SPL energy Need for flexibility 1 Risk wrt

SPL energy - Need for flexibility 1. Risk wrt the SPL energy 2. Possible energy range 3. Discussion… R. Garoby PS 2 meeting – 16 April 2009

1. Risk wrt the SPL energy [1/2] SPL energy totally depends upon the accelerating cavities. Medium b cryomodule Energy range: 160 Me. V – 732 Me. V 5 cell cavities Geometrical b: 0. 65 Maximum energy gain: 19. 4 Me. V/m 54 cavities (9 cryomodules) Length of medium b section: ~110. 35 m 10 15 Energy gain (Me. V/m) 1 5 High b cryomodule 100 200 300 Position (m) R. G. 400 Energy range: 732 Me. V – 4 Ge. V 5 cell cavities Geometrical b: 1 Maximum energy gain: 25 Me. V/m 152 cavities (19 cryomodules) Length of medium b section: ~286. 2 m 2 PS 2 meeting – 16 April 2009

1. Risk wrt the SPL energy [2/2] The main challenge and the largest risk in the SPL is with the accelerating cavities: • the availability of the complete set of accelerating modules could be late: The production of >200 state-of-the-art sc cavities, followed by testing and assembly in ~15 m long cryomodules is in itself an industrial exercise of major size. • the yield directly from production might be below expectation: The accelerating gradient will be selected for a production yield >90%, but statistical experience with prototype cavities will be small in 2012 and the situation is likely to be complicated by the presence of multiple manufacturers (in-kind contributions from France, Canada, USA…). • performance could be worse in the cryomodule because of coupling between cavities as in the case of SNS. • ? ? ? R. G. 3 PS 2 meeting – 16 April 2009

2. Possible energy range • It is cautious to be ready for beginning with a lower than nominal SPL energy. • The nominal energy will in any case be available after a couple of years. => What is the minimum energy which would already provide “acceptable” beam characteristics during the first years of operation? Space charge effect R. G. Kinetic energy [Ge. V] Intensity wrt PS 2 nominal (4 1011 p/b) Intensity wrt LHC ultimate (2 1011 p/b) 4 1 2 3. 6 0. 84 1. 68 3. 4 0. 77 1. 54 3. 2 0. 70 1. 4 3 0. 63 1. 26 4 PS 2 meeting – 16 April 2009

3. Discussion • From the point of view of the SPL, 3 Ge. V is a safe value (25 % of cavities missing or average gradient 25% below nominal), which still allows PS 2 to comfortably exceed the PS performance (factor 1. 26 x 1. 18 ~ 1. 5). • ~3. 3 Ge. V would allow for the “Large Piwinski Angle” option in the LHC (4. 9 1011 p/b with 50 ns spacing). • What does it imply for PS 2 to be able to inject at such energies? • ? ? ? R. G. 5 PS 2 meeting – 16 April 2009