wire scanners MDW chicane energy collimator 3 MPS collimators in this region end of linac Damage Simulation in MPS Collimators L. Keller Apr. 9, 2006

500 kW beam (0.65 MJ in 1.3 sec) Beam diameter ~ 2000 µ 30 cm Beam scraping the edge of a 30 cm long copper block SLAC Damage Test 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.

MPS energy collimator ΔE/E = ±10% trajectories Diagnostic Chicane Use FLUKA to Model an Off-energy Beam Hitting the Sacrificial Energy Collimator MDW

X (cm) beam axis Z (cm) cm Al melting Beam into Edge of Two Meter Aluminum MPS Collimator FLUKA 200 bunches 1  from edge, E beam = 250 GeV 0.2 cm half-gap 250 GeV beam, 0.16 MJ in 60 µsec Al boiling Above Al melting GeV/e -

X (cm) Y (cm) beam axis into page FLUKA Aluminum melting Aluminum MPS Collimator Near Shower Maximum 200 bunches 1  from edge, E beam = 250 GeV 0.2 cm half-gap 250 GeV beam, 0.16 MJ in 60 µsec GeV/e -

X (cm) beam axis Z (cm) cm Beam into Body of Two Meter Aluminum MPS Collimator FLUKA 200 bunches E beam = 250 GeV 0.2 cm half-gap 250 GeV beam, 0.16 MJ in 60 µsec Al boiling Al melting GeV/e -

X (cm) beam axis Z (cm) cm Beam into Edge of Two Meter Aluminum MPS Collimator FLUKA 200 bunches 1  from edge, E beam = 500 GeV 0.2 cm half-gap 500 GeV beam, 0.32 MJ in 60 µsec Al boiling Al melting Above Al melting GeV/e -

X (cm) beam axis 200 bunches 1  from edge, E beam = 250 GeV Z (cm) cm C melting Beam into Edge of Two Meter Carbon MPS Collimator FLUKA C boiling 250 GeV beam, 0.16 MJ in 60 µsec GeV/e -

MPS Collimator Summary: full energy bunches hitting an aluminum block within 2 mm of the edge will eject molten and vaporized aluminum into the gap over a length of ~1 meter. 2. During accelerator tune up, the bunch intensity would need to be reduced by ~2 orders-of-magnitude and the emittance increased to avoid melting. (This is not new information.) 3. To avoid collimator damage, a spoiler/absorber combination would require a ≈0.5 rl consumable spoiler and many tens of meters of drift to the absorber (not simulated yet). 4. If the first part of the 200-bunch train vaporizes aluminum along the beam path, the longitudinal extent of the collimator damage may be considerably greater than one meter (not simulated). 5. A carbon collimator melts and vaporizes in a much smaller volume than in aluminum.