E. Todesco

FIELD QUALITY IN MQXA

E. TodescoMagnets, Cryostats and Superconductors Group

Accelerator Technology Department, CERN

CERN, 14th February 2008FiDeL meeting

14h January 2008 – Brainstorming on … - 2E. Todesco

CONTENTS

Recall on MQXA

Integrals

DCloop

Decay

14h January 2008 – Brainstorming on … - 3E. Todesco

Recall on MQXA

Interaction region quadrupoles made in JapanQ1 and Q3 parameters

Magnetic length: 6.3 mOperational gradient 215 T/mOperational current: 7150 AInjection current: 435 ANumber: 16+2 sparesID: MQXA2-MQXA19

DesignFour layers, two cables, special gradingIron close to the coil, large saturationA systematic b4 created by the yoke assembly procedure

0

20

40

60

0 20 40 60 80 100 120x (mm)

y (m

m)

14h January 2008 – Brainstorming on … - 4E. Todesco

Recall on MQXA

Magnetic measurements at 1.9 KIntegrals

Measurements at 1.9 K, loadline, ramp upAt 6 currents, from inj. to coll.3 positions: central and two heads, covering all the magnet

DCloopMeasurements at 1.9 K, loadline ramp up and down 2 timesAt 20 values of current for each ramp5 positions: 3 central and 2 heads with 600 mm rotating coils (gaps left)Missing heads for half of the magnets

DecayMeasurements at 1.9 K, at injection and at collisionMeasurements each 3 minutes for 200-300 minutes1 central position with 600 mm rotating coils

14h January 2008 – Brainstorming on … - 5E. Todesco

INTEGRALS

Magnetic measurements at 1.9 KLoadline, 6 values of the current frominjection to high fieldA body measurements, plus two heads

Cover all the magnet5400 mm length in the bodyTransfer function values set to the central value also for the heads, but magnetic lengthis given

These are the reference values for the geometric

14h January 2008 – Brainstorming on … - 6E. Todesco

DCLOOP

DCloopMeasurements at 1.9 K, loadline ramp up and down 2 timesAt 20 values of current for each ramp5 positions: 3 central and 2 heads with 600 mm rotating coils (gaps left)Missing heads for half of the magnets

Current cycleA loadline: down-up-down-up20 currents per ramp from 50 A to 7344 ANote: injection 435 A, collision 7150 AA ramp up (or down) takes 2.5 h

Measuring positions5 positions, 600 mm coil, 2 in heads

Gaps!

0

1000

2000

3000

4000

5000

6000

7000

8000

16:48 18:48 20:48 22:48 0:47 2:47Time (h)

Cu

rre

nt (

A)

0 1 2 3 4 5 6 7 8 9

14h January 2008 – Brainstorming on … - 7E. Todesco

DCLOOP

Post-processingOriginal measurements available in FiDeL formatIntegrals computed assuming that caps behave as straight partsIn case of missing heads (MQXA2-8), the missing measurement is replace by an average of the measurements in the heads (MQXA-9-18)Agreement with the INTEGRAL measurements is within 1-7 units for the transfer functionGood agreement with INTEGRAL measurements for multipoles (less than 0.1 units on averages over 18 magnets, in general within 0.1 units for each magnet, with a few exception up to 0.5 units)

First and second ramp differenceTransfer function reproducible within a few unitsMultipoles: the same within 0.1 units or less

Systematic decrease of b6 of around 0.1 units after the first ramp (?)

14h January 2008 – Brainstorming on … - 8E. Todesco

DCLOOP

Transfer functionWidth of the hysteresis at injection: 33 to 38 unitsSaturation at high field: 5.2-5.3 % (520 to 530 units) – large !! (and different from the MQXB)

29.5

30.0

30.5

31.0

31.5

32.0

0 1000 2000 3000 4000 5000 6000 7000 8000Current (A)

TF

(T

/m/k

A)

MQXA2 transfer function

14h January 2008 – Brainstorming on … - 9E. Todesco

DCLOOP

Transfer functionSpread at injection: 3.5 units (1 )Spread at high field: 3.0 units (1

These are extremely low values compared to other quadrupoles!Confirmed by the independent measurement INTEGRAL

MQXA transfer function at injection

31.50

31.51

31.52

31.53

31.54

31.55

31.56

31.57

31.58

0 5 10 15 20Magnet number

TF

inje

ctio

n (

T/m

/kA

)

-12

-8

-4

0

4

8

12

Un

its

29.93

29.94

29.95

29.96

29.97

29.98

29.99

30.00

30.01

0 5 10 15 20Magnet number

TF

hig

h fi

eld

(T

/m/k

A)

-12

-8

-4

0

4

8

12

Un

its

MQXA transfer function at high field

14h January 2008 – Brainstorming on … - 10E. Todesco

DCLOOP

b6Width of hysteresis at injection: 2.8-2.9 units

b6 in MQXA2

-4

-3

-2

-1

0

1

2

3

4

0 1000 2000 3000 4000 5000 6000 7000 8000Current (A)

b6

(u

nits

)

14h January 2008 – Brainstorming on … - 11E. Todesco

DCLOOP

b6Spread at injection: 0.8 units (1 )Spread at high field: 0.6 units (1

Reasonable values, large variation at high field compared to injection

Average at injection: -1.0 unitsAverage at high field: 0.34 units

Very good optimization

MQXA b6 at injectionMQXA b6 at high field

-1.5-1.4-1.3-1.2-1.1-1.0-0.9-0.8-0.7-0.6-0.5

0 5 10 15 20Magnet number

b6

at i

nje

ctio

n (

un

its)

0.00.10.20.30.40.50.60.70.80.91.0

0 5 10 15 20Magnet number

b6

hig

h fi

eld

(u

nits

)

14h January 2008 – Brainstorming on … - 12E. Todesco

DECAY

DecayMeasurements at 1.9 K, after a cycle at ?Measurements for 200-300 minutes, each 3 minutes1 central position with 600 mm rotating coilsMeasurements at injection and at high fieldAt high field – most critical

No expected decayMeasurements show b1 stable within 0.5 units, and low order multipoles stable within 0.1 units

14h January 2008 – Brainstorming on … - 13E. Todesco

DECAY

Decay of b6 at injectionAfter 20 minutes, from 0.25 to 0.8 unitsAfter 300 minutes, from 0.5 to 1.3 units

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 50 100 150 200 250 300

Time (m)

db6

(uni

ts)

14h January 2008 – Brainstorming on … - 14E. Todesco

DECAY

Decay of b4 at injectionAfter 20 minutes, from -0.25 to 0.1 unitsAfter 300 minutes, from -0.4 to 0.4 units

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0 50 100 150 200 250 300

Time (m)

db4

(uni

ts)

14h January 2008 – Brainstorming on … - 15E. Todesco

DECAY

Decay of transfer function at injectionAfter 20 minutes, from -4 to 1 unitAfter 300 minutes, from -8 to 3 units

-10

-8

-6

-4

-2

0

2

4

6

0 50 100 150 200 250 300

Time (m)

db2

(uni

ts)