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e - cloud simulations (update)

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e- cloud simulations

(update)

C.Octavio Domínguez, Giovanni Rumolo, Frank Zimmermann

11hFebruary 2011 - e-cloudsimulations

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

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11hFebruary 2011 - e-cloudsimulations

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

SPS simulations (2003)

Goal: to reproduce this plot

R?

emax?

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11hFebruary 2011 - e-cloudsimulations

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

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations

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

SPS simulations (2003)

Only 100 G simulations

(No multipacting at 150 G!)

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11hFebruary 2011 - e-cloudsimulations

SPS simulations (2003)

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11hFebruary 2011 - e-cloudsimulations

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”? …

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11hFebruary 2011 - e-cloudsimulations

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

LCH arcs - Nb scan

From 17/1/2011:

P=1 nTorr; nisteps=400

No stripes!!!

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11hFebruary 2011 - e-cloudsimulations

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

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

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations

LCH arcs - Nb scan

The pressure definitely has an impact on the stripes

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11hFebruary 2011 - e-cloudsimulations

LCH arcs - Nb scan

Nb = 1.5·1011ppb

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11hFebruary 2011 - e-cloudsimulations

LCH arcs - Nb scan

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11hFebruary 2011 - e-cloudsimulations

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

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

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

LCH IR3

Measurement

ECLOUD

(from qlosswh.data)

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11hFebruary 2011 - e-cloudsimulations

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

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

LCH IR3

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11hFebruary 2011 - e-cloudsimulations

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