Statera, M., LASA lab, INFN Milano, Segrate, MI, Italy, 20090 (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Alessandria, F., INFN-LASA Sez. di Milano, Milan, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Broggi, F., Milano, LASA lab., INFN, Milano, MI, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Bellomo, G., University of Milan and INFN-LASA, Milan, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Imeri, L., INFN - LASA, Milan, Milan, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Leone, A., INFN-LASA Sez. di Milano, Milan, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Mariotto, S., Fisica, Universita degli Studi di Milano, 9304 Milano, Milano, Italy, 20122 (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Paccalini, A., INFN-LASA Sez. di Milano, Milan, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Pasini, A., INFN-LASA Sez. di Milano, Milan, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Pedrini, D., LASA, INFN, Segrate, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Prioli, M., LASA, INFN, Segrate, MI, Italy, 20090 (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Sorbi, M., Physics, University of Milan and INFN-LASA, Segrate, Milan, Italy, 20090 (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Todero, M., INFN-LASA Sez. di Milano, Milan, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Uva, C., Milano, LASA lab., INFN, Milano, MI, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Valente, R.U., University of Rome La Sapienza Faculty of Mathematical Physical and Natural Sciences, 99011 Roma, Italy, 00185 (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Musso, A., TE, CERN, Geneva, Switzerland, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Todesco, E., TE, CERN, Geneva, Switzerland, 1211 (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Campaniello, M., SAES Getters, 68230 Lainate, Lombardy, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Canetti, M., SAES Rial Vacuum, Parma, Parma, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Gangini, F., SAES Rial Vacuum, Parma, Parma, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Manini, P., SAES Getters, 68230 Lainate, Lombardy, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Santini, C., SAES Rial Vacuum, Parma, Parma, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.); Zanichelli, A., Rodofil, Bogolese, Parma, Italy, (e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.)