UST_1 stellarator, satisfactorily built and operated  (2004 - 2007)

Summary of UST_1 stellarator features

UST_1 is a low cost small R&D stellarator built in a private laboratory. It was devised, designed, built and operated from 2005 up to 2007. UST_1 was built using an innovative fabrication method consisting of a new toroidal milling machine able to mechanise all the groove coils only in twelve mechanising operations.

UST_1 is the 3rd modular stellarator in the world, the most economical with acceptable quality, the first designed and built by only one person. It has shown good magnetic surfaces as designed and simulated, and plasmas have been produced (Te>2eV , n~2e17) as calculated.

UST_1 is a 2 field periods compact modular st. with aspect ratio 6 and R=119mm, 12 resistive modular coils with precision ~0.3mm, partially optimised confinement using SimPIMF code, present power supplies 21 Kw and Bo 46mT (possible 87mT), 0.8kW 2.45GHz ECRH  system, installation cost 2700€.

Results from one of the last plasma pulses in UST_1

13-06-2007. Pulses from #261 to #265 :

Plasma density  =   2 x 1017 m-3   +-1 x 1017m-3

Plasma temperature Te = 3eV   +- 1eV

The signal from the Langmuir probe located at 0.5a, and for several pulses, have been analysed. The uncertainty is large due to limitations, errors, and interferences in the A/D cards and because the data come from several pulses (presently only pulse #264 & #265). Some unknown errors and inaccuracies might appear in the future.

___________________

06-06-2007. Pulse #248,

Evolution of the parameters during the pulse.  More      Expand

 The Langmuir probes are not installed yet during this pulse.

Chronological Milestones

13 - June  2007 :  Recorded data from Langmuir probe and other plasma parameters.

 24 - January  2007 :  First plasma   Video 

24-01-2007 : Pulse #222. First plasma, but still a low quality plasma. The period of higher quality plasma lasts 0.7 seconds and later it almost disappears, perhaps due to excessive outgassing. However the plasma is very unstable at any time. TF coils are ON (Bo=~43mT , 2nd harmonic at 2.45GHz) while the plasma is or seems toroidal although it is difficult to assure because of the perspective of the camera. A Type N connector is used to feed the RF. Pressure raised from~0.06Pa to 1Pa in 0.5 seconds (P from inverted magnetron, 1Pa~1x1020 m-3). The outgassing is excessive.

23 - August 2006 : Magnetic Surfaces recorded  Video

More        

Expand

In cyan (505nm from the fluorescent P24 phosphor) the poloidal projections of the e-beam for pulse #202. Several images are overlapped and not digitally modified. The successive theoretical intersections of the orbit with a poloidal plane at 0º toroidal angle are numbered and coloured. Intersection 1 is near the red circle but it is faint due to saturation of the image and the same for intersections 4, 7 and 8. Intersections 2, 3, 5, 6 and 9 are clearly defined.  SimPIMF code simulates the orbit and projections. Poor vacuum still limits the number of turns. Circles are 3mm in diameter so the e-beam diameter is ~1.5mm, a good value but too large for this small stellarator.