Prime pagine RA2010FUS:Copia di Layout 1 - ENEA - Fusione

superconductivity (cont’d.)
progress report
2010
095
Intensity (Arb. units)
(0.04)
(0.05)
26 30 34 38 42
2θ(Deg)
*
795°C+10
795°C
750°C
725°C
700°C
550°C
Pyrolysed
Figure 4.10 – XRD analyses for the samples
quenched at different temperatures. Continuous line
represent the Ba(O,F) reflection, while dashed line
are the peak ascribable to the Y 2 Cu 2 O 5 phase. (004)
and (005) are two reflection of the YBCO film, while
* is a substrate feature
Pinning force density (GN/m3)
10 11 a)
10 9
10 7
(MOD)YBCO
82 K
65 K
77 K
10 5 0.1 1 10
Magnetic induction (T)
10 K
30 K
50 K
Critical current density (A/m 2 )
10 5 T=77 K
10 3
10 1
10 -1
10 -3
10- 5
Correlated
Isotropic
γ=4
4 T
6 T
8 T
-20 20 60 100
Angle (degree)
b)
Figure 4.11 – a) Pinning force
densities of pure YBCO (red)
and 10 mol. % YBCO–BZO
(blue) measured as a function
of the applied field at several
temperatures; b) critical
current density as a function
of the applied field direction
measured for 10 mol.%
YBCO–BZO at 77 K at different
field field intensity. The green
line represent the isotropic
contribution while the black
arrow shows the correlated
contribution at 0° and 8 T
0.5
0
-0.5
0.4
0.2
0
-0.2
Figure 4.12 – Map of the magnetic flux density axial component B z
in the plane of the coil generated by the actual copper coil and by
one of the proposed version of superconducting coil having the
same internal bore. Copper coil characteristics: I op = 8 kA, coil is a
stack of 8 layer connected in series. HTS coil: I op =100 A, coil is
obtained as a stack of 2 layer with 320 turns each
0.8
0.4
0
-0.4
films, even though a clear dependence of J c
(0) values on the BZO content cannot be established. The results,
as shown in figure 4.11, revealed an improvement in the pinning efficiency if compared with pure YBCO
samples, as evidenced by the upward shift of the irreversibility field value (from 6.8 T to 8 T) and the increase
in the maximum pinning force density (from 4.5 to 11.5 GN/m 3 ) measured at 77 K. This result is consistent
with the presence of the BZO nano–particles acting as additional pinning sources.
Conceptual design of YBCO coil for the toroidal magnetic system of ISTTOK tokamak
The aim of this activity is to evaluate the possibility of operating ISTTOK tokamak with a HTS toroidal
magnetic field, thus allowing a continuous operation in steady state. The feasibility of a tokamak operating
with HTS is extremely relevant and ISTTOK is the ideal candidate for a meaningful test in this sense, due to
its small size, the possibility to operate in a steady–state inductive operation and therefore at lower cost. A finite
element analysis has been carried out to calculate the distribution of magnetic field components. It is found
that the operation at 77 K with 0.45 Tesla field on plasma axis would require 17 km of 12 mm wide tape
commercially available today. In Figure 4.12 the maps of the magnetic flux density axial component as
obtained from numerical analysis for a single actual copper a) and HTS coil b) are plotted.