Materials

Reusable material definitions for gprMax models. eccosorb.json contains the existing three-pole Debye fits for Eccosorb LS14, LS16, LS18, LS20, LS22, LS26, LS28 and LS30.

Files to use

Materials/
    eccosorb.json           # Material properties and Debye poles.
    eccosorb_slab.in        # Complete example using LS22.
    legacy/eccosorb.txt     # Original definitions for older models.

The JSON uses the original material names, such as eccosorb_ls22, so your geometry can keep those names. Every original coefficient is preserved. The text file is retained unchanged in legacy/.

Use a material in your model

Hash-command input

Copy eccosorb.json beside your input file. Load the required material with #material_from_database and use its name in your geometry:

#material_from_database: eccosorb eccosorb_ls22
#box: 0.010 0.010 0.022 0.038 0.038 0.028 eccosorb_ls22 n

Here eccosorb is the JSON filename without its extension, and eccosorb_ls22 is an entry inside it. These two lines belong in a complete model with a domain, discretisation, time window and excitation.

To update a model that used #include_file: .../eccosorb.txt, replace that line with one #material_from_database line for each grade your geometry uses. The JSON already includes all three Debye poles; no separate dispersion command is needed. Only the selected materials are loaded.

Python API

For a model built directly with the Python API, copy eccosorb.json into the directory from which you run Python. Add the material to your scene before using it in geometry:

import gprMax

# Add these to your scene after defining the domain, mesh and time window.
scene.add(gprMax.MaterialFromDatabase(
    database="eccosorb",
    material="eccosorb_ls22",
))
scene.add(gprMax.Box(
    p1=(0.010, 0.010, 0.022),
    p2=(0.038, 0.038, 0.028),
    material_id="eccosorb_ls22",
    averaging=False,
))

The direct API looks for a local database in the working directory, even if the output file is written elsewhere. For a hash-command model it looks beside the input file. See Material databases for local material aliases and the complete schema.

Run the example

From the repository root, in your gprMax Python environment:

mkdir -p materials_results
python -m gprMax gprMax/toolboxes/Materials/eccosorb_slab.in -o materials_results/eccosorb_slab

The editable slab example uses a 1 mm mesh, a 3 GHz Ricker source, and a receiver on the other side of a 6 mm thick LS22 slab. Change the material name in the material and box lines to try another grade. The comments separate the model settings, material, geometry, and excitation.

The output is materials_results/eccosorb_slab.h5. Read the receiver’s electric field and its time axis with:

import h5py
import numpy as np

with h5py.File("materials_results/eccosorb_slab.h5", "r") as output:
    ex = output["rxs/rx1/Ex"][...]
    time_s = np.arange(ex.size) * float(output.attrs["dt"])

This is a small example of loading a dispersive material and running a model. Its receiver signal includes propagation and diffraction around the finite slab; it is not a measurement of the material’s attenuation per unit length.

Inspect or edit the properties

List the entries or check the database without running a simulation:

python -m gprMax.toolboxes.MaterialDatabase list eccosorb --directory gprMax/toolboxes/Materials
python -m gprMax.toolboxes.MaterialDatabase validate eccosorb --directory gprMax/toolboxes/Materials

In each JSON entry, model is debye and base contains the infinite-frequency relative permittivity, electric conductivity in S/m, relative permeability, and magnetic conductivity in Ohm/m. Each item in poles contains a relative-permittivity increment and its relaxation time in seconds. The static relative permittivity is the base value plus the sum of the three increments. Loss is included in these poles even though the separate electric conductivity is zero.

Edit a project copy of the JSON when changing properties. Keep its filename and database.id consistent if you rename the database.

Fit reference

These are the original gprMax fits to manufacturer permittivity data, with the original comparison figures below. They have not been refitted to current product data. Current product information and datasheet downloads are available on the manufacturer’s Eccosorb LS page. The figures show the fit quality; check its suitability over your operating band.

Fig. 66 3-pole Debye fit for Eccosorb LS14 absorber (HN indicates data from manufacturer datasheet)

Fig. 67 3-pole Debye fit for Eccosorb LS16 absorber (HN indicates data from manufacturer datasheet)

Fig. 68 3-pole Debye fit for Eccosorb LS18 absorber (HN indicates data from manufacturer datasheet)

Fig. 69 3-pole Debye fit for Eccosorb LS20 absorber (HN indicates data from manufacturer datasheet)

Fig. 70 3-pole Debye fit for Eccosorb LS22 absorber (HN indicates data from manufacturer datasheet)

Fig. 71 3-pole Debye fit for Eccosorb LS26 absorber (HN indicates data from manufacturer datasheet)

Fig. 72 3-pole Debye fit for Eccosorb LS28 absorber (HN indicates data from manufacturer datasheet)

Fig. 73 3-pole Debye fit for Eccosorb LS30 absorber (HN indicates data from manufacturer datasheet)