2. LHC Dipole Diode Insulation Consolidation Review (I) INTRODUCTION
J.Ph. Tock (TE-MSC)

3. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Why ?
Scope
(Dipole diodes only, not the quadrupole ones)
Where are we now ?
Conclusions
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

4. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Why ?
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)
Courtesy M Bednarek

5. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
The LHC dipole diode stack
Why ?
Half Moon
(Diode side)
Diode box
BB to Heat sink connection
Upper Heat Sink
Lower Heat Sink
More details in next presentation
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

6. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Previous short circuits in dipole diode containers
Why ?
Presence of metal (not only) debris in the cold masses, residues from the manufacturing is known.
The mechanism is also known
This can create a short to ground
At room temperature, the corrective intervention is straightforward and short (a few days)
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

7. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Why ?
Previous short circuits in dipole diode containers #
EDMS
Date
Sequence
R short [Ohm]
Secteur
Location
Magnet
Temperature 1
745903
Jun-06
Installation 45
30R4
2152 RT 2
853097
Jun-07
Installation (TBC)
30L5
3186 3
871858
Oct-07
After flushing 81
B11L1
1158 4
883010
Nov-07
Cool down ? 56
B15L6
2264 5
888746
Jan-08
B30R8
1164 6
May-13
After warm-up 12
B30L2
2409 7
Sep-13
0.2
A30R8
3141 8
Mar-15
During training
1.2 34
C19L4
2174
Cryo 9
Dec-16
0.5
C12L4
1127
9 (TBC) shorts to ground in dipole diode containers since June 2006
No correlation with sector or magnet manufacturer
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

8. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Why ?
Previous short circuits in dipole diode containers #
EDMS
Date
Sequence
R short [Ohm]
Secteur
Location
Magnet
Temperature 1
745903
Jun-06
Installation 45
30R4
2152 RT 2
853097
Jun-07
Installation (TBC)
30L5
3186 3
871858
Oct-07
After flushing 81
B11L1
1158 4
883010
Nov-07
Cool down ? 56
B15L6
2264 5
888746
Jan-08
B30R8
1164 6
May-13
After warm-up 12
B30L2
2409 7
Sep-13
0.2
A30R8
3141 8
Mar-15
During training
1.2 34
C19L4
2174
Cryo 9
Dec-16
0.5
C12L4
1127
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

9. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
How to solve this at cold ?
Why ?
Warming-up a sector, solving the NC and cooling it down : ≈ 3 months
 (Too) huge impact on operation
See risk analysis in next presentation
This method was successfully applied twice but is not risk free
(and depends on the fault characteristics)
> 2 orders of magnitude on R value
If necessary, a dedicated presentation can be given later
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)
Courtesy M Bednarek

10. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Why ?
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)
Courtesy M Bednarek

11. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
CMAC Recommendation
Why ?
Perform a quantitative risk analysis of the impact of potential problems caused by magnet training [and operation] and develop a mitigation plan. Study the possibility to (remove debris in all magnets, to clean and) better insulate the diode boxes and establish the necessary time and resources required to do it.
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

12. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Insulating half moon pieces
Why ?
Installed on 15% of the cryodipoles
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

13. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Why ?
Previous short circuits in dipole diode containers #
EDMS
Date
Sequence
R short [Ohm]
Secteur
Location
Magnet
Temperature 1
745903
Jun-06
Installation 45
30R4
2152 RT 2
853097
Jun-07
Installation (TBC)
30L5
3186 3
871858
Oct-07
After flushing 81
B11L1
1158 4
883010
Nov-07
Cool down ? 56
B15L6
2264 5
888746
Jan-08
B30R8
1164 6
May-13
After warm-up 12
B30L2
2409 7
Sep-13
0.2
A30R8
3141 8
Mar-15
During training
1.2 34
C19L4
2174
Cryo 9
Dec-16
0.5
C12L4
1127
All cases were in dipole where insulating pieces are not installed (85%)
This has a low statistical significance (At least no counter-example)
This nevertheless tends to show that, when installed, a good (sufficient ?) level of protection is achieved
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

14. Why not consolidating quadrupole diodes insulation ?
Comparison with main dipole circuits :
No short circuit in quadrupole diodes containers (so far)
About 1/3 of magnets (wrt dipole magnets)
Energy stored : 25 MJ (<< 1350 MJ for the dipoles) [2%]
Time constant : much lower ≈ 33 s (< ≈ 105 s for the dipoles)
Much less quenches for training and during operation
Hydraulic configuration is favourable (less risk to have debris transported to the quad diode container)
 next slide
Better insulated than the dipole diodes
Present insulation level is the same as the one that will be achieved in dipole diodes after implementing the proposed consolidation
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)
Based on a presentation of L Grand-Clement

15. Why not consolidating quadrupole diodes insulation ?
LHCLQMJS0001
Insulation pieces
Tube 168.3x2.6 He
Helium flows to the diode stack from behind
Most of debris likely blocked by the insulation pieces behind the diode
The insulation sleeve is already in the container unlike MB diode
It insulates all active parts of the diode stack with respect to ground
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)
Based on a presentation of L Grand-Clement

16. Why not consolidating quadrupole diodes insulation ?
All quadrupole diodes have been consolidated during LS1
Much less debris than in the dipole containers
All were cleaned during LS1
All NCs (from assembly) have been corrected during LS1
Worst cases
< 10 / 392
Quadrupole diodes insulation is as robust as dipole ones after the proposed consolidation
No need to intervene on the quadrupole diodes
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)
Based on a presentation of L Grand-Clement

17. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Where are we now ?
What happened since end January 2017 ?
A task force was set-up involving CRG, MPE, MSC (7 meetings)
+ Scope of the project was defined
+ Consolidation decided / approved by ATSMB on
Priorities during LS2
P0 : Safety
P1 : Activities needed to reach 300fb-1 during run 3
P2 : HL-LHC & LIU projects
P3 : Approved projects
P3A: Approved project if budgeted*
P4 : Approved studies
P5 : Others
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

18. A consolidation was defined, based on 3 main pillars
Where are we now ?
What happened since end January 2017 ?
A technical working group started (February 2017) [C Scheuerlein]
(Thank to all participants – not a planned activity)
A consolidation was defined, based on 3 main pillars
Removal of accessible debris
Improvement of bare diodes BB
Installation of optimised half-moon insulation pieces
Will be the subject of the next presentations
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

19. LHC Dipole Diode Insulation Consolidation Review (I) Introduction
Conclusions
The consolidation of the LHC dipole diodes insulation is required before training campaigns to go to 7+ TeV (Design/ultimate energy for run III)
A technical solution consisting in :
Installing optimised half moon insulating pieces
Reinforcing the present insulation
Removing the accessible metal debris
is under development
Quadrupole diodes insulation does not have to be consolidated
No CSCM is needed
Achievements from the last months will be presented
A preliminary solution has been developed that needs to be confirmed by detailed calculations and mechanical, electrical and cryogenic validation tests. This is the opportunity to incorporate review outcome
Inputs from the committee are WELCOME
Recommendations on most important criteria
Points missing (design, qualification,…. organisation)
Are we on good track to be successful in consolidating LHC dipole diodes insulation during LS2 and increasing safely the LHC centre of mass energy (> 13 TeV,  15 TeV)
What should we focus on ? What is critical ?
LHC Dipole Diode Insulation Consolidation Review (I) Introduction
J.Ph. Tock (TE-MSC)

21. Based on a presentation of S Le Naour
Insulating half moon pieces
Why ?
Radiographic inspections done:
During LS1 (W-bellows open)
For the 2 earth faults during training (W bellows closed)
During this EYETS (W bellows closed)
Based on a presentation of S Le Naour

22. Based on a presentation of S Le Naour
Insulating half moon pieces
Why ?
Radiographic inspections allow to check the presence of the protection
About 15 % of the dipole diodes are protected
53 diodes have been analysed
Based on a presentation of S Le Naour

23. Next steps
Functional specification of the LHC dipole diodes insulation for Summer
Internal design review for October 2017
Design finalised and first components in Autumn
Testing in SM18/cryolab end 2017
Spring 2018: Final design and project readiness review
December 2018 : Ready to start
Summer 2020 : End of the project

24. Based on a presentation of A Verweij
Risk analysis in a nutshell
Why ?
Probability of O(1%) [2/254* quench events since 2014] to have a single short to ground per quench event at high current
Probability of O (0.01%) to have a double short to ground dissipating sufficient energy to melt a hole in the helium enclosure
O(500) training quenches required to reach 7 TeV [E
2 shorts at cold were solved using the EFB.
Reliability ?
Time taken ?
Risk ?
Non-negligible O (5%) (non-acceptable?) probability to have a double short to ground with major consequences
*including the 2 training quenches in S12 for the recommissioning in 2017
Study the possibility to reinforce the (dipole) diodes insulation during LS2 ( )
Based on a presentation of A Verweij

25. First Internal LHC Dipole Diode Insulation Consolidation Review Introduction J.Ph. Tock (TE-MSC)