Experimental results on 700 MHz multicell superconducting cavity for proton linac

Visentin, B.; Charrier, J.P.; Roudier, Dominique; Simoens, F.; Jacques, Emmanuel; Aspart, A.; Gasser, Y.; Poupeau, Jean Pierre; Sahuquet, Patrick; Braud, D.; Saugnac, H.; Szott, P.; Bousson, S.; Biarrotte, Jean‐Luc; Junquera, T.; Blivet, S.

doi:10.1109/pac.2003.1289686

Cited by 4 publications

(4 citation statements)

References 1 publication

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“…Two 5 MeV RFQs at CEA/Saclay [7] and INFN/LNL [8] have been designed and engineered and are under construction. Single cell and multi cell superconducting cavities of the elliptical type have been built and tested both at CEA [10] and INFN/MI [11], and CNRS/Orsay built and tested spoke structures [12]. Single cell and multi cell superconducting cavities of the elliptical type have been built and tested both at CEA [10] and INFN/MI [11], and CNRS/Orsay built and tested spoke structures [12].…”

Section: The National Programsmentioning

confidence: 99%

European Studies for Nuclear Waste Transmutation

Pierini¹

2005

AIP Conference Proceedings

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Section: The National Programsmentioning

confidence: 99%

European Studies for Nuclear Waste Transmutation

Pierini¹

2005

AIP Conference Proceedings

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“…Second, it was demonstrated by cavity anodizing experiments [4,5] that modifications introduced by mild baking at 100-120 C, which are affecting the high field Q slope, are confined to only $20-30 nanometers from the surface. It was also shown that vacuum conditions for mild baking may not be crucial and Ar or even atmospheric air can be used [6]. While anodizing studies provided an indication of the crucial length scales for the mild baking effect on the high field Q slope, it is important to study in detail how all of the Q slopes (and not only HFQS) evolve when bakingmodified material is being removed.…”

Section: Introductionmentioning

confidence: 99%

Effect of mild baking on superconducting niobium cavities investigated by sequential nanoremoval

Romanenko

Grassellino

Barkov

et al. 2013

Phys. Rev. ST Accel. Beams

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The near-surface nanostructure of niobium determines the performance of superconducting microwave cavities. Subtle variations in surface nanostructure lead to yet unexplained phenomena such as the dependence of the quality factor of these resonating structures on the magnitude of rf fields-an effect known as the ''Q slopes''. Understanding and controlling the Q slopes is of great practical importance for particle accelerators. Here we investigate the mild baking effect-120 C vacuum baking for 48 hours-which strongly affects the Q slopes. We used a hydrofluoric acid rinse alternating with oxidation in water as a tool for stepwise material removal of about 2 nanometers=step from the surface of superconducting niobium cavities. Applying removal cycles on mild baked cavities and measuring the quality factor dependence on the rf fields after one or several such cycles allowed us to explore the distribution of lossy layers within the first several tens of nanometers from the surface. We found that a single HF rinse results in the increase of the cavity quality factor. The low field Q slope was shown to be mostly controlled by the material structure within the first six nanometers from the surface. The medium field Q slope evolution was fitted using linear (/ B peak surface magnetic field) and quadratic (/ B 2 ) terms in the surface resistance and it was found that best fits do not require the quadratic term. We found that about 10 nanometers of material removal are required to bring back the high field Q slope and about 20-50 nanometers to restore the onset field to the prebaking value.

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“…The primary effect of these treatments is to alter the impurities within the radio frequency penetration depth of Nb, which is close to ∼50 nm [6]. It was found that, if the phosphoric acid in the BCP solution is replaced with sulphuric acid, the Q-slope improves in comparison to the standard BCP treated cavity [5], which further highlights the role of impurities. Various forms of impurities, which included interstitials [7,8], metals and nonmetals [9,10], hydrocarbons [11,12] and oxides [10,[13][14][15][16][17][18], combined with their locations, which included surface [9][10][11][19][20][21], subsurface [7,8,14,16,17,22], inside penetration depth [7,13], bulk [4] and grain boundaries [15,23], were directly or indirectly linked to the cavity performance [7][8][9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 97%

“…Moreover, low temperature baking (LTB), improves the gradient and Q O in EP as well as BCP treated cavities [4]. However, in some exceptional cases, stand-alone BCP treated 1.3 GHz cavities have also reached 40 MV m −1 , which adds complexity to the above subject [5]. Since large numbers of cavities are required to build a superconducting accelerator, these treatments should ensure repeatability in their performance.…”

Section: Introductionmentioning

confidence: 99%

Study of impurity distribution in mechanically polished, chemically treated and high vacuum degassed pure niobium samples using the TOFSIMS technique

Bose

Joshi

2015

Supercond. Sci. Technol.

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The performance of Superconducting radio frequency cavities (SRF) is strongly influenced by various impurities within the penetration depth (~50nm) of Nb, which in turn depends on the applied surface treatments. The effect of these surface treatments on the impurities of Nb has been explored using various surface analytical treatments.But, the results are still inadequate in many aspects and the effect of sequential SRF treatments on the impurity distribution has not been explored. The present study analyses various impurities within the penetration depth of Nb samples, treated by SRF cavity processing techniques like colloidal silica polishing (simulating centrifugal barrel polishing), buffer chemical polishing (BCP), high pressure rinsing (HPR) and degassing under high vacuum (HV) condition at 600°C for 10hrs. Static, dynamic and slow sputtering modes of Time of flight secondary ion mass spectrometry (TOFSIMS) technique was employed to study the effect of the above treatments on interstitial impurities, hydrocarbons, oxides, acidic residuals, reaction products and metallic contaminations. The study confirms that the impurity distribution in Nb is not only sensitive to the surface treatment, but also to their sequence. Varying the treatment sequence prior to HV degassing treatments affected the final impurity levels in HV degassed bulk Nb samples. BCP treated samples, exhibited minimum hydrocarbon and metallic contamination but, led to extensive contamination of the oxide layer with residuals and reaction products of acids used in BCP solution. HPR treatment, on the other hand was effective in reducing the acidic impurities on the top surface. The study also establishes the application of TOFSIMS technique to analyze and evolve SRF treatments.

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Experimental results on 700 MHz multicell superconducting cavity for proton linac

Cited by 4 publications

References 1 publication

European Studies for Nuclear Waste Transmutation

European Studies for Nuclear Waste Transmutation

Effect of mild baking on superconducting niobium cavities investigated by sequential nanoremoval

Study of impurity distribution in mechanically polished, chemically treated and high vacuum degassed pure niobium samples using the TOFSIMS technique

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