Publications

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Multijunction thermal converters are routinely used at many primary standards laboratories for ac voltage measurements and calibrations. After nearly two decades of inactivity, the Primary Standards Laboratory at Sandia National Laboratories has reestablished the process of fabricating silicon based multijunction thermal converters. Initial results indicate the devices perform similarly to devices fabricated circa 2001 with ac-dc differences of less than 2 mu mathrm{V}/mathrm{V} over the frequency range of 20 Hz to 20 kHz. From 20 kHz to 1 MHz, the ac-dc difference was higher, but remained below 200 mu mathrm{V}/mathrm{V}. In addition to presenting these results, new design considerations, such as high-resistivity substrates for high-frequency applications, are discussed.

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The basis of this project was to characterize the various uncertainty contributors of an acoustic chamber. The acoustic chamber will be used to calibrate and characterize infrasound sensors used in the field in the frequency range of 0.001 Hz to 4 Hz. The components characterized include the internal volume of the chamber, the piston area of the speaker creating the dynamic sound wave, the environmental stabilization of the chamber and the chamber's leak rate. Also, the resonant frequency of the chamber was evaluated and found to be far outside the frequency band of interest. ACKNOWLEDGEMENTS The authors would like to acknowledge Randy Rembold and John Merchant for supporting and funding this project through the Defense Threat Reduction Agency (DTRA). We would also like to thank Henry Lorenzo and Monico Lucero of Manufacturing Liaison working along with Robert Jones and Tony Bryce of Mechanical Calibration for performing the dimensional measurements of the Acoustic Chamber. We would like to thank Curt Mowry and Adam Pimentel of Organization 01852 for measuring the density of a sample of the fiber-reinforced material of the grate. We would also like to thank the two main reviewers of this document Raegan Johnson and Dalai la Mora whose comments/suggestions helped improve and clarify this report.

This SAND report fulfills the final report requirement for the Born Qualified Grand Challenge LDRD. Born Qualified was funded from FY16-FY18 with a total budget of ~$13M over the 3 years of funding. Overall 70+ staff, Post Docs, and students supported this project over its lifetime. The driver for Born Qualified was using Additive Manufacturing (AM) to change the qualification paradigm for low volume, high value, high consequence, complex parts that are common in high-risk industries such as ND, defense, energy, aerospace, and medical. AM offers the opportunity to transform design, manufacturing, and qualification with its unique capabilities. AM is a disruptive technology, allowing the capability to simultaneously create part and material while tightly controlling and monitoring the manufacturing process at the voxel level, with the inherent flexibility and agility in printing layer-by-layer. AM enables the possibility of measuring critical material and part parameters during manufacturing, thus changing the way we collect data, assess performance, and accept or qualify parts. It provides an opportunity to shift from the current iterative design-build-test qualification paradigm using traditional manufacturing processes to design-by-predictivity where requirements are addressed concurrently and rapidly. The new qualification paradigm driven by AM provides the opportunity to predict performance probabilistically, to optimally control the manufacturing process, and to implement accelerated cycles of learning. Exploiting these capabilities to realize a new uncertainty quantification-driven qualification that is rapid, flexible, and practical is the focus of this effort.

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