Behavior of the magnets during low b squeeze

Behavior of the magnets during low squeeze

W. Venturini Delsolaro

Acknolowgements

M. Giovannozzi, S.Sanfilippo

28 February 2007

LHCCWG meeting

Position of the problem From a magnet standpoint, the low

squeeze is a sequence of current ramps, eventually with changes of sign and stops for beam measurements and corrections

There are two possible implications, i.e.Hysteresis crossingDecay and snapback

Both change the actual field produced for a given current (transfer function)

Magnets

All the DS and MS quadrupoles: MQM, MQY but also MQTL and MQT

Working at 4.4 K (from Q4 to Q6) and at 1.9 K (from Q7 to Q13)

All currents in the -5390,5390 A range Magnetization effects ~ Jc(T,B)

Assumptions and approach Squeeze from injection optics scaled at 7 TeV (plus

change from injection to collision tunes). In some older measurements squeeze followed a cycle to nominal current

Squeezing cycles from MADX (β* = 11 m in IP5/IP1) Linear TF used to generate currents Measure fields on (some) squeezing cycles

Evaluate deviations due to hysteresis Measure decay on last steps (where stops are more

likely )

Example, MQM in Q7L5, applying squeeze cycle after cycle to nominal current

2.1420

2.1425

2.1430

2.1435

2.1440

2.1445

2.1450

0.00 1000.00 2000.00 3000.00 4000.00 5000.00 6000.00

Current (A)

TF

(T

m/K

A)

.

2.3 units

Q7L5 squeeze after cycle to nominal

0

1000

2000

3000

4000

5000

6000

0 20 40 60 80

step

Cu

rren

t (A

)

.

Q7L5

Same MQM in Q5L5

2.1420

2.1430

2.1440

2.1450

2.1460

2.1470

2.1480

2.1490

2.1500

0.00 1000.00 2000.00 3000.00 4000.00 5000.00 6000.00

Current (A)

TF

(T

m/K

A)

.

Q5L5Q5L5 Squeeze after cycle to nominal

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

0 20 40 60 80

step

Cu

rren

t (A

)

~ 5 units

Still another example, in Q9R8

2.1420

2.1425

2.1430

2.1435

2.1440

2.1445

2.1450

0.00 1000.00 2000.00 3000.00 4000.00 5000.00 6000.00

Current (A)

Tra

nsf

er F

un

ctio

n (

Tm

/kA

)

.

Q9R8

Q9R8 after cycle to nominal

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

0 10 20 30 40 50 60 70step

Cu

rren

t (A

)

2.3 units

A recent measurement: Q6R5B2 squeeze cyclewith stops on the last 3

steps (to measure decay)and a more realistic pre

cycle (starts from injection optics scaled at 7 TeV)

Measurements from injection current up to

nominal

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

3500.00

4000.00

0 2 4 6 8 10 12

β*

Cu

rren

t (A

)

.

Q6R5B2

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

3500.00

4000.00

0 20 40 60 80 100 120 140

step

Cu

rren

t (A

)

2.1420

2.1430

2.1440

2.1450

2.1460

2.1470

2.1480

2.1490

2.1500

0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00 3500.00

Current (A)

Tra

nsf

er F

un

ctio

n [

Tm

/KA

] 4.66 units2.1450

2.1460

2.1470

2.1480

2.1490

2.1500

2.1510

0 10 20 30 40 50 60 70 80 90 100

injection current for Q6R5 B2 = 207 A

No decay, or if any, below measurement noise (pretty high in this particular case)

Small loop

Q11R8B2

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

0 2 4 6 8 10 12

steps

MQ

TL

cu

rren

t (A

)MQTL test in SM18 on 12/12/2006, Q11R8B2 squeeze cycle

0.0047

0.00475

0.0048

0.00485

0.0049

0.00495

-200 -150 -100 -50 0 50 100 150 200

standard load line

Squeeze Q11R86

2

1

104 units

3, 4

5

7

MQTL, Q11R8, B2

0.0017

0.0022

0.0027

0.0032

0.0037

0.0042

0.0047

-100 -80 -60 -40 -20 0 20 40 60 80 100

standard load line

Squeeze Q11R8

104 units

8 !

7

9

10

More examples of hysteresis crossing at low current…

5

5.2

5.4

5.6

5.8

6

6.2

6.4

-70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70

Current (A)

TF

(Tm

/kA

)

Q11L5B1

-80

-60

-40

-20

0

20

40

0 10 20 30 40 50

step

Cu

rren

t (A

)

Q11L5B1 (MQTL)

4%

4.8

4.85

4.9

4.95

5

5.05

5.1

5.15

5.2

5.25

5.3

-500 -400 -300 -200 -100 0 100 200 300 400 500

Current (A)

TF

(Tm

/kA

)

1%

Q11R5B2

-400

-300

-200

-100

0

100

200

300

400

500

600

0 10 20 30 40 50 60

step

Cu

rren

t (A

)

5.1

5.15

5.2

5.25

5.3

5.35

5.4

5.45

5.5

5.55

5.6

-50 -40 -30 -20 -10 0 10 20 30 40 50

Current (A)

TF

(Tm

/kA

)

Q11L5B2

-60

-40

-20

0

20

40

0 10 20 30 40step

Cu

rren

t (A

)

1 %

MQT (all cycles for Q12, Q13 in IP5 measured)

1.15

1.2

1.25

1.3

1.35

-70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100

Current (A)

TF

(Tm

/kA

)

Q12R5 B2

-40

-20

0

20

40

60

80

100

120

0 10 20 30 40 50

step

Cu

rre

nt

(A)

2.5 %

in terms of field strength…

0.0E+002.0E-034.0E-036.0E-038.0E-031.0E-021.2E-021.4E-021.6E-021.8E-022.0E-022.2E-022.4E-022.6E-022.8E-023.0E-023.2E-023.4E-023.6E-023.8E-024.0E-024.2E-024.4E-024.6E-024.8E-025.0E-025.2E-025.4E-025.6E-025.8E-026.0E-02

0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000 9.000 10.000

Current (A)

Inte

gra

ted

B2

(Tm

@ 1

7 m

m)

Q11L5B2

-50

-40

-30

-20

-10

0

10

20

30

40

0 10 20 30 40step

Cu

rren

t (

A)

Max setting errors, from hysteresis loops

(without modeling hysteresis crossing)

• MQM ~ 30 units at 320 A, 10 units at 1000 A, 5 units at 2000 A

• MQY ~ 25 units at 200 A, ~10 units at 300 A

• MQTL ~ 90 units at 17 A, ~ 25 units at 34 A, etc..

• MQT ( same as MQTL) …diverging at zero

-0.008

-0.006

-0.004

-0.002

0

0.002

0.004

0.006

0.008

0 200 400 600 800 1000 1200 1400

Current [A]

TF

Off

set

[Tm

/KA

]

MQY26_A2MQY26_A2_MinCurr-200AMQY25_A2MQY24_A1MQY24_A2SSS 621 A1 (SM18)SSS621 A2 (SM18)MQY30 A1MQY30 A2MQY 29 A1MQY29 A2MQY28 A1MQY28 A2MQY27 A1

8 units

-5.00E-03

-3.00E-03

-1.00E-03

1.00E-03

3.00E-03

5.00E-03

7.00E-03

9.00E-03

0 1000 2000 3000 4000 5000 6000

Current (A)

TF

-O

ffset

(Tm

/kA

)

MQM33 A2 MQM33 A1 MQM31 A2


MQM30 A2 MQM29 A1 MQM 29 A2








10 units

4.4 K

Decay of MQY, MQM for the reference cycle

MQY

MQM

decayTF

(units)b6 (units)

Average -4 0.7

sigma 1 0.2

MQY

decayTF

(units)b6

(units)

Average -5.7 0.5

sigma 2 0.15

MQM

from S. Sanfilippo, FQWG meeting on 30.1.2007

16 apertures 6 apertures

Do MQT and MQTL Decay ?

Not really…

y = 2E-09x + 0.0261

0.0258

0.0259

0.026

0.0261

0.0262

0.0263

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Time (s)

Inte

gra

l B

2 o

f M

QT

at

20 A

(T

m @

17

mm

)

σ ~ 2 units

Concluding remarks (1) Δk = f(k) can be extracted from hysteresis loops These errors due to hysteresis add to global uncertainty

on gradients, with the present FIDEL model FIDEL modeling of hysteresis crossing should bring

errors in the range of few units, but this gets harder at low currents

Very low settings for MQTL and MQT, difficult to manage: transfer functions diverge, it is difficult to get the desired field

No decay in MQT and MQTL On MQM and MQY full decay characterization needs

more data (measurement foreseen in 2007) Data are available at the median injection current, which is only indicative.

(2) Squeeze on the ramp, from a magnet standpoint

Would possibly reduce the number of hysteresis crossings

Ramp rates could be chosen such that there would be no need to “stop and wait for the arc”, decay would probably be reduced as measurements on the last steps (lowest β*) would take place with the insertion quads already sitting on their final values

Benefit in terms of optics errors remains to be evaluated

Would simplify magnetic model if all ramps are kept monotonous

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Behavior of the magnets during low b squeeze

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