diff --git a/gprMax/cython/geometry_outputs.pyx b/gprMax/cython/geometry_outputs.pyx
index f93c58d4..df074aee 100644
--- a/gprMax/cython/geometry_outputs.pyx
+++ b/gprMax/cython/geometry_outputs.pyx
@@ -45,7 +45,7 @@ cpdef get_line_properties(
             material IDs for each line.
     """
     cdef np.ndarray material_data = np.zeros(number_of_lines, dtype=np.uint32)
-    cdef np.ndarray connectivity = np.zeros(2 * number_of_lines, dtype=np.intc)
+    cdef np.ndarray connectivity = np.zeros(2 * number_of_lines, dtype=np.int32)
     cdef int line_index = 0
     cdef int connectivity_index = 0
     cdef int point_id = 0
diff --git a/gprMax/geometry_outputs.py b/gprMax/geometry_outputs.py
index 3416e8cb..9f971568 100644
--- a/gprMax/geometry_outputs.py
+++ b/gprMax/geometry_outputs.py
@@ -101,9 +101,9 @@ class GeometryView(ABC):
             grid: FDTDGrid class describing a grid in a model.
         """
 
-        self.start = np.array([xs, ys, zs], dtype=np.intc)
-        self.stop = np.array([xf, yf, zf], dtype=np.intc)
-        self.step = np.array([dx, dy, dz], dtype=np.intc)
+        self.start = np.array([xs, ys, zs], dtype=np.int32)
+        self.stop = np.array([xf, yf, zf], dtype=np.int32)
+        self.step = np.array([dx, dy, dz], dtype=np.int32)
         self.size = (self.stop - self.start) // self.step
 
         self.filename = Path(filename)
@@ -224,7 +224,7 @@ class GeometryViewLines(GeometryView):
         n_lines = 3 * self.nx * self.ny * self.nz
 
         self.cell_types = np.full(n_lines, VtkCellType.LINE)
-        self.cell_offsets = np.arange(0, 2 * n_lines + 2, 2, dtype=np.intc)
+        self.cell_offsets = np.arange(0, 2 * n_lines + 2, 2, dtype=np.int32)
 
         self.connectivity, self.material_data = get_line_properties(
             n_lines, self.nx, self.ny, self.nz, ID
@@ -330,7 +330,7 @@ class Metadata:
 
         self.gprmax_version = __version__
         self.dx_dy_dz = self.grid.dl
-        self.nx_ny_nz = np.array([self.grid.nx, self.grid.ny, self.grid.nz], dtype=np.intc)
+        self.nx_ny_nz = np.array([self.grid.nx, self.grid.ny, self.grid.nz], dtype=np.int32)
 
         self.materials = self.materials_comment()
 
@@ -427,8 +427,8 @@ class Metadata:
     def dx_dy_dz_comment(self) -> npt.NDArray[np.float64]:
         return self.grid.dl
 
-    def nx_ny_nz_comment(self) -> npt.NDArray[np.intc]:
-        return np.array([self.grid.nx, self.grid.ny, self.grid.nz], dtype=np.intc)
+    def nx_ny_nz_comment(self) -> npt.NDArray[np.int32]:
+        return np.array([self.grid.nx, self.grid.ny, self.grid.nz], dtype=np.int32)
 
     def materials_comment(self) -> List[str]:
         if not self.averaged_materials:
diff --git a/gprMax/grid/mpi_grid.py b/gprMax/grid/mpi_grid.py
index 88797a22..c3e3d1a8 100644
--- a/gprMax/grid/mpi_grid.py
+++ b/gprMax/grid/mpi_grid.py
@@ -57,7 +57,7 @@ class MPIGrid(FDTDGrid):
     COORDINATOR_RANK = 0
 
     def __init__(self, comm: MPI.Cartcomm):
-        self.size = np.zeros(3, dtype=np.intc)
+        self.size = np.zeros(3, dtype=np.int32)
 
         self.comm = comm
         self.x_comm = comm.Sub([False, True, True])
@@ -65,12 +65,12 @@ class MPIGrid(FDTDGrid):
         self.z_comm = comm.Sub([True, True, False])
         self.pml_comm = MPI.COMM_NULL
 
-        self.mpi_tasks = np.array(self.comm.dims, dtype=np.intc)
+        self.mpi_tasks = np.array(self.comm.dims, dtype=np.int32)
 
-        self.lower_extent = np.zeros(3, dtype=np.intc)
-        self.upper_extent = np.zeros(3, dtype=np.intc)
+        self.lower_extent = np.zeros(3, dtype=np.int32)
+        self.upper_extent = np.zeros(3, dtype=np.int32)
         self.negative_halo_offset = np.zeros(3, dtype=np.bool_)
-        self.global_size = np.zeros(3, dtype=np.intc)
+        self.global_size = np.zeros(3, dtype=np.int32)
 
         self.neighbours = np.full((3, 2), -1, dtype=int)
         self.neighbours[Dim.X] = self.comm.Shift(direction=Dim.X, disp=1)
@@ -164,7 +164,7 @@ class MPIGrid(FDTDGrid):
         """
         return self.rank == self.COORDINATOR_RANK
 
-    def get_grid_coord_from_coordinate(self, coord: npt.NDArray[np.intc]) -> npt.NDArray[np.intc]:
+    def get_grid_coord_from_coordinate(self, coord: npt.NDArray[np.int32]) -> npt.NDArray[np.int32]:
         """Get the MPI grid coordinate for a global grid coordinate.
 
         Args:
@@ -224,8 +224,8 @@ class MPIGrid(FDTDGrid):
         return [coord_to_rank(coord) for coord in np.ndindex(*(stop - start))]
 
     def global_to_local_coordinate(
-        self, global_coord: npt.NDArray[np.intc]
-    ) -> npt.NDArray[np.intc]:
+        self, global_coord: npt.NDArray[np.int32]
+    ) -> npt.NDArray[np.int32]:
         """Convert a global grid coordinate to a local grid coordinate.
 
         The returned coordinate will be relative to the current MPI
@@ -240,7 +240,9 @@ class MPIGrid(FDTDGrid):
         """
         return global_coord - self.lower_extent
 
-    def local_to_global_coordinate(self, local_coord: npt.NDArray[np.intc]) -> npt.NDArray[np.intc]:
+    def local_to_global_coordinate(
+        self, local_coord: npt.NDArray[np.int32]
+    ) -> npt.NDArray[np.int32]:
         """Convert a local grid coordinate to a global grid coordinate.
 
         Args:
@@ -252,7 +254,7 @@ class MPIGrid(FDTDGrid):
         return local_coord + self.lower_extent
 
     def global_coord_inside_grid(
-        self, global_coord: npt.NDArray[np.intc], allow_inside_halo: bool = False
+        self, global_coord: npt.NDArray[np.int32], allow_inside_halo: bool = False
     ) -> bool:
         """Check if a global coordinate falls with in the local grid.
 
@@ -277,7 +279,7 @@ class MPIGrid(FDTDGrid):
         return all(global_coord >= lower_bound) and all(global_coord <= upper_bound)
 
     def global_bounds_overlap_local_grid(
-        self, start: npt.NDArray[np.intc], stop: npt.NDArray[np.intc]
+        self, start: npt.NDArray[np.int32], stop: npt.NDArray[np.int32]
     ) -> bool:
         local_start = self.global_to_local_coordinate(start)
         local_stop = self.global_to_local_coordinate(stop)
@@ -285,10 +287,10 @@ class MPIGrid(FDTDGrid):
 
     def limit_global_bounds_to_within_local_grid(
         self,
-        start: npt.NDArray[np.intc],
-        stop: npt.NDArray[np.intc],
-        step: npt.NDArray[np.intc] = np.ones(3, dtype=np.intc),
-    ) -> Tuple[npt.NDArray[np.intc], npt.NDArray[np.intc], npt.NDArray[np.intc]]:
+        start: npt.NDArray[np.int32],
+        stop: npt.NDArray[np.int32],
+        step: npt.NDArray[np.int32] = np.ones(3, dtype=np.int32),
+    ) -> Tuple[npt.NDArray[np.int32], npt.NDArray[np.int32], npt.NDArray[np.int32]]:
         local_start = self.global_to_local_coordinate(start)
 
         # Bring start into the local grid (and not in the negative halo)
@@ -801,7 +803,7 @@ class MPIGrid(FDTDGrid):
         if p[2] < 0 or p[2] > self.gz:
             raise ValueError("z")
 
-        local_point = self.global_to_local_coordinate(np.array(p, dtype=np.intc))
+        local_point = self.global_to_local_coordinate(np.array(p, dtype=np.int32))
 
         return all(local_point >= self.negative_halo_offset) and all(local_point <= self.size)
 
diff --git a/gprMax/mpi_model.py b/gprMax/mpi_model.py
index 72aee350..73da3c28 100644
--- a/gprMax/mpi_model.py
+++ b/gprMax/mpi_model.py
@@ -74,8 +74,8 @@ class MPIModel(Model):
         self.geometryobjects = []
 
         for go in objects:
-            start = np.array([go.xs, go.ys, go.zs], dtype=np.intc)
-            stop = np.array([go.xf, go.yf, go.zf], dtype=np.intc)
+            start = np.array([go.xs, go.ys, go.zs], dtype=np.int32)
+            stop = np.array([go.xf, go.yf, go.zf], dtype=np.int32)
             if self.G.global_bounds_overlap_local_grid(start, stop):
                 comm = self.comm.Split()
                 assert isinstance(comm, MPI.Intracomm)
@@ -83,7 +83,7 @@ class MPIModel(Model):
                 stop_grid_coord = self.G.get_grid_coord_from_coordinate(stop) + 1
                 go.comm = comm.Create_cart((stop_grid_coord - start_grid_coord).tolist())
 
-                go.global_size = np.array([go.nx, go.ny, go.nz], dtype=np.intc)
+                go.global_size = np.array([go.nx, go.ny, go.nz], dtype=np.int32)
                 start, stop, offset = self.G.limit_global_bounds_to_within_local_grid(start, stop)
                 go.size = stop - start
                 go.start = start
diff --git a/gprMax/receivers.py b/gprMax/receivers.py
index 467f94fa..f27dae23 100644
--- a/gprMax/receivers.py
+++ b/gprMax/receivers.py
@@ -31,8 +31,8 @@ class Rx:
     def __init__(self):
         self.ID: str
         self.outputs = {}
-        self.coord = np.zeros(3, dtype=np.intc)
-        self.coordorigin = np.zeros(3, dtype=np.intc)
+        self.coord = np.zeros(3, dtype=np.int32)
+        self.coordorigin = np.zeros(3, dtype=np.int32)
 
     @property
     def xcoord(self) -> int:
diff --git a/gprMax/snapshots.py b/gprMax/snapshots.py
index 48e93770..976f2eec 100644
--- a/gprMax/snapshots.py
+++ b/gprMax/snapshots.py
@@ -130,10 +130,10 @@ class Snapshot:
         self.grid_dl = grid_dl
         self.grid_dt = grid_dt
 
-        self.start = np.array([xs, ys, zs], dtype=np.intc)
-        self.stop = np.array([xf, yf, zf], dtype=np.intc)
-        self.step = np.array([dx, dy, dz], dtype=np.intc)
-        self.size = np.ceil((self.stop - self.start) / self.step).astype(np.intc)
+        self.start = np.array([xs, ys, zs], dtype=np.int32)
+        self.stop = np.array([xf, yf, zf], dtype=np.int32)
+        self.step = np.array([dx, dy, dz], dtype=np.int32)
+        self.size = np.ceil((self.stop - self.start) / self.step).astype(np.int32)
         self.slice: list[slice] = list(map(slice, self.start, self.stop + self.step, self.step))
 
         self.nbytes = 0
@@ -365,14 +365,14 @@ class MPISnapshot(Snapshot):
             xs, ys, zs, xf, yf, zf, dx, dy, dz, time, filename, fileext, outputs, grid_dl, grid_dt
         )
 
-        self.offset = np.zeros(3, dtype=np.intc)
+        self.offset = np.zeros(3, dtype=np.int32)
         self.global_size = self.size.copy()
 
         self.comm: MPI.Cartcomm = None  # type: ignore
 
     def initialise_snapfields(self):
         # Start and stop may have changed since initialisation
-        self.size = np.ceil((self.stop - self.start) / self.step).astype(np.intc)
+        self.size = np.ceil((self.stop - self.start) / self.step).astype(np.int32)
         return super().initialise_snapfields()
 
     def has_neighbour(self, dimension: Dim, direction: Dir) -> bool:
diff --git a/gprMax/sources.py b/gprMax/sources.py
index 9a55017d..1ed6782d 100644
--- a/gprMax/sources.py
+++ b/gprMax/sources.py
@@ -33,8 +33,8 @@ class Source:
     def __init__(self):
         self.ID: str
         self.polarisation = None
-        self.coord = np.zeros(3, dtype=np.intc)
-        self.coordorigin = np.zeros(3, dtype=np.intc)
+        self.coord = np.zeros(3, dtype=np.int32)
+        self.coordorigin = np.zeros(3, dtype=np.int32)
         self.start = 0.0
         self.stop = 0.0
         self.waveform: Waveform
diff --git a/gprMax/vtkhdf_filehandlers/vtk_image_data.py b/gprMax/vtkhdf_filehandlers/vtk_image_data.py
index 9cc44622..0d2b3137 100644
--- a/gprMax/vtkhdf_filehandlers/vtk_image_data.py
+++ b/gprMax/vtkhdf_filehandlers/vtk_image_data.py
@@ -29,7 +29,7 @@ class VtkImageData(VtkHdfFile):
     def __init__(
         self,
         filename: Union[str, PathLike],
-        shape: npt.NDArray[np.intc],
+        shape: npt.NDArray[np.int32],
         origin: Optional[npt.NDArray[np.float32]] = None,
         spacing: Optional[npt.NDArray[np.float32]] = None,
         direction: Optional[npt.NDArray[np.float32]] = None,
@@ -68,11 +68,11 @@ class VtkImageData(VtkHdfFile):
         if len(shape) > self.DIMENSIONS:
             raise ValueError(f"Shape must not have more than {self.DIMENSIONS} dimensions.")
         elif len(shape) < self.DIMENSIONS:
-            shape = np.concatenate((shape, np.ones(self.DIMENSIONS - len(shape), dtype=np.intc)))
+            shape = np.concatenate((shape, np.ones(self.DIMENSIONS - len(shape), dtype=np.int32)))
 
         self.shape = shape
 
-        whole_extent = np.zeros(2 * self.DIMENSIONS, dtype=np.intc)
+        whole_extent = np.zeros(2 * self.DIMENSIONS, dtype=np.int32)
         whole_extent[1::2] = self.shape
         self._set_root_attribute(self.WHOLE_EXTENT_ATTR, whole_extent)
 
@@ -89,7 +89,7 @@ class VtkImageData(VtkHdfFile):
         self.set_direction(direction)
 
     @property
-    def whole_extent(self) -> npt.NDArray[np.intc]:
+    def whole_extent(self) -> npt.NDArray[np.int32]:
         return self._get_root_attribute(self.WHOLE_EXTENT_ATTR)
 
     @property
@@ -141,7 +141,7 @@ class VtkImageData(VtkHdfFile):
         self._set_root_attribute(self.DIRECTION_ATTR, direction)
 
     def add_point_data(
-        self, name: str, data: npt.NDArray, offset: Optional[npt.NDArray[np.intc]] = None
+        self, name: str, data: npt.NDArray, offset: Optional[npt.NDArray[np.int32]] = None
     ):
         """Add point data to the VTKHDF file.
 
@@ -163,7 +163,7 @@ class VtkImageData(VtkHdfFile):
         return super().add_point_data(name, data, points_shape, offset)
 
     def add_cell_data(
-        self, name: str, data: npt.NDArray, offset: Optional[npt.NDArray[np.intc]] = None
+        self, name: str, data: npt.NDArray, offset: Optional[npt.NDArray[np.int32]] = None
     ):
         """Add cell data to the VTKHDF file.
 
diff --git a/gprMax/vtkhdf_filehandlers/vtk_unstructured_grid.py b/gprMax/vtkhdf_filehandlers/vtk_unstructured_grid.py
index 095bd1b1..fa4a687e 100644
--- a/gprMax/vtkhdf_filehandlers/vtk_unstructured_grid.py
+++ b/gprMax/vtkhdf_filehandlers/vtk_unstructured_grid.py
@@ -101,20 +101,20 @@ class VtkUnstructuredGrid(VtkHdfFile):
     @property
     def number_of_cells(self) -> int:
         number_of_cells = self._get_root_dataset(self.Dataset.NUMBER_OF_CELLS)
-        return np.sum(number_of_cells, dtype=np.intc)
+        return np.sum(number_of_cells, dtype=np.int32)
 
     @property
     def number_of_connectivity_ids(self) -> int:
         number_of_connectivity_ids = self._get_root_dataset(self.Dataset.NUMBER_OF_CONNECTIVITY_IDS)
-        return np.sum(number_of_connectivity_ids, dtype=np.intc)
+        return np.sum(number_of_connectivity_ids, dtype=np.int32)
 
     @property
     def number_of_points(self) -> int:
         number_of_points = self._get_root_dataset(self.Dataset.NUMBER_OF_POINTS)
-        return np.sum(number_of_points, dtype=np.intc)
+        return np.sum(number_of_points, dtype=np.int32)
 
     def add_point_data(
-        self, name: str, data: npt.NDArray, offset: Optional[npt.NDArray[np.intc]] = None
+        self, name: str, data: npt.NDArray, offset: Optional[npt.NDArray[np.int32]] = None
     ):
         """Add point data to the VTKHDF file.
 
@@ -143,7 +143,7 @@ class VtkUnstructuredGrid(VtkHdfFile):
         return super().add_point_data(name, data, shape, offset)
 
     def add_cell_data(
-        self, name: str, data: npt.NDArray, offset: Optional[npt.NDArray[np.intc]] = None
+        self, name: str, data: npt.NDArray, offset: Optional[npt.NDArray[np.int32]] = None
     ):
         """Add cell data to the VTKHDF file.
 
diff --git a/gprMax/vtkhdf_filehandlers/vtkhdf.py b/gprMax/vtkhdf_filehandlers/vtkhdf.py
index dab3f676..1c29da83 100644
--- a/gprMax/vtkhdf_filehandlers/vtkhdf.py
+++ b/gprMax/vtkhdf_filehandlers/vtkhdf.py
@@ -185,8 +185,8 @@ class VtkHdfFile(AbstractContextManager):
         self,
         name: "VtkHdfFile.Dataset",
         data: npt.ArrayLike,
-        shape: Optional[npt.NDArray[np.intc]] = None,
-        offset: Optional[npt.NDArray[np.intc]] = None,
+        shape: Optional[npt.NDArray[np.int32]] = None,
+        offset: Optional[npt.NDArray[np.int32]] = None,
         xyz_data_ordering=True,
     ):
         """Write specified dataset to the root group of the VTKHDF file.
@@ -211,8 +211,8 @@ class VtkHdfFile(AbstractContextManager):
         self,
         path: str,
         data: npt.ArrayLike,
-        shape: Optional[npt.NDArray[np.intc]] = None,
-        offset: Optional[npt.NDArray[np.intc]] = None,
+        shape: Optional[npt.NDArray[np.int32]] = None,
+        offset: Optional[npt.NDArray[np.int32]] = None,
         dtype: Optional[npt.DTypeLike] = None,
         xyz_data_ordering=True,
     ):
@@ -301,8 +301,8 @@ class VtkHdfFile(AbstractContextManager):
         self,
         name: str,
         data: npt.NDArray,
-        shape: Optional[npt.NDArray[np.intc]] = None,
-        offset: Optional[npt.NDArray[np.intc]] = None,
+        shape: Optional[npt.NDArray[np.int32]] = None,
+        offset: Optional[npt.NDArray[np.int32]] = None,
     ):
         """Add point data to the VTKHDF file.
 
@@ -321,8 +321,8 @@ class VtkHdfFile(AbstractContextManager):
         self,
         name: str,
         data: npt.NDArray,
-        shape: Optional[npt.NDArray[np.intc]] = None,
-        offset: Optional[npt.NDArray[np.intc]] = None,
+        shape: Optional[npt.NDArray[np.int32]] = None,
+        offset: Optional[npt.NDArray[np.int32]] = None,
     ):
         """Add cell data to the VTKHDF file.
 
@@ -341,8 +341,8 @@ class VtkHdfFile(AbstractContextManager):
         self,
         name: str,
         data: npt.ArrayLike,
-        shape: Optional[npt.NDArray[np.intc]] = None,
-        offset: Optional[npt.NDArray[np.intc]] = None,
+        shape: Optional[npt.NDArray[np.int32]] = None,
+        offset: Optional[npt.NDArray[np.int32]] = None,
         dtype: Optional[npt.DTypeLike] = None,
     ):
         """Add field data to the VTKHDF file.