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e - cloud simulations (update). C.Octavio Dom ínguez , Giovanni R umolo, Frank Zimmermann. 11 h February 2011 - e - cloud simulations. C ontents. SPS simulations (2003) reproduction Method Partial conclusions 2) LHC simulations N b scan with higher seed pressure

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slide1

e- cloud simulations

(update)

C.Octavio Domínguez, Giovanni Rumolo, Frank Zimmermann

11hFebruary 2011 - e-cloudsimulations

slide2

Contents

  • SPS simulations (2003) reproduction
    • Method
    • Partial conclusions
  • 2) LHC simulations
    • Nb scan with higher seed pressure
    • Parameter studies at the LHC IR3: State of the art

2

11hFebruary 2011 - e-cloudsimulations

slide3

Contents

  • SPS simulations (2003) reproduction
    • Method
    • Partial conclusions
  • 2) LHC simulations
    • Nb scan with higher seed pressure
    • Parameter studies at the LHC IR3: State of the art

3

11hFebruary 2011 - e-cloudsimulations

slide4

SPS simulations (2003)

Goal: to reproduce this plot

R?

emax?

4

11hFebruary 2011 - e-cloudsimulations

slide5

SPS simulations (2003)

No agreement at the beginning (especially for 150 G)  Let’s try whit those plots:

Parameters:

sz=0.225 m;

eNx=(1.66Nb + 1)mm

1 batch, 72 bunches, 25 ns

e- cloud monitor

P=9 nTorr

R=0.3, 0.5, 0.7; emax= 230, 260

No agreement yet

5

11hFebruary 2011 - e-cloudsimulations

slide6

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations

slide7

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations

slide8

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations

slide9

SPS simulations (2003)

Neither with 4 batches

It seems there were several sensitive changes in the code

9

11hFebruary 2011 - e-cloudsimulations

slide10

SPS simulations (2003)

Only 100 G simulations

(No multipacting at 150 G!)

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11hFebruary 2011 - e-cloudsimulations

slide11

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations

slide12

SPS simulations (2003)

  • Conclusions
  • The code has suffered sensitive changes along these years mainly due to the correction (by G.Belodi) of the bug in the model for the angular dependence of dmax
  • “100% option” seems to agree slightly better with measurements (?)
  • We cannot simulate yet the measurements accurately enough
  • BUT: We see the stripes  We can trust our results  not enough seed pressure in the Nb scan study at the LHC arcs? Was the inter-bunch time step too “coarsy”? …

12

11hFebruary 2011 - e-cloudsimulations

slide13

Contents

  • SPS simulations (2003) reproduction
    • Method
    • Partial conclusions
  • 2) LHC simulations
    • Nb scan with higher seed pressure
    • Parameter studies at the LHC IR3: State of the art

13

11hFebruary 2011 - e-cloudsimulations

slide14

LCH arcs - Nb scan

From 17/1/2011:

P=1 nTorr; nisteps=400

No stripes!!!

14

11hFebruary 2011 - e-cloudsimulations

slide15

LCH arcs - Nb scan

  • The Nb scan at the LHC arcs was repeated for 4 different cases:
  • - P=32 nTorr; 90% created e- in the beam volume
  • - P=320 nTorr; 90% created e- in the beam volume
  • - P=32 nTorr; 100% created e- in the beam volume
  • - P=32 nTorr; 100% created e- in the beam volume
  • For all cases: nbstep=200 and nistep=2500 (not so course; nistep(fine)=7462)
  • Other parameters used were: dmax=2.6, R=0.5, emax=230 eV

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11hFebruary 2011 - e-cloudsimulations

slide16

LCH arcs - Nb scan

For 100% of the e- generated in the beam volume no stripes at all!!!!

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11hFebruary 2011 - e-cloudsimulations

slide17

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations

slide18

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations

slide19

LCH arcs - Nb scan

The pressure definitely has an impact on the stripes

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11hFebruary 2011 - e-cloudsimulations

slide20

LCH arcs - Nb scan

Nb = 1.5·1011ppb

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11hFebruary 2011 - e-cloudsimulations

slide21

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations

slide22

LCH arcs - Nb scan

Even if we don’t know the exact energy of the e- at which the effects in the walls start to be important, the scrubbing strategy shouldn’t depend on this parameter

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11hFebruary 2011 - e-cloudsimulations

slide23

LCH arcs - Nb scan

  • Conclusions
  • The stripes formation depends radically on the assumed
  • amount of e- created in the beam volume
  • Pressure shows also an effect in the position as well as in the
  • shape of the stripes
  • The scrubbing strategy should not depend on the energy
  • threshold for e- impinging the walls

23

11hFebruary 2011 - e-cloudsimulations

slide24

Contents

  • SPS simulations (2003) reproduction
    • Method
    • Partial conclusions
  • 2) LHC simulations
    • Nb scan with higher seed pressure
    • Parameter studies at the LHC IR3: State of the art

24

11hFebruary 2011 - e-cloudsimulations

slide25

LCH IR3

Measurement

ECLOUD

(from qlosswh.data)

25

11hFebruary 2011 - e-cloudsimulations

slide26

LCH IR3 – Method allaD.Schulte

1 or 2 batches

2 different batch spacings

Absolute flux

Total # of e-

# of with e- E>10eV

26

11hFebruary 2011 - e-cloudsimulations

slide27

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide28

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide29

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide30

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide31

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide32

LCH IR3

32

11hFebruary 2011 - e-cloudsimulations

slide33

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide34

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide35

LCH IR3

35

11hFebruary 2011 - e-cloudsimulations

slide36

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide37

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide38

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide39

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide40

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide41

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

slide42

LCH IR3

  • Preliminary conclusions (maybe too optimistic?):
  • 2.1 < dmax < 2.3
  • 0.4 < R < 0.7
  • Work to do:
  • Identify better the interesting regions for each batch spacing
  • Make finer grids
  • Try to do simulations setting as seed pressure the value from the
  • measurement for each batch spacing
  • Cross the fingers and hope that we get a good agreement, .

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11hFebruary 2011 - e-cloudsimulations

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