electron cloud meeting 16-05-2014
DESCRIPTION
Simulation of EC detectors: implementation and results A. Romano, G. Iadarola , G. Rumolo Many thanks to: Christina Yin Vallgren. Electron Cloud meeting 16-05-2014. Outline. Introduction Simulation of EC detectors in PyECLOUD First results for SPS like strip monitor - PowerPoint PPT PresentationTRANSCRIPT
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 ?
13
• 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 ?
14
• 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 ?
15
• 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 ?
16
• 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