Transport and Fluctuations in High Temperature Spheromak Plasmas
Globally coherent magnetic fluctuations often observed during the driven phase after spheromak formation in the Sustained Spheromak Physics Experiment (SSPX) can be reduced to small amplitude by programming the magnetic flux = {Psi}{sub gun} and the discharge current = I{sub gun} in the formation gun. Scanning the edge normalized current = {lambda}{sub edge} = {lambda}{sub gun} = {mu}{sub 0}I{sub gun}/{Psi}{sub gun} above and below the minimum energy eigenvalue = {lambda}{sub FC} of the flux conserver provides a variation in the internal q = safety factor profile producing the expected q = m/n = poloidal/toroidal mode spectrum. By driving the edge with the proper {lambda}{sub gun}, the system can be operated with the poloidal/toroidal mode spectrum between the m/n = 1/2 and 2/3 modes producing low magnetic fluctuation amplitudes and high electron temperature = T{sub e} > 350 eV. Transport and confinement parameters calculated using Thomson scattering-measured T{sub e} and N{sub e} profiles coupled with the equilibrium code internal current profiles show a reduction in electron thermal diffusivity as T{sub e} increases. This scaling behavior is more classical-like than Bohm or open field line transport models where thermal diffusivity increases with T{sub e}. Electron diffusivity is calculated to be less than 10 m{sup 2}/s, approaching levels seen in tokamaks.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 886662
- Report Number(s):
- UCRL-JRNL-216651; PHPAEN; TRN: US0604007
- Journal Information:
- Physics of Plasmas, Vol. 13, Issue 5; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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