Prediction models of the ionization coefficient and ionization cross-section based on multi-layer molecular parameters

Prediction models were proposed to estimate the reduced Townsend ionization coefficient and ionization cross-section. A shape function of the reduced Townsend ionization coefficient curves was derived from the ionization collision probability model. The function had three parameters:the first ionization potential energy, A_α, and B_α. A_α and B_α were related to the molecule symmetry and size. The polarization of molecules could characterize the molecule s...     

Measurement of boron isotopes by negative thermal ionization mass spectrometry

The isobaric interference for boron isotopic measurement by negative thermal ionization mass spectrometry (NTIMS) has been studied,The result shows that the CNO^- is not only from the organic material,but also from nitrate in loading reagent in NTIMS,Monitoring the mass 43 ion intensity and 43/42 ratio of blank are also necessaary fro the boron isotopic measurement by NTIMS,other than is only boron content.     

Measurement of ionization distributions at nanometre level in tissue—equivalent gas

The developed track detector consists of two parts:a small drift region to obtain a good tracking and a relatively large multiplication region for getting an enough high gain at low pressure.All the track detector can be moved in the direction perpendicular to the beam by means of a micrometric screw.An automatic system allows the counting gas to flow continuously at constant pressure through the detector during the measurements.The system can measure ionization distributions at a few nanometer range.     

Determination of energy absorption in a mixed flux of fast neutrons and γ-rays by an ionization method

The possibility of separate determinations of the energy absorption of fast neutrons and -rays in the mixed radiation flux from a reactor has been studied with ioni/ation chambers. Three chambers with different hydrogenous fillers were used: polyethylene with an ethylene filler; graphite with a CO₂ filler and a chamber made from aerion, a conducting plastic, which was filled with a mixture of ethylene and CO₂. Calculations have been carried out to ascertain the sensitivity of these chambers to neutrons with energies ranging from 0.2–8 Mev. Variation of the neutron spectrum over wide limits has no effect on the accuracy in the determination of the absorbed dose in the hydrogenous substrates. A calculation shows that the error in the determination of the absorbed energy for fast neutrons is approximately 15% and is a weak function of the relative doses of neutrons and -rays.In conclusion the authors wish to express their gratitude to Yu. F. Chernilin for help in this experiment and T. B. Radzievskii for discussion of the results.     

Measurement of 8～25keV electron impact K－shell ionization cross sections of Cu and Co elements

Ｍｅａｓｕｒｅｍｅｎｔｏｆ８～２５ｋｅＶｅｌｅｃｔｒｏｎｉｍｐａｃｔＫ－ｓｈｅｌｌｉｏｎｉｚａｔｉｏｎｃｒｏｓｓｓｅｃｔｉｏｎｓｏｆＣｕａｎｄＣｏｅｌｅｍｅｎｔｓＡｎＺｈｕ（安竹），ＬｉＴａｉ－Ｈｕａ（李泰华），ＷａｎｇＬｉａｎｇ－Ｍｉｎｇ（王良明）...     

Measurement of 8—25keV electron impact K—shell ionization cross sections of Cu and Co elements

The influence of substrate of thin targets on ionization cross sections has been corrected by a new method based upon the bipartition model of electron transport.The measured cross sections for Cu element are in good agreement with existing experimental data and those produced by the empirical formula of Green and Cosslett.Cross sections for Co element are measured for the first time.     

Measurement of Sc and V K—shell ionization cross sections by slow electron impact

Electron-induced Sc and V K-shell ionization cross sections,which are scarce have been obtained from measurement of KαX-ray emission cross sections at energies from near threshold to 25keV.The influence of substrate of thin targets on ionization cross sections has been corrected using the bipartition model of electron transprot.     

Measurements of K-shell ionization cross-sections of S,Ca and Zn by 7–30 keV electron impact

The absolute K-shell ionization cross-sections of S, Ca and Zn by 7–30 keV electron impact have been measured. The targets were prepared by evaporating the compounds ZnS and CaF₂ to the thick pure carbon substrates. The effects of multiple scattering of electrons penetrating the target films, electrons reflected from the thick pure carbon substrates and Bremsstrahlung photons produced when incident electrons impacted on the targets are corrected by using Monte Carlo method. The uncertainties of our measured K-shell ionization cross-sections are, respectively, ～13% for S, ～15% for Ca and ～12% for Zn. The experimental results were compared with some theoretical results and available experimental data from the literature. The experimental data for S K-shell ionization cross-sections by 7–30 keV electron impact are given here for the first time.     

HPXe ionization chambers for γ spectrometry at room temperature

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.     

Analysis of cesium isotope compositions in environmental samples by thermal ionization mass spectrometry – 1. A preliminary study for source analysis of radioactive contamination in Fukushima prefecture

Cesium was recovered from plant samples obtained from Fukushima prefecture. The isotopic ratios of ¹³⁴Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs were analyzed by thermal ionization mass spectrometry with a single filament method using a TaO activator. Samples containing 5 Bq of ¹³⁷Cs were analyzed with typical analytical errors of approximately 0.5% for ¹³⁴Cs/¹³⁷Cs and approximately 0.1% for ¹³⁵Cs/¹³⁷Cs. Measurements of both ratios showed profiles that were characteristic of the measurements of among other environmental samples reported in the literature. The results showed the isotopic ratios of ¹³⁴Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs were applicable for the source analysis of radioactive Cs in Fukushima prefecture.     

State selective Rydberg charge transfer and ionization in low energy ion–atom collisions

The Classical Trajectory Monte Carlo (CTMC) simulation method with a core modified interaction potential has been used to study the single charge transfer in Na⁺and Ar⁺ ions colliding with a variety of state selected Na Rydberg atom targets (n=24, 28, 33, 40 and l=2) in the reduced velocity region v=0.2–2.0. The experimentally observed structures in the total capture cross section versus reduced velocity curves are reproduced by CTMC method. The n-distribution of final capture state has got two peaks viz. first one at n_f=n_i and the second one at a higher n_f depending on the initial angular momentum in the velocity regime 0.4–0.6. These structures have been explained in terms of quasimolecular-ion formation and a classical model proposed by Roy et al. (B.N. Roy, D.N. Tripathi, D.K. Rai, Phys. Rev. A 5 (1972) 1252). The CTMC ionization cross section results are benchmarked with the recent experimental measurement of Makarov et al. (O.P. Makarov, D.M. Homan, O.P. Sorokina, K.B. MacAdam, in: F. Aumayr, G. Betz, H.P. Winter (Eds.), Proceedings of the 20th International Conference on the Physics of Electronics and Atomic Collisions, Vienna, 1997, p. FR052) for Na⁺–Na(24 d).     

K-shell ionization cross sections of Cl and Lα, Lβ X-ray production cross sections of Ba by 6-30 keV electron impact

The absolute K-shell ionization cross sections of Cl and L_α, L_β X-ray production cross sections of Ba by 6-30 keV electron impact have been measured. The target was prepared by evaporating the thin film of compound BaCl₂ to the thick pure carbon substrate. The effects of multiple scattering of electrons penetrating the target films, electrons reflected from the thick pure carbon substrates and Bremsstrahlung photons produced when incident electrons impacted on the targets are corrected by using Monte Carlo method. For Ba L-shell X-ray characteristic peaks, the spectra were fitted by using spectrum-fitting program ALLFIT to extract more accurately the L_α and L_β peak counts. The experimental results, reported here for the first time in the energy region of 6-30 keV, were compared with some theoretical results developed recently.