Progress toward Fusion Energy Breakeven and Gain as Measured against the Lawson Criterion

The Lawson criterion is a key concept in the pursuit of fusion energy, relating the fuel density n, (en- ergy) confinement time τ, and fuel temperature T to the energy gain Q of a fusion plasma. The purpose of this paper is to explain and review the Lawson crite- rion and to provide a compilation of achieved parame- ters for a broad range of historical and contemporary fusion experiments. Although this paper focuses on the Lawson criterion, it is only one of many equally impor- tant factors in assessing the progress and ultimate like- lihood of any fusion concept becoming a commercially viable fusion energy system. Only experimentally mea- sured or inferred values of n, τ, and T that have been published in the peer-reviewed literature are included in this paper. For extracting these parameters, we dis- cuss methodologies that are necessarily specific to dif- ferent fusion approaches (including magnetic, inertial, and magneto-inertial fusion). This paper is intended to serve as a reference for fusion researchers and a tutorial for all others interested in fusion energy.