Most of us walk around with a smart phone, but I bet it’s news to many that the tools first built to understand the workings of the nucleus of the atom, the same tools used here at Jefferson Lab, became the tools to ultimately create smart phones (and more). Having my smartphone is great; it helps me get through my busy day. It lets me stay in touch with my family, and gives me the ability to me check my email on the go. I can text the dog sitter, take pictures and share them on social media, and so on and so on. The inner workings of any smart phone, and in fact all digital electronics, is a reality because of the development of the semiconductor based integrated circuit (IC) made through the use of particle accelerators. Ok, so now I have to explain some things (geek alert).
“Semi” used here means that something that is not that great of an electrical conductor can still be very useful. For example, take semisweet chocolate. It’s not super sweet, just semisweet, which makes it perfect for chocolate chip cookies. The development of semiconductor-based ICs made possible the most basic component of modern electronics: the transistor. A transistor is an itsy bitsy electrical switch, like the ones everyone uses in their home to turn lights on and off, but really small. In fact, transistors can be so small you need a microscope to see them. It’s all these tiny on/off switches that are packed into electronic components.
Now here comes some really geeky stuff. Semiconductors are materials found in nature that are neither good electrical conductors nor are they good electrical insulators. For instance silicon and germanium are semiconductors. Metals such as copper and gold are good electrical conductors. Ceramic, rubber and glass make good electrical insulators.
Bring on the Ion Implanter
So what do semiconductors have to do with ICs? Physicists have developed particle accelerators that fire particles, such as electrons and protons, at an atom’s nucleus and into target material to study the properties of that nucleus. For instance, experimenters at Jefferson Lab have used carbon, lead and many others as targets for its electron beam based experiments. The lab has even used liquid hydrogen as a target, resulting in a better understanding of the 3D structure of a proton (you can read more about that here: https://www.nature.com/articles/d41586-018-05186-x). These same accelerators can be used to accelerate individual atoms. Just like accelerators are used to plow electrons into the nucleus of an atom, accelerators can be used to implant or push ions (atoms that have had an electron or two missing) into a material. When that material is a semiconductor, such as silicon crystal, it is possible to carefully change the electrical conductivity of that crystal so it can be used as a tiny electrical switch.
ICs are everywhere
ICs are essential for any smart phone, any computer, and all of the digital electronics used in cameras, clothes washers, refrigerators, cars, satellites and more. Even the SpaceX Falcon Heavy Lift rocket (https://www.youtube.com/watch?v=A0FZIwabctw, video courtesy of SpaceX) was made possible by the development of the semiconductor based ICs and the technologies that flowed from them. And this all stems from physicists being driven to understand nature. According to the US Department of Labor in 2017 there were 16,710 physicists working in the U.S. today. That equates to only about a quarter of the number of people who attend each Super Bowl! The nuclear physics experiments done today by this small number of physicists to solve the mysteries that tie this universe together will most likely yield big benefits tomorrow. And, if you don’t believe me, look it up on your smart phone!
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Chief Technology Officer