• M. Jonker, E.B. Holzer, S. Mallows, D. Manglunki, G. Morpurgo, Th. Otto, M. Sapinski, F. Tecker, J.A. Uythoven
  CERN, Geneva

The pro­posed Com­pact Lin­ear Col­lid­er (CLIC) is based on a two-beam ac­cel­er­a­tion scheme. The en­er­gy of high in­ten­si­ty, low en­er­gy drive beams is ex­tract­ed and trans­ferred to low in­ten­si­ty, high en­er­gy main beams. Di­rect ion­iza­tion loss by the beam par­ti­cles is the prin­ci­pal dam­age mech­a­nism. The total charge gives a sin­gle drive beam-train a dam­age po­ten­tial that is two or­ders of mag­ni­tude above the level caus­ing struc­tural dam­age in cop­per. For the main beam, it is the ex­treme charge den­si­ty due to the mi­cro­scop­ic beam size that gives it a dam­age po­ten­tial of four or­ders of mag­ni­tude above the safe level. The ma­chine pro­tec­tion sys­tem has to cope with a wide va­ri­ety of fail­ures, from real time fail­ures (RF break­downs, kick­ers mis­fir­ing), to slow equip­ment fail­ures, to beam in­sta­bil­i­ties (caused by e.g. tem­per­a­ture drifts, slow ground mo­tions). This paper dis­cuss­es the base­line for the CLIC ma­chine pro­tec­tion sys­tem which is based on pas­sive, ac­tive and per­mit based pro­tec­tion. As the per­mit based pro­tec­tion de­pends on the mea­sured per­for­mance of the pre­vi­ous pulse, the boot­strap pro­ce­dure with safe beams and step­wise in­crease in beam in­ten­si­ties, is also dis­cussed.

• M. Sapinski, B. Dehning, E.B. Holzer, M. Jonker, S. Mallows, Th. Otto
  CERN, Geneva
• C.P. Welsch
  Cockcroft Institute, Warrington, Cheshire

The Com­pact Lin­ear Col­lid­er (CLIC) is a pro­posed mul­ti-TeV lin­ear elec­tron-positron col­lid­er being de­signed by a world-wide col­lab­o­ra­tion. It is based on a novel two-beam ac­cel­er­a­tion scheme in which two beams (drive and main beam) are placed in par­al­lel to each other and en­er­gy is trans­ferred from the drive beam to the main one. Beam loss­es on ei­ther of them can have catas­troph­ic con­se­quences for the ma­chine be­cause of high in­ten­si­ty (drive beam) or high en­er­gy and small emit­tance (main beam). In the frame­work of ma­chine pro­tec­tion, a Beam Loss Mon­i­tor­ing sys­tem has to be put in place. This paper dis­cuss­es the re­quire­ments for the beam loss sys­tem in terms of de­tec­tor sen­si­tiv­i­ty, res­o­lu­tion, dy­nam­ic range and abil­i­ty to dis­tin­guish loss­es orig­i­nat­ing from var­i­ous sources. A par­tic­u­lar at­ten­tion is given to the two-beam mod­ule where the pro­tec­tion from beam loss­es is par­tic­u­lar­ly chal­leng­ing and im­por­tant.