Properties of Detector Description

This pages documents and defines the properties that are part of the detector description

Antenna Table

  • position_x: The x position of the antenna feed point relative to the station position

  • position_y: The y position of the antenna feed point relative to the station position

  • position_z: The z position of the antenna feed point relative to the station position

The orientation of the antenna is described with 2 vectors. The first vector (referred to as ‘orientation’) is the orientation of the antenna, in case of an LPDA the boresight direction (pointing into the main sensitivity direction) and in case of dipoles this vector is parallel to the rod. The second vector describes a rotation around the first vector and needs to be perpendicular to the ‘orientation’ vector. For LPDAs, it is perpendicular to the antenna tines and points into the same direction as the connector of the create LPDAs. For dipoles, it can point in any direction that is perpendicular to the first vector because of the radial symmetry of dipoles.

../../../_images/orientation_sketch.png

The vectors are each described by two angles:

  • orientation_theta: orientation of the antenna, as a zenith angle (0deg is the zenith, 180deg is straight down); for LPDA: outward along boresight; for dipoles: upward along axis of azimuthal symmetry

  • orientation_phi: orientation of the antenna, as an azimuth angle (counting from East counterclockwise); for LPDA: outward along boresight; for dipoles: upward along axis of azimuthal symmetry

  • rotation_theta: rotation of the antenna, is perpendicular to ‘orientation’, for LPDAs: vector perpendicular to the plane containing the the tines

  • rotation_phi: rotation of the antenna, is perpendicular to ‘orientation’, for LPDAs: vector perpendicular to the plane containing the the tines

The user must specify both the orientation vector and the rotation vector.

Here are a few examples.

1. For an LPDA, the following points the LPDA straight down, with tines aligned with (parallel to) the x-axis (i.e. the east-west direction), and therefore the orientation vector points northwards.

orientation_phi = 0
orientation_theta = 180
rotation_phi = 90
rotation_theta = 90

For an LPDA, the orientation vector is along the boresight direction, and so to point the antenna downward, we specify orientation_theta=180. Because the antenna is completely pointed down, orientation_phi can be any value, so we specify 0 for simplicity. Because the orientation vector points down (orientation_theta = 180), and because the rotation vector is perpendicular to the orientation vector, we must specify the rotation vector to point sideways, and so we set rotation_theta = 90. Finally, to orient the tines correctly: the rotation vector is in the plane perpendicular to the tines, so we must rotate by 90 (rotation_phi = 90) to have the tines themselves be aligned with the x-axis.

2. For a dipole, the following specifies a traditional “upright” dipole.

orientation_phi = 0
orientation_theta = 0
rotation_phi = 0
rotation_theta = 90

For an dipole, the orientation vector is along the rod direction (i.e., going vertically through the cones). Because we want the antenna to be vertical, we set orientation_theta=0. Because the antenna is completely vertical, orientation_phi can be any value, so we specify 0 for simplicity. Because the orientation vector points vertically (orientation_theta = 0), and because the rotation vector is perpendicular to the orientation vector, we must specify the rotation vector to point sideways, and so we set rotation_theta = 90. Because the dipole is azimuthally symmetric, we can fix rotation_phi to any value, and choose 0 for simplicity.

Antenna positions can be visualized in 3D using the script NuRadioReco/detector/visualize_detector.py my_detector.json

Additionally, for the antenna, the user must specify

  • deployment_time: the time of antenna deployment aka the time when the antenna depth was measured (relevant because the depth changes because of snow accumulation)

  • type: the type of antenna. A list of available antenna types and their descriptions is given here

Further Discussion on Antenna Coordinates

In principle, the orientation of the antenna is uniquely defined by the three Euler angles. However, the Euler angles are relatively un-intuitive in everyday use. The solution was instead to specify the antenna orientation with two orthogonal vectors that are more intuitive, and that together over-determine the three Euler angles, and therefore, the antenna orientation.

orientation_phi is roughly the equivalent of the first Euler angle, the rotation around the z-axis. orientation_theta is roughly the equivalent of the second Euler angle, the rotation around the x’-axis. rotation_theta and rotation_phi together specify the third Euler angle, the rotation around the z’’-axis. (Here referring to the intrinsic Euler angle definition in the z-x’-z’’ convention).

ADC Table

We document here the properties that are part of the analog-to-digital converter (ADC) description.

  • adc_nbits: the number of bits of the ADC

  • adc_reference_voltage: the reference voltage in volts, that is, the maximum voltage the ADC can convert without saturating which is the voltage corresponding to 2**(adc_nbits-1)-1

  • adc_sampling_frequency, the sampling frequency in GHz

If the user wants to use an ADC for triggering but wants to keep the analog voltage waveforms or wants to use a different ADC for saving the channel data, the following properties can be used:

  • trigger_adc_nbits: the number of bits of the ADC for the trigger ADC

  • trigger_adc_reference_voltage: the reference voltage in volts for the trigger ADC

  • trigger_adc_sampling_frequency, the sampling frequency in GHz for the trigger ADC