1 / 10

SOL and Limiter Configuration in HT-7 (for discussion)

SOL and Limiter Configuration in HT-7 (for discussion). Wan Baonian For the HT-7 Team. Outline. What is SOL? Elementary properties of SOL How does SOL affect RF coupling Suggestion for modification of the HT-7 limiter Conclusion. What is SOL?. SOL-Scrap of Layer Connection length

torgny
Download Presentation

SOL and Limiter Configuration in HT-7 (for discussion)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SOL and Limiter Configurationin HT-7(for discussion) Wan Baonian For the HT-7 Team

  2. Outline • What is SOL? • Elementary properties of SOL • How does SOL affect RF coupling • Suggestion for modification of the HT-7 limiter • Conclusion

  3. What is SOL? • SOL-Scrap of Layer • Connection length 2LC: the distance along a B-line in the SOL measured from one point of contact with a limiter to the next Single T-limiter: LC~Rq Single P-limiter: LC~R

  4. Properties of SOL & sheath • The total cross-field particle (energy) flux is balanced by the flux reaching to the limiter: n=(2DLC/cs)1/2 • Typically Bohm diffusion at the edg: Dbohm=0.6Te/B • Cross-field particle flux: Sp~nD/ n2 • Sheath at the limiter surface: Vsf~ 3Te • The limiter material affects the SOL through: secondary electron emission and ion backscatter distribution

  5. Properties of SOL & limiter • 通过径向输运的能量PT-PR将沉积到限制器上，但直接沉积到与等离子体相切的限制器面上的能量很小。绝大部分能量将进入SOL后经平行输运到达限制器侧表面。 • 环向限制器与等离子体不相切的面积充当了SOL区域，分散了热流密度。面积～2Rw or 2R/sin。 • 对极向限制器而言，热流密度集中在环向的两侧，面积<2r。 • 限制器的不连续造成复杂的SOL特性 环向限制器与等离子体相切的面积比极向限制器要大很多，并且对于等离子体水平位移不敏感。

  6. Properties of SOL & sheath • before top-bottom T-limiters : n~15-18mm Te~18mm e~ 8-10ms (OH) P~ 8-20ms • With top-bottom T-limiters : n~6-8mm (local) Te~??mm e~ 5-8ms(OH) P~ 4-8ms No detectable ion saturation current at r~29cm by Langmuir probes means extreme low density. The electron density at 28cm is one order lower than that at the limiter radius.

  7. How does SOL affect RF coupling • For LHCD, required density: nopt = N||2nc (at mouth of grill) In HT-7, fLHW=2.45GHz, nc~7.5 1016/m3, N||=2.35, nopt > 4.1 1017/m3, the optimised density is about 4 times the cut-off density which is 1.6x1018/m3. • For IBW, the mode transformation near ffpi=0.21(ni/A)1/2 Hz; at 30MHz, ni~4.1 1016/m3, at 27MHz, ni~3.3 1016/m3. When the density at the IBW antenna is lower, MT of EPW to IBW is sensitive to the density gradient scale length, hence to ponderomotive effects & parametric instabilities. There is a mode called the cold electrostatic ion cyclotron wave (CESICW) between H and ii (24-26.3MHz at 2T & H/(H+D)~20-30%). It is possible to couple directly to CESICW and then transform to IBW. • Heat load on the antenna, another big issue.

  8. Modification of the HT-7 limiter • Very small  between tile gap, hence enhanced local particle & heat sink, might cause strong local recycling. • Complicated SOL properties, hence nonuniform density at the antenna. • High capability of heat exhaust.

  9. Modification of the HT-7 limiter • Significantly extend Lc ~Rq/2 hence larger & more uniform  • Relative simple SOL properties, hence uniform density at the antenna. • Improved heat load density at end of the limiter. • Reduced limiter surface by a factor of 2/3, remains high capability of heat exhaust.

  10. Conclusion • Critism and more suggestion wanted.

More Related