Proceeding with PIP-II, Fermilab’s accelerator upgrade project

Adapted from Fermilab’s Fermilab gets ready to upgrade accelerator complex for more powerful particle beams, 24 July 2018.

A major milestone

Fermilab’s accelerator complex has achieved a major milestone: The U.S. Department of Energy formally approved Fermi National Accelerator Laboratory to proceed with its design of PIP-II, an accelerator upgrade project that will provide increased beam power to generate an unprecedented stream of neutrinos and enable a broad program of physics research for many years to come.

The PIP-II (Proton Improvement Plan II) accelerator upgrades are integral to the Fermilab-hosted Deep Underground Neutrino Experiment (DUNE), which requires enormous quantities of neutrinos to study the mysterious particle in exquisite detail. With the latest approval for PIP-II, Fermilab is positioned to be the world leader in accelerator-based neutrino research. The Long-Baseline Neutrino Facility (LBNF), which will also support DUNE, had its groundbreaking ceremony in July 2017.

Partners in PIP-II

The opportunity to contribute to PIP-II has drawn scientists and engineers from around the world to Fermilab: PIP-II is the first accelerator project on U.S. soil that will have significant contributions from international partners, representing a new paradigm in U.S. accelerator projects. Currently the international partners include laboratories in India (BARC, IUAC, RRCAT, VECC) and institutions in Italy, funded by the National Institute for Nuclear Physics (INFN), in the UK, funded by the Science and Technology Facilities Council (STFC), and potentially in France (CEA and CNRS).

The Department of Energy’s Argonne and Lawrence Berkeley national laboratories are also major PIP-II participants.

“The international scientific community brings world-leading expertise and capabilities to the project. Their engagement and shared sense of ownership in the project’s success are among the most compelling strengths of PIP-II,” said Fermilab PIP-II Project Director Lia Merminga.

Creating intense neutrino beams

PIP-II capitalizes on recent particle accelerator advances developed at Fermilab and other institutions that will allow its accelerators to generate particle beams at higher powers than previously available. The high-power particle beams will in turn create intense neutrino beams.

The goal of PIP-II is to produce a proton beam of more than 1 megawatt, about 60 percent higher than the existing accelerator complex supplies. Eventually, enabled by PIP-II, Fermilab could upgrade the accelerator to double that power to more than 2 megawatts.

“At that power, we can just flood the detectors with neutrinos,” said DUNE co-spokesperson and University of Chicago physicist Ed Blucher. “That’s what is so exciting. Every neutrino that stops in our detectors adds a bit of information to our picture of the universe. And the more neutrinos that stop, the closer we get to filling in the picture.”

Accelerating superconducting technology

The centerpiece of the PIP-II project is the construction of a new superconducting radio-frequency (SRF) linear accelerator, which will become the initial stage of the upgraded Fermilab accelerator chain. It will replace the current Fermilab Linac. The plan is to install the SRF linac under 25 feet of dirt in the infield of the now-decommissioned Tevatron ring.

The new SRF linac will provide a big boost to its particle beam from the get-go, doubling the beam energy of its predecessor from 400 million to 800 million electronvolts. That boost will enable the Fermilab accelerator complex to achieve megawatt-scale beam power.

Many current and future particle accelerators are based on superconducting technology, and the advances that help scientists study neutrinos have multiplying effects outside fundamental science. Researchers are developing superconducting accelerators for medicine, environmental cleanup, quantum computing, industry and national security.

The beam scheme

In PIP-II, a beam of protons will be injected into the linac. Over the course of its 176 meters — three-and-a-half Olympic-size pool lengths — the beam will accelerate to an energy of 800 million electronvolts. Once it passes through the superconducting linac, it will enter the rest of Fermilab’s current accelerator chain — a further three accelerators — which will also undergo significant upgrades over the next few years to handle the higher-energy beam from the new linac. By the time the beam exits the final accelerator, it will have an energy of up to 120 billion electronvolts and more than 1 megawatt of power. This initial proton beam can be delivered in pulses or as a continuous proton stream.

After the proton beam exits the chain, it will strike a segmented cylinder of carbon. The beam-carbon collision creates a shower of other particles, which will be routed to various Fermilab experiments. Some of these post-collision particles will decay into neutrinos, which will by this point already be on the path toward their detectors.

Fermilab expects to complete the project by the mid-2020s, in time for the startup of LBNF/DUNE.

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