AsianScientist (Jun. 16, 2015) – A group of researchers have successfully used the world’s largest laser to heat fusion fuel to 20,000,000°C. Their findings, published in Physical Review Letters, bring us one step closer to harnessing nuclear fusion for clean energy.
The group was led by Dr. Yoneyoshi Kitagawa, specially appointed professor, The Graduate School for the Creation of New Photonics Industries and Dr. Yasunobu Arikawa, instructor, Institute of Laser Engineering, Osaka University in cooperation with research institutes such as the High Power Laser Group Development Department at Hamamatsu Photonics and Toyota Motor Corporation, among others.
In their research, a pre-imploded core was predominantly heated by energetic ions driven by the Laser for Fast Ignition Experiment (LFEX), an extremely energetic ultra-short pulse laser. LFEX is also the world’s largest petawatt laser, located at Osaka University’s Institute of Laser Engineering.
An examination of the beam-fusion neutrons verified that the ions directly collide with the core plasma. While the hot electrons heated the whole core volume, the energetic ions deposited their energies locally in the core, forming hot spots for fuel ignition. As evidenced in the spectrum, the process simultaneously excited thermal neutrons with the yield, raising the local core temperature.
The researchers were successful in heating fusion fuel to a temperature of about 20,000,000°C. The group also set a new record in neutron yield through fast ignition, an advanced technique in laser fusion.
However, they noted that the core density was limited to 2 g/cm3 in the experiments conducted. The researchers hope to achieve a higher core density (>10 g/cm3) in future experiments, predicting that hot electrons could contribute more to the core heating via drag heating.
Together with hot electrons, the ion contribution to fast ignition is indispensable for realizing high-gain fusion. By virtue of its core heating and ignition, the proposed scheme can potentially achieve high gain fusion.
Nonetheless, the group has contributed to the knowledge on the ignition of fusion fuel and demonstrated the potential of fast ignition.
The article can be found at: Kitagawa et al. (2015) Direct Heating Of A Laser-Imploded Core By Ultraintense Laser-Driven Ions.
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Source: Osaka University.
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