1. Giorgio on behalf of ELQA team
ELQA plan for LS2
Introduction ELQA
ELQA into general planning
Activities per sector
Hardware & Manpower
Conclusion
Giorgio on behalf of ELQA team

2. ELQA: Introduction
The Electrical Quality Assurance concerns all superconducting circuits of the LHC machine (more than 1600 circuits).
The objectives of the ELQA tests are:
Electrical qualification of each superconducting electrical circuit, including the current leads and the active systems connected to the circuit.
Measurement of electrical parameters of each superconducting electrical circuit in order to verify reference values for the initial operation of the power converters and for the machine operation.
Verification of the integrity of the instrumentation used for the protection of the superconducting magnets and current leads.
All the ELQA tests are documented, based on approved procedure, with predefined conditions and safety aspects
The parameters of the circuits are stored in DB (Electrical Layout DB)
The ELQA test results are recorded in ELQA DB
The follow-up of a circuit is ensure via Manufacturing and Test Folder (MTF) as a part of EDMS
Non Conformities are reported and stored in MTF
The goal of ELQA is to validate the entire chain of circuit and instrumentation included!

3. ELQA: Who?...How ?
The ELQA tests are performed by trained Engineers and Technicians that have specific knowledge on the electrical measurement and LHC circuit topology.
The parameters of the circuits and the criteria applied are predefined and stored in the database.
The automated analysis allows reproducibility and online validation of the tests.
Hardware and Software have been developed according to ELQA needs, using components from the industry and adapted to our specificities.
The main goal of ELQA is to qualify the circuits at various stages of HWC. The ELQA team is focusing on the precision and the quality of the measurements but at the same time a great effort is put to stick to the schedule.
At the end of the test campaign, the ELQA project engineer validates the test results and finally gives the green light to proceed with powering tests.

4. ELQA during LS2: always present
Time constraints are very tight, see general planning !
Many sectors in different phases in parallel, up to 2 at cold, and more at warm: up to 5 sectors !!
The planning for ELQA activities was, and still is very tight!
Elqa is present from the very beginning of LS2: Diagnostics at the end of the run, and then Standard ELQA campaign at cold, 2 sectors in //
Then present during the consolidation of the LHC at room temperature: replacement of superconducting magnets, Diode insulation consolidation, 11 T installation
Finally, ELQA team is the last to leave the floor and give the green light for powering test, and then restart of LHC. 4

5. Summary of ELQA activities during LS2
before LS2
Non-conformities diagnostics at cold, with powering.
TP4-E
MIC-C
DOC-C
NCs solving
Warm-up
TP4C: Monitoring system of spool and 13kA circuits
before LS2
TP4-A & B
MIC-W
DOC-W
Warm Bus bar measurement
ELQA during LS2
Non conformities treatment and Follow-up at warm
Diode Insulation Consolidation
Magnet replacement: AIV & PAQ.
11 T dipole electrical tests and validation.
before cool-down
Elqa during cool-down
TP4-C: Monitoring system of spool and 13kA circuits
before powering
DC Cables connection
NCs during powering tests
Circuit diagnostics at cold, before warm-up: following MP3 recommendations
cold: serves as reference for the qualification of the circuits at cold, after RUN2, before LS2.
Elqa during warm-up: detect eventual fault to ground of the main circuits: thermal expansion
warm before massive maintenance: make sure no defect revealed during warm up and as reference for circuit status before massive maintenance. In case of need, there is still time to intervene at warm.
Elqa during LS2, at room temperature:
Non conformities treatment at warm : re-routing of bus bars, bypass, etc…
Follow-up diode insulation consolidation and make sure that the consolidation work do not degrade the circuits integrity, react on the spot!
Magnet replacement
Consolidation of different measuring system
warm after consolidation: qualification of the circuit before cool down
Elqa during cool down: detect eventual fault to ground of the main circuits: thermal contraction
cold: qualification of the circuits, readiness for powering
DC Cable connection
More than tests performed during a Long Shutdown !

6. ELQA activities at cold, before warm-up
Non Conformities diagnostics: 2-3 Sectors in parallel
Lockout, measuring system installation, unlockout, Powering tests (measurement), analysis, and need of repetition?
ELQA campaign at cold: 2 Sectors in parallel, 10 days/sector
Lockout, and then DC Cables disconnection, galvanic insulation installation
ELQA campaign at cold: low voltage and high voltage tests
The goal is to verify the integrity of all circuits, including their instrumentation and protection equipment (quench heaters). This campaign should reveal any weaknesses before the warm-up, and serves as a reference at the end of RUN2.
ELQA fault to ground monitoring during warm-up: 4 Sectors in parallel
Monitoring system installation at the end of cold campaign, then remote measurements 6

7. ELQA activities at warm, during LS2
ELQA campaign at warm + BB segment measurement (TBC): 2 Sectors in parallel, 10 days/sector
ELQA campaign at warm: (low voltage and high voltage test), P=6 bar
Similar to the ELQA at cold campaign, with adequate parameters. Detect any changes that appeared during the warm-up of the machine.
Magnet replacement: AIV & PAQ: many sectors in parallel
Local tests: (low voltage and high voltage test)
About 22 magnets to be replaced (TBC).
The goal is to ensure the correct connectivity of the magnet including all the circuits passing through it (Line N, etc…)
11 T dipole electrical tests and validation: Sector 67 and 78
Electrical test during the 11T dipole installation.
Electrical integration verification
Non Conformities follow-up at room temperature: all sectors in parallel
Follow-up of the Non conformities revealed, analysis, treatment and reporting 7

8. ELQA activities at warm, during LS2
Diode Insulation Consolidation: this would include the diode lead measurement and shifted in the day, the insulation verification (HV test, like PAQ during LS1).
Local low voltage test.
Global insulation verification outside normal working hours (in the ARC, from DFBA to DFBA).
A full Diode Lead Measurement campaign has been performed on the dipoles, during LS1 (without opening the diode container):
All Dipole Diode Leads were measured during LS1: 2464 leads V
Only a sum of all 3 contacts and the copper bus can be measured!
Courtesy of M. Bednarek 8

9. Schematics of the DLM set-up (LS1)
By moving from magnet to magnet we switch between MBA and MBB lines
3 people are required to move the system smoothly
Courtesy of M. Bednarek 9

10. DLM Measurement in LS1
Current is applied in steps of 30%, 60%, 80% and 100% of the maximum current value.
For reversed mode the max current is 1.5 A.
For forward mode the max current is 10 A.
Plateau length is 10 s.
Linear fit is calculated to get the final resistance value and cancel the offset.
Courtesy of M. Bednarek 10

11. Acceptance criteria during LS1
Global diode lead measurement:
3 contacts together.
The most sensitive is the half-moon contact
Simulation => 450K if R = 14.5 μΩ,
Details → Arjan and Zinur
Remaining 2 contacts are unlikely to be below 0.5 μΩ.
If more than 15.5 μΩ is measured, the diode lead may be weak.
Diode container opening is needed!
Courtesy of M. Bednarek 11

12. Data from all sectors (LS1)
Note: logarithmic vertical scale!
Diode lead contact resistances from sectors:
1-2, 2-3, partly 3-4, 5-6, 6-7, 7-8 and 8-1
1858 diode leads
8 diode stacks where the contact resistances exceed the threshold of 15.5 μΩ,
One diode stack with extremely high half-moon resistances: 210 μΩ and 90 μΩ
15.5 µΩ (threshold set by the Diode Working Group)
Represented is the sum of 3 contact resistances.
Courtesy of M. Bednarek 12

13. A15L8 (3058) during LS1
90 μΩ
210 μΩ
Diode container opened on Tuesday, 13
Photo by Ludovic Grand-Clement
Courtesy of M. Bednarek

14. Data from all sectors (LS1)
All dipole diode leads in the LHC machine were measured during LS1.
Measured data after Non Conformities treatment: 17 NCs, 8 Diode container opened :
Previous data from SM18 give good correlation on the half-moon resistance at warm versus cold  No need of CSCM repetition
Represented is the sum of 3 contact resistances. 14

15. Diode Lead Measurement during LS2
Before opening of the diode container and after closing the diode container
Similar to Diode Lead Measurement during LS1.
Local test with possible co-activities.
15 min per magnet 1 sector / week, with one team of 3 persons
After consolidation of the diode container, before closing
Additional voltage measuring points: (below half-moon connection)
Make sure that the consolidation did not influence the diode lead connection
Local measurement that would allow the half-moon connection confidence, after consolidation
15 min per magnet 1 sector / week
High Voltage tests to qualify the insulation
Global insulation verification without coactivity and very
limited access (ELQA team only, DFBA to DFBA).
After 17h00, after patrolling the sector, 2x / week
High Voltage tests to qualify the insulation: 500 V, 2 min
Grounding of circuits after test. V V 15

16. Main MPE - EE activities, during LS2
warm, before cool-down (TP4 A&B) + BB segment measurement (TBC): 2 Sectors in parallel, 10 days/sector
similar to warm, after warm-up.
ELQA during cool down, (TP4-C):
similar to ELQA during warm-up
cold (1.9K) end of LS2, before powering (TP4-E): 2 Sectors in parallel, 10 days/sector
similar to cold (1.9K) before warm-up
Preparation for powering (DQHDS + DC cables connection) 16

17. ELQA manpower during LS1
5 CERN Staff + 1 Fellow + 1 FSUs + 25 HNINP
Very similar situation during LS2: CERN staff + ~25 P.A.
In order to achieve this huge amount of work, we need a lot of qualified and experience manpower:
-We were 5 CERN staff + 1 Fellow + 1 FSU and about 25 persons from HNINP. 17

18. Hardware and Logistics: 8 TP4s + …
Use of 8 existing TP4 measuring systems: used for both standard campaign and diagnostics + 2 AIV systems.
Development of additional measuring systems for Diode Lead Measurement
Electrical and standard bicycles
12 Pefras, cars allocated to HNINP + TE/MPE car pool
To be able to achieve ELQA commitment, we needed substantial hardware and logistics:
8 TP4 measuring systems
Additional measuring systems for DLM
Use of electrical bikes (4) + about 10 normal bikes
12 Pefras to pull and power the TP4-System
Car pool to transport personnel and equipment 18

19. Conclusion
Detecting and resolving electrical non conformities is our duty and it has been a success so far.
Electrical Quality Assurance is mandatory for operating safely the machine.
Most of the ELQA tests would have been performed without the diode insulation consolidation. Extra manpower of the order of 20% due to diode insulation consolidation.
Fruitful collaboration with HNINP based on a long experience and knowledge of LHC.
Still a lot of preparation work to be accomplished before LS2, but we are on good track ! 19

20. Thank you for your attention!

21. Extra slides

22. ELQA: When ? Machine assembly: Hardware Commissioning of the machine:
ELQA tests were present during machine assembly to ensure the circuit correctness (Arc Interconnection Verification or AIV procedure, Partial Arc Qualification or PAQ procedure).
Hardware Commissioning of the machine:
ELQA tests are performed at warm to detect any major defect before cool down in order to intervene in case of need.
During the cool down of the machine, some of the circuits have an insulation to ground monitoring. If a fault is detected due to thermal contraction, the cool down might be stop and dedicated diagnostics could be launched.
Finally, ELQA tests are performed at cold in order to ensure the readiness and parameters of the circuits before powering test can start.
Machine Operation:
According to procedure, whenever a cold mass or part of the circuit being cold reaches 80 K, an ELQA test is required.
On request, after a powering fault that requires an electrical diagnostic on superconducting circuits.
Now that the machine is running, whenever there is a need of a magnet replacement, the type of test that were performed during machine assembly, are adapted, and repeated.

23. Recommendation at CERN: Safety 1st !!
Safety aspect…
Working in the LHC tunnel, on electrical circuit:
Habilitation éléctrique B1, B2
Self Rescue mask course
Portable ODH
Safety equipment to access the tunnel: bio-cell, helmet, mobile phone, front light, safety shoes, jacket...
Grounding of the circuit after ELQA HV Test
Recommendation at CERN: Safety 1st !!
Working in the LHC tunnel means taking care about safety.
For that, whole ELQA team had to follow different safety courses and wear appropriate equipment….
Priority for CERN : Safety 1st, Quality 2nd and Planning 3rd…