H. Hojo

S. Oikawa

T. Nagaura

T. Watanabe

Y. Itoh

Y. Matsumoto

National Institute for Fusion Science (NIFS-Repository)

§31. Proton-Boron Fusion Reactor of LHD Type Helical Magnetic Field Watanabe, T., Matsumoto, Y., Nagaura, T., Itoh, Y., Oikawa, S. (Hokkaido Univ.), Hojo, H. (Plasma Research Center, Univ. Tsukuba) Main branch of the p_11 B reaction is neutron free P +11 B --+ 3 4He + QF, (QF ~ 8.7MeV), but the endothermal side reaction p+11 B --+ n + 11C - 2.8MeV produce slow neutrons. Under ICRF heating III LHD, it is expected that there is no ultra-high energy proton though the proton distribution function has high energy plateau t ail. This situation is desirable for the highly efficient and neutron free fusion reactor. Then , we have studied the fusion reaction rate under the quasilinear plat eau distribution function(QLPLDF) for protons. N N S X 4.0 .----_....;.<...::.o....;.v....:..>-...;....FO.;;:,.:....:R....:..P....:..R..:...;;O;....T;....:°rN..:....-=B...::.0-'rR:....::O-'-N....:..R . E=A....:..Cr:-T-'-'-r0_N'-r-T""O 3.0 MAXWELLIAN ~ 2.0 en 1\ > b V 1.0 0.8 L..-.._i:.....L_L---L-__ --1-._--L_--L---:--l-:--.l....-.l....-J-...J 100 200 300 400 600 1,000 T P (KEV) Figure 1: Vertical axis is reaction rate for the p-ll B reaction and horizontal axis is proton temperature. Boron is assumed to be Maxwellian velocity distribution with temperature T B (= Tp or = Tp / 20). Proton is assumed to be quasilinear plateau distribution function (red line: QLPLDF) or Maxwellian(black line). T p is defined by eq.(2) for the case of quasilinear plateau distribution function. f(v) 206 1 E = -Mv 2 2 (2) where a = 1/1.92420··· and TeJ J = T x 0.959735· . '. The fusion reaction rate < Cl v > for p_11 B are obtained numerically based on the cross section data u [1] (Fig. 1 ). To study the most basic self sustained burning condi-tion, we have estimated a power balance relation between fusion power PF, proton temperature Tp, electron tem-perature TE, Bremsstrahlung loss PB and slowing down process of proton by electron drug. 3 1 1 PB = -NpTp- = -NpNB < Cl V > QF (TJ> 1) 2 TE TJ T?/2 TE ~ 0.5 X 1018_ e_ (sec) : T e(keV) N e PB ~ 4.71 X 10- 37 N e(Z1NB + N p)T; /2 where T E is proton energy loss time due to electron drug and TJ is the ratio between the fusion output power and the ICRF power, that is needed to sustain the proton temperature. The numerical results are shown in Fig.2. 2.0.-------------,------~--~--~--r-~~~~ 200 300 400 Tp (EV) Tp ITB =20 1,000 Figure 2: Vertical axis T) is the ratio between the p-ll B fusion output power and the ICRF power. Horizontal axis is proton tem-perature. Boron ' temperature TB is assumed to be Tp / 20. The density ratio between proton and boron is fixed to optimal value (n B / np = 0 .141858804· , . ) . Electron temperature T e is given by Te = 14.9819·· , x VTP, where Te and T p are in keV unit. This figure shows that the possibility of self sustained burning of p-ll B fusion, if proton is in quasilinear plateau distribution function. References [1] R. Feldbacher, INDC(AUS)-12/ G, verso 1 (IAEA In-ternational Nuclear Data Comittee, 1987). 

Proton-Boron Fusion Reactor of LHD Type Helical Magnetic Field

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