分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: X-ray spectrometer is one of the satellite payloads on Chang'E-2 satellite. The soft X-ray detector is one of the device on X-ray spectrometer which is designed to detect the major rock-forming elements within 0.5-10keV range on lunar surface. In this paper, energy linearity and energy resolution calibration is done using a weak Fe55 source, while temperature and time effect is considered not take big error. The total uncertainty is estimated to be within 5% after correction.
分类: 地球科学 >> 空间物理学 提交时间: 2016-12-26
摘要: The paper presents a method estimating the HY-2A altimeter ultra stable oscillator (USO) drift with a reconstructive transponder. The frequency of the USO of the in-orbit altimeter changes with age, and a bias between the actual frequency and the nominal one exists. The USO bias contributes a portion of the altimeter range drift. The HY-2A altimeter transmits signals at a fixed time interval during calibration, and the actual interval between adjacent altimeter transitions, which is controlled by the USO, is different from the nominal one due to the USO drift. The reconstructive transponder measures the arrival times of the altimeter transmitted signals accurately with the atomic clock. The drift of the USO on-board the HY-2A altimeter can be estimated accurately by using the ranges from the reconstructive transponder and the HY-2A altimeter. The USO drifts of around 40 cm/year are presented. Furthermore, the multi-mission crosscalibration provides preliminary validation of HY-2A altimeter USO drift.
分类: 地球科学 >> 空间物理学 提交时间: 2016-12-26
摘要: Independent clocks provide time tags for the precision orbit determination (POD) equipment and the radar altimeter onboard the HY-2A satellite, and a bias between POD data' time tag and corresponding range observation's time tag from the HY-2A altimeter exists. The time tag bias contributes a bias in the sea surface height observation due to the nonzero time rate of change of the HY-2A altimeter's height. A transponder for in-orbit radar altimeter calibration provides an approach to estimate the time tag bias. The altimeter receives the responding signals from the transponder and generates ranges. Pertinent reference ranges are obtained fromthe POD data and the transponder's coordinate. Using the ranges from the radar altimeter and the reference ranges, the time tag bias between the POD data and the altimeter observations can be estimated. During an in situ HY-2A altimeter calibration campaign using a reconstructive transponder from August 9, 2012, to July 20, 2014, 17 estimations of the altimeter's time tag bias were obtained. The preliminary results are presented in this letter.
分类: 地球科学 >> 空间物理学 提交时间: 2016-05-03
摘要: GNSS buoys are innovative ocean instruments, and can provide calibrations of the sea surface height and significant wave height (SWH) products of satellite altimeters. This paper investigated the principles of the wave retrieval by GNSS buoys, and proposed a method of calibration of altimeter SWH product by GNSS buoys. The error sources in the calibration procedure were analyzed. Ocean calibration campaigns were implemented to measure the SWH at the HY-2 altimeter nadir points, and acquired a SWH bias of +7.92 +/- 5.04 cm using four-parameters retracking algorithm. The SWH bias was +20.37 +/- 12.79 cm base on the HY-2 operational SWH products. The calibration campaigns showed that, GNSS buoys could serve for the satellite altimeter SWH calibration under low sea state condition, and the four-parameters retracking algorithm outperformed the conventional three-parameters retracking algorithm in accuracy and consistency, at least for SWH retrieving.
分类: 地球科学 >> 空间物理学 提交时间: 2017-03-10
摘要: In this paper, an SMMW interferometric radiometer concept is demonstrated by a two-element interferometer with dedicated high accuracy SMMW devices. Point-source calibration method is introduced in order to reduce instrument errors. Interference fringes and point target images are presented by this SMMW interferometer. The linear phase error of the interference fringes is less than 2�and the angular resolution is better than 0.57� The measured performance characteristics of the two-element interferometer are consistent with the theoretical analysis. This interferometer demonstrates a new method for passive SMMW remote sensing. �2016, Science Press. All right reserved.
分类: 地球科学 >> 空间物理学 提交时间: 2016-12-26
摘要: This letter presents a method for matching satellite radar altimeter data and transponder data generated during in situ calibration. The transponder generates a measurement error when it measures the arrival time of the altimeter’s transmitted signal and embeds the error in both the transponder’s recorded data and the altimeter’s recorded data. The secondorder finite difference sequence of this error sequence can be extracted from the raw data, thus, the correspondence between two identical but mismatched second-order difference sequences can be uniquely established. The measurement error is utilized,and a data matching method that can uniquely establish the correspondence between the altimeter’s recorded data sequence and the transponder’s recorded data sequence is presented.This post-processing method does not increase the real-time signal processing workload of the transponder. Furthermore,The principles underlying this method can be used for any transponder that can adjust the response signal delay during calibration.
分类: 地球科学 >> 空间物理学 提交时间: 2016-05-03
摘要: An airborne delay Doppler altimeter was flown in autumn 2014. A calibration suite including a GNSS buoy, two tide gauges and two GPS stations were established. An experiment was carried out to test the GNSS buoy as a whole under dynamic ocean condition, to validate its performance and accuracy via the inter-comparison of tide gauges, and to demonstrate the altimetry calibration methods and to estimate the altimeter system bias. This paper presented some methods and results. The GNSS buoy system was proven to have the ability of measuring the sea surface height within 1cm, and the altimeter system bias had a consistency of centimeter level.
分类: 物理学 >> 核物理学 提交时间: 2023-07-18
摘要: With the advancement in X-ray astronomical detection technology, various celestial polarization detection projects have been initiated. To meet the calibration requirements of polarimeters on the ground, a polarized X-ray radiation facility was designed for this study. The design was based on the principle that X-rays incident at 45$^\circ$ on a crystal produce polarized X-rays, and a second crystal was used to measure the polarization of the X-rays produced by the facility after rotation. The effects of different diaphragm sizes on the degree of polarization were compared, and the facility produced X-rays with polarization degrees of up to 99.55$\pm$0.96\% using LiF200 and LiF220 crystals. This result revealed that the polarization of incident X-rays is one of the factors affecting the diffraction efficiency of crystals. The replacement of different crystals can satisfy the calibration requirements of polarized X-ray detectors with more energy points in the energy range (410) keV. In the future, the facility should be placed in a vacuum environment to meet the calibration requirements at lower energies.
分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Oxygen control technology is a critical issue for compatibility of candidate structural materials with liquid lead-bismuth eutectic (LBE) in accelerator driven systems. Performances of a self-developed Pt/air sensor and another one from Karlsruher Institute of Technology (KIT) were tested in stagnant oxygen-saturated liquid LBE. Calibrations showed that the trend and values of corrected electromotive force (EMF) of the self-developed sensor, with a bias voltage of 20 mV, were consistent with theoretical results above 425 ℃, and similar results were obtained in cross-calibration test with EMF value of KIT sensor as reference. In stability test at 450 ℃ for 100 hours, the KIT sensor performed better than the self-developed one, which showed signal fluctuations. Both sensors exhibited quick response to temperature variations in the responsiveness test.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The four electrodes in the stripline beam position monitor (BPM) for Hefei Light Source (HLS II) storage ring are of axially symmetric type. We have derived a new calibration method of electrode gains for this type stripline BPM. The gain fit error of different data grids was analyzed, and the � 5 mm by � 5 mm grid is the best. The electrode gains of two stripline BPMs (HLS II SR-BD-STLB1 and HLS II SR-BD-STLB2) were obtained based on offline calibrated data. The results show that data after fitting gains are improved, with the electrode gains being between 0.94 and 1.15.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Wire position monitor (WPM) is designed to monitor contraction of the cold masses during the cooling-down operation in an accelerator driven system. Because of material difference, machining error, assembly error, etc., each WPM has to be calibrated. The sensing voltage and wire position are of a nonlinear relationship, which is expressed by high order polynomial. Root mean square (RMS) of the polynomial fitting error were 3.8 m and 7.4 m at x and y directions, respectively. The alignment test was carried out on the beta cryostat. Optical instruments were used to verify the WPM measuring results. The differences between WPM measuring results and optical measurements were 0.044 and 0.05 mm in x and y direction, respectively. A significant asymmetric contraction was detected, and asymmetry of material was taken as the main reason through analysis.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: The effects of absolute energy calibration on BESIII physics are discussed in detail, which mainly involve the effects on τ mass measurement, cross section scan measurement, and generic error determination in other measurements.
分类: 地球科学 >> 空间物理学 提交时间: 2016-05-03
摘要: Target brightness temperature maps can be used in geostationary interferometric microwave sounder (GIMS) system simulation. System simulation with accurate target brightness temperature maps can evaluate system performance in near real case and thus help adjust design parameters for the sensor before it is finally put into use. In this paper, method of simulating target brightness temperature using Weather Research and Forecasting Model and Radiative Transfer for TOVS (RTTOV) has been discussed. Target brightness temperature simulation results at oxygen absorption band and water-vapor absorption band have been presented. Some preliminary analyses of simulated brightness temperature for GIMS' observation have also been given.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In order to realize the on-line real-time measurement of neutron spectrum of ITER fusion, this paper presents a multi-sphere spectrometer system which consists of eight thermal neutron detectors, namely SP9 3He proportional counter, embedded in eight different diameter polyethylene spheres. The response function of eight polyethylene spheres of multi-sphere neutron spectrometer was calculated after the simulation of the neutron transport processes in multi-sphere spectrometer by adopting software Geant4. The peak of the response function is in the low energy region for smaller diameter polyethylene sphere. As the polyethylene sphere diameter increased, the peak of the response function moves to the high energy region. The experimental calibration adopts 241Am-Be neutron source. The relative error between normalized data of experiment 4 solid angle counts and normalized data of simulated detection efficiency of 4in to 8in polyethylene sphere is from 1.152% to 12.222%.The experimental results verify the response function of the simulation. All these results provide a theoretical and experimental basis for solving the on-line real-time neutron spectrum of ITER fusion.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: FWHM calibration is one of the essential procedures in gamma-ray spectra analysis. Traditional method is time consumption and poor flexibility because of extra measurement on calibration source. This paper introduces an implicit calibration method based on symmetric zero-area conversion. The single peaks can be differentiated from doublets. Meanwhile, the extracted FWHM values can be applied in the fitting process. Various forms of calibration equations are introduced and compared with practical spectrum data under this method.
分类: 核科学技术 >> 粒子加速器 提交时间: 2021-12-31
摘要: Precise measurements of the cavity forward (Vf) and reflected signals (Vr) are essential for characterizing other key parameters such as the cavity detuning and forward power. In practice, it is challenging to measure Vf and Vr precisely because of crosstalk between the forward and reflected channels (e.g., coupling between the cavity reflected and forward signals in a directional coupler with limited directivity). For DESY, a method based on the cavity differential equation was proposed to precisely calibrate the actual Vf and Vr. In this study, we verified the validity and practicability of this approach for the Chinese ADS front-end demo superconducting linac (CAFe) facility at the Institute of Modern Physics and a compact energy recovery linac (cERL) test ma#2;chine at KEK. At the CAFe facility, we successfully calibrated the actual Vf signal using this method. The result demonstrated that the directivity of directional couplers might seriously affect the accuracy of Vf measurement. At the cERL facility, we calibrated the Lorentz force detuning (LFD) using the actual Vf. Our study confirmed that the precise calibration of Vf significantly improves the accuracy of the cavity LFD measurement.
分类: 地球科学 >> 空间物理学 提交时间: 2016-05-03
摘要: HY-2 satellite, the first ocean dynamic satellite of China, was launched in August 2011, carrying a dual frequency (Ku band and C band) altimeter, to measure the global mean sea level [1]. To provide truly sea level measurements, in-orbit calibration is essential. This paper concerns the transponder in-orbit calibration method. A signal reconstructive transponder for HY-2 altimeter in-orbit calibration is presented. Different from the existing bent-pipe ones, this kind of transponder can capture and track altimeter pulses, record them, and reconstruct the chirp pulses, transmit them back to the altimeter. It is carried on a SUV, reduces requirement for a permanent installation site. With the characteristics of capture and record altimeter signals, the HY-2 altimeter inner path delay and clock drift could be derived from the calibration data.
分类: 地球科学 >> 地球科学史 提交时间: 2018-10-29 合作期刊: 《干旱区科学》
摘要: Stable isotopes in tree-ring cellulose provide important data in ecological, archaeological, and paleoenvironmental researches, thereby, the demand for stable isotope analyses is increasing rapidly. Simultaneous measurement of cellulose 13C and 18O values from tree rings would reduce the cost of isotopic commodities and improve the analytical efficiency compared with conventional separate measurement. In this study, we compared the 13C and 18O values of tree-ring -cellulose from Tianshan spruce (Picea schrenkiana) in an arid site in the drainage basin of the Urumqi River in Xinjiang of northwestern China based on separate and simultaneous measurements, using the combustion method (at 1050°C) and the high-temperature pyrolysis method (at 1350°C and 1400°C). We verified the results of simultaneous measurement using the outputs from separate measurement and found that both methods (separate and simultaneous) produced similar 13C values. The two-point calibrated method improved the results (range and variation) of 13C and 18O values. The mean values, standard deviations, and trends of the tree-ring 13C obtained by the combustion method were similar to those by the pyrolysis method followed by two-point calibration. The simultaneously measured 18O from the pyrolysis method at 1400°C had a nearly constant offset with that the pyrolysis method at 1350°C due to isotopic-dependence on the reaction temperature. However, they showed similar variations in the time series. The climate responses inferred from simultaneously and separately measured 13C and 18O did not differ between the two methods. The tree-ring 13C and 18O values were negatively correlated with standardized precipitation evapotranspiration index from May to August. In addition, the 18O was significantly correlated with temperature (positive), precipitation (negative), and relative humidity (negative) from May to August. The tree-ring 13C and 18O values determined simultaneously through the high-temperature pyrolysis method could produce acceptable and reliable stable isotope series. The simultaneous isotopic measurement can greatly reduce the cost and time requirement compared with the separate isotopic measurement. These results are consistent with the previous studies at humid sites, suggesting that the simultaneous determination of 13C and 18O in tree-ring -cellulose can be used in wide regions.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2021-12-31
摘要: Doped elements in alloys significantly impact their performance. Conventional methods usually sputter the surface material of the sample, or their performance is limited to the surface of alloys owing to their poor penetration ability. The X-ray K-edge subtraction (KES) method exhibits great potential for the nondestructive in situ detection of element contents in alloys. However, the signal of doped elements usually deteriorates because of the strong absorption of the principal component and scattering of crystal grains. This in turn prevents the extensive application of X-ray KES imaging to alloys. In this study, methods were developed to calibrate the linearity between the grayscale of the KES image and element content. The methods were aimed at the sensitive analysis of elements in alloys. Furthermore, experiments with phantoms and alloys demonstrated that, after elaborate calibration, X-ray KES imaging is capable of nondestructive and sensitive analysis of doped elements in alloys.
分类: 地球科学 >> 空间物理学 提交时间: 2017-03-10
摘要: The inter-element phase calibration plays an important role in the overall calibration scheme for synthetic aperture radiometer. The traditional relative phase calibration approach is to use correlated noise injection network, which will be difficult to be implemented in millimeter wave band due to the complexity of the waveguide divider network. A novel self-calibration method for interferometric radiometers with rotating thinned array, especially for the geostationary interferometric microwave sounder(GIMS), has been proposed in this paper. By using this approach, neither dedicated hardware nor dedicated calibration working model is needed to achieved the relative phase calibration. The self-calibration approach is inherently merged with the nominal observation working model of GIMS, thanks to the continuous array rotating of GIMS instrument. A running average scheme has been introduced into the self-calibration approach to enhance the SNR of the calibration data, which is normally very low with the natural earth scene. The method is demonstrated by both simulation and field imaging experiment. �2016 IEEE.