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Interactions of two distinct shapes of the pulses namely positive/negative chirped pulse and fast/slow rising-edge pulse with plasma are studied using particle-in-cell simulation. It is found that, for a pulse duration of 34 fs and intensity a0 = 12, proton acceleration could be enhanced by asymmetric pulses with either pulse envelope or pulse frequency modification. The number of accelerated protons, as well as the proton energy cut-off, is increased by asymmetric pulses. In this work, for positive chirped pulse, electrostatic field at the rear side of the target is improved by about 30%, which in turns leads to an increase in the proton energy cut-off more than 40%. Moreover, in contrary to the fast pulses, the slow one could enhance the proton energy cut-off up to 65% for 34 fs pulse with 20 fs rising-edge.

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Unit-1 of the Bushehr nuclear power plant (BNPP-1) is a VVER-type reactor with 1,000-MWe power constructed near Bushehr city at the coast of the Persian Gulf, Iran. The reactor has been recently operational to near its full power. The radiological impact of nuclear power plant (NPP) accidents is of public concern, and the assessment of radiological consequences of any hypothetical nuclear accident on public exposure is vital. The hypothetical accident scenario considered in this paper is a design-basis accident, that is, a primary coolant leakage to the secondary circuit. This scenario was selected in order to compare and verify the results obtained in the present paper with those reported in the Final Safety Analysis Report (FSAR 2007) of the BNPP-1 and to develop a well-proven methodology that can be used to study other and more severe hypothetical accident scenarios for this reactor. In the present study, the version 2.01 of the PC COSYMA code was applied. In the early phase of the accidental releases, effective doses (from external and internal exposures) as well as individual and collective doses (due to the late phase of accidental releases) were evaluated. The surrounding area of the BNPP-1 within a radius of 80 km was subdivided into seven concentric rings and 16 sectors, and distribution of population and agricultural products was calculated for this grid. The results show that during the first year following the modeled hypothetical accident, the effective doses do not exceed the limit of 5 mSv, for the considered distances from the BNPP-1. The results obtained in this study are in good agreement with those in the FSAR-2007 report. The agreement obtained is in light of many inherent uncertainties and variables existing in the two modeling procedures applied and proves that the methodology applied here can also be used to model other severe hypothetical accident scenarios of the BNPP-1 such as a small and large break in the reactor coolant system as well as beyond design-basis accidents. Such scenarios are planned to be studied in the near future, for this reactor.

Here, a homemade gold fineness analyzer is fabricated based on calibration-free spark assisted laser-induced breakdown spectroscopy (CF SA-LIBS). The experimental arrangement consists of a Q -switched Nd:YAG laser combined with a spark generator and a single-channel CCD spectrometer. The well-arranged optical system, coupled with an electrical setup, allows us to successfully run SA-LIBS even at low energy single shots. The electric discharge contributes LIBS to reheat and promote more energetic plasma. Subsequently, plasma temperature elevates up to ∼ 20 % , and its lifetime is elongated as much as 6 times. As a consequence, the relative signal intensity is enhanced up to 1 order of magnitude against that of LIBS at the same pulsed energy. Furthermore, the electron density is also measured based on the broadened spectral width of the intensified H α line. The latter is used to obtain the ionic species concentrations more accurately according to the Saha–Eggert equation. As a result, we have assessed the gold karat with an analytical error less than 0.5% using CF SA-LIBS. In addition, the surface patterns recorded by the stylus profilometer reveal that the single-shot SA-LIBS benefits a smaller ablative mass against standard LIBS.

The results of an experimental investigation of neutron emission characteristics in the Filippov-type plasma focus facility "Dena" (90 kJ, 25 kV, 288 µF) with D2 + %1 Kr as working gas are presented. From the experimental results, one can conclude that both thermonuclear and nonthermonuclear mechanisms are always present in neutron production, but their contributions to the total neutron yield are strongly dependent on the initial pressure and discharge voltage. It has been found that at constant discharge voltages and low pressures the beam-target interaction mechanism plays an important role in the neutron production and with increasing the pressure, its role decreases and the importance of thermonuclear mechanism increases. Also at constant pressures, the contribution of beam-target interaction mechanism in neutron production decreases with increasing the discharge energy. The value of the α index in the empirical neutron yield scaling law Yn ∝ I α ∝ E α/2 was found to be about 3.82.

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