`CELL_SIZE[d]` -> `cellSize[d]` 
and this does not work, since `particle_locationNow` is defined in `radiation/vector.hpp` and creates the following error:
```bash
/picongpu/src/picongpu/include/plugins/radiation/vector.hpp(86): error: qualifiers dropped in binding reference of type "picongpu::float_X &" to initializer of type "const picongpu::precision32Bit::float_X"
```