electron cloud meeting 16-05-2014

Electron Cloud meeting 16-05-2014

Simulation of EC detectors: implementation and results

A. Romano, G. Iadarola, G. Rumolo

Many thanks to: Christina Yin Vallgren

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• Introduction

• Simulation of EC detectors in PyECLOUD

– First results for SPS like strip monitor

– Comparison against previous ECLOUD simulations

• Summary and future Work

Outline

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• Introduction

• Simulation of EC detectors in PyECLOUD

– First results for SPS like strip monitor

– Comparison against previous ECLOUD simulations

• Summary and future Work

Outline

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New PS EC Detector

Biased Electrode:Measure current from EC

Grid

• New electron cloud (EC) detectors have been installed in one of the PS main magnets to study EC effects in strong magnetic field conditions (B>1 T)

[By Teddy Capelli EN/MME]

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V_bias

I_ ec

e-

EC Detector

• EC detectors are used to measure the electron flux onto the chamber’s wall

• Electrons are collected by a shielded electrode and measured as a current signal

Many thanks to M.Taborelli

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• In a drift space (B=0) electrons are free to move inside the chamber.

• In a strong dipolar magnetic field, the electrons move along helicoidal trajectories around the field lines.

o Inside the hole there is no multipactor effect, electrons come only from the edge

EC Detector: effect of the magnetic field

B

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• Introduction

• Simulation of EC detectors in PyECLOUD

– First results for SPS like strip monitor

– Comparison against previous ECLOUD simulations

• Summary and future Work

Outline

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Simulation method development

• For the development we considered the EC detector installed in the SPS (strip detector) since we can compare against previous simulations and measurements (also with applied B)

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Simulation method development

• For the development we considered the EC detector installed in the SPS (strip detector) since we can compare against previous simulations and measurements (also with applied B)

64 rows of holes shifted with respect to each other to explore different horizontal positions

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Simulation strategy

What we have done ?• Due to the symmetric and periodic

geometry of detector, it is possible to calculate the total current considering only 7 different rows

• Each row has a different position of the holes on the top wall of the beam pipe

• The surface of beam pipe is made of adjacent segments of different size and SEY:

zx

• d= 2 mm• SEY = 0 (absorbing

surface)hole

• SEY=[1.3,1.4,1.5]chamber

What we have done ?

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• Due to the symmetric and periodic geometry of detector, it is possible to calculate the total current considering only 7 different rows

• Each row has a different position of the holes on the top wall of the beam pipe

• The surface of beam pipe is made of adjacent segments of different size and SEY:

zx

• d= 2 mm• SEY = 0 (absorbing

surface)hole

• SEY=[1.3,1.4,1.5]chamber

Simulation strategy

What we have done ?

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• Due to the symmetric and periodic geometry of detector, it is possible to calculate the total current considering only 7 different rows

• Each row has a different position of the holes on the top wall of the beam pipe

• The surface of beam pipe is made of adjacent segments of different size and SEY:

zx

• d= 2 mm• SEY = 0 (absorbing

surface)hole

• SEY=[1.3,1.4,1.5]chamber

Simulation strategy

What we have done ?

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• Due to the symmetric and periodic geometry of detector, it is possible to calculate the total current considering only 7 different rows

• Each row has a different position of the holes on the top wall of the beam pipe

• The surface of beam pipe is made of adjacent segments of different size and SEY:

zx

• d= 2 mm• SEY = 0 (absorbing

surface)hole

• SEY=[1.3,1.4,1.5]chamber

Simulation strategy

What we have done ?

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• Due to the symmetric and periodic geometry of detector, it is possible to calculate the total current considering only 7 different rows

• Each row has a different position of the holes on the top wall of the beam pipe

• The surface of beam pipe is made of adjacent segments of different size and SEY:

zx

• d= 2 mm• SEY = 0 (absorbing

surface)hole

• SEY=[1.3,1.4,1.5]chamber

Simulation strategy

What we have done ?

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• Due to the symmetric and periodic geometry of detector, it is possible to calculate the total current considering only 7 different rows

• Each row has a different position of the holes on the top wall of the beam pipe

• The surface of beam pipe is made of adjacent segments of different size and SEY:

zx

• d= 2 mm• SEY = 0 (absorbing

surface)hole

• SEY=[1.3,1.4,1.5]chamber

Simulation strategy

What we have done ?

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• Due to the symmetric and periodic geometry of detector, it is possible to calculate the total current considering only 7 different rows

• Each row has a different position of the holes on the top wall of the beam pipe

• The surface of beam pipe is made of adjacent segments of different size and SEY:

zx

• d= 2 mm• SEY = 0 (absorbing

surface)hole

• SEY=[1.3,1.4,1.5]chamber

Simulation strategy

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…… what are the results?

Effect of the magnetic field on the EC distributionFor B > 400 G the distribution stays practically constant

Hole

Simulation results

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…… what are the results?

Effect of the magnetic field on the EC distributionFor B > 400 G the distribution stays practically constant

For large B the hole gets depleted

Simulation results

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Simulation results

Similar results for the different arrays of hole(through the chamber)

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Similar results for the different arrays of holes(through the chamber)

Simulation results

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Similar results for the different arrays of holes(through the chamber)

Simulation results

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Simulation results

Similar results for the different arrays of holes(through the chamber)

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Similar results for the different arrays of holes(through the chamber)

Simulation results

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Similar results for the different arrays of holes(through the chamber)

Simulation results

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Similar results for the different arrays of holes(through the chamber)

Simulation results

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Simulations Comparison

The total currents (through the holes) for the different configurations look very similar

Aver.

Small differences for intermediate B values

SEY=1.4

I [u

A]

Total current calculated considering the 64 rows of the detector

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Simulations Comparison

SEY=1.4

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• B=0 Threshold influenced by the holes (holes weaken the EC)• B=1000 G Threshold independent from the holes

Effect of the presence of the holes on the multipacting threshold

Simulation results

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Decreasing the number of holes the threshold converges to the unperturbed case

Simulation results

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Simulation results

B = 0.1 T, SEY = 1.35

Electron flux profile with and without the holes for strong B

• EC is suppressed at the hole locations but gets enhanced elsewhere the effect could be related to the electron space charge

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Previous ECLOUD simulation results

Simulations Comparison

PyECLOUD simulations

Simulation results are compatible with results of previous studies

G. Rumolo, 2009

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• Introduction

• Simulation of EC detectors in PyECLOUD

– First results for SPS like strip monitor

– Comparison against previous ECLOUD simulations

• Summary and future Work

Outline

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• The capability of simulating EC detectors has been implemented in PyECLOUD

- First application study of SPS strip detector

• The presence of the holes in the chamber perturbs the EC distribution- For low B, leads to a significant increase of the multipacting threshold- For high B, results in no change in threshold but stronger multipacting between

holes because of less space charge

• Successful benchmark with existing ECLOUD simulations for an SPS strip detector

- Results reproduce well previous simulation performed with ECLOUD

• Next steps - Apply model to PS shielded pick up in SS98 and compare with 2011/2012 time

resolved data- Apply model for the new PS ecloud detectors in MU98 and predict 2014

measurements

Summary and future work

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Thanks for your attention!

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• Mean value of current considering the first 7 rows, for different SEY.

Simulations Comparison