Stark S.

Paper	Title	Page
TUP38	A Novel Sputtered Medium Beta Cavity for ALPI	216
	S. Stark, A. M. Porcellato, A. Palmieri, V. Palmieri, P. Favaron, E. Bissiato, F. Stivanello, F. Chiurlotto, G. Dona, D. Giora, M. DeLazzari INFN-LNL
	The installed medium beta ALPI cavities were produced by Nb sputtering on old Cu substrates, which were originally Pb plated. The cavity renew could practically double the previous average operational accelerating field but the performance obtained in high beta resonators, whose Cu bases were designed to be sputtered, could not be reached [1, 2]. To overcome this performance gap, we designed, built and tested a novel medium beta cavity, which has the shorting plate rounded as in high beta cavities, while the beam ports are obtained by plastic deformation of the outer conductor instead of being brazed to the cavity body as in the previous medium beta QWRs. The paper describes cavity design, substrate construction technology, surface treatments and results of the first resonator cold test.
TUP58	First Cold Tests of the Beta=0.12 Ladder Resonator at LNL	264
	G. Bisoffi, E. Bissiato, F. Chiurlotto, A. Palmieri, A. M. Porcellato, F. Scarpa, S. Stark INFN-LNL
	The Ladder resonator is a 4-gap full Nb cavity suitable for the 0.1< beta <0.2 range of high current proton linacs. A beta=0.12 Nb prototype of this cavity has been built by E. Zanon SpA (Schio, Italy) on the basis of LNL design. In this paper the construction procedure of such cavity, as well as the tuning steps necessary to match field and frequency requirements are recalled. Finally, the main outcomes of the first cryogenic test performed at LNL in July 2007 are described.
WE202	Different sputtering configurations for coating 1.5 GHZ copper cavities	384
	G. Lanza, V. Palmieri, N. Patron, C. Pira, S. Stark Laboratori Nazionali di Legnaro, STITUTO NAZIONALE DI FISICA NUCLEARE E. Bemporad, F. Carassiti, M. Sebastiani University of Rome H. Padamsee Cornell University
	In the framework of the attempts to densify the sputtering discharge, two different sputtering configuration are reported: - a mixed bias magnetron sputtering technique has been explored for depositing niobium into 1,5 GHz copper cavities. Results are presented and compared with the standard CERN technique. The superconducting and high resolution morphological and mechanical properties of niobium films sputtered onto the inner walls of electropolished cavities, have been studied as a function of the deposition technique. Even if niobium films coated with the bias technique show a higher density and Tc similar to the other films, they don't present higher RRR values. Preliminary RF tests are presented. - post Magnetron sputtering in thermoelectric emission regime have been investigated and is under improvement in order to increase the RRR values of sputtered Nb: superconducting and structural properties of the obtained films have been measured to check the technique capability and its possible application for coating cavities.
	Slides(PDF)
WE203	The Progress on Nb3Sn and V3Si	392
	S. M. Deambrosis, N. Patron, A. Rossi, V. Palmieri INFN-LNL/Padua University G. Keppel, N. Pretto, V. Rampazzo, S. Stark, F. Stivanello INFN-LNL R. G. Sharma Inter-University Accelerator Centre
	In the framework of the research for a valid alternative to Nb for RF applications, Nb3Sn and V3Si have been investigated at LNL. The chosen technique to obtain Nb3Sn is based on the molten Tin diffusion method and it has been progressively modified to improve the samples superconducting properties (Tc and Delta Tc) and to eliminate Sn traces on the Nb3Sn surface. Our "Hybrid process" seems to be the most promising (Tc = 16,8 K and Delta Tc = 0,16 K, no residual Sn traces on the sample surface, no Sn rich phases). The present point is to test the obtained material RF properties: the best recipe used for samples has been applied to coat a 6 GHz Nb cavity. At the same time we are going to study different techniques to achieve Nb3Sn good superconducting cavities. One of them is the so called mechanical plating. Secondly we are going to study the multilayer technique: the first attempt gave a superconducting deposition with Tc = 17,9 K and Delta Tc =.0,02 (four contacts measurement). The V3Si intermetallic compound has been obtained using the thermal diffusion of Silicon into Vanadium: bulk V is heat treated in a SiH4 atmosphere for several hours and then annealed in vacuum. The samples superconducting properties are encouraging (Tc ~= 15,5 K and Delta Tc ~= 0,2 K). To check the material RF performances we prepared a V3Si 6 GHz cavity (sylanized for 4h at 850 degree C with p(SiH4) = 5x10-3 mbar): it has been measured several times after a heating treatment in vacuum progressively longer (6h, 12h, 36h, 84h at 850 degree C). At the moment, we are trying to use plasma during the silanization process to avoid the hydrogen presence into the growing films. The first V3Si coating grown has Tc = 15,7 K and Delta Tc = 0,22 K: this result is already comparable to what we had with the "traditional" technique.
	Slides(PDF)
WE204	Application of plasma cleaning to cavities processing	400
	N. Patron, S. Deambrosis, S. Stark, V. Palmieri INFN-LNL M. Baecker Fachhochschule Aachen L. Phillips TJLNAF
	very versatile and inexpensive technique used in a variety of surface processes such as dry etching, surface treatments and modification of surface wettability. After initial studies on different configurations of RF, MW and DC atmospheric plasma devices we have analyzed the modification of water wettability induced by helium atmospheric plasma. We have applied a resonance atmospheric plasma cleaning step to further clean a 6 GHz Nb seamless cavity observing an increment in the Q0 from 7x1e6 to 2x1e7 in only 30 minutes of process. The increased wettability due to the plasma action on the inner cavity surface has proved to enhance the beneficial action of water rinsing pushing the Q0 value further up close to 3x1e7.
	Slides(PDF)