Nikolai V. Nikitin

Narrow-directed fast-ion flow generation from targets irradiated by a picosecond laser pulse

The proton and deuteron yields from thin targets irradiated by a picosecond laser pulse with an average radiation intensity of ≤4×1018 W/cm2 at the target were measured in the megaelectron-volt energy range. A ring structure was observed for the outgoing ions, and the angular ion-beam divergence was found to be extremely small (0.5°). The fast-ion generation mechanism allowing for the appearance of ring structure is discussed, and the characteristic energies and spatioangular ion-beam distribution are estimated.

The “Progress-P” 30 TW picosecond Nd:glass facility

Chirped pulse amplification was implemented in one of six amplifier chains “Progress” phosphate Nd:glass laser system. Laser system configuration and performance are presented. Formation of 300 ps chirped pulse at 1053 nm with energy up to 1 J is made by using developed starting laser which consists of Nd:YLF oscillator, optical fiber, stretcher and three amplifiers with output aperture 20 mm. The large amplifier chain of the laser system includes three rod amplifiers with the aperture of output rod of 85 mm. Preliminary experiments have been carried out yielding output chirped pulses of up to 55 J and compression them to 1.5 ps by grating compressor.

Resolution limit of laser-plasma protonography

It was found that maximum particle output and best possible spatial uniformity of proton beam took place for two-layer target when the front layer was the high-Z film. It was shown that the ion radiography of the convenient objects with using the two-layer targets allow to get the projecting pictures with high spatial resolution that was about one micron. Threshold spatial sensitivity of proton radiography is estimated.

Some results of experiments for laser plasma proton source for radiography

Laser plasma produced with high-intensity picosecond laser pulse like proton source for radiography was investigated. It was found that maximum particle output and best possible spatial uniformity of proton beam took place for two-layer target when the front layer was the high-Z film. It was shown that the ion radiography of the convenient objects with using the two-layer targets allow to get the projecting pictues with high spatial resolution that was about one micron. The explanation of such high spatial resolution is in laminar motion of ion flow. Threshold spatial sensitivity of proton radiography is estimated.

Generation of fast ion beams from multiterawatt laser-irradiated targets

Results of fast light ion yield measurements are presented. Laser-plasma experiments were carried out on picosecond laser PROGRESS-P at laser intensities on a target to be 1 ÷ 4•1018 W/cm2. Ring image and extremely small angular divergence of fast ion beam were found. Hard ions with energy more than 8 MeV were recorded. Model of fast ion generation is discussed and typical energy and spatial distribution of fast ion extension are estimated.

Methods and control-driving devices for high-precision remote alignment of multichannel high-power laser facility

The results of work on creation of a system for remote control alignment of high-power multichannel Nd·glass laser systems, being created in VNIIEF and NlffiF A, are presented. Methods and principles of alignment, high·accuracy driving units for mirrors tilts and pinholes travels, CCD-sensor capable of accepting weak radiation fluxes with a wavelength A.=l,053 μmare considered.

Absorption and transformation of laser energy in picosecond laser-plasma experiments at intensity of 10 16 to 10 19 W/cm 2

The interaction of a 1053 nm picosecond laser pulse with a solid target for focused intensities of up to 1019 W/cm2 are studied by measurements of the absorption of the laser light in the plasma and by measurements of the production of hard x-rays. Absorption measurements are made by collecting the scattered light in set of calorimeters. Light scattered in backward and specular directions is collected separately. Measurements are presented for both high and low Z targets. Hard x-ray spectrum in range 15-1000 keV and hot electron production in range 1-22 MeV are measured using a multichannel filter/scintillator and filter/semiconductor spectrometers. Spatial parameters of fast ions are studied.

Front end of the high-energy Nd:glass laser fusion system with shaped nanosecond laser pulses

The design and performance of front end system for the upgrade six-channel Nd:glass laser facility PROGRESS are presented. The system consists of a single-mode Q-switch Nd:YLF master oscillator, pulse shaping system and preamplifier. The pulse shaping system comprises a LiTaO3 electro optic deflector pair driven by high-voltage generators on drift step recovery diodes. The system produces the shaped laser pulses in 1-10 nanosecond duration range. In one-pass preamplifier including a sequence of Nd:glass rod amplifiers with output aperture of 30mm the shaped pulses are amplified up to 5 J energy level.

Formation of high-contrast laser pulses on multiterawatt laser facility PROGRESS-P

We present the key features of design and performance of PROGRESS-P CPA Nd:YLF/Nd:glass laser facility capable of producing 1.5-ps pulses and a power up to 30 TW at the wavelength 1053 nm for laser- plasma experiments in ultrahigh irradiance on the target up to 1019 W/cm2. We describe voltage pulse drivers based on drift step recovery diodes which produce output voltage up to 15 kV, rise time approximately 1 ns, jitter of 100 ps and repetition rate up to 10 kHz to electro-optical devices.

Methods for the shaping high-power picosecond laser pulses with a high-contrast ratio

We present the performance of the electrooptical system based on four Pockels cells with 10 and 20 mm diameters, each of them is driving by its own drift step recovery diode pulse generator. We are developing electro-optic deflector system for CPA laser using two identical deflectors (diverging and converging) and three spatial filters. The results of numerical modeling of the time-dependent distributions of the intensity in the beam are presented. A peak-to-background intensity ratio more than five orders is achieved by this technique. We have developed a new pulse generator based on single drift step recovery diode producing two identical electrical pulses with output voltage up to 15 kV, FWHM of 1.5 ns, rise time of 0.7 ns and jitter of 100 ps at a 100 Hz repetition rate to electro-optic deflectors.