RADIATION MONITORING DEVICES, INC. — Department of Energy SBIR Phase II: C51-14a

Description

The waveguide Radio Frequency (RF) vacuum window is a common point of failure at particle accelerators, especially during high-peak and high-average-power pulsed RF operations. At particle accelerators, such as the Spallation Neutron Source (SNS), the operating conditions can range from 300 to 1000 MHz frequencies, peak power of >3 MW, pulsed at >10% duty factor. Manufacturing waveguide window for high-power RF applications has proven to be challenging throughout the industry. One of the key challenges is the quality of the Titanium Nitride (TiN) coatings that is applied to the alumina ceramics for the suppression of multipacting. RMD will address this challenge by deploying Atomic Layer Deposition (ALD) technique to deposit TiN, which will overcome the current issues faced by the traditional Physical Vapor Deposition (PVD) methods. The key advantage of the proposed ALD technique is that the “self- limiting” chemical growth mechanism facilitates atomically conformal coating of TiN and with an excellent control on thickness, irrespective of the substrate size or the growth chamber design. The ALD TiN process developed in the Phase I successfully demonstrated: (1) nanoscale control of film thickness, (2) high step-coverage (up to 20:1 aspect ratio) for encapsulating micron- sized surface defects native to ceramics, (3) desired stoichiometry, (4) large-area surface coverage with good lateral uniformity on ceramics up to 16” dia, (4) low Secondary Electron emission Yield (SEY <1.0), and (5) thin film electrical continuity for preventing surface charge buildup. In Phase II, RMD will focus efforts on 3 key areas- (1) Optimize the TiN ALD coating thickness and composition for large ceramics; (2) Design and fabricate a complete RF waveguide vacuum window for 402.5 MHz with the coated ceramic; and (3) Test the RF waveguide window at >3 MW pulsed peak at >10 % duty cycle. The proposed development of TiN coatings by ALD will allow the scheduled proton power upgrades for SNS at ORNL. The conformal TiN thin films are also much-sought for gun in-barrels for improving the lifetime and performance of the guns used by the US soldiers. Electronic-grade TiN coatings are also sought by the microelectronic industry as ALD coatings, to realize the performance and miniaturization roadmap goals. This work will also lead to advances in technologies with significant commercial impact and will help maintain US technological edge over competing nations.