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A new approach to theoretical investigations of high harmonics generation by means of fs laser interaction with overdense plasma layers. Combining particle-in-cell simulations with machine learning.

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JOURNAL OF INSTRUMENTATION 2016年第12期11卷 C12004-C12004页

作者： Mihailescu, A. Natl Inst Laser Plasma & Radiat Phys POB MG 36 Magurele 077125 Romania

Within the past decade, various experimental and theoretical investigations have been performed in the field of high-order harmonics generation (HHG) by means of femtosecond (fs) laser pulses interacting with laser produced plasmas. Numerous potential future applications thus arise. Beyond achieving higher conversion efficiency for higher harmonic orders and hence harmonic power and brilliance, there are more ambitious scientific goals such as attaining shorter harmonic wavelengths or reducing harmonic pulse durations towards the attosecond and even the zeptosecond range. High order harmonics are also an attractive diagnostic tool for the laser-plasma interaction process itself. Particle-in-Cell (PIC) simulations are known to be one of the most important numerical instruments employed in plasma physics and in laser-plasma interaction investigations. The novelty brought by this paper consists in combining the PIC method with several machine learning approaches. For predictive modelling purposes, a universal functional approximator is used, namely a multi-layer perceptron (MLP), in conjunction with a self-organizing map (SOM). The training sets have been retrieved from the PIC simulations and also from the available literature in the field. The results demonstrate the potential utility of machine learning in predicting optimal interaction scenarios for gaining higher order harmonics or harmonics with particular features such as a particular wavelength range, a particular harmonic pulse duration or a certain intensity. Furthermore, the author will show how machine learning can be used for estimations of electronic temperatures, proving that it can be a reliable tool for obtaining better insights into the fs laser interaction physics.

关键词： data processing methods Pattern recognition cluster finding calibration and fitting methods Analysis and statistical methods Simulation methods and programs

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Temperature fitting of partially resolved rotational spectra

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JOURNAL OF INSTRUMENTATION 2012年第02期7卷 C02054-C02054页

作者： van Gessel, A. F. H. Hrycak, B. Jasinski, M. Mizeraczyk, J. van der Mullen, J. J. A. M. Bruggeman, P. J. Eindhoven Univ Technol Dept Appl Phys NL-5600 MB Eindhoven Netherlands Polish Acad Sci Szewalski Inst Fluid Flow Machinery Ctr Plasma & Laser Engn PL-80231 Gdansk Poland

In this paper we present a method to automatically fit the temperature of a rotational spectrum. It is shown that this fitting method yields similar results as the traditional Boltzmann plot, but is applicable in situations where lines of the spectrum overlap. The method is demonstrated on rotational spectra of nitric oxide from an atmospheric pressure microwave plasma jet operated with a flow of helium and air, obtained with two different methods: laser induced fluorescence and optical emission spectroscopy. Axial profiles of the rotational temperatures are presented for the ground NO X state and the excited NO A state.

关键词： data processing methods Plasma diagnostics - interferometry, spectroscopy and imaging

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Simulation and reconstruction of the PANDA Barrel DIRC detector

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JOURNAL OF INSTRUMENTATION 2011年第11期6卷

作者： Patsyuk, M. Schwarz, C. Dutta, D. Goetzen, K. Peters, K. Schwiening, J. GSI Helmholtzzentrum Schwerionenforschung GmbH D-64291 Darmstadt Germany Goethe Univ Frankfurt D-60325 Frankfurt Germany Bhabha Atom Res Ctr Div Nucl Phys Bombay 400085 Maharashtra India

The PANDA experiment at the future Facility for Antiproton and Ion Research (FAIR) at GSI, Darmstadt, aims at studying the strong interacting matter by precision spectroscopy. A detector system with excellent particle identification over a large range of solid angle and momentum is therefore mandatory. Charged hadron identification in the barrel region will be performed by a compact ring imaging Cherenkov detector based on the DIRC principle (Detection of Internally Reflected Cherenkov light), designed to separate pions from kaons with at least 3 standard deviations in the momentum range from 0.5 GeV/c to 3.5 GeV/c. We present details of the simulation of the PANDA Barrel DIRC and a study of the detector performance using a fast reconstruction algorithm to determine the single photon Cherenkov angle resolution and photon yield for several design options.

关键词： data processing methods Particle identification methods Cherenkov detectors Cherenkov and transition radiation

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Performance measurements of a depth-encoding TraPET detector module

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JOURNAL OF INSTRUMENTATION 2011年第11期6卷

作者： Chung, Y. H. Lee, C. Y. Baek, C. -H. An, S. J. Kim, H. Il Choi, Y. Kang, J. Hu, W. Yonsei Univ Coll Hlth Sci Dept Radiol Sci Wonju 220710 Kangwon Do South Korea Yonsei Univ Inst Hlth Sci Wonju 220710 Kangwon Do South Korea Sogang Univ Dept Elect Engn Seoul 121742 South Korea Sungkyunkwan Univ Sch Med Samsung Med Ctr Dept Nucl Med Seoul 135710 South Korea

The new method to correct a parallax error and the loss of coincidence counts caused by the gap between modules was developed for a small animal PET scanner. We proposed the TraPET scanner composed of 6 dual-layer phoswich detector modules. Each detector module consists of a 5.0 mm-thick trapezoidal-shaped monolithic LSO crystal and a 23 x 23 array of GSO crystal. The layer of interaction is identified by the pulse shape discrimination method. One detector module was built and the algorithm for layer identification was optimized. The dual-layer crystals were optically coupled to a Hamamatsu H8500 position-sensitive PMT and a resistive charge divider was used to multiplex 64-channel anode outputs into 4-channel position signals. The 4 signals have been sampled continuously by 14-bit ADC at a sampling rate of 105 MHz and the pulse shape discrimination algorithm was achieved through FPGA programming. The detector module was irradiated with a Na-22 point source from the side of the crystals to obtain flood images of each layer and two layers were clearly identified, thus verifying the DOI capability. The TraPET detector proved to be a reliable design for correcting the parallax error and improving the sensitivity simultaneously in the small animal PET.

关键词： Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA) data processing methods Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc) Front-end electronics for detector readout

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Spectral X-ray computed tomography image denoising using weighted local regression and noise-insensitive feature dimensionality reduction

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JOURNAL OF INSTRUMENTATION 2024年第8期19卷 P08020页

作者： Hotta, T. Yatagawa, T. Ohtake, Y. Matsukawa, M. Suzuki, H. Aoki, T. Shizuoka Univ Grad Sch Med Photon 3-5-1 JohokuChuo Ku Hamamatsu Shizuoka 4328011 Japan Hitotsubashi Univ Sch Social Data Sci 2-1 Naka Kunitachi Tokyo 1868601 Japan Univ Tokyo Dept Precis Engn 7-3-1 Hongo Bunkyo City Tokyo 1138654 Japan Zodiac Inc 145-1 TokiwachoChuo Ku Hamamatsu Shizuoka 4300917 Japan

This study introduces a novel denoising method for spectral X-ray computed tomography (CT) images using weighted local regression (WLR). The proposed method exploits the common structural information present across different energy bins. Denoised pixel intensities of a certain energy bin are estimated using the intensities of the other energy bins via WLR. Denoising is achieved by applying a WLR model to the noisy pixel intensities of all energy bins, excluding the target bin, which obtains approximate noise-free intensities for the target energy bin. The performance of our approach was assessed using synthetic spectral X-ray CT images produced using a Monte Carlo photon simulator called the Electron Gamma Shower 5 (EGS5). Both qualitative and quantitative evaluations demonstrated that our approach effectively reduced noise across all energy bins while maintaining image sharpness. Comparisons with common denoising methods demonstrate the effectiveness of the proposed method.

关键词： Analysis and statistical methods Computerized Tomography (CT) and Computed Radiography (CR) data processing methods Image filtering

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Enhancing spatial resolution in MONCH for electron microscopy via deep learning

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JOURNAL OF INSTRUMENTATION 2024年第1期19卷 C01020页

作者： Xie, X. Flores, L. Barba Haro, B. Bejar Bergamaschi, A. Frojdh, E. Muller, E. Paton, K. A. Poghosyana, E. Remlinger, C. Paul Scherrer Inst CH-5232 Villigen Switzerland Swiss Data Sci Ctr SDSC Hub PSI CH-5232 Villigen Switzerland Swiss Data Sci Ctr CH-1015 Lausanne Switzerland

Hybrid Pixel Detectors (HPDs) are highly suitable in diffraction -based electron microscopy due to their high frame rates (> 1 kHz), high dynamic range, and good radiation hardness. However, their use in imaging applications has been limited by their relatively large pixel size (>= 55 mu m) and high-energy (> 80 keV) electrons scattering over multiple pixels in the sensor layer. To realize the full potential of fast, radiation -hard HPDs across electron microscopy modalities, we developed deep learning techniques to precisely localize the impact point of incident electrons in MUNCH, a charge integrating HPD with 25 mu m pixel size. With neural network models trained using labeled data via simulations and experimental measurements, the best spatial resolution obtained, defined in terms of the root mean squared error, was 0.60 pixels for 200 keV electrons, a three -fold improvement over a simple charge centroid method. This article presents the training sample generation, deep learning model design, training results, and imaging outcomes for a sample containing gold nanoparticles.

关键词： data processing methods Hybrid detectors Pixelated detectors and associated VLSI electronics

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Automated detection of arterial input function in DSC perfusion MRI in a stroke rat model

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JOURNAL OF INSTRUMENTATION 2009年第5期4卷 P05021-P05021页

作者： Yeh, M. -Y. Lee, T. -H. Yang, S. -T. Kuo, H. -H. Chyi, T. -K. Liu, H. -L. Chang Gung Univ Grad Inst Med Phys & Imaging Sci Tao Yuan Taiwan Chang Gung Mem Hosp MRI Ctr Tao Yuan Taiwan Chang Gung Mem Hosp Stroke Sect Dept Neurol Tao Yuan Taiwan Chang Gung Mem Hosp Mol Imaging Ctr Tao Yuan Taiwan

Quantitative cerebral blood flow (CBF) estimation requires deconvolution of the tissue concentration time curves with an arterial input function (AIF). However, image-based determination of AIF in rodent is challenged due to limited spatial resolution. We evaluated the feasibility of quantitative analysis using automated AIF detection and compared the results with commonly applied semi-quantitative analysis. Permanent occlusion of bilateral or unilateral common carotid artery was used to induce cerebral ischemia in rats. The image using dynamic susceptibility contrast method was performed on a 3-T magnetic resonance scanner with a spin-echo echo-planar-image sequence (TR/TE= 700/80 ms, FOV=41 mm, matrix=64, 3 slices, SW=2 mm), starting from 7 s prior to contrast injection (1.2ml/kg) at four different time points. For quantitative analysis, CBF was calculated by the AIF which was obtained from 10 voxels with greatest contrast enhancement after deconvolution. For semi-quantitative analysis, relative CBF was estimated by the integral divided by the first moment of the relaxivity time curves. We observed if the AIFs obtained in the three different ROIs (whole brain, hemisphere without lesion and hemisphere with lesion) were similar, the CBF ratios (lesion/normal) between quantitative and semi-quantitative analyses might have a similar trend at different operative time points. If the AIFs were different, the CBF ratios might be different. We concluded that using local maximum one can define proper AIF without knowing the anatomical location of arteries in a stroke rat model.

关键词： data processing methods MRI (whole body, cardiovascular, breast, others) MR-angiography (MRA)

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Fast iterative reconstructions for animal CT

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JOURNAL OF INSTRUMENTATION 2009年第06期4卷 P06017-P06017页

作者： Huang, H. -M. Hsiao, I. -T. Jan, M. -L. Chang Gung Univ Dept Med Imaging & Radiol Sci Tao Yuan 333 Taiwan Case Western Reserve Univ Dept Biomed Engn Cleveland OH 44106 USA Chang Gung Mem Hosp Mol Imaging Ctr Kwei Shan Taoyuan 333 Taiwan INER Div Phys Tao Yuan 32546 Taiwan

For iterative x-ray computed tomography (CT) reconstruction, the convex algorithm combined with ordered subset (OSC) [1] is a relatively fast algorithm and has shown its potential for low-dose situations. But it needs one forward projection and two backprojections per iteration. Unlike convex algorithm, the gradient algorithm only requires one forward projection and one backprojection per iteration. Here, we applied ordered subsets of projection data to a modified gradient algorithm. In order to further reduce computation time, the new algorithm, the ordered subset gradient (OSG) algorithm, can be adjusted with a step size. We also implemented another OS-type algorithm called OSTR. The OSG algorithm is compared with OSC algorithm and OSTR algorithm using three-dimensional simulated helical cone-beam CT data. The performance is evaluated in terms of log-likelihood, contrast recovery, and bias-variance studies. Results show that images of OSG has compatible visual image quality to those of OSC and OSTR, but in the resolution and bias-variance studies, OSG seems to reach stable values with faster speed. In particular, OSTR has better recovery in a smoother region, but both OSG and OSC have better recovery in the high-frequency regions. Moreover, in terms of log likelihood with respect to computation time, OSG has faster convergence rate than that of OSC and similar to that of OSTR. We conclude that OSG has potential to provide comparable image quality and is more computationally efficient, and thus could be suitable for low-dose, helical cone-beam CT image reconstruction.

关键词： Image reconstruction in medical imaging data processing methods

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A new generation scanning system for the high-speed analysis of nuclear emulsions

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JOURNAL OF INSTRUMENTATION 2016年第6期11卷 P06002-P06002页

作者： Alexandrov, A. Buonaura, A. Consiglio, L. D'Ambrosio, N. De Lellis, G. Di Crescenzo, A. Galati, G. Lauria, A. Montesi, M. C. Tioukov, V. Vladymyrov, M. INFN Sez Napoli I-80125 Naples Italy Russian Acad Sci LPI Lebedev Phys Inst RUS-119991 Moscow Russia Ist Nazl Fis Nucl Lab Nazl Gran Sasso I-67100 Laquila Italy Univ Naples Federico II I-80125 Naples Italy LHEP Bern Bern Switzerland

The development of automatic scanning systems was a fundamental issue for large scale neutrino detectors exploiting nuclear emulsions as particle trackers. Such systems speed up significantly the event analysis in emulsion, allowing the feasibility of experiments with unprecedented statistics. In the early 1990s, R&D programs were carried out by Japanese and European laboratories leading to automatic scanning systems more and more efficient. The recent progress in the technology of digital signal processing and of image acquisition allows the fulfillment of new systems with higher performances. In this paper we report the description and the performance of a new generation scanning system able to operate at the record speed of 84 cm(2)/hour and based on the Large Angle Scanning System for OPERA (LASSO) software infrastructure developed by the Naples scanning group. Such improvement, reduces the scanning time by a factor 4 with respect to the available systems, allowing the readout of huge amount of nuclear emulsions in reasonable time. This opens new perspectives for the employment of such detectors in a wider variety of applications.

关键词： data acquisition concepts data processing methods Image processing Optics

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A method for the near real-time production of quasi-definitive magnetic observatory data

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EARTH PLANETS AND SPACE 2013年第11期65卷 1363-1374页

作者： Clarke, Ellen Baillie, Orsi Reay, Sarah J. Turbitt, Chris W. British Geol Survey Edinburgh EH9 3LA Midlothian Scotland

Magnetic observatory data are widely used in the derivation of time-varying magnetic field models, often in combination with satellite magnetic data, when available. Traditionally the definitive observatory results are used, the availability of which can often lag those of the satellite data by months and even years. The recently defined quasi-definitive observatory data type has been introduced to meet the need to provide observatory data suitable for use in field modeling in a more rapid time frame and for producing Level 2 products planned for the upcoming European Space Agency Swarm mission. A method for producing quasi-definitive data is presented and the essential steps described. To evaluate the method, provisional data published on a next day basis since 2000 are tested against definitive data at five INTERMAGNET observatories. The means and standard deviations of the differences between the candidate quasi-definitive and definitive data are within the accuracy of 5 nT set by INTERMAGNET. Since the tested data were published on-line on a next day basis, they also easily meet the INTERMAGNET requirement of availability within three months. These results demonstrate that prompt production of quasi-definitive data is possible for observatories that already perform to the standards set by INTERMAGNET.

关键词： Geomagnetic observatory quasi-definitive data observatory baselines data processing methods

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