Parameters Of X-ray Radiation Research Articles

X-ray radiation and runaway electron beams generated during discharges in atmospheric-pressure air at rise times of voltage pulse of 500 and 50 ns

AbstractThe parameters of X-ray radiation and runaway electron beams (RAEBs) generated at long-pulse discharges in atmospheric-pressure air were investigated. In the experiments, high-voltage pulses with the rise times of 500 and 50 ns were applied to an interelectrode gap. The gap geometry provided non-uniform distribution of the electric field strength. It was founded that at the voltage pulse rise time of 500 ns and the maximum breakdown voltage Um for 1 cm-length gap, a duration [full width at half maximum (FWHM)] of a RAEB current pulse shrinks to 0.1 ns. A decrease in the breakdown voltage under conditions of a diffuse discharge leads to an increase in the FWHM duration of the electron beam current pulse up to several nanoseconds. It was shown that when the rise time of the voltage pulse is of 500 ns and the diffuse discharge occurs in the gap, the FWHM duration of the X-ray radiation pulse can reach ≈100 ns. It was established that at a pulse-periodic diffuse discharge fed by high-voltage pulses with the rise time of 50 ns, an energy of X-ray quanta and their number increase with increasing breakdown voltage. Wherein the parameter Um/pd is saved.

Soft X-ray point source based on a gas pinch

The results of a study of a radiating Z-pinch with a profiled initial gas-density distribution over the z axis are presented. The gas distribution with the density maximum and transverse-size minimum at the discharge-gap center is formed by a pulsed gas valve with a specially designed nozzle. The parameters of X-ray radiation are measured for pinches formed in gaseous neon at currents of up to 200 kA. The experimentally selected gas density ensures the formation of a region with a typical size of less than 1 mm at the discharge-gap center. This region emits X-ray radiation in the keV photon-energy range in a time of less than 5 ns. Prospects for the development of an X-ray source based on this mechanism are discussed.

ID-02M Small X-Ray Dosimeter for Monitoring Radiation Output

Scientific-Research Institute of Introscopy. Spektr ScientificManufacturing Association, Moscow, Russia; E-mail: spektr@co.ru New regulations for hygiene and sanitation (SanPiN 2.6.1.802-99: Ionizing Radiation, Radiation Safety. Hygienic Requirements for Medical X-Ray Rooms, XRay Apparatuses, and X-Ray Examination Procedure) for the first time impose requirements on the following parameters: – reproducibility of radiation dose in manual and automatic modes of X-ray photography; – dose linearity in relation to anode current or quantity of electricity; – monitoring of radiation output. It is recommended to normalize the radiation output H to the focal distance of 1 m and the anode current of 1 mA. Within the anode voltage range from 40 to 200 kV, it is recommended to install an additional Al filter 2 mm thick. At the anode voltage of 250 kV, an additional filter 0.5 mm Cu should be installed. According to the recommendations of SanPiN 2.6.1.802-99, the radiation output H should be measured in mGy⋅m/mA⋅min. Reference data on radiation output for various anode voltages are given in Supplement 7 to SanPiN 2.6.1.80299 [3]. For anode voltage of 40, 50, 75, 100, 150, 200, and 250 kV, the radiation output is 2, 3, 6.3, 9, 18, 25, and 20 mGy⋅m/mA⋅min, respectively. In the majority of X-ray diagnostic apparatuses, the exposure time in the mode of X-ray photography does not exceed 5 sec. In addition, X-ray photographs are often made in the mode of reduction of the radiation load [2]: during exposure, the anode voltage remains constant, while the anode current decreases according to a certain algorithm. Thus, it is expedient to normalize the radiation output to the value of the quantity of electricity (mA⋅sec) given on the control panel. Parameters of X-ray radiation in a direct beam are measured using the following models of X-ray dosimeters: VA-J-18, 27012 (Germany), PTW-Freiburg, PTWUnidos (Germany), Diados, Nomex, Multidos, etc. These dosimeters have good metrological characteristics. However, rather large size and heavy weight hinder their use for periodic testing of X-ray diagnostic apparatuses at the radiologists’ workplaces. To solve this problem, the ID-02M portable small-size dosimeter (Fig. 1) was developed at the Scientific-Research Institute of Introscopy. The metrological characteristics of the ID-02M dosimeter meet the requirements of SanPiN 2.6.1.802-99, ch.10/13. The functional diagram of the dosimeter is shown in Fig. 2. The control panel of the dosimeter contains two feather-touch buttons: Reset/Measurement and mGy/ μGy. The Reset/Measurement button is supplied with a red-green LED indicator (red light indicates resetting; green, measurement). The mGy/μGy button is supplied with two red LED indicators. A third button (Control) activates the mode of the dosimeter operation testing before measurement.

X-ray Source with Photon Energy 5 keV Pumped by Laser

Investigation of a monochromatic point x-ray source of photon energy ~5 keV has been carried out. The source was set up using a laser produced aluminium plasma as a cathode and a point-tip titanium anode. Optimum parameters of the diode were determined from experimental measurements of x-ray intensity dependence on laser pulse energy, applied accelerating voltage, and distance between target (cathode) and anode, using Nd:glass laser pulses (FWHM 30 ns) of 2 mJ to 4 J energy. Electron temperature characterization of the target plasma was also performed from the XUV emission spectrum (5 to 80 Å). Parameters of x-ray radiation in Ti K-shells are 1) spectral brightness of ~1020 photons/cm2-sec-sr-keV, 2) spatial size ~300 microns, and 3) x-ray pulse duration less than 20 ns.