Calibration and non-uniformity correction of near-infrared polarization detector

Based on in-depth analysis of the relative radiation scaling theorem and acquired scaling data of pixel response nonuniformity correction of CCD (charge-coupled device) in spaceborne visible interferential imaging spectrometer, a pixel response nonuniformity correction method of CCD adapted to visible and infrared interferential imaging spectrometer system was studied out, and it availably resolved the engineering technical problem of nonuniformity correction in detector arrays for interferential imaging spectrometer system. The quantitative impact of CCD nonuniformity on interferogram correction and recovery spectrum accuracy was given simultaneously. Furthermore, an improved method with calibration and nonuniformity correction done after the instrument is successfully assembled was proposed. The method can save time and manpower. It can correct nonuniformity caused by other reasons in spectrometer system besides CCD itself's nonuniformity, can acquire recalibration data when working environment is changed, and can also more effectively improve the nonuniformity calibration accuracy of interferential imaging

MINOS is a long-baseline neutrino oscillation experiment designed to search for conclusive evidence of neutrino oscillations and to measure the oscillation parameters precisely. MINOS comprises two iron tracking calorimeters located at Fermilab and Soudan. The Calibration Detector at CERN is a third MINOS detector used as part of the detector response calibration programme. A correct energy calibration between these detectors is crucial for the accurate measurement of oscillation parameters. This thesis presents a calibration developed to produce a uniform response within a detector using cosmic muons. Reconstruction of tracks in cosmic ray data is discussed. This data is utilized to calculate calibration constants for each readout channel of the Calibration Detector. These constants have an average statistical error of 1.8%. The consistency of the constants is demonstrated both within a single run and between runs separated by a few days. Results are presented from applying the calibration to test beam particles measured by the Calibration Detector. The responses are calibrated to within 1.8% systematic error. The potential impact of the calibration on the measurement of oscillation parameters by MINOS is also investigated. Applying the calibration reduces the errors in the measured parameters by {approx} 10%, which is equivalent to increasingmore » the amount of data by 20%.« less

Time-resolved laser-induced incandescence (TiRe-LII) is an optical in situ diagnostics method for particle-size determination of gas-borne nanoparticles that has been established over the last decades. Recent inter-laboratory comparisons have shown that there are unresolved issues concerning measurement artifacts and noise, and discrepancies exist in reported results from similar measurement conditions. Moving from the established two-color technique (for pyrometric temperatures determination) to spectrally resolved (and multi-color) measurements reveals additional open questions. The difficulty in LII science is that in literature, a wide range of different LII models and corresponding materials properties is available, and often, for new application cases, new models are composed from various published LII models to match the results from literature or ex situ determined quantities (e.g., particle-size distributions). In addition, signal shapes that cannot be explained by previously published LII models lead to the adjustment of the physical models and properties instead of focusing on technical issues of the LII signal acquisition. The variation in calibration, measurement and analysis procedures across the LII community motivates for the development towards standardization of LII signal acquisition and processing to increase the quality of signals that can then later be used as input for future LII model developments. This work focuses on practical aspects of multi-color TiRe-LII as detector performance/calibration, experimental design, and signal acquisition and on the improvement of the robustness of the measurement technique using multiple detection channels. In the scope of this work, a multi-color LII device was developed along with a software solution for data acquisition and signal processing. Modular and flexible components in the setup and the analysis help to broaden the way for the application of LII on various materials systems and processes, and can build a foundation for future inter-laboratory comparisons. For multi-color LII techniques, proper detector performance and calibration is essential to produce data that can be used as input for further processing. The detector performance is investigated for photomultiplier tubes (PMT) using pulsed and continuously operated light-emitting diodes at similar light levels as typical LII experiments. The influence of non-linear behavior during LII measurements is demonstrated for different two-color ratios and the importance of linearity as detector requirement is shown. The mathematical description for the calibration of PMTs in the context of LII is presented along with a detailed methodology for the calibration of all components within a typical LII detection system. For this purpose, the suitability of different calibration light sources is assessed and additional measurement issues that could affect the signal quality are discussed. For data acquisition and processing of LII data, a software solution was developed, following a modular approach, making it suitable for the application on various materials systems and with individual processing steps. The software is published as open-source software to allow transparency and adjustments by other researchers. In order to improve the LII signal acquisition further, a new sequential detection technique was developed that takes advantage of gated photomultiplier tubes and is capable to increase the dynamic range of the LII technique. Having resolved many of the above-mentioned issues is an important step towards harmonization of the experimental procedure, calibration, measurement and interpretation of data.

We will present our current efforts on single photon quantum metrology using high-efficiency superconducting detectors and high-efficiency single-photon sources based on spontaneous parametric downconversion. Optical power measurements based on single photon counting could establish a quantum standard for optical power calibration in the future. At NIST we are pursuing the development of single photon sources and single photon detectors for metrology, quantum and classical applications. As part of these efforts, we are pursuing the establishment of a measurement service for the calibration of single photon detectors. We present how our calibration is tied to the calibration of our transfer standard optical fiber power meters. Using the beamsplitter method, we have implemented a fiber-coupled and free-space measurement system. Also, we have developed testbeds and measurement protocols for the characterization of single photon sources and single photon detectors. We will review several methods, which allow for the characterization of the spatial and spectral degree of freedom in spontaneous parametric downconversion.

This paper presents the spectral responsivity calibrations of two indium gallium arsenide (InGaAs) and one germanium based near-infrared photovoltaic detectors using a wavelength tunable laser source based on a supercontinuum laser developed at the Metrology Research Institute, Aalto University. The setup consists of a supercontinuum laser based on a photonic crystal fiber as the light source, a laser line tunable filter, and coupling optics. These responsivity calibrations are performed against a pyroelectric radiometer over a wide spectral range of 800–2000 nm. Our wavelength tunable laser source has a high spectral power up to 2.5 mW with a narrow spectral full-width-at-half-maximum of 3 nm at a wavelength of 1100 nm. Despite the sharp spectral intensity variations, no artifacts are observed in the spectral responsivities of the detectors. Comparison of the spectral responsivities of the InGaAs detectors measured using the wavelength tunable laser and the earlier calibrations performed at the Metrology Research Institute in 2010 and 2016, shows that the higher spectral power of wavelength tunable light source decreases the expanded uncertainty from approximately 4% to 2.2–2.6% over the spectral range of 820–1600 nm. Temperature dependence of the spectral responsivities near the band gap edges are also measured and analysed.

Calibration of photon-counting detectors (PCDs) is necessary for quantitatively accurate spectral computed tomography (CT), but the calibration process can be complicated by nonlinear flux-dependent physical factors such as pulsepile-up. This work develops a method for spectral sensitivity calibration of a PCD-based spectral CT system that incorporates nonlinear flux dependence and can thus be employed at high photonflux. A calibration model for the spectral response and polynomial flux dependence is proposed, which incorporates prior x-ray source spectrum and PCD models and that has a small set of parameters for adjusting to the spectral CT system of interest. The model parameters are determined by fitting transmission data from a known object of known composition: a step-wedge phantom composed of different thicknesses of aluminum, a bone equivalent, and polymethyl methacrylate (PMMA), a soft-tissue equivalent. This fitting employs Tikhonov regularization, and the regularization strength and the polynomial order for the intensity modeling are determined by bias and variance analysis. The spectral calibration and nonlinear intensity correction is validated on transmission measurements through a third material, Teflon, at different x-ray photon fluxlevels. The nonlinear intensity dependence is determined to be accurately accounted for with a third-order polynomial. The calibrated spectral CT model accurately predicts Teflon transmission to within 1% for flux levels up to 50% of the detectormaximum. The proposed PCD calibration method enables accurate physical modeling necessary for quantitative imaging in spectral CT. Furthermore, the model applies to high flux settings so that acquisition times will not be limited by restricting the spectral CT system to low fluxlevels.

The radiation hardness, the chemical resistance, and the capabilities to operate at high temperature conditions make diamond detectors a good option for carrying out fast neutron measurements on fusion plasma experiments or facilities using accelerator-driven neutron sources. A correct energy calibration of pulse-height spectra acquired through diamond detectors allows to perform fast neutron spectrometry. As a general rule, energy calibration of diamond detectors is performed using an alpha source, e.g. 239Pu, 241Am, 244Cm, whose characteristic emission energies are in the range from 5 to 6 MeV. Calibration at higher energies, such as those related to charged particles (about 8.4 MeV) produced by the 12C(n,alpha)9Be induced by fast neutrons coming from D-T fusion reaction, is traditionally extrapolated with the hypothesis of linearity for the energy calibration curve. In this work an evaluation of the diamond detector energy calibration based on alpha source emissions is performed at higher energies by means of a compact D-T neutron generator, able to produce neutrons within a broad energy range, by changing the accelerator voltage and the neutron emission angle. A relative deviation less than 2% between experimental and theoretical energies was observed, showing that the energy calibration through alpha sources could be still valid for fast neutrons coming from D-T fusion reactions.

The Zero Degree Calorimeter (ZDC) of the ATLAS experiment at CERN is placed in the TAN of the LHC collider, covering the pseudorapidity region higher than 8.3. It is composed by 2 calorimeters, each one longitudinally segmented in 4 modules, located at 140 m from the IP exactly on the beam axis. The ZDC can detect neutral particles during pp collisions and it is a tool for diffractive physics. Here we present results on the forward photon energy distribution obtained using p-p collision data at sqrt{s} = 7 TeV. First the pi0 reconstruction will be used for the detector calibration with photons, then we will show results on the forward photon energy distribution in p-p collisions and the same distribution, but obtained using MC generators. Finally a comparison between data and MC will be shown.

This thesis work has been developed in the framework of a new experimental campaign, proposed by the NUCL-EX Collaboration (INFN III Group), in order to progress in the understanding of the statistical properties of light nuclei, at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation reactions. The determination of the nuclear level density in the A~20 region, the understanding of the statistical behavior of light nuclei with excitation energies ~3 A.MeV, and the measurement of observables linked to the presence of cluster structures of nuclear excited levels are the main physics goals of this work. On the theory side, the contribution to this project given by this work lies in the development of a dedicated Monte-Carlo Hauser-Feshbach code for the evaporation of the compound nucleus. The experimental part of this thesis has consisted in the participation to the measurement 12C+12C at 95 MeV beam energy, at Laboratori Nazionali di Legnaro - INFN, using the GARFIELD+Ring Counter(RCo) set-up, from the beam-time request to the data taking, data reduction, detector calibrations and data analysis. Different results of the data analysis are presented in this thesis, together with a theoretical study of the system, performed with the new statistical decay code. As a result of this work, constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg are given. Moreover, pre-equilibrium effects, tentatively interpreted as alpha-clustering effects, are put in evidence, both in the entrance channel of the reaction and in the dissipative dynamics on the path towards thermalisation.

In this paper, we present a compact hybrid video sensor that combines perspective and omnidirectional vision to achieve a 360deg field of view, as well as high-resolution images. Those characteristics, in association with 3D metric reconstruction capabilities, are suitable for vision tasks such as surveillance and obstacle detection for autonomous robot navigation. We describe the sensor calibration procedure, with particular regard to mirror-to-camera positioning. We also present some results obtained in testing the accuracy of 3D reconstruction, which have confirmed the correctness of the calibration.

The ATLAS first-level calorimeter trigger is a hardware-based system designed to identify high-pT jets, electron/photon and tau candidates and to measure total and missing ET in the ATLAS calorimeters. The complete trigger system consists of over 300 customdesignedVME modules of varying complexity. These modules are based around FPGAs or ASICs with many configurable parameters, both to initialize the system with correct calibrations and timings and to allow flexibility in the trigger algorithms. The control, testing and monitoring of these modules requires a comprehensive, but well-designed and modular, software framework, which we will describe in this paper.

Nanowire superconducting single photon detectors (SSPDs) [1] are characterized by very high sensitivity in the near infrared (detection efficiency η up to 30%, for a dark count rate DK of few Hz), speed (up to ∼1 GHz repetition rate) and time resolution (jitter of 20 ps full width at half maximum, FWHM). They can be operated at temperatures near 4 K, so they can be packaged in cryogenic dipsticks or cryogen-free refrigerators. These features make SSPDs the most promising detectors for telecom-wavelength single-photon counting applications. The basic structure of an SSPD is a narrow (w=50 to 120 nm), thin (th∼4-10 nm) NbN superconducting nanowire folded in a meander pattern. The typical detector active area (i.e. the size of the pixel) is Ad=10 × 10 µm2 (which allows an efficient coupling with the core of optical fibers at telecom wavelengths) with filling factor (f, the ratio of the area occupied by the superconducting meander to the device total area) ranging from 40% to 60%. The meanders are embedded in a 50 Ω coplanar transmission line. At present, the SSPD detection efficiency is limited by its absorbance (α, the ratio of the number of photons absorbed in the nanowire to the number of incident photons on the device active area). Indeed, it has been shown that in the classic front-illumination configuration α cannot exceed 30%. Our approach to increase α consists in integrating SSPDs with advanced optical structures such as distributed Bragg reflectors (DBRs) and optical waveguides. This requires to transfer the challenging SSPD technology (i.e. the deposition of high-quality few-nm thick NbN films and the nano-patterning by electron beam lithography, EBL) from the usual comfortable substrates, i.e. sapphire and MgO, which are known to allow the deposition of few-nm thick NbN films of excellent quality, to an optical substrate like GaAs, on which DBRs and waveguides can be easily obtained. Our first task was then to optimize a process for the deposition of high-quality few-nm thick NbN films on GaAs and AlAs/GaAs-based DBRs. Because of the requirement of compatibility with GaAs, the substrate temperature used for the depositions is 400°C, in order to prevent As evaporation. As GaAs and DBRs are highly mismatched substrates, the deposition parameters were first optimized with respect to the superconducting properties of NbN films on MgO substrates, which allow the growth of high crystal quality NbN films at low temperature. This made easier to separate the influence of stoichiometry from that of microstructure. The optimized deposition parameters were then used to grow NbN films on GaAs and DBRs, under the reasonable assumption (later checked and confirmed) that changing the substrate would not produce a change in film stoichiometry, but only in its microstructure. NbN films ranging from 150nm to 3nm in thickness were then deposited on epitaxial-quality single crystal MgO, GaAs and DBRs structures. The deposition technique is the current controlled DC magnetron sputtering (planar, circular, balanced configuration) of Nb in an Ar + N2 plasma. NbN films deposited on MgO exhibit superconducting critical temperature ΤC=10 Κ, superconducting transition width ΔΤC=0.8 Κ and residual resistivity ratio RRR=R(20K)/R(300K)=0.8 for th=4 nm, which are state of the art values, proof of the excellent quality of our low-temperature deposition process. The quality of films deposited on GaAs and on DBRs is lower than that of NbN deposited on MgO, as for any thickness they systematically exhibit higher ΔΤC and lower ΤC and RRR. However, 5.5 nm-thick NbN films on GaAs still exhibit ΤC=10.7 Κ, ΔΤC=1.1 Κ and RRR=0.7, which compares with 4.5 nm thick films on MgO, making them suitable for device fabrication. To our knowledge, the growth of such high quality thin NbN films on GaAs and DBRs, has never been reported in literature. The degradation of the superconducting properties exhibited by NbN films on GaAs and DBRs was attributed to a highly defected microstructure, due both to a higher lattice misfit between NbN and GaAs and to a poorer quality of the substrate surface. Encouraging preliminary results show that the quality of these films can be improved either cleaning the GaAs/DBR substrate surface more effectively or adding an MgO buffer layer. SSPDs were fabricated on thin NbN films (th=3-7 nm) deposited under optimal conditions on MgO and GaAs by EBL and reactive ion etching. The geometrical parameters of our detectors are: Ad=5×5 µm2, w=60-200 nm, f=40%-60%. The devices were then characterized both electrically and optically. I-V curves of test structures were measured, from which it was possible to deduce important physical parameters used as figures of merit to estimate the superconducting properties of the nanowires, or for the design and the simulation of the devices. The quality of the devices fabricated on GaAs is poorer than those on MgO, most likely due to the lower quality of NbN films deposited on GaAs and to issues related to the EBL nano-patterning step. Measurements of η and of DK as a function of the bias current were performed on SSPDs fabricated on MgO and GaAs. The best performance was exhibited by a w=100 nm, f=40%, th=4 nm meander, showing η=20% and noise equivalent power NEP=10-16 W/Hz1/2 (at λ=1.3 µm and T=4.2 K), which are state of the art values. This result showed for the first time that high performance NbN SSPDs can be realized on a different substrate and from a deposition process at lower temperature than previously reported. High detection efficiencies could not be measured with SSPDs fabricated on GaAs, but it should be noted that at present only first-generation devices (fabricated on GaAs substrates of poor surface quality) have been tested. Better results are expected from devices fabricated on the improved NbN films grown on clean or MgO-buffered GaAs substrates. Although SSPDs on MgO have shown high detection efficiency, the fabrication yield of high performance detectors has to be improved. Variations of the critical current along a nanowire are responsible for the wide distribution in efficiency values of nominally identical SSPDs. In order to understand the physical origin of the nanowire constrictions (i.e. regions of suppressed superconductivity) we performed a spatially-resolved characterization of η of a long straight nanowire, followed by a high resolution SEM (scanning electron microscope) scan on its whole length. Two types of inhomogeneities were evidenced, corresponding to localized efficiency dips and peaks. The peaks likely correspond to constrictions. SEM observations did not evidence any width narrowing at the position of the efficiency peaks, which suggests that constrictions might be due to thickness or quality inhomogeneities of the film occurring during the film deposition or later in the process. On the other hand, the efficiency dips have been correlated with lithography problems discovered on SEM images. Finally, a new photon number resolving detector, the Parallel Nanowire Detector (PND), has been demonstrated, which significantly outperforms existing approaches in terms of sensitivity, speed and multiplication noise in the telecommunication wavelength range. In particular, it provides a repetition rate (80 MHz) three orders of magnitude larger than any existing detector at telecom wavelength, and a sensitivity (NEP=4.2×10-18 W/Hz1/2) one-two orders of magnitude better, with the exception of transition-edge sensors (which require a much lower operating temperature). An electrical equivalent model of the device was developed in order to study its operation. The modeling predicts a physical limit to the reset time of the PND, which is lower than initially estimated. Furthermore, the figures of merit of the device performance in terms of efficiency, speed and sensitivity were defined and their dependency on the design parameters analyzed. Additionally, we developed modeling tools to fully characterize the device and an algorithm to estimate the photon number statistics of an unknown light using the PND. The reconstruction proved to be successful only for low photon fluxes, most likely due to the limited counting capability and the poor calibration of the detector. The PND, with its high repetition rate and high sensitivity, is then suitable for measuring an unknown photon number probability distribution assuming accurate calibration and sufficient counting capability. ______________________________[1] G. N. Gol'tsman, O. Okunev, G. Chulkova, A. Lipatov, A. Semenov, K. Smirnov, B. Voronov, A. Dzardanov, C. Williams, and R. Sobolewski, Appl. Phys. Lett. 79, 705 (2001).

A method for calibration of single-photon detectors without the need of input photon flux calibration is presented. The method relies on the use of waveguide-coupled single photon detectors and a series of photon-counting measurements using a single-photon source. It is shown that the method can yield relative uncertainties of less than 1% including counting statistics and fiber splice loss uncertainties with a total measurement time of about 1 h under the assumptions that the fractional losses of the waveguide-coupled detectors are known or zero and the loss along the waveguide is constant. It is also shown that the fractional losses of the waveguide-coupled detectors can be determined if they are equal. However, in this case an input photon flux calibration is required.

Present status of the MINOS calibration detector

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