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Sample records for air ionization chambers

  1. IONIZATION CHAMBER

    DOEpatents

    Redman, W.C.; Shonka, F.R.

    1958-02-18

    This patent describes a novel ionization chamber which is well suited to measuring the radioactivity of the various portions of a wire as the wire is moved at a uniform speed, in order to produce the neutron flux traverse pattern of a reactor in which the wire was previously exposed to neutron radiation. The ionization chamber of the present invention is characterized by the construction wherein the wire is passed through a tubular, straight electrode and radiation shielding material is disposed along the wire except at an intermediate, narrow area where the second electrode of the chamber is located.

  2. Ionization chamber

    DOEpatents

    Walenta, Albert H.

    1981-01-01

    An ionization chamber has separate drift and detection regions electrically isolated from each other by a fine wire grid. A relatively weak electric field can be maintained in the drift region when the grid and another electrode in the chamber are connected to a high voltage source. A much stronger electric field can be provided in the detection region by connecting wire electrodes therein to another high voltage source. The detection region can thus be operated in a proportional mode when a suitable gas is contained in the chamber. High resolution output pulse waveforms are provided across a resistor connected to the detection region anode, after ionizing radiation enters the drift region and ionize the gas.

  3. Ionization chamber

    DOEpatents

    Walenta, A.H.

    An ionization chamber is described which has separate drift and detection regions electrically isolated from each other by a fine wire grid. A relatively weak electric field can be maintained in the drift region when the grid and another electrode in the chamber are connected to a high voltage source. A much stronger electric field can be provided in the detection region by connecting wire electrodes therein to another high voltage source. The detection region can thus be operated in a proportional mode when a suitable gas is contained in the chamber. High resolution output pulse waveforms are provided across a resistor connected to the detection region anode, after ionizing radiation enters the drift region and ionizes the gas.

  4. Characterization of a free air ionization chamber for low energy X-rays

    NASA Astrophysics Data System (ADS)

    Silva, N. F.; Xavier, M.; Vivolo, V.; Caldas, L. V. E.

    2016-07-01

    Free air ionization chambers are used by most primary metrology laboratories as primary standards of the quantities air kerma and exposure in X-ray beams. The free air ionization chamber for low energies of the Calibration Laboratory (LCI) of IPEN showed in a characterization test a problem in the set responsible for the variation of its sensitive volume. After a modification in the support of the micrometers used for the movement of the internal cylinder and the establishment of a new alignment system protocol, the tests were redone. The objective of this work was to present the results obtained in the new condition.

  5. High-resolution ion pulse ionization chamber with air filling for the 222Rn decays detection

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, Yu. M.; Gangapshev, A. M.; Gezhaev, A. M.; Etezov, R. A.; Kazalov, V. V.; Kuzminov, V. V.; Panasenko, S. I.; Ratkevich, S. S.; Tekueva, D. A.; Yakimenko, S. P.

    2015-11-01

    The construction and characteristics of the cylindrical ion pulse ionization chamber (CIPIC) with a working volume of 3.2 L are described. The chamber is intended to register α-particles from the 222Rn and its daughter's decays in the filled air sample. The detector is less sensitive to electromagnetic pick-ups and mechanical noises. The digital pulse processing method is proposed to improve the energy resolution of the ion pulse ionization chamber. An energy resolution of 1.6% has been achieved for the 5.49 MeV α-line. The dependence of the energy resolution on high voltage and working media pressure has been investigated and the results are presented.

  6. Large-angle ionization chambers for brachytherapy air-kerma-strength measurements

    NASA Astrophysics Data System (ADS)

    Culberson, Wesley S.

    There has been a significant increase in the use of low-energy photon-emitting radionuclides in the past decade to treat cancer with a special form of radiation therapy called brachytherapy. For treating prostate cancer, brachytherapy sources are approximately the size of a grain of rice and are normally radioactive 125I or 103Pd sources encapsulated in titanium or plastic. Although these sources have proven effective in the treatment of cancer, the clinical dosimetry is difficult due to the unique varieties available and their typically. A large-angle free-air chamber at the National Institute of Standards and Technology (NIST) called the Wide-Angle Free-Air Chamber (WAFAC) is the current standard for measuring the strength of low-energy photon-emitting radionuclides for brachytherapy. This chamber has served the clinical medical physics community well and is a significant improvement over previous standards. However, it has some shortcomings. This thesis describes the development of a new large-angle ionization chamber at the University of Wisconsin called the Variable-Aperture Free-Air Chamber (VAFAC) to measure brachytherapy sources with extended capabilities. This chamber is constructed to explore characteristics in the calibration of brachytherapy seeds by quantifying potential variations caused by anisotropy and the change in response with integration angle. In addition, the characterization of yet another large-angle free-air chamber called the Grossvolumen Extrapolationskammer (GROVEX) in the German national standards institute Physikalisch-Technische Bundesanstalt (PTB) is also presented. The objective of this thesis is to present improved measurement techniques with free-air ionization chambers that will improve the accuracy of the dose delivered to patients. First, it will be shown that the UW VAFAC is capable of measuring conventional 125I or 103Pd seeds as well as longer sources, coiled sources, and miniature x-ray tubes. Additionally, the VAFAC

  7. A new approach to the determination of air kerma using primary-standard cavity ionization chambers

    NASA Astrophysics Data System (ADS)

    Burns, D. T.

    2006-02-01

    A consistent formalism is presented using Monte Carlo calculations to determine the reference air kerma from the measured energy deposition in a primary-standard cavity ionization chamber. A global approach avoiding the use of cavity ionization theory is discussed and its limitations shown in relation to the use of the recommended value for W. The role of charged-particle equilibrium is outlined and the consequent requirements placed on the calculations are detailed. Values for correction factors are presented for the BIPM air-kerma standard for 60Co, making use of the Monte Carlo code PENELOPE, a detailed geometrical model of the BIPM 60Co source and event-by-event electron transport. While the wall correction factor kwall = 1.0012(2) is somewhat lower than the existing value, the axial non-uniformity correction kan = 1.0027(3) is significantly higher. The use of a point source in the evaluation of kan is discussed. A comparison is made of the calculated dose ratio with the Bragg-Gray and Spencer-Attix stopping-power ratios, the results indicating a preference for the Bragg-Gray approach in this particular case. A change to the recommended value for W of up to 2 parts in 103 is discussed. The uncertainties arising from the geometrical models, the use of phase-space files, the radiation transport algorithms and the underlying radiation interaction coefficients are estimated.

  8. Dependence with air density of the response of the PTW SourceCheck ionization chamber for low energy brachytherapy sources

    SciTech Connect

    Tornero-López, Ana M.; Guirado, Damián; Ruiz-Arrebola, Samuel; Perez-Calatayud, Jose; Simancas, Fernando; Lallena, Antonio M.; Gazdic-Santic, Maja

    2013-12-15

    Purpose: Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is corrected to standard atmospheric conditions using the usual temperature and pressure correction factor. Nevertheless, when assessing low energy sources, the ionization chambers may not fulfill that condition and a residual density dependence still remains after correction. In this work, the authors examined the behavior of the PTW 34051 SourceCheck ionization chamber when measuring the air kerma strength of {sup 125}I seeds.Methods: Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for {sup 125}I selectSeed{sup TM} brachytherapy sources were performed inside a pressure chamber and varying the pressure in a range from 747 to 1040 hPa (560 to 780 mm Hg). The temperature and relative humidity were kept basically constant. An analogous experiment was performed by taking measurements at different altitudes above sea level.Results: Contrary to other well-known ionization chambers, like the HDR1000 PLUS, in which the temperature-pressure correction factor overcorrects the measurements, in the SourceCheck ionization chamber they are undercorrected. At a typical atmospheric situation of 933 hPa (700 mm Hg) and 20 °C, this undercorrection turns out to be 1.5%. Corrected measurements show a residual linear dependence on the density and, as a consequence, an additional density dependent correction must be applied. The slope of this residual linear density dependence is different for each SourceCheck chamber investigated. The results obtained by taking measurements at different altitudes are compatible with those obtained with the pressure chamber.Conclusions: Variations of the altitude and

  9. Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer

    SciTech Connect

    Crosbie, Jeffrey C.; Rogers, Peter A. W.; Stevenson, Andrew W.; Hall, Christopher J.; Lye, Jessica E.; Nordstroem, Terese; Midgley, Stewart M.; Lewis, Robert A.

    2013-06-15

    Purpose: Novel, preclinical radiotherapy modalities are being developed at synchrotrons around the world, most notably stereotactic synchrotron radiation therapy and microbeam radiotherapy at the European Synchrotron Radiation Facility in Grenoble, France. The imaging and medical beamline (IMBL) at the Australian Synchrotron has recently become available for preclinical radiotherapy and imaging research with clinical trials, a distinct possibility in the coming years. The aim of this present study was to accurately characterize the synchrotron-generated x-ray beam for the purposes of air kerma-based absolute dosimetry. Methods: The authors used a theoretical model of the energy spectrum from the wiggler source and validated this model by comparing the transmission through copper absorbers (0.1-3.0 mm) against real measurements conducted at the beamline. The authors used a low energy free air ionization chamber (LEFAC) from the Australian Radiation Protection and Nuclear Safety Agency and a commercially available free air chamber (ADC-105) for the measurements. The dimensions of these two chambers are different from one another requiring careful consideration of correction factors. Results: Measured and calculated half value layer (HVL) and air kerma rates differed by less than 3% for the LEFAC when the ion chamber readings were corrected for electron energy loss and ion recombination. The agreement between measured and predicted air kerma rates was less satisfactory for the ADC-105 chamber, however. The LEFAC and ADC measurements produced a first half value layer of 0.405 {+-} 0.015 and 0.412 {+-} 0.016 mm Cu, respectively, compared to the theoretical prediction of 0.427 {+-} 0.012 mm Cu. The theoretical model based upon a spectrum calculator derived a mean beam energy of 61.4 keV with a first half value layer of approximately 30 mm in water. Conclusions: The authors showed in this study their ability to verify the predicted air kerma rate and x-ray attenuation

  10. Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam

    SciTech Connect

    Groetz, J.-E. Mavon, C.; Fromm, M.; Ounoughi, N.; Belafrites, A.

    2014-08-15

    We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays.

  11. Multi-anode ionization chamber

    DOEpatents

    Bolotnikov, Aleksey E.; Smith, Graham; Mahler, George J.; Vanier, Peter E.

    2010-12-28

    The present invention includes a high-energy detector having a cathode chamber, a support member, and anode segments. The cathode chamber extends along a longitudinal axis. The support member is fixed within the cathode chamber and extends from the first end of the cathode chamber to the second end of the cathode chamber. The anode segments are supported by the support member and are spaced along the longitudinal surface of the support member. The anode segments are configured to generate at least a first electrical signal in response to electrons impinging thereon.

  12. Ionization-chamber smoke detector system

    DOEpatents

    Roe, Robert F.

    1976-10-19

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system is designed to reduce false alarms caused by fluctuations in ambient temperature. Means are provided for periodically firing the gas discharge triode and each time recording the triggering voltage required. A computer compares each triggering voltage with its predecessor. The computer is programmed to energize an alarm if the difference between the two compared voltages is a relatively large value indicative of particulates in the measuring chamber and to disregard smaller differences typically resulting from changes in ambient temperature.

  13. HATCH CONNECTING TEMPERED AIR CHAMBER AND HOT AIR CHAMBER OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    HATCH CONNECTING TEMPERED AIR CHAMBER AND HOT AIR CHAMBER OF PLENUM WITH ATTACHED DRAFT REGULATOR. - Hot Springs National Park, Bathhouse Row, Superior Bathhouse: Mechanical & Piping Systems, State Highway 7, 1 mile north of U.S. Highway 70, Hot Springs, Garland County, AR

  14. SU-E-T-552: Monte Carlo Calculation of Correction Factors for a Free-Air Ionization Chamber in Support of a National Air-Kerma Standard for Electronic Brachytherapy

    SciTech Connect

    Mille, M; Bergstrom, P

    2015-06-15

    Purpose: To use Monte Carlo radiation transport methods to calculate correction factors for a free-air ionization chamber in support of a national air-kerma standard for low-energy, miniature x-ray sources used for electronic brachytherapy (eBx). Methods: The NIST is establishing a calibration service for well-type ionization chambers used to characterize the strength of eBx sources prior to clinical use. The calibration approach involves establishing the well-chamber’s response to an eBx source whose air-kerma rate at a 50 cm distance is determined through a primary measurement performed using the Lamperti free-air ionization chamber. However, the free-air chamber measurements of charge or current can only be related to the reference air-kerma standard after applying several corrections, some of which are best determined via Monte Carlo simulation. To this end, a detailed geometric model of the Lamperti chamber was developed in the EGSnrc code based on the engineering drawings of the instrument. The egs-fac user code in EGSnrc was then used to calculate energy-dependent correction factors which account for missing or undesired ionization arising from effects such as: (1) attenuation and scatter of the x-rays in air; (2) primary electrons escaping the charge collection region; (3) lack of charged particle equilibrium; (4) atomic fluorescence and bremsstrahlung radiation. Results: Energy-dependent correction factors were calculated assuming a monoenergetic point source with the photon energy ranging from 2 keV to 60 keV in 2 keV increments. Sufficient photon histories were simulated so that the Monte Carlo statistical uncertainty of the correction factors was less than 0.01%. The correction factors for a specific eBx source will be determined by integrating these tabulated results over its measured x-ray spectrum. Conclusion: The correction factors calculated in this work are important for establishing a national standard for eBx which will help ensure that dose

  15. The GODDESS ionization chamber: developing robust windows

    NASA Astrophysics Data System (ADS)

    Blanchard, Rose; Baugher, Travis; Cizewski, Jolie; Pain, Steven; Ratkiewicz, Andrew; Goddess Collaboration

    2015-10-01

    Reaction studies of nuclei far from stability require high-efficiency arrays of detectors and the ability to identify beam-like particles, especially when the beam is a cocktail beam. The Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies (GODDESS) is made up of the Oak Ridge-Rutgers University Barrel Array (ORRUBA) of silicon detectors for charged particles inside of the gamma-ray detector array Gammasphere. A high-rate ionization chamber is being developed to identify beam-like particles. Consisting of twenty-one alternating anode and cathode grids, the ionization chamber sits downstream of the target chamber and is used to measure the energy loss of recoiling ions. A critical component of the system is a thin and robust mylar window which serves to separate the gas-filled ionization chamber from the vacuum of the target chamber with minimal energy loss. After construction, windows were tested to assure that they would not break below the required pressure, causing harm to the wire grids. This presentation will summarize the status of the ionization chamber and the results of the first tests with beams. This work is supported in part by the U.S. Department of Energy and National Science Foundation.

  16. Making MUSIC: A multiple sampling ionization chamber

    NASA Astrophysics Data System (ADS)

    Shumard, B.; Henderson, D. J.; Rehm, K. E.; Tang, X. D.

    2007-08-01

    A multiple sampling ionization chamber (MUSIC) was developed for use in conjunction with the Atlas scattering chamber (ATSCAT). This chamber was developed to study the (α, p) reaction in stable and radioactive beams. The gas filled ionization chamber is used as a target and detector for both particles in the outgoing channel (p + beam particles for elastic scattering or p + residual nucleus for (α, p) reactions). The MUSIC detector is followed by a Si array to provide a trigger for anode events. The anode events are gated by a gating grid so that only (α, p) reactions where the proton reaches the Si detector result in an anode event. The MUSIC detector is a segmented ionization chamber. The active length of the chamber is 11.95 in. and is divided into 16 equal anode segments (3.5 in. × 0.70 in. with 0.3 in. spacing between pads). The dead area of the chamber was reduced by the addition of a Delrin snout that extends 0.875 in. into the chamber from the front face, to which a mylar window is affixed. 0.5 in. above the anode is a Frisch grid that is held at ground potential. 0.5 in. above the Frisch grid is a gating grid. The gating grid functions as a drift electron barrier, effectively halting the gathering of signals. Setting two sets of alternating wires at differing potentials creates a lateral electric field which traps the drift electrons, stopping the collection of anode signals. The chamber also has a reinforced mylar exit window separating the Si array from the target gas. This allows protons from the (α, p) reaction to be detected. The detection of these protons opens the gating grid to allow the drift electrons released from the ionizing gas during the (α, p) reaction to reach the anode segment below the reaction.

  17. Nuclear Fission Investigation with Twin Ionization Chamber

    SciTech Connect

    Zeynalova, O.; Zeynalov, Sh.; Nazarenko, M.; Hambsch, F.-J.; Oberstedt, S.

    2011-11-29

    The purpose of the present paper was to report the recent results, obtained in development of digital pulse processing mathematics for prompt fission neutron (PFN) investigation using twin ionization chamber (TIC) along with fast neutron time-of-flight detector (ND). Due to well known ambiguities in literature (see refs. [4, 6, 9 and 11]), concerning a pulse induction on TIC electrodes by FF ionization, we first presented detailed mathematical analysis of fission fragment (FF) signal formation on TIC anode. The analysis was done using Ramo-Shockley theorem, which gives relation between charged particle motion between TIC electrodes and so called weighting potential. Weighting potential was calculated by direct numerical solution of Laplace equation (neglecting space charge) for the TIC geometry and ionization, caused by FF. Formulae for grid inefficiency (GI) correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and discussed.

  18. 41. AUXILIARY CHAMBER, CONCRETE ENCLOSURE CHAMBER AIR LOCK (EXTERIOR), LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    41. AUXILIARY CHAMBER, CONCRETE ENCLOSURE CHAMBER AIR LOCK (EXTERIOR), LOOKING NORTHEAST FROM SOUTHWEST CORNER (LOCATION AAA) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  19. Characterization of a homemade ionization chamber for radiotherapy beams.

    PubMed

    Neves, Lucio P; Perini, Ana P; dos Santos, Gelson P; Xavier, Marcos; Khoury, Helen J; Caldas, Linda V E

    2012-07-01

    A homemade cylindrical ionization chamber was studied for routine use in therapy beams of (60)Co and X-rays. Several characterization tests were performed: leakage current, saturation, ion collection efficiency, polarity effect, stability, stabilization time, chamber orientation and energy dependence. All results obtained were within international recommendations. Therefore the homemade ionization chamber presents usefulness for routine dosimetric procedures in radiotherapy beams. PMID:22153889

  20. Characterization tests of a homemade ionization chamber in mammography standard radiation beams

    NASA Astrophysics Data System (ADS)

    Silva, J. O.; Nonato, F. B. C.; Caldas, L. V. E.

    2014-02-01

    A mammography homemade ionization chamber was developed to be applied for mammography energy range dosimetry. This chamber has a sensitive volume of 6 cm3 and is made of a Lucite body and graphite coated collecting electrode. Characteristics such as saturation, ion collection efficiency, linearity of chamber response versus air kerma rate and energy dependence were determined. The results obtained with the mammography homemade ionization chamber are within the limits stated in international recommendations. This chamber can be used in quality control programs in the diagnostic radiology area. All measurements were carried out at the Calibration Laboratory of IPEN.

  1. Investigation of electric field distribution on FAC-IR-300 ionization chamber

    NASA Astrophysics Data System (ADS)

    Mohammadi, S. M.; Tavakoli-Anbaran, H.; Zeinali, H. Z.

    2016-07-01

    One of the important parameters for establishing charge particle equilibrium (CPE) conditions of free-air ionization chamber is an electric field distribution. In this paper, electric field distribution inside the ionization chamber was investigated by finite element method. For this purpose, the effects of adding guard plate and guard strips on the electric field distribution in the ionization chamber were studied. it is necessary to apply a lead box around the ionization chamber body to avoid of scattered radiation effects on the ionization chamber operation, but the lead box changes the electric field distribution. In the following, the effect of lead box on the electric field distribution was studied. Finally, electric field distribution factor (kfield) was calculated by the simulation. The results of the simulation showed that presence of the guard plate and guard strips, and applying a suitable potential to lead box, a convergence of kfield to 1 was achieved.

  2. Development of an optical digital ionization chamber

    SciTech Connect

    Turner, J.E.; Hunter, S.R.; Hamm, R.N.; Wright, H.A.; Hurst, G.S.; Gibson, W.A.

    1988-01-01

    We are developing a new device for optically detecting and imaging the track of a charged particle in a gas. The electrons in the particle track are made to oscillate rapidly by the application of an external, short-duration, high-voltage, RF electric field. The excited electrons produce additional ionization and electronic excitation of the gas molecules in their immediate vicinity, leading to copious light emission (fluorescence) from the selected gas, allowing the location of the electrons along the track to be determined. Two digital cameras simultaneously scan the emitted light across two perpendicular planes outside the chamber containing gas. The information thus obtained for a given track can be used to infer relevant quantities for microdosimetry and dosimetry, e.g., energy deposited, LET, and track structure in the gas. The design of such a device now being constructed and methods of obtaining the dosimetric data from the digital output will be described. 4 refs., 4 figs.

  3. Gas turbine combustion chamber with air scoops

    SciTech Connect

    Mumford, S.E.; Smed, J.P.

    1989-12-19

    This patent describes a gas turbine combustion chamber. It comprises: means for admission of fuel to the upstream end thereof and discharge of hot gases from the downstream end thereof, and a combustion chamber wall, having an outer surface, with apertures therethrough, and air scoops provided through the apertures to direct air into the combustion chamber.

  4. A new ring-shaped graphite monitor ionization chamber

    NASA Astrophysics Data System (ADS)

    Yoshizumi, M. T.; Caldas, L. V. E.

    2010-07-01

    A ring-shaped monitor ionization chamber was developed at the Instituto de Pesquisas Energéticas e Nucleares. This ionization chamber presents an entrance window of aluminized polyester foil. The guard ring and collecting electrode are made of graphite coated Lucite plates. The main difference between this new ionization chamber and commercial monitor chambers is its ring-shaped design. The new monitor chamber has a central hole, allowing the passage of the direct radiation beam without attenuation; only the penumbra radiation is measured by the sensitive volume. This kind of ionization chamber design has already been tested, but using aluminium electrodes. By changing the electrode material from aluminium to a graphite coating, an improvement in the chamber response stability was expected. The pre-operational tests, as saturation curve, recombination loss and polarity effect showed satisfactory results. The repeatability and the long-term stability tests were also evaluated, showing good agreement with international recommendations.

  5. Practical method for determination of air kerma by use of an ionization chamber toward construction of a secondary X-ray field to be used in clinical examination rooms.

    PubMed

    Maehata, Itsumi; Hayashi, Hiroaki; Kimoto, Natsumi; Takegami, Kazuki; Okino, Hiroki; Kanazawa, Yuki; Tominaga, Masahide

    2016-07-01

    We propose a new practical method for the construction of an accurate secondary X-ray field using medical diagnostic X-ray equipment. For accurate measurement of the air kerma of an X-ray field, it is important to reduce and evaluate the contamination rate of scattered X-rays. To determine the rate quantitatively, we performed the following studies. First, we developed a shield box in which an ionization chamber could be set at an inner of the box to prevent detection of the X-rays scattered from the air. In addition, we made collimator plates which were placed near the X-ray source for estimation of the contamination rate by scattered X-rays from the movable diaphragm which is a component of the X-ray equipment. Then, we measured the exposure dose while changing the collimator plates, which had diameters of 25-90 mm(ϕ). The ideal value of the exposure dose was derived mathematically by extrapolation to 0 mm(ϕ). Tube voltages ranged from 40 to 130 kV. Under these irradiation conditions, we analyzed the contamination rate by the scattered X-rays. We found that the contamination rates were less than 1.7 and 2.3 %, caused by air and the movable diaphragm, respectively. The extrapolated value of the exposure dose has been determined to have an uncertainty of 0.7 %. The ionization chamber used in this study was calibrated with an accuracy of 5 %. Using this kind of ionization chamber, we can construct a secondary X-ray field with an uncertainty of 5 %. PMID:26994011

  6. The FiR 1 photon beam model adjustment according to in-air spectrum measurements with the Mg(Ar) ionization chamber.

    PubMed

    Koivunoro, H; Schmitz, T; Hippeläinen, E; Liu, Y-H; Serén, T; Kotiluoto, P; Auterinen, I; Savolainen, S

    2014-06-01

    The mixed neutron-photon beam of FiR 1 reactor is used for boron-neutron capture therapy (BNCT) in Finland. A beam model has been defined for patient treatment planning and dosimetric calculations. The neutron beam model has been validated with an activation foil measurements. The photon beam model has not been thoroughly validated against measurements, due to the fact that the beam photon dose rate is low, at most only 2% of the total weighted patient dose at FiR 1. However, improvement of the photon dose detection accuracy is worthwhile, since the beam photon dose is of concern in the beam dosimetry. In this study, we have performed ionization chamber measurements with multiple build-up caps of different thickness to adjust the calculated photon spectrum of a FiR 1 beam model. PMID:24588987

  7. A Fast Ionization Chamber for GODDESS

    NASA Astrophysics Data System (ADS)

    Lumb, R. T.; Lipman, A. S.; Baugher, T.; Cizewski, J. A.; Ratkiewicz, A.; Pain, S. D.; Kozub, R. L.

    2014-09-01

    Transfer reactions are among the main methods used in nuclear physics to probe the structure of nuclei. Such information is needed to constrain nuclear models and to understand various nucleosynthesis processes. In many cases, the nuclear level densities are too high to be resolved in transfer reactions via charged particle detection alone. This problem and issues arising from contaminants in radioactive beams can be addressed by using particle- γ coincidence techniques along with heavy recoil identification in inverse kinematics. A device to accomplish these tasks is Gammasphere ORRUBA: Dual Detectors for Experimental Structure Studies (GODDESS), currently being commissioned for the ATLAS facility at ANL. We are currently building a compact, tilted grid ionization chamber for GODDESS to detect and identify beam-like recoils near zero degrees in the lab. The tilt (30 degrees off normal to the beam) helps the ion pairs to be detected quickly, after drifting only a short distance away from the beam axis. This reduces the response time, allowing counting rates of ~500,000/s. The design and current status of the project will be presented. Research supported by the U. S. DOE.

  8. The Analysis of Ionization Chambers Used for Detecting Smoke Particles

    NASA Astrophysics Data System (ADS)

    Turlej, Z. (Bish).

    Ionization type cells using a radioactive source of primary ions have been used as fire detectors for many years. They have proven sufficiently sensitive to give an alarm when exposed to the relatively small concentration of smoke particles that occur during the early stages of combustion when control of a fire is still possible. In this work the charging of smoke particles in ionization chambers such as typically employed in ionization smoke detectors are investigated theoretically and experimentally. The ionization chambers investigated in this work have parallel plate and spherical electrode geometries. In the absence of smoke particles, the ionization chambers were operated at some ambient electrode current, which depends upon the ion generation rate, the electrode geometries, the potential difference between the electrodes, and the thermodynamic properties of the gas within the chamber volume. When smoke particles are introduced into the ionization chamber they act as an additional sink for the ions, so that the ion current is reduced. The smoke particles in the experiment performed in this work were transferred from the particle generator to the volume surrounding the ionization chamber and allowed to diffuse inside the ionization chamber. An Aitken nuclei counter was employed to measure the concentration of smoke particles inside the ionization chamber. The electric current flowing through the ionization chamber was recorded as a function of time and concentration of the smoke particles inside the chamber. The current loss due to the particles present inside the chamber was calculated and compared with the experimental results. It was found that at the certain level of ambient electrode current, the current loss due to the smoke particles assumes a maximum value. This optimum operating electrode current was predicted by the mathematical model employed in this work. In the light of this model experimental ionization chambers of both parallel and spherical

  9. Radiation damage to tetramethlysilane and tetramethlygermanium ionization chambers

    NASA Astrophysics Data System (ADS)

    Hoshi, Y.; Higuchi, M.; Oyama, K.; Akaishi, H.; Yuta, H.; Abe, K.; Hasegawa, K.; Suekane, F.; Nagamine, T.; Kawamura, N.

    1994-08-01

    Two detector media suitable for a warm liquid, ionization chamber filled with tetramethylsilane(TMS) and tetramethylgermanium(TMG) were exposed to y radiation from a (sup 60)Co source up to dose 579Gray and 902Gray, respectively. The electron lifetimes and the free ion yields were measured as a function of accumulated radiation dose. A similar behavior of the electron lifetimes and the free ion yields with increasing radiation dose was observed between the TMS and TMG ionization chambers.

  10. Absolute dosimetry on a dynamically scanned sample for synchrotron radiotherapy using graphite calorimetry and ionization chambers

    NASA Astrophysics Data System (ADS)

    Lye, J. E.; Harty, P. D.; Butler, D. J.; Crosbie, J. C.; Livingstone, J.; Poole, C. M.; Ramanathan, G.; Wright, T.; Stevenson, A. W.

    2016-06-01

    The absolute dose delivered to a dynamically scanned sample in the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter anticipated to be established as a primary standard for synchrotron dosimetry. The calorimetry was compared to measurements using a free-air chamber (FAC), a PTW 31 014 Pinpoint ionization chamber, and a PTW 34 001 Roos ionization chamber. The IMBL beam height is limited to approximately 2 mm. To produce clinically useful beams of a few centimetres the beam must be scanned in the vertical direction. In practice it is the patient/detector that is scanned and the scanning velocity defines the dose that is delivered. The calorimeter, FAC, and Roos chamber measure the dose area product which is then converted to central axis dose with the scanned beam area derived from Monte Carlo (MC) simulations and film measurements. The Pinpoint chamber measures the central axis dose directly and does not require beam area measurements. The calorimeter and FAC measure dose from first principles. The calorimetry requires conversion of the measured absorbed dose to graphite to absorbed dose to water using MC calculations with the EGSnrc code. Air kerma measurements from the free air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. The two ionization chambers are secondary standards requiring calibration with kilovoltage x-ray tubes. The Roos and Pinpoint chambers were calibrated against the Australian primary standard for air kerma at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Agreement of order 2% or better was obtained between the calorimetry and ionization chambers. The FAC measured a dose 3–5% higher than the calorimetry, within the stated uncertainties.

  11. Absolute dosimetry on a dynamically scanned sample for synchrotron radiotherapy using graphite calorimetry and ionization chambers.

    PubMed

    Lye, J E; Harty, P D; Butler, D J; Crosbie, J C; Livingstone, J; Poole, C M; Ramanathan, G; Wright, T; Stevenson, A W

    2016-06-01

    The absolute dose delivered to a dynamically scanned sample in the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter anticipated to be established as a primary standard for synchrotron dosimetry. The calorimetry was compared to measurements using a free-air chamber (FAC), a PTW 31 014 Pinpoint ionization chamber, and a PTW 34 001 Roos ionization chamber. The IMBL beam height is limited to approximately 2 mm. To produce clinically useful beams of a few centimetres the beam must be scanned in the vertical direction. In practice it is the patient/detector that is scanned and the scanning velocity defines the dose that is delivered. The calorimeter, FAC, and Roos chamber measure the dose area product which is then converted to central axis dose with the scanned beam area derived from Monte Carlo (MC) simulations and film measurements. The Pinpoint chamber measures the central axis dose directly and does not require beam area measurements. The calorimeter and FAC measure dose from first principles. The calorimetry requires conversion of the measured absorbed dose to graphite to absorbed dose to water using MC calculations with the EGSnrc code. Air kerma measurements from the free air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. The two ionization chambers are secondary standards requiring calibration with kilovoltage x-ray tubes. The Roos and Pinpoint chambers were calibrated against the Australian primary standard for air kerma at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Agreement of order 2% or better was obtained between the calorimetry and ionization chambers. The FAC measured a dose 3-5% higher than the calorimetry, within the stated uncertainties. PMID:27192396

  12. RADIATION MONITOR CONTAINING TWO CONCENTRIC IONIZATION CHAMBERS AND MEANS FOR INSULATING THE SEPARATE CHAMBERS

    DOEpatents

    Braestrup, C.B.; Mooney, R.T.

    1964-01-21

    This invention relates to a portable radiation monitor containing two concentric ionization chambers which permit the use of standard charging and reading devices. It is particularly adapted as a personnel x-ray dosimeter and to this end comprises a small thin walled, cylindrical conductor forming an inner energy dependent chamber, a small thin walled, cylindrical conductor forming an outer energy independent chamber, and polymeric insulation means which insulates said chambers from each other and holds the chambers together with exposed connections in a simple, trouble-free, and compact assembly substantially without variation in directional response. (AEC)

  13. Construction and commissioning of a position-sensitive ionization chamber

    NASA Astrophysics Data System (ADS)

    Kwag, M. S.; Chae, K. Y.; Cha, S. M.; Kim, A.; Kim, M. J.; Lee, E. J.; Lee, J. H.

    2016-05-01

    A position-sensitive ionization chamber has been constructed and commissioned at the Physics Department of Sungkyunkwan University to extract position information on incident charged particles for future nuclear reaction measurements. By utilizing the newly-designed position-sensitive anodes and the previously-commissioned portable gas-filled ionization chamber by Chae et al., position information on incident particles could be obtained. The device was tested with an 241Am α-emitting source, and the standard deviation of the fitted Gaussian distribution was measured to be 1.76 mm when a collimator with a 2 mm hole was used.

  14. The response of ionization chambers to relativistic heavy nuclei

    NASA Technical Reports Server (NTRS)

    Newport, B. J.; Stone, E. C.; Waddington, C. J.; Binns, W. R.; Fixsen, D. J.; Garrard, T. L.; Grimm, G.; Israel, M. H.; Klarmann, J.

    1985-01-01

    The LBL Bevalac for the Heavy Nuclei Experiment on HEAO-3, compared the response of a set of laboratory ionization chambers to beams of 26Fe, 36Kr, 54Xe, 67 Ho, and 79Au nuclei at maximum energies ranging from 1666 MeV/amu for Fe to 1049 MeV/amu for Au. The response of these chambers shows a significant deviation from the expected energy dependence, but only a slight deviation from Z sq scaling.

  15. Stability of A-150 plastic ionization chamber response over a ~30 year period

    SciTech Connect

    Kroc, Thomas K.; Lennox, Arlene J.; /Fermilab

    2007-08-01

    At the NIU Institute for Neutron Therapy at Fermilab, the clinical tissue-equivalent ionization chamber response is measured every treatment day using a cesium source that was configured to match readings obtained at the National Bureau of Standards. Daily measurements are performed in air using the air-to-tissue dose conversion factors given in AAPM Report no. 7. The measured exposure calibration factors have been tabulated and graphed as a function of time from 1978 to present. For A-150 plastic ionization chambers, these factors exhibit a sinusoidal variation with a period of approximately one year and amplitude of {+-} 1%. This variation, attributable to the hygroscopic nature of A-150 plastic, is correlated with the relative humidity of the facility, and is greater than the humidity corrections for gas described in the literature. Our data suggest that chamber calibration should be performed at least weekly to accommodate these variations.

  16. Direct experimental determination of Frisch grid inefficiency in ionization chamber

    NASA Astrophysics Data System (ADS)

    Khriachkov, V. A.; Goverdovski, A. A.; Ketlerov, V. V.; Mitrofanov, V. F.; Semenova, N. N.

    1997-07-01

    The present work describes the method of direct experimental determination of the Frisch grid inefficiency in an ionization chamber. The method is based on analysis of the anode signal after Waveform Digitizer. It is shown that the calculated grid inefficiency value can differ much from the measured ones.

  17. A multiple sampling ionization chamber for the External Target Facility

    NASA Astrophysics Data System (ADS)

    Zhang, X. H.; Tang, S. W.; Ma, P.; Lu, C. G.; Yang, H. R.; Wang, S. T.; Yu, Y. H.; Yue, K.; Fang, F.; Yan, D.; Zhou, Y.; Wang, Z. M.; Sun, Y.; Sun, Z. Y.; Duan, L. M.; Sun, B. H.

    2015-09-01

    A multiple sampling ionization chamber used as a particle identification device for high energy heavy ions has been developed for the External Target Facility. The performance of this detector was tested with a 239Pu α source and RI beams. A Z resolution (FWHM) of 0.4-0.6 was achieved for nuclear fragments of 18O at 400 AMeV.

  18. Source geometry factors for HDR 192Ir brachytherapy secondary standard well-type ionization chamber calibrations

    NASA Astrophysics Data System (ADS)

    Shipley, D. R.; Sander, T.; Nutbrown, R. F.

    2015-03-01

    Well-type ionization chambers are used for measuring the source strength of radioactive brachytherapy sources before clinical use. Initially, the well chambers are calibrated against a suitable national standard. For high dose rate (HDR) 192Ir, this calibration is usually a two-step process. Firstly, the calibration source is traceably calibrated against an air kerma primary standard in terms of either reference air kerma rate or air kerma strength. The calibrated 192Ir source is then used to calibrate the secondary standard well-type ionization chamber. Calibration laboratories are usually only equipped with one type of HDR 192Ir source. If the clinical source type is different from that used for the calibration of the well chamber at the standards laboratory, a source geometry factor, ksg, is required to correct the calibration coefficient for any change of the well chamber response due to geometric differences between the sources. In this work we present source geometry factors for six different HDR 192Ir brachytherapy sources which have been determined using Monte Carlo techniques for a specific ionization chamber, the Standard Imaging HDR 1000 Plus well chamber with a type 70010 HDR iridium source holder. The calculated correction factors were normalized to the old and new type of calibration source used at the National Physical Laboratory. With the old Nucletron microSelectron-v1 (classic) HDR 192Ir calibration source, ksg was found to be in the range 0.983 to 0.999 and with the new Isodose Control HDR 192Ir Flexisource ksg was found to be in the range 0.987 to 1.004 with a relative uncertainty of 0.4% (k = 2). Source geometry factors for different combinations of calibration sources, clinical sources, well chambers and associated source holders, can be calculated with the formalism discussed in this paper.

  19. HPXe ionization chambers for γ spectrometry at room temperature

    NASA Astrophysics Data System (ADS)

    Ottini-Hustache, S.; Monsanglant-Louvet, C.; Haan, S.; Dmitrenko, V.; Grachev, V.; Ulin, S.

    2004-01-01

    High pressure xenon (HPXe) ionization chambers exhibit many characteristics which make them particularly suitable for industrial γ spectrometry at room or higher temperature. The use of a gas as detection medium allows one to reach very large effective volumes and makes these chambers relatively insensitive to radiation damage. Further, the high atomic number of xenon ( Z=54) enhances the total absorption of incident photons and provides, combined to high pressure, a good enough detection efficiency with respect to solid state detectors. Furthermore, such ionization chambers with Frisch grid appear to be very stable over wide periods (e.g. a research prototype has been used aboard MIR orbital station for several years) and temperature range (up to 180°), without maintenance. The characteristics of different prototypes are presented. Their detection efficiency and energy resolution are studied as a function of incident γ ray energy. New developments in electronics and signal processing are also investigated to improve their performances.

  20. Microwave remote sensing of ionized air.

    SciTech Connect

    Liao, S.; Gopalsami, N.; Heifetz, A.; Elmer, T.; Fiflis, P.; Koehl, E. R.; Chien, H. T.; Raptis, A. C.

    2011-07-01

    We present observations of microwave scattering from ambient room air ionized with a negative ion generator. The frequency dependence of the radar cross section of ionized air was measured from 26.5 to 40 GHz (Ka-band) in a bistatic mode with an Agilent PNA-X series (model N5245A) vector network analyzer. A detailed calibration scheme is provided to minimize the effect of the stray background field and system frequency response on the target reflection. The feasibility of detecting the microwave reflection from ionized air portends many potential applications such as remote sensing of atmospheric ionization and remote detection of radioactive ionization of air.

  1. Poster — Thur Eve — 24: Commissioning and preliminary measurements using an Attix-style free air ionization chamber for air kerma measurements on the BioMedical Imaging and Therapy beamlines at the Canadian Light Source

    SciTech Connect

    Anderson, D; McEwen, M; Shen, H; Siegbahn, EA; Fallone, BG; Warkentin, B

    2014-08-15

    Synchrotron facilities, including the Canadian Light Source (CLS), provide opportunities for the development of novel imaging and therapy applications. A vital step progressing these applications toward clinical trials is the availability of accurate dosimetry. In this study, a refurbished Attix-style (cylindrical) free air chamber (FAC) is tested and used for preliminary air kerma measurements on the two BioMedical Imaging and Therapy (BMIT) beamlines at the CLS. The FAC consists of a telescoping chamber that relies on a difference measurement of collected charge in expanded and collapsed configurations. At the National Research Council's X-ray facility, a Victoreen Model 480 FAC was benchmarked against two primary standard FACs. The results indicated an absolute accuracy at the 0.5% level for energies between 60 and 150 kVp. A series of measurements were conducted on the small, non-uniform X-ray beams of the 05B1-1 (∼8 – 100 keV) and 05ID-2 (∼20 – 200 keV) beamlines for a variety of energies, filtrations and beam sizes. For the 05B1-1 beam with 1.1 mm of Cu filtration, recombination corrections of less than 5 % could only be achieved for field sizes no greater than 0.5 mm × 0.6 mm (corresponding to an air kerma rate of ∼ 57 Gy/min). Ionic recombination thus presents a significant challenge to obtaining accurate air kerma rate measurements using this FAC in these high intensity beams. Future work includes measurements using a smaller aperture to sample a smaller and thus more uniform beam area, as well as experimental and Monte Carlo-based investigation of correction factors.

  2. The response of ionization chambers to relativistic heavy nuclei

    NASA Technical Reports Server (NTRS)

    Newport, B. J.; Stone, E. C.; Waddington, C. J.; Binns, W. R.; Fixsen, D. J.; Garrard, T. L.; Grimm, G.; Israel, M. H.; Klarmann, J.

    1985-01-01

    As part of a recent calibration at the LBL Bevalac for the Heavy Nuclei Experiment on HEAO-3, the response of a set of laboratory ionization chambers were compared to beams of 26Fe, 36 Kr, 54Xe, 67 Ho, and 79 Au nuclei at maximum energies ranging from 1666 MeV/amu for Fe to 1049 MeV/amu for Au. The response of these chambers shows a significant deviation from the expected energy dependence, but only a slight deviation from Z squared scaling.

  3. Ionization chamber for measurements of high-level tritium gas

    SciTech Connect

    Carstens, D.H.W.; David, W.R.

    1980-01-01

    The construction and calibration of a simple ionization-chamber apparatus for measurement of high level tritium gas is described. The apparatus uses an easily constructed but rugged chamber containing the unknown gas and an inexpensive digital multimeter for measuring the ion current. The equipment after calibration is suitable for measuring 0.01 to 100% tritium gas in hydrogen-helium mixes with an accuracy of a few percent. At both the high and low limits of measurements deviations from the predicted theoretical current are observed. These are briefly discussed.

  4. Ionization chamber response in intensity-modulated radiotherapy beams

    NASA Astrophysics Data System (ADS)

    Markovic, Alexander

    The response of ionization chambers in IMRT fields has been investigated. Differences between measured and calculated values of average chamber dose associated with chamber position, volume averaging and low monitor unit effects were assessed with regards to patient specific IMRT quality assurance (QA). Calculations were performed with a commercially available treatment planning system (TPS). Inaccuracy of chamber positioning during QA was shown to adversely affect measurements due to steep dose gradients in the vicinity of penumbras generated by MLC leaf-tips. The measurement error was inversely related to chamber size. The Exradin A12 chamber showed errors of 4.1% and 9.6% in its short (0.61 cm) and long dimensions (2.2 cm) while the Exradin T14 Microchamber showed an error of 15.4% in its useful dimension (0.1 cm). A QA phantom was designed to improve positional accuracy and reproducibility. Setup reproducibility results showed a standard deviation of 0.93 and 1.1 mm in the longitudinal and lateral directions through the use of this phantom. The effect of leaf shadowing of a measurement chamber during IMRT QA was correlated to the error in point dose results. The error between calculation and measurement increased with a higher degree of chamber shadowing, which indicated that point dose results could be improved by placing the chamber in areas where the effect of shadowing was minimized. A linear systems approach was utilized to determine the chamber response function of three chambers for subsequent implementation in a TPS. Improvement in dose calculation accuracy was expected. The response functions were used in a TPS to design special chambers that had the same averaging properties as exhibited during water phantom measurements. Results were improved over using a chamber represented by a perfect cylinder, but spatial resolution limitations prevented optimal results. Another chamber design that was based on a heuristic approach yielded desired results with

  5. Development of a portable gas-filled ionization chamber

    NASA Astrophysics Data System (ADS)

    Chae, K. Y.; Cha, S. M.; Gwak, M. S.

    2014-02-01

    A new portable gas-filled ionization chamber has been designed and constructed at the Physics Department of Sung Kyun Kwan University. To overcome the maximum count rate of ˜105 particles per second of a conventional ionization chamber, which utilizes a Frisch grid, and to enhance the portability of a detector, we adopted the design of multiple electrodes and modified it from the original designs by Kimura et al. and Chae et al. The new design utilizes a stack of multiple electrodes installed perpendicular to the optical beam axis. This configuration provides a fast response time for the detector, which is essential for high-rate counting. The device has been tested with a 241Am ( t 1/2 = 432.2 years) radioactive α source, which mainly emits 5.486-MeV (branching ratio of 85%) and 5.443-MeV (branching ratio of 13%) α particles. An energy resolution of 6.3% was achieved.

  6. An ionization chamber shower detector for the LHC Luminosity Monitor

    SciTech Connect

    Speziali, V.; Beche, J.F.; Burks, M.T.; Datte, P.S.; Haguenauer, M.; manfredi, P.F.; Millaud, J.E.; Placidi, M.; Ratti, L.; Re, V.; Riot, V.J.; Schmickler, H.; Turner, W.C.

    2000-10-01

    The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (~;;235W at design luminosity 1034cm-2s-1). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multi-gap, pressurized gas ionization chamber is being developed for sampling the energy deposited near the maxima of the hadronic/ electromagnetic showers in these absorbers. The system design choices have been strongly influenced by optimization of signal to noise ratio and by the very high radiation environment. The ionization chambers are instrumented with low noise, fast, pulse shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. Data on each bunch are to be separately accumulated over multiple bunch crossings until the desired statistical accuracy is obtained. At design luminosity approximately 2x103 bunch crossings will suffice for a 1percent luminosity measurement. In this paper we report the first experimental results of the ionization chamber and analog electronics. Single 450GeV protons from the SPS at CERN are used to simulate the hadronic/electromagnetic showers produced by the forward collision products from the interaction regions of the LHC.

  7. Two-dimensional position sensitive ionization chamber with GEM

    NASA Astrophysics Data System (ADS)

    Kitamura, Noritaka; Noro, Tetsuo; Sakaguchi, Satoshi; Takao, Hideaki; Nishio, Yasutaka

    2014-09-01

    We have been developing a multi-anode ionization chamber for Accelerator Mass Spectrometry (AMS) at Kyushu University. Furthermore, we are planning to construct a neutron detector with high position resolution by combining the chamber with Gas Electron Multiplier (GEM) and a neutron converter. One of purposes is the measurement of p-> , pn knockout reaction from unstable nuclei. The multi-anode ionization chamber is composed of subdivided multiple anodes, a cathode to produce an uniform electric field, and a Frisch grid. The chamber must have position sensitivity because obtaining a beam profile is required for AMS measurements, where counting loss should be avoided. Also in the case of the neutron detector, it is necessary to measure the position to deduce the scattering angles. We have recently established a two-dimensional position readout system by the following methods: the measurement of horizontal position is enabled by trimming some anodes into wedge-like shape, and vertical position can be determined by the ratio of induced charge on the grid to the total charge on anodes. In addition, improvement of S/N ratio is important for isotope separation and position resolution. We installed a rectangular-shaped GEM and tried improving S/N ratio by electron amplification.

  8. Development of a multi-anode ionization chamber

    NASA Astrophysics Data System (ADS)

    Makino, Hiroki; Morikawa, Tsuneyasu; Noro, Tetsuo; Maeda, Toyokazu

    2009-10-01

    A multi-anode ionization chamber with a Frisch grid has been developed. An immediate purpose is the use in accelerator mass spectrometry (AMS), but the system will also be applied to measurements in heavy-ion nuclear physics. In order to identify the incident heavy ions, the anode is divided into 16 sections so that the ionization distribution along the ion trajectory (Bragg curve) can be analyzed. Layout of the electrodes, for field shaping, has been determined based on calculations by using a computer code, Poisson-Superfish. A good discrimination of ^36Cl ions from background ^36S ions has been shown by the Monte Carlo simulation. For the signal readout, an originally designed charge-sensitive preamplifier was newly made by using conventional operational amplifiers so as to integrate the ionization charge and interface the shaped signal to the electronic modules of existing data acquisition system. These developments are still in progress. In the meeting, the overall performance of the ionization-chamber system investigated by using accelerated heavy ion beams will be presented.

  9. Response of ionization chamber based pocket dosimeter to beta radiation.

    PubMed

    Kumar, Munish; Gupta, Anil; Pradhan, S M; Bakshi, A K; Chougaonkar, M P; Babu, D A R

    2013-12-01

    Quantitative estimate of the response of ionization chamber based pocket dosimeters (DRDs) to various beta sources was performed. It has been established that the ionization chamber based pocket dosimeters do not respond to beta particles having energy (Emax)<1 MeV and same was verified using (147)Pm, (85)Kr and (204)Tl beta sources. However, for beta particles having energy >1 MeV, the DRDs exhibit measureable response and the values are ~8%, ~14% and ~27% per mSv for natural uranium, (90)Sr/(90)Y and (106)Ru/(106)Rh beta sources respectively. As the energy of the beta particles increases, the response also increases. The response of DRDs to beta particles having energy>1 MeV arises due to the fact that the thickness of the chamber walls is less than the maximum range of beta particles. This may also be one of the reasons for disparity between doses measured with passive/legal dosimeters (TLDs) and DRDs in those situations in which radiation workers are exposed to mixed field of gamma photons and beta particles especially at uranium processing plants, nuclear (power and research) reactors, waste management facilities and fuel reprocessing plants etc. The paper provides the reason (technical) for disparity between the doses recorded by TLDs and DRDs in mixed field of photons and beta particles. PMID:23978508

  10. Developing a fast ionization chamber for transfer reaction studies

    NASA Astrophysics Data System (ADS)

    Chae, K. Y.; Bardayan, D. W.; Smith, M. S.; Schmitt, K. T.; Ahn, S. H.; Peters, W. A.; Strauss, S.

    2011-10-01

    Detection of beam and beam like recoils at far forward angles is often critical for radioactive beam measurements in inverse kinematics. Gas-filled ionization chambers are well suited for these applications, since they have moderately good energy resolution and can take prolonged exposure to beam compared to fragile semiconductor detectors. Conventional ion counters using a Frisch grid, however, have slow response times because the ionized electrons must travel long distances to the anodes. To reduce response times, a fast ion counter using a tilted window and tilted electrodes was developed and tested at ORNL's Holifield Radioactive Ion Beam Facility, modified from an original design by Kimura et al.. The maximum counting rate and energy resolution, along with future plans for using the new ion counter, will be presented. This work was sponsored by the Office of Nuclear Physics, U.S. Department of Energy.

  11. Performance parameters of a liquid filled ionization chamber array

    SciTech Connect

    Poppe, B.; Stelljes, T. S.; Looe, H. K.; Chofor, N.; Harder, D.; Willborn, K.

    2013-08-15

    Purpose: In this work, the properties of the two-dimensional liquid filled ionization chamber array Octavius 1000SRS (PTW-Freiburg, Germany) for use in clinical photon-beam dosimetry are investigated.Methods: Measurements were carried out at an Elekta Synergy and Siemens Primus accelerator. For measurements of stability, linearity, and saturation effects of the 1000SRS array a Semiflex 31013 ionization chamber (PTW-Freiburg, Germany) was used as a reference. The effective point of measurement was determined by TPR measurements of the array in comparison with a Roos chamber (type 31004, PTW-Freiburg, Germany). The response of the array with varying field size and depth of measurement was evaluated using a Semiflex 31010 ionization chamber as a reference. Output factor measurements were carried out with a Semiflex 31010 ionization chamber, a diode (type 60012, PTW-Freiburg, Germany), and the detector array under investigation. The dose response function for a single detector of the array was determined by measuring 1 cm wide slit-beam dose profiles and comparing them against diode-measured profiles. Theoretical aspects of the low pass properties and of the sampling frequency of the detector array were evaluated. Dose profiles measured with the array and the diode detector were compared, and an intensity modulated radiation therapy (IMRT) field was verified using the Gamma-Index method and the visualization of line dose profiles.Results: The array showed a short and long term stability better than 0.1% and 0.2%, respectively. Fluctuations in linearity were found to be within ±0.2% for the vendor specified dose range. Saturation effects were found to be similar to those reported in other studies for liquid-filled ionization chambers. The detector's relative response varied with field size and depth of measurement, showing a small energy dependence accounting for maximum signal deviations of ±2.6% from the reference condition for the setup used. The σ-values of the

  12. Influence of field size on a PTW type 23342 plane-parallel ionization chamber's response

    SciTech Connect

    Austerlitz, C.; Villar, H.P.; Santos, M.A.P.

    2004-12-01

    The response of a PTW type 23342 plane-parallel ionization chamber, both in air and in phantom, was evaluated for x-ray tube potentials between 30 and 100 kV and radiation field diameters ranging from 30 to 70 mm. The experiments were performed with a calibrated Pantak x-ray machine and made use of the same set of x-ray qualities adopted by the PTB primary laboratory for the calibration of such chambers. A Plexiglas registered phantom (1.18 g cm{sup -3}) 110 mm long, 110 mm wide, and 80 mm deep was used for phantom measurements. X-ray qualities were characterized by using 99.99% pure aluminum filters. On the basis of the IAEA's TRS 398, the article discusses the dependence of the plane-parallel ionization chamber readings with field size in air and in phantom, its implication with regard to clinical dosimetry, cross-calibration, and dissemination of calibration factors.

  13. Study of the replacement correction factors for ionization chamber dosimetry by Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Wang, Lilie

    In ionization chamber radiation dosimetry, the introduction of the ion chamber into medium will unavoidably distort the radiation field near the chamber because the chamber cavity material (air) is different from the medium. A replacement correction factor, Prepl was introduced in order to correct the chamber readings to give an accurate radiation dose in the medium without the presence of the chamber. Generally it is very hard to measure the values of Prepl since they are intertwined with the chamber wall effect. In addition, the P repl values always come together with the stopping-power ratio of the two media involved. This makes the problem of determining the P repl values even more complicated. Monte Carlo simulation is an ideal method to investigate the replacement correction factors. In this study, four different methods of calculating the values of Prepl by Monte Carlo simulation are discussed. Two of the methods are designated as 'direct' methods in the sense that the evaluation of the stopping-power ratio is not necessary. The systematic uncertainties of the two direct methods are estimated to be about 0.1-0.2% which comes from the ambiguous definition of the energy cutoff Delta used in the Spencer-Attix cavity theory. The two direct methods are used to calculate the values of P repl for both plane-parallel chambers and cylindrical thimble chambers in either electron beams or photon beams. The calculation results are compared to measurements. For electron beams, good agreements are obtained. For thimble chambers in photon beams, significant discrepancies are observed between calculations and measurements. The experiments are thus investigated and the procedures are simulated by the Monte Carlo method. It is found that the interpretation of the measured data as the replacement correction factors in dosimetry protocols are not correct. In applying the calculation to the BIPM graphite chamber in a 60Co beam, the calculated values of P repl differ from those

  14. A new standard cylindrical graphite-walled ionization chamber for dosimetry in 60Co beams at calibration laboratories

    NASA Astrophysics Data System (ADS)

    Neves, Lucio P.; Perini, Ana P.; Caldas, Linda V. E.

    2014-11-01

    60Co sources are used mostly at dosimetry laboratories for calibration of ionization chambers utilized for radiotherapy dosimetry, mainly in those laboratories where there is no linear accelerator available. In this work, a new cylindrical ionization chamber was developed and characterized to be used as a reference dosimeter at the Calibration Laboratory of the IPEN. The characterization tests were performed according to the IEC 60731 standard, and all tests presented results within its recommended limits. Furthermore, the correction factors for the wall, stem, central collecting electrode, nonaxial uniformity and the mass-energy absorption coefficient were determined using the EGSnrc Monte Carlo code. The air kerma rate determined with this new dosimeter was compared to the one obtained with the IPEN standard, presenting a difference of 1.5%. Therefore, the new ionization chamber prototype developed and characterized in this work presents potential use as a primary standard dosimeter at radiation metrology laboratories.

  15. A model for electron/ion recombination in ionization chambers

    SciTech Connect

    Sailor, W.C.

    1988-05-01

    The recombination of free electrons and positive ions along charged particle tracks in gases has been modeled using electron tranport equations, which assume homogeneous distribution in the vicinity of the tracks. The equations include space charge terms, which have been negelected in previous models. A formula for the electron yield as a function of detector applied potential is obtained from a perturbation solution valid when the ratio of the Debye length to the charge column radius is larger then unity. When this ratio is very large, the formula reduces to that of previous models. Pulse height measurements in a /sup 3/He ionization chamber indicate 2% to 30% losses to recombination which vary with applied field, particle type, and energy. Using reasonable values for the electron transport coefficients, the calculated loss of signal to recommendation is generally in agreement with experiment, but the variation with applied bias is stronger in the experiment.

  16. NIST Ionization Chamber “A” Sample-Height Corrections

    PubMed Central

    Fitzgerald, Ryan

    2012-01-01

    For over 30 years scientists in the NIST radioactivity group have been using their pressurized ionization chamber “A” (PIC “A”) to make measurements of radioactivity and radioactive half-lives. We now have evidence that some of those reported measurements were incorrect due to slippage of the source positioning ring over time. The temporal change in the holder caused an error in the source-height within the chamber, which was thought to be invariant. This unaccounted-for height change caused a change in the detector response and thus a relative error in measured activity on the order of 10−5 to 10−3 per year, depending on the radionuclide. The drifting detector response affected calibration factors and half-life determinations. After discovering the problem, we carried out historic research and new sensitivity tests. As a result, we have created a quantitative model of the effect and have used that model to estimate corrections to some of the past measurement results from PIC “A”. In this paper we report the details and results of that model. Meanwhile, we have fixed the positioning ring and are recalibrating the detector using primary measurement methods and enhanced quality control measures. PMID:26900515

  17. An evaluation of ionization chambers for the relative dosimetry of kilovoltage x-ray beams

    SciTech Connect

    Hill, Robin; Mo Zhao; Haque, Mamoon; Baldock, Clive

    2009-09-15

    In this work, the authors have evaluated ten different ionization chambers for the relative dosimetry of kilovoltage x-ray beams in the energy range of 50-280 kVp. Percentage depth doses in water and relative detector response (in Solid Water and in air) were measured for each of the x-ray beams studied using a number of chambers. Measured depth dose data were compared with Monte Carlo calculated depth doses using the EGSnrc Monte Carlo package and the BEAMnrc user code. The accuracy of the phase space files generated by BEAMnrc was verified by calculating the half-value layer and comparing with the measured half-value layer of each x-ray beam. The results indicate that the Advanced Markus, Markus, NACP, and Roos parallel plate ionization chambers were suitable for the measurement of depth dose data in this beam quality range with an uncertainty of less than 3%, including in the regions close to the water surface. While the relative detector response of the Farmer and scanning thimble chambers exhibited a better energy response, they were not suitable for depth dose measurements in the first 5 mm below the water surface with differences of up to 12% in the surface dose measurement for the 50 kVp x-ray beam. These differences were due to dose artifacts generated by the chamber size and the dose gradient. However, at depths greater than 5 mm, the Farmer and thimble scanning chambers gave uncertainties of less than 3% for the depth dose measurements for all beam energies. The PTW PinPoint 31006 chamber was found to give varying dose differences of up to 8% depending on the x-ray beam energy; this was attributed to the steel central electrode. The authors recommend that one of the parallel plate ionization chambers investigated be used to determine depth dose data for kilovoltage x-ray beams in the energy range studied and give correct dose information close to the surface and at depth in the water phantom.

  18. Dosimetric characteristics of the novel 2D ionization chamber array OCTAVIUS Detector 1500

    SciTech Connect

    Stelljes, T. S. Looe, H. K.; Chofor, N.; Poppe, B.; Harmeyer, A.; Reuter, J.; Harder, D.

    2015-04-15

    Purpose: The dosimetric properties of the OCTAVIUS Detector 1500 (OD1500) ionization chamber array (PTW-Freiburg, Freiburg, Germany) have been investigated. A comparative study was carried out with the OCTAVIUS Detector 729 and OCTAVIUS Detector 1000 SRS arrays. Methods: The OD1500 array is an air vented ionization chamber array with 1405 detectors in a 27 × 27 cm{sup 2} measurement area arranged in a checkerboard pattern with a chamber-to-chamber distance of 10 mm in each row. A sampling step width of 5 mm can be achieved by merging two measurements shifted by 5 mm, thus fulfilling the Nyquist theorem for intensity modulated dose distributions. The stability, linearity, and dose per pulse dependence were investigated using a Semiflex 31013 chamber (PTW-Freiburg, Freiburg, Germany) as a reference detector. The effective depth of measurement was determined by measuring TPR curves with the array and a Roos chamber type 31004 (PTW-Freiburg, Freiburg, Germany). Comparative output factor measurements were performed with the array, the Semiflex 31010 ionization chamber and the Diode 60012 (both PTW-Freiburg, Freiburg, Germany). The energy dependence of the OD1500 was measured by comparing the array’s readings to those of a Semiflex 31010 ionization chamber for varying mean photon energies at the depth of measurement, applying to the Semiflex chamber readings the correction factor k{sub NR} for nonreference conditions. The Gaussian lateral dose response function of a single array detector was determined by searching the convolution kernel suitable to convert the slit beam profiles measured with a Diode 60012 into those measured with the array’s central chamber. An intensity modulated dose distribution measured with the array was verified by comparing a OD1500 measurement to TPS calculations and film measurements. Results: The stability and interchamber sensitivity variation of the OD1500 array were within ±0.2% and ±0.58%, respectively. Dose linearity was within 1

  19. Ionization collection efficiencies of some ionization chambers in pulsed and continuous radiation beams.

    PubMed

    Holt, J G; Stanton, R E; Sell, R E

    1978-01-01

    The most commonly used method of calibrating high-energy photon or electron beams consists in converting cavity ionization to dose by the application of the appropriate Clambda or CE multipled by the 60Co correction factor. The correct interpretation of calibration data for pulsed photon or electron beams requires a knowledge of the charge collection efficiencies of the ionization chambers used. The results are presented of efficiency measurements for both pulsed and continuous beams made with these chambers: 0.6-cm3 Farmer, 0.5-cm3 Spokas, 3-cm3 Shonka, 1-cm3 PTW, and 1-cm3 Memorial pancake. The dependence of collection efficiency on collection voltage, dose rate, and dose per pulse is demonstrated. These results are shown to agree with Boag's formulas for collection efficiency. Attention is drawn to the fact that several kinds of dosimeters provide only minimal collection voltages for efficient collection of charge at high dose rates, especially in Linac electron beams. It is recommended to check the collection efficiency of chambers which are to be used at high dose rates, and a simple method for this purpose is described. PMID:683147

  20. Polarity correction factor for flattening filter free photon beams in several cylindrical ionization chambers.

    PubMed

    Ogata, Toshiyuki; Uehara, Kazuyuki; Nakayama, Masao; Tsudou, Shinji; Masutani, Takashi; Okayama, Takanobu

    2016-07-01

    In this study, we aimed to compare the polarity correction factor in ionization chambers for flattening filter free (FFF) photon beams and flattening filter (FF) beams. Measurements were performed with both 6 and 10 MV FFF and FF beams. Five commercial ionization chambers were evaluated: PTW TN30013; IBA Dosimetry CC01, CC04, and CC13; and Exradin A12S. Except for the CC01 ionization chamber, the other four chambers showed less than a 0.3 % difference in the polarity effect between the FFF and the FF beams. The CC01 chamber showed a strong field-size-dependence, unlike the other chambers. The polarity effect for all chambers with FFF beams did not change with the dose rate. Except in the case of the CC01 chamber, the difference in the polarity effect between FFF and FF beams was not significant. PMID:26873138

  1. Monte Carlo calculations of correction factors for plane-parallel ionization chambers in clinical electron dosimetry

    SciTech Connect

    Araki, Fujio

    2008-09-15

    Recent standard dosimetry protocols recommend that plane-parallel ionization chambers be used in the measurements of depth-dose distributions or the calibration of low-energy electron beams with beam quality R{sub 50}<4 g/cm{sup 2}. In electron dosimetry protocols with the plane-parallel chambers, the wall correction factor, P{sub wall}, in water is assumed to be unity and the replacement correction factor, P{sub repl}, is taken to be unity for well-guarded plane-parallel chambers, at all measurement depths. This study calculated P{sub wall} and P{sub repl} for NACP-02, Markus, and Roos plane-parallel chambers in clinical electron dosimetry using the EGSnrc Monte Carlo code system. The P{sub wall} values for the plane-parallel chambers increased rapidly as a function of depth in water, especially at lower energy. The value around R{sub 50} for NACP-02 was about 10% greater than unity at 4 MeV. The effect was smaller for higher electron energies. Similarly, P{sub repl} values with depth increased drastically at the region with the steep dose gradient for lower energy. For Markus P{sub repl} departed more than 10% from unity close to R{sub 50} due to the narrow guard ring width. P{sub repl} for NACP-02 and Roos was close to unity in the plateau region of depth-dose curves that includes a reference depth, d{sub ref}. It was also found that the ratio of the dose to water and the dose to the sensitive volume in the air cavity for the plane-parallel chambers, D{sub w}/[D{sub air}]{sub pp}, at d{sub ref} differs significantly from that assumed by electron dosimetry protocols.

  2. Evaluation of Gas-filled Ionization Chamber Method for Radon Measurement at Two Reference Facilities

    SciTech Connect

    Ishikawa, Tetsuo; Tokonami, Shinji; Kobayashi, Yosuke; Sorimachi, Atsuyuki; Yatabe, Yoshinori; Miyahara, Nobuyuki

    2008-08-07

    For quality assurance, gas-filled ionization chamber method was tested at two reference facilities for radon calibration: EML (USA) and PTB (Germany). Consequently, the radon concentrations estimated by the ionization chamber method were in good agreement with the reference radon concentrations provided by EML as well as PTB.

  3. High spatial resolution dosimetric response maps for radiotherapy ionization chambers measured using kilovoltage synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Butler, D. J.; Stevenson, A. W.; Wright, T. E.; Harty, P. D.; Lehmann, J.; Livingstone, J.; Crosbie, J. C.

    2015-11-01

    Small circular beams of synchrotron radiation (0.1 mm and 0.4 mm in diameter) were used to irradiate ionization chambers of the types commonly used in radiotherapy. By scanning the chamber through the beam and measuring the ionization current, a spatial map of the dosimetric response of the chamber was recorded. The technique is able to distinguish contributions to the large-field ionization current from the chamber walls, central electrode and chamber stem. Scans were recorded for the NE 2571 Farmer chamber, the PTW 30013, IBA FC65-G Farmer-type chambers, the NE 2611A and IBA CC13 thimble chambers, the PTW 31006 and 31014 pinpoint chambers, the PTW Roos and Advanced Markus plane-parallel chambers, and the PTW 23342 thin-window soft x-ray chamber. In all cases, large contributions to the response arise from areas where the incident beam grazes the cavity surfaces. Quantitative as well as qualitative information about the relative chamber response was extracted from the maps, including the relative contribution of the central electrode. Line scans using monochromatic beams show the effect of the photon energy on the chamber response. For Farmer-type chambers, a simple Monte Carlo model was in good agreement with the measured response.

  4. High spatial resolution dosimetric response maps for radiotherapy ionization chambers measured using kilovoltage synchrotron radiation.

    PubMed

    Butler, D J; Stevenson, A W; Wright, T E; Harty, P D; Lehmann, J; Livingstone, J; Crosbie, J C

    2015-11-21

    Small circular beams of synchrotron radiation (0.1 mm and 0.4 mm in diameter) were used to irradiate ionization chambers of the types commonly used in radiotherapy. By scanning the chamber through the beam and measuring the ionization current, a spatial map of the dosimetric response of the chamber was recorded. The technique is able to distinguish contributions to the large-field ionization current from the chamber walls, central electrode and chamber stem. Scans were recorded for the NE 2571 Farmer chamber, the PTW 30013, IBA FC65-G Farmer-type chambers, the NE 2611A and IBA CC13 thimble chambers, the PTW 31006 and 31014 pinpoint chambers, the PTW Roos and Advanced Markus plane-parallel chambers, and the PTW 23342 thin-window soft x-ray chamber. In all cases, large contributions to the response arise from areas where the incident beam grazes the cavity surfaces. Quantitative as well as qualitative information about the relative chamber response was extracted from the maps, including the relative contribution of the central electrode. Line scans using monochromatic beams show the effect of the photon energy on the chamber response. For Farmer-type chambers, a simple Monte Carlo model was in good agreement with the measured response. PMID:26510214

  5. A new mini gas ionization chamber for IBA applications

    NASA Astrophysics Data System (ADS)

    Müller, A. M.; Cassimi, A.; Döbeli, M.; Mallepell, M.; Monnet, I.; Simon, M. J.; Suter, M.; Synal, H.-A.

    2011-12-01

    Novel prototypes of high resolution gas ionization chambers ( GIC) were designed with increased compactness and simplicity of the setup. They have no Frisch-grid and a simple anode wire. Under certain operating conditions these mini detectors have an energy resolution comparable with that of state-of-the-art GICs of much higher complexity. They can be operated both under vacuum and atmospheric pressure. First measurements were made with protons in the energy range of 0.3-1.0 MeV. For protons at 0.3 MeV an energy resolution of about 12 keV was achieved. With a 72 MeV 129Xe beam a relative resolution of 1.4% was obtained. Due to their versatility and reduced size the detectors can easily be applied in the field of ion beam analysis ( IBA) and accelerator mass spectrometry ( AMS) . Since they are almost completely insensitive to radiation damage they are especially suited for use in high fluence applications such as scanning transmission ion microscopy ( STIM). A comparison of the radiation hardness of the mini GIC with a Si PIN diode was therefore performed. The GIC showed no peak shift or change in energy resolution at all after collecting 10 15 protons per cm 2 while the performance of the Si detector clearly started to degrade at 10 12 particles per cm 2.

  6. Coplanar anode implementation in compressed xenon ionization chambers

    NASA Astrophysics Data System (ADS)

    Kiff, Scott Douglas

    This dissertation examines the problem of microphonic degradation of high-pressure xenon ionization chambers' energy spectra. A detector design that utilizes coplanar anodes is proposed to mitigate this problem, and an optimization study finds the best geometry given some constraints on the system. A radial position-sensing method is developed from theory and implemented in experiments, demonstrating usefulness in the areas of hardware diagnostics and energy spectrum enhancement. Detailed simulations quantify the effects of various physical processes on the measured energy spectrum; the processes that degrade the photopeak most severely also show promise for improvement via design and operational changes. Simulations show multiple-site events are undesirable due to resolution degradation. A hydrogen cooling admixture is implemented to improve energy resolution after detailed simulations predict advantageous performance changes. The detector linearity is shown to be quite good over the range tested, 80-1330 keV. The best measured energy resolution is 4.2% FWHM at 662 keV, which is near the range that would be considered competitive with the less-rugged detectors employing Frisch grids.

  7. Comparison of pencil-type ionization chamber calibration results and methods between dosimetry laboratories.

    PubMed

    Hourdakis, Costas J; Büermann, Ludwig; Ciraj-Bjelac, Olivera; Csete, Istvan; Delis, Harry; Gomola, Igor; Persson, Linda; Novak, Leos; Petkov, Ivailo; Toroi, Paula

    2016-01-01

    A comparison of calibration results and procedures in terms of air kerma length product, PKL, and air kerma, K, was conducted between eight dosimetry laboratories. A pencil-type ionization chamber (IC), generally used for computed tomography dose measurements, was calibrated according to three calibration methods, while its residual signal and other characteristics (sensitivity profile, active length) were assessed. The results showed that the "partial irradiation method" is the preferred method for the pencil-type IC calibration in terms of PKL and it could be applied by the calibration laboratories successfully. Most of the participating laboratories achieved high level of agreement (>99%) for both dosimetry quantities (PKL and K). Estimated relative standard uncertainties of comparison results vary among laboratories from 0.34% to 2.32% depending on the quantity, beam quality and calibration method applied. Detailed analysis of the assigned uncertainties have been presented and discussed. PMID:26508013

  8. Monte Carlo calculation of energy deposition in ionization chambers for tritium measurements

    NASA Astrophysics Data System (ADS)

    Zhilin, Chen; Shuming, Peng; Dan, Meng; Yuehong, He; Heyi, Wang

    2014-10-01

    Energy deposition in ionization chambers for tritium measurements has been theoretically studied using Monte Carlo code MCNP 5. The influence of many factors, including carrier gas, chamber size, wall materials and gas pressure, has been evaluated in the simulations. It is found that β rays emitted by tritium deposit much more energy into chambers flowing through with argon than with deuterium in them, as much as 2.7 times higher at pressure 100 Pa. As chamber size gets smaller, energy deposition decreases sharply. For an ionization chamber of 1 mL, β rays deposit less than 1% of their energy at pressure 100 Pa and only 84% even if gas pressure is as high as 100 kPa. It also indicates that gold plated ionization chamber results in the highest deposition ratio while aluminum one leads to the lowest. In addition, simulations were validated by comparison with experimental data. Results show that simulations agree well with experimental data.

  9. Perturbation correction factors for the NACP-02 plane-parallel ionization chamber in water in high-energy electron beams.

    PubMed

    Verhaegen, F; Zakikhani, R; Dusautoy, A; Palmans, H; Bostock, G; Shipley, D; Seuntjens, J

    2006-03-01

    Recent dosimetry protocols for clinical high-energy electron beams recommend measurements of absorbed dose-to-water with a plane-parallel or cylindrical ionization chamber. For well-guarded plane-parallel ionization chambers, the ionization chamber perturbation factor in water, p(Q), has a recommended value of unity in all protocols. This assumption was investigated in detail in this study for one of the recommended ionization chambers in the protocols: the Scanditronix NACP-02 plane-parallel ionization chamber. Monte Carlo (MC) simulations of the NACP-02 ionization chamber with the EGSnrc code were validated against backscatter experiments. MC simulations were then used to calculate p(wall), p(cav) and p(Q) perturbation factors and water-to-air Spencer-Attix stopping powers in 4-19 MeV electron beams of a calibration laboratory (NPL), and in 6-22 MeV clinical electron beams from a Varian CL2300 accelerator. Differences between calculated and the currently recommended (Burns et al 1996 Med. Phys. 23 383-8) stopping powers, water-to-air, were found to be limited to 0.9% at depths between the reference depth z(ref) and the depth where the dose has decreased to 50% of the maximum dose, R50. p(wall) was found to exceed unity by 2.3% in the 4 MeV NPL calibration beam at z(ref). For higher energy electron beams p(wall) decreased to a value of about 1%. Combined with a p(cav) about 1% below unity for all energies at z(ref), this was found to cause p(Q) to exceed unity significantly for all energies. In clinical electron beams all three perturbation factors were found to increase with depth. Our findings indicate that the perturbation factors have to be taken into account in calibration procedures and for clinical depth dose measurements with the NACP-02 ionization chamber. PMID:16481689

  10. Calculated calibrations for ion chambers fabricated from plastics simulating air and muscle; determination of W and tauRa.

    PubMed

    Rose, J E; Shonka, F R

    1968-12-01

    An experiment is described utilizing two 16-liter ionization chambers, fabricated from electrically conducting plastics which closely simulate air and human muscle, designed to minimize most of the errors inherent in the use of cavity chambers. A careful calibration was done, using a 226Ra source in 0.5 mm platinum, in an almost scatter-free environment which permitted the derivation of accurate corrections for scatter and air attenuation. Calibrations calculated from the physical measurements of the ion chambers are compared with the experimental calibrations. Values of Wbeta for air, and muscle gas and of tauRa are derived. PMID:17387873

  11. On the Frisch-Grid signal in ionization chambers

    NASA Astrophysics Data System (ADS)

    Al-Adili, A.; Hambsch, F.-J.; Bencardino, R.; Pomp, S.; Oberstedt, S.; Zeynalov, Sh.

    2012-04-01

    A recent theoretical approach concerning the grid-inefficiency (GI) problem in Twin Frisch-Grid Ionization Chambers was validated experimentally. The experimental verification focused on the induced signal on the anode plate. In this work the investigation was extended by studying the grid signal. The aim was to verify the grid-signal dependency on the grid inefficiency σ. The measurements were made with fission fragments from Cf(sf)252, using two different grids, with 1 and 2 mm wire distances, leading to the GI values: σ=0.031 and σ=0.083, respectively. The theoretical grid signal was confirmed because the detected grid pulse-height distribution was smaller for the larger σ. By applying the additive GI correction approach, the two grid pulse heights were consistent. In the second part of the work, the corrected grid signal was used to deduce emission angles of the fission fragments. It is inconvenient to treat the grid signal by means of conventional analogue electronics, because of its bipolarity. Therefore, the anode and grid signals were summed to create a unipolar, angle-dependent pulse height. Until now the so-called summing method has been the well-established approach to deduce the angle from the grid signal. However, this operation relies strongly on an accurate and stable calibration between the two summed signals. By application of digital-signal processing, the grid signal's bipolarity is no longer an issue. Hence one can bypass the intermediate summation step of the two different pre-amplifier signals, which leads to higher stability. In this work the grid approach was compared to the summing method in three cases: Cf(sf)252, U(n,f)235 and U(n,f)234. By using the grid directly, the angular resolution was found equally good in the first case but gave 7% and 20% improvements, respectively, in the latter cases.

  12. Liquid ionization chamber measurements of dose distributions in small 6 MV photon beams

    NASA Astrophysics Data System (ADS)

    Dasu, Alexandru; Löfroth, Per-Olov; Wickman, Göran

    1998-01-01

    A new liquid ionization chamber (LIC) design optimized for high spatial resolution was used for measurements of dose distributions in radiation fields intended for stereotactic radiosurgery (SRS). This work was mainly focused on the properties of this detector in radiation fields from linear accelerators for clinical radiotherapy (pulsed radiation with dose rates from approximately 0.5 to and beam diameters down to 8 mm). The narrow beams used in stereotactic radiosurgery require detectors with small sizes in order to provide a good spatial resolution. The LIC is investigated to see whether it can be used as a detector for dose measurements in beams currently used for stereotactic radiosurgery. Its properties are compared with those of silicon diodes. The comparisons include output factor (OF), depth dose and profile measurements in 6 MV photon fields of different sizes. For OF measurements, an NACP air ionization chamber was also used in the comparison. The dependence of the response on the detector orientation in the photon beam is also investigated for the diodes and the LIC. The results suggest that LICs can provide better properties than diodes for measuring dose distributions in narrow photon beams.

  13. Construction of an ionization chamber for the measurement of dose of low energy x-rays

    SciTech Connect

    Perez, Y. B. Alcantara; Jimenez, F. J. Ramirez

    2008-08-11

    We designed and constructed the prototype of an ionization chamber to measure the dose of an X-ray tube with Molybdenum anode. This X-ray tube is located in the Physics department at CINVESTAV and is used for medical physics purposes in the imaging area. The ionization chamber is designed to measure doses on biological samples exposed to X-rays and will be applied in radiation protection studies.

  14. Pencil beam proton radiography using a multilayer ionization chamber.

    PubMed

    Farace, Paolo; Righetto, Roberto; Meijers, Arturs

    2016-06-01

    A pencil beam proton radiography (PR) method, using a commercial multilayer ionization chamber (MLIC) integrated with a treatment planning system (TPS) was developed. A Giraffe (IBA Dosimetry) MLIC (±0.5 mm accuracy) was used to obtain pencil beam PR by delivering spots uniformly positioned at a 5.0 mm distance in a 9  ×  9 square of spots. PRs of an electron-density (with tissue-equivalent inserts) phantom and a head phantom were acquired. The integral depth dose (IDD) curves of the delivered spots were computed by the TPS in a volume of water simulating the MLIC, and virtually added to the CT at the exit side of the phantoms. For each spot, measured and calculated IDD were overlapped in order to compute a map of range errors. On the head-phantom, the maximum dose from PR acquisition was estimated. Additionally, on the head phantom the impact on the range errors map was estimated in case of a 1 mm position misalignment. In the electron-density phantom, range errors were within 1 mm in the soft-tissue rods, but greater in the dense-rod. In the head-phantom the range errors were  -0.9  ±  2.7 mm on the whole map and within 1 mm in the brain area. On both phantoms greater errors were observed at inhomogeneity interfaces, due to sensitivity to small misalignment, and inaccurate TPS dose computation. The effect of the 1 mm misalignment was clearly visible on the range error map and produced an increased spread of range errors (-1.0  ±  3.8 mm on the whole map). The dose to the patient for such PR acquisitions would be acceptable as the maximum dose to the head phantom was  <2cGyE. By the described 2D method, allowing to discriminate misalignments, range verification can be performed in selected areas to implement an in vivo quality assurance program. PMID:27164479

  15. Pencil beam proton radiography using a multilayer ionization chamber

    NASA Astrophysics Data System (ADS)

    Farace, Paolo; Righetto, Roberto; Meijers, Arturs

    2016-06-01

    A pencil beam proton radiography (PR) method, using a commercial multilayer ionization chamber (MLIC) integrated with a treatment planning system (TPS) was developed. A Giraffe (IBA Dosimetry) MLIC (±0.5 mm accuracy) was used to obtain pencil beam PR by delivering spots uniformly positioned at a 5.0 mm distance in a 9  ×  9 square of spots. PRs of an electron-density (with tissue-equivalent inserts) phantom and a head phantom were acquired. The integral depth dose (IDD) curves of the delivered spots were computed by the TPS in a volume of water simulating the MLIC, and virtually added to the CT at the exit side of the phantoms. For each spot, measured and calculated IDD were overlapped in order to compute a map of range errors. On the head-phantom, the maximum dose from PR acquisition was estimated. Additionally, on the head phantom the impact on the range errors map was estimated in case of a 1 mm position misalignment. In the electron-density phantom, range errors were within 1 mm in the soft-tissue rods, but greater in the dense-rod. In the head-phantom the range errors were  ‑0.9  ±  2.7 mm on the whole map and within 1 mm in the brain area. On both phantoms greater errors were observed at inhomogeneity interfaces, due to sensitivity to small misalignment, and inaccurate TPS dose computation. The effect of the 1 mm misalignment was clearly visible on the range error map and produced an increased spread of range errors (‑1.0  ±  3.8 mm on the whole map). The dose to the patient for such PR acquisitions would be acceptable as the maximum dose to the head phantom was  <2cGyE. By the described 2D method, allowing to discriminate misalignments, range verification can be performed in selected areas to implement an in vivo quality assurance program.

  16. Possibility of using cylindrical ionization chambers for percent depth-dose measurements in clinical electron beams

    SciTech Connect

    Ono, Takeshi; Araki, Fujio; Yoshiyama, Fumiaki

    2011-08-15

    Purpose: This study investigated the possibility of using cylindrical ionization chambers for percent depth-dose (PDD) measurements in high-energy clinical electron beams. Methods: The cavity correction factor, P{sub cav}, for cylindrical chambers with various diameters was calculated as a function of depth from the surface to R{sub 50}, in the energy range of 6-18 MeV electrons with the EGSnrc C ++ -based user-code CAVITY. The results were compared with those for IBA NACP-02 and PTW Roos parallel-plate ionization chambers. The effective point of measurement (EPOM) for the cylindrical chamber and the parallel-plate chamber was positioned according to the IAEA TRS-398 code of practice. The overall correction factor, P{sub Q}, and the percent depth-ionization (PDI) curve for a PTW30013 Farmer-type chamber were also compared with those of NACP-02 and Roos chambers. Results: The P{sub cav} values at depths between the surface and R{sub 50} for cylindrical chambers were all lower than those with parallel-plate chambers. However, the variation in depth for cylindrical chambers equal to or less than 4 mm in diameter was equivalent to or smaller than that for parallel-plate chambers. The P{sub Q} values for the PTW30013 chamber mainly depended on P{sub cav}, and for parallel-plate chambers depended on the wall correction factor, P{sub wall}, rather than P{sub cav}. P{sub Q} at depths from the surface to R{sub 50} for the PTW30013 chamber was consequently a lower value than that with parallel-plate chambers. However, the variation in depth was equivalent to that of parallel-plate chambers at electron energies equal to or greater than 9 MeV. The shift to match calculated PDI curves for the PTW30013 chamber and water (perturbation free) varied from 0.65 to 0 mm between 6 and 18 MeV beams. Similarly, the shifts for NACP-02 and Roos chambers were 0.5-0.6 mm and 0.2-0.3 mm, respectively, and were nearly independent of electron energy. Conclusions: Calculated PDI curves for PTW

  17. Ionization statistics and diffusion: analytical estimate of their contribution to spatial resolution of drift chambers

    SciTech Connect

    Tarnopolsky, G.J.

    1983-01-01

    The spatial resolution of a drift chamber often is the foremost design parameter. The calculation described here - a design tool - permits us to estimate the contributions of ionization statistics and diffusion to the spatial resolution when actually sampling the drift pulse waveform. Useful formulae are derived for the cylindrical and jet-chamber cell geometries.

  18. 33 CFR 183.112 - Flotation material and air chambers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Flotation material and air... SECURITY (CONTINUED) BOATING SAFETY BOATS AND ASSOCIATED EQUIPMENT Flotation Requirements for Inboard Boats, Inboard/Outdrive Boats, and Airboats § 183.112 Flotation material and air chambers. (a)...

  19. Beam tests of ionization chambers for the NuMI neutrino beam

    SciTech Connect

    Robert M. Zwaska et al.

    2003-09-25

    We have conducted tests at the Fermilab Booster of ionization chambers to be used as monitors of the NuMI neutrino beamline. The chambers were exposed to proton fluxes of up to 10{sup 12} particles/cm{sup 2}/1.56 {micro}s. We studied space charge effects which can reduce signal collection from the chambers at large charged particle beam intensities.

  20. The effect of low-energy electrons on the response of ion chambers to ionizing photon beams

    NASA Astrophysics Data System (ADS)

    La Russa, Daniel J.

    Cavity ionization chambers are one of the most popular and widely used devices for quantifying ionizing photon beams. This popularity originates from the precision of these devices and the relative ease with which ionization measurements are converted to quantities of interest in therapeutic radiology or radiation protection, collectively referred to as radiation dosimetry. The formalisms used for these conversions, known as cavity theory, make several assumptions about the electron spectrum in the low-energy range resulting from the incident photon beam. These electrons often account for a significant fraction of the ion chamber response. An inadequate treatment of low-energy electrons can therefore significantly effect calculated quantities of interest. This thesis sets out to investigate the effect of low-energy electrons on (1) the use of Spencer-Attix cavity theory with 60Co beams; and (2) the standard temperature-pressure correction factor, P TP, used to relate the measured ionization to a set of reference temperature and pressure conditions for vented ion chambers. Problems with the PTP correction are shown to arise when used with kilovoltage x rays, where ionization measurements are due primarily to electrons that do not have enough energy to cross the cavity. A combination of measurements and Monte Carlo calculations using the EGSnrc Monte Carlo code demonstrate the breakdown of PTP in these situations when used with non-air-equivalent chambers. The extent of the breakdown is shown to depend on cavity size, energy of the incident photons, and the composition of the chamber. In the worst case, the standard P TP factor overcorrects the response of an aluminum chamber by ≈12% at an air density typical of Mexico City. The response of a more common graphite-walled chamber with similar dimensions at the same air density is undercorrected by ≈ 2%. The EGSnrc Monte Carlo code is also used to investigate Spencer-Attix cavity theory as it is used in the

  1. Investigation of the applicability of a special parallel-plate ionization chamber for x-ray beam dosimetry

    NASA Astrophysics Data System (ADS)

    Perini, Ana P.; P. Neves, Lucio; E. Caldas, Linda V.

    2014-02-01

    Diagnostic x-rays are the greatest source of exposition to ionizing radiation of the population worldwide. In order to obtain accurate and lower-cost dosimeters for quality control assurance of medical x-ray facilities, a special ionization chamber was designed at the Calibration Laboratory of the IPEN, for dosimetry in diagnostic radiology beams. For the chamber characterization some tests were undertaken. Monte Carlo simulations were proposed to evaluate the distribution of the deposited energy in the sensitive volume of the ionization chamber and the collecting electrode effect on the chamber response. According to the obtained results, this special ionization chamber presents potential use for dosimetry of conventional diagnostic radiology beams.

  2. Laser-induced air ionization microscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Zhang, N.; Yang, J.; Zhu, X.

    2006-06-01

    A nonlinear scanning imaging method is introduced that uses the highly localized air ionization initiated by photoelectrons from the sample surface under irradiation of femtosecond laser pulses as the microprobe. This type of microscopy with realizable subdiffraction spatial resolution has the unique advantages of being highly sensitive to both elemental and topographical properties of the samples of interest. Microscopic images of a femtosecond laser ablated micropattern, the cross section and the side view profile of an optical fiber, and a fresh mulberry leaf are obtained with this imaging technique, which demonstrate this technique's broad applicability in microscopic studies of different materials.

  3. Determination of small-field correction factors for cylindrical ionization chambers using a semiempirical method

    NASA Astrophysics Data System (ADS)

    Park, Kwangwoo; Bak, Jino; Park, Sungho; Choi, Wonhoon; Park, Suk Won

    2016-02-01

    A semiempirical method based on the averaging effect of the sensitive volumes of different air-filled ionization chambers (ICs) was employed to approximate the correction factors for beam quality produced from the difference in the sizes of the reference field and small fields. We measured the output factors using several cylindrical ICs and calculated the correction factors using a mathematical method similar to deconvolution; in the method, we modeled the variable and inhomogeneous energy fluence function within the chamber cavity. The parameters of the modeled function and the correction factors were determined by solving a developed system of equations as well as on the basis of the measurement data and the geometry of the chambers. Further, Monte Carlo (MC) computations were performed using the Monaco® treatment planning system to validate the proposed method. The determined correction factors (k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} ) were comparable to the values derived from the MC computations performed using Monaco®. For example, for a 6 MV photon beam and a field size of 1  ×  1 cm2, k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} was calculated to be 1.125 for a PTW 31010 chamber and 1.022 for a PTW 31016 chamber. On the other hand, the k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} values determined from the MC computations were 1.121 and 1.031, respectively; the difference between the proposed method and the MC computation is less than 2%. In addition, we determined the k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} values for PTW 30013, PTW 31010, PTW 31016, IBA FC23-C, and IBA CC13 chambers as well. We devised a method for determining k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} from both the measurement of the output factors and model-based mathematical computation. The proposed method can be useful in case the MC simulation would not be applicable for the clinical settings.

  4. Theoretical study of energy deposition in ionization chambers for tritium measurements

    NASA Astrophysics Data System (ADS)

    Chen, Zhilin; Peng, Shuming; Meng, Dan; He, Yuehong; Wang, Heyi

    2013-10-01

    Energy deposition in ionization chambers has been theoretically studied for tritium measurements in gaseous form. A one-dimension model is introduced to establish the quantitative relationship between energy deposition rate and many factors, including carrier gas, gas pressure, wall material, chamber size, and gas temperature. Energy deposition rate has been calculated at pressure varying from 5 kPa to 500 kPa based on some approximations. It is found that energy deposition rate varies greatly for different parameters, especially at low gas pressure. For the same chamber, energy deposition rate in argon is much higher than in deuterium, as much as 70.7% higher at 5 kPa. Gold plated chamber gives highest energy deposition rate in the calculations while aluminum chamber results in the lowest. As chamber size gets smaller, β ray emitted by tritium will deposit less energy in the sensitive region of the chamber. For chambers flowing through with the same gas, energy deposition rate in a 10 L chamber is 23.9% higher than in a 0.05 L chamber at 5 kPa. Gas temperature also places slight influence on energy deposition rate, and 373 K will lead to 6.7% lower deposition rate than 233 K at 5 kPa. In addition, experiments have been performed to obtain energy deposition rate in a gold plated chamber, which show good accordance with theoretical calculations.

  5. Theoretical study of energy deposition in ionization chambers for tritium measurements

    SciTech Connect

    Chen, Zhilin; Peng, Shuming; Meng, Dan; He, Yuehong; Wang, Heyi

    2013-10-15

    Energy deposition in ionization chambers has been theoretically studied for tritium measurements in gaseous form. A one-dimension model is introduced to establish the quantitative relationship between energy deposition rate and many factors, including carrier gas, gas pressure, wall material, chamber size, and gas temperature. Energy deposition rate has been calculated at pressure varying from 5 kPa to 500 kPa based on some approximations. It is found that energy deposition rate varies greatly for different parameters, especially at low gas pressure. For the same chamber, energy deposition rate in argon is much higher than in deuterium, as much as 70.7% higher at 5 kPa. Gold plated chamber gives highest energy deposition rate in the calculations while aluminum chamber results in the lowest. As chamber size gets smaller, β ray emitted by tritium will deposit less energy in the sensitive region of the chamber. For chambers flowing through with the same gas, energy deposition rate in a 10 L chamber is 23.9% higher than in a 0.05 L chamber at 5 kPa. Gas temperature also places slight influence on energy deposition rate, and 373 K will lead to 6.7% lower deposition rate than 233 K at 5 kPa. In addition, experiments have been performed to obtain energy deposition rate in a gold plated chamber, which show good accordance with theoretical calculations.

  6. Tuning Fano resonances with a nano-chamber of air.

    PubMed

    Chen, Jianjun; He, Keke; Sun, Chengwei; Wang, Yujia; Li, Hongyun; Gong, Qihuang

    2016-05-15

    By designing a polymer-film-coated asymmetric metallic slit structure that only contains one nanocavity side-coupled with a subwavelength plasmonic waveguide, the Fano resonance is realized in the experiment. The Fano resonance originates from the interference between the narrow resonant spectra of the radiative light from the nanocavity and the broad nonresonant spectra of the directly transmitted light from the slit. The lateral dimension of the asymmetric slit is only 825 nm. Due to the presence of the soft polymer film, a nano-chamber of air is constructed. Based on the opto-thermal effect, the air volume in the nano-chamber is expanded by a laser beam, which blueshifts the Fano resonance. This tunable Fano resonance in such a submicron slit structure with a nano-chamber is of importance in the highly integrated plasmonic circuits. PMID:27176948

  7. Dosimetric application of a special pencil ionization chamber in radiotherapy X-ray beams

    NASA Astrophysics Data System (ADS)

    Neves, Lucio P.; Perini, Ana P.; Fernández-Varea, José M.; Cassola, Vagner F.; Kramer, Richard; Khoury, Helen J.; Caldas, Linda V. E.

    2014-02-01

    The aim of this work was to study the performance of a pencil ionization chamber with a sensitive volume of only 1.06 cm3 and a length of 3.0 cm, developed at the Calibration Laboratory of the IPEN, in very low-energy radiotherapy X-ray beams. These beams are still used for certain skin cancer treatments due to their rapid attenuation in tissue. The dosimeter performance was evaluated in some tests proposed by the IEC 60731 standard: short- and long-term stability and linearity of response. For a complete analysis of the dosimeter response, the EGSnrc Monte Carlo simulation was utilized to investigate the influence of its different parts on the ionization chamber response. All results of the tests were in accordance with the recommended limits, and this work shows that it is possible to extend the application of this pencil-type ionization chamber developed at the LCI.

  8. Virtual Frisch-grid ionization chambers filled with high-pressure Xe

    NASA Astrophysics Data System (ADS)

    Bolotnikov, Aleksey E.; Austin, Robert; Bolozdynya, Alexander; Richards, John D.

    2004-10-01

    New approaches to the design of high-pressure Xe (HPXe) ionization chambers are described. HPXe ionization chambers represent a well-known technique for detecting gamma rays in the energy range between 50 keV and 3 MeV. Since the HPXe detector is an electron-only carrier device, its commonly accepted design includes a Frisch-grid-a metal mesh employed for the electrostatic shielding from the immobile positive ions. The grid is a key element of the device"s design which provides good energy resolution of the detector, typically 2-3% FWHM at 662 keV. However, the grid makes the design more complex and less rugged, especially for field applications. Recently, we developed several designs of HPXe ionization chambers without shielding grids. The results obtained from the testing of these devices are presented here.

  9. Performance of three pencil-type ionization chambers (10 cm) in computed tomography standard beams

    NASA Astrophysics Data System (ADS)

    de Castro, Maysa C.; Xavier, Marcos; Caldas, Linda V. E.

    2016-07-01

    The use of computed tomography (CT) has increased over the years, thus generating a concern about the doses received by patients undergoing this procedure. Therefore, it is necessary to perform routinely beam dosimetry with the use of a pencil-type ionization chamber. This detector is the most utilized in the procedures of quality control tests on this kind of equipment. The objective of this work was to perform some characterization tests in standard CT beams, as the saturation curve, polarity effect, ion collection efficiency and linearity of response, using three ionization chambers, one commercial and two developed at the IPEN.

  10. Response and Monte Carlo evaluation of a reference ionization chamber for radioprotection level at calibration laboratories

    NASA Astrophysics Data System (ADS)

    Neves, Lucio P.; Vivolo, Vitor; Perini, Ana P.; Caldas, Linda V. E.

    2015-07-01

    A special parallel plate ionization chamber, inserted in a slab phantom for the personal dose equivalent Hp(10) determination, was developed and characterized in this work. This ionization chamber has collecting electrodes and window made of graphite, and the walls and phantom made of PMMA. The tests comprise experimental evaluation following international standards and Monte Carlo simulations, employing the PENELOPE code to evaluate the design of this new dosimeter. The experimental tests were conducted employing the radioprotection level quality N-60 established at the IPEN, and all results were within the recommended standards.

  11. A multiple sampling time projection ionization chamber for nuclear fragment tracking and charge measurement

    NASA Astrophysics Data System (ADS)

    Bauer, G.; Bieser, F.; Brady, F. P.; Chance, J. C.; Christie, W. F.; Gilkes, M.; Lindenstruth, V.; Lynen, U.; Müller, Walter F. J.; Romero, J. L.; Sann, H.; Tull, C. E.; Warren, P.

    1997-02-01

    A detector has been developed for the tracking and charge measurement of the projectile fragment nuclei produced in relativistic nuclear collisions. This device, MUSIC II, is a second generation Multiple Sampling Ionization Chamber (MUSIC), and employs the principles of ionization and time projection chambers. It provides unique charge determination for charges Z≥6, and excellent track position measurement. MUSIC II has been used most recently with the EOS (Equation of State) TPC and other EOS Collaboration detectors. Earlier it was used with other systems in experiments at the Heavy Ion Superconducting Spectrometer (HISS) facility at Lawrence Berkeley Laboratory and the ALADIN spectrometer at GSI.

  12. Pulse mode readout techniques for use with non-gridded industrial ionization chambers

    SciTech Connect

    Popov, Vladimir E.; Degtiarenko, Pavel V.

    2011-10-01

    Highly sensitive readout technique for precision long-term radiation measurements has been developed and tested in the Radiation Control Department at Jefferson Lab. The new electronics design is used to retrieve ionization data in a pulse mode. The dedicated data acquisition system works with M=Audio Audiophile 192 High-Definition 24-bit/192 kHz audio cards, taking data in continuous waveform recording mode. The on-line data processing algorithms extract signals of the ionization events from the data flow and measure the ionization value for each event. Two different ion chambers are evaluated. The first is a Reuter-Stokes Argon-filled (at 25 atm) High Pressure Ionization Chamber (HPIC), commonly used as a detector part in many GE Reuter-Stokes instruments of the RSS series. The second is a VacuTec Model 70181, 5 atm Xenon-filled ionization chamber. Results for both chambers indicate that the techniques allow using industrial ICs for high sensitivity and precision long-term radiation measurements, while at the same time providing information about spectral characteristics of the radiation fields.

  13. Assessment of small volume ionization chambers as reference dosimeters in high-energy photon beams

    NASA Astrophysics Data System (ADS)

    Le Roy, M.; de Carlan, L.; Delaunay, F.; Donois, M.; Fournier, P.; Ostrowsky, A.; Vouillaume, A.; Bordy, J. M.

    2011-09-01

    LNE-LNHB is involved in a European project aiming at establishing absorbed dose-to-water standards for photon-radiation fields down to 2 × 2 cm2. This requires the calibration of reference ionization chambers of small volume. Twenty-four ionization chambers of eight different types with volume ranging from 0.007 to 0.057 cm3 were tested in a 60Co beam. For each chamber, two major characteristics were investigated: (1) the stability of the measured current as a function of the irradiation time under continuous irradiation. At LNE-LNHB, the variation of the current should be less than ±0.1% in comparison with its first value (over a 16 h irradiation time); (2) the variation of the ionization current with the applied polarizing voltage and polarity. Leakage currents were also measured. Results show that (1) every tested PTW (31015, 31016 and 31014) and Exradin A1SL chambers demonstrate a satisfying stability under irradiation. Other types of chambers have a stability complying with the stability criterion for some or none of them. (2) IBA CC01, IBA CC04 and Exradin A1SL show a proper response as a function of applied voltage for both polarities. PTW, Exradin A14SL and Exradin A16 do not. Only three types of chambers were deemed suitable as reference chambers according to LNE-LNHB requirements and specifications from McEwen (2010 Med. Phys. 37 2179-93): Exradin A1SL chambers (3/3), IBA CC04 (2/3) and IBA CC01 (1/3). The Exradin A1SL type with an applied polarizing voltage of 150 V was chosen as an LNE-LNHB reference chamber type in 2 × 2 cm2 radiation fields.

  14. Microwave Triggered Laser Ionization of Air

    NASA Astrophysics Data System (ADS)

    Vadiee, Ehsan; Prasad, Sarita; Jerald Buchenauer, C.; Schamiloglu, Edl

    2012-10-01

    The goal of this work is to study the evolution and dynamics of plasma expansion when a high power microwave (HPM) pulse is overlapped in time and space on a very small, localized region of plasma formed by a high energy laser pulse. The pulsed Nd:YAG laser (8 ns, 600mJ, repetition rate 10 Hz) is focused to generate plasma filaments in air with electron density of 10^17/cm^3. When irradiated with a high power microwave pulse these electrons would gain enough kinetic energy and further escalate avalanche ionization of air due to elastic electron-neutral collisions thereby causing an increased volumetric discharge region. An X-band relativistic backward wave oscillator(RBWO) at the Pulsed Power,Beams and Microwaves laboratory at UNM is constructed as the microwave source. The RBWO produces a microwave pulse of maximum power 400 MW, frequency of 10.1 GHz, and energy of 6.8 Joules. Special care is being given to synchronize the RBWO and the pulsed laser system in order to achieve a high degree of spatial and temporal overlap. A photodiode and a microwave waveguide detector will be used to ensure the overlap. Also, a new shadowgraph technique with a nanosecond time resolution will be used to detect changes in the shock wave fronts when the HPM signal overlaps the laser pulse in time and space.

  15. Breast in vivo dosimetry by a portal ionization chamber

    SciTech Connect

    Grimaldi, Luca; D'Onofrio, Guido; Cilla, Savino; Fidanzio, Andrea; Stimato, Gerardina; Azario, Luigi; Deodato, Francesco; Macchia, Gabriella; Morganti, Alessio; Piermattei, Angelo

    2007-03-15

    This work reports a practical method for the determination of the in vivo breast middle dose value, D{sub m}, on the beam central axis, using a signal S{sub t}, obtained by a small thimble ion chamber positioned at the center of the electronic portal imaging device, and irradiated by the x-ray beam transmitted through the patient. The use of a stable ion chamber reduces many of the disadvantages associated with the use of diodes as their periodic recalibration and positioning is time consuming. The method makes use of a set of correlation functions obtained by the ratios S{sub t}/D{sub m}, determined by irradiating cylindrical water phantoms with different diameters. The method proposed here is based on the determination of the water-equivalent thickness of the patient, along the beam central axis, by the treatment planning system that makes use of the electron densities obtained by a computed tomography scanner. The method has been applied for the breast in vivo dosimetry of ten patients treated with a manual intensity modulation with four asymmetric beams. In particular, two tangential rectangular fields were first delivered, thereafter a fraction of the dose (typically less than 10%) was delivered with two multi leaf-shaped beams which included only the mammarian tissue. Only the two rectangular fields were tested and for every checked field five measurements were carried out. Applying a continuous quality assurance program based on the tests of patient setup, machine settings and dose planning, the proposed method is able to verify agreements between the computed dose D{sub m,TPS} and the in vivo dose value D{sub m}, within 4%.

  16. SU-E-T-415: An Ionization Chamber Array with High Spatial Resolution for External Beam Radiotherapy

    SciTech Connect

    Togno, M; Wilkens, J; Menichelli, D

    2014-06-01

    Purpose: To characterize an ionization chamber array technology with high spatial resolution and high charge collection efficiency for external beam radiotherapy. Methods: The prototype under test is a linear array of air vented ionization chambers developed by IBA Dosimetry, consisting of 80 pixels with 3.5mm spatial resolution and 4mm{sup 3} sensitive volume. The detector was characterized in a plastic phantom with {sup 60} Co radiation and MV X-rays from an ELEKTA Agility LINAC (with flattened and unflattened beam qualities). Bias voltage was varied in order to evaluate charge collection efficiency. A commercial array of ionization chambers (MatriXX Evolution, IBA Dosimetry) and an amorphous silicon flat panel in direct conversion configuration were used as references. Results: Repeatability (0.4%) and stability under continuous gamma irradiation (0.3%) are very good, in spite of low active volume and sensitivity (∼200pC/Gy). Charge collection efficiency is higher than 99% already at 150V with ∼2mGy dose per pulse, leading to a ±1.1% sensitivity change with dose per pulse in the range 0.09-2mGy (covering all flattened and unflattened applications). Measured dose profiles are in agreement with MatriXX for fields larger than 2×2cm{sup 2}, in which case the linear array offers a much better characterization of the penumbra region. Down to 1×1cm{sup 2}, measured profiles are in very good agreement with the flat panel. Conclusion: The array represents a valuable tool for the characterization of treatment fields in which high spatial resolution is required, together with the dosimetric performance of air vented ionization chambers. Such a technology would be particularly valuable in association with advanced treatment modalities such as rotational radiotherapy, stereotactic treatments (even with unflattened beam qualities) and proton therapy, due to the insensitivity of the chambers on dose per pulse. In the future, a two dimensional prototype based on this

  17. Overview of Atmospheric Ionizing Radiation (AIR)

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Maiden, D. L.; Goldhagen, P.; Tai, H.; Shinn, J. L.

    2003-01-01

    The SuperSonic Transport (SST) development program within the US was based at the Langley Research Center as was the Apollo radiation testing facility (Space Radiation Effects Laboratory) with associated radiation research groups. It was natural for the issues of the SST to be first recognized by this unique combination of research programs. With a re-examination of the technologies for commercial supersonic flight and the possible development of a High Speed Civil Transport (HSCT), the remaining issues of the SST required resolution. It was the progress of SST radiation exposure research program founded by T. Foelsche at the Langley Research Center and the identified remaining issues after that project over twenty-five years ago which became the launch point of the current atmospheric ionizing radiation (AIR) research project. Added emphasis to the need for reassessment of atmospheric radiation resulted from the major lowering of the recommended occupational exposure limits, the inclusion of aircrew as radiation workers, and the recognition of civil aircrew as a major source of occupational exposures. Furthermore, the work of Ferenc Hajnal of the Environmental Measurements Laboratory brought greater focus to the uncertainties in the neutron flux at high altitudes. A re-examination of the issues involved was committed at the Langley Research Center and by the National Council on Radiation Protection (NCRP). As a result of the NCRP review, a new flight package was assembled and flown during solar minimum at which time the galactic cosmic radiation is at a maximum (June 1997). The present workshop is the initial analysis of the new data from that flight. The present paper is an overview of the status of knowledge of atmospheric ionizing radiations. We will re-examine the exposures of the world population and examine the context of aircrew exposures with implications for the results of the present research. A condensed version of this report was given at the 1998

  18. Biomass production chamber air analysis of wheat study (BWT931)

    NASA Technical Reports Server (NTRS)

    Batten, J. H.; Peterson, B. V.; Berdis, E.; Wheeler, E. M.

    1993-01-01

    NASA's Controlled Ecological Life Support System (CELSS) biomass production chamber at John F. Kennedy Space Center provides a test bed for bioregenerative studies using plants to provide food, oxygen, carbon dioxide removal, and potable water to humans during long term space travel. Growing plants in enclosed environments has brought about concerns regarding the level of volatile organic compounds (VOC's) emitted from plants and the construction materials that make up the plant growth chambers. In such closed systems, the potential exists for some VOC's to reach toxic levels and lead to poor plant growth, plant death, or health problems for human inhabitants. This study characterized the air in an enclosed environment in which wheat cv. Yocora Rojo was grown. Ninty-four whole air samples were analyzed by gas chromatography/mass spectrometry throughout the eighty-four day planting. VOC emissions from plants and materials were characterized and quantified.

  19. Determination of ion recombination correction factors for a liquid ionization chamber in megavoltage photon beams

    NASA Astrophysics Data System (ADS)

    Choi, Sang Hyoun; Kim, Kum-Bae; Ji, Young Hoon; Kim, Chan Hyeong; Kim, Seonghoon; Huh, Hyun Do

    2015-05-01

    The aim of this study is to determine the ion recombination correction factor for a liquid ionization chamber in a high energy photon beam by using our experimental method. The ion recombination correction factors were determined by using our experimental method and were compared with theoretical and experimental methods proposed by using the theoretical method (Greening, Johansson) and the two-dose rate method in a cobalt beam and a high energy photon beam. In order to apply the liquid ionization chamber in a reference and small field dosimetry, we acquired the absorbed dose to water correction coefficient, the beam quality correction factor, and the influence quantities for the microLion chamber according to the TRS-398 protocol and applied the results to a high energy photon beam used in clinical fields. As a result, our experimental method for ion recombination in a cobalt beam agreed with the results from the heoretical method (Greening theory) better than it did with the results from the two-dose rate method. For high energy photon beams, the two-dose rate and our experimental methods were in good agreement, less than 2% deviation, while the theoretical general collection efficiency (Johansson et al.) deviated greatly from the experimental values. When we applied the factors for the absorbed dose to water measurement, the absorbed dose to water for the microLion chamber was in good agreement, within 1%, compared with the values for the PTW 30013 chamber in 6 and 10 MV Clinac iX and 6 and 15 MV Oncor impression. With these results, not only can the microLion ionization chamber be used to measure the absorbed dose to water in a reference condition, it can also be used to a the chamber for small, non-standard field dosimetry.

  20. Thimble ionization chambers in medium-energy x-ray beams and the role of constructive details of the central electrode: Monte Carlo simulations and measurements

    NASA Astrophysics Data System (ADS)

    Ubrich, F.; Wulff, J.; Kranzer, R.; Zink, K.

    2008-09-01

    This paper presents investigations of thimble ionization chamber response in medium-energy kilovoltage x-ray beams (70-280 kVp, 0.09-3.40 mm Cu HVL). Two thimble ionization chambers (PTW30015 and PTW30016) were investigated, regarding the influence of the central electrode dimensions made of aluminum. Measurements were carried out in photon fields of different beam quality. Corresponding Monte Carlo simulations employing the EGSnrc Monte Carlo code system were performed. The simulations included the modelling of the x-ray tube and measurement setup for generation of x-ray spectra. These spectra were subsequently used to calculate the absorbed energy in the air cavity of the two thimble ionization chamber models and the air kerma at the reference point of the chambers. Measurements and simulations revealed an optimal diameter of the central electrode, concerning an almost energy-independent response of the ionizaton chamber. The Monte Carlo simulations are in good agreement with the measured values, expressed in beam quality correction factors kQ. The agreement was generally within 0.6% but could only be achieved with an accurate model of the central electrode including its exact shape. Otherwise, deviations up to 8.5% resulted, decreasing with higher photon energies, which can be addressed to the high yield of the photoelectric effect in the electrode material aluminum at low photon energies.

  1. Towards reference dosimetry for the MR-linac: magnetic field correction of the ionization chamber reading

    NASA Astrophysics Data System (ADS)

    Smit, K.; van Asselen, B.; Kok, J. G. M.; Aalbers, A. H. L.; Lagendijk, J. J. W.; Raaymakers, B. W.

    2013-09-01

    In the UMC Utrecht a prototype MR-linac has been installed. The system consists of a 6 MV Elekta (Crawley, UK) linear accelerator and a 1.5 T Philips (Best, The Netherlands) Achieva MRI system. This paper investigates the feasibility to correct the ionization chamber reading for the magnetic field within the dosimetry calibration method described by Almond et al (1999 Med. Phys. 26 1847-70). Firstly, the feasibility of using an ionization chamber in an MR-linac was assessed by investigating possible influences of the magnetic field on NE2571 Farmer-type ionization chamber characteristics: linearity, repeatability, orientation in the magnetic field; and AAPM TG51 correction factor for voltage polarity and ion recombination. We found that these AAPM correction factors for the NE2571 chamber were not influenced by the magnetic field. Secondly, the influence of the permanent 1.5 T magnetic field on the NE2571 chamber reading was quantified. The reading is influenced by the magnetic field; therefore, a correction factor has been added. For the standardized setup used in this paper, the NE2571 chamber reading increases by 4.9% (± 0.2%) due to the transverse 1.5 T magnetic field. Dosimetry measurements in an MR-linac are feasible, if a setup-specific magnetic field correction factor (P1.5 T) for the charge reading is introduced. For the setup investigated in this paper, the P1.5 T has a value of 0.953.

  2. Towards reference dosimetry for the MR-linac: magnetic field correction of the ionization chamber reading.

    PubMed

    Smit, K; van Asselen, B; Kok, J G M; Aalbers, A H L; Lagendijk, J J W; Raaymakers, B W

    2013-09-01

    In the UMC Utrecht a prototype MR-linac has been installed. The system consists of a 6 MV Elekta (Crawley, UK) linear accelerator and a 1.5 T Philips (Best, The Netherlands) Achieva MRI system. This paper investigates the feasibility to correct the ionization chamber reading for the magnetic field within the dosimetry calibration method described by Almond et al (1999 Med. Phys. 26 1847-70). Firstly, the feasibility of using an ionization chamber in an MR-linac was assessed by investigating possible influences of the magnetic field on NE2571 Farmer-type ionization chamber characteristics: linearity, repeatability, orientation in the magnetic field; and AAPM TG51 correction factor for voltage polarity and ion recombination. We found that these AAPM correction factors for the NE2571 chamber were not influenced by the magnetic field. Secondly, the influence of the permanent 1.5 T magnetic field on the NE2571 chamber reading was quantified. The reading is influenced by the magnetic field; therefore, a correction factor has been added. For the standardized setup used in this paper, the NE2571 chamber reading increases by 4.9% (± 0.2%) due to the transverse 1.5 T magnetic field. Dosimetry measurements in an MR-linac are feasible, if a setup-specific magnetic field correction factor (P1.5 T) for the charge reading is introduced. For the setup investigated in this paper, the P1.5 T has a value of 0.953. PMID:23938362

  3. Improving the accuracy of ionization chamber dosimetry in small megavoltage x-ray fields

    NASA Astrophysics Data System (ADS)

    McNiven, Andrea L.

    The dosimetry of small x-ray fields is difficult, but important, in many radiation therapy delivery methods. The accuracy of ion chambers for small field applications, however, is limited due to the relatively large size of the chamber with respect to the field size, leading to partial volume effects, lateral electronic disequilibrium and calibration difficulties. The goal of this dissertation was to investigate the use of ionization chambers for the purpose of dosimetry in small megavoltage photon beams with the aim of improving clinical dose measurements in stereotactic radiotherapy and helical tomotherapy. A new method for the direct determination of the sensitive volume of small-volume ion chambers using micro computed tomography (muCT) was investigated using four nominally identical small-volume (0.56 cm3) cylindrical ion chambers. Agreement between their measured relative volume and ionization measurements (within 2%) demonstrated the feasibility of volume determination through muCT. Cavity-gas calibration coefficients were also determined, demonstrating the promise for accurate ion chamber calibration based partially on muCT. The accuracy of relative dose factor measurements in 6MV stereotactic x-ray fields (5 to 40mm diameter) was investigated using a set of prototype plane-parallel ionization chambers (diameters of 2, 4, 10 and 20mm). Chamber and field size specific correction factors ( CSFQ ), that account for perturbation of the secondary electron fluence, were calculated using Monte Carlo simulation methods (BEAM/EGSnrc simulations). These correction factors (e.g. CSFQ = 1.76 (2mm chamber, 5mm field) allow for accurate relative dose factor (RDF) measurement when applied to ionization readings, under conditions of electronic disequilibrium. With respect to the dosimetry of helical tomotherapy, a novel application of the ion chambers was developed to characterize the fan beam size and effective dose rate. Characterization was based on an adaptation of the

  4. A liquid xenon ionization chamber in an all-fluoropolymer vessel

    NASA Astrophysics Data System (ADS)

    LePort, F.; Pocar, A.; Bartoszek, L.; DeVoe, R.; Fierlinger, P.; Flatt, B.; Gratta, G.; Green, M.; Koffas, T.; Montero Díez, M.; Neilson, R.; O'Sullivan, K.; Waldman, S.; Wodin, J.; Woisard, D.; Baussan, E.; Breidenbach, M.; Conley, R.; Fairbank, W.; Farine, J.; Hall, C.; Hall, K.; Hallman, D.; Hargrove, C.; Hodgson, J.; Jeng, S.; Leonard, D. S.; Mackay, D.; Martin, Y.; Odian, A.; Ounalli, L.; Piepke, A.; Prescott, C. Y.; Rowson, P. C.; Skarpaas, K.; Schenker, D.; Sinclair, D.; Stekhanov, V.; Strickland, V.; Virtue, C.; Vuilleumier, J.-L.; Vuilleumier, J.-M.; Wamba, K.; Weber, P.

    2007-08-01

    A novel technique has been developed to build vessels for liquid xenon ionization detectors entirely out of an ultra-clean fluoropolymer. One such detector was operated inside a welded, He leak tight, all-fluoropolymer chamber. The measured energy resolution for 570 keV gamma rays is σ/E=5.1% at a drift field of 1.5 kV/cm, in line with the best values obtained for ionization only detectors run in LXe using conventional, metal vessels.

  5. Total diesel exhaust particulate length measurements using a modified household smoke alarm ionization chamber.

    PubMed

    Vojtisek-Lom, Michal

    2011-02-01

    To evaluate the effectiveness of various means to combat the negative health effects of ultrafine particles emitted by internal combustion engines, a reliable, low-cost instrument for dynamic measurements of the exhaust emissions of ultrafine particulate matter (PM) is needed. In this study, an ordinary ionization-type building smoke detector was modified to serve as a measuring ionization chamber and utilized for dynamic measurements of PM emissions from diesel engines. When used with diluted exhaust, the readings show an excellent correlation with total particulate length. The instrument worked well with raw and diluted exhaust and with varying emission levels and is well suitable for on-board use. PMID:21387930

  6. Validation of the neutron and gamma fields in the JSI TRIGA reactor using in-core fission and ionization chambers.

    PubMed

    Žerovnik, Gašper; Kaiba, Tanja; Radulović, Vladimir; Jazbec, Anže; Rupnik, Sebastjan; Barbot, Loïc; Fourmentel, Damien; Snoj, Luka

    2015-02-01

    CEA developed fission chambers and ionization chambers were utilized at the JSI TRIGA reactor to measure neutron and gamma fields. The measured axial fission rate distributions in the reactor core are generally in good agreement with the calculated values using the Monte Carlo model of the reactor thus verifying both the computational model and the fission chambers. In future, multiple absolutely calibrated fission chambers could be used for more accurate online reactor thermal power monitoring. PMID:25479432

  7. Simulations of ^12C Break Up In A Twin Ionization Chamber

    NASA Astrophysics Data System (ADS)

    Segal, C. B.; Patel, N. R.; Greife, U.; Rehm, K. E.; Deibel, C. M.; Greene, J.; Henderson, D.; Jiang, C. L.; Kay, B. P.; Lee, H. Y.; Pardo, R.; Notani, M.; Marley, S. T.; Tang, X. D.

    2008-10-01

    In stellar explosions the triple α decay process is key to forming the life-giving ^12C . This experiment is to further investigate the energy region in ^12C around 10 MeV where a theoretically predicted 2^+ state has yet to be observed. The motivation for studying this is to better understand the ^12C nucleosynthesis process that occurs in red giant stars where the short lived ^8Be interacts with alphas at extreme temperature and pressure scenarios which then in turn creates ^12C. We study the particle-unbound states by implanting ^12B into a twin Frisch grid ionization chamber and following the decay into ^12C and subsequently into three α particles. The response of this ionization chamber to the detection of multiple α particles was studied using various simulation programs. Results of these simulations and limits for the predicted 2^+ state will be presented.

  8. Neutron and gamma detector using an ionization chamber with an integrated body and moderator

    DOEpatents

    Ianakiev, Kiril D.; Swinhoe, Martyn T.; Lestone, John Paul

    2006-07-18

    A detector for detecting neutrons and gamma radiation includes a cathode that defines an interior surface and an interior volume. A conductive neutron-capturing layer is disposed on the interior surface of the cathode and a plastic housing surrounds the cathode. A plastic lid is attached to the housing and encloses the interior volume of the cathode forming an ionization chamber, into the center of which an anode extends from the plastic lid. A working gas is disposed within the ionization chamber and a high biasing voltage is connected to the cathode. Processing electronics are coupled to the anode and process current pulses which are converted into Gaussian pulses, which are either counted as neutrons or integrated as gammas, in response to whether pulse amplitude crosses a neutron threshold. The detector according to the invention may be readily fabricated into single or multilayer detector arrays.

  9. Hard disk drive based microsecond X-ray chopper for characterization of ionization chambers and photodiodes.

    PubMed

    Müller, O; Lützenkirchen-Hecht, D; Frahm, R

    2015-03-01

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper. PMID:25832273

  10. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    SciTech Connect

    Müller, O. Lützenkirchen-Hecht, D.; Frahm, R.

    2015-03-15

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  11. Application of the Shockley-Ramo theorem on the grid inefficiency of Frisch grid ionization chambers

    NASA Astrophysics Data System (ADS)

    Göök, A.; Hambsch, F.-J.; Oberstedt, A.; Oberstedt, S.

    2012-02-01

    The concept of grid inefficiency in Frisch grid ionization chambers and its influence on the anode pulse shape is explained in terms of the Shockley-Ramo theorem for induced charges. The grid inefficiency correction is deduced from numerically calculated weighting potentials. A method to determine the correction factor experimentally is also presented. Experimental and calculated values of the correction factor are shown to be in good agreement.

  12. Comparative study of ionization chamber detectors vis-a-vis a CCD detector for dispersive XAS measurement in transmission geometry

    SciTech Connect

    Poswal, A. K.; Agrawal, A.; Bhattachryya, D.; Jha, S. N.; Sahoo, N. K.

    2013-02-05

    We have designed and fabricated parallel plate ionization chamber detectors and voltage vs. current characteristics (V-I curve) of the detectors were recorded with synchrotron radiation to qualify for use in X-ray Absorption Spectroscopy (XAS) measurements. After qualifying the ionization chambers, the detectors were used in the dispersive EXAFS beamline (BL-08) at INDUS-2 SRS in Turbo-XAS geometry. Using the same setup and under the same setting, XAS spectra were also recorded with a CCD detector and the observation on relative performance of the ionization chamber vis-a-vis the CCD detector is presented in this paper.

  13. Comparative study of ionization chamber detectors vis-à-vis a CCD detector for dispersive XAS measurement in transmission geometry

    NASA Astrophysics Data System (ADS)

    Poswal, A. K.; Agrawal, A.; Bhattachryya, D.; Jha, S. N.; Sahoo, N. K.

    2013-02-01

    We have designed and fabricated parallel plate ionization chamber detectors and voltage vs. current characteristics (V-I curve) of the detectors were recorded with synchrotron radiation to qualify for use in X-ray Absorption Spectroscopy (XAS) measurements. After qualifying the ionization chambers, the detectors were used in the dispersive EXAFS beamline (BL-08) at INDUS-2 SRS in Turbo-XAS geometry. Using the same setup and under the same setting, XAS spectra were also recorded with a CCD detector and the observation on relative performance of the ionization chamber vis-a-vis the CCD detector is presented in this paper.

  14. A position-sensitive twin ionization chamber for fission fragment and prompt neutron correlation experiments

    NASA Astrophysics Data System (ADS)

    Göök, A.; Geerts, W.; Hambsch, F.-J.; Oberstedt, S.; Vidali, M.; Zeynalov, Sh.

    2016-09-01

    A twin position-sensitive Frisch grid ionization chamber, intended as a fission fragment detector in experiments to study prompt fission neutron correlations with fission fragment properties, is presented. Fission fragment mass and energies are determined by means of the double kinetic energy technique, based on conservation of mass and linear momentum. The position sensitivity is achieved by replacing each anode plate in the standard twin ionization chamber by a wire plane and a strip anode, both readout by means of resistive charge division. This provides information about the fission axis orientation, which is necessary to reconstruct the neutron emission process in the fully accelerated fragment rest-frame. The energy resolution compared to the standard twin ionization chamber is found not to be affected by the modification. The angular resolution of the detector relative to an arbitrarily oriented axis is better than 7° FWHM. Results on prompt fission neutron angular distributions in 235U(n,f) obtained with the detector in combination with an array of neutron scintillation detectors is presented as a proof of principle.

  15. An ionization chamber with Frisch grids for studies of high-energy neutron-induced fission

    NASA Astrophysics Data System (ADS)

    Tutin, G. A.; Ryzhov, I. V.; Eismont, V. P.; Kireev, A. V.; Condé, H.; Elmgren, K.; Olsson, N.; Renberg, P.-U.

    2001-01-01

    A gridded ionization chamber for fission fragment detection is described. The chamber has been specially designed for use at the quasi-monoenergetic 7Li(p, n) neutron source at the The Svedberg Laboratory, Uppsala, Sweden. The detector permits measurements of fission fragment energy and emission angle for two targets with diameter of up to 10 cm. The time response of the chamber (⩽5 ns FWHM) is adequate to apply time-of-flight discrimination against background events induced by non-peak neutrons. Results of angular anisotropy measurements for the 232Th (n, f) and 238U(n, f) reactions in the 20-160 MeV energy range are given.

  16. Theoretical study of Jesse effect in tritium measurements using ionization chambers

    NASA Astrophysics Data System (ADS)

    Chen, Zhilin; Peng, Shuming; Lu, Hanghang; Tan, Zhaoyi; Wang, Heyi; Long, Xingui; Masao, Matsuyama

    2016-01-01

    Jesse effect caused by impurities in helium might enhance the output signal significantly in tritium measurements with ionization chamber, which will lead to overestimation of tritium concentration in experiments. A theoretical method was proposed to evaluate Jesse effect quantitatively. Results indicate that besides Penning ionization, sub-excitation electrons also place very important influence on ionization enhancement by Jesse effect. An experiential expression about the relationship between enhancement factor and impurity concentration was established, in which second order of it fits experimental results very well. Theoretical calculation method in this paper is also applicable to evaluate Jesse effect in other kinds of mixtures besides hydrogen as impurities in helium. In addition, Jesse effects about tritium molecules as impurities have also been investigated.

  17. Photodegradation of polyaromatic hydrocarbons in passive air samplers: Field testing different deployment chambers

    USGS Publications Warehouse

    Bartkow, M.E.; Kennedy, K.E.; Huckins, J.N.; Holling, N.; Komarova, T.; Muller, J.F.

    2006-01-01

    Semi-permeable membrane devices (SPMDs) were loaded with deuterated anthracene and pyrene as performance reference compounds (PRCs) and deployed at a test site in four different chambers (open and closed box chamber, bowl chamber and cage chamber) for 29 days. The losses of PRCs and the uptake of polyaromatic hydrocarbons (PAHs) from the ambient air were quantified. UV-B levels measured in each deployment chamber indicated that SPMDs would be exposed to the most UV-B in the cage chamber and open box chamber. Significantly less PAHs were quantified in SPMDs deployed in the cage chamber and open box chamber compared to samplers from the other two chambers, suggesting that photodegradation of PAHs had occurred. The loss of PRCs confirmed these results but also showed that photodegradation was occurring in the closed box chamber. The bowl chamber appears to provide the best protection from the influence of direct photodegradation. ?? 2006 Elsevier Ltd. All rights reserved.

  18. An online proton beam monitor for cancer therapy based on ionization chambers with micro pattern readout

    NASA Astrophysics Data System (ADS)

    Basile, E.; Carloni, A.; Castelluccio, D. M.; Cisbani, E.; Colilli, S.; De Angelis, G.; Fratoni, R.; Frullani, S.; Giuliani, F.; Gricia, M.; Lucentini, M.; Santavenere, F.; Vacca, G.

    2012-03-01

    A unique compact LINAC accelerator for proton therapy is under development in Italy within the TOP-IMPLART project. The proton beam will reach the kinetic energy of 230 MeV, it will have a widely variable current intensity (0.1-10 μA, with average up to 3.5 nA) associated with a high pulse repetition frequency (1-3.5 μs long pulses at 10-100 Hz). The TOP-IMPLART system will provide a fully active 3+1D dose delivery, that is longitudinal (energy modulation), transverse active spot scanning, and current intensity modulation. These accelerator features will permit a highly conformational dose distribution, which therefore requires an effective, online, beam monitor system with wide dynamic range, good sensitivity, adequate spatial resolution and rapid response. In order to fulfill these requisites a new device is under development for the monitoring of the beam intensity profile, its centroid and direction; it is based on transmission, segmented, ionization chambers with typical active area of 100 × 100 mm2. Micro pattern x/y pad like design has been used for the readout plane in order to maximize the field uniformity, reduce the chamber thickness and obtain both beam coordinates on a single chamber. The chamber prototype operates in ionization region to minimize saturation and discharge effects. Simulations (based on FLUKA) have been carried on to study the perturbation of the chamber on the beam parameters and the effects on the delivered dose (on a water phantom). The charge collected in each channel is integrated by dedicated auto-ranging readout electronics: an original scheme has been developed in order to have an input dynamic range greater than 104 with sensitivity better than 3%. This is achieved by a dynamical adjustment of the integrating capacitance to the signal intensity.

  19. Ion recombination corrections of ionization chambers in flattening filter-free photon radiation.

    PubMed

    Wang, Yuenan; Easterling, Stephen B; Ting, Joseph Y

    2012-01-01

    The flattening filter free (FFF) X-rays can provide much higher dose rate at the treatment target compared to the conventional flattened X-rays. However, the substantial increase of dose rate for FFF beams may affect the ion recombination correction factor, which is required for accurate measurements using ionization chambers in clinical dosimetry. The purpose of this work is to investigate the ion recombination of three types of commonly used ion chambers (Farmer, PinPoint and plane-parallel) in the FFF photon radiation. Both 6 MV and 10 MV flattened and FFF beams were fully commissioned on a Varian TrueBeam linear accelerator. The ion recombination correction factor, P(ion), was determined using the two-voltage technique for a 0.6 cc Farmer chamber, a 0.015 cc PinPoint chamber, and a 0.02 cc parallel-plate chamber at different source-to-axis distances (SAD) in a solid water phantom or water tank phantom at a depth of 10 cm in a 10 × 10 cm(2) field. Good repeatability of measurements was demonstrated. Less than 1% difference in P(ion) between the flattened and FFF photons for all three ion chambers was observed. At a SAD of 100 cm and a depth of 10 cm for a 10 × 10 cm(2) field, P(ion) for the Farmer chamber was 1.004 and 1.008 for the 6 MV flattened and FFF beams, respectively. At the same setup using the Farmer chamber, P(ion) was 1.002 and 1.015 for the 10MV flattened and FFF beams, respectively. All P(ion) results for the Farmer, PinPoint, or parallel plate chamber in the 6 MV and 10 MV flattened and FFF beams were within 2% from the unity (1 ≤ P(ion) < 1.02). The P(ion) ratio of the FFF to flattened beams was 0.99~1.01 for both 6 MV and 10 MV photons. The ion recombination effect of the Farmer, PinPoint, and plane-parallel chamber in the FFF beams is not substantially different from that in the conventional flattened beams. PMID:22955642

  20. Use of relativistic rise in ionization chambers for measurement of high energy heavy nuclei

    NASA Technical Reports Server (NTRS)

    Barthelmy, S. D.; Israel, M. H.; Klarmann, J.; Vogel, J. S.

    1983-01-01

    A balloon-borne instrument has been constructed to measure the energy spectra of cosmic-ray heavy nuclei in the range of about 0.3 to about 100 GeV/amu. It makes use of the relativistic rise portion of the Bethe-Bloch curve in ionization chambers for energy determination in the 10- to 100-GeV/amu interval. The instrument consists of six layers of dual-gap ionization chambers for energy determination above 10 GeV/amu. Charge is determined with a NE114 scintillator and a Pilot 425 plastic Cerenkov counter. A CO2 gas Cerenkov detector (1 atm; threshold of 30 GeV/amu) calibrates the ion chambers in the relativistic rise region. The main emphasis of the instrument is the determination of the change of the ratio of Iron (26) to the Iron secondaries (21-25) in the energy range of 10 to 100 GeV/amu. Preliminary data from a balloon flight in the fall of 1982 from Palestine, TX is presented.

  1. Measurement of photon flux with a miniature gas ionization chamber in a Material Testing Reactor

    NASA Astrophysics Data System (ADS)

    Fourmentel, D.; Filliatre, P.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Carcreff, H.

    2013-10-01

    Nuclear heating measurements in Material Testing Reactors (MTR) are crucial for the design of the experimental devices and the prediction of the temperature of the hosted samples. Nuclear heating in MTR materials (except fuel) is mainly due to the energy deposition by the photon flux. Therefore, the photon flux is a key input parameter for the computer codes which simulate nuclear heating and temperature reached by samples/devices under irradiation. In the Jules Horowitz MTR under construction at the CEA Cadarache, the maximal expected nuclear heating levels will be about 15 to 18 W g-1 and it will be necessary to assess this parameter with the best accuracy. An experiment was performed at the OSIRIS reactor to combine neutron flux, photon flux and nuclear heating measurements to improve the knowledge of the nuclear heating in MTR. There are few appropriate sensors for selective measurement of the photon flux in MTR even if studies and developments are ongoing. An experiment, called CARMEN-1, was conducted at the OSIRIS MTR and we used in particular a gas ionization chamber based on miniature fission chamber design to measure the photon flux. In this paper, we detail Monte-Carlo simulations to analyze the photon fluxes with ionization chamber measurements and we compare the photon flux calculations to the nuclear heating measurements. These results show a good accordance between photon flux measurements and nuclear heating measurement and allow improving the knowledge of these parameters.

  2. Ambiguities in the grid-inefficiency correction for Frisch-Grid Ionization Chambers

    NASA Astrophysics Data System (ADS)

    Al-Adili, A.; Hambsch, F.-J.; Bencardino, R.; Oberstedt, S.; Pomp, S.

    2012-05-01

    Ionization chambers with Frisch grids have been very successfully applied to neutron-induced fission-fragment studies during the past 20 years. They are radiation resistant and can be easily adapted to the experimental conditions. The use of Frisch grids has the advantage to remove the angular dependency from the charge induced on the anode plate. However, due to the Grid Inefficiency (GI) in shielding the charges, the anode signal remains slightly angular dependent. The correction for the GI is, however, essential to determine the correct energy of the ionizing particles. GI corrections can amount to a few percent of the anode signal. Presently, two contradicting correction methods are considered in literature. The first method adding the angular-dependent part of the signal to the signal pulse height; the second method subtracting the former from the latter. Both additive and subtractive approaches were investigated in an experiment where a Twin Frisch-Grid Ionization Chamber (TFGIC) was employed to detect the spontaneous fission fragments (FF) emitted by a 252Cf source. Two parallel-wire grids with different wire spacing (1 and 2 mm, respectively), were used individually, in the same chamber side. All the other experimental conditions were unchanged. The 2 mm grid featured more than double the GI of the 1 mm grid. The induced charge on the anode in both measurements was compared, before and after GI correction. Before GI correction, the 2 mm grid resulted in a lower pulse-height distribution than the 1 mm grid. After applying both GI corrections to both measurements only the additive approach led to consistent grid independent pulse-height distributions. The application of the subtractive correction on the contrary led to inconsistent, grid-dependent results. It is also shown that the impact of either of the correction methods is small on the FF mass distributions of 235U(nth, f).

  3. Evaluation of ozone generation and indoor organic compounds removal by air cleaners based on chamber tests

    NASA Astrophysics Data System (ADS)

    Yu, Kuo-Pin; Lee, Grace Whei-May; Hsieh, Ching-Pei; Lin, Chi-Chi

    2011-01-01

    Ozone can cause many health problems, including exacerbation of asthma, throat irritation, cough, chest ache, shortness of breath, and respiratory infections. Air cleaners are one of the sources of indoor ozone, and thus the evaluation of ozone generated by air cleaners is desired significant issue. Most evaluation methods proposed are based on chamber tests. However, the adsorption and desorption of ozone on the wall of test chamber and the deposition of ozone resulted from the surface reaction can influence the evaluation results. In this study, we developed a mass balance model that took the adsorption, desorption and deposition of ozone into consideration to evaluate the effective ozone emission rates of six selected air cleaners. The experiments were conducted in a stainless steel chamber with a volume of 11.3 m 3 at 25 °C and 60% relative humidity. The adsorption, desorption and deposition rate constants of ozone obtained by fitting the model to the experimental data were k a = 0.149 ± 0.052 m h -1, k d = 0.013 ± 0.007 h -1, and k r = 0.050 ± 0.020 h -1, respectively. The effective ozone emission rates of Air Cleaners No. 1, 2, and 3 ranged between 13,400-24,500 μg h -1, 7190-10,400 μg h -1, and 4880-6560 μg h -1, respectively, which were more stable than those of No.4, 5, and 6. The effective ozone emission rates of Air Cleaners No. 4, 5, and 6 increased with the time of operation which might be relevant to the decrease of ozone removal by the "aging" filter installed in these cleaners. The removal of toluene and formaldehyde by these six air cleaners were also evaluated and the clean air delivery rates (CADRs) of these two pollutants ranged from non-detectable to 0.42 ± 0.08 m 3 h -1, and from non-detectable to 0.75 ± 0.07 m 3 h -1, respectively. The CADRs showed an insignificant relationship with the effective ozone emission rates. Thus, the removal of toluene and formaldehyde might be resulted from the adsorption on the filters and the

  4. Multi-Sampling Ionization Chamber (MUSIC) for measurements of fusion reactions with radioactive beams

    NASA Astrophysics Data System (ADS)

    Carnelli, P. F. F.; Almaraz-Calderon, S.; Rehm, K. E.; Albers, M.; Alcorta, M.; Bertone, P. F.; Digiovine, B.; Esbensen, H.; Fernández Niello, J.; Henderson, D.; Jiang, C. L.; Lai, J.; Marley, S. T.; Nusair, O.; Palchan-Hazan, T.; Pardo, R. C.; Paul, M.; Ugalde, C.

    2015-11-01

    A detection technique for high-efficiency measurements of fusion reactions with low-intensity radioactive beams was developed. The technique is based on a Multi-Sampling Ionization Chamber (MUSIC) operating as an active target and detection system, where the ionization gas acts as both target and counting gas. In this way, we can sample an excitation function in an energy range determined by the gas pressure, without changing the beam energy. The detector provides internal normalization to the incident beam and drastically reduces the measuring time. In a first experiment we tested the performance of the technique by measuring the 10,13,15C+12C fusion reactions at energies around the Coulomb barrier.

  5. Atmospheric Ionizing Radiation (AIR) ER-2 Preflight Analysis

    NASA Technical Reports Server (NTRS)

    Tai, Hsiang; Wilson, John W.; Maiden, D. L.

    1998-01-01

    Atmospheric ionizing radiation (AIR) produces chemically active radicals in biological tissues that alter the cell function or result in cell death. The AIR ER-2 flight measurements will enable scientists to study the radiation risk associated with the high-altitude operation of a commercial supersonic transport. The ER-2 radiation measurement flights will follow predetermined, carefully chosen courses to provide an appropriate database matrix which will enable the evaluation of predictive modeling techniques. Explicit scientific results such as dose rate, dose equivalent rate, magnetic cutoff, neutron flux, and air ionization rate associated with those flights are predicted by using the AIR model. Through these flight experiments, we will further increase our knowledge and understanding of the AIR environment and our ability to assess the risk from the associated hazard.

  6. Application of patent BR102013018500-0 in well type ionization chambers

    NASA Astrophysics Data System (ADS)

    Sousa, C. H. S.; Peixoto, J. G. P.

    2016-07-01

    The definition of the radioactive sample position in a well type ionization chamber is the largest source of uncertainty in the measurement of quantity activity. The determination of this parameter in two activimeters helped to improve their accuracies, from 2.62 and 2.59% to 3.87 and 1.74%, with and without the use of the positioning device, concluding, that with their use has reached an uncertainty of U =2276 and 0.2677% (k = 2) 95.45%.

  7. Surface-catalyzed air oxidation of hydrazines: Environmental chamber studies

    NASA Technical Reports Server (NTRS)

    Kilduff, Jan E.; Davis, Dennis D.; Koontz, Steven L.

    1988-01-01

    The surface-catalyzed air oxidation reactions of fuel hydrazines were studied in a 6500-liter fluorocarbon-film chamber at 80 to 100 ppm concentrations. First-order rate constants for the reactions catalyzed by aluminum, water-damaged aluminum (Al/Al2O3), stainless steel 304L, galvanized steel and titanium plates with surface areas of 2 to 24 sq m were determined. With 23.8 sq m of Al/Al2O3 the surface-catalyzed air oxidation of hydrazine had a half-life of 2 hours, diimide (N2H2) was observed as an intermediate and traces of ammonia were present in the final product mixture. The Al/Al2O3 catalyzed oxidation of monomethylhydrazine yielded methyldiazine (HN = NCH3) as an intermediate and traces of methanol. Unsymmetrical dimethylhydrazine gave no detectable products. The relative reactivities of hydrazine, MMH and UDMH were 130 : 7.3 : 1.0, respectively. The rate constants for Al/Al2O3-catalyzed oxidation of hydrazine and MMH were proportional to the square of the surface area of the plates. Mechanisms for the surface-catalyzed oxidation of hydrazine and diimide and the formation of ammonia are proposed.

  8. Strip Ionization Chamber as Beam Monitor in the Proton Therapy Eye Treatment

    NASA Astrophysics Data System (ADS)

    Marchetto, F.; Cirio, R.; Garella, M. A.; Giordanengo, S.; Boriano, A.; Givehchi, N.; La Rosa, A.; Peroni, C.; Donetti, M.; Bourhaleb, F.; Pitta', G.; Cirrone, G. A. P.; Cuttone, G.; Raffaele, L.; Sabini, M. G.; Valastro, L.

    2006-04-01

    Since spring 2002, ocular pathologies have been treated in Catania at the Centro di AdroTerapia e Applicazioni Nucleari Avanzate (CATANA) within a collaboration between INFN Laboratori Nazionali del Sud (LNS), Physics Department, Ophthalmology Institute, Radiology Institute of the Catania University and CSFNSM Catania. A beam line from a 62 MeV Superconducting Cyclotron is used to treat shallow tumors. The beam is conformed to the tumor shape with a passive delivery system. A detector system has been developed in collaboration with INFN-Torino to be used as real time beam monitor. The detector, placed upstream of the patient collimator, consists of two parallel plate ionization chambers with the anode segmented in strips. Each anode is made of 0.5 mm-wide 256 strips corresponding to (12.8 × 12.8) cm2 sensitive area. With the two strip ionization chambers one can measure the relevant beam parameters during treatment to probe both asymmetry and flatness. In the test carried out at CATANA the detector has been used under different and extreme beam conditions. Preliminary results are given for profiles and skewness, together with a comparison with reference detectors.

  9. Air entry into the anterior chamber post intravitreal injection of Eylea.

    PubMed

    Lim, Wei Sing; Sikandar, Munir; Jackson, Heather

    2016-01-01

    An 84-year-old man had air entry into the anterior chamber following intravitreal injection. The air bubble was reabsorbed over time without any complications. No further problems occurred with subsequent intravitreal injections. PMID:27440854

  10. Response of air-filled ion chambers to high-intensity radiation pulses

    SciTech Connect

    Plum, M.; Brown, D.

    1993-01-01

    Ion chambers are one of the most popular types of detectors used for beam loss-monitor systems. To provide a foundation for the development of future loss-monitor systems, and to fully characterize the ion chambers in use at LAMPF, we have studied the response of air-filled cylindrical ion chambers to high-intensity, short-duration radiation pulses. The most intense pulses were about 180 rad in 250 ns (the equivalent steady-state dose rate was about 700 Mrad/h). We filled our chambers with nitrogen gas at 760 Torr and air at 600 Torr. The ion chambers were driven into extreme nonlinear response. We hope these data will be used to design loss-monitor systems based on air-filled ion chambers, thus eliminating the need for gas-flow systems and/or airtight ion chambers.

  11. Response of air-filled ion chambers to high-intensity radiation pulses

    SciTech Connect

    Plum, M.; Brown, D.

    1993-06-01

    Ion chambers are one of the most popular types of detectors used for beam loss-monitor systems. To provide a foundation for the development of future loss-monitor systems, and to fully characterize the ion chambers in use at LAMPF, we have studied the response of air-filled cylindrical ion chambers to high-intensity, short-duration radiation pulses. The most intense pulses were about 180 rad in 250 ns (the equivalent steady-state dose rate was about 700 Mrad/h). We filled our chambers with nitrogen gas at 760 Torr and air at 600 Torr. The ion chambers were driven into extreme nonlinear response. We hope these data will be used to design loss-monitor systems based on air-filled ion chambers, thus eliminating the need for gas-flow systems and/or airtight ion chambers.

  12. Technical Note: Experimental determination of the effective point of measurement of two cylindrical ionization chambers in a clinical proton beam

    SciTech Connect

    Sugama, Yuya; Nishio, Teiji; Onishi, Hiroshi

    2015-07-15

    Purpose: IAEA TRS-398 notes that cylindrical ionization chambers are preferred for reference proton dosimetry. If a cylindrical ionization chamber is used in a phantom to measure the dose as a function of depth, the effective point of measurement (EPOM) must be taken into account. IAEA TRS-398 recommends a displacement of 0.75 times the inner cavity radius (0.75R) for heavy ion beams. Theoretical models by Palmans and by Bhullar and Watchman confirmed this value. However, the experimental results vary from author to author. The purpose of this study is to accurately measure the displacement and explain the past experimental discrepancies. Methods: In this work, we measured the EPOM of cylindrical ionization chambers with high accuracy by comparing the Bragg-peak position obtained with cylindrical ionization chambers (PTW 30013, PTW 31016) to that obtained using a plane-parallel ionization chamber (PTW 34045). Results: The EPOMs of PTW 30013 and 31016 were shifted by 0.92 ± 0.07 R with R = 3.05 mm and 0.90 ± 0.14 R with R = 1.45 mm, respectively, from the reference point toward the source. Conclusions: The EPOMs obtained were greater than the value of 0.75R proposed by the IAEA TRS-398 and the analytical results.

  13. Developing of a New Atmospheric Ionizing Radiation (AIR) Model

    NASA Technical Reports Server (NTRS)

    Clem, John M.; deAngelis, Giovanni; Goldhagen, Paul; Wilson, John W.

    2003-01-01

    As a result of the research leading to the 1998 AIR workshop and the subsequent analysis, the neutron issues posed by Foelsche et al. and further analyzed by Hajnal have been adequately resolved. We are now engaged in developing a new atmospheric ionizing radiation (AIR) model for use in epidemiological studies and air transportation safety assessment. A team was formed to examine a promising code using the basic FLUKA software but with modifications to allow multiple charged ion breakup effects. A limited dataset of the ER-2 measurements and other cosmic ray data will be used to evaluate the use of this code.

  14. Hydrophilic strips for preventing air bubble formation in a microfluidic chamber.

    PubMed

    Choi, Munseok; Na, Yang; Kim, Sung-Jin

    2015-12-01

    In a microfluidic chamber, unwanted formation of air bubbles is a critical problem. Here, we present a hydrophilic strip array that prevents air bubble formation in a microfluidic chamber. The array is located on the top surface of the chamber, which has a large variation in width, and consists of a repeated arrangement of super- and moderately hydrophilic strips. This repeated arrangement allows a flat meniscus (i.e. liquid front) to form when various solutions consisting of a single stream or two parallel streams with different hydrophilicities move through the chamber. The flat meniscus produced by the array completely prevents the formation of bubbles. Without the array in the chamber, the meniscus shape is highly convex, and bubbles frequently form in the chamber. This hydrophilic strip array will facilitate the use of a microfluidic chamber with a large variation in width for various microfluidic applications. PMID:26382942

  15. Microwave diagnostics of laser-induced avalanche ionization in air

    SciTech Connect

    Zhang Zhili; Shneider, Mikhail N.; Miles, Richard B.

    2006-10-01

    This work presents a simplified model of microwave scattering during the avalanche ionization stage of laser breakdown and corresponding experimental results of microwave scattering from laser breakdown in room air. The model assumes and measurements confirm that the breakdown regime can be viewed as a point dipole scatterer of the microwave radiation and thus directly related to the time evolving number of electrons. The delay between the laser pulse and the rise of the microwave scattering signal is a direct measure of the avalanche ionization process.

  16. Performance of a multi-axis ionization chamber array in a 1.5 T magnetic field

    NASA Astrophysics Data System (ADS)

    Smit, K.; Kok, J. G. M.; Lagendijk, J. J. W.; Raaymakers, B. W.

    2014-04-01

    At the UMC Utrecht a prototype MR-linac has been installed. The system consists of an 8 MV Elekta linear accelerator and a 1.5 T Philips MRI system. This paper investigates the performance of the IC PROFILER™, a multi-axis ionization chamber array, in a 1.5 T magnetic field. The influence of the magnetic field on the IC PROFILER™ reproducibility, dose response linearity, pulse rate frequency dependence, power to electronics, panel orientation and ionization chamber shape were investigated. The linearity, reproducibility, pulse rate frequency dependence, panel orientation and ionization chamber shape are unaffected by the magnetic field. When the measurements results are normalized to the centre reference chamber, the measurements can commence unaltered. Orientation of the ionization chambers in the magnetic field is of importance, therefore caution must be taken when comparing or normalizing results from several different axes. IC PROFILER™ dose profiles were compared with film dose profiles obtained simultaneously in the MR-linac. Deviation between the film and the IC PROFILER™ data was caused by the noise in the film, indicating correct performance of the IC PROFILER™ in the transverse 1.5 T magnetic field.

  17. Electron beam quality k(Q,Q0) factors for various ionization chambers: a Monte Carlo investigation with PENELOPE.

    PubMed

    Erazo, F; Brualla, L; Lallena, A M

    2014-11-01

    In this work we calculate the beam quality correction factor k(Q,Q0) for various plane-parallel ionization chambers. A set of Monte Carlo calculations using the code PENELOPE/PENEASY have been carried out to calculate the overall correction factor f(c,Q) for eight electron beams corresponding to a Varian Clinac 2100 C/D, with nominal energies ranging between 6 MeV and 22 MeV, for a (60)Co beam, that has been used as the reference quality Q0 and also for eight monoenergetic electron beams reproducing the quality index R50 of the Clinac beams. Two field sizes, 10 × 10 cm(2) and 20 × 20 cm(2) have been considered. The k(Q,Q0) factors have been calculated as the ratio between f(c,Q) and f(c,Q0). Values for the Exradin A10, A11, A11TW, P11, P11TW, T11 and T11TW ionization chambers, manufactured by Standard Imaging, as well as for the NACP-02 have been obtained. The results found with the Clinac beams for the two field sizes analyzed show differences below 0.6%, even in the case of the higher energy electron beams. The k(Q,Q0) values obtained with the Clinac beams are 1% larger than those found with the monoenergetic beams for the higher energies, above 12 MeV. This difference can be ascribed to secondary photons produced in the linac head and the air path towards the phantom. Contrary to what was quoted in a previous work (Sempau et al 2004 Phys. Med. Biol. 49 4427-44), the beam quality correction factors obtained with the complete Clinac geometries and with the monoenergetic beams differ significantly for energies above 12 MeV. Material differences existing between chambers that have the same geometry produce non-negligible modifications in the value of these correction factors. PMID:25325343

  18. Electron beam quality kQ,Q0 factors for various ionization chambers: a Monte Carlo investigation with penelope

    NASA Astrophysics Data System (ADS)

    Erazo, F.; Brualla, L.; Lallena, A. M.

    2014-11-01

    In this work we calculate the beam quality correction factor {{k}\\text{Q,{{\\text{Q}}0}}} for various plane-parallel ionization chambers. A set of Monte Carlo calculations using the code penelope/penEasy have been carried out to calculate the overall correction factor fc,Q for eight electron beams corresponding to a Varian Clinac 2100 C/D, with nominal energies ranging between 6 MeV and 22 MeV, for a 60Co beam, that has been used as the reference quality Q0 and also for eight monoenergetic electron beams reproducing the quality index R50 of the Clinac beams. Two field sizes, 10 × 10 cm2 and 20 × 20 cm2 have been considered. The {{k}\\text{Q,{{\\text{Q}}0}}} factors have been calculated as the ratio between fc,Q and {{f}\\text{c,{{\\text{Q}}0}}} . Values for the Exradin A10, A11, A11TW, P11, P11TW, T11 and T11TW ionization chambers, manufactured by Standard Imaging, as well as for the NACP-02 have been obtained. The results found with the Clinac beams for the two field sizes analyzed show differences below 0.6%, even in the case of the higher energy electron beams. The {{k}\\text{Q,{{\\text{Q}}0}}} values obtained with the Clinac beams are 1% larger than those found with the monoenergetic beams for the higher energies, above 12 MeV. This difference can be ascribed to secondary photons produced in the linac head and the air path towards the phantom. Contrary to what was quoted in a previous work (Sempau et al 2004 Phys. Med. Biol. 49 4427-44), the beam quality correction factors obtained with the complete Clinac geometries and with the monoenergetic beams differ significantly for energies above 12 MeV. Material differences existing between chambers that have the same geometry produce non-negligible modifications in the value of these correction factors.

  19. Beta and Gamma Correction Factors for the Eberline R0-20 Ionization Chamber Survey Instrument

    SciTech Connect

    Johnson, Michelle L.; Rathbone, Bruce A.; Bratvold, Thomas E.

    2001-08-10

    This technical document provides details of derived correction factors for the Eberline R0-20 survey meter, which uses an ionization chamber to measure ambient exposure rates. A thin end window allows the instrument to measure exposure rates from non-penetrating radiation (i.e., beta radiation). Correction factors are provided for contact measurements with beta and gamma disk sources, gamma beams and, finally, general area beta fields. Beta correction factors are based on the instrument's response to 204Tl, selected as the most conservative isotope for beta correction factors, as indicated in previous studies of similar instruments using 204Tl, 147Pm, and 90Sr(Y) isotopes (LANL 1982). Gamma correction factors are based on 137Cs, considered the predominant source of gamma radiation on the Hanford Site.

  20. Particle emission angle determination in Frisch grid ionization chambers by electron drift-time measurements

    NASA Astrophysics Data System (ADS)

    Göök, A.; Chernykh, M.; Enders, J.; Oberstedt, A.; Oberstedt, S.

    2010-09-01

    The double kinetic energy measurement of fission fragments with a double-sided Frisch grid ionization chamber allows a careful determination of the emission angle, which is essential in order to apply appropriate energy-loss corrections. We present a drift-time method, which uses the time that free electrons need to drift from the location of their creation, e.g. by a fission fragment in the counting gas, to the grid, before inducing a signal on the anode. Such a measurement leaves energy and angular information fully decoupled. We demonstrate the applicability of the drift-time method for the example of the 234,238U (γ,f) reactions performed at the superconducting Darmstadt electron linear accelerator. The angular resolutions achieved with this method are comparable to those obtained with other methods.

  1. The mass dependence of the signal peak height of a Bragg-curve ionization chamber

    NASA Astrophysics Data System (ADS)

    Shenhav, N. J.; Stelzer, H.

    1985-01-01

    The Bragg-curve detector of the parallel plate ionization chamber type generates a signal that is a distorted replica of the original Bragg-curve. In result of this distortion, the signal peak height is not only a function of the atomic number of the heavy ion, as it is often stated, but also of the particle mass. This mass effect was studied with the aid of computer simulation, and it was found to be dependent on the Frisch grid to anode gap width and on the detector gas. The charge resolution of the detector is affected very significantly by this mass dependence of the signal peak height. Therefore, a careful selection of the detector gas and the grid to anode gap width is necessary, if good charge resolution over a wide range of heavy ions is required.

  2. Energy resolution of gas ionization chamber for high-energy heavy ions

    NASA Astrophysics Data System (ADS)

    Sato, Yuki; Taketani, Atsushi; Fukuda, Naoki; Takeda, Hiroyuki; Kameda, Daisuke; Suzuki, Hiroshi; Shimizu, Yohei; Nishimura, Daiki; Fukuda, Mitsunori; Inabe, Naohito; Murakami, Hiroyuki; Yoshida, Koichi; Kubo, Toshiyuki

    2014-01-01

    The energy resolution is reported for high-energy heavy ions with energies of nearly 340 MeV/nucleon and was measured using a gas ionization chamber filled with a 90%Ar/10%CH4 gas mixture. We observed that the energy resolution is proportional to the inverse of the atomic number of incident ions and to the inverse-square-root of the gas thickness. These results are consistent with the Bethe-Bloch formula for the energy loss of charged particles and the Bohr expression for heavy ion energy straggling. In addition, the influence of high-energy δ-rays generated in the detector on the energy deposition is discussed.

  3. Quality assurance of proton beams using a multilayer ionization chamber system

    SciTech Connect

    Dhanesar, Sandeep; Sahoo, Narayan; Kerr, Matthew; Taylor, M. Brad; Summers, Paige; Zhu, X. Ronald; Poenisch, Falk; Gillin, Michael

    2013-09-15

    Purpose: The measurement of percentage depth-dose (PDD) distributions for the quality assurance of clinical proton beams is most commonly performed with a computerized water tank dosimetry system with ionization chamber, commonly referred to as water tank. Although the accuracy and reproducibility of this method is well established, it can be time-consuming if a large number of measurements are required. In this work the authors evaluate the linearity, reproducibility, sensitivity to field size, accuracy, and time-savings of another system: the Zebra, a multilayer ionization chamber system.Methods: The Zebra, consisting of 180 parallel-plate ionization chambers with 2 mm resolution, was used to measure depth-dose distributions. The measurements were performed for scattered and scanned proton pencil beams of multiple energies delivered by the Hitachi PROBEAT synchrotron-based delivery system. For scattered beams, the Zebra-measured depth-dose distributions were compared with those measured with the water tank. The principal descriptors extracted for comparisons were: range, the depth of the distal 90% dose; spread-out Bragg peak (SOBP) length, the region between the proximal 95% and distal 90% dose; and distal-dose fall off (DDF), the region between the distal 80% and 20% dose. For scanned beams, the Zebra-measured ranges were compared with those acquired using a Bragg peak chamber during commissioning.Results: The Zebra demonstrated better than 1% reproducibility and monitor unit linearity. The response of the Zebra was found to be sensitive to radiation field sizes greater than 12.5 × 12.5 cm; hence, the measurements used to determine accuracy were performed using a field size of 10 × 10 cm. For the scattered proton beams, PDD distributions showed 1.5% agreement within the SOBP, and 3.8% outside. Range values agreed within −0.1 ± 0.4 mm, with a maximum deviation of 1.2 mm. SOBP length values agreed within 0 ± 2 mm, with a maximum deviation of 6 mm. DDF

  4. Investigation of Ignition and Combustion Processes of Diesel Engines Operating with Turbulence and Air-storage Chambers

    NASA Technical Reports Server (NTRS)

    Petersen, Hans

    1938-01-01

    The flame photographs obtained with combustion-chamber models of engines operating respectively, with turbulence chamber and air-storage chambers or cells, provide an insight into the air and fuel movements that take place before and during combustion in the combustion chamber. The relation between air velocity, start of injection, and time of combustion was determined for the combustion process employing a turbulence chamber.

  5. SU-D-213-04: Accounting for Volume Averaging and Material Composition Effects in An Ionization Chamber Array for Patient Specific QA

    SciTech Connect

    Fugal, M; McDonald, D; Jacqmin, D; Koch, N; Ellis, A; Peng, J; Ashenafi, M; Vanek, K

    2015-06-15

    Purpose: This study explores novel methods to address two significant challenges affecting measurement of patient-specific quality assurance (QA) with IBA’s Matrixx Evolution™ ionization chamber array. First, dose calculation algorithms often struggle to accurately determine dose to the chamber array due to CT artifact and algorithm limitations. Second, finite chamber size and volume averaging effects cause additional deviation from the calculated dose. Methods: QA measurements were taken with the Matrixx positioned on the treatment table in a solid-water Multi-Cube™ phantom. To reduce the effect of CT artifact, the Matrixx CT image set was masked with appropriate materials and densities. Individual ionization chambers were masked as air, while the high-z electronic backplane and remaining solid-water material were masked as aluminum and water, respectively. Dose calculation was done using Varian’s Acuros XB™ (V11) algorithm, which is capable of predicting dose more accurately in non-biologic materials due to its consideration of each material’s atomic properties. Finally, the exported TPS dose was processed using an in-house algorithm (MATLAB) to assign the volume averaged TPS dose to each element of a corresponding 2-D matrix. This matrix was used for comparison with the measured dose. Square fields at regularly-spaced gantry angles, as well as selected patient plans were analyzed. Results: Analyzed plans showed improved agreement, with the average gamma passing rate increasing from 94 to 98%. Correction factors necessary for chamber angular dependence were reduced by 67% compared to factors measured previously, indicating that previously measured factors corrected for dose calculation errors in addition to true chamber angular dependence. Conclusion: By comparing volume averaged dose, calculated with a capable dose engine, on a phantom masked with correct materials and densities, QA results obtained with the Matrixx Evolution™ can be significantly

  6. Measurement of absorbed dose-to-water for an HDR {sup 192}Ir source with ionization chambers in a sandwich setup

    SciTech Connect

    Araki, Fujio; Kouno, Tomohiro; Ohno, Takeshi; Kakei, Kiyotaka; Yoshiyama, Fumiaki; Kawamura, Shinji

    2013-09-15

    Purpose: In this study, a dedicated device for ion chamber measurements of absorbed dose-to-water for a Nucletron microSelectron-v2 HDR {sup 192}Ir brachytherapy source is presented. The device uses two ionization chambers in a so-called sandwich assembly. Using this setup and by taking the average reading of the two chambers, any dose error due to difficulties in absolute positioning (centering) of the source in between the chambers is cancelled to first order. The method's accuracy was examined by comparing measurements with absorbed dose-to-water determination based on the AAPM TG-43 protocol.Methods: The optimal source-to-chamber distance (SCD) for {sup 192}Ir dosimetry was determined from ion chamber measurements in a water phantom. The {sup 192}Ir source was sandwiched between two Exradin A1SL chambers (0.057 cm{sup 3}) at the optimal SCD separation. The measured ionization was converted to the absorbed dose-to-water using a {sup 60}Co calibration factor and a Monte Carlo-calculated beam quality conversion factor, k{sub Q}, for {sup 60}Co to {sup 192}Ir. An uncertainty estimate of the proposed method was determined based on reproducibility of measurements at different institutions for the same type of source.Results: The optimal distance for the A1SL chamber measurements was determined to be 5 cm from the {sup 192}Ir source center, considering the depth dependency of k{sub Q} for {sup 60}Co to {sup 192}Ir and the chamber positioning. The absorbed dose to water measured at (5 cm, 90°) on the transverse axis was 1.3% lower than TG-43 values and its reproducibility and overall uncertainty were 0.8% and 1.7%, respectively. The measurement doses at anisotropic points agreed within 1.5% with TG-43 values.Conclusions: The ion chamber measurement of absorbed dose-to-water with a sandwich method for the {sup 192}Ir source provides a more accurate, direct, and reference dose compared to the dose-to-water determination based on air-kerma strength in the TG-43 protocol

  7. A multiple sampling ionization chamber (MUSIC) for measuring the charge of relativistic heavy ions

    NASA Astrophysics Data System (ADS)

    Christie, W. B.; Romero, J. L.; Brady, F. P.; Tull, C. E.; Castaneda, C. M.; Barasch, E. F.; Webb, M. L.; Drummond, J. R.; Crawford, H. J.; Flores, I.; Greiner, D. E.; Lindstrom, P. J.; Sann, H.; Young, J. C.

    1987-04-01

    A large area (1 m × 2 m) multiple sampling ionization chamber (MUSIC) has been constructed and tested. The MUSIC detector makes multiple measurements of energy "loss", d E/d x, for a relativistic heavy ion. Given the velocity, the charge of the ion can be extracted from the energy loss distributions. The widths of the distributions we observe are much narrower than predicted by Vavilov's theory for energy loss while agreeing well with the theory of Badhwar which deals with the energy deposited. The versatile design of MUSIC allows a variety of anode configurations which results in a large dynamic range of charge. In our tests to date we have observed charge resolutions of 0.25e fwhm for 727 MeV/nucleon40A and 0.30e fwhm for 1.08 GeV/nucleon139La and139La fragments. Vertical position and multiple track determination are obtained by using time projection chamber electronics. Preliminary tests indicate that the position resolution is also very good with α ≅ 100 μm.

  8. Photon beam quality correction factors for the NE2571A and NE2581A thimble ionization chambers using PENELOPE.

    PubMed

    Erazo, Fabián; Lallena, Antonio M

    2016-01-01

    The beam quality correction factor kQ,Q0 and the perturbation factor pQ for photon beams were calculated for the NE2571A and NE2581A ionization chambers, using the Monte Carlo simulation code PENELOPE. Results are compared to those quoted for the NE2571 and NE2581 chambers in previous works. Both kQ,Q0 and pQ obtained for NE2571A and NE2581A chambers agree with those of their predecessors NE2571 and NE2581 ones. PMID:26602965

  9. Fast-neutron spectrometry using a ³He ionization chamber and digital pulse shape analysis.

    PubMed

    Chichester, D L; Johnson, J T; Seabury, E H

    2012-08-01

    Digital pulse shape analysis (dPSA) has been used with a Cuttler-Shalev type (3)He ionization chamber to measure the fast-neutron spectra of a deuterium-deuterium electronic neutron generator, a bare (252)Cf spontaneous fission neutron source, and of the transmitted fast neutron spectra of a (252)Cf source attenuated by water, graphite, liquid nitrogen, and magnesium. Rise-time dPSA has been employed using the common approach for analyzing n +(3)He→(1)H+(3)H ionization events and improved to account for wall-effect and pile-up events, increasing the fidelity of these measurements. Simulations have been performed of the different experimental arrangements and compared with the measurements, demonstrating general agreement between the dPSA-processed fast-neutron spectra and predictions. The fast-neutron resonance features of the attenuation cross sections of the attenuating materials are clearly visible within the resolution limits of the electronics used for the measurements, and the potential applications of high-resolution fast-neutron spectrometry for nuclear nonproliferation and safeguards measurements are discussed. PMID:22728128

  10. Considerations of Air Flow in Combustion Chambers of High-Speed Compression-Ignition Engines

    NASA Technical Reports Server (NTRS)

    Spanogle, J A; Moore, C S

    1932-01-01

    The air flow in combustion chambers is divided into three fundamental classes - induced, forced, and residual. A generalized resume is given of the present status of air flow investigations and of the work done at this and other laboratories to determine the direction and velocity of air movement in auxiliary and integral combustion chambers. The effects of air flow on engine performance are mentioned to show that although air flow improves the combustion efficiency, considerable induction, friction, and thermal losses must be guarded against.

  11. Ionization chamber measurements of the half-lives of 24Na, 42K, 76As and 198Au.

    PubMed

    Unterweger, M P; Lindstrom, R M

    2004-01-01

    Samples of 24Na, 42K, 76As and 198Au were produced by irradiation in the National Institute of Standards and Technology (NIST) reactor, and examined for impurities before and after measurement. Half-life measurements were carried out in the NIST 4pigamma pressurized ionization chamber. The results are compared to presently accepted values and previous NIST measurements. PMID:14987662

  12. SMOG CHAMBERS: A TOOL TO EXAMINE EFFECTS OF PHOTOCHEMICALLY AGED AIR POLLUTANTS ON BIOLOGICAL SYSTEMS

    EPA Science Inventory

    Irradiative exposure chambers or 'Smog chambers' have been used at the University of North Carolina for over 30 years to study photochemically active mixtures of volatile organic compounds and their transformation products (a significant sub-set of Hazardous Air Pollutants, HAPs)...

  13. Absorbed dose to water determination with ionization chamber dosimetry and calorimetry in restricted neutron, photon, proton and heavy-ion radiation fields.

    PubMed

    Brede, H J; Greif, K-D; Hecker, O; Heeg, P; Heese, J; Jones, D T L; Kluge, H; Schardt, D

    2006-08-01

    Absolute dose measurements with a transportable water calorimeter and ionization chambers were performed at a water depth of 20 mm in four different types of radiation fields, for a collimated (60)Co photon beam, for a collimated neutron beam with a fluence-averaged mean energy of 5.25 MeV, for collimated proton beams with mean energies of 36 MeV and 182 MeV at the measuring position, and for a (12)C ion beam in a scanned mode with an energy per atomic mass of 430 MeV u(-1). The ionization chambers actually used were calibrated in units of air kerma in the photon reference field of the PTB and in units of absorbed dose to water for a Farmer-type chamber at GSI. The absorbed dose to water inferred from calorimetry was compared with the dose derived from ionometry by applying the radiation-field-dependent parameters. For neutrons, the quantities of the ICRU Report 45, for protons the quantities of the ICRU Report 59 and for the (12)C ion beam, the recommended values of the International Atomic Energy Agency (IAEA) protocol (TRS 398) were applied. The mean values of the absolute absorbed dose to water obtained with these two independent methods agreed within the standard uncertainty (k = 1) of 1.8% for calorimetry and of 3.0% for ionometry for all types and energies of the radiation beams used in this comparison. PMID:16861773

  14. Affect of Air Leakage into a Thermal-Vacuum Chamber on Helium Refrigeration Heat Load

    NASA Technical Reports Server (NTRS)

    Garcia, Sam; Meagher, Daniel; Linza, Robert; Saheli, Fariborz; Vargas, Gerardo; Lauterbach, John; Reis, Carl; Ganni, Venkatarao (Rao); Homan, Jonathan

    2008-01-01

    NASA s Johnson Space Center (JSC) Building 32 houses two large thermal-vacuum chambers (Chamber A and Chamber B). Within these chambers are liquid nitrogen shrouds to provide a thermal environment and helium panels which operate at 20K to provide cryopumping. Some amount of air leakage into the chambers during tests is inevitable. This causes "air fouling" of the helium panel surfaces due to the components of the air that adhere to the panels. The air fouling causes the emittance of the helium panels to increase during tests. The increase in helium panel emittance increases the heat load on the helium refrigerator that supplies the 20K helium for those panels. Planning for thermal-vacuum tests should account for this increase to make sure that the helium refrigerator capacity will not be exceeded over the duration of a test. During a recent test conducted in Chamber B a known-size air leak was introduced to the chamber. Emittance change of the helium panels and the affect on the helium refrigerator was characterized. A description of the test and the results will be presented.

  15. Time-resolved dosimetry using a pinpoint ionization chamber as quality assurance for IMRT and VMAT

    SciTech Connect

    Louwe, Robert J. W. Satherley, Thomas; Day, Rebecca A.; Greig, Lynne; Wendling, Markus; Monshouwer, René

    2015-04-15

    Purpose: To develop a method to verify the dose delivery in relation to the individual control points of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) using an ionization chamber. In addition to more effective problem solving during patient-specific quality assurance (QA), the aim is to eventually map out the limitations in the treatment chain and enable a targeted improvement of the treatment technique in an efficient way. Methods: Pretreatment verification was carried out for 255 treatment plans that included a broad range of treatment indications in two departments using the equipment of different vendors. In-house developed software was used to enable calculation of the dose delivery for the individual beamlets in the treatment planning system (TPS), for data acquisition, and for analysis of the data. The observed deviations were related to various delivery and measurement parameters such as gantry angle, field size, and the position of the detector with respect to the field edge to distinguish between error sources. Results: The average deviation of the integral fraction dose during pretreatment verification of the planning target volume dose was −2.1% ± 2.2% (1 SD), −1.7% ± 1.7% (1 SD), and 0.0% ± 1.3% (1 SD) for IMRT at the Radboud University Medical Center (RUMC), VMAT (RUMC), and VMAT at the Wellington Blood and Cancer Centre, respectively. Verification of the dose to organs at risk gave very similar results but was generally subject to a larger measurement uncertainty due to the position of the detector at a high dose gradient. The observed deviations could be related to limitations of the TPS beam models, attenuation of the treatment couch, as well as measurement errors. The apparent systematic error of about −2% in the average deviation of the integral fraction dose in the RUMC results could be explained by the limitations of the TPS beam model in the calculation of the beam penumbra. Conclusions: This

  16. A micro-gap, air-filled ionisation chamber as a detector for criticality accident dosimetry.

    PubMed

    Murawski, Ł; Zielczyński, M; Golnik, N; Gryziński, M A

    2014-10-01

    A micro-gap air-filled ionisation chamber was designed for criticality dosimetry. The special feature of the chamber is its very small gap between electrodes of only 0.3 mm. This prevents ion recombination at high dose rates and minimises the influence of gas on secondary particles spectrum. The electrodes are made of polypropylene because of higher content of hydrogen in this material, when compared with soft tissue. The difference between neutron and gamma sensitivity in such chamber becomes practically negligible. The chamber's envelope contains two specially connected capacitors, one for polarising the electrodes and the other for collecting the ionisation charge. PMID:24324250

  17. Effect of air sparging on fate and transport of trichloroethylene in chambers with alfalfa plants

    SciTech Connect

    Zhang, Q.; Hu, J.; Erickson, L.E.; Davis, L.C.

    1997-12-31

    To study the effect of air sparging in soil with trichloroethylene present as a dense nonaqueous phase, air was supplied through pipes installed at the bottom of two chambers planted with alfalfa. Air input rate was 2.14 L/m{sup 2}/day. The fate of trichloroethylene (TCE) was investigated by monitoring TCE concentration in both outflow groundwater and soil gas. Comparison of these results with those of the previous study without air sparging indicates that air sparging appreciably increases the groundwater concentration of TCE. The soil gas at the surface shows even greater concentration difference. The flux of TCE to the atmosphere is increased significantly by air input. Accordingly, the authors can conclude that air sparging improved mass transfer of TCE from the nonaqueous phase to groundwater phase. Air sparging appeared to negatively impact the health of the alfalfa because of the elevated TCE present in the vadose zone of the chamber.

  18. Assaying of targets for nuclear measurements with a gridded ionization chamber

    NASA Astrophysics Data System (ADS)

    Budtz-Jørgensen, C.; Knitter, H. H.; Bortels, G.

    1985-06-01

    An ionization chamber with a Frisch grid is used to determine both the energy ( E) of the charge particles emitted from the sample positioned coplanar with the cathode, and the cosine of the emission angle (ϑ) with respect to the normal of the cathode Using the combined information on cosϑ and E, problems in particle counting due to sample absoprtion and scattering effect can be circumvented and sample source strengths are readily determined to an accurary of 0.3%. However, it is emphasized that the source strength can be determined from the particles emitted in a large solid angle close to 2τ sr, which means a considerable higher efficiency than for the conventional low geometry counting techniques. Moreover the present method, within reasonable limits is insensitive to source shape and thickness homogeneity. The technique will be illustrated by measurements of alpha particles and fission fragments emitted from a set of four vacuum evaporated UF 4, three electrodeposited and one suspension-sprayed 235U 3O 8 layers. The energy and angular distributions of alpha particles and of the heavy alpha recoils emitted from a self transferred 224Ra source will be discussed. The low energetic alpha recoils might be useful as probes for the investigation of ultrathin ( < 400 Å) layers.

  19. Detecting MLC errors in stereotactic radiotherapy plans with a liquid filled ionization chamber array.

    PubMed

    O'Connor, Patrick; Seshadri, Venkatakrisnan; Charles, Paul

    2016-03-01

    Quality assurance of stereotactic radiotherapy demands the use of equipment with the highest resolution and sensitivity available. This study examines the sensitivity of a commercially available liquid-filled ionization chamber array-the Octavius 1000 SRS (PTW, Frieburg, Germany) for detecting small (sub-millimetre) multi-leaf collimator (MLC) alignment errors in static square fields (side length 16-40 mm). Furthermore, the effectiveness of detecting small MLC errors in clinical stereotactic radiotherapy patient plans using the device was also evaluated. The commonly used gamma pass rate metric (of the measurements compared with treatment planning system generated results) was used. The gamma pass rates were then evaluated as a function of MLC position error (MLC error size 0.1-2.5 mm). The detector array exhibited a drop in pass rate between plans without error and those which had MLC errors induced. For example a drop in pass rate of 4.5 % (gamma criteria 3 %, 1 mm) was observed when a 0.8 mm error was introduced into a 16 mm square field. Furthermore the drop in pass rate increased as the MLC position error increased. This study showed that the Octavius 1000 SRS array could be a useful tool for applications requiring the detection of small geometric delivery uncertainties. PMID:26979835

  20. The control system of the multi-strip ionization chamber for the HIMM

    NASA Astrophysics Data System (ADS)

    Li, Min; Yuan, Y. J.; Mao, R. S.; Xu, Z. G.; Li, Peng; Zhao, T. C.; Zhao, Z. L.; Zhang, Nong

    2015-03-01

    Heavy Ion Medical Machine (HIMM) is a carbon ion cancer treatment facility which is being built by the Institute of Modern Physics (IMP) in China. In this facility, transverse profile and intensity of the beam at the treatment terminals will be measured by the multi-strip ionization chamber. In order to fulfill the requirement of the beam position feedback to accomplish the beam automatic commissioning, less than 1 ms reaction time of the Data Acquisition (DAQ) of this detector must be achieved. Therefore, the control system and software framework for DAQ have been redesigned and developed with National Instruments Compact Reconfigurable Input/Output (CompactRIO) instead of PXI 6133. The software is Labview-based and developed following the producer-consumer pattern with message mechanism and queue technology. The newly designed control system has been tested with carbon beam at the Heavy Ion Research Facility at Lanzhou-Cooler Storage Ring (HIRFL-CSR) and it has provided one single beam profile measurement in less than 1 ms with 1 mm beam position resolution. The fast reaction time and high precision data processing during the beam test have verified the usability and maintainability of the software framework. Furthermore, such software architecture is easy-fitting to applications with different detectors such as wire scanner detector.

  1. Proton beam dosimetry: a comparison between the Faraday cup and an ionization chamber.

    PubMed

    Cambria, R; Hérault, J; Brassart, N; Silari, M; Chauvel, P

    1997-06-01

    From the theoretical point of view, the Faraday cup (FC) is an absolute instrument for fluence measurements of proton beams. As the FC is easily manufactured it can be considered an 'in-house' calibration system. Moreover, at the moment no national standards for proton dosimetry are available. Up to now the experimental tests of these instruments show that much study still has to be done to better understand their use in reference dosimetry. To investigate the possibility of using an FC as a secondary standard, an FC was jointly designed by the 'TERA Collaboration' and 'Centre Antoine-Lacassagne' (Nice, France) to evaluate the main parameters of the instrument. A comparison between two FCs of different designs--the 'TERA FC' and the 'Nice FC'--and an ionization chamber (IC) used for routine proton dosimetry was carried out. Results show that the two FCs agree to within 1.5-3.6%. While the differences between FC and IC are larger--6% for the 'TERA FC' and 8.2% for the 'Nice FC', the FC giving a lower dose evaluation--they follow the same trend shown by the calorimetric measurements. The data show that once the beam characteristics are defined, the fluence measurements are reproducible and show a good accuracy. PMID:9194137

  2. IMPACT OF AN OZONE GENERATOR AIR CLEANER ON STYRENE CONCENTRATIONS IN AN INDOOR AIR QUALITY RESEARCH CHAMBER

    EPA Science Inventory

    The paper gives results of an investigation of the impact of an ozone generator air cleaner on vapor-phase styrene concentrations in a full-scale indoor air quality test chamber. The time history of the concentrations of styrene and ozone is well predicted by a simulation model u...

  3. 33 CFR 183.222 - Flotation material and air chambers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Flotation material and air... SECURITY (CONTINUED) BOATING SAFETY BOATS AND ASSOCIATED EQUIPMENT Flotation Requirements for Outboard Boats Rated for Engines of More Than 2 Horsepower General § 183.222 Flotation material and air...

  4. A patient-specific quality assurance study on absolute dose verification using ionization chambers of different volumes in RapidArc treatments

    SciTech Connect

    Syam Kumar, S.A.; Sukumar, Prabakar; Sriram, Padmanaban; Rajasekaran, Dhanabalan; Aketi, Srinu; Vivekanandan, Nagarajan

    2012-01-01

    The recalculation of 1 fraction from a patient treatment plan on a phantom and subsequent measurements have become the norms for measurement-based verification, which combines the quality assurance recommendations that deal with the treatment planning system and the beam delivery system. This type of evaluation has prompted attention to measurement equipment and techniques. Ionization chambers are considered the gold standard because of their precision, availability, and relative ease of use. This study evaluates and compares 5 different ionization chambers: phantom combinations for verification in routine patient-specific quality assurance of RapidArc treatments. Fifteen different RapidArc plans conforming to the clinical standards were selected for the study. Verification plans were then created for each treatment plan with different chamber-phantom combinations scanned by computed tomography. This includes Medtec intensity modulated radiation therapy (IMRT) phantom with micro-ionization chamber (0.007 cm{sup 3}) and pinpoint chamber (0.015 cm{sup 3}), PTW-Octavius phantom with semiflex chamber (0.125 cm{sup 3}) and 2D array (0.125 cm{sup 3}), and indigenously made Circular wax phantom with 0.6 cm{sup 3} chamber. The measured isocenter absolute dose was compared with the treatment planning system (TPS) plan. The micro-ionization chamber shows more deviations when compared with semiflex and 0.6 cm{sup 3} with a maximum variation of -4.76%, -1.49%, and 2.23% for micro-ionization, semiflex, and farmer chambers, respectively. The positive variations indicate that the chamber with larger volume overestimates. Farmer chamber shows higher deviation when compared with 0.125 cm{sup 3}. In general the deviation was found to be <1% with the semiflex and farmer chambers. A maximum variation of 2% was observed for the 0.007 cm{sup 3} ionization chamber, except in a few cases. Pinpoint chamber underestimates the calculated isocenter dose by a maximum of 4.8%. Absolute dose

  5. Combination of emulsion chamber and air shower array at Mt. Chacaltaya

    SciTech Connect

    Kawasumi, N.; Tsushima, I.; Honda, K.; Hashimoto, K. ); Matano, T. ); Mori, K.; Inoue, N.; Ticona, R. ); Ohsawa, A. ); Tamada, M. ); Martinic, N.; Aliaga, Z.; Reguerin, A.; Aguirre, C. )

    1993-06-15

    Data of 34 familes with the accompanying air showers, observed by the combination of emulsion chamber and air shower array at Mt. Chacaltaya, are presented. Comparison with the simulation calculation concludes that a change is necessary in the characteristics of hadron interactions in [ital E][sub 0][ge]10[sup 15] eV.

  6. Indoor air pollution by organic emissions from textile floor coverings. Climate chamber studies under dynamic conditions

    NASA Astrophysics Data System (ADS)

    Sollinger, S.; Levsen, K.; Wünsch, G.

    The time dependence of the emission of organic compounds from a polyamide floor covering with styrene-butadiene-rubber (SBR) backing was studied in three climate chambers (0.03, 1.0 and 38 m 3) at 23°C 5nd 45% RH. While volatile compounds such as toluene reach a maximum concentration in the gas phase within 1 h and decrease in concentration to less than 2% within 60 h, the concentration of less volatile compounds, such as 4-phenylcyclohexene, decreases slowly over a period of months. If the chamber is well mixed and a defined chamber loading is maintained the observed concentrations do not depend on the chamber size, the wall material and air velocity. The concentration of the observed emissions is roughly proportional to the chamber loading. Surprisingly it is not inversely proportional to the air exchange rate. Rather, at high air exchange rates mass transfer from the carpet to the gas phase is enhanced. The "decreasing source models" of Dunn and Tichenor ( Atmospheric Environment22, 885-894, 1988) have been applied to the data. They allow the extrapolation of experimental data beyond the time available for measurement. The model calculations reveal the presence of sink effects. The role of the chamber walls as sinks can be determined more reliably if constant sources of an organic compound are placed into the chamber and their increase in concentration with time is compared with the theoretical predictions neglecting sink effects.

  7. Electroslag welding of the longitudinal joints of air cooler chambers

    SciTech Connect

    Khakimov, A.N.; Antonov, V.V.; Malyarevskaya, E.K.; Prygaev, A.K.

    1986-09-01

    This paper presents a method and equipment for electroslag welding with regulation of the thermal cycle. The method enables one, as the result of external action on the parameters of the welding production cycles, to provide the optimum zonal structural and mechanical uniformity, and consequently, the level of properties of the weld joint which eliminates the expensive normalizing procedure. The welding conditions for chambers of 90G2S and 16GS steels and the cooling parameters are shown. The mechanical properties of weld joints made with the method are presented.

  8. A standard Fricke dosimeter compared to an ionization chamber used for dosimetric characterization of 60Co photon beam

    NASA Astrophysics Data System (ADS)

    Moussous, Ouiza; Medjadj, Toufik

    2016-06-01

    The main objective of this study was to investigate the Fricke dosimeter water equivalent system for measurement of dosimetric parameters for photon beam. The parameters measured with the Fricke dosimeter were compared to those obtained with an ionization chamber. In this work characteristics for 60Co γ-rays of field sizes ranging from 5 × 5 cm2 to 20 × 20 cm2 are reported. The measurements were carried out in the secondary standard dosimetry laboratory using a collimated 60Co gamma source therapy unit. The 60Co beam output in terms of absorbed dose to water was obtained as per IAEA TRS 398 recommendations using cylindrical ionization chamber, whose ND,w has been supplied by the IAEA's reference laboratory. Specific quantities measured include: output factors, peak scatter factor, lateral beam profiles and percentage depth dose. The Fricke dosimeters were irradiated in a water phantom using the suitable poly (methyl methacrylate), PMMA stand. Our results demonstrate that Fricke dosimeter and ionization chamber agree with each other.

  9. Chemical ionization mass spectrometric measurements of SO2 emissions from jet engines in flight and test chamber operations

    NASA Astrophysics Data System (ADS)

    Hunton, D. E.; Ballenthin, J. O.; Borghetti, J. F.; Federico, G. S.; Miller, T. M.; Thorn, W. F.; Viggiano, A. A.; Anderson, B. E.; Cofer, W. R.; McDougal, D. S.; Wey, C. C.

    2000-11-01

    We report the results of two measurements of the concentrations and emission indices of gas-phase sulfur dioxide (EI(SO2)) in the exhaust of an F100-200E turbofan engine. The broad goals of both experiments were to obtain exhaust sulfur speciation and aerosol properties as a function of fuel sulfur content. In the first campaign, an instrumented NASA T-39 Sabreliner aircraft flew in close formation behind several F-16 fighter aircraft to obtain near-field plume composition and aerosol properties. In the second, an F-100 engine of the same type was installed in an altitude test chamber at NASA Glenn Research Center where gas composition and nonvolatile aerosol concentrations and size distributions were obtained at the exit plane of the engine. In both experiments, SO2 concentrations were measured with the Air Force Research Laboratory chemical ionization mass spectrometer as a function of altitude, engine power, and fuel sulfur content. A significant aspect of the program was the use of the same fuels, the same engine type, and many of the same diagnostics in both campaigns. Several different fuels were purchased specifically for these experiments, including high-sulfur Jet A (˜1150 ppmm S), low-sulfur Jet A (˜10 ppmm S), medium-sulfur mixtures of these two fuels, and military JP-8+100 (˜170 and ˜300 ppmm S). The agreement between the flight and test cell measurements of SO2 concentrations was excellent, showing an overall precision of better than ±10% and an estimated absolute accuracy of ±20%. The EI(SO2) varied from 2.49 g SO2/kg fuel for the high-sulfur fuel in the test chamber to less than 0.01 g/kg for the lowest-sulfur fuel. No dependence of emission index on engine power, altitude or simulated altitude, separation distance or plume age, or the presence of contrails was observed. In all experiments the measured EI(SO2) was consistent with essentially all of the fuel sulfur appearing as gas-phase SO2 in the exhaust. However, accurate determination of S

  10. Use of a novel two-dimensional ionization chamber array for pencil beam scanning proton therapy beam quality assurance.

    PubMed

    Lin, Liyong; Kang, Minglei; Solberg, Timothy D; Mertens, Thierry; Baeumer, Christian; Ainsley, Christopher G; McDonough, James E

    2015-01-01

    The need to accurately and efficiently verify both output and dose profiles creates significant challenges in quality assurance of pencil beam scanning (PBS) proton delivery. A system for PBS QA has been developed that combines a new two-dimensional ionization chamber array in a waterproof housing that is scanned in a water phantom. The MatriXX PT has the same detector array arrangement as the standard MatriXX(Evolution) but utilizes a smaller 2 mm plate spacing instead of 5mm. Because the bias voltage of the MatriXX PT and Evolution cannot be changed, PPC40 and FC65-G ionization chambers were used to assess recombination effects. The PPC40 is a parallel plate chamber with an electrode spacing of 2mm, while the FC65-G is a Farmer chamber FC65-G with an electrode spacing of 2.8 mm. Three bias voltages (500, 200, and 100 V) were used for both detectors to determine which radiation type (continuous, pulse or pulse-scanned beam) could closely estimate Pion from the ratios of charges collected. In comparison with the MatriXX(Evolution), a significant improvement in measurement of absolute dose with the MatriXX PT was observed. While dose uncertainty of the MatriXX(Evolution) can be up to 4%, it is < 1% for the MatriXX PT. Therefore the MatriXX(Evolution) should not be used for QA of PBS for conditions in which ion recombination is not negligible. Farmer chambers should be used with caution for measuring the absolute dose of PBS beams, as the uncertainty of Pion can be > 1%; chambers with an electrode spacing of 2 mm or smaller are recommended. PMID:26103492

  11. Controlled environment fumigation chambers for the study of reactive air pollutant effects on plants

    NASA Astrophysics Data System (ADS)

    Stokes, N. J.; Lucas, P. W.; Nicholas Hewitt, C.

    The design and construction of eight 1-m 3 fumigation chambers for exposing plants to reactive air pollutants at low concentrations are reported. Teflon surfaces are used where possible to minimize the adsorption, absorption, desorption and chemical reaction of the pollutants. A purified ambient air supply, to which metered quantities of gaseous pollutants are added, is used to give two air changes per minute at constant, low, pollutant concentrations. Comparative analysis of the chambers indicates that conditions may be maintained with a significant degree of precision, i.e. temperature ±0.3°C, RH ±6%, light intensity ±5 μmol m -2 s -1. Boundary layer analysis from models of cherry tree ( Prunus avium) leaves indicate that the minimum conductance value within these chambers is 2 cm s -1.

  12. Off-site air monitoring following methyl bromide chamber and building fumigations and evaluation of the ISCST air dispersion model

    SciTech Connect

    Barry, T.; Swgawa, R.; Wofford, P.

    1995-12-31

    The Department of Pesticide Regulation`s preliminary risk characterization of methyl bromide indicated an inadequate margin of safety for several exposure scenarios. Characterization of the air concentrations associated with common methyl bromide use patterns was necessary to determine specific scenarios that result in an unacceptable margin of safety. Field monitoring data were used in conjunction with the Industrial Source Complex, Short Tenn (ISCST) air dispersion model to characterize air concentrations associated with various types of methyl bromide applications. Chamber and building fumigations were monitored and modelled. For each fumigation the emission rates, chamber or building specifications and on-site meteorological data were input into the ISCST model. The model predicted concentrations were compared to measured air concentrations. The concentrations predicted by the ISCST model reflect both the pattern and magnitude of the measured concentrations. Required buffer zones were calculated using the ISCST output.

  13. Dependence of charge collection distributions and dose on the gas type filling the ionization chamber for a p(66)Be(49) clinical neutron beam

    SciTech Connect

    Awschalom, M.; Haken, R.K.T.

    1985-01-01

    Measurements of central axis depth charge distributions (CADCD) in a p(66)Be(49) clinical neutron beam using A-150 TE plastic ionization chambers (IC) have shown that these distributions are dependent on the gas type filling the ICs. IC volumes from 0.1 to 8 cm/sup 3/ and nine different gases were investigated. Off axis ratios and build-up measurements do not seem to be as sensitive to gas type. The gas dosimetry constants given in the AAPM Protocol for Neutron Beam Dosimetry for air and methane based TE gases were tested for consistency in water and in TE solution filled phantoms at depths of 10 cm, when used in conjunction with an IC having 5 mm thick walls of A-150. 29 refs., 7 figs., 1 tab.

  14. New standards for ionizing radiation measurements

    SciTech Connect

    Lamperti, P.J.; Johnson, C.M.

    1995-12-31

    The Ionizing Radiation Division has developed new national standards for mammographic X rays and for brachytherapy sources, such as iodine-125. The Attix chamber, a variable volume free-air ionization chamber, has been established as the primary national standard for mammographic X rays. The Attix chamber resides in the newly developed NIST Mammography Calibration Range and will be used to perform routine calibrations. The wide-angle free-air ionization chamber utilizes a large volume and a novel electric field configuration in order to circumvent the limitations of conventional free-air chambers. Seventeen beam qualities for X rays from molybdenum (Mo) and rhodium (Rh) anodes have been parameterized for the calibration of mammographic ionization chambers. The beam qualities available include anode/filter combinations of Mo/Mo, Mo/Rh and Rh/Rh. The mammography range was developed in collaborations with the U.S. Food and Drug Administration`s (FDA) Center for Devices and Radiological Health, the implementors of the Mammography Quality Standards Act (MQSA) of 1992. The wide-angle free-air ionization chamber has been used to measure the output of two types of iodine-125 seeds, those with resin balls and those with silver wire. Both free-air chambers have been intercompared with the Ritz parallel-plate free-air ionization chamber.

  15. Detecting excess ionizing radiation by electromagnetic breakdown of air

    SciTech Connect

    Granatstein, Victor L.; Nusinovich, Gregory S.

    2010-09-15

    A scheme is proposed for detecting a concealed source of ionizing radiation by observing the occurrence of breakdown in atmospheric air by an electromagnetic wave whose electric field surpasses the breakdown field in a limited volume. The volume is chosen to be smaller than the reciprocal of the naturally occurring concentration of free electrons. The pulse duration of the electromagnetic wave must exceed the avalanche breakdown time (10-200 ns) and could profitably be as long as the statistical lag time in ambient air (typically, microseconds). Candidate pulsed electromagnetic sources over a wavelength range, 3 mm>{lambda}>10.6 {mu}m, are evaluated. Suitable candidate sources are found to be a 670 GHz gyrotron oscillator with 200 kW, 10 {mu}s output pulses and a Transversely Excited Atmospheric-Pressure (TEA) CO{sub 2} laser with 30 MW, 100 ns output pulses. A system based on 670 GHz gyrotron would have superior sensitivity. A system based on the TEA CO{sub 2} laser could have a longer range >100 m.

  16. Technique for measuring air flow and carbon dioxide flux in large, open-top chambers

    SciTech Connect

    Ham, J.M.; Owensby, C.E.; Coyne, P.I.

    1993-10-01

    Open-Top Chambers (OTCs) are commonly used to evaluate the effect of CO{sub 2},O{sub 3}, and other trace gases on vegetation. This study developed and tested a new technique for measuring forced air flow and net CO{sub 2} flux from OTCs. Experiments were performed with a 4.5-m diam. OTC with a sealed floor and a specialized air delivery system. Air flow through the chamber was computed with the Bernoulli equation using measurements of the pressure differential between the air delivery ducts and the chamber interior. An independent measurement of air flow was made simultaneously to calibrate and verify the accuracy of the Bernoulli relationship. The CO{sub 2} flux density was calculated as the product of chamber air flow and the difference in CO{sub 2} concentration between the air entering and exhausting from the OTC (C{sub in}-C{sub out}). Accuracy was evaluated by releasing CO{sub 2} within the OTC at known rates. Data were collected with OTCs at ambient and elevated CO{sub 2} ({approx}700 {mu}mol{sup -1}). Results showed the Bernoulli equation, with a flow coefficient of 0.7, accurately measured air flow in the OTC within {+-}5% regardless of flow rate and air duct geometry. Experiments in ambient OTCs showed CO{sub 2} flux density ({mu}mol m{sup -2} s{sup -1}), computed from 2-min averages of air flow and C{sub in} - C{sub out,} was typically within {+-} 10% of actual flux, provided that the exit air velocity at the top of the OTC was greater than 0.6 m s{sup -1}. Obtaining the same accuracy in CO{sub 2}-enriched OTCs required a critical exit velocity near 1.2 m s{sup -1} to minimize the incursion of ambient air and prevent contamination of exit gas sample. When flux data were integrated over time to estimate daily CO{sub 2} flux ({mu}mol m{sup -2} d{sup -1}), actual and measured values agreed to within {+-}2% for both ambient and CO{sub 2}-enriched chambers, suggesting that accurate measurements of daily net C exchange are possible with this technique.

  17. A Liquid Xenon Ionization Chamber in an All-fluoropolymer Vessel

    SciTech Connect

    LePort, F.; Pocar, A.; Bartoszek, L.; DeVoe, R.; Fierlinger, P.; Flatt, B.; Gratta, G.; Green, M.; Montero Diez, M.; Neilson, R.; O'Sullivan, K.; Wodin, J.; Woisard, D.; Baussan, E.; Breidenbach, M.; Conley, R.; Fairbank, W., Jr.; Farine, J.; Hall, K.; Hallman, D.; Hargrove, C.; /Stanford U., Phys. Dept. /Applied Plastics Technology, Bristol /Neuchatel U. /SLAC /Colorado State U. /Laurentian U. /Carleton U. /Alabama U. /Moscow, ITEP

    2007-02-26

    A novel technique has been developed to build vessels for liquid xenon ionization detectors entirely out of ultra-clean fluoropolymer. We describe the advantages in terms of low radioactivity contamination, provide some details of the construction techniques, and show the energy resolution achieved with a prototype all-fluoropolymer ionization detector.

  18. MECHANISMS OF PHOTOCHEMICAL REACTIONS IN URBAN AIR. VOLUME II. CHAMBER STUDIES

    EPA Science Inventory

    The smog chamber facility of the Statewide Air Pollution Research Center has been employed in a study designed to provide experimental data required for the validation of kinetic computer models of chemical transformations in polluted atmospheres. A 5800-l, Teflon-coated, evacuab...

  19. FULL-SCALE CHAMBER INVESTIGATION AND SIMULATION OF AIR FRESHENER EMISSIONS IN THE PRESENCE OF OZONE

    EPA Science Inventory

    The paper discusses results of tests, conducted in the EPA large chamber facility, determining emissions and chemical degradation of volatile organic compounds (VOCs) from one electrical plug-in type pine-scented air freshener in the presence of ozone supplied by a device markete...

  20. Direct measurement of absorbed dose to water in HDR {sup 192}Ir brachytherapy: Water calorimetry, ionization chamber, Gafchromic film, and TG-43

    SciTech Connect

    Sarfehnia, Arman; Kawrakow, Iwan; Seuntjens, Jan

    2010-04-15

    Purpose: Gafchromic film and ionometric calibration procedures for HDR {sup 192}Ir brachytherapy sources in terms of dose rate to water are presented and the experimental results are compared to the TG-43 protocol as well as with the absolute dose measurement results from a water calorimetry-based primary standard. Methods: EBT-1 Gafchromic films, an A1SL Exradin miniature Shonka thimble type chamber, and an SI HDR 1000 Plus well-type chamber (Standard Imaging, Inc., Middleton, WI) with an ADCL traceable S{sub k} calibration coefficient (following the AAPM TG-43 protocol) were used. The Farmer chamber and Gafchromic film measurements were performed directly in water. All results were compared to direct and absolute absorbed dose to water measurements from a 4 deg. C stagnant water calorimeter. Results: Based on water calorimetry, the authors measured the dose rate to water to be 361{+-}7 {mu}Gy/(h U) at a 55 mm source-to-detector separation. The dose rate normalized to air-kerma strength for all the techniques agree with the water calorimetry results to within 0.83%. The overall 1-sigma uncertainty on water calorimetry, ionization chamber, Gafchromic film, and TG-43 dose rate measurement amounts to 1.90%, 1.44%, 1.78%, and 2.50%, respectively. Conclusions: This work allows us to build a more realistic uncertainty estimate for absorbed dose to water determination using the TG-43 protocol. Furthermore, it provides the framework necessary for a shift from indirect HDR {sup 192}Ir brachytherapy dosimetry to a more accurate, direct, and absolute measurement of absorbed dose to water.

  1. Dosimetric Verification and Validation of Conformal and IMRT Treatments Fields with an Ionization Chamber 2D-Array

    NASA Astrophysics Data System (ADS)

    Evangelina, Figueroa M.; Gabriel, Reséndiz G.; Miguel, Pérez P.

    2008-08-01

    A three-dimensional treatment planning system requires comparisons of calculated and measured dose distributions. It is necessary to confirm by means of patient specific QA that the dose distributions are correctly calculated, and that the patient data is correctly transferred to and delivered by the treatment machine. We used an analysis software for bi-dimensional dosimetric verification of conformal treatment and IMRT fields using as objective criterion the gamma index. An ionization chamber bi-dimensional array was used for absolute dose measurement in the complete field area.

  2. Correction factors for ionization chamber dosimetry in CyberKnife: Machine-specific, plan-class, and clinical fields

    SciTech Connect

    Gago-Arias, Araceli; Antolin, Elena; Fayos-Ferrer, Francisco; Simon, Rocio; Gonzalez-Castano, Diego M.; Palmans, Hugo; Sharpe, Peter; Gomez, Faustino; Pardo-Montero, Juan

    2013-01-15

    Purpose: The aim of this work is the application of the formalism for ionization chamber reference dosimetry of small and nonstandard fields [R. Alfonso, P. Andreo, R. Capote, M. S. Huq, W. Kilby, P. Kjaell, T. R. Mackie, H. Palmans, K. Rosser, J. Seuntjens, W. Ullrich, and S. Vatnitsky, 'A new formalism for reference dosimetry of small and nonstandard fields,' Med. Phys. 35, 5179-5186 (2008)] to the CyberKnife robotic radiosurgery system. Correction factors for intermediate calibration fields, a machine-specific reference field (msr) and two plan-class specific reference fields (pcsr), have been studied. Furthermore, the applicability of the new formalism to clinical dosimetry has been analyzed through the investigation of two clinical treatments. Methods: PTW31014 and Scanditronix-Wellhofer CC13 ionization chamber measurements were performed for the fields under investigation. Absorbed dose to water was determined using alanine reference dosimetry, and experimental correction factors were calculated from alanine to ionization chamber readings ratios. In addition, correction factors were calculated for the intermediate calibration fields and one of the clinical treatment fields using the Monte Carlo method and these were compared with the experimental values. Results: Overall correction factors deviating from unity by approximately 2% were obtained from both measurements and simulations, with values below and above unity for the studied intermediate calibration fields and clinical fields for the ionization chambers under consideration. Monte Carlo simulations yielded correction factors comparable with those obtained from measurements for the machine-specific reference field, although differences from 1% to 3.3% were observed between measured and calculated correction factors for the composite intermediate calibration fields. Dose distribution inhomogeneities are thought to be responsible for such discrepancies. Conclusions: The differences found between overall

  3. Discovery of multiple, ionization-created CS{sub 2} anions and a new mode of operation for drift chambers

    SciTech Connect

    Snowden-Ifft, Daniel P.

    2014-01-15

    This paper focuses on the surprising discovery of multiple species of ionization-created CS{sub 2} anions in gas mixtures containing electronegative CS{sub 2} and O{sub 2}, identified by their slightly different drift velocities. Data are presented to understand the formation mechanism and identity of these new anions. Regardless of the micro-physics, however, this discovery offers a new, trigger-less mode of operation for the drift chambers. A demonstration of trigger-less operation is presented.

  4. Quality assurance for radon exposure chambers at the National Air and Radiation Environmental Laboratory, Montgomery, Alabama

    SciTech Connect

    Semler, M.O.; Sensintaffar, E.L.

    1993-12-31

    The Office of Radiation and Indoor Air, U.S. Environmental Protection Agency (EPA), operates six radon exposure chambers in its two laboratories, the National Air and Radiation Environmental Laboratory (NAREL) in Montgomery, Alabama, and the Las Vegas Facility, Las Vegas, Nevada. These radon exposure chambers are used to calibrate and test portable radon measuring instruments, test commercial suppliers of radon measurement services through the Radon Measurement Proficiency Program, and expose passive measurement devices to known radon concentrations as part of a quality assurance plan for federal and state studies measuring indoor radon concentrations. Both laboratories participate in national and international intercomparisons for the measurement of radon and are presently working with the National Institute of Standards and Technology (NIST) to receive a certificate of traceability for radon measurements. NAREL has developed an estimate of the total error in its calibration of each chamber`s continuous monitors as part of an internal quality assurance program. This paper discusses the continuous monitors and their calibration for the three chambers located in Montgomery, Alabama, as well as the results of the authors intercomparisons and total error analysis.

  5. 42 CFR 84.143 - Terminal fittings or chambers; Type B supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Terminal fittings or chambers; Type B supplied-air... HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.143 Terminal fittings or chambers; Type...

  6. 24 CFR 3280.406 - Air chamber test method for certification and qualification of formaldehyde emission levels.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... HOME CONSTRUCTION AND SAFETY STANDARDS Testing § 3280.406 Air chamber test method for certification and... wrapped until preconditioning is initiated. (2) Panels selected for testing in the air chamber shall not be taken from the top or bottom of the stack. (b) Testing. Testing must be conducted in...

  7. 24 CFR 3280.406 - Air chamber test method for certification and qualification of formaldehyde emission levels.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... HOME CONSTRUCTION AND SAFETY STANDARDS Testing § 3280.406 Air chamber test method for certification and... wrapped until preconditioning is initiated. (2) Panels selected for testing in the air chamber shall not be taken from the top or bottom of the stack. (b) Testing. Testing must be conducted in...

  8. 24 CFR 3280.406 - Air chamber test method for certification and qualification of formaldehyde emission levels.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... HOME CONSTRUCTION AND SAFETY STANDARDS Testing § 3280.406 Air chamber test method for certification and... wrapped until preconditioning is initiated. (2) Panels selected for testing in the air chamber shall not be taken from the top or bottom of the stack. (b) Testing. Testing must be conducted in...

  9. 24 CFR 3280.406 - Air chamber test method for certification and qualification of formaldehyde emission levels.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... HOME CONSTRUCTION AND SAFETY STANDARDS Testing § 3280.406 Air chamber test method for certification and... wrapped until preconditioning is initiated. (2) Panels selected for testing in the air chamber shall not be taken from the top or bottom of the stack. (b) Testing. Testing must be conducted in...

  10. Assaying multiple 125I seeds with the well-ionization chamber SourceCheck4π 33005 and a new insert

    PubMed Central

    Ballester, Facundo; Perez-Calatayud, Jose; Vijande, Javier

    2015-01-01

    Purpose To provide a practical solution that can be adopted in clinical routine to fulfill the AAPM-ESTRO recommendations regarding quality assurance of seeds used in prostate permanent brachytherapy. The aim is to design a new insert for the well-ionization chamber SourceCheck4π 33005 (PTW, Germany) that allows evaluating the mean air-kerma strength of up to ten 125I seeds with one single measurement instead of measuring each seed individually. Material and methods The material required is: a) the SourceCheck4π 33005 well-ionization chamber provided with a PTW insert to measure the air-kerma strength S K of one single seed at a time; b) a newly designed insert that accommodates ten seeds in one column, which allows measuring the mean S K of the ten seeds in one single measurement; and c) a container with ten seeds from the same batch and class of the seeds used for the patient implant, and a set of nine non-radioactive seeds. The new insert is characterized by determining its calibration coefficient, used to convert the reading of the well-chamber when ten seeds are measured to their mean S K. The proposed method is validated by comparing the mean S K of the ten seeds obtained from the new insert with the individual measurement of S K of each seed, evaluated with the PTW insert. Results The ratio between the calibration coefficient of the new insert and the calibration coefficient of the PTW insert for the SourceCheck4π 33005 is 1.135 ± 0.007 (k = 1). The mean S K of a set of ten seeds evaluated with this new system is in agreement with the mean value obtained from measuring independently the S K of each seed. Conclusions The new insert and procedure allow evaluating the mean S K of ten seeds prior to the implant in a single measurement. The method is faster and more efficient from radiation protection point of view than measuring the individual S K of each seed. PMID:26816507

  11. Thermophysics Characterization of Multiply Ionized Air Plasma Absorption of Laser Radiation

    NASA Technical Reports Server (NTRS)

    Wang, Ten-See; Rhodes, Robert; Turner, Jim (Technical Monitor)

    2002-01-01

    The impact of multiple ionization of air plasma on the inverse Bremsstrahlung absorption of laser radiation is investigated for air breathing laser propulsion. Thermochemical properties of multiply ionized air plasma species are computed for temperatures up to 200,000 deg K, using hydrogenic approximation of the electronic partition function; And those for neutral air molecules are also updated for temperatures up to 50,000 deg K, using available literature data. Three formulas for absorption are calculated and a general formula is recommended for multiple ionization absorption calculation. The plasma composition required for absorption calculation is obtained by increasing the degree of ionization sequentially, up to quadruple ionization, with a series of thermal equilibrium computations. The calculated second ionization absorption coefficient agrees reasonably well with that of available data. The importance of multiple ionization modeling is demonstrated with the finding that area under the quadruple ionization curve of absorption is found to be twice that of single ionization. The effort of this work is beneficial to the computational plasma aerodynamics modeling of laser lightcraft performance.

  12. Hand and shoe monitor using air ionization probes

    DOEpatents

    Fergus, Richard W.

    1981-01-01

    A hand and shoe radiation monitor is provided which includes a probe support body defining a plurality of cells, within each cell there being an ionization probe. The support body provides structural strength for protecting the ionization probes from force applied to the support body during a radiation monitoring event. There is also provided a fast response time amplifier circuit for the output from the ionization probes.

  13. Effect of recombination in a high quantum efficiency prototype ionization-chamber-based electronic portal imaging device

    SciTech Connect

    Gopal, A.; Samant, S. S.

    2007-08-15

    The quantum efficiency (QE) of an imaging detector can be increased by utilizing a thick, high-density detection medium to increase the number of quantum interactions. However, image quality is more accurately described by the detection quantum efficiency (DQE). If a significant fraction of the increase in the number of detected quanta from a thick, dense detector were to result in useful imaging signal, this represents a favorable case where enhanced QE leads to increased DQE. However, for ionization-type detectors, one factor that limits DQE is the recombination between ion pairs that acts as a secondary quantum sink due to which enhancement in QE may not result in higher DQE depending on the extent of the signal loss from recombination. Therefore, an analysis of signal loss mechanisms or quantum sinks in an imaging system is essential for validating the overall benefit of high QE detectors. In this paper, a study of ion recombination as a secondary quantum sink is presented for a high QE prototype ion-chamber-based electronic portal imaging device (EPID): the kinestatic charge detector (KCD). The KCD utilizes a high pressure noble gas (krypton or xenon at 100 atm) and an arbitrarily large detector thickness (of the order of centimeters), resulting in a high QE imager. Compared with commercial amorphous silicon flat panel imagers that provide DQE(0){approx_equal}0.01, the KCD has much higher DQE. Studies indicated that DQE(0)=0.20 for 6.1 cm thick, 100 atm ({rho}=3.4 g/cm{sup 3}) xenon chamber, and DQE(0)=0.34 for a 9.1 cm thick chamber. A series of experiments was devised and conducted to determine the signal loss due to recombination for a KCD chamber. The measurements indicated a fractional recombination loss of about 14% for a krypton chamber and about 18% for a xenon chamber under standard operating conditions (100 atm chamber pressure and 1275 V/cm electric field intensity). A theoretical treatment of the effect of recombination on imaging signal

  14. Investigation and performance tests of a new parallel plate ionization chamber with double sensitive volume for measuring diagnostic X-rays

    NASA Astrophysics Data System (ADS)

    Sharifi, B.; Zamani Zeinali, H.; Soltani, J.; Negarestani, A.; Shahvar, A.

    2015-01-01

    Medical diagnostic equipment, like diagnostic radiology and mammography require a dosimeter with high accuracy for dosimetry of the diagnostic X-ray beam. Ionization chambers are suitable instruments for dosimetry of diagnostic-range X-ray beams because of their appropriate response and high reliability. This work introduces the design and fabrication of a new parallel plate ionization chamber with a PMMA body, graphite-coated PMMA windows (0.5 mm thick) and a graphite-foil central electrode (0.1 mm thick, 0.7 g/cm3 dense). This design improves upon the response characteristics of existing designs through the specific choice of materials as well as the appropriate size and arrangement of the ionization chamber components. The results of performance tests conducted at the Secondary Standard Dosimetry laboratory in Karaj-Iran demonstrated the short and long-term stability, the low leakage current, the low directional dependence, and the high ion collection efficiency of the design. Furthermore, the FLUKA Monte Carlo simulations confirmed the low effect of central electrode on this new ionization chamber response. The response characteristics of the parallel plate ionization chamber presented in this work makes the instrument suitable for use as a standard dosimeter in laboratories.

  15. DAVID—a translucent multi-wire transmission ionization chamber for in vivo verification of IMRT and conformal irradiation techniques

    NASA Astrophysics Data System (ADS)

    Poppe, B.; Thieke, C.; Beyer, D.; Kollhoff, R.; Djouguela, A.; Rühmann, A.; Willborn, K. C.; Harder, D.

    2006-03-01

    Permanent in vivo verification of IMRT photon beam profiles by a radiation detector with spatial resolution, positioned on the radiation entrance side of the patient, has not been clinically available so far. In this work we present the DAVID system, which is able to perform this quality assurance measurement while the patient is treated. The DAVID system is a flat, multi-wire transmission-type ionization chamber, placed in the accessory holder of the linear accelerator and constructed from translucent materials in order not to interfere with the light field. Each detection wire of the chamber is positioned exactly in the projection line of a MLC leaf pair, and the signal of each wire is proportional to the line integral of the ionization density along this wire. Thereby, each measurement channel essentially presents the line integral of the ionization density over the opening width of the associated leaf pair. The sum of all wire signals is a measure of the dose-area product of the transmitted photon beam and of the total radiant energy administered to the patient. After the dosimetric verification of an IMRT plan, the values measured by the DAVID system are stored as reference values. During daily treatment the signals are re-measured and compared to the reference values. A warning is output if there is a deviation beyond a threshold. The error detection capability is a leaf position error of less than 1 mm for an isocentric 1 cm × 1 cm field, and of 1 mm for an isocentric 20 cm × 20 cm field.

  16. DAVID--a translucent multi-wire transmission ionization chamber for in vivo verification of IMRT and conformal irradiation techniques.

    PubMed

    Poppe, B; Thieke, C; Beyer, D; Kollhoff, R; Djouguela, A; Rühmann, A; Willborn, K C; Harder, D

    2006-03-01

    Permanent in vivo verification of IMRT photon beam profiles by a radiation detector with spatial resolution, positioned on the radiation entrance side of the patient, has not been clinically available so far. In this work we present the DAVID system, which is able to perform this quality assurance measurement while the patient is treated. The DAVID system is a flat, multi-wire transmission-type ionization chamber, placed in the accessory holder of the linear accelerator and constructed from translucent materials in order not to interfere with the light field. Each detection wire of the chamber is positioned exactly in the projection line of a MLC leaf pair, and the signal of each wire is proportional to the line integral of the ionization density along this wire. Thereby, each measurement channel essentially presents the line integral of the ionization density over the opening width of the associated leaf pair. The sum of all wire signals is a measure of the dose-area product of the transmitted photon beam and of the total radiant energy administered to the patient. After the dosimetric verification of an IMRT plan, the values measured by the DAVID system are stored as reference values. During daily treatment the signals are re-measured and compared to the reference values. A warning is output if there is a deviation beyond a threshold. The error detection capability is a leaf position error of less than 1 mm for an isocentric 1 cm x 1 cm field, and of 1 mm for an isocentric 20 cm x 20 cm field. PMID:16481690

  17. SU-D-19A-01: Can Farmer-Type Ionization Chambers Be Used to Improve the Accuracy of Low-Energy Electron Beam Reference Dosimetry?

    SciTech Connect

    Muir, B R; McEwen, M R

    2014-06-01

    Purpose: To investigate the use of cylindrical Farmer-type ionization chambers to improve the accuracy of low-energy electron beam calibration. Historically, these chamber types have not been used in beams with incident energies less than 10 MeV (R{sub 5} {sub 0} < 4.3 cm) because early investigations suggested large (up to 5 %) fluence perturbation factors in these beams, implying that a significant component of uncertainty would be introduced if used for calibration. More recently, the assumptions used to determine perturbation corrections for cylindrical chambers have been questioned. Methods: Measurements are made with cylindrical chambers in Elekta Precise 4, 8 and 18 MeV electron beams. Several chamber types are investigated that employ graphite walls and aluminum electrodes with very similar specifications (NE2571, NE2505/3, FC65-G). Depth-ionization scans are measured in water in the 8 and 18 MeV beams. To reduce uncertainty from chamber positioning, measurements in the 4 MeV beam are made at the reference depth in Virtual Water™. The variability of perturbation factors is quantified by comparing normalized response of various chambers. Results: Normalized ion chamber response varies by less than 0.7 % for similar chambers at average electron energies corresponding to that at the reference depth from 4 or 6 MeV beams. Similarly, normalized measurements made with similar chambers at the reference depth in the 4 MeV beam vary by less than 0.4 %. Absorbed dose calibration coefficients derived from these results are stable within 0.1 % on average over a period of 6 years. Conclusion: These results indicate that the uncertainty associated with differences in fluence perturbations for cylindrical chambers with similar specifications is only 0.2 %. The excellent long-term stability of these chambers in both photon and electron beams suggests that these chambers might offer the best performance for all reference dosimetry applications.

  18. A novel convolution-based approach to address ionization chamber volume averaging effect in model-based treatment planning systems

    NASA Astrophysics Data System (ADS)

    Barraclough, Brendan; Li, Jonathan G.; Lebron, Sharon; Fan, Qiyong; Liu, Chihray; Yan, Guanghua

    2015-08-01

    The ionization chamber volume averaging effect is a well-known issue without an elegant solution. The purpose of this study is to propose a novel convolution-based approach to address the volume averaging effect in model-based treatment planning systems (TPSs). Ionization chamber-measured beam profiles can be regarded as the convolution between the detector response function and the implicit real profiles. Existing approaches address the issue by trying to remove the volume averaging effect from the measurement. In contrast, our proposed method imports the measured profiles directly into the TPS and addresses the problem by reoptimizing pertinent parameters of the TPS beam model. In the iterative beam modeling process, the TPS-calculated beam profiles are convolved with the same detector response function. Beam model parameters responsible for the penumbra are optimized to drive the convolved profiles to match the measured profiles. Since the convolved and the measured profiles are subject to identical volume averaging effect, the calculated profiles match the real profiles when the optimization converges. The method was applied to reoptimize a CC13 beam model commissioned with profiles measured with a standard ionization chamber (Scanditronix Wellhofer, Bartlett, TN). The reoptimized beam model was validated by comparing the TPS-calculated profiles with diode-measured profiles. Its performance in intensity-modulated radiation therapy (IMRT) quality assurance (QA) for ten head-and-neck patients was compared with the CC13 beam model and a clinical beam model (manually optimized, clinically proven) using standard Gamma comparisons. The beam profiles calculated with the reoptimized beam model showed excellent agreement with diode measurement at all measured geometries. Performance of the reoptimized beam model was comparable with that of the clinical beam model in IMRT QA. The average passing rates using the reoptimized beam model increased substantially from 92.1% to

  19. Intelligent monitor functional model with ionization chamber for mixed nuclear radiation field measurements

    SciTech Connect

    Valcov, N.; Purghel, L.; Celarel, A.

    1998-12-31

    By using the statistical discrimination technique, the components of an ionization current, due to a mixed radiation field, may be simultaneously measured. A functional model, including a series manufactured gamma-ray ratemeter was done, as an intermediate step in the design of specialized nuclear instrumentation, in order to check the concept of statistical discrimination method. The obtained results are in good agreement with the estimations of the statistical discrimination method.

  20. Two-dimensional and quasi-three-dimensional dosimetry of hadron and photon beams with the Magic Cube and the Pixel Ionization Chamber.

    PubMed

    Cirio, R; Garelli, E; Schulte, R; Amerio, S; Boriano, A; Bourhaleb, F; Coutrakon, G; Donetti, M; Giordanengo, S; Koss, P; Madon, E; Marchetto, F; Nastasi, U; Peroni, C; Santuari, D; Sardo, A; Scielzo, G; Stasi, M; Trevisiol, E

    2004-08-21

    Two detectors for fast two-dimensional (2D) and quasi-three-dimensional (quasi-3D) verification of the dose delivered by radiotherapy beams have been developed at University and Istituto Nazionale di Fisica Nucleare (INFN) of Torino. The Magic Cube is a stack of strip-segmented ionization chambers interleaved with water-equivalent slabs. The parallel plate ionization chambers have a sensitive area of 24 x 24 cm2, and consist of 0.375 cm wide and 24 cm long strips. There are a total of 64 strips per chamber. The Magic Cube has been tested with the clinical proton beam at Loma Linda University Medical Centre (LLUMC), and was shown to be capable of fast and precise quasi-3D dose verification. The Pixel Ionization Chamber (PXC) is a detector with pixel anode segmentation. It is a 32 x 32 matrix of 1024 cylindrical ionization cells arranged in a square 24 x 24 cm2 area. Each cell has 0.4 cm diameter and 0.55 cm height, at a pitch of 0.75 cm separates the centre of adjacent cells. The sensitive volume of each single ionization cell is 0.07 cm3. The detectors are read out using custom designed front-end microelectronics and a personal computer-based data acquisition system. The PXC has been used to verify dynamic intensity-modulated radiotherapy for head-and-neck and breast cancers. PMID:15446800

  1. Two-dimensional and quasi-three-dimensional dosimetry of hadron and photon beams with the Magic Cube and the Pixel Ionization Chamber

    NASA Astrophysics Data System (ADS)

    Cirio, R.; Garelli, E.; Schulte, R.; Amerio, S.; Boriano, A.; Bourhaleb, F.; Coutrakon, G.; Donetti, M.; Giordanengo, S.; Koss, P.; Madon, E.; Marchetto, F.; Nastasi, U.; Peroni, C.; Santuari, D.; Sardo, A.; Scielzo, G.; Stasi, M.; Trevisiol, E.

    2004-08-01

    Two detectors for fast two-dimensional (2D) and quasi-three-dimensional (quasi-3D) verification of the dose delivered by radiotherapy beams have been developed at University and Istituto Nazionale di Fisica Nucleare (INFN) of Torino. The Magic Cube is a stack of strip-segmented ionization chambers interleaved with water-equivalent slabs. The parallel plate ionization chambers have a sensitive area of 24 × 24 cm2, and consist of 0.375 cm wide and 24 cm long strips. There are a total of 64 strips per chamber. The Magic Cube has been tested with the clinical proton beam at Loma Linda University Medical Centre (LLUMC), and was shown to be capable of fast and precise quasi-3D dose verification. The Pixel Ionization Chamber (PXC) is a detector with pixel anode segmentation. It is a 32 × 32 matrix of 1024 cylindrical ionization cells arranged in a square 24 × 24 cm2 area. Each cell has 0.4 cm diameter and 0.55 cm height, at a pitch of 0.75 cm separates the centre of adjacent cells. The sensitive volume of each single ionization cell is 0.07 cm3. The detectors are read out using custom designed front-end microelectronics and a personal computer-based data acquisition system. The PXC has been used to verify dynamic intensity-modulated radiotherapy for head-and-neck and breast cancers.

  2. Chamber and field evaluations of air pollution tolerances of urban trees

    SciTech Connect

    Karnosky, D.F.

    1981-04-01

    Results are presented for a study of the relative air pollution tolerances of 32 urban-tree cultivars as determined by both chamber fumigations and field exposures. Tolerances to ozone and sulfur dioxide, alone and in combination, were determined using short-term, acute doses administered while the plants were inside a plastic fumigation chamber located inside the Cary Arboretum greenhouses. In a follow-up study still underway, representatives of the same cultivars were outplanted at four locations in the greater New York City area. To date, only oxidant-type injury has been observed on trees in the field plots. Cultivars tolerant to all chamber and field exposures were Acer platanoides Cleveland, Crimson King, Emerald Queen, Jade Glen, and Summershade; Acer rubrum Autumn Flame and Red Sunset; Acer saccharum Green Mountain and Temple's Upright; Fagus sylvatica Rotundifolia; Fraxinus pennsylvanica Summit; and Ginkgo biloba Fastigate and Sentry. Cultivars sensitive to ozone as determined by the chamber and field tests and that may serve as bioindicators of the presence of ozone were Gleditsia triacanthos inermis imperial and Platanus acerifolia Bloodgood.

  3. Simulation of the Mg(Ar) ionization chamber currents by different Monte Carlo codes in benchmark gamma fields

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Chun; Liu, Yuan-Hao; Nievaart, Sander; Chen, Yen-Fu; Wu, Shu-Wei; Chou, Wen-Tsae; Jiang, Shiang-Huei

    2011-10-01

    High energy photon (over 10 MeV) and neutron beams adopted in radiobiology and radiotherapy always produce mixed neutron/gamma-ray fields. The Mg(Ar) ionization chambers are commonly applied to determine the gamma-ray dose because of its neutron insensitive characteristic. Nowadays, many perturbation corrections for accurate dose estimation and lots of treatment planning systems are based on Monte Carlo technique. The Monte Carlo codes EGSnrc, FLUKA, GEANT4, MCNP5, and MCNPX were used to evaluate energy dependent response functions of the Exradin M2 Mg(Ar) ionization chamber to a parallel photon beam with mono-energies from 20 keV to 20 MeV. For the sake of validation, measurements were carefully performed in well-defined (a) primary M-100 X-ray calibration field, (b) primary 60Co calibration beam, (c) 6-MV, and (d) 10-MV therapeutic beams in hospital. At energy region below 100 keV, MCNP5 and MCNPX both had lower responses than other codes. For energies above 1 MeV, the MCNP ITS-mode greatly resembled other three codes and the differences were within 5%. Comparing to the measured currents, MCNP5 and MCNPX using ITS-mode had perfect agreement with the 60Co, and 10-MV beams. But at X-ray energy region, the derivations reached 17%. This work shows us a better insight into the performance of different Monte Carlo codes in photon-electron transport calculation. Regarding the application of the mixed field dosimetry like BNCT, MCNP with ITS-mode is recognized as the most suitable tool by this work.

  4. WIND TUNNEL STUDY OF THE FLOW FIELD WITHIN AND AROUND OPEN-TOP CHAMBERS USED FOR AIR POLLUTION STUDIES

    EPA Science Inventory

    The EPA Meteorological Wind Tunnel was used to examine the flow field in and around models of open-top field plant growth chambers used to assess the effects of pollutant gases on plant growth. Baffles designed to reduce the ingress of ambient air into the chamber through the ope...

  5. Air-soil exchange of organochlorine pesticides in a sealed chamber.

    PubMed

    Yang, Bing; Han, Baolu; Xue, Nandong; Zhou, Lingli; Li, Fasheng

    2015-01-01

    So far little is known about air-soil exchange under any sealed circumstances (e.g., in plastic and glass sheds), which however has huge implications for the soil-air-plant pathways of persistent organic pollutants including organochlorine pesticides (OCPs). A newly designed passive air sampler was tested in a sealed chamber for measuring the vertical concentration profiles of gaseous phase OCPs (hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs)). Air was sampled at 5, 15, and 30 cm above ground level every 10th day during a 60-day period by deploying polyurethane foam cylinders housed in acrylonitrile butadiene styrene-covered cartridges. Concentrations and compositions of OCPs along the vertical sections indicated a clear relationship with proximity to the mixture of HCHs and DDTs which escapes from the soils. In addition, significant positive correlations were found between air temperatures and concentrations of HCHs and DDTs. These results indicated revolatilization and re-deposition being at or close to dynamic pseudo-equilibrium with the overlying air. The sampler used for addressing air-soil exchange of persistent organic pollutants in any sealed conditions is discussed. PMID:25597683

  6. Characterization and performances of a monitoring ionization chamber dedicated to IBA-universal irradiation head for Pencil Beam Scanning

    NASA Astrophysics Data System (ADS)

    Courtois, C.; Boissonnat, G.; Brusasco, C.; Colin, J.; Cussol, D.; Fontbonne, J. M.; Marchand, B.; Mertens, T.; de Neuter, S.; Peronnel, J.

    2014-02-01

    Every radiotherapy center has to be equipped with real-time beam monitoring devices. In 2008, we developed an ionization chamber in collaboration with the IBA (Ion Beam Applications) company. This monitoring device called IC2/3 was developed to be used in IBA universal irradiation head for Pencil Beam Scanning (PBS). Here we present the characterization of the IC2/3 monitor in the energy and flux ranges used in protontherapy. The equipment has been tested with an IBA cyclotron able to deliver proton beams from 70 to 230 MeV. This beam monitoring device has been validated and is now installed at the Westdeutsches Protonentherapiezentrum Essen protontherapy center (WPE, Germany). The results obtained in both terms of spatial resolution and dose measurements are at least equal to the initial specifications needed for PBS purposes. The detector measures the dose with a relative uncertainty lower than 1% in the range from 0.5 Gy/min to 8 Gy/min while the spatial resolution is better than 250 μm. The technology has been patented and five IC2/3 chambers were delivered to IBA. Nowadays, IBA produces the IC2/3 beam monitoring device as a part of its Proteus 235 product.

  7. Swept source OCT with air puff chamber for corneal dynamics measurements

    NASA Astrophysics Data System (ADS)

    Karnowski, Karol; Alonso-Caneiro, David; Kaluzny, Bartlomiej; Kowalczyk, Andrzej; Wojtkowski, Maciej

    2012-03-01

    None of currently used tonometers produce estimated IOP values that are free of errors. Measurement incredibility arises from indirect measurement of corneal deformation and the fact that pressure calculations are based on population averaged parameters of anterior segment. Reliable IOP values are crucial for understanding and monitoring of number of eye pathologies e.g. glaucoma. We have combined high speed swept source OCT with air-puff chamber. System provides direct measurement of deformation of cornea and anterior surface of the lens. This paper describes in details the performance of air-puff ssOCT instrument. We present different approaches of data presentation and analysis. Changes in deformation amplitude appears to be good indicator of IOP changes. However, it seems that in order to provide accurate intraocular pressure values an additional information on corneal biomechanics is necessary. We believe that such information could be extracted from data provided by air-puff ssOCT.

  8. Numerical Simulation of Flows in a Cyclone Chamber with Different Conditions of Air Inlet and Outlet

    NASA Astrophysics Data System (ADS)

    Pitsukha, E. A.

    2014-09-01

    A numerical investigation of flows in a cyclone chamber has been carried out at the fraction of bottom blast φ =0-0.5, at the values of the dimensionless pinch diameter dout/D =0.7 with different locations and configurations of nozzles for air intake. In the simulation of swirling flows, the well-known k-ɛ and k-ω turbulence models, as well as the laminar flow model, were used. A satisfactory agreement between the results of numerical simulation and experimental data at dout/D =0.5-0.7 is obtained. For a chamber with a relative pinch diameter dout/D =0.3 the calculated flow parameters differ substantially from experimental values.

  9. Chamber bioaerosol study: outdoor air and human occupants as sources of indoor airborne microbes.

    PubMed

    Adams, Rachel I; Bhangar, Seema; Pasut, Wilmer; Arens, Edward A; Taylor, John W; Lindow, Steven E; Nazaroff, William W; Bruns, Thomas D

    2015-01-01

    Human occupants are an important source of microbes in indoor environments. In this study, we used DNA sequencing of filter samples to assess the fungal and bacterial composition of air in an environmental chamber under different levels of occupancy, activity, and exposed or covered carpeting. In this office-like, mechanically ventilated environment, results showed a strong influence of outdoor-derived particles, with the indoor microbial composition tracking that of outdoor air for the 2-hour sampling periods. The number of occupants and their activity played a significant but smaller role influencing the composition of indoor bioaerosols. Human-associated taxa were observed but were not particularly abundant, except in the case of one fungus that appeared to be transported into the chamber on the clothing of a study participant. Overall, this study revealed a smaller signature of human body-associated taxa than had been expected based on recent studies of indoor microbiomes, suggesting that occupants may not exert a strong influence on bioaerosol microbial composition in a space that, like many offices, is well ventilated with air that is moderately filtered and moderately occupied. PMID:26024222

  10. Chamber Bioaerosol Study: Outdoor Air and Human Occupants as Sources of Indoor Airborne Microbes

    PubMed Central

    Adams, Rachel I.; Bhangar, Seema; Pasut, Wilmer; Arens, Edward A.; Taylor, John W.; Lindow, Steven E.; Nazaroff, William W.; Bruns, Thomas D.

    2015-01-01

    Human occupants are an important source of microbes in indoor environments. In this study, we used DNA sequencing of filter samples to assess the fungal and bacterial composition of air in an environmental chamber under different levels of occupancy, activity, and exposed or covered carpeting. In this office-like, mechanically ventilated environment, results showed a strong influence of outdoor-derived particles, with the indoor microbial composition tracking that of outdoor air for the 2-hour sampling periods. The number of occupants and their activity played a significant but smaller role influencing the composition of indoor bioaerosols. Human-associated taxa were observed but were not particularly abundant, except in the case of one fungus that appeared to be transported into the chamber on the clothing of a study participant. Overall, this study revealed a smaller signature of human body-associated taxa than had been expected based on recent studies of indoor microbiomes, suggesting that occupants may not exert a strong influence on bioaerosol microbial composition in a space that, like many offices, is well ventilated with air that is moderately filtered and moderately occupied. PMID:26024222

  11. Fast-Neutron Spectrometry Using a 3He Ionization Chamber and Digital Pulse Shape Analysis

    SciTech Connect

    D. L. Chichester; J. T. Johnson; E. H. Seabury

    2010-05-01

    Digital pulse shape analysis (dPSA) has been used with a Cuttler-Shalev type 3He proportional counter to measure the fast neutron spectra of bare 252Cf and 241AmBe neutron sources. Measurements have also been made to determine the attenuated fast neutron spectra of 252Cf shielded by several materials including water, graphite, liquid nitrogen, magnesium, and tungsten. Rise-time dPSA has been employed using the common rise-time approach for analyzing n +3He ? 1H + 3H ionization events and a new approach has been developed to improve the fidelity of these measurements. Simulations have been performed for the different experimental arrangements and are compared, demonstrating general agreement between the dPSA processed fast neutron spectra and predictions.

  12. Dosimetry for the MRI accelerator: the impact of a magnetic field on the response of a Farmer NE2571 ionization chamber.

    PubMed

    Meijsing, I; Raaymakers, B W; Raaijmakers, A J E; Kok, J G M; Hogeweg, L; Liu, B; Lagendijk, J J W

    2009-05-21

    The UMC Utrecht is constructing a 1.5 T MRI scanner integrated with a linear accelerator (Lagendijk et al 2008 Radiother. Oncol. 86 25-9). The goal of this device is to facilitate soft-tissue contrast based image-guided radiotherapy, in order to escalate the dose to the tumour while sparing surrounding normal tissues. Dosimetry for the MRI accelerator has to be performed in the presence of a magnetic field. This paper investigates the feasibility of using a Farmer NE2571 ionization chamber for absolute dosimetry. The impact of the mcagnetic field on the response of this ionization chamber has been measured and simulated using GEANT4 Monte Carlo simulations. Two orientations of the ionization chamber with respect to the incident beam and the magnetic field which are feasible in the MRI accelerator configuration are taken into account. Measurements are performed using a laboratory magnet ranging from 0 to 1.2 T. In the simulations a range from 0 to 2 T is used. For both orientations, the measurements and simulations agreed within the uncertainty of the measurements and simulations. In conclusion, the response of the ionization chamber as a function of the magnetic field is understood and can be simulated using GEANT4 Monte Carlo simulations. PMID:19387100

  13. NOTE: Determination of the recombination correction factor kS for some specific plane-parallel and cylindrical ionization chambers in pulsed photon and electron beams

    NASA Astrophysics Data System (ADS)

    Bruggmoser, G.; Saum, R.; Schmachtenberg, A.; Schmid, F.; Schüle, E.

    2007-01-01

    It has been shown from an evaluation of the inverse reading of the dosemeter (1/M) against the inverse of the polarizing voltage (1/V), obtained with a number of commercially available ionization chambers, using dose per pulse values between 0.16 and 5 mGy, that a linear relationship between the recombination correction factor kS and dose per pulse (DPP) can be found. At dose per pulse values above 1 mGy the method of a general equation with coefficients dependent on the chamber type gives more accurate results than the Boag method. This method was already proposed by Burns and McEwen (1998, Phys. Med. Biol. 43 2033) and avoids comprehensive and time-consuming measurements of Jaffé plots which are a prerequisite for the application of the multi-voltage analysis (MVA) or the two-voltage analysis (TVA). We evaluated and verified the response of ionization chambers on the recombination effect in pulsed accelerator beams for both photons and electrons. Our main conclusions are: (1) The correction factor kS depends only on the DPP and the chamber type. There is no influence of radiation type and energy. (2) For all the chambers investigated there is a linear relationship between kS and DPP up to 5 mGy/pulse, and for two chambers we could show linearity up to 40 mGy/pulse. (3) A general formalism, such as that of Boag, characterizes chambers exclusively by the distance of the electrodes and gives a trend for the correction factor, and therefore (4) a general formalism has to reflect the influence of the chamber construction on the recombination by the introduction of chamber-type dependent coefficients.

  14. Comparison of two dose-area-product ionization chambers with different conductive surface coating for over-table and under-table tube configurations

    SciTech Connect

    Bednarek, D.R.; Rudin, S.

    2000-03-01

    A custom-built graphite-coated transmission ionization chamber is compared to the VacuDAP 2001 (VacuTec, Dresden, Germany), which has transparent conductive electrodes. A study was made of the dependence of response on x-ray tube potential for both types of chamber under identical conditions of exposure using over-table and under-table x-ray tubes. Since the calibration factor is the dose-area product of the radiation incident on the patient per chamber reading, it depends on the intrinsic response of the chamber as well as the effect of material in the beam between the x-ray tube and patient. Differences of about 20% were measured between the intrinsic and the over-table calibration factors and between the over-table and the under-table calibration factors for both chambers. The VacuDAP display is specifically calibrated for the over-table condition and would overstate the actual DAP in the under-table case. The intrinsic response of the graphite chamber is nearly independent of tube potential. Although the variation of response with tube potential of the graphite chamber is increased when it is used as an over-table and an under-table patient monitor, it shows less overall variation of response than the VacuDAP. The average deviation of each range of 40 to 140 kVp for both chambers.

  15. Experimental analysis of general ion recombination in a liquid-filled ionization chamber in high-energy photon beams

    SciTech Connect

    Chung, Eunah; Seuntjens, Jan; Davis, Stephen

    2013-06-15

    Purpose: To study experimentally the general ion recombination effect in a liquid-filled ionization chamber (LIC) in high-energy photon beams. Methods: The general ion recombination effect on the response of a micro liquid ion chamber (microLion) was investigated with a 6 MV photon beam in normal and SRS modes produced from a Varian{sup Registered-Sign} Novalis Tx{sup TM} linear accelerator. Dose rates of the linear accelerator were set to 100, 400, and 1000 MU/min, which correspond to pulse repetition frequencies of 60, 240, and 600 Hz, respectively. Polarization voltages applied to the microLion were +800 and +400 V. The relative collection efficiency of the microLion response as a function of dose per pulse was experimentally measured with changing polarization voltage and pulse repetition frequencies and was compared with the theoretically calculated value. Results: For the 60 Hz pulse repetition frequency, the experimental relative collection efficiency was not different from the theoretical one for a pulsed beam more than 0.3% for both polarization voltages. For a pulsed radiation beam with a higher pulse repetition frequency, the experimental relative collection efficiency converged to the theoretically calculated efficiency for continuous beams. This result indicates that the response of the microLion tends toward the response to a continuous beam with increasing pulse repetition frequency of a pulsed beam because of low ion mobility in the liquid. Conclusions: This work suggests an empirical method to correct for differences in general ion recombination of a LIC between different radiation fields. More work is needed to quantitatively explain the LIC general ion recombination behavior in pulsed beams generated from linear accelerators.

  16. Resonant- and avalanche-ionization amplification of laser-induced plasma in air

    SciTech Connect

    Wu, Yue; Zhang, Zhili; Jiang, Naibo; Roy, Sukesh; Gord, James R.

    2014-10-14

    Amplification of laser-induced plasma in air is demonstrated utilizing resonant laser ionization and avalanche ionization. Molecular oxygen in air is ionized by a low-energy laser pulse employing (2 + 1) resonance-enhanced multi-photon ionization (REMPI) to generate seed electrons. Subsequent avalanche ionization of molecular oxygen and nitrogen significantly amplifies the laser-induced plasma. In this plasma-amplification effect, three-body attachments to molecular oxygen dominate the electron-generation and -loss processes, while either nitrogen or argon acts as the third body with low electron affinity. Contour maps of the electron density within the plasma obtained in O₂/N₂ and O₂/Ar gas mixtures are provided to show relative degrees of plasma amplification with respect to gas pressure and to verify that the seed electrons generated by O₂ 2 + 1 REMPI are selectively amplified by avalanche ionization of molecular nitrogen in a relatively low-pressure condition (≤100 Torr). Such plasma amplification occurring in air could be useful in aerospace applications at high altitude.

  17. Laser Induced Fluorescence Spectroscopy of Neutral and Ionized Polycyclic Aromatic Hydrocarbons in a Cosmic Simulation Chamber

    NASA Astrophysics Data System (ADS)

    Bejaoui, Salma; Salama, Farid

    2015-08-01

    Polycyclic aromatic hydrocarbon (PAH) molecules are considered the best carriers to account for the ubiquitous infrared emission bands. PAHs have also been proposed as candidates to explain the diffuse interstellar bands (DIBs), a series of absorption features seen on the interstellar extinction curve and are plausible carriers for the extended red emission (ERE), a photoluminescent process associated with a wide variety of interstellar environments. Extensive efforts have been devoted over the past two decades to characterize the physical and chemical properties of PAH molecules and ions in space. Absorption spectra of PAH molecules and ions trapped in solid matrices have been compared to the DIBs [1, 2]. Absorption spectra of several cold, isolated gas-phase PAHs have also been measured under experimental conditions that mimic the interstellar conditions [see 3 for a review]. The purpose of this study is to provide a new dimension to the existing spectroscopic database of neutral and single ionized PAHs that is largely based on absorption spectra by adding emission spectroscopy data. The measurements are based on the laser-induced fluorescence (LIF) technique [4] and are performed with the Pulsed Discharge Nozzle (PDN) of the COSmIC laboratory facility at NASA Ames laboratory. The PDN generates plasma in a free supersonic jet expansion to simulate the physical and the chemical conditions in interstellar environments. We focus, here, on the fluorescence spectra of large neutral PAHs and their cations where there is a lack of fluorescence spectroscopy data. The astronomical implications of the data (e.g., ERE) are examinedReferences[1] F. Salama, E. Bakes, L.J. Allamandola, A.G.G.M. Tielens, Astrophys. J., 458 (1996) p.621[2] F. Salama, The ISO Revolution, EDP Sciences, Les Ulis, France (1999) p.65[3] Salama F., In Organic Matter in Space, IAU Symposium 251, Kwok & Sandford Eds.Cambridge University Press,4, S251,(2008), p. 357 (2008) and references therein.[4

  18. Experimental determination of the absorbed dose to water in a scanned proton beam using a water calorimeter and an ionization chamber

    NASA Astrophysics Data System (ADS)

    Gagnebin, Solange; Twerenbold, Damian; Pedroni, Eros; Meer, David; Zenklusen, Silvan; Bula, Christian

    2010-03-01

    The absorbed dose to water is the reference physical quantity for the energy absorbed in tissue when exposed to beams of ionizing radiation in radiotherapy. The SI unit of absorbed dose to water is the gray (Gy = 1 J/kg). Ionization chambers are used as the dosimeters of choice in the clinical environment because they show a high reproducibility and are easy to use. However, ionization chambers have to be calibrated in order to convert the measured electrical charge into absorbed dose to water. In addition, protocols require these conversion factors to be SI traceable to a primary standard of absorbed dose to water. We present experimental results where the ionization chamber used for the dosimetry for the scanned proton beam facility at PSI is compared with the direct determination of absorbed dose to water from the METAS primary standard water calorimeter. The agreement of 3.2% of the dose values measured by the two techniques are within their respective statistical uncertainties.

  19. On the interpretation of current-voltage curves in ionization chambers using the exact solution of the Thomson problem

    NASA Astrophysics Data System (ADS)

    Ridenti, M. A.; Pascholati, P. R.; Gonçalves, J. A. C.; Bueno, C. C.

    2015-09-01

    The I - ΔV characteristic curve of a well type ionization chamber irradiated with 192Ir sources (0.75 Ci-120 Ci) was fitted using the exact solution of the Thomson problem. The recombination coefficient and saturation current were estimated using this new approach. The saturation current was compared with the results of the conventional method based on Boag-Wilson formula. It was verified that differences larger than 1% between both methods only occurred at activities higher than 55 Ci. We concluded that this new approach is recommended for a more accurate estimate of the saturation current when it is not possible to measure currents satisfying the condition I /Isat > 0.95. From the calibration curve the average value of pairs of carriers created per unit volume was estimated to be equal to η = 8.1 ×10-3cm-3s-1 Bq-1 and from that value it was estimated that ~ 17 pairs were created on average per second for each decay of the source.

  20. Development of a high-resolution room-temperature compressed-xenon cylindrical ionization-chamber gamma radiation detector

    NASA Astrophysics Data System (ADS)

    Tepper, Gary C.; Losee, Jon R.; Palmer, Robert L.

    1998-07-01

    Highly compressed and purified xenon is emerging as an important detection medium for high resolution, room temperature gamma radiation spectroscopy. Detectors based on compressed xenon offer a unique combination of thermal stability, high energy resolution and large volume. Furthermore, fluid based detectors are not susceptible to radiation damage, and can be constructed in a variety of geometries. However, some important factors have delayed the development of practical xenon detectors for widespread use. These factors include the relatively high operational pressures and voltages and the need to maintain extremely high xenon purity. We have recently developed a 0.7 liter gridded ionization chamber xenon gamma radiation detector in a cylindrical geometry. The detector operates at room temperature and provides an intrinsic energy resolution of 1.8% at 662 keV which is five times greater than scintillation based spectrometers. The detector design and performance variables are discussed in comparison to a previous detector constructed in a planar geometry. Our results indicate that practical xenon detectors can now be developed for a wide variety of applications.

  1. Time-of-flight ERD with a 200 mm2 Si3N4 window gas ionization chamber energy detector

    NASA Astrophysics Data System (ADS)

    Julin, Jaakko; Laitinen, Mikko; Sajavaara, Timo

    2014-08-01

    Low energy heavy ion elastic recoil detection work has been carried out in Jyväskylä since 2009 using home made timing detectors, a silicon energy detector and a timestamping data acquisition setup forming a time-of-flight-energy telescope. In order to improve the mass resolution of the setup a new energy detector was designed to replace the silicon solid state detector, which suffered from radiation damage and had poor resolution for heavy recoils. In this paper the construction and operation of an isobutane filled gas ionization chamber with a 14 × 14 mm2 100 nm thick silicon nitride window are described. In addition to greatly improved energy resolution for heavy ions, the detector is also able to detect hydrogen recoils simultaneously in the energy range of 100-1000 keV. Additionally the detector has position sensitivity by means of timing measurement, which can be performed without compromising the performance of the detector in any other way. The achieved position sensitivity improves the depth resolution near the surface.

  2. Performance of a Compression-ignition Engine with a Precombustion Chamber Having High-Velocity Air Flow

    NASA Technical Reports Server (NTRS)

    Spanogle, J A; Moore, C S

    1931-01-01

    Presented here are the results of performance tests made with a single-cylinder, four stroke cycle, compression-ignition engine. These tests were made on a precombustion chamber type of cylinder head designed to have air velocity and tangential air flow in both the chamber and cylinder. The performance was investigated for variable load and engine speed, type of fuel spray, valve opening pressure, injection period and, for the spherical chamber, position of the injection spray relative to the air flow. The pressure variations between the pear-shaped precombustion chamber and the cylinder for motoring and full load conditions were determined with a Farnboro electric indicator. The combustion chamber designs tested gave good mixing of a single compact fuel spray with the air, but did not control the ensuing combustion sufficiently. Relative to each other, the velocity of air flow was too high, the spray dispersion by injection too great, and the metering effect of the cylinder head passage insufficient. The correct relation of these factors is of the utmost importance for engine performance.

  3. A two-dimensional liquid-filled ionization chamber array prototype for small-field verification: characterization and first clinical tests.

    PubMed

    Brualla-González, Luis; Gómez, Faustino; Vicedo, Aurora; González-Castaño, Diego M; Gago-Arias, Araceli; Pazos, Antonio; Zapata, Martín; Roselló, Joan V; Pardo-Montero, Juan

    2012-08-21

    In this work we present the design, characterization and first clinical tests of an in-house developed two-dimensional liquid-filled ionization chamber prototype for the verification of small radiotherapy fields and treatments containing such small fields as in radiosurgery, which consists of 2 mm × 2 mm pixels arranged on a 16×8 rectangular grid. The ionization medium is isooctane. The characterization of the device included the study of depth, field-size and dose-rate dependences, which are sufficiently moderate for a good operation at therapy radiation levels. However, the detector presents an important anisotropic response, up to ≃ 12% for front versus near-lateral incidence, which can impact the verification of full treatments with different incidences. In such a case, an anisotropy correction factor can be applied. Output factors of small square fields measured with the device show a small systematic over-response, less than 1%, when compared to unshielded diode measurements. An IMRT radiosurgery treatment has been acquired with the liquid-filled ionization chamber device and compared with film dosimetry by using the gamma method, showing good agreement: over 99% passing rates for 1.2% and 1.2 mm for an incidence-per-incidence analysis; 100% passing rates for tolerances 1.8% and 1.8 mm when the whole treatment is analysed and the anisotropy correction factor is applied. The point dose verification for each incidence of the treatment performed with the liquid-filled ionization chamber agrees within 1% with a CC01 ionization chamber. This prototype has shown the utility of this kind of technology for the verification of small fields/treatments. Currently, a larger device covering a 5 cm × 5 cm area is under development. PMID:22850081

  4. Design and characterization of a small chamber for chemical and biological evaluation of sources of indoor air contamination

    SciTech Connect

    Mason, M.A.; Roache, N.F.; Guo, Z.; Costa, D.

    1996-12-31

    The potential for emissions from materials used indoors to cause sensory irritation has prompted several researchers to adapt the mouse bioassay, ASTM E 981, for evaluation of irritancy potential of product emissions.Standardized test procedures that produce comparable results are needed if bioassays, such as ASTM E 981, are to be used to rank and compare products based upon the irritation potential of product emissions. The authors designed, constructed, and determined performance characteristics for a 34-L source emissions chamber, which mates directly to the 2.3-L mouse exposure chamber specified by ASTM E 981 and found the glass chamber to be without significant air leaks and background emissions. Reversible adsorption of decane and p-dichlorobenzene was noted. They found it necessary to add a circulation fan inside the chamber to create air velocities that are representative of those found in indoor environments. The well controlled thermal environment and straightforward connection of the chamber to the mouse exposure chamber used in ASTM E 981 are features that may make this chamber useful in development and evaluation of protocols for biological characterization of product emissions.

  5. Laser filamentation induced air-flow motion in a diffusion cloud chamber.

    PubMed

    Sun, Haiyi; Liu, Jiansheng; Wang, Cheng; Ju, Jingjing; Wang, Zhanxin; Wang, Wentao; Ge, Xiaochun; Li, Chuang; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2013-04-22

    We numerically simulated the air-flow motion in a diffusion cloud chamber induced by femtosecond laser filaments for different chopping rates. A two dimensional model was employed, where the laser filaments were treated as a heat flux source. The simulated patterns of flow fields and maximum velocity of updraft compare well with the experimental results for the chopping rates of 1, 5, 15 and 150 Hz. A quantitative inconsistency appears between simulated and experimental maximum velocity of updraft for 1 kHz repetition rate although a similar pattern of flow field is obtained, and the possible reasons were analyzed. Based on the present simulated results, the experimental observation of more water condensation/snow at higher chopping rate can be explained. These results indicate that the specific way of laser filament heating plays a significant role in the laser-induced motion of air flow, and at the same time, our previous conclusion of air flow having an important effect on water condensation/snow is confirmed. PMID:23609636

  6. Exposure chamber

    DOEpatents

    Moss, Owen R.

    1980-01-01

    A chamber for exposing animals, plants, or materials to air containing gases or aerosols is so constructed that catch pans for animal excrement, for example, serve to aid the uniform distribution of air throughout the chamber instead of constituting obstacles as has been the case in prior animal exposure chambers. The chamber comprises the usual imperforate top, bottom and side walls. Within the chamber, cages and their associated pans are arranged in two columns. The pans are spaced horizontally from the walls of the chamber in all directions. Corresponding pans of the two columns are also spaced horizontally from each other. Preferably the pans of one column are also spaced vertically from corresponding pans of the other column. Air is introduced into the top of the chamber and withdrawn from the bottom. The general flow of air is therefore vertical. The effect of the horizontal pans is based on the fact that a gas flowing past the edge of a flat plate that is perpendicular to the flow forms a wave on the upstream side of the plate. Air flows downwardly between the chamber walls and the outer edges of the pan. It also flows downwardly between the inner edges of the pans of the two columns. It has been found that when the air carries aerosol particles, these particles are substantially uniformly distributed throughout the chamber.

  7. Ozone deposition to an oat crop ( Avena sativa L.) grown in open-top chambers and in the ambient air

    NASA Astrophysics Data System (ADS)

    Pleijel, H.; Wallin, G.; Karlsson, P. E.; Skarby, L.; Sellden, G.

    Fluxes and deposition velocities for ozone were determined for open-top chambers with and without an oat crop, and for the adjacent field, using a resistance analogue model and the aerodynamic wind-profile method, respectively. During a period when the canopy was green and the ambient wind speeds modest, the fluxes and deposition velocities were higher in the chamber with plants than in the field crop. The deposition to chamber walls and soil in the chamber only accounted for part of that difference. The deposition velocity for ozone to the crop was light-dependent both in the chamber with plants and in the ambient air. With increasing plant senescence, the deposition velocity declined and the light dependence disappeared. Fluctuations in deposition velocity superimposed on the overall declining trend followed the same temporal pattern in the chambers with and without plants. These fluctuations in deposition velocity may partly be explained by variations in surface wetness. Differences in boundary layer conductance between chamber and ambient, which under certain conditions may significantly influence the validity of the chamber as a test system, were observed.

  8. Gas gain operations with single photon resolution using an integrating ionization chamber in small-angle X-ray scattering experiments

    NASA Astrophysics Data System (ADS)

    Menk, R. H.; Sarvestani, A.; Besch, H. J.; Walenta, A. H.; Amenitsch, H.; Bernstorff, S.

    2000-01-01

    In this work a combination of an ionization chamber with one-dimensional spatial resolution and a MicroCAT structure will be presented. Initially, MicroCAT was thought of as a shielding grid (Frisch-grid) but later was used as an active electron amplification device that enables single X-ray photon resolution measurements at low fluxes even with integrating readout electronics. Moreover, the adjustable gas gain that continuously covers the entire range from pure ionization chamber mode up to high gas gains (30 000 and more) provides stable operation yielding a huge dynamic range of about 10 8 and more. First measurements on biological samples using small angle X-ray scattering techniques with synchrotron radiation will be presented.

  9. Comparison of depth-dose distributions of proton therapeutic beams calculated by means of logical detectors and ionization chamber modeled in Monte Carlo codes

    NASA Astrophysics Data System (ADS)

    Pietrzak, Robert; Konefał, Adam; Sokół, Maria; Orlef, Andrzej

    2016-08-01

    The success of proton therapy depends strongly on the precision of treatment planning. Dose distribution in biological tissue may be obtained from Monte Carlo simulations using various scientific codes making it possible to perform very accurate calculations. However, there are many factors affecting the accuracy of modeling. One of them is a structure of objects called bins registering a dose. In this work the influence of bin structure on the dose distributions was examined. The MCNPX code calculations of Bragg curve for the 60 MeV proton beam were done in two ways: using simple logical detectors being the volumes determined in water, and using a precise model of ionization chamber used in clinical dosimetry. The results of the simulations were verified experimentally in the water phantom with Marcus ionization chamber. The average local dose difference between the measured relative doses in the water phantom and those calculated by means of the logical detectors was 1.4% at first 25 mm, whereas in the full depth range this difference was 1.6% for the maximum uncertainty in the calculations less than 2.4% and for the maximum measuring error of 1%. In case of the relative doses calculated with the use of the ionization chamber model this average difference was somewhat greater, being 2.3% at depths up to 25 mm and 2.4% in the full range of depths for the maximum uncertainty in the calculations of 3%. In the dose calculations the ionization chamber model does not offer any additional advantages over the logical detectors. The results provided by both models are similar and in good agreement with the measurements, however, the logical detector approach is a more time-effective method.

  10. Large area neutron detector based on Li6 ionization chamber with integrated body-moderator of high density polyethylene

    SciTech Connect

    Ianakiev, Kiril D.; Swinhoe, Martyn T.; Chung, Kiwhan; Makela, Mark F.

    2009-06-30

    A detector was developed and funded by DHS to be a lower cost alternative to 3He detectors. A 6Li foil-lined ionization chamber was prepared with fill gas at one atmosphere and pulse mode operation. The high-density polyethylene (HOPE) body serves also as a neutron moderator. All electrodes, including high voltage bias supply, are hermetically sealed within the plastic slabs.

  11. Study on the stability of waterpower-speed control system for hydropower station with air cushion surge chamber

    NASA Astrophysics Data System (ADS)

    Guo, W. C.; Yang, J. D.; Chen, J. P.; Teng, Y.

    2014-03-01

    According to the fact that the effects of penstock, unit and governor on stability of water level fluctuation for hydropower station with air cushion surge chamber are neglected in previous researches, in this paper, Thoma assumption is broken through, the complete mathematical model of waterpower-speed control system for hydropower station with air cushion surge chamber is established, and the comprehensive transfer function and linear homogeneous differential equation that characterize the dynamic characteristics of system are derived. The stability domain that characterizes the good or bad of stability quantitatively is drawn by using the stability conditions. The effects of the fluid inertia in water diversion system, the air cushion surge chamber parameters, hydraulic turbine characteristics, generator characteristics, and regulation modes of governor on the stability of waterpower-speed control system are analyzed through stability domain. The main conclusions are as follows: The fluid inertia in water diversion system and hydraulic turbine characteristics have unfavorable effects on the system while generator characteristics have favorable effect. The stability keeps getting better with the increase of chamber height and basal area and the decrease of air pressure and air polytropic exponent. The stability of power regulation mode is obviously better than that of frequency regulation mode.

  12. SU-E-T-561: Development of Depth Dose Measurement Technique Using the Multilayer Ionization Chamber for Spot Scanning Method

    SciTech Connect

    Takayanagi, T; Fujitaka, S; Umezawa, M; Ito, Y; Nakashima, C; Matsuda, K

    2014-06-01

    Purpose: To develop a measurement technique which suppresses the difference between profiles obtained with a multilayer ionization chamber (MLIC) and with a water phantom. Methods: The developed technique multiplies the raw MLIC data by a correction factor that depends on the initial beam range and water equivalent depth. The correction factor is derived based on a Bragg curve calculation formula considering range straggling and fluence loss caused by nuclear reactions. Furthermore, the correction factor is adjusted based on several integrated depth doses measured with a water phantom and the MLIC. The measured depth dose profiles along the central axis of the proton field with a nominal field size of 10 by 10 cm were compared between the MLIC using the new technique and the water phantom. The spread out Bragg peak was 20 cm for fields with a range of 30.6 cm and 6.9 cm. Raw MLIC data were obtained with each energy layer, and integrated after multiplying by the correction factor. The measurements were performed by a spot scanning nozzle at Nagoya Proton Therapy Center, Japan. Results: The profile measured with the MLIC using the new technique is consistent with that of the water phantom. Moreover, 97% of the points passed the 1% dose /1mm distance agreement criterion of the gamma index. Conclusion: We have demonstrated that the new technique suppresses the difference between profiles obtained with the MLIC and with the water phantom. It was concluded that this technique is useful for depth dose measurement in proton spot scanning method.

  13. The effect of a compression paddle on energy response, calibration and measurement with mammographic dosimeters using ionization chambers and solid-state detectors

    NASA Astrophysics Data System (ADS)

    Hourdakis, C. J.; Boziari, A.; Koumbouli, E.

    2009-02-01

    A compression paddle is always used in mammography x-ray examinations, in order to improve image quality and reduce patient doses. Although clinical dose measurements should be performed with the paddle to interfere with the x-ray beam, calibration of mammography dosimeters is performed free in air without the presence of the paddle. The paddle hardens the x-ray beam, which has an impact on a dosimeter performance, particularly on high-energy-dependent detectors. Due to the paddle, clinical mammography x-ray systems may exhibit beams with HVL values exceeding those of the IEC 61267 RQR-M series qualities at which dosimeters are usually calibrated. In this study, the influence of the paddle in mammography dosimetry is examined, in Mo/Mo anode/filter x-ray qualities. PMMA slabs of 1, 2 and 3 mm thickness and Al foils of 0.05, 0.10 and 0.15 mm thicknesses were used to simulate the paddles, producing beams with HVL values from 0.28 up to 0.43 mmAl. In these qualities, four solid-state (ST) detectors and three ionizations chambers (IC) were calibrated in terms of Kair and NK and kQ were deduced. The results showed that all IC and two modern-type ST dosimeters have a flat energy response in the above HVL range (less than 3%), so their calibration factor at RQR-M2 quality could be safely used for clinical measurements. Two other ST dosimeters exhibit up to 20% energy response, so differences up to 15% in dose measurement may be observed if the effect of paddle on their performance is ignored. Finally, the need of additional mammographic calibration qualities to the existing IEC 61267 RQR-M series is examined and discussed.

  14. The effect of a compression paddle on energy response, calibration and measurement with mammographic dosimeters using ionization chambers and solid-state detectors.

    PubMed

    Hourdakis, C J; Boziari, A; Koumbouli, E

    2009-02-21

    A compression paddle is always used in mammography x-ray examinations, in order to improve image quality and reduce patient doses. Although clinical dose measurements should be performed with the paddle to interfere with the x-ray beam, calibration of mammography dosimeters is performed free in air without the presence of the paddle. The paddle hardens the x-ray beam, which has an impact on a dosimeter performance, particularly on high-energy-dependent detectors. Due to the paddle, clinical mammography x-ray systems may exhibit beams with HVL values exceeding those of the IEC 61267 RQR-M series qualities at which dosimeters are usually calibrated. In this study, the influence of the paddle in mammography dosimetry is examined, in Mo/Mo anode/filter x-ray qualities. PMMA slabs of 1, 2 and 3 mm thickness and Al foils of 0.05, 0.10 and 0.15 mm thicknesses were used to simulate the paddles, producing beams with HVL values from 0.28 up to 0.43 mmAl. In these qualities, four solid-state (ST) detectors and three ionizations chambers (IC) were calibrated in terms of Kair and N(K) and k(Q) were deduced. The results showed that all IC and two modern-type ST dosimeters have a flat energy response in the above HVL range (less than 3%), so their calibration factor at RQR-M2 quality could be safely used for clinical measurements. Two other ST dosimeters exhibit up to 20% energy response, so differences up to 15% in dose measurement may be observed if the effect of paddle on their performance is ignored. Finally, the need of additional mammographic calibration qualities to the existing IEC 61267 RQR-M series is examined and discussed. PMID:19168939

  15. Quantitative and enantioselective analysis of monoterpenes from plant chambers and in ambient air using SPME

    NASA Astrophysics Data System (ADS)

    Yassaa, N.; Custer, T.; Song, W.; Pech, F.; Kesselmeier, J.; Williams, J.

    2010-08-01

    A solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) system has been developed for quantifying enantiomeric and nonenantiomeric monoterpenes in plant chamber studies and ambient air. Performance of this system was checked using a capillary diffusion system to produce monoterpene standards. The adsorption efficiency, competitive adsorption and chromatographic peak resolution of monoterpene enantiomer pairs were compared for three SPME fibre coatings: 75 μm Carboxen-PDMS (CAR-PDMS), 50/30 μm, divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) and 65 μm divinylbenzene-polydimethyl-siloxane (DVB-PDMS). Key parameters such as the linearity and reproducibility of the SPME system have been investigated in this work. The best compromise between the enantiomeric separation of monoterpenes and competitive adsorption of the isoprenoids on the solid SPME fibre coating was found for DVB-PDMS fibres. The optimum conditions using DVB-PDMS fibres were applied to measure the exchange rates of monoterpenes in the emission of Quercus ilex using a laboratory whole plant enclosure under light and dark conditions, as well as in ambient air. With 592 and 223 ng m-2 s-1, respectively, β-myrcene and limonene were the predominant monoterpenes in the emission of Q. ilex. These values were closely comparable to those obtained using a zNose and cartridge GC-FID systems.

  16. Quantitative and enantioselective analysis of monoterpenes from plant chambers and in ambient air using SPME

    NASA Astrophysics Data System (ADS)

    Yassaa, N.; Custer, T.; Song, W.; Pech, F.; Kesselmeier, J.; Williams, J.

    2010-11-01

    A headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) system has been developed for quantifying enantiomeric and nonenantiomeric monoterpenes in plant chamber studies and ambient air. Performance of this system was checked using a capillary diffusion system to produce monoterpene standards. The adsorption efficiency, competitive adsorption and chromatographic peak resolution of monoterpene enantiomer pairs were compared for three SPME fibre coatings: 75 μm Carboxen-PDMS (CAR-PDMS), 50/30 μm divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) and 65 μm divinylbenzene-polydimethylsiloxane (DVB-PDMS). Key parameters such as the linearity and reproducibility of the SPME system have been investigated in this work. The best compromise between the enantiomeric separation of monoterpenes and competitive adsorption of the isoprenoids on the solid SPME fibre coating was found for DVB-PDMS fibres. The optimum conditions using DVB-PDMS fibres were applied to measure the exchange rates of monoterpenes in the emission of Quercus ilex using a laboratory whole plant enclosure under light and dark conditions, as well as in ambient air. With 592 and 223 ng m-2 s-1 respectively, β-myrcene and limonene were the predominant monoterpenes in the emission of Q. ilex. These values were closely comparable to those obtained using a zNose and cartridge GC-FID systems.

  17. Deformation mechanisms and impact attenuation characteristics of thin-walled collapsible air chambers used in head protection.

    PubMed

    Lamb, L; Hoshizaki, T B

    2009-11-01

    Head injuries are a major cause of morbidity and mortality worldwide, many resulting from sporting activities. There is a constant need in the head protection industry for improved methods to manage impacts and to reduce the risk of mild and severe head injuries. Contemporary head protection primarily consists of foam with several inherent disadvantages, including a limited ability to provide effective energy absorption under both low and high impact velocities. Recently, thin-walled collapsible chambers were engineered to address this problem and have been implemented into sport helmets. The chambers consist of four engineering elements which define their dynamic performance: geometry, air volume, material, and venting system. This research analysed the contribution of air flow through an orifice to the chamber's management of impact energy. The objective of this study was to determine the effect of the chamber's vent diameter and material stiffness on peak force and venting rate during an impact. Two material stiffnesses (thermoplastic polyurethane 45D and thermoplastic polyurethane 90A) and five vent diameters (1 mm, 2 mm, 3 mm, 4 mm, and 5 mm) were tested at three inbound velocities (1.3 m/s, 2.3 m/s, and 3.0 m/s). Each chamber was impacted ten times using a monorail drop system. Analysis of the results revealed that the material stiffness, vent diameter, and inbound velocity all had a significant effect on peak force and venting rate (p < 0.001). Under low inbound velocities the largest vent diameters transmitted a lower force than the smallest vent, while this relationship reversed at high inbound velocities. Under low velocities the air flowrate was negatively correlated and the flow duration was positively correlated to the peak force. Under high velocities, the air flowrate was positively correlated and the duration was negatively correlated to the peak force. This suggested that, under low velocities, chambers performed optimally when air was dissipated

  18. Limitations to soybean photosynthesis at elevated carbon dioxide in free-air enrichment and open top chamber systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It has been suggested that the stimulation of soybean photosynthesis by elevated carbon dioxide concentration was less in free-air carbon dioxide enrichment (FACE) systems than in open top chambers (OTC). However, this has not been tested using the same cultivars grown in the same location. We tes...

  19. 24 CFR 3280.406 - Air chamber test method for certification and qualification of formaldehyde emission levels.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 24 Housing and Urban Development 5 2012-04-01 2012-04-01 false Air chamber test method for certification and qualification of formaldehyde emission levels. 3280.406 Section 3280.406 Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued) OFFICE OF ASSISTANT SECRETARY FOR HOUSING-FEDERAL HOUSING...

  20. Dynamics of ionization processes in high-pressure nitrogen, air, and SF{sub 6} during a subnanosecond breakdown initiated by runaway electrons

    SciTech Connect

    Tarasenko, V. F. Beloplotov, D. V.; Lomaev, M. I.

    2015-10-15

    The dynamics of ionization processes in high-pressure nitrogen, air, and SF{sub 6} during breakdown of a gap with a nonuniform distribution of the electric field by nanosecond high-voltage pulses was studied experimentally. Measurements of the amplitude and temporal characteristics of a diffuse discharge and its radiation with a subnanosecond time resolution have shown that, at any polarity of the electrode with a small curvature radius, breakdown of the gap occurs via two ionization waves, the first of which is initiated by runaway electrons. For a voltage pulse with an ∼500-ps front, UV radiation from different zones of a diffuse discharge is measured with a subnanosecond time resolution. It is shown that the propagation velocity of the first ionization wave increases after its front has passed one-half of the gap, as well as when the pressure in the discharge chamber is reduced and/or when SF{sub 6} is replaced with air or nitrogen. It is found that, at nitrogen pressures of 0.4 and 0.7 MPa and the positive polarity of the high-voltage electrode with a small curvature radius, the ionization wave forms with a larger (∼30 ps) time delay with respect to applying the voltage pulse to the gap than at the negative polarity. The velocity of the second ionization wave propagating from the plane electrode is measured. In a discharge in nitrogen at a pressure of 0.7 MPa, this velocity is found to be ∼10 cm/ns. It is shown that, as the nitrogen pressure increases to 0.7 MPa, the propagation velocity of the front of the first ionization wave at the positive polarity of the electrode with a small curvature radius becomes lower than that at the negative polarity.

  1. Dynamics of ionization processes in high-pressure nitrogen, air, and SF6 during a subnanosecond breakdown initiated by runaway electrons

    NASA Astrophysics Data System (ADS)

    Tarasenko, V. F.; Beloplotov, D. V.; Lomaev, M. I.

    2015-10-01

    The dynamics of ionization processes in high-pressure nitrogen, air, and SF6 during breakdown of a gap with a nonuniform distribution of the electric field by nanosecond high-voltage pulses was studied experimentally. Measurements of the amplitude and temporal characteristics of a diffuse discharge and its radiation with a subnanosecond time resolution have shown that, at any polarity of the electrode with a small curvature radius, breakdown of the gap occurs via two ionization waves, the first of which is initiated by runaway electrons. For a voltage pulse with an ˜500-ps front, UV radiation from different zones of a diffuse discharge is measured with a subnanosecond time resolution. It is shown that the propagation velocity of the first ionization wave increases after its front has passed one-half of the gap, as well as when the pressure in the discharge chamber is reduced and/or when SF6 is replaced with air or nitrogen. It is found that, at nitrogen pressures of 0.4 and 0.7 MPa and the positive polarity of the high-voltage electrode with a small curvature radius, the ionization wave forms with a larger (˜30 ps) time delay with respect to applying the voltage pulse to the gap than at the negative polarity. The velocity of the second ionization wave propagating from the plane electrode is measured. In a discharge in nitrogen at a pressure of 0.7 MPa, this velocity is found to be ˜10 cm/ns. It is shown that, as the nitrogen pressure increases to 0.7 MPa, the propagation velocity of the front of the first ionization wave at the positive polarity of the electrode with a small curvature radius becomes lower than that at the negative polarity.

  2. Ignition of hydrocarbon-air supersonic flow by volumetric ionization

    NASA Astrophysics Data System (ADS)

    Goldfeld, Marat A.; Pozdnyakov, George A.

    2015-11-01

    The paper describes the results of the electron-beam initiation of the combustion in the mixtures of hydrogen, natural gas or kerosene vapors with air. Electron beam characteristics were studied in closed volume with immobile gas. The researches included definition of an integrated current of an electronic beam, distribution of a current density and an estimation of average energy of electrons. Possibility of fuel mixtures ignition by means of this approach in the combustor at high velocity at the entrance was demonstrated. Experiments were carried out at Mach numbers of 4 and 5. Process of ignition and combustion under electron beam action was researched. It was revealed that ignition of mixture occurs after completion of electron gun operation. Data obtained have confirmed effectiveness of electron beam application for ignition of hydrogen and natural gas. The numerical simulation of the combustion of mixture in channel was carried out by means of ANSYS CFD 12.0 instrumentation on the basis of Reynolds averaged Navier-Stokes equation using SST/k-ω turbulence model. For combustion modeling, a detailed kinetic scheme with 38 reactions of 8 species was implemented taking into account finite rate chemistry. Computations have shown that the developed model allow to predict ignition of a mixture and flame propagation even at low flow temperatures.

  3. SU‐C‐105‐05: Reference Dosimetry of High‐Energy Electron Beams with a Farmer‐Type Ionization Chamber

    SciTech Connect

    Muir, B; Rogers, D

    2013-06-15

    Purpose: To investigate gradient effects and provide Monte Carlo calculated beam quality conversion factors to characterize the Farmer‐type NE2571 ion chamber for high‐energy reference dosimetry of clinical electron beams. Methods: The EGSnrc code system is used to calculate the absorbed dose to water and to the gas in a fully modeled NE2571 chamber as a function of depth in a water phantom. Electron beams incident on the surface of the phantom are modeled using realistic BEAMnrc accelerator simulations and electron beam spectra. Beam quality conversion factors are determined using calculated doses to water and to air in the chamber in high‐energy electron beams and in a cobalt‐60 reference field. Calculated water‐to‐air stopping power ratios are employed for investigation of the overall ion chamber perturbation factor. Results: An upstream shift of 0.3–0.4 multiplied by the chamber radius, r-cav, both minimizes the variation of the overall ion chamber perturbation factor with depth and reduces the difference between the beam quality specifier (R{sub 5} {sub 0}) calculated using ion chamber simulations and that obtained with simulations of dose‐to‐water in the phantom. Beam quality conversion factors are obtained at the reference depth and gradient effects are optimized using a shift of 0.2r-cav. The photon‐electron conversion factor, k-ecal, amounts to 0.906 when gradient effects are minimized using the shift established here and 0.903 if no shift of the data is used. Systematic uncertainties in beam quality conversion factors are investigated and amount to between 0.4 to 1.1% depending on assumptions used. Conclusion: The calculations obtained in this work characterize the use of an NE2571 ion chamber for reference dosimetry of high‐energy electron beams. These results will be useful as the AAPM continues to review their reference dosimetry protocols.

  4. Long-term stability of liquid ionization chambers with regard to their qualification as local reference dosimeters for low dose-rate absorbed dose measurements in water.

    PubMed

    Bahar-Gogani, J; Grindborg, J E; Johansson, B E; Wickman, G

    2001-03-01

    The long-term sensitivity and calibration stability of liquid ionization chambers (LICs) has been studied at a local and a secondary standards dosimetry laboratory over a period of 3 years. The chambers were transported several times by mail between the two laboratories for measurements. The LICs used in this work are designed for absorbed dose measurements in the dose rate region of 0.1-100 mGy min(-1) and have a liquid layer thickness of 1 mm and a sensitive volume of 16.2 mm3. The liquids used as sensitive media in the chambers are mixtures of isooctane (C8H18) and tetramethylsilane (Si(CH3)4) in different proportions (about 2 to 1). Operating at a polarizing voltage of 300 V the leakage current of the chambers was stable and never exceeded 3% of the observable current at a dose rate of about 1 mGy min(-1). The volume sensitivity of the chambers was measured to be of the order of 10(-9) C Gy(-1) mm3. No systematic changes in the absorbed dose to water calibration was observed for any of the chambers during the test period (sigma < 0.2%). Variations in chamber dose response with small changes in the polarizing voltage as well as sensitivity changes with accumulated absorbed dose were also investigated. Measurements showed that the LIC response varies by 0.15% per 1% change in applied voltage around 300 V. No significant change could be observed in the LIC sensitivity after a single absorbed dose of 15 kGy. The results indicate that the LIC can be made to serve as a calibration transfer instrument and a reference detector for absorbed dose to water determinations providing good precision and long-term reproducibility. PMID:11277221

  5. Ionizing air affects influenza virus infectivity and prevents airborne-transmission.

    PubMed

    Hagbom, Marie; Nordgren, Johan; Nybom, Rolf; Hedlund, Kjell-Olof; Wigzell, Hans; Svensson, Lennart

    2015-01-01

    By the use of a modified ionizer device we describe effective prevention of airborne transmitted influenza A (strain Panama 99) virus infection between animals and inactivation of virus (>97%). Active ionizer prevented 100% (4/4) of guinea pigs from infection. Moreover, the device effectively captured airborne transmitted calicivirus, rotavirus and influenza virus, with recovery rates up to 21% after 40 min in a 19 m(3) room. The ionizer generates negative ions, rendering airborne particles/aerosol droplets negatively charged and electrostatically attracts them to a positively charged collector plate. Trapped viruses are then identified by reverse transcription quantitative real-time PCR. The device enables unique possibilities for rapid and simple removal of virus from air and offers possibilities to simultaneously identify and prevent airborne transmission of viruses. PMID:26101102

  6. Ionizing air affects influenza virus infectivity and prevents airborne-transmission

    PubMed Central

    Hagbom, Marie; Nordgren, Johan; Nybom, Rolf; Hedlund, Kjell-Olof; Wigzell, Hans; Svensson, Lennart

    2015-01-01

    By the use of a modified ionizer device we describe effective prevention of airborne transmitted influenza A (strain Panama 99) virus infection between animals and inactivation of virus (>97%). Active ionizer prevented 100% (4/4) of guinea pigs from infection. Moreover, the device effectively captured airborne transmitted calicivirus, rotavirus and influenza virus, with recovery rates up to 21% after 40 min in a 19 m3 room. The ionizer generates negative ions, rendering airborne particles/aerosol droplets negatively charged and electrostatically attracts them to a positively charged collector plate. Trapped viruses are then identified by reverse transcription quantitative real-time PCR. The device enables unique possibilities for rapid and simple removal of virus from air and offers possibilities to simultaneously identify and prevent airborne transmission of viruses. PMID:26101102

  7. Design, simulation, and fabrication of a MEMS-based air amplifier for electrospray ionization

    NASA Astrophysics Data System (ADS)

    Jurčíček, Petr; Zou, Helin; Gao, Shuai

    2013-04-01

    Recent developments in electrospray ionization mass spectrometry (ESI-MS) show that air amplifiers can be utilized to significantly enhance droplet desolvation and to focus gas-phase ions when provided between an electrospray (ES) source and the mass spectrometer (MS). However, these devices are bulky and expensive, which may be a factor prohibiting their broader utilization. We have developed a simple but effective method based on Bernoulli's principle, the Coanda effect and MEMS processing to focus electrosprayed droplets and liberated gas-phase ions. We demonstrate a computer simulation and fabrication process for a micromachined air amplifier. The simulation results are used to optimize the geometry and to meet performance requirements. The optimized results then provide a design guideline for the device's fabrication. The air amplifier is formed from two bonded polydimethylsiloxane (PDMS) casts. Each PDMS cast is fabricated through a molding process using a micromachined two-layer SU-8 mold. Experimental results show a 30-fold improvement in the ES current for certain operation conditions while the air amplifier is incorporated in the nano-electrospray ionization (nano-ESI) process. Compared with traditional air amplifiers, the micro-electro-mechanical systems (MEMS) based air amplifier provides good performance while keeping the fabrication process simple and cost effective.

  8. Monte Carlo simulations and benchmark measurements on the response of TE(TE) and Mg(Ar) ionization chambers in photon, electron and neutron beams

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Chun; Huang, Tseng-Te; Liu, Yuan-Hao; Chen, Wei-Lin; Chen, Yen-Fu; Wu, Shu-Wei; Nievaart, Sander; Jiang, Shiang-Huei

    2015-06-01

    The paired ionization chambers (ICs) technique is commonly employed to determine neutron and photon doses in radiology or radiotherapy neutron beams, where neutron dose shows very strong dependence on the accuracy of accompanying high energy photon dose. During the dose derivation, it is an important issue to evaluate the photon and electron response functions of two commercially available ionization chambers, denoted as TE(TE) and Mg(Ar), used in our reactor based epithermal neutron beam. Nowadays, most perturbation corrections for accurate dose determination and many treatment planning systems are based on the Monte Carlo technique. We used general purposed Monte Carlo codes, MCNP5, EGSnrc, FLUKA or GEANT4 for benchmark verifications among them and carefully measured values for a precise estimation of chamber current from absorbed dose rate of cavity gas. Also, energy dependent response functions of two chambers were calculated in a parallel beam with mono-energies from 20 keV to 20 MeV photons and electrons by using the optimal simple spherical and detailed IC models. The measurements were performed in the well-defined (a) four primary M-80, M-100, M120 and M150 X-ray calibration fields, (b) primary 60Co calibration beam, (c) 6 MV and 10 MV photon, (d) 6 MeV and 18 MeV electron LINACs in hospital and (e) BNCT clinical trials neutron beam. For the TE(TE) chamber, all codes were almost identical over the whole photon energy range. In the Mg(Ar) chamber, MCNP5 showed lower response than other codes for photon energy region below 0.1 MeV and presented similar response above 0.2 MeV (agreed within 5% in the simple spherical model). With the increase of electron energy, the response difference between MCNP5 and other codes became larger in both chambers. Compared with the measured currents, MCNP5 had the difference from the measurement data within 5% for the 60Co, 6 MV, 10 MV, 6 MeV and 18 MeV LINACs beams. But for the Mg(Ar) chamber, the derivations reached 7

  9. EFFECTS OF ACTIVATED CHARCOAL FILTRATION AND OZONATION ON HYDROCARBON AND CARBONYL LEVELS OF AMBIENT AIR USED IN CONTROLLED-EXPOSURE CHAMBER STUDIES OF AIR POLLUTANT HUMAN HEALTH EFFECTS

    EPA Science Inventory

    Air sampling experiments were done in 1985, 1987, and 1993 at the human-exposure chamber facility of the U.S. EPA Health Effects Research Laboratory in Chapel Hill, NC. easurements of VOC's by GC-FID and aldehyde measurements by the DNPH silica gel cartridge method were made, com...

  10. A correlation to predict the heat flux on the air-side of a vapor chamber with overturn-U flattened tubes

    NASA Astrophysics Data System (ADS)

    Srimuang, Wasan; Limkaisang, Viroj

    2016-08-01

    The heat transfer characteristics of a conventional vapor chamber (CVC) and a loop vapor chamber (LVC) are compared. The vapor chambers consisted of a stainless steel box with different covers. The results indicated that the heat flux and convective heat transfer coefficient of the air-side of LVC is higher than CVC. An empirical correlation was developed to predict the convective heat transfer coefficient of the air-side of the LVC.

  11. Monte Carlo correction factors for the ARPANSA kilovoltage free-air chambers and the effect of moving the limiting aperture

    NASA Astrophysics Data System (ADS)

    Lye, J. E.; Butler, D. J.; Webb, D. V.

    2010-02-01

    ARPANSA has calculated new Monte Carlo corrections for their low and medium energy x-ray free-air chambers. The new calculations include a diverging beam and details of the limiting aperture. The diverging beam simulations are compared with previous parallel beam simulations. The electron loss, scattering and fluorescence corrections do not change when beam divergence is included, even for the short source-detector distance of 30 cm used in post-2008 low energy calibrations. Transmission and scattering from the aperture are significant for both free-air chambers and dependent on the beam divergence. The constancy of the correction factors with changing air path length was investigated at low energies. In the extreme conditions of 100 kV and a distance of 30 cm the correction factors showed significant deviation.

  12. Olive mill wastewater treatment in single-chamber air-cathode microbial fuel cells.

    PubMed

    Bermek, Hakan; Catal, Tunc; Akan, S Süha; Ulutaş, Mehmet Sefa; Kumru, Mert; Özgüven, Mine; Liu, Hong; Özçelik, Beraat; Akarsubaşı, Alper Tunga

    2014-04-01

    Olive mill wastewaters create significant environmental issues in olive-processing countries. One of the most hazardous groups of pollutants in these wastewaters is phenolic compounds. Here, olive mill wastewater was used as substrate and treated in single-chamber air-cathode microbial fuel cells. Olive mill wastewater yielded a maximum voltage of 381 mV on an external resistance of 1 kΩ. Notable decreases in the contents of 3,4-dihydroxybenzoic acid, tyrosol, gallic acid and p-coumaric acid were detected. Chemical oxygen demand removal rates were 65 % while removal of total phenolics by the process was lower (49 %). Microbial community analysis during the olive mill wastewater treating MFC has shown that both exoelectrogenic and phenol-degrading microorganisms have been enriched during the operation. Brevundimonas-, Sphingomonas- and Novosphingobium-related phylotypes were enriched on the anode biofilm, while Alphaproteobacteria and Bacteriodetes dominated the cathode biofilm. As one of the novel studies, it has been demonstrated that recalcitrant olive mill wastewaters could be treated and utilized for power generation in microbial fuel cells. PMID:24165748

  13. Absolute dose measurements by means of a small cylindrical ionization chamber for very high dose per pulse high energy electron beams

    SciTech Connect

    Karaj, E.; Righi, S.; Di Martino, F.

    2007-03-15

    Very high dose per pulse (3-13 cGy/pulse) high energy electron beams are currently produced by special linear accelerators (linac) dedicated to Intra Operative Radiation Therapy (IORT). The electron beams produced by such linacs are collimated by special Perspex applicators of various size and cylindrically shaped. The biggest problems from the dosimetric point of view are caused by the high dose-per-pulse values and the use of inclined applicators. In this work measurements of absolute dose for the inclined applicators were done by using a small cylindrical ionization chamber, type CC01 (Wellhofer), a parallel plane ionization chamber type Markus (PTW 23343) and radiochromic films type EBT. We show a method which allows calculating the quality correction factors for CC01 chamber with an uncertainty of 1% and the absolute dose value for the inclined applicators using CC01 with an uncertainty of 3.1% for electron beams of energy of 6 and 7 MeV produced by the linac dedicated to IORT Novac7.

  14. Spectral Evidence for Ionization in Air-Filled Glow Discharge Tubes: Application to Sprites

    NASA Astrophysics Data System (ADS)

    Armstrong, R. A.; Williams, E. R.; Golka, R. K.; Williams, D. R.

    2001-12-01

    The question of ionization in sprites and the evidence for VLF backscatter from sprites has motivated a quantitative spectral analysis of the various (classical) regions of the glow discharge tube under DC excitation and at air densities appropriate for sprites in the mesosphere. A PR-650 colorimeter (Photo Research, Inc.) has enabled calibrated irradiance measurements for localized zones along the axis of the discharge tube--in the dominantly blue negative glow, in the Faraday dark space and in the red/pink positive column. Consistent with historical nomenclature, nitrogen first and second positive emission is dominant in the positive column (associated with neutral N2), and nitrogen first negative emission, with a prominent peak at 4278 A, is dominant in the blue negative glow (associated with ionized N2+). Whereas nitrogen first and second positive emission are also detected in the negative glow, no spectral evidence for ionization (no 4279, no 3914, no Meinel) is found in the red/pink positive column. This negative result is attributed not to an absence of ionization in the positive column, but rather to a sparse population of N2+ relative to neutral nitrogen in this region, and to the prominent emission in the blue part of the spectrum due to nitrogen second positive. A similar interpretation may be appropriate for the time-integrated spectra from the red body of sprites, also lacking direct evidence for ionization.

  15. Predictable surface ablation of dielectrics with few-cycle laser pulse even beyond air ionization

    NASA Astrophysics Data System (ADS)

    Pasquier, C.; Sentis, M.; Utéza, O.; Sanner, N.

    2016-08-01

    We study surface ablation of dielectrics with single-shot few-cycle optical pulse (˜10 fs) in air, at intensities below and above the onset of air ionization. We perform 3D analysis and careful calibration of the fluence distribution at the laser focus, spanning from linear- to nonlinear- focusing regimes, enabling to thoroughly characterize the severe limitation of the fluence delivered onto the sample surface upon increase of incident pulse energy. Despite significant beam reshaping taking place at high fluence, we demonstrate that it is nevertheless possible to confidently predict the resulting crater profiles on fused silica surface, even in the regime of filamentation.

  16. Electrophysical and optophysical properties of air ionized by a short pulse of fast electrons

    NASA Astrophysics Data System (ADS)

    Vagin, Iu. P.; Stal', N. L.; Khokhlov, V. D.; Chernoiarskii, A. A.

    A method for solving the nonstationary kinetic equation of electron deceleration is developed which is based on the multigroup approximation. The electron distribution function in air ionized by nonstationary sources of primary electrons is determined, and the avalanche formation of secondary electrons is considered. Theoretical and experimental results are presented on the time dependence of the air luminescence intensity in two spectral intervals, one including the 391.4 nm N2(+) band and the other including the 337.1 nm N2 band, for different values of gas pressure under the effect of a short beam of electrons with energies of 100 keV.

  17. [Transportation and transformation of 14C-phenanthrene in closed chamber (nutrient solution-lava-plant-air) system].

    PubMed

    Jiang, X; Ou, Z; Ying, P; Yediler, A; Ketrrup, A

    2001-06-01

    The transportation and transformation of 14C-phenanthrene in a closed 'plant-lava-nutrient solution-air' chamber system was studied by using radioactivity technology. The results showed that in this closed chamber system, phenanthrene was degraded fast. The radioactivity of 14C left at 23d in the nutrient solution was only 25% of applied. At the end of experiment (46d), the distribution sequence of 14C activity in the components of closed chamber system was root (38.55%) > volatile organic compounds (VOCs, 17.68%) > lava (14.35%) > CO2 (11.42%) > stem (2%). 14C-activities in plant tissue were combined with the tissue, and existed in the forms of lava-bound(root 4.68%; stem and leaves 0.68%) and polar metabolites (root 23.14%; stem 0.78%). PMID:11758435

  18. Two-phase air/oil flow in aero engine bearing chambers: Characterization of oil film flows

    SciTech Connect

    Glahn, A.; Wittig, S.

    1996-07-01

    For the design of secondary air and lubrication oil systems, a sufficient knowledge of two-phase flow and heat transfer phenomena under bearing chamber flow conditions is required. The characterization of oil film flows at the bearing chamber walls is one of the major tasks for a better understanding of these processes and, therefore, a necessity for improvements of the efficiency of aero engines. The present paper gives a contribution to this subject. Utilizing a fiber-optic LDV setup, measurements of oil film velocity profiles have been performed in the high-speed bearing chamber rig simulating real engine conditions. All data have been compared with different theoretical approaches, which have been derived from a force balance at a liquid film element, including geometric conditions and temperature dependent fluid properties, and by approaches for the eddy viscosity available in the literature.

  19. The influence of negative ionization of the air on motor activity in Syrian hamsters ( Masocricetus auratus Waterhouse) in light conditions

    NASA Astrophysics Data System (ADS)

    Lenkiewicz, Zofia; Dabrowska, Barbara; Schiffer, Zofia

    1989-12-01

    The motor activity of Syrian hamsters ( Mesocricetus auratus Waterhouse) under the influence of negative ionization of the atmosphere applied for 10, 20 or 30 min per day was investigated. An ionizer with output of 14000 light negative ions per 1 cm3 of air was used. Studies carried out in the light phase of a 12∶12 h light/dark regime revealed a relation between the reaction of the animal and the time of day at which ionization was applied. Ionization for 20 or 30 min in the light phase decreased motor activity, while 10 min of ionization increased it compared to control animals. Ionization in the dark phase gave a more distinct rise in activity than that applied in the light phase for all three durations of ionization.

  20. (18)F primary standard at ENEA-INMRI by three absolute techniques and calibration of a well-type IG11 ionization chamber.

    PubMed

    Capogni, Marco; Carconi, Pierluigi; De Felice, Pierino; Fazio, Aldo

    2016-03-01

    A new (18)F primary standardization carried out at ENEA-INMRI by three different absolute techniques, i.e. 4πγNaI(Tl)γ high-efficiency counting, TDCR and 4πβ(LS)-γ[NaI(Tl)] coincidence counting method, allowed the calibration of a fixed well-reentrant IG11 ionization chamber (IC), with an uncertainty lower than 1%, and to check the calibration factor of a portable well-type IC NPL-CRC model, previously calibrated. By the new standard the ENEA-INMRI was linked to the BIPM International Reference System (SIR) through the BIPM SIR Transfer Instrument (SIRTI). PMID:26774395

  1. Instantaneous and continuous measurement of /sup 14/C-labeled substrate oxidation to /sup 14/CO2 by minute tissue specimens: an ionization chamber method

    SciTech Connect

    Davidson, W.D.; Klein, K.L.; Kurokawa, K.; Soll, A.H.

    1981-06-01

    The vibrating reed electrometer and ionization chamber have been adapted for the instantaneous and continuous measurement of /sup 14/C-labeled substrate oxidation to /sup 14/CO2 by minute quantities of isolated tissues. This modified technique, utilizing a ''closed'' circulation incubation system, is 10-50 times as sensitive as the previously described ''open'' circulation techniques. Substrate oxidation curves are described for human erythrocytes and polymorphonuclear leucocytes, canine parietal cells and isolated segments of the rat nephron. This apparatus should prove to be a useful tool for metabolic studies of small quantities of isolated tissue.

  2. COMPENSATING FOR WALL EFFECTS IN IAQ (INDOOR AIR QUALITY) CHAMBER TESTS BY MATHEMATICAL MODELING

    EPA Science Inventory

    The paper presents mechanistic mathematical models that account for two phenomena: interior surfaces of a state-of-the-art emissions test chamber acting as a transient sink for organic emissions; the effect of increasing chamber concentration on the emission rate of the source. A...

  3. A wind tunnel study of the flow field within and around open-top chambers used for air pollution studies

    NASA Astrophysics Data System (ADS)

    Davis, J. M.; Riordan, A. J.; Lawson, R. E.

    1983-02-01

    The EPA Meteorological Wind Tunnel was used to examine the flow field in and around models of open-top field-plant growth chambers used to assess the effects of pollutant gases on plant growth. Baffles designed to reduce the ingress of ambient air into the chamber through the open top were tested; the mean flow and turbulence in the simulated boundary layer with and without the chambers were compared (the chamber was operated with and without the pollutant flow system on); and the effects of surrounding chambers on the concentration field were measured. Results showed that a baffle with a reduced opening vertically above the test area maintained the highest uniform concentration in the test area. The major differences between the three (no chamber and the chamber with flow on and off) mean velocity profiles occurred below z/h = 2.0 ( h is chamber height) and at z/h ≤ 4.2. The three Reynolds stress profiles were similar above z/h = 2.0. Downwind of the chamber, the Reynolds stresses in the on-mode were greater than those in the off-mode above z/h = 1.1. The reverse was true below that point. Both longitudinal and vertical intensities above and downwind of the chamber were greater with the mixture flow system on rather than off, below about z/h < 1.5. Lateral variations in the mean wind indicated that the mean velocity was greater with the mixture flow system on except near the centerline where the reverse was true. The concentrations in the downwind wake resembled those for a cube. The location of a cylinder within a regular array had some effect on its internal gas concentration. Locations near the upwind and downwind edges of the array were associated with lower concentrations, although for all locations the highest internal values were always found at the lowest portion of the upwind wall. With active cylinders downwind, the gas plume emitted from a source cylinder at the windward edge of the array was forced 0.5 h higher and the centerline meandered laterally

  4. DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines - Simulation of Flight Conditions in Test Chambers by Density Matching

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Thurman, Douglas R.

    2011-01-01

    Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it

  5. Accuracy of the electron transport in mcnp5 and its suitability for ionization chamber response simulations: A comparison with the egsnrc and penelope codes

    SciTech Connect

    Koivunoro, Hanna; Siiskonen, Teemu; Kotiluoto, Petri; Auterinen, Iiro; Hippelaeinen, Eero; Savolainen, Sauli

    2012-03-15

    Purpose: In this work, accuracy of the mcnp5 code in the electron transport calculations and its suitability for ionization chamber (IC) response simulations in photon beams are studied in comparison to egsnrc and penelope codes. Methods: The electron transport is studied by comparing the depth dose distributions in a water phantom subdivided into thin layers using incident energies (0.05, 0.1, 1, and 10 MeV) for the broad parallel electron beams. The IC response simulations are studied in water phantom in three dosimetric gas materials (air, argon, and methane based tissue equivalent gas) for photon beams ({sup 60}Co source, 6 MV linear medical accelerator, and mono-energetic 2 MeV photon source). Two optional electron transport models of mcnp5 are evaluated: the ITS-based electron energy indexing (mcnp5{sub ITS}) and the new detailed electron energy-loss straggling logic (mcnp5{sub new}). The electron substep length (ESTEP parameter) dependency in mcnp5 is investigated as well. Results: For the electron beam studies, large discrepancies (>3%) are observed between the mcnp5 dose distributions and the reference codes at 1 MeV and lower energies. The discrepancy is especially notable for 0.1 and 0.05 MeV electron beams. The boundary crossing artifacts, which are well known for the mcnp5{sub ITS}, are observed for the mcnp5{sub new} only at 0.1 and 0.05 MeV beam energies. If the excessive boundary crossing is eliminated by using single scoring cells, the mcnp5{sub ITS} provides dose distributions that agree better with the reference codes than mcnp5{sub new}. The mcnp5 dose estimates for the gas cavity agree within 1% with the reference codes, if the mcnp5{sub ITS} is applied or electron substep length is set adequately for the gas in the cavity using the mcnp5{sub new}. The mcnp5{sub new} results are found highly dependent on the chosen electron substep length and might lead up to 15% underestimation of the absorbed dose. Conclusions: Since the mcnp5 electron

  6. Human breath measurements in a clean-air chamber to determine half-lives for volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Gordon, Sydney M.; Wallace, Lance A.; Pelllzzari, Edo D.; O'Neill, Hugh J.

    The expired breath of four non-occupationally exposed subjects was monitored following exposure at near-normal environmental concentrations using a specially developed pulmonary clearance technique. The four were exposed to polluted air on a heavily trafficked freeway or at a local dry-cleaning establishment, then spent the next 10 h in a clean-air environmental chamber. Breath and chamber-air samples were collected at regular intervals throughout the 10-h period and analyzed for the presence of selected target compounds. The breath levels of two of the compounds were elevated and decreased slowly with time once the subjects began to breathe clean air. Nonlinear least-squares fitting of the decay-uptake curves permitted the calculation of biological half-lives. Several of the target compounds occurred, however, at very low levels, and the resultant experimental scatter limited the value of these measurements. Higher initial exposures to most of the target compounds would have improved the reliability of the estimates.

  7. Response of ozone to changes in hydrocarbon and nitrogen oxide concentrations in outdoor smog chambers filled with Los Angeles air

    NASA Astrophysics Data System (ADS)

    Kelly, Nelson A.; Gunst, Richard F.

    During the summer portion of the 1987 Southern California Air Quality Study (SCAQS), outdoor smog chamber experiments were performed on Los Angeles air to determine the response of maximum ozone levels, O 3(max), to changes in the initial concentrations of hydrocarbons, HC, and nitrogen oxides, NO x. These captive-air experiments were conducted in downtown Los Angeles and in the downwind suburb of Claremont. Typically, eight chambers were filled with LA air in the morning. In some chambers the initial HC and/or NO x concentrations were changed by 25% to 50% by adding various combinations of a mixture of HC, clean air, or NO x. The O 3 concentration in each chamber was monitored throughout the day to determine O 3(max). An empirical mathematical model for O 3(max) was developed from regression fits to the initial HC and NO x concentrations and to the average daily temperature at both sites. This is the first time that a mathematical expression for the O 3-precursor relationship and the positive effect of temperature on O 3(max) have been quantified using captive-air experiments. An ozone isopleth diagram prepared from the empirical model was qualitatively similar to those prepared from photochemical mechanisms. This constitutes the first solely empirical corroboration of the O 3 contour shape for Los Angeles. To comply with the Federal Ozone Standard in LA, O 3(max) must be reduced by approximately 50%. Several strategies for reducing O 3(max) by 50% were evaluated using the empirical model. For the average initial conditions that we measured in LA, the most efficient strategy is one that reduces HC by 55-75%, depending on the ambient HC/NO x ratio. Any accompanying reduction in NO x would be counter-productive to the benefits of HC reductions. In fact, reducing HC and NO x simultaneously requires larger percentage reductions for both than the reduction required when HC alone is reduced. The HC-reduction strategy is the most efficient on average, but no single

  8. Lateral distribution of high energy hadrons and gamma ray in air shower cores observed with emulsion chambers

    NASA Technical Reports Server (NTRS)

    Matano, T.; Machida, M.; Honda, K.; Hashimoto, K.; Navia, C. E.; Kawasumi, N.; Tsushima, I.; Matinic, N.; Aquirre, C.

    1985-01-01

    A high energy event of a bundle of electrons, gamma rays and hadronic gamma rays in an air shower core were observed. The bundles were detected with an emulsion chamber with thickness of 15 cm lead. This air shower is estimated to be initiated with a proton with energy around 10 to the 17th power to 10 to the 18th power eV at an altitude of around 100 gmc/2. Lateral distributions of the electromagnetic component with energy above 2 TeV and also the hadronic component of energy above 6 TeV of this air shower core were determined. Particles in the bundle are produced with process of the development of the nuclear cascade, the primary energy of each interaction in the cascade which produces these particles is unknown. To know the primary energy dependence of transverse momentum, the average products of energy and distance for various average energies of secondary particles are studied.

  9. Dosimetry for electron Intra-Operative RadioTherapy: Comparison of output factors obtained through alanine/EPR pellets, ionization chamber and Monte Carlo-GEANT4 simulations for IORT mobile dedicate accelerator

    NASA Astrophysics Data System (ADS)

    Marrale, Maurizio; Longo, Anna; Russo, Giorgio; Casarino, Carlo; Candiano, Giuliana; Gallo, Salvatore; Carlino, Antonio; Brai, Maria

    2015-09-01

    In this work a comparison between the response of alanine and Markus ionization chamber was carried out for measurements of the output factors (OF) of electron beams produced by a linear accelerator used for Intra-Operative Radiation Therapy (IORT). Output factors (OF) for conventional high-energy electron beams are normally measured using ionization chamber according to international dosimetry protocols. However, the electron beams used in IORT have characteristics of dose per pulse, energy spectrum and angular distribution quite different from beams usually used in external radiotherapy, so the direct application of international dosimetry protocols may introduce additional uncertainties in dosimetric determinations. The high dose per pulse could lead to an inaccuracy in dose measurements with ionization chamber, due to overestimation of ks recombination factor. Furthermore, the electron fields obtained with IORT-dedicated applicators have a wider energy spectrum and a wider angular distribution than the conventional fields, due to the presence of electrons scattered by the applicator's wall. For this reason, a dosimetry system should be characterized by a minimum dependence from the beam energy and from angle of incidence of electrons. This become particularly critical for small and bevelled applicators. All of these reasons lead to investigate the use of detectors different from the ionization chamber for measuring the OFs. Furthermore, the complete characterization of the radiation field could be accomplished also by the use of Monte Carlo simulations which allows to obtain detailed information on dose distributions. In this work we compare the output factors obtained by means of alanine dosimeters and Markus ionization chamber. The comparison is completed by the Monte Carlo calculations of OFs determined through the use of the Geant4 application "iort _ therapy" . The results are characterized by a good agreement of response of alanine pellets and Markus

  10. Comparison of dosimeter response: ionization chamber, TLD, and Gafchromic EBT2 film in 3D-CRT, IMRT, and SBRT techniques for lung cancer

    NASA Astrophysics Data System (ADS)

    Fitriandini, A.; Wibowo, W. E.; Pawiro, S. A.

    2016-03-01

    This research was conducted by measuring point dose in the target area (lungs), heart, and spine using four dosimeters (PTW N30013, Exradin A16, TLD, and the Gafchromic EBT2 film). The measurement was performed in CIRS 002LFC thorax phantom. The main objective of this study was to compare the dosimetry of those different systems. Dose measurements performed only in a single fraction of irradiation. The measurements result shown that TLD has the least accuracy and precision. As the effect of volume averaging, ionization chamber reaches the discrepancy value up to -13.30% in the target area. EBT2 film has discrepancy value of <1% in the 3D-CRT and IMRT techniques. This dosimeter is proposed to be an appropriate alternative dosimeter to be used at point dose verification.

  11. Characterization of radiation beams used to determinate the correction factor for a CyberKnife® unit reference field using ionization chambers

    NASA Astrophysics Data System (ADS)

    Aragón-Martínez, Nestor; Gómez-Muñoz, Arnulfo; Massillon-JL, Guerda

    2014-11-01

    This paper aimed to characterize a 6 MV x-ray beam from a Varian® iX linear accelerator in order to obtain the correction factors needed by the IAEA/AAPM new formalism1. The experiments were performed in a liquid water phantom under different irradiation conditions: a) Calibration of the reference field of 10 cm × 10 cm at 90 cm SSD and 10 cm depth was carried out according to the TRS-398 protocol using three ionization chambers (IC) calibrated in different reference laboratory and b) Measurement of the absorbed dose rate at 70 cm SSD and 10 cm depth in a 10 cm × 10 cm and 5.4 cm × 5.4 cm fields was obtained in order to simulate the CyberKnife® conditions where maximum distance between the source and the detector is equal to 80 cm and the maximum field size is 6 cm diameter. Depending where the IC was calibrated, differences between 0.16% and 2.24% in the absorbed dose rate measured in the 10 cm × 10 cm field at 90 cm SSD were observed, while for the measurements at 70 cm SSD, differences between 1.27% and 3.88% were obtained. For the 5.4 cm × 5.4 cm field, the absorbed dose measured with the three ICs varies between 1.37% and 3.52%. The increase in the difference on the absorbed dose when decreasing the SSD could possibly be associated to scattering radiation generated from the collimators and/or the energy dependence of the ionization chambers to low-energy radiation. The results presented in this work suggest the importance of simulating the CyberKnife® conditions using other linear accelerator for obtaining the correction factors as proposed by the IAEA/AAPM new formalism in order to measure the absorbed dose with acceptable accuracy.

  12. Characterization of radiation beams used to determinate the correction factor for a CyberKnife® unit reference field using ionization chambers

    SciTech Connect

    Aragón-Martínez, Nestor Massillon-JL, Guerda; Gómez-Muñoz, Arnulfo

    2014-11-07

    This paper aimed to characterize a 6 MV x-ray beam from a Varian® iX linear accelerator in order to obtain the correction factors needed by the IAEA/AAPM new formalism{sup 1}. The experiments were performed in a liquid water phantom under different irradiation conditions: a) Calibration of the reference field of 10 cm × 10 cm at 90 cm SSD and 10 cm depth was carried out according to the TRS-398 protocol using three ionization chambers (IC) calibrated in different reference laboratory and b) Measurement of the absorbed dose rate at 70 cm SSD and 10 cm depth in a 10 cm × 10 cm and 5.4 cm × 5.4 cm fields was obtained in order to simulate the CyberKnife® conditions where maximum distance between the source and the detector is equal to 80 cm and the maximum field size is 6 cm diameter. Depending where the IC was calibrated, differences between 0.16% and 2.24% in the absorbed dose rate measured in the 10 cm × 10 cm field at 90 cm SSD were observed, while for the measurements at 70 cm SSD, differences between 1.27% and 3.88% were obtained. For the 5.4 cm × 5.4 cm field, the absorbed dose measured with the three ICs varies between 1.37% and 3.52%. The increase in the difference on the absorbed dose when decreasing the SSD could possibly be associated to scattering radiation generated from the collimators and/or the energy dependence of the ionization chambers to low-energy radiation. The results presented in this work suggest the importance of simulating the CyberKnife® conditions using other linear accelerator for obtaining the correction factors as proposed by the IAEA/AAPM new formalism in order to measure the absorbed dose with acceptable accuracy.

  13. Measurements of miniature ionization chamber currents in the JSI TRIGA Mark II reactor demonstrate the importance of the delayed contribution to the photon field in nuclear reactors

    NASA Astrophysics Data System (ADS)

    Radulović, Vladimir; Fourmentel, Damien; Barbot, Loïc; Villard, Jean-François; Kaiba, Tanja; Gašper, Žerovnik; Snoj, Luka

    2015-12-01

    The characterization of experimental locations of a research nuclear reactor implies the determination of neutron and photon flux levels within, with the best achievable accuracy. In nuclear reactors, photon fluxes are commonly calculated by Monte Carlo simulations but rarely measured on-line. In this context, experiments were conducted with a miniature gas ionization chamber (MIC) based on miniature fission chamber mechanical parts, recently developed by the CEA (French Atomic Energy and Alternative Energies Commission) irradiated in the core of the Jožef Stefan Institute TRIGA Mark II reactor in Ljubljana, Slovenia. The aim of the study was to compare the measured MIC currents with calculated currents based on simulations with the MCNP6 code. A discrepancy of around 50% was observed between the measured and the calculated currents; in the latter taking into consideration only the prompt photon field. Further experimental measurements of MIC currents following reactor SCRAMs (reactor shutdown with rapid insertions of control rods) provide evidence that over 30% of the total measured signal is due to the delayed photon field, originating from fission and activation products, which are untreated in the calculations. In the comparison between the measured and calculated values, these findings imply an overall discrepancy of less than 20% of the total signal which is still unexplained.

  14. Derivation of a formula describing the saturation correction of plane-parallel ionization chambers in pulsed fields with arbitrary repetition rate

    NASA Astrophysics Data System (ADS)

    Karsch, Leonhard

    2016-04-01

    Gas-filled ionization chambers are widely used radiation detectors in radiotherapy. A quantitative description and correction of the recombination effects exists for two cases, for continuous radiation exposure and for pulsed radiation fields with short single pulses. This work gives a derivation of a formula for pulsed beams with arbitrary pulse rate for which the prerequisites of the two existing descriptions are not fulfilled. Furthermore, an extension of the validity of the two known cases is investigated. The temporal evolution of idealized charge density distributions within a plane parallel chamber volume is described for pulsed beams of vanishing pulse duration and arbitrary pulse repetition rate. First, the radiation induced release, movement and collection of the charge carriers without recombination are considered. Then, charge recombination is calculated basing on these simplified charge distributions and the time dependent spatial overlap of positive and negative charge carrier distributions. Finally, a formula for the calculation of the saturation correction factor is derived by calculation and simplification of the first two terms of a Taylor expansion for small recombination. The new formula of saturation correction contains the two existing cases, descriptions for exposure by single pulses and continuous irradiation, as limiting cases. Furthermore, it is possible to determine the pulse rate range for which each of the three descriptions is applicable by comparing the dependencies of the new formula with the two existing cases. As long as the time between two pulses is lower than one third of the collection time of the chamber, the formalism for a continuous exposure can be used. The known description for single pulse irradiation is only valid if the repetition rate is less than 1.2 times the inverse collection time. For all other repetition rates in between the new formula should be used. The experimental determination by Jaffe diagrams can be

  15. Homolytic Reactive Mass Spectrometry of Fullerenes: Peculiarities of the Reactions of C60 with Aromatic Compounds in the Ionization Chambers of Mass Spectrometers and in Solution

    NASA Astrophysics Data System (ADS)

    Lyakhovetsky, Yury I.; Shilova, Elena A.; Belokon, Alexander I.; Panz, Larisa I.; Tumanskii, Boris L.

    2013-04-01

    C60 reacted with PhH, PhCl, BnH, BnNH2, and o-C2H2B10H10 in the electron impact (EI) ion source of a mass spectrometer at 300 °C forming phenyl, benzyl, and o-carboranyl adducts, respectively, stabilized by hydrogen addition and loss. Besides, the additions to C60 of methyl and phenyl radicals for toluene, and a phenyl radical for benzylamine were observed. A homolytic reaction mechanism was suggested involving the reaction of the radicals formed from the aromatics under EI with C60 at the ionization chamber walls. While the ion/molecule reaction of C60 with benzene performed by Sun et al. under chemical ionization conditions at 200 °C afforded the complex C60•PhH+•, quite a different isomer, HC60Ph+•, was detected in the present study as a sequence of the different reaction mechanisms. C60 also reacted with benzyl bromide in the laser desorption/ionization (LDI) source of a mass spectrometer to give C60CPh+. Phenyl and benzyl derivatives of C60 were found, respectively, when the reactions of the fullerene with PhCl, BnH, and BnBr were performed in solution under ultra violet irradiation. For the reaction with toluene, the strong chemically induced dynamic electron polarization of the intermediate benzylfullerenyl radical with the reverse phase effect was found. The coincidence of the results of the mass spectrometry and solution reactions of C60 with aromatics, even though incomplete, additionally supports the hypothesis, formulated earlier, that the former results can predict the latter ones to a significant extent and shows that this conclusion is valid for both EI and LDI initiated reactions in mass spectrometers.

  16. Test and evaluation of the Argonne BPAC10 Series air chamber calorimeter designed for 20 minute measurements

    SciTech Connect

    Perry, R.B.; Fiarman, S.; Jung, E.A. ); Cremers, T. )

    1990-10-01

    This paper is the final report on DOE-OSS Task ANLE88002 Fast Air Chamber Calorimetry.'' The task objective was to design, construct, and test an isothermal air chamber calorimeter for plutonium assay of bulk samples that would meet the following requirements for sample power measurement: average sample measurement time less than 20 minutes. Measurement of samples with power output up to 10 W. Precision of better than 1% RSD for sample power greater than 1 W. Precision better than 0.010 watt SD, for sample power less than 1 W. This report gives a description of the calorimeter hardware and software and discusses the test results. The instrument operating procedure, included as an appendix, gives examples of typical input/output and explains the menu driven software. Sample measurement time of less than 20 minutes was attained by pre-equilibration of the samples in low cost precision preheaters and by prediction of equilibrium measurements. Tests at the TA55 Plutonium Facility at Los Alamos National Laboratory, on typical samples, indicates that the instrument meets all the measurement requirements.

  17. Characteristics of emissions of air pollutants from mosquito coils and candles burning in a large environmental chamber

    NASA Astrophysics Data System (ADS)

    Lee, S. C.; Wang, B.

    The objective of this study was to characterize the emissions of air pollutants from mosquito coils and candles burning in a large environmental test chamber. The target pollutants included particulate matters (PM 10, PM 2.5), carbon monoxide (CO), nitrogen oxides (NO x), methane (CH 4), non-methane hydrocarbons (NMHC), volatile organic compounds (VOCs) and carbonyl compounds. The average PM 10 concentrations for all tested mosquito coils exceeded Excellent and Good Classes objectives specified by Indoor Air Quality Objectives for Office Buildings and Public Places (IAQO) [ HKEPD, 2003. Guidance Notes for the Management of Indoor Air Quality in Offices and Public Places. Indoor Air Quality Management Group, The Government of the Hong Kong Special Administrative Region]. The emission factors (mg g -1 mosquito coil) of mosquito coils combustion were: PM 2.5, 20.3-47.8; PM 10, 15.9-50.8; CO, 74.6-89.1; NO, 0.1-0.5; NO 2, n.d.-0.1; NO x, 0.1-0.5; CH 4, n.d.-4.7; NMHC, 0.1-5.7. Formaldehyde and acetaldehyde were the most abundant carbonyls species in the coil smoke. The average concentrations of formaldehyde and benzene of all tested mosquito coils exceeded Good Class of IAQO. Nitrogen oxides were the most abundant gas pollutants relating to candle burning among all target air pollutants. The candle made of gel (CAN 4) would emit more air pollutants than the paraffin candles (CAN 1, 2 and 3) and beeswax candle (CAN 5). Among five candles tested, CAN 5, the one made of beeswax, generated relatively smaller amount of air pollutants. It was noted that the concentrations of most VOCs from candles combustion were below the detection limit.

  18. Laboratory chamber experiments exploring the potential use of artificially ionized layers of gas as a Bragg reflector for over-the-horizon signals

    NASA Astrophysics Data System (ADS)

    Kuo, S. P.; Zhang, Y. S.; Lee, M. C.; Kossey, Paul; Barker, Robert J.

    1992-12-01

    A set of parallel plasma layers is generated by two intersecting microwave pulses in a chamber containing dry air at a pressure comparable to the upper atmosphere. The dependence of the breakdown conditions on the pressure and pulse length is examined. The results are shown to be consistent with the appearance of tail erosion of microwave pulse caused by air breakdown. Bragg scattering experiments, using the plasma layers as a Bragg reflector are then performed. Both time domain and frequency domain measurements of wave scattering are conducted. The experimental results are found to agree very well with the theory. Moreover, the time domain measurement of wave scattering provides an unambiguous way for determining the temporal evolution of electron density during the first 100-microsec period.

  19. Laboratory chamber experiments exploring the potential use of artificially ionized layers of gas as a Bragg reflector for over-the-horizon signals

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Zhang, Y. S.; Lee, M. C.; Kossey, Paul; Barker, Robert J.

    1992-01-01

    A set of parallel plasma layers is generated by two intersecting microwave pulses in a chamber containing dry air at a pressure comparable to the upper atmosphere. The dependence of the breakdown conditions on the pressure and pulse length is examined. The results are shown to be consistent with the appearance of tail erosion of microwave pulse caused by air breakdown. Bragg scattering experiments, using the plasma layers as a Bragg reflector are then performed. Both time domain and frequency domain measurements of wave scattering are conducted. The experimental results are found to agree very well with the theory. Moreover, the time domain measurement of wave scattering provides an unambiguous way for determining the temporal evolution of electron density during the first 100-microsec period.

  20. Recommended direct simulation Monte Carlo collision model parameters for modeling ionized air transport processes

    NASA Astrophysics Data System (ADS)

    Swaminathan-Gopalan, Krishnan; Stephani, Kelly A.

    2016-02-01

    A systematic approach for calibrating the direct simulation Monte Carlo (DSMC) collision model parameters to achieve consistency in the transport processes is presented. The DSMC collision cross section model parameters are calibrated for high temperature atmospheric conditions by matching the collision integrals from DSMC against ab initio based collision integrals that are currently employed in the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) and Data Parallel Line Relaxation (DPLR) high temperature computational fluid dynamics solvers. The DSMC parameter values are computed for the widely used Variable Hard Sphere (VHS) and the Variable Soft Sphere (VSS) models using the collision-specific pairing approach. The recommended best-fit VHS/VSS parameter values are provided over a temperature range of 1000-20 000 K for a thirteen-species ionized air mixture. Use of the VSS model is necessary to achieve consistency in transport processes of ionized gases. The agreement of the VSS model transport properties with the transport properties as determined by the ab initio collision integral fits was found to be within 6% in the entire temperature range, regardless of the composition of the mixture. The recommended model parameter values can be readily applied to any gas mixture involving binary collisional interactions between the chemical species presented for the specified temperature range.

  1. Measurement of the First Townsend's Ionization Coefficients in Helium, Air, and Nitrogen at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Ran, Junxia; Luo, Haiyun; Yue, Yang; Wang, Xinxin

    2014-07-01

    In the past the first Townsend’s ionization coefficient α could only be measured with Townsend discharge in gases at low pressure. After realizing Townsend discharge in some gases at atmospheric pressure by using dielectric barrier electrodes, we had developed a new method for measuring α coefficient at atmospheric pressure, a new optical method based on the discharge images taken with ICCD camera. With this newly developed method α coefficient in helium, nitrogen and air at atmospheric pressure were measured. The results were found to be in good agreement with the data obtained at lower pressure but same reduced field E/p by other groups. It seems that the value of α coefficient is sensitive to the purity of the working gas.

  2. Inhibition of microbial growth on air cathodes of single chamber microbial fuel cells by incorporating enrofloxacin into the catalyst layer.

    PubMed

    Liu, Weifeng; Cheng, Shaoan; Sun, Dan; Huang, Haobin; Chen, Jie; Cen, Kefa

    2015-10-15

    The inevitable growth of aerobic bacteria on the surface of air cathodes is an important factor reducing the performance stability of air cathode single-chamber membrane-free microbial fuel cells (MFCs). Thus searching for effective methods to inhibit the cathodic microbial growth is critical for the practical application of MFCs. In this study, enrofloxacin (ENR), a broad spectrum fluoroquinolone antibiotic, was incorporated into the catalyst layer of activated carbon air cathodes (ACACs) to inhibit the cathodic microbial growth. The biomass content on ACACs was substantially reduced by 60.2% with ENR treatment after 91 days of MFCs operation. As a result of the inhibited microbial growth, the oxygen reduction catalytic performance of the ENR treated ACACs was much stable compared to the fast performance decline of the untreated control. Consequently, a quite stable electricity production was obtained for the MFCs with the ENR treated ACACs, in contrast with a 22.5% decrease in maximum power density of the MFCs with the untreated cathode. ENR treatment of ACACs showed minimal effects on the anode performance. These results indicate that incorporating antibiotics into ACACs should be a simple and effective strategy to inhibit the microbial growth and improve the long-term stability of the performance of air cathode and the electricity production of MFCs. PMID:25957076

  3. A new dynamical atmospheric ionizing radiation (AIR) model for epidemiological studies

    NASA Technical Reports Server (NTRS)

    De Angelis, G.; Clem, J. M.; Goldhagen, P. E.; Wilson, J. W.

    2003-01-01

    A new Atmospheric Ionizing Radiation (AIR) model is currently being developed for use in radiation dose evaluation in epidemiological studies targeted to atmospheric flight personnel such as civilian airlines crewmembers. The model will allow computing values for biologically relevant parameters, e.g. dose equivalent and effective dose, for individual flights from 1945. Each flight is described by its actual three dimensional flight profile, i.e. geographic coordinates and altitudes varying with time. Solar modulated primary particles are filtered with a new analytical fully angular dependent geomagnetic cut off rigidity model, as a function of latitude, longitude, arrival direction, altitude and time. The particle transport results have been obtained with a technique based on the three-dimensional Monte Carlo transport code FLUKA, with a special procedure to deal with HZE particles. Particle fluxes are transformed into dose-related quantities and then integrated all along the flight path to obtain the overall flight dose. Preliminary validations of the particle transport technique using data from the AIR Project ER-2 flight campaign of measurements are encouraging. Future efforts will deal with modeling of the effects of the aircraft structure as well as inclusion of solar particle events. Published by Elsevier Ltd on behalf of COSPAR.

  4. The development of new devices for accurate radiation dose measurement: A guarded liquid ionization chamber and an electron sealed water calorimeter

    NASA Astrophysics Data System (ADS)

    Stewart, Kristin J.

    In this work we developed two new devices that aim to improve the accuracy of relative and reference dosimetry for radiation therapy: a guarded liquid ionization chamber (GLIC) and an electron sealed water (ESW) calorimeter. With the GLIC we aimed to develop a perturbation-free energy-independent detector with high spatial resolution for relative dosimetry. We achieved sufficient stability for short-term measurements using the GLIC-03, which has a sensitive volume of approximately 2 mm3. We evaluated ion recombination in pulsed photon beams using a theoretical model and also determined a new empirical method to correct for relative differences in general recombination which could be used in cases where the theoretical model was not applicable. The energy dependence of the GLIC-03 was 1.1% between 6 and 18 MV photon beams. Measurements in the build-up region of an 18 MV beam indicated that this detector produces minimal perturbation to the radiation field and confirmed the validity of the empirical recombination correction. The ESW calorimeter was designed to directly measure absorbed dose to water in clinical electron beams. We obtained reproducible measurements for 6 to 20 MeV beams. We determined corrections for perturbations to the radiation field caused by the glass calorimeter vessel and for conductive heat transfer due to the dose gradient and non-water materials. The overall uncertainty on the ESW calorimeter dose was 0.5% for the 9 to 20 MeV beams and 1.0% for 6 MeV, showing for the first time that the development of a water-calorimeter-based standard for electron beams over a wide range of energies is feasible. Comparison between measurements with the ESW calorimeter and the NRC photon beam standard calorimeter in a 6 MeV beam revealed a discrepancy of 0.7+/-0.2% which is still under investigation. Absorbed-dose beam quality conversion factors in electron beams were measured using the ESW calorimeter for the Exradin A12 and PTW Roos ionization chambers

  5. Simultaneous processes of electricity generation and ceftriaxone sodium degradation in an air-cathode single chamber microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Wen, Qing; Kong, Fanying; Zheng, Hongtao; Yin, Jinling; Cao, Dianxue; Ren, Yueming; Wang, Guiling

    2011-03-01

    A single chamber microbial fuel cell (MFC) with an air-cathode is successfully demonstrated using glucose-ceftriaxone sodium mixtures or ceftriaxone sodium as fuel. Results show that the ceftriaxone sodium can be biodegraded and produce electricity simultaneously. Interestingly, these ceftriaxone sodium-glucose mixtures play an active role in production of electricity. The maximum power density is increased in comparison to 1000 mg L-1 glucose (19 W m-3) by 495% for 50 mg L-1 ceftriaxone sodium + 1000 mg L-1 glucose (113 W m-3), while the maximum power density is 11 W m-3 using 50 mg L-1 ceftriaxone sodium as the sole fuel. Moreover, ceftriaxone sodium biodegradation rate reaches 91% within 24 h using the MFC in comparison with 51% using the traditional anaerobic reactor. These results indicate that some toxic and bio-refractory organics such as antibiotic wastewater might be suitable resources for electricity generation using the MFC technology.

  6. Thermal characteristics of air flow cooling in the lithium ion batteries experimental chamber

    SciTech Connect

    Lukhanin A.; Rohatgi U.; Belyaev, A.; Fedorchenko, D.; Khazhmuradov, M.; Lukhanin, O; Rudychev, I.

    2012-07-08

    A battery pack prototype has been designed and built to evaluate various air cooling concepts for the thermal management of Li-ion batteries. The heat generation from the Li-Ion batteries was simulated with electrical heat generation devices with the same dimensions as the Li-Ion battery (200 mm x 150 mm x 12 mm). Each battery simulator generates up to 15W of heat. There are 20 temperature probes placed uniformly on the surface of the battery simulator, which can measure temperatures in the range from -40 C to +120 C. The prototype for the pack has up to 100 battery simulators and temperature probes are recorder using a PC based DAQ system. We can measure the average surface temperature of the simulator, temperature distribution on each surface and temperature distributions in the pack. The pack which holds the battery simulators is built as a crate, with adjustable gap (varies from 2mm to 5mm) between the simulators for air flow channel studies. The total system flow rate and the inlet flow temperature are controlled during the test. The cooling channel with various heat transfer enhancing devices can be installed between the simulators to investigate the cooling performance. The prototype was designed to configure the number of cooling channels from one to hundred Li-ion battery simulators. The pack is thermally isolated which prevents heat transfer from the pack to the surroundings. The flow device can provide the air flow rate in the gap of up to 5m/s velocity and air temperature in the range from -30 C to +50 C. Test results are compared with computational modeling of the test configurations. The present test set up will be used for future tests for developing and validating new cooling concepts such as surface conditions or heat pipes.

  7. Comparison of the response of a NaI scintillation crystal with a pressurized ionization chamber as a function of altitude, radiation level and Ra-226 concentration

    SciTech Connect

    Provencher, R.; Smith, G.; Borak, T.B.; Kearney, P.

    1986-01-01

    The Grand Junction Uranium Mill Tailings Remedial Action-Radiological Survey Activities Group (UMTRA-RASA) program employs a screening method in which external exposure rates are used to determine if a property contaminated with uranium mill tailings is eligible for remedial action. Portable NaI detectors are used by survey technicians to locate contaminated areas and determine exposure rates. The exposure rate is calculated using a regression equation derived from paired measurements made with a pressurized ionization chamber (PIC) and a NaI detector. During July of 1985 extensive measurements were taken using a PIC and a NaI scintillator with both analogue and digital readout for a wide range of exposure rates and at a variety of elevations. The surface soil was sampled at most of these locations and analyzed for /sup 226/Ra. The response of the NaI detectors was shown to be highly correlated to radiation level but not to /sup 226/Ra concentration or elevation.

  8. Temporal variations of cathode performance in air-cathode single-chamber microbial fuel cells with different separators

    NASA Astrophysics Data System (ADS)

    Ma, Jinxing; Wang, Zhiwei; Suor, Denis; Liu, Shumeng; Li, Jiaqi; Wu, Zhichao

    2014-12-01

    An ideal separator is essential for efficient power production from air-cathode single-chamber microbial fuel cells (MFCs). In this study, we use different kinds of membranes as separators, including Nafion 117 proton exchange membrane, polyethersulfone and poly(vinylidene fluoride) microfiltration membranes. Temporal variations of cathode performance are monitored during the experiment. Results show that MFCs with microfiltration membranes present higher power output but deterioration is still observed after about 600-h operation. With the utilization of appropriate separators (e.g., polyethersulfone membrane), biofouling, cation fouling and chemical scale fouling of the cathodes are alleviated while reaction fouling seems inevitable. Moreover, it is found that Coulombic efficiency (CE) and energy efficiency (EE) are also related to the cathode performance. Despite relatively high oxygen diffusivity (1.49 × 10-5 cm2 s-1), CE and EE of the MFC with 0.1 μm pore-size polyethersulfone membrane can reach 92.8% and 13.7%, respectively, when its average power density registers 403.5 mW m-2. This phenomenon might be attributed to the finding that the overall substrate consumption rate due to oxygen reduction and respiration is almost constant in the air-cathode MFCs. Oxygen leakage into the electrolyte can be inhibited due to the efficient oxygen reduction reaction on the surface of the cathode.

  9. Dust particle charge screening in the dry-air plasma produced by an external ionization source

    SciTech Connect

    Derbenev, I. N.; Filippov, A. V.

    2015-08-15

    The ionic composition of the plasma produced by an external ionization source in dry air at atmospheric pressure and room temperature and the screening of the electric field of a dust particle in such a plasma have been investigated. The point sink model based on the diffusion-drift approximation has been used to solve the screening problem. We have established that the main species of ions in the plasma under consideration are O{sub 4}{sup +}, O{sub 2}{sup -}, and O{sub 4}{sup -} and that the dust particle potential distribution is described by a superposition of four exponentials with four different constants. We show that the first constant coincides with the inverse Debye length, the second is described by the inverse ambipolar diffusion length of the positive and negative plasma components in the characteristic time of their recombination, the third is determined by the conversion of negative ions, and the fourth is determined by the attachment and recombination of electrons and diatomic ions.

  10. Gas phase formation of extremely oxidized pinene reaction products in chamber and ambient air

    NASA Astrophysics Data System (ADS)

    Ehn, M.; Kleist, E.; Junninen, H.; Petäjä, T.; Lönn, G.; Schobesberger, S.; Dal Maso, M.; Trimborn, A.; Kulmala, M.; Worsnop, D. R.; Wahner, A.; Wildt, J.; Mentel, Th. F.

    2012-06-01

    High molecular weight (300-650 Da) naturally charged negative ions have previously been observed at a boreal forest site in Hyytiälä, Finland. The long-term measurements conducted in this work showed that these ions are observed practically every night between spring and autumn in Hyytiälä. The ambient mass spectral patterns could be reproduced in striking detail during additional measurements of α-pinene (C10H16) oxidation at low-OH conditions in the Jülich Plant Atmosphere Chamber (JPAC). The ions were identified as clusters of the nitrate ion (NO3-) and α-pinene oxidation products reaching oxygen to carbon ratios of 0.7-1.3, while retaining most of the initial ten carbon atoms. Attributing the ions to clusters instead of single molecules was based on additional observations of the same extremely oxidized organics in clusters with HSO4- (Hyytiälä) and C3F5O2- (JPAC). The most abundant products in the ion spectra were identified as C10H14O7, C10H14O9, C10H16O9, and C10H14O11. The mechanism responsible for forming these molecules is still not clear, but the initial reaction is most likely ozone attack at the double bond, as the ions are mainly observed under dark conditions. β-pinene also formed highly oxidized products under the same conditions, but less efficiently, and mainly C9 compounds which were not observed in Hyytiälä, where β-pinene on average is 4-5 times less abundant than α-pinene. Further, to explain the high O/C together with the relatively high H/C, we propose that geminal diols and/or hydroperoxide groups may be important. We estimate that the night-time concentration of the sum of the neutral extremely oxidized products is on the order of 0.1-1 ppt (~106-107 molec cm-3). This is in a similar range as the amount of gaseous H2SO4 in Hyytiälä during day-time. As these highly oxidized organics are roughly 3 times heavier, likely with extremely low vapor pressures, their role in the initial steps of new aerosol particle formation and

  11. Gas phase formation of extremely oxidized pinene reaction products in chamber and ambient air

    NASA Astrophysics Data System (ADS)

    Ehn, M.; Kleist, E.; Junninen, H.; Petäjä, T.; Lönn, G.; Schobesberger, S.; Dal Maso, M.; Trimborn, A.; Kulmala, M.; Worsnop, D. R.; Wahner, A.; Wildt, J.; Mentel, Th. F.

    2012-02-01

    High molecular weight (300-650 Da) naturally charged negative ions have previously been observed at a boreal forest site in Hyytiälä, Finland. The long-term measurements conducted in this work showed that these ions are observed practically every night during spring and summer in Hyytiälä. The ambient mass spectral patterns could be reproduced in striking detail during additional measurements of α-pinene (C10H16) oxidation at low-OH conditions in the Jülich Plant Atmosphere Chamber (JPAC). The ions were identified as clusters of the nitrate ion (NO3-) and α-pinene oxidation products reaching oxygen to carbon ratios of 0.7-1.3, while retaining most of the initial ten carbon atoms. Attributing the ions to clusters instead of single molecules was based on additional observations of the same extremely oxidized organics in clusters with HSO4- (Hyytiälä) and C3F5O2- (JPAC). The most abundant products in the ion spectra were identified as C105H14O7, C10H14O9, C10H16O9, and C10H14O11. The mechanism responsible for forming these molecules is still not clear, but the initial reaction is most likely ozone attack at the double bond, as the ions are mainly observed under dark conditions. β-pinene also formed highly oxidized products under the same conditions, but less efficiently, and mainly C9 compounds which were not observed in Hyytiälä, where β-pinene on average is 4-5 times less abundant than α-pinene. Further, to explain the high O/C together with the relatively high H/C, we propose that geminal diols and/or hydroperoxide groups may be important. We estimate that the night-time concentration of the sum of the neutral extremely oxidized products is on the order of 0.1-1 ppt (~106-107 molec cm-3). This is in a similar range as the amount of gaseous H2SO4 in Hyytiälä during day-time. As these highly oxidized organics are roughly 3 times heavier, likely with extremely low vapor pressures, their role in the initial steps of new aerosol particle formation and

  12. Desorption/ionization of acrylamide in aqueous solutions in atmospheric pressure air using a microdischarge with vortex focusing of ions

    NASA Astrophysics Data System (ADS)

    Pervukhin, V. V.; Sheven', D. G.

    2014-09-01

    A method of desorption/ionization in a microdischarge with ion vortex focusing (vortex focusing microdischarge, VFM) is suggested. A glow microdischarge is initiated in an air flow, and resulting ions act on the surface of interest. As a model compound, an aqueous solution of acrylamide is taken. Desorption/ionization taking place under atmospheric pressure is followed by the mass-spectrometric identification of the ions. The operating parameters of the VFM system are studied and optimized. Upon optimization of the system, the detection limit of acrylamide trace amounts in aqueous solutions is determined using the suggested method of desorption/ionization and analyte ion focusing with a vortex (swirling) jet. The acrylamide detection limit is found to be 2 × 10-3 g/L.

  13. Three chamber negative ion source

    DOEpatents

    Leung, Ka-Ngo; Ehlers, Kenneth W.; Hiskes, John R.

    1985-01-01

    A negative ion vessel is divided into an excitation chamber, a negative ionization chamber and an extraction chamber by two magnetic filters. Input means introduces neutral molecules into a first chamber where a first electron discharge means vibrationally excites the molecules which migrate to a second chamber. In the second chamber a second electron discharge means ionizes the molecules, producing negative ions which are extracted into or by a third chamber. A first magnetic filter prevents high energy electrons from entering the negative ionization chamber from the excitation chamber. A second magnetic filter prevents high energy electrons from entering the extraction chamber from the negative ionizing chamber. An extraction grid at the end of the negative ion vessel attracts negative ions into the third chamber and accelerates them. Another grid, located adjacent to the extraction grid, carries a small positive voltage in order to inhibit positive ions from migrating into the extraction chamber and contour the plasma potential. Additional electrons can be suppressed from the output flux using ExB forces provided by magnetic field means and the extractor grid electric potential.

  14. DESIGN AND CHARACTERIZATION OF A SMALL CHAMBER FOR CHEMICAL AND BIOLOGICAL EVALUATION OF SOURCES OF INDOOR AIR CONTAMINATION

    EPA Science Inventory

    The paper discusses exposure generation considerations prior to implementation of sensory irritation bioassays for product emissions. mall chambers are used to generate source emissions from products for chemical and biological evaluation. esign of the source emissions chamber an...

  15. The injection of air/oxygen bubble into the anterior chamber of rabbits as a treatment for hyphema in patients with sickle cell disease.

    PubMed

    Ayintap, Emre; Keskin, Uğurcan; Sadigov, Fariz; Coskun, Mesut; Ilhan, Nilufer; Motor, Sedat; Semiz, Hilal; Parlakfikirer, Nihan

    2014-01-01

    Purpose. To investigate the changes of partial oxygen pressure (PaO2) in aqueous humour after injecting air or oxygen bubble into the anterior chamber in sickle cell hyphema. Methods. Blood samples were taken from the same patient with sickle cell disease. Thirty-two rabbits were divided into 4 groups. In group 1 (n = 8), there was no injection. Only blood injection constituted group 2 (n = 8), both blood and air bubble injection constituted group 3 (n = 8), and both blood and oxygen bubble injection constituted group 4 (n = 8). Results. The PaO2 in the aqueous humour after 10 hours from the injections was 78.45 ± 9.9 mmHg (Mean ± SD) for group 1, 73.97 ± 8.86 mmHg for group 2, 123.35 ± 13.6 mmHg for group 3, and 306.47 ± 16.5 mmHg for group 4. There was statistically significant difference between group 1 and group 2, when compared with group 3 and group 4. Conclusions. PaO2 in aqueous humour was increased after injecting air or oxygen bubble into the anterior chamber. We offer to leave an air bubble in the anterior chamber of patients with sickle cell hemoglobinopathies and hyphema undergoing an anterior chamber washout. PMID:24808955

  16. Anolyte recirculation effects in buffered and unbuffered single-chamber air-cathode microbial fuel cells.

    PubMed

    Zhang, Liang; Zhu, Xun; Kashima, Hiroyuki; Li, Jun; Ye, Ding-ding; Liao, Qiang; Regan, John M

    2015-03-01

    Two identical microbial fuel cells (MFCs) with a floating air-cathode were operated under either buffered (MFC-B) or bufferless (MFC-BL) conditions to investigate anolyte recirculation effects on enhancing proton transfer. With an external resistance of 50 Ω and recirculation rate of 1.0 ml/min, MFC-BL had a 27% lower voltage (9.7% lower maximal power density) but a 64% higher Coulombic efficiency (CE) than MFC-B. MFC-B had a decreased voltage output, batch time, and CE with increasing recirculation rate resulting from more oxygen transfer into the anode. However, increasing the recirculation rate within a low range significantly enhanced proton transfer in MFC-BL, resulting in a higher voltage output, a longer batch time, and a higher CE. A further increase in recirculation rate decreased the batch time and CE of MFC-BL due to excess oxygen transfer into anode outweighing the proton-transfer benefits. The unbuffered MFC had an optimal recirculation rate of 0.35 ml/min. PMID:25514399

  17. Combustor with fuel preparation chambers

    NASA Technical Reports Server (NTRS)

    Zelina, Joseph (Inventor); Myers, Geoffrey D. (Inventor); Srinivasan, Ram (Inventor); Reynolds, Robert S. (Inventor)

    2001-01-01

    An annular combustor having fuel preparation chambers mounted in the dome of the combustor. The fuel preparation chamber comprises an annular wall extending axially from an inlet to an exit that defines a mixing chamber. Mounted to the inlet are an air swirler and a fuel atomizer. The air swirler provides swirled air to the mixing chamber while the atomizer provides a fuel spray. On the downstream side of the exit, the fuel preparation chamber has an inwardly extending conical wall that compresses the swirling mixture of fuel and air exiting the mixing chamber.

  18. Experimental and numerical study of premixed hydrogen/air flame propagating in a combustion chamber.

    PubMed

    Xiao, Huahua; Sun, Jinhua; Chen, Peng

    2014-03-15

    An experimental and numerical study of dynamics of premixed hydrogen/air flame in a closed explosion vessel is described. High-speed shlieren cinematography and pressure recording are used to elucidate the dynamics of the combustion process in the experiment. A dynamically thickened flame model associated with a detailed reaction mechanism is employed in the numerical simulation to examine the flame-flow interaction and effect of wall friction on the flame dynamics. The shlieren photographs show that the flame develops into a distorted tulip shape after a well-pronounced classical tulip front has been formed. The experimental results reveal that the distorted tulip flame disappears with the primary tulip cusp and the distortions merging into each other, and then a classical tulip is repeated. The combustion dynamics is reasonably reproduced in the numerical simulations, including the variations in flame shape and position, pressure build-up and periodically oscillating behavior. It is found that both the tulip and distorted tulip flames can be created in the simulation with free-slip boundary condition at the walls of the vessel and behave in a manner quite close to that in the experiments. This means that the wall friction could be unimportant for the tulip and distorted tulip formation although the boundary layer formed along the sidewalls has an influence to a certain extent on the flame behavior near the sidewalls. The distorted tulip flame is also observed to be produced in the absence of vortex flow in the numerical simulations. The TF model with a detailed chemical scheme is reliable for investigating the dynamics of distorted tulip flame propagation and its underlying mechanism. PMID:24486615

  19. Electron Transport Coefficients and Effective Ionization Coefficients in SF6-O2 and SF6-Air Mixtures Using Boltzmann Analysis

    NASA Astrophysics Data System (ADS)

    Wei, Linsheng; Xu, Min; Yuan, Dingkun; Zhang, Yafang; Hu, Zhaoji; Tan, Zhihong

    2014-10-01

    The electron drift velocity, electron energy distribution function (EEDF), density-normalized effective ionization coefficient and density-normalized longitudinal diffusion velocity are calculated in SF6-O2 and SF6-Air mixtures. The experimental results from a pulsed Townsend discharge are plotted for comparison with the numerical results. The reduced field strength varies from 40 Td to 500 Td (1 Townsend=10-17 V·cm2) and the SF6 concentration ranges from 10% to 100%. A Boltzmann equation associated with the two-term spherical harmonic expansion approximation is utilized to gain the swarm parameters in steady-state Townsend. Results show that the accuracy of the Boltzmann solution with a two-term expansion in calculating the electron drift velocity, electron energy distribution function, and density-normalized effective ionization coefficient is acceptable. The effective ionization coefficient presents a distinct relationship with the SF6 content in the mixtures. Moreover, the E/Ncr values in SF6-Air mixtures are higher than those in SF6-O2 mixtures and the calculated value E/Ncr in SF6-O2 and SF6-Air mixtures is lower than the measured value in SF6-N2. Parametric studies conducted on these parameters using the Boltzmann analysis offer substantial insight into the plasma physics, as well as a basis to explore the ozone generation process.

  20. Characterization of 2 MeV, 4 MeV, 6 MeV and 18 MeV buildup caps for use with a 0.6 cubic centimeter thimble ionization chamber

    SciTech Connect

    Salyer, R.L.; VanDenburg, J.W.; Prinja, A.K.; Kirby, T.; Busch, R.; Hong-Nian Jow

    1996-07-01

    The purpose of this research is to characterize existing 2 MeV, 4 MeV and 6 MeV buildup caps, and to determine if a buildup cap can be made for the 0.6 cm{sup 3} thimble ionization chamber that will accurately measure exposures in a high-energy photon radiation field. Two different radiation transport codes were used to computationally characterize existing 2 MeV, 4 MeV, and 6 MeV buildup caps for a 0.6 cm{sup 3} active volume thimble ionization chamber: ITS, The Integrated TIGER Series of Coupled Electron-Photon Monte Carlo Transport Codes; and CEPXS/ONEDANT, A One-Dimensional Coupled Electron-Photon Discrete Ordinates Code Package. These codes were also used to determine the design characteristics of a buildup cap for use in the 18 MeV photon beam produced by the 14 TW pulsed power HERMES-III electron accelerator. The maximum range of the secondary electron, the depth at which maximum dose occurs, and the point where dose and collision kerma are equal have been determined to establish the validity of electronic equilibrium. The ionization chamber with the appropriate buildup cap was then subjected to a 4 MeV and a 6 MeV bremmstrahlung radiation spectrum to determine the detector response.

  1. Chemistry of α-pinene and naphthalene oxidation products generated in a Potential Aerosol Mass (PAM) chamber as measured by acetate chemical ionization mass spectrometry

    DOE PAGESBeta

    Chhabra, P. S.; Lambe, A. T.; Canagaratna, M. R.; Stark, H.; Jayne, J. T.; Onasch, T. B.; Davidovits, P.; Kimmel, J. R.; Worsnop, D. R.

    2014-07-01

    Recent developments in high resolution, time-of-flight chemical ionization mass spectrometry (HR-ToF-CIMS) have made possible the direct detection of atmospheric organic compounds in real-time with high sensitivity and with little or no fragmentation, including low volatility, highly oxygenated organic vapors that are precursors to secondary organic aerosol formation. Here, for the first time, we examine gas-phase O3 and OH oxidation products of α-pinene and naphthalene formed in the PAM flow reactor with an HR-ToF-CIMS using acetate reagent ion chemistry. Integrated OH exposures ranged from 1.2 × 1011 to 9.7 × 1011 molec cm−3 s, corresponding to approximately 1.0 to 7.5 daysmore » of equivalent atmospheric oxidation. Measured gas-phase organic acids are similar to those previously observed in environmental chamber studies. For both precursors, we find that acetate-CIMS spectra capture both functionalization (oxygen addition) and fragmentation (carbon loss) as a function of OH exposure. The level of fragmentation is observed to increase with increased oxidation. We present a method that estimates vapor pressures of organic molecules using the measured O/C ratio, H/C ratio, and carbon number for each compound detected by the CIMS. The predicted condensed-phase SOA average acid yields and O/C and H/C ratios agree within uncertainties with previous AMS measurements and ambient CIMS results. While acetate reagent ion chemistry is used to selectively measure organic acids, in principle this method can be applied to additional reagent ion chemistries depending on the application.« less

  2. Isobar separation of 93Zr and 93Nb at 24 MeV with a new multi-anode ionization chamber

    NASA Astrophysics Data System (ADS)

    Martschini, Martin; Buchriegler, Josef; Collon, Philippe; Kutschera, Walter; Lachner, Johannes; Lu, Wenting; Priller, Alfred; Steier, Peter; Golser, Robin

    2015-10-01

    93Zr with a half-life of 1.6 Ma is produced with high yield in nuclear fission, and thus should be present as a natural or anthropogenic trace isotope in all compartments of the general environment. Sensitive measurements of this isotope would immediately find numerous applications, however, its detection at sufficiently low levels has not yet been achieved. AMS measurements of 93Zr suffer from the interference of the stable isobar 93Nb. At the Vienna Environmental Research Accelerator VERA a new multi-anode ionization chamber was built. It is optimized for isobar separation in the medium mass range and is based on the experience from AMS experiments of 36Cl at our 3-MV tandem accelerator facility. The design provides high flexibility in anode configuration and detector geometry. After validating the excellent energy resolution of the detector with 36S, it was recently used to study iron-nickel and zirconium-niobium-molybdenum isobar separation. To our surprise, the separation of 94Zr (Z = 40) from 94Mo (Z = 42) was found to be much better than that of 58Fe (Z = 26) from 58Ni (Z = 28), despite the significantly larger ΔZ/Z of the latter pair. This clearly contradicts results from SRIM-simulations and suggests that differences in the stopping behavior may unexpectedly favor identification of 93Zr. At 24 MeV particle energy, a 93Nb (Z = 41) suppression factor of 1000 is expected based on a synthetic 93Zr spectrum obtained by interpolation between experimental spectra from the two neighboring stable isotopes 92Zr and 94Zr. Assuming realistic numbers for chemical niobium reduction, a detection level of 93Zr/Zr below 10-9 seems feasible.

  3. Enrichment of anodic biofilm inoculated with anaerobic or aerobic sludge in single chambered air-cathode microbial fuel cells.

    PubMed

    Gao, Chongyang; Wang, Aijie; Wu, Wei-Min; Yin, Yalin; Zhao, Yang-Guo

    2014-09-01

    Aerobic sludge after anaerobic pretreatment and anaerobic sludge were separately used as inoculum to start up air-cathode single-chamber MFCs. Aerobic sludge-inoculated MFCs arrived at 0.27 V with a maximum power density of 5.79 W m(-3), while anaerobic sludge-inoculated MFCs reached 0.21 V with 3.66 W m(-3). Microbial analysis with DGGE profiling and high-throughput sequencing indicated that aerobic sludge contained more diverse bacterial populations than anaerobic sludge. Nitrospira species dominated in aerobic sludge, while anaerobic sludge was dominated by Desulfurella and Acidithiobacillus species. Microbial community structure and composition in anodic biofilms enriched, respectively from aerobic and anaerobic sludges tended gradually to be similar. Potentially exoelectrogenic Geobacter and Anaeromusa species, biofilm-forming Zoogloea and Acinetobacter species were abundant in both anodic biofilms. This study indicated that aerobic sludge performed better for MFCs startup, and the enrichment of anodic microbial consortium with different inocula but same substrate resulted in uniformity of functional microbial communities. PMID:24973773

  4. Theoretical model for diffusive greenhouse gas fluxes estimation across water-air interfaces measured with the static floating chamber method

    NASA Astrophysics Data System (ADS)

    Xiao, Shangbin; Wang, Chenghao; Wilkinson, Richard Jeremy; Liu, Defu; Zhang, Cheng; Xu, Wennian; Yang, Zhengjian; Wang, Yuchun; Lei, Dan

    2016-07-01

    Aquatic systems are sources of greenhouse gases on different scales, however the uncertainty of gas fluxes estimated using popular methods are not well defined. Here we show that greenhouse gas fluxes across the air-water interface of seas and inland waters are significantly underestimated by the currently used static floating chamber (SFC) method. We found that the SFC CH4 flux calculated with the popular linear regression (LR) on changes of gas concentration over time only accounts for 54.75% and 35.77% of the corresponding real gas flux when the monitoring periods are 30 and 60 min respectively based on the theoretical model and experimental measurements. Our results do manifest that nonlinear regression models can improve gas flux estimations, while the exponential regression (ER) model can give the best estimations which are close to true values when compared to LR. However, the quadratic regression model is proved to be inappropriate for long time measurements and those aquatic systems with high gas emission rate. The greenhouse gases effluxes emitted from aquatic systems may be much more than those reported previously, and models on future scenarios of global climate changes should be adjusted accordingly.

  5. Flow chamber

    DOEpatents

    Morozov, Victor

    2011-01-18

    A flow chamber having a vacuum chamber and a specimen chamber. The specimen chamber may have an opening through which a fluid may be introduced and an opening through which the fluid may exit. The vacuum chamber may have an opening through which contents of the vacuum chamber may be evacuated. A portion of the flow chamber may be flexible, and a vacuum may be used to hold the components of the flow chamber together.

  6. Precursor ionization ahead of laser-supported detonation wave in air and argon

    NASA Astrophysics Data System (ADS)

    Shimamura, Kohei; Komurasaki, Kimiya; Koizumi, Hiroyuki; Arakawa, Yoshihiro

    2012-10-01

    Laser-produced plasma in a gaseous form is considered, which has attracted great interest for use in many devices. After breakdown one of possible mechanisms of occurrence of this process is noted as laser-supported detonation wave. This wave consisting of the shock wave and the beam absorbing plasma travels at several kilometers per second along the laser beam channel in the direction opposite to the beam incidence. A Nd: Glass laser and a TEA CO2 laser were utilized. According to shadowgraph and spectroscopic studies, the wave has a velocity of 1-10 km/s, an electron temperature of 2-5 eV and an electron density of 10^24 m-3 after breakdown. For simplicity, the discussion is restricted to one-dimensional flows that considers the radiation from plasma and the collisional ionization by laser irradiation. Assuming that UV photons radiating from laser plasma induce photoionization ahead of ionization front, this ionization frequency fp at the distance lp (mean free path of photon) from the wave front corresponds to 10^10 s-1. This is higher than the collisional ionization frequency (10^5-6 s-1). Analytical velocities (fplp) describing the avalanche ionization in the pre-ionization layer agree with the experimentally observed velocities. These results does not depend on background gas and laser-wavelength.

  7. Influence of air-staging on the concentration profiles of NH{sub 3} and HCN in the combustion chamber of a CFB boiler burning coal

    SciTech Connect

    Kassman, H.; Karlsson, M.; Aamand, L.E.

    1999-07-01

    The characterization of the concentration profiles of NH{sub 3} and HCN are of great importance for increasing the knowledge of the formation and destruction pathways of NO and N{sub 2}O in a fluidized bed boiler. Further improvements of the sampling methods for the determination of both NH{sub 3} and HCN in the combustion chamber in full-scale CFB boilers are also needed. A gas-sampling probe connected to a Fourier Transform Infrared (FTIR) instrument and a gas-quenching (GQ) probe in which the sample is quenched directly in the probe tip by a circulating trapper solution were used. The FTIR technique is based on analysis of hot combustion gases, whereas the trapper solutions from the GQ probe were analyzed by means of wet chemistry. The tests were performed during coal combustion in a 12 MW CFB boiler, which was operated at three air-staging cases with the addition of limestone for sulfur capture. The concentration profiles of NH{sub 3} and HCN in the combustion chamber showed a different pattern concerning the influence of air-staging. The highest levels of NH{sub 3} were observed during reducing condition (severe air-staging), and the lowest were found under oxidizing conditions (no air-staging). The levels of HCN were much lower than those measured for NH{sub 3}. The highest levels of HCN were observed for reversed air-staging and severe air-staging showed almost no HCN. The potential reactors involving NH{sub 3} and HCN in the combustion chamber as well as the potential measurement errors in each sampling technique are discussed for the three air-staging cases.

  8. Excitational energy transfer enhancing ionization and spatial-temporal evolution of air breakdown with UV laser radiation

    NASA Astrophysics Data System (ADS)

    Hummelt, Jason S.; Scharer, John E.

    2010-11-01

    This paper examines the role multiphoton excitation of oxygen has on the ionization of nitrogen in laser air breakdown. Plasma is created by focusing a 193 nm ArF excimer laser using an 18 cm focal length lens, producing a cylindrical 540 μm wide spot of intensity 6.5 GW/cm2, well below the classical limit for collisional cascade (CC) breakdown. By spectroscopically monitoring the B Σ2u+ to X Σ2g+ transition at 391.4 nm of N2+ in N2 and O2 mixes, collisions between N2 and metastable O2 states that have undergone 1+1 absorption processes are shown to lower the degree of nonlinearity (i.e., the number of photons involved in the rate limiting multiphoton absorption process) in the ionization of N2. This process is also found to dominate the 2+1 resonant enhanced multiphoton ionization of N2 in air and be the primary source for ionization of N2 to the B Σ2u+ state. Plasma formation and evolution is also examined using a 1.3 cm focal length objective lens creating a 40 μm wide spot of intensity 1.25 TW/cm2, above the classical limit for breakdown. This plasma is imaged with a fast (1.2 ns) gating intensified charge coupled device camera. Early plasma formation is seen to be inhomogeneous in nature, and significant ion density is found to exist up to 20 μs after the laser pulse.

  9. Calorimetric determination of kQ factors for NE 2561 and NE 2571 ionization chambers in 5 cm × 5 cm and 10 cm × 10 cm radiotherapy beams of 8 MV and 16 MV photons

    NASA Astrophysics Data System (ADS)

    Krauss, Achim; Kapsch, Ralf-Peter

    2007-10-01

    The relative uncertainty of the ionometric determination of the absorbed dose to water, Dw, in the reference dosimetry of high-energy photon beams is in the order of 1.5% and is dominated by the uncertainty of the calculated chamber- and energy-dependent correction factors kQ. In the present investigation, kQ values were determined experimentally in 5 cm × 5 cm and 10 cm × 10 cm radiotherapy beams of 8 MV and 16 MV bremsstrahlung by means of a water calorimeter operated at 4 °C. Ionization chambers of the types NE 2561 and NE 2571 were calibrated directly in the water phantom of the calorimeter. The measurements were carried out at the linear accelerator of the Physikalisch-Technische Bundesanstalt. It is shown that the kQ factor of a single ionization chamber can be measured with a standard uncertainty of less than 0.3%. No significant variations of kQ were found for the different lateral sizes of the radiation fields used in this investigation.

  10. Reply to comment on 'Proton beam monitor chamber calibration'.

    PubMed

    Gomà, Carles; Lorentini, Stefano; Meer, David; Safai, Sairos

    2016-09-01

    This reply shows that the discrepancy of about 3% between Faraday cup dosimetry and reference dosimetry using a cylindrical ionization chamber found in Gomà (2014 Phys. Med. Biol. 59 4961-71) seems to be due to an overestimation of the beam quality correction factors tabulated in IAEA TRS-398 for the cylindrical chamber used, rather than to 'unresolved problems with Faraday cup dosimetry', as suggested by Palmans and Vatnitsky (2016 Phys. Med. Biol. 61 6585-93). Furthermore, this work shows that a good agreement between reference dosimetry and Faraday cup dosimetry is possible, provided accurate beam quality correction factors for proton beams are used. The review on W air values presented by Palmans and Vatnitsky is believed to be inaccurate, as it is based on the imprecise assumption of ionization chamber perturbation correction factors in proton beams being equal to unity. PMID:27535895

  11. Ionization detection system for aerosols

    DOEpatents

    Jacobs, Martin E.

    1977-01-01

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system utilizes a measuring ionization chamber which is modified to minimize false alarms and reductions in sensitivity resulting from changes in ambient temperature. In the preferred form of the modification, an annular radiation shield is mounted about the usual radiation source provided to effect ionization in the measuring chamber. The shield is supported by a bimetallic strip which flexes in response to changes in ambient temperature, moving the shield relative to the source so as to vary the radiative area of the source in a manner offsetting temperature-induced variations in the sensitivity of the chamber.

  12. Measurements of neutron-induced fission cross-sections of 205Tl, 204,206,207,208Pb and 209Bi with a multi-section Frisch-gridded ionization chamber

    NASA Astrophysics Data System (ADS)

    Ryzhov, I. V.; Tutin, G. A.; Mitryukhin, A. G.; Oplavin, V. S.; Soloviev, S. M.; Blomgren, J.; Renberg, P.-U.; Meulders, J. P.; El Masri, Y.; Keutgen, Th.; Prieels, R.; Nolte, R.

    2006-06-01

    Neutron-induced fission cross-sections of 205Tl, 204,206,207,208Pb and 209Bi have been measured in the energy range from 30 to 180 MeV. The measurements were performed with quasi-monoenergetic neutron beams using a multi-section Frisch-gridded ionization chamber. The neutron-induced fission cross-sections of 238U were used as reference data. The experimental techniques are described in detail as well as the data processing. The results are compared with existing experimental data.

  13. Development of a 12-Thrust Chamber Kerosene /Oxygen Primary Rocket Sub-System for an Early (1964) Air-Augmented Rocket Ground-Test System

    NASA Technical Reports Server (NTRS)

    Pryor, D.; Hyde, E. H.; Escher, W. J. D.

    1999-01-01

    Airbreathing/Rocket combined-cycle, and specifically rocket-based combined- cycle (RBCC), propulsion systems, typically employ an internal engine flow-path installed primary rocket subsystem. To achieve acceptably short mixing lengths in effecting the "air augmentation" process, a large rocket-exhaust/air interfacial mixing surface is needed. This leads, in some engine design concepts, to a "cluster" of small rocket units, suitably arrayed in the flowpath. To support an early (1964) subscale ground-test of a specific RBCC concept, such a 12-rocket cluster was developed by NASA's Marshall Space Flight Center (MSFC). The small primary rockets used in the cluster assembly were modified versions of an existing small kerosene/oxygen water-cooled rocket engine unit routinely tested at MSFC. Following individual thrust-chamber tests and overall subsystem qualification testing, the cluster assembly was installed at the U. S. Air Force's Arnold Engineering Development Center (AEDC) for RBCC systems testing. (The results of the special air-augmented rocket testing are not covered here.) While this project was eventually successfully completed, a number of hardware integration problems were met, leading to catastrophic thrust chamber failures. The principal "lessons learned" in conducting this early primary rocket subsystem experimental effort are documented here as a basic knowledge-base contribution for the benefit of today's RBCC research and development community.

  14. Bakeout Chamber Within Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    Taylor, Daniel M.; Soules, David M.; Barengoltz, Jack B.

    1995-01-01

    Vacuum-bakeout apparatus for decontaminating and measuring outgassing from pieces of equipment constructed by mounting bakeout chamber within conventional vacuum chamber. Upgrade cost effective: fabrication and installation of bakeout chamber simple, installation performed quickly and without major changes in older vacuum chamber, and provides quantitative data on outgassing from pieces of equipment placed in bakeout chamber.

  15. Evaluation of Wall Correction Factor of INER's Air-Kerma Primary Standard Chamber and Dose Variation by Source Displacement for HDR 192Ir Brachytherapy

    PubMed Central

    Lee, J. H.; Wang, J. N.; Huang, T. T.; Su, S. H.; Chang, B. J.; Su, C. H.; Hsu, S. M.

    2013-01-01

    The aim of the present study was to estimate the wall effect of the self-made spherical graphite-walled cavity chamber with the Monte Carlo method for establishing the air-kerma primary standard of high-dose-rate (HDR) 192Ir brachytherapy sources at the Institute of Nuclear Energy Research (INER, Taiwan). The Monte Carlo method established in this paper was also employed to respectively simulate wall correction factors of the 192Ir air-kerma standard chambers used at the National Institute of Standards and Technology (NIST, USA) and the National Physical Laboratory (NPL, UK) for comparisons and verification. The chamber wall correction calculation results will be incorporated into INER's HDR 192Ir primary standard in the future. For the brachytherapy treatment in the esophagus or in the bronchi, the position of the isotope may have displacement in the cavity. Thus the delivered dose would differ from the prescribed dose in the treatment plan. We also tried assessing dose distribution due to the position displacement of HDR 192Ir brachytherapy source in a phantom with a central cavity by the Monte Carlo method. The calculated results could offer a clinical reference for the brachytherapy within the human organs with cavity. PMID:24222907

  16. Proton beam monitor chamber calibration.

    PubMed

    Gomà, C; Lorentini, S; Meer, D; Safai, S

    2014-09-01

    The first goal of this paper is to clarify the reference conditions for the reference dosimetry of clinical proton beams. A clear distinction is made between proton beam delivery systems which should be calibrated with a spread-out Bragg peak field and those that should be calibrated with a (pseudo-)monoenergetic proton beam. For the latter, this paper also compares two independent dosimetry techniques to calibrate the beam monitor chambers: absolute dosimetry (of the number of protons exiting the nozzle) with a Faraday cup and reference dosimetry (i.e. determination of the absorbed dose to water under IAEA TRS-398 reference conditions) with an ionization chamber. To compare the two techniques, Monte Carlo simulations were performed to convert dose-to-water to proton fluence. A good agreement was found between the Faraday cup technique and the reference dosimetry with a plane-parallel ionization chamber. The differences-of the order of 3%-were found to be within the uncertainty of the comparison. For cylindrical ionization chambers, however, the agreement was only possible when positioning the effective point of measurement of the chamber at the reference measurement depth-i.e. not complying with IAEA TRS-398 recommendations. In conclusion, for cylindrical ionization chambers, IAEA TRS-398 reference conditions for monoenergetic proton beams led to a systematic error in the determination of the absorbed dose to water, especially relevant for low-energy proton beams. To overcome this problem, the effective point of measurement of cylindrical ionization chambers should be taken into account when positioning the reference point of the chamber. Within the current IAEA TRS-398 recommendations, it seems advisable to use plane-parallel ionization chambers-rather than cylindrical chambers-for the reference dosimetry of pseudo-monoenergetic proton beams. PMID:25109620

  17. Compensating for wall effects in IAQ (indoor air quality) chamber tests by mathematical modeling. Report for June 1986-February 1987

    SciTech Connect

    Dunn, J.E.; Tichenor, B.A.

    1987-04-01

    The paper presents mechanistic mathematical models that account for two phenomena: interior surfaces of a state-of-the-art emissions test chamber acting as a transient sink for organic emissions; and the effect of increasing chamber concentration on the emission rate of the source. As a consequence of this mathematical development, a source emission rate as a function of time and a steady-state emission rate factor are given precise definitions. Applications involve modeling 1,4 dichlorobenzene emission from moth crystals, and mixed emissions from latex caulk.

  18. Potential Energy Curves and Collisions Integrals of Air Components. 2; Interactions Involving Ionized Atoms

    NASA Technical Reports Server (NTRS)

    Stallcop, James R.; Partridge, Harry; Levin, Eugene; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Collision integrals are fundamental quantities required to determine the transport properties of the environment surrounding aerospace vehicles in the upper atmosphere. These collision integrals can be determined as a function of temperature from the potential energy curves describing the atomic and molecular collisions. Ab initio calculations provide a practical method of computing the required interaction potentials. In this work we will discuss recent advances in scattering calculations with an emphasis on the accuracy that is obtainable. Results for interactions of the atoms and ionized atoms of nitrogen and oxygen will be reviewed and their application to the determination of transport properties, such as diffusion and viscosity coefficients, will be examined.

  19. Suitability of small environmental chambers to test the emission of biocides from treated materials into the air

    NASA Astrophysics Data System (ADS)

    Horn, Wolfgang; Jann, Oliver; Wilke, Olaf

    Biocides are used to protect materials that might be damaged by fungal, microbial or insect activity. The aim of this study is to develop a method for the measurement of these organic compounds, which generally have low or moderate vapor pressures. The biocides considered in this study are permethrin, dichlofluanid, tolylfluanid, iodpropinylbutylcarbamat, octylisothiazolinone, tebuconazole and propiconazole. The emission from two commercial products (plastic foil, wool carpet) containing biocides and of seven types of biocidal formulations applied to wood or clay tiles were investigated in 20-l glass emission test chambers. Each chamber test was performed over a period of 100-200 days, and one investigation was conducted over several years. Compared to volatile organic compounds, low-volatility compounds show totally different emission curves in chamber tests; maximal emission values may be reached in days or weeks. A period of 3 months is sometimes necessary for the determination of area-specific emission rates (SER a's). The SER a's (μg m -2 h -1) from biocide-containing products were determined for permethrin (0.006), propiconazole (0.3), dichlofluanid (2.0), tolylfluanid (1.0), octylisothiazolinone (2.5) and iodpropinylbutylcarbamat (2). In most cases, the SER a stayed at its maximum value or declined slowly over the test period. Additionally, a chamber test begun in 1994 with a piece of wood treated with a typical mixture of biocides dissolved in a technical solvent was continued. SER a's (μg m -2 h -1) for dichlofluanid (0.20), tebuconazole (0.49) and permethrin (0.08) remained detectable after the period of nearly 9 years during which the sample remained continuously in the chamber. This test proved the very slow decrease of emission of low-volatility compounds like permethrin and tebuconazole.

  20. SU-E-T-625: Use and Choice of Ionization Chambers for the Commissioning of Flattened and Flattening-Filter-Free Photon Beams: Determination of Recombination Correction Factor (ks)

    SciTech Connect

    Stucchi, C; Mongioj, V; Carrara, M; Pignoli, E; Bonfantini, F; Bresolin, A

    2014-06-15

    Purpose: To evaluate the recombination effect for some ionization chambers to be used for linacs commissioning for Flattened Filter (FF) and Flattening Filter Free (FFF) photon beams. Methods: A Varian TrueBeam linac with five photon beams was used: 6, 10 and 15 MV FF and 6 and 10 MV FFF. Measurements were performed in a water tank and in a plastic water phantom with different chambers: a mini-ion chamber (IC CC01, IBA), a plane-parallel ion chamber (IC PPC05, IBA) and two Farmer chambers (NE2581 and FPC05-IBA). Measurement conditions were Source- Surface Distance of 100 cm, two field sizes (10x10 and 40x40 cm2) and five depths (1cm, maximum buildup, 5cm, 10cm and 20cm). The ion recombination factors (kS), obtained from the Jaffe's plots (voltage interval 50-400 V), were evaluated at the recommended operating voltage of +300V. Results: Dose Per Pulse (DPP) at dmax was 0.4 mGy/pulse for FF beams, 1.0 mGy/pulse and 1.9 mGy/pulse for 6MV and 10 MV FFF beams respectively. For all measurement conditions, kS ranged between 0.996 and 0.999 for IC PPC05, 0.997 and 1.008 for IC CC01. For the FPC05 IBA Farmer IC, kS varied from 1.001 to 1.011 for FF beams, from 1.004 to 1.015 for 6 MV FFF and from 1.009 to 1.025 for 10 MV FFF. Whereas, for NE2581 IC the values ranged from 1.002 to 1.009 for all energy beams and measurement conditions. Conclusion: kS depends on the chamber volume and the DPP, which in turn depends on energy beam but is independent of dose rate. Ion chambers with small active volume can be reliably used for dosimetry of FF and FFF beams even without kS correction. On the contrary, for absolute dosimetry of FFF beams by Farmer ICs it is necessary to evaluate and apply the kS correction. Partially supported by Lega Italiana Lotta contro i Tumori (LILT)

  1. Microionization chamber air-kerma calibration coefficients as a function of photon energy for x-ray spectra in the range of 20-250 kVp relative to {sup 60}Co

    SciTech Connect

    Snow, J. R.; Micka, J. A.; DeWerd, L. A.

    2013-04-15

    Purpose: To investigate the applicability of a wide range of microionization chambers for reference dosimetry measurements in low- and medium-energy x-ray beams. Methods: Measurements were performed with six cylindrical microchamber models, as well as one scanning chamber and two Farmer-type chambers for comparison purposes. Air-kerma calibration coefficients were determined at the University of Wisconsin Accredited Dosimetry Calibration Laboratory for each chamber for a range of low- and medium-energy x-ray beams (20-250 kVp), with effective energies ranging from 11.5 keV to 145 keV, and a {sup 60}Co beam. A low-Z proof-of-concept microchamber was developed and calibrated with and without a high-Z silver epoxy on the collecting electrode. Results: All chambers composed of low-Z materials (Z{<=} 13), including the Farmer-type chambers, the scanning chamber, and the PTW TN31014 and the proof-of-concept microchambers, exhibited air-kerma calibration coefficients with little dependence on the quality of the beam. These chambers typically exhibited variations in calibration coefficients of less than 3% with the beam quality, for medium energy beams. However, variations in air-kerma calibration coefficients of greater than 50% were measured over the range of medium-energy x-ray beams for each of the microchambers containing high-Z collecting electrodes (Z > 13). For these high-Z chambers, which include the Exradin A14SL and A16 chambers, the PTW TN31006 chamber, the IBA CC01 chamber, and the proof-of-concept chamber containing silver, the average variation in air-kerma calibration coefficients between any two calibration beams was nearly 25% over the entire range of beam qualities investigated. Conclusions: Due to the strong energy dependence observed with microchambers containing high-Z components, these chambers may not be suitable dosimeters for kilovoltage x-ray applications, as they do not meet the TG-61 requirements. It is recommended that only microchambers

  2. A practical approach to estimate emission rates of indoor air pollutants due to the use of personal combustible products based on small-chamber studies.

    PubMed

    Szulejko, Jan E; Kim, Ki-Hyun

    2016-02-01

    As emission rates of airborne pollutants are commonly measured from combusting substances placed inside small chambers, those values need to be re-evaluated for the possible significance under practical conditions. Here, a simple numerical procedure is investigated to extrapolate the chamber-based emission rates of formaldehyde that can be released from various combustible sources including e-cigarettes, conventional cigarettes, or scented candles to their concentration levels in a small room with relatively poor ventilation. This simple procedure relies on a mass balance approach by considering the masses of pollutants emitted from source and lost through ventilation under the assumption that mixing occurs instantaneously in the room without chemical reactions or surface sorption. The results of our study provide valuable insights into re-evaluation procedure of chamber data to allow comparison between extrapolated and recommended values to judge the safe use of various combustible products in confined spaces. If two scented candles with a formaldehyde emission rate of 310 µg h(-1) each were lit for 4 h in a small 20 m(3) room with an air change rate of 0.5 h(-1), then the 4-h (candle lit) and 8-h (up to 8 h after candle lighting) TWA [FA] were determined to be 28.5 and 23.5 ppb, respectively. This is clearly above the 8-h NIOSH recommended exposure limit (REL) time weighted average of 16 ppb. PMID:26495830

  3. Measurements of VOC/SVOC emission factors from burning incenses in an environmental test chamber: influence of temperature, relative humidity, and air exchange rate.

    PubMed

    Manoukian, A; Buiron, D; Temime-Roussel, B; Wortham, H; Quivet, E

    2016-04-01

    This study investigates the influence of three environmental indoor parameters (i.e., temperature, relative humidity, and air exchange rate) on the emission of 13 volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) during incense burning. Experiments have been carried out using an environmental test chamber. Statistical results from a classical two-level full factorial design highlight the predominant effect of ventilation on emission factors. The higher the ventilation, the higher the emission factor. Moreover, thanks to these results, an estimation of the concentration range for the compounds under study can be calculated and allows a quick look of indoor pollution induced by incense combustion. Carcinogenic substances (i.e., benzene, benzo(a)pyrene, and formaldehyde) produced from the incense combustion would be predicted in typical living indoors conditions to reach instantaneous concentration levels close to or higher than air quality exposure threshold values. PMID:26614451

  4. AUTOMATED DECONVOLUTION OF COMPOSITE MASS SPECTRA OBTAINED WITH AN OPEN-AIR IONIZATIONS SOURCE BASED ON EXACT MASSES AND RELATIVE ISOTIPIC ABUNDANCES

    EPA Science Inventory

    Chemicals dispersed by accidental, deliberate, or weather-related events must be rapidly identified to assess health risks. Mass spectra from high levels of analytes obtained using rapid, open-air ionization by a Direct Analysis in Real Time (DART®) ion source often contain

  5. REAL TIME, ON-LINE CHARACTERIZATION OF DIESEL GENERATOR AIR TOXIC EMISSIONS BY RESONANCE ENHANCED MULTI-PHOTON IONIZATION TIME OF FLIGHT MASS SPECTROMETRY

    EPA Science Inventory

    The laser based resonance, enhanced multi-photon ionization time-of-flight mass spectrometry (REMPI-TOFMS) technique has been applied to the exhaust gas stream of a diesel generator to measure, in real time, concentration levels of aromatic air toxics. Volatile organic compounds ...

  6. Atmospheric Ionizing Radiation (AIR): Analysis, Results, and Lessons Learned From the June 1997 ER-2 Campaign

    NASA Technical Reports Server (NTRS)

    Wilson, J. W. (Editor); Jones, I. W. (Editor); Maiden, D. L. (Editor); Goldhagen, P. (Editor)

    2003-01-01

    The United States initiated a program to assess the technology required for an environmentally safe and operationally efficient High Speed Civil Transport (HSCT) for entrance on the world market after the turn of the century. Due to the changing regulations on radiation exposures and the growing concerns over uncertainty in our knowledge of atmospheric radiations, the NASA High Speed Research Project Office (HSRPO) commissioned a review of "Radiation Exposure and High-Altitude Flight" by the National Council on Radiation Protection and Measurements (NCRP). On the basis of the NCRP recommendations, the HSRPO funded a flight experiment to resolve the environmental uncertainty in the atmospheric ionizing radiation levels as a step in developing an approach to minimize the radiation impact on HSCT operations. To minimize costs in this project, an international investigator approach was taken to assure coverage with instrument sensitivity across the range of particle types and energies to allow unique characterization of the diverse radiation components. The present workshop is a result of the flight measurements made at the maximum intensity of the solar cycle modulated background radiation levels during the month of June 1997.

  7. Exposure chamber

    DOEpatents

    Moss, Owen R.; Briant, James K.

    1983-01-01

    An exposure chamber includes an imperforate casing having a fluid inlet at the top and an outlet at the bottom. A single vertical series of imperforate trays is provided. Each tray is spaced on all sides from the chamber walls. Baffles adjacent some of the trays restrict and direct the flow to give partial flow back and forth across the chambers and downward flow past the lowermost pan adjacent a central plane of the chamber.

  8. SU-E-T-96: Demonstration of a Consistent Method for Correcting Surface Dose Measurements Using Both Solid State and Ionization Chamber Detectors

    SciTech Connect

    Reynolds, T; Gerbi, B; Higgins, P

    2014-06-01

    Purpose: To compare the surface dose (SD) measured using a PTW 30-360 extrapolation chamber with different commonly used dosimeters (Ds): parallel plate ion chambers (ICs): RMI-449 (Attix), Capintec PS-033, PTW 30-329 (Markus) and Memorial; TLD chips (cTLD), TLD powder (pTLD), optically stimulated (OSLs), radiochromic (EXR2) and radiographic (EDR2) films, and to provide an intercomparison correction to Ds for each of them. Methods: Investigations were performed for a 6 MV x-ray beam (Varian Clinac 2300, 10x10 cm{sup 2} open field, SSD = 100 cm). The Ds were placed at the surface of the solid water phantom and at the reference depth dref=1.7cm. The measurements for cTLD, OSLs, EDR2 and EXR2 were corrected to SD using an extrapolation method (EM) indexed to the baseline PTW 30-360 measurements. A consistent use of the EM involved: 1) irradiation of three Ds stacked on top of each other on the surface of the phantom; 2) measurement of the relative dose value for each layer; and, 3) extrapolation of these values to zero thickness. An additional measurement was performed with externally exposed OSLs (eOSLs), that were rotated out of their protective housing. Results: All single Ds measurements overestimated the SD compared with the extrapolation chamber, except for Attix IC. The closest match to the true SD was measured with the Attix IC (− 0.1%), followed by pTLD (0.5%), Capintec (4.5%), Memorial (7.3%), Markus (10%), cTLD (11.8%), eOSL (12.8%), EXR2 (14%), EDR2 (14.8%) and OSL (26%). The EM method of correction for SD worked well for all Ds, except the unexposed OSLs. Conclusion: This EM cross calibration of solid state detectors with an extrapolation or Attix chamber can provide thickness corrections for cTLD, eOSLs, EXR2, and EDR2. Standard packaged OSLs were not found to be simply corrected.

  9. SU-E-P-35: Real-Time Patient Transit Dose Verification of Volumetric Modulated Arc Radiotherapy by a 2D Ionization Chamber Array

    SciTech Connect

    Liu, X

    2015-06-15

    Purpose: To explore the real-time dose verification method in volumetric modulated arc radiotherapy (VMAT) with a 2D array ion chamber array. Methods: The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source-detector distance (SDD)was 140cm. 8mm RW3 solid water was added to the detector panel to achieve maximum readings.The patient plans for esophageal, prostate and liver cancers were selected to deliver on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real-time patient transit dose measurements were performed at each fraction. Dose distributions wereevaluated using gamma index criteria of 3mm DTA and 3% dose difference referred to the firsttime Result. Results: The gamma index pass rate in the Cheese phantom were about 98%; The gamma index pass rate for esophageal, liver and prostate cancer patient were about 92%,94%, and 92%, respectively; Gamma pass rate for all single fraction were more than 90%. Conclusion: The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.

  10. Effect of electron divergence in air gaps on the measurement of the energy of cascades in emulsion chambers

    NASA Technical Reports Server (NTRS)

    Apanasenko, A. V.; Baradzey, L. T.; Kanevskaya, Y. A.; Smorodin, Y. A.

    1975-01-01

    The effect of an increase in electron density in the vicinity of the cascade axis caused by an avalanche passing through the gap between lead filters of the emulsion chamber was investigated experimentally. Optical densities were measured in three X-ray films spaced at 400, 800 and 1200 micrometer from the filter surface having a thickness of 6 cascade units. The optical densities of blackening spots caused by electron photon cascades of 1 to 2, 2 to 7 and greater than 7 BeV energies were measured. The results prove the presence of a gap between the filter and the nuclear emulsion which results in the underestimation of energy by several tenths of a percent.

  11. Application of FIGAERO (Filter Inlet for Gases and AEROsol) coupled to a high resolution time of flight chemical ionization mass spectrometer to field and chamber organic aerosol: Implications for carboxylic acid formation and gas-particle partitioning from monoterpene oxidation

    NASA Astrophysics Data System (ADS)

    Lopez-Hilfiker, F.; Mohr, C.; Ehn, M.; Rubach, F.; Mentel, T. F.; Kleist, E.; Wildt, J.; Thornton, J. A.

    2013-12-01

    We present measurements of a large suite of gas and particle phase carboxylic acid containing compounds made with a Filter Inlet for Gas and AEROsol (FIGAERO) coupled to a high resolution time of flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. A prototype operated with acetate negative ion proton transfer chemistry was deployed on the Julich Plant Atmosphere Chamber to study a-pinene oxidation, and a modified version was deployed at the SMEAR II forest station in Hyytiälä, Finland and SOAS, in Brent Alabama. We focus here on results from JPAC and Hyytiälä, where we utilized the same ionization method most selective towards carboxylic acids. In all locations, 100's of organic acid compounds were observed in the gas and particles and many of the same composition acids detected in the gas-phase were detected in the particles upon temperature programmed thermal desorption. Particulate organics detected by FIGAERO are highly correlated with organic aerosol mass measured by an AMS, providing additional volatility and molecular level information about collected aerosol. The fraction of a given compound measured in the particle phase follows expected trends with elemental composition, but many compounds would not be well described by an absorptive partitioning model assuming unity activity coefficients. Moreover the detailed structure in the thermal desorption signals reveals a contribution from thermal decomposition of large molecular weight organics and or oligomers with implications for partitioning measurements and model validation

  12. Post-flight Analysis of the Argon Filled Ion Chamber

    NASA Technical Reports Server (NTRS)

    Tai, H.; Goldhagen, P.; Jones, I. W.; Wilson, J. W.; Maiden, D. L.; Shinn, J. L.

    2003-01-01

    Atmospheric ionizing radiation is a complex mixture of primary galactic and solar cosmic rays and a multitude of secondary particles produced in collision with air nuclei. The first series of Atmospheric Ionizing Radiation (AIR) measurement flights on the NASA research aircraft ER-2 took place in June 1997. The ER-2 flight package consisted of fifteen instruments from six countries and were chosen to provide varying sensitivity to specific components. These AIR ER-2 flight measurements are to characterize the AIR environment during solar minimum to allow the continued development of environmental models of this complex mixture of ionizing radiation. This will enable scientists to study the ionizing radiation health hazard associated with the high-altitude operation of a commercial supersonic transport and to allow estimates of single event upsets for advanced avionics systems design. The argon filled ion chamber representing about 40 percent of the contributions to radiation risks are analyzed herein and model discrepancies for solar minimum environment are on the order of 5 percent and less. Other biologically significant components remain to be analyzed.

  13. Novel chamber to measure equilibrium soil-air partitioning coefficients of low-volatility organic chemicals under conditions of varying temperature and soil moisture.

    PubMed

    Wolters, André; Linnemann, Volker; Smith, Kilian E C; Klingelmann, Eva; Park, Byung-Jun; Vereecken, Harry

    2008-07-01

    The need to determine soil-air partitioning coefficients (K(SA)) of low-volatility organic chemicals as a measure of their distribution in the soil surface after release into the environment resulted in the development of a novel chamber system, which has been filed for patent. A major advantage of this pseudo-static system is that sufficient time can be factored into the experiment to ensure that the system has achieved equilibrium. In a highly precise method, the air is collected in adsorption tubes and subsequently liberated in a thermodesorption system for the quantitation of the adsorbed compound. The precision of the method is great enough that even the effects of temperature and soil moisture on the soil-air partitioning of very low-volatility compounds can be quantified. Because of analytical detection limits, quantitation of these influences has not been possible to date. Functionality of the setup was illustrated by measurements on the fungicide fenpropimorph. K(SA) values of fenpropimorph displayed a negative relationship with temperature and soil moisture. The type of application (spraying or incorporation) and the use of formulated compounds was shown to have a major impact on the measured K(SA) values. Comparison with calculations using an estimation method revealed that the use of experimentally determined K(SA) values will facilitate a more adequate consideration of volatilization in recent model approaches. PMID:18678019

  14. Roos and NACP-02 ion chamber perturbations and water-air stopping-power ratios for clinical electron beams for energies from 4 to 22 MeV.

    PubMed

    Bailey, M; Shipley, D R; Manning, J W

    2015-02-01

    Empirical fits are developed for depth-compensated wall- and cavity-replacement perturbations in the PTW Roos 34001 and IBA / Scanditronix NACP-02 parallel-plate ionisation chambers, for electron beam qualities from 4 to 22 MeV for depths up to approximately 1.1 × R₅₀,D. These are based on calculations using the Monte Carlo radiation transport code EGSnrc and its user codes with a full simulation of the linac treatment head modelled using BEAMnrc. These fits are used with calculated restricted stopping-power ratios between air and water to match measured depth-dose distributions in water from an Elekta Synergy clinical linear accelerator at the UK National Physical Laboratory. Results compare well with those from recent publications and from the IPEM 2003 electron beam radiotherapy Code of Practice. PMID:25586026

  15. Calibration of the RSS-131 high efficiency ionization chamber for radiation dose monitoring during plasma experiments conducted on plasma focus device

    NASA Astrophysics Data System (ADS)

    Szewczak, Kamil; Jednoróg, Sławomir

    2014-10-01

    Plasma research poses a radiation hazard. Due to the program of deuterium plasma research using the PF-1000 device, it is an intensive source of neutrons (up to 1011 n · pulse -1) with energy of 2,45 MeV and ionizing electromagnetic radiation with a broad energy spectrum. Both types of radiation are mostly emitted in ultra-short pulses (˜100 ns). The aim of this work was to test and calibrate the RSS-131 radiometer for its application in measurements of ultra-short electromagnetic radiation pulses with broad energy spectrum emitted during PF-1000 discharge. In addition, the results of raw measurements performed in the control room are presented.

  16. Design, Modeling, Fabrication, and Evaluation of the Air Amplifier for Improved Detection of Biomolecules by Electrospray Ionization Mass Spectrometry

    PubMed Central

    Robichaud, Guillaume; Dixon, R. Brent; Potturi, Amarnatha S.; Cassidy, Dan; Edwards, Jack R.; Sohn, Alex; Dow, Thomas A.; Muddiman, David C.

    2010-01-01

    Through a multi-disciplinary approach, the air amplifier is being evolved as a highly engineered device to improve detection limits of biomolecules when using electrospray ionization. Several key aspects have driven the modifications to the device through experimentation and simulations. We have developed a computer simulation that accurately portrays actual conditions and the results from these simulations are corroborated by the experimental data. These computer simulations can be used to predict outcomes from future designs resulting in a design process that is efficient in terms of financial cost and time. We have fabricated a new device with annular gap control over a range of 50 to 70 μm using piezoelectric actuators. This has enabled us to obtain better aerodynamic performance when compared to the previous design (2× more vacuum) and also more reproducible results. This is allowing us to study a broader experimental space than the previous design which is critical in guiding future directions. This work also presents and explains the principles behind a fractional factorial design of experiments methodology for testing a large number of experimental parameters in an orderly and efficient manner to understand and optimize the critical parameters that lead to obtain improved detection limits while minimizing the number of experiments performed. Preliminary results showed that several folds of improvements could be obtained for certain condition of operations (up to 34 folds). PMID:21499524

  17. Experimental determination of beam quality factors, kQ, for two types of Farmer chamber in a 10 MV photon and a 175 MeV proton beam.

    PubMed

    Medin, Joakim; Ross, Carl K; Klassen, Norman V; Palmans, Hugo; Grusell, Erik; Grindborg, Jan-Erik

    2006-03-21

    Absorbed doses determined with a sealed water calorimeter operated at 4 degrees C are compared with the results obtained using ionization chambers and the IAEA TRS-398 code of practice in a 10 MV photon beam (TPR(20,10) = 0.734) and a 175 MeV proton beam (at a depth corresponding to the residual range, R(res) = 14.7 cm). Three NE 2571 and two FC65-G ionization chambers were calibrated in terms of absorbed-dose-to-water in (60)Co at the Swedish secondary standard dosimetry laboratory, directly traceable to the BIPM. In the photon beam quality, calorimetry was found to agree with ionometry within 0.3%, confirming the k(Q) values tabulated in TRS-398. In contrast, a 1.8% deviation was found in the proton beam at 6 g cm(-2) depth, suggesting that the TRS-398 tabulated k(Q) values for these two ionization chamber types are too high. Assuming no perturbation effect in the proton beam for the ionization chambers, a value for (w(air)/e)(Q) of 33.6 J C(-1) +/- 1.7% (k = 1) can be derived from these measurements. An analytical evaluation of the effect from non-elastic nuclear interactions in the ionization chamber wall indicates a perturbation effect of 0.6%. Including this estimated result in the proton beam would increase the determined (w(air)/e)(Q) value by the same amount. PMID:16510959

  18. Wire chamber

    DOEpatents

    Atac, Muzaffer

    1989-01-01

    A wire chamber or proportional counter device, such as Geiger-Mueller tube or drift chamber, improved with a gas mixture providing a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor.

  19. Formic and Acetic Acid Observations over Colorado by Chemical Ionization Mass Spectrometry and Organic Acids' Role in Air Quality

    NASA Astrophysics Data System (ADS)

    Treadaway, V.; O'Sullivan, D. W.; Heikes, B.; Silwal, I.; McNeill, A.

    2015-12-01

    Formic acid (HFo) and acetic acid (HAc) have both natural and anthropogenic sources and a role in the atmospheric processing of carbon. These organic acids also have an increasing importance in setting the acidity of rain and snow as precipitation nitrate and sulfate concentrations have decreased. Primary emissions for both organic acids include biomass burning, agriculture, and motor vehicle emissions. Secondary production is also a substantial source for both acids especially from biogenic precursors, secondary organic aerosols (SOAs), and photochemical production from volatile organic compounds (VOCs) and oxygenated volatile organic compounds (OVOCs). Chemical transport models underestimate organic acid concentrations and recent research has sought to develop additional production mechanisms. Here we report HFo and HAc measurements during two campaigns over Colorado using the peroxide chemical ionization mass spectrometer (PCIMS). Iodide clusters of both HFo and HAc were recorded at mass-to-charge ratios of 173 and 187, respectively. The PCIMS was flown aboard the NCAR Gulfstream-V platform during the Deep Convective Clouds and Chemistry Experiment (DC3) and aboard the NCAR C-130 during the Front Range Air Pollution and Photochemistry Experiment (FRAPPE). The DC3 observations were made in May and June 2012 extending from the surface to 13 km over the central and eastern United States. FRAPPE observations were made in July and August 2014 from the surface to 7 km over Colorado. DC3 measurements reported here are focused over the Colorado Front Range and complement the FRAPPE observations. DC3 HFo altitude profiles are characterized by a decrease up to 6 km followed by an increase either back to boundary layer mixing ratio values or higher (a "C" shape). Organic acid measurements from both campaigns are interpreted with an emphasis on emission sources (both natural and anthropogenic) over Colorado and in situ photochemical production especially ozone precursors.

  20. Electrochemically exfoliated graphene anodes with enhanced biocurrent production in single-chamber air-breathing microbial fuel cells.

    PubMed

    Najafabadi, Amin Taheri; Ng, Norvin; Gyenge, Előd

    2016-07-15

    Microbial fuel cells (MFCs) present promising options for environmentally sustainable power generation especially in conjunction with waste water treatment. However, major challenges remain including low power density, difficult scale-up, and durability of the cell components. This study reports enhanced biocurrent production in a membrane-free MFC, using graphene microsheets (GNs) as anode and MnOx catalyzed air cathode. The GNs are produced by ionic liquid assisted simultaneous anodic and cathodic electrochemical exfoliation of iso-molded graphite electrodes. The GNs produced by anodic exfoliation increase the MFC peak power density by over 300% compared to plain carbon cloth (i.e., 2.85Wm(-2) vs 0.66Wm(-2), respectively), and by 90% compared to conventional carbon black (i.e., Vulcan XC-72) anode. These results exceed previously reported power densities for graphene-containing MFC anodes. The fuel cell polarization results are corroborated by electrochemical impedance spectroscopy indicating three times lower charge transfer resistance for the GN anode. Material characterizations suggest that the best performing GN samples were of relatively smaller size (~500nm), with higher levels of ionic liquid induced surface functionalization during the electrochemical exfoliation process. PMID:26926591

  1. The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 plus.

    PubMed

    Bohm, Tim D; Griffin, Sheridan L; DeLuca, Paul M; DeWerd, Larry A

    2005-04-01

    The determination of the air kerma strength of a brachytherapy seed is necessary for effective treatment planning. Well ionization chambers are used on site at therapy clinics to determine the air kerma strength of seeds. In this work, the response of the Standard Imaging HDR 1000 Plus well chamber to ambient pressure is examined using Monte Carlo calculations. The experimental work examining the response of this chamber as well as other chambers is presented in a companion paper. The Monte Carlo results show that for low-energy photon sources, the application of the standard temperature pressure PTP correction factor produces an over-response at the reduced air densities/pressures corresponding to high elevations. With photon sources of 20 to 40 keV, the normalized PTP corrected chamber response is as much as 10% to 20% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. At air densities corresponding to an elevation of 1524 m (5000 ft), the normalized PTP-corrected chamber response is 5% to 10% over unity for these photon sources. With higher-energy photon sources (>100 keV), the normalized PTP corrected chamber response is near unity. For low-energy beta sources of 0.25 to 0.50 MeV, the normalized PTP-corrected chamber response is as much as 4% to 12% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. Higher-energy beta sources (>0.75 MeV) have a normalized PTP corrected chamber response near unity. Comparing calculated and measured chamber responses for common 103Pd- and 125I-based brachytherapy seeds show agreement to within 2.7% and 1.9%, respectively. Comparing MCNP calculated chamber responses with EGSnrc calculated chamber responses show agreement to within 3.1% at photon energies of 20 to 40 keV. We conclude that Monte Carlo transport calculations accurately model the response of this well chamber. Further, applying the standard PTP correction

  2. The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 Plus

    SciTech Connect

    Bohm, Tim D.; Griffin, Sheridan L.; DeLuca, Paul M. Jr.; DeWerd, Larry A.

    2005-04-01

    The determination of the air kerma strength of a brachytherapy seed is necessary for effective treatment planning. Well ionization chambers are used on site at therapy clinics to determine the air kerma strength of seeds. In this work, the response of the Standard Imaging HDR 1000 Plus well chamber to ambient pressure is examined using Monte Carlo calculations. The experimental work examining the response of this chamber as well as other chambers is presented in a companion paper. The Monte Carlo results show that for low-energy photon sources, the application of the standard temperature pressure P{sub TP} correction factor produces an over-response at the reduced air densities/pressures corresponding to high elevations. With photon sources of 20 to 40 keV, the normalized P{sub TP} corrected chamber response is as much as 10% to 20% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. At air densities corresponding to an elevation of 1524 m (5000 ft), the normalized P{sub TP}-corrected chamber response is 5% to 10% over unity for these photon sources. With higher-energy photon sources (>100 keV), the normalized P{sub TP} corrected chamber response is near unity. For low-energy {beta} sources of 0.25 to 0.50 MeV, the normalized P{sub TP}-corrected chamber response is as much as 4% to 12% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. Higher-energy {beta} sources (>0.75 MeV) have a normalized P{sub TP} corrected chamber response near unity. Comparing calculated and measured chamber responses for common {sup 103}Pd- and {sup 125}I-based brachytherapy seeds show agreement to within 2.7% and 1.9%, respectively. Comparing MCNP calculated chamber responses with EGSnrc calculated chamber responses show agreement to within 3.1% at photon energies of 20 to 40 keV. We conclude that Monte Carlo transport calculations accurately model the response of this well

  3. Exchange of atmospheric formic and acetic acids with trees and crop plants under controlled chamber and purified air conditions

    NASA Astrophysics Data System (ADS)

    Kesselmeier, J.; Bode, K.; Gerlach, C.; Jork, E.-M.

    We investigated the exchange of formic and acetic acids between the atmosphere and various tree species such as beech ( Fagus sylvatica L.), ash ( Fraxinus excelsior L.), spruce ( Picea abies L.) Karst, holm oak ( Quercus ilex L.), and birch ( Betula pendula L.). and some crop-plant species such as corn ( Zea mays, var. Banjo), pea ( Pisum sativum, var. Solara), barley ( Hordeum vulgare, var. Igri) and oat (Avena sativa, var. Wiesel). All experiments were done with dynamic enclosures flushed with purified oxidant-free air, containing only low or controlled amounts of the two acids. Significant and light-triggered emission of both acids from all tree species was observed. For one tree species (ash) a seasonal large increase in fall due to early leaf decomposition was found. The standard emission factors (30°C and PAR=1000 μmol m 2 s -1) given as (nmol m -2 min -1) for acetic and formic acids, respectively, were 8.1 and 29.7 (ash, autumn), 1.0 and 3.3 (ash, summer), 0.9 and 1.4 (beech), 0.7 and 1.45 (spruce), 1.9 and 2.4 (Holm oak) and 1.7 and 6.7 (birch). Rough estimation of global annual emissions range between 20 and 130 Gmol formic acid and 10 and 33 Gmol acetic acid. These numbers reflect a 15-30% contribution by forest emissions to the continental organic acid budget. As compared to the global total NMHC emissions low molecular weight organic acids are of minor importance. In contrast to the trees, none of the crop-plant species investigated showed an emission, but always a clear deposition of both acids. Both emission from trees as well as uptake by the agricultural plants could be related to transpiration rates and leaf conductances.

  4. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  5. Method for automatic determination of soybean actual evapotranspiration under open top chambers (OTC) subjected to effects of water stress and air ozone concentration.

    PubMed

    Rana, Gianfranco; Katerji, Nader; Mastrorilli, Marcello

    2012-10-01

    The present study describes an operational method, based on the Katerji et al. (Eur J Agron 33:218-230, 2010) model, for determining the daily evapotranspiration (ET) for soybean inside open top chambers (OTCs). It includes two functions, calculated day par day, making it possible to separately take into account the effects of concentrations of air ozone and plant water stress. This last function was calibrated in function of the daily values of actual water reserve in the soil. The input variables of the method are (a) the diurnal values of global radiation and temperature, usually measured routinely in a standard weather station; (b) the daily values of the AOT40 index accumulated (accumulated ozone over a threshold of 40 ppb during daylight hours, when global radiation exceeds 50 Wm(-2)) determined inside the OTC; and (c) the actual water reserve in the soil, at the beginning of the trial. The ensemble of these input variables can be automatable; thus, the proposed method could be applied in routine. The ability of the method to take into account contrasting conditions of ozone air concentration and water stress was evaluated over three successive years, for 513 days, in ten crop growth cycles, excluding the days employed to calibrate the method. Tests were carried out in several chambers for each year and take into account the intra- and inter-year variability of ET measured inside the OTCs. On the daily scale, the slope of the linear regression between the ET measured by the soil water balance and that calculated by the proposed method, under different water conditions, are 0.98 and 1.05 for the filtered and unfiltered (or enriched) OTCs with root mean square error (RMSE) equal to 0.77 and 1.07 mm, respectively. On the seasonal scale, the mean difference between measured and calculated ET is equal to +5% and +11% for the filtered and unfiltered OTCs, respectively. The ability of the proposed method to estimate the daily and seasonal ET inside the OTCs is

  6. Development of a particle-trap preconcentration-soft ionization mass spectrometric technique for the quantification of mercury halides in air.

    PubMed

    Deeds, Daniel A; Ghoshdastidar, Avik; Raofie, Farhad; Guérette, Élise-Andrée; Tessier, Alain; Ariya, Parisa A

    2015-01-01

    Measurement of oxidized mercury, Hg(II), in the atmosphere poses a significant analytical challenge as Hg(II) is present at ultra-trace concentrations (picograms per cubic meter air). Current technologies are sufficiently sensitive to measure the total Hg present as Hg(II) but cannot determine the chemical speciation of Hg(II). We detail here the development of a soft ionization mass spectrometric technique coupled with preconcentration onto nano- or microparticle-based traps prior to analysis for the measurement of mercury halides in air. The current methodology has comparable detection limits (4-11 pg m(-3)) to previously developed techniques for the measurement of total inorganic mercury in air while allowing for the identification of HgX2 in collected samples. Both mercury chloride and mercury bromide have been sporadically detected in Montreal urban and indoor air using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). We discuss limitations and advantages of the current technique and discuss potential avenues for future research including quantitative trace measurements of a larger range of mercury compounds. PMID:25837315

  7. Iron-nitrogen-activated carbon as cathode catalyst to improve the power generation of single-chamber air-cathode microbial fuel cells.

    PubMed

    Pan, Yajun; Mo, Xiaoping; Li, Kexun; Pu, Liangtao; Liu, Di; Yang, Tingting

    2016-04-01

    In order to improve the performance of microbial fuel cell (MFC), iron-nitrogen-activated carbon (Fe-N-C) as an excellent oxygen reduction reaction (ORR) catalyst was prepared here using commercial activated carbon (AC) as matrix and employed in single chamber MFC. In MFC, the maximum power density increased to 2437±55mWm(-2), which was 2 times of that with AC. The open circuit potential (OCP) of Fe-N-C cathode (0.47) was much higher than that of AC cathode (0.21V). The R0 of Fe-N-C decreased by 47% from 14.36Ω (AC) to 7.6Ω (Fe-N-C). From X-ray photoelectron spectroscopy (XPS), pyridinic nitrogen, quaternary nitrogen and iron species were present, which played an important role in the ORR performance of Fe-N-C. These results demonstrated that the as-prepared Fe-N-C material provided a potential alternative to Pt in AC air cathode MFC for relatively desirable energy generation and wastewater treatment. PMID:26898678

  8. Effect of chemically modified Vulcan XC-72R on the performance of air-breathing cathode in a single-chamber microbial fuel cell.

    PubMed

    Duteanu, N; Erable, B; Senthil Kumar, S M; Ghangrekar, M M; Scott, K

    2010-07-01

    The catalytic activity of modified carbon powder (Vulcan XC-72R) for oxygen reduction reaction (ORR) in an air-breathing cathode of a microbial fuel cell (MFC) has been investigated. Chemical modification was carried out by using various chemicals, namely 5% nitric acid, 0.2N phosphoric acid, 0.2N potassium hydroxide and 10% hydrogen peroxide. Electrochemical study was performed for ORR of these modified carbon materials in the buffer solution pH range of 6-7.5 in the anodic compartment. Although, these treatments influenced the surface properties of the carbon material, as evident from the SEM-EDX analysis, treatment with H(2)PO(4), KOH, and H(2)O(2) did not show significant activity during the electrochemical test. The HNO(3) treated Vulcan demonstrated significant ORR activity and when used in the single-chamber MFC cathode, current densities (1115mA/m(2), at 5.6mV) greater than those for a Pt-supported un-treated carbon cathode were achieved. However, the power density for the latter was higher. Such chemically modified carbon material can be a cheaper alternative for expensive platinum catalyst used in MFC cathode construction. PMID:20171090

  9. CONTINUOUSLY SENSITIVE BUBBLE CHAMBER

    DOEpatents

    Good, R.H.

    1959-08-18

    A radiation detector of the bubble chamber class is described which is continuously sensitive and which does not require the complex pressure cycling equipment characteristic of prior forms of the chamber. The radiation sensitive element is a gas-saturated liquid and means are provided for establishing a thermal gradient across a region of the liquid. The gradient has a temperature range including both the saturation temperature of the liquid and more elevated temperatures. Thus a supersaturated zone is created in which ionizing radiations may give rise to visible gas bubbles indicative of the passage of the radiation through the liquid. Additional means are provided for replenishing the supply of gas-saturated liquid to maintaincontinuous sensitivity.

  10. Sensitive monitoring of volatile chemical warfare agents in air by atmospheric pressure chemical ionization mass spectrometry with counter-flow introduction.

    PubMed

    Seto, Yasuo; Kanamori-Kataoka, Mieko; Tsuge, Koichiro; Ohsawa, Isaac; Iura, Kazumitsu; Itoi, Teruo; Sekiguchi, Hiroyuki; Matsushita, Koji; Yamashiro, Shigeharu; Sano, Yasuhiro; Sekiguchi, Hiroshi; Maruko, Hisashi; Takayama, Yasuo; Sekioka, Ryoji; Okumura, Akihiko; Takada, Yasuaki; Nagano, Hisashi; Waki, Izumi; Ezawa, Naoya; Tanimoto, Hiroyuki; Honjo, Shigeru; Fukano, Masumi; Okada, Hidehiro

    2013-03-01

    A new method for sensitively and selectively detecting chemical warfare agents (CWAs) in air was developed using counter-flow introduction atmospheric pressure chemical ionization mass spectrometry (MS). Four volatile and highly toxic CWAs were examined, including the nerve gases sarin and tabun, and the blister agents mustard gas (HD) and Lewisite 1 (L1). Soft ionization was performed using corona discharge to form reactant ions, and the ions were sent in the direction opposite to the airflow by an electric field to eliminate the interfering neutral molecules such as ozone and nitrogen oxide. This resulted in efficient ionization of the target CWAs, especially in the negative ionization mode. Quadrupole MS (QMS) and ion trap tandem MS (ITMS) instruments were developed and investigated, which were movable on the building floor. For sarin, tabun, and HD, the protonated molecular ions and their fragment ions were observed in the positive ion mode. For L1, the chloride adduct ions of L1 hydrolysis products were observed in negative ion mode. The limit of detection (LOD) values in real-time or for a 1 s measurement monitoring the characteristic ions were between 1 and 8 μg/m(3) in QMS instrument. Collision-induced fragmentation patterns for the CWAs were observed in an ITMS instrument, and optimized combinations of the parent and daughter ion pairs were selected to achieve real-time detection with LOD values of around 1 μg/m(3). This is a first demonstration of sensitive and specific real-time detection of both positively and negatively ionizable CWAs by MS instruments used for field monitoring. PMID:23339735

  11. Comparison of negative-ion proton-transfer with iodide ion chemical ionization mass spectrometry for quantification of isocyanic acid in ambient air

    NASA Astrophysics Data System (ADS)

    Woodward-Massey, Robert; Taha, Youssef M.; Moussa, Samar G.; Osthoff, Hans D.

    2014-12-01

    Isocyanic acid (HNCO) is a trace gas pollutant of potential importance to human health whose measurement has recently become possible through the development of negative-ion proton-transfer chemical ionization mass spectrometry (NI-PT-CIMS) with acetate reagent ion. In this manuscript, an alternative ionization and detection scheme, in which HNCO is quantified by iodide CIMS (iCIMS) as a cluster ion at m/z 170, is described. The sensitivity was inversely proportional to water vapor concentration but could be made independent of humidity changes in the sampled air by humidifying the ion-molecule reaction (IMR) region of the CIMS. The performance of the two ionization schemes was compared and contrasted using ambient air measurements of HNCO mixing ratios in Calgary, AB, Canada, by NI-PT-CIMS with acetate reagent ion from Dec 16 to 20, 2013, and by the same CIMS operated in iCIMS mode from Feb 3 to 7, 2014. The iCIMS exhibited a greater signal-to-noise ratio than the NI-PT-CIMS, not because of its sensitivity, which was lower (˜0.083 normalized counts per second (NCPS) per parts-per-trillion by volume (pptv) compared to ˜9.7 NCPS pptv-1), but because of a much lower and more stable background (3 ± 4 compared to a range of ˜2 × 103 to ˜6 × 103 NCPS). For the Feb 2014 data set, the HNCO mixing ratios in Calgary air ranged from <12 to 94 pptv (median 34 pptv), were marginally higher at night than during day, and correlated with nitrogen oxide (NOx = NO + NO2) mixing ratios and submicron particle volume. The ratios of HNCO to NOx observed are within the range of emission ratios reported for gasoline-powered motor vehicles.

  12. Multisegmented ion chamber for CT scanner dosimetry

    SciTech Connect

    Moore, M.M.; Cacak, R.K.; Hendee, W.R.

    1981-01-01

    A multisegmented, ionization chamber capable of determining dosimetric profiles from a CT scanner has been developed and tested. The chamber consists of a number of 2 mm wide electrically isolated segments from which ionization currents may be measured. Presented here are the performance characteristics of the chamber including energy response, dose linearity, and corrections for ''cross talk'' between segments. Sample dosimetric profiles are depicted for 3 and 6 mm nominal beam widths at two locations in a dosimetric phantom positioned in the x-ray beam of a fourth generation CT scanner. The results agree well with the conventional method of obtaining dosimetry measurements with TLD chips.

  13. Ultrafast imaging the light-speed propagation of a focused femtosecond laser pulse in air and its ionized electron dynamics and plasma-induced pulse reshaping

    NASA Astrophysics Data System (ADS)

    Yu, Yanwu; Jiang, Lan; Cao, Qiang; Shi, Xueshong; Wang, Qingsong; Wang, Guoyan; Lu, Yongfeng

    2016-03-01

    The light-speed propagation of a focused femtosecond (fs) laser pulse in air was recorded by a pump-probe shadowgraph imaging technique with femtosecond time resolution. The ultrafast dynamics of the laser-ionized electrons were studied, which revealed a strong reshaping of the laser field due to laser-air nonlinear interaction. The influence of laser fluence and focusing conditions on the pulse reshaping was studied, and it was found that: (1) double foci are formed due to the refocusing effect when the laser fluence is higher than 500 J/cm2 and the focusing numeric aperture (NA) is higher than 0.30; and (2) a higher NA focusing lens can better inhibit the prefocusing effect and nonlinear distortion in the Gaussian beam waist.

  14. Evaluation and guidelines for using polyurethane foam (PUF) passive air samplers in double-dome chambers to assess semi-volatile organic compounds (SVOCs) in non-industrial indoor environments.

    PubMed

    Bohlin, Pernilla; Audy, Ondřej; Škrdlíková, Lenka; Kukučka, Petr; Vojta, Šimon; Přibylová, Petra; Prokeš, Roman; Čupr, Pavel; Klánová, Jana

    2014-11-01

    Indoor air pollution has been recognized as an important risk factor for human health, especially in areas where people tend to spend most of their time indoors. Many semi-volatile organic compounds (SVOCs) have primarily indoor sources and are present in orders of magnitude higher concentrations indoors than outdoors. Despite this, awareness of SVOCs in indoor air and assessment of the link between indoor concentrations and human health have lagged behind those of outdoor air. This is partially related to challenges associated with indoor sampling of SVOCs. Passive air samplers (PASs), which are widely accepted in established outdoor air monitoring networks, have been used to fill the knowledge gaps on indoor SVOCs distribution. However, their applicability for indoor environments and the assessment of human health risks lack sufficient experimental data. To address this issue, we performed an indoor calibration study of polyurethane foam (PUF) PAS deployed in a double-dome chamber, covering both legacy and new SVOC classes. PUF-PAS and a continuous low-volume active air sampler (AAS) were co-deployed for a calibration period of twelve weeks. Based on the results from this evaluation, PUF-PAS in a double-bowl chamber is recommended for indoor sampling and health risk assessment of gas phase SVOCs, including novel brominated flame retardants (nBFR) providing sufficient exposure time is applied. Data for particle associated SVOCs suffered from significant uncertainties caused by low level of detection and low precision in this study. A more open chamber design for indoor studies may allow for higher sampling rates (RS) and better performance for the particle associated SVOCs. PMID:25274245

  15. Sensitive and comprehensive detection of chemical warfare agents in air by atmospheric pressure chemical ionization ion trap tandem mass spectrometry with counterflow introduction.

    PubMed

    Seto, Yasuo; Sekiguchi, Hiroshi; Maruko, Hisashi; Yamashiro, Shigeharu; Sano, Yasuhiro; Takayama, Yasuo; Sekioka, Ryoji; Yamaguchi, Shintaro; Kishi, Shintaro; Satoh, Takafumi; Sekiguchi, Hiroyuki; Iura, Kazumitsu; Nagashima, Hisayuki; Nagoya, Tomoki; Tsuge, Kouichiro; Ohsawa, Isaac; Okumura, Akihiko; Takada, Yasuaki; Ezawa, Naoya; Watanabe, Susumu; Hashimoto, Hiroaki

    2014-05-01

    A highly sensitive and specific real-time field-deployable detection technology, based on counterflow air introduction atmospheric pressure chemical ionization, has been developed for a wide range of chemical warfare agents (CWAs) comprising gaseous (two blood agents, three choking agents), volatile (six nerve gases and one precursor agent, five blister agents), and nonvolatile (three lachrymators, three vomiting agents) agents in air. The approach can afford effective chemical ionization, in both positive and negative ion modes, for ion trap multiple-stage mass spectrometry (MS(n)). The volatile and nonvolatile CWAs tested provided characteristic ions, which were fragmented into MS(3) product ions in positive and negative ion modes. Portions of the fragment ions were assigned by laboratory hybrid mass spectrometry (MS) composed of linear ion trap and high-resolution mass spectrometers. Gaseous agents were detected by MS or MS(2) in negative ion mode. The limits of detection for a 1 s measurement were typically at or below the microgram per cubic meter level except for chloropicrin (submilligram per cubic meter). Matrix effects by gasoline vapor resulted in minimal false-positive signals for all the CWAs and some signal suppression in the case of mustard gas. The moisture level did influence the measurement of the CWAs. PMID:24678766

  16. Magma chambers

    NASA Technical Reports Server (NTRS)

    Marsh, Bruce D.

    1989-01-01

    Recent observational and theoretical investigations of terrestrial magma chambers (MCs) are reviewed. Consideration is given to the evidence for MCs with active convection and crystal sorting, problems of direct MC detection, theoretical models of MC cooling, the rheology and dynamics of solidification fronts, crystal capture and differentiation, convection with solidification, MC wall flows, and MC roof melting. Diagrams, graphs, and a list of problems requiring further research are provided.

  17. Analytical method validation for the determination of 2,3,3,3-tetrafluoropropene in air samples using gas chromatography with flame ionization detection.

    PubMed

    Mawn, Michael P; Kurtz, Kristine; Stahl, Deborah; Chalfant, Richard L; Koban, Mary E; Dawson, Barbara J

    2013-01-01

    A new low global warming refrigerant, 2,3,3,3-tetrafluoro propene, or HFO-1234yf, has been successfully evaluated for automotive air conditioning, and is also being evaluated for stationary refrigeration and air conditioning systems. Due to the advantageous environmental properties of HFO-1234yf versus HFC-134a, coupled with its similar physical properties and system performance, HFO-1234yf is also being evaluated to replace HFC-134a in refrigeration applications where neat HFC-134a is currently used. This study reports on the development and validation of a sampling and analytical method for the determination of HFO-1234yf in air. Different collection media were screened for desorption and simulated sampling efficiency with three-section (350/350/350 mg) Anasorb CSC showing the best results. Therefore, air samples were collected using two 3-section Anasorb CSC sorbent tubes in series at 0.02 L/min for up to 8 hr for sample volumes of up to 9.6 L. The sorbent tubes were extracted in methylene chloride, and analyzed by gas chromatography with flame ionization detection. The method was validated from 0.1× to 20× the target level of 0.5 ppm (2.3 mg/m(3)) for a 9.6 L air volume. Desorption efficiencies for HFO-1234yf were 88 to 109% for all replicates over the validation range with a mean overall recovery of 93%. Simulated sampling efficiencies ranged from 87 to 104% with a mean of 94%. No migration or breakthrough to the back tube was observed under the sampling conditions evaluated. HFO-1234yf samples showed acceptable storage stability on Anasorb CSC sorbent up to a period of 30 days when stored under ambient, refrigerated, or frozen temperature conditions. PMID:24116663

  18. Microplasma Ionization of Volatile Organics for Improving Air/Water Monitoring Systems On-Board the International Space Station.

    PubMed

    Bernier, Matthew C; Alberici, Rosana M; Keelor, Joel D; Dwivedi, Prabha; Zambrzycki, Stephen C; Wallace, William T; Gazda, Daniel B; Limero, Thomas F; Symonds, Josh M; Orlando, Thomas M; Macatangay, Ariel; Fernández, Facundo M

    2016-07-01

    Low molecular weight polar organics are commonly observed in spacecraft environments. Increasing concentrations of one or more of these contaminants can negatively impact Environmental Control and Life Support (ECLS) systems and/or the health of crew members, posing potential risks to the success of manned space missions. Ambient plasma ionization mass spectrometry (MS) is finding effective use as part of the analytical methodologies being tested for next-generation space module environmental analysis. However, ambient ionization methods employing atmospheric plasmas typically require relatively high operation voltages and power, thus limiting their applicability in combination with fieldable mass spectrometers. In this work, we investigate the use of a low power microplasma device in the microhollow cathode discharge (MHCD) configuration for the analysis of polar organics encountered in space missions. A metal-insulator-metal (MIM) structure with molybdenum foil disc electrodes and a mica insulator was used to form a 300 μm diameter plasma discharge cavity. We demonstrate the application of these MIM microplasmas as part of a versatile miniature ion source for the analysis of typical volatile contaminants found in the International Space Station (ISS) environment, highlighting their advantages as low cost and simple analytical devices. Graphical Abstract ᅟ. PMID:27080004

  19. Microplasma Ionization of Volatile Organics for Improving Air/Water Monitoring Systems On-Board the International Space Station

    NASA Astrophysics Data System (ADS)

    Bernier, Matthew C.; Alberici, Rosana M.; Keelor, Joel D.; Dwivedi, Prabha; Zambrzycki, Stephen C.; Wallace, William T.; Gazda, Daniel B.; Limero, Thomas F.; Symonds, Josh M.; Orlando, Thomas M.; Macatangay, Ariel; Fernández, Facundo M.

    2016-04-01

    Low molecular weight polar organics are commonly observed in spacecraft environments. Increasing concentrations of one or more of these contaminants can negatively impact Environmental Control and Life Support (ECLS) systems and/or the health of crew members, posing potential risks to the success of manned space missions. Ambient plasma ionization mass spectrometry (MS) is finding effective use as part of the analytical methodologies being tested for next-generation space module environmental analysis. However, ambient ionization methods employing atmospheric plasmas typically require relatively high operation voltages and power, thus limiting their applicability in combination with fieldable mass spectrometers. In this work, we investigate the use of a low power microplasma device in the microhollow cathode discharge (MHCD) configuration for the analysis of polar organics encountered in space missions. A metal-insulator-metal (MIM) structure with molybdenum foil disc electrodes and a mica insulator was used to form a 300 μm diameter plasma discharge cavity. We demonstrate the application of these MIM microplasmas as part of a versatile miniature ion source for the analysis of typical volatile contaminants found in the International Space Station (ISS) environment, highlighting their advantages as low cost and simple analytical devices.

  20. Microplasma Ionization of Volatile Organics for Improving Air/Water Monitoring Systems On-Board the International Space Station

    NASA Astrophysics Data System (ADS)

    Bernier, Matthew C.; Alberici, Rosana M.; Keelor, Joel D.; Dwivedi, Prabha; Zambrzycki, Stephen C.; Wallace, William T.; Gazda, Daniel B.; Limero, Thomas F.; Symonds, Josh M.; Orlando, Thomas M.; Macatangay, Ariel; Fernández, Facundo M.

    2016-07-01

    Low molecular weight polar organics are commonly observed in spacecraft environments. Increasing concentrations of one or more of these contaminants can negatively impact Environmental Control and Life Support (ECLS) systems and/or the health of crew members, posing potential risks to the success of manned space missions. Ambient plasma ionization mass spectrometry (MS) is finding effective use as part of the analytical methodologies being tested for next-generation space module environmental analysis. However, ambient ionization methods employing atmospheric plasmas typically require relatively high operation voltages and power, thus limiting their applicability in combination with fieldable mass spectrometers. In this work, we investigate the use of a low power microplasma device in the microhollow cathode discharge (MHCD) configuration for the analysis of polar organics encountered in space missions. A metal-insulator-metal (MIM) structure with molybdenum foil disc electrodes and a mica insulator was used to form a 300 μm diameter plasma discharge cavity. We demonstrate the application of these MIM microplasmas as part of a versatile miniature ion source for the analysis of typical volatile contaminants found in the International Space Station (ISS) environment, highlighting their advantages as low cost and simple analytical devices.

  1. Evaluation of w values for carbon beams in air, using a graphite calorimeter.

    PubMed

    Sakama, Makoto; Kanai, Tatsuaki; Fukumura, Akifumi; Abe, Kyoko

    2009-03-01

    Despite recent progress in carbon therapy, accurate values for physical data such as the w value in air or stopping power ratios for ionization chamber dosimetry have not been obtained. The absorbed dose to graphite obtained with the graphite calorimeter was compared with that obtained using the ionization chambers following the IAEA protocol in order to evaluate the w values in air for mono-energetic carbon beams of 135, 290, 400 and 430 MeV/n. Two cylindrical chambers (PTW type 30001 and PTW type 30011, Farmer) and two plane-parallel chambers (PTW type 23343, Markus and PTW type 34001, Roos) calibrated by the absorbed dose to graphite and exposure to the (60)Co photon beam were used. The comparisons to our calorimeter measurements revealed that, using the ionization chambers, the absorbed dose to graphite comes out low by 2-6% in this experimental energy range and with these chamber types and calibration methods. In the therapeutic energy range, the w values in air for carbon beams indicated a slight energy dependence; we, however, assumed these values to be constant for practical use because of the large uncertainty and unknown perturbation factors of the ionization chambers. The w values in air of the carbon beams were evaluated to be 35.72 J C(-1) +/- 1.5% in the energy range used in this study. This value is 3.5% larger than that recommended by the IAEA TRS 398 for heavy-ion beams. Using this evaluated result, the absorbed dose to water in the carbon beams would be increased by the same amount. PMID:19174597

  2. Determination of Hazardous Air Pollutant Surrogates Using Resonance Enhanced Multi Photon Ionization - Time of Flight Mass Spectrometry

    EPA Science Inventory

    EPA?s preferred approach for regulatory emissions compliance is based upon real-time monitoring of individual hazardous air pollutants (HAPs). Real-time, continuous monitoring not only provides the most comprehensive assurance of emissions compliance, but also can serve as a pro...

  3. Monitoring of Hazardous Air Pollutant Surrogates Using Resonance Enhanced Multiphoton Ionization/Time of Flight Mass Spectrometry

    EPA Science Inventory

    EPA’s preferred approach for regulatory emissions compliance is based upon real-time monitoring of individual hazardous air pollutants (HAPs). Real-time, continuous monitoring not only provides the most comprehensive assurance of emissions compliance, but also can serve as...

  4. Generation of Diffuse Large Volume Plasma by an Ionization Wave from a Plasma Jet

    NASA Astrophysics Data System (ADS)

    Laroussi, Mounir; Razavi, Hamid

    2015-09-01

    Low temperature plasma jets emitted in ambient air are the product of fast ionization waves that are guided within a channel of a gas flow, such as helium. This guided ionization wave can be transmitted through a dielectric material and under some conditions can ignite a discharge behind the dielectric material. Here we present a novel way to produce large volume diffuse low pressure plasma inside a Pyrex chamber that does not have any electrodes or electrical energy directly applied to it. The diffuse plasma is ignited inside the chamber by a plasma jet located externally to the chamber and that is physically and electrically unconnected to the chamber. Instead, the plasma jet is just brought in close proximity to the external wall/surface of the chamber or to a dielectric tubing connected to the chamber. The plasma thus generated is diffuse, large volume and with physical and chemical characteristics that are different than the external plasma jet that ignited it. So by using a plasma jet we are able to ``remotely'' ignite volumetric plasma under controlled conditions. This novel method of ``remote'' generation of a low pressure, low temperature diffuse plasma can be useful for various applications including material processing and biomedicine.

  5. Surface ionization of terpene hydrocarbons

    SciTech Connect

    Zandberg, E.Y.; Nezdyurov, A.L.; Paleev, V.I.; Ponomarev, D.A.

    1986-09-01

    By means of a surface ionization indicator for traces of materials in the atmosphere it has been established that many natural materials containing terpenes and their derivatives are ionized on the surface of heated molybdenum oxide at atmospheric air pressure. A mass-spectrometer method has been used to explain the mechanism of ionization of individual terpene hydrocarbons and to establish its principles. The ionization of ..cap alpha..-pinene, alloocimene, camphene, and also adamantane on oxidized tungsten under vacuum conditions has been investigated. The ..cap alpha..-pinene and alloocimene are ionized by surface ionization but camphene and adamantane are not ionized under vacuum conditions. The surface ionization mass spectra of ..cap alpha..-pinene and alloocimene are of low line brightness in comparison with electron ionization mass spectra and differ between themselves. The temperature relations for currents of the same compositions of ions during ionization of ..cap alpha..-pinene and alloocimene are also different, which leads to the possibility of surface ionization analysis of mixtures of terpenes being ionized. The ionization coefficients of alloocimene and ..cap alpha..-pinene on oxidized tungsten under temperatures optimum for ionization and the ionization potentials of alloocimene molecules and of radicals (M-H) of both compounds have been evaluated.

  6. High-efficiency electron ionizer for a mass spectrometer array

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor); Darrach, Murray R. (Inventor); Orient, Otto J. (Inventor)

    2001-01-01

    The present invention provides an improved electron ionizer for use in a quadrupole mass spectrometer. The improved electron ionizer includes a repeller plate that ejects sample atoms or molecules, an ionizer chamber, a cathode that emits an electron beam into the ionizer chamber, an exit opening for excess electrons to escape, at least one shim plate to collimate said electron beam, extraction apertures, and a plurality of lens elements for focusing the extracted ions onto entrance apertures.

  7. Establishment of air kerma reference standard for low dose rate Cs-137 brachytherapy sources.

    PubMed

    Sharma, Sunil Dutt; Kumar, Sudhir; Srinivasan, P; Chourasiya, G

    2011-01-01

    A guarded cylindrical graphite ionization chamber of nominal volume 1000 cm3 was designed and fabricated for use as a reference standard for low-dose rate 137Cs brachytherapy sources. The air kerma calibration coefficient (N(K)) of this ionization chamber was estimated analytically using Burlin's general cavity theory, as well as by the Monte Carlo simulation and validated experimentally using Amersham CDCS-J-type 137Cs reference source. In the analytical method, the N(K) was calculated for 662 keV gamma rays of 137Cs brachytherapy source. In the Monte Carlo method, the geometry of the measurement setup and physics-related input data of the 137Cs source and the surrounding material were simulated using the Monte Carlo N-Particle code. The photon energy fluence was used to arrive at the reference air kerma rate (RAKR) using mass energy absorption coefficient. The energy deposition rates were used to simulate the value of charge rate in the ionization chamber, and the N(K) was determined. The analytical and Monte Carlo values of N(K) of the cylindrical graphite ionization chamber for 137Cs brachytherapy source are in agreement within 1.07%. The deviation of analytical and Monte Carlo values from experimental values of N(K) is 0.36% and 0.72%, respectively. This agreement validates the analytical value, and establishes this chamber as a reference standard for RAKR or AKS measurement of 137Cs brachytherapy sources. PMID:22089009

  8. Effects of Post-Pyrolysis Air Oxidation of Biomass Chars on Adsorption of Neutral and Ionizable Compounds.

    PubMed

    Xiao, Feng; Pignatello, Joseph J

    2016-06-21

    This study was conducted to understand the effects of thermal air oxidation of biomass chars experienced during formation or production on their adsorptive properties toward various compounds, including five neutral nonpolar and polar compounds and seven weak acids and bases (pKa = 3-5.2) selected from among industrial chemicals and the triazine and phenoxyacetic acid herbicide classes. Post-pyrolysis air oxidation (PPAO) at 400 °C of anoxically prepared wood and pecan shell chars for up to 40 min enhanced the mass-normalized adsorption at pH ∼ 7.4 of all test compounds, especially the weak acids and bases, by up to 100-fold. Both general and specific effects were identified. The general effect results from "reaming" of pores by the oxidative removal of pore wall matter and/or tarry deposits generated during the pyrolysis step. Reaming creates new surface area and enlarges nanopores, which helps relieve steric hindrance to adsorption. The specific effect results from creation of new acidic functionality that provides sites for the formation of very strong, charge-assisted hydrogen bonds (CAHB) with solutes having comparable pKa. The CAHB hypothesis was supported by competition experiments and the finding that weak acid anion adsorption increased with surface carboxyl content, despite electrostatic repulsion from the growing negative charge. The results provide insight into the effects of air oxidation on pollutant retention. PMID:27152745

  9. Characterization of the new free-air primary standard for low-energy X-rays at CMI

    NASA Astrophysics Data System (ADS)

    Šolc, Jaroslav; Sochor, Vladimír

    2014-11-01

    In 2011 a decision was made by Czech Metrology Institute to build a free-air ionization chamber (FAC) intended to be used as a primary standard of air kerma rate for low-energy X-rays (photon energy below 50 keV, including mammography X-ray qualities) in order to replace the currently used secondary ionization chamber and to decrease the uncertainty of air kerma reference value. In the period 2011-2012, the FAC has been designed, manufactured and put into operation. Its performance was tested using a calibrated secondary chamber and then by an informal comparison with a national primary standard of BEV (Austria). Physical characteristics of the FAC are described and individual correction factors are discussed focusing on computational methods utilized in their estimation. Summary of the correction factors with the uncertainty budget is presented.

  10. DESIGN, CONSTRUCTION, AND EVALUATION OF A CHAMBER FOR AEROBIOLOGY

    EPA Science Inventory

    A chamber was designed and constructed for aeromicrobiology applications. An ultraviolet (UV) radiation source was incorporated to sterilize the chamber between trials. Twelve bacterial species originally isolated from air samples and obtained from the American Type Culture Colle...

  11. DETAIL OF VACUUM PIPE OPENING WITHIN ALTITUDE CHAMBER R, FACING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF VACUUM PIPE OPENING WITHIN ALTITUDE CHAMBER R, FACING SOUTHEAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  12. In-Line Ozonation for Sensitive Air-Monitoring of a Mustard-Gas Simulant by Atmospheric Pressure Chemical Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Okumura, Akihiko

    2015-09-01

    A highly sensitive method for real-time air-monitoring of mustard gas (bis(2-chloroethyl) sulfide, HD), which is a lethal blister agent, is proposed. Humidified air containing a HD simulant, 2-chloroethyl ethyl sulfide (2CEES), was mixed with ozone and then analyzed by using an atmospheric pressure chemical ionization ion trap tandem mass spectrometer. Mass-spectral ion peaks attributable to protonated molecules of intact, monooxygenated, and dioxygenated 2CEES (MH+, MOH+, and MO2H+, respectively) were observed. As ozone concentration was increased from zero to 30 ppm, the signal intensity of MH+ sharply decreased, that of MOH+ increased once and then decreased, and that of MO2H+ sharply increased until reaching a plateau. The signal intensity of MO2H+ at the plateau was 40 times higher than that of MH+ and 100 times higher than that of MOH+ in the case without in-line ozonation. Twenty-ppm ozone gas was adequate to give a linear calibration curve for 2CEES obtained by detecting the MO2H+ signal in the concentration range up to 60 μg/m3, which is high enough for hygiene management. In the low concentration range lower than 3 μg/m3, which is equal to the short-term exposure limit for HD, calibration plots unexpectedly fell off the linear calibration curve, but 0.6-μg/m3 vapor was actually detected with the signal-to-noise ratio of nine. Ozone was generated from instrumentation air by using a simple and inexpensive home-made generator. 2CEES was ozonated in 1-m extended sampling tube in only 1 s.

  13. Calculation of gas temperature at the outlet of the combustion chamber and in the air-gas channel of a gas-turbine unit by data of acceptance tests in accordance with ISO

    NASA Astrophysics Data System (ADS)

    Kostyuk, A. G.; Karpunin, A. P.

    2016-01-01

    This article describes a high accuracy method enabling performance of the calculation of real values of the initial temperature of a gas turbine unit (GTU), i.e., the gas temperature at the outlet of the combustion chamber, in a situation where manufacturers do not disclose this information. The features of the definition of the initial temperature of the GTU according to ISO standards were analyzed. It is noted that the true temperatures for high-temperature GTUs is significantly higher than values determined according to ISO standards. A computational procedure for the determination of gas temperatures in the air-gas channel of the gas turbine and cooling air consumptions over blade rims is proposed. As starting equations, the heat balance equation and the flow mixing equation for the combustion chamber are assumed. Results of acceptance GTU tests according to ISO standards and statistical dependencies of required cooling air consumptions on the gas temperature and the blade metal are also used for calculations. An example of the calculation is given for one of the units. Using a developed computer program, the temperatures in the air-gas channel of certain GTUs are calculated, taking into account their design features. These calculations are performed on the previously published procedure for the detailed calculation of the cooled gas turbine subject to additional losses arising because of the presence of the cooling system. The accuracy of calculations by the computer program is confirmed by conducting verification calculations for the GTU of the Mitsubishi Comp. and comparing results with published data of the company. Calculation data for temperatures were compared with the experimental data and the characteristics of the GTU, and the error of the proposed method is estimated.

  14. Extraction of depth-dependent perturbation factors for parallel-plate chambers in electron beams using a plastic scintillation detector

    SciTech Connect

    Lacroix, Frederic; Guillot, Mathieu; McEwen, Malcolm; Cojocaru, Claudiu; Gingras, Luc; Beddar, A. Sam; Beaulieu, Luc

    2010-08-15

    Purpose: This work presents the experimental extraction of the overall perturbation factor P{sub Q} in megavoltage electron beams for NACP-02 and Roos parallel-plate ionization chambers using a plastic scintillation detector (PSD). Methods: The authors used a single scanning PSD mounted on a high-precision scanning tank to measure depth-dose curves in 6, 12, and 18 MeV clinical electron beams. The authors also measured depth-dose curves using the NACP-02 and PTW Roos chambers. Results: The authors found that the perturbation factors for the NACP-02 and Roos chambers increased substantially with depth, especially for low-energy electron beams. The experimental results were in good agreement with the results of Monte Carlo simulations reported by other investigators. The authors also found that using an effective point of measurement (EPOM) placed inside the air cavity reduced the variation of perturbation factors with depth and that the optimal EPOM appears to be energy dependent. Conclusions: A PSD can be used to experimentally extract perturbation factors for ionization chambers. The dosimetry protocol recommendations indicating that the point of measurement be placed on the inside face of the front window appear to be incorrect for parallel-plate chambers and result in errors in the R{sub 50} of approximately 0.4 mm at 6 MeV, 1.0 mm at 12 MeV, and 1.2 mm at 18 MeV.

  15. EFFECTS OF OPEN-TOP CHAMBERS ON 'VALENCIA' ORANGE TREES

    EPA Science Inventory

    Young 'Valencia' orange trees (Citrus sinensis(L) Osbeck) were grown for four years in large open-top chambers with ambient (nonfiltered) air or in outside air to determine any effects of the chambers on the air pollutant susceptibility of the trees. ong-term ozone average concen...

  16. Double window viewing chamber assembly

    NASA Technical Reports Server (NTRS)

    Keller, V. W. (Inventor); Owen, R. B. (Inventor); Elkins, B. R. (Inventor); White, W. T. (Inventor)

    1986-01-01

    A viewing chamber which permits observation of a sample retained therein includes a pair of double window assemblies mounted in opposed openings in the walls thereof so that a light beam can directly enter and exit from the chamber. A flexible mounting arrangement for the outer windows of the window assemblies enables the windows to be brought into proper alignment. An electrical heating arrangement prevents fogging of the outer windows whereas desiccated air in the volume between the outer and inner windows prevents fogging of the latter.

  17. A fitting formula for radiative cooling based on non-local thermodynamic equilibrium population from weakly-ionized air plasma

    NASA Astrophysics Data System (ADS)

    Ogino, Yousuke; Nagano, Atsushi; Ishihara, Tomoaki; Ohnishi, Naofumi

    2013-08-01

    A fitting formula for radiative cooling with collisional-radiative population for air plasma flowfield has been developed. Population number densities are calculated from rate equations in order to evaluate the effects of nonequilibrium atomic and molecular processes. Many elementary processes are integrated to be applied to optically-thin plasmas in the number density range of 1012/cm3 <= N <= 1019/cm3 and the temperature range of 300 K <= T <= 40,000 K. Our results of the total radiative emissivity calculated from the collisional-radiative population are fitted in terms of temperature and total number density. To validate the analytic fitting formula, numerical simulation of a laser-induced blast wave propagation with the nonequilibrium radiative cooling is conducted and successfully reproduces the shock and plasma wave front time history observed by experiments. In addition, from the comparison between numerical simulations with the radiation cooling effect based on the fitting formula and those with a gray gas radiation model that assumes local thermodynamic equilibrium, we find that the displacement of the plasma front is slightly different due to the deviation of population probabilities. By using the fitting formula, we can easily and more accurately evaluate the radiative cooling effect without solving detailed collisional-radiative rate equations.

  18. An inexpensive dual-chamber particle monitor: laboratory characterization

    SciTech Connect

    Rufus Edwards; Kirk R. Smith; Brent Kirby; Tracy Allen; Charles D. Litton; Susanne Hering

    2006-06-15

    In developing countries, high levels of particle pollution from the use of coal and biomass fuels for household cooking and heating are a major cause of ill health and premature mortality. Existing monitoring equipment makes routine quantification of household particle pollution levels difficult. Recent advances have enabled the development of a small, portable, data-logging particle monitor modified from commercial smoke alarm technology that can meet the needs of surveys in the developing world at reasonable cost. Laboratory comparisons of a prototype particle monitor developed at the University of California at Berkeley (UCB) with gravimetric filters, a tapered element oscillating microbalance, and a TSI DustTrak to quantify the UCB particle monitor response as a function of both concentration and particle size and to examine sensor response in relation to changes in temperature, relative humidity, and elevation are presented. UCB particle monitors showed good linearity in response to different concentrations of laboratory-generated oleic acid aerosols with a coarse and fine size distributions. The photoelectric and ionization chamber showed a wide range of responses based on particle size and, thus, require calibration with the aerosol of interest. The ionization chamber was five times more sensitive to fine rather than coarse particles, whereas the photoelectric chamber was five times more sensitive to coarse than fine. The ratio of the response between the two sensors has the potential for mass calibration of individual data points based on estimated parameters of the size distribution. The results demonstrate the significant potential of this monitor, which will facilitate the evaluation of interventions (improved fuels, stoves, and ventilation) on indoor air pollution levels and research on the impacts of indoor particle levels on health in developing countries. 10 refs., 10 figs., 2 tabs.

  19. Determination of triazole pesticide residues in edible oils using air-assisted liquid-liquid microextraction followed by gas chromatography with flame ionization detection.

    PubMed

    Farajzadeh, Mir Ali; Feriduni, Behruz; Mogaddam, Mohammad Reza Afshar

    2015-03-01

    In the present study, a rapid, simple, and highly efficient sample preparation method based on air-assisted liquid-liquid microextraction followed by gas chromatography with flame ionization detection was developed for the extraction, preconcentration, and determination of five triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, and triticonazole) in edible oils. Initially, the oil samples were diluted with hexane and a few microliter of a less soluble organic solvent (extraction solvent) in hexane was added. To form fine and dispersed extraction solvent droplets, the mixture of oil sample solution and extraction solvent is repeatedly aspirated and dispersed with a syringe. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 2.2-6.1 and 7.3-20 μg/L, respectively. Enrichment factors and extraction recoveries were in the ranges of 71-96 and 71-96%, respectively. The relative standard deviations for the extraction of 100 and 250 μg/L of each pesticide were less than 5% for intraday (n = 6) and interday (n = 3) precisions. Finally edible oil samples were successfully analyzed using the proposed method, and hexaconazole was found in grape seed oil. PMID:25580590

  20. Calcium - ionized

    MedlinePlus

    ... at both ionized calcium and calcium attached to proteins. You may need to have a separate ionized calcium test if you have factors that increase or decrease total calcium levels. These may include abnormal blood levels ...

  1. Liquid argon Time Projection Chamber

    SciTech Connect

    Doe, P.J.; Mahler, H.J.; Chen, H.H.

    1984-01-01

    The principal features of the liquid argon TPC are outlined and the status of development efforts, particularly at UCI, are discussed. Technical problems associated with liquid TPC's are: the liquid must be maintained at a high level of purity to enable long distance drifting of ionization electrons, and the signal size is small due to the absence of practical charge multiplication as found in gas chambers. These problems have been largely resolved in studies using small (1 to 100 l) detectors, thus allowing a realistic consideration of the physics potential of such devices.

  2. Right/left assignment in drift chambers and proportional multiwire chambers (PWC's) using induced signals

    DOEpatents

    Walenta, Albert H.

    1979-01-01

    Improved multiwire chamber having means for resolving the left/right ambiguity in the location of an ionizing event. The chamber includes a plurality of spaced parallel anode wires positioned between spaced planar cathodes. Associated with each of the anode wires are a pair of localizing wires, one positioned on either side of the anode wire. The localizing wires are connected to a differential amplifier whose output polarity is determined by whether the ionizing event occurs to the right or left of the anode wire.

  3. Calibration and performance of a secondary emission chamber as a beam intensity monitor

    SciTech Connect

    Sivertz, M.; Chiang, I-H,; Rusek, A.

    2011-03-28

    We report on a study of the behavior of a secondary emission chamber (SEC). We show the dependence of the SEC signal on the charge and velocity of the primary beam for beams of protons, and heavy ions including Helium, Neon, Chlorine and Iron. We fill the SEC with a selection of different gases including Hydrogen, Helium, Nitrogen, Argon, and air, studying the SEC response when it is acting as an ion chamber. We also investigate the behavior of the SEC at intermediate pressures between 10{sup -8} torr and atmospheric pressure. The SEC uses thin conducting foils as the source and collector of electrons in a vacuum chamber. When charged particles traverse the vacuum chamber, they pass through a series of thin conducting foils, alternating anode and cathode. Ionization produced in the cathode foils travels across the intervening gap due to an applied high voltage and is collected on the anode foils. Electron production is very inefficient because most of the ionization in the foils remains trapped within the foil due to the short range of most delta-rays and the work function of the foil. It is this inefficiency that allows the SEC to operate at high dose rates and short pulse duration where the standard ion chambers cannot function reliably. The SEC was placed in the NSRL ion beam to receive a variety of heavy ion beams under different beam conditions. We used these ion beams to study the response of the SEC to different species of heavy ion, comparing with proton beams. We studied the response to beam of different energies, and as a function of different counting rate. We compared the behaviour of the SEC when operating under positive and negative high voltage. The SEC can operate as an ion chamber if it is filled with gas. We measured the response of the SEC when filled with a variety of gases, from Hydrogen to Helium, Nitrogen, Argon and air. The performance of the SEC as an ion chamber is compared with the standard NSRL ion chamber, QC3. By evacuating the SEC and

  4. Atmospheric sampling glow discharge ionization source

    DOEpatents

    McLuckey, Scott A.; Glish, Gary L.

    1989-01-01

    An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above.

  5. Atmospheric sampling glow discharge ionization source

    DOEpatents

    McLuckey, S.A.; Glish, G.L.

    1989-07-18

    An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above. 3 figs.

  6. Evaluation of the desiccation tolerance of blastospores of Paecilomyces fumosoroseus (Deuteromycotina: Hyphomyces)using a lab- scale, air-drying chamber with controlled relative humidity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The stabilization of living microbial agents for use as biological control agents is often accomplished through desiccation. The drying process must be conducive to the survival of the living microbial agent during desiccation and storage. Our air-drying studies with liquid culture-produced blasto...

  7. Performance analysis and determination of the p(wall) correction factor for 60Co gamma-ray beams for Wellhöfer Roos-type plane-parallel chambers.

    PubMed

    Palm, Asa; Czap, Ladislav; Andreo, Pedro; Mattsson, Olof

    2002-02-21

    The wall perturbation correction factor p(wall) in 60Co for Wellhöfer Roos-type plane-parallel ionization chambers is determined experimentally and compared with the results of a previous study using PTW-Roos chambers (Palm et al 2000 Phys. Med. Biol. 45 971-81). Five ionization chambers of the type Wellhöfer PPC-35 (or its equivalent PPC-40) are used for the analysis. Wall perturbation correction factors are obtained by assuming N(D,air) chamber factors determined by cross-calibration in a high-energy electron and in a 60Co gamma-ray beam to be equal, and by assigning any differences to the wall perturbation factor. The procedure yields a p(wall) value of 1.018 (u(c) = 0.010), which is slightly higher than the value 1.014 (u(c) = 0.010) formerly obtained for the PTW-Roos chambers using the N(D,air) method. The chamber-to-chamber variation in p(wall) for the Wellhöfer-Roos chambers is found to be very small, with a maximum difference of 0.3%. The effect of using new p(cav) values for graphite-walled Farmer-type chambers used in water in electron beams is to decrease p(wall) by approximately 0.5%. The long- and short-term stability of the Roos-type chambers manufactured by Wellhöfer is investigated by measurements at the IAEA Dosimetry Laboratory in Vienna, Austria, and at the Sahlgrenska University Hospital in Göteborg, Sweden. Calibrations made at the IAEA over several months show variations in the N(D,w) calibration factors larger than expected. based on previous experiences with PTW-Roos chambers. Measurements of the short-term stability of the Wellhöfer-Roos chambers show a marked increase in chamber response for the time the chambers are immersed in water, pointing to a possible problem in the chamber design. As a consequence of these findings, Wellhöfer is currently working on a re-design of the chamber to solve the stability problem. PMID:11900195

  8. Roos and NACP-02 ion chamber perturbations and water-air stopping-power ratios for clinical electron beams for energies from 4 to 22 MeV

    NASA Astrophysics Data System (ADS)

    Bailey, M.; Shipley, D. R.; Manning, J. W.

    2015-02-01

    Empirical fits are developed for depth-compensated wall- and cavity-replacement perturbations in the PTW Roos 34001 and IBA / Scanditronix NACP-02 parallel-plate ionisation chambers, for electron beam qualities from 4 to 22 MeV for depths up to approximately 1.1 × R50,D. These are based on calculations using the Monte Carlo radiation transport code EGSnrc and its user codes with a full simulation of the linac treatment head modelled using BEAMnrc. These fits are used with calculated restricted stopping-power ratios between air and water to match measured depth-dose distributions in water from an Elekta Synergy clinical linear accelerator at the UK National Physical Laboratory. Results compare well with those from recent publications and from the IPEM 2003 electron beam radiotherapy Code of Practice.

  9. Semiclosed-circuit atmosphere control in a portable recompression chamber

    NASA Technical Reports Server (NTRS)

    Riegel, P. S.; Caudy, D. W.

    1972-01-01

    A small portable recompression chamber is described that can be used both to treat a diver for decompression sickness or to transport him to a larger chamber complex. The device can be operated in either open circuit or semiclosed circuit atmospheres, permits two way conversation between patient and attendant, and uses an air injector for circulation of the chamber atmosphere.

  10. X-ray film chamber with carbon target of Tien-Shan complex array

    NASA Technical Reports Server (NTRS)

    Dubovy, A. G.; Nikolsky, S. I.; Vildanov, N. G.; Cherdyntseva, K. V.; Chubenko, A. P.; Krutikova, N. P.; Nesterova, N. M.; Nikolskaja, N. M.; Tukish, E. I.; Yakovleva, T. I.

    1985-01-01

    X-ray films were exposed inside the ionization calorimeter under 74g/sq cm of carbon and 5 cm of lead. The X-ray film chamber area is 35 sq. m. Moving X-ray films were used, 50% of the events, which succeeded to determine incidence time, were identified with corresponding extensive air showers (EAS). For such events the size spectrum of associated EAS was derived. Two methods of energy measurement using X-ray films and ionization calorimeter were compared. The energy transfer from selected hadron to electromagnetic component is illustrated. It is found that in cascades with high energy release into electromagnetic components the hadron component is practically absent.

  11. Ionization, Charging and Electric Field Effects on Cloud Particles in the CLOUD Experiment

    NASA Astrophysics Data System (ADS)

    Nichman, L.; Järvinen, E.; Wagner, R.; Dorsey, J.; Dias, A. M.; Ehrhart, S.; Kirkby, J.; Gallagher, M. W.; Saunders, C. P.

    2015-12-01

    Ice crystals and frozen droplets play an important role in atmospheric charging and electrification processes, particularly by collision and aggregation. The dynamics of charged particles in the atmosphere can be modulated by Galactic Cosmic Rays (GCR). High electric fields also affect the alignment of charged particles, allowing more time for interactions. The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN has the ability to conduct ionization, charging and high electric field experiments on liquid or ice clouds created in the chamber by adiabatic pressure reductions. A pion secondary beam from the CERN Proton Synchrotron is used to ionize the molecules in the chamber, and Ar+ Corona Ion Generator for Atmospheric Research (CIGAR) is used to inject unipolar charged ions directly into the chamber. A pressurized airgun provides rapid pressure shocks inside the chamber and induces charged ice nucleation. The cloud chamber is accompanied by a variety of analysing instruments e.g. a 3View Cloud Particle Imager (3V-CPI) coupled with an induction ring, a Scattering Intensity Measurements for the Optical detection of icE (SIMONE) and a Nano-aerosol and Air Ion Spectrometer (NAIS). Using adiabatic expansion and high electric fields we can replicate the ideal conditions for adhesion, sintering and interlocking between ice crystals. Charged cloud particles produced measurable variations in the total induced current pulse on the induction ring. The most influential factors comprised initial temperature, lapse rate and charging mechanism. The ions produced in the chamber may deposit onto larger particles and form dipoles during ice nucleation and growth. The small ion concentration was monitored by the NAIS during these runs. Possible short-term aggregates or alignment of particles were observed in-situ with the SIMONE. These and future chamber measurements of charging and aggregation could shed more light on the ambient conditions and dynamics for electrification

  12. Using a glass fiber separator in a single-chamber air-cathode microbial fuel cell shortens start-up time and improves anode performance at ambient and mesophilic temperatures.

    PubMed

    Zhang, Xiaoyuan; Liang, Peng; Shi, Juan; Wei, Jincheng; Huang, Xia

    2013-02-01

    A shorter start-up time and highly negative anode potentials are needed to improve single-chamber air-cathode microbial fuel cells (MFCs). Using a glass fiber separator reduced the start-up time from 10d to 8d at 20°C, and from 4d to 2d at 30°C, and enhanced coulombic efficiency (CE) from <60% to 89% (20°C) and 87% (30°C). Separators also reduced anode potentials by 20-190mV, charge transfer resistances by 76% (20°C) and 19% (30°C), and increased CV peak currents by 24% (20°C) and 8% (30°C) and the potential range for redox activity (-0.55 to 0.10mV vs. -0.49 to -0.24mV at 20°C). Using a glass fiber separator in an air-cathode MFC, combined with inoculation at a mesophilic temperature, are excellent strategies to shorten start-up time and to enhance anode performance and CE. PMID:23334007

  13. Cosmic muon detector using proportional chambers

    NASA Astrophysics Data System (ADS)

    Varga, Dezső; Gál, Zoltán; Hamar, Gergő; Sára Molnár, Janka; Oláh, Éva; Pázmándi, Péter

    2015-11-01

    A set of classical multi-wire proportional chambers was designed and constructed with the main purpose of efficient cosmic muon detection. These detectors are relatively simple to construct, and at the same time are low cost, making them ideal for educational purposes. The detector layers have efficiencies above 99% for minimum ionizing cosmic muons, and their position resolution is about 1 cm, that is, particle trajectories are clearly observable. Visualization of straight tracks is possible using an LED array, with the discriminated and latched signal driving the display. Due to the exceptional operating stability of the chambers, the design can also be used for cosmic muon telescopes.

  14. Two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1998-05-05

    A vertical two chamber reaction furnace is described. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 C and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  15. Two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D.

    1998-05-05

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  16. Ionizing radiation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter gives a comprehensive review on ionizing irradiation of fresh fruits and vegetables. Topics include principles of ionizing radiation, its effects on pathogenic and spoilage microorganisms, shelf-life, sensory quality, nutritional and phytochemical composition, as well as physiologic and...

  17. Comment on 'Proton beam monitor chamber calibration'.

    PubMed

    Palmans, Hugo; Vatnitsky, Stanislav M

    2016-09-01

    We comment on a recent article (Gomà et al 2014 Phys. Med. Biol. 59 4961-71) which compares different routes of reference dosimetry for the energy dependent beam monitor calibration in scanned proton beams. In this article, a 3% discrepancy is reported between a Faraday cup and a plane-parallel ionization chamber in the experimental determination of the number of protons per monitor unit. It is further claimed that similar discrepancies between calorimetry and ionization chamber based dosimetry indicate that [Formula: see text]-values tabulated for proton beams in IAEA TRS-398 might be overestimated. In this commentary we show, however, that this supporting argument misrepresents the evidence in the literature and that the results presented, together with published data, rather confirm that there exist unresolved problems with Faraday cup dosimetry. We also show that the comparison in terms of the number of protons gives a biased view on the uncertainty estimates for both detectors while the quantity of interest is absorbed dose to water or dose-area-product to water, even if a beam monitor is calibrated in terms of the number of protons. Gomà et al (2014 Phys. Med. Biol. 59 4961-71) also report on the discrepancy between cylindrical and plane-parallel ionization chambers and confirm experimentally that in the presence of a depth dose gradient, theoretical values of the effective point of measurement, or alternatively a gradient correction factor, account for the discrepancy. We believe this does not point to an error or shortcoming of IAEA TRS-398, which prescribes taking the centre of cylindrical ionization chambers as reference point, since it recommends reference dosimetry to be performed in the absence of a depth dose gradient. But these observations reveal that important aspects of beam monitor calibration in scanned proton beams are not addressed in IAEA TRS-398 given that those types of beams were not widely implemented at the time of its publication

  18. Effects of open-top chambers on 'Valencia' orange trees

    SciTech Connect

    Olszyk, D.M.; Takemoto, B.K.; Kats, G.; Dawson, P.J.; Morrison, C.L.

    1992-01-01

    Young 'Valencia' orange trees (Citrus sinensis(L) Osbeck) were grown for four years in large open-top chambers with ambient (nonfiltered) air or in outside air to determine any effects of the chambers on the air pollutant susceptibility of the trees. Long-term ozone average concentrations (12 hours, growing season) were 8% lower, and cumulative ozone dose (hourly values >0.1 microL/L) was 29% lower in ambient chambers compared to outside air. Fruit yields were much higher (>39%) for ambient chamber trees than for outside trees over three harvests, due at least partly to less fruit drop during the growing season for ambient chamber trees. Ambient chamber trees were much larger than outside trees and produced over twice as much leaf material over four years of study. Leaves on ambient chamber trees were larger and less dense than on outside trees. Leaves on ambient chamber trees were under more stress than leaves on outside trees during summer months; with lower stomatal conductances (14% average) and transpiration rates (12%), and more negative leaf water pressure potentials (28%). In contrast, leaves on ambient chamber trees had higher net photosynthetic rates (13%) and higher leaf starch concentrations prior to tree flowering (31%), than leaves on outside trees. While these results indicated large long-term impacts on tree growth which must be considered when using open-top chambers, they did not indicate any net effect of chambers on the air pollutant susceptibility of trees which would limit the usefulness of chamber tree data for air quality impact assessment purposes.

  19. On the wall perturbation correction for a parallel-plate NACP-02 chamber in clinical electron beams

    SciTech Connect

    Zink, K.; Wulff, J.

    2011-02-15

    Purpose: In recent years, several Monte Carlo studies have been published concerning the perturbation corrections of a parallel-plate chamber in clinical electron beams. In these studies, a strong depth dependence of the relevant correction factors (p{sub wall} and p{sub cav}) for depth beyond the reference depth is recognized and it has been shown that the variation with depth is sensitive to the choice of the chamber's effective point of measurement. Recommendations concerning the positioning of parallel-plate ionization chambers in clinical electron beams are not the same for all current dosimetry protocols. The IAEA TRS-398 as well as the IPEM protocol and the German protocol DIN 6800-2 interpret the depth of measurement within the phantom as the water equivalent depth, i.e., the nonwater equivalence of the entrance window has to be accounted for by shifting the chamber by an amount {Delta}z. This positioning should ensure that the primary electrons traveling from the surface of the water phantom through the entrance window to the chamber's reference point sustain the same energy loss as the primary electrons in the undisturbed phantom. The objective of the present study is the determination of the shift {Delta}z for a NACP-02 chamber and the calculation of the resulting wall perturbation correction as a function of depth. Moreover, the contributions of the different chamber walls to the wall perturbation correction are identified. Methods: The dose and fluence within the NACP-02 chamber and a wall-less air cavity is calculated using the Monte Carlo code EGSnrc in a water phantom at different depths for different clinical electron beams. In order to determine the necessary shift to account for the nonwater equivalence of the entrance window, the chamber is shifted in steps {Delta}z around the depth of measurement. The optimal shift {Delta}z is determined from a comparison of the spectral fluence within the chamber and the bare cavity. The wall perturbation

  20. An anechoic chamber facility for investigating aerodynamic noise

    NASA Technical Reports Server (NTRS)

    Massier, P. F.; Parthasarathy, S. P.

    1972-01-01

    The aerodynamic noise facility was designed to be used primarily for investigating the noise-generating mechanisms of high-temperature supersonic and subsonic jets. The facility consists of an anechoic chamber, an exhaust jet silencer, instrumentation equipment, and an air heater with associated fuel and cooling systems. Compressed air, when needed for jet noise studies, is provided by the wind tunnel compressor facility on a continuous basis. The chamber is 8.1 m long, 5.0 m wide, and 3.0 m high. Provisions have been made for allowing outside air to be drawn into the anechoic chamber in order to replenish the air that is entrained by the jet as it flows through the chamber. Also, openings are provided in the walls and in the ceiling for the purpose of acquiring optical measurements. Calibration of the chamber for noise reflections from the wall was accomplished in octave bands between 31.2 Hz and 32 kHz.

  1. Comparison of the energy response of an ionization spectrometer for pions and protons

    NASA Technical Reports Server (NTRS)

    Jones, W. V.; Verma, S. D.

    1971-01-01

    An ionization spectrometer consisting of a sandwich of iron absorbers and plastic scintillation counters was used to measure the energy of pions and protons in the interval 10 to 1000 GeV. For the limited energy interval of 10 to 40 GeV, pions and protons were identified by an air cerenkov counter. Interactions in carbon were studied in a multiplate cloud chamber placed between the cerenkov counter and the spectrometer. Knowledge of these interactions were used in conjunction with a Monte Carlo simulation of the cascade process to study differences in the response of the spectrometer to pions and protons.

  2. The method for on-site determination of trace concentrations of methyl mercaptan and dimethyl sulfide in air using a mobile mass spectrometer with atmospheric pressure chemical ionization, combined with a fast enrichment/separation system.

    PubMed

    Kudryavtsev, Andrey S; Makas, Alexey L; Troshkov, Mikhail L; Grachev, Mikhail А; Pod'yachev, Sergey P

    2014-06-01

    A method for fast simultaneous on-site determination of methyl mercaptan and dimethyl sulfide in air was developed. The target compounds were actively collected on silica gel, followed by direct flash thermal desorption, fast separation on a short chromatographic column and detection by means of mass spectrometer with atmospheric pressure chemical ionization. During the sampling of ambient air, water vapor was removed with a Nafion selective membrane. A compact mass spectrometer prototype, which was designed earlier at Trofimuk Institute of Petroleum Geology and Geophysics, was used. The minimization of gas load of the atmospheric pressure ion source allowed reducing the power requirements and size of the vacuum system and increasing its ruggedness. The measurement cycle is about 3 min. Detection limits in a 0.6 L sample are 1 ppb for methyl mercaptan and 0.2 ppb for dimethyl sulfide. PMID:24725876

  3. New plasma source based on contact ionization

    SciTech Connect

    Schrittwieser, R.; Koslover, R.; Karim, R.; Rynn, N.

    1985-07-01

    A new type of plasma source is presented: A collisionless plasma is formed by producing ions on one end and electrons on the other of a cylindrical vacuum chamber in a solenoidal magnetic field. The ions are produced by contact ionization of potassium on tungsten. The source of electrons is a LaB/sub 6/ plate. In the usual single-ended Q machine the elements rhenium, iridium, and platinum are tested as ionizing metals for potassium and barium.

  4. The Mobile Chamber

    NASA Technical Reports Server (NTRS)

    Scharfstein, Gregory; Cox, Russell

    2012-01-01

    A document discusses a simulation chamber that represents a shift from the thermal-vacuum chamber stereotype. This innovation, currently in development, combines the capabilities of space simulation chambers, the user-friendliness of modern-day electronics, and the modularity of plug-and-play computing. The Mobile Chamber is a customized test chamber that can be deployed with great ease, and is capable of bringing payloads at temperatures down to 20 K, in high vacuum, and with the desired metrology instruments integrated to the systems control. Flexure plans to lease Mobile Chambers, making them affordable for smaller budgets and available to a larger customer base. A key feature of this design will be an Apple iPad-like user interface that allows someone with minimal training to control the environment inside the chamber, and to simulate the required extreme environments. The feedback of thermal, pressure, and other measurements is delivered in a 3D CAD model of the chamber's payload and support hardware. This GUI will provide the user with a better understanding of the payload than any existing thermal-vacuum system.

  5. Target chambers for gammashpere

    SciTech Connect

    Carpenter, M.P.; Falout, J.W.; Nardi, B.G.

    1995-08-01

    One of our responsibilities for Gammasphere, was designing and constructing two target chambers and associated beamlines to be used with the spectrometer. The first chamber was used with the early implementation phase of Gammasphere, and consisted of two spun-Al hemispheres welded together giving a wall thickness of 0.063 inches and a diameter of 12 inches.

  6. Static diffusion cloud chambers

    NASA Technical Reports Server (NTRS)

    Ayers, G.

    1981-01-01

    The chamber geometry and optical arrangement are described. The supersaturation range is given and consists of readings taken at five fixed points: 0.25%, 0.5%, 0.75%, 1.0%, and 1.25%. The detection system is described including light source, cameras, and photocell detectors. The temperature control and the calibration of the chamber are discussed.

  7. High resolution drift chambers

    SciTech Connect

    Va'vra, J.

    1985-07-01

    High precision drift chambers capable of achieving less than or equal to 50 ..mu..m resolutions are discussed. In particular, we compare so called cool and hot gases, various charge collection geometries, several timing techniques and we also discuss some systematic problems. We also present what we would consider an ''ultimate'' design of the vertex chamber. 50 refs., 36 figs., 6 tabs.

  8. The emulsion chamber technology experiment

    NASA Technical Reports Server (NTRS)

    Gregory, John C.

    1992-01-01

    Photographic emulsion has the unique property of recording tracks of ionizing particles with a spatial precision of 1 micron, while also being capable of deployment over detector areas of square meters or 10's of square meters. Detectors are passive, their cost to fly in Space is a fraction of that of instruments of similar collecting. A major problem in their continued use has been the labor intensiveness of data retrieval by traditional microscope methods. Two factors changing the acceptability of emulsion technology in space are the astronomical costs of flying large electronic instruments such as ionization calorimeters in Space, and the power and low cost of computers, a small revolution in the laboratory microscope data-taking. Our group at UAH made measurements of the high energy composition and spectra of cosmic rays. The Marshall group has also specialized in space radiation dosimetry. Ionization calorimeters, using alternating layers of lead and photographic emulsion, to measure particle energies up to 10(exp 15) eV were developed. Ten balloon flights were performed with them. No such calorimeters have ever flown in orbit. In the ECT program, a small emulsion chamber was developed and will be flown on the Shuttle mission OAST-2 to resolve the principal technological questions concerning space exposures. These include assessments of: (1) pre-flight and orbital exposure to background radiation, including both self-shielding and secondary particle generation; the practical limit to exposure time in space can then be determined; (2) dynamics of stack to optimize design for launch and weightlessness; and (3) thermal and vacuum constraints on emulsion performance. All these effects are cumulative and affect our ability to perform scientific measurements but cannot be adequately predicted by available methods.

  9. DETAIL OF VACUUM PIPE AT 0’0” LEVEL, ALTITUDE CHAMBER R, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF VACUUM PIPE AT 0’-0” LEVEL, ALTITUDE CHAMBER R, FACING NORTHEAST - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  10. Theoretical and observational determinations of the ionization coefficient of meteors

    NASA Astrophysics Data System (ADS)

    Jones, William

    1997-07-01

    We examine the problem of the determination of the ionization coefficient beta from both the theoretical and observational points of view. In the past, theoretical evaluations of beta in terms of the relevant scattering cross-sections have used the Massey-Sida formula, which we show to give results which are plainly incorrect. We derive an integral equation for beta and compare the results of its application to copper and iron with laboratory simulations. Agreement for the variation of the ionization coefficient with velocity is good. The ionization coefficient has been determined observationally by Verniani & Hawkins from a comparison of radar and visual observations, employing the luminous efficiency tau also obtained observationally by Verniani. However, this determination of tau would appear to be invalidated by fragmentation. There is good evidence that the radiation of cometary meteors is dominated by that of iron in the visual range, and we have accordingly re-analysed the data of Verniani & Hawkins using the luminous efficiency of iron obtained in simulation experiments. However, it is not possible to choose an iron concentration which gives agreement between the determination of the ionization coefficient by this means and its determination from the theoretical equation in terms of either scattering coefficients or simulation methods. The observational ionization coefficients are much lower than predicted by the present theory and we provisionally explain this as a consequence of transfer of charge from the meteoric ion to a molecule of the air. It is now possible for the meteoric atom to be re-ionized, but it is also possible at sufficiently high initial line densities for significant dissociative recombination of the electrons and nitrogen or oxygen to take place. This recombination will not take place in meteor trains simulated in an ionization chamber. We thus conclude that the present theory is limited to faint radio meteors at lower velocities (v<~35

  11. [Development of a chemical ionization time-of-flight mass spectrometer for continuous measurements of atmospheric hydroxyl radical].

    PubMed

    Dou, Jian; Hua, Lei; Hou, Ke-Yong; Jiang, Lei; Xie, Yuan-Yuan; Zhao, Wu-Duo; Chen, Ping; Wang, Wei-Guo; Di, Tian; Li, Hai-Yang

    2014-05-01

    A home-made chemical ionization time-of-flight mass spectrometer (TOFMS) has been developed for continuous measurements of atmospheric hydroxyl radical. Based on the atmospheric pressure chemical ionization technique, an ionization source with orthogonal dual tube structure was adopted in the instrument, which minimized the interference between the reagent gas ionization and the titration reaction. A 63Ni radioactive source was fixed inside one of the orthogonal tubes to generate reactant ion of NO(-)(3) from HNO3 vapor. Hydroxyl radical was first titrated by excess SO2 to form equivalent concentrations of H2SO4 in the other orthogonal tube, and then reacted with NO(-)(3) ions in the chemical ionization chamber, leading to HSO(-)(4) formation. The concentration of atmospheric hydroxyl radical can be directly calculated by measuring the intensities of the HSOj product ions and the NO(-)(3) reactant ions. The analytical capability of the instrument was demonstrated by measuring hydroxyl radical in laboratory air, and the concentration of the hydroxyl radical in the investigated air was calculated to be 1.6 x 106 molecules*cm ', based on 5 seconds integration. The results have shown that the instrument is competent for in situ continuous measurements of atmospheric trace radical. PMID:25055654

  12. Comparison of sodium naphthenate and air-ionization corona discharge as surface treatments for the ethylene-tetrafluoroethylene polymer (ETFE) to improve adhesion between ETFE and acrylonitrile-butadiene-styrene polymer (ABS) in the presence of a cyanoacrylate adhesive (CAA)

    NASA Astrophysics Data System (ADS)

    Lucía Johanning-Solís, Ana; Stradi-Granados, Benito A.

    2014-09-01

    This study compares two ethylene-tetrafluoroethylene (ETFE) surface activation treatments, namely chemical attack with a solution of sodium naphthenate and plasma erosion via air-ionization corona discharge in order to improve the adhesive properties of the ETFE. An experimental design was prepared for both treatments in order to assess the effect of the treatment characteristics on the tensile load needed to break the bond between the ETFE and the acrylonitrile-butadiene-styrene polymer (ABS) formed with a cyanoacrylate adhesive (CAA) applied between them. The reason for the selection of this problem is that both polymers are frequently used in the biomedical industry for their properties, and they need to be joined firmly in biomedical devices, and the cyanoacrylate adhesive is the adhesive traditionally used for fluoropolymers, in this case the ETFE, and the same CAA has also shown good adhesion with ABS. However, the strength of the bond for the triplet ETFE-CAA-ABS has not been reported and the improvement of the strength of the bond with surface treatments is not found in scholarly journals for modern medical devices such as stents and snares. Both treatments were compared based on the aforementioned design of experiments. The case where ETFE receives no surface treatment serves as the reference. The results indicated that the three factors evaluated (initial drying of the material, temperature of the chemical bath, and immersion time), and their interactions have no significant effect over the tensile load at failure (tensile strength) of the adhesive bond being evaluated. For the air-ionization corona discharge treatment, two factors were evaluated: discharge exposition time and air pressure. The results obtained from this experimental design indicate that there is no significant difference between the levels of the factors evaluated. These results were unexpected as the ranges used were representative of the maximum ranges permissible in manufacturing

  13. Multiphoton ionization of N2 by the third harmonic of a Nd:YAG laser - A new avenue for air diagnostics

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Krauss, Roland H.; Grinstead, Jay H.

    1991-01-01

    Laser-induced N2 ionization is accomplished using a commercially available Nd:YAG laser, and confirmed by means of ion-collection and spectral measurements. Neutral N2 is excited by six photons of the third harmonic frequency, or 355 nm, and is transformed to an ionized state. The radiation at 355 nm is separated from the fundamental and frequency-doubled Nd:YAG radiation to guarantee monochromatic incident radiation. Intense lines near 391.4 nm are found in the initial laser polarization and for a 90-degree rotation of polarization. The radiation at 391.4 nm is associated with an incoherent laser-induced flourescence process related to an ionized-state transition, and increases quadratically with laser power. A 45-mJ laser pulse focused to a diameter of 17 microns can produce an ion concentration of 3.25 x 10 to the 13th ions/cu cm. The large ion concentration and robust fluorescence signal make this technique an efficient method for time-of-flight velocimetry and in-flight testing.

  14. Investigation on temperature separation and flow behaviour in vortex chamber

    NASA Astrophysics Data System (ADS)

    Matsuno, Yuhi; Fukushima, Yusuke; Matsuo, Shigeru; Hashimoto, Tokitada; Setoguchi, Toshiaki; Kim, Heuy Dong

    2015-04-01

    In the previous researches, it is known that the swirl flow in circular pipe causes the temperature separation. Recently, it is shown that the temperature separation occurs in a vortex chamber when compressed air are pumped into this device from the periphery. Especially, in a cavity installed in the periphery of the chamber, the highest temperature was observed. Therefore, it is expected that this device can be used as a heat source in the engineering field. In recent researches, the mechanism of temperature separation in vortex chamber has been investigated by some researchers. However, there are few researches for the effect of diameter and volume of vortex chamber, height of central rod and position of cavity on the temperature separation. Further, no detailed physical explanation has been made for the temperature separation phenomena in the vortex chamber. In the present study, the effects of chamber configuration and position of the cavity on temperature separation in the vortex chamber were investigated experimentally.

  15. 45. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION DDD), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    45. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION DDD), VIEW LOOKING EAST. LEAD ENCLOSED PIPING IS DRAIN FROM BOILER CHAMBER No. 1 - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  16. Compact Raman Lidar Measurement of Liquid and Vapor Phase Water Under the Influence of Ionizing Radiation

    NASA Astrophysics Data System (ADS)

    Shiina, Tatsuo; Chigira, Tomoyuki; Saito, Hayato; Manago, Naohiro; Kuze, Hiroaki; Hanyu, Toshinori; Kanayama, Fumihiko; Fukushima, Mineo

    2016-06-01

    A compact Raman lidar has been developed for studying phase changes of water in the atmosphere under the influence of ionization radiation. The Raman lidar is operated at the wavelength of 349 nm and backscattered Raman signals of liquid and vapor phase water are detected at 396 and 400 nm, respectively. Alpha particles emitted from 241Am of 9 MBq ionize air molecules in a scattering chamber, and the resulting ions lead to the formation of liquid water droplets. From the analysis of Raman signal intensities, it has been found that the increase in the liquid water Raman channel is approximately 3 times as much as the decrease in the vapor phase water Raman channel, which is consistent with the theoretical prediction based on the Raman cross-sections. In addition, the radius of the water droplet is estimated to be 0.2 μm.

  17. Comsol Simulations as a Tool in Validating a Measurement Chamber

    NASA Astrophysics Data System (ADS)

    Lakka, Antti; Sairanen, Hannu; Heinonen, Martti; Högström, Richard

    2015-12-01

    The Centre for Metrology and Accreditation (MIKES) is developing a temperature-humidity calibration system for radiosondes. The target minimum air temperature and dew-point temperature are -80° C and -90° C, respectively. When operating in this range, a major limiting factor is the time of stabilization which is mainly affected by the design of the measurement chamber. To find an optimal geometry for the chamber, we developed a numerical simulation method taking into account heat and mass transfer in the chamber. This paper describes the method and its experimental validation using two stainless steel chambers with different geometries. The numerical simulation was carried out using Comsol Multiphysics simulation software. Equilibrium states of dry air flow at -70° C with different inlet air flow rates were used to determine the geometry of the chamber. It was revealed that the flow is very unstable despite having relatively small Reynolds number values. Humidity saturation abilities of the new chamber were studied by simulating water vapor diffusion in the chamber in time-dependent mode. The differences in time of humidity stabilization after a step change were determined for both the new chamber model and the MIKES Relative Humidity Generator III (MRHG) model. These simulations were used as a validation of the simulation method along with experimental measurements using a spectroscopic hygrometer. Humidity saturation stabilization simulations proved the new chamber to be the faster of the two, which was confirmed by experimental measurements.

  18. Real-time air monitoring of mustard gas and Lewisite 1 by detecting their in-line reaction products by atmospheric pressure chemical ionization ion trap tandem mass spectrometry with counterflow ion introduction.

    PubMed

    Okumura, Akihiko; Takada, Yasuaki; Watanabe, Susumu; Hashimoto, Hiroaki; Ezawa, Naoya; Seto, Yasuo; Sekiguchi, Hiroshi; Maruko, Hisashi; Takayama, Yasuo; Sekioka, Ryoji; Yamaguchi, Shintaro; Kishi, Shintaro; Satoh, Takafumi; Kondo, Tomohide; Nagashima, Hisayuki; Nagoya, Tomoki

    2015-01-20

    A new method enabling sensitive real-time air monitoring of highly reactive chemical warfare agents, namely, mustard gas (HD) and Lewisite 1 (L1), by detecting ions of their in-line reaction products instead of intact agents, is proposed. The method is based on corona discharge-initiated atmospheric pressure chemical ionization coupled with ion trap tandem mass spectrometry (MS(n)) via counterflow ion introduction. Therefore, it allows for highly sensitive and specific real-time detection of a broad range of airborne compounds. In-line chemical reactions, ionization reactions, and ion fragmentations of these agents were investigated. Mustard gas is oxygenated in small quantity by reactive oxygen species generated in the corona discharge. With increasing air humidity, the MS(2) signal intensity of protonated molecules of mono-oxygenated HD decreases but exceeds that of dominantly existing intact HD. This result can be explained in view of proton affinity. Lewisite 1 is hydrolyzed and oxidized. As the humidity increases from zero, the signal of the final product, namely, didechlorinated, dihydroxylated, and mono-oxygenated L1, quickly increases and reaches a plateau, giving the highest MS(2) and MS(3) signals among those of L1 and its reaction products. The addition of minimal moisture gives the highest signal intensity, even under low humidity. The method was demonstrated to provide sufficient analytical performance to meet the requirements concerning hygienic management and counter-terrorism. It will be the first practical method, in view of sensitivity and specificity, for real-time air monitoring of HD and L1 without sample pretreatment. PMID:25553788

  19. Photocopy of drawing, RIGHT ALTITUDE CHAMBER REACTIVATION. NASA, John F. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of drawing, RIGHT ALTITUDE CHAMBER REACTIVATION. NASA, John F. Kennedy Space Center, Florida. Drawing 82K06032, Boeing, December, 1997. ACCESS PLATFORM INSTALLATION. Sheet S2 - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  20. Photocopy of drawing. RIGHT ALTITUDE CHAMBER REACTIVATION. NASA, John F. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of drawing. RIGHT ALTITUDE CHAMBER REACTIVATION. NASA, John F. Kennedy Space Center, Florida. Drawing 82K06032, Boeing, December, 1997. 15 FT LEVEL EQUIPMENT LAYOUT. Sheet E13 - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  1. Photocopy of drawing. RIGHT ALTITUDE CHAMBER REACTIVATION. NASA, John F. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of drawing. RIGHT ALTITUDE CHAMBER REACTIVATION. NASA, John F. Kennedy Space Center, Florida. Drawing 82K06032, Boeing, December, 1997. ACCESS PLATFORM DEMOLITION. Sheet S1 - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  2. Ionized cluster beam deposition

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, A. R.

    1983-01-01

    Ionized Cluster Beam (ICB) deposition, a new technique originated by Takagi of Kyoto University in Japan, offers a number of unique capabilities for thin film metallization as well as for deposition of active semiconductor materials. ICB allows average energy per deposited atom to be controlled and involves impact kinetics which result in high diffusion energies of atoms on the growth surface. To a greater degree than in other techniques, ICB involves quantitative process parameters which can be utilized to strongly control the characteristics of films being deposited. In the ICB deposition process, material to be deposited is vaporized into a vacuum chamber from a confinement crucible at high temperature. Crucible nozzle configuration and operating temperature are such that emerging vapor undergoes supercondensation following adiabatic expansion through the nozzle.

  3. 48. AUXILIARY CHAMBER (EAST END), VIEW LOOKING EAST SHOWING ELECTRICAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    48. AUXILIARY CHAMBER (EAST END), VIEW LOOKING EAST SHOWING ELECTRICAL PENETRATION AND AIR LOCK (LOCATION GGG) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  4. The Mars Chamber

    NASA Video Gallery

    The Mars chamber is a box about the size of a refrigerator that re-creates the temperatures, pressures, and atmosphere of the Martian surface, essentially creating a Mars environment on Earth! Scie...

  5. Expandable Purge Chambers Would Protect Cryogenic Fittings

    NASA Technical Reports Server (NTRS)

    Townsend, Ivan I., III

    2004-01-01

    Expandable ice-prevention and cleanliness-preservation (EIP-CP) chambers have been proposed to prevent the accumulation of ice or airborne particles on quick-disconnect (QD) fittings, or on ducts or tubes that contain cryogenic fluids. In the original application for which the EIP-CP chambers were conceived, there is a requirement to be able to disconnect and reconnect the QD fittings in rapid succession. If ice were to form on the fittings by condensation and freezing of airborne water vapor on the cold fitting surfaces, the ice could interfere with proper mating of the fittings, making it necessary to wait an unacceptably long time for the ice to thaw before attempting reconnection. By keeping water vapor away from the cold fitting surfaces, the EIP-CP chambers would prevent accumulation of ice, preserving the ability to reconnect as soon as required. Basically, the role of an EIP-CP chamber would be to serve as an enclosure for a flow of dry nitrogen gas that would keep ambient air away from QD cryogenic fittings. An EIP-CP chamber would be an inflatable device made of a fabriclike material. The chamber would be attached to an umbilical plate holding a cryogenic QD fitting.

  6. Chamber for Growing and Observing Fungi

    NASA Technical Reports Server (NTRS)

    Pierson, Duane L.; Molina, Thomas C.

    2005-01-01

    A chamber has been designed to enable growth and observation of microcolonies of fungi in isolation from the external environment. Unlike prior fungus-growing apparatuses, this chamber makes it possible to examine a fungus culture without disrupting it. Partly resembling a small picture frame, the chamber includes a metal plate having a rectangular through-thethickness opening with recesses for a top and a bottom cover glass, an inlet for air, and an inlet for water. The bottom cover glass is put in place and held there by clips, then a block of nutrient medium and a moisture pad are placed in the opening. The block is inoculated, then the top cover glass is put in place and held there by clips. Once growth is evident, the chamber can be sealed with tape. Little (if any) water evaporates past the edges of the cover glasses, and, hence there is little (if any) need to add water. A microscope can be used to observe the culture through either cover glass. Because the culture is sealed in the chamber, it is safe to examine the culture without risking contamination. The chamber can be sterilized and reused.

  7. Sleeve reaction chamber system

    SciTech Connect

    Northrup, M. Allen; Beeman, Barton V.; Benett, William J.; Hadley, Dean R.; Landre, Phoebe; Lehew, Stacy L.; Krulevitch, Peter A.

    2009-08-25

    A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.

  8. Air conditioned suit

    NASA Technical Reports Server (NTRS)

    Carl, G. R. (Inventor)

    1973-01-01

    An environmentally controlled suit is described consisting of an airtight outergarment attached by an airtight bellows to the wall of a sterile chamber, an undergarment providing for circulation of air near the skin of the wearer, and a circulation system comprised of air supply and distribution to the extremities of the undegarment and central collection and exhaust of air from the midsection of the undergarment. A workman wearing the undergarment and attached circulation system enters the outer garment through a tunnel in the chamber wall and the attached bellows to work in the chamber without any danger of spreading bacteria.

  9. The coated cathode conductive layer chamber

    NASA Astrophysics Data System (ADS)

    Bouclier, R.; Gaudaen, J.; Sauli, F.

    1991-12-01

    We describe a gaseous detector consisting of thin anode strips vacuum-evaporated on one side of a 100 μm thick plastic layer, alternating on the back side of the same foil with wider parallel cathode strips. Ionization released in a drift space on the anode side is amplified and detected much in the same way as in the microstrip gas chamber; in our detector however spontaneous breakdown due to surface currents is completely avoided by the presence of the insulating layer between anodes and cathodes. To reduce surface and volume charging up, we have used polymer foils with a moderate volume resistivity. The first results show good efficiency, good plateaux and time resolution in detecting low-rate minimum ionizing electrons. Although not suited for high rate or good energy resolution applications, this kind of detector seems rather promising for realizing cheaply large active surfaces.

  10. Improved Rhenium Thrust Chambers

    NASA Technical Reports Server (NTRS)

    O'Dell, John Scott

    2015-01-01

    Radiation-cooled bipropellant thrust chambers are being considered for ascent/ descent engines and reaction control systems on various NASA missions and spacecraft, such as the Mars Sample Return and Orion Multi-Purpose Crew Vehicle (MPCV). Currently, iridium (Ir)-lined rhenium (Re) combustion chambers are the state of the art for in-space engines. NASA's Advanced Materials Bipropellant Rocket (AMBR) engine, a 150-lbf Ir-Re chamber produced by Plasma Processes and Aerojet Rocketdyne, recently set a hydrazine specific impulse record of 333.5 seconds. To withstand the high loads during terrestrial launch, Re chambers with improved mechanical properties are needed. Recent electrochemical forming (EL-Form"TM") results have shown considerable promise for improving Re's mechanical properties by producing a multilayered deposit composed of a tailored microstructure (i.e., Engineered Re). The Engineered Re processing techniques were optimized, and detailed characterization and mechanical properties tests were performed. The most promising techniques were selected and used to produce an Engineered Re AMBR-sized combustion chamber for testing at Aerojet Rocketdyne.

  11. Sensing circuits for multiwire proportional chambers

    NASA Technical Reports Server (NTRS)

    Peterson, H. T.; Worley, E. R.

    1977-01-01

    Integrated sensing circuits were designed, fabricated, and packaged for use in determining the direction and fluence of ionizing radiation passing through a multiwire proportional chamber. CMOS on sapphire was selected because of its high speed and low power capabilities. The design of the proposed circuits is described and the results of computer simulations are presented. The fabrication processes for the CMOS on sapphire sensing circuits and hybrid substrates are outlined. Several design options are described and the cost implications of each discussed. To be most effective, each chip should handle not more than 32 inputs, and should be mounted on its own hybrid substrate.

  12. Automated Electrostatics Environmental Chamber

    NASA Technical Reports Server (NTRS)

    Calle, Carlos; Lewis, Dean C.; Buchanan, Randy K.; Buchanan, Aubri

    2005-01-01

    The Mars Electrostatics Chamber (MEC) is an environmental chamber designed primarily to create atmospheric conditions like those at the surface of Mars to support experiments on electrostatic effects in the Martian environment. The chamber is equipped with a vacuum system, a cryogenic cooling system, an atmospheric-gas replenishing and analysis system, and a computerized control system that can be programmed by the user and that provides both automation and options for manual control. The control system can be set to maintain steady Mars-like conditions or to impose temperature and pressure variations of a Mars diurnal cycle at any given season and latitude. In addition, the MEC can be used in other areas of research because it can create steady or varying atmospheric conditions anywhere within the wide temperature, pressure, and composition ranges between the extremes of Mars-like and Earth-like conditions.

  13. Air cleaning system

    SciTech Connect

    Tidwell, J.H.

    1987-06-16

    This patent describes an air cleaning system comprising: a motor housing; a motor mounted within the housing; a fan attached to and rotatably driven by the motor; a fan chamber surrounding the fan and having an air inlet and outlet; a separator housing means mounted adjacent to and in spaced relation with the motor housing, the separator housing means having an inlet disposed in communication with a chamber within separator housing means; an outlet disposed in communication with the fan chamber; an air driven separator means mounted in chamber of the separator housing means to receive airflow from inlet for rotation of the separator means and removal of foreign matter from airflow by centrifugal force responsive to rotation of the separator means; the airflow is further directed through the outlet of separator housing means to the fan chamber to be ejected by the fan.

  14. Verification of difference of ion-induced nucleation rate for kinds of ionizing radiation

    NASA Astrophysics Data System (ADS)

    Suzuki, A.; Masuda, K.; Takeuchi, Y.; Itow, Y.; Sako, T.; Matsumi, Y.; Nakayama, T.; Ueda, S.; Miura, K.; Kusano, K.

    2014-12-01

    Correlation between the global cloud cover and the galactic cosmic rays intensity has been pointed out. So as one of hypotheses, the promotion of creation of cloud condensation nuclei by cosmic rays can be considered. In this study, we have carried out verification experiment of this hypothesis using an atmospheric reaction chamber at room temperature focusing on the kind of ionizing radiation. We introduced pure air, a trace of water vapor, ozone and sulfur dioxide gas in a chamber with a volume of 75[L]. The sulfur dioxide reacts chemically in the chamber to form sulfate aerosol. After introducing the mixed gas into the chamber, it was irradiated with ultraviolet light, which simulate solar ultraviolet radiation and with anthropogenic ionizing radiation for cosmic rays, particles and new particle formation due to ion-induced nucleation was observed by measuring and recording the densities of ions and aerosol particles, the particle size distribution, the concentrations of ozone and sulfur dioxide, the temperature and the relative humidity. Here, the experimental results of aerosol nucleation rate for different types of radiation are reported. In this experiment, we conducted experiments of irradiation with heavy ions and β-rays. For ionizing radiation Sr-90 β-rays with an average energy of about 1[MeV] and a heavy ion beam from a particle accelerator facility of HIMAC at NIRS (Heavy Ion Medical Accelerator in Chiba, National Institute of Radiological Sciences) were used. The utilized heavy ion was 14N ions of 180[MeV/n] with intensities from 200[particles/spill] to 10000[particles/spill]. In this experimental run the chamber was irradiated for 10 hours and, the relationship between aerosol particle density for the particle size of > of 2.5[nm] and the generated ion density was verified. In the middle, the chamber was irradiated with β-rays for comparison. Increases in the ion density with the increase of the beam intensity were confirmed. Also, a rise in the

  15. Search for the best timing strategy in high-precision drift chambers

    SciTech Connect

    Va'vra, J.

    1983-06-01

    Computer simulated drift chamber pulses are used to investigate various possible timing strategies in the drift chambers. In particular, the leading edge, the multiple threshold and the flash ADC timing methods are compared. Although the presented method is general for any drift geometry, we concentrate our discussion on the jet chambers where the drift velocity is about 3 to 5 cm/..mu..sec and the individual ionization clusters are not resolved due to a finite speed of our electronics.

  16. Filament wound rocket motor chambers

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The design, analysis, fabrication and testing of a Kevlar-49/HBRF-55A filament wound chamber is reported. The chamber was fabricated and successfully tested to 80% of the design burst pressure. Results of the data reduction and analysis from the hydrotest indicate that the chamber design and fabrication techniques used for the chamber were adequate and the chamber should perform adequately in a static test.

  17. Automated soil gas monitoring chamber

    DOEpatents

    Edwards, Nelson T.; Riggs, Jeffery S.

    2003-07-29

    A chamber for trapping soil gases as they evolve from the soil without disturbance to the soil and to the natural microclimate within the chamber has been invented. The chamber opens between measurements and therefore does not alter the metabolic processes that influence soil gas efflux rates. A multiple chamber system provides for repetitive multi-point sampling, undisturbed metabolic soil processes between sampling, and an essentially airtight sampling chamber operating at ambient pressure.

  18. Method and apparatus to monitor a beam of ionizing radiation

    SciTech Connect

    Blackburn, Brandon W.; Chichester, David L.; Watson, Scott M.; Johnson, James T.; Kinlaw, Mathew T.

    2015-06-02

    Methods and apparatus to capture images of fluorescence generated by ionizing radiation and determine a position of a beam of ionizing radiation generating the fluorescence from the captured images. In one embodiment, the fluorescence is the result of ionization and recombination of nitrogen in air.

  19. Device for detecting ionizing radiation

    SciTech Connect

    Anatychuk, L.I.; Kharitonov, J.P.; Kusniruk, V.F.; Meir, V.A.; Melnik, A.P.; Ponomarev, V.S.; Skakodub, V.A.; Sokolov, A.D.; Subbotin, V.G.; Zhukovsky, A.N.

    1980-10-28

    The present invention relates to ionizing radiation sensors, and , more particularly, to semiconductor spectrometers with thermoelectric cooling, and can most advantageously be used in mineral raw material exploration and evaluation under field conditions. The spectrometer comprises a vacuum chamber with an entrance window for passing the radiation therethrough. The vacuum chamber accommodates a thermoelectric cooler formed by a set of peltier elements. A heat conducting plate is mounted on the cold side of the thermoelectric cooler, and its hot side is provided with a radiator. Mounted on the heat conducting plate are sets of peltier elements, integral with the thermoelectric cooler and independent of one another. The peltier elements of these sets are stacked so as to develop the minimum temperature conditions on one set carrying a semiconductor detector and to provide the maximum refrigeration capacity conditions on the other set provided with the field-effect transistor mounted thereon.

  20. Ionization Gas Sensor using Aligned Multiwalled Carbon Nanotubes Array

    SciTech Connect

    Kermany, A. R.; Mohamed, N. M.; Singh, B. S. M.

    2011-05-25

    The challenge with current conventional gas sensors which are operating using semiconducting oxides is their size. After the introduction of nanotechnology and in order to reduce the dimension and consequently the power consumption and cost, new materials such as carbon nanotubes (CNTs) are being introduced. From previous works and characterization results, it was proven that the CNTs based gas sensor has better sensitivity, selectivity and faster response time in compared with semiconducting oxides based gas sensors. As in this work, a fabrication and successful testing of an ionization-based gas sensor using aligned Multiwalled CNTs (MWCNTs) as sensing element is discussed, in which MWCNTs array and Al film are used as anode and cathode plates respectively with electrode separation ranging from 80 {mu}m to 140 {mu}m. Aligned MWCNTs array was incorporated into a sensor configuration in the gas chamber for testing of gases such as argon, air, and mixed gas of 2%H{sub 2} in air. Obtained results show that among the three gases, argon has the lowest breakdown voltage whilst air has the highest value and the breakdown voltage was found to decrease as the electrode spacing was reduced from 140 {mu}m to 80 {mu}m for all three gases.

  1. Photocopy of drawing. ALTITUDE CHAMBERS “L” & “R” STRUCTURES. NASA, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of drawing. ALTITUDE CHAMBERS “L” & “R” STRUCTURES. NASA, John F. Kennedy Space Center, Florida. Drawing 68-K-L-11213, NASA KSC, November, 1968. CHAMBER “R” ELEVATION. Sheet 4 - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  2. Photocopy of drawing. ALTITUDE CHAMBERS “L” & “R” STRUCTURES. NASA, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of drawing. ALTITUDE CHAMBERS “L” & “R” STRUCTURES. NASA, John F. Kennedy Space Center, Florida. Drawing 68-K-L-11213, NASA KSC, November, 1968. CHAMBER “L” ELEVATION. Sheet 3 - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  3. Photocopy of drawing. ALTITUDE CHAMBER LIGHTING MODS., O&C BUILDING. NASA, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of drawing. ALTITUDE CHAMBER LIGHTING MODS., O&C BUILDING. NASA, John F. Kennedy Space Center, Florida. Drawing 203-644, U.S. Army Corps of Engineers, February, 1967. LIGHTING LAYOUT, RIGHT CHAMBER. Sheet 4 - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  4. Photocopy of drawing. ALTITUDE CHAMBER LIGHTING MODS., O&C BUILDING. NASA, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Photocopy of drawing. ALTITUDE CHAMBER LIGHTING MODS., O&C BUILDING. NASA, John F. Kennedy Space Center, Florida. Drawing 203-644, U.S. Army Corps of Engineers, May, 1967. LIGHTING LAYOUT, LEFT CHAMBER. Sheet 5 - Cape Canaveral Air Force Station, Launch Complex 39, Altitude Chambers, First Street, between Avenue D and Avenue E, Cape Canaveral, Brevard County, FL

  5. Advanced Thin Ionization Calorimeter (ATIC)

    NASA Technical Reports Server (NTRS)

    Wefel, John P.

    1998-01-01

    This is the final report for NASA grant NAGW-4577, "Advanced Thin Ionization Calorimeter (ATIC)". This grant covered a joint project between LSU and the University of Maryland for a Concept Study of a new type of fully active calorimeter to be used to measure the energy spectra of very high energy cosmic rays, particularly Hydrogen and Helium, to beyond 1014 eV. This very high energy region has been studied with emulsion chamber techniques, but never investigated with electronic calorimeters. Technology had advanced to the point that a fully active calorimeter based upon Bismuth Germanate (BGO) scintillating crystals appeared feasible for balloon flight (and eventually space) experiments.

  6. Ultrasonic Drying Processing Chamber

    NASA Astrophysics Data System (ADS)

    Acosta, V.; Bon, J.; Riera, E.; Pinto, A.

    The design of a high intensity ultrasonic chamber for drying process was investigated. The acoustic pressure distribution in the ultrasonic drying chamber was simulated solving linear elastic models with attenuation for the acoustic-structure interaction. Together with the government equations, the selection of appropriate boundary conditions, mesh refinement, and configuration parameters of the calculation methods, which is of great importance to simulate adequately the process, were considered. Numerical solution, applying the finite element method (FEM), of acoustic-structure interactions involves to couple structural and fluid elements (with different degrees of freedom), whose solution implies several problems of hardware requirements and software configuration, which were solved. To design the drying chamber, the influence of the directivity of the drying open camera and the staggered reflectors over the acoustic pressure distribution was analyzed. Furthermore, to optimize the influence of the acoustic energy on the drying process, the average value of the acoustic energy distribution in the drying chamber was studied. This would determine the adequate position of the food samples to be dried. For this purpose, the acoustic power absorbed by the samples will be analyzed in later studies.

  7. Improved wire chamber

    DOEpatents

    Atac, M.

    1987-05-12

    An improved gas mixture for use with proportional counter devices, such as Geiger-Mueller tubes and drift chambers. The improved gas mixture provides a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor. 2 figs.

  8. Liquid Wall Chambers

    SciTech Connect

    Meier, W R

    2011-02-24

    The key feature of liquid wall chambers is the use of a renewable liquid layer to protect chamber structures from target emissions. Two primary options have been proposed and studied: wetted wall chambers and thick liquid wall (TLW) chambers. With wetted wall designs, a thin layer of liquid shields the structural first wall from short ranged target emissions (x-rays, ions and debris) but not neutrons. Various schemes have been proposed to establish and renew the liquid layer between shots including flow-guiding porous fabrics (e.g., Osiris, HIBALL), porous rigid structures (Prometheus) and thin film flows (KOYO). The thin liquid layer can be the tritium breeding material (e.g., flibe, PbLi, or Li) or another liquid metal such as Pb. TLWs use liquid jets injected by stationary or oscillating nozzles to form a neutronically thick layer (typically with an effective thickness of {approx}50 cm) of liquid between the target and first structural wall. In addition to absorbing short ranged emissions, the thick liquid layer degrades the neutron flux and energy reaching the first wall, typically by {approx}10 x x, so that steel walls can survive for the life of the plant ({approx}30-60 yrs). The thick liquid serves as the primary coolant and tritium breeding material (most recent designs use flibe, but the earliest concepts used Li). In essence, the TLW places the fusion blanket inside the first wall instead of behind the first wall.

  9. SU-E-T-382: Influence of Compton Currents On Profile Measurements in Small- Volume Ion Chambers

    SciTech Connect

    Tanny, S; Parsai, E; Holmes, S

    2014-06-01

    Purpose: Ionization chambers in electron radiation fields are known to exhibit polarity effects due to Compton currents. Previously we have presented a unique manifestation of this effect observed with a microionization chamber. We have expanded that investigation to include three micro-ionization chambers commonly used in radiation therapy. The purpose of this project is to determine what factors influence this polarity effect for micro-chambers and how it might be mitigated. Methods: Three chambers were utilized: a PTW 31016, an Exradin A-16, and an Exradin A- 26. Beam profile scans were obtained on a Varian TrueBeam linear accelerator in combination with a Wellhofer water phantom for 6, 9, and 12 MeV electrons. Profiles were obtained parallel and perpendicular to the chamber's long axis, with both positive and negative collecting bias. Profiles were obtained with various chamber components shielded by 5 mm of Pb at 6 MeV to determine their relative contributions to this polarity effect. Results: The polarity effect was observed for all three chambers, and the ratio of the polarity effect for the Exradin chambers is proportional to the ratio of chamber volumes. Shielding the stem of both Exradin chambers diminished, but did not remove the polarity effect. However, they demonstrated no out-of-field effect when the cable was shielded with Pb. The PTW chamber demonstrated a significantly reduced polarity effect without any shielding despite its comparable volume with the A-26. Conclusions: The sensitive volume of these micro-chambers is relatively insensitive to collecting polarity. However, charge deposition within the cable can dramatically alter measured ionization profiles. This is demonstrated by the removal of the out-of-field ionization when the cable is shielded for the Exradin chambers. We strongly recommend analyzing any polarity dependence for small-volume chambers used in characterization of electron fields.

  10. Explaining cloud chamber tracks

    SciTech Connect

    Broyles, A.A.

    1992-06-16

    The operation of many detection devices is usually explained in terms of the ionization tracks produced by particles despite the fact that the corresponding incident wave functions extended over the entire sensitive regions of the detectors. The mechanisms by which the wave function appears to collapse to a track is analyzed here.

  11. Flow visualisation studies of aerodynamic characteristics of an open-top chamber.

    PubMed

    Schmitt, F; Ruck, B

    1987-01-01

    Studies to determine potential locations of ingress of ambient air into an open-top chamber, using flow visualisation, are described. Rates of chamber ventilation necessary to avoid ambient air entrainment have been estimated from wind tunnel experiments. The dependence of the exit velocity of air from the chamber on the ambient air velocity was non-linear, so that for low wind speeds other mechanisms are more important than for high ambient air flows. Wind speeds ranged from 0.5m s(-1)

  12. Determining aerodynamic conductance of spar chambers from energy balance measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aerodynamic conductance (gA) of SPAR chambers was determined from measurements of energy balance and canopy temperature over a peanut canopy. gA was calculated from the slope of sensible heat flux (H) versus canopy-to-air temperature difference. H and the canopy-to-air temperature were varied by...

  13. An improved high performance liquid chromatography-photodiode array detection-atmospheric pressure chemical ionization-mass spectrometry method for determination of chlorophylls and their derivatives in freeze-dried and hot-air-dried Rhinacanthus nasutus (L.) Kurz.

    PubMed

    Kao, Tsai Hua; Chen, Chia Ju; Chen, Bing Huei

    2011-10-30

    Rhinacanthus nasutus (L.) Kurz, a traditional Chinese herb possessing antioxidant and anti-cancer activities, has been reported to contain functional components like carotenoids and chlorophylls. However, the variety and amount of chlorophylls remain uncertain. The objectives of this study were to develop a high performance liquid chromatography-photodiode array detection-atmospheric pressure chemical ionization-mass spectrometry (HPLC-DAD-APCI-MS) method for determination of chlorophylls and their derivatives in hot-air-dried and freeze-dried R. nasutus. An Agilent Eclipse XDB-C18 column and a gradient mobile phase composed of methanol/N,N-dimethylformamide (97:3, v/v), acetonitrile and acetone were employed to separate internal standard zinc-phthalocyanine plus 12 cholorophylls and their derivatives within 21 min, including chlorophyll a, chlorophyll a', hydroxychlorophyll a, 15-OH-lactone chlorophyll a, chlorophyll b, chlorophyll b', hydroxychlorophyll b, pheophytin a, pheophytin a', hydroxypheophytin a, hydroxypheophytin a' and pheophytin b in hot-air-dried R. nasutus with flow rate at 1 mL/min and detection at 660 nm. But, in freeze-dried R. nasutus, only 4 chlorophylls and their derivatives, including chlorophyll a, chlorophyll a', chlorophyll b and pheophytin a were detected. Zinc-phthalocyanine was found to be an appropriate internal standard to quantify all the chlorophyll compounds. After quantification by HPLC-DAD, both chlorophyll a and pheophytin a were the most abundant in hot-air-dried R. nasutus, while in freeze-dried R. nasutus, chlorophyll a and chlorophyll b dominated. PMID:22063550

  14. Chamberless residential warm air furnace design

    SciTech Connect

    Godfree, J.

    1996-07-01

    This brief paper is an introduction to the concept of designing residential warm air furnaces without combustion chambers. This is possible since some small burners do not require the thermal support of a combustion chamber to complete the combustion process.

  15. Multi-chamber deposition system

    DOEpatents

    Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.

    1989-10-17

    A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.

  16. Multi-chamber deposition system

    DOEpatents

    Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.

    1989-06-27

    A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.

  17. 50. BOILER CHAMBER No. 1, LOOKING SOUTHEAST BETWEEN CHAMBER AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    50. BOILER CHAMBER No. 1, LOOKING SOUTHEAST BETWEEN CHAMBER AND ENCLOSURE (LOCATION III) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  18. 61. BOILER CHAMBER No. 2, LOOKING SOUTHWEST BETWEEN CHAMBER AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    61. BOILER CHAMBER No. 2, LOOKING SOUTHWEST BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION PPP) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  19. 44. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION CCC), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    44. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION CCC), LOOKING NORTHEAST SHOWING DRAIN PIPE FROM SUMP - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  20. 72. VISITOR'S CENTER, MODEL OF BOILER CHAMBER, AUXILIARY CHAMBER, REACTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    72. VISITOR'S CENTER, MODEL OF BOILER CHAMBER, AUXILIARY CHAMBER, REACTOR AND CANAL (LOCATION T) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  1. Quantifying the "chamber effect" in CO2 flux measurements

    NASA Astrophysics Data System (ADS)

    Vihermaa, Leena; Childs, Amy; Long, Hazel; Waldron, Susan

    2014-05-01

    The significance of aquatic CO2 emissions has received attention in recent years. For example annual aquatic emissions in the Amazon basin have been estimated as 500 Mt of carbon1. Methods for determining the flux rates include eddy covariance flux tower measurements, flux estimates calculated from partial pressure of CO2 (pCO2) in water and the use floating flux chambers connected to an infra-red gas analyser. The flux chamber method is often used because it is portable, cheaper and allows smaller scale measurements. It is also a direct method and hence avoids problems related to the estimation of the gas transfer coefficient that is required when fluxes are calculated from pCO2. However, the use of a floating chamber may influence the flux measurements obtained. The chamber shields the water underneath from effects of wind which could lead to lower flux estimates. Wind increases the flux rate by i) causing waves which increase the surface area for efflux, and ii) removing CO2 build up above the water surface, hence maintaining a higher concentration gradient. Many floating chambers have an underwater extension of the chamber below the float to ensure better seal to water surface and to prevent any ingress of atmospheric air when waves rock the chamber. This extension may cause additional turbulence in flowing water and hence lead to overestimation of flux rates. Some groups have also used a small fan in the chamber headspace to ensure thorough mixing of air in the chamber. This may create turbulence inside the chamber which could increase the flux rate. Here we present results on the effects of different chamber designs on the detected flux rates. 1Richey et al. 2002. Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416: 617-620.

  2. Multiwire proportional chamber development

    NASA Technical Reports Server (NTRS)

    Doolittle, R. F.; Pollvogt, U.; Eskovitz, A. J.

    1973-01-01

    The development of large area multiwire proportional chambers, to be used as high resolution spatial detectors in cosmic ray experiments is described. A readout system was developed which uses a directly coupled, lumped element delay-line whose characteristics are independent of the MWPC design. A complete analysis of the delay-line and the readout electronic system shows that a spatial resolution of about 0.1 mm can be reached with the MWPC operating in the strictly proportional region. This was confirmed by measurements with a small MWPC and Fe-55 X-rays. A simplified analysis was carried out to estimate the theoretical limit of spatial resolution due to delta-rays, spread of the discharge along the anode wire, and inclined trajectories. To calculate the gas gain of MWPC's of different geometrical configurations a method was developed which is based on the knowledge of the first Townsend coefficient of the chamber gas.

  3. Advanced thrust chamber designs

    NASA Technical Reports Server (NTRS)

    Dietrich, F. J.; Leach, A. E.

    1971-01-01

    A regeneratively cooled thrust chamber has been designed and fabricated, consisting of an inner TD nickel liner which was spin formed, welded, and machined and an outer shell of electroformed nickel. Coolant channels were produced in the outer surface of the inner liner by the electric discharge machining process before electroforming the shell. Accessory manifolds and piping were attached by welding. Manufacturing processes employed are described.

  4. Digital optical spark chambers

    NASA Technical Reports Server (NTRS)

    Evenson, Paul; Tuska, Evelyn

    1989-01-01

    The authors constructed and tested a prototype digital readout system for optical spark chambers using a linear, solid-state charge-coupled-device detector array. Position resolution of 0.013 mm (sigma) over a 25-cm field of view has been demonstrated. It is concluded that this technique should permit the construction of economical, lightweight and low-power trajectory hodoscopes for use in cosmic-ray instrumentation on balloons and in spacecraft.

  5. A new plant chamber facility PLUS coupled to the atmospheric simulation chamber SAPHIR

    NASA Astrophysics Data System (ADS)

    Hohaus, T.; Kuhn, U.; Andres, S.; Kaminski, M.; Rohrer, F.; Tillmann, R.; Wahner, A.; Wegener, R.; Yu, Z.; Kiendler-Scharr, A.

    2015-11-01

    A new PLant chamber Unit for Simulation (PLUS) for use with the atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) has been build and characterized at the Forschungszentrum Jülich GmbH, Germany. The PLUS chamber is an environmentally controlled flow through plant chamber. Inside PLUS the natural blend of biogenic emissions of trees are mixed with synthetic air and are transferred to the SAPHIR chamber where the atmospheric chemistry and the impact of biogenic volatile organic compounds (BVOC) can be studied in detail. In PLUS all important enviromental parameters (e.g. temperature, PAR, soil RH etc.) are well-controlled. The gas exchange volume of 9.32 m3 which encloses the stem and the leafes of the plants is constructed such that gases are exposed to FEP Teflon film and other Teflon surfaces only to minimize any potential losses of BVOCs in the chamber. Solar radiation is simulated using 15 LED panels which have an emission strength up to 800 μmol m-2 s-1. Results of the initial characterization experiments are presented in detail. Background concentrations, mixing inside the gas exchange volume, and transfer rate of volatile organic compounds (VOC) through PLUS under different humidity conditions are explored. Typical plant characteristics such as light and temperature dependent BVOC emissions are studied using six Quercus Ilex trees and compared to previous studies. Results of an initial ozonolysis experiment of BVOC emissions from Quercus Ilex at typical atmospheric concentrations inside SAPHIR are presented to demonstrate a typical experimental set up and the utility of the newly added plant chamber.

  6. A new plant chamber facility, PLUS, coupled to the atmosphere simulation chamber SAPHIR

    NASA Astrophysics Data System (ADS)

    Hohaus, T.; Kuhn, U.; Andres, S.; Kaminski, M.; Rohrer, F.; Tillmann, R.; Wahner, A.; Wegener, R.; Yu, Z.; Kiendler-Scharr, A.

    2016-03-01

    A new PLant chamber Unit for Simulation (PLUS) for use with the atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) has been built and characterized at the Forschungszentrum Jülich GmbH, Germany. The PLUS chamber is an environmentally controlled flow-through plant chamber. Inside PLUS the natural blend of biogenic emissions of trees is mixed with synthetic air and transferred to the SAPHIR chamber, where the atmospheric chemistry and the impact of biogenic volatile organic compounds (BVOCs) can be studied in detail. In PLUS all important environmental parameters (e.g., temperature, photosynthetically active radiation (PAR), soil relative humidity (RH)) are well controlled. The gas exchange volume of 9.32 m3 which encloses the stem and the leaves of the plants is constructed such that gases are exposed to only fluorinated ethylene propylene (FEP) Teflon film and other Teflon surfaces to minimize any potential losses of BVOCs in the chamber. Solar radiation is simulated using 15 light-emitting diode (LED) panels, which have an emission strength up to 800 µmol m-2 s-1. Results of the initial characterization experiments are presented in detail. Background concentrations, mixing inside the gas exchange volume, and transfer rate of volatile organic compounds (VOCs) through PLUS under different humidity conditions are explored. Typical plant characteristics such as light- and temperature- dependent BVOC emissions are studied using six Quercus ilex trees and compared to previous studies. Results of an initial ozonolysis experiment of BVOC emissions from Quercus ilex at typical atmospheric concentrations inside SAPHIR are presented to demonstrate a typical experimental setup and the utility of the newly added plant chamber.

  7. An Ethanol Vapor Chamber System for Small Animals

    PubMed Central

    Wang, Jie; Jiang, Lihong; Du, Hongying; Mason, Graeme F.

    2012-01-01

    Ethanol vapor chambers have been utilized widely in alcohol research since their introduction in 1971, and implementations of these systems are now available commercially. Here, we present a modification of the chamber that can be built at lower cost and greater simplicity of operation. The six-chamber system for rats has multiple air pumps. Ethanol vapor levels are adjusted with the air flow rate, ethanol drip rate, and dilution with room air, without a heater or fans. Ethanol vapor concentrations are measured with a breathalyzer, using room air to dilute the vapor chamber output into the range of the breathalyzer. Multiple pumps provide backup to ensure animal survival in the case of failure of the primary air pump. Tests in animals demonstrated comfortable and stable elevation of blood ethanol, with tight control of the ethanol vapor concentrations and the ability to select from a broad range of levels. The ethanol vapor measurement was rapid and efficient. The parts cost was a few thousand U.S. dollars. This vapor chamber system features low cost, ease of use, and convenient and inexpensive measurement of ethanol vapor concentrations. The lack of a heater and electrical components that could come into contact with ethanol in our case facilitated institutional approval. PMID:22575431

  8. An ethanol vapor chamber system for small animals.

    PubMed

    Wang, Jie; Jiang, Lihong; Du, Hongying; Mason, Graeme F

    2012-06-30

    Ethanol vapor chambers have been utilized widely in alcohol research since their introduction in 1971, and implementations of these systems are now available commercially. Here, we present a modification of the chamber that can be built at lower cost and greater simplicity of operation. The six-chamber system for rats has multiple air pumps. Ethanol vapor levels are adjusted with the air flow rate, ethanol drip rate, and dilution with room air, without a heater or fans. Ethanol vapor concentrations are measured with a breathalyzer, using room air to dilute the vapor chamber output into the range of the breathalyzer. Multiple pumps provide backup to ensure animal survival in the case of failure of the primary air pump. Tests in animals demonstrated comfortable and stable elevation of blood ethanol, with tight control of the ethanol vapor concentrations and the ability to select from a broad range of levels. The ethanol vapor measurement was rapid and efficient. The parts cost was a few thousand U.S. dollars. This vapor chamber system features low cost, ease of use, and convenient and inexpensive measurement of ethanol vapor concentrations. The lack of a heater and electrical components that could come into contact with ethanol in our case facilitated institutional approval. PMID:22575431

  9. Triggering the LBL time projection chamber

    SciTech Connect

    Ronan, M.; Millaud, J.; McGathen, T.

    1981-10-01

    A fast digital trigger was built for the LBL Time Projection Chamber (TPC) installed in the PEP-4 detector at SLAC. The TPC is an innovative High Energy Physics detector which will provide particle identification from dE/dx information within the tracking volume. The TPC trigger uses discriminator signals from 2220 dE/dx wire channels to require a track of ionization in the TPC which originates from the colliding beam intersection region. The trigger processing is performed as the ionization drifts onto the proportional wires and is completed 17 ..mu..s after beam crossing. This report describes the basic operation of the TPC detector and its trigger; a pretrigger which uses prompt TPC information from the endcap region; and the electronic implementation. The trigger can be tested with realistic simulated patterns of ionization deposits in the TPC which are stored in local memories. Test results from electronic simulations and first results of a test with cosmic rays are shown.

  10. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1999-03-16

    A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  11. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D.

    1999-03-16

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  12. Organic Aerosol Nucleation and Growth at the CERN CLOUD chamber

    NASA Astrophysics Data System (ADS)

    Tröstl, Jasmin; Lethipalo, Katrianne; Bianchi, Federico; Sipilä, Mikko; Nieminen, Tuomo; Wagner, Robert; Frege, Carla; Simon, Mario; Weingartner, Ernest; Gysel, Martin; Dommen, Josef; Baltensperger, Urs

    2014-05-01

    the beam, different ion concentrations can be simulated, from the planetary boundary layer to the upper troposphere (Kirkby et al. 2011). Precursor concentration and oxidiation products were measured with one proton transfer reaction time-of-flight mass spectrometer (precursor concentration), two atmospheric pressure interface time-of-flight mass spectrometer (APi-ToF, charged cluster composition) and two chemical ionization APi-ToF (neutral cluster composition and concentration). Aerosol formation and growth rates were determined using particle size magnifier (size rage: 1-3 nm), neutral air ion spectrometer (size rage: 0.8 -30 nm), nano scanning mobility particle sizer (size rage: 5-80 nm) and several low cut-off condensation particle counters. The presented results will include nucleation and growth rates depending on oxidized organics and sulfuric acid concentration. Another focus will be on the contribution of organics to aerosol growth. For this, different size ranges will be considered. The results will also include the influence of ions on nucleation and growth. References: Almeida, J., et al. Nature 502.7471 (2013): 359-363. IPCC, 2007: Climate Change 2007: The Physical Science Basis. IPCC, 2013: Climate Change 2013: The Physical Science Basis. Kirkby, J., et al. Nature 476.7361 (2011): 429-433. Merikanto, J., et al. Atmospheric Chemistry and Physics 9.21 (2009): 8601-8616.

  13. Experimental studies on an air-air jet exhaust pump

    SciTech Connect

    Chou, S.K.

    1986-01-01

    Industrial ventilation employing an air-air jet exhaust pump connected to a compressed-air line was investigated. The motive air supply pressure was maintained between 2 and 3 bar. A unique ejector housing was constructed to receive both the convergent-divergent primary nozzle and the mixing chamber. The entire unit adapts readily to any existing compressed-air system. The mixing chamber was so constructed that the length of its cylindrical section may be changed. Pressure variations along the mixing chamber were recorded, and this offered a valuable appreciation of the effects of the length-to-diameter ratios. Results indicate the influence of the supply air pressure and pressure ratio on the jet entrainment capacity and efficiency. It has also been shown that the present design is capable of achieving the maximum reported jet-pump efficiency of around 25% corresponding to a nozzle-to-mixing chamber area ratio of 0.15.

  14. Plant growth chamber based on space proven controlled environment technology

    SciTech Connect

    Ignatius, R.W.; Ignatius, M.H.; Imberti, H.J.

    1997-01-01

    Quantum Devices, Inc., in conjunction with Percival Scientific, Inc., and the Wisconsin Center for Space Automation and Robotics (WCSAR) have developed a controlled environment plant growth chamber for terrestrial agricultural and scientific applications. This chamber incorporates controlled environment technology used in the WCSAR ASTROCULTURE{trademark} flight unit for conducting plant research on the Space Shuttle. The new chamber, termed CERES 2010, features air humidity, temperature, and carbon dioxide control, an atmospheric contaminant removal unit, an LED lighting system, and a water and nutrient delivery system. The advanced environment control technology used in this chamber will increase the reliability and repeatability of environmental physiology data derived from plant experiments conducted in this chamber. {copyright} {ital 1997 American Institute of Physics.}

  15. Weakly ionized cosmic gas: Ionization and characterization

    NASA Technical Reports Server (NTRS)

    Rosenberg, M.; Mendis, D. A.; Chow, V. W.

    1994-01-01

    Since collective plasma behavior may determine important transport processes (e.g., plasma diffusion across a magnetic field) in certain cosmic environments, it is important to delineate the parameter space in which weakly ionized cosmic gases may be characterized as plasmas. In this short note, we do so. First, we use values for the ionization fraction given in the literature, wherein the ionization is generally assumed to be due primarily to ionization by cosmic rays. We also discuss an additional mechanism for ionization in such environments, namely, the photoelectric emission of electrons from cosmic dust grains in an interstellar Far Ultra Violet (FUV) radiation field. Simple estimates suggest that under certain conditions this mechanism may dominate cosmic ray ionization, and possibly also the photoionization of metal atoms by the interstellar FUV field, and thereby lead to an enhanced ionization level.

  16. Low-density-solvent-based air-assisted liquid-liquid microextraction followed by gas chromatography with flame ionization detection for the determination of synthetic phenolic antioxidants in milk samples.

    PubMed

    Farajzadeh, Mir Ali; Afshar Mogaddam, Mohammad Reza

    2016-03-01

    A simple and rapid sample pretreatment technique termed low-density-solvent-based air-assisted liquid-liquid microextraction has been developed for the extraction and preconcentration of three synthetic phenolic antioxidants including butylated hydroxyanisole, butylated hydroxytoluene, and tert-butyl hydroquinone from milk samples prior to their analysis by gas chromatography with flame ionization detection. In this method, initially trichloroacetic acid as a proteins precipitation agent is added to the sample, and then it is sonicated and centrifuged. The obtained aqueous phase is removed and the analytes extracted by the proposed method using a low-density organic solvent. Some important parameters such as type and volume of extraction solvent, ionic strength, pH, and centrifugation rate and time were studied. Under the optimum conditions, enrichment factors were obtained in the range of 501-614. LODs and quantification were between 0.76-1.16 and 2.66-3.96 ng mL(-1) , respectively. This method is rapid and requires less than 15 min for sample preparation. PMID:26763356

  17. Wire chambers revisited.

    PubMed

    Ott, R J

    1993-04-01

    Detectors used for radioisotope imaging have, historically, been based on scintillating crystal/photomultiplier combinations in various forms. From the rectilinear scanner through to modern gamma cameras and positron cameras, the basic technology has remained much the same. Efforts to overcome the limitations of this form of technology have foundered on the inability to reproduce the required sensitivity, spatial resolution and sensitive area at acceptable cost. Multiwire proportional chambers (MWPCs) have long been used as position-sensitive charged particle detectors in nuclear and high-energy physics. MWPCs are large-area gas-filled ionisation chambers in which large arrays of fine wires are used to measure the position of ionisation produced in the gas by the passage of charged particles. The important properties of MWPCs are high-spatial-resolution, large-area, high-count-rate performance at low cost. For research applications, detectors several metres square have been built and small-area detectors have a charged particle resolution of 0.4 mm at a count rate of several million per second. Modification is required to MWPCs for nuclear medicine imaging. As gamma rays or X-rays cannot be detected directly, they must be converted into photo- or Compton scatter electrons. Photon-electron conversion requires the use of high atomic number materials in the body of the chamber. Pressurised xenon is the most useful form of "gas only" photon-electron convertor and has been used successfully in a gamma camera for the detection of gamma rays at energies below 100 keV. This camera has been developed specifically for high-count-rate first-pass cardiac imaging. This high-pressure xenon gas MWPC is the key to a highly competitive system which can outperform scintillator-based systems. The count rate performance is close to a million counts per second and the intrinsic spatial resolution is better than the best scintillator-based camera. The MWPC camera produces quantitative

  18. Review of wire chamber aging

    SciTech Connect

    Va'Vra, J.

    1986-02-01

    This paper makes an overview of the wire chamber aging problems as a function of various chamber design parameters. It emphasizes the chemistry point of view and many examples are drawn from the plasma chemistry field as a guidance for a possible effort in the wire chamber field. The paper emphasizes the necessity of variable tuning, the importance of purity of the wire chamber environment, as well as it provides a practical list of presently known recommendations. In addition, several models of the wire chamber aging are qualitatively discussed. The paper is based on a summary talk given at the Wire Chamber Aging Workshop held at LBL, Berkeley on January 16-17, 1986. Presented also at Wire Chamber Conference, Vienna, February 25-28, 1986. 74 refs., 18 figs., 11 tabs.

  19. Statistical analysis of environmental variability within the CELSS breadboard project's biomass production chamber

    NASA Technical Reports Server (NTRS)

    Stutte, G. W.; Chetirkin, P. V.; Mackowiak, C. L.; Fortson, R. E.

    1993-01-01

    Variability in the aerial and root environments of NASA's Breadboard Project's Biomass Production Chamber (BPC) was determined. Data from two lettuce and two potato growouts were utilized. One growout of each crop was conducted prior to separating the upper and lower chambers; the other was subsequent to separation. There were little or no differences in pH, EC, or solution temperature between the upper and lower chamber or within a chamber. Variation in the aerial environment within a chamber was two to three times greater than variation between chambers for air temperature, relative humidity, and PPF. High variability in air velocity, relative to tray position, was observed. Separating the BPC had no effect on PPF, air velocity, solution temperature, pH, or EC. Separation reduced the gradient in air temperature and relative humidity between the upper and lower chambers, but increased the variability within a chamber. Variation between upper and lower chambers was within 5 percent of environmental set-points and of little or no physiological significance. In contrast, the variability within a chamber limits the capability of the BPC to generate statistically reliable data from individual tray treatments at this time.

  20. Diesel exhaust cleaner with burner vortex chamber

    SciTech Connect

    Riddel, J.W.

    1983-05-17

    A diesel engine exhaust cleaner and burner system includes at least one exhaust cleaner member with a filter positioned therein to effect removal of particulates from a stream of exhaust gas delivered thereto via an inlet manifold. A fuel burner supplied with fuel by a fuel nozzle is operatively associated with the inlet manifold to supply the necessary heat to effect incineration of particulates collected on the filter. A cyclone duct providing a vortex chamber therein is operatively positioned downstream of the fuel nozzle and is supplied with sufficient air so as to effect both the complete combustion of the fuel and the controlled incineration of the particulates by increasing the residence time of the fuel in the reaction region within the vortex chamber and also effecting a more uniform distribution of the heat of combustion across the inlet face of the filter for the uniform heating of the particulates thereon to their combustion temperature.

  1. Thermochromic behaviors and ionization potentials of organopolysilanes

    NASA Astrophysics Data System (ADS)

    Yokoyama, Kenji; Yokoyama, Masaaki

    1989-04-01

    Ionization potentials of organopolysilanes with different kinds of substituents were evaluated from the low energy photo-electron emission measurements in air. An aryl-substituted organopolysilane capable of σ - π mixing between Si backbone σ and side-group π electrons gave smaller ionization potential by about 0.1˜0.15 eV compared with alkyl-substituted organopolysilanes. The value of ionization potentials in some alkyl-substituted organopolysilanes which showed thermochromic behaviors was found to vary substantially with thermally induced reversible changes in polymer backbone conformation, indicating that the effective conjugation length of σ electrons decreases above the thermochromic transition temperature.

  2. A new plasma source based on contact ionization

    NASA Astrophysics Data System (ADS)

    Schrittwieser, R.; Koslover, R.; Karim, R.; Rynn, N.

    1985-07-01

    A new type of plasma source is presented: A collisionless plasma is formed by producing ions on one end and electrons on the other of a cylindrical vacuum chamber in a solenoidal magnetic field. The ions are produced by contact ionization of potassium on tungsten. The source of electrons is a LaB6 plate. In the usual single-ended Q machine the elements rhenium, iridium, and platinum are tested as ionizing metals for potassium and barium.

  3. Development of Non-proximate Probe Electrospray Ionization for Real-Time Analysis of Living Animal

    PubMed Central

    Yoshimura, Kentaro; Chen, Lee Chuin; Johno, Hisashi; Nakajima, Mayutaka; Hiraoka, Kenzo; Takeda, Sen

    2014-01-01

    Ambient ionization mass spectrometry is one of the most challenging analytical tools in the field of biomedical research. We previously demonstrated that probe electrospray ionization mass spectrometry (PESI-MS) could potentially be used in the rapid diagnosis of cancer. Although this technique does not require a tedious sample pretreatment process, it was not possible for our previously reported setup to be applied to cases involving the direct sampling of tissues from living animal and large animal subjects, because there would not be enough room to accommodate the larger bodies juxtaposed to the ion inlet. To make PESI-MS more applicable for the real-time analysis of living animals, a long auxiliary ion sampling tube has been connected to the ion inlet of the mass spectrometer to allow for the collection of ions and charged droplets from the PESI source (hereafter, referred to as non-proximate PESI). Furthermore, an additional ion sampling tube was connected to a small diaphragm pump to increase the uptake rate of air carrying the ions and charged droplets to the ion inlet. This modification allows for the extended ion sampling orifice to be positioned closer to the specimens, even when they are too large to be placed inside the ionization chamber. In this study, we have demonstrated the use of non-proximate PESI-MS for the real-time analysis for biological molecules and pharmacokinetic parameters from living animals. PMID:26819892

  4. Diogene pictorial drift chamber

    SciTech Connect

    Gosset, J.

    1984-01-01

    A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive).

  5. Mush Column Magma Chambers

    NASA Astrophysics Data System (ADS)

    Marsh, B. D.

    2002-12-01

    Magma chambers are a necessary concept in understanding the chemical and physical evolution of magma. The concept may well be similar to a transfer function in circuit or time series analysis. It does what needs to be done to transform source magma into eruptible magma. In gravity and geodetic interpretations the causative body is (usually of necessity) geometrically simple and of limited vertical extent; it is clearly difficult to `see' through the uppermost manifestation of the concentrated magma. The presence of plutons in the upper crust has reinforced the view that magma chambers are large pots of magma, but as in the physical representation of a transfer function, actual magma chambers are clearly distinct from virtual magma chambers. Two key features to understanding magmatic systems are that they are vertically integrated over large distances (e.g., 30-100 km), and that all local magmatic processes are controlled by solidification fronts. Heat transfer considerations show that any viable volcanic system must be supported by a vertically extensive plumbing system. Field and geophysical studies point to a common theme of an interconnected stack of sill-like structures extending to great depth. This is a magmatic Mush Column. The large-scale (10s of km) structure resembles the vertical structure inferred at large volcanic centers like Hawaii (e.g., Ryan et al.), and the fine scale (10s to 100s of m) structure is exemplified by ophiolites and deeply eroded sill complexes like the Ferrar dolerites of the McMurdo Dry Valleys, Antarctica. The local length scales of the sill reservoirs and interconnecting conduits produce a rich spectrum of crystallization environments with distinct solidification time scales. Extensive horizontal and vertical mushy walls provide conditions conducive to specific processes of differentiation from solidification front instability to sidewall porous flow and wall rock slumping. The size, strength, and time series of eruptive behavior

  6. Modeling Chamber Transport for Heavy-Ion Fusion

    SciTech Connect

    Sharp, W M; Niller, D A C; Tabak, M; Yu, S S; Peterson, P F; Welch, D R; Rose, D V; Olson, C L

    2002-08-02

    In a typical thick-liquid-wall scenario for heavy-ion fusion (HIF), between seventy and two hundred high-current beams enter the target chamber through ports and propagate about three meters to the target. Since molten-salt jets are planned to protect the chamber wall, the beams move through vapor from the jets, and collisions between beam ions and this background gas both strip the ions and ionize the gas molecules. Radiation from the preheated target causes further beam stripping and gas ionization. Due to this stripping, beams for heavy-ion fusion are expected to require substantial neutralization in a target chamber. Much recent research has, therefore, focused on beam neutralization by electron sources that were neglected in earlier simulations, including emission from walls and the target, photoionization by the target radiation, and pre-neutralization by a plasma generated along the beam path. When these effects are included in simulations with practicable beam and chamber parameters, the resulting focal spot is approximately the size required by a distributed radiator target.

  7. Modeling chamber transport for heavy-ion fusion

    SciTech Connect

    Sharp, W.M.; Callahan, D.A.; Tabak, M.; Yu, S.S.; Peterson, P.F.; Welch, D.R.; Rose, D.V.; Olson, C.L.

    2002-10-01

    In a typical thick-liquid-wall scenario for heavy-ion fusion (HIF), between seventy and two hundred high-current beams enter the target chamber through ports and propagate about three meters to the target. Since molten-salt jets are planned to protect the chamber wall, the beams move through vapor from the jets, and collisions between beam ions and this background gas both strip the ions and ionize the gas molecules. Radiation from the preheated target causes further beam stripping and gas ionization. Due to this stripping, beams for heavy-ion fusion are expected to require substantial neutralization in a target chamber. Much recent research has, therefore, focused on beam neutralization by electron sources that were neglected in earlier simulations, including emission from walls and the target, photoionization by the target radiation, and pre-neutralization by a plasma generated along the beam path. When these effects are included in simulations with practicable beam and chamber parameters, the resulting focal spot is approximately the size required by a distributed radiator target.

  8. Cooling electronic equipment at simulated high altitude in hypobaric chambers

    NASA Astrophysics Data System (ADS)

    Devine, James A.

    1987-08-01

    An air cooling system has been designed to minimize electronic equipment failures during simulated exposures to 9,000 meters (29,000 ft) in hypobaric chambers. Air density, critical to convective heat transfer during electronic equipment operations, diminishes rapidly below 830 grams cubic meter (16,000 ft, 5,000 meters) resulting in equipment failures. Forced convection, using fans, can be effective up to 6,000meters but extensive equipment failures occur at higher altitudes. A newly designed cooling system incorporates a micrometer-like air flow control nozzle that directs compressed air onto the subject area. The design also accelerates surrounding air molecules to create a highly amplified flow by adding the entrained ambient air to the compressed air. Air flows may be directed on heat exchangers, power supplies, through ventilation ports, ports, to assist fan units, and for general in-cabinet cooling.

  9. Condensate Recycling in Closed Plant Growth Chambers

    NASA Technical Reports Server (NTRS)

    Bledsoe, J. O.; Sager, J. C.; Fortson, R. E.

    1994-01-01

    Water used in the the Controlled Ecological Life Support System (CELSS) Breadboard Project at the Kennedy Space Center is being recycled. Condensation is collected in the air ducts, filtered and deionized, and resupplied to the system for nutrient solutions, supplemental humidification, solvents and diluents. While the system functions well from a process control standpoint, precise and accurate tracking of water movement through the system to answer plant physiological questions is not consistent. Possible causes include hardware errors, undetected vapor loss from chamber leakage, and unmeasured changes in water volume in the plant growth trays.

  10. Changes in the U.S. Primary Standards for the Air Kerma From Gamma-Ray Beams

    PubMed Central

    Seltzer, Stephen M.; Bergstrom, Paul M.

    2003-01-01

    Monte Carlo photon-electron transport calculations have been done to derive new wall corrections for the six NBS-NIST standard graphite-wall, air-ionization cavity chambers that serve as the U.S. national primary standard for air kerma (and exposure) for gamma rays from 60Co, 137Cs, and 192Ir sources. The data developed for and from these calculations have also been used to refine a number of other factors affecting the standards. The largest changes are due to the new wall corrections, and the total changes are +0.87 % to +1.11 % (depending on the chamber) for 60Co beams, +0.64 % to +1.07 % (depending on the chamber) for 137Cs beams, and −0.06 % for the single chamber used in the measurement of the standardized 192Ir source. The primary standards for air kerma will be adjusted in the near future to reflect the changes in factors described in this work.

  11. Demonstration of real-time monitoring of a photolithographic exposure process using chemical ionization mass spectrometry

    SciTech Connect

    Mowry, C.D.

    1998-02-01

    Silicon wafers are coated with photoresist and exposed to ultraviolet (UV) light in a laboratory to simulate typical conditions expected in an actual semiconductor manufacturing process tool. Air is drawn through the exposure chamber and analyzed using chemical ionization mass spectrometry (CI/MS). Species that evaporate or outgas from the wafer are thus detected. The purpose of such analyses is to determine the potential of CI/MS as a real-time process monitoring tool. Results demonstrate that CI/MS can remotely detect the products evolved before, during, and after wafer UV exposure; and that the quantity and type of products vary with the photoresist coated on the wafer. Such monitoring could provide semiconductor manufacturers benefits in quality control and process analysis. Tool and photoresist manufacturers could also realize benefits from this measurement technique with respect to new tool, method, or photoresist development. The benefits realized can lead to improved device yields and reduced product and development costs.

  12. Wire chamber radiation detector with discharge control

    DOEpatents

    Perez-Mendez, Victor; Mulera, Terrence A.

    1984-01-01

    A wire chamber radiation detector (11) has spaced apart parallel electrodes (16) and grids (17, 18, 19) defining an ignition region (21) in which charged particles (12) or other ionizing radiations initiate brief localized avalanche discharges (93) and defining an adjacent memory region (22) in which sustained glow discharges (94) are initiated by the primary discharges (93). Conductors (29, 32) of the grids (18, 19) at each side of the memory section (22) extend in orthogonal directions enabling readout of the X-Y coordinates of locations at which charged particles (12) were detected by sequentially transmitting pulses to the conductors (29) of one grid (18) while detecting transmissions of the pulses to the orthogonal conductors (36) of the other grid (19) through glow discharges (94). One of the grids (19) bounding the memory region (22) is defined by an array of conductive elements (32) each of which is connected to the associated readout conductor (36) through a separate resistance (37). The wire chamber (11) avoids ambiguities and imprecisions in the readout of coordinates when large numbers of simultaneous or near simultaneous charged particles (12) have been detected. Down time between detection periods and the generation of radio frequency noise are also reduced.

  13. High-Compression-Ratio; Atkinson-Cycle Engine Using Low-Pressure Direct Injection and Pneumatic-Electronic Valve Actuation Enabled by Ionization Current and Foward-Backward Mass Air Flow Sensor Feedback

    SciTech Connect

    Harold Schock; Farhad Jaberi; Ahmed Naguib; Guoming Zhu; David Hung

    2007-12-31

    This report describes the work completed over a two and one half year effort sponsored by the US Department of Energy. The goal was to demonstrate the technology needed to produce a highly efficient engine enabled by several technologies which were to be developed in the course of the work. The technologies included: (1) A low-pressure direct injection system; (2) A mass air flow sensor which would measure the net airflow into the engine on a per cycle basis; (3) A feedback control system enabled by measuring ionization current signals from the spark plug gap; and (4) An infinitely variable cam actuation system based on a pneumatic-hydraulic valve actuation These developments were supplemented by the use of advanced large eddy simulations as well as evaluations of fuel air mixing using the KIVA and WAVE models. The simulations were accompanied by experimental verification when possible. In this effort a solid base has been established for continued development of the advanced engine concepts originally proposed. Due to problems with the valve actuation system a complete demonstration of the engine concept originally proposed was not possible. Some of the highlights that were accomplished during this effort are: (1) A forward-backward mass air flow sensor has been developed and a patent application for the device has been submitted. We are optimistic that this technology will have a particular application in variable valve timing direct injection systems for IC engines. (2) The biggest effort on this project has involved the development of the pneumatic-hydraulic valve actuation system. This system was originally purchased from Cargine, a Swedish supplier and is in the development stage. To date we have not been able to use the actuators to control the exhaust valves, although the actuators have been successfully employed to control the intake valves. The reason for this is the additional complication associated with variable back pressure on the exhaust valves when

  14. Ionization and scintillation of nuclear recoils in gaseous xenon

    NASA Astrophysics Data System (ADS)

    Renner, J.; Gehman, V. M.; Goldschmidt, A.; Matis, H. S.; Miller, T.; Nakajima, Y.; Nygren, D.; Oliveira, C. A. B.; Shuman, D.; Álvarez, V.; Borges, F. I. G.; Cárcel, S.; Castel, J.; Cebrián, S.; Cervera, A.; Conde, C. A. N.; Dafni, T.; Dias, T. H. V. T.; Díaz, J.; Esteve, R.; Evtoukhovitch, P.; Fernandes, L. M. P.; Ferrario, P.; Ferreira, A. L.; Freitas, E. D. C.; Gil, A.; Gómez, H.; Gómez-Cadenas, J. J.; González-Díaz, D.; Gutiérrez, R. M.; Hauptman, J.; Hernando Morata, J. A.; Herrera, D. C.; Iguaz, F. J.; Irastorza, I. G.; Jinete, M. A.; Labarga, L.; Laing, A.; Liubarsky, I.; Lopes, J. A. M.; Lorca, D.; Losada, M.; Luzón, G.; Marí, A.; Martín-Albo, J.; Martínez, A.; Moiseenko, A.; Monrabal, F.; Monserrate, M.; Monteiro, C. M. B.; Mora, F. J.; Moutinho, L. M.; Muñoz Vidal, J.; Natal da Luz, H.; Navarro, G.; Nebot-Guinot, M.; Palma, R.; Pérez, J.; Pérez Aparicio, J. L.; Ripoll, L.; Rodríguez, A.; Rodríguez, J.; Santos, F. P.; dos Santos, J. M. F.; Seguí, L.; Serra, L.; Simón, A.; Sofka, C.; Sorel, M.; Toledo, J. F.; Tomás, A.; Torrent, J.; Tsamalaidze, Z.; Veloso, J. F. C. A.; Villar, J. A.; Webb, R. C.; White, J.; Yahlali, N.

    2015-09-01

    Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope α-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

  15. Combustion chamber and thermal vapor stream producing apparatus and method

    DOEpatents

    Sperry, John S.; Krajicek, Richard W.; Cradeur, Robert R.

    1978-01-01

    A new and improved method and apparatus for burning a hydrocarbon fuel for producing a high pressure thermal vapor stream comprising steam and combustion gases for injecting into a subterranean formation for the recovery of liquefiable minerals therefrom, wherein a high pressure combustion chamber having multiple refractory lined combustion zones of varying diameters is provided for burning a hydrocarbon fuel and pressurized air in predetermined ratios injected into the chamber for producing hot combustion gases essentially free of oxidizing components and solid carbonaceous particles. The combustion zones are formed by zones of increasing diameters up a final zone of decreasing diameter to provide expansion zones which cause turbulence through controlled thorough mixing of the air and fuel to facilitate complete combustion. The high pressure air and fuel is injected into the first of the multiple zones where ignition occurs with a portion of the air injected at or near the point of ignition to further provide turbulence and more complete combustion.

  16. A Temperature-Controlled Chamber Based on Vortex Cooling

    SciTech Connect

    Krider, John; Nguyen, Hogan; /Fermilab

    2007-11-01

    We describe the construction and performance of a temperature-controlled chamber, based on a 'vortex' cooler. The chamber is capable of operation between room temperature and -42 C. The only nontrivial infrastructure requirement is dry compressed gas at 100 psi and 8 cfm. The chamber is economical, easy to operate and to build using commercially available parts. Since the refrigerant is compressed air, the chamber has minimal environmental impact. It does not generate mechanical vibrations nor electrical noise. It is suitable for testing electronically sensitive and low-power electronics at cold temperatures. We measured the reserve cooling capacity of the cold plate to be 17 watts at -27 C. At the limiting temperature of -42 C, reserve cooling power reduces to zero.

  17. Measurement of organic compound emissions using small test chambers

    SciTech Connect

    Tichenor, B.A.

    1989-01-01

    The paper discusses the measurement of organic emissions from a variety of indoor materials, using small (166 liter) environmental test chambers. The following materials were tested: adhesives, caulks, pressed wood products, floor waxes, paints, and solid insecticides. For each material, chamber concentration of organics has been determined for a range of environmental conditions (e.g., air exchange rate, temperature, and relative humidity). Various product loading ratios (area of sample/volume of chamber) have also been investigated. Emission rates for individual organic compounds, as well as total measured organics, were calculated. The effects of environmental variables on emission rates have been evaluated. Models are used to evaluate the effect of chamber walls and concentration on emission rates.

  18. Environmental test chamber

    NASA Astrophysics Data System (ADS)

    Qian, Li

    2016-04-01

    Increasing of particulates in the air in city became a serious problem , but in the Beijing area students rarely research such questions. The intelligent instrument of suspended particulate matter sampler which introduce from the institute of geology and geophysics, Chinese academy of sciences can be collected for all kinds of grain size of suspended matter in the air.We put them near schools,so the PM2.5 in the air near our shool can be collected. The method for analysis is the environmental magnetism, etc. Numerous studies have demonstrated rapid and non-destructive magnetic parameters measurement for rapid estimation of particulate sources of heavy metals and provides a very effective means. Environmental magnetism is a frontier science among earth science, environmental science and magnetism,which has been applied into many fields because it is capable of providing important information for studying the regional or global environmental changes and the impact of human activity on environment. Testing magnetic parameters of the particle can extract atmospheric particulate matter source, distribution, pollution level and dynamic change information. Measured the magnetic parameters of ARM, IRM, hysteresis loop , element composition, soil particle size of the soil, leaf, the river and dustfall samples and PM2.5 of the atmospheric dustfall samples on campus and the Beijing city.By means of environmental magnetism analysis of atmospheric pollutants category, amount, etc. Magnetic properties of pollutants may indicate the source of the pollutants, the nature of the analysis of pollutants, monitoring pollutant change over time.

  19. Performance of Several Combustion Chambers Designed for Aircraft Oil Engines

    NASA Technical Reports Server (NTRS)

    Joachim, William F; Kemper, Carlton

    1928-01-01

    Several investigations have been made on single-cylinder test engines to determine the performance characteristics of four types of combustion chambers designed for aircraft oil engines. Two of the combustion chambers studied were bulb-type precombustion chambers, the connecting orifice of one having been designed to produce high turbulence by tangential air flow in both the precombustion chamber and the cylinder. The other two were integral combustion chambers, one being dome-shaped and the other pent-roof shaped. The injection systems used included cam and eccentric driven fuel pumps, and diaphragm and spring-loaded fuel-injection valves. A diaphragm type maximum cylinder pressure indicator was used in part of these investigations with which the cylinder pressures were controlled to definite valves. The performance of the engines when equipped with each of the combustion chambers is discussed. The best performance for the tests reported was obtained with a bulb-type combustion chamber designed to give a high degree of turbulence within the bulb and cylinder. (author)

  20. Autoignition Chamber for Remote Testing of Pyrotechnic Devices

    NASA Technical Reports Server (NTRS)

    Harrington, Maureen L.; Steward, Gerald R.; Dartez, Toby W.

    2009-01-01

    The autoignition chamber (AIC) performs by remotely heating pyrotechnic devices that can fit the inner diameter of the tube furnace. Two methods, a cold start or a hot start, can be used with this device in autoignition testing of pyrotechnics. A cold start means extending a pyrotechnic device into the cold autoignition chamber and then heating the device until autoignition occurs. A hot start means heating the autoignition chamber to a specified temperature, and then extending the device into a hot autoignition chamber until autoignition occurs. Personnel are remote from the chamber during the extension into the hot chamber. The autoignition chamber, a commercially produced tubular furnace, has a 230-V, single-phase, 60-Hz electrical supply, with a total power output of 2,400 W. It has a 6-in. (15.2-cm) inner diameter, a 12-in. (30.4-cm) outer diameter and a 12-in.- long (30.4-cm), single-zone, solid tubular furnace (element) capable of heating to temperatures up to 2,012 F (1,100 C) in air.