Follow up and checkpoints of cable properties

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1 Follow up and checkpoints of cable properties Luc OBERLI 1

2 Outline Cable properties relevant for the field quality Follow up of the cable properties during the production Status and trend of the cable dimensions Conclusion 2

3 Cable properties relevant for field quality Cable dimensions : Tolerances were given by the estimation of the errors generated by variation of the conductor placement (to minimize the field errors components) Mid-thickness at ± 6 µm The mid-thickness is defined at 50 MPa (prestress in the dipole) Keystone angle at ± 0.05 Width mm +0/+80 µm 3

minimize the field errors components) Mid-thickness at ± 6 µm The mid-thickness is

4 Cable properties relevant for field quality Cable magnetization The persistent currents are eddy currents flowing inside the NbTi filaments. The field created by the persistent currents opposes the main field. The persistent currents in dipole are seen at injection as variation of the magnetic field errors b3 most important error coming for 70% from the outer layer b7 coming from the inner layer To control the effect of the persistent currents, the width of the magnetization loop at 1.9 K shall be : 2 µom 30 mt for the inner strand 2 µom 23 mt for the outer strand Strand magnetization value should remain fixed with a maximum variation of ± 4.5% around the Center Line. 4

The persistent currents in dipole are seen at injection as variation of the magnetic field errors b3 most important error coming for 70% from the outer layer b7 coming

5 Cable properties relevant for field quality Interstrand cross contact resistance Rc of the cable Interstrand eddy currents are flowing between the strands of a cable. They are the source of field errors generated mainly from the inner layer cable. They are kept under control by oxidizing the SnAg layer of the strands at 200 C to get a contact resistance Rc 20 µω for the inner layer cable Rc 40 µω for the outer layer cable Cables with different Rc between upper pole and lower pole (up-down asymmetry) will be the source of skew components a2 and a4. 5

They are kept under control by oxidizing the SnAg layer of the strands at 200 C to get a contact resistance Rc 20 µω for the inner layer

6 Follow-up of the cable properties during the production 1. Billet approval The strand piece lengths produced from a billet shall be approved by CERN before to be used for cabling A magnetization measurement is mandatory for the approval of every billet. Strand magnetization values of each supplier are followed by SPC. Strand magnetization is only measured by CERN, reproducibility better than ± 1%. 6

be used for cabling A magnetization measurement is mandatory for the approval of every billet.

7 Magnetization of the reference wire to follow the reproducibility of the test station (Courtesy of S. Le Naour) 7

8 Follow-up of the cable properties during the production 2. Cable strand map approval The contractor must submit to CERN a cable strand map for each unit length and must get CERN s approval before to start cabling (only strands from approved billets can be used for cabling). The cable heat treatment duration is given to the contractor to get the correct Rc according to the average thickness of the SnAg layer of the strand map. The magnetization of the cable is calculated as the sum of the strand magnetization of each strand position in the map. The contract follower checks that the magnetization is within the control limits of ± 4.5% around the center line determined for each manufacturer. 8

approved billets can be used for cabling).

9 Dashboard for cable strand map approval 9

10 Follow-up of the cable properties during the production 3. Cable shipment approval To get approval to ship a cable unit length to CERN, the manufacturer must provide : the cable dimension statistic over the unit length (average, min, max, sigma) and the cable fabrication data written into database tables a certificate of conformity and the graphs of the cable dimensions a 5 m long cable sample for every continuous length of cable a record of the cable heat treatment 10

dimension statistic over the unit length (average, min, max, sigma) and the cable fabrication data written into

11 Graphs of a cabling run 11

12 Graph of a cable unit length 12

13 Follow-up of the cable properties during the production 4. Cable acceptance To give the cable acceptance, acceptance tests are made by sampling, 1 cable Unit Length over 4 from every box delivered to CERN trying to test 1 UL from each cable strand map. Dimensional measurement in building 103 along the whole UL. 10-stack measurement made at 50 MPa at the end of the UL to correct the mid-thickness measurement made at 20 MPa by the Cable Measuring Machine (CMM). Rc measurements on samples cut at both extremities of the cable Unit Length. 13

delivered to CERN trying to test 1 UL from each cable strand map. Dimensional measurement in building 103 along the whole UL.

14 Average corrected Mid-thickness Cable 02K Cable mid-thickness Cable from 02K00100 to 23K K16103A 02K00100A 02K00702A 02K01401A 02K01901A 02K02402A 02K03101C 02K03602A 02K04200A 02K04701A 02K05100D 02K05601C 02K06101D 02K06801C 02K07301C 02K07801B 02K08301A 02K08801A 02K09501A 02K10102A 02K10801C 02K11401B 02K12001A 02K12401D 02K13001C 02K13701B 02K14201A 02K14601D 02K15101D 02K15701D 02K16701D 02K17401D 02K17901C 02K18401B 03K03301A 03K09001D 03K10901C 03K16001A 03K17301C Cable mid-thickness [mm] 23K15401A Date : 13-Mar-03 Contract: F269 Prepared by OBERLI Corr avg CMM mid-thick by CERN Avg CMM mid-thick by Firm

473 14 12K16103A 02K00100A 02K00702A 02K01401A 02K01901A 02K02402A 02K03101C 02K03602A 02K04200A 02K04701A 02K05100D 02K05601C 02K06101D 02K06801C 02K07301C 02K07801B 02K08301A

15 Average corrected Mid-thickness Cable 01B Cable mid-thickness Cable from 01B10001 to 01B B10001A 01B10008A 01B10019A 01B10031A 01B10043A 01B10050F 01B10057B 01B10070A 01B10081B 01B10093B 01B10106B 01B10116F 01B10129B 01B10142A 01B10155B 01B10165A 01B10173B 01B10181F 01B10192B 01B10196F 01B10205B 01B10212A 01B10225C 01B10228H 01B10234D 01B10243H 01B10249D 01B10257H 01B10263D 01B10268B 01B10274D 01B10280B 01B10295A 01B10304A 01B10314A 01B10319A 01B10333A 01B10338E Cable mid-thickness [mm] 01B10345A 01B10356G Date : 13-Mar-03 Contract: F264 Prepared by OBERLI Avg CMM mid-thick by Firm Corr avg CMM mid-thick by CERN

894 15 01B10001A 01B10008A 01B10019A 01B10031A 01B10043A 01B10050F 01B10057B 01B10070A 01B10081B 01B10093B 01B10106B 01B10116F 01B10129B 01B10142A 01B10155B 01B10165A 01B10173B

16 Average Mid-thickness Correlation between CERN and supplier measurements Date : 13-Mar-03 Contract: F264 Prepared by OBERLI Cable mid-thickness Cable from 01B10001 to 01B Cable mid-thickness [mm] by FIRM Cable mid-thickness [mm] by CERN 16

903 1.902 1.901 1.900 1.899 1.898 1.897 1.896 1.895 1.894 1.894 1.895 1.896 1.897 Cable mid-thickness [mm] by FIRM 1.

17 Average Mid-thickness Correlation between CERN and supplier measurements Date : 13-Mar-03 Contract: F266 Prepared by OBERLI Cable mid-thickness Cable from 01E00001 to 01E Cable mid-thickness [mm] by FIRM Cable mid-thickness [mm] by CERN 17

18 Cable dimensions statistic on the production Cable type Midthickness (CERN -Firm) Midthickness CERN Sigma [µm] Keystone Angle (Firm) Sigma 01B E G K B C

016 01E + 0.9 1.9018 2.1 1.245 0.012 02G + 2.4 1.4816 1.6 0.897 0.015 02K + 1.9 1.4815 1.

19 Conclusion According to CERN measurements, the midthickness of the cable covers 2 third of the tolerance interval (± 6 µm) The average keystone angle of the cables is within the tolerances. Cable dimensions, magnetization and Rc are well under control with the 4 holding points introduced in the follow-up of the cable production. 19

Lecture VI Magnetic Design

Lecture VI Magnetic Design Field Quality Adjustment After Construction (or After the Start of Production Run) Ramesh Gupta Superconducting Brookhaven National Laboratory US Particle Accelerator School