The following may be helpful in understanding the conversion of electricity to laser light and various derivations of "wall plug efficiency" printed after the December 5, 2022 breakeven fusion shot.
Engineering breakeven in a laser inertial fusion setup – net electrical power generation – is achieved approximately[a] when the fusion gain multiplied by the drive laser efficiency equals 1. In the case of the December 5 breakeven shot, 1.5 × 0.0066 = 1% (roughly). This is why commentators have stated it needs to gain two orders of magnitude somewhere to become a meaningful fusion power source.[2]
However, note that the report cited below also says that one order of magnitude improvement can be made by replacing the flashlamps with diodes for laser pumping,[b] and a more-or-less complete redesign can result in 20x gain over the original NIF design. So maybe "just" another order of magnitude improvement in fusion gain is required.[c]
NIF drive laser efficiency
editThe report where this table appeared used the term "drive laser efficiency" which appears to be interchangeable with the definition at wall-plug efficiency.
The "lamp-pumped" column is for the current (as of 2022) NIF design using flashlamp pumping. The "diodes" column is for an upgrade using laser diodes instead, making it a diode-pumped solid-state laser.
| Item | NIF (3 ω) lamp-pumped | NIF (3 ω) & diodes |
|---|---|---|
| Power conditioning | 82 | 88 |
| Diodes/Lamps | 50 | 60 |
| Pump transport | 63 | 98 |
| Absorption | 40 | 98 |
| Quantum defect | 60 | 83 |
| 1-(decay fraction)[d] | 45 | 50 |
| Extraction, fill & 1 ω | 37 | 37 |
| Freq. conv & 3 ω transport | 64 | 64 |
| Total efficiency (%) | 0.66 | 5.0 |
Notes
edit- ^ order of magnitude, ignoring heat/electricity conversion and tritium breeder blanket gain; see fusion tutorial[1] slide 15 for full equation
- ^ see Mercury laser
- ^ Two more orders of magnitude in fusion gain with existing technology are discussed in the fusion tutorial.[1]
- ^ Includes spontaneous emission, amplified spontaneous emission, and non-radiative decay processes in the Nd:glass lasing medium prior to shot
References
editSources
edit- Caird, John; Agrawal, Vivek; Bayramian, A.; Beach, Ray; Britten, Jerry; Chen, Diana; Cross, Robert; Ebbers, Christopher; Erlandson, A.; Feit, Michael; Freitas, Barry; Ghosh, Chuni; Haefner, Constantin; Homoelle, Doug; Ladran, Tony; Latkowski, Jeff; Molander, William; Murray, John; Rubenchik, Sasha; Barty, Christopher (August 2009), "Nd:Glass Laser Design for Laser ICF Fission Energy (LIFE)" (PDF), Fusion Science and Technology, 56 (2): 607–617, doi:10.13182/FST18-P8031, section 7, "Drive laser efficiency", table 2: 7
- Betti, R. (2011). "Tutorial on the Physics of Inertial Confinement Fusion for energy applications" (PDF).
Gains > 100 are predicted for shock and fast ignition for driver energies of about 1MJ (slide 24)
3rd Meeting of the NAS panel on Inertial Fusion Energy Systems, Albuquerque, NM, March 29-April 1, 2011 - "Department of Energy announces successful nuclear fusion ignition". Official website. International Committee of the Fourth International. December 16, 2022.