JAEA-Conf 2011-002 - 日本原子力研究開発機構

fslp at Teff = 593 keV and neff = 2.46 × 10 16 m -3 ,
especially in the energy range of 0.5- 2 MeV (See
).
shows a correlation between plasma
temperature T and Teff. As T rises, the fraction of αparticles
at energy above 3.5 MeV increases, which
allows α knock-on tritons to have high energy even
above 4 MeV. As a result, when T rises from 10- to
50 keV, Teff increases monotonically.
The γ-ray yield Y0.981 found for T = 1050 keV and nLi /nT = 1 % are plotted in . We can see
that the emission of 0.981-MeV γ-rays is dominated by the knock-on tritons; the roles of other
energetic or thermal tritons can be ignored. In other words, the 0.981-MeV -line clearly reflects the
presence of the knock-on tritons.
It is interesting to compare the -ray flux predicted here with that from other diagnostic processes.
We choose the 9 Be (,n1) 12 C * reaction, which generates 4.44-MeV photons and has been vigorously used
for energetic particle diagnostics in JET plasma experiments. 1316 Under the plasma conditions considered
here, nBe / nT = 1 % and T = 20 keV the 9 Be (,n1) reaction yield was estimated to be Y4.44 ~ 410 10 m -3 s -1 .
At the same time, Fig. 5 shows that the yield Y0.981 is at the level of 710 10 m -3 s -1 , proving to be twice
higher. Thus, the 0.981-MeV -ray flux is not small, and the 6 Fig. 4. Correlation between plasma temperature T
and effective knock-on triton temperature Teff. Li (t,p1) reaction may be considered for
plasma diagnostics in machines of next generation. However, detection of the 0.981-MeV -signal would
be more difficult than 4.44-MeV γ-rays because of unfavorable background condition in the range of
low low-energy energy photons.
Fig. 5. 0.981-MeV -ray yields calculated for
n Li/n T = 1 %.
JAEA-Conf 2011-002
Fig. 6. Emission spectrum of the 0.981-MeV -rays in the
case of T = 20 keV and n D = n T = n e/2 = 0.510 20 m -3
together with Gaussian function fitting.
The emission spectrum of the 0.981-MeV -rays, dY / dE, is determined by the spectrum of 8 Li *
ions produced in the 6 Li (t, p1) 8 Li * reaction. The function dY /dE calculated for T = 20 keV and nd = nt
= ne /2 = 0.5 10 20 m -3 is shown in . The full width of half-maximum of this spectrum is estimated
to be 18 keV. This broadening reflects the 8 Li * spectrum which in turn is governed by the shape of the
energy distribution of the knock-on tritons.