Nuclear Science Centre Research Articles

Neutron irradiation and electrical characterisation of the first 8” silicon pad sensor prototypes for the CMS calorimeter endcap upgrade

As part of its HL-LHC upgrade program, the CMS collaboration is replacing its existing endcap calorimeters with a high-granularity calorimeter (CE). The new calorimeter is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic and hadronic compartments. Due to its compactness, intrinsic time resolution, and radiation hardness, silicon has been chosen as active material for the regions exposed to higher radiation levels. The silicon sensors are fabricated as 20 cm (8”) wide hexagonal wafers and are segmented into several hundred pads which are read out individually. As part of the sensor qualification strategy, 8” sensor irradiation with neutrons has been conducted at the Rhode Island Nuclear Science Center (RINSC) and followed by their electrical characterisation in 2020-21. The completion of this important milestone in the CE's R&D program is documented in this paper and it provides detailed account of the associated infrastructure and procedures. The results on the electrical properties of the irradiated CE silicon sensors are presented.

H2 generation by the 10B(n,α)7Li reaction in high temperature water

H2 produced in water from the 10B(n,α)7Li fission reaction has been measured up to 300 °C. Thermal energy neutrons from the Rhode Island Nuclear Science Center's 2 MW reactor interact with boric acid-containing water in temperature-controlled high-pressure cells made from tubing of either titanium or zirconium alloy. After exposure for a minimum of 1 h, the solution sample is extracted and sparged with argon. The H2 entrained by the sparging gas is sampled with a small mass spectrometer. A small amount of sodium is included in the boric acid solution so that after sparging, samples can be collected for 24Na activation measurements in a gamma spectrometer to determine the neutron exposure and thus the total energy deposited in solution. The G-value (μmol/J) for H2 production is obtained for water at a pressure of 25 MPa, over a temperature range from 20 °C to 300 °C. The weak temperature dependence of this yield between 150 °C and 200 °C demonstrates that the bimolecular reaction of pairs of eaq− is a very minor source of H2 in high LET tracks.

Weight loss and burst testing investigations of sintered silicon carbide under oxidizing environments for next generation accident tolerant fuels for SMR applications

Accident tolerant fuel (ATF) cladding is one of the most active area for research to advance the global contribution of nuclear energy since ATF will ensure and enhance the reactor safety allowing long refueling cycles and higher burnup. Silicon Carbide (SiC) is one material that can potentially be a solution to this long standing challenge. This study offers both computational reactor physics modeling and experimental investigation to examine the behavior of SiC in nuclear reactor environment. With recent interest in small modular reactors (SMR), this study selected SMR compact core as a reference assembly for Computational Burnup Modeling (CBM). Results of CBM suggest that SiC cladding will provide the highest burnup and maximum uranium utilization. Therefore, subsequent experimental investigations were focused on SiC only. Rhode Island Nuclear Science Center (RINSC)’s nuclear research reactor was used to investigate effects of irradiation on sintered tubular SiC material samples under pure steam at 1 atm, initially at 120 °C, followed by high temperatures between 850 °C and 1350 °C to simulate harsh reactor environment.Experimental analyzes of (a) weight loss and (b) burst testing are considered for SiC samples. For the weight loss experiment, we have considered both types of samples: (1) Non-irradiated and (2) Neutron-irradiated samples. Weight loss was found to be dependent on sample geometry. Irradiated samples show ∼2%–10% higher weight loss per area than that of the non-irradiated samples. Besides, considering the medium flow rate (less than 10 g/min), it has been observed that the irradiated samples exhibit ∼10%–40% higher weight loss than that of the non-irradiated samples over temperatures of 120 °C, 850 °C to 1350 °C. It is also seen that material loss rates are generally more sensitive at higher temperatures than at lower temperatures, and irradiated samples are more prone to weight loss. Furthermore, for the burst testing experimental investigations, experiments were conducted for (1) As-received samples (2) Non-irradiated samples and (3) Irradiated samples. Considering the three types of samples, it was observed that the maximum and minimum peak load values are ∼70% higher and ∼60% lower than the average peak load while fracture hoop stress is consistently ∼70%–75% higher than the internal pressure for all as-received samples. Experimental and computational investigations suggest that SiC is a viable candidate for ATF cladding material.

Atomic physics at the HIAF under extreme conditions: QED effects from strong Coulomb fields to beyond Schwinger limits

The high-intensity heavy ion accelerator facility (HIAF) is one of the major large-scale research facilities at the nuclear science center planned for Huizhou City in Guangdong Province. HIAF and its experimental terminals can be used to realize unprecedented research progresses in nuclear physics, atomic physics, materials, high-energy-density physics, and applications related to heavy ion beams such as cancer therapy, material modification, and radiobiology. In addition, they will provide excellent possibilities for atomic physics to investigate the quantum electrodynamics (QED) effects from strong electromagnetic fields to super-critical electromagnetic fields beyond the Schwinger limit. Starting from modern atomic spectroscopy based on the accelerator technology and in combination with the beam characteristics of the HIAF, this paper discusses the cutting-edge research topics that could be performed at HIAF and the upgrades to HIAF that could be implemented in the near future. The research fields include the QED effects in super-strong fields, parity nonconservation in highly charged ions, few-body processes in relativistic collisions, and testing the locality of matter waves of massive particles. This paper also discusses the possibility to perform laser spectroscopy with respect to radioactive ions. Furthermore, we believe that the latest high harmonic extreme ultraviolet (XUV) laser technology can be combined with HIAF for realizing high-precision measurements.

Radionuclide Selection for Emergency Response Exercise at Disaster City® Using Unsealed Radioactive Contamination.

The Department of Nuclear Engineering at Texas A&M University currently supports exercises at Disaster City, a mock community used for emergency response training that features full-scale, collapsible structures designed to simulate various levels of disaster and wreckage. Emergency response exercises can be enhanced by using unsealed radioactive sources to simulate a more realistic response environment following an incident involving the dispersion of radioactive material. Limited exercises are performed worldwide using unsealed radioactive sources, and most of that information is not publicly available. This research compiles the publicly available information along with additional information acquired through discussion with experts and presents the process for selection of a short-lived radionuclide for use at Disaster City. The historically-used radionuclides were F, Tc, Br, and La. These radionuclides were considered for the Disaster City exercise, as well as other short-lived radionuclides commonly used or capable of being produced at Texas A&M. The selection process described in this paper identified seven radionuclides that could be used in an unsealed contamination exercise at Disaster City. Radiopharmaceuticals Tc and F are suitable and available for purchase from nearby vendors. In addition, the Texas A&M Nuclear Science Center TRIGA reactor could be used to produce Na, Mn, Cu, Br, and La via thermal neutron activation.

Background studies for the MINER Coherent Neutrino Scattering reactor experiment

The proposed Mitchell Institute Neutrino Experiment at Reactor (MINER) experiment at the Nuclear Science Center at Texas A&M University will search for coherent elastic neutrino-nucleus scattering within close proximity (about 2m) of a 1MW TRIGA nuclear reactor core using low threshold, cryogenic germanium and silicon detectors. Given the Standard Model cross section of the scattering process and the proposed experimental proximity to the reactor, as many as 5–20events/kg/day are expected. We discuss the status of preliminary measurements to characterize the main backgrounds for the proposed experiment. Both in situ measurements at the experimental site and simulations using the MCNP and GEANT4 codes are described. A strategy for monitoring backgrounds during data taking is briefly discussed.

Sensitivity to oscillation with a sterile fourth generation neutrino from ultralow threshold neutrino-nucleus coherent scattering

We discuss prospects for probing short-range sterile neutrino oscillation using neutrino-nucleus coherent scattering with ultra-low energy ($\sim 10$ eV - 100 eV) recoil threshold cryogenic Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A\&M University, and references developing technology based upon economical and scalable detector arrays. The baseline of the experiment is substantially shorter than existing measurements, as near as about 2 meters from the reactor core, and is moreover variable, extending continuously up to a range of about 10 meters. This proximity and variety combine to provide extraordinary sensitivity to a wide spectrum of oscillation scales, while facilitating the tidy cancellation of leading systematic uncertainties in the reactor source and environment. With 100~eV sensitivity, for exposures on the order of 200 kg$\cdot$y, we project an estimated sensitivity to first/fourth neutrino oscillation with a mass gap $\Delta m^2 \sim 1 \, {\rm eV}^2$ at an amplitude $\sin^2 2\theta \sim 10^{-1}$, or $\Delta m^2 \sim 0.2 \, {\rm eV}^2$ at unit amplitude. Larger exposures, around 5,000 kg$\cdot$y, together with 10 eV sensitivity are capable of probing more than an additional order of magnitude in amplitude.

Sensitivity toZ-prime and nonstandard neutrino interactions from ultralow threshold neutrino-nucleus coherent scattering

We discuss prospects for probing Z-prime and non-standard neutrino interactions using neutrino-nucleus coherent scattering with ultra-low energy (~ 10 eV) threshold Si and Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A&M University, and referencing available technology based upon economical and scalable detector arrays. For expected exposures, we show that sensitivity to the Z-prime mass is on the order of several TeV, and is complementary to the LHC search with low mass detectors in the near term. This technology is also shown to provide sensitivity to the neutrino magnetic moment, at a level that surpasses terrestrial limits, and is competitive with more stringent astrophysical bounds. We demonstrate the benefits of combining silicon and germanium detectors for distinguishing between classes of models of new physics, and for suppressing correlated systematic uncertainties.

2014 Founders Award Memorialization--James E. Turner.

Department of Nuclear and Radiological Engineering Nuclear Science Center University of Florida Gainesville, FL [email protected] The authors declare no conflicts of interest.

Subchannel analysis of fuel temperature and departure of nucleate boiling of TRIGA Mark I

An evaluation of fuel temperature and departure of nucleate boiling as a function of bulk pool temperature was performed at the Texas A&M University Nuclear Science Center’s TRIGA Mark I reactor. A subchannel analysis code was written with the support of experimentally determined correlations, including the development of a gap conductance model. The code was validated for predicting peak fuel temperature at all operational power levels. The peak fuel temperature was calculated using different correlations for forced and natural convection flows for pool temperatures of 30°C and 60°C. The forced convection correlation predicted a fuel temperature rise of 2°C for the difference in pool temperatures, contrary to the predicted rise of 26°C from natural convection relationships. Experimental data shows that the relationship of fuel temperature rise with increasing pool temperature is more accurately represented by the natural convection correlation. The peak fuel temperature, for the validated natural convection relationship, is predicted to be 441°C and 457°C at a pool temperature of 30°C and 60°C, respectively. The minimum departure of nucleate boiling ratio is calculated as 2.14 and 1.72 for a pool temperature of 30°C and 60°C, respectively, using the Bernath correlation.

English

This study provides an insight into affecting factors on the development of nuclear research in agriculture from scientists and researchers perspective and also explores the correlations between them.  A questionnaire was developed and distributed to 165 scientists and researchers who work in Nuclear Science and Technology Research center and Biotechnology Institute, Tehran, Iran. Collected data were analyzed using the statistical package SPSS. Statistical measurements were used for description (standard deviations, means, percent and frequencies). For promotion of agricultural research, accurate inspection of government on research activities and governmental policies were identified as the main factors for governmental supports and political factors, respectively. The majority of researchers believed that investing in specialists’ education and using of external researchers in order to exchange information are the top socio-economic and communication factors, respectively. There was a significant correlation between governmental supports, political factors, socio-economic factors, communication factors, years of employment, knowledge of researchers about nuclear technology in agriculture, participation level in agricultural projects with development of nuclear agricultural research. Backward regression of the study indicated that 75% (R2= 0.75) of variance on development of nuclear agricultural research could be explained by variables.   Key words: Communication factors, governmental supports, nuclear research, political factors, socio-economic factors.

English

Swift heavy ions (SHI) available with 15 million Volt Pelletron accelerator at Inter University Accelerator Centre (IUAC) Delhi, formerly known as Nuclear Science Centre, (NSC), provide a unique opportunity to researchers for accelerator based materials science research. The major research areas can be broadly categorised as electronic sputtering, interface modifications, synthesis and modification of nanostructures, phase transitions and ion beam-induced epitaxial crystallisation. In, general, SHI irradiation based-materials may not be economically feasible, still it could be of interest for very specific cases in defence and space research. The paper gives a glimpse of the current research activities in materials science with SHIs, at IUAC.Defence Science Journal, 2009, 59(4), pp.401-412, DOI:http://dx.doi.org/10.14429/dsj.59.1540

Accelerator-Based Materials Science Research Activities at IUAC Delhi

Swift heavy ions (SHI) available with 15 MV Pelletron accelerator at Inter University Accelerator Centre (IUAC) Delhi, formerly known as Nuclear Science Centre, NSC, are utilized for modification and characterization of materials. Out of a vast variety of research areas, the problems related to electronic sputtering, interface modifications, nano phase generation and their modification by SHIs, phase transitions, and ion beam induced epitaxial crystallization have been of major interest. An overview of the current research activities in materials science with SHIs, at IUAC, is given.

Detection system built from commercial integrated circuits for real-time measurement of radiation dose and quality using the variance method

A small, specialised amplifier using commercial integrated circuits (ICs) was developed to measure radiation dose and quality in real time using a microdosimetric ion chamber and the variance method. The charges from a microdosimetric ion chamber, operated in the current mode, were repeatedly collected for a fixed period of time for 20 cycles of 100 integrations, and processed by this specialised amplifier to produce signal pulse heights between 0 and 10 V. These signals were recorded by a multi-channel analyser coupled to a computer. FORTRAN programs were written to calculate the dose and dose variance. The dose variance produced in the ion chamber is a microdosimetric measure of radiation quality. Benchmark measurements of different brands of ICs were conducted. Results demonstrate that this specialised amplifier is capable of distinguishing differences of radiation quality in various high-dose-rate radiation fields including X rays, gamma rays and mixed neutron-gamma radiation from the research reactor at Texas A&M University Nuclear Science Center.

Micronuclei induction in human fibroblasts exposed in vitro to Los Alamos high-energy neutrons

High-energy secondary neutrons, produced by the interaction of galactic cosmic rays with the atmosphere, spacecraft structure and planetary surfaces, contribute to a significant fraction to the dose equivalent in crew members and passengers during commercial aviation travel, and astronauts in space missions. The Los Alamos Nuclear Science Center (LANSCE) neutron facility’s ICE House 30L beamline is known to generate neutrons that simulate the secondary neutron spectra of earth’s atmosphere. The neutron spectrum is also similar to that measured onboard spacecraft like the MIR and International Space Station (ISS). To evaluate the biological damage, we exposed human fibroblasts in vitro to the LANSCE neutron beams without degrader at an entrance dose rate of 25 mGy/h and analyzed the micronuclei (MN) induction. The cells were also placed behind a 9.9 cm water column to study the effect of shielding in the protection of neutron induced damages. It was found that the dose response in the MN frequency was linear for the samples with and without shielding and the slope of the MN yield behind the shielding was reduced by a factor of 3.5. Compared to the MN induction in human fibroblasts exposed to a γ source at a similar low dose rate, the RBE was found to be 16.7 and 10.0 for the neutrons without and with the 9.9 cm water shielding, respectively.

Physico-chemical modifications induced in Makrofol-N polycarbonate by swift heavy ions

Optical, chemical and thermal properties of the polymers can be modified by swift heavy ion (SHI) irradiation. Fifty microns thick films of Makrofol-N were irradiated with 70MeV C5+ ions to the fluences of 107, 108 and 9.3×1011 and 9.3×1012ions/cm2 from Pelletron accelerator at Nuclear Science Centre, New Delhi, India. The characterization of the radiation induced modifications has been carried out with FTIR, UV–Vis and differential scanning calorimetry (DSC). No change has been observed at lower fluences of 107 and 108ions/cm2. At higher fluences, slight shift in the optical absorption edge towards the red end of the spectrum has been observed with increase in fluence. FTIR and thermal data show changes at higher fluences.

Characterization of Nanocomposite Polymeric Membrane

Composite membrane has good permeability and selectivity for gases, which depends upon the operating conditions. The solubility and diffusivity of the penetrant in the polymer matrix control the transport through non-porous dense membrane. In the present work, the nano sized particles of Co0.6Zn0.4Fe2O4 were prepared by the co-precipitation method and characterized by the XRD technique with particle size of 10 nm. Nanocomposite polycarbonate membranes were studied before and after irradiation by the 35Cl9+ ion of 120 MeV at the Nuclear Science Centre, New Delhi. The distribution of nanoparticles throughout the membrane was characterized by the optical microscope. Gas transport properties of H2, CO2 and air for these nanocomposite membranes were investigated. It was found that membrane containing nanoparticles shows low permeability with high permselectivity. After irradiation by swift heavy ions (SHI), high gas permeability and high permselectivity has been observed for these nanocomposite membranes.

Performance of first high temperature superconducting ECRIS

High temperature superconducting (HTS) electron cyclotron resonance ion source called PKDELIS was designed, developed as a collaborative project mainly between Inter University Accelerator Centre (formerly Nuclear Science Centre) and Pantechnik. One of the major criteria of the design was to get a high performance source suitable for cryogen-free operation on a high voltage platform with minimum requirements of electrical power and cooling water. Ion beams having A∕q of ∼7 are required from this source for the high current injector of the superconducting linear accelerator. The HTS coils have been operational since 2003. A 80mm gap, medium resolution, “third order” corrected analyzing magnet having a bending radius of 300mm has been coupled close to the source. The analyzed beam is collected using a high power, water cooled Faraday cup. The design and performance of the source and issues related to the extraction and transport of the beam are discussed in detail.

Development of Zn and Eu beams by plasma sputtering

Accelerated ion beams of various species are important tools to engineer the materials. The low energy ion beam facility (LEIBF) at Nuclear Science Centre (NSC) provides the ion beams of energy in the range of a few keV to a few MeV. The LEIBF is fully operational since 2001 and its performance has been tested very well with ion beams from noble gases. Metallic and rare earth ion beams have important role in the field of nano-technology and enhancement of optical properties of semiconducting nano-particles inside various matrices. During the last few years, an effort was made to extract ion beams of various metal and rare earth elements using different techniques. Here we describe the successful development of Zn and Eu ion beams using sputtering technique in electron cyclotron resonance (ECR) ion source. Operational experience to produce such kind of beams and results on beam analysis are described in the paper.

SHI induced surface modification studies of HOPG using STM

The highly oriented pyrolytic graphite (HOPG) samples (Grade ZYB with grain size ∼1mm) are irradiated with 150MeV Au beam with fluences varying from 1×1011 ions/cm2 to 2×1013 ions/cm2. The surface topography and the I–V characteristics are studied using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) at Nuclear Science Centre, New Delhi. The formation of hillocks is observed for the samples irradiated with fluences of 1×1011 ions/cm2, 1×1012 ions/cm2 and 1×1013 ions/cm2 with typical diameters of 6.2, 2.2 and 1.5nm, respectively. No hillocks are observed for the sample irradiated with fluence of 2×1013 ions/cm2, though the formation of small craters at some places are observed. The formation of hillocks is attributed to nuclear energy loss induced collision cascades near the surface. The reduction in hillocks size and formation of craters at higher fluence is attributed to the electronic sputtering from the surface. The STS studies of I–V characteristics show an increasing ohmic behavior with fluence which is attributed to increasing metallic state for HOPG surface due to irradiation induced increase of carbon bond lengths.