Currently, there are 4 existing methods that are used for alpha particle detection in water: Gas flow proportional counter, PMT-based scintillation counter, liquid scintillation counting and alpha-particle spectrometry. However, NONE of these existing methods can be tested directly in water or in real-time due mainly to the limitation of the detector material itself as well as associated device design. These existing detector technologies all require some form of evaporation, sample preparation as well as laboratories test procedures in the lab, which is clearly not practical for time-critical situations as in war-fare environment or future threads. In this work, we report the development of a novel scintillation detector material and its associated device design, the ultra-compact, lightweight SiPM-based Hg2Br2 scintillation detector that can directly detect gross alpha in drinking water in the field, and in real-time while being wearable as needed, especially for soldiers and military personnel in general. This novel detector does not require test sample preparation. Besides environmental and health safety, the detector also has additional capabilities such as energy discrimination and good counting efficiency so that it can be practically used in low radioactivity scenarios. Moreover, the novel Hg2Br2 scintillation detector material is also simultaneously capable of detecting other forms of radiation emanating from radioactive materials, including dual gamma-neutron detection capability, and having excellent radiation hardness.
We present a photodetector capable of detecting both optical and x-ray picosecond pulses, based on our in-house grown cadmium magnesium telluride (Cd,Mg)Te single crystals. We focused on a specific Cd0.97Mg0.03Te, In-doped crystal composition, because of its bandgap suitable for 800-nm-wavelength light detection and a single-picosecond optical photoresponse. The detector was fabricated as a planar metal-semiconductor-metal structure with interdigitated electrodes and exhibited a linear, Schottky-free, current-voltage characteristics with <40-pA dark current and up to 20-mA/W responsivity. The detector temporal resolution was measured to be ~200-ps full-width-at-half-maximum transient, in response of ~100-fs-wide pulses consisting of either optical (800-nm wavelength) or x-ray (4.5-keV) photons and was limited by the detector housing and 15-GHz bandwidth of the readout oscilloscope. The latter demonstrates the detector is suitable for coarse timing in x-ray free-electron laser/optical femtosecond pump-probe spectroscopy applications. We also demonstrated that due to its very high stopping power, the Cd0.97Mg0.03Te detector responded well to various nuclear gamma sources with energy ranging from 59.6-keV to 660-keV.
Existing COTS inorganic scintillators all have the characteristic of being very good at certain desirable properties, but not sufficient at other desirable properties for HEP. The demand for suitable scintillators (with regards to both scintillation detector properties and suitable pricing), to be used for modern intensities frontier (Mu2e-II), energy frontier (High luminosity large hadron collider) and future e+e- collider projects (aimed as Higgs bosons factory, such as the International Linear Collider (ILC) and the Future Circular Collider (FCC) are putting even higher challenges on crystal scintillators. In this work, we report the development of a novel high-performance scintillators that can address the issues associated with existing scintillators, the activator doped Hg2Br2. Initial results are very encouraging on the detection of gamma and alpha particles using a solid-state photomultiplier (SSPM). The responses have been stable and repeatable. Hg2Br2 also has many advantages over existing COTS scintillators such as: high density, bright, fast, good energy resolution, no intrinsic radiation, radiation hard and cost-effectiveness. We present here why Hg2Br2 is the next generation scintillator for high energy physics experiments as well as other scientific and imaging applications such as planetary science and medical imaging.
Tellurium dioxide is the most widely used uniaxial crystal for acousto-optic devices. Acousto-optic tunable filters based on this material can cover spectral range from UV to MWIR in a non-collinear configuration. The diffracted narrow band output beams have orthogonal linear polarizations, propagating in different directions, allowing the filter to act as polarizing beam splitter/analyzer as well. To achieve full electronic tuning, two liquid crystal variable retarders are used to measure all six polarization states used in the calculation of Stokes vector. We will present the design of the instrument, test results, and performance considerations.
We report on the development of an acousto-optic tunable filter (AOTF) based novel, high speed spectropolarimeter system operating over the visible and near-IR spectral bands to extract Stokes and Mueller matrices. Developed primarily for planetary composition and analysis applications, the wavelength tunable polarimetric system is configured with tellurium dioxide based AOTF and liquid crystal based variable retarders (LCVR) with no movable mechanical parts. Fitted with a standard silicon camera for operation up to 900 nm and a Mercury Cadmium Telluride (MCT) camera for operation up to 2500 nm, the spectropolarimetric system is currently configured for passive operation. The operation of this spectropolarimetric system is fully automated with an interactive and user friendly graphical user interface, and accordingly provides a snapshot polarimetric measurement capability in minutes.
In this paper, development of single crystalline n- and p- type PbTe crystals and PbTe bulk nanocomposites using PbTe
nano powders and emerging field assisted sintering technology (FAST) are discussed. Materials requirements for efficient
thermoelectric power generation using waste heat at intermediate temperature range (6500 to 8500 K) will be discussed.
Recent results on production of n- and p- type PbTe crystals and their thermoelectric characterization will be presented.
Relative characteristics and performance of PbTe bulk single crystals and nano composites for thermoelectric power
generation will be discussed.
Polycrystalline ceramic laser materials are gaining importance in the development of novel diode-pumped solid-state
lasers. Compared to single-crystals, ceramic laser materials offer advantages in terms of ease of fabrication, shape, size,
and control of dopant concentrations. Recently, we have developed Neodymium doped Yttria (Nd:Y2O3) as a solid-state
ceramic laser material. A scalable production method was utilized to make spherical non agglomerated and
monodisperse metastable ceramic powders of compositions that were used to fabricate polycrystalline ceramic material
components. This processing technique allowed for higher doping concentrations without the segregation problems that
are normally encountered in single crystalline growth. We have successfully fabricated undoped and Neodymium doped
Yttria material up to 2" in diameter, Ytterbium doped Yttria, and erbium doped Yttria. We are also in the process of
developing other sesquioxides such as scandium Oxide (Sc2O3) and Lutesium Oxide (Lu2O3) doped with Ytterbium,
erbium and thulium dopants. In this paper, we present our initial results on the material, optical, and spectroscopic
properties of the doped and undoped sesquioxide materials. Polycrystalline ceramic lasers have enormous potential
applications including remote sensing, chem.-bio detection, and space exploration research. It is also potentially much
less expensive to produce ceramic laser materials compared to their single crystalline counterparts because of the shorter
fabrication time and the potential for mass production in large sizes.
Satellite and space-based applications of photonic devices and systems require operational reliability in the harsh
environment of space for extended periods of time. This in turn requires every component of the systems and their
packaging to meet space qualifications. Acousto- and electro-optical devices form the major components of many
current space based optical systems, which is the focus of this paper. The major space qualification issues are related to:
mechanical stability, thermal effects and operation of the devices in the naturally occurring space radiation environment.
This paper will discuss acousto- and electro-optic materials and devices with respect to their stability against mechanical
vibrations, thermal cycling in operating and non-operating conditions and device responses to space ionizing and
displacement radiation effects. Selection of suitable materials and packaging to meet space qualification criteria will also
be discussed. Finally, a general roadmap for production and testing of acousto- and electro-optic devices will be
discussed.
In this paper, recent progress made towards the development of transparent Nd doped ceramic yttria is presented.
Using 99.99% pure raw materials and with improved material processing techniques, Nd doped ceramic yttria test
samples greater than 99% transmission at 2000nm wavelength and bandedge <250nm have been produced. The test
samples were >1" x 1" x 10mm in dimensions. Nd ions were successfully incorporated into undoped ceramic yttria
material through diffusion process.
AOTF spectrometers have found useful role in space exploration due to their ruggedness, tunability and absence of moving parts. We discuss their
space qualification issues.
High power solid state tunable lasers have played an important role in providing the technology necessary for active remote sensing and would be very useful for space exploration. Many recent studies on diode-pumped solid state lasers have focused on polycrystalline ceramic lasers. We present our initial results on the material, optical, and spectroscopic properties of a solid-state ceramic laser material using neodymium doped Yttria (Nd:Y2O3). Using a proprietary scalable production method, spherical non agglomerated and monodisperse ceramic powders of Nd:Y2O3 are made that can be used to fabricate polycrystalline ceramic material disks with sintered grain size in a suitable range. Initially, we produced translucent material with good emission properties. In further studies we have successfully prepared transparent Nd:Yttria ceramic material. Polycrystalline ceramic lasers have enormous potential commercial applications, which include remote sensing, chemical detection and space exploration research. Furthermore, the cost to produce ceramic laser materials is potentially much lower than that for single crystal materials because of the shorter time it takes to fabricate the material and also because of the possibility of mass production. The polycrystalline ceramic material that we have produced will be characterized for its suitability as a diode pumped solid state laser. Different laser designs will be discussed including end-pumping schemes and the thin-disk laser configuration.
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