ASTA facility produces first electrons

The new photoinjector gun at the Advanced Superconducting Test Accelerator recently produced its first electrons. Photo: Jerry Leibfritz, AD

Around 4 p.m. on June 20, spikes started appearing in data being collected at the Advanced Superconducting Test Accelerator facility. They signaled the presence of electrons, and they were lined up exactly with the timing of ultraviolet laser pulses striking the cathode of a new photoinjector gun.

“We saw very clear, very distinct feedback,” said Jerry Leibfritz, ASTA project engineer.

The spikes were evidence of a major milestone for ASTA: The photoinjector gun had produced its first electrons, a step six years in the making. When the team was given the go-ahead to turn the machine on, Leibfritz expected it to take a few days before the first electrons were created; instead, it took only hours.

“There are so many complex systems involved, and all it would take is one thing not set properly, and it wouldn’t work,” Leibfritz said. “The fact that it worked so quickly is really a testament to everyone’s hard work and attention to detail. We were quite thrilled. It’s a big deal because you can’t run an accelerator unless you can generate a beam.”

ASTA will use superconducting radio-frequency technology to accelerate electrons down a 140-meter linear tunnel and into a beam dump. SRF allows for highly efficient particle accelerators, achieving more beam acceleration in shorter distances.

ASTA’s initial function is as an accelerator research and development facility both for SRF technology and beam dynamics and imaging—proposed accelerators such as Project X and the International Linear Collider would use similar technology. But design elements are in place to allow researchers to eventually use it as a test accelerator for various physics experiments. The beam will eventually accelerate through multiple cryomodules and split off into a low-energy test beam, three high-energy test beams and a storage ring.

“ASTA is Fermilab’s first serious foray into electron accelerators,” said Elvin Harms, head of the SRF Electron Linac Department. “The big deal to me is that the way we’re going to accelerate the electrons is using superconducting radio-frequency cavities. The fact that it’s based on superconducting RF technology says that this could be a natural precursor to Project X.”

The June 20 milestone saw electrons generated in the gun and accelerated into a Faraday cup, which stops the beam and measures the deposited energy. The next goal for ASTA is to complete the installation of the injector and accelerate the electron beam up to a peak energy of about 50 MeV. Leibfritz hopes this can be accomplished by the end of this year.

“Once it’s complete, it will be a unique facility,” Leibfritz said. “It uses the newest technology and provides capabilities that other facilities don’t have.”

Achieving first beam by the end of June was a goal the project team set for themselves, in part to honor Mike Church, the former SRF Electron Linac Department head, who led the project’s scientific efforts for three years. He retired on June 28.

Laura Dattaro