An approach for accelerating ions, with the use of a cluster-gas target and an ultrashort pulse laser of 150-mJ energy and 40-fs duration, is presented. Ions with energy 10-20 MeV per nucleon having ...a small divergence (full angle) of 3.4 degrees are generated in the forward direction, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using solid targets. It is inferred from a particle-in-cell simulation that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in subcritical density plasmas.
The initial stage of a nanosecond discharge in gaps with a high electric field at a cathode is studied by laser methods (interferometric, shadow, schlieren methods). The studies are performed in air ...at atmospheric pressure. Prominence is given to studying the evolution (appearance and growth) of the plasma channels at an anode and to estimating their parameters.
The initial stage of the nanosecond explosion of 1–15 μm-thick flat foils in a diode with a current of 40–80 kA is studied. Projection radiography is used to take images of exploded foils at a ...spatial resolution of 3–4 μm using the soft X-ray radiation (
E
= 2.5–5 keV) of a hybrid X-pinch and at a time resolution of 0.1 ns. Foil strips 0.3–2 mm wide and 0.5–7 mm long were introduced in the return circuit of the diode in a high-current BIN generator with a current amplitude of 270 kA and a current rise time of 100 ns; the main load of the generator is an X-pinch. The experiments demonstrate that small-scale structures, the shape and the size of which depend on the foil material and the current density and distribution in a foil, are formed in a foil. Possible scenarios of the structure formation are discussed.
The possibility of using the relative intensities of the 1
snp
1
P
1
–1
s
2
1
S0 transitions with
n
= 3–6 in He-like multicharged ions to diagnose plasma in a nonstationary ionization state is ...considered. The calculations performed for F VIII ions show that, at electron temperatures of
T
e
= 10–100 eV, the intensity ratios are sensitive to the plasma electron density in the range of
N
e
= 10
16
–10
20
cm
–3
. The universal calculated dependences can be used to diagnose various kinds of recombining or ionizing plasmas containing such ions.
We report about nonlinear growth of x-ray emission intensity emitted from plasma generated by femtosecond petawatt laser pulses irradiating stainless steel foils. X-ray emission intensity increases ...as ∼ I4.5 with laser intensity I on a target. High spectrally resolved x-ray emission from front and rear surfaces of 5 μm thickness stainless steel targets were obtained at the wavelength range 1.7-2.1 Å, for the first time in experiments at femtosecond petawatt laser facility J-KAREN-P. Total intensity of front x-ray spectra three times dominates to rear side spectra for maximum laser intensity I ≈ 3.2×1021 W/cm2. Growth of x-ray emission is mostly determined by contribution of bremsstrahlung radiation that allowed estimating bulk electron plasma temperature for various magnitude of laser intensity on target.
A superbright X-ray source with a radiation temperature of ~1.2 keV making it possible to create a solid-state plasma whose kinetics is determined by the radiative processes has been implemented ...under the impact of a 170-TW pulse of the PEARL femtosecond laser facility on an aluminum target with submicron thickness. The diagnostics of the created plasma is performed by X-ray spectral methods using spectral transitions in hollow multicharged ions.
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A technique for studying the spatial structure of hybrid X-pinch plasma objects in the X-ray range is described, and main experimental results are presented. The spectral characteristics of X-ray ...sources of plasma objects have been measured. The investigations have been carried out using thermoluminescent detectors based on lithium fluorides LiF(Mg, Ti).
The prebreakdown stage of a gas discharge in a diode with strongly overloaded cathode is studied by laser methods (by simultaneous use of multiframe interferometry and shadow and schlieren ...photographing) at atmospheric pressure. The spatial resolution of the methods is about 20 μm. A probing pulse of a laser (LS-2151 Nd: YAG laser with a half amplitude duration of 70 ps and a pulse energy of up to 40 mJ) is synchronized with a voltage pulse with accuracy of about 1 ns. High field strength at the cathode is achieved due to the use of thin individual metal tips on the electrodes. It is shown that the initial stage of breakdown of a discharge gap is accompanied by the emergence of a dense plasma cloud at the end of a tip with electron density of about 5 × 10
19
cm
–3
with a size of tens of microns, as well as by a sharp increase in the total current through the diode. After the emergence of a dense plasma cloud at the end of a cathode tip, a similar cloud is formed on the surface of the anode; sometime later, these clouds join together and form a tubular current channel. The dynamics of the breakdown, as well as the parameters of the plasma are studied by the abovementioned techniques in three independent optical channels.
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