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Applications of Bonner sphere detectors in neutron field dosimetry

Description: The theory of neutron moderation and spectroscopy are briefly reviewed, and moderators that are useful for Bonner sphere spectrometers are discussed. The choice of the neutron detector for a Bonner sphere spectrometer is examined. Spectral deconvolution methods are briefly reviewed, including derivative, parametric, quadrature, and Monte Carlo methods. Calibration is then discussed. (LEW)
Date: September 1, 1983
Creator: Awschalom, M. & Sanna, R.S.
Partner: UNT Libraries Government Documents Department

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

Description: 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.
Date: January 1, 1985
Creator: Awschalom, M. & Haken, R.K.T.
Partner: UNT Libraries Government Documents Department

New look at displacement factor and point of measurement corrections in ionization chamber dosimetry

Description: A new technique is presented for determination of the effective point of measurement when cavity ionization chambers are used to measure the absorbed dose due to ionizing radiation in a dense medium. An algorithm is derived relating the effective point of measurement to the displacement correction factor. This algorithm relates variations of the displacement factor to the radiation field gradient. The technique is applied to derive the magnitudes of the corrections for several chambers in a p(66)Be(49) neutron therapy beam. 30 references, 4 figures, 1 table.
Date: January 1, 1983
Creator: Awschalom, M.; Rosenberg, I. & Ten Haken, R.K.
Partner: UNT Libraries Government Documents Department

Update of neutron dose yields as a function of energy for protons and deuterons incident on beryllium targets

Description: Neutron absorbed dose yields (absorbed dose rates per unit incident current on targets at a given SAD or SSD) increase with incident charged particle energy for both protons and deuterons. Analyses of neutron dose yield versus incident particle energy have been performed for both deuterons and protons. It is the purpose of this report to update those analyses by pooling all of the more recent published results and to reanalyze the trend of yield, Y, versus incident energy, E, which in the past has been described by an expression of the form Y = aE/sup b/, where a and b are empirical constants. From the reanalyzed trend it is concluded that for a given size cyclotron (E/sub p/ = 2E/sub d/), the dose yields using protons are higher than those using deuterons up to a proton energy E/sub p/ of 64 MeV.
Date: November 1, 1982
Creator: Ten Haken, R.K.; Awschalom, M. & Rosenberg, I.
Partner: UNT Libraries Government Documents Department

Scaling neutron absorbed dose distributions from one medium to another

Description: Central axis depth dose (CADD) and off-axis absorbed dose ratio (OAR) measurements were made in water, muscle and whole skeletal bone TE-solutions, mineral oil and glycerin with a clinical neutron therapy beam. These measurements show that, for a given neutron beam quality and field size, there is a universal CADD distribution at infinity if the depth in the phantom is expressed in terms of appropriate scaling lengths. These are essentially the kerma-weighted neutron mean free paths in the media. The method used in ICRU No. 26 to scale the CADD by the ratio of the densities is shown to give incorrect results. the OAR's measured in different media at depths proportional to the respective mean free paths were also found to be independent of the media to a good approximation. It is recommended that relative CADD and OAR measurements be performed in water because of its universality and convenience. A table of calculated scaling lengths is given for various neutron energy spectra and for various tissues and materials of practical importance in neutron dosimetry.
Date: November 1, 1982
Creator: Awschalom, M.; Rosenberg, I. & Ten Haken, R.K.
Partner: UNT Libraries Government Documents Department

Variable curvature phantom

Description: The design of a variable curvature dosimetry phantom is briefly described. The phantom was developed to test the accuracy of the dose modification algorithms used to estimate dose distributions inside patient contours. 1 fig. (ACR)
Date: April 1, 1985
Creator: Rosenberg, I.; Awschalom, M. & Ten Haken, R.K.
Partner: UNT Libraries Government Documents Department

Muon shielding calculations: heterogeneous passive and active shields, applicat�ons to experimental beams and areas

Description: With the advent of a new generation of high-energy and high-intensity proton accelerators such as the one being built at the National Accelerator Laboratory and the one proposed by CERN, the problem of shielding external proton targets, the secondary beams produced from these targets, and even the secondary targets in the experimental areas becomes quite a massive and expensive project. In addition to the massive hadron shielding required, the high-energy muons produced by the decay of pions and kaons add large amounts of shielding especially in the forward (beam) direction. Homogeneous shields can be designed with programs which have been discussed previously. They have developed a computer program which allows them to design heterogeneous shields with voids and/or magnetic fields. The heterogeneous shields without magnetic fields are called passive shields and those with magnetic fields are called active shields. Results of some of the studies made on the design of such shields are presented. Specific application to the design of shielding for a primary external proton beam target and for a specific experiment are discussed.
Date: January 1, 1971
Creator: Theriot, D.; Awschalom, M.; Lee, K. & /Fermilab
Partner: UNT Libraries Government Documents Department

Characteristics of A-150 plastic-equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons

Description: The evaluation of a gas mixture having an atomic composition similar to that of A-150 TE-plastic has been extended to a high energy neutron therapy beam. A-150 gas, air and methane-based TE gas were each flowed through A-150 plastic-walled ion chambers of different sizes and irradiated with p(66)Be(49) neutrons. A tentative value for anti W(A-150) of 27.3 +- 0.5 J C/sup -1/ was derived for this beam. The anti W value of the A-150 gas mixture is compared to those of methane-based TE gas and of air for the p(66)Be(49) neutron beam as well as to corresponding values found in similar experiments using 14.8 MeV monoenergetic neutrons. 17 references, 3 figures, 3 tables.
Date: July 8, 1982
Creator: Awschalom, M.; Rosenberg, I.; Ten Haken, R.K.; Pearson, D.W.; Attix, F.H. & DeLuca, P.M.
Partner: UNT Libraries Government Documents Department

Anti W comparisons for A150 plastic-equivalent gases, TE gas, and air

Description: As part of our continuing evaluation of A150 plastic equivalent gases for neutron dosimetry, we have measured ionization ratios which are related to anti W ratios between gases in the p(66)Be(49) neutron beam at Fermilab. Additionally we have extended our earlier measurements (DeLuca, et al., 1980) at the UW gas target /sup 3/H(d,n)/sup 4/He neutron source to include an uncollimated beam geometry with ion chambers close to the target. Observed differences from the earlier results can probably be explained on the basis of neutron spectra, which await further determination.
Date: January 1, 1981
Creator: Pearson, D.W.; DeLuca, P.M. Jr.; Schell, M.C.; Attix, F.H.; Awschalom, M.; Rosenberg, I. et al.
Partner: UNT Libraries Government Documents Department

Hadron spectra from high energy proton proton interactions

Description: It is proposed to measure the hadron spectra resulting from high energy proton-proton collisions using a single arm focusing spectrometer. These measurements will provide elastic and inelastic P-P cross sections for incident beam energies up to 200 GeV/c and for momentum transfers |t| from 0.01 up to about 10 to 15 (BeV/c){sup 2}. In addition, they will obtain yields of pions and kaons produced in the interactions.
Date: June 1, 1970
Creator: Diebold, R.; /Argonne; Guerriero, L.; U., /Bari; Lanou, R.; U., /Brown et al.
Partner: UNT Libraries Government Documents Department