1. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Field Quality measurements at cold. Standard program v.s extended tests. Presented by: Stephane Sanfilippo and Nicholas Sammut AT-MTM-AS Contributors: Luca Bottura. M.Calvi. G.Greco, A.Masi

2. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Standard program of cold magnetic measurements Description of the standard tests (MB,MQ) Dipole :status of the warm/cold correlation-sampling. Dipole families. Status for the field quality of the MQ’s. Extended test program Geometry change due to powering and thermal cycles. Cable coupling currents. Degaussing. Powering history dependence (N.Sammut). Modeling of the snap-back (N.Sammut). Conclusions. Overview

3. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS What we measured so far. about 142 dipoles, 16 MQ’s magnets cold tested by December 2004. 2004: ~ 46 dipoles, 14 MQ’ s. 264 apertures considered in the statistics (some data missing) fair mix of (dipoles)  3 producers  three X-sections  4 cables manufacturers MQ : 16 X-section 1+1 X-section 2 you can have access to the data through http://sma.cern.ch Cable combination 01B-02 (B,C,G,K)01E-02 (B,C,G,K,E) number 11017 NB : For the rest, other combinations or unknown.

4. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS  Quantities measured for MB and MQ:  Main field integral strength (rotating coil, SSW), magnetic length, as a function of the current.  Integrated and local harmonics as a function of the current (rotating coil).  Magnetic axis for the MQ and the correctors in the SSS (SSW)  Two measurement cycles: Standard program of magnetic measurements Measurements performed after the training of the MB or MQ. Simulated Machine Cycle with a reference pre-cycle. Load-line (static measurements) 11850 A 760 A 5000 AGeometric saturation magnetization 11850 A 1000 s 760 A Quench Duration : 2h 30 mn Duration : 3 h

5. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS What do we get from… Standard program  Transfer function, multipoles.  Geometric component.  DC magnetization from persistent currents.  iron saturation component.  decay of multipoles at injection for a reference cycle.  snap-back at acceleration (amplitude only). Extended tests  Snapback scaling law (b3/b5 hall probe)  Powering history effect on the decay/snapback  Geometry changes due to Lorenz force, thermal cycle…  Coupling currents effects.  Cycling stress effects on FQ.  Degaussing effect on multipoles.  …..

6. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Warm/cold correlation evolution (dipole). Warm (CM)/cold- offsets Stable offsets and  : Quality of the w/c correlation did not change since 2003. warm data courtesy E. Todesco, b3 Transfer Function

7. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Sampling size for dipoles ( L. Bottura, November 2003 ). cold measurement projection warm measurement and W/C correlation Batches of 50 magnets for each population variant (firms, X-section, cables…): With 50x8 (octants) = 400 cold tests minimum to meet the commissioning specs. Minimum of 50 magnets to satisfy commisioning specifications 200 to 250 magnets to reach magnet stability limit

8. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Searching for the different behaviours….  No dependence of the W/C correlation on the X-section, on the manufacturer.  Differences generated by the variation of Rc in the cable production: coupling currents effects, decay via transport current redistribution. no correlation visible for the moment between Rc and decay.  Families generated by different filament magnetizations in the inner layer cables (27 mT for 01B, 30 mT 01E) : persistent current effects, decay. N.Sammut and L.Bottura, A.Verweij, “classification of LHC dipole at injection” (part II), EDMS 501792 N.Sammut and L.Bottura, “classification of LHC dipole at injection” EDMS 501792 V.Granata et al., “a strategy for sampling in the FQ of the LHC dipoles”, EPAC 2004

9. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Modeling of the persistent current at injection. OK for 02B-01B, 02C-01B 02K-01B cable combination. For the 02K-01E cable combination: b1 hysteresis not understood…. ~ 5 units of discrepancy between calculation and experimental data calculation courtesy V. Granata 02K-01B

10. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Decay of magnetization at injection. N.Sammut and L.Bottura, “classification of LHC dipole at injection”, EDMS 501792 Family 1 : Magnets with 01B cableFamily 2 : Magnets with 01E cable. Magnets with cable 01E to be measured in priority (50 minimum). 02 B-01 B 02 K-01 E Study on 10 magnets Decay of these magnets not scalable yet.Decay of these magnets follows a scaling law.

11. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS And the snap/back? One point very 10-20 s… Extended tests. Hall-probe device for 10 Hz b3 (and b5) measurement Scaling law for the snap-back waveform. Standard tests. 15-m long rotating coils Not enough for a phenomena study

12. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Warm/cold correlation status (MQ). MQ 120 Offset of~15 units between the two systems. Chaconsa not properly calibrated ? MQ 120 (X section-2) out of the correlation. Different permeability of the collar? W/C correlation not validated for the MQ. Standard measurements (shaft + SSW) have to be maintained for MQ ‘s in the SSS until validation.  w/c ~5 u  w/c ~3 u (established at nominal current)

13. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS W/C correlations status for MQ and sampling. Keep 3  W/C below specs and unknowns u=   spec  spec (b 2 )~10 units   =0.2, measure ≈ 50 magnets minimum.  spec (b 6 ) ±1 units   =0.1, measure ≈ 36 magnets minimum. Warm (CM)/Cold (nominal) Transfer functionb6b6 Warm-cold offset (units) 23-0.34 Warm-cold rms (units) 50.22 ( MQ 120 excluded)

14. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Conclusions for the standard tests  The W/C correlation for dipoles did not changed since last year (~ 40 magnets more). A minimum of 50 dipoles per population variant is needed.  Two population variants :dipoles with 01B and dipoles with 01E cables. The b1 magnetization and decay for dipoles with the 01E cable are not understood: measurements and studies on this family variant are the priority.  Information not sufficient for modeling the decays, snap-back..  For MQ’s, systematic measurements have to be maintained: -to confirm the W/C correlation for b 2 and b 6. -to measure MQ’s with X-section 2. - no knowledge about : B 2 dl decay at injection?, B 2 snap-back?, B 2 during ramps.

15. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Extended tests status.  Geometry changes due to Lorenz force and long term storage.  Cable coupling currents effect.  Degaussing cycle.  Scaling law of the snap/back (N.Sammut).  Powering history effect on the decay/snapback (N.Sammut).

16. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Dipole geometry change.  the change in geometric b 3, b 5 caused by:  the maximum Lorentz force experienced by the magnet  thermal cycles/ storage  thermal transients from quench  the effect is broadly systematic, most magnets behave similarly.  this effect is small (order of 0.1 … 0.3 units of b3)  a model of the above effects is not available to-date because of  lack of detailed understanding on the mechanism  lack of sufficient data. Aims: Confirm these characteristics on a sample of 5 dipoles. Change of multipoles between two magnet states: Before powering and after the training. Change of multipoles after one year of storage for the 2054. Statistic on 10 magnets.

17. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Cable coupling currents. Small effect, below 0.1 unit, consistent with R c above 50 . R c control works. Measurements as spot check (5 magnets /year). expected systematic +/- 1  expected values at 10 A/s, referred to injection field Calculated field errors based on Rc~15  and  ~30% for 1/Rc: R.Wolf (2002). Units @ 17 mm NB: 44 magnets tested. 3 measurements in 2004!

18. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Degaussing. Degaussing cycle Normal cycle. AC current modulation is added before injection De-gaussing cycle works:  It produces a stable magnetic state in the SC magnets with a decay smaller than  0.05 units of allowed multipoles.  The de-gaussed state can be predicted (from cold geometric component) within  0.4 units of b3, 0.05 units of b5.  Snap-back: multipole change equals the full persistent current effect. Tested on the first 35 magnets. Stopped in July 2003. Measurements to be combined with detailed study of the snap-back with b3-b5 hall probes. No decay b 3 geom But giant snap/back (L.Bottura, LCC 23/10/02) decay Without degaussing

19. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Standard tests and extended ones: priorities Priorities (MB)  Standard Tests of dipoles with O1E cables (25 magnets/year)  Powering history dependence of the decay/snap-back (6/ year)  B3/b5 with HP+ degaussing cycles (6/year) As spot checks (MB)  Standard Tests of dipoles with other type of cables (25 magnets /year)  Coupling current effects and field advance (5/year).  Effect of powering, storage on FQ (5 magnets). Priorities (MQ)  B2 measurements (minimum of 50 MQ’s and more if W/C doubtful) As spot checks (MQ)  Multipoles measurements (15/years) if problem with  is solved.  Dynamic effects on B2 (ramp, decay) : 5/ year.

20. Field Quality Working Group-14/12/04 - Stephane Sanfilippo AT-MTM-AS Annex : sampling dipole