Despite the pandemic, a Jefferson Lab team is finessing an injector upgrade so they can better tame the electron beams for experiments
NEWPORT NEWS, VA – A major injector upgrade at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility was well underway early last year when the pandemic hit, throwing scientists and their long-anticipated project for a loop.
Literally overnight, they had to leave their desks, control room and colleagues behind and rapidly learn how to work together from the confines of their own homes.
“We were going 100 mph on design work for the injector upgrade in March when we stopped for COVID,” said Jefferson Lab injector scientist and project manager Joe Grames. “It was a crazy time and remained so for months. But what impressed me the most is how efficiently we all pivoted and adapted to working remotely.”
Designers, engineers and scientists accustomed to sitting at their office computers and conducting two or three meetings a day with blueprints and drawings had to figure out how to run virtual meetings and video conferences, as well as how to access their work computers remotely.
“And in a pretty short time, like two or three weeks,” Grames said, “we were able to start working remotely as if we were sitting in the same room together.”
It didn’t happen without some initial hiccups.
During one video conference, for instance, an engineer had to pause for a moment when workers arrived to repair a window that had been smashed by a tree branch during a major windstorm. In yet another, a scientist started screaming when she saw her young son about to tumble backward down a flight of stairs.
Even Grames had his own moment of crazy when a power washer that his wife had scheduled fired a high-pressure hose at the window behind Grames’ desk.
“It was in the spring, and the windows were open,” said Grames. “I jumped out of my chair, knocked my coffee over, and it was like, ‘What’s wrong?’
“It was just normal life, mixed with work. You don’t bring your home life to work, but people are home now. We’re doing the same things, but everybody was experiencing whatever was being thrown at them that day.”
By June, the injector upgrade was deemed an essential task for the lab, and Grames’ team was cleared to return to on-site work as needed, especially since much of it involved hands-on installation of vital equipment.
That meant adapting to yet another new work ethic. The lab’s mandatory coronavirus-related safety guidelines meant using new personal protective equipment, getting trained on N95 masks and wearing acceptable types of clothing and gloves. A second accelerator control room had to be set up to enable social distancing.
“We had to figure out how many people are allowed to work in a room, how far apart,” Grames said. “Normally, we work shoulder to shoulder and we just talk, and people come and go. But now we were sequencing things — one person could touch tools and then another person would clean tools and then use them. So, it’s very orchestrated.
“I think it’s increased our skillset, our ability. Adapting always makes you stronger, and sometimes it makes you more clever. So, I think it’s been an advantage.”
From July to September, the lab fired up its world-class Continuous Electron Beam Accelerator Facility, a DOE Office of Science User Facility, to finish up some experiments that had been interrupted when the pandemic hit. Once those makeup weeks were completed, CEBAF was shut down again to enable the injector upgrade and other maintenance activities.
Grames expects the team will still make its deadline to finish the installation by April. Then, after 4-6 weeks to commission the new injector with beam, they expect to have a working injector by Memorial Day and in time for the next scheduled start of CEBAF operations.
Taming the electrons
The upgrade project was split into two phases, both working in parallel.
Phase 1, which Grames is managing, involves where the electrons are produced at the injector — the initial section of CEBAF that gets the electrons all spinning in the same direction, and then quickly revs them up from zero to nearly the speed of light.
To do this, they first produce free electrons by firing short laser bursts hundreds of millions of times a second at a semiconductor made of a crystal called gallium arsenide. The laser bursts are critical for two purposes. First, the laser bursts select electrons in the crystal that have their spins mainly aligned, and second, the bursts also provide the essential energy the electrons need to escape into the vacuum of the accelerator.
Once freed, these electrons can see 130,000 volts, which is enough to push the particles up to near-lightspeed. The upgraded injector will increase that voltage to 200,000.
“That change is pretty significant,” Grames said. “It gets the particles going closer to the speed of light.”
It also, according to Grames, helps electrons overcome their tendency to repel other electrons due to the powerful electrical force. As electrically charged particles, the electrons all have the same charge, and like charges repel.
“There's a passage in the Feynman lectures I recall, an analogy about electrons and the electrical force: ‘All matter is a mixture of positive protons and negative electrons which are attracting and repelling with this great force. So perfect is the balance, however, that when you stand near someone else you don’t feel any force at all. If there were even a little bit of unbalance you would know it. If you were standing at arm’s length from someone and each of you had one percent more electrons than protons, the repelling force would be incredible. How great? Enough to lift the Empire State Building? No! To lift Mount Everest? No! The repulsion would be enough to lift a “weight” equal to that of the entire earth!"
But, within the space of a few inches inside the CEBAF injector, the electron repulsion is greatly reduced as they approach the speed of light, a key motivation to going to even higher energy.
This brings us to Phase 2, which has been underway for several years. It involves upgrading devices in the next section of the injector, roughly 30 yards from where the electrons are first produced, to boost the speed of the electrons up to essentially the full speed of light. These devices are called cryomodules.
Inside the cryomodules are hollow, bell-shaped cavities, stored in liquid helium to super-cool them. The cryomodules speed up electrons by creating waves of energy that the particles can ride on, much like a bodysurfer riding an ocean wave.
“If we shove surfers onto the wave and they’re going too slow, they just won’t get accelerated, and they get lost,” Grames said. “So, the first part of the injector is to shoot them out at the right frequency and spin, and the rest of the injector is to make sure they all stay together really well and are going fast enough so that they’re on the wave.”
The Phase 2 booster is being actively tested now using a smaller accelerator at the lab. If all goes well, it’s set to be installed in CEBAF later this year.
The overall objective of the upgrade is to provide better beam for users from around the world.
“We have this long history of doing experiments that require greater and greater precision,” Grames said. “And that requires the beam quality to continue to be better, and that’s going to give us a better tool for nuclear physics.”
Originally from New Jersey, Grames arrived at Jefferson Lab as a graduate student in 1994, eventually finishing his Ph.D. in physics by helping to commission CEBAF. He joined the staff in January 2000. The lab just named him acting department head for the Center for Injectors and Sources, which builds and maintains all of the lab’s high-performance particle beam sources for injectors and accelerators.
The last time the injector was rebuilt was about a decade ago, and Grames was involved in that project, too. This latest upgrade is twice as big, he said, and “much more significant.” He said he expects this injector will be used for more than a decade.
“I think I’m going to look back on this experience as being really unusual,” Grames said. “Because, of all the different projects I’ve been part of or led, this one was all different. It had the stamp of COVID on everything we did. It had the stamp of pandemic. And everything we did, we did it differently. I don’t know if we’ll keep doing it this way again, but I’ll be really proud that we managed to do it. Everybody just got onboard and we all learned how to, like, hop on one leg for a while. Together.”
By Tamara Dietrich
Contact: Kandice Carter, Jefferson Lab Communications Office, 757-269-7263, firstname.lastname@example.org