PMT ID Numbers
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of the Offline Documentation
The PMT ID numbers as defined in NuWa offline software are explained.
In counting PMT IDs the number zero is reserved as illegal.
In the software, PMTs are addressed using a single bit-packed
int which is packed/unpacked by the
"Conventions/Detectors.h" classes. This number provides
a globally unique The packing is:
- Byte 1
- site ID (
- Byte 2
- detector ID (
- Bytes 3 & 4
- local PMT ID (
Local PMT ID is unique within the detector subsystem.
AD PMTs are addressed by a cylindrical coordinate system made up of a grid of PMT rings and PMT columns.
Main AD PMTs
The AD PMT local ID bytes are:
- Byte 3
- rings number, 1-8 counted from bottom to top.
- Byte 4
- column number, 1-24 counted counter-clockwise looking down at the AD cylinders.
Note: in G4dyb and pre-validated DetSim the convention is that column 1 is at 0 degrees (on positive X-axis). The real ADs will have column 1 at +7.5 degrees.
AD Calibration PMTs
There are 6 calibration PMTs which are packed by giving them the illegal ring number (zero) and column numbers:
- 1: top, target-viewing
- 2: bottom, target-viewing
- 3: top, gamma-catcher-viewing
- 4: bottom, gamma-catcher-viewing
- 5: top, mineral-oil-viewing
- 6: bottom, mineral-oil-viewing
This packing above will produce a sparse set of numbers. When a compact set is needed, for example to index an array, the convention is followed that the numbers 1-192 are given mapped such that
- ring-1, column-1 is PMT #1
- counting continues around the ring counter-clockwise up to PMT #24
- ring-2, column-1 is PMT #25
- PMT #192 is ring-8, column-24
The calibration PMT indices are:
- 193: top, target-viewing
- 194: bottom, target-viewing
- 195: top, gamma-catcher-viewing
- 196: bottom, gamma-catcher-viewing
- 197: top, mineral-oil-viewing
- 198: bottom, mineral-oil-viewing
The offline does not know about ladders but they are used by some people, particularly during commissioning. Laddder-based counting uses:
- Ladder numbers 1-8 starting with #1 just above the x-axis (holding offline column numbers 1-3) and proceeds counter-clockwise.
- LadderColumn numbers 1-3, progressing counter-clockwise w/in one ladder. Note, this is a different "column" convention than what offline uses.
- Ring numbers 1-8, same convention as offline.
Ladder-based numbering is usually expressed like:
Conversion between Ladder-based numbering and Offline convention is as follows (note, integer division)
Lx = (column-1)/3 + 1 Cy = (column-1)%3 + 1
column = (Lx-1)*3 + Cy
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