Digital Data Acquisition Research Articles

Characterization of a neutron–beta counting system with beta-delayed neutron emitters

A new detection system for the measurement of beta-delayed neutron emission probabilities has been characterized using fission products with well known β-delayed neutron emission properties. The setup consists of BELEN-20, a 4π neutron counter with twenty 3He proportional tubes arranged inside a large polyethylene neutron moderator, a thin Si detector for β counting and a self-triggering digital data acquisition system. The use of delayed-neutron precursors with different neutron emission windows allowed the study of the effect of energy dependency on neutron, β and β–neutron rates. The observed effect is well reproduced by Monte Carlo simulations. The impact of this dependency on the accuracy of neutron emission probabilities is discussed. A new accurate value of the neutron emission probability for the important delayed-neutron precursor 137I was obtained, Pn=7.76(14)%.

Thermal Management Solutions for enhanced Digital Flight Data Acquisition Unit in Avionics Applications

According to the Federal Aviation Administration, the commercial airline industry should expect to see the number of passengers traveling per year to grow from its current level of 750 million to nearly 1 billion by 2030. To meet this demand, airlines are placing orders for thousands of new aircraft over the next decade and beyond. With this increase in airline traffic, newer aircraft systems will generate an ever increasing amount of data per flight, data that allows airlines to further enhance their flight operations, flight safety, and reliability. For commercial avionics, the migration of the data acquisition and reporting functions from the traditional interface environments to newer, faster, and more network-centric architectures is creating a new generation of “smart” aircraft. Teledyne Controls' enhanced Digital Flight Data Acquisition Unit is an integral part of a new generation of aircraft and combines the functions of Mandatory Data Acquisition and Recording with a sophisticated Aircraft Conditioning Monitoring System that the aircraft operator uses to monitor the performance and reliability of each aircraft in its fleet. Some of the critical goals in the development of the Digital Flight Data Acquisition Unit are reducing the size and weight over previous generations, while maximizing performance and reducing cost. All of these opposing requirements make the design and fabrication very challenging. One such challenge includes dissipating high power in a confined space, and this makes thermal management a critical component of the overall LRU (line-replaceable unit) design. In addition, to increase the reliability over the lifespan of the unit, passive cooling systems are often required in place of internal fans. This presents another set of challenges, such as optimizing the airflow provided by the aircraft in the electronics bay compartment. This paper will present some of the critical elements in thermal management such as heat sinks, components placement, thermal interface materials, thermal vias, thermal links, packaging approaches and cooling strategy. The design and optimization of the system are based on analytical solutions, conjugated heat transfer and experimental results. The LRU should safely operate under various environmental conditions: ground operation, flight operation, high operating temperature and loss of cooling air where each environmental condition has different parameters for coolant airflow rate, effect of the surroundings, and ambient and coolant air temperature. Draw-Through and Blow-Through cooling analysis were performed using CFD (Computational Fluid Dynamics). The thermal analysis problems solved are conjugated heat transfer for laminar flow with radiation in steady-state or transient regimes. Multiple approaches were identified to remove heat from the critical components through optimization of the components and subsystems. These same approaches can also be used to increase the system's performance and reliability.

Introduction to compressed sensing

Compressed sensing (CS) is an emerging field of mathematics and engineering that challenges the conventional paradigms of digital data acquisition. Since the seminal publication of Candès et al. (2006) , the field has developed a substantial academic literature and has provided the foundation for major innovations in medical imaging, astronomy, and digital photography. Although CS is very mathematical, it can be conceptually intuitive. This tutorial provides a brief introduction to CS concepts through simple examples and interactive figures in an accompanying Jupyter notebook at github.com/seg/tutorials .

Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in ^{254}Rf.

Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) μs have been discovered in the heavy ^{254}Rf nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the K^{π}=8^{-}, ν^{2}(7/2^{+}[624],9/2^{-}[734]) two-quasineutron and the K^{π}=16^{+}, 8^{-}ν^{2}(7/2^{+}[624],9/2^{-}[734])⊗8^{-}π^{2}(7/2^{-}[514],9/2^{+}[624]) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N=150 isotones. The four-quasiparticle isomer is longer lived than the ^{254}Rf ground state that decays exclusively by spontaneous fission with a half-life of 23.2(1.1) μs. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.

A Combined Remote Sensing–Numerical Modelling Approach to the Stability Analysis of Delabole Slate Quarry, Cornwall, UK

Rock slope geometry and discontinuity properties are among the most important factors in realistic rock slope analysis yet they are often oversimplified in numerical simulations. This is primarily due to the difficulties in obtaining accurate structural and geometrical data as well as the stochastic representation of discontinuities. Recent improvements in both digital data acquisition and incorporation of discrete fracture network data into numerical modelling software have provided better tools to capture rock mass characteristics, slope geometries and digital terrain models allowing more effective modelling of rock slopes. Advantages of using improved data acquisition technology include safer and faster data collection, greater areal coverage, and accurate data geo-referencing far exceed limitations due to orientation bias and occlusion. A key benefit of a detailed point cloud dataset is the ability to measure and evaluate discontinuity characteristics such as orientation, spacing/intensity and persistence. This data can be used to develop a discrete fracture network which can be imported into the numerical simulations to study the influence of the stochastic nature of the discontinuities on the failure mechanism. We demonstrate the application of digital terrestrial photogrammetry in discontinuity characterization and distinct element simulations within a slate quarry. An accurately geo-referenced photogrammetry model is used to derive the slope geometry and to characterize geological structures. We first show how a discontinuity dataset, obtained from a photogrammetry model can be used to characterize discontinuities and to develop discrete fracture networks. A deterministic three-dimensional distinct element model is then used to investigate the effect of some key input parameters (friction angle, spacing and persistence) on the stability of the quarry slope model. Finally, adopting a stochastic approach, discrete fracture networks are used as input for 3D distinct element simulations to better understand the stochastic nature of the geological structure and its effect on the quarry slope failure mechanism. The numerical modelling results highlight the influence of discontinuity characteristics and kinematics on the slope failure mechanism and the variability in the size and shape of the failed blocks.

Spectroscopy of fission fragments using prompt-delayed coincidence technique

The time-stamp structure of the digital data acquisition system of the Indian National Gamma Array (INGA) has been utilized to carry out prompt-delayed coincidence technique for the spectroscopic study of fission fragments. This technique was found to be useful to determine the states above the long-lived isomer (with half-life up to ∼5 μs), present in the fission fragments. The angular correlation of γ-rays, emitted by the fission fragments, has also been used in the present INGA geometry to determine the spins of the de-exciting states.

A novel and inexpensive digital system for eye movement recordings using magnetic scleral search coils

After their introduction by Robinson (IEEE Trans Biomed Eng 10:137-145, 1963), magnetic scleral search coils quickly became an accepted standard for precise eye movement recordings. While other techniques such as video-oculography or electro-oculography may be more suitable for routine applications, search coils still provide the best low-noise and low-drift characteristics paired with the highest temporal and spatial resolution. The problem with search coils is that many research laboratories still have their large and expensive coil systems installed and are acquiring eye movement data with old, analog technology. Typically, the number of recording channels is limited and modifications to an existing search coil system can be difficult. We propose a system that allows to retro-fit an existing analog search coil system to become a digital recording system. The system includes digital data acquisition boards and a reference coil as the hardware part, receiver software, and a new calibration method. The circuit design has been kept simple and robust, and the proposed software calibration allows the calibration of a single coil within a few seconds.

A High-Resolution TDC-Based Board for a Fully Digital Trigger and Data Acquisition System in the NA62 Experiment at CERN

A time-to-digital converter-based system, to be used for most subdetectors in the high-flux rare-decay experiment NA62 at CERN SPS, was built as part of the NA62 fully digital trigger and data acquisition system in which the TDC Board (TDCB) and a general-purpose motherboard (TEL62) will play a fundamental role. While TDCBs, housing four high-performance time-to-digital converters (HPTDCs), measure hit times from subdetectors, the motherboard processes and stores them in a buffer, produces trigger primitives from different detectors, and extracts only data related to the lowest trigger level decision, once this is taken on the basis of the trigger primitives themselves. The features of the TDCB developed by the Pisa NA62 group are extensively discussed and performance data are presented in order to show its compliance with the experiment requirements.

Optimization of the National Superconducting Cyclotron Laboratory Digital Data Acquisition System for use with fast scintillator detectors

The Digital Data Acquisition System (DDAS) at the National Superconducting Cyclotron Laboratory (NSCL) has expanded to instrument arrays composed of fast-scintillator detectors. The expansion has motivated the development of software designed to optimize the time- and energy-resolving capabilities of the system, which is a collection of 16-channel FPGA-programmable modules running 12- and 14-bit ADCs with sampling frequencies of 100 and 250MSPS, respectively. Using the techniques described herein, the time resolution of the DDAS electronics has been substantially improved. For signal amplitudes occupying <10% the full range of the ADC, the time resolution of the DDAS electronics, measured online, has been reduced to <100ps and <40ps for 100MSPS and 250MSPS modules, respectively. A time resolution of ≈ 350ps, at 511keV, between two 38mm×38mm lanthanum bromide (LaBr3) detectors, equipped with Hamamatsu R6231 photomultiplier tubes (PMTs), has also been realized. Similar optimization techniques applied to the DDAS energy-extraction algorithms have yielded energy resolutions below 2% at 1.33MeV for both the 100 and 250MSPS digitizers using the same LaBr3 detectors. The techniques described in this work are broadly applicable to other digital acquisition systems that are capable of recording the digitized raw detector signals.

Digital data acquisition and processing.

A flow cytometer is made up of many different subsystems that work together to measure the optical properties of individual cells within a sample. The data acquisition system (also called the data system) is one of these subsystems, and it is responsible for converting the electrical signals from the optical detectors into list-mode data. This unit describes the inner workings of the data system, and provides insight into how the instrument functions as a whole. Some of the information provided in this unit is applicable to everyday use of these instruments, and, at minimum, should make it easier for the reader to assemble a specific data system. With the considerable advancement of electronics technology, it becomes possible to build an entirely functional data system using inexpensive hobbyist-level electronics. This unit covers both analog and digital data systems, but the primary focus is on the more prevalent digital data systems of modern flow cytometric instrumentation.

Autoclassification versus Cognitive Interpretation of Digital Bathymetric Data in Terms of Geomorphological Features for Seafloor Characterization

Finkl, C.W. and Makowski, C., 2015. Autoclassification versus cognitive interpretation of digital bathymetric data in terms of geomorphological features for seafloor characterization.The determination of seafloor geomorphological features has always been a difficult task, and it was not until the advent of marine remote sensing techniques that seafloor features could be accurately discerned. Airborne acquisition of digital bathymetric data provides a wealth of information that can be interpreted in different ways. This paper considers the pros and cons of computerized autoclassifications versus cognitive interpretations of seafloor features. The continental shelf off the southeast Florida coast contains LADS (laser airborne depth sounding) surveys that are here used to compare and contrast automated classifications of bathymetry with cognitive differentiation of marine geomorphological features. There are advantages and disadvantages associated with each approach, and the choice of methods depends on the purpose or goals of the project. Once seafloor features have been cognitively discerned from enhanced, color ramped, and vertically exaggerated bathymetry, machine classifications can be compared with known units. Using ArcGIS® ArcMap software, five- and seven-class unsupervised isocluster autoclassifications were found to moderately represent known bottom topography, whereas the interactive supervised autoclassification closely approximated cognitively discerned bathymetric patterns. Hand-drawn or digitized cognitively derived maps were more generalized than supervised computerized classifications based on training fields. Overall, both methods were found to be beneficial approaches, as they complement each other.

New Opportunities in Decay Spectroscopy with the GRIFFIN and DESCANT Arrays

The GRIFFIN (Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei) project is a major upgrade of the decay spectroscopy capabilities at TRIUMF-ISAC. GRIFFIN will replace the 8π spectrometer with an array of up to 16 large-volume HPGe clover detectors and use a state-of-the-art digital data acquisition system. The existing ancillary detector systems that had been developed for 8π, such as the SCEPTAR array for β-tagging, PACES for high-resolution internal conversion electron spectroscopy, and the DANTE array of LaBr3/BaF2 scintillators for fast γ-ray timing, will be used with GRIFFIN. GRIFFIN can also accommodate the new neutron detector array DESCANT (Deuterated Scintillator Array for Neutron Tagging), enabling the study of β-delayed neutron emitters. DESCANT consists of up to 70 detectors, each filled with approximately 2 liters of deuterated benzene, a liquid scintillator that provides pulse-shape discrimination (PSD) capabilities to distinguish between neutrons and γ-rays interacting with the detector. In addition, the anisotropic nature of n-d scattering as compared to the isotropic n-p scattering allows for the determination of the neutron energy spectrum directly from the pulse-height spectrum, complementing the time-of-flight (TOF) information. The installation of GRIFFIN is under way and first experiments are planned for the fall of 2014. The array will be completed in 2015 with the full complement of 16 clovers. DESCANT will be tested coupled with GRIFFIN in spring of 2015.

High Rate Measurements of the Neutron Camera and Broadband Neutron Spectrometer at JET

The Joint European Torus (JET, Culham, UK) is the largest tokamak in the world. JET has been upgraded over the years and recently it has also become a test facility of the components designed for ITER, the next step fusion machine under construction in Cadarache (France). At JET, the neutron emission profile of Deuterium (D) or Deuterium-Tritium (DT) plasmas is reconstructed using the neutron camera (KN3). In 2010 KN3 was equipped with a new digital data acquisition system (DAQ) based on Field Programmable Gated Array (FPGA). According to specifications, the DAQ is capable of high rate measurements up to 0.5 MCps. A new compact broadband spectrometer (KM12) based on BC501A organic liquid scintillating material was also installed in the same year and implements a similar DAQ as for KN3. This article illustrates the observations on the DAQ high count rate performance of both KN3 and KM12 in the latest JET D plasma experiments related to hybrid scenario and runaway electrons. For the latter, >1 MCps event rate was achieved with consequences on the behavior of the FPGA and on the reliability of the measurements.

Recent results from digital INGA at BARC–TIFR Pelletron Linac Facility and future plans

An experimental campaign aimed at studying various high spin phenomena using the Indian National Gamma Array (INGA) at the BARC–TIFR Pelletron Linac Facility has been successfully completed. The array consisting of a large number of Compton-suppressed clover detectors was coupled to a digital data acquisition system with 96 channels. The present system provides higher throughput, better energy resolution and better stability of gain for the multidetector Compton-suppressed clover array compared to its previous conventional system with analog shaping. Selected results from this array are discussed which highlight the exotic shapes, novel excitation modes and interesting isomers of the nuclei. The preliminary results from the experimental efforts to improve the sensitivity and capability of the array by adding ancillary detectors are also described briefly.

Expanding the potential of standard flow cytometry by extracting fluorescence lifetimes from cytometric pulse shifts.

Fluorescence lifetime measurements provide information about the fluorescence relaxation, or intensity decay, of organic fluorophores, fluorescent proteins, and other inorganic molecules that fluoresce. The fluorescence lifetime is emerging in flow cytometry and is helpful in a variety of multiparametric, single cell measurements because it is not impacted by nonlinearity that can occur with fluorescence intensity measurements. Yet time-resolved cytometry systems rely on major hardware modifications making the methodology difficult to reproduce. The motivation of this work is, by taking advantage of the dynamic nature of flow cytometry sample detection and applying digital signal processing methods, to measure fluorescence lifetimes using an unmodified flow cytometer. We collect a new lifetime-dependent parameter, referred to herein as the fluorescence-pulse-delay (FPD), and prove it is a valid representation of the average fluorescence lifetime. To verify we generated cytometric pulses in simulation, with light emitting diode (LED) pulsation, and with true fluorescence measurements of cells and microspheres. Each pulse is digitized and used in algorithms to extract an average fluorescence lifetime inherent in the signal. A range of fluorescence lifetimes is measurable with this approach including standard organic fluorophore lifetimes (∼1 to 22 ns) as well as small, simulated shifts (0.1 ns) under standard conditions (reported herein). This contribution demonstrates how digital data acquisition and signal processing can reveal time-dependent information foreshadowing the exploitation of full waveform analysis for quantification of similar photo-physical events within single cells. © 2014 The Authors. Published by Wiley Periodicals, Inc.

Fully Digital FPGA-Based Data Acquisition System for Dual Head PET Detectors

We present the development of a new fully digital, flexible, cost-efficient data acquisition system (DAQ) suitable for dual head Positron Emission Tomography (PET) scanners for small animal imaging applications. A free-running 12 bit octal channel Analog to Digital Converter (ADC), with 65 MHz sampling rate, was used for the digitization of the detector signals. The digitized data were fed into a Spartan 6 Field Programmable Gate Array (FPGA) for event processing. An embedded system was developed for the acquisition, using Xilinx’s Embedded Development Kit (EDK) and Microblaze processor. A digital version of the Constant Fraction Discriminator (CFD) method was implemented in the FPGA, in order to achieve higher time resolution than the ADC sampling period, eliminating the need of an external mixed-signal device. The obtained information using FPGA includes: event timing, energy determination-discrimination, position determination and coincidence processing. The online processing of potential coincident events, significantly reduces the amount of data that will be transmitted to the computer. Coincident events are written temporarily to an external memory provided on a development board and are transferred to a Personal Computer (PC), via Ethernet link, for image reconstruction. Minimal post processing of the data is required prior to reconstruction. A small detector pair consisting of a BGO array coupled to a Position Sensitive Photomultiplier Tube (PSPMT) was used for the evaluation of the readout system. Obtained results prove that the proposed architecture can be used for the readout of dual head PET detectors for small animal imaging applications.

Digital data acquisition for a CAD/CAM-fabricated titanium framework and zirconium oxide restorations for an implant-supported fixed complete dental prosthesis

This dental technique report describes a digital workflow with digital data acquisition at the implant level, computer-aided design and computer-aided manufacturing fabricated, tissue-colored, anodized titanium framework, individually luted zirconium oxide restorations, and autopolymerizing injection-molded acrylic resin to fabricate an implant-supported, metal-ceramic-resin fixed complete dental prosthesis in an edentulous mandible. The 1-step computer-aided design and computer-aided manufacturing fabrication of titanium framework and zirconium oxide restorations can provide a cost-effective alternative to the conventional metal-resin fixed complete dental prosthesis.

Evaluation of a Thermal-Tuft Probe for Turbulent Separating and Reattaching Flows

The validation and testing of a thermal-tuft probe is described in detail. The thermal tuft consists of three parallel wires where the middle wire is heated and the two lateral wires act as resistance thermometers, thereby sensing the flow direction. The probe's function principle is validated in an acoustic resonator that generates a nearly sinusoidal velocity perturbation with zero mean. It is shown that the variation in electrical resistance of the sensing wires is a measure of the flow direction. The probe's sensitivity to the heater current in the central wire and to the flow angle is also investigated. The electronic circuit is validated by placing the probe on a mechanical shaker. The output voltage is shown to be consistent with the variation in electrical resistance of the sensing wires. The flow direction can thus simply be measured by recording the probe's output voltage with a single digital data-acquisition channel. Finally, the thermal tuft is evaluated in a low-speed, pressure-driven, turbulent, separation-bubble flow. It is shown that the forward-flow fraction and the intermittent frequency can be measured with an uncertainty of about ±1.5%. The positions of separation and reattachment in the test section, measured with the thermal tuft, are consistent with flow-visualization experiments reported elsewhere.

WIRELESS DATA ACQUISITION SYSTEM USING BLUETOOTH TECHNOLOGY FOR INFRASONIC RECORDS

Advancements in electronics provide a vital new option for implementation of low-frequency smart sensors that can perform signal processing close to the sensors and transmit the data wirelessly. These smart sensors can improve the efficiency of an automatic classification system and reduce the cost of actual infrasound microphones. The design of a digital wireless data acquisition system using a QF4512 programmable signal converter from Quickfilter Technologies, a MSP430 microcontroller from Texas Instruments and a F2M03GLA Bluetooth module from Free2move for infrasonic records is presented in this paper. The digital wireless data acquisition system has passed extensive laboratory and field tests (e.g. with man-made explosions).

RESCUE - reduction of MR-SNR-degradation by using an MR-synchronous low interfering PET acquisition technique.

The combination of PET and MRI is a challenging task, since both imaging modalities might influence each other. For unaffected imaging performance, PET detectors need to be untouched by the MR operation (MR-compatible) and RF-silent. The latter requirement is demanding, as the digital Data Acquisition and Control Architecture (DACA) produce noise in the MRI receive chain and thus deteriorate the Signal-to-Noise Ratio (SNR). To reduce these MRI-SNR degradations, we propose “RESCUE”, a MR-synchronously gated PET data acquisition technique. By controlling the PET-modules’ digital data acquisition in terms of interrupting the digital SiPM (dSiPM) operation during the MR signal receive phases, potential RF interferences can be reduced. The concept and design of RESCUE are based on the DACA of Hyperion-IID using 960 dSiPMs from Philips which are spread over 10 PET modules, every module containing 6 detector stacks. 16 dSiPMs are populated on one detector stack and a local FPGA per stack is used to clock and configure the dSiPMs and acquire data from them. To interrupt the PET data acquisition when the MRI is in receive-mode, an MRI trigger signal is sent via the backbone of the PET insert to all PET modules. In the stacks, the dSiPM-operation is interrupted by gating the dSiPMs’ input clock signals. This clock switch-off needs to be performed at a point in time when no dSiPM cell recharge takes place, as sensor-damage might otherwise occur. We implemented FPGA firmware to stop the above described dSiPM operation and to restart it upon release of the gating. PET-data was acquired using gating-sequences and analysis of sensor data acquired before and after interruption showed that the sensors were working properly after reapplying their clock signals. More details and MRI SNR-measurement results to demonstrate the interference reduction obtained with RESCUE will be presented at the conference.