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Fischer, J. F.

Publications and source records attributed to Fischer, J. F..

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Cavity Qualification and Production Update for SNS-PPU Cryomodules at Jefferson Lab

The Proton Power Upgrade (PPU) project at Oak Ridge National Lab’s Spallation Neutron Source (SNS) currently being constructed will double the proton beam power capability from 1.4 to 2.8 MW by adding seven cryomodules, each containing four six-cell high-beta (β = 0.81) superconducting radio frequency cavities. Research Instruments, located in Germany, built and processed the cavities at the vendor site, including electropolishing as the final active chemistry step. Twenty-eight cavities for seven cryomodules and an additional four cavities for a spare cryomodules were delivered to Jefferson Lab and first qualification tests were completed on all cavities as received from the vendor. The performance largely exceeded the requirements on quality factor and accelerating gradient. Here we present the status of initial cavity qualification tests, rework on unqualified cavities and final cavity qualification with helium vessel prior to installation in cryomodules. In addition, an update on cryomodule production is presented.

Dhakal, P.↗
DOE OSTI2022

Cavity Production and Testing of the First C75 Cryomodule for CEBAF

The CEBAF cryomodule rework program was updated over the last few years to increase the energy gain of refurbished cryomodules to 75 MeV. The concept recycles the waveguide end-groups from original CEBAF cavities fabricated in the 1990s and replaces the five elliptical cells in each with a new optimized cell shape fabricated from large-grain, ingot Nb material. Eight cavities were fabricated at Research Instruments, Germany, and two cavities were built at Jefferson Lab. Each cavity was processed by electropolishing and tested at 2.07 K. The best eight cavities were assembled into ’cavity pairs’ and re-tested at 2.07 K, before assembly into the cryomodule. All but one cavity in the cryomodule were within 10% of the target accelerating gradient of 19 MV/m with a quality factor of 8·10⁹. The performance limitations were field emission and multipacting.

Ciovati, G.↗
DOE OSTI2022

Cavity Production and Testing of the First C75 Cryomodule for CEBAF

The CEBAF cryomodule rework program was updated over the last few years to increase the energy gain of refurbished cryomodules to 75 MeV. The concept recycles the waveguide end-groups from original CEBAF cavities fabricated in the 1990s and replaces the five elliptical cells in each with a new optimized cell shape fabricated from large-grain, ingot Nb material. Eight cavities were fabricated at Research Instruments, Germany, and two cavities were built at Jefferson Lab. Each cavity was processed by electropolishing and tested at 2.07 K. The best eight cavities were assembled into ’cavity pairs’ and re-tested at 2.07 K, before assembly into the cryomodule. All but one cavity in the cryomodule were within 10% of the target accelerating gradient of 19 MV/m with a quality factor of 8·10⁹. The performance limitations were field emission and multipacting.

Ciovati, G.↗
DOE OSTI2022

Status of SNS Proton Power Upgrade SRF Cavities Production Qualification

The Pro­ton Power Up­grade pro­ject at Oak Ridge Na­tional Lab’s Spal­la­tion Neu­tron Source (SNS PPU) cur­rently being con­structed will dou­ble the pro­ton beam power from 1.4 to 2.8 MW by adding 7 ad­di­tional cry­omod­ules, each con­tains four six-cell high beta (\beta = 0.81) su­per­con­duct­ing radio fre­quency cav­i­ties. The cav­i­ties were built by Re­search In­stru­ments, Ger­many, with all the cav­ity pro­cess­ing done at the ven­dor site, in­clud­ing elec­trop­o­l­ish­ing as the final ac­tive chem­istry step. All 28 cav­i­ties needed for 7 cry­omod­ules were de­liv­ered to Jef­fer­son Lab, ready to be tested. The cryo­genic RF qual­i­fi­ca­tions and he­lium ves­sel weld­ing were done at Jef­fer­son Lab. The per­for­mance largely ex­ceed the re­quire­ments, and greatly ex­ceeded the per­for­mance of the orig­i­nal SNS cav­ity pro­duc­tion se­ries. Here, we pre­sent the sum­mary of RF test on pro­duc­tion cav­i­ties to this date.

Dhakal, P.↗
DOE OSTI2021

Development of Helium Vessel Welding Process for SNS PPU Cavities

The Spallation Neutron Source Proton Power Upgrade cavities are produced by Research Instrument with all the cavity processing done at vendor sites with final chemistry applied to the cavity to be electropolishing. Cavities are delivered to Jefferson Lab, ready to be tested. One of the tasks to be completed before the arrival of production-ready PPU cavities is to develop a robust helium vessel welding protocol. We have successfully developed the process and applied it to three six-cell high beta cavities. Here, we present the summary of RF results, welding process development, and post helium vessel RF results.

Dhakal, P.↗
DOE OSTI2021

Status of SNS Proton Power Upgrade SRF Cavities Production Qualification

The Pro­ton Power Up­grade pro­ject at Oak Ridge Na­tional Lab’s Spal­la­tion Neu­tron Source (SNS PPU) cur­rently being con­structed will dou­ble the pro­ton beam power from 1.4 to 2.8 MW by adding 7 ad­di­tional cry­omod­ules, each con­tains four six-cell high beta (\beta = 0.81) su­per­con­duct­ing radio fre­quency cav­i­ties. The cav­i­ties were built by Re­search In­stru­ments, Ger­many, with all the cav­ity pro­cess­ing done at the ven­dor site, in­clud­ing elec­trop­o­l­ish­ing as the final ac­tive chem­istry step. All 28 cav­i­ties needed for 7 cry­omod­ules were de­liv­ered to Jef­fer­son Lab, ready to be tested. The cryo­genic RF qual­i­fi­ca­tions and he­lium ves­sel weld­ing were done at Jef­fer­son Lab. The per­for­mance largely ex­ceed the re­quire­ments, and greatly ex­ceeded the per­for­mance of the orig­i­nal SNS cav­ity pro­duc­tion se­ries. Here, we pre­sent the sum­mary of RF test on pro­duc­tion cav­i­ties to this date.

Dhakal, P.↗