PowerPoint Presentation:
A .2.a . BPTX measurements done with scope, until 09/12/09. After , tests with LHCb BPIM ( Beam Phase and Intensity Monitor), so values not valid Calculation of deltaT as if our measurement was in ATLAS ( not very precise) or LHCb ( shifted IP ~ 11.25m – good one ) Last value measured was - 0.148ns @ IP8 ( uncertainty is due to position of BPTX and knowledge of cable length ) A .2.b . In case of multibunching , only look at colliding pairs . Values were always consistent . In the future, will monitor per bunch and the cogging value will be averaged . Our Homeworks 2009 (BPTX) Federico Alessio 2
PowerPoint Presentation:
A.2.a . VELO measured continuously , but not always for entire fill for the commissioning procedure o nly few modules at a time (first runs) at the beginning of run (fill) However, resolution was not the best because VELO was always out at 450GeV BPTX measurements were “compatible” with measured Vertex position from LHCb VELO (crossing angle effect …) On 07/12/2009, Vertex measured -31.7 +/- 1.3 mm On 11/12/2009, Vertex measured +8.0 +/- 1.0 mm However, a lways in terms of time and not Z (crossing angle!) Expt LHCb spent most of December with the cogging downstream but the actual z-location of the vertex upstream due to the x-transversal position of beams The associated timing difference as a result of the shift reduces the effect and the luminosity…. Cogging/angle/transversal beam position in crossing angle plane interplay… A.2.c . LHCb can tolerate a shift of +/- 0.5ns, +/- 15cm (VELO) Our Homeworks 2009 (Vertex) Federico Alessio 3
PowerPoint Presentation:
B.1. See slides from Richard after … B.2 No need of BCref for 2010. LHCb always locks on BCLK1 B.3.a Clock phase wrt beam passage will be monitored online by electronics board LHCb BPIM if bunch intensity > 5*10^9. Value will be averaged over all the bunches and published (in ps) every second (lower limit) via DIP. Resolution is ~35ps (systematics from cable length and BPTX positions). B.3.d Rephasing could be done in “stable beam” and feedback can be given in O(minutes) with the rates expected at the beginning this year Our Homeworks 2010 Federico Alessio 4
Clock switching - recapitulation:
Clock switching - recapitulation Handling of clock switching General rule: Experiment locked on LHC during physics fills , local at all other times May occasionally do differently but at “own responsibility” - RFers are free to do what they need “During physics fill” = Beam Mode (Injection* Beam Dump) Handshake = Protocol to switch LHC (and experiments) from a state to a critical state Critical state meaning “unsafe” in some respect Handshake “states” (as in state machine) do not (should not) reflect stable states (as in ready condition) of any system This is the job of the Beam Mode meaning that systems may take different times to get ready for the beam mode change at different times and may even require retries. Thus, we should not associate assumptions on the readiness of a system based on the handshake state! “All systems ready” (Experiments and all LHC subsystems including RF) declared by the Beam Mode change. 5
Clock switching:
Clock switching Thus The point of no return (no ambiguity or “no need for another resynch”) is to clock switch at change of mode to “Injection*”. Difference: 2-3 minutes but a lot more clear and logical From experiment point of view the states IMMINENT & OK are of no (active) use IMMINENT is nicely informative READY should be the state of the Handshake during the entire “unsafe” phase Exception handling: If RF sees any exception in which they would have to redo the resynch while already in “Injection”, well, it means going back to Beam Setup with the associated switching to internal clocks, including redoing handshake (fast, <1min, since we are already ready!) LHC Clocks should be reliable until end of “Beam Dump” mode Automatic switching to internal in the experiments Remember we will quickly want to get rid of the “data taking dependence on the beam dump handshake”! That is, take data until last two protons leave machine Issue with disappearance of Turn Signal at dump? (LHCb no problem, BCLK critical) 6