MicroBooNE Document 1895-v4

MicroBooNE Liquid Argon Flow Manipulation and Ion Buildup Model

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Document type:
Design or Technical Note
Submitted by:
Erik A. Voirin
Updated by:
Erik A. Voirin
Document Created:
03 Feb 2012, 15:03
Contents Revised:
16 Mar 2012, 08:46
Metadata Revised:
14 Feb 2014, 10:51
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07 Feb 2012, 23:13
Results of a Computational Fluid Dynamics model of the natural convection flow profile in the MicroBooNE cryostat (MicroBooNE Doc-15) showed it would be possible for positive ions to build up in the field cage since a portion of the velocity field would be flowing quite steadily at the opposite of the positive ion drift, roughly (8u, 0v, 0w) mm/sec (directly to the right in the analysis). This means any portion of liquid argon flow with a velocity, which we call the “reverse ion drift velocity”, of (-8u, 0v, 0w) mm/sec will begin to build up positive ions since diffusion, instead of convection, would be the only means of shedding these ions. The amount positive ions built up in an area is proportional to the size and the time duration that any part of the flow field is near the reverse ion drift velocity. This set of analyses intends to find solutions to manipulate the liquid argon flow field to minimize the area in the field cage flow field at the reverse ion drift velocity or cause unsteady turbulent behavior, reducing the time duration at the reverse ion drift velocity. Several possible solutions will be analyzed and posted as videos in this document as they are completed. From these, the most promising design can be chosen and reanalyzed in greater depth.
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Notes and Changes:
Changed Ion absorption scheme. __Made Public
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