• T. Baer, B. Araujo Meleiro, T.B. Bogey, J. Wenninger
  CERN, Geneva
• T. Baer
  DESY, Hamburg

The Super Pro­ton Syn­chrotron (SPS) at CERN with a peak en­er­gy of 450GeV is at the top of the LHC preac­cel­er­a­tor-com­plex. Apart from the LHC, SPS is with Teva­tron the ac­cel­er­a­tor with the largest stored beam en­er­gy of up to 2.5MJ. The SPS has a known vul­ner­a­bil­i­ty to fast equip­ment fail­ures that led to an un­con­trolled loss of a high in­ten­si­ty beam in 2008, which re­sult­ed in major dam­age of a main dipole. The beam loss was caused by a fast tune de­crease to­wards an in­te­ger res­o­nance. Sim­u­la­tions and dis­tinct ex­per­i­men­tal stud­ies pro­vide clear un­der­stand­ing of the beam dy­nam­ics at dif­fer­ent SPS tune res­o­nances. Di­verg­ing closed orbit os­cil­la­tions, dis­per­sion ex­plo­sion and in­creased be­ta-beat­ing are the driv­ing ef­fects that lead to a com­plete beam loss in as lit­tle as 3 turns (70μs). Ded­i­cat­ed ex­per­i­ments of fast fail­ures of the main power con­vert­ers re­veal that the cur­rent in­ter­lock sys­tems are much too slow for an ad­e­quate ma­chine pro­tec­tion. To coun­ter­act the vul­ner­a­bil­i­ty of the SPS, cur­rent re­search fo­cus­es on a new fast po­si­tion in­ter­lock sys­tem which is planned to be­come op­er­a­tional in 2010.