Hall A/C Staff Scientist Simona Malace works on the new electron calorimeter's photomultiplier tubes. (Jefferson Lab photo/Aileen Devlin)
The team behind a new detector in Experimental Hall A thrives on mutual trust and expertise. This story is part of the “Mission Critical” series highlighting the various, specialized groups that enable Jefferson Lab's mission of exploring the nature of matter.
NEWPORT NEWS, VA – Designed to obtain precise measurements on the subatomic scale, detectors for nuclear physics experiments require many rounds of careful calibration.
The same goes for the teams of people who build them at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility.
“To me, it’s about working with a group of people toward a common goal,” said Simona Malace, a staff scientist in Jefferson Lab’s Experimental Hall A/C (the group managing experiments in two of the lab’s research areas, Experimental Hall A and Experimental Hall C). Malace is a leading member of the team currently building and testing a new electron calorimeter called “ECal.”
“It’s coming together and creating the space for people around you to be themselves and do the best they can,” she said.
ECal will become the latest detector to operate in Experimental Hall A when the GEp experiment begins in early 2025. A large apparatus comprising 1,656 lead-glass crystals, each outfitted with its own photomultiplier tube and readout electronics, ECal is designed to convert electrons scattered from the Continuous Electron Beam Accelerator Facility (CEBAF) into photons. A DOE Office of Science user facility, CEBAF enables the research of more than 1,900 nuclear physicists worldwide.
Careful analysis of the spray of light from these photons is used to measure the charge distribution of the proton, allowing scientists to better understand the proton’s internal structure of quarks and gluons. Protons are composed of three valence quarks, elementary particles that are a fundamental constituent of matter. Gluons are massless elementary particles that bind quarks together.
Hall A/C Postdoctoral Fellow Jimmy Caylor works along the high-voltage power supply for the electron calorimeter (ECal) in Hall A. (Jefferson Lab photo/Aileen Devlin)
Malace is joined by fellow Hall A/C Staff Scientist Don Jones and Hall A/C Postdoctoral Fellow Jimmy Caylor as the lead scientists responsible for the physical assembly and testing of ECal. Assembled two years ago, this team continues the development and testing efforts spearheaded by Albert Shahinyan of the A.I. Alikhanyan National Science Laboratory in Armenia, which began more than 10 years ago. Shahinyan and Hall A/C Staff Scientist Bogdan Wojtsekhowski were the original designers of ECal. Shahinyan remains involved in the project and organizes teams of engineers from Armenia who each have specific expertise that is instrumental to the project.
“GEp was given a high-impact rating by the Program Advisory Committee because it has huge differentiating power between quantum chromodynamics models,” said Caylor, who joined the team in 2023. “The idea is that we will be able to push further and further into the unknown space of proton charge distribution.”
Malace agreed.
“We are looking at the dynamics of the quarks and gluons inside the proton in the region where the proton sticks together. Instead of seeing each individual component surrounded by this flurry of gluons, you see the proton more as a whole,” she added.
Building the Detector
But for the GEp experiment to probe ever deeper to reveal new information about the proton, it requires specialized, custom-built equipment; ECal is a key component that will make this possible. Though work on the apparatus began long before their involvement in the project, Jones, Malace and Caylor are the three lab staff members who devote nearly all of their efforts to ECal.
However, a constellation of lab scientists, technicians, mechanical designers, engineers, scientific users and students are integral to the project.
“There are a lot of different teams that are working together,” Jones said. “We have the Data Acquisition team; our team, which is building all of the components; teams of people from Armenia who come in, build the cables and label everything; and a lot of support from the Detector Support Group.”
Hall A/C Staff Scientist Donald Jones uses a volt meter on ECal's heating system. (Jefferson Lab photo/Aileen Devlin)
He added that the project is also supported by students from Virginia Tech, James Madison University, the University of Connecticut, the University of Tennessee, the University of Massachusetts Amherst and other institutions.
“We are very lucky to work with a great group of students and postdocs,” Malace said. “I am very grateful for their involvement and for the care and maturity they bring to the project. I have such a great experience working with Ryan McLaughlin, Keagan Bell, Mahmoud Gomina, Debaditya “Deb" Biswas, Kip Hunt and Jhih-Ying Su. Due to them, there's been a lot of progress on the project and a lot of laughter.”
Malace leads the efforts of assembling the photomultiplier tubes, the bases that power them, and the installation of the cables that extract data from the detector.
Jones is responsible for managing the project and assembling the system that heats the lead-glass crystals, which darken from being exposed to radiation from the electron beam. By heating the crystals to 200 degrees Celsius (392 F), the crystals become clear once again. The clarity of the crystals can be maintained during beam operation, which is critical for optimal operation of the detector.
An up-close look at photomultiplier tubes used for ECal. (Jefferson Lab photo/Aileen Devlin)
To counteract the effects of heating the crystals, a cooling system is needed for the photomultiplier tubes. That’s one of Caylor’s areas of responsibility, in addition to assembling high-voltage systems and front-end electronics.
Every aspect of the design, assembly, testing and eventual installation of ECal requires careful coordination and orchestration. The team meets weekly, bringing in the collaborators needed for each stage of the project as it progresses. This is where the human element intersects with the technical and scientific.
Dynamic Collaboration
“There are interesting personalities involved,” Malace said. “But the group is relaxed and inclusive. People give enough space to others to have ideas, give them a try and execute them.”
Caylor agreed and explained more about the collaboration.
“This isn’t a top-down collaboration. We have the ability to do the work the way it needs to be done and do it at a reasonable pace. We can get work done without worrying about someone looking over your shoulder, and if you take it seriously, it allows you to do better work,” he added.
As with any project of ECal’s magnitude and complexity, there can be occasional moments of interpersonal tension as the myriad pieces are set into place as the clock continues to tick toward run time. Much like detectors need calibration, there are ample opportunities for the team to adjust their dynamics throughout the process.
“One should never forget about being a loving person and making sure that you create a good experience for someone, not a bad one,” Malace said. “I’ve become more and more aware of the impact I can have on someone I work with.”
Jones agreed.
“When stress levels rise, the human element becomes trickier. But when you work together for a while, you start learning personalities and how to interact with them. It’s really important to have cohesiveness and try to keep the communication as good as we can,” he said.
One of ECal’s supporting staff scientists, Chandan Ghosh, believes it’s important to get to know you colleagues to enable harmonious work.
“In order to make progress, you have to have a good understanding of how much you can ask of a person. This is something you learn as you work with someone. From a human perspective, this is a very good thing and part of a lifelong process of learning,” Ghosh said.
University of Massachusetts Amherst graduate student Jhih-Ying Su, left, Caylor, Malace, Virginia Tech postdoc Debaditya Biswas, Jones, and Virginia Tech graduate student Mahmoud Gomina pose next to ECal. (Jefferson Lab photo/Aileen Devlin)
The immense amount of work, preparation and coordination will culminate when the GEp experiment begins and ECal will receive CEBAF’s beam for the first time as a fully operational detector. According to Jones, it’s inevitable that something will not go as planned as the experiment gets underway; there are just too many components for everything to work perfectly. However, the team is thorough and dedicated to testing every aspect of the detector possible.
Malace, Jones and Caylor agreed that they are confident that it will work as designed, but that doesn’t come without mixed emotions.
“There’s a certain amount of nervousness because that’s the moment when it has to work, and you have to sit there and get it calibrated,” Jones said. “Anything that happens during beam time is under pressure.”
Malace said that beam startup is the part of the process she enjoys the most.
“I do run coordination and operations because it’s a bit like the emergency room – if I would have been a medical doctor, I would have been an emergency room doctor because it’s unpredictable, and there are a lot of wild cards. I thrive in that kind of environment.”
Caylor added, “You have to be able to do some thinking under pressure and make timely and reasonable decisions, especially if you’re working on a new detector that has never run before. If you let it be, it can be frantic if you’re not prepared. We are going to have nearly 1,700 channels, and all of them have to work. But some of them are inevitably not going to look perfect.”
According to Caylor, the true rewards of working on a project like ECal extends beyond the realm of science.
“It’s very much about the interpersonal relationships that we have,” Caylor said. “When you’re solving these problems and developing these technologies, there are students that come through and learn critical-thinking and problem-solving skills. Many of those people may not do physics as a career, but they can apply those skills to their communities or anything they pursue.
“Physicists problem-solve and to find solutions to complex problems. Those are the things you learn from this kind of work, and you can apply those to other places.”
Further Reading:
Cryomodule Assembly Technicians Rev Up Jefferson Lab's Electron-Beam Racetrack
Contact: John Streit, Jefferson Lab Communications Office, streit@jlab.org