TOF Technique Research Articles

Measurement and analysis of leakage neutron spectra from Lead slab samples with D–T neutrons

The leakage neutron spectra from three different sizes of Lead samples were measured by a TOF technique at 60° and 120°. The essential characteristic properties of the experimental measurement spectra can be reproduced well by MCNP code simulations with the ENDF/B-VIII.0, CENDL-3.2, JENDL-5.0, JEFF-3.3 and TENDL-2021 evaluated nuclear data libraries. The calculated results of JENDL-5.0 and JEFF-3.3 libraries agree better with the experimental data in the whole energy range. The results from ENDF/B-VIII.0 and CENDL-3.2 are overestimated in the 4–9 MeV range at 60° and in the 4–12.5 MeV range at 120°. The differences of the leakage neutron spectra by MCNP simulations using five evaluated nuclear data libraries mainly originate from the differences of the spectrum distributions of neutron reaction channels in these libraries. And the secondary neutron energy distribution and angular distribution from the five libraries have been present to explain it.

Mass identification by means of Energy-Time-of-Flight technique using large area silicon detector in a 4[formula omitted] array: The CHIMERA case

The study of heavy-ion reactions in the Fermi energy regime requires detection systems covering a high portion of the solid angle and using several identification techniques. Silicon detectors are widely used in this field. The so called E−ToF identification technique combines the energy and time of arrival of ions stopped in the detector to perform mass identification and calculate the velocity. However, when dealing with time measurements non-linear effects in detector and electronics responses have to be taken into account. We present an empirical method, as developed in the case of CHIMERA multi-detector, describing these non-linear effects and allowing for mass identification of ions stopped in the silicon detector by means of a semi-automatic procedure. Correlation between the non-linear effects affecting the ToF technique and the rise-time of the silicon detector signal will also be presented and discussed.

Picosecond Timing Electronics for a DIRC-Like Detector at the Super Tau-Charm Facility

The DIRC-like time-of-flight detector (DTOF) at the Super Tau-Charm Facility (STCF) in China is a Cherenkov light detector that uses the TOF technique to identify charged particles. To achieve the expected target that provides a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma \pi $ </tex-math></inline-formula> /K separation at 2-Ge/c momentum, a single-photon time resolution of better than 50 ps is required, while the contribution from electronics should be lower than 15 ps. To meet the requirements with high channel count integration, the timing electronics using leading-edge discrimination and field-programmable gate array (FPGA)-based time-to-digital converters (TDCs) are employed in the DTOF detector. This article reports the results of the first phase of project where the timing electronics with 128 channels has been constructed and its performance has been evaluated. Including the uncertainty of system clock distribution and synchronization, the intrinsic timing resolution of the electronics is better than 10-ps rms. Taking fast microchannel plate photomultiplier tubes (MCP-PMTs) as Cherenkov photodetectors and adopting time-over-threshold (TOT) measurement for time walk correction, the measured single-photon time resolutions are better than 40-ps rms. The test results confirm that the proposed timing electronics has advantages of high precision and high integration, which is highly demanded in future picosecond timing detectors.

Vascular and Vasogenic Manifestations of Systemic ANCA-Associated Vasculitis with Renal Involvement in Non-Contrast Brain MRI in Patients with Acute Disease Onset.

Background. Data concerning central nervous system (CNS) alterations in ANCA-associated vasculitis with renal involvement (AAVR) are sparse. The study aimed to assess vascular and vasogenic brain alterations in patients with acute onset of AAVR and the applicability of non-contrast magnetic resonance imaging (MRI) techniques in this diagnosis. Methods. Thirty-eight patients with acute onset of AAVR were included in the study. BVAS/WG, c-ANCA, p-ANCA, renal function and perfusion, neurological assessment, and brain MRI were performed. Results. Cerebral vascular alternating narrowing and dilatation (VAND) was detected in 42.1% of patients, and the black-blood was significantly more diagnostic than the TOF technique (p < 0.001). VAND occurrence was independently associated with the concentration of p-ANCA. The vasogenic white matter lesions (VWML) were found in 94.4% of patients, and in their detection, SWAN was significantly better than the FLAIR technique (p = 0.002). The number of VWML correlated with age and cranial nerve damage. Hemosiderin deposits were found in 21.6% of patients and were associated with a gait impairment and paresthesia. Conclusions. Vascular and vasogenic alterations in the CNS are frequent in patients with acute onset of systemic ANCA-associated vasculitis with renal involvement. Non-contrast MRI is useful in the diagnosis of brain vasculitis.

Isolation and antimicrobial resistance profile for Enterococcus spp in goat milk processing plants

The antimicrobial resistance of Enterococcus spp in the dairy industry has been reported over the years, making it a potential source of contamination for the finished product as this microorganism is resistant to the pasteurization process. Thus, the present study aimed to evaluate the antimicrobial resistance profile of Enterococcus spp isolated from goat milk processing plants. Samples were collected and seeded on agar with 5% defibrinated goat blood. The isolates were confirmed by the MALDI TOF technique. The greatest resistance was observed for norfloxacin, followed by tetracycline and chloramphenicol and vancomycin. Nitrofurantoin and linezolid showed the highest sensitivity rates for the strains studied. This research demonstrates the need for sanitary policies for the quality control of goat's milk with the presence of pathogens resistant to pasteurization processes with antimicrobial resistance, making it a potential risk to the health of the population.

First report of the presence of Vibrio vulnificus in the Gulf of Gdansk.

Vibrio infections are becoming more frequent in the Baltic Sea region, which is caused by an increase in the sea surface temperature. Climate change creates the conditions for the emergence of new environmental niches that are beneficial for Vibrio spp., especially in the summer months. Vibrio vulnificus, which causes wound infections and septicaemia, represents a particularly dangerous species of Vibrio spp. There are numerous publications on the prevalence of V. vulnificus in various regions of the Baltic Sea, but there is a lack of such data for the Polish coast. This prompted us to conduct a pilot study into the prevalence of the bacteria in the Gulf of Gdansk. The study aimed to detect Vibrio spp. in the coastal waters and the wet sand at the beaches and bathing areas in the Gulf of Gdansk. During the period from June 16th to September 23rd 2020, 112 samples of seawater and 105 samples of wet sand were collected at 16 locations along the coast of the Gulf of Gdansk and Hel peninsula. Isolation of Vibrio spp. was conducted by filtering method and the isolated bacteria was cultured on CHROM agar Vibrio and TCBS agar. Final genus identification was performed by the MALDI TOF technique. In the present study, 10 isolates of Vibrio spp. were obtained from seawater and wet sand samples collected in the Gulf of Gdansk and Hel peninsula coast. Three of the isolates were identified as V. vulnificus; the presence of the species was confirmed in the seawater samples which had been collected in Hel (1 isolate), Jastarnia (1 isolate), and Chalupy (1 isolate). One strain of Vibrio alginolyticus was isolated from the seawater sample collected in Hel. Moreover, identification was incomplete for 6 of the isolated strains, these were identified as Vibrio cholerae/mimicus These strains were collected in Jastarnia (1 isolate), Kuznica (1 isolate), Gdansk-Brzezno (1 isolate), Puck (2 isolates), Chalupy (1 isolate). Our preliminary research study confirmed the presence of potentially pathogenic V. vulnificus in the Gulf of Gdansk in the summer months. Therefore, further monitoring of the presence of Vibrio spp. in the Baltic coast area is necessary.

Observation of TOF–MIEZE Signals with Focusing Mirrors at BL06, MLF, J-PARC

A neutron spin echo experiment for tiny samples with high energy resolution can be realized by combining modulated intensity by zero effort (MIEZE) technique and ellipsoidal neutron focusing supermirrors. We observed TOF–MIEZE (the time-of-flight method with MIEZE) signals with an effective frequency of 108 kHz with focusing beam. The Fourier time range 0.48–5.3 ns was covered at once by using TOF technique with neutron wavelength 0.65–1.45 nm. The contrasts of TOF–MIEZE signal were 0.62 ± 0.02 and 0.50 ± 0.05 with each neutron wavelength of 0.68 nm and 1.35 nm, respectively.

Measurement of leakage neutron spectra with D-T neutrons and evaluated nuclear data

Benchmarking of evaluated neutron nuclear data libraries was performed for ∼14.8 MeV neutrons on the several targets, such as gallium, graphite, silicon carbide, uranium and tungsten samples. The experiments were performed at China Institute of Atomic Energy (CIAE). The neutron leakage spectra from the samples were measured at 60◦ and 120◦ by a TOF technique with a BC501A scintillation detector. The measured spectra are rather well reproduced by MCNP-4C simulations with the CENDL3.1, JENDL-4.0 and the new release ENDF/B-VIII.0, JEFF-3.3 evaluated nuclear data libraries and so on. There have some difference between experiments and simulations for the elastic and inelastic contributions in the partial energy range. And the discrepancies of the neutron leakage spectra in the MCNP simulations originate simply from the differences in the spectra distributions of the neutron reaction channels in the evaluated nuclear data libraries.

Shortening of the twitch stabilization period by tetanic stimulation in acceleromyography in infants, children and young adults (STSTS-Study): a prospective randomised, controlled trial.

Acceleromyography is characterised by an increase of the twitch response T1 (first twitch of the train-of-four [TOF]) during first 30min of monitoring known as the staircase phenomenon. In adults the staircase phenomenon can be avoided by tetanic prestimulation. This study examined, if tetanic prestimulation eliminates the staircase phenomenon in children. After written informed consent, the neuromuscular function of 80 children, 10 in each age group (< 6months, 6-12months, 12-24months, 2-3years, 3-6years, 6-12years, 12-18years, and ≥ 18years) was measured on both arms simultaneously over 30min under general anaesthesia. The ulnaris nerve was stimulated using the TOF technique every 15s. The twitch response (T1, TOF ratio [TOFR]) was measured by acceleromyography. Before calibration, tetanic prestimmulation (50Hz for 5s) was administered to one randomly selected arm. The effect of tetanic prestimulation and age was analysed using general linear models based on the normalized T1 and TOFRs of both arms. Tetanic prestimulation significantly affected T1 values avoiding the staircase phenomenon (p < 0.0001). After 5.8min [1.0-17.2min] the normalized T1 values increased to 117% [102-147%] without prestimulation (p < 0.0001) independent of the age group (p = 0.539). The normalized TOFR was stable throughout the observation period of 30min 100% [95-107%]. Infants (> 12weeks), children, and young adults (< 18years) develop similar characteristics of the staircase phenomenon than adults. Tetanic prestimulation prevents the staircase phenomenon in these age groups. The stability of the TOFR reading confirms its value to monitor neuromuscular function over time.Registration: The study was registered as NCT02552875 on Clinical Trials.gov on July 29, 2014.

2-Phenylbenzothiophene-based liquid crystalline semiconductors

We report herein the design and synthesis of some novel liquid crystalline semiconductors constructed from a biologically and pharmacologically active building block molecule, namely 6-methoxy-2-(4-methoxyphenyl)benzo[b]thiophene, presenting efficient luminescence and medium charge mobility rate. A first series of mesogenic 2-phenylbenzothiophene derivatives (nPBT) was simply and rapidly obtained in good yields by successive demethylation/alkylation reactions of the available methoxy precursor. The further stepwise oxidations moreover resulted in two new sets of the corresponding sulfoxide (nPBTO) and sulfone (nPBTO2) derivatives, respectively, that were also mesomorphic. The liquid crystalline behaviour was comprehensively characterized by DSC, POM and SAXS: all compounds exhibit smectic-like behaviour in agreement with their calamitic shape. More specifically, mesogens nPBT showed a SmA phase, with in addition, a higher ordered smectic phase at lower temperature. As for the oxidized mesogens, they displayed a SmA phase only, and over particularly large temperature ranges for the nPBTO with longer chain lengths (n ≥ 8). The photo-physical properties have also been studied both in solution and thin films, and the molecules were found to display strong absorption in the UV/vis domain and intense luminescence in the range of 400–650 nm (yellowish green light) in high quantum yields (up to 62%). Both absorption and luminescence were also found to be affected by the oxidation of the benzothiophene moiety. Finally, the semi-conducting behaviour of three PBT compounds in the various mesophases was investigated by photocurrent TOF technique. Hole mobility rates of ca. 4 × 10−3 cm2 V−1 s−1 were measured in the lower temperature ordered mesophase for all of them, with the best performances (temperature range and mobility values) however obtained for the shortest homolog (n = 6). With such highly reasonable mesomorphic, light-emitting and semiconducting functional features, as well as being cheap and easy to synthesize and to process, these materials become very attractive and may be incorporated into various kinds of electronic devices (OFET and OLED).

Hybrid assembled MEMS scanner array with large aperture for fast scanning LIDAR systems

Abstract This article presents a large aperture micro scanning mirror (MSM) array especially developed for the panoramic 3D-ToF camera Fovea-3D. The Fovea-3D system uses a fiber amplified pulsed laser ToF technique at λ = 1550 nm \lambda =1550\hspace{0.1667em}\text{nm} with 1 MVoxel distance measuring rate. It targets for real time 3D imaging with a panoramic optical field of view (FOV) of 360 ° × 60 ° 360^\circ \times 60^\circ (horizontal × vertical) combined with a large distance measurement range of 100 m and a video-like frame rate of 10 Hz. For fast vertical scan axis a MEMS scanner module with large receiver aperture was especially developed. It increases the scanning rate to 3200 Hz which is four times faster in comparison to state-of-the-art fast macroscopic polygon scanning systems used for LIDAR systems. To guarantee at the same time a large reception aperture of D eff = 23 mm {D_{\mathit{eff}}}=23\hspace{0.1667em}\text{mm} , large FOV of 60 ° 60^\circ and high vertical scanning rate of 3200 Hz, a hybrid assembled MSM array was developed consisting of 22 reception mirrors and a separate emitting mirror for laser scanning of the target. For Fovea3D hybrid assembly of frequency selected scanner elements was chosen instead of a monolithic MEMS scanner array to guaranty a high yield of MEMS fabrication. All MSM are driven in parametric resonance to enable a fully synchronized operation of all individual MEMS scanner elements. Therefore, piezo-resistive position sensors are integrated on each MEMS chip for position feedback of driving control. The paper discusses details of the MEMS system integration including the synchronized operation of multiple MEMS scanning elements.

Improved visualization of superficial temporal artery using segmentedtime-of-flight MR angiography with venous suppression at 7T.

To evaluate the quality of time-of-flight MR angiography (TOF-MRA) with venous suppression at 7T on imaging superficial temporal artery (STA). A recently developed segmented TOF technique with reduced specific absorption rate (SAR) of venous suppression (VS) module was employed to achieve high-resolution arterial angiography without the contamination of venous signal. Images of segmented TOF with VS at 7T, TOF without VS at 7T, and TOF with VS at 3T were collected on 17 healthy volunteers. The number of STA branches and their local contrast achieved by the three methods were quantified and compared using paired t test. Segmented TOF with VS at 7T successfully suppressed venous signal without reducing the contrast of arterial angiography. The numbers of STA branches in 7T images were significantly higher than that in 3T images (5.79 vs. 4.50, p < 0.001). The contrast of 7T segmented TOF was significantly higher than 3T TOF (7.21 vs. 5.56, p = 0.006). Segmented TOF with VS at 7T displayed more branches of STA, while eliminating the signal of superficial temporal vein (STV). The improved visualization of STA will potentially facilitate the pre-operative assessment of STA in STA-MCA bypass surgery.

Neutron transport and benchmark on granular tungsten samples with 14.8 MeV neutrons

The leakage neutron spectrum from granular tungsten samples was measured by a TOF technique at 60°. The neutron transport and benchmark on granular tungsten samples were investigated using MCNP-4C simulations with the ENDF/B-VII.1, CENDL-3.1, JEFF-3.2, JENDL-4.0 and TENDL-2015 evaluated nuclear data libraries. And four different geometry lattices (FCC, BCC, CHPOP and SC) were considered for the granular tungsten target. The simulated results show that the leakage neutron spectrum mainly depends on the filling factor of granular tungsten. The general trend of the experimental leakage neutron spectrum is well reproduced by MCNP simulation with the ENDF/B-VII.1 library within 15% error. However, the inelastic contribution at around En = 10 MeV with CENDL-3.1 library largely underestimates the cross section. The discrepancies of the leakage neutron spectra in the MCNP simulations originate simply from the differences in the spectra distributions of the neutron reaction channels in the evaluated nuclear data libraries.

Plasma-laser ion discrimination by TOF technique applied to coupled SiC detectors.

The rate estimation of nuclear reactions induced in high intensity laser-target interaction (≥1016 W/cm2), is strongly depending on the neutron detection efficiency and ion charge discrimination, according to particles involved in exit open-channels. Ion discrimination is basically performed by means of analysis of pits observed on track detector, which is critically dependent on calibration and/or fast TOF devices based on SiC and diamond detectors. Last setup is used to determine the ion energy and to obtain a rough estimation of yields. However, for each TOF interval, the dependence of yield from the energy deposited in the detector sensitive region, introduces a distortion in the ion spectra. Moreover, if two ion species are present in the same spectrum, the discrimination of their contribution is not attainable. In this paper a new method is described which allows to discriminate the contribution of two ion species in the wide energy range of nuclear reactions induced in laser-target interactions. The method is based on charge response of two TOF-SiC detectors, of suitable thicknesses, placed in adjacent positions. In presence of two ion species, the response of the detectors, associated with different energy losses, can determine the ion specific contribution to each TOF interval.

Beam choppers for neutron reflectometers at steady flux reactors

Realizations of the TOF technique for neutron reflectometers at steady flux reactors are compared. Beam choppers for neutron reflectometers divide into choppers of type 1 (Δλ=const) and 2 (Δλ∕λ=const). It follows from Monte-Carlo simulations that choppers of type 1 do not yield to more intricate choppers of type 2, widely used at neutron reflectometers. Because of a very fast drop of neutron reflectivities with the momentum transfer q, non-optimality of measurements with a chopper of type 1 is fully compensated by better statistics at large q, and is not so much essential at small q. To vary the TOF resolution with choppers of type 1, a phasing of two discs and a turning of the system of two discs are suggested. The fluxes of neutrons with wavelengths beyond the working range and the efficiencies of their elimination by means of a bandwidth limiting prechopper are evaluated.

Laser-accelerated ion beam diagnostics with TOF detectors for the ELIMED beam line

Laser-accelerated ion beams could represent the future of particle acceleration in several multidisciplinary applications, as for instance medical physics, hadrontherapy and imaging field, being a concrete alternative to old paradigm of acceleration, characterized by huge and complex machines. In this framework, following on from the ELIMED collaboration, launched in 2012 between INFN-LNS and ELI-Beamlines, in 2014 a three-years contract has been signed between the two institutions for the design and the development of a complete transport beam-line for high-energy ion beams (up to 60 MeV) coupled with innovative diagnostics and in-air dosimetry devices. The beam-line will be installed at the ELI-Beamlines facility and will be available for users. The measurement of the beam characteristics, such as energy spectra, angular distributions and dose-rate is mandatory to optimize the transport as well as the beam delivery at the irradiation point. In order to achieve this purpose, the development of appropriate on-line diagnostics devices capable to detect high-pulsed beams with high accuracy, represents a crucial point in the ELIMED beamline development. The diagnostics solution, based on the use of silicon carbide (SiC) and diamond detectors using TOF technique, will be presented together with the preliminary results obtained with laser-accelerated proton beams.

Molecular fragmentation by electron impact investigated using a time delayed spectroscopic technique

A new technique based on time-of-flight mass spectrometry with delayed extraction, in which it is possible to determine the amount of ions with a given energy distribution, is presented. Unlike most techniques designed to measure the energy distribution of molecular fragments, its sensitivity is higher in the low range of the energy distribution, for ions with kinetic energy from thermal energy up to 3 eV. In this progress report we show that this technique is able to open new perspectives for mass spectrometry based on the well established TOF technique, presenting some selected results for collisions of electrons with energy between 15 eV and 400 eV with N2, O2 and CHClF2, which have interesting features involving their low energy fragments.

Contribution of mass spectrometry in assessing quality of petroleum fractions

This study presents the results of an analysis of crude oil and asphaltene samples using the MALDI TOF technique. Thirty crude petroleum samples (24.53–32.05 API gravity) obtained from a Brazilian refinery were used in this study. Asphaltenes were precipitated from the corresponding crude oil samples with n-heptane. Mass spectra were acquired with a MALDI TOF mass spectrometer in a mass range of 100–1000 Da. The main purpose of this study was to analyze the composition of the asphaltene molecules extracted from oil samples according to their molecular composition (molecular weight and composition heteroatoms). The mean composition of the group analyzed was calculated as follows: 17% sulfur-containing molecules, 28% nitrogen-containing molecules, 19% oxygen-containing molecules, 12% sulfur–oxygen-containing molecules and 17% nitrogen–oxygen containing molecules; only 7% of the compounds contained only hydrogen and carbon in their composition. Finally, MALDI TOF analysis can be a very efficient process with a great potential for estimating the physicochemical properties of asphaltenes. A VBA (Visual Basic for Applications) algorithm allowed us to determine the elemental composition of components of asphaltene samples. The elemental composition showed that, despite having the same physical characteristics, the chemical composition of the samples was different.

Time-of-flight discrimination between gamma-rays and neutrons by using artificial neural networks

In gamma-ray spectroscopy, a number of neutrons are emitted from the nuclei together with the gamma-rays. These neutrons influence gamma-ray spectra. An obvious method for discrimination between neutrons and gamma-rays is based on the time-of-flight (tof) technique. In this work, the tof distributions of gamma-rays and neutrons were obtained both experimentally and by using artificial neural networks (ANNs). It was shown that, ANN can correctly classify gamma-ray and neutron events. Also, for highly nonlinear detector response for tof, we have constructed consistent empirical physical formulas (EPFs) by appropriate ANNs. These ANN–EPFs can be used to derive further physical functions which could be relevant to discrimination between gamma-rays and neutrons.

Angiography of Azygos Continuation of Inferior Vena Cava with Polysplenia

This report demonstrates an angiography of azygos continuation of inferior vena cava with polysplenia. In this patient computed tomography with contrast enhancement, magnetic resonance angiography of the thorax with TOF technique and angiography of IVC by seldinger technique with entering right main femoral vein was performed. It was exhibited azygos continuation of IVC, polysplenia and hepatic veins which connected to the right atrium. Congenital malformations of IVC are rare. Patients are usually asymptomatic and this developmental anomaly is detected incidentally during abdominal surgery or radiologic evaluation. The recognition of this congenital venous anomaly is important for the cardiopulmonary bypass or palliative systemic venous–pulmonary artery shunt surgery, IVC filter placement and cardiologist especially for conditions such as venous thromboembolism.