scholarly journals Hydrodynamic instability experiments with three-dimensional modulations at the National Ignition Facility

2015 ◽  
Vol 3 ◽  
Author(s):  
V.A. Smalyuk ◽  
S.V. Weber ◽  
D.T. Casey ◽  
D.S. Clark ◽  
J.E. Field ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Hydrodynamic Instability ◽  
Three Dimensional ◽  
Initial Surface ◽  
National Ignition Facility ◽  
Signal To Noise ◽  
Time Resolved ◽  
Pinhole Imaging ◽  
Instability Growth ◽  
Noise Ratio

The first hydrodynamic instability growth measurements with three-dimensional (3D) surface-roughness modulations were performed on CH shell spherical implosions at the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)]. The initial capsule outer-surface amplitudes were increased approximately four times, compared with the standard specifications, to increase the signal-to-noise ratio, helping to qualify a technique for measuring small 3D modulations. The instability growth measurements were performed using x-ray through-foil radiography based on time-resolved pinhole imaging. Averaging over 15 similar images significantly increased the signal-to-noise ratio, making possible a comparison with 3D simulations. At a convergence ratio of ${\sim}2.4$ , the measured modulation levels were ${\sim}3$ times larger than those simulated based on the growth of the known imposed initial surface modulations. Several hypotheses are discussed, including increased instability growth due to modulations of the oxygen content in the bulk of the capsule. Future experiments will be focused on measurements with standard 3D ‘native-roughness’ capsules as well as with deliberately imposed oxygen modulations.

A new method for ultrasonic detection of peel ply at the bondline of out-of-autoclave composite assemblies

2018 ◽  
Vol 53 (2) ◽  
pp. 245-259
Author(s):  
Gary S LeMay ◽  
Davood Askari
Keyword(s):  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Ultrasonic Pulse ◽  
Woven Fabric ◽  
Material System ◽  
Signal To Noise ◽  
Structural Applications ◽  
Peel Ply ◽  
Noise Ratio ◽  
Out Of Autoclave

Out-of-autoclave materials have long been an established material system for secondary structural applications; however, recent advancements in material properties allow for more advanced structural applications. Even though certain out-of-autoclave properties have achieved parity with autoclaved cured materials, out-of-autoclave materials are cured at reduced temperatures and pressures resulting in less compaction and homogeneity. The consequence is extraneous ultrasonic signals, due to internal reflections and refractions that cause attenuation, potentially masking defects leading to unidentifiable indications. Advanced algorithms were developed to improve the signal to noise ratio between constituents of similar acoustic impedance in bonded out-of-autoclave carbon fiber reinforced polymer assemblies. Conventional ultrasonic nondestructive testing techniques and analysis software cannot consistently achieve signal to noise ratios that meet quantifiable rejection thresholds of accurately sized peel ply inserts at the bonded interface of composite assemblies. Ultrasonic pulse echo with full waveform capture was used to inspect a reference standard with peel ply inserts placed between the adhesive and three-dimensional-woven fabric preform. The ultrasonic signal was produced by a 64 element array transducer with a central frequency of 2.8 MHz. Waveform post-acquisition analysis with post processing software was used to analyze and enhance the signal response between the peel ply and the bondline resulting in the final algorithm. To verify the results, the signal to noise ratio of each insert was calculated for both the raw and processed data. As the measure of detectability, the method relies on principles of statistical measurement to provide an industry standard signal to noise response of 3:1.

scholarly journals Three-Dimensional Imaging via Time-Correlated Single-Photon Counting

2020 ◽  
Vol 10 (6) ◽  
pp. 1930
Author(s):  
Chengkun Fu ◽  
Huaibin Zheng ◽  
Gao Wang ◽  
Yu Zhou ◽  
Hui Chen ◽  
...  
Keyword(s):  
3D Imaging ◽  
Single Photon ◽  
Signal To Noise Ratio ◽  
Photon Counting ◽  
Three Dimensional ◽  
Similarity Index ◽  
Signal To Noise ◽  
Single Photon Counting ◽  
Imaging Results ◽  
Noise Ratio

Three-dimensional (3D) imaging under the condition of weak light and low signal-to-noise ratio is a challenging task. In this paper, a 3D imaging scheme based on time-correlated single-photon counting technology is proposed and demonstrated. The 3D imaging scheme, which is composed of a pulsed laser, a scanning mirror, single-photon detectors, and a time-correlated single-photon counting module, employs time-correlated single-photon counting technology for 3D LiDAR (Light Detection and Ranging). Aided by the range-gated technology, experiments show that the proposed scheme can image the object when the signal-to-noise ratio is decreased to −13 dB and improve the structural similarity index of imaging results by 10 times. Then we prove the proposed scheme can image the object in three dimensions with a lateral imaging resolution of 512 × 512 and an axial resolution of 4.2 mm in 6.7 s. At last, a high-resolution 3D reconstruction of an object is also achieved by using the photometric stereo algorithm.

Three-Dimensional Optical Bit Memory in Sm(DBM)3Phen-Doped and Un-Doped Poly(methyl methacrylate)

2011 ◽  
Vol 284-286 ◽  
pp. 2251-2254
Author(s):  
Zhao Gang Nie ◽  
Xin Zhong Li ◽  
Yu Ping Tai ◽  
Ki Soo Lim ◽  
Myeongkyu Lee
Keyword(s):  
Refractive Index ◽  
Methyl Methacrylate ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Pulsed Laser ◽  
High Signal ◽  
Signal To Noise ◽  
Fluorescent Signal ◽  
Poly Methyl Methacrylate ◽  
Noise Ratio

The feasibility of three-dimensional optical bit memory is demonstrated by using the change of fluorescence and refractive index in Sm(DBM)3Phen-doped and un-doped Poly(methyl methacrylate). After a femtosecond pulsed laser irradiation, a refractive-index bit and a fluorescent bit can be formed at the same position inside the bulk sample. Multilayer patterns recorded by tightly focusing the pulsed laser beam were read out by a reflection-type fluorescent confocal microscope, which can detect the reflection signal and also the fluorescent signal of the stored bits. The signal-to-noise ratio via the two retrieval modes was compared as a function of recording depth. The stored bits were retrieved with a high signal-to-noise ratio in the absence of any crosstalk and the detection of the fluorescent signal enables retrieval of the stored bits with a higher S/N ratio.

scholarly journals Impact of lossy compression of X-ray projections onto reconstructed tomographic slices

2020 ◽  
Vol 27 (5) ◽  
pp. 1326-1338
Author(s):  
Federica Marone ◽  
Jakob Vogel ◽  
Marco Stampanoni
Keyword(s):  
Signal To Noise Ratio ◽  
Lossy Compression ◽  
High Signal ◽  
Signal To Noise ◽  
Time Resolved ◽  
Data Archiving ◽  
X Ray ◽  
Compression Factor ◽  
Significant Burden ◽  
Noise Ratio

Modern detectors used at synchrotron tomographic microscopy beamlines typically have sensors with more than 4–5 mega-pixels and are capable of acquiring 100–1000 frames per second at full frame. As a consequence, a data rate of a few TB per day can easily be exceeded, reaching peaks of a few tens of TB per day for time-resolved tomographic experiments. This data needs to be post-processed, analysed, stored and possibly transferred, imposing a significant burden onto the IT infrastructure. Compression of tomographic data, as routinely done for diffraction experiments, is therefore highly desirable. This study considers a set of representative datasets and investigates the effect of lossy compression of the original X-ray projections onto the final tomographic reconstructions. It demonstrates that a compression factor of at least three to four times does not generally impact the reconstruction quality. Potentially, compression with this factor could therefore be used in a transparent way to the user community, for instance, prior to data archiving. Higher factors (six to eight times) can be achieved for tomographic volumes with a high signal-to-noise ratio as it is the case for phase-retrieved datasets. Although a relationship between the dataset signal-to-noise ratio and a safe compression factor exists, this is not simple and, even considering additional dataset characteristics such as image entropy and high-frequency content variation, the automatic optimization of the compression factor for each single dataset, beyond the conservative factor of three to four, is not straightforward.

Quantitative analysis and time-resolved characterization of simulated tokamak exhaust gas by laser-induced breakdown spectroscopy

2021 ◽  
Author(s):  
Yaxiong He ◽  
Tao Xu ◽  
Yong Zhang ◽  
Chuan Ke ◽  
Yong Zhao ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Standard Method ◽  
Signal To Noise Ratio ◽  
Laser Induced Breakdown Spectroscopy ◽  
Exhaust Gas ◽  
Signal To Noise ◽  
Time Resolved ◽  
Breakdown Spectroscopy ◽  
Laser Induced Breakdown ◽  
Noise Ratio

Abstract Tokamak exhaust is an important part of the deuterium-tritium fuel cycle system in fusion reaction. In this work, we present a laser-induced breakdown spectroscopy (LIBS) based method to monitor the gas compositions from exhaust system in the Tokamak device. Helium (He), a main impurity in the exhaust gas, was mixed with hydrogen (H2) in different ratios through a self-designed gas distribution system, and sealed into a measurement chamber as a standard specimen. A 532 nm wavelength laser pulse with an output power of 100 mJ was used for plasma excitation. The time-resolved LIBS is used to study the time evolution characteristics of the signal strength, signal-to-background-ratio (SBR), signal-to-noise-ratio (SNR) and relative standard deviation (RSD) of the helium and hydrogen characteristic lines. The Boltzmann two-line method was employed to estimate the plasma temperature of laser-induced plasma (LIP). The Stark-broadened profile of He I 587.56 nm was exploited to measure the electron density. From these studies, an appropriate time was determined in which the low RSD% were consistent with the high signal-to-noise ratio. The He I 587.56 nm and Hα emission lines with good signal-to-noise ratio were extracted from the spectrum and used in the external standard method and internal standard method for quantitative analysis. The test results for mixed gas showed that the average relative error of prediction was less than 11.15%, demonstrating the great potential of LIBS in detecting impurities in plasma exhaust gas.

Improved Signal-to-Noise Ratio in Laboratory-Based Phase Contrast Tomography

2012 ◽  
Vol 18 (2) ◽  
pp. 399-405 ◽  
Author(s):  
Matthieu N. Boone ◽  
Yoni De Witte ◽  
Manuel Dierick ◽  
Ana Almeida ◽  
Luc Van Hoorebeke
Keyword(s):  
Phase Contrast ◽  
Phase Retrieval ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
X Rays ◽  
Signal To Noise ◽  
Retrieval Algorithms ◽  
Significant Phenomenon ◽  
Noise Ratio ◽  
3D Volume

AbstractIn conventional X-ray microtomography (μCT), the three-dimensional (3D) distribution of the attenuation coefficient of X-rays is measured and reconstructed in a 3D volume. As spatial resolution increases, the refraction of X-rays becomes a significant phenomenon in the imaging process. Although this so-called phase contrast was initially a cumbersome feature in lab-based μCT, special phase retrieval algorithms were developed to exploit these effects. Clear advantages in terms of visualization and analysis can be seen when phase retrieval algorithms are applied, including an increased signal-to-noise ratio. In this work, this is demonstrated both on simulated and measured data.

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