1. On behalf of the CERN Collimation Team and FLUKA team…
2nd EuCARD-2 ColMat-HDED Annual Meeting GSI Darmstadt (Germany), December 4-5, 2014
Updated failure scenarios and damage limit of TCTs and status of SixTrack simulations
Elena Quaranta
On behalf of the CERN Collimation Team and FLUKA team…

2. Motivation of the study Eucard2 WP11 – Task 11.4
Outline
Motivation of the study
Eucard2 WP11 – Task 11.4
Updated failure scenarios and damage limit of TCTs
Status of SixTrack simulations with advanced collimators
Summary and Outlook
WP11 annual meeting – GSI, Dec 4th 2014

3. Motivation of the study

4. The LHC upgrade challenge
Increase luminosity
Increase stored beam energy up to 700 MJ
HL-LHC
LHC
(design)
≈ factor 5 than present value!
LHC
(run 1)
Increase beam energy
up to 7 TeV
NEVER
reached so far
in accelerator rings!
WP11 annual meeting – GSI, Dec 4th 2014

5. Why collimation upgrade?
The collimation system plays a crucial role to achieve the future LHC challenges:
Cleaning performance determines the maximum beam intensity
Collimator materials defines the machine impedance at high energy
Collimation hierarchy determines β* reach
The upgrade of the collimation system is integral part of the design study for HL-LHC.
β* reach is the minimum β reached at the IP
WP11 annual meeting – GSI, Dec 4th 2014

6. Each collimator plays its role
Collimators installed in IR7 (betatron cleaning) and IR3 (momentum cleaning)
Tertiary collimators (TCTs) installed around the experiments to protect magnets and detectors
Beam dump protection devices in IR6 – should intercept beam in case of fast dump failures
More than 100 collimators organized in
a multi-stage system
WP11 annual meeting – GSI, Dec 4th 2014

7. The multi-stage collimation system
Collimators are designed for:
Cleaning: protect cold aperture from unavoidable beam losses as particles drift out from the core of the beam (SLOW losses).
Protection: protection of accelerator components in case of abnormal beam losses. Critical: VERY FAST losses not protected by BLMs (Asynchronous Dump).
The system performance relies on the well-defined hierarchy between collimator families and machine aperture.
WP11 annual meeting – GSI, Dec 4th 2014

8. Collimator materials and upgrade
TCP and TCSG made of Carbon-Fiber-Carbon composite (CFC)
Very robust to beam impact
High impedance (not metallic material) (main contribution from TCSGs)
TCT and Absorbers made of tungsten heavy alloy (Inermet180)
High particle absorption
Low robustness to beam impact
Looking towards the
collimator upgrade
New materials and new designs for secondary collimator jaws to decrease impedance contribution
Guarantee same or higher level of beam cleaning
Compatibility with failure scenarios and improved robustness at critical locations (TCT by factor higher)
WP11 annual meeting – GSI, Dec 4th 2014

9. Studies and programs ongoing
CERN LHC Collimation project: Overall responsibility of LHC collimation, including operation, performance monitoring and optimization, remote handling, improvements of present system, …
FP7 HiLumi WP5: Design of collimation in the interaction regions, upgrade for cleaning.
FP7 EuCARD2 W11: New materials and new collimator design concepts.
Strong and long-standing external collaborations: US-LARP, Kurchatov, Fermilab (energy deposition),...
WP11 annual meeting – GSI, Dec 4th 2014

10. WP11 objectives
WP11: Collimator MATerials – High Density Energy Deposition
Task 11.1: Coordination and Communication
Task 11.2: Material testing for fast energy density deposition and high irradiation doses
Task 11.3: Material mechanical modelling
Task 11.4: Material specification
Simulation results used to iterate on material specifications
Use simulation codes to evaluate potential advantages and disadvantages of materials studied in 11.2 and 11.3
WP11 annual meeting – GSI, Dec 4th 2014

11. Updated failure scenarios and damage thresholds of TCT

12. How to calculate damage limits for fast dump failures?
So far:
Shock waves formation
and propagation
(Autodyn)
1 single bunch impact
TCT as “isolated” system
parallel impacting beam
Energy deposition in TCT
(FLUKA)
Now…
Present damage estimates for Beam Dump Failure:
5e9 protons (Plastic damage)
2e10 protons (Fragment ejection)
1e11 protons (“5th axis” – catastrophic case)
To more details, see A. Bertarelli-MPP workshop 2013
Shock waves formation
and propagation
(Autodyn)
Energy deposition in TCT
(FLUKA)
Particle tracking
(SixTrack)
In the past: limit based on FLUKA simulations…
All LHC ring
Many bunches
All collimation system
1 dump kicker pre-firing
Realistic particle tracking
Which the advantages in adding one more step in the simulation chain?
To get VERY REALISTIC PARTICLE DISTRIBUTION AT TCT!
WP11 annual meeting – GSI, Dec 4th 2014

13. SixTrack simulation setup
Single dump kicker magnet pre-firing (Time profiles provided by B. Goddard)
Energy: 7 TeV
Gaussian beam (beam emittance=3.5 μm)
Separate simulations for each bunch in the train (25ns spacing), different kicks.
Perfect machine (only “error” due to IR1/5 TCTs setting: put further in as they should be to simulate beam losses in these collimators after dump failure)
Collimator settings: 2 σ retraction between primary and secondary collimators
Different optics used:
Nominal 7 TeV (β*=55cm): B1 and B2
HL-LHC (β*=15cm): B2
ATS 2015 (β*=55cm): B2
WP11 annual meeting – GSI, Dec 4th 2014

14. Simulated failure scenarios
Scan over TCT settings for different machine optics
Compare with previous damage estimates
Select few relevant cases for further studies with higher statistics, trying to have cases with significantly different number of impacts
TCT setting < “dump protection”
TCT setting >≈ “dump protection”
TCT sees also primary beam.
TCT sees only particles scattered out by dump protection collimators.
WP11 annual meeting – GSI, Dec 4th 2014

15. Summary of simulation results
Average impact coordinate of each simulated bunch on the TCT in different scenarios.
Similar to what we expect for the LHC restart in 2015
Please pay attention to the different scale!!
WP11 annual meeting – GSI, Dec 4th 2014

16. From SixTrack to FLUKA Nominal 7 TeV optics B2 (IR1/5 TCT @ 10.5σ)
Impact distribution
(SixTrack)
Courtesy E. Skordis
Distance from center of collimator [cm]
Energy density [GeV/p/cm3]
Energy deposition
map (FLUKA)
Courtesy E. Skordis
WP11 annual meeting – GSI, Dec 4th 2014

17. Energy deposition in TCT
Status of the study
DONE!
Particle tracking
(SixTrack)
Provide impact particle coordinates for different scenarios (input for FLUKA)
ON GOING!
Provide energy density maps (input for AUTODYN)
Energy deposition in TCT
(FLUKA)
ON GOING!
Hydrodynamic simulations to estimate new thresholds of damage for tertiary collimators
Shock waves formation
and propagation
(Autodyn)
WP11 annual meeting – GSI, Dec 4th 2014

18. Sixtrack simulations with advanced collimators

19. Introduction MoGr CuCD
Novel advanced composites under development for the next generation of collimators to address impedance issue shown by CFC secondary collimators during run.
MoGr
CuCD
Copper-Diamond composite
Molybdenum-Graphite-based composite
Effect of advanced collimators on the LHC beam cleaning has to be studied:
SixTrack material database up to date to model new composites.
Particle tracking simulations of collimation efficiency with advanced collimators
Energy deposition studies in the IR7 with new loss profiles  feedback to the new collimator design
Importanza di questi studi:
Come cleaning non cambierà molto (e lo sappiamo già) ma ci servono come feedback per aggiornare collimator design e come input per dpa calculation
WP11 annual meeting – GSI, Dec 4th 2014

20. Updated SixTrack material database
2 materials added: MoGr, CuCD
“Atomic” properties and reference cross sections at 450 GeV calculated averaging the property (pi) of the i-th component on its weight percentage (wti%) in the composite:
Material
Properties
MoGR
CuCD
Composition (wt%)
20%v (init) Mo
80%v C (graph. + carbon fibers)
62% Cu 37.5% diamonds 0.5% B
ρ [g/cm3]
2.65
5.4 Z
7.384
11.78
A [g/mol]
14.809
24.142
X0 [cm]
13.878
4.801
Nuclear radius [fm]
2.947
3.468
Mean Ex. Energy [eV]
92.22
147.15
σpNtot [barn]
0.4762
0.6572
σpNinel [barn]
0.3088
0.4158
σruth [10-2barn]
0.012
0.027
pi from Particle Data Group database
Note: values in the table to compare with models and database used for FLUKA simulations.
based on MG5220-S grade
WP11 annual meeting – GSI, Dec 4th 2014

21. A closer look inside the code (I)
block data scdata …
data irmat/9/
Reference data at pRef=450Gev
data (mname(i),i=1,nrmat)/ 'Be', 'Al', 'Cu’, 'W', 'Pb', 'C', 'C2’,
'MoGr', 'CuCD'/
data (anuc(i),i=6,nrmat)/ 12.01d0, 12.01d0, 14.81d0, 24.14d0/
data (zatom(i),i=6,nrmat)/ 6d0, 6d0, 7.38d0, 11.8d0/
data (rho(i),i=6,nrmat)/ 1.67d0, 4.52d0, 2.65d0, 5.4d0/
data (radl(i),i=6,nrmat)/ d0, 0.094d0, d0, d0/
data (emr(i),i=6,nrmat)/ 0.25d0, 0.25d0, 0.295d0, 0.347d0/
data (exenergy(i),i=6,nrmat)/ 78e-9, 78.0e-9, 92.22e-9, e-9/
Atomic properties
WP11 annual meeting – GSI, Dec 4th 2014

22. A closer look inside the code (II)…
! All cross-sections are in barns, nuclear values from RPP at 20geV
! Coulomb is integerated above t=tLcut[Gev2] (+-1% out Gauss mcs) !
! in Cs and CsRef, 1st index: Cross-sections for processes, 2nd index: Material
! 0:Total
! 1:absorption
! 2:nuclear elastic
! 3:pp or pn elastic
! 4:Single Diffractive pp or pn
! 5:Coulomb for t above mcs
data csref(0,8),csref(1,8),csref(5,8)/0.476d0, 0.309d0, 0.012d-2/
data csref(0,9),csref(1,9),csref(5,9)/0.657d0, 0.416d0, 0.027d-2/
Total
Inelastic
Rutherford scattering
Changes done in other parts of the code accordingly
WP11 annual meeting – GSI, Dec 4th 2014

23. SixTrack simulation setup
Energy: 7 TeV
Beam 1, Hor. halo
Statistics: 6.4 x 106 SixTrack particles
Nominal 7 TeV optics and post LS1 layout
Collimator settings at 7 TeV [σ]
IR7
TCP 6
TCSG 7
TCL 10
IR6
7.5
TCDQ 8
IR3 15 18 20
IR1/5
TCT
8.3
IR2/8 25
Simulated scenarios:
Reference case: no advanced collimator. TCPs and TCSGs made of CFC
Case 1: only TCSGs in IR7 replaced
Case 2: TCSGs in IR7 + TCP.C6L7.B1 replaced
More relevant case to address impedance issue
WP11 annual meeting – GSI, Dec 4th 2014

24. Beam loss distribution in LHC
MoGR
CuCD
CFC
As expected
No relevant change in cleaning (affected mainly by TCPs in IR7)
WP11 annual meeting – GSI, Dec 4th 2014

25. Losses in TCSGs in IR7 (I)
First two TCSG more loaded than in CFC case
Distribution of losses in downstream TCSGs influenced by different scattering behavior of the different materials
More particle absorbed in CuCD according to higher density
WP11 annual meeting – GSI, Dec 4th 2014

26. Losses in TCSGs in IR7 (II)
% losses in advanced collimators
Without accounting for additional factor 2 from HL-LHC beam intensity, the load on collimators by beam impact should be still in line with dynamic deformation limits (to be confirmed by FLUKA and AUTODYN simulations for failure scenarios)
WP11 annual meeting – GSI, Dec 4th 2014

27. Inelastic interaction distribution
Distribution of absorbed particles along the length of the most loaded TCSG in IR7
WP11 annual meeting – GSI, Dec 4th 2014

28. Losses in other collimators
Losses decreased in all system (momentum cleaning, dump, IR1/5 triplet protection...)
Collimators globally more efficient!
WP11 annual meeting – GSI, Dec 4th 2014

29. Summary and Outlook
Importance of collimation in the LHC upgrade remarked.
Fast failure scenarios reviewed and updated with more realistic conditions to use in the simulations: discussed TCTs, TCSG studies ongoing.
Impacts for energy deposition studies now available for several scenarios.
SixTrack collimator material database updated with two novel composites: MoGr and CuCD.
Preliminary results from simulations with new material collimators in line with expected cleaning efficiency.
More materials will be included soon in the database (ex: MoGr Mo-coated).
New inputs for future collimator design provided.
Energy deposition studies and thermo-mechanical simulations will be performed in the coming months.
WP11 annual meeting – GSI, Dec 4th 2014

30. Thank you for your attention

31. Backup slides
WP11 annual meeting – GSI, Dec 4th 2014

32. β* reach in IP5 for B1
β* reach in IP5 for different possible optics in the scenario post LS1:
Courtesy of D. Mirarchi

33. Summary of collimator settings
Simulated scenarios (E=7 TeV)
Collimator half gap
Nominal optics
HL-LHC optics B2
ATS B2
nom. B1
nom. B2
HL-LHC 1
HL-LHC 2
HL-LHC 3
IR7
TCPs
5.7
TCSGs
7.7
TCLs
10.5
IR6
TCSG.4R6
8.5
TCDQAs
9.0
IR3
15.0
18.0
20.0
IR1/5
TCTs
7.9
IR2/8 30
Expected integrated losses on TCT.4R5 (B2)
Expected integrated losses on TCT.4L1 (B1)
Nom. B2 only secondary halo  180 degree (good) phase advance between dump kicker and IR6 protection
3e9 “real protons” (1.7e11p per bunch)
Safe!
2e9 “real protons” (2.2e11p per bunch)
Safe!
2e10 “real protons” (2.2e11p per bunch) fragment ejection!
2e11 “real protons” (2.2e11p per bunch)
> 5th axis limit!!
8e9 “real protons” (1.7e11p per bunch very optimistic!!)
plastic deformation!
9e8 “real protons” (1.7e11p per bunch)
Safe!
A priori, only secondary halo for this case
Beam 2 is the most critical one!
CollUSM

34. Impact parameter distribution Nominal 7 TeV optics B2 (IR1/5 TCT @ 10
In this case only secondary halo particles are intercepted by TCTH.4R5.B2 due to good phase advance (180°) from the MKD.
Primary halo particles
Secondary halo particles
CollUSM

35. Impact parameter distribution HL-LHC optics B2 (IR1/5 TCT @ 7.9 σ)
Primary halo particles
Secondary halo particles
CollUSM

36. Preliminary results from case 2
Losses on IR7 TCSGs + TCP.C6L7 after material replacement
WP11 annual meeting – GSI, Dec 4th 2014