Absorbed dose measurements of a handheld 50 kVP X-ray source in water with thermoluminescence dosemeters

Absorbed dose rate measurements of a 50 kV(p) handheld X-ray probe source in a water phantom are described. The X-ray generator is capable of currents of up to 40 microA, and is designed for cranial brachytherapy and intraoperative applications with applicators. The measurements were performed in a computer-controlled water phantom in which both the source and the detectors are mounted. Two different LiF thermoluminescence dosemeter (TLD) phosphors were employed for the measurements, MTS-N (LiF:Mg,Ti) and MCP-N (LiF:Mg,Cu,P). Two small ionisation chambers (0.02 and 0.0053 cm(3)) were also employed. The TLDs and chambers were positioned in watertight mounts made of water-equivalent plastic. The chambers were calibrated in terms of air-kerma rate, and conventional protocols were used to convert the measurements to absorbed dose rate. The TLDs were calibrated at National Institute of Standards and Technology (NIST) in terms of absorbed dose rate using a (60)Co teletherapy beam and narrow-spectrum X-ray beams. For the latter, absorbed dose was inferred from air-kerma rate using calculated air-kerma-to-dose conversion factors. The reference points of the various detectors were taken as the center of the TLD volumes and the entrance windows of the ionisation chambers. Measurements were made at distances of 3-45 mm from the detector reference point to the source center. In addition, energy dependence of response measurements of the TLDs used was made using NIST reference narrow spectrum X-ray beams. Measurement results showed reasonable agreement in absorbed dose rate determined from the energy dependence corrected TLD readings and from the ionisation chambers. Volume averaging effects of the TLDs at very close distances to the source were also evident.     

Performance of a personal neutron dosemeter based on direct ion storage at workplace fields in the nuclear industry

In the framework of the EVIDOS project, funded by the EC, measurements were carried out using dosemeters, based on ionisation chambers with direct ion storage (DIS-N), at several workplace fields, namely, at a fuel processing plant, a boiling and a pressurised water reactor, and near transport and storage casks. The measurements and results obtained with the DIS-N in these workplaces, which are representative for the nuclear industry, are described in this study. Different dosemeter configurations of converter and shielding materials were considered. The results are compared with values for personal dose equivalent which were assessed within the EVIDOS project by other partners. The advantages and limitations of the DIS-N dosemeter are discussed.     

Characteristics of a Self-Initiating Pulse-Periodic Discharge in a Kr/SF6 Gas Mixture

The characteristics are given of a low-pressure, volume, pulse-periodic discharge in a krypton/SF₆ gas mixture, accompanied by the formation of a domain in a spherical anode–flat cathode system of electrodes. It is shown that, when a dc voltage of U _ch 1.0 kV is applied to the anode, a volume pulse-periodic discharge with a pulse repetition rate of 0.1 to 120 kHz is ignited in the interelectrode gap. The static and dynamic current–voltage characteristics of the discharge are investigated, as well as the plasma radiation spectra in the range from 130 to 350 nm, oscillograms of voltage across the discharge gap, of the current and radiation of plasma, the dependence of the radiation brightness of the 249-nm KrF(B–X) band on the mean discharge current, and the resource characteristics of radiation on the electronic-vibrational transitions of an excimer molecule. It is demonstrated that the domain plasma may be used in a low-pressure pulse-periodic excimer lamp emitting in the 230 nm KrF(D–X)/249 nm KrF(B–X) band system. The active medium proper plays the role of the commutator in the lamp, and a dc voltage source is used to ignite the discharge. Such lamps can be used in polymer chemistry, biology, potable water purification systems, for the sterilization of medical instruments, and in micro- and quantum electronics.     

Secondary ion MS imaging of lipids in picoliter vials with a buckminsterfullerene ion source

Investigation of the spatial distribution of lipids in cell membranes can lead to an improved understanding of the role of lipids in biological function and disease. Time-of-flight secondary ion mass spectrometry is capable of molecule-specific imaging of biological molecules across single cells and has demonstrated potential for examining the functional segregation of lipids in cell membranes. In this paper, standard SIMS spectra are analyzed for phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine, phosphatidylinositol, cholesterol, and sulfatide. Importantly, each of the lipids result in signature mass spectral peaks that allow them to be identified. These signature peaks are also useful for imaging experiments and are utilized here to simultaneously image lipids on a micrometer scale in picoliter vials. Because the low secondary ion signal achieved for lipids from an atomic primary ion source makes cell-imaging experiments challenging, improving signal with cluster primary ion sources is of interest. Here, we compare the secondary ion yield for seven lipids using atomic (Ga+ or In+) ion sources and a buckminsterfullerene (C60+) primary ion source. A 40-1000-fold improvement in signal is found with C60+ relative to the other two ion sources, indicating great promise for future cellular imaging applications using the C60+ probe.     

Parameters of high-frequency vacuum breakdown in a mass-spectrometer ion source

The electrical and optical characteristics of hf vacuum breakdown are experimentally investigated. It is shown that the breakdown current amplitude can reach 20 A with a voltage of up to 30 kV on the electrodes and a discharge duration of 20–25 nsec.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 4, pp. 645–648, April, 1982.     

Characteristics of the pressure profile in the accelerator on the RF negative ion source at ASIPP

Neutral beam injection(NBI) systems based on negative hydrogen ion sources—rather than the positive ion sources that have typically been used to date—will be used in the future magnetically confine nuclear fusion experiments to heat the plasma. The collisions between the fast negative ions and neutral background gas result in a significan number of high-energy positive ions being produced in the acceleration area, and for the high-power long-pulse operation of NBI systems, this acceleration of p...     

Simulations of negative ion extraction from a multi-aperture ion source in the presence of the magnetic filter

The particle-in-cell method based numerical model of negative ion beam extraction from a large volume multi-aperture ion source is briefly described. The model takes into account the influence of the transversal magnetic field and diffusion of electrons across the field. The current-voltage curves for H^- ions and electrons are presented. The results are compared for the three cases: without filter field; with the field but without diffusion; and with the field and electron diffusion. The presence of the magnetic filter field increases H^? yields significantly (by 200%). A random-walk electron diffusion model enables electrons to travel through the magnetic field, which reduces a nonphysical effect of excessive electron aggregation in the filter region. The changes of filter width do not alter H^? current more than 10%.     

Surface topography of eroded Cu and Si cathodes in a PIG ion source

The surface topography development on a Cu sheet and a Si(111) wafer was studied after being sputtered in a Penning ionization gauge (PIG) ion source using Ar gas. In the case of Cu, a high density of conical structure was developed on the surface. The most striking feature was that the individual cones, relatively large in size, were often coated with impurity layers. Some cones were decorated with concentric ring-like patterns on their surfaces. The overlying coating was thought to be responsible for the initial growth of the cones and subsequent evolution of secondary protuberances on the surfaces of the cones. In the case of Si, though a few impurity-induced conical protrusions were formed, the dominant morphology was in the form of etch pits. In addition to usual single cones, Si surface developed cones of dimeric structure and cluster of cones.     

Studies of radioactive decays of completely ionized nuclei in a heavy ion storage ring

With a heavy ion synchrotron and a storage ring currently under construction at GSI in Darmstadt it will be possible to look for the still undiscovered mode of β⁻ decay to bound electron states. This mode has played a key role in nuclear synthesis at high temperatures. Possible detection techniques and the decay of ¹⁶³Dy as a test case as well as the decays of ¹⁸⁷Re and ²⁰⁵Tl, which are of astrophysical interest, are discussed.     

Some features of the discharge in an ion source based on a Penning cell

Results of investigating the operating regimes of a Penning cell in the absence of a magnetic field are discussed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 2, pp. 364–365, February, 1981.     

Extrasampling and thermal behavior of diode lasers used as a reference source in a Fourier transform IR spectrometer

The diode laser is often used as a reference source in an interferometer because its interferogram zero crossings allow for precise intervals to be used for sampling the measured interferogram. The diode laser side modes, the features of which depend on the laser's temperature and power, may generate extra sampling points. The number of extra sampling points is analytically evaluated, and the synthetic spectra are compared with those obtained experimentally using the Planetary Fourier Spectrometer. The conclusion is that the theoretical resolution is guaranteed in practice only when no more than one extra sampling point is generated. This is the case when either the diode laser side mode amplitudes are less than one half of the main mode amplitude or the distance in wave numbers between the side modes and the main mode times the maximum optical path difference is less than 1. Finally, once an appropriate diode laser has been chosen, the actual spectral resolution might be degraded by poor device-operating conditions.     

Characteristics of an acoustic emission source from a thermal crack in glass

Thermal cracks of mode I type oriented normal to the surface along an initial scratch were generated by blowing cold nitrogen gas through a small nozzle onto the surface of a glass plate. Acoustic emission (AE) signals emitted from the thermal cracks were detected on the opposite side of the plate, both at epicentral and at off-epicentral positions with a nine-channel AE system. AE source characteristics, such as moment tensor components, source-time function, radiation pattern, and dipole strength, were obtained from the detected waveforms. The strength of dipoles associated with the thermal cracks was determined from comparing the crack signals to those generated when a glass capillary was broken at the crack site prior to crack formation. It is shown that the AE source-time function, together with the dipole strength, can provide valuable information on the dynamic behavior of fracture.

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Résumé On a créé des fissures thermiques de Mode I orientées normalement à une surface en projetant de l'azote froid par un petit ajustage sur une rainure initiale à la surface d'une plaque de verre. Les signaux d'émission acoustique émis par la fissure thermique ont été détectés sur la face opposée de la plaque, à l'épicentre et en d'autres positions par rapport à la fissure, en utilisant un système de captation à neux canaux. Les formes d'ondes détectées fournissent les caractéristiques de la source acoustique, telles que les composantes du tenseur de moment, la fonction sourcetemps, la répartition de la radiation et la puissance du dipole. Cette dernière grandeur a été déterminée, lorsqu'elle est associée aux fissures thermiques, en comparant les signaux obtenus à ceux que produit un capillaire de verre rompu à l'endroit de la fissure, avant que celle-ci se forme. On montre que la fonction d'émission acoustique source-temps ainsi que la puissance dipole peuvent fournir des informations valables sur le comportement dynamique d'une rupture.

     

Determination of the content of <Superscript>85</Superscript>Kr and <Superscript>133</Superscript>Xe in air using a krypton-xenon mixture

A procedure was developed for determining radioactive isotopes of Kr and Xe in air using a krypton-xenon mixture (KXM) produced at air separation plants. The procedure allows determination of background volume concentrations of Kr and Xe at long distances from sites of their injection using common spectrometric apparatus. The results of monitoring volume concentrations of ⁸⁵Kr and ¹³³Xe in Cherepovets in 2006–2008 are presented.     

Non-equilibrium grain boundary segregation of phosphorus under a high applied tensile stress in a 2.25Cr1Mo steel

Grain boundary segregation of phosphorus under a 350 MPa tensile stress at 520 °C in a 0.025 wt.% P-doped 2.25Cr1Mo steel, which has already been thermally equilibrated, is examined using Auger electron spectroscopy. The segregation of phosphorus during stress ageing has a non-equilibrium characteristic, which has two phosphorus segregation peaks over its equilibrium segregation level, one of which is mainly due to the vacancy–phosphorus complex effect and the other due to the diffusional creep effect.     

Nitriding of AISI 304 stainless steel in a 85% H2/15% N2 mixture with an inductively coupled plasma source

We present some results obtained from nitriding of AISI 304 stainless steel substrates. The process take place in an inductively coupled plasma discharge supplied by a ∼300 W source at 13.56 MHz in a 85% hydrogen and 15% nitrogen gas mixture. The samples, placed into a pyrex glass discharge chamber (3.5 cm diameter and 60 cm long) were biased by DC power from 0 to −300 V with respect to ground. The resulting hardness is a function of the increasing nitrogen concentration in the substrate and this, in turn, of the temperature which varied from 200 to 470 °C. After nitriding at −300 V, hardness values of 1790 HV under 10 g loads and of 632 HV for 300 g were measured. X-ray diffraction indicates that the expanded phase amplitude (γ_N) depends on the substrate temperature.     

Direct quantitative analysis of organic compounds in the gas and particle phase using a modified atmospheric pressure chemical ionization source in combination with ion trap mass spectrometry

A slightly modified atmospheric pressure chemical ionization source is employed for direct quantitative analysis of volatile or semivolatile organic compounds in air. The method described here is based on the direct introduction of an analyte in the gas or particle phase, or both, into the ion source of a commercial ion trap mass spectrometer. For quantitation, a standard solution is directly transferred into the vaporizer unit of the ion source via a deactivated fused-silica capillary by using the sheath liquid syringe pump, which is part of the mass spectrometer. The standard addition procedure is conducted by varying the pump rate of a diluted solution of the standard compound in methanol/water. A N2 sheath gas flow is applied for optimal vaporization and mixing with the analyte gas stream. By performing detailed reagent ion monitoring experiments, it is shown that the relative signal intensity of [M + H]+ ions is dependent on the relative humidity of the analyte gas stream as well as the composition and concentration of CI reagent ions. The method is validated by a comparison of the standard addition results with a calibration test gas of known concentration. To demonstrate the potential of atmospheric pressure chemical ionization mass spectrometry as a quantitative analytical technique for on-line investigations, a tropospherically relevant reaction is carried out in a 493-L reaction chamber at atmospheric pressure and 296 K in synthetic air at 50% relative humidity. Finally, the applicability of the technique to rapidly differentiate between analytes in the gas and particle phase is demonstrated.     

Reduction of space charge effects in inductively coupled plasma mass spectrometry using a supplemental electron source inside the skimmer: ion transmission and mass spectral characteristics

An electron source consisting of a heated filament has been added to the skimmer to suppress space charge effects in inductively coupled plasma mass spectrometry (ICPMS). Electrons from this source can reduce the space charge repulsion between the positive ions in the ion beam. As a result, ion transmission efficiency and analyte ion sensitivities are significantly improved across the full mass range. MO+/M+ abundance ratios are not affected, M2+/M+ abundance ratios increase only slightly, and no new background ions are created by this electron injection technique.     

Characteristics of a gas-discharge co-laser in generation on an overtone 1. Steady-state regime

The work presents the parametric dependences of the energy and spectral characteristics of the gas-discharge CO-laser in steady-state regime in generation on the first overtone on the gas temperature, the pumping power, and the cavity Q-factor of the resonator. The article examines questions of the selection of the individual vibrational and rotational lines. Comparisons with experimental results are made.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 2, pp. 289–294, August, 1981.