1. RC1 Prototype Conceptual Design Review 15 December, 2005
US LHC Accelerator Research Program
BNL - FNAL- LBNL - SLAC
RC1 Prototype Conceptual Design Review December, 2005
Energy Deposition Simulation in Phase II
Secondary Collimators
Two aspects:
How to deal with accidental damage.
How to safely handle power in normal LHC operation.
L. Keller

2. secondary collimator - causing it to melt within a substantial volume.
Problem: 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 9E11 protons
(8 bunches) on secondary Jaw
120 cm
3D ANSYS model, E. Doyle
Cross section at shower max.
Copper
Jaw
Copper
2.5 cm
Fracture temp. of copper
is about 200 deg C
2000 °C (not incl.
heat of fusion)

3. 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
e- beam
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.

4. FLUKA-generated Simulation Model
IR-7
dipoles
Beam 2
Beam 1
First
secondary
collimator
Primary
collimators
40 m

5. TCSM1 Beam’s Eye View of a Phase I Skew Secondary Collimator
stainless steel frame
water
“upper right” jaw, 8.0 cm parallel to
gap, 2.5 cm perpendicular to gap
TCSM1
So far, all FLUKA energy deposition simulations at SLAC have used this model
for the primary and secondary collimators and varied the jaw material, length,
and gap.

6. One-sigma Beam Sizes in IR-7

7. Energy Spectra of Particles Hitting TCSM1
Total energy of particles hitting both jaws is ≈ 3400 Gev/p
seven s gap
Keller:

8. Power into the One Jaw of the First Secondary Collimator vs. Length
More than 80% of the total power deposition is EM showers, mainly from π0 decays
4 x 1011 p/s lost

9. Transverse Power Distributions in TCSM1 at Shower Maximum
Power lost in a 5 cm longitudinal slice from halo interacting
in 60 cm primary collimator, TCPH, total 6.8 kW

10. Comparing TCPV with TCPH,
the main differences occur in
the 1st three secondary colls.
Data from SixTrack
Y. Cai
4 x 1011 p/s lost

11. Power Deposition on First Secondary Collimator in 12 Min. Lifetime
(kW per jaw, 120 cm long jaw)
Primary
Collimator
(source)
TCSM.A6.L7
Copper Jaws
at 7 sigma
TCP.D6.L7
(TCPV) 68
TCP.C6.L7
(TCPH) 55
The most recent ANSYS simulations have been for this case. Reduce jaw length to 75 cm: 68 kW => 58.5 kW
120 cm long collimator
Notes:
Ray files for 60 cm long carbon primary collimators from LHC Collimator web page, July

12. Next Steps for FLUKA and ANSYS
(for completeness, in parallel with construction)
In the Phase II configuration with all 95 cm long copper cylinders, recalculate the energy absorbed by the down-beam superconducting magnets. In the CERN full-blown FLUKA model of IR7, must add secondary 95 cm, water-cooled, copper cylinders with 10 cm tapered ends and leave the Phase I carbon secondaries in place with their jaws withdrawn. Need help from the CERN group for this work.
In the “short” FLUKA model change the first secondary collimator to a 95 cm water-cooled cylinder with tapered ends and include the water channels. Update the ANSYS model accordingly.
3. 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.
c) Predict the volume of the molten zone.