FF-1’s repeatability improves six-fold, with fusion yield staying within 3%
Reprinted from the LPPX November 23, 2011 Report.
FF-1 has taken a long step toward demonstrating the level of repeatable firing needed for a fusion generator.
On November 2, FF-1 fired five shots in a row, under the same conditions, with fusion yield varying by only plus or minus 2.6% from an average of 0.9x1011 neutrons. While dense plasma focus (DPF) devices preceding FF-1 have had a reputation for large shot-to-shot variability, a fusion generator (as well as most other applications) requires repeatable functioning. In May 2011, LPP reported that our research team had succeeded in stabilizing FF-1’s output to within a range of plus or minus 15%. The latest, tighter stability of function represents a six-fold improvement over the May results and achieves approximately the range of reliability that would be required in a generator pulsing many times per second.
The greater repeatability, we believe, is due to our tighter control of asymmetries in the device, including the centering of the electrodes (see more below). But the axial field coil (AFC), a magnetic coil which imposes a small field along the axis, probably contributes as well. The coil’s field of only 2 gauss, just 6 times the earth’s magnetic field in the vertical direction, imparts spin to the plasma which is greatly amplified while the current sheath moves down the electrodes. As with a spinning bullet, the spin can stabilize the sheath, making the output more repeatable. The sequence of five highly similar shots ended when the team deliberately changed the axial field to 4 gauss. While this is suggestive of a positive effect, more data will be needed to unequivocally demonstrate the role of the AFC.