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Plans for Increasing the Magnetic Field and Plasma Temperature in the SSPX Spheromak
| Author: | Hill D.N. |
| Coauthor: | E.B. Hooper, H.S. McLean, R.D. Wood |
| Institution : | Lawrence Livermore National Laboratory |
| Abstract text: | In this paper we present plans for modifying the SSPX spheromak to increase the magnetic field produced by coaxial helicity injection. Based on existing SSPX data showing operation at fixed beta, we expect that higher fields will yield much higher central electron temperature at fixed density. During the coming year we plan to modify the capacitor bank to provide a choice of higher peak gun current (up to 1MA) or multiple (10) pulses spaced out over 8msec. Higher peak gun current will provide a robust method to significantly increase Te and B and thereby obtain valuable data for density control and energy transport studies. Multi-pulse operation will let us extend present double-pulse experiments that have produced the highest magnetic fields in SSPX to date. An important consequence of these experiments is that we can explore current amplification (A_I=Itor/Igun) over a broader range of operating parameters (gun flux, currents, and fields) while mainting high termperature low collisionality plasmas. Present SSPX data show a fairly robust linear relationship between gun current and spheromak magnetic field with a single short formation pulse; multi-pulse and extended high-current operation made possible with a new modular bank may let us exceed this limit. Other planned modifications of SSPX include installation of a small diameter gun to increase the voltage and magnetic pressure in the coaxial region, which may also increase the spheromak field while allowing us to compare several models of field saturation. Various possible scaling relations for predicting performance at higher magnetic field will also be discussed. |
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