External Detector Research Articles

A Quarter Ellipsoidal Reflector Enhancing Fluorescence Collection Efficiency For Multiphoton Microscopes

In this paper, we present a fluorescence collection enhancement method for multiphoton microscopy by a quarter ellipsoidal reflector (QER). It is proven to be compatible with commercially available two-photon microscopes without significant customization. The structure and working principle of the QER is demonstrated. A QER was fabricated to collect most backscattered photons not collected by an objective lens of an epifluorescence microscope and then reflected photons into an external detector. Fluorescence collection efficiency improvement of 2.75-fold in numerical simulation is obtained. The method is also validated by imaging turbid phantoms and ex vivo biological tissue. Quantum efficiency (QE) corrected experimental results obtained by our method are comparable with those obtained by a nondescanned detection (NDD) scheme of a commercially available multiphoton microscope system. Finally, our method is shown to have potential in neuroscience research for deep tissue imaging.

MONDE: MOmentum Neutron DEtector

MONDE is a large area neutron momentum detector, consisting of a 70x160x5 cm3 plastic scintillator slab surrounded by 16 photomultiplier tubes, standard NIM signal processing electronics and a CAMAC data acquisition system. In this work we present data from a characterization run using an external trigger. For that purpose, coincident gamma rays from a 60Co radioactive source were used together with a NaI external detector. First results with an "external" trigger are presented.

Apertureless near-field terahertz imaging using the self-mixing effect in a quantum cascade laser

We report two-dimensional apertureless near-field terahertz (THz) imaging using a quantum cascade laser (QCL) source and a scattering probe. A near-field enhancement of the scattered field amplitude is observed for small tip-sample separations, allowing image resolutions of ∼1 μm (∼λ/100) and ∼7 μm to be achieved along orthogonal directions on the sample surface. This represents the highest resolution demonstrated to date with a THz QCL. By employing a detection scheme based on self-mixing interferometry, our approach offers experimental simplicity by removing the need for an external detector and also provides sensitivity to the phase of the reinjected field.

Application of capacitively coupled contactless conductivity as an external detector for zone electrophoresis in poly(dimethylsiloxane) chips.

In this work, lab-made PDMS microfluidic chips were matched to a capacitively coupled contactless conductivity detector (C(4) D) having external in-plane electrodes (eDAQ, Australia). The advantages of this type of C(4) D are the choice to reversibly place or remove the microchip onto/from the detector and to freely variate the position of the detection (separation length) on the microchip. The thickness of the bottom layer of the PDMS chip was optimized to achieve sensitive detection during the electrophoretic separation. PDMS chips with 100 μm bottom layer used with the C(4) D platform were tested by CZE of a mixture of seven anions and different types of real samples. Using split-flow pressure sample injection and effective length of 6.5 cm, the numbers of theoretical plates were in the range of 4000-6000 (63,000-93,000/m) and the LODs amounted to 3.66-14.7 μmol/L (0.13-2.26 μg/mL) for the studied anions.

Ejection of Coulomb Crystals from a Linear Paul Ion Trap for Ion-Molecule Reaction Studies.

Coulomb crystals are being increasingly employed as a highly localized source of cold ions for the study of ion-molecule chemical reactions. To extend the scope of reactions that can be studied in Coulomb crystals-from simple reactions involving laser-cooled atomic ions, to more complex systems where molecular reactants give rise to multiple product channels-sensitive product detection methodologies are required. The use of a digital ion trap (DIT) and a new damped cosine trap (DCT) are described, which facilitate the ejection of Coulomb-crystallized ions onto an external detector for the recording of time-of-flight (TOF) mass spectra. This enables the examination of reaction dynamics and kinetics between Coulomb-crystallized ions and neutral molecules: ionic products are typically cotrapped, thus ejecting the crystal onto an external detector reveals the masses, identities, and quantities of all ionic species at a selected point in the reaction. Two reaction systems are examined: the reaction of Ca(+) with deuterated isotopologues of water, and the charge exchange between cotrapped Xe(+) with deuterated isotopologues of ammonia. These reactions are examples of two distinct types of experiment, the first involving direct reaction of the laser-cooled ions, and the second involving reaction of sympathetically-cooled heavy ions to form a mixture of light product ions. Extensive simulations are conducted to interpret experimental results and calculate optimal operating parameters, facilitating a comparison between the DIT and DCT approaches. The simulations also demonstrate a correlation between crystal shape and image shape on the detector, suggesting a possible means for determining crystal geometry for nonfluorescing ions.

Experimentally quantifying the advantages of weak-value-based metrology

We experimentally investigate the relative advantages of implementing weak-value-based metrology versus standard methods. While the techniques outlined herein apply more generally, we measure small optical beam deflections both using a Sagnac interferometer with a monitored dark port (the weak-value-based technique), and by focusing the entire beam to a split detector (the standard technique). By introducing controlled external transverse detector modulations and transverse beam deflection momentum modulations, we quantify the mitigation of these sources in the weak-value-based experiment versus the standard focusing experiment. The experiments are compared using a combination of deterministic and stochastic methods. In all cases, the weak-values technique performs the same or better than the standard technique by up to two orders of magnitude in precision for our parameters. We further measure the statistical efficiency of the weak-values-based technique. By postselecting on $1\%$ of the photons, we obtain $99\%$ of the available Fisher information of the beam deflection parameter.

Accurate assessment of whole-body retention for PRRT with <sup>177</sup>Lu using paired measurements with external detectors

The aim of this study was to assess the accuracy of the results of whole-body measurements by comparison with the urine collection method in the PRRT with (177)Lu and furthermore to develop a more accurate method of paired measurements. Excreted samples were collected at given intervals and activities were measured by a dose calibrator. Traditionally, whole-body activities during subsequent measurements are normalized individually to the administered activity. In order to correct for the effects of the activity in the bladder during the baseline measurement before the first voiding and activity redistributions in the patient body during subsequent measurements, a series of paired measurements before and after each voiding were carried out. Time-dependent detector responses at given times were derived and time-activity retentions were then determined. Compared to the results of the urine collection, whole-body activities by traditional whole-body measurements were overestimated by ca. 14% at 1 h after administration and randomly varied from -29% to 49% at 24 h. Measurement uncertainties of whole-body activities were from ± 4% (the coverage factor k=2) at 1 h to >± 20% at 24 h by the urine collection and ± 7% by paired measurements, respectively. Whole-body activities at 1 h by paired measurements were validated using the results by measurements of the collected first urine. The new method of paired measurements has an equivalent measurement accuracy and even better during the later measurements with respect to the urine collection method and therefore can replace urine approach for assessing the time-activity remaining in the patient body.

Glass‐based Manufacturing and Prototyping Platform PhotPack

AbstractThere has been considerable progress in utilizing fully automated machines for the assembly of micro‐optical systems in recent years. Such systems integrate laser sources, passive optical elements, electro‐optical components and detectors into tight packages, and efficiently couple light to waveguides in photonic integrated circuits (PIC), optical backplanes, free space or optical fibers. The required electro‐optical and optical components are placed and aligned passively and actively, depending on optical and mechanical component tolerances. For one, the relative placing of all components is controlled actively by camera systems, and, more importantly, some or all active components are actually operated, and actively aligned with live feedback from internal and external power and beam image detectors. High precision (and also fast) active optical alignment machines nowadays exist, with more than adequate degrees of freedom and accuracies, so that best optical beam qualities and coupling efficiencies can be achieved.

Magnetometer Application for GAMMA-400 Telescope Switching into the Mode with Increased Low Energy Charged Particles Intensity Registration

GAMMA-400 is an international project of a high apogee orbital astrophysical observatory for studying the characteristics of high-energy gamma-emission, electrons/positrons and light nuclei fluxes. The energy range for γ-rays and electrons/positrons registration in the main aperture is from ∼0.1GeV to ∼3.0 TeV. Also, this aperture allows high energy light nuclei fluxes characteristics investigation. Moreover, special aperture configuration allows registering of gamma-quanta, electrons (positrons) and light nuclei from the lateral directions too.The spacecraft GAMMA-400 orbit will be located in the Earth's magnetosphere and will pass front shock wave from magnetosphere interaction with the solar wind, turbulent-transition region, magnetopause and so on. During the satellite's movement through various Earth's magnetosphere regions its anticoincidence detectors will register high intensity fluxes of low energy charged particles captured by the magnetic field. The working area sections of GAMMA-400 detector systems used as anticoincidence shield are about 1 m2 each. The high intensity low energy charged particles flux influence on anticoincidence detectors should be taken into account during particle identification.This article presents a comparison between Earth's magnetosphere theoretical model according to SPENVIIS package and real data measured by detectors onboard THEMIS series satellites. The differences between these two datasets indicate that the calculated data are not sufficient to make short time predictions of variations of magnetic induction in the outer magnetosphere. A special trigger marker flag will be produced by GAMMA-400 counting and triggers signals formation system accordingly to the data of two onboard magnetometers. This flag's presence leads to special algorithms execution start, putting the plastic detectors into a dedicated working mode taking into account possible high count rates of external detector layers.

Quality control of the TSV multi-pixel photon counter arrays, and modules for the external plate of EndoTOF-PET ultrasound detector

The aim of the EndoTOFPET-US collaboration is to develop a multi-modal imaging tool combining ultrasound with time-of-flight positron emission tomography into an endoscopic imaging device. One of the objectives of this scanner is to reach a coincidence time resolution of 200ps full width at half maximum. The external detector is constructed with 256 matrices of 4×4 lutetium–yttrium oxyorthosilicate scintillating crystals, each with a size of 3.5×3.5×15mm3, coupled to 256 Hamamatsu TSV multi-pixel photon counter arrays (S12643-050CN). A full characterisation of these arrays has been performed in order to assure the quality of the arrays prior to the gluing to the crystal matrices. The breakdown voltage, dark count rate and single photon time resolution have been measured both at DESY and CERN. After this characterisation, the crystal matrices were glued to the multi-pixel photon counter arrays. The coincidence time resolution of each module has been measured at CERN using an ultra-fast amplifier-discriminator as the reference readout ASIC. Results of the characterisation of multi-pixel photon counter arrays and the crystal modules are presented here.

Electrically-detected electron paramagnetic resonance of point centers in 6H-SiC nanostructures

The results of investigation of electrically-detected electron paramagnetic resonance (EDEPR) and classical electron paramagnetic resonance (EPR) (X-band) for the identification of shallow and deep boron centers, NVSi defects, and isolated silicon vacancies (VSi), which are formed directly during the preparation of planar nanostructures under conditions of silicon-vacancy injection at the SiO2/n-6H-SiC interface without any subsequent irradiation, are presented. The prepared sandwich nanostructures are an ultra-narrow p-type quantum well, confined by δ barriers heavily doped with boron on an n-6H-SiC surface, which are self-ordered during pyrolytic-oxide deposition and subsequent short-time boron diffusion. The EDEPR data of point centers in sandwich nanostructures, prepared within the framework of Hall geometry, are recorded by measuring the field dependences of the magnetoresistance without an external cavity, microwave source and detector, due to the presence of microcavities embedded in the quantum-well plane and microwave generation under conditions of a stabilized source-drain current from δ barriers containing dipole boron centers. The obtained EDEPR spectra of the shallow and deep boron centers are analyzed using the data of EPR studies in 6H-SiC bulk crystals [10]. The EDEPR spectrum of the isolated silicon vacancy reveals both the negatively charged state VSi− (S = 3/2) and the neutral state in hexagonal (VSi(h)) and quasicubic (VSi(k1, k2)) states (S = 1). In turn, NVSi defects are detected not only by the EDEPR method at 77 K, but also through the use of a Bruker ELEXSYS E580 EPP spectrometer at 9.7 GHz, in a temperature range of 5–40 K. The EDEPR and EPR spectra recorded on the same sandwich nanostructure are virtually identical and correspond to the center in the triplet state with spin S = 1. The EPR spectrum, which is a lowintensity line doublet with a splitting value equal to ΔB = 237.6 mT, is observed in the background of the EPR spectrum from donors of nitrogen, the concentration of which in the n-6H-SiC initial sample was 5 × 1018 cm−3, whereas nitrogen donor centers are not revealed in the EDEPR spectrum because of total occupation by silicon vacancies inside the 6H-SiC sandwich nanostructure.

Minimum detectable activity for NaI(Tl) airborne γ-ray spectrometry based on Monte Carlo simulation

The determination of the effective minimum detectable activity (MDA) of radionuclides by a detection system plays an important role in environmental radiation monitoring. In this study, the responses of an NaI(Tl) airborne γ ray spectrometry (AGRS) system to different radionuclides (137Cs and 131I) were investigated using the Monte Carlo technique. The MDA values were determined under different conditions according to the counting spectra obtained from the Monte Carlo simulation. The equivalent mass thickness method was applied to the Monte Carlo modeling for monitoring ground radiation to reduce statistical uncertainty. The secondary source method was used to monitor both air and ground radiation. A quadratic relationship was found between the MDA and activity concentration. An exponential relationship was found between the MDA and altitude. The MDA of a specific radionuclide from external detectors was found to be superior to that obtained from internal detectors under the same conditions. The MDA values in an NaI(Tl) AGRS system under different conditions can be estimated based on the results of this study.

Quadrupolar ion excitation for radiofrequency-only mass filter operation.

Trajectory calculations are used to model a mass filter based on the radiofrequency (rf)-only operation of a linear quadrupole with resonant quadrupole excitation of ions (resonant excitation applied with the same spatial electric field as the main quadrupole rf field). Ions are not trapped, but pass continuously through the quadrupole. Excited ions gain axial kinetic energy in the fringe field at the quadrupole exit, overcome a stopping potential and are transmitted to an external detector. No quadrupole direct current is required, unlike conventional operation at the tip of the first stability diagram. Quadrupole excitation can be applied with amplitude or frequency modulation of the main rf voltage, or with an auxiliary excitation voltage. All three methods give the same mass resolution. The mass resolution, R, is given by R ≈ 0.5q(dβ/dq)n where q is a Mathieu parameter, β(q), determines the frequency of ion oscillation and n is the number of cycles of the rf field experienced by an ion, determined by the flight time through the quadrupole. A disadvantage of this mode of operation is that the flight times of the ions and the excitation amplitudes or modulation depths need to be synchronized.

Spherical shields perturbed to ellipsoids in transport theory

One-dimensional spheres are perturbed to ellipsoids, and perturbation theory for inhomogeneous transport problems is applied to estimate the leakage of an uncollided decay gamma ray, a neutron thermal capture gamma ray, and a neutron inelastic scatter gamma ray. Only the shielding is perturbed, not the source. The surface transformation function for the sphere-to-ellipsoid change-of-shape perturbation is derived. Schwinger, Roussopolos, and combined perturbation estimates are applied. The perturbation estimates are defined to estimate the total (4π) flux at an external spherical surface detector, and they were accurate for point-detector fluxes when the leakage estimated from a point detector was similar to the total external surface flux. For uncollided line fluxes, the Schwinger estimate worked very well when the response of interest was the total external surface flux, but perturbation theory did not work well when the response of interest was the flux measured at a single external point (unless extra care was taken to account for geometric effects). For thermal capture line fluxes, the Roussopolos estimate was extremely accurate for one point detector location but its accuracy depended on the detector location. For inelastic scatter line fluxes, the detector fluxes were relatively insensitive to the detector location and the perturbation estimates were fairly accurate.

Demonstration of the self-mixing effect in interband cascade lasers

In this Letter, we demonstrate the self-mixing effect in an interband cascade laser. We show that a viable self-mixing signal can be acquired through the variation in voltage across the laser terminals, thereby removing the need for an external detector. Using this interferometric technique, we have measured the displacement of a remote target, and also demonstrated high resolution imaging of a target. The proposed scheme represents a highly sensitive, compact, and self-aligned sensing technique with potential for materials analysis in the mid-infrared.

On the development of electron microprobe zircon fission-track geochronology

The fission-track method has been applied for decades to quantify rates and timing of processes in the shallow crust. The most widely used approach, the external detector method, involves counting fission-tracks, a decay product resulting from the spontaneous fission of 238U, and a paired set of induced tracks (parent proxy) from the thermal neutron irradiation of 235U. We propose an alternate method of dating zircons that utilizes an electron microprobe to directly measure uranium concentration [U] and image the number of spontaneous fission-tracks or etch figures that intersect the surface of the crystal using an electron backscatter detector. The electron microprobe fission-track (EP-FT) method is used to date six zircon samples, four of which are widely used as standards: Fish Canyon Tuff, Peach Springs Tuff, Buluk Member of the Bakata Formation (tuff), Tardee Rhyolite, Mt. Dromedary Complex (hypabyssal granite), and Browns Park Formation (tuff). All samples yield ages that overlap within two standard deviations of published reference ages determined using other radiometric techniques (i.e., K/Ar, 40Ar/39Ar, and U/Pb) and also by the traditional fission-track external detector method. To correct for poorly constrained parameters such as the spontaneous fission decay constant, weight to volume percent conversions, etching efficiency, and selection bias, we calculate a preliminary Z proportionality factor of 4469±661 (1σ). The EP-FT technique avoids the hazard and expense of thermal neutron irradiation, allows simultaneous chemical compositions to be determined, removes the step of counting an external detector manually, and will likely allow much higher track densities to be counted than would be normally possible with optical microscopy. The technique is ideal for dating moderate to high U zircons (>100 ppm U).

Skin Thickness Estimation for High Precession Optical Head Tracking During Cranial Radiation Therapy: A Simulation Study

Skin Thickness Estimation for High Precession Optical Head Tracking During Cranial Radiation Therapy: A Simulation Study

Nonspherical Perturbations of Spherical Geometries in Transport Theory

It is often desirable to solve radiation transport problems in one-dimensional spherical geometries even if the actual object being modeled is not spherical. It may be possible to use perturbation theory to account for the difference between the real multidimensional system and the spherical approximation. This idea is tested using uncollided as well as multigroup inhomogeneous transport problems with upscattering. Asymmetric and nonuniform perturbations are made to the shielding (not the source) of spherical geometries, including transformations from a sphere to a cube (the surface transformation function is derived), and Schwinger, Roussopolos, and combined perturbation estimates are applied. For uncollided fluxes, perturbation theory, particularly the Schwinger estimate, worked very well when the response of interest was the flux measured at a symmetric spherical 4π detector external to the geometry, but perturbation theory did not work well when the response of interest was the flux measured at a single external point (unless extra care was taken to account for geometric effects). For neutron-induced gamma-ray line fluxes, the Roussopolos estimate worked well when the response of interest was the flux measured at an external 4π detector or an external point detector.

A review of the present state of the absolute calibration for zircon fission track geochronometry using the external detector method

AbstractThe authors have developed and demonstrated an independent calibration of zircon fission track dating with the external detector method. During the past two decades, investigations have continued concerning the issues of the absolute age calibration of fission track dating. The derivation of accurate fission track age equations has been made possible by taking into account the relationships between the latent and etched track lengths. Our dating exercise involving 10 zircon reference samples supports our claim that absolute age determinations can be carried out based on the following three parameters: (1) the 238U spontaneous fission decay constant of 8.5 × 10−17 a−1 (λf) which is recommended by the IUPAC; (2) thermal neutron fluence values based on pre‐irradiated IRMM540 dosimeter glass, which is equivalent to the Au and Co metal activation monitors in the 1990 IUGS recommendation; and (3) a [GQR] correction value of 1.35 which has been experimentally determined for the combination of zircon external surfaces irradiated with mica external detectors. Independent measurements of uranium concentration by the fission track method were also tested. A new method of fission track dating that uses mass spectrometry for uranium measurements was simulated with success using our zircon data. We propose that the Fission Track Community reassesses the situation and formulates a new recommendation, in which the established independent method is placed on at least an equal footing with the standard‐based method.

Further investigation of the initial fission-track length and geometry factor in apatite fission-track thermochronology

The external detector method (EDM) is a widely used technique in fission track thermochronology (FTT) in which two different minerals are concomitantly employed: spontaneous tracks are observed in apatite and induced ones in the muscovite external detector. They show intrinsic differences in detection and etching properties that should be taken into account. In this work, new geometry factor values, g, in apatite, were obtained by directly measuring the ρ ed /ρ is ratios and independently determined [GQR] ed/is values through the measurement of projected lengths. Five mounts, two of which were large area prismatic sections and three samples composed of random-orientation pieces have been used to determine the g-values. A side effect of applying EDM is that the value of the initial confined induced fission track, L 0 , is not measured in routine analyses. The L 0 -value is an important parameter to quantify with good confidence the degree of annealing of the spontaneous fission tracks in unknown-age samples, and is essential for accurate thermal history modeling. The impact of using arbitrary L 0 -values on the inference of sample thermal history is investigated and discussed. The measurement of the L 0 -value for each sample to be dated using an extra irradiated apatite mount is proposed. This extra mount can be also used for determining the g value as an extension of the ρ ed /ρ is ratio method. Eight apatite samples from crystalline basement, with grains at random orientation, were used to determine the g-values. The results found are statistically in agreement with the values found for apatite samples (from Durango, Mexico) measured in prismatic section and also measured at random orientation. There was no observable variation in efficiency regarding crystal orientation, showing that it is relatively safe using non-prismatic grains, especially in samples with paucity of grains, as it is the case of most basin samples. Implications for the ζ-calibration and for the calibration of the direct (spectrometer-based) fission-track dating are also discussed.