We report on the radiation damage to the optical properties of plastic scintillators following irradiation using a 6MeV proton beam produced by the 6MV tandem accelerator of iThemba LABS, Gauteng. A ...comparative is drawn between polyvinyl toluene based commercial scintillators EJ200, EJ208, EJ260 and BC408 as well as polystyrene based scintillator UPS923A and scintillators manufactured for the Tile Calorimeter. Results on the proton induced damage indicate a reduction in the light output and transmission capability of the plastics. Scintillators containing a larger Stokes shift, i.e. EJ260 and EJ208 exhibit the most radiation hardness. The EJ208 is recommended as a candidate to be considered for the replacement of Gap scintillators in the Tile Calorimeter for the 2018 upgrade.
Following the comparative study of proton induced radiation damage on various plastic scintillator samples from the ATLAS-CERN detector, a study on neutron irradiation and damage assessment on the ...same type of samples will be conducted. The samples will be irradiated with different dose rates of neutrons produced in favourable nuclear reactions using a radiofrequency linear particle accelerator as well as from the SAFARI nuclear reactor at NECSA. The MCNP 5 code will be utilized in simulating the neutron transport for determining the dose rate. Light transmission and light yield tests will be performed in order to assess the radiation damage on the scintillators. In addition, Raman spectroscopy and Electron Paramagnetic Resonance (EPR) analysis will be used to characterize the samples after irradiation. The project aims to extent these studies to include radiation assessment damage of any component that processes the scintillating light and deteriorates the quantum efficiency of the Tilecal detector, namely, photomultiplier tubes, wavelength shifting optical fibres and the readout electronics. They will also be exposed to neutron irradiation and the damage assessed in the same manner.
We report on the optical and structural properties of plastic scintillators irradiated with neutron beams produced by the IBR-2 reactor of the Frank Laboratory of Neutron Physics in JINR, Dubna. Blue ...UPS-923A and green plastic scintillators were irradiated with neutron fluence ranging from 1013 to 1017 n/cm2. Discolouring in the plastic scintillators was observed after irradiation. The effects of radiation damage on the optical and structural properties of the samples were characterized by conducting light yield, light transmission, light fluorescence and Raman spectroscopy studies. The results showed that neutron radiation induced damage in the material. The disappearance of the Raman peak features in green scintillators at frequencies of 1165.8, 1574.7 and 1651.2 cm−1 revealed significant structural alterations due to neutron bombardment. Losses in fluorescence intensity, light yield and light transmission in the plastic scintillators were observed.
With the prediction that the plastic scintillators in the gap region of the Tile Calorimeter will sustain a significantly large amount of radiation damage during the HL-LHC run time, the current ...plastic scintillators will need to be replaced during the phase 2 upgrade in 2018. The scintillators in the gap region were exposed to a radiation environment of up to 10 kGy/year during the first run of data taking and with the luminosity being increased by a factor of 10, the radiation environment will be extremely harsh. We report on the radiation damage to the optical properties of plastic scintillators following irradiation using a neutron beam of the IBR-2 pulsed reactor in Joint Institute for Nuclear Research (JINR), Dubna. A comparison is drawn between polyvinyl toluene based commercial scintillators EJ200, EJ208 and EJ260 as well as polystyrene based scintillator from Kharkov. The samples were subjected to irradiation with high energy neutrons and a flux density range of 1 × 106-7.7 × 106. Light transmission, Raman spectroscopy, fluorescence spectroscopy and light yield testing was performed to characterize the damage induced in the samples. Preliminary results from the tests done indicate a minute change in the optical properties of the scintillators with further studies underway to gain a better understanding of the interaction between neutrons with plastic scintillators.
We report on structural and optical properties of neutron irradiated plastic scintillators. These scintillators were subjected to a neutron beam with wide energy range of up to 10MeV and a neutron ...flux range of 1.2 × 1012 - 9.4 × 1012n/cm2 using the IBR-2 pulsed reactor at the Joint Institute for Nuclear Research in Dubna. A study between polyvinyl toluene based commercial scintillators EJ200, EJ208 and EJ260 as well as polystyrene based scintillator from Kharkov is conducted. Light transmission, Raman spectroscopy, fluorescence spectroscopy and light yield testing was performed to characterize the damage induced in the samples. Preliminary results from the tests performed indicate no change in the optical and structural properties of the scintillators. The polystyrene based scintillators were further subjected to a higher neutron flux range of 3.8 × 1012 - 1.8 × 1014n/cm2 using the IBR-2 pulsed reactor.
HEALTH Recent studies have shown that the detection of SARS-CoV-2 genetic material in wastewater may provide the basis for a surveillance system to track the environmental dissemination of this virus ...in communities. An effective wastewater-based epidemiology (WBE) system may prove critical in South Africa (SA), where health systems infrastructure, testing capacity, personal protective equipment and human resource capacity are constrained. In this proof-of-concept study, we investigated the potential of SARS-CoV-2 RNA surveillance in untreated wastewater as the basis for a system to monitor COVID-19 prevalence in the population, an early warning system for increased transmission, and a monitoring system to assess the effectiveness of interventions. The laboratory confirmed the presence (qualitative analysis) and determined the RNA copy number of SARS-CoV-2 viral RNA by reverse transcription polymerase chain reaction (quantitative) analysis from 24-hour composite samples collected on 18 June 2020 from five wastewater treatment plants in Western Cape Province, SA. The study has shown that a WBE system for monitoring the status and trends of COVID-19 mass infection in SA is viable, and its development and implementation may facilitate the rapid identification of hotspots for evidence-informed interventions.
There has been unprecedented progress in vaccine development against SARS-CoV-2, the virus that causes COVID-19. However, given the huge demand for a limited supply of efficacious vaccines, there has ...been global, regional and local outcry regarding the lack of access to vaccines and the equity of distribution. Over 319 million vaccine doses have been administered (at the time of writing), with the majority in high-income countries.1,2 In contrast, by mid-January 2021, Guinea was the sole low-income country to have administered vaccines, but to only 25 individuals.3 Early in February 2021, South Africa (SA) received one million doses of the AstraZeneca vaccine; however, shortly thereafter, data reflected disappointing results on the efficacy of this vaccine on the predominant strain in the country (the 501Y.V2 variant), prompting the country to reverse the decision to utilise these in the national roll-out. With ample agility, on 17 February 2021 SA launched an early-access programme through a phase 3B open-label study using the Johnson & Johnson vaccine candidate, rapidly deploying the first tranche of 80 000 vaccines within hours of the vaccines touching down on SA soil. Despite global surveillance efforts and the promise of numerous vaccine candidates, ongoing public health challenges to fully understand the impact of the COVID-19 pandemic remain a major concern. COVID-19 testing data have become a key metric that informs public health decision-making. However, epidemiological indicators can be flawed, as they may be influenced by insufficient testing capacity, limited access to healthcare facilities and testing bias, as individuals with severe symptoms are more likely to be tested than asymptomatic individuals.4,5 While African countries have reported low COVID-19 case numbers relative to other regions, this may not be indicative of low prevalence or spread containment, but rather low surveillance.6
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