Traveling tunable laser projector for UV-blue disinfection dose determinations.

As the COVID-19 pandemic was overtaking the world in the spring of 2020, the National Institute of Standards and Technology (NIST) began collaborating with the National Biodefense Analysis and Countermeasures Center to study the inactivation of SARS-CoV-2 after exposure to different ultraviolet (UV) and blue light wavelengths. This paper describes a 1 kHz pulsed laser and projection system used to study the doses required to inactive SARS-CoV-2 over the wavelength range of 222 to 488 nm. This paper builds on NIST's previous work for water pathogen inactivation using UV laser irradiation.

SARS-CoV-2 inactivation by ultraviolet radiation and visible light is dependent on wavelength and sample matrix.

Numerous studies have demonstrated that SARS-CoV-2 can be inactivated by ultraviolet (UV) radiation. However, there are few data available on the relative efficacy of different wavelengths of UV radiation and visible light, which complicates assessments of UV decontamination interventions. The present study evaluated the effects of monochromatic radiation at 16 wavelengths from 222 nm through 488 nm on SARS-CoV-2 in liquid aliquots and dried droplets of water and simulated saliva.

National Institute of Standards and Technology transportable tunable ultraviolet laser irradiance facility for water pathogen inactivation.

A method of ultraviolet germicidal irradiation (UVGI) for water pathogen inactivation effectiveness using tunable, narrowband laser light is described. A transportable tunable UV (TTUV) laser system for providing a known irradiance (μW/cm) or dose (mJ/cm) suitable for irradiating water samples in Petri dishes over the wavelength range of 210 nm-300 nm was developed by the National Institute of Standards and Technology. The TTUV facility, consisting of a 1 kHz pulsed UV laser and light-tight enclosure containing the optics necessary to uniformly irradiate a water sample, was used in a microbiology laboratory to dose drinking water pathogens and surrogates as part of a Water Research Foundation study in the summer and fall of 2012.

Gain Calibration of Current-to-Voltage Converters.

Current-to-voltage converters are used in many photometric and radiometric applications. The calibration of current-to-voltage converters at a few input currents is not always sufficient to understand the linearity and the bias of a device. Many devices have structure deviating from a linear response over the operating range of a gain setting.

Calibration of night vision goggles: an SI-units-based gain measurement technique.

A gain measurement technique for the calibration of night vision goggles (NVG) is proposed and evaluated. This technique is based on the radiance measurements at the input and output of the NVG. In contrast to the old definition, which uses a non-International System of Units (SI) traceable luminance, the "equivalent luminance unit," the suggested technique utilizes the radiance quantities that are traceable to the SI units through National Institute of Standards and Technology (NIST) standards.

Comparison of UV-Induced Inactivation and RNA Damage in MS2 Phage across the Germicidal UV Spectrum.

Polychromatic UV irradiation is a common method of pathogen inactivation in the water treatment industry. To improve its disinfection efficacy, more information on the mechanisms of UV inactivation on microorganisms at wavelengths throughout the germicidal UV spectrum, particularly at below 240 nm, is necessary. This work examined UV inactivation of bacteriophage MS2, a common surrogate for enteric pathogens, as a function of wavelength.

Action spectra for validation of pathogen disinfection in medium-pressure ultraviolet (UV) systems.

Ultraviolet (UV) reactors used for disinfecting water and wastewater must be validated and monitored over time. The validation process requires understanding the photochemical properties of the pathogens of concern and the challenge microorganisms used to represent them. Specifically for polychromatic UV systems, the organisms' dose responses to UV light and their sensitivity across the UV spectrum must be known.

Wavelength dependent UV inactivation and DNA damage of adenovirus as measured by cell culture infectivity and long range quantitative PCR.

Adenovirus is regarded as the most resistant pathogen to ultraviolet (UV) disinfection due to its demonstrated resistance to monochromatic, low-pressure (LP) UV irradiation at 254 nm. This resistance has resulted in high UV dose requirements for all viruses in regulations set by the United States Environmental Protection Agency. Polychromatic, medium-pressure (MP) UV irradiation has been shown to be much more effective than 254 nm, although the mechanisms of polychromatic UV inactivation are not completely understood.

Comparison of absolute spectral irradiance responsivity measurement techniques using wavelength-tunable lasers.

Independent methods for measuring the absolute spectral irradiance responsivity of detectors have been compared between the calibration facilities at two national metrology institutes, the Helsinki University of Technology (TKK), Finland, and the National Institute of Standards and Technology (NIST). The emphasis is on the comparison of two different techniques for generating a uniform irradiance at a reference plane using wavelength-tunable lasers. At TKK's Laser Scanning Facility (LSF) the irradiance is generated by raster scanning a single collimated laser beam, while at the NIST facility for Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources (SIRCUS), lasers are introduced into integrating spheres to generate a uniform irradiance at a reference plane.