07-JUL-2003LEADE / JW1 Satellite bunches in the LHC Satellite “definition” Satellite luminosity Satellite detection & tolerances J. Wenninger AB/OP

07-JUL-2003LEADE / JW2 Nominal proton filling

07-JUL-2003LEADE / JW3 Satellites LHC bunch filling and RF : Bunches are separated by a multiple of 25 ns. 400 MHz LHC RF system : 1 RF bucket every 2.5 ns.  ‘room’ for 9 satellite bunches between the nominal ones, spaced by 2.5 ns. Satellite bunch formation : Transfer from one machine to the next (PS  SPS, SPS  LHC) : –Un-captured beam  lost at the beginning of acceleration. –Beam captured in unwanted locations  satellite bunches. –Amount of un-captured beam /satellites depends on : RF settings Longitudinal parameters : emittance, bunch length… –Finally satellites must survive the ramp – not guaranteed.

07-JUL-2003LEADE / JW4 LHC injection into SPS injectioninjection + 1 second Uncaptured beam 72 bunches from PS Un-captured beam : up to ~10 % Satellite bunches :possibly ~ % level - difficult to measure ! Note : The main SPS RF system runs at 200 MHz.

07-JUL-2003LEADE / JW5 Satellite bunch collisions & luminosity IP1, IP2, IP5, IP8 : collisions between satellites every 2.5 ns (same vertex as nominal bunches – worst case ~ 9 times more frequent than normal collisions). per collision : L sat ~ r 2 L r = satellite bunch int./normal bunch int. IP8 / LHCb : additional possibility of collision between satellites & normal bunches at the beginning and end of each 72 bunch train. per collision : L sat ~ r L At all other encounters (upstream & downstream of IP)  beams separated. Totem : no crossing angle ! Possible additional collisions between satellite and normal bunches every 37.5 cm on either side of IP.

07-JUL-2003LEADE / JW6 Satellite Detection LHC : –A high sensitivity longitudinal profile monitor should detect satellites at the per- mill level within minutes. –Either level is OK, or re-filling (and possibly retuning of the SPS and/or LHC RF system) may be required. –For a good RF capture in the LHC there are stringent requirements on transfer conditions SPS-LHC (energy, time jitter, emittance, bunch length…). SPS : –Satellite bunches present in the SPS are likely to create satellites in the LHC. –So far measurements in the SPS are difficult and limited to % level. –Detection of satellites in the SPS may be used to prevent injection into the LHC – but that would require new instrumentation / detection methods that are so far not foreseen.

07-JUL-2003LEADE / JW7 SatelliteTolerances Sensitivity of machine “components” : –So far the main concern is for the beam position monitor (BPM) system. Systematic position errors of 0.1 mm possible with r = 5-10%. Depends strongly on the exact pattern. r ~ 1-2% should be acceptable… –Note that errors on the BPM system may have consequences on other systems (collimation…). Sensitivity of the Experiments : –Are satellites at % level acceptable ? What is (a reasonable) maximum ? –TOTEM must probably be considered a special case that may need more careful treatment.  Acceptable intensity levels for satellites have consequences on requirements for instrumentation (and eventually on beam quality interlocks) in the SPS.