Quartz Target Research Articles

Typomorphic and Technological Characteristics of Quartz of the Mica-Pegmatite Formation on the Example of the Berkutinskaya Vein (South Urals)

Abstract ––Understanding the origin of quartz veins of the mica-pegmatite formation is of great importance for deciphering the emplacement conditions for the of commercially prospective quartz targets. On the example of the Berkutinskaya vein, which is the typical metamorphogenic quartz deposit of the mica-pegmatite formation of the South Urals, we study the source and origin of the mineral-forming fluid, temperatures of quartz formation, the structure of intergranular boundaries, their morphometric feature, the fractal dimension of quartz grains and commercial characteristics of quartz grit. An integrated approach to the study of the typomorphic features of quartz allowed us to assess their impact on the technological characteristics of quartz concentrates. Comparison of data on the content of impurity elements in the Berkutinskaya quartz vein with quartz of the vein No. 175 of OOO Russian Quartz and IOTA-std (Sibelco) showed that the Berkutinskaya quartz vein is promising for commercial development.

Geant4 simulations of monochromatic Cherenkov radiation in thin quartz targets for different experimental conditions

In light of our recent research, we discussed the possibility of observing quasimonochromatic Cherenkov Radiation (ChR) spectral lines from a dispersive medium (thin quartz radiator). Such experimental results were verified on the Mainz Microtron MAMI, Germany [1], while both the polarization currents analytical model [2] and Geant4 [3] simulations were used to analyze the results. To describe the Cherenkov radiation process, the Geant4 toolkit uses only the approximation obtainable for an infinitely thick emitter (cos θ = 1 / βn(λ), where θ is Cherenkov’s angle of emission, β is reduced velocity, and n(λ) is a refractive index as a function of emitted radiation’s wavelength λ) and doesn’t consider its actual dimensions. Tamm’s theory [4] predicts some broadening of the ChR angular distribution with a radiator thinning. Consequently, Geant4 gave inadequate results for the pencil-like electron beams compared to the polarization currents model and the experiment. However, unlike in the analytical calculations, we needed to consider more realistic Gaussian electron beams to obtain better results with Geant4. Therefore, obtained results primarily manifest beam characteristics rather than the ChR itself, i.e., its intrinsic characteristics are masked. Now, the idea is to present additional simulation results with further variations of the quartz’s thickness (in preparation for future experiments), confirming the last conclusion without any doubt.

Spectral pyrometry of non-metallic materials at plasma heating, melting and cooling (Tomsk)

Spectral pyrometry of non-metallic materials under plasma heating, melting and cooling is used in nanotechnology, medicine, energy, metallurgy and other industries, where accurate temperature control is required during processing various materials. Purpose: The aim of this work is to create new spectral pyrometry technique for temperature measurement in difficult conditions of material processing and synthesis, such as plasma heating, melting and cooling of non-metallic materials. Methodology/approach: Small-sized spectrometers for diagnostics of heating, melting and cooling of the quartz target using the plasma jet. HPCS300 Mini Spectrometer with the wavelength range of 380 to 780 nm is used to determine the color temperature of the reference radiation source and for fiber optic calibration. The STS-VIS Microspectrometer based on a 1024×1 element CCD photodetector array with the wavelength range of 350 to 800 nm is used to record the emission spectrum of the object. Research findings: Improvement of production processes, fuel and material cost reduction, increase in the efficiency of plants and equipment, reliability and quality improvement of the final product. Value: During the plasma jet and quartz target interaction, three stages are observed: surface deformation, stable temperature of heating, and cooling of the condensed material with phase-transition points of liquid–pyroplastic–solid states.

First observation of quasi–monochromatic optical Cherenkov radiation in a dispersive medium (quartz)

The present article summarizes the results of a study of optical Cherenkov radiation (ChR) spectral properties both theoretically and experimentally. This type of radiation has a continuous spectral distribution which allows to use it in different fields of physics as for charged particle identification or generation of intense THz radiation. By exploiting the frequency dependency of the target permittivity it is possible to observe quasi–monochromatic radiation. A theoretical model based on a surface current approach is presented which allows to predict angular and spectral properties of ChR. In order to test the model predictions, an experiment was carried out using 855 MeV electrons and a 0.2 mm thick quartz target as radiator which could be rotated with respect to the beam axis. Quasi–monochromatic ChR was observed with a spectrometer placed at a fix observation angle, and tilting the radiator crystal offered the possibility to tune the radiation wavelength. The monochromatization effect is attributed to the frequency dependency of the quartz permittivity, and taking into account the refraction law for emitted ChR crossing the boundary between radiator target and vacuum it is possible to deduce a dispersion relation which connects ChR wavelength and outgoing photon angle - or in an alternative way ChR wavelength and target tilt angle for fixed observation angle. The dispersion relation is clearly confirmed in the experiment, and the model predictions show a satisfactory agreement with the measurements. Exploiting the ChR monochromatization mechanism might offer versatile tools which can find applications for example in beam diagnostics at modern particle accelerators.

Effect of a dielectric cavity on the ion etching of dielectrics by electron beam-produced plasma generated by a forevacuum plasma electron source

We show that etching of a dielectric (quartz) target by ions from the beam-plasma formed using a forevacuum-pressure, plasma-cathode electron source is substantially greater when the beam-plasma and the target are located within a dielectric cavity. The effect of the cavity manifests itself in impeding the negative charge to escape from the dielectric surface of the target irradiated by the electron beam, thereby forming higher negative target potentials which accelerate the ions coming from the plasma and intensify the ion etching. The beam-plasma parameters (plasma density and electron temperature) are greater with the cavity than without the cavity due to additional energy input from secondary electrons emitted from the target and accelerated by a high target potential. Efficient ion etching of dielectrics can be performed in this way.

Runaway electron energy determination by angular distribution of Cherenkov radiation

In this paper, we want to show how to obtain information about the spectrum of runaway electrons with kinetic energy in the range T≈ 0.25–2 MeV using Cherenkov radiation (ChR). We use a quartz target as a radiator which is tilted so that the generated Cherenkov optical photons can leave it. Electrons are light charged particles and such process as multiple scattering has a significant influence on ChR angular distribution since it can blur angular distribution of ChR. In spite of this fact, information about the runaway kinetic energy can be obtained by deconvolving ChR angular distribution.

Measuring Electron Beam Divergence with Cherenkov Light

Theoretical and experimental studies of Cherenkov light in the optical range are reported. Our results demonstrate that Cherenkov light can be used for measuring the angular divergence of a charged particle beam. In this experiment, Cherenkov light is generated by an electron beam with 6-MeV kinetic energy passing through a tilted planar quartz target. The initial beam divergence is extracted from the measured dependence of Cherenkov light intensity on the target tilt angle. The experimental results obtained with the 0.3-, 0.7-, and 1-mm-thick targets agree with theoretical predictions.

Maximizing neutron yields by scaling hollow diameter of a dense plasma focus anode

Experiments were performed to maximize the neutron yield from a 2 kJ dense plasma focus (DPF) and characterize the amount of copper sputtered from the surface of an anode by varying the diameter of the anodes’ on-axis hollow. The hollow is a void in the copper material along the longitudinal axis of the anode. All the anodes had an outer diameter of 1.2 in. and the diameter of the hollow varied from 0 in. (no hollow) to 1 in. The anodes with a hollow produced a greater number of neutrons per discharge than the anode without a hollow. Over 40 discharges, the hollow anode that yielded the most neutrons (9.1±0.4×106 neutrons per discharge produced with the 0.75 in. hollow) produced >6 times more neutrons than the anode with no hollow. A qualitative observation of the anodes after 130 discharges showed less surface damage on anodes with a larger hollow. Quantitative sputter measurements were performed by characterizing the amount of copper sputtered onto on-axis quartz targets for three newly machined anodes, each with a particular hollow diameter. The quantitative results matched the qualitative observations: the copper sputter was reduced using larger hollows. The largest hollow sputtered 17±1.0 nm/sr/discharge of copper, a reduction of 69% compared to the anode with the most damage.

On the Formation of IR-Light-Emitting Ge Nanocrystals in Ge:SiO2 Films

The study is concerned with light-emitting Ge nanocrystals formed during the annealing of Gex[SiO2]1 –x films produced by the high-vacuum cosputtering of germanium and quartz targets onto substrates at a temperature of 100°C. In accordance with the conditions of growth, the Ge molar fraction was varied from 10 to 40%. By means of electron microscopy and Raman spectroscopy, amorphous Ge nanoclusters ~4–5 nm in dimensions are detected in as-deposited films with a Ge content higher than 20 mol %. To crystallize amorphous nanoclusters, annealing at temperatures of up to 650°C is used. The kinetics of the crystallization of Ge nanoclusters is studied, and it is established that up to ~1/3 of the amorphous phase is retained in the system, supposedly at the interfaces between nanocrystals and the surrounding amorphous SiO2 matrix. It is found that, upon annealing in normal atmosphere, germanium nanoclusters are partially or completely oxidized (at a Ge molar fraction of 30% and smaller). An intense infrared photoluminescence signal from quantum-confined Ge nanocrystals and a visible photoluminescence signal defined by defect complexes (oxygen vacancy + excess Ge atoms) are observed.

Stoichiometry of Silicon Dioxide Films Obtained by Ion-Beam Sputtering

The composition of SiOx films produced by ion-beam sputtering (IBS) of silicon and quartz targets were studied by infrared spectrometry. Films with thicknesses of 150–390 nm were formed on silicon substrates. It was found that increase in the partial pressure of oxygen in the working gas, increase in the temperature of the substrate, and the presence of a positive potential on the target during reactive IBS of silicon shifted the main absorption band νas into the high-frequency region and increased the composition index from 1.41 to 1.85. During IBS of a quartz target the stoichiometry of the films deteriorates with increase of the energy of the sputtering argon ions. This may be due to increase of the deposition rate. Increase in the current of the thermionic compensator, increase of the substrate temperature, and addition of oxygen led to the formation of SiOx films with improved stoichiometry.

Формирование светоизлучающих в ИК-диапазоне нанокристаллов германия в плeнках Ge:SiO-=SUB=-2-=/SUB=-

AbstractThe study is concerned with light-emitting Ge nanocrystals formed during the annealing of Ge_ x [SiO_2]_1 –_ x films produced by the high-vacuum cosputtering of germanium and quartz targets onto substrates at a temperature of 100°C. In accordance with the conditions of growth, the Ge molar fraction was varied from 10 to 40%. By means of electron microscopy and Raman spectroscopy, amorphous Ge nanoclusters ~4–5 nm in dimensions are detected in as-deposited films with a Ge content higher than 20 mol %. To crystallize amorphous nanoclusters, annealing at temperatures of up to 650°C is used. The kinetics of the crystallization of Ge nanoclusters is studied, and it is established that up to ~1/3 of the amorphous phase is retained in the system, supposedly at the interfaces between nanocrystals and the surrounding amorphous SiO_2 matrix. It is found that, upon annealing in normal atmosphere, germanium nanoclusters are partially or completely oxidized (at a Ge molar fraction of 30% and smaller). An intense infrared photoluminescence signal from quantum-confined Ge nanocrystals and a visible photoluminescence signal defined by defect complexes (oxygen vacancy + excess Ge atoms) are observed.

X-ray and ion emission studies from subnanosecond laser-irradiated SiO2 aerogel foam targets

AbstractIn this experiment, a comparative study of ion and X-ray emission from both a SiO2 aerogel foam and a quartz target is performed. The experiment is performed using Nd:glass laser system operated at laser energy up to 15 J with a pulse duration of 500 ps with focusable intensity of 1013–1014 W/cm2 on target. X-ray fluxes in different spectral ranges (soft and hard) are measured by using X-ray diodes covered with Al filters of thickness 5 µm (0.9–1.56 keV) and 20 µm (3.4–16 keV). A 2.5 times enhancement in soft X-ray flux (0.9–1.56 keV) and a decrease of 1.8 times in hard X rays (3.4–16 keV) for 50 mg/cc SiO2 aerogel foam is observed compared with the solid quartz. A decrease in the flux of the K-shell line emission spectrum of soft X rays is noticed in the case of the foam targets. The high-resolution K-shell spectra (He-like) of Si ions in both the cases are analyzed for the determination of plasma parameters by comparing with FLYCHK simulations. The estimated plasma temperature and density are Tc = 180 eV, ne = 7 × 1020 cm−3 and Tc = 190 eV, ne = 4 × 1020 cm−3 for quartz and SiO2 aerogel foam, respectively. To measure the evolution of the plasma moving away from the targets, four identical ion collectors are placed at different angles (22.5, 30, 45, and 67.5°) from target normal. The angular distribution of the thermal ions are scaled as cosnθ with respect to target normal, where n = 3.8 and 4.8 for the foam and quartz, respectively. The experimental plasma volume measured from the ion collectors and shadowgraphy images are verified by a two-dimensional Eulerian radiative–hydrodynamic simulation (POLLUX code).

Comparative studies of Laser induced plasma in TEOS and MTMS based aerogels and solid quartz

Abstract:The interaction of laser radiation with low density aerogels is of crucial importance in areas such as the creation of coherent radiation sources in the X-ray range, simulation of astrophysical as well as nuclear fusion phenomena in laboratory and fundamental studies of the properties of soft condensed matter under dynamic pressure in the Mbar range. In the present paper, the experimental results on the X-ray emission of laser induced plasma in TEOS based, MTMS based aerogels and solid quartz targets, are reported. The aerogels were produced by the sol-gel processing of tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMS) followed by supercritical drying. Silica alcogels were produced using 0.001 M oxalic acid (C2H4O4), 0.5 M ammonium hydroxide (NH4OH) catalysts. Different densities of aerogels varying from 0.02 to 0.06 g/cm3 have been obtained using different molar ratios of TEOS, MTMS, ethanol and catalysts. The laser, with intensity up to 2 x 1014 W/m2, interaction with TEOS and MTMS based aerogels have been conducted using 30J/500 ps Nd : glass laser system. The resulting soft (0.8 – 1.56 Kev) and hard (>4 Kev) X-ray emissions have been measured using semiconductor photodiodes. It has been observed that the soft X-ray yield increases by a factor of two for the silica aerogel targets compared to the X-ray emission from the solid quartz target, whereas the hard X-ray yield reduces. The enhanced soft X-ray yield in silica aerogel targets is attributed to the large volume heating.

Laser‐induced melting experiments: Simulation of short‐term high‐temperature impact processes

AbstractThis study introduces an experimental approach using direct laser irradiation to simulate the virtually instantaneous melting of target rocks during meteorite impacts. We aim at investigating the melting and mixing processes of projectile (iron meteorite; steel) and target material (sandstone) under idealized conditions. The laser experiments (LE) were able to produce features very similar to those of impactites from meteorite craters and cratering experiments, i.e., formation of lechatelierite, partial to complete melting of sandstone, and injection of projectile droplets into target melts. The target and projectile melts have experienced significant chemical modifications during interaction of these coexisting melts. Emulsion textures, observed within projectile‐contaminated target melts, indicate phase separation of silicate melts with different chemical compositions during quenching. Reaction times of 0.6 to 1.4 s could be derived for element partitioning and phase‐separation processes by measuring time‐depended temperature profiles with a bolometric detector. Our LE allow (i) separate melting at high temperatures to constrain primary melt heterogeneities before mixing of projectile and target, (ii) quantification of element partitioning processes between coexisting projectile and target melts, (iii) determination of cooling rates, and (iv) estimation of reaction times. Moreover, we used a thermodynamic approach to calculate the entropy gain during laser melting. The entropy changes for laser‐melting of sandstone and iron meteorite correspond to shock pressures and particle velocities produced during the impact of an iron projectile striking a quartz target at a minimum impact velocity of ~6 km s−1, inducing peak shock pressures of ~100 GPa in the target.

Proton inelastic scattering cross section measurements on16O and28Si

A (p, p′γ ) experiment was performed at the Tandem accelerator of IFIN-HH (Bucharest) with the purpose of measuring the proton inelastic cross-sections on 16 O and 28 Si. The goal was to investigate to which extent the neutron cross-sections on these nuclei can be inferred from those obtained with charged particles (i.e., protons). In doing so, we are trying to exploit the isospin symmetry by taking under consideration that the chosen targets are N = Z nuclei and, consequently, two mirror nuclei are formed in the (p ,p ′) and (n ,n ′) reactions. The experimental setup consisted of two HPGe detectors with 100% relative efficiency placed at 110∘ and 150∘ relative to the direction of the incident proton beam. The incident protons, which had energies ranging from 6 up to 17 MeV, were scattered on a thick quartz (SiO2 ) target. A Faraday cup was used to integrate the beam current, thus allowing an absolute determination of the γ production cross sections. We will briefly describe the data analysis procedure, the experimental particularities and difficulties and some preliminary results of the γ production cross sections for the most intense transitions both in 16 O and 28 Si.

Optimizations in Sputtering Glass as Permeation Barrier for Laser Targets

Glass thin films appear particularly interesting as semipermeable barriers for many noncryogenic target applications. This functional layer can be sputtered from quartz targets onto CHx microshells synthesized by glow discharge polymerization. In the present work, we investigate the influence of deposit parameters (pressure, RF power, target-holder distance, and plasma composition) on glass coating microstructure and permeation properties. The permeation properties of CHx/SiO2/CHx capsules are studied by mass spectrometry using deuterium (D2) as the filling gas. The use of a low deposition pressure and a high RF power in a background atmosphere of argon appears essential to obtain the most efficient barrier. The optimized sputtering conditions allow deuterium half-lives of 1 month on 1700-μm CHx capsules, including a 1-μm-thick SiO2 coating (corresponding to a permeation coefficient of 3 × 10-20 mol˙m-1˙s-1˙Pa-1). These capsules could be filled to the required pressures ([approximately]3 MPa) for Laser Mégajoule (LMJ) experiments.

Detailed report of the MuLan measurement of the positive muon lifetime and determination of the Fermi constant

We present a detailed report of the method, setup, analysis and results of a precision measurement of the positive muon lifetime. The experiment was conducted at the Paul Scherrer Institute using a time-structured, nearly 100%-polarized, surface muon beam and a segmented, fast-timing, plastic scintillator array. The measurement employed two target arrangements; a magnetized ferromagnetic target with a ~4 kG internal magnetic field and a crystal quartz target in a 130 G external magnetic field. Approximately 1.6 x 10^{12} positrons were accumulated and together the data yield a muon lifetime of tau_{mu}(MuLan) = 2196980.3(2.2) ps (1.0 ppm), thirty times more precise than previous generations of lifetime experiments. The lifetime measurement yields the most accurate value of the Fermi constant G_F (MuLan) = 1.1663787(6) x 10^{-5} GeV^{-2} (0.5 ppm). It also enables new precision studies of weak interactions via lifetime measurements of muonic atoms.

Laser-driven shock propagation into quartz targets driven by various drive pulse configurations: experiments

Both direct-drive and indirect-drive inertial confinement fusion targets use temporally shaped drive pulses to optimize the target performance. The timing of multiple shock waves is crucial to the performance of inertial confinement fusion ignition targets. This paper reports an experimental study on the shock wave characteristics of laser-irradiated targets. The shock wave velocity profiles are measured using the velocity interferometer system for any reflector (VISAR). Presented are measurements of velocities from shock waves in quartz targets driven by single 120 ps pulse, two 120 ps pulses separated by 1.1 ns and a special shaped pulse. These pulses drive two shock waves that coalesce in the target, and the coalescence times and transit times are observed by VISAR.

3 MV hypervelocity dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies

A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Institüt für Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10(-7) torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10(-10) torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments.

Shock timing experiment based on imaging velocity interferometer system for any reflector

The timing of multiple shock waves is crucial technique to the performance of inertial confinement fusion ignition targets. With the requirement for shock timing, the timing ability of Shen Guang-III prototype is analyzed by experimental data of two shots. The laser pulse in Shen Guang-III prototype is shaped in time scale, and the window material is z-cut quartz. The stream lines of two shock waves in quartz target are presented with Multi-1D program. Two steps of radiation drive two shock waves that coalesce in the quartz target, the resulting history, coalesce times, and transit times are observed in the stream lines. With the experiment results of two shots, the consistence of resulting history and coalesce times of two shock waves is provided under the same condition of laser pulse, target and diagnostic parameter. The differences in shock wave velocity, fringe contrast and quality occur at coalesce times of two shock waves. And the reflectivity of second shock wave does not increase compared with that of first shock wave. These experimental results and method provide the strong support for shock timing technique.