LHC Magnets/Splices Consolidation(20 minutes)

Francesco Bertinelli7 June, 2011

23 slides

Status of LHC: electrical connections Description of shunt consolidation Quality Control Scenario for intervention Missing resources

Joint CERN-Pakistan Committee: 6th meeting

LHC electrical interconnections

2

W bellows (see

later…)

13 kA (“main”) busbar interconnection splices

From L. Rossi, CERN Courier September 2010

3

Poor copper to copper continuity.Provided by butt soldered joints, this electrical quality depends on the:- tolerances of the mating surfaces- relative tolerances between 2 paired bus bars- cleaning of the surfaces- capacity of the soldering to fill the gap providing good contact- correct execution of the soldering.

Lack of internal contact SC cable to bus bar within the same cross-section: partial melting of the Sn-Ag in the bus bar during connection soldering, loss of solder

Need simultaneous presence of two effects:

4

2008-09: new Quench Protection nQPS S

S S

S S

S

EE111 EE112 EE113

EE211EE219

EE119

EE213 EE212

EE015EE014

EE013 EE012R= 100 W

EE111 EE112 EE113

EE211EE219

EE119

EE213 EE212

EE015EE014

EE013 EE012R= 100 W

DC current

MBB line

EE111 EE112 EE113

EE211EE219

EE119

EE213 EE212

EE015EE014

EE013 EE012R= 100 W

MBA line

V

5

Our new “eyes” !

LHC main IC splices today (SC)From Z.

Charifoulline

301 ± 85pΩ

Rmax = 2.7nΩ

Rmax = 3.3nΩ

306** ± 313pΩ

(**) number of splices in the quads segments corrected, 1.3 added

Dipole Buses Quad Buses

12 23 34 45 56 67 78 81

Main Dipoles&Quads Bus, sorted by position, 2048 segmentsAll HWC pyramids and plus ~150 ramps to 3.5TeV analyzed

Top 10 Splice Resistances

2nΩ

6

Dipole magnets internal splicesFr

om

R. Pri

nci

pe, A

. Z

aghlo

ul, P

. Fe

ssia

7

Dipole internal splices today (SC)From Z.

Charifoulline

12 23 34 45 56 67 78 81

12 23 34 45 56 67 78 81

3.1±1.2nΩ8 splices(but not all the same type)

1.4±1.3nΩ3 + 2* splices(* partially)

Main Dipoles

Main Quads

8

Court

esy

R. Fl

ora

, C

. Sch

euerl

ein

(C17-A17)L2 +36μΩR16→+42μΩ(39.6μΩ, 26.6μΩ)

(C30-A30)L2 +36μΩR16→+29μΩ(41.3μΩ, 12.3μΩ)

(B29-A30)R1 +45μΩR16→+44μΩ

(22.8μΩ, 28.5μΩ, 29.9μΩ)

(B32-A33)R1 +39μΩR16→+53μΩ

(52.3μΩ, 24.9μΩ, 10.8μΩ)

(A18-B17)L2 +35μΩR16→+17μΩ

(28.0μΩ, 11.2μΩ, 13.4μΩ)

Biddle measurements: 1-2 main IC splices (NC)

9

The estimated R-8/R-16 random error is ±1 µΩ, and the systematic error is about +10 %.

R8/R16 test: main IC splices (NC)C

ourt

esy

C. Sch

euerl

ein

10

Shunts on dipole interconnect

11

Chosen soldered alloy: Sn60-Pb40 for – Melting temperature (<221.15 Sn-Ag)– Wetting capability– Mechanical and electrical properties

Shunt description

Copper plate 15 mm wide, 3 mm thick.

Copper annealed at 400⁰ C for 2 hours to maximize RRR

12

Total magnet to magnet interconnects in the machine: 1 688

Total 13 kA splices: ~10 200 Number of splices to be redone: ~1 500

(15%)

Number of shunts to be applied: ~27 000

Shunt work in numbers

13

Copper surface machining

14

The shunt soldering process

15

Isostatic assemblyMirror symmetry across H and V planes (assembly facilitate and cost saving)Allowed misalignment default V±5 mm, H±3 mm

Second insulation skin

Pre-stress adjusted with accurate tooling (5kg)

Helium ducts in order to give good cooling for the bus bars (no thermal barrier)

1) Shunt soldering in position2) Central insulation piece introduction between the bus bars3) Lateral insulation pieces introduction4) Polyimide foil wrapping around insulation pieces5) 316L collars tie clamping around

Insulation box and assembly procedure MB

16

Quality Control of main IC splices

R_RT-top-side tests for the QC of individual solder contacts.

After repair the shunt contact on the wedge of M3-QRL-connection, R_RT-top-side is reduced from 10.5 µΩ to 2.1 µΩ.

Comsol R_RT-top-side simulation for shunt with defect (courtesy S. Heck)

R_RT-top-side measurement configuration

17

Examples of damaged cables found in 2009 by the personnel performing the interconnection work

NCR 1002739: Entire cable squeezed between U-piece and wedge

NCR 990852, 2 strands cutNCR 992513: Cable overheated (>580 °C)

NCR 1002739: Entire cable was squeezed between U-piece and wedge 18

i.e. important to have experienced technicians,

specifically for the most critical activities

What activities are involved for IC work?

19

Orbital machining to cut open TIG welds

20

Duration of IC work

at 50 IC/week (!!!) for critical activities, 14 weeks for 1st sector, 5 weeks later for 2nd sector, 49

weeks for 8 sectors 2 shift work (on different activities), some overlap:

• 6h–10h/break/11h-15h• 12h-16h/break/17h-21h

no learning curve, no built-in contingency, no account for holiday/closure periods

must work sequentially to adjacent sector, without access constraints (i.e. first cool-down and HWC powering)

big concern is the “other activities” to be done in parallel: more realistic is to consider an additional 2-3 months 21

Estimate of IC resources needed

22

ActivityIdentified,

trainedIdentified, but need training

Missing resources

Comment

Opening and closing W 8 20 TE-MSC-MNC, FSUs task oriented, Dubna Project Associates

Bellows inspection & protection, endoscopy beamlines 5 3 TE-VSC, Krakow Project Associates

Repair, reinstall & tack PIMs incl. 2 TE-VSC, FSUs

Orbital machining M sleeves and PIMs 3 3 5 FSUs

Busbar copper surfacing machining 7 TE-MSC-MNC

Electrical connections 8 9 3 FSUs, further CERN contribution?

QC electrical connections 4 14 TE-MSC-SCD, BE-OP

ELQA 13 10 Krakow Project Associates

Leak testing 12 7 AL 40-30 (S133 contract)

TIG welding M sleeves and PIMs 6 9 EN-MME and S142 contract

QC Welding 2 4 EN-MME, external contract, BE-OP

QC closing W 4 TE-MSC-MNC, BE-OP

Other 5 5 logistics, coordination, overall QA: further CERN contribution?

DN200 7 1 Dubna Project Associates

Special Intervention IC Team 7 4 9 TE-EPC, FSUs, further CERN contribution?

Total 70 72 57

Note: resources at peak

QPS 9 7 Krakow Project Associates

199

Pakistan Collaboration?

The current scenario

1 “train” only for standard activities A Special Intervention team to prepare non-

standard work before the arrival of the train Long Shutdown starting January (April?) 2013 Jean-Philippe.Tock@cern.ch to replace F. Bertinelli

as IC&Magnet Long Shutdown Project Responsible starting 1 July, 2011

23