Ionization Produced by 5-Mev Alpha Particles in Argon Mixtures

Melton, Charles E.; Hurst, G. S.; Bortner, T.E.

doi:10.1103/physrev.96.643

Cited by 78 publications

(14 citation statements)

References 6 publications

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“…This is the case for the Penning ionization ͑PI͒ and hetero-nuclear associative ionization ͑AI͒ mechanisms involving the Ne 1s and dimer states. [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] Table I is a list of the PI and AI mechanisms and related processes affecting the population of the relevant excited species, together with the rate coefficients used in the simulation. In addition to the listed mechanisms, the simulation includes collisional mixing between Ne 1s or higher excited states and radiative cascading, as well as the imprisonment of resonance radiation, or photon trapping effect, i.e., the repeated absorption and reemission of the Ne( 1 P 1 , 3 P 1 ) spontaneous emissions by neighboring ground-state Ne atoms.…”

Section: A Descriptionmentioning

confidence: 99%

Monte Carlo simulation study of the Fano factor, w value, and energy resolution for the absorption of soft x rays in xenon–neon gas mixtures

Santos

Dias

Rachinhas

et al. 2001

Journal of Applied Physics

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Prediction of the thermophysical properties of pure neon, pure argon, and the binary mixtures neon-argon and argon-krypton by Monte Carlo simulation using ab initio potentials Absolute W value measurements for 5.9 keV x rays in Ne-Xe mixtures at atmospheric pressures Xenon gas proportional-scintillation counters ͑GPSC͒ have many applications in the detection of soft x rays where their energy resolution, R, is comparable to solid-state detectors when large window areas are required. However, R is known to deteriorate for energies E xr below 2-3 keV due to electron loss to the entrance window. Since the addition of a lighter noble gas increases the absorption depth, we have investigated the use of Xe-Ne gas mixtures at atmospheric pressure as detector fillings. The results of a Monte Carlo simulation study of the Fano factor, F, the w value, and the intrinsic energy resolution, Rϭ2.36(Fw/E xr ) 1/2 , are presented for Xe-Ne mixtures and pure Xe and Ne. The results show that the addition of Ne to Xe reduces the intrinsic energy resolution R but this never compensates for the reduction in scintillation yield in GPSC applications, implying that the instrumental energy resolution R will only improve with the addition of Ne when electron loss to the window in pure Xe is significant. The simulation reproduces the photoionization process of the Xe and Ne atoms, the vacancy cascade decay of the residual ions, and the elastic and inelastic scattering of electrons by the gas atoms. The contribution of energy and charge transfer mechanisms such as Penning, associative, and transfer ionization is discussed in detail. It is shown that Penning and associative ionization are the crucial indirect ionization processes which determine the behavior of F and w at low concentrations of Xe. The importance of the nonmetastable Ne states is also assessed.

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Section: A Descriptionmentioning

confidence: 99%

Monte Carlo simulation study of the Fano factor, w value, and energy resolution for the absorption of soft x rays in xenon–neon gas mixtures

Santos

Dias

Rachinhas

et al. 2001

Journal of Applied Physics

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“…The role of impurities in our system can be of great importance in these measurements on account of Penning e!ects [20], which increase the ionization yield, therefore reducing the =-value measured. This was tested by switching o!…”

Section: Impuritiesmentioning

confidence: 99%

A technique for the absolute measurement of the W-value for X-rays in counting gases

Vinagre¹,

Conde²

2000

Nuclear Instruments and Methods in Physics Research Section A:

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A technique was developed for the absolute measurement of the W-value (the mean energy for the production of an electron-ion pair) for low-energy X-rays in a wide range of gases at atmospheric pressures, with a standard uncertainty better than 1%. This technique is based on the absolute measurement of the primary ionization charge produced by X-ray photons from a constant intensity monoenergetic X-ray source, e.g. a long lifetime radioactive source. The ionization charge is calibrated by the number of X-ray photons absorbed in the gas, counted with a photon detector. For this purpose, a hybrid detector system was tested and its use in W-value measurements was investigated. The technique was applied to pure xenon at 825 Torr with 5.9 keV X-rays and a W-value of 21.61> \ eV was obtained for a 68% con"dence level. The required corrections and the di!erent factors contributing to the accuracy of the results are discussed. The advantages and limitations of this technique are explored and future developments are discussed.

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“…L'énergie moyenne nécessaire pour former une paire d'ions est fonction essentiellement du gaz ou du mélange gazeux, et la présence d'impu retés, même en faible quantité, peut entraîner de grandes variations de valeur, en particulier pour les gaz nobles (tableau 2) [53]. Pour un mélange gazeux, Hurst propose la formule [54] : où w, w1, w2 sont les énergies moyennes nécessaires pour former une paire d'ions respectivement dans le mélange gazeux et dans chacun des gaz constitutifs, p1 et p2 les pressions partielles de remplissage, et« a » une constante caractéristique du mélange gazeux déterminé empiriquement. Le tableau ci-dessous donne dif férentes valeurs de « a » : mélange : N2-H2 N2-Ar N2-O2 He-Ar He-H2 «a» : 0,28 0,53 1,06 0,75 3,55 mélange : He-N2…”

Section: Réalisation Des Compteurs : A) Technologie Généraleunclassified

Les compteurs proportionnels et leur utilisation en radioprotection

Marque

Joffre

1967

Radioprotection

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Ionization Produced by 5-Mev Alpha Particles in Argon Mixtures

Cited by 78 publications

References 6 publications

Monte Carlo simulation study of the Fano factor, w value, and energy resolution for the absorption of soft x rays in xenon–neon gas mixtures

Monte Carlo simulation study of the Fano factor, w value, and energy resolution for the absorption of soft x rays in xenon–neon gas mixtures

A technique for the absolute measurement of the W-value for X-rays in counting gases

Les compteurs proportionnels et leur utilisation en radioprotection

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