Absolute Calibration Method Research Articles

The LED calibration system of the SPHERE-2 detector

An absolute calibration method for the PMT mosaic used in the SPHERE-2 experiment is presented. The method is based on the relative calibration of all PMTs in the mosaic to a single stable PMT, incorporated in it, during each measurement event and subsequent absolute calibration of that single PMT using a known stable light source. The results of the SPHERE-2 detector PMTs calibration are presented and are discussed.

Simple and accurate empirical absolute volume calibration of a multi-sensor fringe projection system

This paper suggests a novel absolute empirical calibration method for a multi-sensor fringe projection system. The optical setup of the projector-camera sensor can be arbitrary. The term absolute calibration here means that the centre of the three dimensional coordinates in the resultant calibrated volume coincides with a preset centre to the three-dimensional real-world coordinate system. The use of a zero-phase fringe marking spot is proposed to increase depth calibration accuracy, where the spot centre is determined with sub-pixel accuracy. Also, a new method is proposed for transversal calibration. Depth and transversal calibration methods have been tested using both single sensor and three-sensor fringe projection systems. The standard deviation of the error produced by this system is 0.25mm. The calibrated volume produced by this method is 400mm×400mm×140mm.

An absolute calibration method of an ethyl alcohol biosensor based on wavelength-modulated differential photothermal radiometry.

In this work, laser-based wavelength-modulated differential photothermal radiometry (WM-DPTR) is applied to develop a non-invasive in-vehicle alcohol biosensor. WM-DPTR features unprecedented ethanol-specificity and sensitivity by suppressing baseline variations through a differential measurement near the peak and baseline of the mid-infrared ethanol absorption spectrum. Biosensor signal calibration curves are obtained from WM-DPTR theory and from measurements in human blood serum and ethanol solutions diffused from skin. The results demonstrate that the WM-DPTR-based calibrated alcohol biosensor can achieve high precision and accuracy for the ethanol concentration range of 0-100 mg/dl. The high-performance alcohol biosensor can be incorporated into ignition interlocks that could be fitted as a universal accessory in vehicles in an effort to reduce incidents of drinking and driving.

Radiometric calibration of optical microscopy and microspectroscopy apparata over a broad spectral range using a special thin-film luminescence standard

Application capabilities of optical microscopes and microspectroscopes can be considerably enhanced by a proper calibration of their spectral sensitivity. We propose and demonstrate a method of relative and absolute calibration of a microspectroscope over an extraordinary broad spectral range covered by two (parallel) detection branches in visible and near-infrared spectral regions. The key point of the absolute calibration of a relative spectral sensitivity is application of the standard sample formed by a thin layer of Si nanocrystals with stable and efficient photoluminescence. The spectral PL quantum yield and the PL spatial distribution of the standard sample must be characterized by separate experiments. The absolutely calibrated microspectroscope enables to characterize spectral photon emittance of a studied object or even its luminescence quantum yield (QY) if additional knowledge about spatial distribution of emission and about excitance is available. Capabilities of the calibrated microspectroscope are demonstrated by measuring external QY of electroluminescence from a standard poly-Si solar-cell and of photoluminescence of Er-doped Si nanocrystals.

Tracking radiometric responsivity of optical sensors without on-board calibration systems-case of the Chinese HJ-1A/1B CCD sensors.

The radiometric stability of satellite sensors is crucial for generating highly consistent remote sensing measurements and products. We have presented a radiometric responsivity tracking method designed especially for optical sensors without on-board calibration systems. Using a temporally stable desert site with high reflectance, the sensor responsivity was simulated using the Second Simulation of the Satellite Signal in the Solar Spectrum (6S) radiative transfer model (RTM) with information from validated MODIS atmospheric data. Next, radiometric responsivity drifting was identified using a linear regression of the time series bidirectional reflectance distribution function (BRDF) normalized coefficients. The proposed method was applied to Chinese HJ-1A/1B charge-coupled device (CCD) sensors, which have been on-orbit operations for more than 5 years without continuous assessment of their radiometric performance. Results from the Dunhuang desert site between 2008 and 2013 indicated that the CCD sensors degraded at various rates, with the most significant degradation occurring in the blue bands, ranging from 2.8% to 4.2% yr-1. The red bands were more stable, with a degradation rate of 0.7-3.1% yr-1. A cross-sensor comparison revealed the least degradation for the HJ-1A CCD1 (blue: 2.8%; green: 2.8%; red: 0.7%; and NIR: 0.9% yr-1), whereas the degradation of HJ-1B CCD1 was most pronounced (blue: 3.5%; green: 4.1%; red: 2.3%; and NIR: 3.4% yr-1). The uncertainties of the method were evaluated theoretically based on the propagation of uncertainties from all possible sources of the RT simulations. In addition, a cross comparison with matchup ground-based absolute calibration results was conducted. The comparison demonstrated that the method was useful for continuously monitoring the radiometric performance of remote sensors, such as HJ-1A/1B CCD and GaoFen (GF) series (China's latest high-definition Earth observation satellite), and indicated the potential use of the method for high-precision absolute calibration.

Comparison of spectral radiance responsivity calibration techniques used for backscatter ultraviolet satellite instruments

Methods of absolute radiometric calibration of backscatter ultraviolet (BUV) satellite instruments are compared as part of an effort to minimize pre-launch calibration uncertainties. An internally illuminated integrating sphere source has been used for the Shuttle Solar BUV, Total Ozone Mapping Spectrometer, Ozone Mapping Instrument, and Global Ozone Monitoring Experiment 2 using standardized procedures traceable to national standards. These sphere-based spectral responsivities agree to within the derived combined standard uncertainty of 1.87% relative to calibrations performed using an external diffuser illuminated by standard irradiance sources, the customary spectral radiance responsivity calibration method for BUV instruments. The combined standard uncertainty for these calibration techniques as implemented at the NASA Goddard Space Flight Center’s Radiometric Calibration and Development Laboratory is shown to less than 2% at 250 nm when using a single traceable calibration standard.

Absolute calibration of seismic sensors using a displacement jump: Theory and practice

A method of absolute calibration of electrodynamic seismic sensors by single-sensor displacement is theoretically justified. It is shown that the method can be implemented using simple mechanical devices and a recording system. The required mathematical processing of the step-test impact can also be carried out using only standard software on any modern PC. A practical implementation of the method is shown by the example of calibration of a 10 Hz geophone. Features of the test technology and the mathematical processing of the obtained record are presented. The method is recommended for the calibration of sensors (velocimeters) with natural frequencies from 0.5 to 30 Hz.

Terahertz Spectrometer Based on Femtosecond Laser for a Scientific Research

Terahertz (THz) spectrometer using femtosecond titanium-sapphire laser was developed. Experimental stand of the multi-purpose application was realized by using this spectrometer. It was realized to obtaining of the complex refractive index spectra of a large aperture samples and to research of the emission efficiency of THz radiation in a nonlinear optical media. It was proposed a method of spectrometer's absolute calibration by THz electrical field through an external control of polarization of the probe radiation. The threshold sensitivity to polarization changes was measured. It was 1.4 ± 0.5 μrad. It allows to estimate the threshold of THz field strength ~ 0.1 V/cm when zinc telluride crystal is used to detection. Width of the apparatus function of spectrometer was 9 GHz and it was estimated from the width of narrow lines of the water vapor in absorption spectrum of air gap. It well agrees with the theoretical estimation

Absolute Calibration of Proportional Counter Based Fast Pulsed Neutron Detectors with Resolution Below 105 neutron/pulse

A method for absolute calibration of proportional counters for pulsed fast neutrons is presented. The method is based on the use of an isotopic standard source and development of a model for counting detected events from area of a signal compounded by single piled up neutron pulses. Effects of detection counting statistics and electrical background noise are also considered. The method is applied in detectors used for D-D neutron yield measurements in low emission plasma focus devices.

An improved method of absolute calibration to satellite altimeter: A case study in the Yellow Sea, China

An improved absolute calibration technology based on indirect measurements was developed through two probative experiments, the performance of which was evaluated by applying the approach to in situ sea surface height (SSH) at the Tianheng Island (tidal gauge) and the satellite nadir (GPS buoy). Using Geoid/MSS (mean sea surface) data, which accounted for a constant offset between nadir and onshore tidal gauge water levels, and TMD (tidal model driver), which canceled out the time-varying offsets, nadir SSH (sea surface height) could be indirectly acquired at an onshore tidal gauge instead of from direct offshore observation. The approach extrapolated the onshore SSH out to the offshore nadir with an accuracy of (1.88±0.20) cm and a standard deviation of 3.3 cm, which suggested that the approach presented was feasible in absolute altimeter calibration/validation (Cal/Val), and the approach enormously facilitated the obtaining SSH from the offshore nadir.

Absolute calibration of photon-number-resolving detectors with an analog output using twin beams

A method for absolute calibration of a photon-number resolving detector producing analog signals as the output is developed using a twin beam. The method gives both analog-to-digital conversion parameters and quantum detection efficiency for the photon fields. Characteristics of the used twin beam are also obtained. A simplified variant of the method applicable to fields with high signal to noise ratios and suitable for more intense twin beams is suggested.

Study of CeI3 evaporation in the presence of group 13 metal-iodides

The influences of GaI3, InI, and TlI on the evaporation characteristics of CeI3 have been studied over the temperature range 900 K to 1400 K using x-ray induced fluorescence. The total vapor densities, summed over all atomic and molecular species, of Ce, I, In, and Tl were obtained. Measurements of Ce were limited to temperatures above 1033 K, the melting temperature of CeI3. This is the highest temperature range for which measurements of the vapor pressure of CeI3 have been made. The vapor pressure of the CeI3 monomer above the pure CeI3 salt for temperatures exceeding its melting point can be approximated by log10p/Pa=11.24(±0.03)−10,690(±40) (T/K)−1 where the numbers in parentheses are standard uncertainties. InI and TlI were shown to modestly enhance the presence of Ce in the vapor phase, up to a factor of 5. GaI3 produced no enhancement in this temperature range. Numerical simulations of the thermochemical equilibrium suggest the importance of both liquid-phase and vapor-phase complexes. Significant improvement to the method of absolute calibration is discussed.

Absolute calibration for Fizeau interferometer with the global optimized shift-rotation method

We present an absolute calibration method for Fizeau interferometer with global optimized shift-rotation, which requires rotational and translational measurements. With a data matching method to decrease the alignment error of rotations and translations, the accuracy can be guaranteed. The global optimized shift-rotation method can obtain the surface deviation accurately of both the reference and test surfaces in terms of Zernike polynomials. Experiments have been implemented to verify the validity of the absolute calibration, and the results show that the reference surface deviation agrees well with the calibration result of conventional two-sphere method. Simulations were performed to evaluate the errors introduced by rotations and translations.

NAIS: Nuclear activation-based imaging spectroscopy

In recent years, the development of high power laser systems led to focussed intensities of more than 10(22) W/cm(2) at high pulse energies. Furthermore, both, the advanced high power lasers and the development of sophisticated laser particle acceleration mechanisms facilitate the generation of high energetic particle beams at high fluxes. The challenge of imaging detector systems is to acquire the properties of the high flux beam spatially and spectrally resolved. The limitations of most detector systems are saturation effects. These conventional detectors are based on scintillators, semiconductors, or radiation sensitive films. We present a nuclear activation-based imaging spectroscopy method, which is called NAIS, for the characterization of laser accelerated proton beams. The offline detector system is a combination of stacked metal foils and imaging plates (IP). After the irradiation of the stacked foils they become activated by nuclear reactions, emitting gamma decay radiation. In the next step, an autoradiography of the activated foils using IPs and an analysis routine lead to a spectrally and spatially resolved beam profile. In addition, we present an absolute calibration method for IPs.

Absolute calibration of a large-diameter light source

A method of absolute calibration for large aperture optical systems ispresented, using the example of the Pierre Auger Observatory fluorescencedetectors. A 2.5 m diameter light source illuminated by anultra-violet light emitting diode is calibrated with an overall uncertainty of2.1 % at a wavelength of 365 nm.

Сравнение точности метода абсолютной градуировки и модифицированного метода последовательных стандартных добавок на примере определения 3-(2,2,2-триметилгидразиний)- пропионовой кислоты в моче в условиях нелинейности детектирования (электроспрей)

Contemporary determining of pharmaceuticals in biological liquids for the pur­poses of phar­maco­kine­tic studies and therapeutic drug monitoring implies the use of high-per­formance liquid chromatography coupled with mass spectrometry (LC-MS) with electrospray as a method of ionization. However, this techni­que is cha­rac­terized by a rather narrow linear detection range. It causes the restric­tions in quan­titation of analytes by method of absolute calibration. On the example of the determination of 3-(2,2,2-trimethylhydrazinium) propio­nate (THP) in urine it is shown that the method of successive standard additi­ons provides more precise results comparing with those obtained with non-linear absolu­te calib­ration at the same levels of analyte concentrations. Its principal fea­ture is the need to extrapolate the results to an infinite value of ad­dition. Keywords : 3-(2,2,2-trimethylhydrazinium) propionate, LC-MS, detection non­­­linearity, successive standard addition, non-linear absolute calibration (Russian) DOI: http://dx.doi.org/10.15826/analitika.2013.17.2.008 Т atiana Е . Morozova 1 , Georgy V. Karakashev 1 , Pavel N. Sorokoumov 1 , Elena I. Savelieva 1 , Igor G. Zenkevich 2 1 Research Institute of Hygiene, Occupational Pathology and Human Ecology , Russian Federation , Leningrad Region., Vsevolozhsk district, town Kuzmolovsky, Art. Kapitolovo 2 St. Petersburg State University, Russian Federation , Saint-Petersburg

Calibration of the CMS electromagnetic calorimeter with LHC collision data

The CMS ECAL is a high resolution electromagnetic calorimeter which relies upon precision calibration in order to achieve and maintain its design performance. Variations in light collected from the lead tungstate crystals, due to intrinsic differences in crystals/photodetectors, as well as variations with time due to radiation damage for example, need to be taken into account. Sophisticated and effective methods of inter-crystal and absolute calibration have been devised, using collision data from the 2011 LHC run and a dedicated light injection system. For inter-calibration, low mass particle (π0 and η) decays to two photons are exploited, as well as the azimuthal symmetry of the average energy deposition at a given pseudorapidity. The light injection system monitors the channel response in real-time and enables the re-calibration of the measured energies over time. This is cross-checked by the comparison of E/p measurements of electrons from W decays (where the momentum is measured in the CMS tracker) with/without these re-calibrations applied. Absolute calibration has been performed using Z decays into electron–positron pairs.

A New Method of Precise Jason-2 Altimeter Calibration Using a Microwave Transponder

This study presents a new method of precise altimeter absolute calibration using a dedicated microwave transponder, which acts as an altimeter signal repeater that can be deployed at any sub-track position both in coastal regions and inland. The Austrian Academy of Sciences operates an altimeter transponder at the Gavdos calibration/validation facility located beneath a Jason cross-over point. We discuss the capabilities and strengths of the transponder technique in general and in the particular case of a dedicated calibration campaign carried out in 2011. For the accomplishment of this campaign, including 26 ascending and descending Jason-2 passes, the onboard Poseidon-3 altimeter had to be switched to the DIODE/DEM mode for every overflight. Four different methods have been developed to analyze the transponder generated waveforms, provided by S-IGDR and S-GDR products, respectively. The resulting biases of the altimetric ranges have proven to be stable (3 mm rms) and agree to a large extent among the proposed algorithms. However, the absolute bias value of 25.8 ± 0.3 cm derived from the transponder calibration technique shows a significant deviation of several centimeters compared with the ones resulting from conventional techniques. Possible causes of this behavior are under further investigation.

Multisite Calibration Tracking for FY-3A MERSI Solar Bands

The MEdium-Resolution Spectral Imager (MERSI), onboard the second-generation Chinese polar-orbit meteorological satellite FY-3A, is a MODIS-like sensor with 19 solar bands and one thermal infrared band. Although there is a visible onboard calibration device, it can only be used for tracking temporal instrument degradation. The vicarious calibration (VC) campaign at the Dunhuang site, conducted once a year, has been the main postlaunch absolute radiometric calibration method for MERSI in the solar bands. To increase the in-flight calibration frequency, a multisite radiometric calibration tracking method is presented. This method relies on simulated radiation over several stable sites, and a daily calibration updating model is built from long-term trending of calibration coefficient series. The MERSI calibration reference is evaluated against the observations of Aqua MODIS, showing mean relative biases within 5% from 0.4 to 2.1 μm . The short-wave channels of MERSI are found to experience large degradation, particularly the 412-nm band with an annual degradation rate of 9.7%, whereas the red and near-infrared bands are relatively stable with annual degradation rates within ±1%. Several approaches have been used to analyze the reliability of MERSI calibration results. A comparison of the calibration slopes shows that the relative biases between the multisite method and the annual Dunhuang VC campaign are below 3.8%. Aqua MODIS is used as a reference to monitor the data quality of the recalibrated MERSI. A double-difference analysis shows that the mean relative biases are almost within 5% over stable deserts, and the synchronous nadir observation analysis also reveals good agreement.

Further developments of a robust absolute calibration method utilizing beta/gamma coincidence techniques

Performing accurate and verifiable measurements is often the most challenging goal for any radiation detector and is especially challenging for the radio-xenon detectors deployed by the International Monitoring System (IMS) of the Preparatory Commission of the Comprehensive Test Ban Treaty Organization (CTBTO). Often the accuracy of the measurement is directly tied to how well the detector is calibrated, in both energy and efficiency. Standard methods often rely on using certified sealed sources to determine the absolute efficiency. Similarly, efforts to calibrate the absolute efficiency of radioactive gas cell detectors utilize a number of methodologies which allow adequate calibration but are time consuming and prone to a host of difficulties to determine uncertainties (McIntyre et al, J Radioanal Nucl Chem 282(3):755–759, 2009; Anderson et al, Stat Probab Lett 77(88):769–773, 2007). Utilizing methods developed in the 1960s for absolute measurements of activity with beta–gamma detector systems it has become clear that it is possible to achieve higher precision results that are consistent across a range of isotopes and activities (National Council on Radiation Protection and Measurement, A handbook of radioactivity measurements procedure NCPR report, 1985). Even more compelling is the ease with which this process can be used on routine samples to determine the total activity present in the detector. Additionally, recent advances in the generation of isotopically pure radio-xenon samples of 131mXe, 133Xe, and 135Xe allow these measurement techniques to achieve much better results than have previously been possible when using mixed isotopic radio-xenon sources (Haas et al, J Radioanal Nucl Chem 282(3):677–680, 2009). This paper will discuss the beta/gamma absolute detection efficiency techniques of direct measurement of the efficiencies and the extrapolation method and compare the results using modeled and measured pure sources of 133Xe and 135Xe.