larpix-geometry

Handle pixel and TPC geometry for LArPix

Overview

Pixel geometry and channel assignments are stored in YAML configuration files. pixelplane.py will read a configuration file and allow easy access to channel-to-(x,y) conversion and other convenient relationships.

patterngenerator.py contains code for generating arbitrary configurations of pixel planes. Individual python scripts are needed per pixel/chip geometry.

draw_plane.py reads in a YAML configuration file and draws the pixel plane and channel connections in a PDF file for easy visual inspection and reference.

Usage

The scripts can be executed with no arguments.

Here is how to use the pixelplane module.

from pixelplane import *
import yaml

with open('pixel_geometry.yaml', 'r') as f:
    board = PixelPlane.fromDict(yaml.load(f))

chipids = list(board.chips.keys())
chip0 = board.chips[chipids[0]]
print('Retrieving %d' % chip0.chipid)
# print list of (x, y) for each channel
print('Channel ID |     Position\n-----------|-------------')
for channel, pixel in enumerate(chip0.channel_connections):
    print('  %02d       | (%.1f, %.1f)' % (channel, pixel.x, pixel.y))

# Find which channel corresponds to pixel 100
pixel100 = board.pixels[100]
chip, channel = pixel100.channel_connection
print('Pixel 100 is connected to chip %d, channel %d' %
        (chip.chipid, channel))

# Find which channels correspond to pixels with x locations greater than 100
connection_list = board.channels_where(lambda pixel:pixel.x > 100)
for chip, channel in connection_list:
    print('Chip %d, channel %d' % (chip.chipid, channel))

Units and coordinates

All units in layout-*.py scripts and output YAML files are millimeters unless otherwise explicitly specified. In draw_plane.py, the units are 1/72 of an inch, which is the base unit used by the PDF generator tool reportlab, and all other quantities are converted into the base units using the inch and cm conversion factors provided by reportlab.

The coordinate origin in the layout files is in the top left. X increases to the right as usual, and Y increases down the page, as is the convention for web layout. (Unfortunately, the reportlab tool uses the math/physics convention of Y starting at the bottom and increasing up the page, so the coordinates are explicitly transformed in draw_plane.py.)

YAML layout files

The YAML layout files specify both the pixel geometry and the connection map between pixels and ASIC channels. The meaning of each field is as follows:

• chips: A nested list containing one element per ASIC. Each element is structured as a 2-element list, with the 0th element being the Chip ID, and the 1st element being a list where the i-th element is the Pixel ID connected to Channel i. (A value of null means the channel is not connected/bonded to any pixel.) For example:

chips:
- - 1  # <-- Chip ID = 1
  - - 14  # <-- Channel 0 connected to Pixel 14
    - 13  # <-- Channel 1 connected to Pixel 13
...
- - 20  # <-- Chip ID = 2
  - - 821 # <-- Chip 2, Channel 0 connected to Pixel 821
    - 822 # <-- Chip 2, Channel 1 connected to Pixel 822
    - null # <-- Chip 2, Channel 2 not bonded to a pixel
...

• pixels: A nested list containing one element per pixel. Each element is a 5-element list with the following structure:

  1. Pixel ID
  2. x position
  3. y position
  4. list of vertices of collection pad (may be empty)
  5. list of vertices of focusing grid (may be empty)

• x, y: the x and y positions of the top-left corner of the bounding rectangle of the pixel plane (plus a small margin). Used for determining scaling and placement when drawing the pixel grid.

• width, height: the width and height of the bounding rectangle of the pixel plane. Used for determining scaling and placement when drawing the pixel grid.