J. Giner-Navarro 1

RF BD statistics in the TD26CC accelerating structure

J. Giner-Navarro18/11/2014

CLIC Breakdown meeting

18/11/2014

J. Giner-Navarro 2

BD analysis: TD26CC history

Data taken for the analysis (at similar conditions):250 ns conditioning + BDR measurementFrom 15th-Nov-2013 to 18th-Dec-201318/11/2014

J. Giner-Navarro 3

BD and cell history

REF-TRA method to locate breakdowns in the structure.

0 5 10 15 20 25 30 35 40 45 50

2

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28

#Pulses (M)

BD

cel

l

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J. Giner-Navarro 4

Breakdown cell distribution

102

104

106

0

5

10

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20

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30

pulses between BDs

BD

Cel

l

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Distribution of the BD location for the whole set of breakdowns.Notice the logarithmic scale in the horizontal axis, since events are more likely to happen between less pulses.

0 5 10 15 20 250

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20

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40

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60

70

BD cell

Fre

q

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J. Giner-Navarro 5

Pulses between BDs distribution

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 106

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

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0.9

1

#Pulses between BDs

Data

Poisson fit

First 26,000 pulses outRemoval of the number of first pulses optimized by chi2 minimization

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 106

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

#Pulses between BDs

Data

Poisson fit

Expected distribution

BDR= 5.61e-6 bpp

Total 676 BD eventsBDR = 1.31e-5 bpp

I call this subset of 279 BDs the Poissonian data

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J. Giner-Navarro 6

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 106

10-2

10-1

100

#Pulses between BDs

Data

Poisson fit

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 106

10-2

10-1

100

#Pulses between BDs

Data

Poisson fit

Pulses between BDs distribution

First 26,000 pulses outRemoval of the number of first pulses optimized by chi2 minimization

Expected distribution

BDR= 5.61e-6 bppTotal 676 BD eventsBDR = 1.31e-5 bpp

I call this subset of 279 BDs the Poissonian data

18/11/2014

Better to see in logarithmic scale

J. Giner-Navarro 7

Consecutive BD cell displacementDistribution of cell displacement between two consecutive breakdowns.

If next BD was randomly located, we would expect a triangular distribution (red), due to the effect of edges which can move towards only one direction.

If we normalize the distribution to be uniform, we see more probability of trigger a breakdown in the vicinity of the previous BD cell.

(Poissonian data: first 26000 pulses out)

-30 -20 -10 0 10 20 300

2

4

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14

16

18

20

BD cell displacement

Fre

q

-30 -20 -10 0 10 20 300

0.1

0.2

0.3

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0.5

0.6

0.7

0.8

BD cell displacementF

req

norm

aliz

ed

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J. Giner-Navarro 8

Are the BD clusters also poissonian?

It doesn’t look like poissonian, far from an exponential distribution.

0 0.5 1 1.5 2 2.5 3

x 104

10-2

10-1

100

#Pulses between BDs

Data

Poisson fit

I call this subset of 397 BDs the pre-Poissonian data

0 0.5 1 1.5 2 2.5 3

x 104

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

#Pulses between BDs

Data

Poisson fit

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J. Giner-Navarro 9

-30 -20 -10 0 10 20 300

0.2

0.4

0.6

0.8

1

1.2

1.4

BD cell displacement

Fre

q no

rmal

ized

-30 -20 -10 0 10 20 300

5

10

15

20

25

30

35

BD cell displacement

Fre

q

Are the BD clusters also poissonian?Distribution of cell displacement between two consecutive breakdowns.

(pre-poissonian data: only first 26000 pulses)

Same behaviour as the poissonian data: BDs triggered in near cells to the previous one

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J. Giner-Navarro 10

Correlation Pulses and BD displacement

Pre-poissonian data subset.

We look for a correlation between the number of pulses and cell location variation between two consecutive breakdowns, to check if BDs within a certain number of pulses are more likely to be closer.This would indicate a debris of the previous breakdown which triggers a new one.

0 0.5 1 1.5 2 2.5

x 104

-30

-20

-10

0

10

20

30

pulses between BDs

BD

Cel

l dis

plac

emen

t

0 0.5 1 1.5 2 2.5

x 104

0

5

10

15

20

25

30Correlation coeficient r= 0.14026

pulses between BDs

BD

Cel

l dis

plac

emen

t

Abso

lute

val

ue

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J. Giner-Navarro 11

BD Cell displacement?

Here we normalize the distribution taking into account that a displacement

of 0 cells can come from more cells than a displacement of +28 cells.

Then, it seems that it is more likely that a BD is triggered near the previous one when there were less pulses in between.

pulses between BDs

Cel

l dis

plac

emen

t

102

103

104

105

-25

-20

-15

-10

-5

0

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25

0.5

1

1.5

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3.5

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4.5

5

pulses between BDs

Cel

l dis

plac

emen

t

102

103

104

105

-25

-20

-15

-10

-5

0

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25

0.05

0.1

0.15

0.2

0.25

0.3

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J. Giner-Navarro 12

Conclusions• Data behaves poissonian as we remove clusters separated by

less than 26000 pulses, to compare with the 10000 pulses obtained by Anders’ experiment in the Fixed-Gap system.

• These figures shows qualitatively that most clustered breakdowns appear near the previous one.

• Need of statistics and alternative methods to quantify this correlation between the number of pulses needed to trigger a new BD and its location.

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