scholarly journals Transient Absorption Phenomena in Synthetic HPHT and CVD Diamonds for a Fast Timing in Nuclear Instrumentation

2017 ◽  
Vol 26 (3) ◽  
pp. 253
Author(s):  
O. Buganov ◽  
S. Tikhomirov ◽  
E. Barbarchik ◽  
M. Korjik ◽  
A. Fedorov ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Chemical Vapor ◽  
Laser Pulses ◽  
Linear Absorption ◽  
Transient Phenomena ◽  
Synthetic Diamonds ◽  
High Pressure High Temperature ◽  
Pump And Probe ◽  
Fs Laser ◽  
Short Laser Pulses

In this study, we investigate  transient phenomena in synthetic diamonds  obtained by High Pressure High Temperature and Chemical Vapor Deposition methods. Study was aimed at searching for inorganic crystalline media combining ionizing radiation detecting properties and non-linear absorption of ultra-short laser pulses. The nonlinear pump-and-probe optical absorption technique with of 140 fs laser pulses was used to study the effects.

A STUDY OF FEMTOSECOND LASER POLISHING OF CVD NANOPOLYCRYSTALLINE DIAMOND FILMS

2021 ◽  
pp. 2150023
Author(s):  
YU-XIAO CUI ◽  
PING GUO ◽  
XUEMING ZHU ◽  
YAN-LING TIAN ◽  
DA-WEI ZHANG ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Fluence ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Laser Pulses ◽  
Promising Technique ◽  
Laser Polishing ◽  
Laser Fluences ◽  
Fs Laser ◽  
The Mean

Femtosecond (fs) laser ablation has been recognized as an effective and promising technique for high-precision processing of natural and synthesized diamond. In this work, a study of femtosecond laser polishing for nanopolycrystalline diamond (NCD) films by chemical vapor deposition (CVD) is reported. The laser irradiation is induced by 200-fs laser pulses with a repetition frequency of 50[Formula: see text]MHz, and various laser fluences are employed to investigate their polishing effectiveness. The results show that the optimal laser fluence is 0.7[Formula: see text]J/cm2, at which the nanodiamond grains on top of the cauliflower-like clusters of NCD films can be ablated. With such laser fluence, the mean surface roughness of NCD films reduces from 73.84[Formula: see text]nm to 31.88[Formula: see text]nm, which presents a 57% reduction. Nevertheless, when the laser fluence rises beyond 0.7[Formula: see text]J/cm2, large amount of amorphous carbon (a-C) balls and porous lava-like morphology would come into being, resulting in severe degradation of the NCD surface.

scholarly journals Super continuum generation in water doped with Homeopathic medicines

2021 ◽  
Vol 19 (1-2) ◽  
pp. 26-38
Author(s):  
Paresh K Joshi ◽  
Aditya K Dharmadhikari ◽  
Jayashree A Dharmadhikari ◽  
Praful M Barvalia
Keyword(s):  
Laser Energy ◽  
Visible Region ◽  
Area Under The Curve ◽  
Laser Pulses ◽  
Supercontinuum Generation ◽  
Linear Absorption ◽  
Continuum Generation ◽  
Incident Laser Energy ◽  
Significant Difference ◽  
Fs Laser

We have carried out systematic studies to investigate the effect on supercontinuum generation in water using 40 fs laser pulses when doped with Homeopathic medicines. We perform these studies using five series of medications with different levels of dilution (10-30 to 10-100000). We measure supercontinuum spectra that span from 400-1050 nm. We monitor the area under the curve in the range 450-750 nm for each sample at a fixed incident laser energy. Our observations indicate that the yield of supercontinuum generation, in water containing Homeopathic medicine is significantly different from that obtained in water containing plain ethanol. The measurement for different dilutions shows up to 7 times standard deviation variation in the yield of supercontinuum generation? Even though linear absorption in the UV-visible region does not show any significant difference for different Homeopathic medicines, the supercontinuum yield which depends on the effective nonlinear refractive index changes with different samples.

scholarly journals C12: The building block of hexagonal diamond

2012 ◽  
Vol 10 (5) ◽  
pp. 1676-1680 ◽  
Author(s):  
Gaspar Banfalvi
Keyword(s):  
Building Block ◽  
Model Building ◽  
Chemical Vapor ◽  
Chair Conformation ◽  
Boat Conformation ◽  
Chemical Vapor Deposition Growth ◽  
Growth Technique ◽  
Hexagonal Diamond ◽  
Synthetic Diamonds ◽  
High Pressure High Temperature

AbstractThe crystalline structure of diamond may consist of C8, C10 or C12 building units. C8 was regarded as the building block of the hexagonal diamond also known as Lonsdaleite. Adamantane (C10H16) alicyclic hydrocarbon has the same arrangement of carbon atoms as the basic C10 unit of the cubic diamond lattice. C12 has five rings of mixed type, three of them in boat, two in chair conformation. Model building revealed that the C8 unit containing exclusively three rings in boat conformation does not exist. Further addition of carbon atoms to C8: a) results in C12 unit, b) allows the multiplication of C12 units, and c) by reducing the boat-to-chair ratio explains the hardness of the hexagonal diamond Lonsdaleite. The Lonsdaleite nucleus can be grown to special diamond grains with the outer atoms of the C12 building units replaced by different elements. This recognition can be utilized in the production of synthetic diamonds under high-pressure high-temperature conditions or in the chemical vapor deposition growth technique.

scholarly journals Effect of pre-plasma on the ion acceleration by intense ultra-short laser pulses

2018 ◽  
Vol 36 (2) ◽  
pp. 226-231 ◽  
Author(s):  
Parvin Varmazyar ◽  
Saeed Mirzanejhad ◽  
Taghi Mohsenpour
Keyword(s):  
Laser Pulses ◽  
Complete Analysis ◽  
Ion Acceleration ◽  
Destructive Effect ◽  
Particle In Cell ◽  
Solid Density ◽  
Cell Simulation ◽  
Fs Laser ◽  
Short Laser Pulses ◽  
Plasma Effect

AbstractIn the interaction of short-laser pulses with a solid density target, pre-plasma can play a major role in ion acceleration processes. So far, complete analysis of pre-plasma effect on the ion acceleration by ultra-short laser pulses in the radiation pressure acceleration (RPA) regime has been unknown. Then the effect of pre-plasma on the ion acceleration efficiency is analyzed by numerical results of the particle-in-cell simulation in the RPA regime. It is shown that, for long-laser pulses (τp > 50 fs), the presence of pre-plasma makes a destructive effect on ion acceleration while it may have a contributing effect for short-laser pulses (τp < 50 fs). Therefore, the 35 fs (20 fs) laser pulse can accelerate ions up to 40 MeV (55 eV), which is almost two (three) times larger in energy rather than use of a 100 fs pulse with the same pre-plasma scale length.

Nonlinear excitation and ionization of diatomic molecules by short laser pulses. Model of two active electrons in the field of a frozen core

2002 ◽  
Vol 80 (2) ◽  
pp. 149-171
Author(s):  
A I Pegarkov
Keyword(s):  
Ground State ◽  
Diatomic Molecules ◽  
Laser Pulses ◽  
Electron Excitation ◽  
Quantum Mechanical ◽  
Electron Dynamics ◽  
Nonlinear Excitation ◽  
Fs Laser ◽  
Short Laser Pulses ◽  
Electronic Ground

The dynamics of electron excitation and ionization of diatomic molecules in short laser pulses is studied within a model of two active 1D electrons moving in the field of a frozen core. It is shown for example for the N2 molecule that the model reproduces the spectrum of the pulse-free Σ electronic states very well. The N2 electron dynamics is examined numerically for short τ = 30 fs and ultra-short τ = 5 fs laser pulses with λ = 800 nm and intensity 1013 W/cm2 ÷ 1015 W/cm2 as well as for the resonant pulse with τ = 1 fs and λ = 147 nm, 1014 W/cm2 ÷ 1016 W/cm2. The phenomena of strong above-threshold absorption and resonant revival of electronic ground-state population in the ultra-short resonant pulse are found. Within the model, the quantum-mechanical picture of one-electron, two-electron, sequential, and nonsequential molecular ionizations is analyzed in detail in comparison with recent experimental results of Cornaggia and Hering, and Gibson et al. The model correctly explains the origin and nonlinear dynamics of the well-known "shoulder" in the N2+2 ion yield. PACS Nos.: 33.80Rv, 33.80Wz

Defect Structure of Synthetic Diamond and Related Phases

1987 ◽  
Vol 31 ◽  
pp. 113-128 ◽  
Author(s):  
Andrzej R. Badzian
Keyword(s):  
High Pressure ◽  
Solid Solutions ◽  
Microwave Plasma ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Lattice Matching ◽  
Synthetic Diamonds ◽  
Atom Pairs ◽  
High Pressure High Temperature ◽  
Crystalline Films

AbstractThis paper examines the relationship between the lattice defects and crystallization process of synthetic diamonds. Diamonds synthesized by high pressure, high temperature methods as well as diamonds vapor deposited under metastable conditions are considered. High pressure crystals precipitated from Ni or Co solutions contain inclusions of metastable carbides and metal atoms distributed throughout a small fraction of the octahedral holes in the diamond lattice.Diamonds are grown metastabily by a chemical vapor deposition process in which CH4 and H2 are excited by a microwave plasma. Such diamonds are deposited as individual micro-monocrystals or as solid poly crystalline films. The defects in such crystals are related to impurities such as Si and H which produce point defects and tend to nucleate graphite, which can generate planar defects. Nucleation of a diamond phase on β-SiC is also considered, because of the lattice matching between them.Diamond structure is a prototype of a family of related phases such as cubic BN (sphalerite structure) and solid solutions of diamond and cubic BN, Cubic BN-diamond solid solutions (BN)x(C2)1-x,0<x<l are, in turn, a prototype of AIIIBV-CIV phases, of which (GaP)x(Si2)1-x,0<x<l is an example. Substitution of B-N (or Ga-P) by C-C (or Si-Si) atom pairs at lattice sites is characteristic of these solid solutions.

Cathodoluminescence Microscopy and Spectroscopy of Micro- and Nanodiamonds: An Implication for Laboratory Astrophysics

2012 ◽  
Vol 18 (6) ◽  
pp. 1285-1291 ◽  
Author(s):  
Arnold Gucsik ◽  
Hirotsugu Nishido ◽  
Kiyotaka Ninagawa ◽  
Ulrich Ott ◽  
Akira Tsuchiyama ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Liquid Nitrogen Temperature ◽  
Spectroscopic Properties ◽  
Vacancy Defect ◽  
Laboratory Astrophysics ◽  
Peak Intensity ◽  
Synthetic Diamonds ◽  
High Pressure High Temperature ◽  
Dislocation Defect ◽  
Almost All

AbstractColor centers in selected micro- and nanodiamond samples were investigated by cathodoluminescence (CL) microscopy and spectroscopy at 298 K [room temperature (RT)] and 77 K [liquid-nitrogen temperature (LNT)] to assess the value of the technique for astrophysics. Nanodiamonds from meteorites were compared with synthetic diamonds made with different processes involving distinct synthesis mechanisms (chemical vapor deposition, static high pressure high temperature, detonation). A CL emission peak centered at around 540 nm at 77 K was observed in almost all of the selected diamond samples and is assigned to the dislocation defect with nitrogen atoms. Additional peaks were identified at 387 and 452 nm, which are related to the vacancy defect. In general, peak intensity at LNT at the samples was increased in comparison to RT. The results indicate a clear temperature—dependence of the spectroscopic properties of diamond. This suggests the method is a useful tool in laboratory astrophysics.

scholarly journals Production of ion beams in high-power laser–plasma interactions and their applications

2004 ◽  
Vol 22 (1) ◽  
pp. 19-24 ◽  
Author(s):  
F. PEGORARO ◽  
S. ATZENI ◽  
M. BORGHESI ◽  
S. BULANOV ◽  
T. ESIRKEPOV ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Medical Physics ◽  
Ion Beam ◽  
Laser Pulses ◽  
Ion Beams ◽  
Laser Plasma Interactions ◽  
Physical Mechanisms ◽  
Short Laser Pulses ◽  
Laser Pulse Intensity ◽  
Target Design

Energetic ion beams are produced during the interaction of ultrahigh-intensity, short laser pulses with plasmas. These laser-produced ion beams have important applications ranging from the fast ignition of thermonuclear targets to proton imaging, deep proton lithography, medical physics, and injectors for conventional accelerators. Although the basic physical mechanisms of ion beam generation in the plasma produced by the laser pulse interaction with the target are common to all these applications, each application requires a specific optimization of the ion beam properties, that is, an appropriate choice of the target design and of the laser pulse intensity, shape, and duration.

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