Leading the way in superconducting magnets and accelerators

Hasan Padamsee

Hasan Padamsee, head of the Technical Division, wrote this column.

I feel very fortunate to head the Technical Division in this era of exciting accelerator technology developments. Our division holds the keys to enabling technologies for frontier accelerators, both in magnet development and accelerator cavities.

Our niobium titanium magnet program will guide intense muon beams for precision experiments to determine whether muons, which belong to the lepton family, can spontaneously change into other leptons — specifically electrons — just as neutrinos can change into other neutrinos. The magnets for the Mu2e experiment will be wound with 45 miles of superconducting cable.

Our Nb3Sn magnet advances will enable planned upgrades to LHC luminosity guided by the LARP program, led by Giorgio Apollinari. Our Nb3Sn and high-temperature superconductor high-field magnet program, led by Alexander Zlobin, could enable a roughly 100-TeV proton-proton collider, a most powerful tool for future high-energy physics.

As an expert in superconducting radio-frequency acceleration technology, or SRF, I was thrilled to join Fermilab in June because I saw how the division mastered our new technology to build up the infrastructure and expertise through the International Linear Collider R&D program, which ran under the leadership of Bob Kephart and previous Technical Division Head Dave Harding. To our delight, the SRF Department, led by Slava Yakovlev, had prepared some of the best niobium cavities and assembled them into the world’s highest-gradient ILC cryomodule, with a gradient of 31.5 megavolts per meter. Thus the division played a huge role in getting SRF technology ready for the ILC, if and when it will be built.

A major consequence of the SRF successes is the decision to upgrade LCLS, the world-class light source at SLAC, using SRF technology. While the ILC must be a pulsed accelerator with a one percent duty factor, meaning that the RF power remains on for only one percent of the time, the LCLS-II light source must run continuously to keep its users happy. Continuous operation is now made economically feasible thanks to spectacular discoveries from the Technical Division.

Anna Grassellino and Alexander Romanenko discovered new phenomena in SRF that will raise the Q values — measures of how efficiently a cavity stores energy — of ILC-type accelerating cavities from 10 billion to nearly 30 billion. To appreciate the significance of such high Qs, imagine that Galileo’s pendulum oscillator — in the year 1600 — had a Q of 30 billion. It would still be oscillating today and would continue to oscillate to the year 2800! Such high Qs arise thanks to minuscule RF losses, which make it affordable to run superconducting cavities in LCLS-II continuously. The division is gearing up to provide 17 ILC-type cryomodules with 136 cavities, as well as two cryomodules with higher-frequency cavities.

To reap the benefits at home, SRF is also the foundation of a brand new accelerator, called PIP-II, to be constructed at Fermilab to provide the world’s best neutrino beams. PIP-II will be built in collaboration with other labs to provide a 1-megawatt proton beam accelerated by an 800-MeV superconducting linac. The linac will contain almost 20 cryomodules with more than 110 SRF cavities. The prototype cavities have been constructed and tested successfully, and the first prototype cryomodules will be assembled next year.

Both superconducting magnets and superconducting RF have brilliant futures at Fermilab. I am proud to lead these exciting developments to keep Fermilab at the frontier of high-energy physics.