Digital Spectrometer Research Articles

Effect of Decreasing Aperture Diameter on Signal Transmission from the Scintillator to the Photomultiplier Tube Over a Wide Energy Range

In this paper, we study the effect of decreasing aperture diameter on signal transmission from the scintillator to the PMT. The apertures have been inserted directly between the scintillator and the photomultiplier. Three different aperture diameters have been used over a wide energy range. A newly developed fast digital spectrometer has been utilized for experimental measurement in the radial channel of the VR-1 research reactor. The detector signals with and without inserted apertures have been measured and evaluated. The aim of our research was to determine the effect of the apertures on the spectral quality, energy range and the evaluated physical quantities.

Square Parametric Excitation: A Digital Resonant Method for the Quadrupole Ion Trap.

Digital ion trap technology is an alternate method for driving quadrupole ion traps and mass filters using variable frequency, fixed amplitude RF square waves in place of variable amplitude, fixed frequency RF sine waves. This technique offers some advantages such as an increase in the high mass analysis range by varying frequency and lower overall voltage requirements. Here, we present a complex square waveform developed for resonant parametric excitation in a quadrupole linear ion trap. Unlike traditional resonance methods, the driving RF square wave and auxiliary square wave are coupled using the same digital circuitry without the need for transformer coupling. In this work, we use this complex waveform to selectively excite the first order parametric resonances of ion motion. The square parametric excitation method presented here employs a simple and repetitive circuit design consisting of a low-voltage waveform generator followed by a series of high-voltage MOSFET switches. This design allows for resonance methods to be easily implemented in the all-digital quadrupole. The complex square waveform can perform the same useful functions as sine wave auxiliary signals, such as selective mass elimination and mass isolation. We also demonstrate that the mass resolution performance and S/N of our digital mass spectrometer is improved by applying the complex square waveform during ion ejection.

Time interval distributions of nuclear events in a digital spectrometer

This study compares the theoretical formula for time interval density distributions (TIDs) in counters with pileup rejection to TIDs measured using a digital spectrometer with trapezoid filtering. The TIDs were derived from successive time stamps of 60Co and 133Ba γ rays detected with a HPGe spectrometer. The results demonstrate that the theoretical formula is applicable up to 40% count loss and can be used to retrospectively deduce the incident event rate.

Direct Performance of Triple-Stage Tandem Mass Spectrometry Analysis Using Dual-Direction Dipolar Excitation in a Digital Linear Ion Trap.

The ion trap mass spectrometer offers a unique advantage over other mass spectrometers by enabling multistage tandem mass spectrometry analysis with a single mass analyzer. It is employed to generate fragment ions through collision-induced dissociation (CID) usually by applying alternating current (AC) signals to a pair of electrodes for dipole excitation. The process of achieving double-stage tandem mass spectrometry analysis (MS/MS) in the mass spectrometer involves successive stages of injection, cooling, isolation, excitation, and scanning. For triple-stage tandem mass spectrometry analysis (MS/MS/MS), additional stages of isolation, cooling, and excitation need to be added based on the MS/MS analysis, resulting in a complex and time-consuming mass spectrometry workflow. In this study, a digital ion trap technology with the method of simultaneously applying dipole excitation signals to two pairs of electrodes in the ion trap was developed. This allows fragmentation of the precursor ion in one direction while exciting the first-generation product ions in the other direction, enabling direct acquisition of MS/MS/MS spectra. This approach simplifies the process of tandem mass spectrometry, as demonstrated by experimental studies on methamphetamine, which show that dual-direction excitation effectively reduces workflow and enhances the intensity of product ions. Additionally, the method of direct MS/MS/MS spectra achieved through dual-direction excitation in a digital ion trap mass spectrometer allows for a lower q value of the precursor ion owing to a pseudopotential well depth that is 1.648 times greater than that of a traditional sinusoidal ion trap. The experiments of analyzing high concentration n-butyl acetate and isobutyl acetate have shown that the implementation of MS/MS/MS analysis using dual-direction excitation can provide more mass spectral information and effectively distinguish between the two isomeric samples. The results of direct triple-stage spectra obtained by this technique for several typical volatile hazardous chemicals demonstrate the method's capability for rapid analysis and detection of such substances. In summary, the developed method of dual-directional excitation coupled with digital ion trap technology enables direct performance of triple-stage tandem mass spectrometry analysis, improving fragment ion intensities and providing more valuable mass spectral information. It offers advantages such as simplified workflows, faster analysis, and enhanced accuracy for analyzing compounds with low mass fragment ions.

Development of a low-cost digital gamma spectrometer using an STM32F4 microcontroller

The digital pulse processing unit is the main part of a digital gamma spectrometer.

Mathematical Considerations in Energy Spectrum Recovery for Digital Energy Spectrometers

Mathematical Considerations in Energy Spectrum Recovery for Digital Energy Spectrometers

Development of low-cost digital gamma spectrometer using ARM Cortex-M Type Microcontroller Unit

Recently, digital gamma spectrometers have replaced analog ones due to their durability, flexibility, and compact size. The main part of the digital gamma spectrometer is the digital pulse processing (DPP) unit. The implementation of the DPP unit using the ARM Cortex-M-based microcontroller units is a recent attractive approach. This originates from their advanced features and low cost. In this paper, we propose an implementation of the DPP unit using the ARM Cortex-M3-based microcontroller unit. The targeted detector with this implementation is the sodium iodide detector. However, this implementation is based on less than 2 MS/s sampling rate, it is guaranteed experimentally to cope with input count rates up to 47 kC/s. This results from our specific proposed methodology for extracting pulse height from the trapezoidal-shaped pulses.

Synthesis of Silver Nanoparticles Using Novel Chemical Solution Method as Antibacterial Applied on Cosmetic Cotton Balls

This research aimed at preparing silver nanoparticles using the Novel chemical method, obtained as a black precipitate silver NPs. The sample was examined by using digital spectrometer device to find a degree of absorbency and its wavelength and particle by mathematical equation. Microbiology tests were carried out to determine the effectiveness of the sample in killing bacteria using the dilution method. After dissolving Silver NP`S in 5% acetic acid concentration, and covering the cotton balls with a solution of silver NPs to test the effectiveness of the sample using Two different concentrations of (0.5ml/g), and (0.25ml/g) and using two types of bacteria which causes skin blisters staphylococcus and streptococcus it is found that more concentration of the silver NPs solution has increased of killing both types of bacteria by staphylococcus (100%) and streptococcus (75%).

Health risk assessment and statistical analysis of natural radioactivity in the uranium exploration area of Zabili, Chad

ABSTRACT The activity concentrations of natural radionuclides 226Ra, 232Th and 40K in 19 soil samples from Zabili uranium exploration area were measured using a low-background digital gamma-ray spectrometer equipped with broad energy germanium detector. The activity concentrations of 238U, 232Th, and 40K range from 16.5 to 1110.9 Bq.kg−1, 19.45 to 76.97 Bq.kg−1, and 3.28 to 839.5 Bq.kg−1, with their mean values of 478.0, 58.9, and 562.5, respectively. In addition, radiological hazard parameters from the activity concentrations obtained were assessed by estimating radium equivalent activity, external and internal hazard index, indoor and outdoor absorbed gamma dose rate and the corresponding annual effective dose, effective dose rate to different body organs and tissues, and excess lifetime cancer risk. Derived radiological hazard indices have been revised in accordance with relevant national and international legislation and guidelines. The radiological hazard parameter values were found to be above the relevant limit values for soils. In order to investigate the distribution of radionuclides and associated health hazard parameters in the study area, a statistical study was performed.

Synchronized Reverse Scan Collision Induced Dissociation in Digital Ion Trap Mass Spectrometer for Improving Fragment Ion Detection

Development of fragment ion detection methods is of great importance for mass spectrometer advancement or substance identification. To date, collision induced dissociation (CID) remains the most commonly used ion activation method in MS/MS experiments, and the effectiveness of CID in an ion trap mass spectrometer is limited by low mass cutoff and weak fragmentation yields. Theoretically, controlling the q value is the key to maintain the fragment efficiency and trapping efficiency of MS/MS, thus improving the detection of fragment ion, while currently reported techniques usually require complex circuitry and often produce different CID patterns. In this paper, with the developed synchronized reversed scanning-collision induced dissociation (SRS-CID) technique, we demonstrate its effective improvement in fragment ion detection. The SRS-CID is implemented on a digital ion trap mass spectrometer (DITMS) by reverse scanning the q values during CID process, or specifically, the frequency is increased during the CID process. With the SRS-CID technique, the fragmentation efficiency of precursor ions can be slightly improved. For reserpine analyte, the trapping efficiency for low-mass fragment ions is improved at least 3 times, and for YGGFL, the trapping efficiency for low-mass fragment ions is improved at least 9 times. These experimental results can also be validated by simulations, and the kinetic energy variation plot suggests consecutive fragmentation occurs. In any case, the SRS-CID provides a solution to the low efficiency of fragment ion detection during tandem MS analysis, which will certainly be useful in the future.

Study of timing performance parameters for a SiPM-based digital positron annihilation lifetime spectrometer

Abstract Positron annihilation lifetime spectroscopy (PALS) is a popular method for studying defects in materials. With the development of fast digital oscilloscopes and digitizers, the conventional analog positron annihilation lifetime (PAL) spectrometer is being replaced by a digital PAL spectrometer. Recently, newly conducted research has developed a PAL spectrometer using a silicon photomultiplier (SiPM) instead of a photomultiplier tube (PMT). Timing resolution of PAL spectrometer needs to be improved to identify the lifetimes of positrons. Many parameters affect the timing performance of a SiPM-based digital PAL spectrometer: bias voltage, pulse smoothing, and the constant fraction value of digital constant fraction discrimination (dCFD). Timing resolution depends on the radiation energy, but only a few studies have considered the energy difference of 1274 keV and 511 keV. In this study, we optimized the timing performance parameters of the SiPM-based digital PAL spectrometer by conducting the timing resolution measurements using two γ-ray sources (22Na and 60Co). With a 32 V bias voltage, 5th degree polynomial fitting method, and optimal constant fraction value, we optimized the timing resolution of our SiPM-based digital PAL spectrometer. Furthermore, the optimal constant fraction value depended on the γ-ray energy and we verified it by timing resolution measurement using 207Bi. We studied the reason why performance parameters have optimal conditions and the optimal constant fraction value varies depending on the γ-ray energy. With optimized performance parameters, we measured the lifetime spectrum of pure silicon to confirm the SiPM-based digital PAL spectrometer. The timing resolution function of the SiPM-based digital PAL spectrometer was 185.6 ps.

Experimental investigation of the ADC sampling rate effect on the digital gamma spectrometry

Gamma spectrometer is not available in many laboratories because it is very expensive. Analog to digital converter ADC is the basic component of digital gamma spectrometers. The sampling rate of the ADC plays an important role in determining the performance and the cost of the gamma spectrometers. This paper investigates experimentally the ADC's sampling rate effect on the performance of the gamma spectroscopy. The conducted experiment started by sampling a real pre-amplifier output. Then, the acquired samples have been processed at different sampling rates to build the dedicated gamma spectrums. During the processing of the sampled signals, three different digital filters have been tested to distinguish their effect on the energy resolution when the sampling rate is reduced. The results of this experimental investigation will help later in proposing new low-cost and efficient gamma spectrometer prototypes.

Detection of Trace Explosives Using a Novel Sample Introduction and Ionization Method.

A novel sample introduction and ionization method for trace explosives detection is proposed and investigated herein, taking into consideration real-world application requirements. A thermal desorption sampling method and dielectric barrier discharge ionization (DBDI) source, with air as the discharge gas, were developed. The counter flow method was adopted firstly into the DBDI source to remove the interference of ozone and other reactive nitrogen oxides. A separated reaction region with an ion guiding electric field was developed for ionization of the sample molecules. Coupled with a homemade miniature digital linear ion trap mass spectrometer, this compact and robust design, with further optimization, has the advantages of soft ionization, a low detection limit, is free of reagent and consumable gas, and is an easy sample introduction. A range of common nitro-based explosives including TNT, 2,4-DNT, NG, RDX, PETN, and HMX has been studied. A linear response in the range of two orders of magnitude with a limit of detection (LOD) of 0.01 ng for TNT has been demonstrated. Application to the detection of real explosives and simulated mixed samples has also been explored. The work paves the path to developing next generation mass spectrometry (MS) based explosive trace detectors (ETDs).

An Integrated Digital Magnetic Resonance Imaging Spectrometer

An integrated digital magnetic resonance imaging spectrometer was proposed in this study. By using the FPGA chip Artix7 200T, timing control, data processing, digital frequency conversion and phase control were implemented into a single-chip, thus effectively improved timing accuracy and phase accuracy, while avoided the structural design complexity caused by multi-board connection and improved system integration and imaging quality.

Portable Digital Linear Ion Trap Mass Spectrometer Based on Separate-Region Corona Discharge Ionization Source for On-Site Rapid Detection of Illegal Drugs.

As narcotic control has become worse in the past decade and the death toll of drug abuse hits a record high, there is an increasing demand for on-site rapid detection of illegal drugs. This work developed a portable digital linear ion trap mass spectrometer based on separate-region corona discharge ionization source to meet this need. A separate design of discharge and reaction regions was adopted with filter air as both carrier gas for the analyte and protection of the corona discharge needle. The linear ion trap was driven by a digital waveform with a low voltage (±100 V) to cover a mass range of 50–500 Da with a unit resolution at a scan rate of 10,000 Da/s. Eighteen representative drugs were analyzed, demonstrating excellent qualitative analysis capability. Tandem mass spectrometry (MS/MS) was also performed by ion isolation and collision-induced dissociation (CID) with air as a buffer gas. With cocaine as an example, over two orders of magnitude dynamic range and 10 pg of detection limit were achieved. A single analysis time of less than 10 s was obtained by comparing the information of characteristic ions and product ions with the built-in database. Analysis of a real-world sample further validated the feasibility of the instrument, with the results benchmarked by GC-MS. The developed system has powerful analytical capability without using consumables including solvent and inert gas, meeting the requirements of on-site rapid detection applications.

A real-time multi-function digital coincidence spectrometer for neutron copper activation diagnostics

Copper activation has been a standard diagnostic for measuring 14.1-MeV neutron yields in deuterium-tritium fusion experiments, which is essential to evaluate their performance for potential ignition in the future. Copper-activation equipment, especially data-acquisition systems, is updated constantly thanks to the rapid developments in electronics. Here, a multi-function digital coincidence spectrometer for neutron copper-activation diagnostics was developed. The digital pulse processing includes pulse shaping, multichannel pulse analysis, coincidence event picks, and coincidence multichannel time analysis were implemented on a single field-programmable gate array (FPGA) chip. The results demonstrate that the coincidence background is 0.013 counts per second. By using the multi-function digital coincidence spectrometer, the copper-activation diagnostics could be performed at the SG-III Laser facility when the neutron yield is ≥ 1.0 × 1010/hit.

A four-channel coincidence digital positron annihilation lifetime spectrometer

Positron annihilation lifetime (PAL) spectrometer is an effective tool to investigate material microstructures. Commonly used PAL spectrometers are conventional PAL spectrometer based on nuclear instrument modules (NIMs) and digital PAL spectrometer based on ultra-high-speed digitizer. Limited by the detection efficiency of the detectors, the coincidence count rate of the PAL spectrometer is always low, causing long time consumption of measurement. To solve this problem, a multi-channel coincidence method based on the ultra-high-speed digitizer was proposed. However, the ultra-high-speed digitizer is usually excessively expensive for research institutes. In this paper, we introduce a four-channel coincidence digital PAL spectrometer. Through the improvement of the timing and trigger circuit, all channels can act as start and stop channels during one measurement. Hence the coincidence count rate can be increased by an order of magnitude. The time measurement shows good linearity and high resolution with a full width half maximum (FWHM) at a level of several tens picoseconds. The effective number of bits (ENOB) of the analog-to-digital converter (ADC) reaches 10.72 bits. The energy resolution of the 511 keV photopeak reaches 4.16% when using LaBr 3: 5% Ce3+ scintillator, better than 4.62% of the conventional spectrometer. The time resolution of our PAL spectra when one channel receives start signals and one channel receives stop signals reaches 193.7 ps, better than that of the conventional spectrometer (212.8 ps). The FWHMs of the lifetime spectra of the two and four channel coincidence measurements are 205.8 ps and 212.4 ps respectively. Moreover, the coincidence count rate of our system increases significantly by using the four-channel coincidence method, which can be 10 times higher than the conventional spectrometer.

Monitoring of total acidity content in continuous vinegar fermentation using a self-made modification of a micro-electro-mechanical system near-infrared spectrometer

This study evaluated the potential of a micro-electro-mechanical system (MEMS) near-infrared spectrometer for the on-line monitoring of total acids in the continuous fermentation process of rice vinegar and white vinegar. A self-made modification of the digital light processing NIRscan nano spectrometer was used for this purpose. As best pretreatment method, the multiplicative scatter correction was used to pretreat the raw spectra, which were subsequently subjected to a partial least square regression calibration. The results showed that total acids could be determined by this experimental setup with root-mean-square errors of predictions of 0.12% (w/v) and 0.27% (w/v) for rice vinegar and white vinegar, respectively. In conclusion, this low-cost MEMS near-infrared instrument can be applied to monitor total acids in the industrial continuous fermentation process of rice and white vinegar.

Analysis and suppression of scattering interference for arsenic using dispersive atomic fluorescence spectrometry based on an ultraviolet digital micromirror device spectrometer

A combination of UV-DMD-AFS and NFLR methods has been successfully used in the real-time suppression of scattering interference for arsenic, achieving long-term accuracy >99.20% (within 3 hours) in water quality samples.

Application of Artificial Neural Networks in Analysis of Time-Variable Optical Reflectance Spectra in Digital Light Projection Spectroscopy

This article undertakes the subject matter of applying artificial neural networks to analyze optical reflectance spectra of objects exhibiting a change of optical properties in the domain of time. A compact Digital Light Projection NIRscan Nano Evaluation Module spectrometer was used to record spectra. Due to the miniature spectrometer’s size and its simplicity of measurement, it can be used to conduct tests outside of a laboratory. A series of plant-derived objects were used as test subjects with rapidly changing optical properties in the presented research cycle. The application of artificial neural networks made it possible to determine the aging time of plants with a relatively low mean squared error, reaching 0.56 h for the Levenberg–Marquardt backpropagation training method. The results of the other ten training methods for artificial neural networks have been included in the paper.