Single and double passage interferometric analysis of Pseudo-Random-Phase-Plates

2015 ◽  
Vol 345 ◽  
pp. 37-46 ◽  
Author(s):  
Richa Sharma ◽  
C.S. Narayanamurthy
Keyword(s):  
Random Phase ◽  
Phase Plates

scholarly journals High-density compression experiments at ILE, Osaka

1991 ◽  
Vol 9 (2) ◽  
pp. 193-207 ◽  
Author(s):  
H. Azechi ◽  
T. Jitsuno ◽  
T. Kanabe ◽  
M. Katayama ◽  
K. Mima ◽  
...  
Keyword(s):  
Random Phase ◽  
Mass Conservation ◽  
Liquid Density ◽  
Direct Drive ◽  
One Dimensional ◽  
X Ray ◽  
Calculation Results ◽  
Phase Plates ◽  
Thermonuclear Ignition ◽  
Ablated Mass

Direct-drive implosion experiments on the GEKKO XII laser (9 kJ, 0.5 μm, 2 ns) with deuterium and tritium (DT) exchanged plastic hollow shell targets demonstrated fuel areal densities (ρR) of ˜0.1 g/cm2 and fuel densities of ˜600 times liquid density at fuel temperatures of ˜0.3 keV. (The density and ρR values refer only to DT and do not include carbons in the plastic targets.) These values are to be compared with thermonuclear ignition conditions, i.e., fuel densities of 500–1000 times liquid density, fuel areal densities greater than 0.3 g/cm2, and fuel temperatures greater than 5 keV. The irradiation nonuniformity in these experiments was significantly reduced to a level of <5% in root mean square by introducing random-phase plates. The target irregularity was controlled to a 1% level. The fuel ρR was directly measured with the neutron activation of Si, which was originally compounded in the plastic targets. The fuel densities were estimated from the ρR values using the mass conservation relation, where the ablated mass was separately measured using the time-dependent X-ray emission from multilayer targets. Although the observed densities were in agreement with one-dimensional calculation results with convergence ratios of 25–30, the observed neutron yields were significantly lower than those of the calculations. This suggests the implosion uniformity is not sufficient to create a hot spark in which most neutrons should be generated.

scholarly journals Focused beam control in super-ASHURA KrF laser system

1999 ◽  
Vol 17 (4) ◽  
pp. 693-699
Author(s):  
I. MATSUSHIMA ◽  
I. OKUDA ◽  
Y. MATSUMOTO ◽  
T. TOMIE ◽  
E. MIURA ◽  
...  
Keyword(s):  
High Efficiency ◽  
Laser System ◽  
Random Phase ◽  
Divergence Angle ◽  
Laser Fusion ◽  
Profile Control ◽  
Krf Laser ◽  
Speckle Patterns ◽  
Phase Plates ◽  
Focused Beam

Beam smoothing techniques and focused beam profile control techniques for high efficiency KrF laser fusion are reported. We have developed 1D and 2D broadband random phase (BRP) irradiation techniques. Our next idea is the combination of a laser oscillator with a wide beam divergence angle and phase plates. The wide divergence angle laser beam eliminates the speckle patterns caused by the phase plates. Well characterized focal spot patterns have been observed with the front-end pulse of the Super-ASHURA KrF laser system. Amplification experiments are on going.

scholarly journals Implementation of a phase plate for the generation of homogeneous focal-spot intensity distributions at the high-energy short-pulse laser facility PHELIX

2019 ◽  
Vol 7 ◽  
Author(s):  
V. Bagnoud ◽  
J. Hornung ◽  
M. Afshari ◽  
U. Eisenbarth ◽  
C. Brabetz ◽  
...  
Keyword(s):  
Short Pulse ◽  
Random Phase ◽  
High Energy ◽  
Phase Plate ◽  
Work Related ◽  
Nanosecond Lasers ◽  
Short Pulse Laser ◽  
Laser Facility ◽  
Ultrashort Pulse Lasers ◽  
Phase Plates

We propose and demonstrate the use of random phase plates (RPPs) for high-energy sub-picosecond lasers. Contrarily to previous work related to nanosecond lasers, an RPP poses technical challenges with ultrashort-pulse lasers. Here, we implement the RPP near the beginning of the amplifier and image-relay it throughout the laser amplifier. With this, we obtain a uniform intensity distribution in the focus over an area 1600 times the diffraction limit. This method shows no significant drawbacks for the laser and it has been implemented at the PHELIX laser facility where it is now available for users.

scholarly journals Random-phase plate effects on burn-through measurements of laser-irradiated plane-layered targets

1994 ◽  
Vol 12 (1) ◽  
pp. 111-120
Author(s):  
R. Evans ◽  
Z. Ahmad ◽  
T.A. Hall ◽  
Y.A. Zakharenkov
Keyword(s):  
Hot Spots ◽  
Energy Transport ◽  
Random Phase ◽  
Outer Region ◽  
Local Maximum ◽  
Phase Plate ◽  
Energy Redistribution ◽  
Laser Focal Spot ◽  
Phase Plates ◽  
Burn Through

The application of random-phase plates in laser beams to improve the uniformity of target ablation is investigated by combining the simultaneous X-ray and particle emission measurements of ablation characteristics. It is shown that if some hot spots with dimensions of a few µm exist on target they persist at least during the initial stages of the laser interaction process, producing a local maximum in the ablation pressure. Lateral energy transport, inferred from the neutral particle measurements, has little influence on absorbed energy redistribution (only 1% of the energy is transported from the laser focal spot to an outer region of 2 mm size).

Random phase plates for beam smoothing on the Nova laser

1993 ◽  
Vol 32 (14) ◽  
pp. 2543 ◽  
Author(s):  
S. N. Dixit ◽  
I. M. Thomas ◽  
B. W. Woods ◽  
A. J. Morgan ◽  
M. A. Henesian ◽  
...  
Keyword(s):  
Random Phase ◽  
Phase Plates

scholarly journals A study of random phased laser spots

1995 ◽  
Vol 13 (4) ◽  
pp. 469-480 ◽  
Author(s):  
T. Ceccotti ◽  
S. Bastiani ◽  
S. Bastiani ◽  
A. Giulietti ◽  
V. Biancalana ◽  
...  
Keyword(s):  
Random Phase ◽  
Ccd Camera ◽  
Diffraction Theory ◽  
Probability Density Distribution ◽  
Charge Coupled Device ◽  
Laser Plasma Interactions ◽  
Pattern Structures ◽  
Phase Plates ◽  
A Charge ◽  
Pulsed Laser Beam

Far-field images produced using different random phase plates on a pulsed laser beam focused with variousf/numbers were recorded by a charge-coupled device (CCD) camera and then analyzed. Envelope spot sizes agree with diffraction theory while mean sizes of the pattern structures have been found to be larger than the diffraction limit. The probability density distribution of intensity in the focal plane is not the expected exponential. A central symmetry of the pattern has also been seen after suitably aperturing the beam. Some consequences for the use of powerful RPP-treated laser beams in laser-plasma interactions are discussed.

scholarly journals Preparation of random-phase plates for laser-beam smoothing

1995 ◽  
Author(s):  
Ian M. Thomas ◽  
Sham N. Dixit ◽  
Michael C. Rushford
Keyword(s):  
Laser Beam ◽  
Random Phase ◽  
Phase Plates

SBS reflectivity from spatially smoothed laser beams: Random phase plates versus polarization smoothing

1998 ◽  
Vol 5 (7) ◽  
pp. 2706-2711 ◽  
Author(s):  
S. Hüller ◽  
Ph. Mounaix ◽  
V. T. Tikhonchuk
Keyword(s):  
Random Phase ◽  
Laser Beams ◽  
Phase Plates

scholarly journals Second harmonic emission from laser-preformed plasmas as a diagnostic for filamentation in various interaction conditions

1994 ◽  
Vol 12 (3) ◽  
pp. 435-444 ◽  
Author(s):  
E. Schifano ◽  
S.D. Baton ◽  
C. Labaune ◽  
N. Renard ◽  
V. Biancalana ◽  
...  
Keyword(s):  
Second Harmonic ◽  
Random Phase ◽  
Forward Direction ◽  
Beam Axis ◽  
Harmonic Emission ◽  
Phase Plates ◽  
Filamentation Instability

Second harmonic emission from underdense laser-preformed plasmas has been investigated in forward direction with respect to the interaction beam axis. Two series of measurements have been performed using two focusing conditions and changing the intensity of the interaction beam. Effects of beam smoothing by random phase plates on second harmonic emission were also tested. Novel information on density and intensity gradients driven by filamentation instability was obtained.

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