Synthetic Diagnostics
Synthetic diagnostics compute what a real instrument would measure from a simulation, enabling apples-to-apples comparison between code and experiment.
Simulating the measurement
A simulation produces the full plasma state, but a diagnostic sees only a filtered, line-integrated, noise-corrupted projection of that state. A synthetic diagnostic is a forward model that takes the simulation output and computes the signal the real instrument would record, including its geometry, spatial and temporal resolution, and physics of the measurement process.
This closes the gap between simulation and experiment. Rather than comparing a local simulated temperature to a smeared, integrated measurement, the synthetic diagnostic renders the simulation the way the instrument would, so the comparison is fair.
Examples of the forward model
An interferometer synthetic integrates density along the chord; a Thomson-scattering synthetic applies the instrument function and photon statistics; a reflectometer synthetic models wave reflection from a cutoff layer; a magnetics synthetic evaluates the field at sensor locations. Each embeds the specific physics that maps plasma state to signal.
Two directions of use
Synthetic diagnostics validate codes by testing predictions against measurements on equal footing, and they support instrument design by predicting whether a planned diagnostic will resolve the quantity of interest. The latter feeds reconstruction studies that size the sensor set.
Design relevance
Because the Hyperion breeder is not yet built, synthetic diagnostics run against its design simulations to specify the diagnostic suite: which sensors, where, and with what resolution, so the machine will be measurable once it operates. This is design work preceding the Q2 2027 construction start.
- Forward model from plasma state to signal
- Makes code-experiment comparison fair
- Includes instrument geometry, resolution, noise
- Guides diagnostic design and sensor placement