Absolute Detector Research Articles

Planckintermediate results

Measurements of flux density are described for five planets, Mars, Jupiter, Saturn, Uranus, and Neptune, across the sixPlanckHigh Frequency Instrument frequency bands (100–857 GHz) and these are then compared with models and existing data. In our analysis, we have also included estimates of the brightness of Jupiter and Saturn at the three frequencies of thePlanckLow Frequency Instrument (30, 44, and 70 GHz). The results provide constraints on the intrinsic brightness and the brightness time-variability of these planets. The majority of the planet flux density estimates are limited by systematic errors, but still yield better than 1% measurements in many cases. Applying data fromPlanckHFI, theWilkinsonMicrowave Anisotropy Probe (WMAP), and the Atacama Cosmology Telescope (ACT) to a model that incorporates contributions from Saturn’s rings to the planet’s total flux density suggests a best fit value for the spectral index of Saturn’s ring system ofβring= 2.30 ± 0.03 over the 30–1000 GHz frequency range. Estimates of the polarization amplitude of the planets have also been made in the four bands that have polarization-sensitive detectors (100–353 GHz); this analysis provides a 95% confidence level upper limit on Mars’s polarization of 1.8, 1.7, 1.2, and 1.7% at 100, 143, 217, and 353 GHz, respectively. The average ratio between thePlanck-HFI measurements and the adopted model predictions for all five planets (excluding Jupiter observations for 353 GHz) is 1.004, 1.002, 1.021, and 1.033 for 100, 143, 217, and 353 GHz, respectively. Model predictions for planet thermodynamic temperatures are therefore consistent with the absolute calibration ofPlanck-HFI detectors at about the three-percent level. We compare our measurements with published results from recent cosmic microwave background experiments. In particular, we observe that the flux densities measured byPlanckHFI and WMAP agree to within 2%. These results allow experiments operating in the mm-wavelength range to cross-calibrate againstPlanckand improve models of radiative transport used in planetary science.

Absolute detector-based spectrally tunable radiant source using digital micromirror device and supercontinuum fiber laser.

High-accuracy absolute detector-based spectroradiometric calibration techniques traceable to cryogenic absolute radiometers have made progress rapidly in recent decades under the impetus of atmospheric quantitative spectral remote sensing. A high brightness spectrally tunable radiant source using a supercontinuum fiber laser and a digital micromirror device (DMD) has been developed to meet demands of spectroradiometric calibrations for ground-based, aeronautics-based, and aerospace-based remote sensing instruments and spectral simulations of natural scenes such as the sun and atmosphere. Using a supercontinuum fiber laser as a radiant source, the spectral radiance of the spectrally tunable radiant source is 20 times higher than the spectrally tunable radiant source using conventional radiant sources such as tungsten halogen lamps, xenon lamps, or LED lamps, and the stability is better than ±0.3%/h. Using a DMD, the spectrally tunable radiant source possesses two working modes. In narrow-band modes, it is calibrated by an absolute detector, and in broad-band modes, it can calibrate for remote sensing instrument. The uncertainty of the spectral radiance of the spectrally tunable radiant source is estimated at less than 1.87% at 350 nm to 0.85% at 750 nm, and compared to only standard lamp-based calibration, a greater improvement is gained.

Direct calibration of click-counting detectors

We introduce and experimentally implement a method for the absolute detector calibration of photon-number-resolving time-bin multiplexing layouts based on the measured click statistics of superconduncting nanowire detectors. In particular, the quantum efficiencies, the dark count rates, and the positive operator-valued measures of these measurement schemes are directly obtained with high accuracy. The method is based on the moments of the click-counting statistics for coherent states with different coherent amplitudes. The strength of our analysis is that we can directly conclude -- on a quantitative basis -- that the detection strategy under study is well described by a linear response function for the light-matter interaction and that it is sensitive to the polarization of the incident light field. Moreover, our method is further extended to a two-mode detection scenario. Finally, we present possible applications for such well characterized detectors, such as sensing of atmospheric loss channels and phase sensitive measurements.

Characterization of a scintillating lithium glass ultra-cold neutron detector

A $^{6}$Li glass based scintillation detector developed for the TRIUMF neutron electric dipole moment experiment was characterized using the ultra-cold neutron source at the Paul Scherrer Institute (PSI). The data acquisition system for this detector was demonstrated to perform well at rejecting backgrounds. An estimate of the absolute efficiency of background rejection of $99.7\pm0.1$% is made. For variable ultra-cold neutron rate (varying from $<$1 kHz to approx. 100 kHz per channel) and background rate seen at the Paul Scherrer Institute, we estimate that the absolute detector efficiency is $89.7^{+1.3}_{-1.9}$%. Finally a comparison with a commercial Cascade detector was performed for a specific setup at the West-2 beamline of the ultra-cold neutron source at PSI.

Accurate calculation of well-type detector geometrical efficiency using sources with different shapes and geometries

The well-type detectors are widely used to determine the low level activity in small samples, thus the absolute detector efficiency is required. The calculation of the absolute efficiency of well-type HPGe or NaI(Tl) detectors depends mainly on the value of the geometrical efficiency. The geometrical efficiency depends on the solid angle subtended by various sources situated at different locations from the detector surface. The present work is essentially concerned to introduce a numerical simulation method (NSM) to calculate the geometrical efficiency and give the ability to use it in the theoretical calibration process of γ-ray well-type detectors for using isotropic radiating γ-ray (point, disk or volumetric) sources. The results are compared with some published data to show the approach validity and shows how much this work is important in the efficiency calibration process for the complicated γ-ray detection system.

An Implicit Correlation Method for Cross-Correlation Sampling, with MCNPX-PoliMi Validation

Monte Carlo particle transport codes used to model detector responses are traditionally run in analog mode. However, analog simulations of cross-correlation measurements are extremely time-consuming because the probability of coincident detection is small, approximately equal to the product of the probabilities of a single detection in each detector. The new implicit correlation method described here increases the number of correlated event scores, thereby reducing variance and required computation times. The cost of the implicit correlation method is comparable to the cost of simulating single-event detection for the lowest absolute detector efficiency in the problem. The new method is especially useful in the nuclear nonproliferation and safeguards fields for simulating correlation measurements of shielded special nuclear material.The new method was implemented in MCNPX-PoliMi for neutron-neutron cross-correlations with a 252Cf spontaneous fission source measured by 14 detectors at various angles. The method demonstrated good agreement with analog simulation and reference measurement results. Small differences between nonanalog and analog cross-correlation distributions are attributed to discretization errors that are often not present in practical applications. Improvement in the figure of merit was greater than a factor of 100 in all tested cases.

Absolute pulse energy measurements of soft x-rays at the Linac Coherent Light Source.

This paper reports novel measurements of x-ray optical radiation on an absolute scale from the intense and ultra-short radiation generated in the soft x-ray regime of a free electron laser. We give a brief description of the detection principle for radiation measurements which was specifically adapted for this photon energy range. We present data characterizing the soft x-ray instrument at the Linac Coherent Light Source (LCLS) with respect to the radiant power output and transmission by using an absolute detector temporarily placed at the downstream end of the instrument. This provides an estimation of the reflectivity of all x-ray optical elements in the beamline and provides the absolute photon number per bandwidth per pulse. This parameter is important for many experiments that need to understand the trade-offs between high energy resolution and high flux, such as experiments focused on studying materials via resonant processes. Furthermore, the results are compared with the LCLS diagnostic gas detectors to test the limits of linearity, and observations are reported on radiation contamination from spontaneous undulator radiation and higher harmonic content.

Photoacoustic measurement of the Grüneisen parameter using an integrating sphere.

A method that uses an integrating sphere as a platform for photoacoustic measurement of the Grüneisen parameter Γ of absorbing liquids is developed. Derivation of a simple equation for determining Γ is presented. This equation only requires the voltage peak-to-peak value of the photoacoustic signal detected by a flat transducer and the relative energy of the incident light measured by a photodetector. Absolute detector sensitivities are not required. However, a calibration procedure is necessary. An experimental setup is constructed in order to implement and verify the method. Aqueous ink solutions are used as absorbing liquids to determine the calibration (instrument) constants. Validation of the equation is done by determining Γ of ethanol at room temperature. The obtained value of Γ(ethanol) = 0.72 ± 0.06 has a 7% relative difference to the calculated value from known thermal properties reported in literature.

Application of A Tiered Approach to The Validation of Accelerator MS Assays

Since its introduction into the drug-development arena, accelerator mass spectrometry (coupled with liquid chromatography fractionation) has been used to support a variety of study types. The uses to which the technique has been put include parent and/or metabolite quantification in pharmacokinetic studies, total radioactivity measurement in adsorption, metabolism and excretion studies, and quantitative metabolite profiling. A tiered approach has been applied to the verification of accelerator mass spectrometry assays, dependant on in which type of study and at what stage of drug development they are used. As accelerator mass spectrometry is an absolute detector that can quantify without the use of analyte-related standards, the specific assay verification requirements differ from those for LC-MS/MS assays. This article describes when screening, qualified and validated assay verification procedures should be applied, and suggests what parameters should be assessed in each case.

Recent Development of SANS BATAN Spectrometer (SMARTer) in Serpong for Simultaneous and Automatic Measurements

The 36 meter SANS BATAN spectrometer (SMARTer) in Serpong Indonesia has been developed for simultaneous and automatic measurements. The existing motor controller of ISA (Industry Standard Architecture) interface was replaced by the programmable motor controller of PCI (Peripheral Component Interconnect) interface, since it has speed and interrupt-sharing advantages, to drive all stepper motors for collimator, pinhole, and detector movements of the spectrometer. The recent development makes all motors moved and controlled simultaneously in setting up the instrument configuration before performing the experiment. Along with that improvement, the data acquisition software has been also developed to drive the beam stopper movement in two directions as well as to read the absolute collimator and detector positions, to acquire neutron counts on the monitor and the main detector, and also to control automatically up to 12 sample positions of the sample changer. The collected neutron counts is displayed in real time on the main monitor window, and the counts is saved in a special format for further data reduction and analysis. The developed data acquisition software has been implemented and performed for experiment that use preset time or preset count mode, and the automatic sample changer. Received: 08 November 2013; Revised: 23 December 2013; Accepted: 27 December 2013

Absolute beam brightness detector

In generally accepted emittance measurement, main attention is concentrated on emittance areas ɛ(x), ɛ(y) occupied by desired part of ion beam in transverse phase space and shape of these areas. The absolute beam phase density (brightness) as usually is not measured directly and the average beam brightness B is calculated from a beam intensity I and the transverse emittances. In the ion source and low energy beam transport (LEBT) optimization, it is important to preserve the beam brightness because some aberration of ion optic and beam instabilities can decrease the brightness of the central part of ion beam significantly. For these brightness measurements, it is convenient to use an absolute beam brightness detector with the brightness determination from one short considered in this article.

Determination of self shielding factors and gamma attenuation effects for tree ring samples

Determination of tree ring chemistry using Neutron Activation Analysis (NAA) is part of an ongoing research between Penn State University (PSU) and Cornell University, The Malcolm and Carolyn Wiener Laboratory for Aegean and Near Eastern Dendrochronology. Tree-ring chemistry yields valuable data for environmental event signatures. These signatures are a complex function of elemental concentration. To be certain about concentration of signature elements, it is necessary to perform the measurements and corrections with the lowest error and maximum accuracy possible. Accurate and precise values of energy dependent neutron flux at dry irradiation tubes and detector efficiency for tree ring sample are calculated for Penn State Breazeale Reactor (PSBR). For the calculation of energy dependent and self shielding corrected neutron flux, detailed model of the TRIGA Mark III reactor at PSU with updated fuel compositions was prepared using the MCNP utility for reactor evolution (MURE) libraries. Dry irradiation tube, sample holder and sample were also included in the model. The thermal flux self-shielding correction factors due to the sample holder and sample for were calculated and verified with previously published values. The Geant-4 model of the gamma spectroscopy system, developed at Radiation Science and Engineering Center (RSEC), was improved and absolute detector efficiency for tree-ring samples was calculated.

Use of phosphor image plates for measuring intensities in vacuum ultraviolet spectra

We describe the use of phosphor image plates for recording spectra in the vacuum ultraviolet (VUV) and for determining accurate relative and absolute intensities. We investigated the spatial uniformity, noise, linearity of the response to VUV light, fading characteristics, saturation characteristics, reproducibility of the image when scanned multiple times, and long-term stability and lifetime of the plates. We find that the plates have a linear intensity response with a dynamic range of more than 4 orders of magnitude. We also show that they have potential as an absolute detector for VUV radiation.

Evidence for relative disparity matching in the perception of an ambiguous stereogram

To compute depth from binocular disparity, the visual system must correctly link corresponding points between two images, given multiple possible correspondences. Typically, model solutions to this problem use some form of local spatial smoothing, with many physiologically inspired models doing so implicitly, through the use of local cross-correlation-like procedures. In this paper we show that implicit smoothing, without the explicit consideration of relative disparity, cannot account for biases in the perception of a novel ambiguous stereo stimulus. Observers viewed a stereogram consisting of multiple strips of periodic random-dot patterns, perceived as either a slanted surface, or a triangular wedge in depth, and reported their perception in a 4AFC task. Biases in the perception of this stimulus are shown to depend upon the stimulus configuration in its entirety, and cannot be accounted for by low-level preferences for disparity sign. Such results are not consistent with local smoothing effects arising solely at the level of cross-correlation-like absolute disparity detectors. Instead, our results suggest the presence of smoothing constraints that consider the differences in disparity between neighboring image regions. These results further suggest that such smoothing generally biases matching toward solutions that minimize relative disparity, regardless of the presence of changes in disparity sign.

Note: Tangential x-ray diagnosis for investigating fast MHD events in EAST tokamak

A tangential x-ray diagnosis has been installed in the experimental advanced superconducting tokamakvacuum vessel for the study of fast magnetohydrodynamics (MHD) events. This system is based on absolute x-ray ultraviolet detectors with a collimator which is processed by laser machine. The first experimental results have proved its ability to measure the small-scale and transient MHD perturbations.

테이블 방법을 이용한 절대위치 검출기에 대한 개선된 위상 오차 보상

Existing error compensation method of industrial electronic absolute displacement detector only depends on skilled engineers. This paper proposes a new table method in order to automatize error compensation. An waveform changes according to the parallel resistance for each pole were tabularized and four waveforms were superimposed to minimize total phase error. These process was verified using simulink. As a result of applying proposed method to the real sensor, peak to peak error was reduced from <TEX>$3.428^{\circ}$</TEX> to <TEX>$0.879^{\circ}$</TEX>. In this case, compensation resistance is <TEX>$4.7k\Omega$</TEX> in B pole and <TEX>$20k\Omega$</TEX> in C pole. This compensation rate is comparable to skilled engineers, and it takes 0.8 second which is far shorter than 15 minutes when expert does.

Evaluation of In-Pile Neutron Signals During the Start-Up Phase of the FRM II Compact Core Reactor

Wide range detector signals accompanied all steps of the start up of FRM II. The work describes the quantitatively analysis of the absolute detector signal strengths at the different nuclear start up steps. A further interest was to assess on the reactivity of the core as early as possible.

Absolute measurements of fast neutrons using yttrium

Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f(n) approximately 4.1x10(-4) with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10(8) neutrons per discharge.

Systematic error in the precision measurement of the mean wavelength of a nearly monochromatic neutron beam due to geometric errors

Many experiments at neutron scattering facilities require nearly monochromatic neutron beams. In such experiments, one must accurately measure the mean wavelength of the beam. We seek to reduce the systematic uncertainty of this measurement to approximately 0.1%. This work is motivated mainly by an effort to improve the measurement of the neutron lifetime determined from data collected in a 2003 in-beam experiment performed at NIST. More specifically, we seek to reduce systematic uncertainty by calibrating the neutron detector used in this lifetime experiment. This calibration requires simultaneous measurement of the responses of both the neutron detector used in the lifetime experiment and an absolute black neutron detector to a highly collimated nearly monochromatic beam of cold neutrons, as well as a separate measurement of the mean wavelength of the neutron beam. The calibration uncertainty will depend on the uncertainty of the measured efficiency of the black neutron detector and the uncertainty of the measured mean wavelength. The mean wavelength of the beam is measured by Bragg diffracting the beam from a nearly perfect silicon analyzer crystal. Given the rocking curve data and knowledge of the directions of the rocking axis and the normal to the scattering planes in the silicon crystal, one determines the mean wavelength of the beam. In practice, the direction of the rocking axis and the normal to the silicon scattering planes are not known exactly. Based on Monte Carlo simulation studies, we quantify systematic uncertainties in the mean wavelength measurement due to these geometric errors. Both theoretical and empirical results are presented and compared.

Cryogenic radiometry in the hard x-ray range

For many applications in radiometry, spectroscopy or astrophysics, absolute measurement of radiant power with low uncertainty is essential. Cryogenic electrical substitution radiometers (ESRs) are regarded as the highest-accuracy primary standard detector in radiometry, from the infrared to the ultraviolet region; in combination with tuneable monochromatized synchrotron radiation from electron storage rings, their range of operation has been extended to the soft x-ray region. ESRs are absolute thermal detectors, based on the equivalence of electrical power and radiant power that can be traced back to electrical SI units and be measured with low uncertainties. Their core piece is a cavity absorber, which is typically made of copper to achieve a short response time suitable for use with synchrotron radiation. At higher photon energies, the use of copper prevents the operation of ESRs due to increasing transmittance. A new absorber design for hard x-rays has been developed at the laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY II. The Monte Carlo simulation code Geant4 was applied to optimize its absorptance for photon energies of up to 60 keV, resulting in a cavity absorber with a gold base and a cylindrical shell made of copper, in combination with a thermal sensitivity of around 150 mK µW−1 and a time constant of less than 3 min, which is short compared with the lifetime of many hours for the storage ring current. The measurement of the radiant power of monochromatized synchrotron radiation was achieved with relative standard uncertainties of less than 0.2%, covering the entire photon energy range of three beamlines from 50 eV to 60 keV. Monochromatized synchrotron radiation of high spectral purity was used to calibrate silicon photodiodes against the ESR for photon energies up to 60 keV with relative standard uncertainties below 0.3%.