Maximum X-ray Intensity Research Articles

Enhancement of X-ray emission from nanocolloidal gold suspensions under double-pulse excitation.

Enhancement of X-ray emission was observed from a micro-jet of a nano-colloidal gold suspension in air under double-pulse excitation of ultrashort (40 fs) near-IR laser pulses. Temporal and spatial overlaps between the pre-pulse and the main pulse were optimized for the highest X-ray emission. The maximum X-ray intensity was obtained at a 1–7 ns delay of the main pulse irradiation after the pre-pulse irradiation with the micro-jet position shifted along the laser beam propagation. It was revealed that the volume around gold nanoparticles where the permittivity is near zero, ε ≈ 0, accounts for the strongest absorption, which leads to the effective enhancements of X-ray emission.

Effect of electron focusing in x-ray sources using LiTaO3 crystals excited by neodymium-doped yttrium lithium fluoride laser light

The intensity of x-rays from a 15 mm-diameter metal target bombarded by electrons emitted from a LiTaO3 crystal is found to depend upon the distance, h, between the crystal and the target. The electron emission of the LiTaO3 crystal is generated by being excited with light from a neodymium-doped yttrium lithium fluoride laser. The x-ray intensity is highest for h = 6 mm, coinciding also with a minimum electron spot size. The coincidence of the minimum electron spot size and maximum x-ray intensity with the 15 mm-diameter target is a result of self-focusing of the electrons by the higher electric field at the edge of the cylindrical crystal. The maximum electron energy at h = 6 mm with 120 s of laser irradiation is 47 keV, which is estimated from the maximum energy of bremsstrahlung x-rays.

X-ray and runaway electron generation in repetitive pulsed discharges in atmospheric pressure air with a point-to-plane gap

In this paper, using two repetitive nanosecond generators, x-rays were detected in atmospheric air with a highly inhomogeneous electric field by a point-to- plane gap. The rise times of the generators were about 15 and 1 ns. The x-rays were directly measured by various dosimeters and a NaI scintillator with a photomultiplier tube. X-rays were detected in the continuous mode at pulse repetition frequency up to 1 kHz and a voltage pulse rise time of ∼15 ns. It is shown that the maximum x-ray intensity is attainable at different pulse repetition frequencies depending on the voltage pulse parameters and cathode design. In atmospheric pressure air the x-ray intensity is found to increase with increasing the pulse repetition frequency up to 1 kHz. It is confirmed that the maximum x-ray intensity is attained in a diffuse discharge in a point-to-plane gap.

Optimization of X-ray target parameters for a high-brightness microfocus X-ray tube

Parameters of a transmission-type X-ray target have been optimized for a microfocus X-ray tube with an emphasis on maximizing the intensity of X-rays generated from the target while reducing the X-ray focal spot size. Monte Carlo simulation code MCNPX was used for the calculation of X-ray intensity generated from the X-ray tube. The calculation shows that the target thickness plays a dominant role in the enhancement of X-ray intensity. The optimum thickness to get maximum X-ray intensity for a given beam current was derived from the calculation for a broad range of electron energies from 30 keV to 150 keV. In addition, stability of a transmission-type target against localized thermal loading, which is attributed to the electron beam impinging on a micron-sized target region, was also investigated by the calculation of the temperature distribution within the target. From the analysis, we present the maximum allowable electron-beam power loading for a stable operation of the transmission-type target at different incident electron beam energies.

Determination of Hg from Cu concentrates by X-ray fluorescence through preconcentration on polyurethane foam

A methodology was developed for the separation and determination of microamounts of mercury from copper concentrate samples by wavelength dispersive X-ray fluorescence (WDXRF) after solid-phase extraction of mercury from iodide medium using polyurethane foam (PUF). The best sorption conditions for the Hg–KI–PUF system were settled using X-ray fluorescence technique after collection of ground PUF on a filter paper by vacuum filtration and direct measurement of the intensity signal of the sorbed mercury on PUF. The main parameters of sorption such as iodide concentration, pH, shaking time and sample dilution effect were studied. The system shows rapid kinetic sorption and maximum X-ray intensity signal was achieved after shaking for 2 min a 0.01 mol l −1 iodide solution containing microamounts of mercury in the pH range from 1.0 to 9.0. Effective sorption up to a volume of 0.9 l allows preconcentration of mercury. A linear fit up to 50 μg mercury was obtained by the plot of the initial mercury mass in the bulk solution (0.5 l) vs. its respective XRF intensity signal measurement on ground PUF after the sorption process. The calibration sensitivity, quantification and detection limits found were 9.09 CPS μg −1, 9.0 and 2.7 μg, respectively. The sorption of many elements was also evaluated under the best conditions. High concentrations of Cu(II) and Fe(III) interfere seriously. Mercury-selective separation could be achieved using citrate or EDTA as masking agent; no interference due to copper matrix samples was observed in citrate medium. This methodology was evaluated by recovery for mercury determination in copper concentrate ore samples supplied by a mining industry and copper sulfate salts; the results were between 98% and 106%.

Determination of Hg from Cu concentrates by X-ray fluorescence through preconcentration on polyurethane foam

A methodology was developed for the separation and determination of microamounts of mercury from copper concentrate samples by wavelength dispersive X-ray fluorescence (WDXRF) after solid-phase extraction of mercury from iodide medium using polyurethane foam (PUF). The best sorption conditions for the Hg–KI–PUF system were settled using X-ray fluorescence technique after collection of ground PUF on a filter paper by vacuum filtration and direct measurement of the intensity signal of the sorbed mercury on PUF. The main parameters of sorption such as iodide concentration, pH, shaking time and sample dilution effect were studied. The system shows rapid kinetic sorption and maximum X-ray intensity signal was achieved after shaking for 2 min a 0.01 mol l−1 iodide solution containing microamounts of mercury in the pH range from 1.0 to 9.0. Effective sorption up to a volume of 0.9 l allows preconcentration of mercury. A linear fit up to 50 μg mercury was obtained by the plot of the initial mercury mass in the bulk solution (0.5 l) vs. its respective XRF intensity signal measurement on ground PUF after the sorption process. The calibration sensitivity, quantification and detection limits found were 9.09 CPS μg−1, 9.0 and 2.7 μg, respectively. The sorption of many elements was also evaluated under the best conditions. High concentrations of Cu(II) and Fe(III) interfere seriously. Mercury-selective separation could be achieved using citrate or EDTA as masking agent; no interference due to copper matrix samples was observed in citrate medium. This methodology was evaluated by recovery for mercury determination in copper concentrate ore samples supplied by a mining industry and copper sulfate salts; the results were between 98% and 106%.

Experimental Investigations of x-ray Emission in a New Filippov-Type Plasma Focus

We present an experimental study of the soft and hard x-ray performance characteristics of neon and neon-krypton mixture (Pkr up to 0.2 torr) plasma produced by a new Filippov-type plasma focus device named “Dena”, with 90 kJ (25 kV, 288 µF) operating at pressures in the range 0.3–1.5 torr. In this investigation, the soft and hard x-ray intensities are measured using a filtered PIN diode, a pinhole camera with a Be filter (10 µm thickness), a plastic and NaI scintillators. Using pure neon as the filling gas, and a charging voltage of 16 kV with 37 kJ stored energy, the maximum intensities of the soft and hard x-rays were found to be about 5 V/shot and 2.2 V/shot, respectively. These measurements were obtained at an optimum operating pressure in the range of 0.5–0.9 torr (for the soft x-ray) and about 0.8 torr (for the hard x-ray). The relationships between the optimum neon pressure range and the time of spike appearances on the discharge current signal were experimentally studied. The results indicate that, the x-ray emission is more sensitive to the time of spike appearances than the neon filling gas pressure. By using a krypton admixture to the neon filling gas (PNe = 1 torr), the most pronounced effect is observed for the hard x-ray yield (up to eight times of the initial value) at the optimum krypton pressure of about 0.1 torr. The measurements of maximum x-ray intensity, performed with krypton admixture, show that as the pressure of krypton admixture increases, the optimum discharge voltages fall to a value depending on the quantity of krypton admixtures used. This effect was generally an intensity decreasing matter for the soft x-ray.

Repetitive flash x-ray generator having a high-durability diode driven by a two-cable-type line pulser

The fundamental studies of a repetitive soft flash x-ray generator having a high-durability diode for high-speed radiography in biomedical and technological fields are described. This generator consisted of the following essential components: a constant negative high-voltage power supply, a line-type high-voltage pulser with two 10 m coaxial-cable condensers, each with a capacity of 1.0 nF, a thyratron pulser as a trigger device, an oil-diffusion pump, and a flash x-ray tube. The x-ray tube was of a diode type which was evacuated by an oil-diffusion pump with a pressure of approximately 6.7×10−3 Pa and was composed of a planar tungsten anode, a planar ferrite cathode, and a polymethylmethacrylate tube body. The space between the anode and cathode electrodes (AC space) could be regulated from the outside of the tube. The two cable condensers were charged from −40 to −60 kV by a power supply, and the output voltage was about −1.5 times the charged voltage. Both the first peak voltage and current increased according to increases in the charged voltage, and the maximum values of the voltage and current were about 90 kV and 0.72 kA, respectively. The pulse widths had values of less than 100 ns, and the maximum x-ray intensity was approximately 1.1 μC/kg at 0.5 m per pulse. The repetition rate was less than 54 Hz, and the maximum focal spot size was about 2.0×2.5 mm.

Comparison of Solar X-Ray Line Emission with Microwave Emission during Flares

view Abstract Citations (652) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Comparison of Solar X-Ray Line Emission with Microwave Emission during Flares Neupert, Werner M. Abstract An analysis of X-ray emission at 1.87 A observed during three solar flares by OSO-ITI indicates that maximum line emission is observed to occur 0.5-5 mm after impulsive microwave maximum. The time integral of the centimetric radio burst corresponds best to the 1.87 A line intensity during the rise to maximum X-ray intensity. The constancy of line emission from Fe ix through Fe xv, coupled with strong enhancements in higher ionization stages, suggests that additional material, not originally at coronal temperature, is rapidly heated and elevated to high stages of ionization during the event. Such heating and ionization may be the result of collisional losses by energetic electrons which are also responsible for the impulsive microwave burst Publication: The Astrophysical Journal Pub Date: July 1968 DOI: 10.1086/180220 Bibcode: 1968ApJ...153L..59N full text sources ADS |