• W. Fischer, E.N. Beebe, D. Bruno, D.M. Gassner, X. Gu, R.C. Gupta, J. Hock, A.K. Jain, R.F. Lambiase, Y. Luo, M. Mapes, W. Meng, C. Montag, B. Oerter, M. Okamura, A.I. Pikin, D. Raparia, Y. Tan, R. Than, J.E. Tuozzolo, W. Zhang
  BNL, Upton, Long Island, New York

In po­lar­ized pro­ton op­er­a­tion the lu­mi­nos­i­ty of RHIC is lim­it­ed by the head-on beam-beam ef­fect, and meth­ods that mit­i­gate the ef­fect will re­sult in high­er peak and av­er­age lu­mi­nosi­ties. Two elec­tron lens­es, one for each ring, are being con­struct­ed to par­tial­ly com­pen­sate the head-on beam-beam ef­fect in the two rings. An elec­tron lens con­sists of a low en­er­gy elec­tron beam that cre­ates the same am­pli­tude de­pen­dent trans­verse kick as the pro­ton beam. We dis­cuss de­sign con­sid­er­a­tion, pre­sent the main pa­ram­e­ters, and es­ti­mate the per­for­mance gains.

• M.A. Plum, J. Galambos, S.-H. Kim, P. Ladd, Y. Polsky, R.W. Shaw
  ORNL, Oak Ridge, Tennessee
• C.F. Luck, C.C. Peters
  ORNL RAD, Oak Ridge, Tennessee
• R.J. Macek
  LANL, Los Alamos, New Mexico
• D. Raparia
  BNL, Upton, Long Island, New York

The di­a­mond strip­per foils in use at the Spal­la­tion Neu­tron Source worked suc­cess­ful­ly with no fail­ures until May 3, 2009, when we start­ed ex­pe­ri­enc­ing a rash of foil fail­ures after in­creas­ing the beam power to ~840 kW. The main con­tri­bu­tions to foil fail­ure are thought to be 1) con­voy elec­trons, stripped from the in­com­ing H− beam, that strike the foil brack­et and may also re­flect back from the elec­tron catch­er, and 2) vac­u­um break­down from the charge de­vel­oped on the foil by sec­ondary elec­tron emis­sion. In this paper we will de­tail these and other fail­ure mech­a­nisms, and de­scribe the im­prove­ments we have made to mit­i­gate them.