1. US LHC Accelerator Research Program
BNL - FNAL- LBNL - SLAC
(Recent) Energy Deposition Simulation in Phase II Secondary Collimators April 26, 2006
Two aspects:
Accidental damage.
Power in normal LHC operation.
L. Keller

2. SLAC Damage Test
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.

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

4. 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 9E11protons,
1 MJ on secondary Jaw
Copper
Jaw
120 cm
melting
25-30 cm
3D ANSYS model, E. Doyle
above Cu melting

5. Cross Section at Shower Maximum Showing Copper Melting and Possible Fracture Regions in a Mis-steering Accident
3D ANSYS model, E. Doyle
Copper
Jaw
Fracture zone,
radius = 7 mm
2.5 cm
Melting zone (grey),
radius = 3.3 mm

6. Cross Section at Shower Maximum Showing Copper Boiling
in a Mis-steering Accident
3D ANSYS model, E. Doyle
Copper
Jaw
2.5 cm
Boiling zone (grey),
radius = 2.2 mm

7. Phase II Energy Depostion Simulations
A. Before Jan. ‘06 had only simulated energy deposition in the primary collimators
and the first secondary collimator where about 80% of the collimated energy is
deposited.
B. Decided to construct a simple FLUKA model of IR7 to make particular checks
of the CERN sophisticated, comprehensive model. The “simple” model
includes:
cm carbon primary collimators
secondary collimators, jaws only
a) Phase 1, 120 cm rectangular carbon jaws
b) Phase 2, 95 cm cylindrical copper jaws
4 tungsten absorbers, jaws only
24 warm quadrupoles, 2 SC quadrupoles
4 warm dipoles
6. All copper beam pipes

8. Simple FLUKA Model of IR7
dipoles
dipoles
quadrupoles
3 carbon
primary
collimators
beam 2
MQTLH
beam 1
11 rotating-jaw, copper secondary collimators, 4 absorbers
200
400
meters

9. Cross section of 2-jaw rotating-cylinder, secondary collimator, B4L7
(cut at y = 0)
each cylinder 6.8 cm o.r., 4.3 cm i.r.
X (cm)
left jaw
Z (cm)
beam
right jaw
95 cm

10. Phase 1 RESULTS Comparison of Energy Deposition in Carbon
Secondary Collimators for CERN and SLAC IR7 Models
Notes:
1. Twelve min. lifetime, power in last seven collimators (>200 m) dominated by direct beam interactions

11. Phase 2 RESULTS Comparison of Energy Deposition in Copper
Secondary Collimators for CERN and SLAC IR7 Models
Notes:
1. Twelve min. lifetime, power in last seven collimators (>200 m) dominated by direct beam interactions

12. Off-energy Protons from Primary Collimator TCPH Entering the LHC Arc
Integral = 1.7 x 10-3 / int. beam proton
12 min. lifetime => 7 x 108/sec into arc
CERN quench level estimate = 7.6 x 106 p/m/sec
ΔE/Eb = -16.4%

13. Next Steps for Energy Deposition
FLUKA simulations:
In the Phase II configuration with all 95 cm long copper cylinders, simulate the energy absorbed by the down-beam superconducting dipole magnets – compare with ray-tracing program TURTLE.
ANSYS accident simulations:
a) Use quasi-static (few hundred msec) model to estimate permanent
deformation.
b) Use transient thermal shock analysis to estimate fracture damage.
3. A beam test to simulate the LHC accident conditions in a copper, cylindrical collimator is highly desirable.