wire scanners observations in sps lhc g. trad emittance working group 26/08/2015
DESCRIPTION
SPS WS 416TRANSCRIPT
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??