Detector Response Research Articles

Treating detector systematics via a likelihood free inference method

Estimating the impact of systematic uncertainties in particle physics experiments is challenging, especially since the detector response is unknown analytically in most situations and needs to be estimated through Monte Carlo (MC) simulations. Typically, detector property variations are parameterized in ways that implicitly assume a specific physics model, which can introduce biases on quantities measured by an analysis. In this paper, we present a method to recover a model-independent, event-wise estimation of the detector response variation by applying a likelihood-free inference method to a set of MC simulations representing discrete detector realizations. The method provides a re-weighting scheme for every event, which can be used to apply the effects of detector property variations fully decoupled from the assumed physics model. Using a toy MC example inspired by fixed-baseline neutrino oscillation experiments, we demonstrate the performance of our method. We show that it fully decouples the modeling of the detector response from the physics parameters to be measured in a MC forward-folding analysis.

Structural Design and Verification of an Effective-Area Measurement Device Detection System.

The effective-area method is a new way to measure aperture area. It defines aperture area by directly using the beam-limiting effect of the aperture in radiometric measurement. Due to the special structure of the measurement device, it is necessary to find a suitable method to design the detection system. In this paper, the measurement system model is constructed in the TracePro program. The real circumstances of light propagation for the measurement beam are simulated, and the responses of the detector are given. It is proved that the relative change in the detector response is the lowest when the detector is at the position of 132°. And this is the best structure design of the detection system. The experimental results are designed to verify the feasibility of the structure design of the detection system.

Electrophoretic Determination of L-Carnosine in Health Supplements Using an Integrated Lab-on-a-Chip Platform with Contactless Conductivity Detection.

The health supplement industry is one of the fastest growing industries in the world, but there is a lack of suitable analytical methods for the determination of active compounds in health supplements such as peptides. The present work describes an implementation of contactless conductivity detection on microchip technology as a new strategy for the electrophoretic determination of L-carnosine in complex health supplement formulations without pre-concentration and derivatization steps. The best results were obtained in the case of +1.00 kV applied for 20 s for injection and +2.75 kV applied for 260 s for the separation step. Under the selected conditions, a linear detector response of 5 × 10-6 to 5 × 10-5 M was achieved. L-carnosine retention time was 61 s. The excellent reproducibility of both migration time and detector response confirmed the high precision of the method. The applicability of the method was demonstrated by the determination of L-carnosine in three different samples of health supplements. The recoveries ranged from 91 to 105%. Subsequent analysis of the samples by CE-UV-VIS and HPLC-DAD confirmed the accuracy of the obtained results.

Reconstruction of point events in liquid-scintillator detectors subjected to total internal reflection

The outer water buffer is an economic option to shield the external radiative backgrounds for liquid-scintillator neutrino detectors. Since the refractive index of the liquid scintillator is larger than that of water, the consequential total internal reflection of scintillation light at the media boundary introduces extra complexity to the detector optics. This paper develops a precise detector-response model by investigating how total internal reflection complicates photon propagation and degrades reconstruction. We first parameterize the detector response by regression, providing an unbiased energy and vertex reconstruction in the total internal reflection region while keeping the number of parameters under control. From the experience of event degeneracy at the Jinping prototype, we identify the root cause as the multimodality in the reconstruction likelihood function, determined by the refractive index of the buffer, detector scale and PMT coverage. To avoid multimodality, we propose a straightforward criterion based on the expected photo-electron-count ratios between neighboring PMTs. The criterion will be valuable for the success in future liquid-scintillator detectors by guaranteeing the effectiveness of event reconstruction.

Dispersion-corrected extracorporeal arterial input functions in PET studies of mice: a comparison to intracorporeal microprobe measurements

BackgroundKinetic modelling of dynamic PET typically requires knowledge of the arterial radiotracer concentration (arterial input function, AIF). Its accurate determination is very difficult in mice. AIF measurements in an extracorporeal shunt can be performed; however, this introduces catheter dispersion. We propose a framework for extracorporeal dispersion correction and validated it by comparison to invasively determined intracorporeal AIFs using implanted microprobes.ResultsThe response of an extracorporeal radiation detector to radioactivity boxcar functions, characterised by a convolution-based dispersion model, gave best fits using double-gamma variate and single-gamma variate kernels compared to mono-exponential kernels for the investigated range of flow rates. Parametric deconvolution with the optimal kernels was performed on 9 mice that were injected with a bolus of 39 ± 25 MBq [18F]F-PSMA-1007 after application of an extracorporeal circulation for three different flow rates in order to correct for dispersion. Comparison with synchronous implantation of microprobes for invasive aortic AIF recordings showed favourable correspondence, with no significant difference in terms of area-under-curve after 300 s and 5000 s. One-tissue and two-tissue compartment model simulations were performed to investigate differences in kinetic parameters between intra- and extracorporeally measured AIFs. Results of the modelling study revealed kinetic parameters close to the chosen simulated values in all compartment models.ConclusionThe high correspondence of simultaneously intra- and extracorporeally determined AIFs and resulting model parameters establishes a feasible framework for extracorporeal dispersion correction. This should allow more precise and accurate kinetic modelling in small animal experiments.

Increasing Flame Ionization Detector Response by Silylation: The Effective Carbon Number of Carboxylic Acids

Detector response of carboxylic acids (C2–C12, straight and branched chain) were investigated using a flame ionization detector (FID) in a capillary gas chromatographic system. The response of the FID for hydrocarbons is almost directly proportional to the carbon quantity introduced into the flame. Heteroatoms in the molecule reduce signal magnitude, depending on their quality and on the bond they are involved in. We expressed this reduced response with the effective carbon number (ECN). We determined the ECN contribution (ΔECN) of the carboxyl group on the alkyl skeleton. We examined how the responses of carboxylic acids change if trimethylsilyl derivatives are evaluated and we compared the ECN of the neat and derivatized form.

Universal response method for accurate quantitative analysis of the impurities in quinolone antibiotics using liquid chromatography coupled with diode array detector and charged aerosol detector

HPLC method is the standard method for the separation and quantification of impurities from quinolone antibiotics. However, due to the large differences in the UV absorption of the impurities in quinolone antibiotics, quantitative analysis without the availability of corresponding reference substances currently poses a challenge. A sensitive and direct method using high performance liquid chromatography coupled with diode array detector and charged aerosol detector (HPLC-DAD-CAD) was developed for the analysis of impurities in quinolone antibiotics. The chromatographic conditions were optimized for good separation and output signal of CAD detector by response surface method (RSM). The systematic variation of CAD parameter settings, such as nebulization temperature, filter constant and power function value (PFV), were used to study the effect of on the detector response of signal-to-noise ratios (S/N) and linearity for ofloxacin, ciprofloxacin and their impurities. In the method validation, good linearity of each component was obtained with coefficient of determination (r) greater than 0.999 in the range of 0.5–300 μg mL−1. The average recoveries of each component were 99.02–102.39 % by DAD, were 98.22–101.91 % by CAD, RSDs were less than 2.5 % for intra-day and inter-day precision by DAD-CAD, with good precision and accuracy. The correction factor experimental results showed that the developed method provided a uniform response to the impurities with differences chromophores and could unbiasedly and directly detect the impurities in quinolone antibiotics. The method is first reported application of HPLC-DAD-CAD method for the analysis of impurities in quinolone antibiotics and it can be used for quality control of quinolone antibiotics.

Degradation of polysorbate investigated by a high-performance liquid chromatography multi-detector system with charged aerosol and mass detection

Polysorbate 80 is widely used as a formulation component in biopharmaceutical drug products. Recent studies have shown that polysorbate 80 is readily degraded either through direct or indirect means. The degradation of polysorbate 80 causes a concern for the long-term stability of biopharmaceutical drug product, as the breakdown products of polysorbate 80 have been shown to cause adverse effects, such as formation of sub-visible and visible particles and mAb aggregation. Understanding the path and extent of degradation is of a paramount importance for the formulator during formulation development. A multi-detector HPLC system using charged aerosol and mass detection was developed and optimized for the characterization of polysorbate 80 standards. The system included a post-column make-up flow, i.e. an inverse gradient, that enabled constant eluent composition at the detectors. The inverse gradient eliminated the main source of variability for the charged aerosol detector response, thereby enabling the calculation of the mass balance between polysorbate components with different degrees of esterification. Extracted ion chromatograms of the mass detector combined with their respective retention times were used to qualitatively characterize the polysorbate samples down to the individual components. The system was applied to study the degradation of several polysorbate standards which occurred by enzymatic digestion or long-term storage. The system provided detailed information on the mechanism of degradation without the need for additional orthogonal analytical techniques.

Monte Carlo analyses and experimental investigation of the vanadium self-powered neutron detector in 60Co source and research pulsed reactor

As the online monitoring apparatus in the reactor, self-powered neutron detectors (SPNDs) have a great potential for development in nuclear energy. To further characterize the SPND response in the actual radiation field, some irradiation experiments and Monte Carlo analyses based on the 60Co gamma-rays source and a research pulsed reactor were performed. During the experiments, the current signals were measured with various reactor irradiation facilities. A series of experimental phenomena, such as the negative current effect of the gamma rays, shutdown attenuation current, and the difference in detector sensitivity, are described and theoretically explained by using a numerical model GEANT4-SPND, an in-house Monte Carlo toolkit for SPND simulation based on Geant4. The numerical model proves to be highly effective in restoring the experimental results for the detector response current, the signal prompt proportion, and the current trend. This work has not only validated the existing calculation method but also provided reference radiation field parameters and detector experimental data for the future development and verification of sensor models. Besides, the analyses results have provided some insights into the study of the mechanism and optimization of detector design.

Quantum Random Number Generation Based on Multi-photon Detection.

We demonstrate quantum random number generation based on a photon-number detection scheme with the use of a silicon photomultiplier. We implement a time integral with detector response signals for resolving photon numbers, which are subsequently digitized into a stream of 4-bit sequences with a generation rate of 13.6 Mbit/s. Our generated random bits pass the statistical randomness validation according to the U.S. National Institute of Standards and Technology (NIST) Special Publication 800-22. This scheme is implementable with inexpensive components, and the system can be miniaturized to the size of a plug-and-play portable cryptographic device.

Tritium Beta Spectrum Measurement and Neutrino Mass Limit from Cyclotron Radiation Emission Spectroscopy.

The absolute scale of the neutrino mass plays a critical role in physics at every scale, from the subatomic to the cosmological. Measurements of the tritium end-point spectrum have provided the most precise direct limit on the neutrino mass scale. In this Letter, we present advances by Project 8 to the cyclotron radiation emission spectroscopy (CRES) technique culminating in the first frequency-based neutrino mass limit. With only a cm^{3}-scale physical detection volume, a limit of m_{β}<155 eV/c^{2} (152 eV/c^{2}) is extracted from the background-free measurement of the continuous tritium beta spectrum in a Bayesian (frequentist) analysis. Using ^{83m}Kr calibration data, a resolution of 1.66±0.19 eV (FWHM) is measured, the detector response model is validated, and the efficiency is characterized overthe multi-keV tritium analysis window. These measurements establish the potential of CRES for a high-sensitivity next-generation direct neutrino mass experiment featuring low background and high resolution.

Determination of underivatized amino acids in human plasma using ion pair liquid chromatography/tandem mass spectrometry

Accurate quantification of amino acids (AA) is essential for several applications, including clinical research, food analysis, and pharmaceutical studies. In this study, we developed an analytical method based on liquid chromatography with electrospray ionization coupled to tandem mass spectrometry detection (LC-ESI-MS/MS). This method was devised to accurately quantify a spectrum of amino acids, notably taurine, creatinine, glutathione (GSH), and sulfur-containing amino acids (SAAs) such as methionine, cysteine, and homocysteine, using only 10 μL of human plasma. A stable isotope derivative of each AA is used as an internal standard (IS) for accurate quantification. For retention and separation on a C18 column, heptafluorobutyric acid (HFBA) was employed as an ion pair agent. Multiple reaction monitoring (MRM) in positive mode with the precursor-to-product ion transitions at m/z is used for quantification. The method showed excellent linearity for all AA with a high correlation coefficient (r > 0.9927). The linear fit indicates that the detector response is linear over the tested range of standard concentrations. The accuracy and precision of the method were within the acceptable range of 92–110% and < 15%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were in the range of 0.001–1.80 µM and 0.004–6.0 µM, respectively. No significant ion suppression or carry over was observed. In conclusion, the assay was validated and found to have adequate accuracy, precision, linearity, sensitivity and selectivity. The assay has been successfully applied to the analysis of human plasma.

Measurement of the neutron energy response curve of 4H-SiC detector based fission target detection system at the CSNS Back-n white neutron source

The fission target detection system, which is based on U-235(or U-238)fission target and large area 4H-SiC detector, has been developed for pulsed neutron detection. However, calibration of its neutron energy response curve is challenging due to its very low detection efficiency to fast neutrons. In the past, the calibration of the neutron sensitivity for the fission target detection system was limited to using ∼ 14 MeV neutrons generated by the Cockcroft-Walton accelerator. To obtain the response function for the complete range of neutron energies, extrapolation based on neutron fission cross sections was required. In this paper, we present the calibration of its energy response at the China Spallation Neutron Source (CSNS) Back-n beam line using the time of flight method, both with double-bunch and single-bunch mode in end-station 1(with a flight path of ∼ 55 m). The SiC detector with a thin sensitive thickness of 30 μm has lower scattering background than the traditional Si-PIN detector . As a result, the energy response curve of the fission target detection system above 0.26 MeV has been successfully acquired. The spectrum of the double-bunch mode was unfolded using the Bayesian algorithm, and the results indicate that, under conditions of sufficient counts, this method can yield results similar to those obtained from the single-bunch mode. The issue of pulse height defect of SiC detector to fission fragments is discussed. This experiment confirms that our detection system of SiC+fission target has a strong signal-to-noise ratio and anti-interference capability. At the same time, it demonstrates that this device has its own advantages in measuring the energy response of low sensitivity detectors.

Ground-based calibration and characterization of LaBr3-SiPM-based gamma-ray detector on GECAM satellite: 8–160 keV

ABSTRACT As the main detector of the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor mission (GECAM), the calibration of the energy response and detection efficiency of the gamma-ray detector (GRD) is the main content of the ground-based calibration. This article mainly focuses on the calibration of the energy response and detection efficiency in the 8–160 keV with a refined measurement around the absorption edges of the lanthanum bromide crystal ($\rm {LaBr_3}$). The GRD performances for different crystal types, data acquisition modes, working modes, and incident positions are also analysed in detail. We show that the calibration campaign is comprehensive, the detector performance meets the flight requirements, and the calibration results generally agree with simulations as expected. The detector’s model was corrected by the ground-based calibration, which led to the establishment of the calibration data base.

Metal–semiconductor–metal detectors ZnS/GaP for the ultraviolet and visible part of the spectrum with electrically tunable spectral photosensitivity

High-quality ZnS epitaxial layers grown on GaP semiconductor substrates by MOCVD method. Photodetectors of the visible and UV parts of the spectrum based on new interdigitated Schottky barrier metal–semiconductor–metal (MSM) contacts to semiconductor structure ZnS/GaP. The detectors exhibit low dark current values. The dependence of the characteristics of the spectral response of detectors on voltage has been established offsets. It was found that the long-wavelength response boundary of ZnS/GaP MSM detectors can shift from 355 to 450 nm when the bias voltage changes from 10 to 30 V. At the maximum photosensitivity wavelength of 450 nm, the ampere-watt sensitivity of the detector was 0.3 A/W at a bias voltage of 60 V, and the quantum efficiency was 82%.

Exposing a fibre-based dual-readout calorimeter to a positron beam

A prototype of a dual-readout calorimeter using brass capillary tubes surrounding scintillating and clear plastic optical fibres was tested using beams of particles with energies between 10 and 100 GeV produced by the CERN SPS. The scope of the test was to characterise the performance of the tube-based detector response to positrons in terms of response linearity, energy resolution, and lateral granularity. After calibrating the detector and processing the output signal to correct for the energy dependency on the particle impact point, the linearity of the measurement was found to be better than 1%. The response to positron was compared to that predicted by a Geant4-based simulation, finding good agreement both in terms of energy resolution and shower profile. These results confirm the validity of the tube-based mechanical option and SiPM readout as a promising one for future developments.

Characterizations of the electrothermal parameters of a transition edge sensor microcalorimeter and its energy resolution

We developed a transition-edge sensor microcalorimeter (μ-calorimeter) using Mo/Au/Au thin films. We report the detector fabrication, the measurements of the electrothermal parameters and the noise characterizations of the transition-edge sensor μ-calorimeters. We estimated the energy resolution of the μ-calorimeter using the measured noise spectrum and the calculated power-to-current responsivity. Using a 55Fe radioactive X-ray source, we characterized the detector responses to incident photons at various working points. The best instrumental energy resolution achieved was 4.13 eV @ 5.9 keV, which agrees qualitatively with the resolution of 4.01 eV estimated from the noise spectrum.

Measuring response functions for a new compact neutron spectrometer

A compact neutron spectrometer consisting of a (0.6 x 0.6 x 12.0 cm3) EJ-276 plastic scintillator coupled to a silicon photomultiplier has been designed. An essential aspect of the characterisation of the spectrometer is the measurement of detector response functions for neutron energies above 20 MeV. The process of producing response functions for neutron energies between 10 MeV and 60 MeV for the compact detector using neutron time-of-flight measurements at iThemba LABS is presented.

Analysis of the Response Characteristics of Smoke and Carbon Monoxide in Non-Fire Conditions

This study confirms the applicability of cross-detection by analyzing the response characteristics of smoke and carbon monoxide detectors, to reduce non-firm alarms. Based on the results of previous studies, various scenarios reflecting non-fire conditions in Korea were selected, to conduct experiments to confirm the change in carbon monoxide concentration and the response of smoke detectors based on the measurement location. Although carbon monoxide was detected earlier than the smoke near the heating source, the smoke detector reacted earlier than the carbon monoxide meter as the distance from the heating source increased. The measured concentration of carbon monoxide was much lower than the concentration generated in the case of a fire, thus confirming the applicability of carbon monoxide cross-sensing for non-fire detection.

Characterization of the Bakelite Prototype Sensor for NEWS-G

The New Experiments With Spheres - Gas (NEWS-G) group at Queen's University uses Spherical Proportional Counters (SPCs) in the search for dark matter. Incoming radiation interacts with the gas inside the SPC through ionization, producing electron/ion pairs [1]. These primary electrons drift towards the central anode under the influence of an electric field [1]. A secondary ionization, termed avalanche, occurs at distances proportional to the size of the anode resulting in the multiplication of charges [1]. The signal that is produced is proportional to the number of secondary charges created during the avalanche [1]. A 30 cm-diameter sphere was used to characterize a six anode, spherical Bakelite prototype sensor. The sensor is divided into north and south three-anode read-out channels. To study the detector's response, an Fe55 source was placed inside the sphere, which was then filled with 1 bar of 40Ar+CH4 2% gas. The source was moved around the sphere with thirty-second data-taking runs taken at each point and high voltages applied to each channel. Cuts were applied to the event properties to isolate the 5.9 keV Fe55 peak. The peak was plotted as a histogram and fit with a Gaussian function with two additional linear terms. The gain and resolution of the sensor were extracted from the fit parameters. The channel dominance change angle was calculated by interpolating the number of events recorded by each channel at each point on the sphere. The gain, number of events and the channel dominance change angle were mapped on the sphere between 20 and 40 cm arc length in the theta direction, and all the way around the sphere in the phi direction to improve the understanding of the Bakelite sensor.