Field quality versus beam dynamics targets in MQ and corrective actions

P. Hagen, E. Todesco AT-MAS-MA With the help of

F. Simon, C. Vollinger

CERN, 8th January 2004

Field Quality Working Group

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 2

Field quality versus beam dynamics targets in MQ and corrective actions

Correction for b6

Update of field quality in collared coilsRandomsSystematics

Spread in field gradient

Contents

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 3

Field quality versus beam dynamics targets in MQ and corrective actions

b6 in collared coils is among 3.5 and 7 unitsAverage:5.5 units Spread: 0.7 units (one sigma)

Correction of b6 - collared coils data

0

2

4

6

8

10

0 20 40 60 80 100 120 140

Aperture progressive number

b6

inte

gra

l (u

nits

)

systematic

AT-MAS & MTM

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 4

Field quality versus beam dynamics targets in MQ and corrective actions

Offset between collared coil and injectionAround -4 units in series [memo by L. Bottura et al.]

Data of prototypes: -3.7 units with sigma of 0.3 units (5 apertures)

This corrects previous estimate of -2.5 units

Target range at injection [-2,0] units [A. Lombardi talk]

Beam screen: small contribution (-0.2 units) [simulations by S. Russenchuck]

Target range in collared coil: [2.2,4.2] units

b6 - target in the collared coils

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 5

Field quality versus beam dynamics targets in MQ and corrective actions

Part of the spread is due to different coil protection sheet thickness used in the production

Between 0.87 and 0.96 mmModel in agreement with dataLarge spread

Hard to obtain 3 unitsCPS too small, prestressproblemsAlready with 0.87 mm, prestress could be too low

b6 - dependence on coil protection sheet

2

3

4

5

6

7

8

0.80 0.85 0.90 0.95 1.00

coil protection sheets [mm]

b6 [u

nits

]

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 6

Field quality versus beam dynamics targets in MQ and corrective actions

Keep the coil protection sheet at 0.87 mm and add 0.125 mm in the coil midplane

Collared coils with 0.87 mm have average b6 of 5 unitsAccording to simulations the expected shift of additional midplane is -2 units

What we should obtainBring b6 in the centre of the rangeGive some more pre-stress to be safer for quench

b6 - solution proposed

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 7

Field quality versus beam dynamics targets in MQ and corrective actions

Field gradient lower of 6 units

b10 lower of 0.2 unitsNow at -0.1 units, will go to -0.3 units

b6 - solution proposed - side effects

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 8

Field quality versus beam dynamics targets in MQ and corrective actions

First results are in agreement with simulations

b6 - solution proposed - first results

0

2

4

6

8

10

0 20 40 60 80 100 120 140 160

Aperture progressive number

b6 in

tegr

al (

units

)

upper target systematic

systematic

AT-MAS & MTM

lower target systematic

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 9

Field quality versus beam dynamics targets in MQ and corrective actions

New targets for systematics have been agreed with AB-ABP (see talk by A. Lombardi)

everything looks fine

Update of target on systematics

-2

-1

0

1

2

3

4

5

6

2 3 4 5 6 7 8 9 10 11

Target

Series

Collared Coil - Systematic normal

-3

-2

-1

0

1

2

3

4

2 3 4 5 6 7 8 9 10 11

Target

Series

Collared Coil - Systematic skew

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 10

Field quality versus beam dynamics targets in MQ and corrective actions

These targets were already reviewed in June 2003everything looks fine, butProblem on spread of field gradient

Situation on randoms

0.0

0.5

1.0

1.5

2.0

2.5

1 2 3 4 5 6 7 8 9 10 11

Target

Series

Collared Coil - Random normal

un

its

un

its/1

0

0

0.5

1

1.5

2

2.5

2 3 4 5 6 7 8 9 10 11

Target

Series

Collared Coil - Random skew

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 11

Field quality versus beam dynamics targets in MQ and corrective actions

A decrease of field gradient of around 30 units is observed after aperture 115. This is a feature due to the use of a new measuring mole (calibration problem)Data have to be corrected soon

Spread of field gradient

17.54

17.58

17.62

17.66

17.70

17.74

-10 10 30 50 70 90 110 130 150

Aperture progressive number

grad

ient

/cur

rent

(T

/kA

m)

-60

-40

-20

0

20

40

60

(uni

ts)

upper limit (3 sigma)

lower limit (3 sigma)

average

AT-MAS & MTM

8th January 2004 P. Hagen, E. Todesco, AT-MAS-MA 12

Field quality versus beam dynamics targets in MQ and corrective actions

Systematic b6Correction proposed: +0.125 mm in coil midplaneFirst results in agreement with simulationsWe should be safely inside the target rangeThis should also increase pre-stress

Review of targets for systematicsSome ranges have been widenedEverything is within specifications

Spread in field gradientWe see a decrease of field gradient due to the use of a new moleCalibration should be checked

Conclusions