MQW magnets: results from the measuring campaign (double aperture resistive quadrupoles for LHC)

Author

CERN – Geneva – CHJacques.Dutour

14th International Magnetic Measurement Workshop26-29 September 2005, Geneva, Switzerland 1 / 16

MQW magnets: results from the measuring campaign (double aperture resistive quadrupoles for LHC)

Didier Cornuet Jacques Dutour Miguel Silva

Author



Topics to be presented:

- ‘MQW magnet’ characteristics

- Characteristics of the measurements

- Measuring sequences

- Results from the analysis of the measurements

- Conclusions

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-Quadrupole magnet: 48 installed,4 reserve), 6 MQW quadrupoles replace 1 superconducting quadrupole.- In cleaning insertions of LHC.- Normal conducting (high radiation levels)- Two apertures in a common yoke (space constraints in the tunnel).- Two different power connections : DF (MQWA) and FF (MQWB).- Precision between pole profiles: 1x10-4m (over a length of 3.1m)

Magnetic length [m] 3.1Apertures separation [mm] 224Aperture diameter [mm] 46

MQW magnet characteristics:

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Characteristics of the measurements

-120 measurements MQWA,90 measurements in MQWB 114 measurements in central position.- “Harmonic Coil” technique (using 5 coils in radial configuration)-“ Mole” (0.75 m) displaced manually with extension shafts (carbon fiber tube ) in 5 positions along the magnet.- 3 measurements (forwards and backwards) in each position for all the measuring currents.- DF measuring currents: 40A, 200A, 710A (nominal) and 810A- FF measuring currents: 40A, 200A and 600A (nominal)

- ‘Integrated field gradient’ measurement errors: ± 2 ‰ at 40A

(Gm.Lm) ± 1,5 ‰ at 200A

± 1 ‰ at 600A

- Sextupolar component: ± 2 units

- Other harmonics: ± 10 %

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Magnetic field lines

DF configuration FF configuration

- High saturation in some regions of the yoke, due to FF configuration, changes the quadrupole and sextupole components of the DF configuration. The values measured in DF1 at 40A, no longer correspond to real magnetic field values (2nd measuring sequence)

Measuring sequences

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Measuring sequences

Influence of the FF configuration: the measuring sequence had to be changed.

The magnets could be remeasured or we could introduce a correctionin the measured values:

-5 cycles not enough to fully magnetize (change ∫Gdl at low current).-Start measurements at high currents and then at low currents(remanent field stabilized, less change of ∫Gdl at low currents).- Change demagnetization cycles (-Imax/3 => -2/3 Imax). -FF mode before DF mode because of change ∫Gdl and sextupole components even after demagnetization (memory of FF mode).

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Improved demagnetization cycle

Measuring sequences

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Analysis of the measurements

Harmonic coefficientsMQWA: nominal current

Average Harmonic coefficientsMQWA - AP1 710A

0.06

5.77

0.05

-1.10

-0.05 0.97 0.03

-0.67

39.73

4.22

-10.00

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

b3 a3 b4 a4 b5 a5 b6 a6 b10 a10

Harmonic coefficents

Ave

rag

e va

lue

[un

its]

Average Harmonic coefficients MQWA - AP2 710A

-5.64

-0.04

-1.12

-0.06 0.97 0.04

4.67

0.64

-38.86

0.10

-50.00

-45.00

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

5.00

10.00

b3 a3 b4 a4 b5 a5 b6 a6 b10 a10


Ave

rag

e va

lue

[un

its]

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Harmonic coefficientsMQWA: nominal current

Harmonic term b5 correlation with the b3 termMQWA 710A aperture 1

4

4.5

5

5.5

6

6.5

7

7.5

25 30 35 40 45 50

b3 harmonic term [units]

b5

har

mo

nic

ter

m [

un

its]

R2=0.6924

Harmonic term b5 correlation with the b3 termMQWA 710A aperture 2

-7.5

-7

-6.5

-6

-5.5

-5

-4.5

-4

-50 -45 -40 -35 -30 -25

b3 harmonic term [units]

b5

har

mo

nic

ter

m [

un

its]

R2=0.7843

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Harmonic coefficients

MQWB: nominal current

Average Harmonic coefficientsMQWB - AP1 600A

-0.03 0.03

-9.37

0.26

2.91 2.34

0.07

-1.07

1.020.03

-14.00

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

b3 a3 b4 a4 b5 a5 b6 a6 b10 a10


Ave

rag

e va

lue

[un

its]

Average Harmonic coefficientsMQWB - AP2 600A

-0.07 0.04

3.39

9.48

-0.43

0.08 -0.02

-2.16-0.99

1.00

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

b3 a3 b4 a4 b5 a5 b6 a6 b10 a10


Ave

rag

e va

lue

[un

its]

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Analysis of the measurements Magnetic length

MQWA:

MQWB:

AP1 & AP2Current [A] Lm [m]

40 3.127200 3.127710 3.109810 3.105

AP1 & AP2Current [A] Lm [m]

40 3.128200 3.128600 3.122

'Magnetic length' variation with the currentMQWB

3.100

3.105

3.110

3.115

3.120

3.125

3.130

3.135

0 100 200 300 400 500 600 700

Current [A]

Lm

[m

] AP1

AP2

'Magnetic length' variation with the currentMQWA

3.100

3.105

3.110

3.115

3.120

3.125

3.130

3.135

0 100 200 300 400 500 600 700 800 900

Current [A]

Lm [m

] AP1

AP2

fit line

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Main field gradient

MQWA:

MQWB:AP1 & AP2Current [A] Gm [T/m] TF [T/m.A]

40 2.10 0.0524200 10.33 0.0517600 30.60 0.0510

Current [A] Gm [‰]40 0.27

200 0.11600 0.14

Averages

AP1 & AP2Current [A] Gm [T/m] TF [T/m.A]

40 2.09 0.0523200 10.37 0.0518710 34.67 0.0488810 37.00 0.0457

Current [A] Gm [‰]40 1.71

200 0.39710 0.26810 0.26

Averages

'Transfer function' variation with the currentMQWB

0.0450

0.0460

0.0470

0.0480

0.0490

0.0500

0.0510

0.0520

0.0530

0 200 400 600 800 1000

Current [A]

TF

[ T

/m.A

]

AP1

AP2 (absolute)

'Transfer function' variation with the currentMWQA

0.0450

0.0460

0.0470

0.0480

0.0490

0.0500

0.0510

0.0520

0.0530

0 100 200 300 400 500 600 700 800 900

Current [A]

TF

[ T

/m.A

]

AP1

AP2

fitting curve


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Analysis of the measurements Main field gradient

Main field gradient of both apertures MQWA - 40A

2.080

2.085

2.090

2.095

2.100

2.105

2.110

0 10 20 30 40 50 60

Magnet's number

Gm

[ T

/m ]

AP1

AP2

Main field gradient of both apertures MQWB - 40A

2.080

2.085

2.090

2.095

2.100

2.105

2.110

0 10 20 30 40 50 60

Magnet's number

Gm

[ T

/m ]

AP1

AP2

Main field gradient of both apertures MQWA - 710A

34.50

34.55

34.60

34.65

34.70

34.75

34.80

34.85

34.90

0 10 20 30 40 50 60

Magnet's number

Gm

[ T

/m ]

AP1

AP2

Main field gradient of both aperturesMQWB - 600A

30.45

30.50

30.55

30.60

30.65

30.70

30.75

0 10 20 30 40 50 60

Magnet's number

Gm

[ T

/m]

AP1

AP2

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Analysis of the measurementsMagnetic centre driftIn horizontal plane

MQWA:- magnetic centres getfurther from each other

MQWB:- magnetic centres getcloser to each other

x' variation with the currentMQWA

-0.400

-0.300

-0.200

-0.100

0.000

0.100

0.200

0.300

0.400

0.500

0 200 400 600 800 1000

Current (A)

x'

[m

m]

AP1

AP2

x' variation with the currentMQWB

-0.400

-0.300

-0.200

-0.100

0.000

0.100

0.200

0.300

0.400

0.500

0 100 200 300 400 500 600 700

Current (A)

x'

[m

m]

AP1

AP2

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Analysis of the measurementsMain field direction

Average values: AP1 = 0.03 mrad ; AP2 = -0.08 mrad

Values are within the expected precision: ± 2 mrad

Main field directionMQWA nominal current

-0.002500

-0.002000

-0.001500

-0.001000

-0.000500

0.000000

0.000500

0.001000

0.001500

0.002000

0 5 10 15 20 25 30 35 40 45 50 55 60

Magnet's number

Bm

[ra

d]

AP1

AP2

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Conclusions

- The measured values are correct, within our expected errors: there’sno need of corrections (MQW magnets in cluster of 5, average improved).

- Each improvement made to get a better precision of the measurements,resulted in a longer time needed for the same measurements.

-If 10 magnets were measured only in ‘FF configuration’ and the other 42 magnets only in ‘DF configuration’ the measurement campaign time would have been much reduced, but the flexibility for the selection of the magnets would have been lost.

MQW magnets: results from the measuring campaign (double aperture resistive quadrupoles for LHC)

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