Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: More ion sources/neutron generators
Date: Jan 18, 7:33 pm
Poster: Jim Lux

On Jan 18, 7:33 pm, Jim Lux wrote:

Something to contemplate with respect to prolific ion sources. Some researchers at Lawrence Berkeley Lab (notably Celata and Perkins, among others.. those were the easy names to search for) have developed a pulsed RF ion source for use in an "intense neutron generation" application (i.e. down hole neutron logging).

Basically, they dump high peak power(50+kW) RF (2 MHz) pulses about 10-20 uSec long (i.e. 20-40 cycles) into a rod antenna in a copper cylinder (2.5 cm diam, 8 cm long). A bunch of SaCo magnets form a multicusp field. The dense plasma is extracted through a small (2mm diam) hole and then run into a 100 kV accelerator to make neutrons. The ion current peaks at 37 mA (through that small hole).

This sounds like a heap of power, but it's not.. That 60 kW pulse for 20 uSec is only 1.2 Joules. Some sort of capacitor discharge into a resonant circuit could generate this handily.. At the rep rate they used (100 Hz), it's a few hundred watts average, much like a smallish Tesla Coil...

Something to think about.. They are expecting average neutron rates of 1E9 n/sec with DT, 100 kV, and 60 uA average beam current. With DD, the rates will be lower, due to the reduced cross section.

This might be a scheme to generate a whole bunch of D+ ions as a pulse. The design of the ion source appears to be quite simple, in any case.