US LHC Accelerator Research Program BNL - FNAL- LBNL - SLAC Accident Simulations in Phase II Secondary Collimators 1 April, 2009 1. 7 TeV => 1.0 MJ 2. 0.45 TeV => 2.2 MJ L. Keller

SLAC Damage Test - 1971 Beam entering a few mm from the edge of a 30 cm long copper block The length and depth of this melted region is comparable to the ANSYS simulation for the LHC accident. 30 cm 500 kW beam 0.65 MJ in 1.3 sec Beam diameter ~ 2000 µ It took about 1.3 sec to melt thru the 30 cm block, but for this relatively large beam, the front two radiation lengths remain intact.

Tevatron Accident – 2003 Beam Lost on Stainless Steel Collimator Energy deposition ~0.5 MJ groove is 25 cm long, 1.5 mm deep

secondary collimator - causing it to melt within a substantial volume. LHC : A kicker failure can deposit 9 x 1011 protons (8 bunches) on any metallic secondary collimator - causing it to melt within a substantial volume. Missteered beam 9x1011 protons, 1 MJ on secondary Jaw Copper Jaw 120 cm melting 25-30 cm 3D ANSYS model, E. Doyle above Cu melting

Cross Section at Shower Maximum Showing Copper Melting and Possible Fracture Regions in a Mis-steering Accident 7 TeV, 8 bunches Copper Jaw 2.5 cm Fracture zone, radius = 7 mm Melting zone (grey), radius = 3.3 mm

FLUKA/ANSYS Simulation of 7 TeV Accident, 1.0 MJ Zoom in at Shower Maximum, Z = 20 cm Melted/vaporized zone 4 mm Zoom 6 mm 2.5 cm Temp (ºC)

7 TeV, 8 bunches, 1 MJ Accident Case – jaw adjacent to the one being directly hit, ≈ 4 mm gap. This jaw may be damaged too. Copper Copper Fracture at 200deg C 840 deg C

7 TeV, 8 bunches Another accident Case – Beam hits the horizontal primary collimator The first jaw in the downbeam secondary collimator (40m away) probably OK. Copper Copper 250 ˚C

ANSYS Simulation of Permanent Deformation in 7 TeV Accident 1.0 MJ J. Amann E. Doyle Virtually no deformation at phi = ±90º Beam side 47 µm X (m) Back side upbeam end downbeam end Z (m)

450 GeV Errant Beam Scraping the TT40 Vacuum Chamber - 2004 (Goddard, et.al., AB-Note-2005-014 BT) 2.2 MJ Side of Beam Impact Vacuum Chamber Wall Opposite from Beam Impact

FLUKA/ANSYS Simulation of Injection Accident, 2.2 MJ Cut at Shower Maximum, Z = 15 cm Melted/vaporized zone Zoom 6 mm 9 mm 2.5 cm J. Amann E. Doyle Temp (ºC)

ANSYS Simulation of Permanent Deformation in 450 GeV Accident 2.2 MJ J. Amann E. Doyle Virtually no deformation at phi = ±90º X (m) 110 µm Beam side Back side upbeam end downbeam end Z (m)

Instantaneous Water Pressure Bump Cooling Tubes 2.5 cm Transverse to Beam Impact Copper yield ≈ 300 bar 1.0 MJ Pressure (bar) 2.2 MJ Pressure (bar)

Summary and Conclusions 1. For 1 MJ @ 7 TeV impacting the edge of a copper cylinder, a) The vaporized/molten zone is ~4 mm deep x ~6 mm high. b) The permanent deformation is ~50 µ toward the beam axis. The cooling water pressure bump is 6 bar. 2. For 2.2 MJ @ 450 GeV impacting the edge of a copper cylinder, a) The vaporized/molten zone is ~6 mm deep x ~9 mm high. b) The permanent deformation is ~110 µ toward the beam axis. The cooling water pressure bump is 25 bar. 3. Accident experience at other accelerators has shown that nearby vertical surfaces are splattered with metal droplets a fair distance above and below the beam axis, so that when moving to a fresh surface a rotatable jaw is preferable to raising or lowering the vertical surface.