Charge Integration Research Articles

Improved neutron-gamma discrimination for a 3He neutron detector using subspace learning methods

3He gas based neutron Linear-Position-Sensitive Detectors (LPSDs) have been used for many neutron scattering instruments. Traditional Pulse-height Analysis (PHA) for Neutron-Gamma Discrimination (NGD) resulted in the neutron-gamma efficiency ratio (NGD ratio) on the order of 105–106. The NGD ratios of 3He detectors need to be improved for even better scientific results from neutron scattering. Digital Signal Processing (DSP) analyses of waveforms were proposed for obtaining better NGD ratios, based on features extracted from rise-time, pulse amplitude, charge integration, a simplified Wiener filter, and the cross-correlation between individual and template waveforms of neutron and gamma events. Fisher Linear Discriminant Analysis (FLDA) and three Multivariate Analyses (MVAs) of the features were performed. The NGD ratios are improved by about 102–103 times compared with the traditional PHA method. Our results indicate the NGD capabilities of 3He tube detectors can be significantly improved with subspace-learning based methods, which may result in a reduced data-collection time and better data quality for further data reduction.

RixsToolBox: software for the analysis of soft X-ray RIXS data acquired with 2D detectors

A software with a graphical user interface has been developed with the aim of facilitating the data analysis for users of a new resonant inelastic X-ray scattering (RIXS) spectrometer installed at the ESRF beamline ID32. The software is organized in modules covering all relevant steps in the data reduction from a stack of several hundred two-dimensional CCD images to a single RIXS spectrum. It utilizes both full charge integration and single-photon centroiding to cope with high-flux and high-resolution requirements. Additional modules for further data analysis and the extraction of instrumental parameters are available. The software has been in routine use for about a year now and in that time many additional features have been incorporated. It now meets the users' need for an easy-to-use data analysis tool that allows looking at and understanding data as it is acquired and thus steering users' experiments more efficiently.

A 0.26-nJ/node, 400-kHz Tx Driving, Filtered Fully Differential Readout IC With Parasitic RC Time Delay Reduction Technique for 65-in $169 \times 97$ Capacitive-Type Touch Screen Panel

This paper presents a readout method and circuit for large, capacitive-type touch-screen panels (TSPs). Despite the considerable amount of RC time delay of large-area TSPs, the proposed readout method with a receiver (Rx) input seriescapacitor improves the settling speed of signals transferred from the transmitter (Tx) to the Rx, by reducing the RC time delay. Combined with the Rx input series-capacitor, a capacitive-input fully differential filtered charge integrator effectively cancels out the display noise and reduces the self-noise in capacitive-type TSPs. The proposed Rx circuit was implemented using 0.35-μm CMOS. Using a 65-in metal-mesh TSP with 169 Tx and 97 Rx electrodes mounted on a liquid-crystal display for testing, the proposed readout method achieved 65% reduction of signal settling time within an accuracy of ≥3τ for the longest signal path of the TSP. Using the RC time delay reduction technique, the Tx driving frequency could be boosted by as much as 400 kHz, and the measured signal-to-noise ratio of 43.5 dB was obtained for finger touch at a 120-Hz scan rate, resulting in a figureof-merit of 0.26 nJ/node, while the overall power consumption was 76 mW.

Measurements with MÖNCH, a 25 μm pixel pitch hybrid pixel detector

MÖNCH is a hybrid silicon pixel detector based on charge integration and with analog readout, featuring a pixel size of 25×25 μm2. The latest working prototype consists of an array of 400×400 identical pixels for a total active area of 1×1 cm2. Its design is optimized for the single photon regime. An exhaustive characterization of this large area prototype has been carried out in the past months, and it confirms an ENC in the order of 35 electrons RMS and a dynamic range of ∼4×12 keV photons in high gain mode, which increases to ∼100×12 keV photons with the lowest gain setting. The low noise levels of MÖNCH make it a suitable candidate for X-ray detection at energies around 1 keV and below. Imaging applications in particular can benefit significantly from the use of MÖNCH: due to its extremely small pixel pitch, the detector intrinsically offers excellent position resolution. Moreover, in low flux conditions, charge sharing between neighboring pixels allows the use of position interpolation algorithms which grant a resolution at the micrometer-level. Its energy reconstruction and imaging capabilities have been tested for the first time at a low energy beamline at PSI, with photon energies between 1.75 keV and 3.5 keV, and results will be shown.

Logical integration device for two-dimensional semiconductor transition metal sulfide

The semiconductor industry has experienced exponential growth for more than 50 years, following the Moore's Law. However, traditional microelectronic devices are currently facing challenges such as high energy consumption and the short-channel effect. As an alternative, two-dimensional layered materials show the ability to restrain the carriers in a 1 nm physical limit, and demonstrate high electron mobility, mutable bandgap, and topological singularity, which will hopefully give birth to revolutionary changes in electronics. The transition metal dichalcogenide (TMDC) is regarded as a prospective candidate, since it has a large bandgap (typically about 1-2 eV for a monolayer) and excellent manufacture compatibility. Here in this paper, we review the most recent progress of two-dimensional TMDC and achievements in logic integration, especially focusing on the following key aspects:charge transport, carrier mobility, contact resistance and integration. We also point out the emerging directions for further research and development.

Preparation for the upgrade of CMS Hadron Endcap Calorimeter front-end

The hadron endcap (HE) calorimeter is one of the major sections of CMS detector, used for measurement of the hadrons energy. Phase1 upgrade of the front-end electronics components in the HE calorimeter is being prepared, in particular to improve ability to handle increased pile-up and mitigate radiation damage of optical system in the high eta region. Tests of Phase1 HE Front-end system including new photo-sensors, silicon photomultipliers (SiPM), as well as new charge integrator encoder (QIE11) were performed in the Burn-in station in b904 at CERN. In this note, analysis and measurement results for the new generation front-end electronics components are presented.

Investigating subsurface damages in semiconductor–insulator–semiconductor solar cells with THz spectroscopy

AbstractThe influence of near‐surface crystal damage on carrier dynamics in silicon has been investigated with optical‐pump THz‐probe and THz emission studies. The surface damage is caused by a plasma process used for the fabrication of the ultrathin insulator within semiconductor–insulator–semiconductor (SIS) solar cells. The ion bombardment during the plasma process introduces a highly damaged subsurface region. Furthermore, the integration of positive interface charges leads to the formation of a depletion region that can be detected via the emitted THz radiation. The results are compared with classic I–U‐characterization demonstrating that THz spectroscopy can be used as a supplementary tool for the investigation of process‐induced surface damages.

New calibration circuitry and concept for AGIPD

AGIPD (adaptive gain integrating pixel detector) is a detector system developed for the European XFEL (XFEL.EU), which is currently being constructed in Hamburg, Germany. The XFEL.EU will operate with bunch trains at a repetition rate of 10 Hz. Each train consists of 2700 bunches with a temporal separation of 220 ns corresponding to a rate of 4.5 MHz. Each photon pulse has a duration of < 100 fs (rms) and contains up to 1012 photons in an energy range between 0.25 and 25 keV . In order to cope with the large dynamic range, the first stage of each bump-bonded AGIPD ASIC is a charge sensitive preamplifier with three different gain settings that are dynamically switched during the charge integration. Dynamic gain switching allows single photon resolution in the high gain stage and can cover a dynamic range of 104 × 12.4 keV photons in the low gain stage. The burst structure of the bunch trains forces to have an intermediate in-pixel storage of the signals. The full scale chip has 352 in-pixel storage cells inside the pixel area of 200 × 200 μm2. This contribution will report on the measurements done with the new calibration circuitry of the AGIPD1.1 chip (without sensor). These results will be compared with the old version of the chip (AGIPD1.0). A new calibration method (that is not AGIPD specific) will also be shown.

Beam charge integration in external beam PIXE–PIGE analysis utilizing proton backscattering with an extraction window

In this study, we present a new method for the indirect integration of beam charges in external beam proton-induced X-ray emission and proton-induced γ-ray emission (PIXE–PIGE) analysis. We recorded proton spectra backscattered by a Kapton film extraction window in different sample situations and under different beam currents. We also simulated backscattering spectra using the simulation of backscattering spectra program (SIMNRA). We determined that in a specific geometrical arrangement, different sample situations did not significantly affect factor CQ (the ratio between integral backscattering proton counts and integral beam charges). We also studied the reproducibility and beam current dependence of factor CQ. The statistic factor of CQ was 28.95 ± 0.6 kilo counts/μC, with a relative standard deviation of 2.0 %. Significantly, in external beam PIXE–PIGE analysis, we were able to calculate beam charge integration from the integral backscattering proton counts in an energy region.

A simulation study on the influence of scattered X-rays in energy-resolved computed tomography

ABSTRACTIn computed tomography (CT), scattered X-rays are known to cause image quality degradation including low contrast and poor uniformity. Energy-resolved CT (ERCT) is a specialized imaging method that utilizes the measured energy distribution and intensity of detected X-rays when creating images. The influence of scatter in ERCT is expected to differ from conventional CT, which only relies on energy (charge) integration during detection. Monte Carlo simulations were performed with different X-ray beam qualities and contrast agents to determine the influence of scatter on ERCT images. The simulation geometry included a 16 cm diameter cylindrical polymethylmethacrylate phantom containing a 1 cm diameter region filled with iodine or gold contrast agent solution at the center. A detector array collected the photon energy, position, and number of scattering. The image contrast and scatter artifact in the simulated ERCT images were compared as a function of photon energy range. Results show that the scatter artifact in ERCT is correlated to energy and is affected by the beam hardness. Care should be taken while obtaining ERCT images in the low-energy region, specifically near the K-edge of iodine.

Design of High-Precision ROIC for Quantum Dot Infrared Photodetector

Read out integrated circuit (ROIC) design for quantum dot infrared photodetector (QDIP) array requires large charge handling capacity, low readout noise, minimum detector bias voltage variations, and minimum power dissipation. ROIC design for such applications is challenging due to complex requirements and often needs iterative fabrications to meet all requirements. In this letter, we propose a decision matrix-based optimization method for large dynamic range ROIC implementation. The optimization method is based on trade off analysis, design, and simulation of identified ROIC parameters. This methodology has been applied to an actual case, and the optimum ROIC topology was selected using the optimization method described in this letter. The critical specifications are charge handling capacity of greater than 5 $\text{M}\overline {e}$ and low readout noise of less than 600 electrons, in 180-nm CMOS process. The large dynamic range ROIC consists of a charge integration stage, charge to voltage converters, correlated double samplers, sample and holds, column amplifiers, analog multiplexer, and a buffer amplifier stage. This letter also highlights the measured test chip results of an ROIC array of 30 $\mu \textrm {m} \times 30~\mu \text{m}$ pixel size, in which we have been able to achieve a charge handling capacity of 9.8 $\text{M}\overline {e}$ and the noise of 350 electrons.

Abstract 2193: Stabilityof injectable phospholipid nanoparticles loaded with paclitaxel: influence oflipid composition, drug concentration, storage temperature, lyophilization, andadditives

Abstract Paclitaxel is one of the most effective chemotherapeutic drugs for solid tumors including breast, lung and ovarian cancers. It has been formulated as a nanoparticle formulation, Abraxane, to improve its solublity (0.35-0.7 μg/mL) and to avoid the use of harmful solvents like cremophor EL. We previously reported the next-generation Abraxane - Cynviloq - a polymeric micelle paclitaxel formulation which uses a chemical polymer instead of biological polymer to stabilize the nanoparticle [1]. Here we investigate and report the use of phospholipids instead of a chemical polymer for the creation of the next-generation Abraxane. The effect of lipid composition on drug loading and physical stability of paclitaxel-loaded lipid-coated nanoparticle formulation was evaluated before and after lyophilization. The nanoparticles were prepared by microfluidization-solvent evaporation method. The formulation parameters included type of phospholipids, phospholipid fatty acid chain length, ratio of phospholipid and lysophospholipid combination, and drug-phospholipid ratio. The process parameters such as microfluidization pressure and number of microfluidization cycles were studied and their impact on drug loading, particle size and physical stability were evaluated. The short-term stability evaluation of nanoparticles prepared with different phospholipid ratios demonstrated that 4:1 as the optimum phospholipid-lysophospholipid ratio to achieve a loading of more than 60% paclitaxel with particle size of approximately ∼200nm. The nanoparticle size increased with an increase of carbon chain length of the phospholipid fatty acid, but no significant trends were observed for drug loading with changes in microfluidization pressure or number of cycles. The stability of the formulation was evaluated at different temperatures before and after lyophilization. The optimization of phospholipid composition, drug-lipid ratio, process parameters and additives for stability on lyophilization led to a physically stable paclitaxel-loaded phopholipid-coated nanoparticulate formulation that maintains size, charge and particulate integrity during storage. Phospholipid bound paclitaxel nanoparticle was successfully manufactured in lab scale with the desired properties. Scaling up and additional work-up for clinical evaluation is being evaluated. Reference: 1. Motamed K, Goodman Y, Hwang L, Hsiao C, Trieu V. (2014). IG-001 - A non-biologic nanoparticle paclitaxel for the treatment of solid tumors. J Nanomater Mol Nanotechnol 3:1. doi:10.4172/2324-8777.1000136. Citation Format: Shrada Prabhulkar, Gary Williams, Steve Miller, Zachary Yim, Walter McConathy, Tapas De. Stabilityof injectable phospholipid nanoparticles loaded with paclitaxel: influence oflipid composition, drug concentration, storage temperature, lyophilization, andadditives. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2193.

Absolute determination of radiation bursts and of proportional counters space charge effect through the influence method

When proportional counters are employed in charge integration mode to determine the magnitude of a radiation pulse, so intense that individual detection events take place in a time too short to produce individual output pulses, mostly in pulsed neutron sources, the strong build-up of positive space charge reduces the electric multiplication factor of the proportional detector. Under such conditions the ensuing measurement underestimates the amount of radiation that interacted with the detector. If the geometric characteristics, the filling gas pressure and the voltage applied to that detector are known, it becomes possible to apply an analytical correction method to the measurement.In this article we present a method that allows to determine the absolute value of the detected radiation burst without the need to know the characteristics of the employed detectors. It is necessary to employ more than one detector, taking advantage of the Influence Method.The “Influence Method” is conceived for the absolute determination of a nuclear particle flux in the absence of known detector efficiency and without the need to register coincidences of any kind. This method exploits the influence of the presence of one detector in the count rate of another detector, when they are placed one behind the other and define statistical estimators for the absolute number of incident particles and for the efficiency (Rios and Mayer, 2015 [1,2]). Its practical implementation in the measurement of a moderated neutron flux arising from an isotopic neutron source was exemplified in (Rios and Mayer, 2016 [3]) and the extension for multiple detectors in (Rios and Mayer 2016 [4]).

Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo

The first wearable multi-wavelength technology for functional near-infrared spectroscopy has been developed, based on a custom-built 8-wavelength light emitting diode (LED) source. A lightweight fibreless probe is designed to monitor changes in the concentrations of multiple absorbers (chromophores) in biological tissue, the most dominant of which at near-infrared wavelengths are oxyhemoglobin and deoxyhemoglobin. The use of multiple wavelengths enables signals due to the less dominant chromophores to be more easily distinguished from those due to hemoglobin and thus provides more complete and accurate information about tissue oxygenation, hemodynamics, and metabolism. The spectroscopic probe employs four photodiode detectors coupled to a four-channel charge-to-digital converter which includes a charge integration amplifier and an analogue-to-digital converter (ADC). Use of two parallel charge integrators per detector enables one to accumulate charge while the other is being read out by the ADC, thus facilitating continuous operation without dead time. The detector system has a dynamic range of about 80 dB. The customized source consists of eight LED dies attached to a 2 mm × 2 mm substrate and encapsulated in UV-cured epoxy resin. Switching between dies is performed every 20 ms, synchronized to the detector integration period to within 100 ns. The spectroscopic probe has been designed to be fully compatible with simultaneous electroencephalography measurements. Results are presented from measurements on a phantom and a functional brain activation study on an adult volunteer, and the performance of the spectroscopic probe is shown to be very similar to that of a benchtop broadband spectroscopy system. The multi-wavelength capabilities and portability of this spectroscopic probe will create significant opportunities for in vivo studies in a range of clinical and life science applications.

Toward a fractal spectrum approach for neutron and gamma pulse shape discrimination*Supported by the National Natural Science Foundation of China (41274109), Sichuan Youth Science and Technology Innovation Research Team (2015TD0020), Scientific and Technological Support Program of Sichuan Province (2013FZ0022), and the Creative Team Program of Chengdu University of Technology.

Accurately selecting neutron signals and discriminating γ signals from a mixed radiation field is a key research issue in neutron detection. This paper proposes a fractal spectrum discrimination approach by means of different spectral characteristics of neutrons and γ rays. Figure of merit and average discriminant error ratio are used together to evaluate the discrimination effects. Different neutron and γ signals with various noise and pulse pile-up are simulated according to real data in the literature. The proposed approach is compared with the digital charge integration and pulse gradient methods. It is found that the fractal approach exhibits the best discrimination performance, followed by the digital charge integration method and the pulse gradient method, respectively. The fractal spectrum approach is not sensitive to high frequency noise and pulse pile-up. This means that the proposed approach has superior performance for effective and efficient anti-noise and high discrimination in neutron detection.

K voprosu sozdaniya prezizionnych klyuchey razryada integratora zaryada dlya primeneniya v spektrometricheskich priborach nablyudeniy v usloviyach dal'nego kosmosa

K voprosu sozdaniya prezizionnych klyuchey razryada integratora zaryada dlya primeneniya v spektrometricheskich priborach nablyudeniy v usloviyach dal'nego kosmosa

External beam IBA set-up with large-area thin Si3N4 window

A compact external beam setup has been constructed for Particle Induced X-ray Emission (PIXE) and Nuclear Reaction (NRA) analyses. The key issue in the design has been to obtain a wide beam spot size with maximized beam current utilizing a thin Si3N4 exit window. The employed specific exit window support enables use of foils with thickness of 100nm for a beam spot size of 4mm in diameter. The durable thin foil and the large beam spot size will be especially important for the complementary external beam NRA measurements. The path between the exit foil and sample is filled with flowing helium to minimize radiation hazard as well as energy loss and straggling, and to cool the samples. For sample-independent beam current monitoring and irradiation fluence measurement, indirect charge integration, based on secondary electron current measurement from a beam profilometer, is utilized.

Comparison of analog and digital pulse-shape-discrimination systems

Pulse shape discrimination (PSD) performance of two optimized PSD systems (one digital and one analog) is compared in this work. One system uses digital charge integration, while the other system uses analog zero crossing. Measurements were conducted with each PSD system using the CAEN V1720 (250MHz) data acquisition system. An organic-liquid scintillator, coupled to a photo-multiplier tube, was used to detect neutrons and gamma rays from a Cf-252 spontaneous-fission source. The PSD performance of both systems was optimized and quantified using a traditional figure-of-merit (FOM) approach. FOM's were found for three, 300 keVee light-output bins, spanning from 100 to 1000keVee, and one larger bin from 100 to 1800keVee. Digital PSD outperformed analog PSD in the lowest light-output bin by approximately 50%, and by 11% for the highest light-output bin.

TOFPET2: a high-performance ASIC for time and amplitude measurements of SiPM signals in time-of-flight applications

We present a readout and digitization ASIC featuring low-noise and low-power for time-of flight (TOF) applications using SiPMs. The circuit is designed in standard CMOS 110 nm technology, has 64 independent channels and is optimized for time-of-flight measurement in Positron Emission Tomography (TOF-PET). The input amplifier is a low impedance current conveyor based on a regulated common-gate topology. Each channel has quad-buffered analogue interpolation TDCs (time binning 20 ps) and charge integration ADCs with linear response at full scale (1500 pC). The signal amplitude can also be derived from the measurement of time-over-threshold (ToT). Simulation results show that for a single photo-electron signal with charge 200 (550) fC generated by a SiPM with 320 pF capacitance the circuit has 24 (30) dB SNR, 75(39) ps r.m.s. resolution, and 4(8) mW power consumption. The event rate is 600 kHz per channel, with up to 2 MHz dark counts rejection.

An hybrid detector GEM-ASIC for 2-D soft X-ray imaging for laser produced plasma and pulsed sources

The following paper presents a new 2-D detector (`GEMpix') in the soft X-ray range, having a wide dynamic range thanks to its intrisic gain, working in charge integration mode to be used for diagnosing laser produced plasma (LPP) or X-ray pulsed sources. It is a gas detector based on the Gas Electron Multiplier (GEM) technology with a quad-medipix chip as read-out electronics. In our prototype, the substitution of semiconductor material with a gas triple-GEM allows several advantages with respect to the detectors commonly used in LPP, as X-ray CCDs and Micro Channel Plates or Image Plates. In these experiments the configuration Time-over-Threshold (ToT) has been used, to measure the total charge released to the gas and collected by each pixel, integrated over the X-ray burst duration. Intensity response and spatial resolution has been measured first in laboratory for calibration, as function of the voltage applied to the GEMs, in single photon regime with energies between 3.7 and 17 keV. Subsequently it has been tested at the ABC laser facility (ENEA, Frascati). In this case, we measured the X-rays produced when the ABC neodymium laser, with pulse of 50 J and 3 ns time width, hits plane targets of aluminum. 2-D images have been acquired by means of a pinhole configuration with magnification 1.5 and 50 μ m of spatial resolution. The results are encouraging regarding the capability of this imaging detector to work in experiments where soft X-ray emissivity varies over many orders of magnitude.