A. Oda

A. Sagara

J. Miyazawa

K. Yamazaki

K.Y. Watanabe

O. Mitarai

O. Motojima

S. Imagawa

National Institute for Fusion Science (NIFS-Repository)

3.5x0.6.6X •0 t'J•X t'J A0 •X t'J •2.5'YHH1.8 10. 06 10205 1020••':'e 41020 •C 03 10. 02 10. 00.20.150.1•D •0.05 X D A0 X D •0 x D A.01.5 2.5 3.5'YHH0.03- 0.020.040.01Fig.2. Ignition characteristics in the FFHR with R=15 mhas a large influence on ignition. Therefore, it isimportant to study how much fraction of the highenergy alpha particle is confined. It should beevaluated the point where the alpha loss takesplace and how much is lost in order to estimate theheat flux to the first wall accurately.In addition, it may be possible that the bootstrapcurrent of 1 MA appears in these FFHR demoand commercial reactors. Therefore, itsinfluence on the high energy particle confinementshould be taken into account.Although it is necessary to know the magneticfield profile in a helical system, it is a timeconsuming to calculate the magnetic fieldconfiguration in each case with the different coilsize. If the size similarity is taken into accountbased on the present LHD system (R=3.9 m, a=0.6m and Bo=3 T), it is relatively easier to calculatethe magnetic field profile and the maximum fieldin a LHD type magnetic field configuration. Inthis respect, the physics design can be donerelatively simply for FFHR reactors with themajor radius of R= 10m with the 2.5 times and R=15 m with 4 times larger than that in the LHDsystem. Further detailed studies are needed withcollaboration.3.410'0 ........ ........--r-.......--......,-....._............,fig.I. ignition characteristics in the .b'.b'Hi{ with 1{=lU m2.6 10. 0'eC 2.2 10. 03 1020§ 1. Optimization of the Burning Plasmain Helical ReactorsWe have surveyed physics plasma parametersincluding the machine size in order to optimize theignited plasmas in FFHR reactors. Although"optimization in a helical reactor is acontroversial problem, for achieving the large Qvalue (Q=PIP EXT= fusion power/heating power)and ignition, we have conducted the sensitivityanalysis of the plasma parameter on the machinesize Ria, the magnetic field strength Bo, theconfinement enhancement factor YHH over theISS95 scaling, and alpha particle confinementfraction lla (=0. 1.0).We have used the following two reactors:[1] FFHR power generation demo-reactor withR=10 m, a=1.0 m, Bo=10 T, and PF1 GW,[2] FFHR commercial reactor with R=15 m,a=1.8 m, Bo= 6 T and P F 3 GW.In this calculation, the heating power is applied soas to keep the density limit over the operatingdensity based on the LHD experiments.In Fig.1 are shown the dependencies of theoperation density and the inverse Q on theconfinement enhancement factor for FFHRdemo-reactor with R=10 m, a=1.0 m and Bo=10 T,for lla=O. 1.0 (Alpha confinement fraction isshown in Fig. I) and PFI GW. As the magneticfield strength is large in FFHR demo-reactor, theconfinement time is long and hence ignition ispossible. The confinement factor YHH (x-axis)required for this reactor is only slightly larger than1.6 achieved in LHD. It has been seen that therequired confinement factor for ignition stronglydepends on the confinement fraction of highenergy alpha particles (the prompt alpha lossfraction). As the FFHR demo-reactor is compact,the high density operation around 1020 m-3should be done to obtain 1 GW. As the highdensity plasma of 3x102o m-3 has been alreadyachieved in W7-AX, such high density of1020 m-3might be possible in the FFHRdemo-reactor.In Fig.2 are shown the dependencies of theoperation density and the inverse Q on theconfinement enhancement factor for the FFHRcommercial reactor with R=15 m, a=1.8 m andBo=6 T for andPF 3GW. Althoughthe magnetic field strength is weaker, it is possibleto operate in the low density of 3x 1020 m-3because the confinement time itself is long due tothe large machine size. It is also seen that thehigh energy alpha particle confinement fractionMitarai, O. (Kyushu Tokai University), Oda, A.(Yatsushiro National College of Technology),Sagara, A., Yamazaki, K., Watanabe, K.Y.,Imagawa, S., Miyazawa, J., Motojima, O.243

Optimization of the Burning Plasma in Helical Reactors

Optimization of the Burning Plasma in Helical Reactors

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