Function load_nexus_events 

pub fn load_nexus_events(
    path: &Path,
    params: &EventBinningParams,
) -> Result<NexusHistogramData, IoError>

Load neutron event data from a NeXus file and histogram into a 3D grid.

Reads /entry/neutrons/event_time_offset (u64), x (f64), y (f64), rescales TOF to the canonical internal unit of microseconds based on the event_time_offset dataset’s units attribute (issue #554), then bins events into a (n_bins, height, width) histogram grid.

TOF units handling (issue #554)

The loader consults the NeXus units attribute on the event_time_offset dataset and rescales the raw u64 channel counts to µs accordingly. See the module-level “Units convention” table for the recognised values. If the units attribute is absent, the loader falls back to the rustpix legacy assumption of nanoseconds (× 1e-3); if it is present but unrecognised, the call returns IoError::InvalidParameter rather than silently guessing a scale factor.

Binning behaviour (D-8)

• Out-of-range events are dropped and counted: events with TOF outside [tof_min_us, tof_max_us), pixel coordinates outside [0, width) / [0, height), or non-finite spatial coordinates are excluded. Per-category drop counts are returned in EventRetentionStats via NexusHistogramData::event_stats.
• Pixel coordinates are rounded to the nearest integer (f64::round() then cast to isize), snapping sub-pixel positions to a discrete grid. Fractional coordinates exactly at 0.5 round up.