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High-Radiopurity Structural Components Made by Chemical Vapor Deposition, Phase II

Award Information
Agency: Department of Energy
Branch: N/A
Contract: DE-SC0022788
Agency Tracking Number: 0000276545
Amount: $1,100,000.00
Phase: Phase II
Program: SBIR
Solicitation Topic Code: C54-34c
Solicitation Number: N/A
Timeline
Solicitation Year: 2023
Award Year: 2023
Award Start Date (Proposal Award Date): 2023-08-21
Award End Date (Contract End Date): 2025-08-20
Small Business Information
12173 Montague Street
Pacoima, CA 91331-2210
United States
DUNS: 052405867
HUBZone Owned: No
Woman Owned: No
Socially and Economically Disadvantaged: No
Principal Investigator
 Arthur Fortini
 (818) 899-0236
 art.fortini@ultramet.com
Business Contact
 Craig Ward
Phone: (818) 899-0236
Email: craig.ward@ultramet.com
Research Institution
N/A
Abstract

High-radiopurity structural materials are needed for a variety of high-energy physics experiments, particularly those involved in the search for dark matter in which background radiation from trace impurities can hide the desired signal. The structural material with the highest radiopurity available is electroformed copper, but its yield strength is only 12 ksi, which limits its utility as a structural material.Chemical vapor deposition (CVD) converts gaseous reactants to solid products, but only when it is thermodynamically favorable to do so. Thermodynamic calculations were performed to identify CVD process conditions where the desired high-strength refractory metal (tungsten) will be deposited, but radioactive species (e.g. 40K, 232Th, 238U, and the progeny in their decay chains) will not. The predictions were verified empirically via inductively coupled plasma mass spectrometry (ICP-MS) of tungsten materials produced by CVD.Additional thermodynamic calculations were performed to identify deposition conditions for both tungsten and tantalum under which the simultaneous deposition of undesirable elements is thermodynamically prohibited, and tungsten CVD runs were performed using the specified conditions. The resulting deposited materials, along with samples of the reactants, were analyzed at Pacific Northwest National Laboratory (PNNL) via an ICP-MS technique that was developed specifically for tungsten matrices. The concentrations of 232Th and 238U were measured to be as low as 80 and 50 parts per quadrillion (ppq) respectively.Additional assay techniques will be developed by PNNL for other long-lived radionuclides of interest, and residual samples from Phase I will be tested. Using those data, additional modeling and CVD runs will be performed to further optimize the purity of the material. This can include redepositing the tungsten, which will essentially purify it twice. For the new samples, ICP-MS will be used to assay five elements of concern, and a high-purity germanium detector will be used to assay for other radionuclides toward the middle of the decay chain. A test article will then be designed, fabricated, and tested to demonstrate the ability of the CVD tungsten to shield sensitive components from cosmic rays and background radiation.Detectors used in high-energy physics experiments, particularly those looking for dark matter, will require materials with extremely high radiopurity. The techniques used to assess the purity of these materials can also be used to quantify the concentrations of heavy metals in consumer plastics, which is an area receiving much greater attention in many countries, including the European Union. The largest near-term commercial market is in quantum computers, which also require shielding to prevent decoherence of quantum bits (qubits). Other potential applications include semiconductor fabrication and the space and biomedical industries.

* Information listed above is at the time of submission. *

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