Contribution à la Mesure de l'Exposition Produite par les Photons Émis par le<sup>60</sup>Co

Allisy, A.

doi:10.1088/0026-1394/3/2/003

Cited by 15 publications

(5 citation statements)

References 23 publications

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“…The air kerma and exposure standards are based upon measurements with a plane parallel graphite cavity chamber described by Boutillon and Niatel(l973) using a theoretical analysis given by Allisy (1967). The data bases for the electron stopping powers, mass energy absorption coefficients and W / e value are the same as at the other laboratories.…”

Section: The Bipm "Co Air Kerma Standardmentioning

confidence: 99%

A comparison of absorbed dose standards for high-energy X-rays

Shortt¹,

Ross²,

Schneider³

et al. 1993

Phys. Med. Biol.

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AbStracL An indirect comparison of the absorbed dose to water standards of lhe FTB and the NRC was carried out for 18/20 MV x-rays using five ionimtion chambers as m s f e r insmmenls. The absorbed dose standard of the Fl% is based on the total absorption of 5.6 MeV electrons in Fncke solution. The NRC standard uses Wcke solution whose calibration is based on measuremenfs made with a water calorimeter Bnd a calculation of the heat defect For high-energy x-rays. the difference found between the standards of 0.4% is within the expected uncertainties. Tbe comparison was linked to existing %o absorbed dose to warer and air kema standards by comparing measurements of those quantities at the PTB, NRC and BIPM. Agreement was better than 0.78 in all cases. For the i o n i d o n chamberr used in Lhi study, the absorbed dose calibration factors for 18/20 MV x-rays are a b u t 2% lower than those for "CO gamma-rays. . IntroductionThe Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig and the National Research Council of Canada (NRC) in Ottawa have developed primary standards of absorbed dose to water for high-energy radiation. Although both groups are carrying out further developments, this comparison indicates the state of the art at the two laboratories for highenergy photon dosimeby. Section I (x-and gamma-radiation; electrons) of the Comit6 Consultatif pour les & I o n s de Mesure des Rayonnements Ionisants (CCEMRI) (BIPM 1988) recommended that primary standards for absorbed dose be compared in collaboration with the Bureau Intemational des Poids et Mesures (BIPM) so that these comparisons could be linked to the existing BIPM 6oCo reference system. Thus measurements of air kerma and absorbed dose to water for %o were made at the BIPM as well as the NRC and the PTB. The results of these measurements are presented here.As can be seen from section 2, the primary standards of absorbed dose to water for high-energy x-rays are more complex than those of air kerma since auxiliary equipment and procedures are involved. Therefore, primary standards are not transportable and comparison of these standards has to be made using transfer instruments. Since ionization chambers are easily transportable, have good precision and long-term stability, and are connected to directly readable measuring assemblies, they were chosen for use as transfer instruments.

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Section: The Bipm "Co Air Kerma Standardmentioning

confidence: 99%

A comparison of absorbed dose standards for high-energy X-rays

Shortt¹,

Ross²,

Schneider³

et al. 1993

Phys. Med. Biol.

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“…where g is the fraction of the initial electron energy which is lost in bremsstrahlung, y is the variable (2,-z), j(T, hv, y ) is an energy dissipation function which is closely related to the energy dissipation function f p c ( x ) of Allisy (1967), and Boutillon and Niatel (1973) for plane conical sources. It has the dimension of the inverse of a length, If @a is the angular distribution of the fluence of the electrons S in the plane z , we have the relation…”

Section: Production and Dissipation Of The Electronsmentioning

confidence: 99%

“…The theoretical determination of the correction factor k p for such a flat chamber was solved by applying the same type of analysis as that used by Allisy (1967), and Boutillon and Niatel (1973), for the determination of exposure at BIPM. k p is calculated for two experimental situations: when the reference plane is taken as the middle plane zm of the cavity, or as its front plane zf (figure 1).…”

Section: Introductionmentioning

confidence: 99%

Perturbation correction for ionometric determination of absorbed dose in a graphite phantom for⁶⁰Co gamma rays

Boutillon¹

1983

Phys. Med. Biol.

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Calculations have been made of the perturbation correction to be applied to a flat cavity ionisation chamber. This makes possible the use of such a chamber as a primary standard of absorbed dose in graphite for 6oCo gamma rays. The good agreement between ionometric measurements and the calorimetric measurements of national laboratories of metrology gives strong support to the reliability of the calculated correction.

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“…For 21 MV x-rays the photon backscatter was assumed to be negligible. Data for backscattering of electrons produced in the phantom were taken from energy deposition calculations by Berger (Allisy 1967) for 6oCo and by Spencer (1959) for higher energies. A backscatter contribution of 3% for 6oCo and 1% for 21 MV x-rays was obtained.…”

Section: Comparison With Experiments and Other Calculation Methodsmentioning

confidence: 99%

Direct nucleophilic functionalization of C(sp²)–H-bonds in arenes and hetarenes by electrochemical methods

Shchepochkin¹,

Чупахин²,

Charushin³

et al. 2013

Russ. Chem. Rev.

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Relative lateral electron surface dose distributions from filters and air in high energy photon beams were determined using the Fermi-Eyges theory of multiple scattering. The model includes transmission and angular scattering in materials and in air. Backscatter from the phantom was also estimated. The variation of surface dose with different parameters such as atomic number, thickness and position of material, field size and photon energy was investigated. The calculated data show good agreement with experiment. For CO y rays, electron filters of medium atomic number give the lowest surface dose, whereas for higher energies a low to medium atomic number material should be used, especially for short material-phantom distances and large field sizes. The contribution to surface dose can be reduced by over 30% by placing a thin foil of high atomic number after a low to medium atomic number filter, thus scattering some electrons from the beam. For 6oCo y rays the air is often the dominant source of contaminating electrons because of high multiple scatter loss at this energy, while for higher photon energies the beam flattening filter is the main electron source because of the small emission angle of the electrons and the small scattering power at high energies. 60

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Contribution à la Mesure de l'Exposition Produite par les Photons Émis par le⁶⁰Co

Cited by 15 publications

References 23 publications

A comparison of absorbed dose standards for high-energy X-rays

A comparison of absorbed dose standards for high-energy X-rays

Perturbation correction for ionometric determination of absorbed dose in a graphite phantom for⁶⁰Co gamma rays

Direct nucleophilic functionalization of C(sp²)–H-bonds in arenes and hetarenes by electrochemical methods

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Contribution à la Mesure de l'Exposition Produite par les Photons Émis par le60Co

Cited by 15 publications

References 23 publications

A comparison of absorbed dose standards for high-energy X-rays

A comparison of absorbed dose standards for high-energy X-rays

Perturbation correction for ionometric determination of absorbed dose in a graphite phantom for60Co gamma rays

Direct nucleophilic functionalization of C(sp2)–H-bonds in arenes and hetarenes by electrochemical methods

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Product

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About

Contribution à la Mesure de l'Exposition Produite par les Photons Émis par le⁶⁰Co

Perturbation correction for ionometric determination of absorbed dose in a graphite phantom for⁶⁰Co gamma rays

Direct nucleophilic functionalization of C(sp²)–H-bonds in arenes and hetarenes by electrochemical methods