1. Consolidation and Upgrade plans for the LHC Vacuum System
Ray Veness
for the Vacuum, Surfaces and Coatings Group
At CERN

2. Ray Veness / LHC Consolidation & Upgrade
Talk Overview
LHC operation schedule
Consolidation of the vacuum system
Following the 2008 incident
Following what we have learned from LHC operation
Requested by LHC experiments
Upgrade highlights
Requested by the LHC experiments
For the LHC machine
Conclusions
And subjects for discussion…
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

3. Ray Veness / LHC Consolidation & Upgrade
LHC Schedule
LHC operation schedule has changed several times over the last 2 years as we learn how things work
Any interventions in the cold arcs require 6 months+ shutdown
We will require 14 months to allow magnets to go to 7 TeV/beam
LHC is currently working better than expected in many ways
The experiments are keen to fully exploit the ‘discovery potential’ at 3.5 TeV/beam
Shutdown strategy
Annual shutdown for ~2 months
Long shutdowns for 12+ months every 3 years, starting 2013
Goals for the next long shutdowns
Consolidation of machine and experiments
Completing the recovery from the 2008 incident so that the LHC can operate at nominal spec.
Making changes based on our experience of LHC operation
Adding final machine elements needed for nominal performance
Upgrades to the machine and experiments
For the machine, the first goal is increased luminosity
The experiments will need re-design to handle the greater event rates and associated radiation and background
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

4. Completing the Consolidation following the 2008 Incident
The LHC was off-line for more than a year following the failure of a superconducting cable splice in 2008
CERN reviewed the causes and effects of this incident and is implementing changes to avoid re-occurance
The main actions concerning the vacuum system involve
Major consolidation of magnet splices, requiring opening of all cold interconnect zones
Mitigation of potential secondary damage to the vacuum system
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

5. Damage during 2008 Incident
This burnt through beam vacuum and cryogenic lines, rapidly releasing ~2 tons of liquid helium into the vacuum enclosure
A faulty bus-bar in a magnet interconnect failed, leading to an electric arc which dissipated some 275 MJ
Conclusion: We need to avoid arcing to beam lines or mitigate damage to sensitive beam vacuum interconnects
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

6. Consolidation: Protect the interconnects
All of the ~1700 beam vacuum interconnects will be fitted with shells made from Ultem (PEI) to prevent arcing and stiffen the module against buckling
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

7. Damage during 2008 Incident
The expanding helium generates forces which lift 30 T magnets off their supports, breaking additional lines
Conclusion: We need to prevent pressure build-up in the insulation vacuum system
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

8. Consolidation: Pressure relief on Insulation Vacuum
120 of these DN160 self-closing ports on stand-alone magnets
~1500 of these DN200 ports will be added to dipoles
~300 DN90 relief valves on the QRL
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

9. Damage during 2008 incident
The pressurised helium enters the beam vacuum, buckling bellows designed for external pressure which are then crushed as the magnets warm-up to room temperature
Conclusion: We need to prevent pressure build-up in the beam vacuum system and strengthen bellows against buckling under internal pressure
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

10. Consolidation: Pressure Relief on Beam Vacuum
A combination of rupture disc, non-return valve and sensor will protect beam vacuum from over-pressure, whilst minimising contamination of the sector and permitting easy identification of vented sectors
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

11. Damage during 2008 Incident
The pressure wave pulls debris – principally metallic soot and fragments of cryogenic ‘super-insulation’ and distributes it over the whole 2.5 km of continuous cryostat
Conclusion: We need to prevent debris propagation in the beam vacuum system
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

12. Consolidation: Fast Shutters
CERN is currently considering two options
Modifying existing sector valves to improve their closing speed should protect from incidents in most of the cold arcs where pressure fronts travel at ~35 ms-1
Commercial or existing dedicate fast shutter systems will be needed in the warm sectors where front speeds reach ~1000 ms-1
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

13. Other Consolidation for 2013
Addition of solenoids on critical non NEG-coated segments for electron cloud suppression
Identification and correction of warm bellows modules causing aperture and impedance problems
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

14. Consolidation & Upgrades for LHC Experiments
Completion of critical spares for special LHC experimental vacuum chambers
Re-optimisation of supports for experimental chambers: getting the best out of the detectors
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

15. 2013 Upgrades: LHC Experiments
Experiments have taken advantage of this to request smaller diameter beampipes, making space for extra detector layers
Results from LHC detectors has given feedback for the real positions of vacuum chambers and detectors
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

16. Future Upgrades: LHC Machine
High-Luminosity LHC (HL-LHC)
Major changes to insertion magnets and vacuum system to increase luminosity
New NbSn insertion magnets, with new vacuum system
Modified apertures in experimental areas, so new vacuum chambers
Deliver more than 10 times higher luminosity, so more transparent chambers needed: ATLAS request 40m of beryllium…
Other longer-term machine options will depend on physics outcomes
LHeC: electron-proton collisions by adding a second ring or recycling LINAC
HE-LHC: Increasing LHC proton-proton collision energy
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

17. Ray Veness / LHC Consolidation & Upgrade
Conclusions
The LHC has started-up and is operating better than expected
Operating and shutdown schedules are evolving as we learn how to operate the LHC and optimise it for physics
There is a large programme of ongoing work to complete the machine and ensure reliable operation
The machine shutdown in 2013 will be extremely busy for our group
What we learn from LHC physics will determine the upgrade path
There are a number of areas where we would appreciate input from the accelerator vacuum community
Damage mitigation following incidents in other labs
Stored energy in cryogenics and vacuum
Reliability and operation of fast shutters
Composite UHV chambers
OLAV-III
Ray Veness / LHC Consolidation & Upgrade

18. Ray Veness / LHC Consolidation & Upgrade
OLAV-III
Ray Veness / LHC Consolidation & Upgrade