Fermilab, Batavia, Illinois, USA
Medium Temperature baking of low beta 650 MHz cavities was conducted in a UHV furnace. A systematic study of cavity surface resistance components, residual and BCS, was conducted, including analyzing surface resistance due to trapped magnetic flux. Cavities showed an average 4.5 nano-ohm surface resistance at 17 MV/m under 2 K, which meets PIP-II specifications with a 40% margin. The results provided helpful information for the PIP-II project to optimize the cavity processing recipe for cryomodule application. The results were compared to the 1.3 GHz cavity that received a similar furnace baking.
Fermilab, Batavia, Illinois, USA
Euclid TechLabs, Solon, Ohio, USA
Traveling wave SRF cavity is a new technology and requires a multi-stage process for development. Concep-tual designs have been proposed to adopt TW resonance in an SRF cavity The early stages of developments have been funded by several SBIR grants to Euclid Techlabs which were completed in collaboration with Fermilab. A 3-cell proof-of-principle TW cavity was fabricated as part of that and demonstrated the TW resonance excita-tion at room temperature. A TW resonance control tuner for the 3-cell was also fabricated and the preliminary tests were performed. Now, the 3-cell cavity is being processed and prepared for the first cryogenic testing.
FRIB, East Lansing, Michigan, USA
Fermilab, Batavia, Illinois, USA
Two different vendors supplied the niobium sheet material for PIP-II 5-cell 650 MHz cavities, which was characterized by multiple different ASTM sizes. Cavities subsequently fabricated from these sheets were heat-treated at various temperatures, then the cavities’ flux-expulsion performance was measured. Where the initial measurements of vendor O materials showed that nearly all flux remained trapped despite a high thermal gradient, 900C heat treatment subsequently improved the flux expulsion to an acceptable rate. Understanding and characterizing vendor O materials in this way is key for upcoming and future projects planning to employ niobium sheet from this supplier.
Fermilab, Batavia, Illinois, USA
FRIB, East Lansing, Michigan, USA
The 650 MHz cavities have a stronger requirement of niobium mechanical properties because of the geometric shape of the cavity due to reduced beta. The mechanical property of the niobium half-cell was measured following various heat treatments. The 5-cell cavities were tested in a controlled drop test fashion and the real-world road test. The result showed that the 900C heat treatment was compatible with cavity handling and transportation during production. The test provides the bases of the transportation specification and shipping container design guidelines.
FRIBA01
FRIB, East Lansing, Michigan, USA
Fermilab, Batavia, Illinois, USA
ANL, Lemont, Illinois, USA
Michigan State University is pursuing SRF R&D for FRIB400 upgrade, doubling the FRIB linac beam energy (400 MeV/u for the heaviest uranium beam) using ßopt=0.65 644 MHz 5-cell elliptical cavities. We have achieved unprecedented Q₀ in this cavity class, Q₀ = 3.5·1010 at Eacc of 17.5 MV/m in a nitrogen-doped bare niobium cavity in collaboration with FNAL and ANL. The next missions are achieving such high Q₀ in jacketed cavities and in cryomodules, achieving field-emission free performance at Epeak of 40 MV/m with reproducibility, developing a compact two-window high-power fundamental power coupler (15 kW CW), and achieving stable resonance control of cavities integrated with tuners in cryomodules. In this talk, we will present progress of the SRF R&D and discuss future plan.
