Betatron cleaning in IR3: results of FLUKA calculations Fluka team R2E Meeting, July 17 th 2008
Goal of the study Verify the impact of the optional temporary functional move of the betatron cleaning to IR3 Outline: Description of the scenario considered Results: Warm section (dose to warm magnets) Cold section (peak power density in cold magnets) Superconducting link cable (peak power density) Dose to cables High-energy hadron fluence in UJ33 and UP33 due to beam-gas interaction, and estimation of level due to collimation Conclusions
Betatron cleaning in IR3: Scenario 2 LHC optics unchanged Four vertical secondary collimators are placed in the location of the phase 2 secondaries and one vertical primary collimator is placed in the location of the phase 1 scraper. Used settings: TCP (hor/ver) at 6s, TCS (hor/ver) at 7s TCLA(hor/ver) at 10s FLUKA simulations use a loss map (provided by R.Assman et. al.) with the following set-up: Beam 1 @ 7 TeV Horizontal halo Nominal losses Normalization factors: Loss rate of 4.3E11 p/s (0.2 h beam lifetime, nominal intensity) Annual losses: 1E16 p/y Scenario description
M M Warm section Normalization: 1E16 p/y MGy/y Stat. Error MBW.C6L 4.6 +-4% MBW.B6L 3.4 +-5% MBW.A6L 3.0 +-6% MQWA.E5L 5.0 +-3% MQWA.D5L 1.7 +-4% MQWA.C5L 4.3 +-3% IR7: MBW.B6L 3.3 MGy/y MQW.E5L 0.9 MGy/y
Cold section Normalization: 4.3E11 p/s Element Peak Error [mw/cm3] % MQ.7R - MQ.8R 0.2 16.4% MQ.9R 6.8 1.9% MQ.10R 3.9 2.4% MQ.11R 7.5 2.9% MQ.12R - MQ.13R 3.4 3.6% MB.A8R 0.3 11.4% MB.B8R 0.2 27.3% MB.A9R 3.6 5.0% MB.B9R 5.2 5.3% MB.A10R 0.6 13.3% MB.B10R 1.8 9.5% MB.A11R 5.0 5.9% MB.B11R 4.4 7.0% MB.A12R 0.4 6.6% MB.B12R 0.1 32.8% MB.C12R 0.0 78.0% MB.A13R 0.0 95.0% MB.B13R 1.7 12.4% MB.C13R 3.4 6.0% TCPs IP UJ33 Peak in MQ.11R MQ.11R Statistical error of the second step of the simulation. To reduce run time a two step approach has been followed: Step 1: mapping of protons entering the DS with a fast simulation (EM cascades disabled, etc.) Step 2: protons obtained from step 1 are tracked with a full simulation in the cold section.
Superconducting link cable Liquid helium Copper Copper Steel Position1
Superconducting link cable Possibly statistics Normalization: 4.3E11 p/s
Dose to cables Normalization: 1E16 p/y
Normalization: High energy hadron fluence in UJ33 and UP33 due to beam-gas interaction Nominal current (3.68E+18 p/s) H 2 density: 1E+15 molecules/m 3 180 full days of operation per year Loss rate: 4.1E11 p m -1 y -1 Very conservative Results: Attenuation factor in UP33: ~10 4 Hadron fluence @ UP33 entrance due to beam gas: 10 9 cm -2, inside of the UJ ~10 5 cm -2 From the beam1 loss map, the respective fluence is obtained from the mirrored position of the UP entrance (z=~22000 cm) due lo losses on collimators. The value obtained is ~10 10 cm -2. Taking into account the attenuation in UP, we expect a fluence inside of the UJ ~10 6 cm -2 (This value is consistent with the one stated by Igor Kurotchkin, November 2005)
Results consistent with IR7 Peak power deposition in superconducting link cable seems quite high (~10-15 mw/cm 3 ): Check the real quench limit for the cable Dose to cables is fully consistent with previous RP calculations (peak of 50 kgy/y). No problems of cable lifetime expected. Beam gas interaction is not a problem for electronics installed in UJ33 High energy hadron fluence in UJ33 seems not to be a problem (~10 6 cm -2 ), but better to check for cryo installations Conclusions Given the probable differences in past and present assumptions the observed mismatch by a factor of 2-3 between MARS (Protvino) and FLUKA results is largely within the expected uncertainties However, for a better understanding it is recommended to study a standard IR3 scenario and get further and more detailed information on past simulations assumptions.