The knock-on tail formations in fuel-ion velocity distribution functions by energetic alpha-particles (by the T(d,n) 4 He reaction) and protons (by the D(d,p)T and 3 He(d,p) 4 He reactions) are investigated by simultaneously solving the Boltzmann-Fokker-Planck (BFP) equations for deuteron, triton, 3 He, alpha-particle and proton in an ITER-like deuterium-tritium (DT) plasma admixed with a small amount of 3 He. As a result of the 3 He inclusion, fraction of the transferred energy from energetic ions to thermal deuterons and tritons via nuclear plus interference (NI) scattering is reduced. Owing to the NI scattering of the energetic protons by fuel-ions, the latters are knocked up to higher energies. The knocking-up effect of fuel ions is enhanced with increasing 3 He concentration. It is shown that if 3 He with relative concentration of 4.2 %, i.e. n 3He /n e = 0.042, is included in T e =20 keV, n e =9.5×10 19 m-3 plasma, the magnitude of the knock-on tail in deuteron distribution function in 300 keV~3 MeV energy range is reduced by about 15 % from the value when 3 He is not externally supplied. Such knock-on tail reduction also results in alternation of the non-Gaussian neutron emission spectrum with energies less than ~13 MeV and above ~15 MeV.
An effect of nuclear elastic scattering ͑NES͒ on the energy transfer to plasma ions and electrons during ͑a͒ neutral beam injection ͑NBI͒ and ͑b͒ ␣-particle heating operations is examined on the basis of the Boltzmann-Fokker-Planck ͑BFP͒ equation for a beam ion and an ␣-particle in deuterium-tritium thermonuclear plasmas. The BFP calculations show that the enhancement in the fraction of the NBI heating power deposited to ions due to NES becomes appreciable when the beam energy is larger than 1 MeV. How the NES effect is influenced by the plasma condition is discussed.
The γ-ray emission rate by 6 Li(d,p) 7 Li * , 7 Li * → 7 Li+γ reaction when 50∼250 keV proton beam is injected into 6 Li containing deuterium plasmas (n e ∼10 19 m −3 and T e = 1∼10 keV) is evaluated by simultaneously solving the Boltzmann-Fokker-Planck (BFP) equations for deuteron and proton. A possible experiment to verify the BFP simulations, e.g. knock-on tail effect on T(d,n) 4 He reaction rate coefficient and/or plasma diagnostics which utilize the tail formation in ion distribution function, is proposed.
In this work, energetic-ion confinement and loss due to energetic-ion driven magnetohydrodynamic modes are studied using comprehensive neutron diagnostics and orbit-following numerical simulations for the Large Helical Device (LHD). The neutron flux monitor is employed in order to obtain global confinement of energetic ions and two installed vertical neutron cameras (VNCs) viewing different poloidal cross-sections are utilized in order to measure the radial profile of energetic ions. A strong helically-trapped energetic-ion-driven resistive interchange mode (EIC) excited in relatively low-density plasma terminated high-temperature state in LHD. Changes in the 2 neutron emission profile due to the EIC excitation are clearly visualized by the VNCs. The reduction in the neutron signal for the helical ripple valley increases with EIC amplitude, which reaches approximately 50%. In addition to the EIC experiment, orbit-following simulations using the DELTA5D code with EIC fluctuations were performed to assess the energetic-ion transport and loss. Two-dimensional temporal evolution results show that the neutron emissivity at the helical ripple decreases significantly due to the EIC. The rapid reduction in neutron emissivity shows that the helically-trapped beam ions immediately escape from the plasma. The reduction in the VNC signals for the helical ripple valley and the total neutron emission rate increase with increasing EIC amplitude, as observed in the experiment. Calculated line-integrated neutron emission results show that the profile measured by VNC1 has one peak, whereas the profile measured by VNC2 has two peaks, as observed in the experiment. Although the neutron emission profile for VNC2 has a relatively wide peak compared with the experimental results, the significant decrease in neutron signal corresponding to the helical ripple valley was successfully reproduced.
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