The ESS Linear Accelerator

2. The ESS Linear Accelerator • P. Bosland, TAC 11, April 2015 2

3. ESS is a big European Effort • J. Weisend, TAC 11, April 2015 3

4. The IPN-Orsay Cryomodule • P. Bosland, TAC 11, April 2015 4

5. INFN-LASA In-kind Contribution • Medium beta and high beta cavities prototyping • These prototypes are not part of the Italian in kind contribution. • Medium beta series cavities • Niobium procurement for the fabrication of 36 medium beta cavities. • Cavity fabrication of 36 (*) medium beta cavities in the industry, including treatments, tuning, Helium tank integration, etc, accomplishing the ESS requirements in terms of performances, functional interfaces. • Certification activities, documentation, ancillaries (flanges, vacuum valves, antennas, frames, etc.) • Cold tests in a qualified infrastructure. • Transportation in special boxes and delivery at the cryomodule assembling facility. • Man power for the above activities. (*)INFN Design, plug compatible with CEA boundary condition 5

6. Pre-series prototypes in progress • We build prototypes of medium and high beta cavities • INFN design, using Large Grain Nb and one FG for comparison, plug compatible with ESS cryomodule • Electromagnetic and mechanical design almost done • Optimization to include Large Grain option • Large Grain Nb ingots procurement from CBMM • Slicing process completed by Heraeus • All treatments (BCP, HPR, clean room) done in industry • Final handling and test will be done at LASA in the qualified infrastructure 6

7. Some specs for the medium beta 7

8. High RRR Ingot from CBMM • Thinking to large elliptical cavities CBMM produced a high RRR niobium ingot with a new crucible: diameter = 530 mm. • Based on our request Ingot was machined to a diameter of 480 mm, for the production of ESS cavity prototypes. • In parallel INFN evaluated the different techniques for Ingot slicing: sawing, lathe cutting, EDM, multiple wire sawing. • Heraeus at Hanau was chosen for the slicing process: multiple wire sawing machine able to cut the 480 mm ingot. • CBMM delivered to INFN two 130 mm length cylinders from the original ingot to be converted in disk. This choice was driven by the high density of Nb with respect to silicon and quartz glass that are usually cut with the multiple wire sawing machine at Heraeus. 8

9. The 2 CBMM Ingots at Heraeus • Photos: courtesy CBMM and U. Weitzel-Hoefler, Heraeus 9

10. Chemical Analysis at CBMM • Courtesy Rogerio Marques Ribas, CBMM 10

11. CBMM Ingots: High RRR 11

12. Slicing at Heraeus of the 2 Ingots • Ingots diameter: 480 mm • Ingots length: 130 mm • Ingots weight: about 200 kg • Settled thickness for disks: 4.675 mm • Number of slices/ingot: about 24 • Slicing estimated time: about 4.5 days • Cutting with “Oxygen protection” technique, to avoid permanent degradation of RRR values (O2 diffusion). Only Hydrogen will increase, but RRR will be recovered by in vacuum heat treatment. 12

13. Expected gas evolution • “Oxygen protection“ by Heraeus reduce gases diffusion and gettering during wire cutting. • Extimated behavior for CBMM current LG material done by Heraeus. 13

14. Preliminary check and Next steps • First mechanical check on slices • Thickness: mostly 0.01 mm, worst case  0.03 mm! • Roughness: Ra mostly  0.5 mm, worst case 1 mm! • Next steps after first coarse cleaning and delivery • Sampling for RRR measurement and gas analysis after cutting. • Short etching (BCP, 1:1:2, 5 – 10 mm) • Sampling for analysis: RRR and gases • In vacuum heat treatment for dehydrogenation • Sampling for analysis: RRR and gases • Half cell forming from January 2016 • First cavity prototype ready for vertical test by summer 2016 14

15. Some pictures from slicing - 1 • Ingot prepared for slicing • Multi wire slicing • Slices from the first ingot • Surface finishing just after the cut • Photos: courtesy Ursula Weitzel-Hoefler, Heraeus 15

16. Some pictures from slicing - 2 • Witness of the • fastening system • Sample for • Interstitials • measurements • Photos: courtesy Ursula Weitzel-Hoefler, Heraeus 16