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HgTl2Te is Cyanogen Chloride-like structured and crystallizes in the orthorhombic Immm space group. The structure is zero-dimensional and consists of two mercury molecules and two thallium telluride molecules.
TlCrO12(SO4)2 crystallizes in the cubic Pa-3 space group. The structure is zero-dimensional and consists of eight sulfuric acid molecules, four thallium molecules, and four CrO12 clusters. In each CrO12 cluster, Cr is bonded in an octahedral geometry to six equivalent O atoms. All Cr–O bond lengths are 2.09 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to one Cr and one O atom. The O–O bond length is 1.26 Å. In the second O site, O is bonded in a single-bond geometry to one O atom.
TaO12Tl is Zintl Phase structured and crystallizes in the cubic Fd-3m space group. The structure is zero-dimensional and consists of eight thallium molecules and eight TaO12 clusters. In each TaO12 cluster, Ta is bonded in a cuboctahedral geometry to twelve equivalent O atoms. All Ta–O bond lengths are 2.24 Å. O is bonded in a distorted single-bond geometry to one Ta atom.
TiF6(Tl)2B is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is zero-dimensional and consists of four boron molecules, eight thallium molecules, and four TiF6 clusters. In each TiF6 cluster, Ti3+ is bonded in an octahedral geometry to six equivalent F1- atoms. All Ti–F bond lengths are 1.98 Å. F1- is bonded in a single-bond geometry to one Ti3+ atom.
(Tl)3S is Uranium Silicide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is zero-dimensional and consists of two hydrogen sulfide molecules and six thallium molecules.
TlSO4 crystallizes in the trigonal R32 space group. The structure is two-dimensional and consists of three thallium molecules and three Tl(SO4)2 sheets oriented in the (0, 0, 1) direction. In each Tl(SO4)2 sheet, Tl is bonded to six equivalent O atoms to form distorted TlO6 pentagonal pyramids that share corners with six equivalent SO4 tetrahedra. All Tl–O bond lengths are 2.29 Å. S is bonded to four O atoms to form SO4 tetrahedra that share corners with three equivalent TlO6 pentagonal pyramids. There is one shorter (1.47 Å) and three longer (1.50 Å) S–O bond length. There are two inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one S atom. In the second O site, O is bonded in a distorted bent 120 degrees geometry to one Tl and one S atom.
TlTlF3 is alpha Rhenium trioxide-like structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional and consists of one thallium molecule and one TlF3 framework. In the TlF3 framework, Tl is bonded to six equivalent F atoms to form corner-sharing TlF6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Tl–F bond lengths are 2.36 Å. F is bonded in a linear geometry to two equivalent Tl atoms.
TlTl(Pt3O4)2 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional and consists of four thallium molecules and one Tl(Pt3O4)2 framework. In the Tl(Pt3O4)2 framework, Pt+2.33+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Pt–O bond lengths are 2.05 Å. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Tl–O bond lengths are 2.42 Å. O2- is bonded to three equivalent Pt+2.33+ and one Tl1+ atom to form a mixture of distorted edge and corner-sharing OTlPt3 tetrahedra.
(Tl)3Si is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is zero-dimensional and consists of one silicon molecule and three thallium molecules.
(Tl)6Cl2 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is zero-dimensional and consists of one hydrochloric acid molecule and three thallium molecules.
TlTl3S4(S)2 crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of four hydrogen sulfide molecules; two thallium molecules; and one Tl3S4 sheet oriented in the (0, 0, 1) direction. In the Tl3S4 sheet, there are three inequivalent Tl3+ sites. In the first Tl3+ site, Tl3+ is bonded in a linear geometry to two S2- atoms. Both Tl–S bond lengths are 2.95 Å. In the second Tl3+ site, Tl3+ is bonded in a rectangular see-saw-like geometry to four equivalent S2- atoms. All Tl–S bond lengths are 3.09 Å. In the third Tl3+ site, Tl3+ is bonded in a square co-planar geometry to four equivalent S2- atoms. All Tl–S bond lengths are 3.09 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to two Tl3+ and one S2- atom. The S–S bond length is 2.04 Å. In the second S2- site, S2- is bonded in a 3-coordinate geometry to two Tl3+ and one S2- atom. The S–S bond length is 2.04 Å.
The objective of this research is to design a portable neutron detector that is lightweight and responds to neutrons with energies of 20 MeV and greater. The instrument will be used as a ‘sniffer’ probe for identifying shielding weaknesses at high-energy particle accelerators and be paired with a plastic scintillator to quantify the high-energy neutron dose equivalent. The sniffer probes are two different sizes and comprised of either cesium iodide or sodium iodide, all doped with thallium, making a total of four detectors. The probes were calibrated to respond only to radiations with 8 MeV electron equivalent energy or higher, vastly reducing detector response from background and lower energy radiations. The sniffer probes were tested using californium- 252 and americium-beryllium sources, followed by high-energy (up to 800 MeV) neutron exposures at the Los Alamos Neutron Science Center Weapons Neutron Research (WNR) facility. The sniffer probes were then used to identify areas around the accelerator facility where elevated levels of high-energy radiation was present and the plastic scintillators were placed in these locations to determine the high-energy neutron dose equivalent. The dose equivalent is calculated by measuring the 12 C(n,2n) 11 C reaction, which has a 20.4 MeV neutron threshold. Two locations behind the WNR facility were identified with the probes and the dose equivalent rates from neutron energies above 20 MeV were calculated to be 1.24 mrem/h behind flightpath 30-left and 1.53 behind flightpath 30-right. Of the four sniffer probes, the 2-inch x 2-inch cesium iodide is the recommended probe for performing high-energy shielding surveys. The larger crystal size yields higher sensitivity at lower count rates and the more dense material increases the likelihood of interaction within the crystal.
This project developed and evaluated advanced remote sensing and machine learning approaches to identify, monitor, and address environmental contamination associated with coal combustion residual (CCR) impoundments and landfills at coal-fired power plants. In Phase I, historical and multi-temporal Sentinel-2 satellite imagery, groundwater monitoring data, and environmental variables were integrated to detect vegetation stress potentially caused by toxic metal leaching from coal ash disposal sites. Multiple vegetation and biophysical indices were analyzed to determine their effectiveness in identifying abnormal vegetation growth patterns linked to contamination. Results from case studies conducted at coal ash–impacted power plant sites in North Carolina and Virginia demonstrated that satellite-based vegetation monitoring can serve as an effective early indicator of environmental stress associated with metals such as arsenic, cadmium, cobalt, lead, lithium, radium, and thallium.
Hadronic matter makes about 14% of the known universe. The remaining 86% is Dark Matter (DM). Since it does not interact with the ordinary matter via electromagnetic force, DM is not visible and, to date, it escaped detection. The search for Dark Matter (DM) is one of the hottest topic in modern physics. Despite the increasing number of astrophysical and cosmological observations proving the existence, so far no particle physics experiment has detected DM yet. Up to now, most of the experimental efforts have been focused on the so called WIMP (Weakly Interacting Massive Particle) paradigm, which predicts heavy DM (10 GeV-10 TeV mass range) interacting with Standard Model (SM) particles via the weak force mediators (W or Z bosons). More recently, due to the lack of clear evidence of WIMPs, other models of DM gained the interest of the physics community. These models consider Light DM particles (LDM), in MeV-GeV mass range. Among LDM theories, the Dark Photon theory predicts the existence of a Dark Sector interacting with SM particles via a new massive vector boson (Dark Photon, Heavy Photon or A0), mediator of a new force. This scenario, despite being theoretically well motivated, is remarkably experimentally unexplored. The Beam Dump eXperiment (BDX), is an approved experiment at Jefferson Lab (JLab), aiming to discover the DM predicted witihn the Dark Photon theory. The experiment uses the CEBAF (Continuous Electron Beam Accelerator Facility) 11 GeV electron beam, impinging on the JLab Hall-A beam-dump, to produce a beam of DM particles, detected by a ~ 1 m3 detector made of thallium doped cesium iodide (CsI(Tl)) crystals located ~ 20 m downstream. In order to achieve excellent background rejection, the experimental setup includes active vetos and passive shielding surrounding CsI(Tl) crystals. Given the weakness of the DM-SM interaction, the scattering of a DM particle in the BDX detector is a rare event. Therefore, the characterization of the expected background is a critical aspect of the experiment. Both cosmogenic and penetrating SM particles produced by the beam interaction in the dump contribute to the background of the experiment. While the cosmogenic contribution can be measured during the experiment when the beam is off, beam-related background can only be estimated via Monte Carlo (MC) simulations. Therefore, a careful assessment of possible systematics introduced by the MC is needed. The beam-correlated background characterization was made by measuring the muon flux produced by the interaction of the CEBAF beam with Hall-A dump in a dedicated experimental campaign in spring 2018 [1]. The comparison to the ?ux predicted by MC allowed us to validate the BDX simulation framework. The reach of BDX, i.e. the region that the experiment can probe in the LDM theory parameter space, depends critically on the background rejection capability and signal detection effciency. For this reason, the detector setup was fine-tuned through a dedicated study. The response to LDM and background events was evaluated for different setups and selection cuts. As a result of this procedure, the configuration resulting in the best sensitivity was selected [2]. The reach calculation was performed taking into account the different LDM production mechanisms, including the contribution of secondary particles produced in the beam-dump. In particular, the effect of the secondary positrons annihilation was found to be extremely significant. In the majority of the sensitivity studies, this contribution is neglected, but recent results [3] [4] demonstrated that this process significantly enhances the sensitivity of lepton beam-dump experiments. Currently, the BDX collaboration is focused on the deployment and operation of a small detector, called BDX-MINI, built to perform a preliminary physics measurement searching for LDM at JLab. This test will pave the way to the realization of the full BDX experiment. The measurement is currently ongoing but results are expected by the end of this year. During my PhD I was involved in all aspects of the BDX experiment: design, simulation, prototyping and data analysis. The main results of my work are reported in this thesis. This manuscript is organized as follows: the first Chapter provides an introduction to the theory of LDM, with particular attention to the Dark Photon paradigm; the second Chapter illustrates the BDX experimental setup, the LDM production and detection mechanisms and the expected backgrounds; Chapter 3 and 4 describe, respectively, the BDX-HODO measurement, with a detailed description of the simulations, and the BDX experimental setup and analysis cuts optimization. Chapter 5 reports about BDXMINI detector characterization, calibration and sensitivity estimate. Finally, Chapter 6 describes in detail the calculation of the secondary positron annihilation contribution to the sensitivity of BDX and other electron-beam thick-target experiment.
This report details the data analysis results from data collected during the September-October 2019 joint survey series between the Department of Energy (DOE) National Nuclear Security Administration (NNSA) Aerial Measuring System (AMS) asset, and the Government of India’s Department of Atomic Energy (DAE) Bhabha Atomic Research Centre (BARC). This joint survey series took place at the Nevada National Security Site (NNSS), areas of public land in Southern Nevada, and at the DOE Office of Legacy Management (LM) Large Area Calibration Pads (LACP) at the Grand Junction Regional Airport in Grand Junction, CO. The data detailed in this report were gathered at the LACP. More details regarding the setup of these surveys and personnel involvement can be found in the AMS / BARC Joint Survey Summary Report. The data from the LACP collected by AMS are consistent with past data collection campaigns at the LACP. The AMS Bell 412 (B412) helicopter, equipped with both the standard AMS thallium-doped sodium iodide (NaI(Tl)) 2"x4"x16" 12-detector system and a subset of the BARC Aerial Gamma Spectroscopy System (AGSS) consisting of two independent 3"x3"cylindrical NaI(Tl) detectors, measured each of the five calibration pads for a minimum of 10 minutes. After the helicopter measurements, a pressurized ion chamber (PIC) was used to directly measure radiation exposure rates on each of the pads for a period 5 minutes. The geophysical calibration procedure published by the International Atomic Energy Agency (IAEA) (Erdi-Krausz et al. 2003) was used to determine the spectral stripping sensitivity matrix for naturally occurring radiological material (NORM). The sensitivity matrix is consistent with the AMS long term average. Additionally, the PIC data was used to calibrate the AMS system for exposure rate. The results of the exposure rate analysis are also consistent with AMS long-term averages.
A series of four Advanced Reactor Technologies (ART) experiments have been conducted in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL). From 2006 through 2020, these experiments supported the development and qualification of the new U.S. tristructural isotropic (TRISO) particle fuel for Very High Temperature Reactors (VHTR). Each Advanced Gas Reactor (AGR) experiment consisted of multiple fueled capsules, each plumbed for independent temperature control using a mix of helium and neon gases. The gas leaving a capsule was routed to individual Fission Product Monitor (FPM) detectors. For intact fuel particles, the TRISO particle coatings provide a substantial barrier to fission product release. However, particles with failed coatings, whether because of a minute percentage of initially defective particles, those which fail during irradiation, or those designed to fail (DTF) particles, can release fission products to the flowing gas stream. Because reactive fission product elements like iodine and cesium quickly deposit on cooler capsule components and piping structures as the effluent gas leaves the reactor core, only the noble fission gas isotopes of Kr and Xe tend to reach FPM detectors. The FPM system utilizes High Purity Germanium (HPGe) detectors coupled with a thallium activated sodium iodide NaI(Tl) scintillator. The HPGe detector provides individual isotopic information, while the NaI(Tl) scintillator is used as a gross count rate meter. During irradiation, the 135mXe concentration reaching the FPM detectors is from both direct fission and by decay of the accumulated 135I. About 2.5 hours after irradiation (ten 15.3 minute 135mXe half lives) the directly produced 135mXe has decayed and only the longer lived 135I remains as a source. Decay systematics dictate that 135mXe will be in secular equilibrium with its 135I parent, such that its production rate very nearly equals the decay rate of the parent, and its concentration in the flowing gas stream will appear to decay with the parent half life. This equilibrium condition enables the determination of the amount of 135I released from the fuel particles by measurement of the 135mXe at the FPM following reactor shutdown. In this paper, the 135I released will be reported.
Inorganic halides (e.g., inorganic halide scintillators) of the general formula A3B2X9, including inorganic halides comprising thallium monovalent cations and/or combinations of different halides, are described. Radiation detectors including the inorganic halide scintillators and methods of using the detectors to detect high energy radiation are also described. In some cases, the scintillators can include a gadolinium cation, a boron cation, a lithium cation, a chloride ion, or combinations thereof and the scintillator can be used to detect neutrons.
Reaction of [CuH(PPh 3 )] 6 with 1 equiv. of Tl(OTf) results in formation of [Cu 6 TlH 6 (PPh 3 ) 6 ][OTf] ([1]OTf]), which can be isolated in good yields. Variable-temperature 1 H NMR spectroscopy, in combination with density functional theory (DFT) calculations, confirms the presence of a rare Tl−H orbital interaction. According to DFT, the 1 H chemical shift of the Tl-adjacent hydride ligands of [1] + includes 7.7 ppm of deshielding due to spin-orbit effects from the heavy Tl atom. In conclusion, this study provides valuable new insights into a rare class of metal hydrides, given that [1][OTf] is only the third isolable species reported to contain a Tl−H interaction.