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Background from injection losses at turn-on

Background from injection losses at turn-on. Giacomo Polesello. Introduction. Follow an action in December EB Discussions with D. Bocian and P.Grafstrom to identify key scenarios, contacted M.Shupe for simulation work First results available in May, some preliminary results presented in July

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Background from injection losses at turn-on

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  1. Background from injection losses at turn-on Giacomo Polesello G. Polesello – EB 22 Oct 2004

  2. Introduction • Follow an action in December EB • Discussions with D. Bocian and P.Grafstrom to identify key scenarios, contacted M.Shupe for simulation work • First results available in May, some preliminary results presented in July • Work going on in summer, TAS scraping scenario discussed with Per Grafstrom and G. Mikenberg and simulated by M. Shupe • Results available as report and table by M. Shupe, attached to today’s agenda. • Caveat: • Normalisation adopted in report is 2808 Bunches, 1.1 X 10^11 protons/bunch • Injection loss scenario implies loss of a single pilot bunch with 5 x 10^11 protons/bunch • All numbers in table (and conclusions of report) should be scaled down by a factor 20X2808 G. Polesello – EB 22 Oct 2004

  3. Motivation LHC optics at IR 1 MCBX, MCBY, MCBC - crossing angle/parallel separation scheme, D1 - separation dipole magnet, D2 - recombination dipole magnet, Q1, Q2, Q3 - low- triplet. Possible wrong settings of MCB magnets or of D1 magnet at injection can induce beam losses in ATLAS G. Polesello – EB 22 Oct 2004

  4. Simulation work • Scenario for DC1 wrong settings • Normalize to pilot bunch of 5x10^9 protons at 450 GeV ( 360 J energy) • Beam spread 500 mm • Consider four representative worst case scenarios, explicitely trying to imagine scenarios that could endanger detector components • Scoring done by simulation volumes, report various energy deposition and dose quantities for two classes of critical volumes: • Shielding and other massive volumes • Sensitive volumes G. Polesello – EB 22 Oct 2004

  5. Impact scenarios I: hit the TAS 6 mm from the edge 2 1 G. Polesello – EB 22 Oct 2004

  6. Impact scenarios 2: graze the TAS 3 4 G. Polesello – EB 22 Oct 2004

  7. Results • Scale a factor 60K with respect to report by M. Shupe • Scenario 1: (front of TAS) Only the TAS affected, but for pilot bunch very small heating (0.1 deg). With full beam it would melt • Scenario 2: (back of TAS) Some deposit in MDT and pixel, negligible for pilot bunch (5-.8 J/60k) • Scenario 3: (scraping, going away from IP) Big deposition in quadrupole, all detector components safe, small hot spot (7J/60K) on back wall MDTS • Scenario 4: (scraping, going towards IP) • Muon system OK: 20 J(/60K) spread over all phi • 116kJ(/60k) deposited in rearmost FCAL • 400-500 J(/60k) in pixel detector, again spread in phi G. Polesello – EB 22 Oct 2004

  8. Conclusions • Muon system seems well protected in all scenarios considered • Some deposition in FCAL and pixel, only significant if the whole beam hitting the TAS • Work continuing in collaboration with beam experts to identify realistic failure modes (also at 7 TeV) G. Polesello – EB 22 Oct 2004

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