Observations regarding chromaticity correction during May 2011

Nicholas AquilinaTE-MSC-MDA

Acknowledgements:M. Strzelczyk, M. Lamont, E. Todesco

CERN, FiDeL meeting, 14th June 2011

2

Overview

• What is the time spent at preparation and flattop?

• Spool pieces, what correction are we applying?

• Behaviours of ramps using an actual pre-cycle• Behaviours of ramps using previous physics

run as a pre-cycle (in particular with flattop time > 10 hours)

06/14/2011

3

0

1000

2000

3000

4000

5000

6000

7000

0 1000 2000 3000 4000 5000 6000 7000

curr

ent (

A)

time (s)

0

50

100

150

200

250

0 20 40 60 80 100 120 140

t FT

(min

)

tprep (min)

machineSM18MD

Preparation and flattop time

06/14/2011

tprep 15’-30’ 30’-60’ >60’

75% 11% 14%

tFT* <60’ 60’-180’ >180’

41% 28% 31%

tinj 30’-60’ 60’-180’ >180’

12% 54% 34%

• 68 ramps analysed, the ramps during May 2011• 75% of the cases have a preparation time

between 15’-30’• The ramps which are pre-cycled using an actual

pre-cycle have a flattop time of 10’, tFT* refers to

the flattop time of the physics ramps • SM18 measurements and the proposed MD

measurements follow the trend in the machine

tinj

tFT

tprep

Preparation and flattop time in May 2011 (pre-cycles included)Preparation and flattop time in May 2011 (pre-cycles excluded)

tFT

4

Correction in the spool pieces• Dynamic correction applied by the spool pieces

was found to be the same (within a fraction of ampere – [why ?]) for all cases analysed

06/14/2011

37.0

37.5

38.0

38.5

39.0

39.5

40.0

40.5

41.0

0 50 100 150 200 250

curr

ent (

A)

time (minutes)Average current in the MCS at injection in May 2011

5

Cases with actual pre-cycle

• 32% (22 cases) of the 68 ramps were pre-cycled with an actual pre-cycle

• In the plot the trims are removed, if the chroma is flat the spool piece correction works well

• Worst case (and unique) fill 1800, drift of 5 units

06/14/2011

drift < 1 unit 60%

drift between 1-2 units 20%

drift >2 units 10%

not enough data 10%

-80-79-78-77-76-75

0 2000 4000 6000 8000 10000

Qh'

b1

(uni

ts)

time (s)

11/05/02 (05)

-80-79-78-77-76-75

0 2000 4000 6000 8000

Qh'

b1

(uni

ts)

time (s)

11/05/29 (02)

-78-76-74-72-70-68

0 5000 10000 15000

Qh'

b1

(uni

ts)

time (s)

11/05/22 (13)

-83-81-79-77-75-73

0 5000 10000 15000 20000 25000 30000

Qh'

b2

(uni

ts)

time (s)

11/05/18 (02)

1755 1813 1800

1787

N.B. drift is the amount of decay observed in the given data

6

Cases with long flattop (>10hours)

• 6 cases analysed, all with flattop > 10 hours• The cases with preparation time less than 35

minutes drifted by about 5 units (under corrected)• The case with long preparation time (fill 1805) was

more stable (slightly overcorrected)06/14/2011

ramp fill no. tFT (min) of previous cycle tprep (min)

11/05/16 (06) 1784 709 32

11/05/19 (02) 1789 686 21

11/05/24 (01) 1804 648 35

11/05/24 (22) 1805 642 239

11/05/30 (01) 1816 data not reliable

11/06/02 (21) 1839 921 24

7

Cases with long flattop (>10hours)

06/14/2011

-85

-80

-75

-70

-65

0 10000 20000

Qh'

b1

time (s)

11/05/16 (06)11/05/19 (02)11/05/24 (01)11/05/24 (22)11/06/02 (21) -85

-80

-75

-70

-65

0 10000 20000

Qh'

b2

time (s)

11/05/16 (06)11/05/19 (02)11/05/24 (01)11/05/24 (22)11/06/02 (21)

-75

-70

-65

-60

-55

0 10000 20000

Qv'

b1

time (s)

11/05/16 (06)11/05/19 (02)11/05/24 (01)11/05/24 (22)11/06/02 (21)

-75

-70

-65

-60

-55

0 10000 20000

Qv'

b2

time (s)

11/05/16 (06)11/05/19 (02)11/05/24 (01)11/05/24 (22)11/06/02 (21)

17841789180418051839

17841789180418051839

17841789180418051839

17841789180418051839

8

Where are we??

06/14/2011

0

100

200

300

400

500

600

700

800

900

1000

0 50 100 150 200 250 300

t FT (m

in)

tprep (min)

pre-cycle, <1 unitpre-cycle, 1-2 unitspre-cycle, >2 unitstFT > 10 hours

OKtFT = 10’tprep 15’ – 20’c = 0 – perfect!

UndercorrectedtFT = 10’tprep = 1’c = 9, increase correction by 50%

Undercorrected: drift of 5 unitstFT > 600’tprep 20’ – 35’c = 9, increase correction by 50%

Slightly overcorrectedtFT > 600’tprep = 239’c = -2, decrease correction by 10%

c is the decay amplitude at t →∞c as found in previous analysis was 18 units

9

Where are we?? Numerical data

06/14/2011

Name Fill no. c hor b1 c hor b2 c vert b1 c vert b2 Description

drift < 1 unit 0 0 0 0 pre-cycle

11/05/05 (13) 1759 Not enough data

pre-cycle, drift 1-2 units

11/05/14 (21) 1780 Not enough data

11/05/16 (10) 1785 3.00 6.00 3.00 3.00

11/05/29 (02) 1813 2.50 3.00 2.50 2.50

11/05/17 (08) 1786 Not enough data pre-cycle, drift > 2 units

11/05/22 (13) 1800 9.00 9.00 7.00 8.00

11/05/16 (06) 1784 9.00 9.00 9.00 9.00

flattop > 10 hours11/05/19 (02) 1789 9.00 9.00 9.00 9.50

11/05/24 (01) 1804 9.00 9.00 8.00 8.00

11/05/24 (22) 1805 Not enough data -3 -2

11/06/02 (21) 1839 9.00 9.00 9.00 9.00

10

Conclusions

• 75 % of the cases have a preparation time between 15’-30’

• Using an actual pre-cycle before a ramp ensures good correction of the chromaticity (60% of cases where within 1 unit) if the preparation time is longer than 10 minutes

• Drift of 5 units was observed in cases with long flattop (> 10 hours)

• Having long preparation time reduces decay which can lead to overcorrection

06/14/2011

11

Conclusions

• The powering history influence on decay is stronger than what we have today in FiDeL

• Beam measurements show consistent results – reproducibility within 1-2 units if powering history is the same

• An update of the coefficients will be given at the end of June

06/14/2011