wire scanners observations in sps lhc g. trad emittance working group 26/08/2015

Wire ScannersObservationsIn SPS & LHC

G. TRAD

Emittance working group26/08/2015

Layout Quantification of the “crosstalk” effect experimentally with beam in

the SPS and LHC WS Crosstalk seen as an overall signal leakage to adjacent 25 ns slots. SPS WS studied are 419 and 519 (rotational), according to OP the

most frequently used. LHC WS studied are the 4 active ones, B1H2-B1V2-B2H1-B2V1

Quantification of the impact on trains emittance measurement

Implementation of a possible cure.

SPSWS 416

Measured SlotsSl

ot 1

Slot

2

Slot

3

Slot

4

Slot

5

Slot

6

Slot

7

Only 1 filled Bucket

Experimental SetupExample of a

measurement output

Bringing these

points to zero

=>Subtracting the slot 1

profile considered as

noise of an empty bucket

SPS.BWS.41677.H_ROTIN SCAN 1 IN SCAN 2 IN SCAN 3 IN SCAN 4

SPS.BWS.41677.V_ROTIN SCAN 1 IN SCAN 2 IN SCAN 3

FITTING

Example:'SPS.BWS.41677.H_ROT'

𝑒− 𝑡𝜏

=13 ns

'SPS.BWS.41677.H_ROT'

13.7%

4.6%1.7%

6% ?

FITTING - SCANNER 1

𝑒− 𝑡𝜏

=13.8 ns

'SPS.BWS.41677.V_ROT'

15.1%

5.3%3%3% ?

FITTING - SCANNER 2

SPSWS 519

SPS.BWS.51995.H_ROTIN SCAN OUT SCAN

Almost the same Intensity!

SPS.BWS.51995.V_ROTIN SCAN OUT SCAN

'SPS.BWS.51995.H_ROT'

Slot

1

Slot

2

Slot

3

Slot

4

Slot

5

Slot

6

Slot

7

As if WS slots have wrong delay:Even though it is not the croostalk originating from the system BW, The result is the same

WS

Slot

1

WS

Slot

2

WS

Slot

3

WS

Slot

4

WS

Slot

5

WS

Slot

6

WS

Slot

7

77.2 %

13 %5.4 %

2.8 % 1.75 % 1.2 %

FITTING - SCANNER 3

FITTING - SCANNER 4

'SPS.BWS.51995.V_ROT'

79.8 %

13.1 %5.4 % 2.6 % 1.5 %

Same Issue for the vertical

scanner

LHC

Slot

1

Slot

2

Slot

3

Slot

4

Slot

5

Slot

6

Slot

7

Slot

179

3

Slot

179

4

Slot

179

5

Slot

179

6

Slot

179

7

Slot

179

8

Slot

179

9

Measured by :LHC.BWS.5R4.B1H2LHC.BWS.5R4.B1V2LHC.BWS.5L4.B2H1LHC.BWS.5L4.B2V1

Experimental Setup

𝑒− 𝑡𝜏

=16.12 ns

‘LHC.BWS.5R4.B1H2'

21.07 %

4.4 % 2.4 %

𝑒− 𝑡𝜏

=18.55 ns

‘LHC.BWS.5R4.B1V2'

26.95 %

4.75 %2.3%

𝑒− 𝑡𝜏

=11.16 ns

‘LHC.BWS.5L4.B2H1'

10 %

3.9 % 2.6 %

𝑒− 𝑡𝜏

=12.02 ns

‘LHC.BWS.5L4.B2V1'

11.6 %

4.7 % 3.2 %

IMPACTA train of 72 bunches (25 ns spacing) has to be measured;

Assuming realistic but still conservative values:Mean Bunch intensity 1.2 e11 prot (+/- 5 %)Mean Bunch Emittance 2 e-6 m (+/- 8 %)

Due to this signal leakage between slots, an error on each bunch profile is introduced by the previous bunches in the train:

Slot 1 Slot 2 Slot 3 Slot 4

30% spread peak to peak

20% spread peak to peak

IMPACT

Slot 1 Slot 2 Slot 3 Slot 4

K1 * Prof S1K2 * Prof S1

K3 * Prof S1

A train of 72 bunches (25 ns spacing) has to be measured;

Assuming realistic but still conservative values:Mean Bunch intensity 1.2 e11 prot (+/- 5 %)Mean Bunch Emittance 2 e-6 m (+/- 8 %)

Due to this signal leakage between slots, an error on each bunch profile is introduced by the previous bunches in the train:

IMPACT

Slot 1 Slot 2 Slot 3 Slot 4

K1 * Prof S2K2 * Prof S2

A train of 72 bunches (25 ns spacing) has to be measured;

Assuming realistic but still conservative values:Mean Bunch intensity 1.2 e11 prot (+/- 5 %)Mean Bunch Emittance 2 e-6 m (+/- 8 %)

Due to this signal leakage between slots, an error on each bunch profile is introduced by the previous bunches in the train:

IMPACT

Slot 1 Slot 2 Slot 3 Slot 4

K1 * Prof S3

A train of 72 bunches (25 ns spacing) has to be measured;

Assuming realistic but still conservative values:Mean Bunch intensity 1.2 e11 prot (+/- 5 %)Mean Bunch Emittance 2 e-6 m (+/- 8 %)

Due to this signal leakage between slots, an error on each bunch profile is introduced by the previous bunches in the train:

Quantified IMPACT

Error on the measured emittance in the slot,

falsed by crosstalk effects

By definition the first bunch has no induced from other

bunches since …it is the first

A Histogram of the obtained errors to

study the distribution patterns

SPS.BWS.41677.H_ROT

Quantified IMPACT

SPS.BWS.41677.V_ROT

Quantified IMPACT

Erro

r on

emitt

ance

det

erm

inati

on %

Bunch slots along the train Error on emittance determination %

SPS.BWS.51995.H_ROT

Quantified IMPACT

Erro

r on

emitt

ance

det

erm

inati

on %

Bunch slots along the train Error on emittance determination %

SPS.BWS.51995.V_ROT

Quantified IMPACT

Erro

r on

emitt

ance

det

erm

inati

on %

Bunch slots along the train Error on emittance determination %

Quantified IMPACT

Scanner 416 H Rot 416 V Rot 519 H Rot 519 V Rot

Max Rel Error Up to 21 % Up to 24 % Up to 45 % Up to 48 %

SPS summary

LHC.BWS.5R4.B1H2

Quantified IMPACT

Erro

r on

emitt

ance

det

erm

inati

on %

Bunch slots along the train Error on emittance determination %

LHC.BWS.5R4.B1V2

Quantified IMPACT

Erro

r on

emitt

ance

det

erm

inati

on %

Bunch slots along the train Error on emittance determination %

LHC.BWS.5R4.B2H1

Quantified IMPACT

Erro

r on

emitt

ance

det

erm

inati

on %

Bunch slots along the train Error on emittance determination %

LHC.BWS.5R4.B2V1

Quantified IMPACT

Erro

r on

emitt

ance

det

erm

inati

on %

Bunch slots along the train Error on emittance determination %

Quantified IMPACT

LHC summary

Scanner B1H2 B1V2 B2H1 B2V1

Max Rel Error Up 24 % Up to 30 % Up to 18% Up to 16%

Solution

Bunch 1 Profile

Bunch 2 Profile

Bunch 3 Profile

Bunch 4 Profile

…………

Bunch n-1 Profile

Bunch n Profile

Obtained by Scan Measured Weights

Bunch 1 Profile

Bunch 2 Profile

Bunch 3 Profile

Bunch 4 Profile

…………

Bunch n-1 Profile

Bunch n Profile

Calculated

1K 1K 2K 3K 4…

K n

% SPS 51995 H Rotcrosstalk_weights=[0.772; 0.13; 0.054; 0.028 ;0.0175; 0.012];

deconvoluted_buckets=zeros(size(buckets));

for bucketID=1:size(deconvoluted_buckets,1)

previous_contributions=zeros(1,size(deconvoluted_buckets,2));

for j=1:length(crosstalk_weights) if bucketID-j>0 previous_contributions=previous_contributions+...

crosstalk_weights(j).*deconvoluted_buckets(bucketID-j,:); end end

deconvoluted_buckets(bucketID,:)=buckets(bucketID,:)-previous_contributions;

end

Easy cure, just a SW routine

Where should it be implemented? FEC or WS applications??