LCLS-II-HE verification cryomodule high gradient performance and quench behavior

Posen, S.; Cravatta, A.; Checchin, Mattia; Aderhold, Sebastian; Adolphsen, C.; Arkan, T.; Bafia, Daniel; Benwell, A.; Bice, D.; Chase, Brian; Crispin, Contreras-Martinez,; Dootlittle, L.; Fuerst, J. D.; Gonnella, D.; Grimm, Chuck; Hansen, Benjamin; Harms, E.; Hartsell, Brian; Hays, G.; Holzbauer, Jeremiah; Hoobler, Sonya; Kaluzny, Joshua; Khabiboulline, T.; Kucera, M.; Lambert, D.; Legg, R.; Lewis, Fred; Makara, J.; Maniar, Harsh; Maniscalco, James; Martinello, Martina; Nelson, J.; Paiagua, Sergio; Pischalnikov, Y.; Prieto, P.; Reid, J.; Ross, M.; Serrano, Carlos; Solyak, N.; A., Syed,; Sun, Ding; Tatkowski, G.; Wang, R.; White, M.; L., Zacarias,

doi:10.48550/arxiv.2110.14580

Cited by 3 publications

(12 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As explained in Posen et al [19], CAV5 was affected by FE during the first two cooldowns here under consideration. The electron activity caused by the field emission may have contributed to CAV5 MP-induced quenches during the first two cooldowns.…”

Section: Comparison Of the Vcm Performance Before And After Plasma Pr...mentioning

confidence: 62%

“…(10) and ( 11) from Posen et al [19], during the first vCM RF test all the eight cavities suffered from multipacting induced quenches, during both the power rise to 21 MV/m (Fig. (10) [19]) or the long duration operation at high gradient (Fig. (11) [19]).…”

Section: Comparison Of the Vcm Performance Before And After Plasma Pr...mentioning

confidence: 95%

“…The vCM average quality factor still exceeded the specification (Q 0 = 2.7×10 10 at 20.8 MV/m), with an average of Q 0 = 3.1 × 10 10 . As explained in Posen et al [19], the admin limit for the gradient in case the ultimate quench field of the cavity was not reached was set to 26.0 MV/m, while the maximum gradient defines the field level at which a cavity would quench consistently without allowing any further field increase. The usable gradient instead is defined as the maximum field at which i) the cavity can operate for more than one hour without quenching, ii) the radiation stays below 50 mR/hr and iii) the cavity is 0.5 MV/m below its ultimate quench field limit.…”

Section: Comparison Of the Vcm Performance Before And After Plasma Pr...mentioning

confidence: 99%

“…Plasma cleaning of the vCM took place at the Cryomodule Test Facility (CMTF) at FNAL, after the completion of extensive RF tests which results are discussed in Posen et al [19] and the subsequent warm up to room temperature. The vCM was RF tested again after plasma cleaning in order to assess the cavity performance changes after the processing.…”

Section: Experimental Set-up and Plasma Processing Proceduresmentioning

confidence: 99%

“…The cryomodule under study is the LCLS-II-HE verification cryomodule (vCM). Before plasma processing the vCM underwent extensive tests, the results are reported in Posen et al [19]. The LCLS-II-HE project requires 1.3 GHz 9-cell niobium cavities operating at quality factor Q 0 > 2.7 × 10 10 and accelerating gradient E acc ≈ 21 MV/m.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Plasma Cleaning of LCLS-II-HE verification cryomodule cavities

Giaccone,

Berrutti,

Martinello

et al. 2022

Preprint

View full text Add to dashboard Cite

Plasma cleaning is a technique that can be applied in superconducting radio-frequency (SRF) cavities in situ in cryomodules in order to decrease their level of field emission. We developed the technique for the Linac Coherent Light Source II (LCLS-II) cavities and we present in this paper the full development and application of plasma processing to the LCLS-II High Energy (HE) verification cryomodule (vCM). We validated our plasma processing procedure on the vCM, fully processing four out of eight cavities of this CM, demonstrating that cavities performance were preserved in terms of both accelerating field and quality factor. Applying plasma processing to this clean, record breaking cryomodule also showed that no contaminants were introduced in the string, maintaining the vCM field emission-free up to the maximum field reached by each cavity. We also found that plasma processing eliminates multipacting (MP) induced quenches that are typically observed frequently within the MP band field range. This suggests that plasma processing could be employed in situ in CMs to mitigate both field emission and multipacting, significantly decreasing the testing time of cryomodules, the linac commissioning time and cost and increasing the accelerator reliability.

show abstract

Section: Comparison Of the Vcm Performance Before And After Plasma Pr...mentioning

confidence: 62%

Section: Comparison Of the Vcm Performance Before And After Plasma Pr...mentioning

confidence: 95%

Section: Comparison Of the Vcm Performance Before And After Plasma Pr...mentioning

confidence: 99%

Section: Experimental Set-up and Plasma Processing Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Plasma Cleaning of LCLS-II-HE verification cryomodule cavities

Giaccone,

Berrutti,

Martinello

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

Plasma Processing for In-Situ Field Emission Mitigation of Superconducting Radiofrequency (SRF) Cryomodules

Martinello,

Berrutti,

Giaccone

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Field emission (FE) is one of the main limiting factors of superconducting radiofrequency (SRF) cavities operating in accelerators and it occurs whenever contaminants, like dust, metal flakes or even absorbates, are present on the surface of the cavity high electric field region. Field emission reduces the maximum achievable accelerating field and generates free electrons that may interact with the beam, damage or activate the beamline. One practical method that can be used to mitigate this problem is in-situ plasma cleaning, or plasma processing. The development of a processing that can be applied in-situ is extremely advantageous, since it enables the recovery of the cryomodule performance without the need of disassembling the whole cryomodule, which is an extremely expensive and time-consuming process. On the other hand, plasma processing only requires the cryomodule warm-up to room-temperature and the subsequent processing of the contaminated cavities. The entire process is reasonably quick and involves a limited number of personnel. For these reasons we would like to advocate for continuing to invest in the R&D of plasma processing to optimize its applicability in cryomodules and for extending the technique to other frequency ranges and cavities geometries.

show abstract

High Gradient Testing of off-Axis Coupled C-band Cu and CuAg Accelerating Structures

Schneider¹,

Zuboraj²,

Dolgashev³

et al. 2022

Preprint

View full text Add to dashboard Cite

We report the high gradient testing results of two single cell off-axis coupled standing wave accelerating structures. Two brazed standing wave off-axis coupled structures with the same geometry were tested: one made of pure copper (Cu), and one made of a copper-silver (CuAg) alloy with a silver concentration of 0.08%. A peak surface electric field of 450 MV/m was achieved in the CuAg structure for a klystron input power of 14.5 MW and a 1 µs pulse length, which was 25% higher than the peak surface electric field achieved in the Cu structure. The superb high gradient performance was achieved because of the two major optimizations in the cavity's geometry: 1) the shunt impedance of the cavity was maximized for a peak surface electric field to accelerating gradient ratio of ∼2 for a fully relativistic particle, 2) the peak magnetic field enhancement due to the input coupler was minimized to limit pulse heating. These tests allow us to conclude that C-band accelerating structures can operate at peak fields similar to those at higher frequencies while providing a larger beam iris for improved beam transport.

show abstract

LCLS-II-HE verification cryomodule high gradient performance and quench behavior

Cited by 3 publications

References 15 publications

Plasma Cleaning of LCLS-II-HE verification cryomodule cavities

Plasma Cleaning of LCLS-II-HE verification cryomodule cavities

Plasma Processing for In-Situ Field Emission Mitigation of Superconducting Radiofrequency (SRF) Cryomodules

High Gradient Testing of off-Axis Coupled C-band Cu and CuAg Accelerating Structures

Contact Info

Product

Resources

About