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
Preliminary DRAFT
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 challanges:
Cleaning performance determine the maximum beam intensity
Collimators define the machine impedance at high energy
The 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. Hierarchy is important
Collimation system designed for:
Cleaning: protect cold aperture from unavoidable beam losses as particles drift out from the core of the beam (SLOW losses). Hierarchy in IR7 and IR3 determines cleaning performance.
Protection: If losses are too high, BLMs trigger a beam dump before a quench of the SC magnets occurs. If single- turn failure (asynchronous dump), BLMs too slow (FAST losses). Rely on robustness of collimators and correct hierarchy to avoid damage. Hierarchy with respect to IR6 is crucial.
Nominal collimator settings at 7 TeV
R. Assmann
WP11 annual meeting – GSI, Dec 4th 2014

8. Collimator materials and upgrade
Primary and Secondary collimators made of Carbon-Fiber-Carbon composite (CFC)
High robustness to beam impact
BUT high impedance (main contribution from TCSGs)
Tertiary collimators and Absorbers made of heavy tungsten allow (Inermet180)
High particle absorption efficiency
BUT low robustness
Looking towards a
collimator upgrade
Collimation upgrade studies to improve impedance and robustness:
New material and new designs for secondary collimator jaws
Compatibility with failure scenarios and improved robustness at critical locations (TCT by factor higher)
Guarantee present or higher level of halo cleaning
R. Assmann
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. Impact parameter distribution Nominal 7 TeV optics B2 (IR1/5 TCT @ 10
Only secondary halo particles are intercepted by the TCT.
Primary halo particles
Secondary halo particles
CollUSM

17. 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

18. 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

19. Sixtrack simulations with advanced collimators

20. 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
Molybdenum-Graphite-based composite
Copper-Diamond composite
The effect of the advanced collimators on the LHC beam cleaning has to be studied:
SixTrack material database updated to model new composites.
Particle tracking simulations of collimation efficiency with advanced collimators
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

21. Updated SixTrack material database
2 materials added so far: 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% Mo2C
80% 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.
Important support will be provided by A. Mereghetti, who will join the Collimation team in early 2015.
WP11 annual meeting – GSI, Dec 4th 2014

22. 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

23. 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

24. SixTrack simulation setup
Energy: 7 TeV
Beam 1 only
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: all TCSGs replaced by advanced collimators
Case 2: only TCSGs in IR7 replaced
Case 3: TCSGs in IR7 + TCP.C6L7.B1 replaced
Case 4: TCSG in IR7 (only in cell 5, upstream and downstream of IR) + TCP.C6L7.B1 replaced
Note: Cases 1 to 4 simulated replacing CFC with MoGr, then same cases with CuCD.
Case 1 not shown: very similar results than Case 2.
WP11 annual meeting – GSI, Dec 4th 2014

25. Beam loss distribution: MoGr
Reference
Case 2
Preliminary results
Case 3
Case 4
WP11 annual meeting – GSI, Dec 4th 2014

26. Beam loss distribution: CuCD
Reference
Case 2
Preliminary results
Case 3
Case 4
WP11 annual meeting – GSI, Dec 4th 2014

27. Comments on simulation results
Not significant difference in cleaning performance observed between reference case and new simulations with advanced collimators (AS EXPECTED)
No worsening of cleaning inefficiency to remark. Some improvements are instead visible.
Case 2 shows the best results for MoGR:
Losses reduced by a factor ≈ 3 in TCSGs in IR6
Losses reduced by a factor ≈ 2 in TCSGs and TCLs in IR7 and TCTs in IP1
No losses in warm and cold magnets in IR3
Case 4 shows the best results for CuCD:
Losses reduced by a factor ≈ 4 in TCSGs in IR6
Losses reduced by a factor ≈ 3 in TCSGs in IR7 and TCTs in IP1
No losses in warm and cold magnets in IR3 an cold magnets IR6
WP11 annual meeting – GSI, Dec 4th 2014

28. Summary and Outlook
Importance of collimation in the LHC upgrade has been remarked
Fast failure scenarios have been reviewed and updated with more realistic condition to use in the simulations
Impact coordinates for several studied cases now available for energy deposition and hydrodynamics studies
SixTrack collimator material database has been updated with two novel composites: MoGr and CuCD
First results from simulation with new advanced collimators in line with what we expected in terms of cleaning, which appears even slightly improved
More materials will be included soon in the collimator database
Compare properties of new material added in SixTrack with FLUKA models (mainly for reference cross-sections): planned in the next months.
WP11 annual meeting – GSI, Dec 4th 2014

29. Thank you for your attention

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

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

32. 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

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