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Results for “Optical radiation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Radiation, optical, power flow, and electrical diagnostics at the Z facility: Layout and techniques utilized to operate in the harsh environment

The Z machine is a current driver producing up to 30 MA in 100 ns that utilizes a wide range of diagnostics to assess accelerator performance and target behavior conduct experiments that use the Z target as a source of radiation or high pressures. Here, we review the existing suite of diagnostic systems, including their locations and primary configurations. The diagnostics are grouped in the following categories: pulsed power diagnostics, x-ray power and energy, x-ray spectroscopy, x-ray imaging (including backlighting, power flow, and velocimetry), and nuclear detectors (including neutron activation). We will also briefly summarize the primary imaging detectors we use at Z: image plates, x-ray and visible film, microchannel plates, and the ultrafast x-ray imager. The Z shot produces a harsh environment that interferes with diagnostic operation and data retrieval. We term these detrimental processes “threats” of which only partial quantifications and precise sources are known. Finally, we summarize the threats and describe techniques utilized in many of the systems to reduce noise and backgrounds.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Combining Clinical and Dosimetric Features in a PBS Proton Therapy Cohort to Develop a NTCP Model for Radiation-Induced Optic Neuropathy

Radiation-induced optic neuropathy (RION) is a rare, yet severe complication following radiation therapy for brain, head and neck, or skull-base tumors. Although several risk factors, such as age, metabolic syndrome, and delivered dose, have been identified, we aimed at expanding the understanding of the mechanisms of interplay regarding dosimetry and patient variables leading to the onset of RION with a focus on proton therapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2023

Temperature dependent index of refraction compensation and radiation resistance in monolithic optical systems

Monolithic catadioptric optical systems are susceptible to defocus errors caused by inhomogeneous temperature within the glass material due to temperature dependent index of refraction. This invention discloses methods to mitigate these errors using tuned materials in its optical design coupled with active optical radiative heating to provide optimal performance and includes methods to enhance radiation resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Origins of radiation-induced optical attenuation in neutron-irradiated single-crystal sapphire at elevated temperatures

Sapphire (α-Al 2 O 3 ) is a candidate fiber-optic sensor material for extreme temperature environments, potentially including those of nuclear reactors. However, its optical transmission under high-dose neutron irradiation is not well understood compared with that of conventional fused silica. This study examined dimensional changes, optical transmission, and irradiation-induced defects in neutron-irradiated α-Al 2 O 3 at temperatures of 298 °C to 688 °C and doses of 3.2 to 12 dpa. Although previous studies attributed radiation-induced attenuation (RIA) at the highest irradiation temperatures to increased optical scattering from radiation-induced voids, our findings indicate that scattering from neither voids nor dislocation loops can explain the measured attenuation. Instead, absorption due to aluminum vacancy centers appears more likely based on a comparison of the spectral features of the measured optical attenuation with previous literature. Significant c-axis swelling (5.51 % ± 0.83 %) was observed in the 12 dpa, 592 °C irradiated sample, much higher than earlier measurements, suggesting temperature sensor drift of 543 °C to 1,140 °C. Void patterning was predominantly observed along the a-axis, differing from previous studies on polycrystalline samples, which showed c-axis patterning. Dislocation loops evolved into network dislocations with increasing temperature and dose; voids formed within these structures, showing no size or density changes, indicating an atypical growth mechanism.

Neutron irradiation↗
DOE OSTI2022

Effects and mitigation of pulsed power radiation on optical fiber velocimetry

We report optical fiber diagnostics are extensively used in pulsed power experiments, such as the Sandia Z machine. However, radiation produced in a pulsed power environment can significantly affect these measurements. Catastrophic fiber darkening may be mitigated with shielding, but no flexible material can stop all radiation produced by the machine and/or target. Radiation-induced refractive index modulations are particularly challenging for optical interferometry. Several approaches for radiation-tolerant photonic Doppler velocimetry are discussed here.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Coated fiber optic chemical and radiation sensors

Distributed fiber optic chemical and radiation sensors formed by coating the fibers with certain types of response materials are provided. For distributed chemical sensors, the coatings are reactive with the targets; the heat absorbed or released during a reaction will cause a local temperature change on the fiber. For distributed radiation sensors, coating a fiber with a scintillator enhances sensitivity toward thermal neutrons, for example, by injecting light into the fiber. The luminescent components in these materials are taken from conjugated polymeric and oligomeric dyes, metal organic frameworks with sorbed dyes, and two-photon-absorbing semiconductors. The compositions may exhibit strong gamma rejection. Other scintillators combining luminescent materials with neutron converters are available. With a multiple-layer coating, it may be possible to identify the presence of both neutrons and gamma rays, for example. Coatings may be applied during manufacture or in the field.

Lamberti, Vincent E.↗
DOE OSTI2020

100 Gbps Radiation Tolerant Optical Transceiver (Final Technical Report)

The overall technical objective in phase I for the Surface Emitting Laser-Electro-Absorption Modulator (EAM) was to demonstrate feasibility of this approach by designing and building the laser-EAM chips, optimizing the fabrication process for the Laser/EAM in a series of 3 fabrication runs, irradiating Laser/EAM chips from each run and DC testing of the chips post radiation. 100 Gbps/channel testing would be done at the end of the phase II program before and after radiation. The overall technical objective for the driver circuit was to demonstrate the radiation tolerance of a circuit using the same technology as the driver, and to design the appropriate driver circuit.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Coated fiber optic chemical and radiation sensors

Distributed fiber optic sensors formed by covering the fibers with tubing are provided. The tubing including responsive materials formulated or configured to, responsive to exposure to one of a target chemical species and a target radiation particle, change a relative size and generate a localized effect on or in the optical fiber.

Lamberti, Vincent E.↗
DOE OSTI2025

A cryogenic white light absorption spectroscopy setup with in situ gamma irradiation and thermo-optical annealing for optical fiber radiation-induced attenuation characterization

Silica optical fiber sensors offer a fast, distributed measurement solution in various cryogenic and radiation environments, such as magnets for fusion power. Under these conditions, light-absorbing point defects limit lifetime via radiation-induced attenuation (RIA). To support RIA kinetics prediction, we present an in situ, broadband absorption spectroscopy setup combining gamma irradiation with liquid nitrogen cooling. The apparatus enables continuous monitoring of narrowband RIA levels and the use of secondary optical annealing light sources, alongside broadband spectrum measurements to characterize RIA defects through spectrum decomposition. Initial results confirm the inevitable photobleaching effect of the probe light source, which must be accounted for. In addition, we report RIA kinetics during cycles of gamma irradiation at 77 K and isochronal thermal annealing steps from liquid nitrogen to room temperature, showcasing the setup’s ability to replicate real fiber operation scenarios. These instruments form an ideal platform to further study the kinetics of RIA coupled with thermal and optical annealing.

Absorption spectroscopy↗
DOE OSTI2020

A study of radiation tolerance in optical cements

We study the effect ionizing radiation has on light transmission in the wavelength range 190–1100 nm for a number of optically clear epoxies. We find that the transmittance of traditional, commercially available, optical epoxies show significant degradation for exposures of 1×10 12 MIPs/cm 2 . Degradation of light transmission progresses from the shortest wavelengths at low doses to longer wavelengths as the dose increases. In epoxy joints that are 0.1 mm thick, we observe that more than 5% of the light is lost for wavelengths less than 400 nm for traditional optical epoxies. Our studies have identified an optically clear epoxy that shows little degradation for radiation exposures up to 5.9× 10 14 MIPs/cm 2 (≈ 220 kGy).

Radiation-hard detectors↗
DOE OSTI2020

Design and Analysis of a Halo-Measurement Diagnostics

A large dynamical-range diagnostics (LDRD) design at Jefferson Lab will be used at the FAST-IOTA injector to measure the transverse distribution of halo associated with a high-charge electron beam. One important aspect of this work is to explore the halo distribution when the beam has significant angular momentum (i.e. is magnetized). The beam distribution is measured by recording radiation produced as the beam impinges a YAG:Ce screen. The optical radiation is split with a fraction directed to a charged-couple device (CCD) camera. The other part of the radiation is reflected by a digital micromirror device (DMD) that masks the core of the beam distribution. Combining the images recorded by the two cameras provides a measurement of the transverse distribution with over a large dynamical range. The design and analysis of the optical system will be discussed including optical simulation using SRW and the result of a mockup experiment to test the performances of the system will be presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Interference effects in the high-order harmonic amplification process in the active medium of a plasma-based X-ray laser modulated by an optical field

We study the process of propagation of high harmonics of optical radiation in an active medium of a plasma-based X-ray laser, simultaneously irradiated by an intense optical field of fundamental frequency. It is shown that for moderate plasma dispersion of the active medium at the frequency of the modulating optical field, the energy and relative amplitudes of the harmonics at the output of the medium are determined by their phases at the entrance to the medium, as well as by the time-delay of the harmonics with respect to the modulating field. These dependences are due to interference of high-order harmonics with a set of multi-frequency fields generated by each of the harmonics in the process of coherent scattering in a modulated active medium. The possibilities of using these effects to increase the efficiency of harmonic amplification, to control the harmonic spectrum, and determine the relative phases at the entrance to the medium are discussed on the example of the active medium of hydrogen-like Li{sup 2+} ions (with a 13.5 nm wavelength of an inverted transition). (paper)

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

(Cd,Mg)Te crystals for picosecond-response optical-to-x-ray radiation detectors

We demonstrate a photodetector sensitive to both optical and x-ray picosecond pulses based on our in-house grown cadmium magnesium telluride (Cd,Mg)Te single crystal. Specifically, we developed In-doped Cd0.96Mg0.04Te material and discuss its femtosecond optical photoresponse, as well as the detector performance, such as <100-pA dark current and up to 0.22-mA/W responsivity for 780-nm wavelength optical radiation. The detector exposed to Ti fluorescence (K alpha) x-ray pulses at 4.5 keV, generated by a free-electron laser beam with the central energy of 9.8 keV and <100 fs pulse width, exhibited readout-electronics-limited 200-ps full-width-at-half-maximum photoresponse, demonstrating that it is suitable for coarse timing in free-electron laser x-ray/optical femtosecond pump–probe spectroscopy applications.

Instruments & Instrumentation↗