A novel method for direct electronic “fast-timing” lifetime measurements of nuclear excited states via γ–γ coincidences using an array equipped with N∈N equally shaped very fast high-resolution ...LaBr3(Ce) scintillator detectors is presented. Analogous to the mirror symmetric centroid difference method, the generalized centroid difference method provides two independent “start” and “stop” time spectra obtained by a superposition of the N(N−1)γ–γ time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific γ–γ cascade. Provided that the energy response and the electronic time pick-off of the detectors are almost equal, a mean prompt response difference between start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing arrays mean γ–γ time-walk characteristics can be determined for 40keV<Eγ<1.3MeV with an accuracy less than 5ps using a 152Eu γ-ray source. Due to reduction and cancellation of many possible systematic errors, the lifetime determination limit of the method over the total dynamic range is mainly determined by the statistics. The setup of an N=4 detector fast-timing array delivered an absolute time resolving power of 3ps for 10000 γ–γ events per total fast timing array start and stop time spectrum. The new method is tested over the total dynamic range by the measurements of known picosecond lifetimes in standard γ-ray sources.
Microscope cover-slip glass for TLD applications Alqahtani, Amal; Sani, S.F. Abdul; Narissa, N.H. Amiera ...
Applied radiation and isotopes,
June 2020, 2020-Jun, 2020-06-00, Letnik:
160
Journal Article
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As a result of the various evolving needs, thermoluminescence dosimetry is constantly under development, with applications intended in environmental and personal radiation monitoring through to the ...sensing of radiotherapy and radiation processing doses. In radiotherapy dosimetry challenges include small-field profile evaluation, encompassing the fine beams of radiosurgery, evaluations confronting the steep dose gradients of electronic brachytherapy and the high dose rates of FLASH radiotherapy. Current work concerns the thermoluminescent dosimetric properties of commercial low-cost borosilicate glass in the form of thin (sub-mm to a few mm) plates, use being made of microscope cover-slips irradiated using clinical external-beam radiotherapy facilities as well as through use of 60Co gamma irradiators. In using megavoltage photons and MeV electrons, characterization of the dosimetric response has been made for cover-slips of thicknesses up to 4 mm. Reproducibility to within +/5% has been obtained. In particular, for doses up to 10 Gy, the borosilicate cover-slips have been demonstrated to have considerable potential for use in high spatial resolution radiotherapy dosimetry, down to 0.13 mm in present work, with a coefficient of determination in respect of linearity of >0.99 for the thinner cover-slips. Results are also presented for 0.13- and 1.00-mm thick cover slips irradiated to 60Co gamma-ray doses, initially in the range 5- to 25 Gy, subsequently extended to 5 kGy–25 kGy, again providing linear response.
The quenching of the experimental spectroscopic factor for proton emission from the short-lived d3/2 isomeric state in 151mLu was a long-standing problem. In the present work, proton emission from ...this isomer has been reinvestigated in an experiment at the Accelerator Laboratory of the University of Jyväskylä. The proton-decay energy and half-life of this isomer were measured to be 1295(5) keV and 15.4(8) μs, respectively, in agreement with another recent study. These new experimental data can resolve the discrepancy in the spectroscopic factor calculated using the spherical WKB approximation. Using the R-matrix approach it is found that the proton formation probability indicates no significant hindrance for the proton decay of 151mLu.
The monitoring of trace element concentrations in roadside dust can be used to evaluate vehicular contributions to the environment. Here we compare the utility of two analytical techniques for ...elemental analysis of dust samples, SEM/EDX and ICP-OES, detecting elements from Mg to Au. In an evaluation of roadside dust at several different sites within the campus of King Saud University, situated in Riyadh, and the University of Qatar, situated in Doha, four elements are observed to be particularly prominent: Al, Fe, Mg, and Si, notwithstanding that they all have natural abundance in desert sands. This study implicates the influence of new technology in vehicle construction, including engine capacity (vehicles in these countries tending to be of relatively large engine capacity). The concentrations of Al, Fe and Mg in Doha show greater elevations compared to that obtained in Riyadh, both cities being centres of large urban populations, the levels in both cities also being enhanced above uncontaminated regional sands. Absolute values have been determined from use of the ICP-OES facility while the SEM/EDX technique has provided evaluation in terms of weight %, offering complementary information on the contribution of elemental concentrations from vehicular emissions.
•Metal element concentrations in roadside dust are investigated.•Comparisons made between concentrations in urban Saudi Arabian and Qatari roadways.•In use of ICP-OES and SEM/EDX, Al, Fe and Mg are observed at elevated levels, less so in the Saudi samples.•The concentrations of Mg show greater elevations in the Qatar samples.
A measurement of the reduced transition probability for the excitation of the ground state to the first 2+ state in 104Sn has been performed using relativistic Coulomb excitation at GSI. 104Sn is the ...lightest isotope in the Sn chain for which this quantity has been measured. The result is a key point in the discussion of the evolution of nuclear structure in the proximity of the doubly magic nucleus 100Sn. The value B(E2; 0+ → 2+) = 0.10(4) e2b2 is significantly lower than earlier results for 106Sn and heavier isotopes. The result is well reproduced by shell model predictions and therefore indicates a robust N = Z = 50 shell closure.
An ambitious program to measure decay properties, primarily β-delayed neutron emission probabilities and half-lives, for a significant number of nuclei near or on the path of the rapid neutron ...capture process, has been launched at the RIKEN Nishina Center. Here, we give an overview of the status of the project.
One of the problems arising from using a conventional linac at high energy (>8MV) is the production of neutrons. One way to reduce neutron production is to remove the flattening filter (FF). The main ...purpose of this work was to study the effect of FF removal on neutron fluence and neutron dose equivalent inside the treatment room at different photon beam energies. Several simulations based on Monte Carlo techniques were carried out in order to calculate the neutron fluence at different locations in the treatment room from different linac energies with and without a FF. In addition, a step-and-shoot intensity modulated radiotherapy (SnS IMRT) for prostate cancer was modelled using the 15MV photon beam with and without a FF on a water phantom to calculate the neutron dose received in a full treatment. The results obtained show a significant drop-off in neutrons fluence and dose equivalent when the FF was removed. For example, the neutron fluence was decreased by 54%, 76% and 75% for 10, 15 and 18MV, respectively. This can decrease the neutron dose to the patient as well as reduce the shielding cost of the treatment room. The neutron dose equivalent of the SnS IMRT for prostate cancer was reduced significantly by 71.3% when the FF was removed. It can be concluded that the flattening filter removal from the head of the linac could reduce the risk of causing secondary cancers and the shielding cost of radiotherapy treatment rooms.
•Neutron fluence decreased inside the treatment room by the flattening filter removal.•The reduction varies with energy due to the dissimilarity in flattening filter compositions.•Neutron doses equivalent of the 15FFF SnS IMRT for prostate decreased by 71.3%.•This reduction reduces the risk of inducing a secondary cancer from 1.2% to 0.3%.
We have recently successfully demonstrated a new technique for production and study of many of the most exotic neutron-rich nuclei at moderate spins. LICORNE, a newly developed directional ...inverse-kinematic fast neutron source at the IPN Orsay, was coupled to the MINIBALL high resolution γ-ray spectrometer to study nuclei the furthest from stability using the 238U(n,f) reaction. This reaction and 232Th(n,f) are the most neutron-rich fission production mechanisms achievable and can be used to simultaneously populate hundreds of neutron-rich nuclei up to spins of ≈ 16ℏ. High selectivity in the experiment was achieved via triple γ-ray coincidences and the use of a 400 ns period pulsed neutron beam, a technique which is unavailable to other population mechanisms such as 235U(nth,f) and 252Cf(SF). The pulsing allows time correlations to be exploited to separate delayed γ rays from isomeric states in the hundreds of nuclei produced, which are then used to cleanly select a particular nucleus and its exotic binary partners. In the recent experiment, several physics cases are simultaneously addressed such as shape coexistence, the evolution of shell closures far from stability, and the spectroscopy of nuclei in the r-process path near N = 82. Preliminary physics results on anomalies in the 238U(n,f) fission yields and the structure of the 138Te and 100Sr nuclei will soon be published. A future project, ν-ball, to couple LICORNE with a hybrid escape-suppressed spectrometer to refine further the technique and achieve a large increase in the observational limit is discussed.
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