Investigation of magnetic field properties in the helical axis stellarator: Asperator NP-4

Yasuyuki Funato, Sumio Kitajima, Hiroshige Watanabe

Research output: Contribution to journalArticlepeer-review


Experimental measurements of the magnetic field properties of a helical axis stellarator were carried out. The results, together with the numerical calculation, are described herein. The toroidal device, Asperator NP-4, has a helical magnetic axis with a pitch angle of 45° and a multi-field period of n=8. The magnetic field of NP-4 is produced by the currents of helical solenoids and L=+1, -1 helical windings. By an electron beam mapping of field lines, the existence of a high rotational transform angle and magnetic surfaces are confirmed and the position if the helical magnetic axis is obtained. The other fundamental magnetic properties such as the shear and the specific volume of the configuration are also deduced from the measurements. Numerical calculations lead to a good agreement with the results of the experiment.

Original languageEnglish
Pages (from-to)821-826
Number of pages6
JournalJapanese journal of applied physics
Issue number5R
Publication statusPublished - 1988 May


  • Aspcrator
  • Electron beam measurement
  • Helical system
  • Stellarator
  • Vacuum magnetic field

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)


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