From turkeys to turn-keys

November 28, 2018, Fermi National Accelerator Laboratory
A superconducting radio-frequency accelerator cavity is mounted and connected to a cryocooler, cooling the cavity without the use of liquid helium. This new device could make it easier to produce high-average-power electron beams for industrial applications. Credit: Marty Murphy

Last week, millions of Americans unwrapped a shrink-wrapped turkey for Thanksgiving. If so, they owe thanks to electron beams, which made the shrink-wrapping possible. But the electron beam can do a lot more: It can sterilize medical equipment, treat wastewater and print metal parts. Industrial accelerators that generate these electron beams are rapidly expanding. The Illinois Accelerator Research Center (IARC) is on a mission to build a high-power, compact, superconducting electron beam accelerator that will serve all of these purposes.

High-power linear electron accelerators are typically made of structures called cavities, which impart energy to the particle , thrusting it forward. One such cavity is the superconducting radio-frequency, or SRF, cavity, which requires extremely cold temperatures to operate. These machines use liquid helium to maintain the temperature necessary for sustaining superconductivity. Liquid-helium operation demands complex infrastructure: a liquefaction plant, distribution lines, gas recovery, purification systems, and cavity cryomodules that can withstand high pressure. Although such an infrastructure is appropriate for large-scale research accelerators, it can be too complex and costly for industrial applications. The barrier is the need for ultracold liquid helium.

With Fermilab's never-say-impossible spirit, our team at IARC has broken this barrier. We have for the first-time cooled an active radio-frequency cavity to cryogenic temperatures without the use of liquid helium. We achieved this by connecting a cavity to a commercially available cryocooler, using a Fermilab-patented technology.

As with any exciting experiment, connecting the cavity to the cryocooler was a significant task that required investigating various materials and designing custom components. Our team produced niobium conduction rings and connected them to the cavity shell using welding. They also developed niobium-aluminum joints that allowed heat to flow easily from the cavity to the cryocooler. To generate heat into the cavity, the team used a simple plug-and-play radio-frequency driver, as in laboratory accelerators.

Electromagnetic gradients are generated within SRF cavities; stronger gradients impart more energy to the beam. This first-ever cryogen‑free operation produced a gradient of 0.5 megavolts per meter on a single-cell, 650-MHz niobium cavity. We plan on achieving gradients up to 10 megavolts per meter by using higher-capacity cryocoolers and capitalizing on other recent advances in technology. The team is exploring the application of conduction cooling technology to higher frequencies, multicell cavities, and other radio-frequency structures.

Replacing with plug-and-play cryocoolers makes SRF accelerators accessible to industry by making accelerators into simple, turn-key systems.

Explore further: Cryocooler cools an accelerator cavity

Related Stories

Cryocooler cools an accelerator cavity

October 18, 2018

Particle accelerators are made of structures called cavities, which impart energy to the particle beam, kicking it forward. One type of cavity is the superconducting radio-frequency, or SRF, cavity. Usually made of niobium, ...

Record quality factor lowers cost of new particle accelerator

December 1, 2015

A team at DOE's Fermi National Accelerator Laboratory achieved a record-high quality factor when testing the first fully dressed radio-frequency cavity built for a particle accelerator project at DOE's SLAC National Accelerator ...

Award enables research for more efficient accelerators

May 12, 2016

Grigory Eremeev wants to double the efficiency of some of the most efficient particle accelerators being used for research. Now, the staff scientist at the Department of Energy's Thomas Jefferson National Accelerator Facility ...

Supercooled cavities for particle acceleration

May 3, 2016

When you think about the coldest places on Earth, the National Synchrotron Light Source II (NSLS-II), a U.S. Department of Energy (DOE) Office of Science User Facility located at the DOE's Brookhaven National Laboratory, ...

Concrete applications for accelerator science

September 22, 2017

Particle accelerators are the engines of particle physics research at Fermilab. They generate nearly light-speed, subatomic particles that scientists study to get to the bottom of what makes our universe tick. Fermilab experiments ...

Recommended for you

Sculpting stable structures in pure liquids

February 21, 2019

Oscillating flow and light pulses can be used to create reconfigurable architecture in liquid crystals. Materials scientists can carefully engineer concerted microfluidic flows and localized optothermal fields to achieve ...

How to freeze heat conduction

February 21, 2019

Physicists have discovered a new effect, which makes it possible to create excellent thermal insulators which conduct electricity. Such materials can be used to convert waste heat into electrical energy.

Water is more homogeneous than expected

February 21, 2019

In order to explain the known anomalies in water, some researchers assume that water consists of a mixture of two phases, even under ambient conditions. However, new X-ray spectroscopic analyses at BESSY II, ESRF and Swiss ...

Correlated nucleons may solve 35-year-old mystery

February 20, 2019

A careful re-analysis of data taken at the Department of Energy's Thomas Jefferson National Accelerator Facility has revealed a possible link between correlated protons and neutrons in the nucleus and a 35-year-old mystery. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.