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Re: TPC Hits not being produced in Mokka [message #1597 is a reply to message #1591] Tue, 21 October 2008 05:58 Go to previous message
vogel
Messages: 83
Registered: March 2005
Location: DESY, Hamburg, Germany
Quote:

Does anyone know if such a gap should exist in the TPC or if there is another reason for this behavior?


Hi Ryan,

the TPC as it is implemented in the latest Mokka geometry models actually consists of two gas volumes that are separated by a thin cathode structure. This cathode consists of two mylar sheets with a thickness of 150 Ám each, and a thin copper coating of 10 Ám. The copper surfaces are 5 mm apart, and the space between the sheets is filled with air. (This need not be the final design of the cathode, but it should be fine as a working model.) The sensitive volume of the TPC only extends from |z| = 2.5 mm up to the endplate.

Unfortunately, the release notes do not contain any information about this new TPC implementation, but you can find it out as follows (type the commands at the Idle> prompt of Mokka):
# to display the volume hierarchy and names
/vis/drawTree
# "TPCSensitive" and "TPCCathode" seem to be what you're interested in

/vis/scene/create
/vis/scene/add/volume TPCSensitive ! 0
/vis/sceneHandler/create OGLIX
/vis/viewer/create
/vis/viewer/set/picking
/vis/viewer/set/culling global false
/vis/viewer/flush
# left-click on the white disk (front view of the volume) to display some detailed information
# calculate the actual geometrical extent from the "half length Z" and "translation" values
# middle-click in the viewer window to exit the picking mode

/vis/scene/create
/vis/scene/add/volume TPCCathode
/vis/sceneHandler/create OGLIX
/vis/viewer/create
/vis/viewer/set/picking
/vis/viewer/set/culling global false
/vis/viewer/set/viewpointThetaPhi 90 0
/vis/viewer/zoomTo 500
/vis/viewer/flush
# left-click on the different volumes (side view of the cathode structure)
# middle-click to exit the picking mode
# now have a closer look at the mylar sheet
/vis/viewer/panTo 2.4 0 mm
/vis/viewer/zoomTo 10000
/vis/viewer/flush
# left-click on the different volumes (side view of one cathode sheet)
# middle-click to exit the picking mode
exit

Hope that answers your question,
Adrian
 
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