field quality working group-14/12/04 - stephane sanfilippo at-mtm-as field quality measurements at...

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


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


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

0

20

40

60

80

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120

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160

ma

gn

ets

nu

mb

er

Dipoles tested

Cable

combination

01B-02 (B,C,G,K) 01E-02 (B,C,G,K,E)

number 110 17

NB : For the rest, other combinations or unknown.


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 measurementsStandard 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 A Geometric

saturation

magnetization

11850 A 11850 A

1000 s

1000 s

760 A

Quench

Duration : 2h 30 mnDuration : 3 h


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. …..


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,

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warm b3-units @ 17 mm

cold

b3

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s @

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injectionnominal b3

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10.05

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warm TF - Tm / kA

cold

TF

(Tm

/ k

A)

BOI NOM

TransferFunction

-8-6-4-202468

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b1

b2

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b3

a3

b4

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b5

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harmonic

off

set

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injection (91 Magnets)

injection (132 magnets)

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flat top (91 magnets)

flat top (132 magnets)


Simple sampling simulation (132 magnets)

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installationcommissioningb1 variationmeasurement reproducibilityuncertainty at BOIuncertainty at NOMuncertainty on CM W/C offset

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

Minimum sample size over the ring

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(-) harmonic

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W/C extrapolation

projection of cold data


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


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

calculation

courtesy V. Granata

02K-01B

M JcD

Jc 1

B

B

Bc

1 B

Bc


Decay of magnetization at injection.N.Sammut and L.Bottura, “classification of LHC dipole at injection”, EDMS 501792

Family 1 : Magnets with 01B cable

Family 2 : Magnets with 01E cable.

Magnets with cable 01E to be measured in priority (50 minimum).

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b1 (u

nits

)

average

02 B-01 B

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02 K-01 E

Study on 10 magnets

Decay of these magnets not scalable yet.Decay of these magnets follows a scaling law.


And the snap/back?

One point very 10-20 s…

Extended tests. Hall-probe device for 10 Hz b3 (and b5) measurement

I

ItI

decaybacksnapn

injection

eb

3c

Scaling law for the snap-back waveform.

Standard tests.15-m long rotating coils

Not enough for a phenomena study


Warm/cold correlation status (MQ).

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warm b6- units @ 17 mm

cold

b6 (

unit

s @

17 m

m)

injectionnominal

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)


W/C correlations status for MQ and sampling.

Keep 3W/C below specs and unknowns u= spec spec (b2 )~10 units

=0.2, measure ≈ 50 magnets minimum. spec (b6 ) ±1 units

=0.1, measure ≈ 36 magnets minimum.

Warm (CM)/Cold (nominal) Transfer function b6

Warm-cold offset (units) 23 -0.34Warm-cold rms

(units)5 0.22

( MQ 120 excluded)


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 b2 and b6. -to measure MQ’s with X-section 2.

- no knowledge about : B2dl decay at injection?, B2 snap-back?, B2 during ramps.


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).


Dipole geometry change. the change in geometric b3, b5 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.

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b2 a2 b3 a3 b4 a4 b5 a5 b7

Multipole order.

Mul

tipol

e va

riat

ion

(uni

ts @

17m

m)

Change of multipoles between two magnet states:Before powering and after the training.

Change of multipoles after one year of storage for the 2054.

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Multipole order

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tipol

e va

riat

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units

@ 1

7mm

aperture 1aperture 2

Statistic on 10 magnets.


Cable coupling currents.

Small effect, below 0.1 unit, consistent with Rc above 50 .Rc control works. Measurements as spot check (5 magnets /year).

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b1 a1 b2 a2 b3 a3 b4 a4 b5 a5

a n,b

n (

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@ 1

7 m

m)

expected systematic +/- 1

average sigma(units) (units)

b1 0.07 0.32a1 0.00 0.00b2 0.00 0.06a2 0.02 0.16b3 -0.02 0.15a3 -0.01 0.02b4 0.00 0.02a4 0.01 0.06b5 0.00 0.04a5 0.00 0.01b6 0.00 0.01a6 0.00 0.01b7 -0.01 0.02

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!


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 b3geom

But giant snap/back

(L.Bottura, LCC 23/10/02)

decayWithout degaussing


Standard tests and extended ones: prioritiesPriorities (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.


Annex : sampling dipoleSimple sampling simulation (132 magnets)

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field quality working group-14/12/04 - stephane sanfilippo at-mtm-as field quality measurements at...

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