E cloud simulations update
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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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E cloud simulations update

e- cloud simulations

(update)

C.Octavio Domínguez, Giovanni Rumolo, Frank Zimmermann

11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

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


E cloud simulations update

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


E cloud simulations update

SPS simulations (2003)

Goal: to reproduce this plot

R?

emax?

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

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

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

SPS simulations (2003)

Neither with 4 batches

It seems there were several sensitive changes in the code

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

SPS simulations (2003)

Only 100 G simulations

(No multipacting at 150 G!)

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

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


E cloud simulations update

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


E cloud simulations update

LCH arcs - Nb scan

From 17/1/2011:

P=1 nTorr; nisteps=400

No stripes!!!

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

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


E cloud simulations update

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


E cloud simulations update

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH arcs - Nb scan

The pressure definitely has an impact on the stripes

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH arcs - Nb scan

Nb = 1.5·1011ppb

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

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


E cloud simulations update

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

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

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


E cloud simulations update

LCH IR3

Measurement

ECLOUD

(from qlosswh.data)

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3 – Method allaD.Schulte

1 or 2 batches

2 different batch spacings

Absolute flux

Total # of e-

# of with e- E>10eV

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

LCH IR3

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11hFebruary 2011 - e-cloudsimulations


E cloud simulations update

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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