1. LHC Physics Debris Simulation Update
L. Nevay
Many thanks to:
A. Mereghetti, D. Mirarchi, A. Abramov, R. Bruce
3rd May 2019

2. Introduction
Measured doses in arcs appear correlated with luminosity and not with stored beam intensity
See:
ColUSM 9 talks (ColUSM meetings website)
IPAC Paper by D. Mirarchi -
LMC #331 - talk by R. Garcia Alia
Extend work to simulate for recent optics and for HL-LHC
Previously presented simulations using Sixtrack only and now with Sixtrack-FLUKA coupling
see LHC Collimation Working Group #238

3. Previous Simulations - Recap
Previous simulations using Sixtrack to predict rate of protons
2017
2016

4. Simulation Setup Using Sixtrack-FLUKA coupling ExtendedSource branch
Special 0.5m 'pipe' insertion for each IP in (1,5,8)
Inelastic / elastic collisions forced in this region
Beam generated at IP and back propagated 0.25m
no energy spread in original beam into simulation
12 scenarios per map
B1,2 x IP 1,5,8 x inelastic,elastic
Simulate 5M particles for each scenario up to 200 turns
Momentum cut of 30% from nominal for tracking
aim is to look far from IPs (ie not immediately at triplets)
Perfect machine used
2017, β*=40 cm, θ=150 µrad optics used initially
Luminosities used:
IP 1& 5: 1.5 x 1034 cm2 s-1
IP 8: x 1034 cm2 s-1

5. p-p Cross-Section for Event Rate
Previously √s = 8 TeV data extrapolated to √s = 14 TeV :
G. Antchev et al., Phy. Rev. Lett., vol. 111, , Jul
J. R. Cudell et al., Phy. Rev. Lett., vol. 89, , Oct
Current measurments for √s = 13 TeV:
The CMS collaboration, Sirunyan, A.M., Tumasyan, A. et al. J. High Energ. Phys. (2018) 161. 
M. Aaboud et al. (ATLAS Collaboration), Phys. Rev. Lett. 117, (2016)
arXiv: (TOTEM elastic & inelastic)
S.M. Stark, EPJ Web of Conferences 141, (2017) (summary)
arXiv: (LHCb inelastic)
Experiment
σ p-p inelastic (mb)
σ p-p elastic (mb)
ATLAS
78.1 ± 2.9
24.33 ± 0.39
CMS
71.3 ± 3.5
TOTEM
79.5 ± 1.8
31.0 ± 1.7
LHCb
75.4 ± 4.5
using
these
values
Don't know the exact ones inside FLUKA
but approximately ok for scaling

6. Distributions
Looking just after the insertion for inelastic collisions
~14.5% transmitted into model
Change in angle due to interaction
Previous method

7. Total Loss Map Combined B1&2 for IP 1,5,& 8 for inelastic
Elastic had nearly no loss at all
in some cases, no losses at all after 20k turns
not shown here as negligible contribution
IP1
Source
Integrated Power (W)
Cold
154.76
Warm
98.14
Collimator
6.44
Total:
259.34
Note: - all IPs -> ~2.5kW burning off in beam

8. Losses From IP1 Looking at the contribution from each IP individually
Source
Integrated Power (W)
Cold
62.01
Warm
62.04
Collimator
3.30

9. Losses From IP5 Source Integrated Power (W) Cold 89.62 Warm 34.59
Collimator
2.92

10. Losses From IP8 Source Integrated Power (W) Cold 3.13 Warm 1.16
Collimator
0.21

11. Sector 1-2 Identify particular cells of losses in Sector 1-2 IP1 IP2
MB.13R1.B1
IP1
IP2
MQ.16R1.B1
MB.A18R1.B1
MBC28L2.B1
MQ.27L2.B1
MQ.23L2.B1
MQ.19L2.B1
MQ.15L2.B1
MQ.16R2.B1
MQ.21R1.B1
MQ.25R1.B1
Mostly from IP5
Mostly from IP8
Mostly from IP1

12. Right of IP1 Looking closer at IP1 right side IP1 MB.C13R1.B1
MB.B11R1.B1
IP1
From IP1

13. IP4 - IP6 Major arc spikes nearly all from IP5 IP4 IP5 IP6 MQ.23L6.B1
MQ.15R4.B1
MQ.23R4.B1
MQ.29L5.B1
MQ.21L5.B1
MQ.20R5.B1
MQ.29R5.B1
Mostly from IP5
Mostly from IP8
Mostly from IP8
Mostly from IP1

14. About IP8 One significant spike IP8 MB.C16L8.B1 MB.B14L8.B1
Direction of B1

15. Comparison
From LMC #331 - talk by R. Garcia Alia

16. Analysis (my) previous analysis didn't weight by energy correctly
Rewritten event-by-event analysis
Ongoing development for traceback of losses
primary or secondary hit aperture?
how many collimators (if any) before interaction
aperture impact due to teritiary particles?

17. Summary 2017, β*=40 cm, θ=150 µrad scenario simulated
for perfect machine
Some spikes similar to measurements
Possible to simulate further scenarios quickly
Analysis development will allow more detailed trace-back
will help with possibly mitigating the losses

18. Thank you