Back

Chemical engineer selected for national engineering symposium

(Download Image) LLNL c hemical engineer Rebecca Dylla-Spears inspects a solid deuterium-tritium fuel layer for use in a National Ignition Facility (NIF) experiment. Photo by Julie Russell.

Rebecca Dylla-Spears will have a chance to collaborate with the nation's top mid-career engineers from industry, academia and government next month.

The chemical engineer in the Physics & Life Sciences Directorate at Lawrence Livermore National Laboratory was selected to represent the Lab at the National Academy of Engineering's 20th annual U.S. Frontiers of Engineering symposium. The event in Irvine, California on Sept. 11 to 13 will feature dozens of engineers from ages 30 to 45 who are performing exceptional engineering research and technical work in a variety of disciplines.

"I feel honored to be selected for this symposium," Dylla-Spears said. "There are many great engineers at Lawrence Livermore, and I feel humbled to be representing them. I hope to be an ambassador for the Lab and show the quality of research here."

In addition to networking, conference attendees will discuss four main topic areas: next generation robotics, frontiers in materials for batteries, shale gas and oil and technologies for the heart. Whether or not these areas are the main focal points of an attendees' research, event organizers seek a variety of engineers to share their expertise and offer new ways of solving problems.

Dylla-Spears has been solving complex problems in support of the National Ignition Facility (NIF) for the past four years. She is a member of NIF's Target Systems and Optics Technology group and is working on multiple projects, including growing solid deuterium-tritium (DT) layers for ignition targets and a new technology for polishing glass optics. The latter was one of four LLNL projects that recently won an R&D 100 award, which is sometimes referred to as the "Oscars of Innovation."

Led by principal investigator Tayyab Suratwala, the team developed a new method for optical polishing known as convergent polishing, which enables the finishing of flat and spherical glass optics in a single iteration, with no metrology or process adjustments, regardless of the initial shape of the glass. 

This technique has the potential to lower the cost of finished laser optics and has broader application to the optics and chemical-mechanical polishing industries. Dylla-Spears' contributions included the development of a chemical stabilization method for common optical polishing slurries that reduces particle agglomeration without reducing material removal rate by using a potentially novel mechanism. 

Dylla-Spears also leads a team charged with optimizing the process for producing round, smooth and defect-free solid DT layers for NIF targets, which are essential for achieving maximum neutron yield in fusion ignition experiments.

Efforts to grow a spherical, single-crystalline layer of deuterium and tritium are complicated by stringent NIF target requirements. Most processes for defect-free crystals start growth from a single seed of known orientation; however, a seed for a NIF DT layer must be generated within the 2-mm capsule and its presence must be inferred because the seed crystal cannot be directly observed.  

Although any given attempt is successful only about 25 percent of the time, the layering team is developing strategies to ensure consistent delivery of layers meeting specifications for NIF experiments within a fixed window of time. These include mining data from previous attempts to look for early developing signatures of good and bad layers and real-time monitoring of the layer formation to make predictions about the likelihood of success of a particular attempt. The goal is ultimately to shorten the time required to deliver in-spec layers.

"We have to be careful because we just cannot abort every layer we think might end badly," Dylla-Spears said. "There is a penalty associated with restarting. Accidentally throwing away good layers can end up costing a considerable amount of time."

Dylla-Spears is excited to use her Lab expertise to contribute to the key discussion areas at the engineering symposium.