Production,installation and test of Nb-sputtered QWRs for ALPI |
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Authors: | A M Porcellato V Palmieri L Bertazzo A Capuzzo D Giora F Stivanello S Y Stark S Kar |
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Institution: | (1) INFN, Laboratori Nazionali di Legnaro (Pd), Italy;(2) Strumenti Scientifici Cinel, Vigonza (Pd), Italy;(3) Nuclear Science Centre, Aruna Asaf Ali Marg, New Delhi, India |
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Abstract: | Eight cryostats, each housing 4 sputtered Nb/Cu, 160 MHz, quarter wave resonators (QWR), are now in operation in ALPI1].
Two of them house high β cavities; the others are equipped with medium β resonators. Another medium β cryostat is ready and will be installed in the early 2002. Pb/Cu medium β accelerating cavities are now present only in four cryostats and they will have their Pb superconducting (SC) layer replaced
by sputtered Nb soon.
The substitution of the Pb SC layer in ALPI medium β resonators did not interfere with ALPI operation; the upgrading of resonators went on parallel to the cryostat maintenance
programme. The average accelerating field of these resonators, at the design power of 7 W, overcomes 4 MV/m, whereas, when
Pb electroplated, their average value was 2.7 MV/m. The sputtered resonator combines the good SC characteristics of Nb with
the higher thermal conductivity and better stability to change of He bath pressure, which is typical of copper resonators.
This leads to a very high reliability, as routinely experienced during beam acceleration. |
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Keywords: | Niobium superconducting cavities heavy ion LINAC Nb sputtering |
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