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Nagarkar, Vivek V.

Publications and source records attributed to Nagarkar, Vivek V..

17 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

SBIR Phase I Final Technical Report MODULAR NEUTRON DETECTOR ARRAY FOR PROTEIN CRYSTALLOGRAPHY BEAM LINES Award Number DE-SC0024828 Prepared for U.S. Department of Energy, Office of Science, SC-1 For the Period July 22, 2024 – April 21, 2025 Report Date November 22, 2024 Submitted by Vivek V. Nagarkar, Ph.D., Principal Investigator Report Contributors Mr. Nicholas Anastasi, Dr. Charles Sosa, Dr. Jun Wang, Dr. Lakshmi Soundara Pandian and Dr. Vivek V. Nagarkar

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Nagarkar, Vivek V.↗
DOE OSTI2024

Alkali semi-metal films and method and apparatus for fabricating them

Methods and systems for fabricating a film, such as, for example, a photocathode, having a tailored band structure and thin-film components that can be tailored for specific applications, such as, for example photocathode having a high quantum efficiency, and simple components fabricated by those methods.

Bhandari, Harish B.↗
DOE OSTI2021

Alkali semi-metal films and method and apparatus for fabricating them

Methods and systems for fabricating a film, such as, for example, a photocathode, having a tailored band structure and thin-film components that can be tailored for specific applications, such as, for example photocathode having a high quantum efficiency, and simple components fabricated by those methods.

Bhandari, Harish B.↗
DOE OSTI2020

Advances in High Resolution Ultrafast Scintillators for Fast timing Applications

Scintillation detectors exhibiting high spatial resolution and fast timing capabilities are of vital importance for synchrotron sources. These detectors may be exposed to a variety of X-ray energies (up to 140 keV) and used in high frame rate applications. Here, we describe the advances in the development of thin-film LuI3:Ce scintillators for higher energy X-ray imaging, with fast timing and high spatial resolution. When grown in a single crystalline form, these scintillators are bright, producing 115 000 photons/MeV. However, to achieve high spatial resolution, these scintillators are grown in thin-film form with a microcolumnar structure, controllable to column diameters of <1-30 mu m. Thus, a much thicker scintillator layer (10 mu m-3 mm or higher) may be grown, providing superior X-ray absorption while achieving high resolutions of 50 mu m or better, at the cost of reduced light yield. To study the timing characteristics of the scintillator, time-resolved X-ray excited optical luminescence (TR-XEOL) was performed on two different sets of three samples of LuI3 at the 1-BM beamline of the Advanced Photon Source at Argonne National Laboratory. Besides, we report timing measurements obtained using a photomultiplier tube (PMT) and oscilloscope at Radiation Monitoring Devices (RMD) Inc. Using the TR-XEOL, we determined the decay constants of LuI3 as a function of Ce doping, recording a fast decay component as low as 3.6 ns (39%), one of the fastest values recorded in inorganic scintillators. This fast decay opens up numerous novel applications, where ultrahigh frame rates are important using synchrotron X-rays. This article will discuss fabrication, characterization, and potential applications for this novel scintillator.

fast timing↗
DOE OSTI2019

How Excitation Conditions Alter the Afterglow Characteristics of CsI:Tl,Sm Microcolumnar Films

Combining high light output with the microcolumnar structure, the CsI:Tl films significantly reduce the need for painful tradeoff between thickness (hence, stopping power) and spatial resolution. But both films and monocrystals share two important deficiencies that hinder their use in many high-speed imaging and computed tomography applications: a persistent afterglow and hysteresis. These properties receive the primary attention of this investigation. In our earlier work, we reported that codoping with Sm 2+ brings about a significant reduction in the afterglow of CsI:Tl. Here, focusing on the microcolumnar films, we examine this afterglow-suppressive effect over a wide range of exposure times, from milliseconds to seconds, and at temperatures between 0 °C and 60 °C. Our measurements reveal well-defined dependences on both parameters. At room temperature (20 °C), defined as the normal operating condition, a 10-ms X-ray pulse leaves an afterglow from the standard (Sm-free) CsI:Tl of about 1% at 2 ms after the end of the pulse, changing little as a function of pulselength. Doping with Sm 2+ , however, reduces that afterglow by at least an order of magnitude, although somewhat less so after longer (100 and 1000 ms) pulses. When we change the temperature, however, we find markedly different behavior. Here, we find that a temperature increase of only 60°, without changing the pulselength, cuts the afterglow of standard CsI:Tl films by a factor of 20. However, films of codoped CsI:Tl,Sm, whose afterglow has already been suppressed by the presence of Sm 2+ , show much less change as a function of either temperature or pulse duration. It is the presence of Sm 2+ that makes the biggest difference. As for hysteresis, we again see an improvement, with the performance of the codoped CsI:Tl,Sm films bettering that of the standard (Sm-free) films. After an exposure of 300 mR, the change in light output falls to within 1% of the original after 1 min, whereas standard CsI:Tl films require 30 min to reach the same level.

42 ENGINEERING↗
DOE OSTI2018

Alkali semi-metal films and method and apparatus for fabricating them

Methods and systems for fabricating a film, such as, for example, a photocathode, having a tailored band structure and thin-film components that can be tailored for specific applications, such as, for example photocathode having a high quantum efficiency, and simple components fabricated by those methods.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Neutron imaging integrated circuit and method for detecting neutrons

The present disclosure provides a neutron imaging detector and a method for detecting neutrons. In one example, a method includes providing a neutron imaging detector including plurality of memory cells and a conversion layer on the memory cells, setting one or more of the memory cells to a first charge state, positioning the neutron imaging detector in a neutron environment for a predetermined time period, and reading a state change at one of the memory cells, and measuring a charge state change at one of the plurality of memory cells from the first charge state to a second charge state less than the first charge state, where the charge state change indicates detection of neutrons at said one of the memory cells.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Neutron detector and fabrication method thereof

A neutron detector and a method for fabricating a neutron detector. The neutron detector includes a photodetector, and a solid-state scintillator operatively coupled to the photodetector. In one aspect, the method for fabricating a neutron detector includes providing a photodetector, and depositing a solid-state scintillator on the photodetector to form a detector structure.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Ultra-fast LuI{sub 3}:Ce scintillators for hard x-ray imaging

We have developed ultra-fast cerium-coped lutetium-iodide (LuI{sub 3}:Ce) films thermally evaporated as polycrystalline, structured scintillator using hot wall epitaxy (HWE) method. The films have shown a 13 ns decay compared to the 28 ns reported for crystals. The fast speed coupled with its high density (∼5.6 g/cm{sup 3}), high effective atomic number (59.7), and the fact that it can be vapor deposited in a columnar form makes LuI{sub 3}:Ce an attractive candidate for high frame rate, high-resolution, hard X-ray imaging. In crystal form, LuI{sub 3}:Ce has demonstrated bright (>100,000 photons/MeV) green (540 nm) emission, which is well matched to commercial CCD/CMOS sensors and is critical for maintaining high signal to noise ratio in light starved applications. Here, we report on the scintillation properties of films and those for corresponding crystalline material. The vapor grown films were integrated into a high-speed CMOS imager to demonstrate high-speed radiography capability. The films were also tested at Advanced Photon Source, Argonne National Laboratory beamline 1-ID under hard X-ray irradiation. The data show a factor of four higher efficiency than the reference LuAG:Ce scintillators, high image quality, and linearity of scintillation response over a wide energy range. The films were employed to perform hard X-ray microtomography, the results of which will also be discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Lanthanum halide nanoparticle scintillators for nuclear radiation detection

Nanoparticles with sizes <10 nm were fabricated and characterized for their nanocomposite radiation detector properties. This work investigated the properties of several nanostructured radiation scintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum trifluoride. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

36 MATERIALS SCIENCE↗