Effects of divertor geometry and pumping on plasma performance on DIII-D
- and others
This paper reports the status of an ongoing investigation to discern the influence of the divertor and plasma geometry on the confinement of both ELM-free and ELMing discharges in DIII-D. The ultimate goal is to achieve a high-performance core plasma which coexists with an advanced divertor plasma. The divertor plasma must reduce the heat flux to acceptable levels; the current technique disperses the heat flux over a wide area by radiation (a radiative divertor). To date, we have obtained our best performance in double-null (DN) high-triangularity ({delta} {approximately} 0.8) ELM-free discharges. As discussed in detail elsewhere, there are several advantages for both the core and divertor plasma with highly-shaped DN operation. Previous radiative-divertor experiments with D{sub 2} injection in DN high-{delta} ELMing H-mode have shown that this configuration is more sensitive to gas puffing ({tau} decreases). Moving the X-point away from the target plate (to {approximately}15 cm above the plate) decreases this sensitivity. Preliminary measurements also indicate that gas puffing reduces the divertor heat flux but does not reduce the plasma pressure along the field line. The up/down heat flux balance can be varied magnetically (by changing the distance between the separatrices), with a slight magnetic imbalance required to balance the heat flux. The overall mission of the Radiative Divertor Project (RDP) is to install a fully pumped and baffled high-{delta} DN divertor. To date, however, both the DIII-D divertor diagnostics and pump were optimized for lower single-null (LSN) low-{delta} ({delta}{approximately} 0.4) plasmas, so much of the divertor physics has been performed in LSN; these results are discussed in Section 2. As part of the first phase of the RDP, we have installed a new high-{delta} USN divertor baffle and pump; these results are discussed in Section 3. Both divertor and core parameters are discussed in each case.
- Research Organization:
- General Atomics, San Diego, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); California Univ., San Diego, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC03-89ER51114; AC05-96OR22464; AC04-94AL85000; FG03-95ER54294; W-7405-ENG-48
- OSTI ID:
- 513529
- Report Number(s):
- GA-A22646; CONF-9706131-17; ON: DE97007208; TRN: 97:014578
- Resource Relation:
- Conference: 24. EPS conference on controlled fusion and plasma physics, Berchtesgaden (Germany), 9-13 Jun 1997; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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