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The superconducting radio-frequency cavities, made of niobium, are cooled to almost absolute zero to enable maximum particle acceleration.

The new ARIEL facility will beam electrons at near light-speed to produce vital new medical isotopes.

Canada has joined a select group of only six countries that have state-of-the art superconductor technology to accelerate particle beams to produce rare isotopes for medicine and industry.

Along with the U.S., Germany, Italy, Japan and China, Canada now belongs to the elite club thanks to work being done at TRIUMF, a particle and nuclear physics complex at the University of B.C.

TRIUMF, which is operated by 18 Canadian universities, has opened ARIEL (Advanced Rare Isotope Laboratory), a facility built to advanced specifications to house an electron linear accelerator (e-linac), which uses superconducting radio-frequency (SRF) cavities technology - essentially, shooting electrons to almost light speed at temperatures near absolute zero.

"The e-linac will be a source to produce exotic nuclei for research and medical isotopes," said Dr. Lia Merminga, head of TRIUMF's accelerator division.

Ontario's Chalk River nuclear facility, which produces up to 40 percent of the world's isotopes and has been plagued by shutdowns since 2009, is forecast to stop production of isotopes in less than two years. The TRIUMF/ARIEL project will help boost production.

But behind ARIEL's three-metre thick walls, output won't be confined solely to medical isotopes. There will be spin-off applications, including emissions-reducing clean technology.

PAVAC Industries, a Richmond, B.C. company that specializes in electron beam technology, is working with TRIUMF on the project.

PAVAC is one of the few firms in the world capable of producing SRF cavities, which are one-metre long, 20-centimetre diameter tubes. The doughnut-shaped tubes are made from pure niobium, a soft metal often used for jet engines, which becomes a superconductor at cryogenic temperatures. To reach such low temperatures, the tubes sit in liquid helium, which cools the niobium to 2 degrees Kelvin (-271°C, only 2 degrees above absolute zero). The process turns the cavities into superconductors, able to efficiently store enough electromagnetic energy to accelerate particles to almost light speed.

ARIEL's e-linac will use five SRF tubes, strung together. Magnets will be used to steer and direct the electrons along the beamline to the target hall, where the electrons strike a stopping material that converts their energy to photons. The photons then bombard a target material, creating isotopes.

At maximum power, the e-linac produces 500 kilowatts of beam power, about 8,000 times more powerful than one 60-watt light bulb.

"At 0.5 megawatts average power, the ARIEL e-linac is a state-of-the-art accelerator without many precedents around the world," said Dr. Merminga, who came to TRIUMF in 2008 from Virginia's Thomas Jefferson National Laboratory.

PAVAC will build two more SRF tubes, which cost around $200,000 each, to complete ARIEL's e-linac. "The quality of the cavities exceeds the specifications," Dr. Merminga said.

Once the tubes are built and tested, they will be hermetically-enclosed in cryomodules that contain all of the complex, ancillary equipment to accelerate the electron beam.

One cryomodule can hold up to eight cavities and costs up to $3-million, Dr. Merminga said.

While TRIUMF scientists have built their own cryomodules, they're keen to transfer their technology to PAVAC, Dr. Merminga said. The goal is to share home-grown knowledge with a national company.

PAVAC has already reaped benefits from its TRIUMF work, securing contracts in the U.S., opening an Illinois facility in 2011 and tripling its staff. "We've given PAVAC a lot of visibility," Dr. Merminga said.

Currently, PAVAC is building a SRF cavity for a lab in India.

PAVAC's marketing manager Tingting Zhang said PAVAC's electron beam technology is used in three areas: The first is PAVAC's work to build SRF cavities for facilities like TRIUMF.

Secondly, it is working with the energy, defence, aviation, aerospace and research industries to provide very precise metal-welding services using electron beams.

The third application is environmental protection. PAVAC's electron beam flue gas treatment system replaces chemicals with electrons to treat flue gas that is emitted by coal-burning plants, Ms. Zhang said.

Scientists from around the world make pilgrimages to the TRIUMF/ARIEL grounds to work on the e-linac. "The scale of the project allows students to master many areas of physics," Dr. Merminga said.

The scientists trained to assemble and maintain the e-linac technology are highly-skilled, and, like the isotopes, rare. "It's expertise you can't just hire out in the street," Dr. Merminga said.


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