PUFFIN will use the LTD5 modules developed at CEA Gramat to drive microsecond long, mega-Ampere level pulses of electrical current. LTDs are Linear Transformer Drivers, a relatively new pulsed-power technology which encloses the capacitive energy store and switch in a single conducting cavity. This reduces the inductance of the system and provides shielding from electromagnetic pulses. PUFFIN will produce microsecond long pulses of current, in contrast to fast rise-time LTDs such as MAIZE and HADES. This will allow PUFFIN to sustain plasmas in a quasi-steady-state, which is ideal for studying fundamental plasma processes.
PUFFIN is currently in the design phase. We have secured a supplier for these LTD5 modules and we are actively seeking funding to build the full scale machine. The conceptual design above uses eight LTD5 modules (or stages) arranged in four lines of two modules each. The modules stacked in series increase the overall voltage of the pulse, and the modules stacked in parallel increase the total current. The capacitors (shown in brown) will be charged to around 70 kV, and then discharged through triggered multi-channel, low inductance switches into a vacuum coaxial transmission line.
The four transmission lines converge inside a vacuum chamber (shown in a cutaway view above) and the transmission line tapers vertically to present a coaxial transmission line at the base of the large cylindrical vacuum chamber. The tall windows will provide excellent diagnostic access for laser based diagnostics such as interferometry, Thomson scattering and Faraday rotation imaging.
- “A primer on pulsed power and linear transformer drivers for high energy density physics applications” by McBride et al. A very thorough review of LTDs and pulsed-power in general.
- “Status on the SPHINX machine based on the 1 microsecond LTD technology” by Lassalle et al. An overview of the LTD5 stages to be used on PUFFIN.