Experimental Advanced Superconducting Tokamak (EAST) employs Extreme Ultraviolet (EUV) spectroscopic diagnostic systems to measure the impurity radiation of the core plasma. However, the sensor chip is significantly affected by the interference from hard X-rays on, resulting in a significant amount of single-pixel noise in the collected spectral image data. This interference presents significant challenges for accurately analyzing the impurity radiation in fusion plasma. To address this issue, hardware algorithms are prepared to be integrated into the detector to optimize the imaging quality. However, since the existing commercial detector could not be modified in terms of hardware and programming, decision to develop an imaging system for EUV spectral diagnosis. This imaging system will be used on EAST for EUV spectral diagnosis and for future research on hardware optimization algorithms. The imaging system is designed with the GSENSE400BSI sensor chip as the photosensitive component and the AC7Z100B board as the control center, and it also includes two high-speed transmission interfaces: USB 3.0 and Camera Link. Finally, to verify the acquisition function and imaging quality of the imaging system, tests were conducted on the established spectral image acquisition platform. The results showed that the imaging system could normally complete the spectral image acquisition with high- quality imaging.
KEYWORDS: Spectroscopy, Optical attenuators, Near infrared, Near infrared spectroscopy, Control systems, Power supplies, Absorption, Signal attenuation, Lamps, Attenuators
A near-infrared spectroscopy system is developed to measure accurately content of grain nutrient. The spectroscopic system mainly consists of near-infrared spectrometer, halogen lamp, stepping motor module, light attenuator, volume weight module. Since the absorbance of grain in NIR range is relatively high, a new type of light attenuator is developed to precisely measure the reference spectra. The method to obtain the transmission spectra is discussed in this study. The control system running on Windows operation system is also developed to acquire spectral data and process the obtained data. The control procedures are presented in detail. The spectroscopic system can automatically complete the measurement by the control system. The results showed that the present design can obtain the transmission spectra of grain effectivly
KEYWORDS: Sensors, Vacuum ultraviolet, Spectroscopy, Control systems, Amplifiers, Electrons, Data acquisition, Photomultipliers, Signal to noise ratio, Optical amplifiers
In present tokamak experiments, radiative-divertor operation mode, achieved by injecting gaseous impurity in the divertor region, can effectively mitigate the erosion in divertor plates due to the huge heat load from main plasma. Precise measurement of injected impurity emissions is crucial to obtain the steady-state radiative-divertor operation mode. A space-resolved vacuum-ultraviolet (VUV) spectroscopy has been developed to observe impurity emissions of injected impurity from the divertor region on Experimental Advanced Superconducting Tokamak (EAST). However, high-frequency detector is still necessary for the vacuum-ultraviolet (VUV) spectroscopy to measure impurity emissions with sufficient sampling rate, e.g., ≥10kHz. Photomultiplier tube (PMT) is widely used in photon counting systems because of its high gain and low light sensing capability. Therefore, a high-frequency PMT-based detector system is developed for the existing VUV spectroscopy to measure the impurity emissions in EAST. The detector system composed by a Hamamatsu R8486 PMT, a 1MHz amplifier and a 1MHz data acquisition board (DAQ). The PMT has sufficient high quantum efficiency in the wavelength range of 115-320 nm, which satisfies the requirement of the VUV spectroscopy. The PMT is installed inside a vacuum chamber which is connected to the VUV spectrometer. The detector system has been preliminarily tested to verify the capability to measure high-frequency signals. The test results show that the performance of PMT detector satisfies the design requirement.
Performance of portable near-infrared spectrometers is easily affected by various factors such as on-site environment, which results in a certain deviation in the on-site predicted results. Partially least square regression (PLSR), as a multiple linear regression method, has been widely used for the analysis of near-infrared (NIR) spectroscopy. However, due to the nonlinear characteristics of the relationship between spectral data and dependent variables, PLSR can easily lead to model errors. Stability and predictability decreased when PLSR is applied in on-site quick detection. How to reduce the errors caused by various environmental factors in the use of portable near-infrared spectrometers is a key issue in promoting the wide application of rapid detection technology based on near-infrared spectral analysis. In this study, the absorption spectra data of glucose solutions of different concentrations are collected by a portable near-infrared spectrometer. Several nonlinear correction algorithms are applied to study the effect of environmental interference during the measurement process. Firstly, the collected spectra data is preprocessed. Secondly, the data is modeled by nonlinear correction algorithms such as optimized artificial neural network (ANN), support vector regression (SVR), and random forest (RF). The impact of different models is compared with to the results using PLSR. It is found that compared with the PLSR linear method, the ANN, SVR and RF nonlinear correction algorithm can eliminate the interference of environmental factors in different degrees. Therefore, ANN, SVR and RF algorithm can improve the prediction accuracy of the model. This study shows that the use of nonlinear correction algorithm for data modeling of portable near-infrared spectrometers can effectively improve the predictive performance of the model.
The Poloidal and Tangential X-ray imaging Crystal Spectrometers (PXCS and TXCS) were developed on Experimental Advanced Superconducting Tokamak (EAST) to provide spatially and temporally resolved plasmas ion temperature (Ti), electron temperature (Te) and rotation velocity (poloidal- and toroidal-, Vp and Vt) profiles. Each spectrometer consisted of a spherically curved crystal and a CMOS pixelated X-ray Detector. Both spectrometers have recently been upgraded to enhance their measurement capabilities and stabilities. A He-like argon crystal (2d=4.913Å) is deployed on the TXCS and a double-crystal assembly including a He-like argon (2d=4.913Å) crystal and a Ne-like xenon (2d=6.686Å) crystal is deployed on the PXCS. To obtain the optimal spatial resolution, the distance from the crystal to the detector and to the plasma center are modified. Meanwhile, the projection angle of the TXCS sightline to the major radial direction is increased from ~ 22.5º to ~ 29.5ºin order to view the plasma with more tangential component. The XCS server is moved from the EAST tokamak hall to an outside lab to avoid harsh electromagnetic environment and thus enhance stability. Finally, the experimental results from the upgraded XCS systems are presented. New spectral lines of Zinc-like, Copper like and Gallium-like tungsten are identified, which are diffracted by the He-like argon crystal. High-quality He-like argon and Ne-like xenon spectra are observed simultaneously on one detector for measurements of plasmas with wide temperature ranges. Comparison of the Ti- and Vt- profiles measured by TXCS with those measured by charge exchange recombination spectroscopy (CXRS) shows that the results are in well agreement, verifying the reliability of the upgrade of the spectrometers.
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