1. Shortening the long RQF/RQD busbar segments in points 1 and 5
Presented by Sandrine Le Naour
with the helpful collaboration of TE-MSC-LMF
Third LHC Splice Review
12 Nov. 2012

2. Third LHC Splice Review
Outline
Present situation on RQF/D bus segments
Technical solution
Quality control
Time estimation
Conclusion
Third LHC Splice Review
12 Nov. 2012

3. RQF/D bus segments in point 1 and 5
In the arc, most of MQ busbar segments contain 8 splices (go through 6 dipoles + 2 quadrupoles, ~107m)
In point 1 and 5 , long bus segments (> 400m long) connect the main quads Q12 to Q11 via 32 splices.
These bus segments go from Q11 to the Q7 and return in the DFBA shuffling module to Q12 (Q10, Q9, Q8, Q7 are MQM magnets and are individually powered in point 1 and 5)
Connection cryostat
Third LHC Splice Review
12 Nov. 2012

4. RQF/D bus segments in point 1 and 5
In LHC, 8 MQ segments contain 32 splices (RQF/RQD, R side, L side, point 1 and 5)
For these segments, if we consider 31 correct splices (with a resistance of 0.3nW), the Max Resistance of one of the splices is
Rmax = Rsegment-(n-1)*Rsplice
For LS1, we suggest at the moment to redo completely all splices in a RQ segment if Rmax > 2nW. (Threshold is 0.82 nW for dipole segments)
With this criteria 102 splices in RQ lines will be de-soldered and re- soldered and the 2 first segments concern already 64 splices!
Bus segment
magnet1
<->
magnet2
Rmax (nΩ)
rang
DCQDQ.11L5.L
MQ.12L5.B2
MQ.11L5.B1
2.86 2
DCQDQ.11L1.L
MQ.12L1.B2
MQ.11L1.B1
2.37 4
DCQFQ.11L1.R
MQ.12L1.B1
MQ.11L1.B2
1.52 14
DCQDE.11R5.L
MQ.12R5.B1
MQ.11R5.B2
1.37 20
DCQFQ.11L5.R
MQ.12L5.B1
MQ.11L5.B2
0.63
173
DCQDE.11R1.R
MQ.12R1.B1
MQ.11R1.B2
0.34
382
DCQFE.11R1.L
MQ.12R1.B2
MQ.11R1.B1
0.31
411
DCQFE.11R5.R
MQ.12R5.B2
MQ.11R5.B1
-0.02
709
Third LHC Splice Review
12 Nov. 2012

5. RQF/D bus segments in point 1 and 5
We propose to shorten the RQ bus segment after the magnet Q11.
The segments will be only 50m long (instead of 400m long), easier to protect
Only 6 splices in the segment (instead of 32)
13 interconnections in RQ lines do not need to be open, reinforced and qualified ( that concern 208 splices which 52 must be completely redone – 104 sleeves not opened)
No change on instrumentation (only soft parameters for QPS)
… But the MQ line will be cut after the connection cryostat
Connection cryostat
Third LHC Splice Review
12 Nov. 2012

6. RQF/D bus segments in point 1 and 5
Better to not leave active bus lines where they are not needed
No Impact for HL-LHC
At the moment, no project is retained to power additionnal magnet(s) on RQF/RQD circuits (BE-ABP is informed).
No Electromagnetic Impact:
M1 and M2 are no more actived between MB11 and Q7 (only M3 stays)  negligeable effect (S. Russenschuck)
Connection cryostat
Third LHC Splice Review
12 Nov. 2012

7. LHC configuration : Room available
L side
R side
Quadrupole Bellow zone Sleeve zone Connection Cryostat
L=217mm, D=80mm L=207mm, D=100mm
Connection Cryostat Bellow zone Sleeve zone Quadrupole
Third LHC Splice Review
12 Nov. 2012

8. Third LHC Splice Review
Proposed solution
Direct U turn
To connect properly the 2 splices, the 2 bus bars are twisted by 90deg. and a superconducting cable covers the 2 cables of the interconnection.
The assembly is then stabilized
with a massive copper piece.
The twisting of the busbar doesn’t damage the SC filaments.
The performance of the busbar out of magnetic field ≥ 40kA !
Third LHC Splice Review
12 Nov. 2012

9. Third LHC Splice Review
A first prototype
Third LHC Splice Review
12 Nov. 2012

10. Quality Control : Gamma Ray
Nice connection shown by g-ray radiography. From busbar to busbar via the central piece (act as a shunt) and along the SC cables.
As only 8 such connections will be done in 2 points, a gamma-ray inspection will be performed systematically.
Spool piece lines will be open for a better access to the main busbar, but it is also a request from ElQA for the qualification of each individual line (spool piece + spare) during the progress of the train.
Thanks to EM-MME-MM for the radiographies
Third LHC Splice Review
12 Nov. 2012

11. Quality control : Electrical test
A QC report is written on the 2 first prototypes : EDMS
Test 1 : unsoldered shunt
Test 2 : soldered shunt
Similarly to R8/R16 qualification at room temperature, R5 and R3 resistance measurements will be performed:
R5 from busbar to central piece
R5 expected value ≤ 6 µΩ
R3 from busbar A to busbar B at the level of the shunt (green points)
R3 expected value ≤ 4 µΩ
Thanks to TE-MSC-SCD
Third LHC Splice Review
12 Nov. 2012

12. Insulation of the connection
The insulation box will be
similar to the one for the
quad connection, with a
comb piece for the spool piece.
Eccobond bag will be also included
The cut busbars will be included in
the insulation box and one leg will be connected to ground.
Hydraulic section still sufficient for helium circulation (A. Perin)
Third LHC Splice Review
12 Nov. 2012

13. Third LHC Splice Review
Time estimation
Time gain for the train (normal teams) : 5-6 days
Time to implement the new connection in Q11 (train special team): 1day/circuit = 8 days
Time estimated to change flanges (SIT) : 4 days
Time estimated to reconnect of spool pieces lines (SIT + ElQA) : 2 days
Gamma ray : 2 or 4 nights
- 6 days
+8 days
+4 days
days
0 days
+6 days
but with new flanges !
Third LHC Splice Review
12 Nov. 2012

14. Third LHC Splice Review
Conclusion 1/2
We propose to shorten the long RQ busbar segments which connect Q11 to Q12 in points 1 and 5.
Reduce them to 50m long and 6 splices instead of 400m long and 32 splices. Deactivation of over-length busbars.
In 4 sectors, 13 interconnections (M1 and M2) don’t need to be open, reinforced, qualified… (it concerns 208 splices which 52 must be re-soldered because of Rmax criteria at cold).
So the risk to damage spool pieces busbar is reduced.
No impact for the HL-LHC project.
Despite a small volume available for a special connection, the direct U turn is an easy configuration to implement.
Gain of time for the regular teams but additional work for the special teams (One of the train + SIT).
The cost is negligeable.
Third LHC Splice Review
12 Nov. 2012

15. Third LHC Splice Review
Conclusion 2/2
This project was presented to the splice task force, TE departement technical meeting (TE-TM) and the LHC Machine Committee (LMC). All teams support the project.
Next steps
Training on the mockup for a last adaptation of the tooling and insulation
Test at cold.
Thermal choc in N2,liq done successfully
Test at 4.2K to be performed
Documentation (ECR)
Third LHC Splice Review
12 Nov. 2012

16. Third LHC Splice Review
Thank you
Third LHC Splice Review
12 Nov. 2012

17. LHC Bus Bar Max Splice Resistances, 2010-2012
Normal: 99.7%=532pΩ (53)
L-L: 99.7%=801pΩ (10)
27 splices
Conclusion:
Measurement error on 700 rumps statistics is about 100±25pΩ for RB and RQ;
Relatively good 3 params fit found for both circuits;
3σ is 0.8nΩ for RB circuit and 2.1nΩ for RQ circuits;
It gives about = 64 splices to be redone if will be applied as a safe criteria;
Normal: 99.7%=1.17nΩ(30)
L-L: 99.7%=2.15nΩ (7)
38 splices
+ 2*32
Third LHC Splice Review
12 Nov. 2012

18. Third LHC Splice Review
Reversibility
If M1 and M2 lines must be reactivated for a future project (hypothesis), it is considered up to now that the empty cryostat will be changed (for a new dimension, for example) and then reconfigured for a possible connection with the Q11 magnet.
If a “quick re-connection” must put in place ( but13 interconnections are not consolidated), the superconducting cable can be kept, copper stabilizer removed on mm to gain cable flexibility. The SC cable will be attached to the insulation box.
Additionnal time estimated : 1 day per circuit.
Third LHC Splice Review
12 Nov. 2012

19. Still to do If the project is accepted
Finalise the design of the shortcut (in progress)
Tooling (in progress)
Design of the insulation of shortcut and insulation of the desactivated busbar (left floatting).
Put the shortcut in place on a interconnection mockup
A method to qualify the shorcut (eqv R8-R16)
Estimate the hydraulic diameter
Do a cold test for the final solution (Still to define). …
Third LHC Splice Review
12 Nov. 2012

20. Busbar segments of Main quad circuits at odd points
x=1,5
Connection cryostat
x=3, 7
Connection cryostat
Third LHC Splice Review
12 Nov. 2012

21. Estimation of electromagnetic forces
Third LHC Splice Review
Calculated by Susana Izquierdo Bermudez
12 Nov. 2012