Coincidence Unit Research Articles

Arduino-Based Readout Electronics for Nuclear and Particle Physics.

Open Hardware-based microcontrollers, especially the Arduino platform, have become a comparably easy-to-use tool for rapid prototyping and implementing creative solutions. Such devices in combination with dedicated front-end electronics can offer low-cost alternatives for student projects, slow control and independently operating small-scale instrumentation. The capabilities can be extended to data taking and signal analysis at mid-level rates. Two detector realizations are presented, which cover the readouts of proportional counter tubes and of scintillators or wavelength-shifting fibers with silicon photomultipliers (SiPMs). The SiPMTrigger realizes a small-scale design for coincidence readout of SiPMs as a trigger or veto detector. It consists of a custom mixed signal front-end board featuring signal amplification, discrimination and a coincidence unit for rates of up to 200 kHz. The nCatcher transforms an Arduino Nano to a proportional counter readout with pulse shape analysis: time over threshold measurement and a 10-bit analog-to-digital converter for pulse heights. The device is suitable for low-to-medium-rate environments up to 5 kHz, where a good signal-to-noise ratio is crucial. We showcase the monitoring of thermal neutrons. For data taking and slow control, a logger board is presented that features an SD card and GSM/LoRa interface.

Development of the digital multichannel analyzer for liquid scintillation detection

The new digital multichannel analyzer (DMCA) based on field programmable gate array (FPGA) technology is successfully developed, and it is used for liquid scintillation detection. The performance of this system has been evaluated. The analog signal output emanating from the photomultiplier tube (PMT) is transformed into digital signals through the utilization of an amplifier and a high-speed analog-to-digital converter (ADC). Information about the energy, timing, and pulse shape characteristics of the radiation event is contained in the digital signal. Subsequently, this digital signal is directed towards the FPGA for digital signal processing. In order to reduce the thermal and electronic noise, the dual-channels configuration and the signal coincidence function are added to DMCA for optimizing the validity of signal. The signal coincidence unit is designed within the FPGA, optimizing the synchronization of signals. The measurement data is transmitted to a computer via USB interface. The energy spectra of gamma sources, namely 22Na, 60Co, and 137Cs, as well as the alpha source 232Th, were measured utilizing the newly developed system. Notably, thermal and electronic noise interference is reduced in the coincidence measurement mode, and the coincidence energy spectra are improved compared to the singles measurement. In contrast to commercially available systems, the advantages of our design in terms of miniaturization, cost-effectiveness, and expandability are demonstrated.

Nuclear astrophysics studies at NIPNE

I will present results of doing nuclear astrophysics research at the National Institute for Physics and Nuclear Engineering, Bucharest-Magurele in the last 2-3 years.Own Nuclear Astrophysics Group (NAG) is focused on the basic types of experiments:-Direct measurements at low and very low energies with ion or alpha beams from the local 3 MV tandetron accelerator. We concentrate on activation measurements. The use of the ultra-low background laboratory in a salt mine at Slanic-Prahova, about 120 km away and of a beta-gamma coincidence unit at home is providing competitive sensitivity.-Indirect measurements done with beams at international facilities with radioactive beams: TAMU and RIBF RIKEN.With help from colleagues, I will mention some theory advances, too.

Recording of Coincidence Signals in a Software Medium

A virtual coincidence unit, a virtual counter and a virtual timer were developed via a software in this study. Different frequency signals supplied from a function generator were sent to a real coincidence unit. The same signals were transmitted to the virtual coincidence unit via a digitizer. Output signals of the real and virtual coincidence units were counted by real and the virtual counters. Count periods were set through real and virtual timers. For different count periods, coincidence counts obtained from the virtual counter were compared with those of the real one. It was seen that obtained results were highly compatible with each other for low frequency (25 – 55 Hz) signals.

Standardization of the radionuclides 60Co and 59Fe by digital 4πβ(PC)-γ(NaI) coincidence counting

The digital coincidence counting (DCC) technique has been developed at NIM, China to replace the classical analog coincidence units in the 4πβ-γ counting system. The detector system comprises two NaI (Tl) γ-ray detectors and a 4πβ proportional counter (PC) operated with a mixture of argon and methane at atmospheric pressure in a gas flow arrangement. To update the activity results of radionuclide 60Co in the KCDB and contribute to the APMP.RI(II)-K2.Fe-59 comparison, 60Co and 59Fe dry sources were prepared and measured using the digital 4πβ(PC)-γ(NaI) coincidence system by applying the efficiency extrapolation method. For 60Co nuclide, the activity concentration value equal to 290.6kBqg−1 with a relative standard uncertainty of 0.26%, is consistent with the result given by the calibrated ionization chamber. For the nuclide 59Fe, the activity concentration value at the reference date was 471.7kBqg−1 with a relative standard uncertainty of 0.34%. This value is in good agreement with the result obtained with the HPGe γ spectrometry, which was calibrated by using a series of standard point sources from PTB.

Design and Implementation of a High Resolution DAQ System for an (e, 2e+ion) Electron Momentum Spectrometer

An (e, 2e+ion) Electron momentum spectrometer (EMS) upgraded from the third-generation (e, 2e) spectrometer is constructed in the University of Science and Technology of China (USTC). In the EMS, the energy-momentum density of electrons is derived through the charge measurement using the signals of the position sensitive detector (PSD). The information of ion fragments is derived through the time measurement and that information will be used for more research on collision dynamics. A PXI-based data acquisition (DAQ) system was designed. The system mainly consists of a 6-channel charge digital module (CDM) and a 9-channel time digital module (TDM). Shaping amplifiers (SAs) are also designed for charge measurement with CDM. According to the design specification, the CDM with SAs needs to measure charge from 100 to 900 fC with an accuracy of better than 1%. The TDM needs to measure the flight time from 0 to 15 us with a resolution of better than 100 ps. The TDM and CDM can be combined to run synchronously using a coincidence unit which also rejects the background events based on the tracking information of the electrons and the ions. Test results indicate that, within the dynamic range, the accuracy of the CDM is better than 0.4%. The RMS time resolution of better than 30 ps is achieved by using the method of time-to-digital converter (TDC) implemented in a field-programmable gate arrays (FPGA). The DAQ system has been assembled and works well with the EMS detectors.

Note: A high-efficiency multi-coincidence method designed for molecular fragmentation studies.

A high-efficiency multi-coincidence method is developed based on the hardware electronic multiple coincidence units. The multi-hit signals originating from one single detector can be selected and measured in coincidence. The performance of the method is tested by the electron impact three-body fragmentation of CO2(3+). Compared to the conventional method, the relative and absolute coincidence efficiencies of the triple-coincidence measurement are improved by about 200 and 3 times, respectively.

A simple digital delay for nuclear physics experiments

A simple high precision digital delay for nuclear physics experiments was developed using fast ECL electronics. The circuit uses an oscillator synchronized with the signal to be delayed and a presettable counter. It is capable of delaying a negative NIM signal by 2µs with a precision better than 50ps. The circuit was developed for use in slow-fast coincidence units for Perturbed Angular Correlation spectrometers but it is not limited to this application.

A Design Configuration of an FPGA-Based Coincident Spectrometry System

In the past, most of popular coincidence spectrometers were normally based on traditional electronics techniques such as time to amplitude conversion or logic selecting coincidence unit. They were complicated and it is not convenient for us to use them. This paper deals with a new design of a contemporary coincidence spectrometer which is based on Field Programmable Gate Arrays (FPGA) devices via Digital Signal Processing (DSP) techniques with Hardware Description Language (VHDL). The outstanding advantage of DSP techniques and FPGA technology is capable of enhancement of the quality of the experimental measurements for nuclear radiation. The designed configuration of the traditional system was tested on the PCI 7811R board of National Instruments while the digital systems were establishing with FPGA devices. The purpose of this work is referring to the principle for construction of an FPGA-based system capable of replacing a conventional system. Therefore, a novel approach for in-house development of digital techniques is presented. The method for designing the system is utilization of slow-fast coincidence configurations with two HPGe detectors obtaining a pair of coincidence events, processing data in DSP algorithms. The significant and noticeable results are the operating frequency of 80 MHz and system timestamp window of approximately 10 ns.

The Basis for Design and Manufacture of a DSP-Based Coincidence Spectrometer

The coincidence technique and the coincidence spectroscopy have been developed and applied for over 40 years. Most of popular coincidence measurement systems were based on analog electronics techniques such as time to amplitude conversion (TAC) or logic selecting coincidence unit. The above-mentioned systems are relatively cumbersome and complicated to use. With the strong growth of digital electronics techniques and computational science, the coincidence measurement systems will be constructed simpler but more efficient with the sake of application. This article presents the design principle and signal processing of a simple two-channel coincidence system by a technique of digital signal processing (DSP) using Field Programmable Gate Arrays (FPGA) devices at Nuclear Research Institute (NRI), Dalat.

Letter of congratulations on the publication of Biomedical Engineering Letters

I congratulate you on the publication of Biomedical Engineering Letters. I have read through the first inaugural issue and find it represents the kind of biomedical engineering that interests me. The review article Recent Research Trends in Nanoscale Electro-mechanical Systems for Bio-medical Applications described electrical recording of the cell potential from a beating cardiomyocyte using a bioprobe with the nanoFET. It also described the problems with interference by noise. The review article Monitoring Physiological Signals Using Nonintrusive Sensors Installed in Daily Life Equipment included useful information to me on the use of capacitively coupled electrodes to measure the ECG without contact to the body. The review article Mitochondrial Medicine and Biomedical Engineering described the way mitrochondia are closely related to the macroscopic energy balance of the human body. The original article Development of FPGAbased Coincidence Units with Veto Function described a field programmable gated array (FPGA)-based coincidence detector for positron emission tomography (PET). The original article An Improved Technique to Consider Mismatches between fMRI and EEG/MEG Sources for fMRI Constrained EEG/MEG Source Imaging addresses the problem that fMRI has slow temporal resolution compared to the fast EEG/ MEG temporal resolution. The original article Characteristics of PLLA Films Blended with PEG Block Copolymers as Additives for Biodegradable Polymer Stents found that PLLA films blended with hydrophilic PEG-based block copolymer as additives demonstrated improved swelling property as well as mechanical properties. The original article Compression Induced Contrast Change in X-ray Mammograms: A Simulation Study on breast electrography found that breast compression may be useful to detect the harder breast tumors. The original article In Vivo Magnetic Resonance Electrical Impedance Tomography of Canine Brain: Disease Model Study of Ischemia and Abscess describes how injecting 5 mA of electric current when using MRI electrical impedance tomography produces a conductivity contrast corresponding to brain ischemia and abscess. The original article A New Approach to Ophthalmic Imaging with Concave Array Transducers describes how using a concave array in ultrasonic imaging yields high-spatial, high-quality ophthalmic images. These articles should assist biomedical engineers who are developing electrical and mechanical sensors to solve important medical problems such as to noninvasively measure intracranial pressure to monitor hydrocephalus, to monitor the elderly who remain in their homes, etc. These articles should assist biomedical engineers who are developing chemical sensors to solve important medical problems such as implantable glucose sensors to develop a closed loop system to treat diabetes, etc. These articles should also assist biomedical engineers who are developing therapeutic medical devices such as cardiac and liver ablation to destroy tissue such as cancer. I look forward to reading more future articles that inform biomedical engineers of the latest information that will help them in their development of diagnostic and therapeutic methods and equipment to contribute to improved health care.

A digital coincidence measurement system using FPGA techniques

Abstract A field programmable gate array (FPGA) based digital coincidence system has been developed to use with NaI scintillators for field applications. The analog output signal from the photomultiplier anode is directly transferred into digital signals by pulse height for pulse width conversion. The digital signal contains the energy and timing information of the radiation events. The pulse width is then measured by a vernier type of time-to-digital converter (TDC). The timing information of radiation events is recorded and analyzed by a coincidence unit. Both the TDC unit and the coincidence unit are implemented using a commercial available FPGA board. The measured data is then sent to a personal computer for spectrum display. Efficiency as well as energy calibration has been performed. The system showed a timing resolution about 13 ns and an energy resolution of 12% for 0.511 MeV annihilation gammas; it also successfully demonstrated the background rejection ability through coincidence measurement.

Development of FPGA-based coincidence units with veto function

Purpose A coincidence detector is an essential unit to acquire distribution of radioisotopes in positron emission tomography (PET) systems. The coincidence pairs rapidly increase as the number of detector modules increase. To make this system compact, flexible, and conveniently controllable, a field programmable gated array (FPGA)-based coincidence detector was developed.

Self-Assembly of MgPc Molecules on Polar FeO Thin Films

The spatial arrangement of magnesium phthalocyanine (MgPc) molecules has been investigated on FeO films grown on Pt(111) with low-temperature STM. The polar oxide film forms a coincidence lattice with the Pt support and exhibits a surface dipole between the Fe δ+ and O δ- layers that varies across the coincidence unit cell. The MgPc molecules preferentially adsorb in regions with large dipole strength. The rotational orientation of the MgPc molecules, on the other hand, is determined by their interaction with the atomic Fe-O lattice.

A prototype of very high-resolution small animal PET scanner using silicon pad detectors

A very high-resolution small animal positron emission tomograph (PET), which can achieve sub-millimeter spatial resolution, is being developed using silicon pad detectors. The prototype PET for a single slice instrument consists of two 1 mm thick silicon pad detectors, each containing a 32×16 array of 1.4×1.4 mm pads readout with four VATAGP3 chips which have 128 channels low-noise self-triggering ASIC in each chip, coincidence units, a source turntable and tungsten slice collimator. The silicon detectors were located edgewise on opposite sides of a 4 cm field-of-view to maximize efficiency. Energy resolution is dominated by electronic noise, which is 0.98% (1.38 keV) FWHM at 140.5 keV. Coincidence timing resolution is 82.1 ns FWHM and coincidence efficiency was measured to be 1.04×10 −3% from two silicon detectors with annihilation photons of 18F source. Image data were acquired and reconstructed using conventional 2-D filtered-back projection (FBP) and a maximum likelihood expectation maximization (ML-EM) method. Image resolution of approximately 1.45 mm FWHM is obtained from 1-D profile of 1.1 mm diameter 18F line source image. Even better resolution can be obtained with smaller detector element sizes. While many challenges remain in scaling up the instrument to useful efficiency including densely packed detectors and significantly improved timing resolution, performance of the test setup in terms of easily achieving sub-millimeter resolution is compelling.

Fast and compact multichannel photon coincidence unit for quantum information processing

We present a fast and compact multichannel coincidence unit to count all possible single and coincidence detection events in an experiment with eight single-photon detectors at once. Using high-speed electronics and a microcontroller, this device is able to process up to 800000events∕s. The coincidence window can be tuned within a range of 4–12ns. The device can be easily scaled to any number of input channels and is thus ideally suited for efficient multiphoton quantum information processing.

Measurement of the two-photon correlation of synchrotron radiation in the VUV region by a delay-time modulation technique.

The two-photon correlation (second-order coherence) of synchrotron radiation in the VUV region (hnu = 55 eV) has been measured using a novel photon-counting method. A new technique has been developed to measure a small bunching effect by using a coincidence unit composed of a constant fraction discriminator, a time-to-amplitude converter (TAC), a single-channel analyzer (SCA) and two solid-state switches. The path of the circuit through which the stop signal for the TAC passes can be changed by a control voltage generated by a function generator, and the relative arrival time of two photons on condition that the output signal from the SCA appears is consequently changed. By modulating the arrival time and measuring the output rate from the SCA with a digital lock-in amplifier, an apparent bunching effect has been observed which is characteristic of the chaotic light. The electron-beam emittance in the horizontal direction was estimated as 39(-8)(+13) nm rad by this experiment, and the value was consistent with the designed value of 36 nm rad.

The precedence effect for noise bursts of different bandwidths. I. Psychoacoustical data

The human ability to localize a direct sound source in the presence of reflected sounds is well known as localization dominance due to the precedence effect, formerly also called ‘‘the law of the first wavefront.’’ The fact that the localization dominance partly fails for signals with a very narrow bandwidth raises the question of whether the localization dominance requires cross-frequency-band interaction. To investigate this, a psychoacoustic experiment was conducted in which the perceived lateralization of a noise burst ( 300s ITD) in the presence of a reflection ( 300s ITD)wasmeasured. The parameters in this experiment were the inter-stimulus interval (ISI) and the bandwidth. The first was varied among the following values: 0.0ms and then from 1.0ms in steps of 0.5ms to 4.0ms. The bandwidth was adjusted to be either 100Hz, 400Hz, or 800Hz. The data of the listeners clearly show that localization dominance becomes more stable, especially with regard to the dependence on the ISI, when the bandwidth is increased. At the smallest bandwidth under examination (100Hz), localization dominance cannot be observed for some of the listeners anymore, while others perceive at least the sound coming from the lateral side where the direct sound source is positioned; nevertheless, their auditory event varies strongly with the ISI. A signal analysis reveals that in the first case, the precedence effect does not seem to have any influence. Here, the listeners rather base their judgements on the ongoing part of the sound. The signal analysis also indicates that it is not necessary to assume that the signals in the different frequency bands interact directly with each other while being processed (e.g., cross-frequency coincidence units). It rather seems to be sufficient to average across those bands.

The muon pretrigger system of the HERA-B experiment

One of the main goals of the HERA-B experiment at DESY in Hamburg, Germany, is to study the properties of B-mesons with the emphasis on CP violation. B-mesons are produced in hadronic interactions of a 920-GeV proton beam with an internal wire target. An effective bunch crossing rate of about 8.5 MHz leads to about 200 charged tracks per event. Therefore, a highly selective and efficient trigger system providing high suppression of background events is required. The HERA-B trigger system consists of four levels. A rate reduction factor of 200 is aimed at by the first-level trigger (FLT). The muon pretrigger system, as a part of the FLT, is a modular system consisting of about 100 large-size VME modules of three different types: the pretrigger link board (PLB), the pretrigger coincidence unit (PCU), and the pretrigger message generator (PMG). The data rate processed by the pretrigger system is about 19.5 GByte/s. The PLBs process digitized hit information in eight independent electronic channels in parallel. Every electronic channel handles 32 bits of hit information received from the front-end driver buffer system. Optical links operating at 800 Mb/s transmit the data after serialization to PCUs, which calculate coincidences using complex programmable logic devices. The PMGs transform this coincidence information into messages for the FLT processors. The concept and design as well as results of the muon pretrigger running at HERA-B are presented.

Studies on electron emission during grazing impact of keV-hydrogen atoms on a LiF(0 0 1) surface via translational spectroscopy

Neutral hydrogen atoms with energies ranging from about 1 to 20 keV are scattered from a clean and flat LiF(0 0 1) surface under grazing angles of incidence. By detection of time-of-flight (TOF) spectra in coincidence with the signal of an electron number detector, we study electron emission and excitation phenomena. We present recent progress in an on-line processing of spectra by means of a double coincidence unit.