Scientists put detectors to the test, a few particles at a time
At the Fermilab Test Beam Facility, scientists from around the world line up to test new detector technologies that will help shape the future of particle physics. Whether experimenters need a few pions or lots of protons, the FTBF can deliver: It offers the only high-energy hadron test beam in the United States.
“We’ve had a group that asked for 10 particles to be delivered every couple of minutes,” said Aria Soha, who coordinates the experiments at the facility. “We were able to do it.”
Since 2005, the FTBF, with its distinctive blue, corrugated-steel roof, has staged 38 experiments, conducted by 528 collaborators from 119 institutions in 23 countries. It is a proving ground for particle detector designs being developed for experiments at accelerator laboratories in the United States, Europe and Japan. Last year alone, the facility accommodated 13 experiments. In the future, it might even host detector tests for medical imaging applications.
Experimentalist Erik Ramberg led the effort to revive an old test beam line at Fermilab in 2002. Then physicists began arriving with their detector prototypes. In 2005, a makeover added capabilities for low-energy particle beams to meet requests from particle detector developers. In 2007, a test beam workshop organized by scientists working on detectors for future particle colliders, attracted more than 100 scientists. And this month, Fermilab hosted a school for 64 graduate students and young scientists who received hands-on training with test beam measurements.
The test beam is so popular among detector and instrumentation aficionados around the world that there is often a waiting line for beam time. Work has begun on a second beam line.
Corrado Gatto, of the Sezione di Napoli of Italy’s Istituto Nazionale di Fisica Nucleare, or INFN, and spokesperson of Fermilab test beam experiment T-1015, described his group’s experience at FTBF as “nothing short of excellent,” praising the great flexibility and individual attention.
“The hard part,” Gatto said, “is that it is becoming increasingly difficult to book beam time at FTBF, with lead times longer than six months.”
The only other laboratory to provide a similar test beam is the European laboratory CERN in Geneva, Switzerland.
Ramberg led the FTBF operation until 2009. The handoff went to Soha, who uses her seven years as an accelerator operator to “translate” between the beam operators and the experimenters. “The facility is thriving under her direction,” Ramberg said.
At present, the FTBF regularly handles two experiments at a time. It has areas for six locations along the beam line where scientists can set up their equipment. The main enclosure has retractable roof panels for access by a crane. Each enclosure has at least one remote-controlled motion table. Almost everywhere are huge arrays of cable in patch panels that seem chaotic, but are actually designed to offer simple “plug-and-play” setup by experimenters.
The beam runs for 12 hours a day, usually 10 a.m. to 10 p.m., seven days a week, with no holiday breaks. Research groups usually spend one or two weeks at the facility, maximizing their beam time. Some stay much longer.
José Repond leads a group from Argonne National Laboratory, just a short drive from Fermilab. Their digital hadron calorimeter, with a world-record 480,000 readout channels, was assembled at Argonne and then transported to Fermilab. The detector spent about four months in the test beam in 2011. “We split the day into two shifts, each manned by two people,” Repond said. “Most of us worked six days a week.”
Repond’s group cashed in on the versatility of the test beam’s makeup. They exposed their detector to broadband muons, positrons and pions, and protons, testing the response of the resistance plate chambers that are the central component of the design. With the muons, the group was able to measure the efficiency and other properties of the chambers. With positrons and pions, the group found the response to be “compatible with predictions based on GEANT4 simulations of the setup,” Repond said.
To bring their equipment to the test facility from the University of Texas in Arlington, Jae Yu and two researchers – an undergraduate and a postdoc – rented a car and drove more than 16 hours and nearly a thousand miles. Yu’s three-man group had everyone on shift throughout their two weeks last August to test detectors known as gas electron multipliers, or GEMs.
“While we had a lot of fun taking data,” Yu said, “by the end of the run we were all quite exhausted. So many 20-hour days filled up our beam test campaign.”
Gatto shipped the intricate glass-and-scintillator plates of the ADRIANO detector to Fermilab from his laboratory in Naples. The detector’s full name is A Dual-Readout Integrally Active Non-segmented Option. The plates weigh less than 50 pounds and are sent through regular commercial carriers. The group then uses electronics available at Fermilab for the readout.
“We tested nine different ADRIANO prototypes at FTBF,” Gatto said. “All of them were successful. Our next step would be to build a large prototype and see if we can achieve the same performance as with the smaller ones.”
Scientists who want to use the facility can visit the FTBF website to learn more about the types of particles and beam intensities that are available and how to sign up for beam tests.