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Search Publications by: Steven Grantham (Fed)

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Displaying 1 - 25 of 131

Laser Beam Metrology for AM-Bench 2022: Approaches, Results, and Lessons Learned

April 1, 2025
Author(s)
David Deisenroth, Jordan Weaver, Sergey Mekhontsev, Steven Grantham, Shawn P. Moylan
One of key parameters of additive manufacturing by laser powder bed fusion of metal parts (PBF-LB/M) is the power density distribution (PDD) of the process laser beam. This paper describes the methods used to measure the beam PDD, discussing well

Instrument Development for Spectroscopic Ellipsometry and Diffractometry in the EUV

April 24, 2024
Author(s)
Stephanie Moffitt, Bryan Barnes, Thomas A. Germer, Steven Grantham, Eric Shirley, Martin Sohn, Daniel Sunday, Charles S. Tarrio
Semiconductor devices are noted for ever-decreasing dimensions but now are also becoming more complex. While scanning probe microscopy can still resolve the smallest features, it does not have the throughput for high-volume characterization of full wafers

NIST efforts in extreme-ultraviolet metrology

November 21, 2023
Author(s)
Charles S. Tarrio, Steven Grantham, Rob Vest, Thomas A. Germer, Bryan Barnes, Stephanie Moffitt, Brian Simonds, Matthew Spidell
For several decades, the National Institute of Standards and Technology (NIST) has actively supported metrology programs for extreme ultraviolet (EUV) lithography. We will describe our existing programs in optics lifetime, reflectometry, and radiometry

Laser Calibration for Powder Bed Fusion Additive Manufacturing Process

July 27, 2022
Author(s)
Ho Yeung, Steven Grantham
Laser powder bed fusion systems use a high-power laser, steered by two galvanometer mirrors to scan a pattern on metal powder layers. The laser spot size, position, and synchronization between the laser power and position are critical to the build quality

NIST Traveling Tunable Laser Projector (TTLP) for UV-Blue Disinfection Dose Determinations

June 21, 2022
Author(s)
Thomas C. Larason, Steven Grantham, Clarence Zarobila, Yuqin Zong, C Cameron Miller, Michael Schuit, Brian Holland, Stewart Wood, Melissa Krause
As COVID-19 was overtaking the world in the spring of 2020, the National Institute of Standards and Technology began collaborating with the National Biodefense Analysis and Countermeasures Center to study the inactivation of SARS-CoV-2 to different UV and

Measurements of Absolute, SI-traceable Lunar Irradiance with the Airborne LUnar Spectral Irradiance (air-LUSI) Instrument

May 5, 2022
Author(s)
John T. Woodward IV, Kevin Turpie, Thomas Stone, S. Andrew Gadsden, Andrew Newton, Stephen Maxwell, Steven Grantham, Thomas Larason, Steven W. Brown
The Airborne LUnar Spectral Irradiance (Air-LUSI) instrument is designed to make low uncertainty, hyperspectral measurements of the lunar spectral irradiance from an ER-2 aircraft from altitudes above 95 % to 99 % of the atmosphere. Measurements cover the

The Irradiance Instrument Subsystem (IRIS) on the Airborne-Lunar Spectral Irradiance (Air-LUSI) Instrument

March 23, 2022
Author(s)
Steven Grantham, Thomas C. Larason, Clarence Zarobila, Stephen Maxwell, John Woodward, Kevin Turpie, S. Andrew Gadsden
The objective of the airborne LUnar Spectral Irradiance (air-LUSI) project is to make low uncertainty, SI-traceable measurements of the lunar spectral irradiance in the visible to near-infrared (VNIR) region from an aircraft above most of the optically

Measurement Uncertainty of Surface Temperature Distributions for Laser Powder Bed Fusion Processes

August 10, 2021
Author(s)
David Deisenroth, Sergey Mekhontsev, Brandon Lane, Leonard M. Hanssen, Ivan Zhirnov, Vladimir Khromchenko, Steven Grantham, Daniel Cardenas-Garcia, Alkan Donmez
This paper describes advances in measuring the characteristic spatial distribution of surface temperature and emissivity during laser-metal interaction under conditions relevant for laser powder bed fusion (LPBF) additive manufacturing processes. Detailed

Optical and Mechanical Design of a Telescope for Lunar Spectral Irradiance Measurements from a High-Altitude Aircraft

September 8, 2020
Author(s)
Clarence Zarobila, Steven Grantham, Steven W. Brown, John T. Woodward IV, Stephen Maxwell, Dana R. Defibaugh, Thomas Larason, Kevin Turpie
We have designed a non-imaging telescope for measurement of the spectral irradiance of the moon. The telescope was integrated into a wing pod of a NASA ER-2 research aircraft to measure lunar spectral irradiance during flight. The telescope and support

Transient Laser Energy Absorption, Co-axial Melt Pool Monitoring, and Relationship to Melt Pool Morphology

August 16, 2020
Author(s)
Brandon M. Lane, Ivan Zhirnov, Sergey Mekhontsev, Steven E. Grantham, Richard E. Ricker, Santosh Rauniyar, Kevin Chou
Many recent and ongoing studies into the complex melt pool physics during laser powder bed fusion (LPBF) metal additive manufacturing (AM) process measure various aspects of energy transport surrounding the laser-induced melt pool, with focus on laser

Influence of optical system operation on stability of single tracks in selective laser melting

August 20, 2019
Author(s)
Ivan Zhirnov, Igor Yadroitsev, Brandon Lane, Sergey Mekhontsev, Steven Grantham, Ina Yadroitsava
Additive manufacturing (AM) technologies are increasingly being studied and introduced into the modern industry, but for wide applications there exists some "lack of confidence" about the quality of the parts produced by AM. This distrust has an objective