Ep 231: Steve Shannon - Professor, Nuclear Engineering, North Carolina State University
How Steve ended up studying plasma physics (1:13)
1:13-13:52 (Steve explains how his interest in science stems from his father. He also gives an introduction to the difference between fission and fusion events.)
Q. Where did your interest in nuclear begin?
A. Steve Shannon contributes his interest in science to his dad who was a self-employed industrial engineer. Steve grew up in Detroit and attended Michigan for both undergraduate and graduate school, earning a PhD in nuclear engineering. He now focuses on plasma physics, which is related to nuclear engineering in the context of fusion energy. Fusion energy comes from the joining of atoms rather than splitting. The mass deficit of combining atoms is released as kinetic energy in the form of helium and a neutron, for example. As they fly off from the fusion event, they create heat. Fusion leverages that heat for two reasons. The first is that the heat can be converted into electrical energy. The second is that the heat can be used to sustain the reaction, which unlike fission, is required in fusion events. The energy produced by the fusion event will sustain the reaction without the need for auxiliary heating, meaning the charged particles will stay in the fusion reaction, creating carryon fusion events. Deuterium and tritium are the isotopes of hydrogen that create the most energy advantageous fusion reactions.
Using plasma in manufacturing (13:53)
13:53-22:39 (Steve discusses what a plasma is and how it can be used to create such things as computer chips and solar panels.)
Q. Where did you take your studies when you decided to research plasma?
A. The difference between a gas and a plasma is a plasma collectively responds. Plasma is ionized gas, meaning the electrons have been torn off the atom to produce positively charged ions and electrons. Ionization is the process of separating the charge from the nucleus.
After graduate school, Steve worked on using plasmas to manufacture computer chips. This process involves the use of electrons and ions in a plasma to modify silicon and other materials. Using plasma creates the ability to control the direction in which a chemical reaction occurs. Because plasmas have a large mass difference between the electrons and ions, heat can be controlled, meaning only the electrons within the plasma are heated. This is beneficial in the creation of film solar cells. Silane gas (SiH4) is heated to deconstruct the molecule, removing the silicon from the hydrogen. The silicon attaches to the glass, creating solar panels. Heating only the electrons enables the molecular deconstruction without heating the entire gas to dangerous temperatures.
Plasma advancements accelerate industry developments (22:40)
22:40-32:22 (Steve explains how plasmas are created. He also discusses more industrial plasma applications.)
Q. Do plasmas only work with gases?
A. Plasmas are the natural progressions of heating up an element. With a volume of gas, an electromagnetic field is applied to add electrons, often times using radio waves. Because the gas is at room temperature, Steve can explore depositing silicon on materials like plastic. This means flexible solar panels and electronics are becoming available. There are many practical industrial applications for plasma. Fusion can be compared to the moon landing in that the actual moon landing did not have a great economic output, but the technological innovations that came out of the moon landing were great. Much of the fusion technology has been used for other applications. For instance, innovations in fusion have accelerated the development of electronics, providing us with products including cell phones and laptops.
Returning to academia (32:23)
32:23-37:30 (Steve explains why he returned to academia after working in Silicon Valley. He also discusses what he hopes his students take away from his classes.)
Q. How did return to academia from industry?
A. After graduate school, Steve moved out to Silicon Valley to work at Applied Materials, which is a company that produces the plasma reactor equipment for computer chip production. While undergoing training, Steve started teaching night classes in the chemicals and engineering department at San Jose State University. While Applied Materials supported his teaching, Steve found that he enjoyed working in academia more than industry and he began working at North Carolina State University as a professor of nuclear engineering.
Steve wants his students to be able to work independently. His biggest goal is for his students will show him what they did and explain to him why they did it rather than wait to be told what to do. Steve believes the ability to find one’s own way is what makes a strong researcher.
The future of plasma applications (37:31)
37:31-41:10 (Steve discusses the future applications for plasmas.)
Q. Where do you expect your students will take plasma research in the next 10 to 15 years?
A. There are many things about the plasma environment that are still not well understood. Much is still to learn before plasmas can be modeled more accurately. Modeling will become more important as new industrial applications for plasma are discovered. Plasmas are already starting to be used in agriculture and medicine, such as for cancer treatment. For example, because plasma produces the same chemical makeup generated by cells under stress, it can be used to accelerate the body’s stress response, such as increased blood clotting. Once the level of understanding associated with computer chip production is reached in other areas, a wide new array of applications can be developed.