SRF2013 - List of Authors (Stivanello, F.)

Paper

Title

Page

Fluorine Free Ionic Liquid Electropolishing of Niobium Cavities

410

V.B. Pastushenko, O.V. Malkova, V. Palmieri, A.A. Rossi, F. Stivanello, G. Yu
INFN/LNL, Legnaro (PD), Italy
G. Yu
CIAE, Beijing, People's Republic of China

Ionic liquids are an emerging breakthrough in green chemistry since the years 2000. In 2006, INFN-LNL was the first to apply a mixture of Choline Chloride and Urea to Niobium electropolishing. It was found that mirror like surfaces could be obtained at temperature higher than 120°C, with high throwing power. Subsequently the process was successfully applied to the electropolishing of a 6 GHz monocell cavity with the addition of sulphamic acid. In this work, we will report an intense investigation of the possible variants of the original recipe. We studied the influence on Niobium surface roughness of several parameters such as: other sulphamic, ammonium and carboxylic containing additives different than sulfamic acid, the possible substitution of Urea with ethylene glycol and malic acid, the current regime; the electrolyte temperature and the cathode shape, rotating horizontal electropolishing versus vertical electropolishing. Due to the cavity hollow cylindrical shape, the electrolyte temperature appeared to be the most crucial parameters among those above mentioned for a uniform dissolution of niobium.

Slides TUIOC03 [14.464 MB]

TUIOC05

Purification of 6 GHz Cavities by Induction Heating

419

A.A. Rossi, A. Battistello, M. Checchin, V. Palmieri, S. Stark, F. Stivanello, R.K. Thakur, G. Yu
INFN/LNL, Legnaro (PD), Italy

We have developed an innovative technique for purification of bulk-Nb 6GHz RF cavities under ultra-high vacuum (UHV) system. The main advantages of 6 GHz bulk-Nb cavities are saving cost, materials and time to collect statistics of surface treatments and RF test. Cavities are RF tested before and after high temperature treatment under UHV conditions. Induction heating method is used to anneal the cavity at temperatures higher than 2000°C and close to the melting point of Nb for less than a minute while few seconds at maximum temperature. Before RF test and UHV annealing, the surface treatment processes like tumbling, chemical, electro-chemical (such as BCP and EP), ultrasonic cleaning and high pressure rinsing (HPR) have been employed. This kind of Nb 6 GHz cavity purification allow to reduce hydrogen, oxygen and other elemental impurities content, which effects on cavity Q-factor degradation, by a rapid annealing over 2000°C and a subsequent rapid reduction at room temperature.

Slides TUIOC05 [42.171 MB]

Paper	Title	Page
TUIOC03	Fluorine Free Ionic Liquid Electropolishing of Niobium Cavities	410
	V.B. Pastushenko, O.V. Malkova, V. Palmieri, A.A. Rossi, F. Stivanello, G. Yu INFN/LNL, Legnaro (PD), Italy G. Yu CIAE, Beijing, People's Republic of China
	Ionic liquids are an emerging breakthrough in green chemistry since the years 2000. In 2006, INFN-LNL was the first to apply a mixture of Choline Chloride and Urea to Niobium electropolishing. It was found that mirror like surfaces could be obtained at temperature higher than 120°C, with high throwing power. Subsequently the process was successfully applied to the electropolishing of a 6 GHz monocell cavity with the addition of sulphamic acid. In this work, we will report an intense investigation of the possible variants of the original recipe. We studied the influence on Niobium surface roughness of several parameters such as: other sulphamic, ammonium and carboxylic containing additives different than sulfamic acid, the possible substitution of Urea with ethylene glycol and malic acid, the current regime; the electrolyte temperature and the cathode shape, rotating horizontal electropolishing versus vertical electropolishing. Due to the cavity hollow cylindrical shape, the electrolyte temperature appeared to be the most crucial parameters among those above mentioned for a uniform dissolution of niobium.
	Slides TUIOC03 [14.464 MB]

TUIOC05	Purification of 6 GHz Cavities by Induction Heating	419
	A.A. Rossi, A. Battistello, M. Checchin, V. Palmieri, S. Stark, F. Stivanello, R.K. Thakur, G. Yu INFN/LNL, Legnaro (PD), Italy
	We have developed an innovative technique for purification of bulk-Nb 6GHz RF cavities under ultra-high vacuum (UHV) system. The main advantages of 6 GHz bulk-Nb cavities are saving cost, materials and time to collect statistics of surface treatments and RF test. Cavities are RF tested before and after high temperature treatment under UHV conditions. Induction heating method is used to anneal the cavity at temperatures higher than 2000°C and close to the melting point of Nb for less than a minute while few seconds at maximum temperature. Before RF test and UHV annealing, the surface treatment processes like tumbling, chemical, electro-chemical (such as BCP and EP), ultrasonic cleaning and high pressure rinsing (HPR) have been employed. This kind of Nb 6 GHz cavity purification allow to reduce hydrogen, oxygen and other elemental impurities content, which effects on cavity Q-factor degradation, by a rapid annealing over 2000°C and a subsequent rapid reduction at room temperature.
	Slides TUIOC05 [42.171 MB]