground controlled studies of different types of radiation on experimental animals and to physically measure radiation on the space station or on space probes. However, the actual biological affects of long-term exposure to the full range of space radiation have not been studied, and little information is available about the biological consequences of solar flares. Biological systems are not simply passive recording instruments. They respond differently under different conditions, and thus it is important to be able to collect data from a living animal. There are technical difficulties that restrict the placement of an experimental organism in a space environment for long periods of time, in a manner that allows for the recovery of genetic data. Use of the self-fertilizing hermaphroditic nematode, Caenorhabditis elegans offers potential for the design of a biological dosimeter. In this paper, we describe the advantages of this model system and review the literature of C. elegans in space.

  16. Lunar Regolith Albedos Using Monte Carlos

    NASA Technical Reports Server (NTRS)

    Wilson, T. L.; Andersen, V.; Pinsky, L. S.

    2003-01-01

    The analysis of planetary regoliths for their backscatter albedos produced by cosmic rays (CRs) is important for space exploration and its potential contributions to science investigations in fundamental physics and astrophysics. Albedos affect all such experiments and the personnel that operate them. Groups have analyzed the production rates of various particles and elemental species by planetary surfaces when bombarded with Galactic CR fluxes, both theoretically and by means of various transport codes, some of which have emphasized neutrons. Here we report on the preliminary results of our current Monte Carlo investigation into the production of charged particles, neutrons, and neutrinos by the lunar surface using FLUKA. In contrast to previous work, the effects of charm are now included.

  17. Diameters and albedos of satellites of Uranus

    NASA Technical Reports Server (NTRS)

    Brown, R. H.; Cruikshank, D. P.; Morrison, D.

    1982-01-01

    Products of the masses of the five known satellites of Uranus, and estimates of their bulk densities and surface albedos, are used to infer their probable dimensions. Spectrophotometry has established the presence of water ice on the surfaces of all save Rhea, and the brightnesses of the satellites have been measured photoelectrically. The diameter measurements presented were made using a photometric/radiometric technique, whose recent recalibration, using independent solar system object measurements, has yielded absolute accuracies better than 5 per cent. The new albedo measurements show that Umbriel, Titania and Oberon are similar to the Jupiter moon Callisto, while Ariel resembles the Saturn moon Hyperion. The diameters of all four are similar to those of the large, icy Saturn satellites Rhea and Iapetus.

  18. Earth Albedo and the orbit of LAGEOS

    NASA Technical Reports Server (NTRS)

    Rubincam, D. P.; Weiss, N. R.

    1985-01-01

    The long-period perturbations in the orbit of the Lageos satellite due to the Earth's albedo have been found using a new analytical formalism. The Earth is assumed to be a sphere whose surface diffusely reflects sunlight according to Lambert's law. Specular reflection is not considered. The formalism is based on spherical harmonics; it produces equations which hold regardless of whether the terminator is seen by the satellite or not. Specializing to the case of a realistic zonal albedo shows that Lageos' orbital semimajor axis changes periodically by only the a few millimeters and the eccentricity by one part in 100,000. The longitude of the node increases secularly. The effect considered here can explain neither the secular decay of 1.1 mm/day in the semimajor axis nor the observed along-track variations in acceleration of order 2 x 10 to the minus 12 power/sq ms.

  19. Description and evaluation of the Hanford personnel dosimeter program from 1944 through 1989. [Contain Glossary

    SciTech Connect

    Wilson, R.H.; Fix, J.J.; Baumgartner, W.V.; Nichols, L.L.

    1990-09-01

    This report describes the evolution of personnel dosimeter technology at Hanford since the inception of Hanford operations in 1944. Each of the personnel dosimeter systems used by people working or visiting Hanford is described. In addition, the procedures used to calibrate and calculate dose for each of the dosimeter systems are described. The accuracy of the recorded dose, primarily whole body deep dose, for the different dosimeter systems is evaluated. The evaluation is based on an extensive review of historical literature, as well as a 1989 intercomparison study of all film dosimeters and performance testing of the thermoluminescent dosimeter, also conducted during 1989. 73 refs., 40 figs., 41 tabs.

  20. Albedo climatology analysis and the determination of fractional cloud cover

    NASA Technical Reports Server (NTRS)

    Curran, R. J.; Wexler, R.; Nack, M. L.

    1978-01-01

    Monthly and zonally averaged surface cover climatology data are presented which are used to construct monthly and zonally averaged surface albedos. The albedo transformations are then applied to the surface albedos, using solar zenith angles characteristic of the Nimbus 6 satellite local sampling times, to obtain albedos at the top of clear and totally cloud covered atmospheres. These albedos are then combined with measured albedo data to solve for the monthly and zonally averaged fractional cloud cover. The measured albedo data were obtained from the wide field of view channels of the Nimbus 6 Earth Radiation Budget experiment, and consequently the fractional cloud cover results are representative of the local sampling times. These fractional cloud cover results are compared with recent studies. The cloud cover results not only show peaks near the intertropical convergence zone, but the monthly migration of the position of these peaks follows general predictions of atmospheric circulation studies.

  1. Estimating big bluestem albedo from directional reflectance measurements

    NASA Technical Reports Server (NTRS)

    Irons, J. R.; Ranson, K. J.; Daughtry, C. S. T.

    1988-01-01

    Multidirectional reflectance factor measurements acquired in the summer of 1986 are used to make estimates of big bluestem grass albedo, evaluating the variation of albedo with changes in solar zenith angle and phenology. On any given day, the albedo was observed to increase by at least 19 percent as solar zenith angle increased. Changes in albedo were found to correspond to changes in the green leaf area index of the grass canopy. Estimates of albedo made using reflectance data acquired within only one or two azimuthal planes and at a restricted range of view zenith angle were evaluated and compared to 'true' albedos derived from all available reflectance factor data. It was found that even a limited amount of multiple direction reflectance data was preferable to a single nadir reflectance factor for the estimation of prarie grass albedo.

  2. High Resolution Mapping of Pluto's Albedo Distribution

    NASA Astrophysics Data System (ADS)

    Stern, S.

    1994-01-01

    This proposal requests time to map Pluto's albedo distribution, using the highest possible resolution of the CYCLE 4 HST. Maps will be made in several key UV and visible bandpasses. Our scientific objectives are to (a) study the distribution of light and dark areas, (b) make the first disk-resolved estimates of Pluto's limb darkening, and (c) compositional discriminate pure from contaminated frost regions. These objectives have not been previously achievable, but are essential to understanding the surface morphology, volatile transport, and the root cause of Pluto's secular lightcurve variations. It may also be possible to detect evidence of the reported limb haze layer(s) in Pluto's atmosphere. These maps will also provide the first direct check on Pluto maps made through indirect techniques. Owing to Pluto's elliptic orbit, we expect the distribution of albedo to change (on a years-to-decade timescale) as Pluto draws away from perihelion and volatile transport proceeds. The proposed observations will document the albedo state at three rotational epochs near the time of perihelion. These maps will be obtained in two colors, by the FOC. No other astronomical instrument has sufficient resolution to accomplish these important scientific objectives.

  3. Charred Forests Increase Snow Albedo Decay: Watershed-Scale Implications of the Postfire Snow Albedo Effect

    NASA Astrophysics Data System (ADS)

    Gleason, K. E.; Nolin, A. W.

    2014-12-01

    Recent work shows that after a high severity forest fire, approximately 60% more solar radiation reaches the snow surface due to the reduction in canopy density. Also, significant amounts of black carbon (BC) particles and larger burned woody debris (BWD) are shed from standing charred trees, which concentrate on the snowpack, darken its surface, and reduce snow albedo by 50% during ablation. The postfire forest environment drives a substantial increase in net shortwave radiation at the snowpack surface, driving earlier and more rapid melt, however hydrologic models do not explicitly incorporate forest fire disturbance effects to snowpack dynamics. In this study we characterized, parameterized, and validated the postfire snow albedo effect: how the deposition and concentration of charred forest debris decreases snow albedo, increases snow albedo decay rates, and drives an earlier date of snow disappearance. For three study sites in the Oregon High Cascade Mountains, a 2-yr old burned forest, a 10-yr burned forest, and a nearby unburned forest, we used a suite of empirical data to characterize the magnitude and duration of the postfire effect to snow albedo decay. For WY 2012, WY2013, and WY2014 we conducted spectral albedo measurements, snow surface sampling, in-situ snow and meteorological monitoring, and snow energy balance modeling. From these data we developed a new parameterization which represents the postfire effect to snow albedo decay as a function of days-since-snowfall. We validated our parameterization using a physically-based, spatially-distributed snow accumulation and melt model, in-situ snow monitoring, net snowpack radiation, and remote sensing data. We modeled snow dynamics across the extent of all burned area in the headwaters of the McKenzie River Basin and validated the watershed-scale implications of the postfire snow albedo effect using in-situ micrometeorological and remote sensing data. This research quantified the watershed scale postfire

  4. PNNL Results from 2010 CALIBAN Criticality Accident Dosimeter Intercomparison Exercise

    SciTech Connect

    Hill, Robin L.; Conrady, Matthew M.

    2011-10-28

    This document reports the results of the Hanford personnel nuclear accident dosimeter (PNAD) and fixed nuclear accident dosimeter (FNAD) during a criticality accident dosimeter intercomparison exercise at the CEA Valduc Center on September 20-23, 2010. Pacific Northwest National Laboratory (PNNL) participated in a criticality accident dosimeter intercomparison exercise at the Commissariat a Energie Atomique (CEA) Valduc Center near Dijon, France on September 20-23, 2010. The intercomparison exercise was funded by the U.S. Department of Energy, Nuclear Criticality Safety Program, with Lawrence Livermore National Laboratory as the lead Laboratory. PNNL was one of six invited DOE Laboratory participants. The other participating Laboratories were: Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), Savannah River Site (SRS), the Y-12 National Security Complex at Oak Ridge, and Sandia National Laboratory (SNL). The goals of PNNL's participation in the intercomparison exercise were to test and validate the procedures and algorithm currently used for the Hanford personnel nuclear accident dosimeters (PNADs) on the metallic reactor, CALIBAN, to test exposures to PNADs from the side and from behind a phantom, and to test PNADs that were taken from a historical batch of Hanford PNADs that had varying degrees of degradation of the bare indium foil. Similar testing of the PNADs was done on the Valduc SILENE test reactor in 2009 (Hill and Conrady, 2010). The CALIBAN results are reported here.

  5. Water-equivalent fiber radiation dosimeter with two scintillating materials

    PubMed Central

    Qin, Zhuang; Hu, Yaosheng; Ma, Yu; Lin, Wei; Luo, Xianping; Zhao, Wenhui; Sun, Weimin; Zhang, Daxin; Chen, Ziyin; Wang, Boran; Lewis, Elfed

    2016-01-01

    An inorganic scintillating material plastic optical fiber (POF) dosimeter for measuring ionizing radiation during radiotherapy applications is reported. It is necessary that an ideal dosimeter exhibits many desirable qualities, including water equivalence, energy independence, reproducibility, dose linearity. There has been much recent research concerning inorganic dosimeters. However, little reference has been made to date of the depth-dose characteristics of dosimeter materials. In the case of inorganic scintillating materials, they are predominantly non water-equivalent, with their effective atomic weight (Zeff) being typically much greater than that of water. This has been a barrier in preventing inorganic scintillating material dosimeter from being used in actual clinical applications. In this paper, we propose a parallel-paired fiber light guide structure to solve this problem. Two different inorganic scintillating materials are embedded separately in the parallel-paired fiber. It is shown that the information of water depth and absorbed dose at the point of measurement can be extracted by utilizing their different depth-dose properties. PMID:28018715

  6. Thermal neutron dosimeter by synthetic single crystal diamond devices.

    PubMed

    Almaviva, S; Marinelli, Marco; Milani, E; Prestopino, G; Tucciarone, A; Verona, C; Verona-Rinati, G; Angelone, M; Pillon, M

    2009-07-01

    We report on a new solid state dosimeter based on chemical vapor deposition (CVD) single crystal diamond fabricated at Roma "Tor Vergata" University laboratories. The dosimeter has been specifically designed for direct neutron dose measurements in boron neutron capture therapy (BNCT). The response to thermal neutrons of the proposed diamond dosimeter is directly due to (10)B and, therefore, the dosimeter response is directly proportional to the boron absorbed doses in BNCT. Two single crystal diamond detectors are fabricated in a p-type/intrinsic/metal configuration and are sandwiched together with a boron containing layer in between the metallic contacts (see Fig.1). Neutron irradiations were performed at the Frascati Neutron Generator (FNG) using the 2.5 MeV neutrons produced through the D(d,n)(3)He fusion reaction. Thermal neutrons were then produced by slowing down the 2.5 MeV neutrons using a cylindrical polymethylmethacrylate (PMMA) moderator. The diamond dosimeter was placed in the center of the moderator. The products of (10)B(n,alpha)Li nuclear reaction were collected simultaneously giving rise to a single peak. Stable performance, high reproducibility, high efficiency and good linearity were observed.

  7. An assessment of radiotherapy dosimeters based on CVD grown diamond

    NASA Astrophysics Data System (ADS)

    Ramkumar, S.; Buttar, C. M.; Conway, J.; Whitehead, A. J.; Sussman, R. S.; Hill, G.; Walker, S.

    2001-03-01

    Diamond is potentially a very suitable material for use as a dosimeter for radiotherapy. Its radiation hardness, the near tissue equivalence and chemical inertness are some of the characteristics of diamond, which make it well suited for its application as a dosimeter. Recent advances in the synthesis of diamond by chemical vapour deposition (CVD) technology have resulted in the improvement in the quality of material and increased its suitability for radiotherapy applications. We report in this paper, the response of prototype dosimeters based on two different types (CVD1 and CVD2) of CVD diamond to X-rays. The diamond devices were assessed for sensitivity, dependence of response on dose and dose rate, and compared with a Scanditronix silicon photon diode and a PTW natural diamond dosimeter. The diamond devices of CVD1 type showed an initial increase in response with dose, which saturates after ≈6 Gy. The diamond devices of CVD2 type had a response at low fields (<1162.8 V/cm) that was linear with dose and dose rate. At high fields (>1162.8 V/cm), the CVD2-type devices showed polarisation and dose-rate dependence. The sensitivity of the CVD diamond devices varied between 82 and 1300 nC/Gy depending upon the sample type and the applied voltage. The sensitivity of CVD diamond devices was significantly higher than that of natural diamond and silicon dosimeters. The results suggest that CVD diamond devices can be fabricated for successful use in radiotherapy applications.

  8. Portable magnetic field dosimeter with data acquisition capabilities

    NASA Astrophysics Data System (ADS)

    Fujita, T. Y.; Tenforde, T. S.

    1982-03-01

    Design concepts, engineering specifications, and performance test results are presented for a compact magnetic field dosimeter that is suitable for monitoring personnel exposures to steady-state and time-varying magnetic fields. The battery-operated dosimeter contains thin-film Hall sensors that record the magnetic induction (B) along three orthogonal axes. The Hall generators are operated in a pulsed mode, and the time rate of change of the magnetic induction (dB/dt) is determined for values of B recorded during consecutive sampling intervals (typically 75 ms). The pulsed mode operation also serves to reduce battery consumption. The dosimeter contains a programmable microprocessor-based logic circuit and 4096 12-bit words of permanent and random-access memory. Stored parameters include: (1) average values of B and dB/dt during a preset time interval (typically 5 min); (2) peak values of B and dB/dt during the preset interval; and (3) the number of times that specified threshold levels for these parameters are exceeded. An audible alarm is activated when B or dB/dt exceeds a specified threshold level. Sensitivity factors and threshold levels can be loaded into the dosimeter from a bench-mounted programmable calculator, which is also used at the end of each workday to record and process data stored in the dosimeter's random-access memory.

  9. Water-equivalent fiber radiation dosimeter with two scintillating materials.

    PubMed

    Qin, Zhuang; Hu, Yaosheng; Ma, Yu; Lin, Wei; Luo, Xianping; Zhao, Wenhui; Sun, Weimin; Zhang, Daxin; Chen, Ziyin; Wang, Boran; Lewis, Elfed

    2016-12-01

    An inorganic scintillating material plastic optical fiber (POF) dosimeter for measuring ionizing radiation during radiotherapy applications is reported. It is necessary that an ideal dosimeter exhibits many desirable qualities, including water equivalence, energy independence, reproducibility, dose linearity. There has been much recent research concerning inorganic dosimeters. However, little reference has been made to date of the depth-dose characteristics of dosimeter materials. In the case of inorganic scintillating materials, they are predominantly non water-equivalent, with their effective atomic weight (Zeff) being typically much greater than that of water. This has been a barrier in preventing inorganic scintillating material dosimeter from being used in actual clinical applications. In this paper, we propose a parallel-paired fiber light guide structure to solve this problem. Two different inorganic scintillating materials are embedded separately in the parallel-paired fiber. It is shown that the information of water depth and absorbed dose at the point of measurement can be extracted by utilizing their different depth-dose properties.

  10. Commissioning and implementation of an implantable dosimeter for radiation therapy.

    PubMed

    Buzurovic, Ivan; Showalter, Timothy N; Studenski, Matthew T; Den, Robert B; Dicker, Adam P; Cao, Junsheng; Xiao, Ying; Yu, Yan; Harrison, Amy

    2013-03-04

    In this article we describe commissioning and implementation procedures for the Dose Verification System (DVS) with permanently implanted in vivo wireless, telemetric radiation dosimeters for absolute dose measurements. The dosimeter uses a semiconductor device called a metal-oxide semiconductor field-effect transistor (MOSFET) to measure radiation dose. A MOSFET is a transistor that is generally used for amplifying or switching electronic signals. The implantable dosimeter was implemented with the goal of verifying the dose delivered to radiation therapy patients. For the purpose of acceptance testing, commissioning, and clinical implementation and to evaluate characteristics of the dosimeter, the following tests were performed: 1) temperature dependence, 2) reproducibility,3) field size dependence, 4) postirradiation signal drift, 5) dependence on average dose rate, 6) linearity test, 7) angular dependence (different gantry angle position), 8) angular dependence (different DVS angle position), 9) dose rate dependence,10) irradiation depth dependence, 11) effect of cone-beam exposure to the dosimeter, and 12) multiple reading effect. The dosimeter is not currently calibrated for use in the kV range; nonetheless, the effect of the cone-beam procedure on the MOSFET dosimeter was investigated. Phantom studies were performed in both air and water using an Elekta Synergy S Beam-Modulator linear accelerator. Commissioning and clinical implementation for prostate cancer patients receiving external-beam radiation therapy were performed in compliance with the general recommendations given for in vivo dosimetry devices. The reproducibility test in water at human body temperature (37°C) showed a 1.4% absolute difference, with a standard deviation of 5.72 cGy (i.e., SD = 2.9%). The constancy test shows that the average readings at room temperature were 3% lower compared to the readings at human body temperature, with a SD = 2%. Measurements were not dependent upon field size

  11. Performance testing of extremity dosimeters against a draft standard

    SciTech Connect

    Harty, R.; Reece, W.D.; Hooker, C.D.; McDonald, J.C.

    1990-09-01

    The assurance of worker radiation safety is directly related to the performance of personnel dosimetry. The US Department of Energy (DOE) has long recognized this critical relationship and has addressed this issue by instituting the DOE Laboratory Accreditation Program (DOELAP) which strives to improve the quality of personnel dosimetry through performance testing, dosimetry calibration, intercomparisons, evaluations and accreditations. One area of personnel dosimetry that has not been specifically addressed by DOELAP is extremity dosimeter testing. This task was directed at assessing the problems of implementing extremity dosimeter performance testing. A series of performance tests were made based on a draft standard written by the Health Physics Society Standards Committee (HPSSC) using extremity dosimeters currently in use at DOE and DOE contractor facilities. The results of this study indicate the need to incorporate performance testing of extremity dosimetry systems into DOELAP. Based on the results of this study, recommendations are made for improvements to the draft standard. 20 refs., 6 figs., 3 tabs.

  12. Imaging of Absorbed Dose in Radiotherapy by a Polymer Gel Dosimeter

    NASA Astrophysics Data System (ADS)

    Vanossi, E.; Gambarini, G.; Carrara, M.; Mariani, M.; Negri, A.

    2008-06-01

    Optical imaging of polymer gel dosimeters in form of layers was investigated to enquire their reliability for in-phantom dose measurements in photon or thermal neutron fields. The obtained dose measurements were compared with those achieved by means of Fricke gel dosimeters. Reliability of Fricke gel dosimeters was confirmed, whereas it has been shown that a conspicuous improvement of the adopted polymer gel dosimeters is necessary.

  13. Implanted Dosimeters Identify Radiation Overdoses During IMRT for Prostate Cancer

    SciTech Connect

    Den, Robert B.; Nowak, Kamila; Buzurovic, Ivan; Cao Junsheng; Harrison, Amy S.; Lawrence, Yaacov R.; Dicker, Adam P.; Showalter, Timothy N.

    2012-07-01

    Purpose: Image-guided dose-escalated radiotherapy is the standard of care for the treatment of prostate cancer. Although many published methods are available that account for prostate motion during delivery, evidence demonstrating that the planned dose is actually delivered on a daily basis is lacking. We report our initial clinical experience using implantable dosimeters to quantify and adjust the dose received during intensity-modulated radiotherapy (IMRT). Methods and Materials: A total of 20 patients undergoing IMRT with cone-beam computed tomography (CT) image guidance for prostate cancer had the dose verification system with radiopaque metal-oxide-semiconductor field effect transistor dosimeters implanted before treatment planning. All patients underwent planning with CT simulation in the supine position with custom immobilization, and the implanted dosimeters were located in the IMRT plans. The predicted dose for each dosimeter was defined and compared with the wireless readings before and after each treatment session. Investigations by physicians and medical physicists were initiated for two or more discrepancies >6% for any five consecutive fractions or for any discrepancy {>=}10%. Results: Using implanted in vivo dosimeters, dose measurements consistently >6% greater than the predicted values were observed during treatment for 3 of 20 prostate cancer patients who received IMRT with daily image guidance. A review of the daily cone-beam CT images revealed acceptable alignment of the prostate target volumes and implanted dosimeters but identified significant anatomic changes within the treated region. Repeat CT simulation and RT planning was performed, with resolution of the dose discrepancies in all 3 cases with the adoption of a new IMRT plan. Conclusions: Our report illustrates the potential effect of implanted in vivo dosimetry for prostate IMRT and emphasizes the importance of careful planning and delivery with attention to systematic shifts or anatomic

  14. A floating gate MOSFET dosimeter requiring no external bias supply

    SciTech Connect

    Tarr, N.G.; Mackay, G.F.; Thomson, I.; Shortt, K.

    1998-06-01

    MOSFET dosimeters incorporating an electrically floating polysilicon gate have been fabricated in a commercial CMOS technology. Charge is placed on the floating gate by tunneling from a small overlapping injector gate. Subsequent irradiation partially discharges the floating gate, producing a change in threshold voltage which can be used to infer the absorbed dose. No external power source is required during this sensing period. Sensitivities up to 70 mVGy{sup {minus}1} (0.7 mV/rad) have been obtained for temperature-compensated matched-pair dosimeters under {sup 60}Co gamma irradiation.

  15. Basic radiological characteristics of a non-scattering gel dosimeter for 3D dosimetry

    NASA Astrophysics Data System (ADS)

    Chang, Kyung Hwan; Ji, Yunseo; Lee, Suk; Kim, Kwang Hyeon; Yang, Dae Sik; Lee, Jung Ae; Park, Young Je; Yoon, Won Sup; Kim, Chul Yong; Cao, Yuanjie; Cho, Samju

    2016-12-01

    We used a spectrophotometer to compare the dosimetric properties of two non-scattering (radiochromic) gel dosimeters: a non-scattering gel dosimeter developed in-house and a PRESAGE™ gel dosimeter. We evaluated the dosimetric characteristics, including spectral absorption, dose linearity, reproducibility, and dose rate dependency of the two gel dosimeters. The non-scattering gel and the PRESAGE™ gel dosimeters showed peak sensitivity at wavelengths of 600 nm and 630 nm, respectively. Over a range of doses the best dose linearities of the non-scattering and the PRESAGE™ gel dosimeters resulted in R2 values of 0.99 at wavelengths of 600 nm and 630 nm, respectively. The reproducibility and dose-rate dependence of each of the two gel dosimeters were within the range of ±3 %. Our results revealed that the peak sensitivities of the two radiochromic gel dosimeters were significantly different; the in-house non-scattering gel dosimeter demonstrated peak sensitivity at a wavelength of 600 nm while the PRESAGE™ gel dosimeter had peak sensitivity at a wavelength of 630 nm. We confirmed that for 3D gel dosimetry, the in-house non-scattering gel dosimeter had a more stable dose response compared with a commercial non-scattering gel dosimeter.

  16. A simple convenient biological dosimeter for monitoring solar UV-B radiation

    SciTech Connect

    Wang, T.C. )

    1991-05-31

    The use of dry Bacillus subtilis spores as a biological dosimeter for the monitoring of solar UV-B (290-330 nm) radiation was described. Our field tests had supported the utility of this dosimeter as a reproducible and reliable sunlight dosimeter.

  17. Sizes and albedos of the larger asteroids

    NASA Technical Reports Server (NTRS)

    Morrison, D.

    1977-01-01

    The purpose of the present paper is to review all asteroid diameter measurements, current through mid-1976, and to combine them in a consistent way to give the best available estimates for a sample totalling 187 objects. From these diameters it is possible to determine the size-distributions of minor planets down to diameters of 50 km in the inner belt and 100 km in the outer belt. The associated albedos further indicate the distribution of objects of the C, S, and M classes throughout the belt.

  18. Albedo and transmittance of inhomogeneous stratus clouds

    SciTech Connect

    Zuev, V.E.; Kasyanov, E.I.; Titov, G.A.

    1996-04-01

    A highly important topic is the study of the relationship between the statistical parameters of optical and radiative charactertistics of inhomogeneous stratus clouds. This is important because the radiation codes of general circulation models need improvement, and it is important for geophysical information. A cascade model has been developed at the Goddard Space Flight Center to treat stratocumulus clouds with the simplest geometry and horizontal fluctuations of the liquid water path (optical thickness). The model evaluates the strength with which the stochastic geometry of clouds influences the statistical characteristics of albedo and the trnasmittance of solar radiation.

  19. Albedo maps of Pluto and Charon - Initial mutual event results

    NASA Technical Reports Server (NTRS)

    Buie, Marc W.; Tholen, David J.; Horne, Keith

    1992-01-01

    By applying the technique of maximum entropy image reconstruction to invert observed lightcurves, surface maps of single-scattering albedo are obtained for the surfaces of Pluto and Charon from 1954 to 1986. The albedo features of the surface of Pluto are similar to those of the Buie and Tholen (1989) spot model maps; a south polar cap is evident. The map of Charon is somewhat darker, with single-scattering albedos as low as 0.03.

  20. Factors Influencing the Mesoscale Variations in Marine Stratocumulus Albedo

    DTIC Science & Technology

    2007-01-01

    aerosols can indeed modulate cloud albedo, other parameters such as sea surface temperature may similarly affect cloud albedo. Additionally, the...major role in determining planetary albedo and tend to be located along the eastern pe- ripheries of the major oceans (Warren et al., 1988). They...cloud, in cloud and from re- motely retrieved parameters all show substantial interflight vari- ability in their spatial patterns. In some flights the

  1. THE ALBEDO-COLOR DIVERSITY OF TRANSNEPTUNIAN OBJECTS

    SciTech Connect

    Lacerda, Pedro; Rengel, Miriam; Fornasier, Sonia; Lellouch, Emmanuel; Delsanti, Audrey; Kiss, Csaba; Vilenius, Esa; Müller, Thomas; Santos-Sanz, Pablo; Duffard, René; Guilbert-Lepoutre, Aurélie

    2014-09-20

    We analyze albedo data obtained using the Herschel Space Observatory that reveal the existence of two distinct types of surface among midsized trans-Neptunian objects. A color-albedo diagram shows two large clusters of objects, one redder and higher albedo and another darker and more neutrally colored. Crucially, all objects in our sample located in dynamically stable orbits within the classical Kuiper Belt region and beyond are confined to the bright red group, implying a compositional link. Those objects are believed to have formed further from the Sun than the dark neutral bodies. This color-albedo separation is evidence for a compositional discontinuity in the young solar system.

  2. Enhancement of the MODIS Daily Snow Albedo Product

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Schaaf, Crystal B.; Wang, Zhuosen; Riggs, George A.

    2009-01-01

    The MODIS daily snow albedo product is a data layer in the MOD10A1 snow-cover product that includes snow-covered area and fractional snow cover as well as quality information and other metadata. It was developed to augment the MODIS BRDF/Albedo algorithm (MCD43) that provides 16-day maps of albedo globally at 500-m resolution. But many modelers require daily snow albedo, especially during the snowmelt season when the snow albedo is changing rapidly. Many models have an unrealistic snow albedo feedback in both estimated albedo and change in albedo over the seasonal cycle context, Rapid changes in snow cover extent or brightness challenge the MCD43 algorithm; over a 16-day period, MCD43 determines whether the majority of clear observations was snow-covered or snow-free then only calculates albedo for the majority condition. Thus changes in snow albedo and snow cover are not portrayed accurately during times of rapid change, therefore the current MCD43 product is not ideal for snow work. The MODIS daily snow albedo from the MOD10 product provides more frequent, though less robust maps for pixels defined as "snow" by the MODIS snow-cover algorithm. Though useful, the daily snow albedo product can be improved using a daily version of the MCD43 product as described in this paper. There are important limitations to the MOD10A1 daily snow albedo product, some of which can be mitigated. Utilizing the appropriate per-pixel Bidirectional Reflectance Distribution Functions (BRDFs) can be problematic, and correction for anisotropic scattering must be included. The BRDF describes how the reflectance varies with view and illumination geometry. Also, narrow-to-broadband conversion specific for snow on different surfaces must be calculated and this can be difficult. In consideration of these limitations of MOD10A1, we are planning to improve the daily snow albedo algorithm by coupling the periodic per-pixel snow albedo from MCD43, with daily surface ref|outanoom, In this paper, we

  3. Entrainment, Drizzle, and Stratocumulus Cloud Albedo

    NASA Technical Reports Server (NTRS)

    Ackerman, A. S.; Kirkpatrick, M. P.; Stevens, D. E.; Toon, O. B.

    2004-01-01

    Globally averaged cloud changes from GCMs on average show a doubling of the Twomey effect, which is the change in cloud albedo with respect to changes in droplet concentrations for fixed cloud water and droplet dispersion. In contrast, ship-track measurements show a much more modest amplification of the Twomey effect, suggesting that the GCMs are exaggerating the indirect aerosol effect. We have run large-eddy simulations with bin microphysics of marine stratocumulus from multiple field campaigns, and find that the large-eddy simulations are in much better agreement with the ship-track measurements. The inversion strength over N. Pacific stratocumulus (as measured during DYCOMS-II) is generally much stronger than over N. Atlantic stratocumulus (as measured during ASTEX), and we have found that the response of cloud water to increasing droplet concentration changes sign as the inversion strengthens. For the different environmental conditions, we will show the overall response of cloud albedo to droplet concentrations, and decompose the response into its contributing factors of changes in cloud water, droplet dispersion, and horizontal inhomogeneity.

  4. Deconnable self-reading pocket dosimeter containment with self-contained light

    DOEpatents

    Stevens, Robyn L.; Arnold, Greg N.; McBride, Ryan G.

    1996-01-01

    A container for a self-reading pocket dosimeter includes a transparent tube for receiving the self-reading pocket dosimeter, a light source mounted at one end of the transparent tube, and an eyepiece mounted on an opposite end of the transparent tube for viewing a read-out of the self-reading pocket dosimeter. The container may further include an activation device for selectively supplying power to the light source. The container both protects the dosimeter from being contaminated and provides a light source for viewing the dosimeter.

  5. Hanford Personnel Dosimeter supporting studies FY-1980. [Lead abstract

    SciTech Connect

    Endres, G.W.R.; Cummings, F.M.; Aldrich, J.M.; Thorson, M.R.; Kathren, R.L.

    1981-02-01

    Separate abstracts were prepared for the 10 sections of this report which describe fundamental characteristics of the Hanford multipurpose personnel dosimeter (HMPD). Abstracts were not prepared for Appendix A and Appendix B which deal with calculated standard deviations for 100 mrem mixed field exposures and detailed calculations of standard deviations, respectively. (KRM)

  6. Validation of an Innovative Satellite-Based UV Dosimeter

    NASA Astrophysics Data System (ADS)

    Morelli, Marco; Masini, Andrea; Simeone, Emilio; Khazova, Marina

    2016-08-01

    We present an innovative satellite-based UV (ultraviolet) radiation dosimeter with a mobile app interface that has been validated by exploiting both ground-based measurements and an in-vivo assessment of the erythemal effects on some volunteers having a controlled exposure to solar radiation.Both validations showed that the satellite-based UV dosimeter has a good accuracy and reliability needed for health-related applications.The app with this satellite-based UV dosimeter also includes other related functionalities such as the provision of safe sun exposure time updated in real-time and end exposure visual/sound alert. This app will be launched on the global market by siHealth Ltd in May 2016 under the name of "HappySun" and available both for Android and for iOS devices (more info on http://www.happysun.co.uk).Extensive R&D activities are on-going for further improvement of the satellite-based UV dosimeter's accuracy.

  7. Portable battery-free charger for radiation dosimeters

    DOEpatents

    Manning, Frank W.

    1984-01-01

    This invention is a novel portable charger for dosimeters of the electrometer type. The charger does not require batteries or piezoelectric crystals and is of rugged construction. In a preferred embodiment, the charge includes a housing which carries means for mounting a dosimeter to be charged. The housing also includes contact means for impressing a charging voltage across the mounted dosimeter. Also, the housing carries a trigger for operating a charging system mounted in the housing. The charging system includes a magnetic loop including a permanent magnet for establishing a magnetic field through the loop. A segment of the loop is coupled to the trigger for movement thereby to positions opening and closing the loop. A coil inductively coupled with the loop generates coil-generated voltage pulses when the trigger is operated to open and close the loop. The charging system includes an electrical circuit for impressing voltage pulses from the coil across a capacitor for integrating the pulses and applying the resulting integrated voltage across the above-mentioned contact means for charging the dosimeter.

  8. Field test of fiber optic hydrazine dosimeters at Cape Canaveral

    NASA Astrophysics Data System (ADS)

    Klimcak, Charles M.; Chan, Y.; Jaduszliwer, B.

    1999-02-01

    We tested seventy-two hydrazine fuel fiber optic dosimeters for periods up to three months or Cape Canaveral in order to determine the effect of the local environment on its lifetime and sensitivity. The dosimeters were deployed at a diverse group of sites including fuel, oxidizer, and hydrocarbon fuel storage and transfer locations, a salt spray corrosion test facility, a satellite processing area, an estuarine marsh, a paint storage locker, and several indoor locations including chemical laboratory fume hoods and bathrooms. In addition, a group were set aside in a sealed enclosure for control purposes. The dosimeters were retrieved at monthly intervals and exposed to measured doses of hydrazine vapor to determine the effects of the field exposure on their hydrazine response. Our analysis indicated that 90% of the exposed dosimeters were able to sense hydrazine at a dose detectivity of less than 15 ppb-hr, a value that meets the current hydrazine sensing requirement. Consequently, we are planning to deploy a full scale, continuously operating fiber optic system for detecting potential hydrazine leaks during launch operations at Cape Canaveral.

  9. Improvements in opti-chromic dosimeters for radiation processing

    NASA Astrophysics Data System (ADS)

    Humpherys, K. C.; Kantz, A. D.

    "Opti-Chromic" dosimeters consisting of radiachromic dye in flourinated polymer tubing have been introduced as a dosimetry system in the range from 10 1 to 5 × 10 4 Gy. Batches of "Opti-Chromic" dosimeters have been produced to evaluate performance under large scale industrial conditions. A systematic study was undertaken to determine the effect of various dosimeter parameters on radiation sensitivity, shelf life, and response characteristics at the higher absorbed doses. These parameters were (A) Type of flourinated polymer tubing; (B) Organic solvent used to activate the radiachromic dye; (C) Concentration of radiachromic dye; (D) Additives to provide proper viscosity, color stability, and high-dose response. Prototype batches were produced and experimental dosimeters exposed to a range of absorbed doses and the response measured as a function of shelf life and dose. The results of the study are presented, and an improved formulation recommended for application to Food Processing. Other formulations may be of value in specific requirements of sensitivity or temperature.

  10. Two methods for examining angular response of personnel dosimeters

    SciTech Connect

    Plato, P.; Leib, R.; Miklos, J.

    1988-06-01

    The American National Standard ANSI N13.11-1983 is used to test the accuracy (bias plus precision) of dosimetry processors as part of the dosimetry accreditation program of the National Voluntary Laboratory Accreditation Program (NVLAP). Section 3.8 of the ANSI N13.11-1983 standard requires that a study of the angular response of a dosimeter be carried out once, although no pass/fail criterion is given for angular response. The NVLAP accreditation program excluded Section 3.8, and thus no angular response data have been generated in an organized fashion. The objective of this project is to examine the feasibility of two alternative methods to test the angular response of personnel dosimeters. The first alternative involves static irradiations with the dosimeters at fixed angles to a radiation source. The second alternative involves dynamic irradiations with the dosimeters mounted on a rotating phantom. A Panasonic UD-802 personnel dosimetry system** was used to generate data to examine both alternatives. The results lead to two major conclusions. Firstly, Section 3.8 of the ANSI N13.11-1983 standard should be amended to require a pass/fail test for angular response. Secondly, a comparison between angular response data generated with a fixed or a rotating phantom shows that the rotating phantom is the more cost-effective method.

  11. Thin thermoluminescent dosimeter and method of making same

    DOEpatents

    Simons, Gale G.; DeBey, Timothy M.

    1987-01-01

    An improved thermoluminescent ionizing radiation dosimeter of solid, extremely thin construction for more accurate low energy beta dosimetry is provided, along with a method of fabricating the dosimeter. In preferred forms, the dosimeter is a composite including a backing support (which may be tissue equivalent) and a self-sustaining body of solid thermoluminescent material such as LiF having a thickness of less than about 0.25 millimeters and a volume of at least about 0.0125 mm.sup.3. In preferred fabrication procedures, an initially thick (e.g., 0.89 millimeters) TLD body is wet sanded using 600 grit or less sandpaper to a thickness of less than about 0.25 millimeters, followed by adhesively attaching the sanded body to an appropriate backing. The sanding procedure permits routine production of extremely thin (about 0.05 millimeters) TLD bodies, and moreover serves to significantly reduce non-radiation-induced thermoluminescence. The composite dosimeters are rugged in use and can be subjected to annealing temperatures for increased accuracy.

  12. Thin thermoluminescent dosimeter and method of making same

    SciTech Connect

    Simons, G.G.; DeBey, T.M.

    1987-01-13

    An improved thermoluminescent ionizing radiation dosimeter of solid, extremely thin construction for more accurate low energy beta dosimetry is provided, along with a method of fabricating the dosimeter. In preferred forms, the dosimeter is a composite including a backing support (which may be tissue equivalent) and a self-sustaining body of solid thermoluminescent material such as LiF having a thickness of less than about 0.25 millimeters and a volume of at least about 0.0125 mm[sup 3]. In preferred fabrication procedures, an initially thick (e.g., 0.89 millimeters) TLD body is wet sanded using 600 grit or less sandpaper to a thickness of less than about 0.25 millimeters, followed by adhesively attaching the sanded body to an appropriate backing. The sanding procedure permits routine production of extremely thin (about 0.05 millimeters) TLD bodies, and moreover serves to significantly reduce non-radiation-induced thermoluminescence. The composite dosimeters are rugged in use and can be subjected to annealing temperatures for increased accuracy. 1 fig.

  13. From Regional Cloud-Albedo to a Global Albedo Footprint - Studying Aerosol Effects on the Radiation Budget Using the Relation Between Albedo and Cloud Fraction

    NASA Astrophysics Data System (ADS)

    Bender, F.; Engström, A.; Karlsson, J.; Wood, R.; Charlson, R. J.

    2015-12-01

    Earth's albedo is the primary determinant of the amount of energy absorbed by the Earth-atmosphere system. The main factor controlling albedo is the amount of clouds present, but aerosols can affect and alter both clear-sky and cloudy-sky reflectance. How albedo depends on cloud fraction and how albedo varies at a given cloud fraction and a given cloud water content, reveals information about these aerosol effects on the radiation budget. Hence, the relation between total albedo and cloud fraction can be used for illustration and quantification of aerosol effects, and as a diagnostic tool, to test model performance. Here, we show examples of the utilisation of this relation focusing on satellite observations from CERES and MODIS on Aqua, as well as from Calipso and CloudSat, and performing comparisons with climate models on the way: In low-cloud regions in the subtropics, we find that climate models well represent a near-constant regional cloud albedo, and this representation has improved from CMIP3 to CMIP5. CMIP5 models indicate more reflective clouds in present-day climate than pre-industrial, as a result of increased aerosol burdens. On monthly mean time scale, models are found to over-estimate the regional cloud-brightening due to aerosols. On the global scale we find an increasing cloud albedo with increasing cloud fraction - a relation that is very well defined in observations, and less so in CMIP5 models. Cloud brightening from pre-industrial to present day is also seen on global scale. Further, controlling for both cloud fraction and cloud water content we can trace small variations in albedo, or perturbations of solar reflectivity, that create a near-global coherent geographical pattern that is consistent with aerosol impacts on climate, with albedo enhancement in regions dominant of known aerosol sources and suppression of albedo in regions associated with high rates of aerosol removal (deduced using CloudSat precipitation estimates). This mapping can be

  14. Surface Albedo Variations Across Opportunity's Traverse in Meridiani Planum

    NASA Astrophysics Data System (ADS)

    Studer-Ellis, G. L.; Rice, M. S.; Johnson, J. R.; Bell, J. F., III

    2015-12-01

    Surface albedo measurements from the Mars Exploration Rover (MER) Opportunity mission can be used to help understand surface-atmosphere interactions at Meridiani Planum. Opportunity has acquired 117 albedo panoramas with the Pancam instrument as of sol 3870, across the first 40 km of its traverse. To date, only the first 32 panoramas have been reported upon in previous studies [1]. Here we present an analysis of the full set of PDS-released albedo observations from Opportunity and correlate our measurements with terrain type and known atmospheric events. To acquire a 360-degree albedo observation, Pancam's L1 ("clear") filter is used to take 27 broad-spectrum images, which are stitched into a mosaic. Pancam images are calibrated to reflectance factor (R*), which is taken as an approximation of the Lambertian albedo. Areas of interest are selected and average albedo calculations are applied to all of the selections. Results include the average albedo of each scene, as well as equal-area corrections where applicable, in addition to measurements of specific classes of surface features (e.g., outcrops, dusty terrain, and rover tracks). Average scene albedo measurements range from 0.11 ± 0.04 to 0.30 ± 0.04, with the highest value observed on sol 1290 (immediately after the planet-encircling dust storm of 2007). We compare these results to distance traveled, surface morphologies, local wind driven events, and dust opacity measurements. Future work will focus on correlating Pancam albedo values with orbital data from cameras such as HiRISE, CTX, MOC, THEMIS-VIS, and MARCI, and completion of the same analysis for the full Pancam albedo dataset from Spirit. References: [1] Bell, J. F., III, M. S. Rice, J. R. Johnson, and T. M. Hare (2008), Surface albedo observations at Gusev Crater and Meridiani Planum, Mars, J. Geophys. Res., 113, E06S18, doi:10.1029/2007JE002976.

  15. Feasibility Study on Applying Radiophotoluminescent Glass Dosimeters for CyberKnife SRS Dose Verification

    PubMed Central

    Hsu, Shih-Ming; Hung, Chao-Hsiung; Liao, Yi-Jen; Fu, Hsiao-Mei; Tsai, Jo-Ting

    2017-01-01

    CyberKnife is one of multiple modalities for stereotactic radiosurgery (SRS). Due to the nature of CyberKnife and the characteristics of SRS, dose evaluation of the CyberKnife procedure is critical. A radiophotoluminescent glass dosimeter was used to verify the dose accuracy for the CyberKnife procedure and validate a viable dose verification system for CyberKnife treatment. A radiophotoluminescent glass dosimeter, thermoluminescent dosimeter, and Kodak EDR2 film were used to measure the lateral dose profile and percent depth dose of CyberKnife. A Monte Carlo simulation for dose verification was performed using BEAMnrc to verify the measured results. This study also used a radiophotoluminescent glass dosimeter coupled with an anthropomorphic phantom to evaluate the accuracy of the dose given by CyberKnife. Measurements from the radiophotoluminescent glass dosimeter were compared with the results of a thermoluminescent dosimeter and EDR2 film, and the differences found were less than 5%. The radiophotoluminescent glass dosimeter has some advantages in terms of dose measurements over CyberKnife, such as repeatability, stability, and small effective size. These advantages make radiophotoluminescent glass dosimeters a potential candidate dosimeter for the CyberKnife procedure. This study concludes that radiophotoluminescent glass dosimeters are a promising and reliable dosimeter for CyberKnife dose verification with clinically acceptable accuracy within 5%. PMID:28046056

  16. Feasibility Study on Applying Radiophotoluminescent Glass Dosimeters for CyberKnife SRS Dose Verification.

    PubMed

    Hsu, Shih-Ming; Hung, Chao-Hsiung; Liao, Yi-Jen; Fu, Hsiao-Mei; Tsai, Jo-Ting; Huang, Yung-Hui; Huang, David Y C

    2017-01-01

    CyberKnife is one of multiple modalities for stereotactic radiosurgery (SRS). Due to the nature of CyberKnife and the characteristics of SRS, dose evaluation of the CyberKnife procedure is critical. A radiophotoluminescent glass dosimeter was used to verify the dose accuracy for the CyberKnife procedure and validate a viable dose verification system for CyberKnife treatment. A radiophotoluminescent glass dosimeter, thermoluminescent dosimeter, and Kodak EDR2 film were used to measure the lateral dose profile and percent depth dose of CyberKnife. A Monte Carlo simulation for dose verification was performed using BEAMnrc to verify the measured results. This study also used a radiophotoluminescent glass dosimeter coupled with an anthropomorphic phantom to evaluate the accuracy of the dose given by CyberKnife. Measurements from the radiophotoluminescent glass dosimeter were compared with the results of a thermoluminescent dosimeter and EDR2 film, and the differences found were less than 5%. The radiophotoluminescent glass dosimeter has some advantages in terms of dose measurements over CyberKnife, such as repeatability, stability, and small effective size. These advantages make radiophotoluminescent glass dosimeters a potential candidate dosimeter for the CyberKnife procedure. This study concludes that radiophotoluminescent glass dosimeters are a promising and reliable dosimeter for CyberKnife dose verification with clinically acceptable accuracy within 5%.

  17. VALIDATION OF HANFORD PERSONNEL AND EXTREMITY DOSIMETERS IN PLUTONIUM ENVIRONMENTS

    SciTech Connect

    Scherpelz, Robert I.; Fix, John J.; Rathbone, Bruce A.

    2000-02-10

    A study was performed in the Plutonium Finishing Plant to assess the performance of Hanford personnel neutron dosimetry. The study was assessed whole body dosimetry and extremity dosimetry performance. For both parts of the study, the TEPC was used as the principle instrument for characterizing workplace neutron fields. In the whole body study, 12.7-cm-diameter TEPCs were used in ten different locations in the facility. TLD and TED personnel dosimeters were exposed on a water-filled phantom to enable a comparison of TEPC and dosimeter response. In the extremity study, 1.27-cm-diameter TEPCs were exposed inside the fingers of a gloveboxe glove. Extremity dosimeters were wrapped around the TEPCs. The glove was then exposed to six different cans of plutonium, simulating the exposure that a worker's fingers would receive in a glovebox. The comparison of TEPC-measured neutron dose equivalent to TLD-measured gamma dose equivalent provided neutron-to-gamma ratios that can be used to estimate the neutron dose equivalent received by a worker's finger based on the gamma readings of an extremity dosimeter. The study also utilized a Snoopy and detectors based on bubble technology for assessing neutron exposures, providing a comparison of the effectiveness of these instruments for workplace monitoring. The study concludes that the TLD component of the HCND performs adequately overall, with a positive bias of 30%, but exhibits excessive variability in individual results due to instabilities in the algorithm. The TED response was less variable but only 20% of the TEPC reference dose on average because of the low neutron energies involved. The neutron response of the HSD was more variable than the TLD component of the HCND and biased high by a factor of 8 overall due to its calibration to unmoderated 252Cf. The study recommends further work to correct instabilities in the HCND algorithm and to explore the potential shown by the bubble-based dosimeters.

  18. a Thermally Desorbable Miniature Passive Dosimeter for Organic Vapors

    NASA Astrophysics Data System (ADS)

    Gonzalez, Jesus Antonio

    A thermally desorbable miniature passive dosimeter (MPD) for organic vapors has been developed in conformity with theoretical and practical aspects of passive dosimeter design. The device was optimized for low sample loadings resulting from short-term and/or low concentration level exposure. This was accomplished by the use of thermal desorption rather than solvent elution, which provided the GC method with significantly higher sensitivity. Laboratory evaluation of this device for factors critical to the performance of passive dosimeters using benzene as the test vapor included: desorption efficiency (97.2%), capacity (1400 ppm-min), sensitivity (7ng/sample or 0.06 ppmv for 15 minutes sampling) accuracy and precision, concentration level, environmental conditions (i.e., air face velocity, relative humidity) and sample stability during short (15 minutes) and long periods of time (15 days). This device has demonstrated that its overall accuracy meets NIOSH and OSHA requirements for a sampling and analytical method for the exposure concentration range of 0.1 to 50 ppm (v/v) and 15 minutes exposures. It was demonstrated that the MPD operates in accordance with theoretically predicted performance and should be adequate for short-term and/or low concentration exposure monitoring of organic vapors in the workplace. In addition a dynamic vapor exposure evaluation system for passive dosimeters have been validated using benzene as the test vapor. The system is capable of generating well defined short-square wave concentration profiles suitable for the evaluation of passive dosimeters for ceiling exposure monitoring.

  19. Greenland surface albedo changes 1981-2012 from satellite observations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Significant melt over Greenland has been observed during the last several decades associated with extreme warming events over the northern Atlantic Ocean. An analysis of surface albedo change over Greenland is presented, using a 32-year consistent satellite albedo product from the Global Land Surfac...

  20. Anthropogenic desertification by high-albedo pollution Observations and modeling

    NASA Technical Reports Server (NTRS)

    Otterman, J.; Rosenberg, N. W.; Rosenberg, E.

    1974-01-01

    ERTS-1 MSS albedo data of Western Negev, Sinai and the Gaza strip are presented. A sharp contrast in albedo exists across the Negev-Sinai and Negev-Gaza strip borders. Anthropogenic desertification has occurred on the Arab side due to overgrazing and Bedouin agriculture, whereas natural vegetation grows much more abundantly on the Israeli side.

  1. Effect of shaddock albedo addition on the properties of frankfurters.

    PubMed

    Shan, Bing; Li, Xingmin; Pan, Teng; Zheng, Limin; Zhang, Hao; Guo, Huiyuan; Jiang, Lu; Zhen, Shaobo; Ren, Fazheng

    2015-07-01

    To explore the potential as a natural auxiliary emulsifier, shaddock albedo was added into frankfurters at six different levels: 0.0, 2.5, 5.0, 7.5, 10 and 12.5 %. The emulsion capacity (EC) of meat batters and cooking properties of frankfurters were evaluated. EC of meat batters was improved with the addition of shaddock albedo and the maximum value was reached at the 5 % albedo concentration. The addition of shaddock albedo resulted in lower cooking losses of frankfurters, with the lowest value obtained at the 7.5 % level. The presence of shaddock albedo decreased the total expressible fluid (TEF) and the proportion of fat in total expressible fluid (PF) which indicated the emulsion stability of frankfurters and the lowest values both occurred at the concentration of 7.5 %. Shaddock albedo inclusion increased the lightness and yellowness of frankfurters and decreased redness. Texture profile analysis showed increased hardness and decreased chewiness of frankfurters with the addition of shaddock albedo. Consequently, shaddock albedo could be a potential source of auxiliary emulsifier filler for emulsion-type meat products.

  2. The albedo of snow for partially cloudy skies

    NASA Technical Reports Server (NTRS)

    Choudhury, B. J.; Chang, A. T. C.

    1980-01-01

    The input parameters of the model are atmospheric precipitable water, ozone content, turbidity, cloud optical thickness, size and shape of ice crystal of snow and surface pressure. The model outputs spectral and integrated solar flux snow reflectance as a function of solar elevation and fractional cloudcover. The model is illustrated using representative parameters for the Antarctic coastal regions. The albedo for a clear sky depends inversely on the solar elevation. At high elevation the albedo depends primarily upon the grain size; at low elevation this dependence is on grain size and shape. The gradient of the albedo-elevation curve increases as the grains get larger and faceted. The albedo for a dense overcast is a few percent higher than the clear sky albedo at high elevations. A simple relation between the grain size and the overcast albedo is obtained. For a set of grain size and shape, the albedo matrices (the albedo as a function of solar elevation and fractional cloudcover) are tabulated.

  3. Solar Radiation Management, Cloud Albedo Enhancement

    NASA Astrophysics Data System (ADS)

    Salter, Stephen H.

    Cloud albedo enhancement is one of several possible methods of solar radiation management by which the rate of increase in world temperatures could be reduced or even reversed. It depends on a well-known phenomenon in atmospheric physics known as the Twomey effect. Twomey argued that the reflectivity of clouds is a function of the size distribution of the drops in the cloud top. In clean mid-ocean air masses, there is a shortage of the condensation nuclei necessary for initial drop formation in addition to high relative humidity. This means that the liquid water in a cloud has to be in relatively large drops. If extra nuclei could be artificially introduced, the same amount of liquid water would be shared among a larger number of smaller drops which would have a larger surface area to reflect a larger fraction of the incoming solar energy back out to space.

  4. Global color and albedo variations on Io

    USGS Publications Warehouse

    McEwen, A.S.

    1988-01-01

    Three multispectral mosaics of Io have been produced from Voyager imaging data: a global mosaic from each of the Voyager 1 and Voyager 2 data sets and a high-resolution mosaic of the region surrounding the volcano Ra Patera. The mosaics are maps of normal albedo and color in accurate geometric map formats. Io's photometric behavior, mapped with a two-image technique, is spatially variable, especially in the bright white areas. The disk-integrated color and albedo of the satellite have been remarkably constant over recent decades, despite the volcanic activity and the many differences between Voyager 1 and 2 images (acquired just 4 months apart). This constancy is most likely due to the consistent occurrence of large Pele-type plumes with relatively dark, red deposits in the region from long 240 to 360??. A transient brightening southeast of Pele during the Voyager 1 encounter was probably due to real changes in surface and/or atmospheric materials, rather than to photometric behavior. The intrinsic spectral variability of Io, as seen in a series of two-dimensional histograms of the multispectral mosaics, consists of continuous variation among three major spectral end members. The data were mapped into five spectral units to compare them with laboratory measurements of candidate surface materials and to show the planimetric distributions. Unit 1 is best fit by the spectral reflectance of ordinary elemental sulfur, and it is closely associated with the Peletype plume deposits. Unit 2 is strongly confined to the polar caps above about latitude ??50??, but its composition is unknown. Unit 5 is probably SO2 with relatively minor contamination; it is concentrated in the equatorial region and near the long-lived Prometheus-type plumes. Units 3 and 4 are gradational between units 1 and 5. In addition to SO2 and elemental sulfur, other plausible components of the surface are polysulfur oxides, FeCl2, Na2S, and NaHS. ?? 1988.

  5. The solar zenith angle dependence of desert albedo

    NASA Astrophysics Data System (ADS)

    Wang, Zhuo; Barlage, Michael; Zeng, Xubin; Dickinson, Robert E.; Schaaf, Crystal B.

    2005-03-01

    Most land models assume that the bare soil albedo is a function of soil color and moisture but independent of solar zenith angle (SZA). However, analyses of the Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) and albedo data over thirty desert locations indicate that bare soil albedo does vary with SZA. This is further confirmed using the in situ data. In particular, bare soil albedo normalized by its value at 60° SZA can be adequately represented by a one-parameter formulation (1 + C)/(1 + 2C * cos(SZA)) or a two-parameter formulation (1 + B1 * f1(SZA) + B2 * f2(SZA)). Using the MODIS and in situ data, the empirical parameters C, B1, and B2 are taken as 0.15, 0.346 and 0.063. The SZA dependence of soil albedo is also found to significantly affect the modeling of land surface energy balance over a desert site.

  6. Fire disturbance effects on land surface albedo in Alaskan tundra

    NASA Astrophysics Data System (ADS)

    French, Nancy H. F.; Whitley, Matthew A.; Jenkins, Liza K.

    2016-03-01

    The study uses satellite Moderate Resolution Imaging Spectroradiometer albedo products (MCD43A3) to assess changes in albedo at two sites in the treeless tundra region of Alaska, both within the foothills region of the Brooks Range, the 2007 Anaktuvuk River Fire (ARF) and 2012 Kucher Creek Fire (KCF). Results are compared to each other and other studies to assess the magnitude of albedo change and the longevity of impact of fire on land surface albedo. In both sites there was a marked decrease of albedo in the year following the fire. In the ARF, albedo slowly increased until 4 years after the fire, when it returned to albedo values prior to the fire. For the year immediately after the fire, a threefold difference in the shortwave albedo decrease was found between the two sites. ARF showed a 45.3% decrease, while the KCF showed a 14.1% decrease in shortwave albedo, and albedo is more variable in the KCF site than ARF site 1 year after the fire. These differences are possibly the result of differences in burn severity of the two fires, wherein the ARF burned more completely with more contiguous patches of complete burn than KCF. The impact of fire on average growing season (April-September) surface shortwave forcing in the year following fire is estimated to be 13.24 ± 6.52 W m-2 at the ARF site, a forcing comparable to studies in other treeless ecosystems. Comparison to boreal studies and the implications to energy flux are discussed in the context of future increases in fire occurrence and severity in a warming climate.

  7. Generating multi-scale albedo look-up maps using MODIS BRDF/Albedo products and landsat imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface albedo determines radiative forcing and is a key parameter for driving Earth’s climate. Better characterization of surface albedo for individual land cover types can reduce the uncertainty in estimating changes to Earth’s radiation balance due to land cover change. This paper presents a mult...

  8. Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

    SciTech Connect

    Liu, Y.; Wu, W.; Jensen, M. P.; Toto, T.

    2011-07-21

    This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surface-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fraction, and cloud albedo. The analytical expression is then used to deduce a new approach for inferring cloud albedo from concurrent surface-based measurements of downwelling surface shortwave radiation and cloud fraction. High-resolution decade-long data on cloud albedos are obtained by use of this surface-based approach over the US Department of Energy's Atmospheric Radiaton Measurement (ARM) Program at the Great Southern Plains (SGP) site. The surface-based cloud albedos are further compared against those derived from the coincident GOES satellite measurements. The three long-term (1997-2009) sets of hourly data on shortwave cloud radiative forcing, cloud fraction and cloud albedo collected over the SGP site are analyzed to explore the multiscale (diurnal, annual and inter-annual) variations and covariations. The analytical formulation is useful for diagnosing deficiencies of cloud-radiation parameterizations in climate models.

  9. Soil Albedo in Relation to Soil Color, Moisture and Roughness

    NASA Astrophysics Data System (ADS)

    Fontes, Adan Fimbres

    Land surface albedo is the ratio of reflected to incident solar radiation. It is a function of several surface parameters including soil color, moisture, roughness and vegetation cover. A better understanding of albedo and how it changes in relation to variations in these parameters is important in order to help improve our ability to model the effects of land surface modifications on climate. The objectives of this study were (1) To determine empirical relationships between smooth bare soil albedo and soil color, (2) To develop statistical relationships between albedo and ground-based thematic mapper (TM) measurements of spectral reflectances, (3) To determine how increased surface roughness caused by tillage reduces bare soil albedo and (4) To empirically relate albedo with TM data and other physical characteristics of mixed grass/shrubland sites at Walnut Gulch Watershed. Albedos, colors and spectral reflectances were measured by Eppley pyranometer, Chroma Meter CR-200 and a Spectron SE-590, respectively. Measurements were made on two field soils (Gila and Pima) at the Campus Agricultural Center (CAC), Tucson, AZ. Soil surface roughness was measured by a profile meter developed by the USDA/ARS. Additional measurements were made at the Maricopa Agricultural Center (MAC) for statistical model testing. Albedos of the 15 smooth, bare soils (plus silica sand) were determined by linear regression to be highly correlated (r^2 = 0.93, p > 0.01) with color values for both wet and dry soil conditions. Albedos of the same smooth bare soils were also highly correlated (r^2>=q 0.86, p > 0.01) with spectral reflectances. Testing of the linear regression equations relating albedo to soil color and spectral reflectances using the data from MAC showed a high correlation. A general nonlinear relationship given by y = 8.366ln(x) + 37.802 r^2 = 0.71 was determined between percent reduction in albedo (y) and surface roughness index (x) for wet and dry Pima and Gila field soils

  10. Modified ferrous ammonium sulfate benzoic acid xyelenol orange (MFBX) and thermoluminescent dosimeters--a comparative study.

    PubMed

    Brindha, S; Rose, J V R; Sathyan, S; Singh I, Rabi Raja; Ravindran, B Paul

    2002-06-07

    Radiation dosimetry deals with the determination of absorbed dose to the medium exposed to ionizing radiation. Chemical dosimetry depends on oxidation or reduction of chemicals by ionizing radiation. A ferrous ammonium sulfate benzoic acid xyelenol orange (FBX) dosimeter based on this principle is being used as a clinical dosimeter at present. Certain modifications were carried out in the preparation and storage of the FBX dosimeter to increase its shelf life. The resulting dosimeter was called a modified FBX (MFBX) dosimeter and has been used in our department for the past few years. An extensive study of the dose, dose rate and energy response of the dosimeter was carried out and compared with a thermoluminescent (LiF7) dosimeter. The results obtained were found to be comparable to the thermoluminescent (LiF7) dosimeter. Hence it was concluded that the MFBX dosimeter could be used for phantom dosimetry, data collection and in vivo measurements. Easier preparation and availability of the reagents are added advantages of using MFBX as a clinical dosimeter in small radiotherapy departments.

  11. ALBEDOS OF SMALL HILDA GROUP ASTEROIDS AS REVEALED BY SPITZER

    SciTech Connect

    Ryan, Erin Lee; Woodward, Charles E. E-mail: chelsea@astro.umn.edu

    2011-06-15

    We present thermal 24 {mu}m observations from the Spitzer Space Telescope of 62 Hilda asteroid group members with diameters ranging from 3 to 12 km. Measurements of the thermal emission, when combined with reported absolute magnitudes, allow us to constrain the albedo and diameter of each object. From our Spitzer sample, we find the mean geometric albedo, p{sub V} = 0.07 {+-} 0.05, for small (D < 10 km) Hilda group asteroids. This Spitzer-derived value of p{sub V} is greater than and spans a larger range in albedo space than the mean albedo of large (D {approx}> 10 km) Hilda group asteroids which is p{sub V} = 0.04 {+-} 0.01. Though this difference may be attributed to space weathering, the small Hilda group population reportedly displays greater taxonomic range from C-, D-, and X-type whose albedo distributions are commensurate with the range of determined albedos. We discuss the derived Hilda size-frequency distribution, color-color space, and geometric albedo for our survey sample in the context of the expected migration induced 'seeding' of the Hilda asteroid group with outer solar system proto-planetesimals as outlined in the 'Nice' formalism.

  12. The Gamma-ray Albedo of the Moon

    SciTech Connect

    Moskalenko, Igor V.; Porter, Troy A.; /UC, Santa Cruz

    2007-09-28

    We use the GEANT4 Monte Carlo framework to calculate the {gamma}-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of {gamma}-rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalization; this makes it a useful 'standard candle' for {gamma}-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of {gamma}-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo {gamma}-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo {gamma}-rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.

  13. The Gamma-Ray Albedo of the Moon

    SciTech Connect

    Moskalenko, I.V.; Porter, T.A.; /UC, Santa Cruz

    2008-03-25

    We use the GEANT4 Monte Carlo framework to calculate the {gamma}-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of {gamma}-rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalization; this makes it a useful 'standard candle' for {gamma}-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of {gamma}-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo {gamma}-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo {gamma}-rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.

  14. Arid land monitoring using Landsat albedo difference images

    USGS Publications Warehouse

    Robinove, Charles J.; Chavez, Pat S.; Gehring, Dale G.; Holmgren, Ralph

    1981-01-01

    The Landsat albedo, or percentage of incoming radiation reflected from the ground in the wavelength range of 0.5 [mu]m to 1.1 [mu]m, is calculated from an equation using the Landsat digital brightness values and solar irradiance values, and correcting for atmospheric scattering, multispectral scanner calibration, and sun angle. The albedo calculated for each pixel is used to create an albedo image, whose grey scale is proportional to the albedo. Differencing sequential registered images and mapping selected values of the difference is used to create quantitative maps of increased or decreased albedo values of the terrain. All maps and other output products are in black and white rather than color, thus making the method quite economical. Decreases of albedo in arid regions may indicate improvement of land quality; increases may indicate degradation. Tests of the albedo difference mapping method in the Desert Experimental Range in southwestern Utah (a cold desert with little long-term terrain change) for a four-year period show that mapped changes can be correlated with erosion from flash floods, increased or decreased soil moisture, and increases or decreases in the density of desert vegetation, both perennial shrubs and annual plants. All terrain changes identified in this test were related to variations in precipitation. Although further tests of this method in hot deserts showing severe "desertification" are needed, the method is nevertheless recommended for experimental use in monitoring terrain change in other arid and semiarid regions of the world.

  15. Simulations of tropical rainforest albedo: is canopy wetness important?

    PubMed

    Yanagi, Silvia N M; Costa, Marcos H

    2011-12-01

    Accurate information on surface albedo is essential for climate modelling, especially for regions such as Amazonia, where the response of the regional atmospheric circulation to the changes on surface albedo is strong. Previous studies have indicated that models are still unable to correctly reproduce details of the seasonal variation of surface albedo. Therefore, it was investigated the role of canopy wetness on the simulated albedo of a tropical rainforest by modifying the IBIS canopy radiation transfer code to incorporate the effects of canopy wetness on the vegetation reflectance. In this study, simulations were run using three versions of the land surface/ecosystem model IBIS: the standard version, the same version recalibrated to fit the data of albedo on tropical rainforests and a modified version that incorporates the effects of canopy wetness on surface albedo, for three sites in the Amazon forest at hourly and monthly scales. The results demonstrated that, at the hourly time scale, the incorporation of canopy wetness on the calculations of radiative transfer substantially improves the simulations results, whereas at the monthly scale these changes do not substantially modify the simulated albedo.

  16. Joint albedo estimation and pose tracking from video.

    PubMed

    Taheri, Sima; Sankaranarayanan, Aswin C; Chellappa, Rama

    2013-07-01

    The albedo of a Lambertian object is a surface property that contributes to an object's appearance under changing illumination. As a signature independent of illumination, the albedo is useful for object recognition. Single image-based albedo estimation algorithms suffer due to shadows and non-Lambertian effects of the image. In this paper, we propose a sequential algorithm to estimate the albedo from a sequence of images of a known 3D object in varying poses and illumination conditions. We first show that by knowing/estimating the pose of the object at each frame of a sequence, the object's albedo can be efficiently estimated using a Kalman filter. We then extend this for the case of unknown pose by simultaneously tracking the pose as well as updating the albedo through a Rao-Blackwellized particle filter (RBPF). More specifically, the albedo is marginalized from the posterior distribution and estimated analytically using the Kalman filter, while the pose parameters are estimated using importance sampling and by minimizing the projection error of the face onto its spherical harmonic subspace, which results in an illumination-insensitive pose tracking algorithm. Illustrations and experiments are provided to validate the effectiveness of the approach using various synthetic and real sequences followed by applications to unconstrained, video-based face recognition.

  17. Fricke Gel Dosimeter Tissue-Equivalence a Monte Carlo Study

    NASA Astrophysics Data System (ADS)

    Valente, M.; Bartesaghi, G.; Gambarini, G.; Brusa, D.; Castellano, G.; Carrara, M.

    2008-06-01

    Gel dosimetry has proved to be a valuable technique for absorbed dose distribution measurements in radiotherapy. FriXy-gel dosimeters consist of Fricke (ferrous sulphate) solution infused with xylenol orange. The solution is incorporated to a gel matrix in order to fix it to a solid structure allowing good spatial resolution and is imaged with a transportable optical system, measuring visible light transmittance before and after irradiation. This paper presents an evaluation of total photon mass attenuation coefficients at energies in the range of 50 keV-10MeV for the radiochromic FriXy gel dosimeter sensitive material. Mass attenuation coefficient estimations have been performed by means of Monte Carlo (PENELOPE) simulations. These calculations have been carried out for the FriXy gel sensitive material as well as for soft tissue (ICRU) and pure liquid water; a comparison of the obtained data shows good agreement between the different materials.

  18. Coherent Backscattering in Los Albedo Media

    NASA Astrophysics Data System (ADS)

    Nelson, R. M.; Hapke, B. W.; Hale, A. S.; Smythe, W. D.; Piatek, J.

    2002-09-01

    The opposition effect [1] observed in phase curves of materials in the lab and on planetary surfaces is attributed to two processes: 'shadow hiding opposition effect' (SHOE) and 'coherent backscattering opposition effect' (CBOE) [2,3,4]. The relative contributions of SHOE and CBOE are studied by measuring reflectance phase curves in circularly polarized light. If single scattering predominates, the circular polarization ratio (CPR) decreases with decreasing phase angle. If multiple scattering predominates, the CPR strongly increases. We observed this increase in CPR in highly reflective media [5,6,7]. In low reflectance media most of the returned signal is singly scattered and CPR is not expected to sharply increase. We have found that most such materials indeed exhibit only a slight CPR increase. However, lunar soils show a strong CPR increase [8]. Recently we encountered another interesting counter example in Boron Carbide-a material with albedo even lower than the Moon's. We find a significant CPR increase, a result inconsistent with the conventional interpretation of CBOE [8]. This suggests that albedo alone is not the principal regulator of CBOE. This CBOE may be due to multiple scattering within individual particles [10]. Unusual particle shapes may facilitate this process. Understanding this behavior contributes to the development of models that can retrieve textural properties from remote sensing data. Work performed at JPL/PITT under NASA PG&G grants. 1.Geherels, T. Astrophys. J, 123, 331-338, 1956. 2. Hapke, B. Icarus, 67, 246-280, 1986. 3. Shkuratov, Yu. SA-A.J., 27, 581-583, 1983. 4. Hapke, B. Icarus, 88, 407-417, 1990. 5. Nelson, R., et al. Icarus 131, 223-230, 1998. 6. Nelson, R., et al Icarus, 147, 545-558, 2000. 7. Nelson, R., et al. Planet. Space Sci, 2002. 8. Hapke B. et al. Science, 260, 509-511. 9. Mishchenko, M.I. Earth, Moon and Planets, 58, 127-144, 1992. 10. Hapke, B. Icarus, 157, 534-537, 2002

  19. An optical dosimeter for monitoring heavy metal ions in water

    NASA Astrophysics Data System (ADS)

    Mignani, Anna G.; Regan, Fiona; Leamy, D.; Mencaglia, A. A.; Ciaccheri, L.

    2005-05-01

    This work presents an optochemical dosimeter for determining and discriminating nickel, copper, and cobalt ions in water that can be used as an early warning system for water pollution. An inexpensive fiber optic spectrophotometer monitors the sensor's spectral behavior under exposure to water solutions of heavy metal ions in the 1-10 mg/l concentration range. The Principal Component Analysis (PCA) method quantitatively determines the heavy metals and discriminates their type and combination.

  20. Accelerator room photoneutron and photon background measurements using thermoluminescent dosimeters.

    PubMed

    Anderson, D W; Hwang, C C

    1983-02-01

    Photoneutron dose equivalents and photon doses in the treatment room of a clinical linear accelerator were measured with sets of isotopically enriched LiF thermoluminescent dosimeters and a moderating sphere. Dosimeter neutron calibrations with 252Cf sources were repeated many times during the extended series of measurements because the 6LiF dosimeter sensitivity increased with successive neutron irradiations. Expressed as a fraction of the primary bremsstrahlung beam dose at maximum, the photoneutron background was 2.04 +/- 0.05 mrem/rad (10(-3) Sv/Gy) at 1 m lateral to beam center in the patient midplane at 25 MV. The fraction of this result due to thermal neutrons was found to be only about 2%. The photon background dose was 2.98 +/- 0.04 mrad/rad (10(-3) Gy/Gy). The photoneutron dose equivalent per unit primary dose was found to be nearly independent of the collimator size used but increased by 40% when the bremsstrahlung endpoint energy was increased from 20 to 35 MeV with no change in flattening filters.

  1. Method for preparing dosimeter for measuring skin dose

    DOEpatents

    Jones, Donald E.; Parker, DeRay; Boren, Paul R.

    1982-01-01

    A personnel dosimeter includes a plurality of compartments containing thermoluminescent dosimeter phosphors for registering radiation dose absorbed in the wearer's sensitive skin layer and for registering more deeply penetrating radiation. Two of the phosphor compartments communicate with thin windows of different thicknesses to obtain a ratio of shallowly penetrating radiation, e.g. beta. A third phosphor is disposed within a compartment communicating with a window of substantially greater thickness than the windows of the first two compartments for estimating the more deeply penetrating radiation dose. By selecting certain phosphors that are insensitive to neutrons and by loading the holder material with neutron-absorbing elements, energetic neutron dose can be estimated separately from other radiation dose. This invention also involves a method of injection molding of dosimeter holders with thin windows of consistent thickness at the corresponding compartments of different holders. This is achieved through use of a die insert having the thin window of precision thickness in place prior to the injection molding step.

  2. Dosimeter for measuring skin dose and more deeply penetrating radiation

    DOEpatents

    Jones, Donald E.; Parker, DeRay; Boren, Paul R.

    1981-01-01

    A personnel dosimeter includes a plurality of compartments containing thermoluminescent dosimeter phosphors for registering radiation dose absorbed in the wearer's sensitive skin layer and for registering more deeply penetrating radiation. Two of the phosphor compartments communicate with thin windows of different thicknesses to obtain a ratio of shallowly penetrating radiation, e.g. beta. A third phosphor is disposed within a compartment communicating with a window of substantially greater thickness than the windows of the first two compartments for estimating the more deeply penetrating radiation dose. By selecting certain phosphors that are insensitive to neutrons and by loading the holder material with netruon-absorbing elements, energetic neutron dose can be estimated separately from other radiation dose. This invention also involves a method of injection molding of dosimeter holders with thin windows of consistent thickness at the corresponding compartments of different holders. This is achieved through use of a die insert having the thin window of precision thickness in place prior to the injection molding step.

  3. Real-time dosimeter targeted to nuclear applications

    NASA Astrophysics Data System (ADS)

    Correia, Alexandre; Rosa, Carla C.; Santos, Pedro M. P.; Falcão, António N.; Lorentz, Katharina

    2014-08-01

    An intrinsic fiber optic dosimeter (FOD) targeted to nuclear applications is presented. The proposed real-time dosimeter provides dose information based on the historic record over time of the effects of ionizing radiation on single- and multimode pure silica fibers, and also on PMMA plastic fibers. The effect of 60Co gamma irradiation on optical links based on silica and plastic fibers were assessed, considering thermal environment effects over a wide range of variation of the operating parameters. Cerenkov radiation and radiation-induced absorption effects were in focus. The corresponding distortion and spectral transmission degradation were evaluated over wide range of the operating parameters. Radiation induced attenuation (RIA) has shown a spectral band dependent behaviour up to 840 Gy dose levels. The performance of different fibers was assessed against the performance of non-irradiated fibers. From the measurements of dose rate and total dose imparted by ionizing radiation in the fibers we verified that fibers with radiation resistance issues showed wavelength-dependent radiation sensitivity increasing with dose rate. Upon evaluation of correlations between the total dose, the induced loss at various dose rates and different wavelengths, it was concluded that intrinsic fiber dosimeters can be used for dose rates in the range 4 - 28 Gy/min., typical of severe radiation environments.

  4. Earth albedo neutrons from 10 to 100 MeV.

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Simnett, G. M.; White, R. S.

    1972-01-01

    We report the measurement of the energy and angular distributions of earth albedo neutrons from 10 to 100 MeV at 40 deg N geomagnetic latitude from a balloon at 120,000 ft, below 4.65 g/sq cm. The albedo-neutron omnidirectional energy distribution is flat to 50 MeV, then decreases with energy. The absolute neutron energy distribution is of the correct strength and shape for the albedo neutrons to be the source of the protons trapped in earth's inner radiation belt.

  5. The effect of aerosols on the earth-atmosphere albedo

    NASA Technical Reports Server (NTRS)

    Herman, B. M.; Browning, S. R.

    1975-01-01

    The paper presents calculations of the change in reflected flux by the earth-atmosphere system in response to increases in the atmospheric aerosol loading for a range of complex indices of refraction, solar elevation angle and ground albedo. Results show that, for small values of ground albedo, the reflected solar flux may either increase or decrease with increasing aerosol loadings, depending upon the complex part of the index of refraction of the aerosols. For high ground albedos, an increase in aerosol levels always results in a decrease of reflected flux (i.e., a warming of the earth-atmosphere system).

  6. Neutron dosimetry with TL albedo dosemeters at high energy accelerators.

    PubMed

    Haninger, T; Fehrenbacher, G

    2007-01-01

    The GSF-Personal Monitoring Service uses the TLD albedo dosemeter as standard neutron personal dosemeter. Due to its low sensitivity for fast neutrons however, it is generally not recommended for workplaces at high-energy accelerators. Test measurements with the albedo dosemeter were performed at the accelerator laboratories of GSI in Darmstadt and DESY in Hamburg to reconsider this hypothesis. It revealed that the albedo dosemeter can also be used as personal dosemeter at these workplaces, because at all measurement locations a significant part of neutrons with lower energies could be found, which were produced by scattering at walls or the ground.

  7. Lunar Terrain and Albedo Reconstruction from Apollo Imagery

    NASA Technical Reports Server (NTRS)

    Nefian, Ara V.; Kim, Taemin; Broxton, Michael; Moratto, Zach

    2010-01-01

    Generating accurate three dimensional planetary models and albedo maps is becoming increasingly more important as NASA plans more robotics missions to the Moon in the coming years. This paper describes a novel approach for separation of topography and albedo maps from orbital Lunar images. Our method uses an optimal Bayesian correlator to refine the stereo disparity map and generate a set of accurate digital elevation models (DEM). The albedo maps are obtained using a multi-image formation model that relies on the derived DEMs and the Lunar- Lambert reflectance model. The method is demonstrated on a set of high resolution scanned images from the Apollo era missions.

  8. Variable control of neutron albedo in toroidal fusion devices

    DOEpatents

    Jassby, Daniel L.; Micklich, Bradley J.

    1986-01-01

    An arrangement is provided for controlling neutron albedo in toroidal fusion devices having inboard and outboard vacuum vessel walls for containment of the neutrons of a fusion plasma. Neutron albedo material is disposed immediately adjacent the inboard wall, and is movable, preferably in vertical directions, so as to be brought into and out of neutron modifying communication with the fusion neutrons. Neutron albedo material preferably comprises a liquid form, but may also take pebble, stringer and curtain-like forms. A neutron flux valve, rotatable about a vertical axis is also disclosed.

  9. Aerial albedos of natural vegetation in South-eastern Australia

    NASA Technical Reports Server (NTRS)

    Howard, J. A.

    1977-01-01

    Black-and-white low-level 70mm photography was used to record the track of the aircraft, which was then plotted on conventional 1:80,000 23 cm photogrammetric photographs and referenced against simultaneous measurements of the beam albedos of vegetation. Using stereoscopic pairs of the 70mm photographs, the vegetation was classified into sub-formations. Marked differences in the 'sub-formation' albedos were observed. A two-way table using stand height and crown cover of the sub-formations clearly showed a very distinctive trend of albedos. This finding may be important in other vegetal studies.

  10. The sizes, albedos, and comae of Centaurs

    NASA Astrophysics Data System (ADS)

    Trilling, David; Mueller, Michael; Noll, Keith; Stansberry, John

    2008-03-01

    The small bodies of the Solar System retain the best information about the era of planet formation and the subsequent evolution of our planetary system. As escaped KBOs that wander close(r) to Earth and to the Sun, we have the opportunity to study KBOs with a sensitivity and resolution that is not generally available in the main Kuiper Belt. Centaurs are both dynamically transitional --- as former Kuiper Belt Objects and potentially future comets --- and physically so, as some display cometary activity that is absent in the Kuiper Belt. We propose here to observe 27 Centaurs with Spitzer to address these fundamental questions about this interesting transitional population. We will determine their physical properties --- size and albedo --- as a probe of their fundamental nature. We will carry out a coma search. This program will more than double the number of Centaurs observed with Spitzer and create a sample of nearly 50 targets in which we can look for correlations among physical properties and derive a true size distribution for Centaurs that can be compared to the best-known KBO and Jupiter family comet size distributions. If any Centaurs in our sample are observed to be binaries in a companion HST program, we will derive their densities, and compare Centaur densities to KBO densities. We will look for common properties among active Centaurs. The results will reveal the physical properties of this interesting transitional population, and help constrain the suggested link between Kuiper Belt Objects and Jupiter family comets.

  11. Investigation of radiological properties and water equivalency of PRESAGE dosimeters

    SciTech Connect

    Gorjiara, Tina; Hill, Robin; Kuncic, Zdenka; Adamovics, John; Bosi, Stephen; Kim, Jung-Ha; Baldock, Clive

    2011-04-15

    Purpose: PRESAGE is a dosimeter made of polyurethane, which is suitable for 3D dosimetry in modern radiation treatment techniques. Since an ideal dosimeter is radiologically water equivalent, the authors investigated water equivalency and the radiological properties of three different PRESAGE formulations that differ primarily in their elemental compositions. Two of the formulations are new and have lower halogen content than the original formulation. Methods: The radiological water equivalence was assessed by comparing the densities, interaction probabilities, and radiation dosimetry properties of the three different PRESAGE formulations to the corresponding values for water. The relative depth doses were calculated using Monte Carlo methods for 50, 100, 200, and 350 kVp and 6 MV x-ray beams. Results: The mass densities of the three PRESAGE formulations varied from 5.3% higher than that of water to as much as 10% higher than that of water for the original formulation. The probability of photoelectric absorption in the three different PRESAGE formulations varied from 2.2 times greater than that of water for the new formulations to 3.5 times greater than that of water for the original formulation. The mass attenuation coefficient for the three formulations is 12%-50% higher than the value for water. These differences occur over an energy range (10-100 keV) in which the photoelectric effect is the dominant interaction. The collision mass stopping powers of the relatively lower halogen-containing PRESAGE formulations also exhibit marginally better water equivalency than the original higher halogen-containing PRESAGE formulation. Furthermore, the depth dose curves for the lower halogen-containing PRESAGE formulations are slightly closer to that of water for a 6 MV beam. In the kilovoltage energy range, the depth dose curves for the lower halogen-containing PRESAGE formulations are in better agreement with water than the original PRESAGE formulation. Conclusions: Based

  12. The Assessment of Effective Dose Equivalent Using Personnel Dosimeters

    NASA Astrophysics Data System (ADS)

    Xu, Xie

    From January 1994, U.S. nuclear plants must develop a technically rigorous approach for determining the effective dose equivalent for their work forces. This dissertation explains concepts associated with effective dose equivalent and describes how to assess effective dose equivalent by using conventional personnel dosimetry measurements. A Monte Carlo computer code, MCNP, was used to calculate photon transport through a model of the human body. Published mathematical phantoms of the human adult male and female were used to simulate irradiation from a variety of external radiation sources in order to calculate organ and tissue doses, as well as effective dose equivalent using weighting factors from ICRP Publication 26. The radiation sources considered were broad parallel photon beams incident on the body from 91 different angles and isotropic point sources located at 234 different locations in contact with or near the body. Monoenergetic photons of 0.08, 0.3, and 1.0 MeV were considered for both sources. Personnel dosimeters were simulated on the surface of the body and exposed to with the same sources. From these data, the influence of dosimeter position on dosimeter response was investigated. Different algorithms for assessing effective dose equivalent from personnel dosimeter responses were proposed and evaluated. The results indicate that the current single-badge approach is satisfactory for most common exposure situations encountered in nuclear plants, but additional conversion factors may be used when more accurate results become desirable. For uncommon exposures involving source situated at the back of the body or source located overhead, the current approach of using multi-badges and assigning the highest dose is overly conservative and unnecessarily expensive. For these uncommon exposures, a new algorithm, based on two dosimeters, one on the front of the body and another one on the back of the body, has been shown to yield conservative assessment of

  13. Albedo neutron dosimetry in Germany: regulations and performance.

    PubMed

    Luszik-Bhadra, M; Zimbal, A; Busch, F; Eichelberger, A; Engelhardt, J; Figel, M; Frasch, G; Günther, K; Jordan, M; Martini, E; Haninger, T; Rimpler, A; Seifert, R

    2014-12-01

    Personal neutron dosimetry has been performed in Germany using albedo dosemeters for >20 y. This paper describes the main principles, the national standards, regulations and recommendations, the quality management and the overall performance, giving some examples.

  14. Cloud condensation nucleus-sulfate mass relationship and cloud albedo

    NASA Technical Reports Server (NTRS)

    Hegg, Dean A.

    1994-01-01

    Analysis of previously published, simultaneous measurements of cloud condensation nucleus number concentration and sulfate mass concentration suggest a nonlinear relationship between the two variables. This nonlinearity reduces the sensitivity of cloud albedo to changes in the sulfur cycle.

  15. Design of Interrogation Protocols for Radiation Dose Measurements Using Optically-Stimulated Luminescent Dosimeters.

    PubMed

    Abraham, Sara A; Kearfott, Kimberlee J; Jawad, Ali H; Boria, Andrew J; Buth, Tobias J; Dawson, Alexander S; Eng, Sheldon C; Frank, Samuel J; Green, Crystal A; Jacobs, Mitchell L; Liu, Kevin; Miklos, Joseph A; Nguyen, Hien; Rafique, Muhammad; Rucinski, Blake D; Smith, Travis; Tan, Yanliang

    2017-03-01

    Optically-stimulated luminescent dosimeters are capable of being interrogated multiple times post-irradiation. Each interrogation removes a fraction of the signal stored within the optically-stimulated luminescent dosimeter. This signal loss must be corrected to avoid systematic errors in estimating the average signal of a series of optically-stimulated luminescent dosimeter interrogations and requires a minimum number of consecutive readings to determine an average signal that is within a desired accuracy of the true signal with a desired statistical confidence. This paper establishes a technical basis for determining the required number of readings for a particular application of these dosimeters when using certain OSL dosimetry systems.

  16. Albedo Pattern Recognition and Time-Series Analyses in Malaysia

    NASA Astrophysics Data System (ADS)

    Salleh, S. A.; Abd Latif, Z.; Mohd, W. M. N. Wan; Chan, A.

    2012-07-01

    Pattern recognition and time-series analyses will enable one to evaluate and generate predictions of specific phenomena. The albedo pattern and time-series analyses are very much useful especially in relation to climate condition monitoring. This study is conducted to seek for Malaysia albedo pattern changes. The pattern recognition and changes will be useful for variety of environmental and climate monitoring researches such as carbon budgeting and aerosol mapping. The 10 years (2000-2009) MODIS satellite images were used for the analyses and interpretation. These images were being processed using ERDAS Imagine remote sensing software, ArcGIS 9.3, the 6S code for atmospherical calibration and several MODIS tools (MRT, HDF2GIS, Albedo tools). There are several methods for time-series analyses were explored, this paper demonstrates trends and seasonal time-series analyses using converted HDF format MODIS MCD43A3 albedo land product. The results revealed significance changes of albedo percentages over the past 10 years and the pattern with regards to Malaysia's nebulosity index (NI) and aerosol optical depth (AOD). There is noticeable trend can be identified with regards to its maximum and minimum value of the albedo. The rise and fall of the line graph show a similar trend with regards to its daily observation. The different can be identified in term of the value or percentage of rises and falls of albedo. Thus, it can be concludes that the temporal behavior of land surface albedo in Malaysia have a uniform behaviours and effects with regards to the local monsoons. However, although the average albedo shows linear trend with nebulosity index, the pattern changes of albedo with respects to the nebulosity index indicates that there are external factors that implicates the albedo values, as the sky conditions and its diffusion plotted does not have uniform trend over the years, especially when the trend of 5 years interval is examined, 2000 shows high negative linear

  17. Improving modeled snow albedo estimates during the spring melt season

    NASA Astrophysics Data System (ADS)

    Malik, M. Jahanzeb; Velde, Rogier; Vekerdy, Zoltan; Su, Zhongbo

    2014-06-01

    Snow albedo influences snow-covered land energy and water budgets and is thus an important variable for energy and water fluxes calculations. Here, we quantify the performance of the three existing snow albedo parameterizations under alpine, tundra, and prairie snow conditions when implemented in the Noah land surface model (LSM)—Noah's default and ones from the Biosphere-Atmosphere Transfer Scheme (BATS) and the Canadian Land Surface Scheme (CLASS) LSMs. The Noah LSM is forced with and its output is evaluated using in situ measurements from seven sites in U.S. and France. Comparison of the snow albedo simulations with the in situ measurements reveals that the three parameterizations overestimate snow albedo during springtime. An alternative snow albedo parameterization is introduced that adopts the shape of the variogram for the optically thick snowpacks and decreases the albedo further for optically thin conditions by mixing the snow with the land surface (background) albedo as a function of snow depth. In comparison with the in situ measurements, the new parameterization improves albedo simulation of the alpine and tundra snowpacks and positively impacts the simulation of snow depth, snowmelt rate, and upward shortwave radiation. An improved model performance with the variogram-shaped parameterization can, however, not be unambiguously detected for prairie snowpacks, which may be attributed to uncertainties associated with the simulation of snow density. An assessment of the model performance for the Upper Colorado River Basin highlights that with the variogram-shaped parameterization Noah simulates more evapotranspiration and larger runoff peaks in Spring, whereas the Summer runoff is lower.

  18. Surface albedo observations at Gusev Crater and Meridiani Planum, Mars

    USGS Publications Warehouse

    Bell, J.F.; Rice, M.S.; Johnson, J. R.; Hare, T.M.

    2008-01-01

    During the Mars Exploration Rover mission, the Pancam instrument has periodically acquired large-scale panoramic images with its broadband (739??338 nm) filter in order to estimate the Lambert bolometric albedo of the surface along each rover's traverse. In this work we present the full suite of such estimated albedo values measured to date by the Spirit and Opportunity rovers along their traverses in Gusev Crater and Meridiani Planum, respectively. We include estimated bolometric albedo values of individual surface features (e.g., outcrops, dusty plains, aeolian bed forms, wheel tracks, light-toned soils, and crater walls) as well as overall surface averages of the 43 total panoramic albedo data sets acquired to date. We also present comparisons to estimated Lambert albedo values taken from the Mars Global Surveyor Mars Orbiter Camera (MOC) along the rovers' traverses, and to the large-scale bolometric albedos of the sites from the Viking Orbiter Infrared Thermal Mapper (IRTM) and Mars Global Surveyor/Thermal Emission Spectrometer (TES). The ranges of Pancam-derived albedos at Gusev Crater (0.14 to 0.25) and in Meridiani Planum. (0.10 to 0.18) are in good agreement with IRTM, TES, and MOC orbital measurements. These data sets will be a useful tool and benchmark for future investigations of albodo variations with time, including measurements from orbital instruments like the Context Camera and High Resolution Imaging Science Experiment on Mars Reconnaissance Orbiter. Long-term, accurate albedo measurements could also be important for future efforts in climate modeling as well as for studies of active surface processes. Copyright 2008 by the American Geophysical Union.

  19. IAU nomenclature for albedo features on the planet Mercury

    NASA Technical Reports Server (NTRS)

    Dollfus, A.; Chapman, C. R.; Davies, M. E.; Gingerich, O.; Goldstein, R.; Guest, J.; Morrison, D.; Smith, B. A.

    1978-01-01

    The International Astronomical Union has endorsed a nomenclature for the albedo features on Mercury. Designations are based upon the mythological names related to the god Hermes; they are expressed in Latin form. The dark-hued albedo features are associated with the generic term Solitudo. The light-hued areas are designated by a single name without generic term. The 32 names adopted are allocated on the Mercury map.

  20. NEOWISE Diameters and Albedos V1.0

    NASA Astrophysics Data System (ADS)

    Mainzer, A. K.; Bauer, J. M.; Cutri, R. M.; Grav, T.; Kramer, E. A.; Masiero, J. R.; Nugent, C. R.; Sonnett, S. M.; Stevenson, R. A.; Wright, E. L.

    2016-06-01

    This PDS data set represents a compilation of published diameters, optical albedos, near-infrared albedos, and beaming parameters for minor planets detected by NEOWISE during the fully cryogenic, 3-band cryo, post-cryo and NEOWISE-Reactivation Year 1 operations. It contains data covering near-Earth asteroids, Main Belt asteroids, active Main Belt objects, Hildas, Jupiter Trojans, Centaurs, and Jovian and Saturnian irregular satellites. Methodology for physical property determination is described in the referenced articles.

  1. Albedo as a modulator of climate response to tropical deforestation

    SciTech Connect

    Dirmeyer, P.A.; Shukla, J.

    1994-10-01

    An atmospheric general circulation model with land surface properties represented by the simplified Simple Biosphere model is used to investigate the effects on local climate due to tropical deforestation for the Amazon basin. One control and three anomaly integrations of 4 years` duration are performed. In the anomaly integrations, rain forest in South America is replaced by degraded grassland. The anomaly integrations differ only in the optical properties of the grassland vegetation, with net surface albedos ranging from the same as to 0.09 lighter than that of rain forest. It is found that the change in climate, particularly rainfall, is strongly dependent on the change in surface albedo that accompanies deforestation. Replacement of forest by grass causes a reduction in transpiration and reduces frictional convergence by decreasing surface roughness. However, precipitation averaged over the deforested area is not necessarily reduced. Average precipitation decreases when the increase in albedo is greater than 0.03. If surface albedo is not increased appreciably as a result of deforestation, moisture flux convergence driven by the increase in surface temperature can offset the other effects, and average precipitation increases. As albedo is increased, surface temperature does not change, but surface latent and sensible heat flux decreases due to reduced radiational energy absorbed at the surface, resulting in a reduction in convection and precipitation. A change in the distribution of precipitation due to deforestation that appears to be independent of the albedo is observed.

  2. Albedo as a modulator of climate response to tropical deforestation

    NASA Technical Reports Server (NTRS)

    Dirmeyer, Paul A.; Shukla, J.

    1994-01-01

    An atmospheric general circulation model with land surface properties represented by the simplified Simple Biosphere model is used to investigate the effects on local climate due to tropical deforestation for the Amazon basin. One control and three anomaly integrations of 4 years' duration are performed. In the anomaly integrations, rain forest in South America is replaced by degraded grassland. The anomaly integrations differ only in the optical properties of the grassland vegetation, with net surface albedos ranging from the same as to 0.09 lighter than that of rain forest. It is found that the change in climate, particularly rainfall, is strongly dependent on the change in surface albedo that accompanies deforestation. Replacement of forest by grass causes a reduction in transpiration and reduces frictional convergence by decreasing surface roughness. However, precipitation averaged over the deforested area is not necessarily reduced. Average precipitation decreases when the increase in albedo is greater than 0.03. If surface albedo is not increased appreciably as a result of deforestation, moisture flux convergence driven by the increase in surface temperature can offset the other effects, and average precipitation increases. As albedo is increased, surface temperature does not change, but surface latent and sensible heat flux decreases due to reduced radiational energy absorbed at the surface, resulting in a reduction in convection and precipitation. A change in the distribution of precipitation due to deforestation that appears to be independent of the albedo is observed.

  3. Accurate albedos of the brightest regions on Io

    NASA Astrophysics Data System (ADS)

    Simonelli, D. P.; Veverka, J.

    1985-04-01

    The brightest, coldest areas on Io, the white regions, may act as cold traps for SO2 gas, and thus have an important role in governing the pressure, diurnal variation, and flow of the satellite's tenuous SO2 atmosphere. Therefore, it is essential to derive accurate albedos for the brightest regions, where the necessary albedos are those in the energy balance equation of the surface used to compute temperatures. Forty-one of the brightest of the white areas, each 60 to 120 km on a side were studied. The simplest way to estimate the required energy balance albedo for each region is to determine the Bond slbedo of a planet covered with that type of material. This process is outlined and resulting albedos are given. with the exception of several darker regions on the poorly-resolved post eclipse face of Io, typical albedos are 0.6 to 0.7. The brightest areas studied are located in the cluster of white regions east of Prometheus (longitudes 90 to 40 deg W). It is possible using Voyager data and fits to Hapke's equation to derive albedos for the bright regions without making any assumptions about the phase integrals.

  4. Spectral albedo and transmittance of thin young Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Taskjelle, Torbjørn; Hudson, Stephen R.; Granskog, Mats A.; Nicolaus, Marcel; Lei, Ruibo; Gerland, Sebastian; Stamnes, Jakob J.; Hamre, Børge

    2016-01-01

    Spectral albedo and transmittance in the range were measured on three separate dates on less than thick new Arctic sea ice growing on Kongsfjorden, Svalbard at , . Inherent optical properties, including absorption coefficients of particulate and dissolved material, were obtained from ice samples and fed into a radiative transfer model, which was used to analyze spectral albedo and transmittance and to study the influence of clouds and snow on these. Integrated albedo and transmittance for photosynthetically active radiation () were in the range 0.17-0.21 and 0.77-0.86, respectively. The average albedo and transmittance of the total solar radiation energy were 0.16 and 0.51, respectively. Values inferred from the model indicate that the ice contained possibly up to 40% brine and only 0.6% bubbles. Angular redistribution of solar radiation by clouds and snow was found to influence both the wavelength-integrated value and the spectral shape of albedo and transmittance. In particular, local peaks and depressions in the spectral albedo and spectral transmittance were found for wavelengths within atmospheric absorption bands. Simulated and measured transmittance spectra were within 5% for most of the wavelength range, but deviated up to 25% in the vicinity of , indicating the need for more optical laboratory measurements of pure ice, or improved modeling of brine optical properties in this near-infrared wavelength region.

  5. Simultaneous Spectral Albedo Measurements Near the Atmospheric Radiation Measurement Southern Great Plains (ARM SGP) Central Facility

    SciTech Connect

    Michalsky, Joseph J.; Min, Qilong; Barnard, James C.; Marchand, Roger T.; Pilewskie, Peter

    2003-04-30

    In this study, a data analysis is performed to determine the area-averaged, spectral albedo at ARM's SGP central facility site. The spectral albedo is then fed into radiation transfer models to show that the diffuse discrepancy is diminished when the spectral albedo is used (as opposed to using the broadband albedo).

  6. Standards for the validation of remotely sensed albedo products

    NASA Astrophysics Data System (ADS)

    Adams, Jennifer

    2015-04-01

    Land surface albedo is important component of the Earth's energy balance, defined as the fraction of shortwave radiation absorbed by a surface, and is one many Essential Climate Variables (ECVS) that can be retrieved from space through remote sensing. To quantify the accuracy of these products, they must be validated with respect to in-situ measurements of albedo using an albedometer. Whilst accepted standards exist for the calibration of albedometers, standards for the use of in-situ measurement schemes, and their use in validation procedures have yet to be developed. It is essential that we can assess the quality of remotely sensed albedo data, and to identify traceable sources of uncertainty during process of providing these data. As a result of the current lack of accepted standards for in-situ albedo retrieval and validation procedures, we are not yet able to identify and quantify traceable sources of uncertainty. Establishing standard protocols for in-situ retrievals for the validation of global albedo products would allow inter-product use and comparison, in addition to product standardization. Accordingly, this study aims to assess the quality of in-situ albedo retrieval schemes and identify sources of uncertainty, specifically in vegetation environments. A 3D Monte Carlo Ray Tracing Model will be used to simulate albedometer instruments in complex 3D vegetation canopies. To determine sources of uncertainty, factors that influence albedo measurement uncertainty were identified and will subsequently be examined: 1. Time of day (Solar Zenith Angle) 2. Ecosytem type 3. Placement of albedometer within the ecosystem 4. Height of albedometer above the canopy 5. Clustering within the ecosystem A variety of 3D vegetation canopies have been generated to cover the main ecosystems found globally, different seasons, and different plant distributions. Canopies generated include birchstand and pinestand forests for summer and winter, savanna, shrubland, cropland and

  7. High-albedo materials for reducing building cooling energy use

    SciTech Connect

    Taha, H.; Sailor, D.; Akbari, H.

    1992-01-01

    One simple and effective way to mitigate urban heat islands, i.e., the higher temperatures in cities compared to those of the surrounds, and their negative impacts on cooling energy consumption is to use high-albedo materials on major urban surfaces such as rooftops, streets, sidewalks, school yards, and the exposed surfaces of parking lots. High-albedo materials can save cooling energy use by directly reducing the heat gain through a building's envelope (direct effect) and also by lowering the urban air temperature in the neighborhood of the building (indirect effect). This project is an attempt to address high-albedo materials for buildings and to perform measurements of roof coatings. We search for existing methods and materials to implement fighter colors on major building and urban surfaces. Their cost effectiveness are examined and the possible related technical, maintenance, and environmental problems are identified. We develop a method for measuring albedo in the field by studying the instrumentation aspects of such measurements. The surface temperature impacts of various albedo/materials in the actual outdoor environment are studied by measuring the surface temperatures of a variety of materials tested on an actual roof. We also generate an albedo database for several urban surfaces to serve as a reference for future use. The results indicate that high-albedo materials can have a large impact on the surface temperature regime. On clear sunny days, when the solar noon surface temperatures of conventional roofing materials were about 40{degrees}C (72{degrees}F) warmer than air, the surface temperature of high-albedo coatings were only about 5{degrees}C warmer than air. In the morning and in the late afternoon, the high-albedo materials were as cool as the air itself. While conventional roofing materials warm up by an average 0.055{degrees}C/(W m{sup {minus}2}), the high-albedo surfaces warm up by an average 0.015{degrees}C/(W m{sup {minus}2}).

  8. High-albedo materials for reducing building cooling energy use

    SciTech Connect

    Taha, H.; Sailor, D.; Akbari, H.

    1992-01-01

    One simple and effective way to mitigate urban heat islands, i.e., the higher temperatures in cities compared to those of the surrounds, and their negative impacts on cooling energy consumption is to use high-albedo materials on major urban surfaces such as rooftops, streets, sidewalks, school yards, and the exposed surfaces of parking lots. High-albedo materials can save cooling energy use by directly reducing the heat gain through a building`s envelope (direct effect) and also by lowering the urban air temperature in the neighborhood of the building (indirect effect). This project is an attempt to address high-albedo materials for buildings and to perform measurements of roof coatings. We search for existing methods and materials to implement fighter colors on major building and urban surfaces. Their cost effectiveness are examined and the possible related technical, maintenance, and environmental problems are identified. We develop a method for measuring albedo in the field by studying the instrumentation aspects of such measurements. The surface temperature impacts of various albedo/materials in the actual outdoor environment are studied by measuring the surface temperatures of a variety of materials tested on an actual roof. We also generate an albedo database for several urban surfaces to serve as a reference for future use. The results indicate that high-albedo materials can have a large impact on the surface temperature regime. On clear sunny days, when the solar noon surface temperatures of conventional roofing materials were about 40{degrees}C (72{degrees}F) warmer than air, the surface temperature of high-albedo coatings were only about 5{degrees}C warmer than air. In the morning and in the late afternoon, the high-albedo materials were as cool as the air itself. While conventional roofing materials warm up by an average 0.055{degrees}C/(W m{sup {minus}2}), the high-albedo surfaces warm up by an average 0.015{degrees}C/(W m{sup {minus}2}).

  9. Electromagnetic field exposure dosimeter. Final report, September 1992-May 1993

    SciTech Connect

    Feaga, A.C.; Hilliard, M.P.; Link, R.

    1994-07-28

    The growing concern about adverse health effects caused by electromagnetic radiation prompted the ideas for this dosimeter. Data have been presented that link prolonged exposure to electromagnetic radiation from power lines to leukemia and some types of cancer. At present, though, there is a lack of recording instrumentation to measure the prolonged exposure of an individual; thus, it is not possible to correlate properly the amount of exposure or dose to health effects. With the recent advances in small, low-power devices, a small measuring device can be developed. Once this is built, a large data base can be obtained to help correlate electromagnetic field exposure to health conditions. The objective of this project is to develop an instrument which can measure electromagnetic fields over a prolonged period of time. The instrument would be small, say about the size of a radio Walkman, and would be worn throughout the day while taking data, as the individual goes about normal activities. A PC would be used to retrieve the data from the instrument at the end of the day. The dosimeter comprises a triaxial ferrite-loaded coil sensor, a set of amplifiers and filters, analog-to-digital converters, a microcontroller, and random access data memory. The signals from the sensor are filtered into three frequency ranges: one to measure 60-Hz exposure and two harmonics, another to measure high-energy pulsed energy, and a third frequency range to record the activity level of the individual. The signals from the filters are digitized and read into a microcontroller. The microcontroller performs a few calculations and controls the flow of the data to either random access memory or to a computer. A computer is used to retrieve the data from the dosimeter, and can store and display the measured data.

  10. FBX aqueous chemical dosimeter for measurement of dosimetric parameters.

    PubMed

    Moussous, O; Medjadj, T; Benguerba, M

    2011-02-01

    We investigated the ferrous sulphate-benzoic acid-xylenol orange (FBX) aqueous chemical dosimeter for measurement of dosimetric parameters such as the output factor, backscatter factor and lateral beam profiles for different square fields sizes for (60)Co γ-rays. A water phantom was employed to measure these parameters. An ionization chamber (IC) was used for calibration and comparison. A comparison of the resulting measurements with an ionization chamber's measured parameters showed good agreement. We thus believe that the tissue equivalent FBX dosimetry system can measure the dosimetric parameters for (60)Co with reasonable accuracy.

  11. An RF dosimeter for independent SAR measurement in MRI scanners

    PubMed Central

    Qian, Di; El-Sharkawy, AbdEl-Monem M.; Bottomley, Paul A.; Edelstein, William A.

    2013-01-01

    Purpose: The monitoring and management of radio frequency (RF) exposure is critical for ensuring magnetic resonance imaging (MRI) safety. Commercial MRI scanners can overestimate specific absorption rates (SAR) and improperly restrict clinical MRI scans or the application of new MRI sequences, while underestimation of SAR can lead to tissue heating and thermal injury. Accurate scanner-independent RF dosimetry is essential for measuring actual exposure when SAR is critical for ensuring regulatory compliance and MRI safety, for establishing RF exposure while evaluating interventional leads and devices, and for routine MRI quality assessment by medical physicists. However, at present there are no scanner-independent SAR dosimeters. Methods: An SAR dosimeter with an RF transducer comprises two orthogonal, rectangular copper loops and a spherical MRI phantom. The transducer is placed in the magnet bore and calibrated to approximate the resistive loading of the scanner's whole-body birdcage RF coil for human subjects in Philips, GE and Siemens 3 tesla (3T) MRI scanners. The transducer loop reactances are adjusted to minimize interference with the transmit RF field (B1) at the MRI frequency. Power from the RF transducer is sampled with a high dynamic range power monitor and recorded on a computer. The deposited power is calibrated and tested on eight different MRI scanners. Whole-body absorbed power vs weight and body mass index (BMI) is measured directly on 26 subjects. Results: A single linear calibration curve sufficed for RF dosimetry at 127.8 MHz on three different Philips and three GE 3T MRI scanners. An RF dosimeter operating at 123.2 MHz on two Siemens 3T scanners required a separate transducer and a slightly different calibration curve. Measurement accuracy was ∼3%. With the torso landmarked at the xiphoid, human adult whole‑body absorbed power varied approximately linearly with patient weight and BMI. This indicates that whole-body torso SAR is on average

  12. An RF dosimeter for independent SAR measurement in MRI scanners

    SciTech Connect

    Qian, Di; Bottomley, Paul A.; El-Sharkawy, AbdEl-Monem M.; Edelstein, William A.

    2013-12-15

    Purpose: The monitoring and management of radio frequency (RF) exposure is critical for ensuring magnetic resonance imaging (MRI) safety. Commercial MRI scanners can overestimate specific absorption rates (SAR) and improperly restrict clinical MRI scans or the application of new MRI sequences, while underestimation of SAR can lead to tissue heating and thermal injury. Accurate scanner-independent RF dosimetry is essential for measuring actual exposure when SAR is critical for ensuring regulatory compliance and MRI safety, for establishing RF exposure while evaluating interventional leads and devices, and for routine MRI quality assessment by medical physicists. However, at present there are no scanner-independent SAR dosimeters. Methods: An SAR dosimeter with an RF transducer comprises two orthogonal, rectangular copper loops and a spherical MRI phantom. The transducer is placed in the magnet bore and calibrated to approximate the resistive loading of the scanner's whole-body birdcage RF coil for human subjects in Philips, GE and Siemens 3 tesla (3T) MRI scanners. The transducer loop reactances are adjusted to minimize interference with the transmit RF field (B{sub 1}) at the MRI frequency. Power from the RF transducer is sampled with a high dynamic range power monitor and recorded on a computer. The deposited power is calibrated and tested on eight different MRI scanners. Whole-body absorbed power vs weight and body mass index (BMI) is measured directly on 26 subjects. Results: A single linear calibration curve sufficed for RF dosimetry at 127.8 MHz on three different Philips and three GE 3T MRI scanners. An RF dosimeter operating at 123.2 MHz on two Siemens 3T scanners required a separate transducer and a slightly different calibration curve. Measurement accuracy was ∼3%. With the torso landmarked at the xiphoid, human adult whole‑body absorbed power varied approximately linearly with patient weight and BMI. This indicates that whole-body torso SAR is on

  13. Preferential cooling of hot extremes from cropland albedo management

    PubMed Central

    Davin, Edouard L.; Seneviratne, Sonia I.; Ciais, Philippe; Olioso, Albert; Wang, Tao

    2014-01-01

    Changes in agricultural practices are considered a possible option to mitigate climate change. In particular, reducing or suppressing tillage (no-till) may have the potential to sequester carbon in soils, which could help slow global warming. On the other hand, such practices also have a direct effect on regional climate by altering the physical properties of the land surface. These biogeophysical effects, however, are still poorly known. Here we show that no-till management increases the surface albedo of croplands in summer and that the resulting cooling effect is amplified during hot extremes, thus attenuating peak temperatures reached during heat waves. Using a regional climate model accounting for the observed effects of no-till farming on surface albedo, as well as possible reductions in soil evaporation, we investigate the potential consequences of a full conversion to no-till agriculture in Europe. We find that the summer cooling from cropland albedo increase is strongly amplified during hot summer days, when surface albedo has more impact on the Earth’s radiative balance due to clear-sky conditions. The reduced evaporation associated with the crop residue cover tends to counteract the albedo-induced cooling, but during hot days the albedo effect is the dominating factor. For heatwave summer days the local cooling effect gained from no-till practice is of the order of 2 °C. The identified asymmetric impact of surface albedo change on summer temperature opens new avenues for climate-engineering measures targeting high-impact events rather than mean climate properties. PMID:24958872

  14. Preferential cooling of hot extremes from cropland albedo management.

    PubMed

    Davin, Edouard L; Seneviratne, Sonia I; Ciais, Philippe; Olioso, Albert; Wang, Tao

    2014-07-08

    Changes in agricultural practices are considered a possible option to mitigate climate change. In particular, reducing or suppressing tillage (no-till) may have the potential to sequester carbon in soils, which could help slow global warming. On the other hand, such practices also have a direct effect on regional climate by altering the physical properties of the land surface. These biogeophysical effects, however, are still poorly known. Here we show that no-till management increases the surface albedo of croplands in summer and that the resulting cooling effect is amplified during hot extremes, thus attenuating peak temperatures reached during heat waves. Using a regional climate model accounting for the observed effects of no-till farming on surface albedo, as well as possible reductions in soil evaporation, we investigate the potential consequences of a full conversion to no-till agriculture in Europe. We find that the summer cooling from cropland albedo increase is strongly amplified during hot summer days, when surface albedo has more impact on the Earth's radiative balance due to clear-sky conditions. The reduced evaporation associated with the crop residue cover tends to counteract the albedo-induced cooling, but during hot days the albedo effect is the dominating factor. For heatwave summer days the local cooling effect gained from no-till practice is of the order of 2 °C. The identified asymmetric impact of surface albedo change on summer temperature opens new avenues for climate-engineering measures targeting high-impact events rather than mean climate properties.

  15. Global Cooling: Effect of Urban Albedo on Global Temperature

    SciTech Connect

    Akbari, Hashem; Menon, Surabi; Rosenfeld, Arthur

    2007-05-22

    In many urban areas, pavements and roofs constitute over 60% of urban surfaces (roof 20-25%, pavements about 40%). The roof and the pavement albedo can be increased by about 0.25 and 0.10, respectively, resulting in a net albedo increase for urban areas of about 0.1. Many studies have demonstrated building cooling-energy savings in excess of 20% upon raising roof reflectivity from an existing 10-20% to about 60%. We estimate U.S. potential savings in excess of $1 billion (B) per year in net annual energy bills. Increasing albedo of urban surfaces can reduce the summertime urban temperature and improve the urban air quality. Increasing the urban albedo has the added benefit of reflecting more of the incoming global solar radiation and countering the effect of global warming. We estimate that increasing albedo of urban areas by 0.1 results in an increase of 3 x 10{sup -4} in Earth albedo. Using a simple global model, the change in air temperature in lowest 1.8 km of the atmosphere is estimated at 0.01K. Modelers predict a warming of about 3K in the next 60 years (0.05K/year). Change of 0.1 in urban albedo will result in 0.01K global cooling, a delay of {approx}0.2 years in global warming. This 0.2 years delay in global warming is equivalent to 10 Gt reduction in CO2 emissions.

  16. THE HIGH ALBEDO OF THE HOT JUPITER KEPLER-7 b

    SciTech Connect

    Demory, Brice-Olivier; Seager, Sara; Madhusudhan, Nikku; Kjeldsen, Hans; Christensen-Dalsgaard, Joergen; Gillon, Michael; Rowe, Jason F.; Borucki, William J.; Koch, David G.; Welsh, William F.; Adams, Elisabeth R.; Dupree, Andrea; McCarthy, Don; Kulesa, Craig

    2011-07-01

    Hot Jupiters are expected to be dark from both observations (albedo upper limits) and theory (alkali metals and/or TiO and VO absorption). However, only a handful of hot Jupiters have been observed with high enough photometric precision at visible wavelengths to investigate these expectations. The NASA Kepler mission provides a means to widen the sample and to assess the extent to which hot Jupiter albedos are low. We present a global analysis of Kepler-7 b based on Q0-Q4 data, published radial velocities, and asteroseismology constraints. We measure an occultation depth in the Kepler bandpass of 44 {+-} 5 ppm. If directly related to the albedo, this translates to a Kepler geometric albedo of 0.32 {+-} 0.03, the most precise value measured so far for an exoplanet. We also characterize the planetary orbital phase light curve with an amplitude of 42 {+-} 4 ppm. Using atmospheric models, we find it unlikely that the high albedo is due to a dominant thermal component and propose two solutions to explain the observed planetary flux. First, we interpret the Kepler-7 b albedo as resulting from an excess reflection over what can be explained solely by Rayleigh scattering, along with a nominal thermal component. This excess reflection might indicate the presence of a cloud or haze layer in the atmosphere, motivating new modeling and observational efforts. Alternatively, the albedo can be explained by Rayleigh scattering alone if Na and K are depleted in the atmosphere by a factor of 10-100 below solar abundances.

  17. Longevity Tests of High-Sensitivity BD-PND Bubble Dosimeters

    SciTech Connect

    Radev, R; Carlberg, E

    2002-07-09

    Medium- and very-high-sensitivity neutron bubble dosimeters (BD-PNDs) made by Bubble Technology Industries (BTI) were used to study the life span of such dosimeters in a standard setup with a {sup 252}Cf source. Although data on the longevity of bubble dosimeters with low and medium sensitivity exist, such data for dosimeters with high and very high sensitivity are not readily available. The manufacturer guarantees optimum dosimeter performance for 3 months after receipt. However, it is important to know the change in the dosimeters' characteristics with time, especially after the first 3 months. The long-term performance of four sets of very high sensitivity and one set of medium-sensitivity bubble dosimeters was examined for periods of up to 13 months. During that time, the detectors were exposed and reset more than 20 times. Although departures from initial detection sensitivity were observed in several cases, the detectors indicated a significantly longer life span than stated in the manufacturer's warranty. In addition, the change in the number of bubbles and in evaluated neutron dose as a function of the time from the end of exposure until the dosimeters were read was investigated.

  18. Ceric and ferrous dosimeters show precision for 50-5000 rad range

    NASA Technical Reports Server (NTRS)

    Frigerio, N. A.; Henry, V. D.

    1968-01-01

    Ammonium thiocyanate, added to the usual ferrous sulfate dosimeter solution, yielded a very stable, precise and temperature-independent system eight times as sensitive as the classical Fricke system in the 50 to 5000 rad range. The ceric dosimeters, promising for use in mixed radiation fields, respond nearly independently of LET.

  19. PRESAGETM - Development and optimization studies of a 3D radiochromic plastic dosimeter - Part 1

    NASA Astrophysics Data System (ADS)

    Adamovics, J.; Jordan, K.; Dietrich, J.

    2006-12-01

    This paper studies the polymerization of six different transparent plastics as potential 3D dosimeter matrices. In addition, six different leuco dyes and sixteen different free radical initiators were evaluated. Finally, the photoreactivity of the dosimeter was studied so that the effect of exposure to UV could be minimized.

  20. PRESAGETM - Development and optimization studies of a 3D radiochromic plastic dosimeter - Part 2

    NASA Astrophysics Data System (ADS)

    Adamovics, J.; Guo, P.; Burgess, D.; Manzoor, A.; Oldham, M.

    2006-12-01

    In a previous paper we described the evaluation of seven different transparent plastics as dosimeter matrices along with six different leuco dyes as the radiochromic agent. Here we present the evaluation of the dosimeter sensitivity and post irradiation stability of an additional plastic matrix and five different leuco dyes.

  1. Comparative study of three types of civil defense high-range pocket dosimeters

    SciTech Connect

    Siskel, R.L.; Sims, C.S.; Swaja, R.

    1987-01-01

    Civil defense shelters are stocked with high-range (0- to 200-R) CDV-742 pocket dosimeters. These dosimeters are intended for use by people that must leave the shelter when the environmental radiation level is either high or unknown. A total of 67 CDV-742 dosimeters were obtained and studied during the summer of 1986 at Oak Ridge National Lab. Health Physics Research Reactor (HPRR). Three different types of dosimeters (27 Bendix, 20 Landsverk-Gold, and 20 Landsverk-Yellow) in various combinations were exposed to 14 separate pulse operations of the HPRR. It can be concluded that the CDV-742 type dosimeters were not suitable for use in a neutron or mixed radiation field unless the spectra is known and correction factors determined in this study are properly applied. Further study is needed to determine the accuracy of these dosimeters in a pure gamma field and to determine their precision at the extreme ends of the dosimeter range. Furthermore, because of their failure rates, shelter occupants should consider exposure data from the Bendix and Landsverk-Yellow dosimeters to be highly unreliable unless sufficient evidence exists to support the exposure readings.

  2. Adaptation of a Pocket PC for Use as a Wearable Voice Dosimeter

    ERIC Educational Resources Information Center

    Popolo, Peter S.; Svec, Jan G.; Titze, Ingo R.

    2005-01-01

    This article deals with the adaptation of a commercially available Pocket PC for use as a voice dosimeter, a wearable device that measures the vocal dose of teachers or other individuals on the job, at home, and elsewhere during the course of an entire day. An engineering approach for designing a voice dosimeter is described, and design data are…

  3. A Continental United States High Resolution NLCD Land Cover – MODIS Albedo Database to Examine Albedo and Land Cover Change Relationships

    EPA Science Inventory

    Surface albedo influences climate by affecting the amount of solar radiation that is reflected at the Earth’s surface, and surface albedo is, in turn, affected by land cover. General Circulation Models typically use modeled or prescribed albedo to assess the influence of land co...

  4. Albedo and Reflection Spectra of Extrasolar Giant Planets

    NASA Astrophysics Data System (ADS)

    Sudarsky, David; Burrows, Adam; Pinto, Philip

    2000-08-01

    We generate theoretical albedo and reflection spectra for a full range of extrasolar giant planet (EGP) models, from Jovian to 51 Pegasi class objects. Our albedo modeling utilizes the latest atomic and molecular cross sections, Mie theory treatment of scattering and absorption by condensates, a variety of particle size distributions, and an extension of the Feautrier technique, which allows for a general treatment of the scattering phase function. We find that, because of qualitative similarities in the compositions and spectra of objects within each of five broad effective temperature ranges, it is natural to establish five representative EGP albedo classes. At low effective temperatures (Teff<~150 K) is a class of ``Jovian'' objects (class I) with tropospheric ammonia clouds. Somewhat warmer class II, or ``water cloud,'' EGPs are primarily affected by condensed H2O. Gaseous methane absorption features are prevalent in both classes. In the absence of nonequilibrium condensates in the upper atmosphere, and with sufficient H2O condensation, class II objects are expected to have the highest visible albedos of any class. When the upper atmosphere of an EGP is too hot for H2O to condense, radiation generally penetrates more deeply. In these objects, designated class III or ``clear'' because of a lack of condensation in the upper atmosphere, absorption lines of the alkali metals, sodium and potassium, lower the albedo significantly throughout the visible. Furthermore, the near-infrared albedo is negligible, primarily because of strong CH4 and H2O molecular absorption and collision-induced absorption (CIA) by H2 molecules. In those EGPs with exceedingly small orbital distance (``roasters'') and 900 K<~Teff<~1500 K (class IV), a tropospheric silicate layer is expected to exist. In all but the hottest (Teff>~1500 K) or lowest gravity roasters, the effect of this silicate layer is likely to be insignificant because of the very strong absorption by sodium and potassium

  5. Relating black carbon content to reduction of snow albedo

    NASA Astrophysics Data System (ADS)

    Brandt, R. E.; Warren, S. G.; Clarke, A. D.

    2011-12-01

    In remote snow of the Northern Hemisphere, the levels of soot pollution are in the parts-per-billion (ppb) range, where the effect on albedo is at the level of a few percent. A reduction of albedo by 1-2% is significant for climate but is difficult to detect experimentally, because snow albedo depends on several other variables. In our work to quantify the climatic effect of black carbon (BC) in snow, we therefore do not directly measure the albedo reduction. Instead, we use a two-step procedure: (1) We collect snow samples, melt and filter them, and analyze the filters spectrophotometrically for BC concentration. (2) We use the BC amount from the filter measurement, together with snow grain size, in a radiative transfer model to compute the albedo reduction. Our radiative transfer model uses the discrete ordinates algorithm DISORT 2.0. We have chosen a representative BC size distribution and optical constants, and have incorporated those of mineral dust as well. While a given mass of BC causes over an order of magnitude more snow albedo reduction compared to dust, a snowpack containing dust mutes the albedo-reducing effect of BC. Because the computed reduction of snow albedo is model-based, it requires experimental verification. We doubt that direct measurement of albedo-reduction will be feasible in nature, because of the vertical variation of both snow grain size and soot content, and because the natural soot content is small. We conclude that what is needed is an artificial snowpack, with uniform grain size and large uniform soot content (ppm not ppb), to produce a large signal on albedo. We have chosen to pursue this experiment outdoors rather than in the laboratory, for the following reasons: (1) The snowpack in the field of view is uniformly illuminated if the source of radiation is the Sun. (2) Visible radiation penetrates into the snow, so photons emerge horizontally distant from where they entered. In the limited width of a laboratory snowpack, radiation

  6. Potential effects of forest management on surface albedo

    NASA Astrophysics Data System (ADS)

    Otto, J.; Bréon, F.-M.; Schelhaas, M.-J.; Pinty, B.; Luyssaert, S.

    2012-04-01

    Currently 70% of the world's forests are managed and this figure is likely to rise due to population growth and increasing demand for wood based products. Forest management has been put forward by the Kyoto-Protocol as one of the key instruments in mitigating climate change. For temperate and boreal forests, the effects of forest management on the stand-level carbon balance are reasonably well understood, but the biophysical effects, for example through changes in the albedo, remain elusive. Following a modeling approach, we aim to quantify the variability in albedo that can be attributed to forest management through changes in canopy structure and density. The modelling approach chains three separate models: (1) a forest gap model to describe stand dynamics, (2) a Monte-Carlo model to estimate the probability density function of the optical path length of photons through the canopy and (3) a physically-based canopy transfer model to estimate the interaction between photons and leaves. The forest gap model provides, on a monthly time step the position, height, diameter, crown size and leaf area index of individual trees. The Monte-Carlo model computes from this the probability density function of the distance a photon travels through crown volumes to determine the direct light reaching the forest floor. This information is needed by the canopy transfer model to calculate the effective leaf area index - a quantity that allows it to correctly represent a 3D process with a 1D model. Outgoing radiation is calculated as the result of multiple processes involving the scattering due to the canopy layer and the forest floor. Finally, surface albedo is computed as the ratio between incident solar radiation and calculated outgoing radiation. The study used two time series representing thinning from below of a beech and a Scots pine forest. The results show a strong temporal evolution in albedo during stand establishment followed by a relatively stable albedo once the canopy

  7. Effects of temperature and humidity during irradiation on the response of a film dosimeter

    NASA Astrophysics Data System (ADS)

    Khan, Hasan M.; Wahid, Mian S.

    1995-09-01

    A commercially available leuco dye containing polyvinyl butyral based film (FWT-63-02) has been investigated ctrophotometrically for its dosimetric characteristic and for its use as routine dosimeter in radiation processing for the absorbed dose range 0.1 to 10 kGy. The present study was carried out to evaluate the performance of dosimeter under different environmental conditions (i.e. effects of temperature and relative humidity during irradiation). The response was measured at peak wavelength of 600 nm as well as at a number of other wavelengths (550, 625, 640 and 650 nm). The dosimeter was found to show quite stable response up to a radiation chamber temperature of 40°C. The dosimeter also showed stable behavior at low or moderate relative humidity conditions (<76%) in the radiation chamber. The characteristics of the dosimeter are suitable for its possible application in radiation processing, food irradiation and sterilization applications.

  8. Feasibility of Ultra-Thin Fiber-Optic Dosimeters for Radiotherapy Dosimetry.

    PubMed

    Lee, Bongsoo; Kwon, Guwon; Shin, Sang Hun; Kim, Jaeseok; Yoo, Wook Jae; Ji, Young Hoon; Jang, Kyoung Won

    2015-11-17

    In this study, prototype ultra-thin fiber-optic dosimeters were fabricated using organic scintillators, wavelength shifting fibers, and plastic optical fibers. The sensor probes of the ultra-thin fiber-optic dosimeters consisted of very thin organic scintillators with thicknesses of 100, 150 and 200 μm. These types of sensors cannot only be used to measure skin or surface doses but also provide depth dose measurements with high spatial resolution. With the ultra-thin fiber-optic dosimeters, surface doses for gamma rays generated from a Co-60 therapy machine were measured. Additionally, percentage depth doses in the build-up regions were obtained by using the ultra-thin fiber-optic dosimeters, and the results were compared with those of external beam therapy films and a conventional fiber-optic dosimeter.

  9. Characterization of a Fricke dosimeter at high energy photon and electron beams used in radiotherapy.

    PubMed

    Moussous, O; Khoudri, S; Benguerba, M

    2011-12-01

    The dosimetric features of the Fricke dosimeter in clinical linear accelerator beams are considered. Experimental data were obtained using various nominal energies 6 and 18 MV, 12 and 15 MeV, including the (60)Co γ-ray beam. The calibration of the dosimeters was performed using the ionization chamber as a reference dosimeter. Some general characteristics of Fricke dosimeter such as energy dependence, optical density (OD)-dose relationship, reproducibility, accuracy, dose rate dependence were analyzed. The Fricke solution shows linearity in OD-dose relationship, energy independence and a good reproducibility over the energy range investigated. The Fricke dosimeter was found to be suitable for carrying out absorbed dose to water measurements in the calibration of high energy electron and photon beams.

  10. An analysis of an implantable dosimeter system for external beam therapy

    SciTech Connect

    Black, Robert D. . E-mail: bblack@siceltech.com; Scarantino, Charles W.; Mann, Gregory G.; Anscher, Mitchell S.; Ornitz, Robert D.; Nelms, Benjamin E.

    2005-09-01

    Background and Purpose: To review the data from an implantable radiation dosimetry system used in a clinical setting and to examine correlations between dosimeter readings and potential causative error sources. Materials and Methods: MOSFET (metal oxide semiconductor field effect transistor) based encapsulated dosimeters were evaluated in a phantom (in vitro) and in a study with 18 patients. The dosimeters were placed in the gross tumor volume or in collateral normal tissue. Predicted dose values were established by imaging the dosimeters in the planning CTs. Results: The in vitro study confirmed that bounding cumulative errors due to setup, planning, and machine output within a {+-}5% level is achievable. In patients, it was found that deviations from the targeted dose often exceeded the 5% level. Conclusions: The use of an implantable dosimeter system could provide an effective empiric check on the dose delivered at depth. Such a tool may have value for institutional quality assurance, as well as for therapy delivered to individual patients.

  11. Feasibility of Ultra-Thin Fiber-Optic Dosimeters for Radiotherapy Dosimetry

    PubMed Central

    Lee, Bongsoo; Kwon, Guwon; Shin, Sang Hun; Kim, Jaeseok; Yoo, Wook Jae; Ji, Young Hoon; Jang, Kyoung Won

    2015-01-01

    In this study, prototype ultra-thin fiber-optic dosimeters were fabricated using organic scintillators, wavelength shifting fibers, and plastic optical fibers. The sensor probes of the ultra-thin fiber-optic dosimeters consisted of very thin organic scintillators with thicknesses of 100, 150 and 200 μm. These types of sensors cannot only be used to measure skin or surface doses but also provide depth dose measurements with high spatial resolution. With the ultra-thin fiber-optic dosimeters, surface doses for gamma rays generated from a Co-60 therapy machine were measured. Additionally, percentage depth doses in the build-up regions were obtained by using the ultra-thin fiber-optic dosimeters, and the results were compared with those of external beam therapy films and a conventional fiber-optic dosimeter. PMID:26593917

  12. THE ALBEDOS OF KEPLER'S CLOSE-IN SUPER-EARTHS

    SciTech Connect

    Demory, Brice-Olivier

    2014-07-01

    Exoplanet research focusing on the characterization of super-Earths is currently limited to the handful of targets orbiting bright stars that are amenable to detailed study. This Letter proposes to look at alternative avenues to probe the surface and atmospheric properties of this category of planets, known to be ubiquitous in our galaxy. I conduct Markov Chain Monte Carlo light-curves analyses for 97 Kepler close-in R{sub P} ≲ 2.0 R {sub ⊕} super-Earth candidates with the aim of detecting their occultations at visible wavelengths. Brightness temperatures and geometric albedos in the Kepler bandpass are constrained for 27 super-Earth candidates. A hierarchical Bayesian modeling approach is then employed to characterize the population-level reflective properties of these close-in super-Earths. I find median geometric albedos A{sub g} in the Kepler bandpass ranging between 0.16 and 0.30, once decontaminated from thermal emission. These super-Earth geometric albedos are statistically larger than for hot Jupiters, which have medians A{sub g} ranging between 0.06 and 0.11. A subset of objects, including Kepler-10b, exhibit significantly larger albedos (A{sub g} ≳ 0.4). I argue that a better understanding of the incidence of stellar irradation on planetary surface and atmospheric processes is key to explain the diversity in albedos observed for close-in super-Earths.

  13. Spectral surface albedo derived from GOME-2/Metop measurements

    NASA Astrophysics Data System (ADS)

    Pflug, Bringfried; Loyola, Diego

    2009-09-01

    Spectral surface albedo is an important input for GOME-2 trace gas retrievals. An algorithm was developed for estimation of spectral surface albedo from top-of-atmosphere (TOA)-radiances measured by the Global Ozone Monitoring Experiment GOME-2 flying on-board MetOp-A. The climatologically version of this algorithm estimates Minimum Lambert-Equivalent Reflectivity (MLER) for a fixed time window and can use data of many years in contrast to the Near-real time version. Accuracy of surface albedo estimated by MLER-computation increases with the amount of available data. Unfortunately, most of the large GOME pixels are partly covered by clouds, which enhance the LER-data. A plot of LER-values over cloud fraction is used within this presentation to account for this influence of clouds. This "cloud fraction plot" can be applied over all surface types. Surface albedo obtained using the "cloud fraction plot" is compared with reference surface albedo spectra and with the FRESCO climatology. There is a general good agreement; however there are also large differences for some pixels.

  14. Climate change due to anthropogenic surface albedo modification

    SciTech Connect

    Potter, G.L.; Ellsaesser, H.W.; MacCracken, M.C.; Ellis, J.S.; Luther, F.M.

    1980-02-01

    Using a statistical dynamic climate model with more realistic surface albedo changes than used in previous experiments, we have conducted a numerical experiment combining desertification of the Sahara and deforestation of the tropical rain forest. Over an area of 9 x 10/sup 6/ km/sup 2/ at 20/sup 0/N the desert albedo was increased from 0.16 to 0.35 and over 7 x 10/sup 6/ km/sup 2/ at the equator and 10/sup 0/S the rain forest albedo was increased from 0.07 to 0.16. While the most significant direct climatic responses were observed in the modified zones, high northern latitudes exhibited the greatest cooling through activation of the ice-albedo feedback process. In contrast to Sagan et al., this experiment suggests that anthropogenic modification of surface albedo over the past few thousand years has had an impact on global climate which is likely quite small and probably undetectable.

  15. A modified Fricke gel dosimeter for fast electron blood dosimetry

    NASA Astrophysics Data System (ADS)

    Del Lama, L. S.; de Góes, E. G.; Sampaio, F. G. A.; Petchevist, P. C. D.; de Almeida, A.

    2014-12-01

    It has been suggested for more than forty years that blood and blood components be irradiated before allogeneic transfusions for immunosuppressed patients in order to avoid the Transfusion-Associated Graft-versus-Host Disease (TA-GVHD). Whole blood, red blood cells, platelets and granulocytes may have viable T cells and should be irradiated before transfusion for different patient clinical conditions. According to international guides, absorbed doses from 25 up to 50 Gy should be delivered to the central middle plane of each blood bag. Although gamma and X-rays from radiotherapy equipments and dedicated cell irradiators are commonly used for this purpose, electron beams from Linear Accelerators (LINACs) could be used as well. In this work, we developed a methodology able to acquire dosimetric data from blood irradiations, especially after fast electrons exposures. This was achieved using a proposed Fricke Xylenol Gel (FXGp) dosimeter, which presents closer radiological characteristics (attenuation coefficients and stopping-powers) to the whole blood, as well as complete absorbed dose range linearity. The developed methodology and the FXGp dosimeter were also able to provide isodose curves and field profiles for the irradiated samples.

  16. MORSE/STORM: A generalized albedo option for Monte Carlo calculations

    SciTech Connect

    Gomes, I.C.; Stevens, P.N. )

    1991-09-01

    The advisability of using the albedo procedure for the Monte Carlo solution of deep penetration shielding problems that have ducts and other penetrations has been investigated. The use of albedo data can dramatically improve the computational efficiency of certain Monte Carlo calculations. However, the accuracy of these results may be unacceptable because of lost information during the albedo event and serious errors in the available differential albedo data. This study was done to evaluate and appropriately modify the MORSE/BREESE package, to develop new methods for generating the required albedo data, and to extend the adjoint capability to the albedo-modified calculations. Major modifications to MORSE/BREESE include an option to save for further use information that would be lost at the albedo event, an option to displace the point of emergence during an albedo event, and an option to use spatially dependent albedo data for both forward and adjoint calculations, which includes the point of emergence as a new random variable to be selected during an albedo event. The theoretical basis for using TORT-generated forward albedo information to produce adjuncton albedos was derived. The MORSE/STORM package was developed to perform both forward and adjoint modes of analysis using spatially dependent albedo data. Results obtained with MORSE/STORM for both forward and adjoint modes were compared with benchmark solutions. Excellent agreement and improved computational efficiency were achieved, demonstrating the full utilization of the albedo option in the MORSE code. 7 refs., 17 figs., 15 tabs.

  17. NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos

    NASA Astrophysics Data System (ADS)

    Nugent, Carolyn; Mainzer, A.; Masiero, J. R.; Bauer, J.; Cutri, R. M.; Grav, T.; Kramer, E.; Sonnett, S.; Stevenson, R.; Wright, E.

    2015-11-01

    The infrared NEOWISE project (Mainzer et al. 2011a) has measured diameters and albedos for ˜20% of the known asteroid population, the majority of these measurements to date (Mainzer et al. 2011b, 2012, 2015; Masiero et al. 2011, 2012; Grav et al. 2011, 2012a; Bauer et al. 2013). Here, we expand the number of asteroids characterized by NEOWISE, deriving diameters and albedos for 7,959 asteroids detected between December 13, 2013, and December 13, 2014 during the first year of the Reactivation mission. 7,758 are Main Belt or Mars-crossing asteroids. 17% of these objects have not been previously characterized using WISE or NEOWISE thermal measurements. Diameters are determined to an accuracy of ~20% or better. If good-quality H magnitudes are available, albedos can be determined to within ~40% or better.

  18. Direct determination of surface albedos from satellite imagery

    NASA Technical Reports Server (NTRS)

    Mekler, Y.; Joseph, J. H.

    1983-01-01

    An empirical method to measure the spectral surface albedo of surfaces from Landsat imagery is presented and analyzed. The empiricism in the method is due only to the fact that three parameters of the solution must be determined for each spectral photograph of an image on the basis of independently known albedos at three points. The approach is otherwise based on exact solutions of the radiative transfer equation for upwelling intensity. Application of the method allows the routine construction of spectral albedo maps from satelite imagery, without requiring detailed knowledge of the atmospheric aerosol content, as long as the optical depth is less than 0.75, and of the calibration of the satellite sensor.

  19. A new parameterization of spectral and broadband ocean surface albedo.

    PubMed

    Jin, Zhonghai; Qiao, Yanli; Wang, Yingjian; Fang, Yonghua; Yi, Weining

    2011-12-19

    A simple yet accurate parameterization of spectral and broadband ocean surface albedo has been developed. To facilitate the parameterization and its applications, the albedo is parameterized for the direct and diffuse incident radiation separately, and then each of them is further divided into two components: the contributions from surface and water, respectively. The four albedo components are independent of each other, hence, altering one will not affect the others. Such a designed parameterization scheme is flexible for any future update. Users can simply replace any of the adopted empirical formulations (e.g., the relationship between foam reflectance and wind speed) as desired without a need to change the parameterization scheme. The parameterization is validated by in situ measurements and can be easily implemented into a climate or radiative transfer model.

  20. Moon: lunar albedo for soft x-rays

    NASA Astrophysics Data System (ADS)

    Ibadov, Subhon

    2016-07-01

    Albedo of the Moon for soft X-rays (0.1-2 keV photons) is determined on the basis of the X-ray luminosity of the Moon detected and measured for the first time by orbital space telescope ROSAT in 1990. It is found that the lunar albedo for the solar soft X-rays is less than the lunar visual region albedo almost thousand times. The data allow to estimate more correctly X-ray luminosity of dusty comets like Hyakutake C/1996 B2 and Hale-Bopp C/1995 O1 due to scattering of solar soft X-rays and to reveal thus the dominant mechanism for production of X-rays in dusty comets.

  1. Albedo dichotomy of Rhea - Hapke analysis of Voyager photometry

    NASA Technical Reports Server (NTRS)

    Verbiscer, Anne J.; Veverka, Joseph

    1989-01-01

    The Hapke (1986) model has been well fitted to both full-disk and disk-resolved Voyager observations. The low phase angle data indicate a substantial opposition effect, and the Hapke analysis results show that while the regolith compaction parameter for Rhea is definitely larger than for Titania, it is comparable to that of the moon. Photometric differences other than albedo are noted between the leading and trailing hemispheres of the satellite. The albedo map of Rhea presented reproduces the observed lightcurve and demonstrates that no terrain or feature in the trailing hemisphere is as bright as any in the leading hemisphere. A quasi-circular low albedo region near the antiapex of motion is discovered.

  2. An Analytical Model for the Prediction of a Micro-Dosimeter Response Function

    NASA Technical Reports Server (NTRS)

    Badavi, Francis F.; Xapsos, Mike

    2008-01-01

    A rapid analytical procedure for the prediction of a micro-dosimeter response function in low Earth orbit (LEO), correlated with the Space Transportation System (STS, shuttle) Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The analytical model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a cylindrical micro-volume of arbitrary aspect ratio (height/diameter) by incoming ions through both direct and indirect (ray) events. At any designated (ray traced) target point within the vehicle, the model accepts the differential flux spectrum of Galactic Cosmic Rays (GCR) and/or trapped protons at LEO as input. On a desktop PC, the response function of TEPC for each ion in the GCR/trapped field is computed at the average rate of 30 seconds/ion. The ionizing radiation environment at LEO is represented by O'Neill fs GCR model (2004), covering charged particles in the 1 less than or equal to Z less than or equal to 28. O'Neill's free space GCR model is coupled with the Langley Research Center (LaRC) angular dependent geomagnetic cutoff model to compute the transmission coefficient in LEO. The trapped proton environment is represented by a LaRC developed time dependent procedure which couples the AP8MIN/AP8MAX, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment is represented by the extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. The charged particle transport calculations correlated with STS 51 and 114 flights are accomplished by using the most recent version (2005) of the LaRC deterministic High charge (Z) and Energy TRaNsport (HZETRN) code. We present the correlations between the TEPC model predictions (response function) and TEPC measured differential/integral spectra in the lineal energy (y) domain for both GCR and trapped protons, with the conclusion

  3. Detailed spatiotemporal albedo observations at Greenland's Mittivakkat Gletscher

    NASA Astrophysics Data System (ADS)

    Mernild, Sebastian H.; Knudsen, Niels T.; Yde, Jacob C.; Malmros, Jeppe K.

    2015-04-01

    Surface albedo is defined as the reflected fraction of incoming solar shortwave radiation at the surface. On Greenland's Mittivakkat Gletscher the mean glacier-wide MODIS-estimated albedo dropped by 0.10 (2000-2013) from 0.43 to 0.33 by the end of the mass balance year (EBY). Hand-held albedo measurements as low as 0.10 were observed over debris-covered ice at the glacier margin at the EBY: these values were slightly below observed values for proglacial bedrock (~0.2). The albedo is highly variable in space - a significant variability occurred within few meters at the glacier margin area ranging from 0.10 to 0.39 due to variability in debris-cover thickness and composition, microbial activity (including algae and cyanobacteria), snow grain crystal metamorphism, bare ice exposure, and meltwater ponding. Huge dark-red-brown-colored ice algae colonies were observed. Albedo measurements on snow patches and bare glacier ice changed significant with increasing elevations (180-600 m a.s.l.) by lapse rates of 0.04 and 0.03 per 100 m, respectively, indicating values as high as 0.82 and 0.40 on the upper part of the glacier. Over a period of two weeks from early August to late August 2014 the hand-held observed mean glacier-wide albedo changed from 0.40 to 0.30 indicating that on average 10% more incoming solar shortwave radiation became available for surface ablation at the end of the melt season.

  4. NEOWISE REACTIVATION MISSION YEAR ONE: PRELIMINARY ASTEROID DIAMETERS AND ALBEDOS

    SciTech Connect

    Nugent, C. R.; Cutri, R. M.; Mainzer, A.; Masiero, J.; Bauer, J.; Kramer, E.; Sonnett, S.; Stevenson, R.; Grav, T.; Wright, E. L.

    2015-12-01

    We present preliminary diameters and albedos for 7956 asteroids detected in the first year of the NEOWISE Reactivation mission. Of those, 201 are near-Earth asteroids and 7755 are Main Belt or Mars-crossing asteroids. 17% of these objects have not been previously characterized using the Near-Earth Object Wide-field Infrared Survey Explorer, or “NEOWISE” thermal measurements. Diameters are determined to an accuracy of ∼20% or better. If good-quality H magnitudes are available, albedos can be determined to within ∼40% or better.

  5. Comparative global albedo and color maps of the Uranian satellites

    NASA Astrophysics Data System (ADS)

    Buratti, B. J.; Mosher, J. A.

    1991-03-01

    The surfaces of the Uranian satellites Ariel, Miranda, Oberon, Titania, and Umbriel are characterized on the basis of Voyager observations. Tables of spectrophotometric data and maps of normal reflectances, green/violet ratios, and possible geological formations are presented and discussed in detail. Variations in albedo are found to be associated with impact features, and it is inferred from color differences that the upper surface of Ariel contains a higher proportion of redder material (tentatively identified as accreted low-albedo meteoritic dust) than those of the other moons.

  6. Comparative global albedo and color maps of the Uranian satellites

    SciTech Connect

    Buratti, B.J.; Mosher, J.A. )

    1991-03-01

    The surfaces of the Uranian satellites Ariel, Miranda, Oberon, Titania, and Umbriel are characterized on the basis of Voyager observations. Tables of spectrophotometric data and maps of normal reflectances, green/violet ratios, and possible geological formations are presented and discussed in detail. Variations in albedo are found to be associated with impact features, and it is inferred from color differences that the upper surface of Ariel contains a higher proportion of redder material (tentatively identified as accreted low-albedo meteoritic dust) than those of the other moons. 42 refs.

  7. Measurement of photon-energy albedo from stratified shielding materials.

    PubMed

    Sinha, A K; Bhattacharjee, A

    1991-11-01

    In the conventional method of measuring photon-energy albedo using a scintillation detector coupled with a multichannel analyzer, tedious efficiency correction by the inverse matrix method was needed. The indigenously designed proportional-response photon counter, with its detection efficiency proportional to energy of incident photons, was used in the present investigation. Use of the proportional-response photon counter makes the measurement straightforward and more accurate. Measurements of energy albedo from stratified layers of aluminum, iron, lead, and concrete using 662-keV and 1250-keV photon energies are reported.

  8. Investigation of albedo neutrons by the Intercosmos-17 satellite

    NASA Astrophysics Data System (ADS)

    Dubinskii, Iu.; Efimov, Iu. E.; Kudela, K.; Mikhaeli, L.; Roiko, I.; Chichikaliuk, Iu. A.

    1982-09-01

    Measurements were made with the Intercosmos-17 scintillation counter in 1977 in order to investigate the contribution of albedo neutrons with energies of 1-30 MeV to the formation of radiation-belt protons of corresponding energies. The differential current density of albedo neutrons is presented for the invariant latitude of 42.7 deg during a quiet period of solar activity (October 8-10, 1977). The following value is obtained for this differential current density: I0 (1 MeV) = 0.104 + or - 0.023 neutrons/sq cm s MeV.

  9. Comparative global albedo and color maps of the Uranian satellites

    NASA Technical Reports Server (NTRS)

    Buratti, Bonnie J.; Mosher, Joel A.

    1991-01-01

    The surfaces of the Uranian satellites Ariel, Miranda, Oberon, Titania, and Umbriel are characterized on the basis of Voyager observations. Tables of spectrophotometric data and maps of normal reflectances, green/violet ratios, and possible geological formations are presented and discussed in detail. Variations in albedo are found to be associated with impact features, and it is inferred from color differences that the upper surface of Ariel contains a higher proportion of redder material (tentatively identified as accreted low-albedo meteoritic dust) than those of the other moons.

  10. Transformation of surface albedo to surface: Atmosphere surface and irradiance, and their spectral and temporal averages

    NASA Technical Reports Server (NTRS)

    Nack, M. L.; Curran, R. J.

    1978-01-01

    The dependence of the albedo at the top of a realistic atmosphere upon the surface albedo, solar zenith angle, and cloud optical thickness is examined for the cases of clear sky, total cloud cover, and fractional cloud cover. The radiative transfer calculations of Dave and Braslau (1975) for particular values of surface albedo and solar zenith angle, and a single value of cloud optical thickness are used as the basis of a parametric albedo model. The question of spectral and temporal averages of albedos and reflected irradiances is addressed, and unique weighting functions for the spectral and temporal albedo averages are developed.

  11. Development and characterization of a three-dimensional radiochromic film stack dosimeter for megavoltage photon beam dosimetry

    SciTech Connect

    McCaw, Travis J. Micka, John A.; DeWerd, Larry A.

    2014-05-15

    Purpose: Three-dimensional (3D) dosimeters are particularly useful for verifying the commissioning of treatment planning and delivery systems, especially with the ever-increasing implementation of complex and conformal radiotherapy techniques such as volumetric modulated arc therapy. However, currently available 3D dosimeters require extensive experience to prepare and analyze, and are subject to large measurement uncertainties. This work aims to provide a more readily implementable 3D dosimeter with the development and characterization of a radiochromic film stack dosimeter for megavoltage photon beam dosimetry. Methods: A film stack dosimeter was developed using Gafchromic{sup ®} EBT2 films. The dosimeter consists of 22 films separated by 1 mm-thick spacers. A Virtual Water™ phantom was created that maintains the radial film alignment within a maximum uncertainty of 0.3 mm. The film stack dosimeter was characterized using simulations and measurements of 6 MV fields. The absorbed-dose energy dependence and orientation dependence of the film stack dosimeter were investigated using Monte Carlo simulations. The water equivalence of the dosimeter was determined by comparing percentage-depth-dose (PDD) profiles measured with the film stack dosimeter and simulated using Monte Carlo methods. Film stack dosimeter measurements were verified with thermoluminescent dosimeter (TLD) microcube measurements. The film stack dosimeter was also used to verify the delivery of an intensity-modulated radiation therapy (IMRT) procedure. Results: The absorbed-dose energy response of EBT2 film differs less than 1.5% between the calibration and film stack dosimeter geometries for a 6 MV spectrum. Over a series of beam angles ranging from normal incidence to parallel incidence, the overall variation in the response of the film stack dosimeter is within a range of 2.5%. Relative to the response to a normally incident beam, the film stack dosimeter exhibits a 1% under-response when the

  12. Characterization of the nanoDot OSLD dosimeter in CT

    SciTech Connect

    Scarboro, Sarah B.; Cody, Dianna; Followill, David; Court, Laurence; Stingo, Francesco C.; Kry, Stephen F.; Alvarez, Paola; Zhang, Di; McNitt-Gray, Michael

    2015-04-15

    Purpose: The extensive use of computed tomography (CT) in diagnostic procedures is accompanied by a growing need for more accurate and patient-specific dosimetry techniques. Optically stimulated luminescent dosimeters (OSLDs) offer a potential solution for patient-specific CT point-based surface dosimetry by measuring air kerma. The purpose of this work was to characterize the OSLD nanoDot for CT dosimetry, quantifying necessary correction factors, and evaluating the uncertainty of these factors. Methods: A characterization of the Landauer OSL nanoDot (Landauer, Inc., Greenwood, IL) was conducted using both measurements and theoretical approaches in a CT environment. The effects of signal depletion, signal fading, dose linearity, and angular dependence were characterized through direct measurement for CT energies (80–140 kV) and delivered doses ranging from ∼5 to >1000 mGy. Energy dependence as a function of scan parameters was evaluated using two independent approaches: direct measurement and a theoretical approach based on Burlin cavity theory and Monte Carlo simulated spectra. This beam-quality dependence was evaluated for a range of CT scanning parameters. Results: Correction factors for the dosimeter response in terms of signal fading, dose linearity, and angular dependence were found to be small for most measurement conditions (<3%). The relative uncertainty was determined for each factor and reported at the two-sigma level. Differences in irradiation geometry (rotational versus static) resulted in a difference in dosimeter signal of 3% on average. Beam quality varied with scan parameters and necessitated the largest correction factor, ranging from 0.80 to 1.15 relative to a calibration performed in air using a 120 kV beam. Good agreement was found between the theoretical and measurement approaches. Conclusions: Correction factors for the measurement of air kerma were generally small for CT dosimetry, although angular effects, and particularly effects due

  13. Characterization of the nanoDot OSLD dosimeter in CT

    PubMed Central

    Scarboro, Sarah B.; Cody, Dianna; Alvarez, Paola; Followill, David; Court, Laurence; Stingo, Francesco C.; Zhang, Di; Kry, Stephen F.

    2015-01-01

    Purpose: The extensive use of computed tomography (CT) in diagnostic procedures is accompanied by a growing need for more accurate and patient-specific dosimetry techniques. Optically stimulated luminescent dosimeters (OSLDs) offer a potential solution for patient-specific CT point-based surface dosimetry by measuring air kerma. The purpose of this work was to characterize the OSLD nanoDot for CT dosimetry, quantifying necessary correction factors, and evaluating the uncertainty of these factors. Methods: A characterization of the Landauer OSL nanoDot (Landauer, Inc., Greenwood, IL) was conducted using both measurements and theoretical approaches in a CT environment. The effects of signal depletion, signal fading, dose linearity, and angular dependence were characterized through direct measurement for CT energies (80–140 kV) and delivered doses ranging from ∼5 to >1000 mGy. Energy dependence as a function of scan parameters was evaluated using two independent approaches: direct measurement and a theoretical approach based on Burlin cavity theory and Monte Carlo simulated spectra. This beam-quality dependence was evaluated for a range of CT scanning parameters. Results: Correction factors for the dosimeter response in terms of signal fading, dose linearity, and angular dependence were found to be small for most measurement conditions (<3%). The relative uncertainty was determined for each factor and reported at the two-sigma level. Differences in irradiation geometry (rotational versus static) resulted in a difference in dosimeter signal of 3% on average. Beam quality varied with scan parameters and necessitated the largest correction factor, ranging from 0.80 to 1.15 relative to a calibration performed in air using a 120 kV beam. Good agreement was found between the theoretical and measurement approaches. Conclusions: Correction factors for the measurement of air kerma were generally small for CT dosimetry, although angular effects, and particularly effects due

  14. CCD imaging for optical tomography of gel radiation dosimeters.

    PubMed

    Wolodzko, J G; Marsden, C; Appleby, A

    1999-11-01

    Several investigations have been carried out by a number of researchers over the past few years to evaluate the utility of imaging gel dosimeters for the three-dimensional measurement of radiation fields. These have been proposed to be of particular value in mapping radiation dose distributions associated with emerging and complex approaches to cancer treatment such as conformal (CRT), intensity modulated (IMRT), "gamma knife," and pencil beam radiotherapies. Imaging of the gels has been successfully accomplished with clinical MRI units and via laser-based optical scanning. However, neither of these methods is generally accessible to all potential users, limiting the broader study and implementation of this valuable tool. We report here the design, methodology, and results of a preliminary study carried out to evaluate the utility of a new, inexpensive, and simplified approach to tomographic imaging of gel radiation dosimeters. For the purpose of this initial investigation, an array of liquid scintillation vials was prepared, containing a ferrous sulphate xylenol orange (FSX) gelatin formulation. The FSX formulation undergoes a change in optical absorption characteristics following irradiation, and the resulting color change can be observed visually. The vials were irradiated individually to different doses. Three-dimensional imaging was accomplished by tomographic reconstruction from two-dimensional optical images acquired using a diffuse, fluorescent light source, a digital charge-coupled device camera, single-photon-emission-computed tomography software, and other simple components designed by the authors. The resulting transverse images were evaluated through a region-of-interest (ROI) analysis to obtain the average change in image density in each vial as a function of radiation dose. These measured ROI values were subjected to a linear regression analysis to fit them to a straight line, and to determine the goodness of fit. Results from multiple imaging trials

  15. Feasibility study of a lead monoxide-based dosimeter for quality assurance in radiotherapy

    NASA Astrophysics Data System (ADS)

    Kim, K. T.; Han, M. J.; Heo, Y. J.; Park, J. E.; Lee, Y. K.; Kim, J. N.; Oh, K. M.; Cho, H. L.; Choi, Y. S.; Kim, J. Y.; Nam, S. H.; Park, S. K.

    2016-11-01

    Lately, cancer has been treated using high-energy radiation, and this requires highly reliable treatment plans. Therefore, a dosimeter with excellent performance, which is capable of precise dose measurement, is critical. In current clinical practices, an ionization chamber and diode utilizing the ionization reaction mechanism are widely used. Several studies have been carried out to determine optimal materials for the detector in a dosimeter to enable diagnostic imaging. Recently, studies with lead monoxide, which was shown to have low drift current and high resolving power at a high bias, were reported with the dosimeter exhibiting a fast response time against incident photons. This research aims to investigate the feasibility of a lead monoxide-based dosimeter for QA (quality assurance) in radiotherapy. In this paper, we report that the manufactured dosimeter shows similar linearity to a silicon diode and demonstrates similar characteristics in terms of PDD (percent depth dose) results for the thimble ionization chamber. Based on these results, it is demonstrated that the lead monoxide-based dosimeter complies with radiotherapy QA requirements, namely rapid response time, dose linearity, dose rate independence. Thus, we expect the lead monoxide-based dosimeter to be used commercially in the future.

  16. The responses of three kinds of passive dosimeters to secondary cosmic rays in the lower atmosphere.

    PubMed

    Yang, Zhen; Chen, Bo; Zhuo, Weihai; Fan, Dunhuang; Zhao, Chao; Zhang, Yu

    2015-12-01

    For accurate measurements of the secondary cosmic rays by using passive dosimeters, the relative responses of the thermoluminescence dosimeter (TLD), optically stimulated luminescence (OSL) dosimeter, and radiophotoluminescent glass dosimeter (RPLGD) were studied. The cosmic-ray shower generator was used to simulate the secondary cosmic rays at the sea level. Monte Carlo simulations were performed to calculate the air kerma and absorbed doses in each kind of dosimeter. The results showed that compared with their responses to gamma rays of (137)Cs, the relative responses of the TLD, OSL, and RPLGD were 0.786, 0.707, and 0.735 to the hard component of cosmic rays, respectively, and the values were 0.904, 0.838, and 0.857 to the soft component of cosmic rays, respectively. To verify the simulations results, an in situ measurement with the three kinds of dosimeters was performed at the same place. The results indicated that the secondary cosmic rays monitored with the three kinds of dosimeters were well consistent with each other provided their relative responses were taken into account.

  17. Monte Carlo-based energy response studies of diode dosimeters in radiotherapy photon beams.

    PubMed

    Arun, C; Palani Selvam, T; Dinkar, Verma; Munshi, Prabhat; Kalra, Manjit Singh

    2013-01-01

    This study presents Monte Carlo-calculated absolute and normalized (relative to a (60)Co beam) sensitivity values of silicon diode dosimeters for a variety of commercially available silicon diode dosimeters for radiotherapy photon beams in the energy range of (60)Co-24 MV. These values were obtained at 5 cm depth along the central axis of a water-equivalent phantom of 10 cm × 10 cm field size. The Monte Carlo calculations were based on the EGSnrc code system. The diode dosimeters considered in the calculations have different buildup materials such as aluminum, brass, copper, and stainless steel + epoxy. The calculated normalized sensitivity values of the diode dosimeters were then compared to previously published measured values for photon beams at (60)Co-20 MV. The comparison showed reasonable agreement for some diode dosimeters and deviations of 5-17 % (17 % for the 3.4 mm brass buildup case for a 10 MV beam) for some diode dosimeters. Larger deviations of the measurements reflect that these models of the diode dosimeter were too simple. The effect of wall materials on the absorbed dose to the diode was studied and the results are presented. Spencer-Attix and Bragg-Gray stopping power ratios (SPRs) of water-to-diode were calculated at 5 cm depth in water. The Bragg-Gray SPRs of water-to-diode compare well with Spencer-Attix SPRs for ∆ = 100 keV and above at all beam qualities.

  18. The responses of three kinds of passive dosimeters to secondary cosmic rays in the lower atmosphere

    SciTech Connect

    Yang, Zhen; Chen, Bo Zhuo, Weihai; Fan, Dunhuang; Zhang, Yu; Zhao, Chao

    2015-12-15

    For accurate measurements of the secondary cosmic rays by using passive dosimeters, the relative responses of the thermoluminescence dosimeter (TLD), optically stimulated luminescence (OSL) dosimeter, and radiophotoluminescent glass dosimeter (RPLGD) were studied. The cosmic-ray shower generator was used to simulate the secondary cosmic rays at the sea level. Monte Carlo simulations were performed to calculate the air kerma and absorbed doses in each kind of dosimeter. The results showed that compared with their responses to gamma rays of {sup 137}Cs, the relative responses of the TLD, OSL, and RPLGD were 0.786, 0.707, and 0.735 to the hard component of cosmic rays, respectively, and the values were 0.904, 0.838, and 0.857 to the soft component of cosmic rays, respectively. To verify the simulations results, an in situ measurement with the three kinds of dosimeters was performed at the same place. The results indicated that the secondary cosmic rays monitored with the three kinds of dosimeters were well consistent with each other provided their relative responses were taken into account.

  19. An NMR relaxometry and gravimetric study of gelatin-free aqueous polyacrylamide dosimeters

    NASA Astrophysics Data System (ADS)

    Babic, Steven; Schreiner, L. John

    2006-09-01

    In conformal radiation therapy, a high dose of radiation is given to a target volume to increase the probability of cure, and care is taken to minimize the dose to surrounding healthy tissue. The techniques used to achieve this are very complicated and the precise verification of the resulting three-dimensional (3D) dose distribution is required. Polyacrylamide gelatin (PAG) dosimeters with magnetic resonance imaging and optical computed tomography scanning provide the required 3D dosimetry with high spatial resolution. Many basic studies have characterized these chemical dosimeters that polymerize under irradiation. However, the investigation of the fundamental properties of the radiation-induced polymerization in PAG dosimeters is complicated by the presence of the background gelatin matrix. In this work, a gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters has been developed. Experiments were performed on gelatin-free dosimeters, named aqueous polyacrylamide (APA) dosimeters, containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide. The APA dosimeters were prepared with four different total monomer concentrations (2, 4, 6 and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all four dosimeters, show a continuous degree of polymerization over the dose range of 0-25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of crosslinked polymer formed at each dose. This model can be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

  20. Ground-based evaluation of dosimeters for NASA high-altitude balloon flight

    NASA Astrophysics Data System (ADS)

    Straume, T.; Mertens, C. J.; Lusby, T. C.; Gersey, B.; Tobiska, W. K.; Norman, R. B.; Gronoff, G. P.; Hands, A.

    2016-11-01

    Results are presented from evaluations of radiation dosimeters prior to a NASA high-altitude balloon flight, the RaD-X mission. Four radiation dosimeters were on board RaD-X: a Far West Hawk (version 3), a Teledyne dosimeter (UDOS001), a Liulin dosimeter (MDU 6SA1), and a RaySure dosimeter (version 3b). The Hawk is a tissue-equivalent proportional counter (TEPC) and the others are solid-state Si sensors. The Hawk served as the "flight standard" and was calibrated for this mission. The Si-based dosimeters were tested to make sure they functioned properly prior to flight but were not calibrated for the radiation environment in the stratosphere. The dosimeters were exposed to 60Co gamma rays and 252Cf fission radiation (which includes both neutrons and gamma rays) at the Lawrence Livermore National Laboratory (LLNL). The measurement results were compared with results from standard "benchmark" measurements of the same sources and source-to-detector distances performed contemporaneously by LLNL calibration facility personnel. For 60Co gamma rays, the dosimeter-to-benchmark ratios were 0.84 ± 0.06, 1.07 ± 0.32, 1.31 ± 0.07, and 0.82 ± 0.24 for the TEPC, Teledyne, Liulin, and RaySure, respectively. For 252Cf radiation, the dosimeter-to-benchmark ratios were 0.94 ± 0.15, 0.55 ± 0.18, 0.58 ± 0.08, and 0.33 ± 0.12 for the TEPC, Teledyne, Liulin, and RaySure. Some examples of how the results were used to help interpret the flight data are also presented.

  1. Review of four novel dosimeters developed for use in radiotherapy

    NASA Astrophysics Data System (ADS)

    Metcalfe, P.; Quinn, A.; Loo, K.; Lerch, M.; Petasecca, M.; Wong, J.; Hardcastle, N.; Carolan, M.; McNamara, J.; Cutajar, D.; Fuduli, I.; Espinoza, A.; Porumb, C.; Rosenfeld, A.

    2013-06-01

    Centre for Medical Radiation Physics (CMRP) is a research strength at the University of Wollongong, the main research theme of this centre is to develop prototype novel radiation dosimeters. Multiple detector systems have been developed by Prof Rosenfelds' group for various radiation detector applications. This paper focuses on four current detector systems being developed and studied at CMRP. Two silicon array detectors include the magic plate and dose magnifying glass (DMG), the primary focus of these two detectors is high spatial and temporal resolution dosimetry in intensity modulated radiation therapy (IMRT) beams. The third detector discussed is the MOSkinTM which is a high spatial resolution detector based on MOSFET technology, its primary role is in vivo dosimetry. The fourth detector system discussed is BrachyView, this is a high resolution dose viewing system based on Medipix detector technology.

  2. Evaluation of commercial programmable floating gate devices as radiation dosimeters

    NASA Astrophysics Data System (ADS)

    Edgecock, R.; Matheson, J.; Weber, M.; Giulio Villani, E.; Bose, R.; Khan, A.; Smith, D. R.; Adil-Smith, I.; Gabrielli, A.

    2009-02-01

    Programmable floating gate MOSFET transistors were tested with gamma radiation with doses up to approximately 100Gy (air equivalent), to evaluate their suitability as dosimeters in radiotherapy. After characterization and programming at different threshold voltages, the devices were irradiated and their Vgs shift with dose monitored in real time. Post-irradiation analysis was carried out to evaluate sensitivity, linearity, reproducibility and voltage threshold annealing. A subsequent re-programming phase followed by characterization was performed to asses their post-irradiation charge restoring capabilities. It was found that up to 73% of the initial maximum threshold voltage could be recovered. A sensitivity of up to 9 mV/Gy with an uncertainty of less than 1%, an excellent linearity up to the maximum programmable threshold voltage and low noise suggest the use of this technology for in vivo dosimetry applications.

  3. Solid state dosimeters used in medical physics 'A review'

    SciTech Connect

    Azorin-Nieto, Juan

    2012-10-23

    Many solid-state detectors have been successfully used to perform the quality control and in vivo dosimetry in medical physics, both in diagnostic radiology and radiotherapy, as they have high sensitivity in a small volume; most of them do not require electrical connection and have dosimetric characteristics of interest such as: good accuracy and reproducibility, as well as a response independent of the energy of radiation, some of them. For this reason, the selection of an appropriate detector for use in medical physics must take into account the energy mass absorption coefficient relative to water for photon sources and the mass stopping power relative to water for beta emitters and electron beams in the energy range of interest in medical physics, as well as the effective atomic number of materials that constitute them. This paper presents a review of the dosimetric characteristics of the solid state dosimeters most suitable for use in medical physics.

  4. A Radiation Dosimeter Concept for the Lunar Surface Environment

    NASA Technical Reports Server (NTRS)

    Adams, James H.; Christl, Mark J.; Watts, John; Kuznetsov, Eugeny N.; Parnell, Thomas A.; Pendleton, Geoff N.

    2007-01-01

    A novel silicon detector configuration for radiation dose measurements in an environment where solar energetic particles are of most concern is described. The dosimeter would also measure the dose from galactic cosmic rays. In the lunar environment a large range in particle flux and ionization density must be measured and converted to dose equivalent. This could be accomplished with a thick (e.g. 2mm) silicon detector segmented into cubic volume elements "voxels" followed by a second, thin monolithic silicon detector. The electronics needed to implement this detector concept include analog signal processors (ASIC) and a field programmable gate array (FPGA) for data accumulation and conversion to linear energy transfer (LET) spectra and to dose-equivalent (Sievert). Currently available commercial ASIC's and FPGA's are suitable for implementing the analog and digital systems.

  5. [AOR characterization and zoning: a dosimeter for blue light].

    PubMed

    Dario, R; Uva, J; Di Lecce, V; Quarto, A

    2011-01-01

    The paper presents the results obtained thanks to an innovative experimental device for the assessment of artificial optical radiation (AOR) exposure in workplace. This . device was developed by 'Politecnico di Bari-DIASS'. The wearable personal dosimeter has three sensors: one is used for measuring head position/movement, therefore there is a color light sensor to determine the AOR and finally there is a video camera to localize sources. Our system is connected to a netbook via USB cable that allows one to obtain the real and extimated value of worker's exposure, also with "augmented reality". The aim of this paper is realizing work place safety zoning for the classifacation of not only specific dangerous areas through the analysis of overlapping information from the device.

  6. Design, Fabrication, Calibration, Testing and Satellite Integration of a Space-Radiation Dosimeter.

    DTIC Science & Technology

    1981-12-01

    IU2I 0 AFGL-TR-81-0354 DESIGN, FABRICATION, CALIBRATION, TESTING AND SATELLITE INTEGRATION OF A SPACE-RADIATION DOSIMETER ~ Bach Sellers Ralph...1978 - Dec. 1981 Radiation Dosimeter 6. PERFoRMu *PG. RgPORT NUges, AUT"OR(a) 4. CONTRACT an calT uMei[ews) Bach Sellers Frederick A. Hanser Ralph...SIOPPLEMENTARy NOTES 9. KEY WORDS (Confnlow ..n tevrs* lie If ft.ea4.# w IioaflFp by bleek ainb,) Dosimeter Particle Fluxes Electron Dose Nuclear Stars

  7. Measurement of a 200 MeV proton beam using a polyurethane dosimeter

    NASA Astrophysics Data System (ADS)

    Heard, Malcolm; Adamovics, John; Ibbott, Geoffrey

    2006-12-01

    PRESAGETM (Heuris Pharma LLC, Skillman, NJ) is a three-dimensional polyurethane dosimeter containing a leuco dye that generates a color change when irradiated. The dosimeter is solid and does not require a container to maintain its shape. The dosimeter is transparent before irradiation and the maximum absorbance of the leuco dye occurs at 633 nm which is compatible with the OCT-OPUSTM laser CT scanner (MGS Research, Inc., Madison, CT). The purpose of this study was to investigate the response of PRESAGETM to proton beam radiotherapy.

  8. Model test of CCN-cloud albedo climate forcing

    NASA Technical Reports Server (NTRS)

    Ghan, S. J.; Taylor, K. E.; Penner, J. E.; Erickson, D. J., III

    1990-01-01

    Cloud condensation nuclei (CCN) influence cloud albedo through their effect on the cloud droplet size distribution. A number of studies have evaluated the climatic impact of the CCN-cloud albedo feedback, but all have assumed that cloud distributions, cloud thicknesses, and cloud liquid water contents would remain constant as the climate adjusted. This assumption has been tested using the Livermore version of the National Center for Atmospheric Research Community Climate Model. The results indicate that there are no significant compensating changes in cloud properties that would counteract the 1.7 percent global albedo increase resulting from a fourfold increase in marine CCN concentration. Furthermore, when ocean surface temperatures are decreased 4 C in a manner broadly consistent with the enhanced cloud albedos, an increase in cloud fraction of 3.5 percent and a reduction in cloud altitude are predicted, leading to a positive feedback from clouds that would imply a climate impact roughly double that calculated from cloud droplet size distribution change alone.

  9. Asteroid magnitudes, UBV colors, and IRAS albedos and diameters

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    1989-01-01

    This paper lists absolute magnitudes and slope parameters for known asteroids numbered through 3318. The values presented are those used in reducing asteroid IR flux data obtained with the IRAS. U-B colors are given for 938 asteroids, and B-V colors are given for 945 asteroids. The IRAS albedos and diameters are tabulated for 1790 asteroids.

  10. Detection of light transformations and concomitant changes in surface albedo.

    PubMed

    Gerhard, Holly E; Maloney, Laurence T

    2010-07-16

    We report two experiments demonstrating that (1) observers are sensitive to information about changes in the light field not captured by local scene statistics and that (2) they can use this information to enhance detection of changes in surface albedo. Observers viewed scenes consisting of matte surfaces at many orientations illuminated by a collimated light source. All surfaces were achromatic, all lights neutral. In the first experiment, observers attempted to discriminate small changes in direction of the collimated light source (light transformations) from matched changes in the albedos of all surfaces (non-light transformations). Light changes and non-light changes shared the same local scene statistics and edge ratios, but the latter were not consistent with any change in direction to the collimated source. We found that observers could discriminate light changes as small as 5 degrees with sensitivity d' > 1 and accurately judge the direction of change. In a second experiment, we measured observers' ability to detect a change in the surface albedo of an isolated surface patch during either a light change or a surface change. Observers were more accurate in detecting isolated albedo changes during light changes. Measures of sensitivity d' were more than twice as great.

  11. Albedo and color maps of the Saturnian satellites

    NASA Technical Reports Server (NTRS)

    Buratti, Bonnie J.; Mosher, Joel A.; Johnson, Torrence V.

    1990-01-01

    The paper discusses the production of maps of the albedos and colors of Mimas, Enceladus, Tethys, Dione, and Rhea over the full range of their imaged surfaces. Voyager images were used to prepare maps of the normal reflectances and color ratios (0.58/0.41 micron) of these satelites.

  12. Using BRDFs for accurate albedo calculations and adjacency effect corrections

    SciTech Connect

    Borel, C.C.; Gerstl, S.A.W.

    1996-09-01

    In this paper the authors discuss two uses of BRDFs in remote sensing: (1) in determining the clear sky top of the atmosphere (TOA) albedo, (2) in quantifying the effect of the BRDF on the adjacency point-spread function and on atmospheric corrections. The TOA spectral albedo is an important parameter retrieved by the Multi-angle Imaging Spectro-Radiometer (MISR). Its accuracy depends mainly on how well one can model the surface BRDF for many different situations. The authors present results from an algorithm which matches several semi-empirical functions to the nine MISR measured BRFs that are then numerically integrated to yield the clear sky TOA spectral albedo in four spectral channels. They show that absolute accuracies in the albedo of better than 1% are possible for the visible and better than 2% in the near infrared channels. Using a simplified extensive radiosity model, the authors show that the shape of the adjacency point-spread function (PSF) depends on the underlying surface BRDFs. The adjacency point-spread function at a given offset (x,y) from the center pixel is given by the integral of transmission-weighted products of BRDF and scattering phase function along the line of sight.

  13. Variable control of neutron albedo in toroidal fusion devices

    DOEpatents

    Jassby, D.L.; Micklich, B.J.

    1983-06-01

    This invention pertains to methods of controlling in the steady state, neutron albedo in toroidal fusion devices, and in particular, to methods of controlling the flux and energy distribution of collided neutrons which are incident on an outboard wall of a toroidal fusion device.

  14. Albedo Study of the Depositional Fans Associated with Martian Gullies

    NASA Astrophysics Data System (ADS)

    Craig, J.; Sears, D. W. G.

    2005-03-01

    This work is a two-part investigation of the albedo of the depositional aprons or fans associated with Martian gully features. Using Adobe Systems Photoshop 5.0 software we analyzed numerous Mars Global Surveyor MOC and Mars Odyssey THEMIS images.

  15. Albedo of Permanently Shadowed Regions of the Lunar Poles

    NASA Astrophysics Data System (ADS)

    Riner, M. A.; Lucey, P. G.; Bussey, B.; Cahill, J. T.; McGovern, A.

    2012-12-01

    Due to the slight tilt in the Moon's spin axis, some topographic depressions near the lunar poles experience permanent shadow and may serve as cold traps, harboring water ice and/or other volatile compounds [1]. Permanently shadowed regions (PSRs) provide an opportunity toward understanding the amount, nature and transport of volatiles on the Moon and may also be a potential resource for human exploration. While many different data sets have suggested the presence of water ice in PSRs near the lunar poles many questions remain. For example, ice does not appear to be uniformly distributed across identified PSRs. More work is needed to understand the distribution of ice in PSRs and how delivery and retention mechanisms influence the distribution. The active illumination of the Lunar Orbiter Laser Altimeter (LOLA) provides a unique contribution toward exploration PSR exploration. While LOLA is principally a laser altimeter used for quantitative topography and related cartographic and geodetic applications [2], LOLA also measures the intensity and width of the return laser pulse (1064 nm) from the surface. Here we use a global mosaic (4 pixels per degree) of LOLA albedo data corrected for instrumental drift, irregular variations, and calibrated to normal albedo using local equatorial measurements of normal albedo obtained by the Kaguya Multiband Imager [3]. Recent work using LOLA albedo shows the floor of Shackleton crater, near the lunar south pole, is brighter than the surrounding terrain (and the interior of nearby craters) at 1064 nm [4]. This albedo difference may be due to decreased space weathering due to shadowing from the Sun or to a 1 μm thick layer with 20% water ice a the surface of the crater floor [4]. Here we use LOLA dayside reflectance measurements to examine the albedo of PSRs catalogued by [5] derived from illumination modeling of a hybrid 100 m/pixel LOLA-LROC digital terrain model (DTM) up to 83° north and south latitudes. The upper latitude

  16. Effective Albedo of Vegetated Terrain at L-Band

    NASA Technical Reports Server (NTRS)

    Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.

    2011-01-01

    This paper derives an explicit expression for an effective albedo of vegetated terrain from the zero- and multiple- order radiative transfer (RT) model comparison. The formulation establishes a direct physical link between the effective vegetation parameterization and the theoretical description of absorption and scattering within the canopy. The paper will present an evaluation of the derived albedo for corn canopies with data taken during an experiment at Alabama A&M Winfield A. Thomas Agricultural Research Station near Huntsville, Alabama in June, 1998. The test site consisted of two 50-m x 60-m plots - one with a bare surface and the other with grass cover - and four 30-m x 50-m plots of corn at different planting densities. One corn field was planted at a full density of 9.5 plants/sq m while the others were planted at 1/3, 1/2 and 2/3 of the full density. The fields were observed with a truck-mounted L-band radiometer at incident angle of 15 degree for the period of two weeks. Soil moisture (SM) changed daily due to irrigation and natural rainfall. Variations in gravimetric SM from 18 % to 34 % were seen during this period. Ground truth data, including careful characterization of the corn size and orientation statistics, and its dielectric, was also collected and used to simulate the effective albedo for the vegetation. The single-scattering albedo is defined as the fractional power scattered from individual vegetation constituents with respect to canopy extinction. It represents single-scattering properties of vegetation elements only, and is independent of ground properties. The values of the albedo get higher when there is dense vegetation (i.e. forest, mature corn, etc.) with scatterers, such as branches and trunks (or stalks in the case of corn), which are large with respect to the wavelength. This large albedo leads to a reduction in brightness temperature in the zero-order RT solution (known as tau-omega model). Higher-order multiple-scattering RT

  17. Effect of atmospheric dust loading on martian albedo measurements

    NASA Astrophysics Data System (ADS)

    Zinzi, Angelo; Palomba, Ernesto; Rinaldi, Giovanna; D'Amore, Mario

    2010-08-01

    This work is devoted to the analysis of the variation of albedo measured by orbiting instruments with atmospheric opacity on Mars. The study has been conduced by analysing Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) data from martian regions with different surface albedo. In support of these data, synthetic spectra with different surface albedo and atmospheric opacities have been computed, so that a comparison has been performed. The synthetic spectra have been retrieved by using two different grain sizes for suspended dust (0.5 and 1.2 μm), allowing a comparison between the two models and the observations. Using the DCI, a parameter describing the quantity of dust deposited on the surface, the effectiveness of the single scattering approximation has been tested for low atmospheric opacity by analysing the quality of the linear fit up to different atmospheric opacity. For more opaque conditions two kinds of fits have been applied to the data, linear and second-order degree polynomial. In this case, we found that the polynomial fit better describes the observations. The analysis of these data made it possible to notice a peculiar trend, already reported by Christensen (1988), of the albedo over Syrtis Major after the occurrence of dust storms, but, differently from that work, now the study of DCI together with atmospheric opacity and albedo allowed us to robustly confirm the hypothesis made by Christensen. Finally, the comparison between observations and synthetic spectra computed with models with different particles grain sizes indicates that dust particles of 0.5 μm diameter are the most effective to change the aerosol atmospheric opacity on Mars.

  18. Influence of polar-cap albedo on past and current Martian climate

    NASA Technical Reports Server (NTRS)

    Kieffer, Hugh H.; Paige, David A.

    1987-01-01

    The finding that the observed albedo of the Martian polar caps increase with increasing isolation is reviewed. Models of the Martian climate system are greatly stabilized when an insolation-dependent frost albedo instead of a constant albedo is used in the energy budget. The authors views on microphysics of the process is then presented. Long term climate models must account for the variability of CO2 frost albedo.

  19. The electromagnetic component of albedo from superhigh energy cascades in dense media

    NASA Technical Reports Server (NTRS)

    Golynskaya, R. M.; Hein, L. A.; Plyasheshnikov, A. V.; Vorobyev, K. V.

    1985-01-01

    Albedo from cascades induced in iron by high energy gamma quanta were Monte Carlo simulated. Thereafter the albedo electromagnetic component from proton induced cascades were calculated analytically. The calculations showed that the albedo electromagnetic component increases more rapidly than the nuclear active component and will dominate at sufficiently high energies.

  20. Effect of land cover change on snow free surface albedo across the continental United States

    EPA Science Inventory

    Land cover changes (e.g., forest to grassland) affect albedo, and changes in albedo can influence radiative forcing (warming, cooling). We empirically tested albedo response to land cover change for 130 locations across the continental United States using high resolution (30 m-&t...

  1. Existence Result for the Kinetic Neutron Transport Problem with a General Albedo Boundary Condition

    NASA Astrophysics Data System (ADS)

    Sanchez, Richard; Bourhrara, Lahbib

    2011-09-01

    We present an existence result for the kinetic neutron transport equation with a general albedo boundary condition. The proof is constructive in the sense that we build a sequence that converges to the solution of the problem by iterating on the albedo term. Both nonhomogeneous and albedo boundary conditions are studied.

  2. New polymer gel dosimeters consisting of less toxic monomers with radiation-crosslinked gel matrix

    NASA Astrophysics Data System (ADS)

    Hiroki, A.; Yamashita, S.; Sato, Y.; Nagasawa, N.; Taguchi, M.

    2013-06-01

    New polymer gel dosimeters consisting of less toxic methacrylate-type monomers such as 2-hydroxymethyl methacrylate (HEMA) and polyethylene glycol 400 dimethacrylate (9G) with hydroxypropyl cellulose (HPC) gel were prepared. The HPC gels were obtained by using a radiation-induced crosslinking technique to be applied in a matrix instead of a gelatin, which is conventionally used in earlier dosimeters, for the polymer gel dosimeters. The prepared polymer gel dosimeters showed cloudiness by exposing to 60Co γ-ray, in which the cloudiness increased with the dose up to 10 Gy. At the same dose, the increase in the cloudiness appeared with increasing concentration of 9G. As a result of the absorbance measurement, it was found that the dose response depended on the composition ratio between HEMA and 9G.

  3. Development and evaluation of a microprocessor-based ergonomic dosimeter for evaluating carpentry tasks.

    PubMed

    Bhattacharya, A; Warren, J; Teuschler, J; Dimov, M; Medvedovic, M; Lemasters, G

    1999-12-01

    This portable and self-contained lightweight microprocessor based Ergonomic Dosimeter is designed to collect continuously postural angles of the torso and the upper arm in the sagittal plane and the number of kneeling activities. Up to 4 h of task performance data can be stored in a non-volatile memory of the dosimeter, which can then be downloaded to a lap-top computer. The portable dosimeter was tested for test-retest reliability, compared with posture data obtained with a computer-based video analysis system and evaluated at a carpenter's apprentices school and at a construction site. The dosimeter was shown to be suitable for collecting posture and kneeling data for a prolonged period at construction sites.

  4. Novel composition of polymer gel dosimeters based on N-(Hydroxymethyl)acrylamide for radiation therapy

    NASA Astrophysics Data System (ADS)

    Basfar, Ahmed A.; Moftah, Belal; Rabaeh, Khalid A.; Almousa, Akram A.

    2015-07-01

    A new composition of polymer gel dosimeters is developed based on radiation induced polymerization of N-(Hydroxymethyl)acrylamide (NHMA) for radiotherapy treatment planning. The dosimeters were irradiated by 10 MV photon beam of a medical linear accelerator at a constant dose rate of 600 cGy/min with doses up to 20 Gy. The polymerization occurs and increases with increasing absorbed dose. The dose response of polymer gel dosimeters was studied using nuclear magnetic imaging (NMR) for relaxation rate (R2) of water proton. Dose rate, energy of radiation and the stability of the polymerization after irradiation were investigated. No appreciable effects of these parameters on the performance of the novel gel dosimeters were observed.

  5. NASA Crew Personal Active Dosimeters (CPADs): Leveraging Novel Terrestrial Personal Radiation Monitoring Capabilities for Space Exploration

    NASA Technical Reports Server (NTRS)

    Leitgab, Martin; Semones, Edward; Lee, Kerry

    2016-01-01

    The NASA Space Radiation Analysis Group (SRAG) is developing novel Crew Personal Active Dosimeters (CAPDs) for upcoming crewed space exploration missions and beyond. To reduce the resource footprint of the project a COTS dosimeter base is used for the development of CPADs. This base was identified from evaluations of existing COTS personal dosimeters against the concept of operations of future crewed missions and tests against detection requirements for radiation characteristic of the space environment. CPADs exploit operations efficiencies from novel features for space flight personal dosimeters such as real-time dose feedback, and autonomous measuring and data transmission capabilities. Preliminary CPAD design, results of radiation testing and aspects of operational integration will be presented.

  6. Performance of KCl:Eu2+ storage phosphor dosimeters for low-dose measurements

    NASA Astrophysics Data System (ADS)

    Li, H. Harold; Xiao, Zhiyan; Hansel, Rachael; Knutson, Nels; Yang, Deshan

    2013-06-01

    Recent research has demonstrated that europium doped potassium chloride (KCl:Eu2+) storage phosphor material has the potential to become the physical foundation of a novel and reusable dosimetry system using either film-like devices or devices similar to thermoluminescent dosimeter chips. The purposes of this work are to quantify the performance of KCl:Eu2+ prototype dosimeters for low-dose measurements and to demonstrate how it can be incorporated into clinical application for in vivo peripheral dose measurements. Pellet-style KCl:Eu2+ dosimeters, 6 mm in diameter, and 1 mm thick, were fabricated in-house for this study. The dosimeters were read using a laboratory photostimulated luminescence detection system. KCl:Eu2+ prototype storage phosphor dosimeter was capable of measuring a dose-to-water as low as 0.01 cGy from a 6 MV photon beam with a signal-to-noise ratio greater than 6. A pre-readout thermal annealing procedure enabled the dosimeter to be read within an hour post-irradiation. After receiving large accumulated doses (˜10 kGy), the dosimeters retained linear response in the low-dose region with only a 20% loss of sensitivity comparing to a fresh sample (zero Gy history). The energy dependence encountered during low-dose peripheral measurements could be accounted for via a single point outside-field calibration per each beam quality. With further development the KCl:Eu2+--based dosimeter could become a versatile and durable dosimetry tool with large dynamic range (sub-cGy to 100 Gy).

  7. Preliminary dose response study of a gel dosimeter using 2-Hydroxyethyl Methacrylate (HEMA).

    PubMed

    Trapp, J V; Leach, M O; Webb, S

    2005-09-01

    In this work we present a gel dosimeter based on 2-Hydroxyethyl Methacrylate (HEMA). The gel dosimeter is manufactured in normal atmospheric oxygen (normoxic) and undergoes a measurable change after irradiation. The gel is shown to provide a signal to noise ratio of up to at least 35 and have a linear change in transverse relaxation rate up to 70 Gy when measured with magnetic resonance imaging.

  8. Neutron Fading Characteristics of Copper Doped Lithium Fluoride (LiF: MCP) Thermoluminescent Dosimeters (TLDs)

    DTIC Science & Technology

    2008-05-21

    Fading Characteristics of Copper-Doped Lithium Fluoride (LiF: MCP) Thermoluminescent Dosimeters (TLDs)" Name of Candidate: L T Jeffrey A. Delzer Master...Lithium Fluoride Thermoluminescent Dosimeters beyond brief excerpts is with the permission of the copyright owner, and will save and hold harmless...Thesis: Author: Thesis directed by: ABSTRACT "Neutron Fading Characteristics of Copper-Doped Lithium Fluoride (LiF: MCP) Thermoluminescent

  9. Long term surface albedo datasets generated with Meteosat images

    NASA Astrophysics Data System (ADS)

    Lattanzio, A.; Govaerts, Y. M.; Theodore, B.

    2009-04-01

    The Global Climate Observing System (GCOS) has recognized the importance and the key-role of the surface albedo in the study of the climate change. This and the other climate variables, called Essential Climate Variables (ECVs), must satisfy the following requirements: (i) a global coverage over long-term periods with adequate spatial and temporal resolution, (ii) reliability and accuracy as well as a (iii) quality control. The Coordination Group for Meteorological Satellites (CGMS) assigned to EUMETSAT an action (T18 (TF7)) in order to prototype and test a new algorithm able to retrieve surface albedo using geostationary satellites as described in the "Implementation plan for the global observing system for climate in support of the UNFCCC" document (WMO/TD No. 1219). In this frame EUMETSAT decided to develop a new specific algorithm, named Meteosat Surface Albedo (MSA), based on a method proposed by Pinty et al. The MSA algorithm is currently running in the operational reprocessing facility of EUMETSAT in order to generate reliable albedo data set starting from 1982. These data have been acquired by six different radiometers. As Meteosat first generation satellites have not been designed for climate monitoring, before proceeding with the interpretation of the complete archive (~ 25 years of data), a detailed temporal consistency analysis of the albedo data set generated with the MSA algorithm has been performed in order to check the compliance with points (ii) and (iii). Specific efforts have been put on the estimation of the measurement error accounting for the observation uncertainties and retrieval method assumptions. Currently 100% of the archive for the prime mission at 0 degree has been processed and the albedo data set can be requested from the EUMETSAT archive facility. This paper will present the method elaborated for the evaluation of the temporal consistency of the MSA data set and illustrate typical problems raising from the processing of old data and

  10. Characterization of a water-equivalent fiber-optic coupled dosimeter for use in diagnostic radiology.

    PubMed

    Hyer, Daniel E; Fisher, Ryan F; Hintenlang, David E

    2009-05-01

    This work reports on the characterization of a new fiber-optic coupled (FOC) dosimeter for use in the diagnostic radiology energy range. The FOC dosimeter was constructed by coupling a small cylindrical plastic scintillator, 500 microm in diameter and 2 mm in length, to a 2 m long optical fiber, which acts as a light guide to transmit scintillation photons from the sensitive element to a photo-multiplier tube (PMT). A serial port interface on the PMT permits real-time monitoring of light output from the dosimeter via a custom computer program. The FOC dosimeter offered excellent sensitivity and reproducibility, allowing doses as low as 0.16 mGy to be measured with a coefficient of variation of only 3.64%. Dose linearity was also excellent with a correlation coefficient of 1.000 over exposures ranging from 0.16 to 57.29 mGy. The FOC dosimeter exhibited little angular dependence from axial irradiation, varying by less than 5% over an entire revolution. A positive energy dependence was observed and measurements performed within a scatter medium yielded a 10% variation in sensitivity as beam quality changed due to hardening and scatter across a 16 cm depth range. The current dosimetry system features an array of five PMTs to allow multiple FOC dosimeters to be monitored simultaneously. Overall, the system allows for rapid and accurate dose measurements relevant to a range of diagnostic imaging applications.

  11. Characterization of a Tissue-Equivalent Dosimeter based on CMOS Solid-State Photomultipliers

    NASA Astrophysics Data System (ADS)

    Johnson, Erik; Benton, Eric; Stapels, Christopher; Chrsitian, James; Jie Chen, Xiao

    Available digital dosimeters are bulky and unable to provide real-time monitoring of dose from space radiation. The complexity of space-flight design requires reliable, fault-tolerant equip-ment capable of providing real-time dosimetry during a mission, which is not feasible with the existing thermoluminescent dosimeter (TLD) technology, especially during extravehicular activity (EVA). Real-time monitoring is important for low-Earth orbiting spacecraft and inter-planetary space flight to alert the crew when Solar Particle Events (SPE) increase the particle flux of the spacecraft environment. A dosimeter-on-a-chip for personal dosimetry is comprised of a tissue-equivalent scintillator coupled to a solid-state photomultiplier (SSPM) built using CMOS technology. The radiation sensitive component of the dosimeter is coupled to analog signal processing components and a microprocessor, which can maintain processing fidelity up to 5x105 events per second. The dynamic range of the dosimeter has been verified from 1-GeV protons (0.22 keV/µm in H20) to 420 MeV/n Fe (201.1 keV/µm in H20). The dosimeter confirmed doses to within 3

  12. Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography

    PubMed Central

    Shih, Cheng-Ting; Lee, Yao-Ting; Wu, Shin-Hua; Yao, Chun-Hsu; Hsieh, Bor-Tsung

    2016-01-01

    With advances in therapeutic instruments and techniques, three-dimensional dose delivery has been widely used in radiotherapy. The verification of dose distribution in a small field becomes critical because of the obvious dose gradient within the field. The study investigates the dose distributions of various field sizes by using NIPAM polymer gel dosimeter. The dosimeter consists of 5% gelatin, 5% monomers, 3% cross linkers, and 5 mM THPC. After irradiation, a 24 to 96 hour delay was applied, and the gel dosimeters were read by a cone beam optical computed tomography (optical CT) scanner. The dose distributions measured by the NIPAM gel dosimeter were compared to the outputs of the treatment planning system using gamma evaluation. For the criteria of 3%/3 mm, the pass rates for 5 × 5, 3 × 3, 2 × 2, 1 × 1, and 0.5 × 0.5 cm2 were as high as 91.7%, 90.7%, 88.2%, 74.8%, and 37.3%, respectively. For the criteria of 5%/5 mm, the gamma pass rates of the 5 × 5, 3 × 3, and 2 × 2 cm2 fields were over 99%. The NIPAM gel dosimeter provides high chemical stability. With cone-beam optical CT readouts, the NIPAM polymer gel dosimeter has potential for clinical dose verification of small-field irradiation. PMID:26974434

  13. Characterization of a water-equivalent fiber-optic coupled dosimeter for use in diagnostic radiology

    SciTech Connect

    Hyer, Daniel E.; Fisher, Ryan F.; Hintenlang, David E.

    2009-05-15

    This work reports on the characterization of a new fiber-optic coupled (FOC) dosimeter for use in the diagnostic radiology energy range. The FOC dosimeter was constructed by coupling a small cylindrical plastic scintillator, 500 {mu}m in diameter and 2 mm in length, to a 2 m long optical fiber, which acts as a light guide to transmit scintillation photons from the sensitive element to a photomultiplier tube (PMT). A serial port interface on the PMT permits real-time monitoring of light output from the dosimeter via a custom computer program. The FOC dosimeter offered excellent sensitivity and reproducibility, allowing doses as low as 0.16 mGy to be measured with a coefficient of variation of only 3.64%. Dose linearity was also excellent with a correlation coefficient of 1.000 over exposures ranging from 0.16 to 57.29 mGy. The FOC dosimeter exhibited little angular dependence from axial irradiation, varying by less than 5% over an entire revolution. A positive energy dependence was observed and measurements performed within a scatter medium yielded a 10% variation in sensitivity as beam quality changed due to hardening and scatter across a 16 cm depth range. The current dosimetry system features an array of five PMTs to allow multiple FOC dosimeters to be monitored simultaneously. Overall, the system allows for rapid and accurate dose measurements relevant to a range of diagnostic imaging applications.

  14. Preparation of polymer gel dosimeters based on less toxic monomers and gellan gum

    NASA Astrophysics Data System (ADS)

    Hiroki, A.; Sato, Y.; Nagasawa, N.; Ohta, A.; Seito, H.; Yamabayashi, H.; Yamamoto, T.; Taguchi, M.; Tamada, M.; Kojima, T.

    2013-10-01

    New polymer gel dosimeters consisting of 2-hydroxyethyl methacrylate (HEMA), triethylene glycol monoethyl ether monomethacrylate (TGMEMA), polyethylene glycol 400 dimethacrylate (9G), tetrakis (hydroxymethyl) phosphonium chloride as an antioxidant, and gellan gum as a gel matrix were prepared. They were optically analyzed by measuring absorbance to evaluate a dose response. The absorbance of the polymer gel dosimeters that were exposed to 60Co γ-rays increased with increasing dose. The dosimeters comprising HEMA and 9G showed a linear increase in absorbance in the dose range from 0 to 10 Gy. The dose response depended on the 9G concentration. For others comprising HEMA, 9G and TGMEMA, the absorbance of the polymer gel dosimeters drastically increased above a certain dose, and then leveled off up to 10 Gy. The optical variations in these polymer gel dosimeters were also induced by x-irradiation from Cyberknife radiotherapy equipment. Furthermore, the exposed region of the latter polymer gel dosimeter exhibited a thermo-responsive behavior.

  15. Radiative transfer in dusty nebulae. III - The effects of dust albedo

    NASA Technical Reports Server (NTRS)

    Petrosian, V.; Dana, R. A.

    1980-01-01

    The effects of an albedo of internal dust, such as ionization structure and temperature of dust grain, were studied by the quasi-diffusion method with an iterative technique for solving the radiative heat transfer equations. It was found that the generalized on-the-spot approximation solution is adequate for most astrophysical applications for a zero albedo; for a nonzero albedo, the Eddington approximation is more accurate. The albedo increases the average energy of the diffuse photons, increasing the ionization level of hydrogen and heavy elements if the Eddington approximation is applied; the dust thermal gradient is reduced so that the infrared spectrum approaches blackbody spectrum with an increasing albedo.

  16. Characterization of a new radiochromic three-dimensional dosimeter

    SciTech Connect

    Guo, P.Y.; Adamovics, J.A.; Oldham, M.

    2006-05-15

    The development of intensity-modulated radiotherapy (IMRT) has created a clear need for a dosimeter that can accurately and conveniently measure dose distributions in three dimensions to assure treatment quality. PRESAGE{sup TM} is a new three dimensional (3D) dosimetry material consisting of an optically clear polyurethane matrix, containing a leuco dye that exhibits a radiochromic response when exposed to ionizing radiation. A number of potential advantages accrue over other gel dosimeters, including insensitivity to oxygen, radiation induced light absorption contrast rather than scattering contrast, and a solid texture amenable to machining to a variety of shapes and sizes without the requirement of an external container. In this paper, we introduce an efficient method to investigate the basic properties of a 3D dosimetry material that exhibits an optical dose response. The method is applied here to study the key aspects of the optical dose response of PRESAGE{sup TM}: linearity, dose rate dependency, reproducibility, stability, spectral changes in absorption, and temperature effects. PRESAGE{sup TM} was prepared in 1x1x4.5 cm{sup 3} optical cuvettes for convenience and was irradiated by both photon and electron beams to different doses, dose rates, and energies. Longer PRESAGE{sup TM} columns (2 x2x13 cm{sup 3}) were formed without an external container, for measurements of photon and high energy electron depth-dose curves. A linear optical scanning technique was used to detect the depth distribution of radiation induced optical density (OD) change along the PRESAGE{sup TM} columns and cuvettes. Measured depth-OD curves were compared with percent depth dose (PDD). Results indicate that PRESAGE{sup TM} has a linear optical response to radiation dose (with a root mean square error of {approx}1%), little dependency on dose rate ({approx}2%), high intrabatch reproducibility (<2%), and can be stable ({approx}2%) during 2 hours to 2 days post irradiation. Accurate

  17. Characterization of a new radiochromic three-dimensional dosimeter.

    PubMed

    Guo, P Y; Adamovics, J A; Oldham, M

    2006-05-01

    The development of intensity-modulated radiotherapy (IMRT) has created a clear need for a dosimeter that can accurately and conveniently measure dose distributions in three dimensions to assure treatment quality. PRESAGE is a new three dimensional (3D) dosimetry material consisting of an optically clear polyurethane matrix, containing a leuco dye that exhibits a radiochromic response when exposed to ionizing radiation. A number of potential advantages accrue over other gel dosimeters, including insensitivity to oxygen, radiation induced light absorption contrast rather than scattering contrast, and a solid texture amenable to machining to a variety of shapes and sizes without the requirement of an external container. In this paper, we introduce an efficient method to investigate the basic properties of a 3D dosimetry material that exhibits an optical dose response. The method is applied here to study the key aspects of the optical dose response of PRESAGE: linearity, dose rate dependency, reproducibility, stability, spectral changes in absorption, and temperature effects. PRESAGE was prepared in 1 x 1 x 4.5 cm3 optical cuvettes for convenience and was irradiated by both photon and electron beams to different doses, dose rates, and energies. Longer PRESAGE columns (2 x 2 x 13 cm3) were formed without an external container, for measurements of photon and high energy electron depth-dose curves. A linear optical scanning technique was used to detect the depth distribution of radiation induced optical density (OD) change along the PRESAGE columns and cuvettes. Measured depth-OD curves were compared with percent depth dose (PDD). Results indicate that PRESAGE has a linear optical response to radiation dose (with a root mean square error of -1%), little dependency on dose rate (-2%), high intrabatch reproducibility (< 2%), and can be stable (-2%) during 2 hours to 2 days post irradiation. Accurate PRESAGE dosimetry requires temperature control within 1 degrees C

  18. An investigation of a PRESAGE® in vivo dosimeter for brachytherapy

    NASA Astrophysics Data System (ADS)

    Vidovic, A. K.; Juang, T.; Meltsner, S.; Adamovics, J.; Chino, J.; Steffey, B.; Craciunescu, O.; Oldham, M.

    2014-07-01

    Determining accurate in vivo dosimetry in brachytherapy treatment with high dose gradients is challenging. Here we introduce, investigate, and characterize a novel in vivo dosimeter and readout technique with the potential to address this problem. A cylindrical (4 mm × 20 mm) tissue equivalent radiochromic dosimeter PRESAGE® in vivo (PRESAGE®-IV) is investigated. Two readout methods of the radiation induced change in optical density (OD) were investigated: (i) volume-averaged readout by spectrophotometer, and (ii) a line profile readout by 2D projection imaging utilizing a high-resolution (50 micron) telecentric optical system. Method (i) is considered the gold standard when applied to PRESAGE® in optical cuvettes. The feasibility of both methods was evaluated by comparison to standard measurements on PRESAGE® in optical cuvettes via spectrophotometer. An end-to-end feasibility study was performed by a side-by-side comparison with TLDs in an 192Ir HDR delivery. 7 and 8 Gy was delivered to PRESAGE®-IV and TLDs attached to the surface of a vaginal cylinder. Known geometry enabled direct comparison of measured dose with a commissioned treatment planning system. A high-resolution readout study under a steep dose gradient region showed 98.9% (5%/1 mm) agreement between PRESAGE®-IV and Gafchromic® EBT2 Film. Spectrometer measurements exhibited a linear dose response between 0-15 Gy with sensitivity of 0.0133 ± 0.0007 ΔOD/(Gy ṡ cm) at the 95% confidence interval. Method (ii) yielded a linear response with sensitivity of 0.0132 ± 0.0006 (ΔOD/Gy), within 2% of method (i). Method (i) has poor spatial resolution due to volume averaging. Method (ii) has higher resolution (˜1 mm) without loss of sensitivity or increased noise. Both readout methods are shown to be feasible. The end-to-end comparison revealed a 2.5% agreement between PRESAGE®-IV and treatment plan in regions of uniform high dose. PRESAGE®-IV shows promise for in vivo dose verification

  19. Validation of an "Intelligent Mouthguard" Single Event Head Impact Dosimeter.

    PubMed

    Bartsch, Adam; Samorezov, Sergey; Benzel, Edward; Miele, Vincent; Brett, Daniel

    2014-11-01

    Dating to Colonel John Paul Stapp MD in 1975, scientists have desired to measure live human head impacts with accuracy and precision. But no instrument exists to accurately and precisely quantify single head impact events. Our goal is to develop a practical single event head impact dosimeter known as "Intelligent Mouthguard" and quantify its performance on the benchtop, in vitro and in vivo. In the Intelligent Mouthguard hardware, limited gyroscope bandwidth requires an algorithm-based correction as a function of impact duration. After we apply gyroscope correction algorithm, Intelligent Mouthguard results at time of CG linear acceleration peak correlate to the Reference Hybrid III within our tested range of pulse durations and impact acceleration profiles in American football and Boxing in vitro tests: American football, IMG=1.00REF-1.1g, R2=0.99; maximum time of peak XYZ component imprecision 3.6g and 370 rad/s2; maximum time of peak azimuth and elevation imprecision 4.8° and 2.9°; maximum average XYZ component temporal imprecision 3.3g and 390 rad/s2. Boxing, IMG=1.00REF-0.9 g, R2=0.99, R2=0.98; maximum time of peak XYZ component imprecision 3.9 g and 390 rad/s2, maximum time of peak azimuth and elevation imprecision 2.9° and 2.1°; average XYZ component temporal imprecision 4.0 g and 440 rad/s2. In vivo Intelligent Mouthguard true positive head impacts from American football players and amateur boxers have temporal characteristics (first harmonic frequency from 35 Hz to 79 Hz) within our tested benchtop (first harmonic frequency<180 Hz) and in vitro (first harmonic frequency<100 Hz) ranges. Our conclusions apply only to situations where the rigid body assumption is valid, sensor-skull coupling is maintained and the ranges of tested parameters and harmonics fall within the boundaries of harmonics validated in vitro. For these situations, Intelligent Mouthguard qualifies as a single event dosimeter in American football and Boxing.

  20. Constraints on the diameter and albedo of 2060 Chiron

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.; Walker, Russell G.

    1991-01-01

    Asteroid 2060 Chiron is the largest known object exhibiting cometary activity. Radiometric observations made in 1983 from a ground-based telescope and the IRAS are used to examine the limits on Chiron's diameter and albedo. It is argued that Chiron's surface temperature distribution at that time is best described by an 'isothermal latitude' or 'rapid-rotator' model. Consequently, Chiron has a maximum diameter of 372 kilometers and a minimum geometric albedo of 2.7 percent. This is much bigger and darker than previous estimates, and suggests that gravity may play a significant role in the evolution of gas and dust emissions. It is also found that for large obliquities, surface temperatures can vary dramatically on time scales of a decade, and that such geometry may play a critical role in explaining Chiron's observed photometric behavior since its discovery in 1977.

  1. Deriving Albedo from Coupled MERIS and MODIS Surface Products

    NASA Technical Reports Server (NTRS)

    Gao, Feng; Schaaf, Crystal; Jin, Yu-Fang; Lucht, Wolfgang; Strahler, Alan

    2004-01-01

    MERIS Level 2 surface reflectance products are now available to the scientific community. This paper demonstrates the production of MERIS-derived surface albedo and Nadir Bidirectional Reflectance Distribution Function (BRDF) adjusted reflectances by coupling the MERIS data with MODIS BRDF products. Initial efforts rely on the specification of surface anisotropy as provided by the global MODIS BRDF product for a first guess of the shape of the BRDF and then make use all of the coincidently available, partially atmospherically corrected, cloud cleared, MERIS observations to generate MERIS-derived BRDF and surface albedo quantities for each location. Comparisons between MODIS (aerosol-corrected) and MERIS (not-yet aerosol-corrected) surface values from April and May 2003 are also presented for case studies in Spain and California as well as preliminary comparisons with field data from the Devil's Rock Surfrad/BSRN site.

  2. Land Surface Albedo from MERIS Reflectances Using MODIS Directional Factors

    NASA Technical Reports Server (NTRS)

    Schaaf, Crystal L. B.; Gao, Feng; Strahler, Alan H.

    2004-01-01

    MERIS Level 2 surface reflectance products are now available to the scientific community. This paper demonstrates the production of MERIS-derived surface albedo and Nadir Bidirectional Reflectance Distribution Function (BRDF) adjusted reflectances by coupling the MERIS data with MODIS BRDF products. Initial efforts rely on the specification of surface anisotropy as provided by the global MODIS BRDF product for a first guess of the shape of the BRDF and then make use all of the coincidently available, partially atmospherically corrected, cloud cleared, MERIS observations to generate MERIS-derived BRDF and surface albedo quantities for each location. Comparisons between MODIS (aerosol-corrected) and MERIS (not-yet aerosol-corrected) surface values from April and May 2003 are also presented for case studies in Spain and California as well as preliminary comparisons with field data from the Devil's Rock Surfrad/BSRN site.

  3. NEOWISE diameters and albedos: now available on PDS!

    NASA Astrophysics Data System (ADS)

    Masiero, Joseph R.; Mainzer, Amy K.; Bauer, James M.; Cutri, Roc M.; Grav, Tommy; Kramer, Emily A.; Nugent, Carolyn; Sonnett, Sarah M.; Stevenson, Rachel; Wright, Edward L.

    2016-10-01

    We present the recent PDS release of minor planet physical property data from the WISE/NEOWISE fully cryogenic, 3-band cryo, and post-cryo surveys as well as the first year of the NEOWISE-Reactivation survey. This release includes 165,865 diameters, visible albedos, near-infrared albedos, and/or beaming parameters for 140,493 unique minor planets. The published data include near-Earth asteroids, Main Belt asteroids, Hildas, Jupiter Trojans, Centaurs, active Main Belt objects and irregular satellites of Jupiter and Saturn. We provide an overview of the available data and discuss the key features of the PDS data set. The data are available online at: http://sbn.psi.edu/pds/resource/neowisediam.html.

  4. Reentrant albedo proton fluxes measured by the PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; Donato, C. De; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Mergé, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

    2015-05-01

    We present a precise measurement of downward going albedo proton fluxes for kinetic energy above ˜70 MeV performed by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment at an altitude between 350 and 610 km. On the basis of a trajectory tracing simulation, the analyzed protons were classified into quasi-trapped, concentrating in the magnetic equatorial region, and untrapped spreading over all latitudes, including both short-lived (precipitating) and long-lived (pseudotrapped) components. In addition, features of the penumbra region around the geomagnetic cutoff were investigated in detail. PAMELA results significantly improve the characterization of the high-energy albedo proton populations at low-Earth orbits.

  5. Exogenic and endogenic albedo and color patterns on Europa

    NASA Technical Reports Server (NTRS)

    Mcewen, A. S.

    1986-01-01

    New global and high-resolution multispectral mosaics of Europa have been produced from the Voyager imaging data. Photometric normalizations are based on multiple-image techniques that explicitly account for intrinsic albedo variations through pixel-by-pixel solutions. The exogenic color and albedo pattern on Europa is described by a second-order function of the cosine of the angular distance from the apex of orbital motion. On the basis of this second-order function and of color trends that are different on the leading and trailing hemispheres, the exogenic pattern is interpreted as being due to equilibrium between two dominant processes: (1) impact gardening and (2) magnetospheric interactions, including sulfur-ion implantation and sputtering redistribution. Removal of the model exogenic pattern in the mosaics reveals the endogenic variations, consisting of only two major units: darker (redder) and bright materials. Therefore Europa's visual spectral reflectivity is simple, having one continuous exogenic pattern and two discrete endogenic units.

  6. Measuring the influence of aerosols and albedo on sky polarization.

    PubMed

    Kreuter, A; Emde, C; Blumthaler, M

    2010-11-01

    All-sky distributions of the polarized radiance are measured using an automated fish-eye camera system with a rotating polarizer. For a large range of aerosol and surface albedo situations, the influence on the degree of polarization and sky radiance is investigated. The range of aerosol optical depth and albedo is 0.05-0.5 and 0.1-0.75, respectively. For this range of parameters, a reduction of the degree of polarization from about 0.7 to 0.4 was observed. The analysis is done for 90° scattering angle in the principal plane under clear sky conditions for a broadband channel of 450 ± 25 nm and solar zenith angles between 55° and 60°. Radiative transfer calculations considering three different aerosol mixtures are performed and and agree with the measurements within the statistical error.

  7. Control of neutron albedo in toroidal fusion reactors

    SciTech Connect

    Micklich, B.J.; Jassby, D.L.

    1983-07-01

    The MCNP and ANISN codes have been used to obtain basic neutron albedo data for materials of interest for fusion applications. Simple physical models are presented which explain albedo dependence on pre- and post-reflection variables. The angular distribution of reflected neutrons. The energy spectra of reflected neutrons are presented, and it is shown that substantial variations in the total neutron current at the outboard wall of a torus can be effected by changing materials behind the inboard wall. Analyses show that a maximum of four isolated incident-current environments may be established simultaneously on the outboard side of a torus. With suitable inboard reflectors, global tritium breeding ratios significantly larger than unity can be produced in limited-coverage breeding blankets when the effects of outboard penetrations are included.

  8. Effect of land cover change on snow free surface albedo across the continental United States

    NASA Astrophysics Data System (ADS)

    Wickham, J.; Nash, M. S.; Barnes, C. A.

    2016-11-01

    Land cover changes (e.g., forest to grassland) affect albedo, and changes in albedo can influence radiative forcing (warming, cooling). We empirically tested albedo response to land cover change for 130 locations across the continental United States using high resolution (30 m-×-30 m) land cover change data and moderate resolution ( 500 m-×-500 m) albedo data. The land cover change data spanned 10 years (2001 - 2011) and the albedo data included observations every eight days for 13 years (2001 - 2013). Empirical testing was based on autoregressive time series analysis of snow free albedo for verified locations of land cover change. Approximately one-third of the autoregressive analyses for woody to herbaceous or forest to shrub change classes were not significant, indicating that albedo did not change significantly as a result of land cover change at these locations. In addition, 80% of mean differences in albedo arising from land cover change were less than ± 0.02, a nominal benchmark for precision of albedo measurements that is related to significant changes in radiative forcing. Under snow free conditions, we found that land cover change does not guarantee a significant albedo response, and that the differences in mean albedo response for the majority of land cover change locations were small.

  9. Durability of high-albedo roof coatings and implications for cooling energy savings. Final report

    SciTech Connect

    Bretz, S.E.; Akbari, H.

    1994-06-01

    Twenty-six spot albedo measurements of roofs were made using a calibrated pyranometer. The roofs were surfaced with either an acrylic elastomeric coating, a polymer coating with an acrylic base, or a cementitious coating. Some of the roofs` albedos were measured before and after washing to determine whether the albedo decrease was permanent. Data indicated that most of the albedo degradation occurred within the first year, and even within the first two months. On one roof, 70% of one year`s albedo degradation occurred in the first two months. After the first year, the degradation slowed, with data indicating small losses in albedo after the second year. Measurements of seasonal cooling energy savings by Akbari et al. (1993) included the effects of over two months of albedo degradation. We estimated {approximately}20% loss in cooling-energy savings after the first year because of dirt accumulation. For most of the roofs we cleaned, the albedo was restored to within 90% of its initial value. Although washing is effective at restoring albedo, the increase in energy savings is temporary and labor costs are significant in comparison to savings. By our calculations, it is not cost-effective to hire someone to clean a high-albedo roof only to achieve energy savings. Thus, it would be useful to develop and identify dirt-resistant high-albedo coatings.

  10. Effect of land cover change on snow free surface albedo across the continental United States

    USGS Publications Warehouse

    Wickham, J.; Nash, M.S.; Barnes, Christopher A.

    2016-01-01

    Land cover changes (e.g., forest to grassland) affect albedo, and changes in albedo can influence radiative forcing (warming, cooling). We empirically tested albedo response to land cover change for 130 locations across the continental United States using high resolution (30 m-×-30 m) land cover change data and moderate resolution (~ 500 m-×-500 m) albedo data. The land cover change data spanned 10 years (2001 − 2011) and the albedo data included observations every eight days for 13 years (2001 − 2013). Empirical testing was based on autoregressive time series analysis of snow free albedo for verified locations of land cover change. Approximately one-third of the autoregressive analyses for woody to herbaceous or forest to shrub change classes were not significant, indicating that albedo did not change significantly as a result of land cover change at these locations. In addition, ~ 80% of mean differences in albedo arising from land cover change were less than ± 0.02, a nominal benchmark for precision of albedo measurements that is related to significant changes in radiative forcing. Under snow free conditions, we found that land cover change does not guarantee a significant albedo response, and that the differences in mean albedo response for the majority of land cover change locations were small.

  11. Albedo of coastal landfast sea ice in Prydz Bay, Antarctica: Observations and parameterization

    NASA Astrophysics Data System (ADS)

    Yang, Qinghua; Liu, Jiping; Leppäranta, Matti; Sun, Qizhen; Li, Rongbin; Zhang, Lin; Jung, Thomas; Lei, Ruibo; Zhang, Zhanhai; Li, Ming; Zhao, Jiechen; Cheng, Jingjing

    2016-05-01

    The snow/sea-ice albedo was measured over coastal landfast sea ice in Prydz Bay, East Antarctica (off Zhongshan Station) during the austral spring and summer of 2010 and 2011. The variation of the observed albedo was a combination of a gradual seasonal transition from spring to summer and abrupt changes resulting from synoptic events, including snowfall, blowing snow, and overcast skies. The measured albedo ranged from 0.94 over thick fresh snow to 0.36 over melting sea ice. It was found that snow thickness was the most important factor influencing the albedo variation, while synoptic events and overcast skies could increase the albedo by about 0.18 and 0.06, respectively. The in-situ measured albedo and related physical parameters (e.g., snow thickness, ice thickness, surface temperature, and air temperature) were then used to evaluate four different snow/ice albedo parameterizations used in a variety of climate models. The parameterized albedos showed substantial discrepancies compared to the observed albedo, particularly during the summer melt period, even though more complex parameterizations yielded more realistic variations than simple ones. A modified parameterization was developed, which further considered synoptic events, cloud cover, and the local landfast sea-ice surface characteristics. The resulting parameterized albedo showed very good agreement with the observed albedo.

  12. Characteristics of meat emulsion systems as influenced by different levels of lemon albedo.

    PubMed

    Sarıçoban, C; Ozalp, B; Yılmaz, M T; Ozen, G; Karakaya, M; Akbulut, M

    2008-11-01

    The effect of the addition of lemon albedo on the functional properties of emulsions was studied by using a model system. Oil/water (O/W) model emulsion systems were prepared by the addition of two types of lemon albedo (raw and dehydrated) at five concentrations (0.0%, 2.5%, 5.0%, 7.5% and 10%) to mechanically deboned chicken meat. The emulsion capacity, stability, viscosity and flow properties of the prepared model emulsions were analyzed. In addition, the colour parameters of cooked emulsion gel were determined. The addition of lemon albedo increased the emulsion capacity (EC) and the highest EC value was reached with 5% of albedo added. However, further increase in the albedo concentration caused an inverse trend in the EC values. A similar trend was observed in the emulsion stability (ES) values. Dehydrated albedo (DA) addition caused higher EC and ES values than did raw albedo (RA). DA increased the L(∗), a(∗) and b(∗) values of the cooked emulsion gels. Emulsion viscosity (EV) values were positively correlated with an increase in albedo concentration and the highest EV value was obtained from the emulsions with 10% albedo. Albedo addition did not change the flow properties of the emulsions and, in addition, increased the pseudoplasticity. As a consequence, the use of lemon albedo might be a potential dietary fiber source to enhance the functional and technological properties for frankfurter-type meat products.

  13. Evaluating biases in simulated land surface albedo from CMIP5 global climate models

    NASA Astrophysics Data System (ADS)

    Li, Yue; Wang, Tao; Zeng, Zhenzhong; Peng, Shushi; Lian, Xu; Piao, Shilong

    2016-06-01

    Land surface albedo is a key parameter affecting energy balance and near-surface climate. In this study, we used satellite data to evaluate simulated surface albedo in 37 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). There was a systematic overestimation in the simulated seasonal cycle of albedo with the highest bias occurring during the Northern Hemisphere's winter months. The bias in surface albedo during the snow-covered season was classified into that in snow cover fraction (SCF) and albedo contrast (β1). There was a general overestimation of β1 due to the simulated snow-covered albedo being brighter than the observed value; negative biases in SCF were not always related to negative albedo biases, highlighting the need for realistic representation of snow-covered albedo in models. In addition, models with a lower leaf area index (LAI) tend to produce a higher surface albedo over the boreal forests during the winter, which emphasizes the necessity of improving LAI simulations in CMIP5 models. Insolation weighting showed that spring albedo biases were of greater importance for climate. The removal of albedo biases is expected to improve temperature simulations particularly over high-elevation regions.

  14. MISR Level 2 TOA/Cloud Albedo parameters (MIL2TCAL_V2)

    NASA Technical Reports Server (NTRS)

    Diner, David J. (Principal Investigator)

    The TOA/Cloud Albedo data contain albedo values, including finely-sampled or local (2.2 km) TOA albedos registered to the RLRA, and two coarsely-sampled (35.2 km resolution) TOA albedos projected to 30-km altitude. The local (2.2 km) albedos do not take the obscuration of cloud features into account, so they should only be treated as traditional albedos when the number of obscured pixels is low. The restrictive and expansive albedos are both available at 35.2 km resolution: the restrictive albedos are only calculated using the radiation upwelling from the pixel under consideration, whereas the expansive albedos use all the radiation emanating from the surrounding area. Therefore, the expansive albedo is closer to the traditional definition of top-of-atmosphere albedos. [Temporal_Coverage: Start_Date=2000-02-24; Stop_Date=] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=1.1 km; Longitude_Resolution=1.1 km; Temporal_Resolution=about 15 orbits/day].

  15. Determining Small Scale Albedos Using High Resolution Multiangle Satellite Measurements

    NASA Astrophysics Data System (ADS)

    Markowski, G. R.; Davies, R.

    2005-05-01

    Current satellite short-wave (SW) albedo measurements, such as CERES's, have only a broad spatial resolution and cannot by themselves accurately measure reflectance (roughly solar "forcing") on small space and time scales. The major difficulty is that earth's surface reflectivity, including the atmosphere and clouds, is substantially anisotropic. However, accurate regional and time-dependent albedos are needed for studying causes of climate variability and change, and improving models from global to at least cloud resolving scales. A first step to obtain these albedos, for which we show results, is to accurately relate (and verify) the high resolution spatial and angular surface narrow-band MISR (Multi-Angle Imaging Spectroradiometer) radiance measurements aboard the Terra satellite to coincident total shortwave broadband (SWB) low resolution measurements from the onboard CERES instrument. Because MISR measures radiance of the same points along an orbital swath, it becomes possible to check and improve Angular (reflection) Distribution Models (ADMs) at small scales (< 1 km). The ADMs can later be used to invert a measured angular radiance to a local albedo. The difficulty lies in obtaining accurate ADMs for earth's highly varied surface and lighting conditions. We show prediction accuracy examples of CERES SWB vs. single and multiple band MISR data regressions. We include view angle dependence (9 angles: nadir plus 26, 46, 60, and 70 degrees fore and aft) and show improved accuracy when surface data, e.g., solar zenith and scattering angle, and surface type are included. In many cases, we predict angular (bidirectional) reflectance to ~ 0.01, or about 10 watts/sq m in irradiance. We also show examples of "difficult" scene types, such as varying levels of broken clouds, where accuracy degrades by a factor of ~2.

  16. Extended HXR Sources - Albedo Patches or Coronal Sources

    NASA Technical Reports Server (NTRS)

    Dennis, Brian R.

    2011-01-01

    Extended HXR sources in the presence of compact footpoints have been reported based on visibility amplitudes from different detectors. Attempts have been made to determine the location and extent of these sources through direct imaging. Results of this work will be described for simulated sources and for specific flares at different solar longitudes, with a discussion of the possible nature of the extended sources as either albedo patches or coronal sources or a combination of the two.

  17. Development of a wavelength-separated type scintillator with optical fiber (SOF) dosimeter to compensate for the Cerenkov radiation effect

    PubMed Central

    Ishikawa, Masayori; Nagase, Naomi; Matsuura, Taeko; Hiratsuka, Junichi; Suzuki, Ryusuke; Miyamoto, Naoki; Sutherland, Kenneth Lee; Fujita, Katsuhisa; Shirato, Hiroki

    2015-01-01

    The scintillator with optical fiber (SOF) dosimeter consists of a miniature scintillator mounted on the tip of an optical fiber. The scintillator of the current SOF dosimeter is a 1-mm diameter hemisphere. For a scintillation dosimeter coupled with an optical fiber, measurement accuracy is influenced by signals due to Cerenkov radiation in the optical fiber. We have implemented a spectral filtering technique for compensating for the Cerenkov radiation effect specifically for our plastic scintillator-based dosimeter, using a wavelength-separated counting method. A dichroic mirror was used for separating input light signals. Individual signal counting was performed for high- and low-wavelength light signals. To confirm the accuracy, measurements with various amounts of Cerenkov radiation were performed by changing the incident direction while keeping the Ir-192 source-to-dosimeter distance constant, resulting in a fluctuation of <5%. Optical fiber bending was also addressed; no bending effect was observed for our wavelength-separated SOF dosimeter. PMID:25618136

  18. Development of a wavelength-separated type scintillator with optical fiber (SOF) dosimeter to compensate for the Cerenkov radiation effect.

    PubMed

    Ishikawa, Masayori; Nagase, Naomi; Matsuura, Taeko; Hiratsuka, Junichi; Suzuki, Ryusuke; Miyamoto, Naoki; Sutherland, Kenneth Lee; Fujita, Katsuhisa; Shirato, Hiroki

    2015-03-01

    The scintillator with optical fiber (SOF) dosimeter consists of a miniature scintillator mounted on the tip of an optical fiber. The scintillator of the current SOF dosimeter is a 1-mm diameter hemisphere. For a scintillation dosimeter coupled with an optical fiber, measurement accuracy is influenced by signals due to Cerenkov radiation in the optical fiber. We have implemented a spectral filtering technique for compensating for the Cerenkov radiation effect specifically for our plastic scintillator-based dosimeter, using a wavelength-separated counting method. A dichroic mirror was used for separating input light signals. Individual signal counting was performed for high- and low-wavelength light signals. To confirm the accuracy, measurements with various amounts of Cerenkov radiation were performed by changing the incident direction while keeping the Ir-192 source-to-dosimeter distance constant, resulting in a fluctuation of <5%. Optical fiber bending was also addressed; no bending effect was observed for our wavelength-separated SOF dosimeter.

  19. Signatures of Volatiles in the Lunar Proton Albedo

    NASA Technical Reports Server (NTRS)

    Schwadron, N. A.; Wilson, J. K.; Looper, M. D.; Jordan, A. P.; Spence, H. E.; Blake, J. B.; Case, A. W.; Iwata, Y.; Kasper, J. C.; Farrell, W. M.; Petro, N.

    2015-01-01

    We find evidence for hydrated material in the lunar regolith using "albedo protons" measured with the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and are inconsistent with the latitude trends of heavy element enrichment (e.g., enhanced Fe abundance). The latitudinal distribution of albedo protons anti-correlates with that of epithermal or high energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in hydrated regolith that is more prevalent near the poles. The CRaTER instrument may thus provide important measurements of volatile distributions within regolith at the Moon and potentially, with similar sensors and observations, at other bodies within the Solar System.

  20. Gamma-ray Albedo of Small Solar System Bodies

    SciTech Connect

    Moskalenko, I.V.

    2008-03-25

    We calculate the {gamma}-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the {gamma}-ray albedo for the Main Belt and KBOs strongly depends on the small-body mass spectrum of each system and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). If detected, it can be used to derive the mass spectrum of small bodies in the Main Belt and Kuiper Belt and to probe the spectrum of CR nuclei at close-to-interstellar conditions. The orbits of the Main Belt asteroids and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. Therefore, the {gamma}-ray emission by the Main Belt and Kuiper Belt has to be taken into account when analyzing weak {gamma}-ray sources close to the ecliptic. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center. For details of our calculations and references see [1].

  1. Supercritical Salt Spray for the Implementation of Cloud Albedo Modification

    NASA Astrophysics Data System (ADS)

    Neukermans, A. P.; Cooper, G.; Foster, J. D.; Galbraith, L.; Ormond, B.; Wang, Q.; Johnston, D.; Cloud Brightening Research

    2011-12-01

    Of all the geo-engineering schemes proposed so far, the Latham-Salter cloud albedo modification scheme is perhaps the most benign and "natural" method. In its full deployment, it proposes to densify and thereby modify the albedo of low-hanging marine boundary clouds by a few percent such that the overall earth albedo might be changed by 1%. The scheme would require the production of vast numbers of salt cloud condensation nuclei (CCN), in one implementation on the order of 10^17 per second from each of some 1500 autonomous sailing vessels. We have investigated a number of possible techniques to create these nuclei. We reported previously the laboratory production of suitable nuclei from saltwater using Taylor cones. This method would require about 10^8 Taylor cones per vessel to get to the required CCN production rate, and hence needs a very extensive scale-up effort. We report here on the use of saltwater sprayed at or near its critical temperature and pressure through small nozzles. Although a number of technical problems remain, results to date suggest that this method might be suitable, at least for research purposes. The mean particle size distributions of nuclei generated (40-100 nm) are acceptable, and the scale-up effort to the estimated number of nozzles required (1000-2000) seems reasonable.

  2. Signatures of volatiles in the lunar proton albedo

    NASA Astrophysics Data System (ADS)

    Schwadron, N. A.; Wilson, J. K.; Looper, M. D.; Jordan, A. P.; Spence, H. E.; Blake, J. B.; Case, A. W.; Iwata, Y.; Kasper, J. C.; Farrell, W. M.; Lawrence, D. J.; Livadiotis, G.; Mazur, J.; Petro, N.; Pieters, C.; Robinson, M. S.; Smith, S.; Townsend, L. W.; Zeitlin, C.

    2016-07-01

    We find evidence for hydrated material in the lunar regolith using "albedo protons" measured with the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and are inconsistent with the latitude trends of heavy element enrichment (e.g., enhanced Fe abundance). The latitudinal distribution of albedo protons anti-correlates with that of epithermal or high energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in hydrated regolith that is more prevalent near the poles. The CRaTER instrument may thus provide important measurements of volatile distributions within regolith at the Moon and potentially, with similar sensors and observations, at other bodies within the Solar System.

  3. Dim waters: side effects of geoengineering using ocean albedo modification

    NASA Astrophysics Data System (ADS)

    Piskozub, J.; Neumann, T.

    2012-04-01

    We use a Monte Carlo radiative transfer code to check how the recently proposed geoengineering by injection of clean or coated microbubbles into the ocean mixed layer would impact in-water light fields. We show that due to massive multiscattering inside a bubble cloud, coating the bubbles with surfactant, needed to stabilize them, would not increase their albedo change effectiveness as much as expected basing on their backscattering coefficients. However, the bubble effect on reflectance is larger than estimated previously using a discrete ordinate method of solving the radiative transfer problem. We show significant side effects of ocean albedo change needed to counter global warming expected in this century and beyond (reduction of euphotic zone depth by respectively 20% and 50% in the case of global ocean albedo change corresponding to -1.25 K and -6 K global surface temperature change and irradiance decrease at 10 m depth by respectively 40% and over 80%) even if all ocean surface was "brightened". We discuss the possible negative side effect of such in-water light dimming on marine life. We conclude that the proposed "ocean brightening" is in fact "ocean dimming" as concerns the marine environment, on a scale that in any other circumstances would be called catastrophic. Finally, we briefly discuss other possible side effect of making the surface ocean waters turbid (both optically and acoustically), of adding large amounts of surfactants to the surface ocean layers and of surface cooling of the ocean, especially within the tropics.

  4. Possible Albedo Proton Signature of Hydrated Lunar Surface Layer

    NASA Astrophysics Data System (ADS)

    Schwadron, N.; Wilson, J. K.; Looper, M. D.; Jordan, A.; Spence, H. E.; Blake, J. B.; Case, A. W.; Iwata, Y.; Kasper, J. C.; Farrell, W. M.; Lawrence, D. J.; Livadiotis, G.; Mazur, J. E.; Petro, N. E.; Pieters, C. M.; Robinson, M. S.; Smith, S. S.; Townsend, L. W.; Zeitlin, C. J.

    2015-12-01

    We find evidence for a surface layer of hydrated material in the lunar regolith using "albedo protons" measured by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high-energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and cannot be accounted for by either heavy element enrichment (e.g., enhanced Fe abundance), or by deeply buried (> 50 cm) hydrogenous material. The latitudinal distribution of albedo protons does not correlate with that of epithermal or high-energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in a thin (~ 1-10 cm) layer of hydrated regolith near the surface that is more prevalent near the poles. The CRaTER instrument thus provides critical measurements of volatile distributions within lunar regolith and potentially, with similar sensors and observations, at other bodies within the Solar System.

  5. Leading/Trailing Albedo Asymmetries of Thebe, Amalthea, and Metis

    NASA Astrophysics Data System (ADS)

    Simonelli, Damon P.; Rossier, Laura; Thomas, Peter C.; Veverka, Joseph; Burns, Joseph A.; Belton, Michael J. S.

    2000-10-01

    Using Galileo clear-filter images (effective wavelength ≈0.64 μm), we have created the first albedo maps of the small inner jovian satellites Thebe, Amalthea, and Metis. These maps clearly show that the leading sides of all three satellites are significantly brighter than their corresponding trailing sides, confirming and extending a result first reported by P. C. Thomas et al. (1998, Icarus135, 360-371). In particular, on all three moons the leading side is brighter than the trailing side by 25 to 30%. The fact that the direction and size of this albedo asymmetry is identical from satellite to satellite suggests that one common physical mechanism is governing the global albedo patterns of all three moons. The most plausible such mechanism is the impact of macroscopic meteoroids that originated outside the jovian system. These impacts, which eject the dust that forms Jupiter's ring system (M. E. Ockert-Bell et al., 1999, Icarus138, 188-213; J. A. Burns et al., 1999, Science284, 1146-1150), are probably also responsible for brightening the leading sides of these small satellites.

  6. Feasibility Study of Glass Dosimeter for In Vivo Measurement: Dosimetric Characterization and Clinical Application in Proton Beams

    SciTech Connect

    Rah, Jeong-Eun; Oh, Do Hoon; Kim, Jong Won; Kim, Dae-Hyun; Suh, Tae-Suk; Ji, Young Hoon; Shin, Dongho; Lee, Se Byeong; Kim, Dae Yong; Park, Sung Yong

    2012-10-01

    Purpose: To evaluate the suitability of the GD-301 glass dosimeter for in vivo dose verification in proton therapy. Methods and Materials: The glass dosimeter was analyzed for its dosimetrics characteristic in proton beam. Dosimeters were calibrated in a water phantom using a stairlike holder specially designed for this study. To determine the accuracy of the glass dosimeter in proton dose measurements, we compared the glass dosimeter and thermoluminescent dosimeter (TLD) dose measurements using a cylindrical phantom. We investigated the feasibility of the glass dosimeter for the measurement of dose distributions near the superficial region for proton therapy plans with a varying separation between the target volume and the surface of 6 patients. Results and Discussion: Uniformity was within 1.5%. The dose-response has good linearity. Dose-rate, fading, and energy dependence were found to be within 3%. The beam profile measured using the glass dosimeter was in good agreement with the profile obtained from the ionization chamber. Depth-dose distributions in nonmodulated and modulated proton beams obtained with the glass dosimeter were estimated to be within 3%, which was lower than those with the ionization chamber. In the phantom study, the difference of isocenter dose between the delivery dose calculated by the treatment planning system and that measured by the glass dosimeter was within 5%. With in vivo dosimetry, the calculated surface doses overestimated measurements by 4%-16% using glass dosimeter and TLD. Conclusion: It is recommended that bolus be added for these clinical cases. We also believe that the glass dosimeter has considerable potential for use with in vivo patient proton dosimetry.

  7. A CCD-based γ-ray dosimeter

    NASA Astrophysics Data System (ADS)

    Harris, E. J.; Royle, G. J.; Mooney, M. J.; Speller, R. D.

    2001-02-01

    This paper investigates the use of charged coupled devices (CCDs) for personal γ-ray dosimetry. Personal dosimeters require high sensitivity to the photon energies likely to be encountered and a sensitivity response across a wide dose rate range, particularly at low dose rates. The principal advantages of CCDs for this application are two-fold: sensitivity at low dose rates due to low-noise operation and a wide dynamic range. Preliminary experimental measurements have been performed on a standard buried channel CCD using a range of isotope sources. One half of the sensor was coated with a 100 μm thick layer of caesium iodide. It is proposed that the differing properties of the two halves of the sensor increases its range for personal dosimetry. Deposition of scintillator coatings of various thicknesses across the surface of the sensor should provide sensitivity to a wide energy range. The results demonstrated that the device has potential for this application. A linear dose rate response was observed over the dose rate range 0.08-35 μSv h -1. It was found that the uncoated side of the sensor demonstrated better response at low dose rates and a better energy response. Whereas the scintillator coated side would improve the detection efficiency at energies beyond 60 keV.

  8. Study of Fricke gel dosimeter response for different gel quality

    NASA Astrophysics Data System (ADS)

    Cavinato, C. C.; Campos, L. L.

    2010-11-01

    The Fricke xylenol gel (FXG) dosimeter has been studied for application in radiotherapy because it is capable of to measure the spatial distribution of radiation doses. The dosimetry is based on the oxidation of ferrous (Fe2+) to ferric (Fe3+) ions radiation induced, related to the radiation dose. The gel material usually employed is the 300 Bloom gelatin, which is imported and very expensive in Brazil. Aiming to analyze the viability of to use a locally produced and low cost gel material, in this work the spectrophotometric responses of FXG solutions prepared using 270 Bloom gelatin commercially available and 300 Bloom gelatin imported were compared. The absorption spectra of solutions prepared with 5% by weight 270 and 300 Bloom gelatins non-irradiated and irradiated with 60Co gamma radiation in the dose range between 0.5 and 100 Gy were analysed, the dose-response curves were evaluated and the useful dose range was established. The obtained results indicate that the FXG solution prepared with 270 Bloom gelatin presents good performance, similar to that presented by the FXG solution prepared with 300 Bloom gelatin and its use can be recommended owing to the low cost and the availability in local market.

  9. Production of element correction factors for thermoluminescent dosimeters

    SciTech Connect

    Plato, P.; Miklos, J.

    1985-11-01

    Approximately 80 processors of personal dosimetry in the United States use thermoluminescent dosimeters (TLDs). Recent demands that dosimetry processors be able to measure radiation doses to within +/- 50% of the correct value have focused attention on the reproducibility of the TL elements within each TLD. The phosphors for these TLDs are manufactured by three companies. A dosimetry processor faces three options concerning the quality of the TL elements purchased; trust the supplier's quality control program, screen new TL elements and discard those that are extremely bad, or use element correction factors (ECFs). The first option results in dosimetry processors failing the +/- 50% accuracy requirement due to excessive variability among the TL elements. The second option still permits large precision errors that come close to the +/- 50% accuracy requirement. This paper advocates the third option and presents a 10-step procedure to produce ECFs. The procedure ensures that the ECFs represent only variations among the TL elements and not variations caused by stability problems with the TLD reader. Following is an example of ECF production for 3000 TLDs.

  10. Spectral discrimination of Cerenkov radiation in scintillating dosimeters.

    PubMed

    Frelin, A M; Fontbonne, J M; Ban, G; Colin, J; Labalme, M; Batalla, A; Isambert, A; Vela, A; Leroux, T

    2005-09-01

    Radiation therapy accelerators require highly accurate dose deposition and the output must be monitored frequently and regularly. Ionization chambers are the primary tool for this control, but their size, their high voltage needed, and the correction needed for electrons make them unsuitable for use during patient treatment. We have developed a small (1-mm-diam and 1-mm-long active part), flexible, and water-equivalent dosimeter. It is suitable for photon and electron beams without corrections, and performs on line dose measurements. This detector is based on only one scintillating fiber and a CCD camera. A new signal processing is used to remove the effect of Cerenkov radiation background, which only requires a preliminary calibration. Central-axis depth-dose distribution comparisons have been achieved with standard ionization chambers, over a range from 8 to 25 MV photons and from 6 to 21 MeV electrons in order to validate this calibration. Results show a very good agreement, with less than 1% difference between the two detectors.

  11. Dose measurements in intraoral radiography using thermoluminescent dosimeters

    NASA Astrophysics Data System (ADS)

    Azorín, C.; Azorín, J.; Aguirre, F.; Rivera, T.

    2015-01-01

    The use of X-ray in medicine demands to expose the patient and the professional to the lowest radiation doses available in agreement with ALARA philosophy. The reference level for intraoral dental radiography is 7 mGy and, in Mexico, a number of examinations of this type are performed annually. It is considered that approximately 25% of all the X-rays examinations carried out in our country correspond to intraoral radiographies. In other hand, most of the intraoral X-ray equipment correspond to conventional radiological systems using film, which are developed as much manual as automatically. In this work the results of determining the doses received by the patients in intraoral radiological examinations made with different radiological systems using LiF:Mg,Cu,P+PTFE thermoluminescent dosimeters are presented. In some conventional radiological systems using film, when films are developed manual or automatically, incident kerma up to 10.61 ± 0.74 mGv were determined. These values exceed that reference level suggested by the IAEA and in the Mexican standards for intraoral examinations.

  12. Multidecadal analysis of forest growth and albedo in boreal Finland

    NASA Astrophysics Data System (ADS)

    Lukeš, Petr; Stenberg, Pauline; Mõttus, Matti; Manninen, Terhikki; Rautiainen, Miina

    2016-10-01

    It is well known that forests serve as carbon sinks. However, the balancing effect of afforestation and increased forest density on global warming due to carbon storage may be lost by low albedo (thus high absorption) of the forests. In the last 30 years, there has been a steady increase in the growing stock of Finnish forests by nearly a quarter while the area of the forests has remained virtually unchanged. Such increase in forest density together with the availability of detailed forest inventories provided by the Multi-Source National Forest Inventory (MS-NFI) in high spatial resolution makes Finland an ideal candidate for exploring the effects of increased forest density on satellite derived estimates of bio-geochemical products e.g. albedo (directional-hemispherical reflectance, DHR), fraction of photosynthetically active radiation absorbed by canopies (fAPAR), leaf area index (LAI) and normalized difference vegetation index (NDVI) in both current and long-term perspective. In this study, we first used MODIS-based vegetation satellite products for Finnish forests to study their seasonal patterns and interrelations. Next, the peak growing season observations are linked to the MS-NFI database to yield the generic relationships between forest density and the satellite-derived vegetation indicators. Finally, long-term GIMMS3g datasets between 1982 and 2011 (2008 for DHR) are analyzed and interpreted using forest inventory data. The vegetation peak growing season NIR DHR and VIS DHR showed weak to moderate negative correlation with fAPAR, whereas there was no correlation between NIR DHR and fAPAR. Next, we show that the spectral albedos in the near-infrared region (NIR DHR) showed weak negative correlation with forest biomass, basal area or canopy cover whereas, as expected, the spectral albedo in the visible region (VIS DHR) correlated negatively with these measures of forest density. Interestingly, the increase in forest density (biomass per ha) of Finnish

  13. Entrance surface dose measurements using a small OSL dosimeter with a computed tomography scanner having 320 rows of detectors.

    PubMed

    Takegami, Kazuki; Hayashi, Hiroaki; Yamada, Kenji; Mihara, Yoshiki; Kimoto, Natsumi; Kanazawa, Yuki; Higashino, Kousaku; Yamashita, Kazuta; Hayashi, Fumio; Okazaki, Tohru; Hashizume, Takuya; Kobayashi, Ikuo

    2017-03-01

    Entrance surface dose (ESD) measurements are important in X-ray computed tomography (CT) for examination, but in clinical settings it is difficult to measure ESDs because of a lack of suitable dosimeters. We focus on the capability of a small optically stimulated luminescence (OSL) dosimeter. The aim of this study is to propose a practical method for using an OSL dosimeter to measure the ESD when performing a CT examination. The small OSL dosimeter has an outer width of 10 mm; it is assumed that a partial dose may be measured because the slice thickness and helical pitch can be set to various values. To verify our method, we used a CT scanner having 320 rows of detectors and checked the consistencies of the ESDs measured using OSL dosimeters by comparing them with those measured using Gafchromic™ films. The films were calibrated using an ionization chamber on the basis of half-value layer estimation. On the other hand, the OSL dosimeter was appropriately calibrated using a practical calibration curve previously proposed by our group. The ESDs measured using the OSL dosimeters were in good agreement with the reference ESDs from the Gafchromic™ films. Using these data, we also estimated the uncertainty of ESDs measured with small OSL dosimeters. We concluded that a small OSL dosimeter can be considered suitable for measuring the ESD with an uncertainty of 30 % during CT examinations in which pitch factors below 1.000 are applied.

  14. SU-E-T-368: Effect of a Strong Magnetic Field On Select Radiation Dosimeters

    SciTech Connect

    Mathis, M; Wen, Z; Tailor, R; Sawakuchi, G; Flint, D; Beddar, S; Ibbott, G

    2014-06-01

    Purpose: To determine the effect of a strong magnetic field on TLD-100, OSLD (Al{sub 2}O{sub 2}:C), and PRESAGE dosimetry devices. This study will help to determine which types of dosimeters can be used for quality assurance and in-vivo dosimetry measurements in a magnetic resonance imaginglinear accelerator (MRI-linac) system. Methods: The dosimeters were separated into two categories which were either exposed or not exposed to a strong magnetic field. In each category a set of dosimeters was irradiated with 0, 2, or 6 Gy. To expose the dosimeters to a magnetic field the samples in that category were place in a Bruker small animal magnetic resonance scanner at a field strength slightly greater than 2.5 T for at least 1 hour preirradiation and at least 1 hour post-irradiation. Irradiations were performed with a 6 MV x-ray beam from a Varian TrueBeam linac with 10×10 cm{sup 2} field at a 600 MU/min dose rate. The samples that received no radiation dose were used as control detectors. Results: The readouts of the dosimeters which were not exposed to a strong magnetic field were compared with the measurements of the dosimetry devices which were exposed to a magnetic field. No significant differences (less than 2% difference) in the performance of TLD, OSLD, or PRESAGE dosimeters due to exposure to a strong magnetic field were observed. Conclusion: Exposure to a strong magnetic field before and after irradiation does not appear to change the dosimetric properties of TLD, OSLD, or PRESAGE which indicates that these dosimeters have potential for use in quality assurance and in-vivo dosimetry in a MRI-linac. We plan to further test the effect of magnetic fields on these devices by irradiating them in the presence of a magnetic fields similar to those produced by a MRI-linac system. Elekta-MD Anderson Cancer Center Research Agreement.

  15. Study of a non-diffusing radiochromic gel dosimeter for 3D radiation dose imaging

    NASA Astrophysics Data System (ADS)

    Marsden, Craig Michael

    2000-12-01

    This thesis investigates the potential of a new radiation gel dosimeter, based on nitro-blue tetrazolium (NBTZ) suspended in a gelatin mold. Unlike all Fricke based gel dosimeters this dosimeter does not suffer from diffusive loss of image stability. Images are obtained by an optical tomography method. Nitro blue tetrazolium is a common biological indicator that when irradiated in an aqueous medium undergoes reduction to a highly colored formazan, which has an absorbance maximum at 525nm. Tetrazolium is water soluble while the formazan product is insoluble. The formazan product sticks to the gelatin matrix and the dose image is maintained for three months. Methods to maximize the sensitivity of the system were evaluated. It was found that a chemical detergent, Triton X-100, in combination with sodium formate, increased the dosimeter sensitivity significantly. An initial G-value of formazan production for a dosimeter composed of 1mM NBTZ, gelatin, and water was on the order of 0.2. The addition of Triton and formate produced a G-value in excess of 5.0. The effects of NBTZ, triton, formate, and gel concentration were all investigated. All the gels provided linear dose vs. absorbance plots for doses from 0 to >100 Gy. It was determined that gel concentration had minimal if any effect on sensitivity. Sensitivity increased slightly with increasing NBTZ concentration. Triton and formate individually and together provided moderate to large increases in dosimeter sensitivity. The dosimeter described in this work can provide stable 3D radiation dose images for all modalities of radiation therapy equipment. Methods to increase sensitivity are developed and discussed.

  16. Searching for Correlation Between Neutron Albedo and Near-IR Albedo of Mars Surface Using HEND/Odyssey and MOLA/MGS Data

    NASA Astrophysics Data System (ADS)

    Demidov, N. E.; Boynton, W. V.; Gilichinsky, D. A.; Litvak, M. L.; Kozyrev, A. S.; Mitrofanov, I. G.; Sanin, A. B.; Saunders, R. S.; Smith, D. E.; Tretykov, V. I.; Zuber, M. T.

    2007-03-01

    Strong negative correlation between HEND neutron albedo and MOLA near-IR albedo is found within two broad latitude belts: 40°N-80°N and 40°S-60°S. Interpretation: water ice in these belts is buried below the dry skin layer, which thickness is determined

  17. Assessment of VIIRS daily BRDF/Albedo product using in situ measurement of SURFRAD sites and MODIS V006 daily BRDF/Albedo product

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Wang, Z.; Sun, Q.; Schaaf, C.; Roman, M. O.

    2014-12-01

    Surface albedo is defined as the ratio of upwelling to downwelling radiative flux. It's important for understanding the global energy budget. Remote sensing albedo products provide global time continuous coverage to help capture global energy variability and change. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP satellite, launched on October 28, 2011, is aiming to provide continues data record with the MODerate resolution Imaging Spectroradiometer (MODIS), which has been providing Bidirectional Reflectance Distribution Function (BRDF)/Albedo product since 2000. By utilizing the same approach that was used for the most recently V006 daily MODIS BRDF/Albedo product, VIIRS has the ability to keep providing products for research and operational users. Validating albedo product of VIIRS using in situmeasured albedo can assure the quality for land surface climate and biosphere models, and comparing with MODIS product can assure time continues of BRDF/albedo product. The daily BRDF/Albedo product still uses 16-day period multispectral, cloud-cleared, atmospherically-corrected surface reflectances to fit the Ross-Thick/Li-Sparse-Reciprocal semi-empirical BRDF model. But the multiday observations are also weighted based on proximity to the production date in order to emphasis on that individual day. Surface Radiation Budget Network (SURFRAD) was established in 1993 through the support of NOAA's Office of Global Programs. In situ albedo was driven from downwelling and upwelling radiative flux measured from the towers. Fraction of diffuse sky light was calculated using the direct and diffuse solar recorded in the data. It was further used to translate VIIRS, MODIS black sky and white sky albedos into actual albedo at local solar noon. Results show that VIIRS, MODIS and in situ albedo agree well at SURFARD spatially representative sites. While the VIIRS surface reflectance, snow, and cloud algorithms are still undergoing revision, the result shows that

  18. Quantifying the Impacts of Surface Albedo on Climate Using the WRF Model

    NASA Astrophysics Data System (ADS)

    Schlosser, C. A.; Xu, L.; Xu, X.; Gregory, J.; Kirchain, R.

    2015-12-01

    Surface albedo is an important part of the energy budget in shaping local and regional climate. It could also be a potential tool to mitigate the anthropogenic effect on climate change. However, the current level of scientific understanding of surface albedo on global warming potential is medium to low. In order to investigate the anthropogenic impact of surface albedo on climate, different scenarios of urban surface albedo over continental US using the WRF model are simulated. In this study, the change in surface albedo applies to rooftops, pavements, and walls of urban land cover grid cells. The two groups of simulations (low and high albedo) were compared to determine the impacts of elevating urban surface albedo and to account for the uncertainty in the errors or noise introduced by the slightly different initial conditions. The results are represented as the differences in surface temperature and the top of the atmosphere radiation between the two scenarios when urban surface albedos are elevated from 0.15 to 0.40. The ensemble mean of all potential outcomes as a whole, instead of individual initial conditions, shows that the impact of elevating surface albedo has a cooling effect that is robust at both local and regional scales during the summer season. More refined analyses of urban areas will provide insights on surface albedo impacts in specific regions. Future analyses may address changes in CO2 equivalence.

  19. Assessment of Greenland albedo variability from the advanced very high resolution radiometer Polar Pathfinder data set

    NASA Astrophysics Data System (ADS)

    Stroeve, Julienne

    2001-12-01

    The advanced very high resolution radiometer Polar Pathfinder (APP) data set is used to examine the variability of the surface albedo over Greenland. Analysis of the APP albedo record from 1981 to 1998 show anomalously low albedo during 1995 and 1998 over most of the ice sheet as compared with the other years. The low albedo encountered during these years suggests that the ice sheet experienced considerable melt in 1995 and 1998, particularly near the western margin of the ice sheet. Conversely, anomalously high albedos were found in 1992 as a result of colder temperatures and hence less melt following the eruption of Mount Pinatubo. The relationship between the annual North Atlantic Oscillation (NAO) index and the mean summer albedo from all the stations reveals a positive correlation of 0.44 and a positive correlation of 0.55 for the southern part of the ice sheet. Therefore variations in the mean summer albedo over Greenland can, in part, be explained by variations in the NAO such that during periods of intensification of the normal mode of the NAO the mean summer albedo is above normal. Trend analysis reveals an overall downward trend in surface albedo from 1981 to 1998, which agrees with recent trends in melt and precipitation. However, the trend was found not to be statistically significant but rather influenced by the low albedo in recent years.

  20. Robust estimation of albedo for illumination-invariant matching and shape recovery.

    PubMed

    Biswas, Soma; Aggarwal, Gaurav; Chellappa, Rama

    2009-05-01

    We present a nonstationary stochastic filtering framework for the task of albedo estimation from a single image. There are several approaches in the literature for albedo estimation, but few include the errors in estimates of surface normals and light source direction to improve the albedo estimate. The proposed approach effectively utilizes the error statistics of surface normals and illumination direction for robust estimation of albedo, for images illuminated by single and multiple light sources. The albedo estimate obtained is subsequently used to generate albedo-free normalized images for recovering the shape of an object. Traditional Shape-from-Shading (SFS) approaches often assume constant/piecewise constant albedo and known light source direction to recover the underlying shape. Using the estimated albedo, the general problem of estimating the shape of an object with varying albedo map and unknown illumination source is reduced to one that can be handled by traditional SFS approaches. Experimental results are provided to show the effectiveness of the approach and its application to illumination-invariant matching and shape recovery. The estimated albedo maps are compared with the ground truth. The maps are used as illumination-invariant signatures for the task of face recognition across illumination variations. The recognition results obtained compare well with the current state-of-the-art approaches. Impressive shape recovery results are obtained using images downloaded from the Web with little control over imaging conditions. The recovered shapes are also used to synthesize novel views under novel illumination conditions.

  1. [Temporal and Spatial Characteristics of Lake Taihu Surface Albedo and Its Impact Factors].

    PubMed

    Cao, Chang; Li, Xu-hui; Zhang, Mi; Liu, Shou-dong; Xiao, Wei; Xiao, Qi-tao; Xu, Jia-ping

    2015-10-01

    Lake surface albedo determines energy balance of water-atmospheric interface and water physical environment. Solar elevation angle, cloudiness, wind speed, water quality and other factors can affect lake surface albedo. Using solar radiation, wind speed, and water quality data (turbidity and chlorophyll-a concentration) which were observed in four eddy covariance sites (Meiliangwan, Dapukou, Bifenggang and Xiaoleishan i. e. MLW, DPK, BFG and XLS) in Lake Taihu and clearness index (k(t)), the influence of these factors on Lake Taihu surface albedo and the reasons that led to its spatial difference were investigated. The results showed that solar elevation angle played a leading role in the diurnal and seasonal change of lake surface albedo; lake surface albedo reached two peaks in 0 < k(t) < 0.1 and 0.4 < k(t) < 0.6 respectively, when solar elevation angle was below 35 degrees. The surface albedo increased with the increasing wind speed, turbidity and chlorophyll-a concentration. However, wind could indirectly affect surface albedo through leading to the changes in sediment resuspension and chlorophyll-a distribution. The sequence of albedo in the four sites was XLS > BFG > DPK > MLW. XLS and BFG belonged to the higher albedo group, while DPK and MLW belonged to the lower albedo group. The different biological environments caused by aquatic macrophytes and algae resulting in the spatial variation of Lake Taihu surface albedo. The relationship between albedo and chlorophyll-a concentration was not a very sensitive factor for indicating the outbreak of algae. This study can provide theoretical reference for lake albedo parameterization.

  2. TH-C-19A-05: Evaluation of a New Reusable 3D Dosimeter

    SciTech Connect

    Juang, T; Adamovics, J; Oldham, M

    2014-06-15

    Purpose: PRESAGE is a radiochromic plastic which has demonstrated strong potential for high resolution single-use 3D dosimetry. This study evaluates a new PRESAGE formulation (Presage-RU) in which the radiochromic response is reversible (the dosimeter optically clears after irradiation), enabling the potential for reusability. Methods: Presage-RU dose response and optical-clearing rates were evaluated in both small volume dosimeters (1×1×4.5cm) and a larger cylindrical dosimeter (8cm diameter, 4.5cm length). All dosimeters were allowed to fully optically clear in dark, room temperature conditions between irradiations. Dose response was determined by irradiating small volume samples from 0–8.0Gy and measuring change in optical density. The cylindrical dosimeter was irradiated with a simple 4-field box plan (parallel opposed pairs of 4cm×4cm AP-PA beams and 2cm×4cm lateral beams) to 20Gy. High resolution 3D dosimetry was achieved utilizing optical-CT readout. Readings were tracked up to 14 days to characterize optical clearing. Results: Initial irradiation yielded a response of 0.0119△OD/(Gy*cm) while two subsequent reirradiations yielded a lower but consistent response of 0.0087△OD/(Gy*cm). Strong linearity of dose response was observed for all irradiations. In the large cylindrical dosimeter, the integral dose within the high dose region exhibited an exponential decay in signal over time (halflife= 23.9 hours), with the dosimeter effectively cleared (0.04% of the initial signal) after 10 days. Subsequent irradiation resulted in 19.5% lower initial signal but demonstrated that the exponential clearing rate remained consistent. Results of additional subsequent irradiations will also be presented. Conclusion: This work introduces a new re-usable radiochromic dosimeter (Presage-RU) compatible with high resolution (sub-millimeter) 3D dosimetry. Sensitivity of the initial radiation was observed to be slightly higher than subsequent irradiations, but the

  3. FlexyDos3D: a deformable anthropomorphic 3D radiation dosimeter: radiation properties

    NASA Astrophysics Data System (ADS)

    De Deene, Y.; Skyt, P. S.; Hil, R.; Booth, J. T.

    2015-02-01

    Three dimensional radiation dosimetry has received growing interest with the implementation of highly conformal radiotherapy treatments. The radiotherapy community faces new challenges with the commissioning of image guided and image gated radiotherapy treatments (IGRT) and deformable image registration software. A new three dimensional anthropomorphically shaped flexible dosimeter, further called ‘FlexyDos3D’, has been constructed and a new fast optical scanning method has been implemented that enables scanning of irregular shaped dosimeters. The FlexyDos3D phantom can be actuated and deformed during the actual treatment. FlexyDos3D offers the additional advantage that it is easy to fabricate, is non-toxic and can be molded in an arbitrary shape with high geometrical precision. The dosimeter formulation has been optimized in terms of dose sensitivity. The influence of the casting material and oxygen concentration has also been investigated. The radiophysical properties of this new dosimeter are discussed including stability, spatial integrity, temperature dependence of the dosimeter during radiation, readout and storage, dose rate dependence and tissue equivalence. The first authors Y De Deene and P S Skyt made an equivalent contribution to the experimental work presented in this paper.

  4. Chemically tuned linear energy transfer dependent quenching in a deformable, radiochromic 3D dosimeter

    NASA Astrophysics Data System (ADS)

    Høye, Ellen Marie; Skyt, Peter S.; Balling, Peter; Muren, Ludvig P.; Taasti, Vicki T.; Swakoń, Jan; Mierzwińska, Gabriela; Rydygier, Marzena; Bassler, Niels; Petersen, Jørgen B. B.

    2017-02-01

    Most solid-state detectors, including 3D dosimeters, show lower signal in the Bragg peak than expected, a process termed quenching. The purpose of this study was to investigate how variation in chemical composition of a recently developed radiochromic, silicone-based 3D dosimeter influences the observed quenching in proton beams. The dependency of dose response on linear energy transfer, as calculated through Monte Carlo simulations of the dosimeter, was investigated in 60 MeV proton beams. We found that the amount of quenching varied with the chemical composition: peak-to-plateau ratios (1 cm into the plateau) ranged from 2.2 to 3.4, compared to 4.3 using an ionization chamber. The dose response, and thereby the quenching, was predominantly influenced by the curing agent concentration, which determined the dosimeter’s deformation properties. The dose response was found to be linear at all depths. All chemical compositions of the dosimeter showed dose-rate dependency; however this was not dependent on the linear energy transfer. Track-structure theory was used to explain the observed quenching effects. In conclusion, this study shows that the silicone-based dosimeter has potential for use in measuring 3D-dose-distributions from proton beams.

  5. Undoped and doped poly(tetraphenylbenzidine) as sensitive material for an impedimetric nitrogen dioxide gas dosimeter

    SciTech Connect

    Marr, I.; Moos, R.; Neumann, K.; Thelakkat, M.

    2014-09-29

    This article presents a nitrogen dioxide (NO{sub 2}) detecting gas dosimeter based on poly(tetraphenylbenzidine) poly(TPD) as nitrogen oxide (NO{sub x}) sensitive layer. Gas dosimeters are suitable devices to determine reliably low levels of analytes over a long period of time. During NO{sub x} exposure, the analyte molecules are accumulated irreversibly in the sensing layer of the dosimeter enhancing the conductivity of the hole conducting poly(TPD), which can be measured by impedance spectroscopy. Due to their possibility for low cost production by simple printing techniques and very good physical, photochemical, and electrochemical properties, poly(TPD)s are suitable for application in gas dosimeters operated at room temperature. We studied the effect of doping with a Co(III)-complex in combination with a conducting salt on the dosimeter behavior. Compared to the undoped material, a strong influence of the doping can be observed: the conductivity of the sensing material increases significantly, the noise of the signal decreases and an unwanted recovery of the sensor signal can be prevented, leading to a NO{sub x} detection limit <10 ppm.

  6. Estimation of biologically damaging UV levels in marine surface waters with DNA and viral dosimeters.

    PubMed

    Wilhelm, Steven W; Jeffrey, Wade H; Suttle, Curtis A; Mitchell, David L

    2002-09-01

    We have surveyed the biologically harmful radiation penetrating the water column along a transect in the western Gulf of Mexico using dosimeters consisting of intact viruses or naked calf-thymus DNA (ctDNA). The indigenous marine bacteriophage PWH3a-P1, which lytically infects the heterotrophic bacterium Vibrio natriegens (strain PWH3a), displayed decay rates for infectivity approaching 1.0 h(-1) in surface waters when deployed in a seawater-based dosimeter. The accumulation of pyrimidine dimers in ctDNA dosimeters provided a strong correlation to these results, with pyrimidine dimers representing more than 0.3% (up to ca 3800 dimers Mb(-1) DNA) of the total DNA in dosimeters exposed to sea surface levels of solar radiation. The results demonstrate a strong correlation between the dimer formation in the DNA dosimeters, the decay rates of viral infectivity and the penetration of UVB radiation into the water column. The decay of viral infectivity attenuated with depth in a manner similar to the decay of solar radiation and was still significant at 10 m in offshore oligotrophic water and at dimer frequencies less than 0.1% (ca 200-300 dimers Mb(-1) DNA).

  7. Photofission Analysis for Fissile Dosimeters Dedicated to Reactor Pressure Vessel Surveillance

    NASA Astrophysics Data System (ADS)

    Bourganel, Stéphane; Faucher, Margaux; Thiollay, Nicolas

    2016-02-01

    Fissile dosimeters are commonly used in reactor pressure vessel surveillance programs. In this paper, the photofission contribution is analyzed for in-vessel 237Np and 238U fissile dosimeters in French PWR. The aim is to reassess this contribution using recent tools (the TRIPOLI-4 Monte Carlo code) and latest nuclear data (JEFF3.1.1 and ENDF/B-VII nuclear libraries). To be as exhaustive as possible, this study is carried out for different configurations of fissile dosimeters, irradiated inside different kinds of PWR: 900 MWe, 1300 MWe, and 1450 MWe. Calculation of photofission rate in dosimeters does not present a major problem using the TRIPOLI-4® Monte Carlo code and the coupled neutron-photon simulation mode. However, preliminary studies were necessary to identify the origin of photons responsible of photofissions in dosimeters in relation to the photofission threshold reaction (around 5 MeV). It appears that the main contribution of high enough energy photons generating photofissions is the neutron inelastic scattering in stainless steel reactor structures. By contrast, 137Cs activity calculation is not an easy task since photofission yield data are known with high uncertainty.

  8. Single and multichannel scintillating fiber dosimeter for radiotherapic beams with SiPM readout

    NASA Astrophysics Data System (ADS)

    Berra, A.; Ferri, A.; Novati, C.; Ostinelli, A.; Paternoster, G.; Piemonte, C.; Prest, M.; Vallazza, E.

    2016-12-01

    The treatment of many neoplastic diseases requires the use of radiotherapy, which consists in the irradiation of the tumor, identified as the target volume, with ionizing radiations generated both by administered radiopharmaceuticals or by linear particle accelerators (LINACs). The radiotherapy beam delivered to the patient must be regularly checked to assure the best tumor control probability: this task is performed with dosimeters, i.e. devices able to provide a measurement of the dose deposited in their sensitive volume. This paper describes the development of two scintillator dosimeter prototypes for radiotherapic applications based on plastic scintillating fibers read out by high dynamic range Silicon PhotoMultipliers. The first dosimeter, consisting of a single-channel prototype with a pair of optical fibers, a scintillating and a white one, read out by two SiPMs, has been fully characterized and led to the development of a second multi-channel dosimeter based on an array of scintillating fibers: this device represents the first step towards the assembly of a "one-shot" device, capable to perform some of the daily quality controls in a few seconds. The dosimeters characterization was performed with a Varian Clinac iX linear accelerator at the Radiotherapy Department of the St. Anna Hospital in Como (IT).

  9. Dose rate dependence for different dosimeters and detectors: TLD, OSL, EBT films, and diamond detectors

    SciTech Connect

    Karsch, L.; Beyreuther, E.; Burris-Mog, T.; Kraft, S.; Richter, C.; Zeil, K.; Pawelke, J.

    2012-05-15

    Purpose: The use of laser accelerators in radiation therapy can perhaps increase the low number of proton and ion therapy facilities in some years due to the low investment costs and small size. The laser-based acceleration technology leads to a very high peak dose rate of about 10{sup 11} Gy/s. A first dosimetric task is the evaluation of dose rate dependence of clinical dosimeters and other detectors. Methods: The measurements were done at ELBE, a superconductive linear electron accelerator which generates electron pulses with 5 ps length at 20 MeV. The different dose rates are reached by adjusting the number of electrons in one beam pulse. Three clinical dosimeters (TLD, OSL, and EBT radiochromic films) were irradiated with four different dose rates and nearly the same dose. A faraday cup, an integrating current transformer, and an ionization chamber were used to control the particle flux on the dosimeters. Furthermore two diamond detectors were tested. Results: The dosimeters are dose rate independent up to 410{sup 9} Gy/s within 2% (OSL and TLD) and up to 1510{sup 9} Gy/s within 5% (EBT films). The diamond detectors show strong dose rate dependence. Conclusions: TLD, OSL dosimeters, and EBT films are suitable for pulsed beams with a very high pulse dose rate like laser accelerated particle beams.

  10. SU-D-213-07: Initial Characterization of a Gel Patch Dosimeter for in Vivo Dosimetry

    SciTech Connect

    Matrosic, C; Culberson, W; Rosen, B; Madsen, E; Frank, G; Bednarz, B

    2015-06-15

    Purpose: In vivo dosimetry, despite being the most direct method for monitoring the dose delivered during radiation therapy and being recommended by several national and international organizations (AAPM, ICRU, NACP), is underutilized in the clinic due to issues associated with dose sensitivity, feasibility, and cost. Given the increasing complexity of radiation therapy modern treatments, there is a compelling need for a robust, affordable in vivo dosimetry option. In this work we present the initial characterization of a novel gel patch in vivo dosimeter. Methods: DEFGEL (6%T) was used to make 1-cm thick small cylindrical patch dosimeters. The optical density of each dosimeter was read before and after irradiation by an in-house laser densitometer. The dosimeters were irradiated using a Varian Clinac EX linac. Three separate batches of gel patches were used to create dose response curves and evaluate repeatability. The development time of the dosimeter was also evaluated. Results: The dose response of the dosimeter was found to be linear from a range of approximately 1-Gy to 20-Gy, which is a larger window of linearity compared to other in vivo dosimeters. At doses below 1-Gy, the cumulative uncertainties were on the order of the measured data. When compared, the three batches demonstrated repeatability from 1-Gy to approximately 13-Gy, with some variation at higher doses. For doses of >8-Gy, the dosimeter reached full optical density after 4-hours, whereas low doses developed within an hour. Conclusion: Initial results indicate that the gel patch dosimeter is a reliable and simple way to measure a large range of doses, including high doses such as those delivered during hypofractionated treatments (e.g. SBRT or MR-guided radiotherapy). The simple fabrication method for the dosimeter and the use of a laser densitometer would allow for the dosimeter to used and read in-house, cheaply and easily.

  11. UV signatures of carbonaceous species on low-albedo asteroids

    NASA Astrophysics Data System (ADS)

    Hendrix, A.; Vilas, F.

    2014-07-01

    Asteroids in the low-albedo classes (C, B, G, F) are known to have spectra that are relatively feature-free in the visible/near-infrared (VNIR) spectral region, making them classically difficult to study in terms of surface mineralogy. Many of these bodies exhibit a 3-micron absorption band (e.g., [1]), which can be used to study hydration and organics. The primary other spectrally active region --- less well studied so far --- is the ultraviolet (UV). In this study, we utilize UV spectra of low-albedo asteroids (C, B, G, and F class) to study surface composition. In particular, we investigate implications for the presence of carbonaceous compounds, including tholins and Polycyclic Aromatic Hydrocarbons (PAHs), which have unique spectral features in the UV. Low-albedo asteroids are typically rather bland spectrally at VNIR wavelengths. Many of these objects exhibit an absorption band near 3 microns, indicative of some type of hydration (OH and-or H_2O). A subset of the asteroids with the 3-micron features also exhibit absorption near 0.7 microns, due to a ferrous-ferric charge-transfer transition likely resulting from aqueous alteration (the interaction of material with liquid water formed by melting of water upon a heating event). Some asteroids likely do not exhibit these features due to a history of heating experienced at some point in the asteroid's evolution. Despite having little spectral activity in the VNIR, all low-albedo asteroids absorb at wavelengths shorter than ˜500 nm. This has been generally attributed to a ferric-iron intervalence charge-transfer transition absorption. Carbon-bearing phases have long been assumed to be important on low-albedo asteroids (e.g., [2]) due to the dark, mostly-featureless VNIR spectra of these bodies. However, there are many forms of carbonaceous species and the species are expected to undergo phase modifications (e.g., due to thermal, aqueous, and radiation processes) that affect the spectra [3,7]. Tholins are residues

  12. Surface Albedo/BRDF Parameters (Terra/Aqua MODIS)

    DOE Data Explorer

    Trishchenko, Alexander

    2008-01-15

    Spatially and temporally complete surface spectral albedo/BRDF products over the ARM SGP area were generated using data from two Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on Terra and Aqua satellites. A landcover-based fitting (LBF) algorithm is developed to derive the BRDF model parameters and albedo product (Luo et al., 2004a). The approach employs a landcover map and multi-day clearsky composites of directional surface reflectance. The landcover map is derived from the Landsat TM 30-meter data set (Trishchenko et al., 2004a), and the surface reflectances are from MODIS 500m-resolution 8-day composite products (MOD09/MYD09). The MOD09/MYD09 data are re-arranged into 10-day intervals for compatibility with other satellite products, such as those from the NOVA/AVHRR and SPOT/VGT sensors. The LBF method increases the success rate of the BRDF fitting process and enables more accurate monitoring of surface temporal changes during periods of rapid spring vegetation green-up and autumn leaf-fall, as well as changes due to agricultural practices and snowcover variations (Luo et al., 2004b, Trishchenko et al., 2004b). Albedo/BRDF products for MODIS on Terra and MODIS on Aqua, as well as for Terra/Aqua combined dataset, are generated at 500m spatial resolution and every 10-day since March 2000 (Terra) and July 2002 (Aqua and combined), respectively. The purpose for the latter product is to obtain a more comprehensive dataset that takes advantages of multi-sensor observations (Trishchenko et al., 2002). To fill data gaps due to cloud presence, various interpolation procedures are applied based on a multi-year observation database and referring to results from other locations with similar landcover property. Special seasonal smoothing procedure is also applied to further remove outliers and artifacts in data series.

  13. Can increasing albedo of existing ship wakes reduce climate change?

    NASA Astrophysics Data System (ADS)

    Crook, Julia A.; Jackson, Lawrence S.; Forster, Piers M.

    2016-02-01

    Solar radiation management schemes could potentially alleviate the impacts of global warming. One such scheme could be to brighten the surface of the ocean by increasing the albedo and areal extent of bubbles in the wakes of existing shipping. Here we show that ship wake bubble lifetimes would need to be extended from minutes to days, requiring the addition of surfactant, for ship wake area to be increased enough to have a significant forcing. We use a global climate model to simulate brightening the wakes of existing shipping by increasing wake albedo by 0.2 and increasing wake lifetime by ×1440. This yields a global mean radiative forcing of -0.9 ± 0.6 Wm-2 (-1.8 ± 0.9 Wm-2 in the Northern Hemisphere) and a 0.5°C reduction of global mean surface temperature with greater cooling over land and in the Northern Hemisphere, partially offsetting greenhouse gas warming. Tropical precipitation shifts southward but remains within current variability. The hemispheric forcing asymmetry of this scheme is due to the asymmetry in the distribution of existing shipping. If wake lifetime could reach ~3 months, the global mean radiative forcing could potentially reach -3 Wm-2. Increasing wake area through increasing bubble lifetime could result in a greater temperature reduction, but regional precipitation would likely deviate further from current climatology as suggested by results from our uniform ocean albedo simulation. Alternatively, additional ships specifically for the purpose of geoengineering could be used to produce a larger and more hemispherically symmetrical forcing.

  14. Using albedo to reform wind erosion modelling, mapping and monitoring

    NASA Astrophysics Data System (ADS)

    Chappell, Adrian; Webb, Nicholas P.

    2016-12-01

    Wind erosion and dust emission models are used to assess the impacts of dust on radiative forcing in the atmosphere, cloud formation, nutrient fertilisation and human health. The models are underpinned by a two-dimensional geometric property (lateral cover; L) used to characterise the three-dimensional aerodynamic roughness (sheltered area or wakes) of the Earth's surface and calibrate the momentum it extracts from the wind. We reveal a fundamental weakness in L and demonstrate that values are an order of magnitude too small and significant aerodynamic interactions between roughness elements and their sheltered areas have been omitted, particularly under sparse surface roughness. We describe a solution which develops published work to establish a relation between sheltered area and the proportion of shadow over a given area; the inverse of direct beam directional hemispherical reflectance (black sky albedo; BSA). We show direct relations between shadow and wind tunnel measurements and thereby provide direct calibrations of key aerodynamic properties. Estimation of the aerodynamic parameters from albedo enables wind erosion assessments over areas, across platforms from the field to airborne and readily available satellite data. Our new approach demonstrated redundancy in existing wind erosion models and thereby reduced model complexity and improved fidelity. We found that the use of albedo enabled an adequate description of aerodynamic sheltering to characterise fluid dynamics and predict sediment transport without the use of a drag partition scheme (Rt) or threshold friction velocity (u∗t). We applied the calibrations to produce global maps of aerodynamic properties which showed very similar spatial patterns to each other and confirmed the redundancy in the traditional parameters of wind erosion modelling. We evaluated temporal patterns of predicted horizontal mass flux at locations across Australia which revealed variation between land cover types that would not

  15. Independent pixel and Monte Carlo estimates of stratocumulus albedo

    NASA Technical Reports Server (NTRS)

    Cahalan, Robert F.; Ridgway, William; Wiscombe, Warren J.; Gollmer, Steven; HARSHVARDHAN

    1994-01-01

    Monte Carlo radiative transfer methods are employed here to estimate the plane-parallel albedo bias for marine stratocumulus clouds. This is the bias in estimates of the mesoscale-average albedo, which arises from the assumption that cloud liquid water is uniformly distributed. The authors compare such estimates with those based on a more realistic distribution generated from a fractal model of marine stratocumulus clouds belonging to the class of 'bounded cascade' models. In this model the cloud top and base are fixed, so that all variations in cloud shape are ignored. The model generates random variations in liquid water along a single horizontal direction, forming fractal cloud streets while conserving the total liquid water in the cloud field. The model reproduces the mean, variance, and skewness of the vertically integrated cloud liquid water, as well as its observed wavenumber spectrum, which is approximately a power law. The Monte Carlo method keeps track of the three-dimensional paths solar photons take through the cloud field, using a vectorized implementation of a direct technique. The simplifications in the cloud field studied here allow the computations to be accelerated. The Monte Carlo results are compared to those of the independent pixel approximation, which neglects net horizontal photon transport. Differences between the Monte Carlo and independent pixel estimates of the mesoscale-average albedo are on the order of 1% for conservative scattering, while the plane-parallel bias itself is an order of magnitude larger. As cloud absorption increases, the independent pixel approximation agrees even more closely with the Monte Carlo estimates. This result holds for a wide range of sun angles and aspect ratios. Thus, horizontal photon transport can be safely neglected in estimates of the area-average flux for such cloud models. This result relies on the rapid falloff of the wavenumber spectrum of stratocumulus, which ensures that the smaller

  16. Revised albedos of Trojan asteroids (911) Agamemnon and (4709) Ennomos

    NASA Astrophysics Data System (ADS)

    Shevchenko, V. G.; Slyusarev, I. G.; Belskaya, I. N.

    2014-01-01

    CCD-photometry was performed for two Jupiter Trojan asteroids (911) Agamemnon and (4709) Ennomos for which the diameters were obtained from occultation events. New data on rotation periods, lightcurve amplitudes, color indices, magnitude-phase slopes, and absolute magnitudes were obtained for these asteroids. We have used the diameters from occultations (166 and 99 km) and new data on absolute magnitudes at the instant occultation (7.95 and 8.85 mag) to revise their albedos to 0.042 (911 Agamemnon) and 0.052 (4709 Ennomos).

  17. Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate

    NASA Astrophysics Data System (ADS)

    Charlson, Robert J.; Warren, Stephen G.; Lovelock, James E.; Andreae, Meinrat O.

    1987-04-01

    The major source of cloud-condensation nuclei (CCN) over the oceans appears to be dimethylsulphide, which is produced by planktonic algae in sea water and oxidizes in the atmosphere to form a sulphate aerosol. Because the reflectance (albedo) of clouds (and thus the earth's radiation budget) is sensitive to CCN density, biological regulation of the climate is possible through the effects of temperature and sunlight on phytoplankton population and dimethylsulphide production. To counteract the warming due to doubling of atmospheric CO2, an approximate doubling of CCN would be needed.

  18. Earth's albedo variations 1998-2014 as measured from ground-based earthshine observations

    NASA Astrophysics Data System (ADS)

    Palle, E.; Goode, P. R.; Montañés-Rodríguez, P.; Shumko, A.; Gonzalez-Merino, B.; Lombilla, C. Martinez; Jimenez-Ibarra, F.; Shumko, S.; Sanroma, E.; Hulist, A.; Miles-Paez, P.; Murgas, F.; Nowak, G.; Koonin, S. E.

    2016-05-01

    The Earth's albedo is a fundamental climate parameter for understanding the radiation budget of the atmosphere. It has been traditionally measured not only from space platforms but also from the ground for 16 years from Big Bear Solar Observatory by observing the Moon. The photometric ratio of the dark (earthshine) to the bright (moonshine) sides of the Moon is used to determine nightly anomalies in the terrestrial albedo, with the aim of quantifying sustained monthly, annual, and/or decadal changes. We find two modest decadal scale cycles in the albedo, but with no significant net change over the 16 years of accumulated data. Within the evolution of the two cycles, we find periods of sustained annual increases, followed by comparable sustained decreases in albedo. The evolution of the earthshine albedo is in remarkable agreement with that from the Clouds and the Earth's Radiant Energy System instruments, although each method measures different slices of the Earth's Bond albedo.

  19. Effect of reflectance model choice on earthshine-based terrestrial albedo determinations.

    NASA Astrophysics Data System (ADS)

    Thejll, Peter; Gleisner, Hans; Flynn, Chris

    2016-04-01

    Earthshine observations can be used to determine near-hemispheric average terrestrial albedos by careful observation of the relative strength of the earthshine-lit half of the Moon coupled with correct modelling of the reflectances of Earth and Moon, as well as lunar single-scattering albedo maps. Using our own observations of the earthshine, from Mauna Loa Observatory in 2011-12, we investigate the influence of the choice of bidirectional reflectance models for the Moon on derived terrestrial albedos. We find a considerable dependence on albedo results in this choice, and discuss ways to determine what the origin of the dependence is - e.g is it in the joint choices of lunar and terrestrial BRDFs, or is the choice of terrestrial BRDF less important than the lunar one? We report on the results of modelling lunar reflectance and albedo in 6 ways and terrestrial reflectance in two ways, assuming a uniform single-scattering albedo on Earth.

  20. A REVISED ASTEROID POLARIZATION-ALBEDO RELATIONSHIP USING WISE/NEOWISE DATA

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Bauer, J. M.; Wright, E. L.; McMillan, R. S.; Tholen, D. J.; Blain, A. W.

    2012-04-20

    We present a reanalysis of the relationship between asteroid albedo and polarization properties using the albedos derived from the Wide-field Infrared Survey Explorer. We find that the function that best describes this relation is a three-dimensional linear fit in the space of log (albedo)-log (polarization slope)-log (minimum polarization). When projected to two dimensions, the parameters of the fit are consistent with those found in previous work. We also define p* as the quantity of maximal polarization variation when compared with the albedo and present the best-fitting albedo-p* relation. Some asteroid taxonomic types stand out in this three-dimensional space, notably the E, B, and M Tholen types, while others cluster in clumps coincident with the S- and C-complex bodies. We note that both low albedo and small (D < 30 km) asteroids are underrepresented in the polarimetric sample, and we encourage future polarimetric surveys to focus on these bodies.

  1. The study of N-isopropylacrylamide gel dosimeter doped iodinated contrast agents

    NASA Astrophysics Data System (ADS)

    Chang, Y. J.; Hsieh, L. L.; Liu, M. H.; Liu, J. S.; Hsieh, B. T.

    2013-06-01

    Low toxicity of N-isopropylacrylamide (NIPAM) dosimeter was doped with clinical iodinated contrast medium agents(Iobitridol (Xenetix® 350) and organically bound iodine (Conray® 60) as radiation sensitizers; The suitable gel dosimeter preparation formula in this research was 5 w/w% gelatin, 5 w/w% N-isopropylacrylamide, 3 w/w% N,N-methylene-bis-acrylamide, and 5 mM Tetrakis phosphonium chloride. The spiral CT was irradiator, and 120 kVp was the operating tube voltage. The maximum radiation dose was 0.6 Gy, and optical CT was the gel measurement device used. The results showed SERs with the addition of radiosensitizers were 10.70 (Xenetix® 350) and 9.67 (Conray® 60), respectively. Thus, the polymerized gel dosimeter could be used in the efficacy evaluation of low-energy and low-radiation dose.

  2. Improving the Success Rate of Delivering Annual Occupational Dosimetry Reports to Persons Issued Temporary External Dosimeters

    SciTech Connect

    Mallett, Michael Wesley

    2014-09-09

    Workers who are not routinely monitored for occupational radiation exposure at LANL may be issued temporary dosimeters in the field. Per 10CFR835 and DOE O 231.1A, the Laboratory's radiation protection program is responsible for reporting these results to the worker at the end of the year. To do so, the identity of the worker and their mailing address must be recorded by the delegated person at the time the dosimeter is issued. Historically, this data has not been consistently captured. A new online application was developed to record the issue of temporary dosimeters. The process flow of the application was structured such that: 1) the worker must be uniquely identified in the Lab's HR database, and 2) the mailing address of record is verified live time via a commercial web service, for the transaction to be completed. A COPQ savings (Type B1) of $96K/year is demonstrated for the new application.

  3. The effects of atmospheric dust on observations of Martian surface albedo

    NASA Technical Reports Server (NTRS)

    Lee, S. W.; Clancy, R. T.

    1991-01-01

    The Mariner 9 and Viking missions provided abundant evidence that aeolian processes are active over much of surface of Mars. A radiative transfer model was developed which allows the effects of atmospheric dust loading and variable surface albedo to be investigated. This model incorporated atmospheric dust opacity, the single scattering albedo, and particle phase function of atmospheric dust, the bidirectional; reflectance of the surface, and variable lighting and viewing geometry. The Cerberus albedo feature was examined in detail using this technique.

  4. Detecting Low-Contrast Features in the Cosmic Ray Albedo Proton Map of the Moon

    NASA Technical Reports Server (NTRS)

    Wilson, J. K.; Schwadron, N.; Spence, H. E.; Golightly, M. J.; Case, A. W.; Smith, S.; Blake, J. B.; Kasper, J.; Looper, M. D.; Mazur, J. E.; Townsend, L. W.; Zeitlin, C.; Stubbs, T. J.

    2014-01-01

    High energy cosmic rays constantly bombard the lunar regolith, producing (via nuclear evaporation) secondary 'albedo' or 'splash' particles like protons and neutrons, some of which escape back to space. Lunar Prospector and the Lunar Reconnaissance Orbiter (LRO), have shown that the energy distribution of albedo neutrons is modulated by the elemental composition of the lunar regolith, and by ice deposits in permanently shadowed polar craters. Here we investigate an analogous phenomenon with high energy ((is) approximately 100 MeV) lunar albedo protons.

  5. DOSIMETRIC PROPERTIES OF THE NEW TLD ALBEDO NEUTRON DOSEMETER AWST-TL-GD 04.

    PubMed

    Haninger, T; Henniger, J

    2016-09-01

    A new official albedo dosemeter based on thermoluminescent detectors has been introduced in 2015 by the individual monitoring service of the Helmholtz Zentrum München for monitoring persons who are exposed occupationally against photon and neutron radiation. To enhance the sensitivity for fast neutrons, a new badge with an enlarged albedo window has been developed at TU Dresden. The properties of the new albedo dosemeter are discussed, and the results of official intercomparisons and field calibrations are shown.

  6. Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover

    DTIC Science & Technology

    2013-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Sunlight, Sea Ice, and the Ice Albedo Feedback in a...ice age, and iv) onset dates of melt and freezeup. 4. Assess the magnitude of the contribution from ice- albedo feedback to the observed decrease of...COVERED 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover 5a

  7. Optical properties of a long dynamic range chemical UV dosimeter based on solvent cast polyvinyl chloride (PVC).

    PubMed

    Amar, Abdurazaq; Parisi, Alfio V

    2013-11-05

    The dosimetric properties of the recently introduced UV dosimeter based on 16 μm PVC film have been fully characterised. Drying the thin film in air at 50 °C for at least 28 days was found to be necessary to minimise the temperature effects on the dosimeter response. This research has found that the dosimeter response, previously reported to be mainly to UVB, has no significant dependence on either exposure temperature or dose rate. The dosimeter has negligible dark reaction and responds to the UV radiation with high reproducibility. The dosimeter angular response was found to have a similar pattern as the cosine function but deviates considerably at angles larger than 70°. Dose response curves exhibit monotonically increasing shape and the dosimeter can measure more than 900 SED. This is about 3 weeks of continuous exposure during summer at subtropical sites. Exposures measured by the PVC dosimeter for some anatomical sites exposed to solar radiation for twelve consecutive days were comparable with those concurrently measured by a series of PPO dosimeters and were in line with earlier results reported in similar studies.

  8. Method for correcting for isotope burn-in effects in fission neutron dosimeters

    DOEpatents

    Gold, Raymond; McElroy, William N.

    1988-01-01

    A method is described for correcting for effect of isotope burn-in in fission neutron dosimeters. Two quantities are measured in order to quantify the "burn-in" contribution, namely P.sub.Z',A', the amount of (Z', A') isotope that is burned-in, and F.sub.Z', A', the fissions per unit volume produced in the (Z', A') isotope. To measure P.sub.Z', A', two solid state track recorder fission deposits are prepared from the very same material that comprises the fission neutron dosimeter, and the mass and mass density are measured. One of these deposits is exposed along with the fission neutron dosimeter, whereas the second deposit is subsequently used for observation of background. P.sub.Z', A' is then determined by conducting a second irradiation, wherein both the irradiated and unirradiated fission deposits are used in solid state track recorder dosimeters for observation of the absolute number of fissions per unit volume. The difference between the latter determines P.sub.Z', A' since the thermal neutron cross section is known. F.sub.Z', A' is obtained by using a fission neutron dosimeter for this specific isotope, which is exposed along with the original threshold fission neutron dosimeter to experience the same neutron flux-time history at the same location. In order to determine the fissions per unit volume produced in the isotope (Z', A') as it ingrows during the irradiation, B.sub.Z', A', from these observations, the neutron field must generally be either time independent or a separable function of time t and neutron energy E.

  9. SU-D-213-06: Dosimetry of Modulated Electron Radiation Therapy Using Fricke Gel Dosimeter

    SciTech Connect

    Gawad, M Abdel; Elgohary, M; Hassaan, M; Emam, M; Desouky, O; Eldib, A; Ma, C

    2015-06-15

    Purpose: Modulated electron radiation therapy (MERT) has been proposed as an effective modality for treatment of superficial targets. MERT utilizes multiple beams of different energies which are intensity modulated to deliver optimized dose distribution. Energy independent dosimeters are thus needed for quantitative evaluations of MERT dose distributions and measurements of absolute doses delivered to patients. Thus in the current work we study the feasibility of Fricke gel dosimeters in MERT dosimetry. Methods: Batches of radiation sensitive Fricke gel is fabricated and poured into polymethyl methacrylate cuvettes. The samples were irradiated in solid water phantom and a thick layer of bolus was used as a buildup. A spectrophotometer system was used for measuring the color changes (the absorbance) before and after irradiation and then we calculate net absorbance. We constructed calibration curves to relate the measured absorbance in terms of absorbed dose for all available electron energies. Dosimetric measurements were performed for mixed electron beam delivery and we also performed measurement for segmented field delivery with the dosimeter placed at the junction of two adjacent electron beams of different energies. Dose measured by our gel dosimetry is compared to that calculation from our precise treatment planning system. We also initiated a Monte Carlo study to evaluate the water equivalence of our dosimeters. MCBEAM and MCSIM codes were used for treatment head simulation and phantom dose calculation. PDDs and profiles were calculated for electron beams incident on a phantom designed with 1cm slab of Fricke gel. Results: The calibration curves showed no observed energy dependence with all studied electron beam energies. Good agreement was obtained between dose calculated and that obtained by gel dosimetry. Monte Carlo results illustrated the tissue equivalency of our Gel dosimeters. Conclusion: Fricke Gel dosimeters represent a good option for the dosimetric

  10. SU-E-T-274: Does Atmospheric Oxygen Affect the PRESAGE Dosimeter?

    SciTech Connect

    Alqathami, M; Ibbott, G; Blencowe, A

    2015-06-15

    Purpose: To experimentally determine the influence of atmospheric oxygen on the efficiency of the PRESAGE dosimeter and its reporting system. Methods: Batches of the reporting system – a mixture of chloroform and leuchomalachite green dye – and PRESAGE were prepared in aerobic and anaerobic conditions. For anaerobic batches, samples were deoxygenated by bubbling nitrogen through the dosimeter precursors or reporting system for 10 min. The dosimeters and reporting systems were prepared in spectrophotometric cuvettes and glass vials, respectively, and were irradiated with 6 MV photons to various radiation doses using a clinical linear accelerator. Changes in optical density of the dosimeters and reporting system before and after irradiation were measured using a spectrophotometer. In addition, the concentrations of dissolved oxygen were measured using a dissolved oxygen meter. Results: The experiments revealed that oxygen has little influence on the characteristics of PRESAGE, with the radical initiator oxidizing the leucomalachite green even in the presence of oxygen. However, deoxygenation of the reporting system leads to an increase in sensitivity to radiation dose by ∼ 30% when compared to the non-deoxygenated system. A slight improvement in sensitivity (∼ 5%) was also achieved by deoxygenating the PRESAGE precursor prior to casting. Measurement of the dissolved oxygen revealed low levels (0.4 ppm) in the polyurethane precursor used to fabricate the dosimeters, as compared to water (8.6 ppm). In addition, deoxygenation had no effect on the retention of the post-response absorption value of the PRESAGE dosimeter. Conclusion: The results suggest that the presence of oxygen does not inhibit the radiochromic properties of the PRESAGE system. In addition, there were no observed changes in the dose linearity, absorption spectrum and post-response photofading characteristics of the PRESAGE under the conditions investigated.

  11. SU-E-T-643: Pure Alanine Dosimeter for Verification Dosimetry in IMRT

    SciTech Connect

    Al-Karmi, Anan M.; Zraiqat, Fadi

    2015-06-15

    Purpose: The objective of this study was evaluation of accuracy of pure alanine dosimeters measuring intensity-modulated radiation therapy (IMRT) dose distributions in a thorax phantom. Methods: Alanine dosimeters were prepared in the form of 110 mg pure L-α-alanine powder filled into clear tissue-equivalent polymethylmethacrylate (PMMA) plastic tubes with the dimensions 25 mm length, 3 mm inner diameter, and 1 mm wall thickness. A dose-response calibration curve was established for the alanine by placing the dosimeters at 1.5 cm depth in a 30×30×30 cm{sup 3} solid water phantom and then irradiating on a linac with 6 MV photon beam at 10×10 cm{sup 2} field size to doses ranging from 1 to 5 Gy. Electron paramagnetic resonance (EPR) spectroscopy was used to determine the absorbed dose in alanine. An IMRT treatment plan was designed for a commercial heterogeneous CIRS thorax phantom and the dose values were calculated at three different points located in tissue, lung, and bone equivalent materials. A set of dose measurements was carried out to compare measured and calculated dose values by placing the alanine dosimeters at those selected locations inside the thorax phantom and delivering the IMRT to the phantom. Results: The alanine dose measurements and the IMRT plan dose calculations were found to be in agreement within ±2%. Specifically, the deviations were −0.5%, 1.3%, and −1.7% for tissue, lung, and bone; respectively. The slightly large deviations observed for lung and bone may be attributed to tissue inhomogeneity, steep dose gradients in these regions, and uncontrollable changes in spectrometer conditions. Conclusion: The results described herein confirmed that pure alanine dosimeter was suitable for in-phantom dosimetry of IMRT beams because of its high sensitivity and acceptable accuracy. This makes the dosimeter a promising option for quality control of the therapeutic beams, complementing the commonly used ionization chambers, TLDs, and films.

  12. Changes on albedo after a large forest fire in Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Quintano, Carmen; Fernández-Manso, Alfonso; Fernández-García, Victor; Marcos, Elena; Calvo, Leonor

    2015-09-01

    Fires are one of the main causes of environmental alteration in Mediterranean forest ecosystems. Albedo varies and evolves seasonally based on solar illumination. It is greatly influenced by changes on vegetation: vegetation growth, cutting/planting forests or forest fires. This work analyzes albedo variations due to a large forest fire that occurred on 19- 21 September 2012 in northwestern Spain. From this area, albedo post-fire images (immediately and 1-year after fire) were generated from Landsat 7 Enhanced Thematic Mapper (ETM+) data. Specifically we considered total shortwave albedo, total-, direct-, and diffuse-visible, and near-infrared albedo. Nine to twelve weeks after fire, 111 field plots were measured (27 unburned plots, 84 burned plots). The relationship between albedo values and thematic class (burned/unburned) was evaluated by one-way analysis of variance. Our results demonstrate that albedo changes were related to burned/unburned variable with statistical significance, indicating the importance of forestry areas as regulators of land surface energy fluxes and revealing the potential of post-fire albedo for assessing burned areas. Future research, however, is needed to evaluate the persistence of albedo changes.

  13. The accuracy of satellite-derived albedo for northern alpine and glaciated land covers

    NASA Astrophysics Data System (ADS)

    Williamson, Scott N.; Copland, Luke; Hik, David S.

    2016-09-01

    Alpine and Arctic land cover can present a challenge for the validation of satellite-derived albedo measurements due, in part, to the complex terrain and logistical difficulty of accessing these regions. We compared measurements of albedo on transects from northern mountain land covers (snowfield, glacier ice, tundra, saline silt river delta) and over a large elevation range to the coincident 8-day MODIS (MCD43) albedo product. We also compared field measurements at snow covered sites to the coincident daily MODIS (MOD10A1) snow albedo product. For each transect, we measured a range of albedo values, with the least variability on the silt river delta (range = 0.084) and the largest over mid-elevation glacier ice (range = 0.307). The highest elevation snowfield (0.170) had nearly the same range of albedo values as tundra (0.164). The MODIS shortwave White Sky Albedo product (MCD43A3) was highly correlated with the field transect albedo (R2 = 0.96), with a Root Mean Square Error (RMSE) of 0.061. The MODIS shortwave Black Sky Albedo product was similarly correlated with field transects (R2 = 0.96; RMSE = 0.063). These results indicate that remote observation of albedo over snow covered and alpine terrain is well constrained and consistent with other studies. Albedo varied by ∼15% both spatially and temporally for the high elevation snowfields at the point in the season where albedo variation should be at its minimum. There were several instances where MCD43A3 albedo was not produced over snow and was instead classified as cloud covered, despite field observations of cloud free skies. There were also several instances where daily MOD10A1 albedo was produced during the coincident 8-day period at these locations. This suggests that the cloud mask in the MCD43 product is overly conservative over snow. Spatial variation in albedo within the MODIS grid cell (500 m), especially for snow and glacier ice, combined with the uncertainty associated with positional accuracy of

  14. A comparative study of the effects of albedo change on drought in semi-arid regions

    NASA Technical Reports Server (NTRS)

    Charney, J.; Quirk, W. J.; Chow, S.-H.; Kornfield, J.

    1977-01-01

    Numerical simulation studies of the effects of changes in albedo on rainfall involve comparisons of semiarid areas, lying at the boundary between a major desert and an adjacent monsoonal region, with areas of the same size located within the monsoonal region itself. The sensitivity of the rainfall to the ground hydrology was determined by performing the albedo simulations with two different evapotranspiration parameterizations, one giving too high evaporation over land and the other giving negligible evaporation over land. The evaporation rate is, in general, found to have as important an effect as changes in albedo. The mechanism by which an increase of albedo reduces the rainfall during conditions of high evaporation is considered.

  15. Natural versus anthropogenic factors affecting low-level cloud albedo over the North Atlantic

    NASA Technical Reports Server (NTRS)

    Falkowski, Paul G.; Kim, Yongseung; Kolber, Zbigniew; Wilson, Cara; Wirick, Creighton; Cess, Robert

    1992-01-01

    Cloud albedo plays a key role in regulating earth's climate. Cloud albedo depends on column-integrated liquid water content and the density of cloud condensation nuclei, which consists primarily of submicrometer-sized aerosol sulfate particles. A comparison of two independent satellite data sets suggests that, although anthropogenic sulfate emissions may enhance cloud albedo immediately adjacent to the east coast of the United States, over the central North Atlantic Ocean the variability in albedo can be largely accounted for by natural marine and atmospheric processes that probably have remained relatively constant since the beginning of the industrial revolution.

  16. Diurnal variability of the planetary albedo - An appraisal with satellite measurements and general circulation models

    NASA Technical Reports Server (NTRS)

    Potter, G. L.; Cess, R. D.; Minnis, P.; Harrison, E. F.; Ramanathan, V.

    1988-01-01

    An atmospheric radiation model is used here to illustrate several features associated with modeling the diurnal cycle of the planetary albedo. It is found that even for clear regions there appear to be deficiencies in our knowledge of how to model this quantity. The diurnal amplitude factor, defined as the ratio of the diurnally averaged planetary albedo to that at noon, between two GCMs and measurements made from a geostationary satellite. While reasonable consistency is found, the comparisons underscore difficulties associated with converting local-time albedo measurements, as made from sun-synchronous satellites, to diurnally averaged albedos.

  17. Vegetation controls on northern high latitude snow-albedo feedback: observations and CMIP5 model simulations.

    PubMed

    Loranty, Michael M; Berner, Logan T; Goetz, Scott J; Jin, Yufang; Randerson, James T

    2014-02-01

    The snow-masking effect of vegetation exerts strong control on albedo in northern high latitude ecosystems. Large-scale changes in the distribution and stature of vegetation in this region will thus have important feedbacks to climate. The snow-albedo feedback is controlled largely by the contrast between snow-covered and snow-free albedo (Δα), which influences predictions of future warming in coupled climate models, despite being poorly constrained at seasonal and century time scales. Here, we compare satellite observations and coupled climate model representations of albedo and tree cover for the boreal and Arctic region. Our analyses reveal consistent declines in albedo with increasing tree cover, occurring south of latitudinal tree line, that are poorly represented in coupled climate models. Observed relationships between albedo and tree cover differ substantially between snow-covered and snow-free periods, and among plant functional type. Tree cover in models varies widely but surprisingly does not correlate well with model albedo. Furthermore, our results demonstrate a relationship between tree cover and snow-albedo feedback that may be used to accurately constrain high latitude albedo feedbacks in coupled climate models under current and future vegetation distributions.

  18. On the importance of interpolation schemes for albedo data from local to global grid

    NASA Astrophysics Data System (ADS)

    Preuschmann, Swantje; Jacob, Daniela; Löw, Alexander

    2013-04-01

    Surface albedo has a key role in Earth's radiation balance. As vegetation cover is influencing the albedo of solid surfaces, it is clear that land cover changes are leading to changes in the radiation balance and further are influencing the whole Earth's energy budget. It is obvious, that a forested area reflects sunlight differently compared to a sparsely vegetated area of shrubs. Different studies have shown, that certain land cover types (even compounds) have a characteristic annual cycle of the albedo (Moody et al. 2005 and Preuschmann, 2012). An annual cycle for one land cover type might vary in a year about 2%. The difference of the surface albedo of a forested area in summer to an agricultural area at the same time is only about 0.5%. A major question in climate modelling under future conditions is to analyse the impact of land cover changes onto climate. Nevertheless for different reasons it is not easy to describe surface albedo changes due to land cover changes within a climate model. One reason is that differences in the albedo of different surfaces are comparatively small. Another reason is based in the spatial resolution of a climate model. Climate models are operating on grids with horizontal resolutions of 10x10 km² for regional models up to about 200x200 km² for global models with a spectral resolution of T63. This means, that spatial (and also temporal) mean values of surface albedo are taken into account. Therefore one grid box of a climate model is representing a composition of different surface albedos. For model validation, it is of interest to compare the modelled albedo data with observed albedo data, but a comparison is not as trivial as it looks in the first sight. One problematic is the necessity of comparing different data types in the same horizontal and temporal resolution. Commonly used satellite based albedo data are available in 0.05° horizontal resolution, which is about 5 km at the equator, for several-day means and monthly

  19. Experimental determination of the influence of oxygen on the PRESAGE® dosimeter.

    PubMed

    Alqathami, Mamdooh; Blencowe, Anton; Ibbott, Geoffrey

    2016-01-21

    It is generally accepted that the PRESAGE(®) radiochromic dosimeter is not sensitive to oxygen, however, this claim has not been supported or verified experimentally. Therefore, the aim of this study was to experimentally determine the potential influence of oxygen on dose sensitivity of the PRESAGE(®) dosimeter and its reporting system. Batches of PRESAGE(®) and its radical initiator-leuco dye reporting system were prepared in aerobic and anaerobic conditions. The anaerobic batches were deoxygenated by bubbling nitrogen through the dosimeter precursors or reporting system for 10 min. The dosimeters and reporting systems were prepared in spectrophotometric cuvettes and glass vials, respectively, and were irradiated with 6 MV photons to various radiation doses. Changes in optical density of the dosimeters and reporting system before and after irradiation were measured using a spectrophotometer. The overall results show that oxygen has some influence on the dosimetric characteristics of PRESAGE(®), although the radical initiator does appear to oxidize the leucomalachite green even in the presence of oxygen. Deoxygenation of the reporting system leads to an increase in sensitivity to radiation dose by ~30% when compared to the non-deoxygenated system. A minor increase in sensitivity (~5%) was also achieved by deoxygenating the PRESAGE(®) precursor prior to casting. In addition, dissolved oxygen measurements revealed low levels of dissolved oxygen (0.40 ± 0.04 mg l(-1)) in the polyurethane precursor used to fabricate the PRESAGE(®) dosimeters, as compared to water (8.60 ± 0.03 mg l(-1)) and the reporting system alone (1.30 ± 0.10 mg l(-1)). The results suggest that the presence of oxygen does not inhibit the radiochromic properties of the PRESAGE(®) system. However, deoxygenation of the dosimeter precursors prior to casting improves the dosimeters dose sensitivity by ~5%, which might be particularly useful for measuring low radiation doses. Nevertheless, we

  20. Experimental determination of the influence of oxygen on the PRESAGE® dosimeter

    NASA Astrophysics Data System (ADS)

    Alqathami, Mamdooh; Blencowe, Anton; Ibbott, Geoffrey

    2016-01-01

    It is generally accepted that the PRESAGE® radiochromic dosimeter is not sensitive to oxygen, however, this claim has not been supported or verified experimentally. Therefore, the aim of this study was to experimentally determine the potential influence of oxygen on dose sensitivity of the PRESAGE® dosimeter and its reporting system. Batches of PRESAGE® and its radical initiator-leuco dye reporting system were prepared in aerobic and anaerobic conditions. The anaerobic batches were deoxygenated by bubbling nitrogen through the dosimeter precursors or reporting system for 10 min. The dosimeters and reporting systems were prepared in spectrophotometric cuvettes and glass vials, respectively, and were irradiated with 6 MV photons to various radiation doses. Changes in optical density of the dosimeters and reporting system before and after irradiation were measured using a spectrophotometer. The overall results show that oxygen has some influence on the dosimetric characteristics of PRESAGE®, although the radical initiator does appear to oxidize the leucomalachite green even in the presence of oxygen. Deoxygenation of the reporting system leads to an increase in sensitivity to radiation dose by ~30% when compared to the non-deoxygenated system. A minor increase in sensitivity (~5%) was also achieved by deoxygenating the PRESAGE® precursor prior to casting. In addition, dissolved oxygen measurements revealed low levels of dissolved oxygen (0.40  ±  0.04 mg l-1) in the polyurethane precursor used to fabricate the PRESAGE® dosimeters, as compared to water (8.60  ±  0.03 mg l-1) and the reporting system alone (1.30  ±  0.10 mg l-1). The results suggest that the presence of oxygen does not inhibit the radiochromic properties of the PRESAGE® system. However, deoxygenation of the dosimeter precursors prior to casting improves the dosimeters dose sensitivity by ~5%, which might be particularly useful for measuring low radiation doses

  1. Neutron dosimetry at commercial nuclear plants. Final report of Subtask B: dosimeter response

    SciTech Connect

    Cummings, F.M.; Endres, G.W.R.; Brackenbush, L.W.

    1983-03-01

    As part of a larger program to evaluate personnel neutron dosimetry at commercial nuclear power plants, this study was designed to characterize neutron dosimeter responses inside the containment structure of commercial nuclear plants. In order to characterize those responses, dosimeters were irradiated inside containment at 2 pressurized water reactors and at pipe penetrations outside the biological shield at two boiling water reactors. The reactors were operating at full power during the irradiations. Measurements were also performed with electronic instruments, the tissue equivalent proportional counter (TEPC), and portable remmeters, SNOOPY, RASCAL and PNR-4.

  2. Novel Multicompartment 3-Dimensional Radiochromic Radiation Dosimeters for Nanoparticle-Enhanced Radiation Therapy Dosimetry

    SciTech Connect

    Alqathami, Mamdooh; Blencowe, Anton; Yeo, Un Jin; Doran, Simon J.; Qiao, Greg; Geso, Moshi

    2012-11-15

    Purpose: Gold nanoparticles (AuNps), because of their high atomic number (Z), have been demonstrated to absorb low-energy X-rays preferentially, compared with tissue, and may be used to achieve localized radiation dose enhancement in tumors. The purpose of this study is to introduce the first example of a novel multicompartment radiochromic radiation dosimeter and to demonstrate its applicability for 3-dimensional (3D) dosimetry of nanoparticle-enhanced radiation therapy. Methods and Materials: A novel multicompartment phantom radiochromic dosimeter was developed. It was designed and formulated to mimic a tumor loaded with AuNps (50 nm in diameter) at a concentration of 0.5 mM, surrounded by normal tissues. The novel dosimeter is referred to as the Sensitivity Modulated Advanced Radiation Therapy (SMART) dosimeter. The dosimeters were irradiated with 100-kV and 6-MV X-ray energies. Dose enhancement produced from the interaction of X-rays with AuNps was calculated using spectrophotometric and cone-beam optical computed tomography scanning by quantitatively comparing the change in optical density and 3D datasets of the dosimetric measurements between the tissue-equivalent (TE) and TE/AuNps compartments. The interbatch and intrabatch variability and the postresponse stability of the dosimeters with AuNps were also assessed. Results: Radiation dose enhancement factors of 1.77 and 1.11 were obtained using 100-kV and 6-MV X-ray energies, respectively. The results of this study are in good agreement with previous observations; however, for the first time we provide direct experimental confirmation and 3D visualization of the radiosensitization effect of AuNps. The dosimeters with AuNps showed small (<3.5%) interbatch variability and negligible (<0.5%) intrabatch variability. Conclusions: The SMART dosimeter yields experimental insights concerning the spatial distributions and elevated dose in nanoparticle-enhanced radiation therapy, which cannot be performed using any of

  3. On the response of electronic personal dosimeters in constant potential and pulsed x- ray beams

    NASA Astrophysics Data System (ADS)

    Guimarães, M. C.; Silva, C. R. E.; Oliveira, P. M. C.; da Silva, T. A.

    2016-07-01

    Electronic personal dosimeters (EPDs) based on solid state detectors have widely been used but some deficiencies in their response in pulsed radiation beams have been reported. Nowadays, there is not an international standard for pulsed x-ray beams for calibration or type testing of dosimeters. Irradiation conditions for testing the response of EPDs in both the constant potential and pulsed x-ray beams were established in CDTN. Three different types of EPDs were tested in different conditions in similar ISO and IEC x-ray qualities. Results stressed the need of performing additional checks before using EPDs in constant potential or pulsed x-rays.

  4. A Bremsstrahlung spectrometer using k-edge and differential filters with image plate dosimeters

    SciTech Connect

    Chen, C. D.; Porkolab, M.; King, J. A.; Beg, F. N.; Key, M. H.; Chen, H.; Mackinnon, A. J.; MacPhee, A. G.; Patel, P. K.; Akli, K. U.; Stephens, R. B.; Freeman, R. R.; Link, A.; Van Woerkom, L. D.

    2008-10-15

    A Bremsstrahlung spectrometer using k-edge and differential filtering has been used with image plate dosimeters to measure the x-ray fluence from short-pulse laser/target interactions. An electron spectrometer in front of the Bremsstrahlung spectrometer deflects electrons from the x-ray line of sight and simultaneously measures the electron spectrum. The response functions were modeled with the Monte Carlo code INTEGRATED TIGER SERIES 3.0 and the dosimeters calibrated with radioactive sources. An electron distribution with a slope temperature of 1.3 MeV is inferred from the Bremsstrahlung spectra.

  5. A Bremsstrahlung Spectrometer using k-edge and Differential Filters with Image plate dosimeters

    SciTech Connect

    Chen, C; Mackinnon, A; Beg, F; Chen, H; Key, M; King, J A; Link, A; MacPhee, A; Patel, P; Porkolab, M; Stephens, R; VanWoerkom, L; Akli, K; Freeman, R

    2008-05-02

    A Bremsstrahlung spectrometer using k-edge and differential filtering has been used with Image Plate dosimeters to measure the x-ray fluence from short-pulse laser/target interactions. An electron spectrometer in front of the Bremsstrahlung spectrometer deflects electrons from the x-ray line of sight and simultaneously measures the electron spectrum. The response functions were modeled with the Monte Carlo code Integrated Tiger Series 3.0 and the dosimeters calibrated with radioactive sources. Electron distributions with slope temperatures in the MeV range are inferred from the Bremsstrahlung spectra.

  6. Study of the absorption spectra of Fricke Xylenol Orange gel dosimeters

    SciTech Connect

    Gambarini, Grazia; Artuso, Emanuele; Liosi, Giulia Maria; Giacobbo, Francesca; Mariani, Mari; Brambilla, Luigi; Castiglioni, Chiara; Carrara, Mauro; Pignoli, Emanuele

    2015-07-01

    A systematic study of the absorption spectra of Fricke Xylenol Orange gel dosimeters has been performed, in the wavelength range from 300 nm to 700 nm. The spectrum of Xylenol Orange (without ferrous sulphate solution) has been achieved, in order to subtract its contribution from the absorption spectra of the irradiated Fricke Xylenol Orange gel dosimeters. The absorbance due to ferric ions chelated by Xylenol Orange has been studied for various irradiation doses. Two absorbance peaks are visible, mainly at low doses: the first peak increases with the dose more slowly than the second one. This effect can explain the apparent threshold dose that was frequently evidenced. (authors)

  7. Initial characterization of a gel patch dosimeter for in vivo dosimetry

    NASA Astrophysics Data System (ADS)

    Matrosic, C.; Culberson, W.; Rosen, B.; Madsen, E.; Frank, G.; Bednarz, B.

    2016-05-01

    In vivo dosimetry is a greatly underutilized tool for patient safety in clinical external beam radiotherapy treatments, despite being recommended by several national and international organizations (AAPM, ICRU, IAEA, NACP). The reasons for this underutilization mostly relate to the feasibility and cost of in vivo dosimetry methods. Due to the increase in the number of beam angles and dose per fraction in modern treatments, there is a compelling need for a novel dosimeter that is robust and affordable while able to operate properly in these complex conditions. This work presents a gel patch dosimeter as a novel method of in vivo dosimetry. DEFGEL, a 6% T normoxic polyacrylamide gel, was injected into 1 cm thick acrylic molds to create 1 cm thick small cylindrical patch dosimeters. To evaluate the change in optical density due to radiation induced polymerization, dosimeters were scanned before and after irradiation using an in-house developed laser densitometer. The dose-responses of three separate batches of gel were evaluated and compared to check for linearity and repeatability. The response development time was evaluated to ensure that the patch dosimeter could be high throughput. Additionally, the potential of this system to be used as an in vivo dosimeter was tested with a clinically relevant end-to-end in vivo phantom test. All irradiations were performed with a Varian Clinac 21EX at the University of Wisconsin Medical Radiation Research Center (UWMRRC). The dose-response of all three batches of gel was found to be linear within the range of 2-20 Gy. At doses below 0.5 Gy the statistical uncertainties were prohibitively large to make quantitative assessments of the results. The three batches demonstrated good repeatability in the range of 2 Gy to up to 10 Gy, with only slight variations in response at higher doses. For low doses the dosimeter fully developed within an hour while at higher doses they fully developed within four hours. During the in vivo

  8. Enhancement in dose sensitivity of polymer gel dosimeters composed of radiation-crosslinked gel matrix and less toxic monomers

    NASA Astrophysics Data System (ADS)

    Hiroki, A.; Yamashita, S.; Taguchi, M.

    2015-01-01

    Polymer gel dosimeters based on radiation-crosslinked hydroxypropyl cellulose gel were prepared, which comprised 2-hydroxyethyl methacrylate (HEMA) and polyethylene glycol #400 dimethacrylate (9G) as less toxic monomers and tetrakis (hydroxymethyl) phosphonium chloride (THPC) as an antioxidant. The dosimeters exposed to 60Co γ-rays became cloudy at only 1 Gy. The irradiated dosimeters were optically analyzed by using a UV- vis spectrophotometer to evaluate dose response. Absorbance of the dosimeters linearly increased in the dose range from 0 to 10 Gy, in which dose sensitivity increased with increasing 9G concentration. The dose sensitivity of the dosimeters with 2 wt% HEMA and 3 wt% 9G was also enhanced by increment in THPC.

  9. A gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters

    NASA Astrophysics Data System (ADS)

    Babic, S.; Park, Y. S.; Schreiner, L. J.

    2004-01-01

    In this presentation we show results of investigations on gelatin-free dosimeters containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide (named Aqueous Polyacrylamide, APA, dosimeters). The dosimeters were prepared with three different total monomer concentrations (2, 6, and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all three dosimeters, show a continuous degree of polymerization over the range of dose 0.5 - 25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of cross-linked polymer formed at each dose. This model may be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

  10. Albedo parametrization and reversibility of sea ice decay

    NASA Astrophysics Data System (ADS)

    Müller-Stoffels, M.; Wackerbauer, R.

    2012-02-01

    The Arctic's sea ice cover has been receding rapidly in recent years, and global climate models typically predict a further decline over the next century. It is an open question whether a possible loss of Arctic sea ice is reversible. We study the stability of Arctic model sea ice in a conceptual, two-dimensional energy-based regular network model of the ice-ocean layer that considers ARM's longwave radiative budget data and SHEBA albedo measurements. Seasonal ice cover, perennial ice and perennial open water are asymptotic states accessible by the model. We show that the shape of albedo parameterization near the melting temperature differentiates between reversible continuous sea ice decrease under atmospheric forcing and hysteresis behavior. Fixed points induced solely by the surface energy budget are essential for understanding the interaction of surface energy with the radiative forcing and the underlying body of ice/water, particularly close to a bifurcation point. Future studies will explore ice edge stability and reversibility in this lattice model, generalized to a latitudinal transect with spatiotemporal lateral atmospheric heat transfer and high spatial resolution.

  11. Soot climate forcing via snow and ice albedos

    PubMed Central

    Hansen, James; Nazarenko, Larissa

    2004-01-01

    Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of +0.3 W/m2 in the Northern Hemisphere. The “efficacy” of this forcing is ∼2, i.e., for a given forcing it is twice as effective as CO2 in altering global surface air temperature. This indirect soot forcing may have contributed to global warming of the past century, including the trend toward early springs in the Northern Hemisphere, thinning Arctic sea ice, and melting land ice and permafrost. If, as we suggest, melting ice and sea level rise define the level of dangerous anthropogenic interference with the climate system, then reducing soot emissions, thus restoring snow albedos to pristine high values, would have the double benefit of reducing global warming and raising the global temperature level at which dangerous anthropogenic interference occurs. However, soot contributions to climate change do not alter the conclusion that anthropogenic greenhouse gases have been the main cause of recent global warming and will be the predominant climate forcing in the future. PMID:14699053

  12. Tackling regional climate change by leaf albedo bio-geoengineering.

    PubMed

    Ridgwell, Andy; Singarayer, Joy S; Hetherington, Alistair M; Valdes, Paul J

    2009-01-27

    The likelihood that continuing greenhouse-gas emissions will lead to an unmanageable degree of climate change has stimulated the search for planetary-scale technological solutions for reducing global warming ("geoengineering"), typically characterized by the necessity for costly new infrastructures and industries. We suggest that the existing global infrastructure associated with arable agriculture can help, given that crop plants exert an important influence over the climatic energy budget because of differences in their albedo (solar reflectivity) compared to soils and to natural vegetation. Specifically, we propose a "bio-geoengineering" approach to mitigate surface warming, in which crop varieties having specific leaf glossiness and/or canopy morphological traits are specifically chosen to maximize solar reflectivity. We quantify this by modifying the canopy albedo of vegetation in prescribed cropland areas in a global-climate model, and thereby estimate the near-term potential for bio-geoengineering to be a summertime cooling of more than 1 degrees C throughout much of central North America and midlatitude Eurasia, equivalent to seasonally offsetting approximately one-fifth of regional warming due to doubling of atmospheric CO(2). Ultimately, genetic modification of plant leaf waxes or canopy structure could achieve greater temperature reductions, although better characterization of existing intraspecies variability is needed first.

  13. Lunar Proton Albedo Anomalies: Soil, Surveyors, and Statistics

    NASA Astrophysics Data System (ADS)

    Wilson, J. K.; Schwadron, N.; Spence, H. E.; Case, A. W.; Golightly, M. J.; Jordan, A.; Looper, M. D.; Petro, N. E.; Robinson, M. S.; Stubbs, T. J.; Zeitlin, C. J.; Blake, J. B.; Kasper, J. C.; Mazur, J. E.; Smith, S. S.; Townsend, L. W.

    2014-12-01

    Since the launch of LRO in 2009, the CRaTER instrument has been mapping albedo protons (~100 MeV) from the Moon. These protons are produced by nuclear spallation, a consequence of galactic cosmic ray (GCR) bombardment of the lunar regolith. Just as spalled neutrons and gamma rays reveal elemental abundances in the lunar regolith, albedo protons may be a complimentary method for mapping compositional variations. We presently find that the lunar maria have an average proton yield 0.9% ±0.3% higher than the average yield in the highlands; this is consistent with neutron data that is sensitive to the regolith's average atomic weight. We also see cases where two or more adjacent pixels (15° × 15°) have significantly anomalous yields above or below the mean. These include two high-yielding regions in the maria, and three low-yielding regions in the far-side highlands. Some of the regions could be artifacts of Poisson noise, but for completeness we consider possible effects from compositional anomalies in the lunar regolith, including pyroclastic flows, antipodes of fresh craters, and so-called "red spots". We also consider man-made landers and crash sites that may have brought elements not normally found in the lunar regolith.

  14. Mars - Experimental study of albedo changes caused by dust fallout

    NASA Technical Reports Server (NTRS)

    Wells, E. N.; Veverka, J.; Thomas, P.

    1984-01-01

    A laboratory apparatus was used to simulate the uniform fallout and deposition of particles 1 to 5 microns in diameter in an experimental study on how the spectral and photometric properties of representative Martian areas are affected by fallout of atmospheric dust (smaller than or equalling 60 microns) suspended during dust storms. In this study, measurements are made in the changes in reflectance at optical and near-infrared wavelengths (0.4 to 1.2 micron) caused by deposition of varying amounts of a Mars-analog dust on bright and dark substrates before and after deposition of 6 x 10 to the -5th to 1.5 x 10 to the -3rd g/sq cm of simulated fallout. It is believed that only small amounts of dust particles (approximately 3 x 10 to the -4th g/sq cm) are needed to make significant albedo changes in dark areas of Mars, and that this would rule out uniform dust deposition on the surface of the planet. Data also indicate that other high albedo features like bright crater-related wind streaks may not be areas of significant sediment deposits. Laboratory simulations have permitted estimates of how much the reflectance of an area on Mars would change given a certain amount of dust fallout (g/sq cm) or reflectance data. These simulations may also be useful in tracking the transport and deposition of the dust.

  15. A cavity radiometer for Earth albedo measurement, phase 1

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Radiometric measurements of the directional albedo of the Earth requires a detector with a flat response from 0.2 to 50 microns, a response time of about 2 seconds, a sensitivity of the order of 0.02 mw/sq cm, and a measurement uncertainty of less than 5 percent. Absolute cavity radiometers easily meet the spectral response and accuracy requirements for Earth albedo measurements, but the radiometers available today lack the necessary sensitivity and response time. The specific innovations addressed were the development of a very low thermal mass cavity and printed/deposited thermocouple sensing elements which were incorporated into the radiometer design to produce a sensitive, fast response, absolute radiometer. The cavity is applicable to the measurement of the reflected and radiated fluxes from the Earth surface and lower atmosphere from low Earth orbit satellites. The effort consisted of requirements and thermal analysis; design, construction, and test of prototype elements of the black cavity and sensor elements to show proof-of-concept. The results obtained indicate that a black body cavity sensor that has inherently a flat response from 0.2 to 50 microns can be produced which has a sensitivity of at least 0.02 mw/sq cm per micro volt ouput and with a time constant of less than two seconds. Additional work is required to develop the required thermopile.

  16. Impacts of Satellite-Based Snow Albedo Assimilation on Offline and Coupled Land Surface Model Simulations

    PubMed Central

    Wang, Tao; Peng, Shushi; Krinner, Gerhard; Ryder, James; Li, Yue; Dantec-Nédélec, Sarah; Ottlé, Catherine

    2015-01-01

    Seasonal snow cover in the Northern Hemisphere is the largest component of the terrestrial cryosphere and plays a major role in the climate system through strong positive feedbacks related to albedo. The snow-albedo feedback is invoked as an important cause for the polar amplification of ongoing and projected climate change, and its parameterization across models is an important source of uncertainty in climate simulations. Here, instead of developing a physical snow albedo scheme, we use a direct insertion approach to assimilate satellite-based surface albedo during the snow season (hereafter as snow albedo assimilation) into the land surface model ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms) and assess the influences of such assimilation on offline and coupled simulations. Our results have shown that snow albedo assimilation in both ORCHIDEE and ORCHIDEE-LMDZ (a general circulation model of Laboratoire de Météorologie Dynamique) improve the simulation accuracy of mean seasonal (October throughout May) snow water equivalent over the region north of 40 degrees. The sensitivity of snow water equivalent to snow albedo assimilation is more pronounced in the coupled simulation than the offline simulation since the feedback of albedo on air temperature is allowed in ORCHIDEE-LMDZ. We have also shown that simulations of air temperature at 2 meters in ORCHIDEE-LMDZ due to snow albedo assimilation are significantly improved during the spring in particular over the eastern Siberia region. This is a result of the fact that high amounts of shortwave radiation during the spring can maximize its snow albedo feedback, which is also supported by the finding that the spatial sensitivity of temperature change to albedo change is much larger during the spring than during the autumn and winter. In addition, the radiative forcing at the top of the atmosphere induced by snow albedo assimilation during the spring is estimated to be -2.50 W m-2, the magnitude of

  17. Spring-summer albedo variations of Antarctic sea ice from 1982 to 2009

    NASA Astrophysics Data System (ADS)

    Shao, Zhu-De; Ke, Chang-Qing

    2015-06-01

    This study examined the spring-summer (November, December, January and February) albedo averages and trends using a dataset consisting of 28 years of homogenized satellite data for the entire Antarctic sea ice region and for five longitudinal sectors around Antarctica: the Weddell Sea (WS), the Indian Ocean sector (IO), the Pacific Ocean sector (PO), the Ross Sea (RS) and the Bellingshausen-Amundsen Sea (BS). Time series data of the sea ice concentrations and sea surface temperatures were used to analyse their relations to the albedo. The results indicated that the sea ice albedo increased slightly during the study period, at a rate of 0.314% per decade, over the Antarctic sea ice region. The sea ice albedos in the PO, the IO and the WS increased at rates of 2.599% per decade (confidence level 99.86%), 0.824% per decade and 0.413% per decade, respectively, and the steepest increase occurred in the PO. However, the sea ice albedo in the BS decreased at a rate of -1.617% per decade (confidence level 95.05%) and was near zero in the RS. The spring-summer average albedo over the Antarctic sea ice region was 50.24%. The highest albedo values were mainly found on the continental coast and in the WS; in contrast, the lowest albedo values were found on the outer edge of the sea ice, the RS and the Amery Ice Shelf. The average albedo in the western Antarctic sea ice region was distinctly higher than that in the east. The albedo was significantly positively correlated with sea ice concentration (SIC) and was significantly negatively correlated with sea surface temperature (SST); these scenarios held true for all five longitudinal sectors. Spatially, the higher surface albedos follow the higher SICs and lower SST patterns. The increasing albedo means that Antarctic sea ice region reflects more solar radiation and absorbs less, leading to a decrease in temperature and much snowfall on sea ice, and further resulted in an increase in albedo. Conversely, the decreasing albedo

  18. Impacts of Satellite-Based Snow Albedo Assimilation on Offline and Coupled Land Surface Model Simulations.

    PubMed

    Wang, Tao; Peng, Shushi; Krinner, Gerhard; Ryder, James; Li, Yue; Dantec-Nédélec, Sarah; Ottlé, Catherine

    2015-01-01

    Seasonal snow cover in the Northern Hemisphere is the largest component of the terrestrial cryosphere and plays a major role in the climate system through strong positive feedbacks related to albedo. The snow-albedo feedback is invoked as an important cause for the polar amplification of ongoing and projected climate change, and its parameterization across models is an important source of uncertainty in climate simulations. Here, instead of developing a physical snow albedo scheme, we use a direct insertion approach to assimilate satellite-based surface albedo during the snow season (hereafter as snow albedo assimilation) into the land surface model ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms) and assess the influences of such assimilation on offline and coupled simulations. Our results have shown that snow albedo assimilation in both ORCHIDEE and ORCHIDEE-LMDZ (a general circulation model of Laboratoire de Météorologie Dynamique) improve the simulation accuracy of mean seasonal (October throughout May) snow water equivalent over the region north of 40 degrees. The sensitivity of snow water equivalent to snow albedo assimilation is more pronounced in the coupled simulation than the offline simulation since the feedback of albedo on air temperature is allowed in ORCHIDEE-LMDZ. We have also shown that simulations of air temperature at 2 meters in ORCHIDEE-LMDZ due to snow albedo assimilation are significantly improved during the spring in particular over the eastern Siberia region. This is a result of the fact that high amounts of shortwave radiation during the spring can maximize its snow albedo feedback, which is also supported by the finding that the spatial sensitivity of temperature change to albedo change is much larger during the spring than during the autumn and winter. In addition, the radiative forcing at the top of the atmosphere induced by snow albedo assimilation during the spring is estimated to be -2.50 W m-2, the magnitude of

  19. Implications of albedo changes following afforestation on the benefits of forests as carbon sinks

    NASA Astrophysics Data System (ADS)

    Kirschbaum, M. U. F.; Whitehead, D.; Dean, S. M.; Beets, P. N.; Shepherd, J. D.; Ausseil, A.-G. E.

    2011-12-01

    Increased carbon storage with afforestation leads to a decrease in atmospheric carbon dioxide concentration and thus decreases radiative forcing and cools the Earth. However, afforestation also changes the reflective properties of the surface vegetation from more reflective pasture to relatively less reflective forest cover. This increase in radiation absorption by the forest constitutes an increase in radiative forcing, with a warming effect. The net effect of decreased albedo and carbon storage on radiative forcing depends on the relative magnitude of these two opposing processes. We used data from an intensively studied site in New Zealand's Central North Island that has long-term, ground-based measurements of albedo over the full short-wave spectrum from a developing Pinus radiata forest. Data from this site were supplemented with satellite-derived albedo estimates from New Zealand pastures. The albedo of a well-established forest was measured as 13 % and pasture albedo as 20 %. We used these data to calculate the direct radiative forcing effect of changing albedo as the forest grew. We calculated the radiative forcing resulting from the removal of carbon from the atmosphere as a decrease in radiative forcing of -104 GJ tC-1 yr-1. We also showed that the observed change in albedo constituted a direct radiative forcing of 2759 GJ ha-1 yr-1. Thus, following afforestation, 26.5 tC ha-1 needs to be stored in a growing forest to balance the increase in radiative forcing resulting from the observed albedo change. Measurements of tree biomass and albedo were used to estimate the net change in radiative forcing as the newly planted forest grew. Albedo and carbon-storage effects were of similar magnitude for the first four to five years after tree planting, but as the stand grew older, the carbon storage effect increasingly dominated. Averaged over the whole length of the rotation, the changes in albedo negated the benefits from increased carbon storage by 17-24 %.

  20. Effects of aerosol and horizontal inhomogeneity on the broadband albedo of marine stratus: Numerical simulations

    SciTech Connect

    Duda, D.P.; Stephens, G.L.; Stevens, B.; Cotton, W.R.

    1996-12-15

    Recent estimates of the effect of increasing of anthropogenic sulfate aerosol on the radiative forcing of the atmosphere have indicated that its impact may be comparable in magnitude to the effect from increases in CO{sub 2}. Much of this impact is expected from the effects of the aerosol on cloud microphysics and the subsequent impact on cloud albedo. A solar broadband version of a 2D radiative transfer model was used to quantify the impact of enhanced aerosol concentrations and horizontal inhomogeneity on the solar broadband albedo of marine stratus. The results of the radiative transfer calculations indicated that in unbroken marine stratus clouds the net horizontal transport of photons over a domain of a few kilometers was nearly zero, and the domain-average broadband albedo computed in a 2D cross section was nearly identical to the domain average calculated from a series of independent pixel approximation (IPA) calculations of the same cross section. However, the horizontal inhomogeneity does affect the cloud albedo compared to plane-parallel approximation (PPA) computations due to the nonlinear relationship between albedo and optical depth. The reduction in cloud albedo could be related to the variability of the distribution of log (cloud optical depth). These results extend the finding of Cahalan et al. to broadband solar albedos in a more realistic cloud model and suggest that accurate computation of domain-averaged broadband albedos in unbroken (or nearly unbroken) marine stratus can be made using IPA calculations with 1D radiative transfer models. Computations of the mean albedo over portions of the 3D RAMS domain show the relative increase in cloud albedo due to a 67% increase in the boundary-layer average CCN concentration was between 6% and 9%. The effects of cloud inhomogeneity on the broadband albedo as measured from the PPA bias ranged from 3% to 5%. 25 refs., 8 figs., 4 tabs.

  1. Quantifying the missing link between forest albedo and productivity in the boreal zone

    NASA Astrophysics Data System (ADS)

    Hovi, Aarne; Liang, Jingjing; Korhonen, Lauri; Kobayashi, Hideki; Rautiainen, Miina

    2016-11-01

    Albedo and fraction of absorbed photosynthetically active radiation (FAPAR) determine the shortwave radiation balance and productivity of forests. Currently, the physical link between forest albedo and productivity is poorly understood, yet it is crucial for designing optimal forest management strategies for mitigating climate change. We investigated the relationships between boreal forest structure, albedo and FAPAR using a radiative transfer model called Forest Reflectance and Transmittance model FRT and extensive forest inventory data sets ranging from southern boreal forests to the northern tree line in Finland and Alaska (N = 1086 plots). The forests in the study areas vary widely in structure, species composition, and human interference, from intensively managed in Finland to natural growth in Alaska. We show that FAPAR of tree canopies (FAPARCAN) and albedo are tightly linked in boreal coniferous forests, but the relationship is weaker if the forest has broadleaved admixture, or if canopies have low leaf area and the composition of forest floor varies. Furthermore, the functional shape of the relationship between albedo and FAPARCAN depends on the angular distribution of incoming solar irradiance. We also show that forest floor can contribute to over 50 % of albedo or total ecosystem FAPAR. Based on our simulations, forest albedos can vary notably across the biome. Because of larger proportions of broadleaved trees, the studied plots in Alaska had higher albedo (0.141-0.184) than those in Finland (0.136-0.171) even though the albedo of pure coniferous forests was lower in Alaska. Our results reveal that variation in solar angle will need to be accounted for when evaluating climate effects of forest management in different latitudes. Furthermore, increasing the proportion of broadleaved trees in coniferous forests is the most important means of maximizing albedo without compromising productivity: based on our findings the potential of controlling forest

  2. Monte Carlo simulations of spectral albedo for artificial snowpacks composed of spherical and nonspherical particles.

    PubMed

    Tanikawa, Tomonori; Aoki, Teruo; Hori, Masahiro; Hachikubo, Akihiro; Abe, Osamu; Aniya, Masamu

    2006-07-20

    The optical properties of snowpacks composed of spherical and nonspherical particles artificially prepared in a cold laboratory are investigated by measuring spectral albedos. The measured spectral albedo in the spectral region lambda=0.35-2.5 microm is compared with the theoretically calculated albedo, for which a Monte Carlo radiative transfer model is employed for multiple scattering combined with the Mie theory and the ray-tracing technique for single scattering by snow particles. Since the spherical particles are a little aggregate, the effects of a cluster of the spheres on snow albedo are examined using a generalized multiparticle Mie-solution model [Appl. Opt. 34, 4573 (1995); J. Quant. Spectrosc. Radiat. Transf. 79-80, 1121 (2003)]. The snow albedo of a cluster of the spheres can be represented with that of the singe sphere slightly larger than its component of the cluster in case of small grains. The observed albedos for the spherical snow particles agree with the theoretically calculated ones for the snow grain size measured in the snow pit work. The snow albedos for the nonspherical particles, which were dendrites, are influenced by the branch width and the branch length, based on a comparison of the theoretically calculated albedo by using circular cylindrical snow particles and the observed albedo. The snow albedo in the near-infrared region depends on the branch width only when the branch length is sufficiently greater than the branch width. The comparison between the spherical and nonspherical snow particles indicates that the spectral albedo of the nonspherical particles can be represented by using an equal volume-area ratio sphere.

  3. Mineralogical Variations Among High Albedo E-Type Asteroids: Implications for Asteroid Igneous Processes

    NASA Technical Reports Server (NTRS)

    Gaffey, Michael J.; Kelley, Michael S.

    2004-01-01

    The link between the E-type asteroids and the enstatite achondrites (aubrites) was first proposed for the original E-asteroid, 44 Nysa. The association was based on the high albedos and the featureless spectra shared by the E-asteroids and the aubrites. Among the plausible geologic and meteoritic materials, only enstatite (the magnesium end-member of the pyroxene solid solution series) is sufficiently abundant to comprise asteroid-sized bodies. However, the presence of a weak 0.89 m absorption feature in the spectrum of 44 Nysa indicates that its pyroxene contains a small amount of Fe(2+) but still substantially more than any aubrite present in the meteorite collection. The original E-class was defined based on its high albedo and flat to slightly reddish spectrum. In the absence of albedo data, the E-type was degenerate with the M- and P-types, and together these were designated as X-types. Recently, a taxonomy has been proposed to identify E-types in the absence of albedo data. In this newer classification system three subdivisions of the X-type have been proposed, including Xc, Xe and Xk. Of nine albedo-defined E-types [d], this newer non-albedo based taxonomy produced the following classifications: X-1 asteroid; Xc-2 asteroids; Xe-5 asteroids; and Xk-1 asteroid. Although the Xe subtype includes the largest number of albedo-defined E-types, most of the remaining 24 Xe-types can be excluded based on their low measured IRAS albedos, ranging from 0.116 to 0.329, which are below the lower albedo limit of the E-class (0.34) and substantially below that of the lowest albedo an actual E-type asteroid (0.41). The present discussion will be limited to unambiguous E-type asteroids determined on albedo criteria.

  4. Impurities in Snow: Effects on Spectral Albedo of Prairie Snowpacks

    NASA Astrophysics Data System (ADS)

    Morris, J. N.; Klein, A. G.

    2007-12-01

    While extensive research on soot in snow has been done in the Polar Regions, there remains a lack of observations addressing the effect of soot on snow albedo in North American prairie snowpacks which causes uncertainty to the overall global effect that soot in snow has on climate. Measurements of snow impurities in freshly fallen prairie snowpacks in northwestern Iowa and central Texas collected from February 28 - March 5, 2007 and April 6, 2007, respectively. Two significant snowfall events occurred in northwestern Iowa during the study; the second snowfall event produced the most severe blizzard conditions in northwestern Iowa in the last thirty years. An unusual snowfall event in central Texas offered a unique sampling opportunity Several types of sites were sampled during the field campaign; this includes: frozen lakes with minimal human impact, agricultural fields impacted by agricultural dust, and human impacted sample sites. At twelve sites in northwestern Iowa samples were collected on multiple days and for both snow events to examine changes in snow impurities over time. At all site locations snow samples, temperature, density, and grain size were recorded. Snow reflectance and snow radiance was collected at a subset of the sites with an ASD VNIR Spectroradiometer (350 - 1500 nm). Snow impurities of light-absorbing particulate matter were measured by filtering the meltwater through a nuclepore 0.4 micrometer filter. Impurity concentration was determined by comparing the filters against a set of standards. A photometer will provide a more exact determination of snow impurities in the near future. Preliminary soot observations indicate prairie snow pack concentrations ranging from 1 ngC/g to 236 ngC/g with an average of 61.4 ngC/g. These measurements are within range of previously published values in the Arctic and can lower snow albedo. Differences in soot concentrations were observed between the two Iowa snowfall events. Impurity concentrations measured

  5. Characteristics of polyacrylamide gel with THPC and Turnbull Blue gel dosimeters evaluated using optical tomography

    NASA Astrophysics Data System (ADS)

    Pilařová (Vávrů), Kateřina; Kozubíková, Petra; Šolc, Jaroslav; Spěváček, Václav

    2014-11-01

    The purpose of this study was to compare characteristics of radiochromic gel - Turnbull Blue gel (TB gel) with polymer gel - polyacrylamide gel and tetrakis hydroxymethyl phosphonium chloride (PAGAT) using optical tomography. Both types of gels were examined in terms of dose sensitivity, dose response linearity and background value of spectrophotometric absorbance. The calibration curve was obtained for 60Co irradiation performed on Gammacell 220 at predefined gamma dose levels between 0 and 140 Gy for TBG and 0-15 Gy for PAGAT. To measure relative dose distributions from stereotactic irradiation, dosimeters were irradiated on Leksell Gamma Knife Perfexion. The cylindrical glass housings filled with gel were attached to the stereotactic frame. They were exposed with single shot and 16 mm collimator by 65 Gy to a 50% prescription isodose for TB gel and 4 Gy to a 50% prescription isodose for PAGAT. Evaluations of dosimeters were performed on an UV-vis Spectrophotometer Helios β and an optical cone beam homemade tomography scanner with a 16-bit astronomy CCD camera with a set of color filters. The advantages and potential disadvantages for both types of gel dosimeters were summarized. Dose distribution in central slice and measured profiles of 16 mm shot shows excellent correspondence with treatment planning system Leksell GammaPlan® for both PAGAT and Turnbull Blue gels. Gel dosimeters are suitable for steep dose gradient verification. An optical tomography evaluation method is successful. Dose response characteristics of TB gel and PAGAT gel are presented.

  6. Area Monitoring Dosimeter Program for the Pacific Northwest National Laboratory: Results for CY 1999

    SciTech Connect

    Bivins, Steven R.; Stoetzel, Gregory A.

    2000-09-19

    In January 1993, PNNL established an area monitoring dosimeter program in accordance with Article 514 of the DOE Radiological Control Manual. This program was to minimize the number of areas requiring issuance of personnel dosimeters and to demonstrate that doses outside Radiological Buffer Areas are negligible. In accordance with 10 CFR Part 835.402 (a)(1)-(4) and Article 511.1 of the DOE Standard Radiological Control, personnel dosimetry shall be provided to 1) radiological workers who are likely to receive at least 100 mrem annually and 2) declared pregnant workers, minors, and members of the public who are likely to receive at least 50 mrem annually. Program results for calendar years 1993-1998 confirmed that personnel dosimetry was not needed for individuals located in areas monitored by the program. A total of 123 area thermoluminescent dosimeters (TLDs) were placed in PNNL facilities during calendar year 1999. The TLDs were exchanged and analyzed quarterly. All routine area monitoring TLD results were less than 50 mrem annually after correcting for worker occupancy. The results support the conclusion that personnel dosimeters are not necessary for staff, declared pregnant workers, minors, or members of the public in these monitored areas.

  7. Considerations in the application of the electronic dosimeter to dose of record

    SciTech Connect

    Swinth, K.L.

    1997-12-01

    This report describes considerations for application of the electronic dosimeter (ED) as a measurement device for the dose of record (primary dosimetry). EDs are widely used for secondary dosimetry and advances in their reliability and capabilities have resulted in interest in their use to meet the needs of both primary and secondary dosimetry. However, the ED is an active device and more complex than the thermoluminescent and film dosimeters now in use for primary dosimetry. The user must evaluate the ED in terms of reliability, serviceability and radiations detected its intended application(s). If an ED is selected for primary dosimetry, the user must establish methods both for controlling the performance of the ED to ensure long term reliability of the measurements and for their proper use as a primary dosimeter. Regulatory groups may also want to develop methods to ensure adequate performance of the ED for dose of record. The purpose of the report is to provide an overview of considerations in the use of the ED for primary dosimetry. Considerations include recognizing current limitations, type testing of EDs, testing by the user, approval performance testing, calibration, and procedures to integrate the dosimeter into the users program.

  8. The dose response of normoxic polymer gel dosimeters measured using X-ray CT.

    PubMed

    Hill, B; Venning, A; Baldock, C

    2005-07-01

    X-ray CT was used to determine the dose response of normoxic polymer gel dosimeters. Normoxic polymer gel dosimeters were manufactured and irradiated up to 150 Gy. Up to 50 CT images were acquired on a Toshiba Aquilion Multislice CT scanner using protocols for 80 kV and 135 kV to determine dose response. HU-dose sensitivity, the linear regression of data for the HU versus dose for the linear part of the curve up to 60 Gy was 0.38+/-0.07 HU Gy(-1) for 135 kV and 0.37+/-0.01 HU Gy(-1) for 80 kV. Dose resolution was found to be < 1.3 Gy for an absorbed dose range up to 70 Gy for 135 kV, similar to that measured previously for polyacrylamide gel (PAG). Although the HU-dose sensitivity was lower than that previously measured for PAG gel dosimeters it had a greater range of absorbed dose indicating that normoxic polymer gel dosimeters have potential in CT gel dosimetry.

  9. Angular response characterization of the Martin Marietta Energy Systems, Inc., personnel dosimeter

    SciTech Connect

    Ahmed, A.B.; McMahan, K.L.; Colwell, D.S.

    1993-08-01

    An evaluation of the Martin Marietta Energy Systems, Inc., personnel dosimeter to radiation incident from non-perpendicular angles was carried out to meet the Department of Energy Laboratory Accreditation Program (DOELAP) requirements. Dosimeters were exposed to six different radiation sources. For each source, dosimeters were rotated about their horizontal and vertical axes at seven different angles each. Raw readings were processed through the dose calculation algorithm used for routine personnel dosimetry to determine dose equivalent values. Dose equivalent responses relative to zero degree incident angle were found to be within {plus_minus} 20% for M150, K-59 and {sup 137}Cs photons when the incident angle was 60{degree} or less. For low-energy photon irradiations (M30 and K-16), responses for angles other than perpendicular incidence are generally unpredictable. Reasons include: (1) failure of dose calculation algorithm to identify the radiation field correctly due to unusual element ratios; and (2) at extreme angles ({plus_minus} 85{degree}), the dosimeter design (in relation to the irradiation geometry) becomes the limiting factor in producing reproducible results. Response to {sup 204}Tl beta particles decreases rapidly with increasing angle of incidence.

  10. Method and apparatus for passive optical dosimeter comprising caged dye molecules

    DOEpatents

    Sandison, David R.

    2001-07-03

    A new class of ultraviolet dosimeters is made possible by exposing caged dye molecules, which generate a dye molecule on exposure to ultraviolet radiation, to an exterior environment. Applications include sunburn monitors, characterizing the UV exposure history of UV-sensitive materials, especially including structural plastics, and use in disposable `one-use` optical equipment, especially medical devices.

  11. Verification of 3D Dose Distributions of a Beta-Emitting Radionuclide Using PRESAGE^ Dosimeters

    NASA Astrophysics Data System (ADS)

    Crowder, Mandi; Grant, Ryan; Ibbott, Geoff; Wendt, Richard

    2010-11-01

    Liquid Brachytherapy involves the direct administration of a beta-emitting radioactive solution into the selected tissue. The solution does not migrate from the injection point and uses the limited range of beta particles to produce a three-dimensional dose distribution. We simulated distributions by beta-dose kernels and validated those estimates by irradiating PRESAGE^ polyurethane dosimeters that measure the three-dimensional dose distributions by a change in optical density that is proportional to dose. The dosimeters were injected with internal beta-emitting radionuclide yttrium-90, exposed for 5.75 days, imaged with optical tomography, and analyzed with radiotherapy software. Dosimeters irradiated with an electron beam to 2 or 3 Gy were used for calibration. The shapes and dose distributions in the PRESAGE^ dosimeters were consistent with the predicted dose kernels. Our experiments have laid the groundwork for future application to individualized patient therapy by ultimately designing a treatment plan that conforms to the shape of any appropriate tumor.

  12. SU-E-T-753: Three-Dimensional Dose Distributions of Incident Proton Particle in the Polymer Gel Dosimeter and the Radiochromic Gel Dosimeter: A Simulation Study with MCNP Code

    SciTech Connect

    Park, M; Kim, G; Ji, Y; Kim, K; Park, S; Jung, H

    2015-06-15

    Purpose: The purpose of this study is to estimate the three-dimensional dose distributions in the polymer and the radiochromic gel dosimeter, and to identify the detectability of both gel dosimeters by comparing with the water phantom in case of irradiating the proton particles. Methods: The normoxic polymer gel and the LCV micelle radiochromic gel were used in this study. The densities of polymer and the radiochromic gel dosimeter were 1.024 and 1.005 g/cm{sup 3}, respectively. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiation transport code (MCNPX, Los Alamos National Laboratory). The shape of phantom irradiated by proton particles was a hexahedron with the dimension of 12.4 × 12.4 × 15.0 cm{sup 3}. The energies of proton beam were 50, 80, and 140 MeV energies were directed to top of the surface of phantom. The cross-sectional view of proton dose distribution in both gel dosimeters was estimated with the water phantom and evaluated by the gamma evaluation method. In addition, the absorbed dose(Gy) was also calculated for evaluating the proton detectability. Results: The evaluation results show that dose distributions in both gel dosimeters at intermediated section and Bragg-peak region are similar with that of the water phantom. At entrance section, however, inconsistencies of dose distribution are represented, compared with water. The relative absorbed doses in radiochromic and polymer gel dosimeter were represented to be 0.47 % and 2.26 % difference, respectively. These results show that the radiochromic gel dosimeter was better matched than the water phantom in the absorbed dose evaluation. Conclusion: The polymer and the radiochromic gel dosimeter show similar characteristics in dose distributions for the proton beams at intermediate section and Bragg-peak region. Moreover the calculated absorbed dose in both gel dosimeters represents similar tendency by comparing with that in water phantom.

  13. ALBEDO MODELS FOR SNOW AND ICE ON A FRESHWATER LAKE. (R824801)

    EPA Science Inventory

    Abstract

    Snow and ice albedo measurements were taken over a freshwater lake in Minnesota for three months during the winter of 1996¯1997 for use in a winter lake water quality model. The mean albedo of new snow was measured as 0.83±0.028, while the...

  14. Time-variable Earth's albedo model characteristics and applications to satellite sampling errors

    NASA Technical Reports Server (NTRS)

    Bartman, F. L.

    1981-01-01

    Characteristics of the time variable Earth albedo model are described. With the cloud cover multiplying factor adjusted to produce a global annual average albedo of 30.3, the global annual average cloud cover is 45.5 percent. Global annual average sunlit cloud cover is 48.5 percent; nighttime cloud cover is 42.7 percent. Month-to-month global average albedo is almost sinusoidal with maxima in June and December and minima in April and October. Month-to-month variation of sunlit cloud cover is similar, but not in all details. The diurnal variation of global albedo is greatest from November to March; the corresponding variation of sunlit cloud cover is greatest from May to October. Annual average zonal albedos and monthly average zonal albedos are in good agreement with satellite-measured values, with notable differences in the polar regions in some months and at 15 S. The albedo of some 10 deg by 10 deg. areas of the Earth versus zenith angle are described. Satellite albedo measurement sampling effects are described in local time and in Greenwich mean time.

  15. MAIN BELT ASTEROIDS WITH WISE/NEOWISE. I. PRELIMINARY ALBEDOS AND DIAMETERS

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Bauer, J. M.; Eisenhardt, P. R. M.; DeBaun, E.; Elsbury, D.; Gautier, T. IV; Gomillion, S.; Wilkins, A.; Cutri, R. M.; Dailey, J.; McMillan, R. S.; Spahr, T. B.; Skrutskie, M. F.; Tholen, D.; Walker, R. G.; Wright, E. L.

    2011-11-10

    We present initial results from the Wide-field Infrared Survey Explorer (WISE), a four-band all-sky thermal infrared survey that produces data well suited for measuring the physical properties of asteroids, and the NEOWISE enhancement to the WISE mission allowing for detailed study of solar system objects. Using a NEATM thermal model fitting routine, we compute diameters for over 100,000 Main Belt asteroids from their IR thermal flux, with errors better than 10%. We then incorporate literature values of visible measurements (in the form of the H absolute magnitude) to determine albedos. Using these data we investigate the albedo and diameter distributions of the Main Belt. As observed previously, we find a change in the average albedo when comparing the inner, middle, and outer portions of the Main Belt. We also confirm that the albedo distribution of each region is strongly bimodal. We observe groupings of objects with similar albedos in regions of the Main Belt associated with dynamical breakup families. Asteroid families typically show a characteristic albedo for all members, but there are notable exceptions to this. This paper is the first look at the Main Belt asteroids in the WISE data, and only represents the preliminary, observed raw size, and albedo distributions for the populations considered. These distributions are subject to survey biases inherent to the NEOWISE data set and cannot yet be interpreted as describing the true populations; the debiased size and albedo distributions will be the subject of the next paper in this series.

  16. Main-belt asteroids with WISE/NEOWISE: Near-infrared albedos

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; Sonnett, S.

    2014-08-20

    We present revised near-infrared albedo fits of 2835 main-belt asteroids observed by WISE/NEOWISE over the course of its fully cryogenic survey in 2010. These fits are derived from reflected-light near-infrared images taken simultaneously with thermal emission measurements, allowing for more accurate measurements of the near-infrared albedos than is possible for visible albedo measurements. Because our sample requires reflected light measurements, it undersamples small, low-albedo asteroids, as well as those with blue spectral slopes across the wavelengths investigated. We find that the main belt separates into three distinct groups of 6%, 16%, and 40% reflectance at 3.4 μm. Conversely, the 4.6 μm albedo distribution spans the full range of possible values with no clear grouping. Asteroid families show a narrow distribution of 3.4 μm albedos within each family that map to one of the three observed groupings, with the (221) Eos family being the sole family associated with the 16% reflectance 3.4 μm albedo group. We show that near-infrared albedos derived from simultaneous thermal emission and reflected light measurements are important indicators of asteroid taxonomy and can identify interesting targets for spectroscopic follow-up.

  17. Dominance of grain size impacts on seasonal snow albedo at open sites in New Hampshire

    NASA Astrophysics Data System (ADS)

    Adolph, Alden C.; Albert, Mary R.; Lazarcik, James; Dibb, Jack E.; Amante, Jacqueline M.; Price, Andrea

    2017-01-01

    Snow cover serves as a major control on the surface energy budget in temperate regions due to its high reflectivity compared to underlying surfaces. Winter in the northeastern United States has changed over the last several decades, resulting in shallower snowpacks, fewer days of snow cover, and increasing precipitation falling as rain in the winter. As these climatic changes occur, it is imperative that we understand current controls on the evolution of seasonal snow albedo in the region. Over three winter seasons between 2013 and 2015, snow characterization measurements were made at three open sites across New Hampshire. These near-daily measurements include spectral albedo, snow optical grain size determined through contact spectroscopy, snow depth, snow density, black carbon content, local meteorological parameters, and analysis of storm trajectories using the Hybrid Single-Particle Lagrangian Integrated Trajectory model. Using analysis of variance, we determine that land-based winter storms result in marginally higher albedo than coastal storms or storms from the Atlantic Ocean. Through multiple regression analysis, we determine that snow grain size is significantly more important in albedo reduction than black carbon content or snow density. And finally, we present a parameterization of albedo based on days since snowfall and temperature that accounts for 52% of variance in albedo over all three sites and years. Our improved understanding of current controls on snow albedo in the region will allow for better assessment of potential response of seasonal snow albedo and snow cover to changing climate.

  18. Robust albedo estimation from a facial image with cast shadow under general unknown lighting.

    PubMed

    Suh, Sungho; Lee, Minsik; Choi, Chong-Ho

    2013-01-01

    Albedo estimation from a facial image is crucial for various computer vision tasks, such as 3-D morphable-model fitting, shape recovery, and illumination-invariant face recognition, but the currently available methods do not give good estimation results. Most methods ignore the influence of cast shadows and require a statistical model to obtain facial albedo. This paper describes a method for albedo estimation that makes combined use of image intensity and facial depth information for an image with cast shadows and general unknown light. In order to estimate the albedo map of a face, we formulate the albedo estimation problem as a linear programming problem that minimizes intensity error under the assumption that the surface of the face has constant albedo. Since the solution thus obtained has significant errors in certain parts of the facial image, the albedo estimate needs to be compensated. We minimize the mean square error of albedo under the assumption that the surface normals, which are calculated from the facial depth information, are corrupted with noise. The proposed method is simple and the experimental results show that this method gives better estimates than other methods.

  19. Intercomparison Between in situ and AVHRR Polar Pathfinder-Derived Surface Albedo over Greenland

    NASA Technical Reports Server (NTRS)

    Stroeve, Julienne C.; Box, Jason E.; Fowler, Charles; Haran, Terence; Key, Jeffery

    2001-01-01

    The Advanced Very High Resolution (AVHRR) Polar Pathfinder Data (APP) provides the first long time series of consistent, calibrated surface albedo and surface temperature data for the polar regions. Validations of these products have consisted of individual studies that analyzed algorithm performance for limited regions and or time periods. This paper reports on comparisons made between the APP-derived surface albedo and that measured at fourteen automatic weather stations (AWS) around the Greenland ice sheet from January 1997 to August 1998. Results show that satellite-derived surface albedo values are on average 10% less than those measured by the AWS stations. However, the station measurements tend to be biased high by about 4% and thus the differences in absolute albedo may be less (e.g. 6%). In regions of the ice sheet where the albedo variability is small, such as the dry snow facies, the APP albedo uncertainty exceeds the natural variability. Further work is needed to improve the absolute accuracy of the APP-derived surface albedo. Even so, the data provide temporally and spatially consistent estimates of the Greenland ice sheet albedo.

  20. Influence of tropospheric aerosol on integral albedo of cloudy atmosphere. Underlying surface system

    NASA Astrophysics Data System (ADS)

    Tarasova, T. A.; Feygelson, Y. M.

    1984-05-01

    The integral albedo which is formed for the most part due to the albedo of clouds and the underlying surface, but aerosol outside the cloud can exert an influence is discussed. The four layer system was examined. Stimulated parameters for the individual layers and stipulated albedo of the underlying surface are used in computing the spectral albedo of the cloud layer of subsystem and transmission. The albedo for the system (a formula for Asys is derived) are determined. The method reduces the problem of determining the albedo of the four layer system to three independent problems, A sub 0, A sub I, A sub II, each of which is solved in the delta-Eddington two-flux approximation on the assumption of homogeneity of the individual layers. The effect of aerosol outside the cloud is indicated. In small absorption aerosol scattering in the layers outside the clouds increases the albedo of the system as a whole. The formula for Asys and other results evaluate the aerosol effect information of the integral albedo of the system.

  1. ANALYTIC MODELS FOR ALBEDOS, PHASE CURVES, AND POLARIZATION OF REFLECTED LIGHT FROM EXOPLANETS

    SciTech Connect

    Madhusudhan, Nikku; Burrows, Adam E-mail: burrows@astro.princeton.edu

    2012-03-01

    New observational facilities are becoming increasingly capable of observing reflected light from transiting and directly imaged extrasolar planets. In this study, we provide an analytic framework to interpret observed phase curves, geometric albedos, and polarization of giant planet atmospheres. We compute the observables for non-conservative Rayleigh scattering in homogeneous semi-infinite atmospheres using both scalar and vector formalisms. In addition, we compute phase curves and albedos for Lambertian, isotropic, and anisotropic scattering phase functions. We provide analytic expressions for geometric albedos and spherical albedos as a function of the scattering albedo for Rayleigh scattering in semi-infinite atmospheres. Given an observed geometric albedo our prescriptions can be used to estimate the underlying scattering albedo of the atmosphere, which in turn is indicative of the scattering and absorptive properties of the atmosphere. We also study the dependence of polarization in Rayleigh scattering atmospheres on the orbital parameters of the planet-star system, particularly on the orbital inclination. We show how the orbital inclination of non-transiting exoplanets can be constrained from their observed polarization parameters. We consolidate the formalism, solution techniques, and results from analytic models available in the literature, often scattered in various sources, and present a systematic procedure to compute albedos, phase curves, and polarization of reflected light.

  2. Effects of refractive index mismatch in optical CT imaging of polymer gel dosimeters

    SciTech Connect

    Manjappa, Rakesh; Makki S, Sharath; Kanhirodan, Rajan; Kumar, Rajesh

    2015-02-15

    Purpose: Proposing an image reconstruction technique, algebraic reconstruction technique-refraction correction (ART-rc). The proposed method takes care of refractive index mismatches present in gel dosimeter scanner at the boundary, and also corrects for the interior ray refraction. Polymer gel dosimeters with high dose regions have higher refractive index and optical density compared to the background medium, these changes in refractive index at high dose results in interior ray bending. Methods: The inclusion of the effects of refraction is an important step in reconstruction of optical density in gel dosimeters. The proposed ray tracing algorithm models the interior multiple refraction at the inhomogeneities. Jacob’s ray tracing algorithm has been modified to calculate the pathlengths of the ray that traverses through the higher dose regions. The algorithm computes the length of the ray in each pixel along its path and is used as the weight matrix. Algebraic reconstruction technique and pixel based reconstruction algorithms are used for solving the reconstruction problem. The proposed method is tested with numerical phantoms for various noise levels. The experimental dosimetric results are also presented. Results: The results show that the proposed scheme ART-rc is able to reconstruct optical density inside the dosimeter better than the results obtained using filtered backprojection and conventional algebraic reconstruction approaches. The quantitative improvement using ART-rc is evaluated using gamma-index. The refraction errors due to regions of different refractive indices are discussed. The effects of modeling of interior refraction in the dose region are presented. Conclusions: The errors propagated due to multiple refraction effects have been modeled and the improvements in reconstruction using proposed model is presented. The refractive index of the dosimeter has a mismatch with the surrounding medium (for dry air or water scanning). The algorithm

  3. Joint AOT-Single Scattering Albedo Retrieval in Algorithm MAIAC

    NASA Astrophysics Data System (ADS)

    Lyapustin, A.

    2015-12-01

    Multi-Angle Implementation of Atmospheric Correction (MAIAC) is a new algorithm which uses time series analysis and processing of groups of pixels for advanced cloud detection and retrieval of aerosol and surface bidirectional reflectance properties. MAIAC C6+ re-processing of MODIS data record, scheduled to begin in November 2015, will create a suite of products MCD19. Due to high 1km resolution, MAIAC provides information about fine scale aerosol variability required in different applications such as urban air quality analysis. During the past year, we developed a new MAIAC capability to retrieve Single Scattering Albedo (SSA) from MODIS by adapting OMI heritage approach of O. Torres. We will describe MAIAC retrieval approach, AERONET AOT and SSA validation for different world biomass burning regions, and will compare MAIAC results with other sensors.

  4. Performance of an albedo collecting bifacial flat module

    SciTech Connect

    Sala, G.; Calleja, M.J.; Eguren, J.; Luque, A.; Romero, S.L.

    1984-05-01

    Bifacial photovoltaic modules have been recently developed and are now commercially available. These modules are able to collect the light reaching them from the surroundings not only on their front side, but also on their back side. This paper presents the performance on the industrially manufactured bifacial modules measured in outdoor conditions. The authors have found a very significative increase in their output power when the albedo light, diffusively reflected by the white painted floor, is collected on the back side of the module at any given condition. A model to calculate the available energy incident on the back is presented, experimentally validated and used to calculate the overall gain of collected energy. The authors obtained an increase of 57% for an array of infinite modules when the reflectivity of the floor is 0.75.

  5. The albedos of Pluto and Charon - Wavelength dependence

    NASA Technical Reports Server (NTRS)

    Marcialis, Robert L.; Lebofsky, Larry A.; Disanti, Michael A.; Fink, Uwe; Tedesco, Edward F.; Africano, John

    1992-01-01

    The March 3, 1987 occultation of Charon by Pluto was monitored simultaneously with three telescopes. Each site covered a distinct wavelength interval with the total range spanning 0.44-2.4 microns. Observing the same event ensures an identical sun-Pluto-earth geometry for all three sites, and minimizes the assumptions which must be made to combine results. This spectrophotometry is used to derive the individual geometric albedos of Pluto and Charon over a factor of at least 5 in wavelength. Combining the results with those of Binzel (1988) improved (B - V) color estimates (on the 'Johnson Pluto' system) are obtained for the components of the system at rotational phase 0.75: (Pluto + Charon) = 0.843 +/- 0.006; Pluto alone = 0.866 +/- 0.007; and Charon alone = 0.702 +/- 0.010.

  6. Contribution to polar albedo from a mesospheric aerosol layer

    NASA Technical Reports Server (NTRS)

    Hummel, J. R.

    1977-01-01

    An examination is made of the impact of a layer of particulate matter, assumed to be ice crystals, on the albedo of the polar region. The model is time dependent, includes the growth of the layer, and incorporates the diffuse nature of radiation reflected from the surface and atmosphere. Although the magnitude of the effect is about an order of magnitude less than previous results, the impact is one of heating instead of cooling. It is also shown that ignoring the diffuse nature of the radiation reflected from the underlying earth-atmosphere system, as has been done in many previous simple models, can result in overestimation of the climatological impact of aerosols in sign and magnitude by a factor of up to 4-6.

  7. Correlating Pluto's Albedo Distribution to Long Term Insolation Patterns

    NASA Astrophysics Data System (ADS)

    Earle, Alissa M.; Binzel, Richard P.; Stern, S. Alan; Young, Leslie A.; Buratti, Bonnie J.; Ennico, Kimberly; Grundy, Will M.; Olkin, Catherine B.; Spencer, John R.; Weaver, Hal A.

    2015-11-01

    NASA's New Horizons' reconnaissance of the Pluto system has revealed striking albedo contrasts from polar to equatorial latitudes on Pluto, as well as sharp boundaries for longitudinal variations. These contrasts suggest Pluto undergoes dynamic evolution that drives the redistribution of volatiles. Using the New Horizons results as a template, in this talk we will explore the volatile migration process driven seasonally on Pluto considering multiple timescales. These timescales include the current orbit (248 years) as well as the timescales for obliquity precession (amplitude of 23 degrees over 3 Myrs) and regression of the orbital longitude of perihelion (3.7 Myrs). We will build upon the long-term insolation history model described by Earle and Binzel (2015, Icarus 250, 405-412) with the goal of identifying the most critical timescales that drive the features observed in Pluto’s current post-perihelion epoch. This work was supported by the NASA New Horizons Project.

  8. A digital file of the lunar normal Albedo

    USGS Publications Warehouse

    Wildey, R.L.

    1977-01-01

    A digital file of the normal albedo of the Moon has been produced at a resolution of about 1/550 of a lunar diameter (about 6.3 km). The file was produced from five photographs taken with the 61-cm reflector of the Northern Arizona University Astrophysical Observatory. No mosaicking was necessary. Spatial control is selenodetic rather than landmark-morphologic. Photometric control is provided through a combination of electrography and regular photoelectric photometry. Pixel photometric function corrections are employed. The file was provided as data base for the Lunar Consortium. Brief discussion of the scientific implications of the frequency histogram is offered, and the negligibility of lunar limb darkening below e{open} = 77?? is affirmed. It is specifically desired not to withhold these data from publication while more significant and detailed scientific interpretation is carried on. ?? 1977 D. Reidel Publishing Company, Dordrecht-Holland.

  9. Color and albedo heterogeneity of Vesta from Dawn.

    PubMed

    Reddy, Vishnu; Nathues, Andreas; Le Corre, Lucille; Sierks, Holger; Li, Jian-Yang; Gaskell, Robert; McCoy, Timothy; Beck, Andrew W; Schröder, Stefan E; Pieters, Carle M; Becker, Kris J; Buratti, Bonnie J; Denevi, Brett; Blewett, David T; Christensen, Ulrich; Gaffey, Michael J; Gutierrez-Marques, Pablo; Hicks, Michael; Keller, Horst Uwe; Maue, Thorsten; Mottola, Stefano; McFadden, Lucy A; McSween, Harry Y; Mittlefehldt, David; O'Brien, David P; Raymond, Carol; Russell, Christopher

    2012-05-11

    Multispectral images (0.44 to 0.98 μm) of asteroid (4) Vesta obtained by the Dawn Framing Cameras reveal global color variations that uncover and help understand the north-south hemispherical dichotomy. The signature of deep lithologies excavated during the formation of the Rheasilvia basin on the south pole has been preserved on the surface. Color variations (band depth, spectral slope, and eucrite-diogenite abundance) clearly correlate with distinct compositional units. Vesta displays the greatest variation of geometric albedo (0.10 to 0.67) of any asteroid yet observed. Four distinct color units are recognized that chronicle processes--including impact excavation, mass wasting, and space weathering--that shaped the asteroid's surface. Vesta's color and photometric diversity are indicative of its status as a preserved, differentiated protoplanet.

  10. The Albedo Dichotomy of Iapetus Measured at UV Wavelengths

    NASA Technical Reports Server (NTRS)

    Hendrix, Amanda R.; Hansen, Candice J.

    2007-01-01

    The dramatic hemispheric dichotomy in albedo displayed by Saturn's moon Iapetus has intrigued astronomers for centuries. Here we report on far-ultraviolet observations of Iapetus' bright and dark terrains from Cassini. We compare the reflectance spectra of Iapetus's dark terrain, Hyperion and Phoebe and find that both Phoebe and Hyperion are richer in water ice than Iapetus' dark terrain. Spectra of the lowest latitudes of the dark terrain display the diagnostic water ice absorption feature; water ice amounts increase within the dark material away from the apex (at 90 deg W longitude, the center of the dark leading hemisphere), consistent with thermal segregation of water ice. The water ice in the darkest, warmest low latitude regions is not expected to be stable and may be a sign of ongoing or recent emplacement of the dark material from an exogenic source.

  11. Global Monitoring of Martian Surface Albedo Changes from Orbital Observations

    NASA Astrophysics Data System (ADS)

    Geissler, P.; Enga, M.; Mukherjee, P.

    2013-12-01

    Martian surface changes were first observed from orbit during the Mariner 9 and Viking Orbiter missions. They were found to be caused by eolian processes, produced by deposition of dust during regional and global dust storms and subsequent darkening of the surface through erosion and transportation of dust and sand. The albedo changes accumulated in the 20 years between Viking and Mars Global Surveyor were sufficient to alter the global circulation of winds and the climate of Mars according to model calculations (Fenton et al., Nature 2007), but little was known about the timing or frequency of the changes. Since 1999, we have had the benefit of continuous monitoring by a series of orbiting spacecraft that continues today with Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Express. Daily synoptic observations enable us to determine whether the surface albedo changes are gradual or episodic in nature and to record the seasons that the changes take place. High resolution images of surface morphology and atmospheric phenomena help identify the physical mechanisms responsible for the changes. From these data, we hope to learn the combinations of atmospheric conditions and sediment properties that produce surface changes on Mars and possibly predict when they will take place in the future. Martian surface changes are particularly conspicuous in low albedo terrain, where even a thin layer of bright dust brightens the surface drastically. Equatorial dark areas are repeatedly coated and recoated by dust, which is later shed from the surface by a variety of mechanisms. An example is Syrtis Major, suddenly buried in bright dust by the global dust storm of 2001. Persistent easterly winds blew much of the dust cover away over the course of the next Martian year, but episodic changes continue today, particularly during southern summer when regional dust storms are rife. Another such region is Solis Planum, south of the Valles Marineris, where changes take place

  12. Remote auditing of radiotherapy facilities using optically stimulated luminescence dosimeters

    SciTech Connect

    Lye, Jessica Dunn, Leon; Kenny, John; Alves, Andrew; Lehmann, Joerg; Williams, Ivan; Kron, Tomas; Oliver, Chris; Butler, Duncan; Johnston, Peter; Franich, Rick

    2014-03-15

    Purpose: On 1 July 2012, the Australian Clinical Dosimetry Service (ACDS) released its Optically Stimulated Luminescent Dosimeter (OSLD) Level I audit, replacing the previous TLD based audit. The aim of this work is to present the results from this new service and the complete uncertainty analysis on which the audit tolerances are based. Methods: The audit release was preceded by a rigorous evaluation of the InLight® nanoDot OSLD system from Landauer (Landauer, Inc., Glenwood, IL). Energy dependence, signal fading from multiple irradiations, batch variation, reader variation, and dose response factors were identified and quantified for each individual OSLD. The detectors are mailed to the facility in small PMMA blocks, based on the design of the existing Radiological Physics Centre audit. Modeling and measurement were used to determine a factor that could convert the dose measured in the PMMA block, to dose in water for the facility's reference conditions. This factor is dependent on the beam spectrum. The TPR{sub 20,10} was used as the beam quality index to determine the specific block factor for a beam being audited. The audit tolerance was defined using a rigorous uncertainty calculation. The audit outcome is then determined using a scientifically based two tiered action level approach. Audit outcomes within two standard deviations were defined as Pass (Optimal Level), within three standard deviations as Pass (Action Level), and outside of three standard deviations the outcome is Fail (Out of Tolerance). Results: To-date the ACDS has audited 108 photon beams with TLD and 162 photon beams with OSLD. The TLD audit results had an average deviation from ACDS of 0.0% and a standard deviation of 1.8%. The OSLD audit results had an average deviation of −0.2% and a standard deviation of 1.4%. The relative combined standard uncertainty was calculated to be 1.3% (1σ). Pass (Optimal Level) was reduced to ≤2.6% (2σ), and Fail (Out of Tolerance) was reduced to >3

  13. The influence of inter-annually varying albedo on regional climate and drought

    NASA Astrophysics Data System (ADS)

    Meng, X. H.; Evans, J. P.; McCabe, M. F.

    2014-02-01

    Albedo plays an important role in land-atmosphere interactions and local climate. This study presents the impact on simulating regional climate, and the evolution of a drought, when using the default climatological albedo as is usually done in regional climate modelling, or using the actual observed albedo which is rarely done. Here, time-varying satellite derived albedo data is used to update the lower boundary condition of the Weather Research and Forecasting regional climate model in order to investigate the influence of observed albedo on regional climate simulations and also potential changes to land-atmosphere feedback over south-east Australia. During the study period from 2000 to 2008, observations show that albedo increased with an increasingly negative precipitation anomaly, though it lagged precipitation by several months. Compared to in-situ observations, using satellite observed albedo instead of the default climatological albedo provided an improvement in the simulated seasonal mean air temperature. In terms of precipitation, both simulations reproduced the drought that occurred from 2002 through 2006. Using the observed albedo produced a drier simulation overall. During the onset of the 2002 drought, albedo changes enhanced the precipitation reduction by 20 % on average, over locations where it was active. The area experiencing drought increased 6.3 % due to the albedo changes. Two mechanisms for albedo changes to impact land-atmosphere drought feedback are investigated. One accounts for the increased albedo, leading to reduced turbulent heat flux and an associated decrease of moist static energy density in the planetary boundary layer; the other considers that enhanced local radiative heating, due to the drought, favours a deeper planetary boundary layer, subsequently decreasing the moist static energy density through entrainment of the free atmosphere. Analysis shows that drought related large-scale changes in the regional climate favour a

  14. The influence of inter-annually varying albedo on regional climate and drought

    NASA Astrophysics Data System (ADS)

    Meng, X. H.; Evans, J. P.; McCabe, M. F.

    2013-05-01

    Albedo plays an important role in land-atmosphere interactions and local climate. This study presents the impact on simulating regional climate, and the evolution of a drought, when using the default climatological albedo as is usually done in regional climate modelling, or using the actual observed albedo which is rarely done. Here, time-varying satellite derived albedo data is used to update the lower boundary condition of the Weather Research and Forecasting regional climate model in order to investigate the influence of observed albedo on regional climate simulations and also potential changes to land-atmosphere feedback over south-east Australia. During the study period from 2000 to 2008, observations show that albedo increased with an increasingly negative precipitation anomaly, though it lagged precipitation by several months. Compared to in-situ observations, using satellite observed albedo instead of the default climatological albedo provided an improvement in the simulated seasonal mean air temperature. In terms of precipitation, both simulations reproduced the drought that occurred from 2002 through 2006. Using the observed albedo produced a drier simulation overall. During the onset of the 2002 drought, albedo changes enhanced the precipitation reduction by 20 % on average, over locations where it was active. The area experiencing drought increased 6.3 % due to the albedo changes. Two mechanisms for albedo changes to impact land-atmosphere drought feedback are investigated. One accounts for the increased albedo, leading to reduced turbulent heat flux and an associated decrease of moist static energy density in the planetary boundary layer; the other considers that enhanced local radiative heating, due to the drought, favours a deeper planetary boundary layer, subsequently decreasing the moist static energy density through entrainment of the free atmosphere. Analysis shows that drought related large-scale changes in the regional climate favour a

  15. Water Ice Albedo Variations on the Martian Northern Polar Cap

    NASA Technical Reports Server (NTRS)

    Hale, A. S.; Bass, D. S.; Tamppari, L. K.

    2003-01-01

    The Viking Orbiters determined that the surface of Mars northern residual cap is water ice. Many researchers have related observed atmospheric water vapor abundances to seasonal exchange between reservoirs such as the polar caps, but the extent to which the exchange between the surface and the atmosphere remains uncertain. Early studies of the ice coverage and albedo of the northern residual Martian polar cap using Mariner 9 and Viking images reported that there were substantial internannual differences in ice deposition on the polar cap, a result which suggested a highly variable Martian climate. However, some of the data used in these studies were obtained at differing values of heliocentric solar longitude (L(sub s)). Reevaluation of this dataset indicated that the residual cap undergoes seasonal brightening throughout the summer, and indicated that this process repeats from year to year. In this study we continue to compare Mariner 9 and Viking Orbiter imaging observations and thermal data of the north residual polar cap to data acquired with Mars Global Surveyor s Mars Orbiter Camera (MOC) instrument. In the current study, our goal is to examine all released data from MGS MOC in the northern summer season, along with applicable TES data in order to better understand the albedo variations in the northern summer and their implications on water transport. To date, work has focused primarily on the MOC dataset. In 1999, data acquisition of the northern polar regions began at L(sub s) = 107, although there was little north polar data acquired from L(sub s)= 107 to L(sub s) = 109. We examined a total of 409 images from L(sub s) = 107 to L(sub s)=148. We have also examined data from 2000 from L(sub s)= 93 to L(sub s)= 110; additional progress is ongoing. Here we present a progress report of our observations, and continue to determine their implications for the Martian water cycle.

  16. Characteristics of a novel polymer gel dosimeter formula for MRI scanning: Dosimetry, toxicity and temporal stability of response.

    PubMed

    Abtahi, S M

    2016-09-01

    The present study intended to investigate the composition of a new polymer gel dosimeter. The new composition would be more suitable for a wide range of applications in comparison to polyacrylamide gel dosimeter since its extremely toxic acrylamide has been replaced with less harmful monomer i.e. 2-Acrylamido-2-MethylPropane Sulfonic acid (AMPS). To this end, the PAGAT gel dosimeter formula was used as a basis to test the new formulation of polymer gel dosimeter with a different monomer (AMPS) instead of acrylamide by using the %6T and %50C to the formula. The new formulation was named PAMPSGAT (Poly AMPS, Gelatin and THPC) polymer gel dosimeter. Moreover, the MRI response (R2) of dosimeters was analyzed in terms of different dose range as well as post-irradiation time. The results indicated that the dose-response (R2) of AMPS/Bis had a linear trend over a wide dose range. Furthermore, the results showed an acceptable temporal stability for the new polymer gel dosimeter.

  17. Determining the applicability of the Landauer nanoDot as a general public dosimeter in a research imaging facility.

    PubMed

    Charlton, Michael A; Thoreson, Kelly F; Cerecero, Jennifer A

    2012-11-01

    The Research Imaging Institute (RII) building at the University of Texas Health Science Center at San Antonio (UTHSCSA) houses two cyclotron particle accelerators, positron emission tomography (PET) machines, and a fluoroscopic unit. As part of the radiation protection program (RPP) and meeting the standard for achieving ALARA (as low as reasonably achievable), it is essential to minimize the ionizing radiation exposure to the general public through the use of controlled areas and area dose monitoring. Currently, thirty-four whole body Luxel+ dosimeters, manufactured by Landauer, are being used in various locations within the RII to monitor dose to the general public. The intent of this research was to determine if the nanoDot, a single point dosimeter, can be used as a general public dosimeter in a diagnostic facility. This was tested by first verifying characteristics of the nanoDot dosimeter including dose linearity, dose rate dependence, angular dependence, and energy dependence. Then, the response of the nanoDot dosimeter to the Luxel+ dosimeter when placed in a continuous, low dose environment was investigated. Finally, the nanoDot was checked for appropriate response in an acute, high dose environment. Based on the results, the current recommendation is that the nanoDot should not replace the Luxel+ dosimeter without further work to determine the energy spectra in the RII building and without considering the limitation of the microStar reader, portable on-site OSL reader, at doses below 0.1 mGy (10 mrad).

  18. Diurnal variability of the planetary albedo: An appraisal with satellite measurements and general circulation models

    SciTech Connect

    Potter, G.L.; Cess, R.D.; Minnis, P.; Harrison, E.F.; Ramanathan, V.

    1988-03-01

    This study addresses two aspects of the planetary albedo's diurnal cycle, the first of which refers to directional models of the planetary albedo. It is found that even for clear regions there appear to be deficiencies in our knowledge of how to model this quantity. Over land surfaces, for example, Nimbus-7 data for the directional planetary albedo compare best with model calculations for which a Lambertian surface is assumed, despite ample evidence that the albedo of land surfaces is dependent upon solar zenith angle. Similarly, over ocean surfaces both GOES and Nimbus-7 data produce a weaker dependence of the planetary albedo upon solar zenith angle than would be suggested by model calculations.

  19. Lemon albedo as a new source of dietary fiber: Application to bologna sausages.

    PubMed

    Fernández-Ginés, J M; Fernández-López, J; Sayas-Barberá, E; Sendra, E; Pérez-Álvarez, J A

    2004-05-01

    The aim of this work was to study the effect of the addition of lemon albedo in bologna sausages. Two types of albedo (raw and cooked) and five concentrations (0%, 2.5%, 5%, 7.5% and 10%) were added to sausages. Chemical, physicochemical and sensory analyses were made. The addition of albedo to bologna sausages represents an improvement in their nutritional properties and may have beneficial effects, possibly due to the presence of active biocompounds which induce a decrease in residual nitrite levels. The formulations which gave products with sensory properties similar to conventional sausages were sausages with 2.5% and 5% raw albedo and 2.5%, 5% and 7.5% cooked albedo.

  20. Carbon-equivalent metrics for albedo changes in land management contexts: relevance of the time dimension.

    PubMed

    Bright, Ryan M; Bogren, Wiley; Bernier, Pierre; Astrup, Rasmus

    2016-09-01

    Surface albedo is an important physical property by which the land surface regulates climate. A wide and growing body of literature suggests that failing to account for surface albedo can result in suboptimal or even counterproductive climate-motivated policies of the land-based sectors. As such, albedo changes are increasingly included in climate impact assessments of forestry and other land sector projects through conversion of radiative forcings into carbon or carbon dioxide equivalents. However, the prevailing methodology does not sufficiently accommodate dynamic albedo changes on land or CO2 in the atmosphere. We present two new metrics designed to address these deficiencies, referring to them as the time-dependent emissions equivalent and the time-independent emissions equivalent of albedo changes. We demonstrate their application in various land management contexts and discuss their merits and uncertainties.

  1. ARM Climate Research Facility Spectral Surface Albedo Value-Added Product (VAP) Report

    SciTech Connect

    McFarlane, S; Gaustad, K; Long, C; Mlawer, E

    2011-07-15

    This document describes the input requirements, output data products, and methodology for the Spectral Surface Albedo (SURFSPECALB) value-added product (VAP). The SURFSPECALB VAP produces a best-estimate near-continuous high spectral resolution albedo data product using measurements from multifilter radiometers (MFRs). The VAP first identifies best estimates for the MFR downwelling and upwelling shortwave irradiance values, and then calculates narrowband spectral albedo from these best-estimate irradiance values. The methodology for finding the best-estimate values is based on a simple process of screening suspect data and backfilling screened and missing data with estimated values when possible. The resulting best-estimate MFR narrowband spectral albedos are used to determine a daily surface type (snow, 100% vegetation, partial vegetation, or 0% vegetation). For non-snow surfaces, a piecewise continuous function is used to estimate a high spectral resolution albedo at 1 min temporal and 10 cm-1 spectral resolution.

  2. Use of albedo for neutron reflector regions in reactor core 3-D simulations

    NASA Astrophysics Data System (ADS)

    Mohanakrishnan, P.

    1989-10-01

    In this paper we present two new simplified schemes for the application of the albedo concept of replacing the reflector in 3-D reactor core simulations. Both involve the numerical derivation of albedoes from the fluxes at the core- (blanket-) reflector interface obtained from sample calculations including the reflector. Diffusion theory is used for core calculations in both cases. In the first scheme a new method for "diagonalising" the albedo matrix is demonstrated. This achieves easy applicability of the albedo parameters in core simulations of a fast breeder reactor core, resulting in significant savings in computing efforts. The second scheme, applied to light water reactors, achieves better accuracy in core periphery power predictions with the use of only uniform coarse meshes throughout the core and the numerically derived albedoes.

  3. An optically stimulated luminescence dosimeter for measuring patient exposure from imaging guidance procedures.

    PubMed

    Ding, George X; Malcolm, Arnold W

    2013-09-07

    There is a growing interest in patient exposure resulting from an x-ray imaging procedure used in image-guided radiation therapy. This study explores a feasibility to use a commercially available optically stimulated luminescence (OSL) dosimeter, nanoDot, for estimating imaging radiation exposure to patients. The kilovoltage x-ray sources used for kV-cone-beam CT (CBCT) imaging acquisition procedures were from a Varian on-board imager (OBI) image system. An ionization chamber was used to determine the energy response of nanoDot dosimeters. The chamber calibration factors for x-ray beam quality specified by half-value layer were obtained from an Accredited Dosimetry Calibration Laboratory. The Monte Carlo calculated dose distributions were used to validate the dose distributions measured by using the nanoDot dosimeters in phantom and in vivo. The range of the energy correction factors for the nanoDot as a function of photon energy and bow-tie filters was found to be 0.88-1.13 for different kVp and bow-tie filters. Measurement uncertainties of nanoDot were approximately 2-4% after applying the energy correction factors. The tests of nanoDot placed on a RANDO phantom and on patient's skin showed consistent results. The nanoDot is suitable dosimeter for in vivo dosimetry due to its small size and manageable energy dependence. The dosimeter placed on a patient's skin has potential to serve as an experimental method to monitor and to estimate patient exposure resulting from a kilovoltage x-ray imaging procedure. Due to its large variation in energy response, nanoDot is not suitable to measure radiation doses resulting from mixed beams of megavoltage therapeutic and kilovoltage imaging radiations.

  4. Development of a high efficiency personal/environmental radon dosimeter using polycarbonate detectors.

    PubMed

    Taheri, M; Jafarizadeh, M; Baradaran, S; Zainali, Gh

    2006-12-01

    Passive radon dosimeters, based on alpha particle etched track detectors, are widely used for the assessment of radon exposure. These methods are often applied in radon dosimetry for long periods of time. In this research work, we have developed a highly efficient method of personal/environmental radon dosimetry that is based upon the detection of alpha particles from radon daughters, (218)Po and (214)Po, using a polycarbonate detector (PC). The radon daughters are collected on the filter surface by passing a fixed flow of air through it and the PC detector, placed at a specified distance from the filter, is simultaneously exposed to alpha particles. After exposure, the latent tracks on the detector are made to appear by means of an electrochemical etching process; these are proportional to the radon dose. The air flow rate and the detector-filter distance are the major factors that can affect the performance of the dosimeter. The results obtained in our experimental investigations have shown that a distance of 1.5 cm between the detector and the filter, an absorber layer of Al with a thickness of 12 microm and an air flow rate of 4 l min(-1) offer the best design parameters for a high efficiency radon dosimeter. Then, the designed dosimeter was calibrated against different values of radon exposures and the obtained sensitivity was found to be 2.1 (tracks cm(-2)) (kBq h m(-3))(-1). The most important advantages of this method are that it is reliable, fast and convenient when used for radon dose assessment. In this paper, the optimized parameters of the dosimeter structure and its calibration procedure are presented and discussed.

  5. Water-equivalent dosimeter array for small-field external beam radiotherapy

    SciTech Connect

    Archambault, Louis; Beddar, A. Sam; Gingras, Luc; Lacroix, Frederic; Roy, Rene; Beaulieu, Luc

    2007-05-15

    With the increasing complexity of dose patterns external beam radiotherapy, there is a great need for new types of dosimeters. We studied the first prototype of a new dosimeter array consisting of water-equivalent plastic scintillating fibers for dose measurement in external beam radiotherapy. We found that this array allows precise, rapid dose evaluation of small photon fields. Starting with a dosimeter system constructed with a single scintillating fiber coupled to a clear optical fiber and read using a charge coupled device camera, we looked at the dosimeter's spatial resolution under small radiation fields and angular dependence. Afterward, we analyzed the camera's light collection to determine the maximum array size that could be built. Finally, we developed a prototype made of ten scintillating fiber detectors to study the behavior and precision of this system in simple dosimetric situations. The scintillation detector showed no measurable angular dependence. Comparison of the scintillation detector and a small-volume ion chamber showed agreement except for 1x1 and 0.5x5.0 cm{sup 2} fields where the output factor measured by the scintillator was higher. The actual field of view of the camera could accept more than 4000 scintillating fiber detectors simultaneously. Evaluation of the dose profile and depth dose curve using a prototype with ten scintillating fiber detectors showed precise, rapid dose evaluation even with placement of more than 75 optical fibers in the field to simulate what would happen in a larger array. We concluded that this scintillating fiber dosimeter array is a valuable tool for dose measurement in external beam radiotherapy. It possesses the qualities necessary to evaluate small and irregular fields with various incident angles such as those encountered in intensity-modulated radiotherapy, radiosurgery, and tomotherapy.

  6. Application of a radiophotoluminescent glass plate dosimeter for small field dosimetry.

    PubMed

    Aaki, Fujio; Ishidoya, Tatsuya; Ikegami, Tohru; Moribe, Nobuyuki; Yamashita, Yasuyuki

    2005-06-01

    We have recently developed a prototypical radiophotoluminescent glass plate dosimeter (GPD) system as a device for small field dosimetry. The purpose of this study is to examine the usefulness of the GPD system for small field dosimetry. The profiles measured with the GPD were evaluated by comparing them to those from Kodak X-Omat V and GAFCROMIC XR type R film dosimeters for 2, 5, 9, and 15 mm circular collimators created by a linear accelerator-based radiosurgery system. The GPD output factors were compared with those of various detectors including an ion chamber, a p-type silicon diode detector, a glass rod dosimeter (GRD), and a diamond detector. The results measured with the GPD were also confirmed by comparing them to those from Monte Carlo simulations. The accuracy of a simulated beam is validated by the excellent agreement between Monte Carlo calculated and measured central axis depth-dose curves for 9- and 15 mm circular collimators using 4- and 10 MV photon beams. The GPD profiles show almost the same full width at half maximum as those of film dosimeters and Monte Carlo simulations at 4- and 10 MV photon beams, but a little narrower penumbrae than the film dosimeters and Monte Carlo simulations. The output factors measured with the GPD are in good agreement with those from a diode detector, a diamond detector, and the GRD with a small active volume and Monte Carlo simulations, except for a very small 2 mm circular collimator. It was found that the GPD is a very useful detector for small field dosimetry.

  7. Dose evaluation of an NIPAM polymer gel dosimeter using gamma index

    NASA Astrophysics Data System (ADS)

    Chang, Yuan-Jen; Lin, Jing-Quan; Hsieh, Bor-Tsung; Yao, Chun-Hsu; Chen, Chin-Hsing

    2014-11-01

    An N-isopropylacrylamide (NIPAM) polymer gel dosimeter has great potential in clinical applications. However, its three-dimensional dose distribution must be assessed. In this work, a quantitative evaluation of dose distributions was performed to evaluate the NIPAM polymer gel dosimeter using gamma analysis. A cylindrical acrylic phantom filled with NIPAM gel measuring 10 cm (diameter) by 10 cm (height) by 3 mm (thickness) was irradiated by a 4×4 cm2 square light field. The irradiated gel phantom was scanned using an optical computed tomography (optical CT) scanner (OCTOPUS™, MGS Research, Inc., Madison, CT, USA) at 1 mm resolution. The projection data were transferred to an image reconstruction program, which was written using MATLAB (The MathWorks, Natick, MA, USA). The program reconstructed the image of the optical density distribution using the algorithm of a filter back-projection. Three batches of replicated gel phantoms were independently measured. The average uncertainty of the measurements was less than 1%. The gel was found to have a high degree of spatial uniformity throughout the dosimeter and good temporal stability. A comparison of the line profiles of the treatment planning system and of the data measured by optical CT showed that the dose was overestimated in the penumbra region because of two factors. The first is light scattering due to changes in the refractive index at the edge of the irradiated field. The second is the edge enhancement caused by free radical diffusion. However, the effect of edge enhancement on the NIPAM gel dosimeter is not as significant as that on the BANG gel dosimeter. Moreover, the dose uncertainty is affected by the inaccuracy of the gel container positioning process. To reduce the uncertainty of 3D dose distribution, improvements in the gel container holder must be developed.

  8. Surface albedo darkening from wildfires in northern sub-Saharan Africa

    NASA Astrophysics Data System (ADS)

    Gatebe, C. K.; Ichoku, C. M.; Poudyal, R.; Román, M. O.; Wilcox, E.

    2014-05-01

    Northern sub-Saharan Africa (NSSA) has a wide variety of climate zones or biomes, where albedo dynamics are highly coupled with vegetation dynamics and fire disturbances. Quantifying surface albedo variations due to fire disturbances on time scales of several months to several years is complex and is made worse by lack of accurate and spatially consistent surface albedo data. Here, we estimate the surface albedo effect from wildfires in different land cover types in the NSSA region using Moderate Resolution Imaging Spectroradiometer (MODIS) multi-year observational data (2003-11). The average decrease in albedo after fires at the scale of 1 km MODIS footprint is -0.002 02 ± 0.000 03 for woody savanna and -0.002 22 ± 0.000 03 for savanna. These two land cover types together account for >86% of the total MODIS fire count between 2003 and 2011. We found that only a small fraction of the pixels (≦̸10%) burn in two successive years and about 47% had any fire recurrence in 9 years. The study also derived the trajectories of post-fire albedo dynamics from the percentages of pixels that recover to pre-fire albedo values each year. We found that the persistence of surface albedo darkening in most land cover types in the NSSA region is limited to about 6-7 years, after which at least 99% of the burnt pixels recover to their pre-fire albedo. Our results provide critical information for deriving necessary input to various models used in determining the effects of albedo change due to wild fires in the NSSA region.

  9. Albedo estimates for land surface models and support for a new paradigm based on foliage nitrogen concentration

    SciTech Connect

    Hollinger, D.; Ollinger, S. V.; Richardson, A. D.; Martin, M. E.; Meyers, T. P.; Dail, D. B.; Scott, N. A.; Arkebauer, T. J.; Baldocchi, D. D.; Clark, K. L.; Curtis, Peter; Davis, K. J.; Desai, Desai Ankur R.; Dragoni, Danilo; Goulden, M. L.; Gu, Lianhong; Katul, G. G.; Pallardy, Stephen G.; Pawu, K. T.; Schmid, H. P.; Stoy, P. C.; Suyker, A. E.; Verma, Shashi

    2009-02-01

    Vegetation albedo is a critical component of the Earth s climate system, yet efforts to evaluate and improve albedo parameterizations in climate models have lagged relative to other aspects of model development. Here, we calculated growing season albedos for deciduous and evergreen forests, crops, and grasslands based on over 40 site-years of data from the AmeriFlux network and compared them with estimates presently used in the land surface formulations of a variety of climate models. Generally, the albedo estimates used in land surface models agreed well with this data compilation. However, a variety of models using fixed seasonal estimates of albedo overestimated the growing season albedo of northerly evergreen trees. In contrast, climatemodels that rely on a common two-stream albedo submodel provided accurate predictions of boreal needle-leaf evergreen albedo but overestimated grassland albedos. Inverse analysis showed that parameters of the two-stream model were highly correlated. Consistent with recent observations based on remotely sensed albedo, the AmeriFlux dataset demonstrated a tight linear relationship between canopy albedo and foliage nitrogen concentration (for forest vegetation: albedo 50.0110.071%N, r250.91; forests, grassland, and maize: albedo50.0210.067%N, r250.80). However, this relationship saturated at the higher nitrogen concentrations displayed by soybean foliage. We developed similar relationships between a foliar parameter used in the two-stream albedo model and foliage nitrogen concentration. These nitrogen-based relationships can serve as the basis for a new approach to land surface albedo modeling that simplifies albedo estimation while providing a link to other important ecosystem processes.

  10. The Dependence of the Ice-Albedo Feedback on Atmospheric Properties

    PubMed Central

    Selsis, F.; Kitzmann, D.; Rauer, H.

    2013-01-01

    Abstract Ice-albedo feedback is a potentially important destabilizing effect for the climate of terrestrial planets. It is based on the positive feedback between decreasing surface temperatures, an increase of snow and ice cover, and an associated increase in planetary albedo, which then further decreases surface temperature. A recent study shows that for M stars, the strength of the ice-albedo feedback is reduced due to the strong spectral dependence of stellar radiation and snow/ice albedos; that is, M stars primarily emit in the near IR, where the snow and ice albedo is low, and less in the visible, where the snow/ice albedo is high. This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) on this feedback, since an atmosphere was neglected in previous studies. A plane-parallel radiative transfer model was used for the calculation of planetary albedos. We varied CO2 partial pressures as well as the H2O, CH4, and O3 content in the atmosphere for planets orbiting Sun-like and M type stars. Results suggest that, for planets around M stars, the ice-albedo effect is significantly reduced, compared to planets around Sun-like stars. Including the effects of an atmosphere further suppresses the sensitivity to the ice-albedo effect. Atmospheric key properties such as surface pressure, but also the abundance of radiative trace gases, can considerably change the strength of the ice-albedo feedback. For dense CO2 atmospheres of the order of a few to tens of bar, atmospheric rather than surface properties begin to dominate the planetary radiation budget. At high CO2 pressures, the ice-albedo feedback is strongly reduced for planets around M stars. The presence of trace amounts of H2O and CH4 in the atmosphere also weakens the ice-albedo effect for both stellar types considered. For planets around Sun-like stars, O3 could also lead to a very strong decrease of the ice-albedo feedback at high CO2 pressures. Key Words

  11. Satellite derived albedoes during spring melt for selected locations in the Arctic

    NASA Astrophysics Data System (ADS)

    Busse, J.; Anderson, M.

    2005-12-01

    Snow and ice surfaces have a high level of reflectance, therefore, a high albedo, compared to open water and soil which have lower albedo values and absorb more sunlight. As the high albedo snow and ice begins to melt, the albedo values drop. This contributes to a positive feedback mechanism. The dropping albedo values indicate that more radiation is being absorbed by the surface. As more radiation is absorbed by the surface, more melt occurs, which then leads to lower albedoes and more absorption. This positive feedback continues until the fall when new snow covers the surface and the albedo begins to increase, disrupting the cycle. In the Arctic, the amount of sea ice surviving the summer melt season continues to decrease, indicating a change in the surface conditions during this important melt season. However, very little is known about the albedoes during the melt period. This study documents the albedo changes that occur during the melt season and compares these changes to melt onset dates derived from passive microwave data in order to obtain a multi-frequency response to the energy conditions. Time series of albedo data from the AVHRR Polar Pathfinder Twice-Daily 25-km EASE-Grid Composites are obtained to show the transition from winter to summer conditions from 13 different points within the Arctic. Areas experiencing melt are explored and melt onset dates are determined. Snow and ice melt can also be detected using SMMR and SSM/I passive microwave data. Microwave data are useful to pinpoint when melt occurs, because microwaves can also detect changes in surface conditions. The albedo data are compared with melt onset dates obtained from microwave sensors to determine relationships between microwave-derived melt and albedo responses. Data from areas experiencing early melt onset and late melt onset are explored. Studying the time series from the 13 different points in the Arctic show the relationship between surface melt and albedo variations during the

  12. The dependence of the ice-albedo feedback on atmospheric properties.

    PubMed

    von Paris, P; Selsis, F; Kitzmann, D; Rauer, H

    2013-10-01

    Ice-albedo feedback is a potentially important destabilizing effect for the climate of terrestrial planets. It is based on the positive feedback between decreasing surface temperatures, an increase of snow and ice cover, and an associated increase in planetary albedo, which then further decreases surface temperature. A recent study shows that for M stars, the strength of the ice-albedo feedback is reduced due to the strong spectral dependence of stellar radiation and snow/ice albedos; that is, M stars primarily emit in the near IR, where the snow and ice albedo is low, and less in the visible, where the snow/ice albedo is high. This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) on this feedback, since an atmosphere was neglected in previous studies. A plane-parallel radiative transfer model was used for the calculation of planetary albedos. We varied CO₂ partial pressures as well as the H₂O, CH₄, and O₃ content in the atmosphere for planets orbiting Sun-like and M type stars. Results suggest that, for planets around M stars, the ice-albedo effect is significantly reduced, compared to planets around Sun-like stars. Including the effects of an atmosphere further suppresses the sensitivity to the ice-albedo effect. Atmospheric key properties such as surface pressure, but also the abundance of radiative trace gases, can considerably change the strength of the ice-albedo feedback. For dense CO₂ atmospheres of the order of a few to tens of bar, atmospheric rather than surface properties begin to dominate the planetary radiation budget. At high CO₂ pressures, the ice-albedo feedback is strongly reduced for planets around M stars. The presence of trace amounts of H₂O and CH₄ in the atmosphere also weakens the ice-albedo effect for both stellar types considered. For planets around Sun-like stars, O₃ could also lead to a very strong decrease of the ice-albedo feedback at high CO₂ pressures.

  13. Evaluation of LLNL's Nuclear Accident Dosimeters at the CALIBAN Reactor September 2010

    SciTech Connect

    Hickman, D P; Wysong, A R; Heinrichs, D P; Wong, C T; Merritt, M J; Topper, J D; Gressmann, F A; Madden, D J

    2011-06-21

    The Lawrence Livermore National Laboratory uses neutron activation elements in a Panasonic TLD holder as a personnel nuclear accident dosimeter (PNAD). The LLNL PNAD has periodically been tested using a Cf-252 neutron source, however until 2009, it was more than 25 years since the PNAD has been tested against a source of neutrons that arise from a reactor generated neutron spectrum that simulates a criticality. In October 2009, LLNL participated in an intercomparison of nuclear accident dosimeters at the CEA Valduc Silene reactor (Hickman, et.al. 2010). In September 2010, LLNL participated in a second intercomparison of nuclear accident dosimeters at CEA Valduc. The reactor generated neutron irradiations for the 2010 exercise were performed at the Caliban reactor. The Caliban results are described in this report. The procedure for measuring the nuclear accident dosimeters in the event of an accident has a solid foundation based on many experimental results and comparisons. The entire process, from receiving the activated NADs to collecting and storing them after counting was executed successfully in a field based operation. Under normal conditions at LLNL, detectors are ready and available 24/7 to perform the necessary measurement of nuclear accident components. Likewise LLNL maintains processing laboratories that are separated from the areas where measurements occur, but contained within the same facility for easy movement from processing area to measurement area. In the event of a loss of LLNL permanent facilities, the Caliban and previous Silene exercises have demonstrated that LLNL can establish field operations that will very good nuclear accident dosimetry results. There are still several aspects of LLNL's nuclear accident dosimetry program that have not been tested or confirmed. For instance, LLNL's method for using of biological samples (blood and hair) has not been verified since the method was first developed in the 1980's. Because LLNL and the other DOE

  14. Development of a high spectral resolution surface albedo product for the ARM Southern Great Plains Central Facility

    SciTech Connect

    McFarlane, Sally A.; Gaustad, Krista L.; Mlawer, Eli J.; Long, Charles N.; Delamere, Jennifer

    2011-09-01

    We present a method for identifying dominant surface type and estimating high spectral resolution surface albedo at the Atmospheric Radiation Measurement (ARM) facility at the Southern Great Plains (SGP) site in Oklahoma for use in radiative transfer calculations. Given a set of 6-channel narrowband visible and near-infrared irradiance measurements from upward and downward looking multi-filter radiometers (MFRs), four different surface types (snow-covered, green vegetation, partial vegetation, non-vegetated) can be identified. A normalized difference vegetation index (NDVI) is used to distinguish between vegetated and non-vegetated surfaces, and a scaled NDVI index is used to estimate the percentage of green vegetation in partially vegetated surfaces. Based on libraries of spectral albedo measurements, a piecewise continuous function is developed to estimate the high spectral resolution surface albedo for each surface type given the MFR albedo values as input. For partially vegetated surfaces, the albedo is estimated as a linear combination of the green vegetation and non-vegetated surface albedo values. The estimated albedo values are evaluated through comparison to high spectral resolution albedo measurements taken during several Intensive Observational Periods (IOPs) and through comparison of the integrated spectral albedo values to observed broadband albedo measurements. The estimated spectral albedo values agree well with observations for the visible wavelengths constrained by the MFR measurements, but have larger biases and variability at longer wavelengths. Additional MFR channels at 1100 nm and/or 1600 nm would help constrain the high resolution spectral albedo in the near infrared region.

  15. Using Remote Sensing to Quantify Roof Albedo in Seven California Cities

    NASA Astrophysics Data System (ADS)

    Ban-Weiss, G. A.; Woods, J.; Millstein, D.; Levinson, R.

    2013-12-01

    Cool roofs reflect sunlight and therefore can reduce cooling energy use in buildings. Further, since roofs cover about 20-25% of cities, wide spread deployment of cool roofs could mitigate the urban heat island effect and partially counter urban temperature increases associated with global climate change. Accurately predicting the potential for increasing urban albedo using reflective roofs and its associated energy use and climate benefits requires detailed knowledge of the current stock of roofs at the city scale. Until now this knowledge has been limited due to a lack of availability of albedo data with sufficient spatial coverage, spatial resolution, and spectral information. In this work we use a novel source of multiband aerial imagery to derive the albedos of individual roofs in seven California cities: Los Angeles, Long Beach, San Diego, Bakersfield, Sacramento, San Francisco, and San Jose. The radiometrically calibrated, remotely sensed imagery has high spatial resolution (1 m) and four narrow (less than 0.1 μm wide) band reflectances: blue, green, red, and near-infrared. To derive the albedo of roofs in each city, we first locate roof pixels within GIS building outlines. Next we use laboratory measurements of the solar spectral reflectances of 190 roofing products to empirically relate solar reflectance (albedo) to reflectances in the four narrow bands; the root-mean-square of the residuals for the albedo prediction is 0.016. Albedos computed from remotely sensed reflectances are calibrated to ground measurements of roof albedo in each city. The error (both precision and accuracy) of albedo values is presented for each city. The area-weighted mean roof albedo (× standard deviation) for each city ranges from 0.17 × 0.08 (Los Angeles) to 0.29 × 0.15 (San Diego). In each city most roofs have low albedo in the range of 0.1 to 0.3. Roofs with albedo greater than 0.4 comprise less than 3% of total roofs and 7% of total roof area in each city. The California

  16. Climate implications of including albedo effects in terrestrial carbon policy

    NASA Astrophysics Data System (ADS)

    Jones, A. D.; Collins, W.; Torn, M. S.; Calvin, K. V.

    2012-12-01

    Proposed strategies for managing terrestrial carbon in order to mitigate anthropogenic climate change, such as financial incentives for afforestation, soil carbon sequestration, or biofuel production, largely ignore the direct effects of land use change on climate via biophysical processes that alter surface energy and water budgets. Subsequent influences on temperature, hydrology, and atmospheric circulation at regional and global scales could potentially help or hinder climate stabilization efforts. Because these policies often rely on payments or credits expressed in units of CO2-equivalents, accounting for biophysical effects would require a metric for comparing the strength of biophysical climate perturbation from land use change to that of emitting CO2. One such candidate metric that has been suggested in the literature on land use impacts is radiative forcing, which underlies the global warming potential metric used to compare the climate effects of various greenhouse gases with one another. Expressing land use change in units of radiative forcing is possible because albedo change results in a net top-of-atmosphere radiative flux change. However, this approach has also been critiqued on theoretical grounds because not all climatic changes associated with land use change are principally radiative in nature, e.g. changes in hydrology or the vertical distribution of heat within the atmosphere, and because the spatial scale of land use change forcing differs from that of well-mixed greenhouse gases. To explore the potential magnitude of this discrepancy in the context of plausible scenarios of future land use change, we conduct three simulations with the Community Climate System Model 4 (CCSM4) utilizing a slab ocean model. Each simulation examines the effect of a stepwise change in forcing relative to a pre-industrial control simulation: 1) widespread conversion of forest land to crops resulting in approximately 1 W/m2 global-mean radiative forcing from albedo

  17. Albedo Properties of Small (0.5 to 20 km) Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Ryan, Erin L.; Woodward, C. E.

    2010-01-01

    Serendipitous observations of main belt asteroids by the Spitzer Space Telescope have enabled determination of main belt asteroid albedos and diameters for targets as small as 0.5 km (eg., Ryan et al. 2009, AJ, 137, 5134). We have used multi-epoch data at 5.8, 8.0 and 24 microns from the MIPSGAL and Taurus Legacy Surveys to obtain diameters and albedos for a sample of approximately 2000 main belt asteroids. Using STM and NEATM, we have obtained diameters ranging from 0.5 to 30 km and albedos ranging from 0.02 to 0.5. Results of this program reveal an albedo distribution that is more diverse in range than the albedo distribution seen in the IRAS and MSX surveys. This diversity may reflect effects of space weathering reddening which is selectively reddening larger asteroids. This reddening effect may reinforce the findings from accretion models that indicate that asteroids in the early solar system were 100 km and larger (Morbidelli et al., 2009, Icarus, in press), by suggesting that the larger asteroids are indeed the oldest members of the main belt. We will present results on the albedo distribution as a function of semi-major axis and new analysis of the mean albedo of dynamical families within the main belt. Support for this work provided in part by a National Science Foundation grant AST-0706980 to the University of Minnesota.

  18. Near-ground cooling efficacies of trees and high-albedo surfaces

    SciTech Connect

    Levinson, Ronnen M.

    1997-05-01

    Daytime summer urban heat islands arise when the prevalence of dark-colored surfaces and lack of vegetation make a city warmer than neighboring countryside. Two frequently-proposed summer heat island mitigation measures are to plant trees and to increase the albedo (solar reflectivity) of ground surfaces. This dissertation examines the effects of these measures on the surface temperature of an object near the ground, and on solar heating of air near the ground. Near-ground objects include people, vehicles, and buildings. The variation of the surface temperature of a near-ground object with ground albedo indicates that a rise in ground albedo will cool a near-ground object only if the object`s albedo exceeds a critical value. This critical value of object albedo depends on wind speed, object geometry, and the height of the atmospheric thermal boundary layer. It ranges from 0.15 to 0.37 for a person. If an object has typical albedo of 0.3, increasing the ground albedo by.

  19. Albedo indicating land degradation around the Badain Jaran Desert for better land resources utilization.

    PubMed

    Liu, Fengshan; Chen, Ying; Lu, Haiying; Shao, Hongbo

    2017-02-01

    Surface albedo is an easy access parameter in reflecting the status of both human disturbed soil and indirectly influenced area, whose characteristic is an important indicator in sustainable development under the background of global climate change. In this study, we employed meteorological data, MODIS 8-day BRDF/Albedo and LAI products from 2000 to 2014 to show the amelioration and mechanism around the Badain Jaran Desert. Results showed that the human-dominated afforestation activities significantly increased the leaf area index (LAI) in summer and autumn. Lower reflectance at visible band was sensed inside the desert compared with the ecozone and the lowest albedo at forested area. The contribution of soil and vegetation reflectance to surface albedo determined the linear sensitivity of albedo to LAI variation. Decreased albedo dominated the spatial-temporal pattern of the Badain Jaran Desert. This study suggested that surface albedo can be regarded as a useful index in indicating the change process and evaluating the sustainable development of biological management around the Badain Jaran Desert.

  20. A global assessment of forest surface albedo and its relationships with climate and atmospheric nitrogen deposition.

    PubMed

    Leonardi, Stefano; Magnani, Federico; Nolè, Angelo; Van Noije, Twan; Borghetti, Marco

    2015-01-01

    We present a global assessment of the relationships between the short-wave surface albedo of forests, derived from the MODIS satellite instrument product at 0.5° spatial resolution, with simulated atmospheric nitrogen deposition rates (Ndep ), and climatic variables (mean annual temperature Tm and total annual precipitation P), compiled at the same spatial resolution. The analysis was performed on the following five forest plant functional types (PFTs): evergreen needle-leaf forests (ENF); evergreen broad-leaf forests (EBF); deciduous needle-leaf forests (DNF); deciduous broad-leaf forests (DBF); and mixed-forests (MF). Generalized additive models (GAMs) were applied in the exploratory analysis to assess the functional nature of short-wave surface albedo relations to environmental variables. The analysis showed evident correlations of albedo with environmental predictors when data were pooled across PFTs: Tm and Ndep displayed a positive relationship with forest albedo, while a negative relationship was detected with P. These correlations are primarily due to surface albedo differences between conifer and broad-leaf species, and different species geographical distributions. However, the analysis performed within individual PFTs, strengthened by attempts to select 'pure' pixels in terms of species composition, showed significant correlations with annual precipitation and nitrogen deposition, pointing toward the potential effect of environmental variables on forest surface albedo at the ecosystem level. Overall, our global assessment emphasizes the importance of elucidating the ecological mechanisms that link environmental conditions and forest canopy properties for an improved parameterization of surface albedo in climate models.