Preliminary results from prototype niobium cavities for the JLAB Ampere-class FEL

Kneisel, P.; Ciovati, Gianluigi; Bundy, R.D.; Clemens, B. M.; Forehand, Daniel; Golden, B.; Manning, S.; Manus, B.; Marhauser, Frank; Overton, R.B.; Rimmer, Robert; Slack, Gary; Turlington, L.; Wang, H.

doi:10.1109/pac.2007.4441292

Cited by 5 publications

(4 citation statements)

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“…Previous studies on etch-pits in ingot Nb samples cut from a cavity showed a correlation between high density of pits and dislocations and the presence of hydrocarbon contamination within pits [27,28]. As a comparison, the results of RF tests at 2 K of few cavities recently built at Jefferson Lab using low-purity finegrain Nb also showed a significant scatter in the values of the quench field: 73 mT for a 1.5 GHz 5-cell cavity [29], 100 mT for a 650 MHz single-cell [30] and 26 mT for a 400 MHz single-cell cavity [31]. The nature of the defects limiting the performance of the cavities was not investigated.…”

Section: Discussionmentioning

confidence: 83%

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

Ciovati

Dhakal

Myneni

2016

Supercond. Sci. Technol.

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Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q 0 -values. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR=100-150) and low (RRR=60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q 0 -value of 2×10 10 at 2 K after standard processing treatments. The performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.

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Section: Discussionmentioning

confidence: 83%

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

Ciovati

Dhakal

Myneni

2016

Supercond. Sci. Technol.

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“…One such multi-cell cavity was the 5-cell, 1.497 MHz HC. The cavity was subjected to several different surface preparation methods which included, besides the ones mentioned in the previous paragraph, barrel polishing (BP) [17,18]. A summary of the RF test results at 2.0 K after various preparation procedures in shown in Fig.…”

Section: Multi-cell Cavitiesmentioning

confidence: 99%

America’s Overview of Superconducting Science and Technology of Ingot Niobium

Kneisel¹,

Myneni²,

Ciovati³

et al. 2011

AIP Conference Proceedings

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This contribution will present an overview of the results from R&D programs in the USA over the past four years towards the development of ingot Niobium as a viable alternative material to fabricate SRF cavities for particle accelerators. Activities at several laboratories and universities include fabrication, surface treatment and RF testing of single-and multi-cell cavities and studies of the thermal, mechanical and superconducting properties of samples from ingots of different purity. Possible advantages of ingot niobium over standard fine-grain (ASTM 6) are discussed and a streamlined treatment procedure to fully exploit those advantages is proposed.

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“…The detail of the cavity fabrication was presented in [11]. Prior to the tests reported in this article, the cavity was processed with buffer chemical polishing (BCP), high temperature annealing (800 °C/3 h), low temperature baking (145 °C/36 h) and rf tested several times [13]. During those tests, the cavity reached ∼40 MV m −1 with quality factor of ∼10 10 at 2 K. The average final thickness of the Nb on Cu was approximately 0.3 mm after ∼0.2 mm was removed via BCP.…”

Section: Methodsmentioning

confidence: 99%

Effect of cooldown and residual magnetic field on the performance of niobium–copper clad superconducting radio-frequency cavity

Dhakal¹,

Ciovati²

2017

Supercond. Sci. Technol.

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We present the results of rf measurements on a niobium-copper clad superconducting radiofrequency cavity with different cooldown conditions and residual magnetic field in a vertical test Dewar in order to explore the effect of thermal current induced magnetic field and its trapping on the performance of the cavity. The residual resistance, extracted from the Q0(T) curves in the temperature range 4.3-1.5 K, showed no dependence on a temperature gradient along the cavity during the cooldown across the critical temperature up to ~50 K/m. The rf losses due to the trapping of residual magnetic field during the cavity cooldown were found to be ~4.3 n/T, comparable to the values measured in bulk niobium cavities. An increase of residual resistance following multiple cavity quenches was observed along with evidence of trapping of magnetic flux generated by thermoelectric currents.

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Preliminary results from prototype niobium cavities for the JLAB Ampere-class FEL

Cited by 5 publications

References 0 publications

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

America’s Overview of Superconducting Science and Technology of Ingot Niobium

Effect of cooldown and residual magnetic field on the performance of niobium–copper clad superconducting radio-frequency cavity

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