Because of their compact form-factor, fast rise-time, low-jitter and relatively low source impedance, the wave-erection Marx generator manufactured by APELC has become very popular as a source for flash x-ray diodes. Over the past 25 years, APELC has matured the design of these Marx generators into robust, low-maintenance, commercially available sources. Paired with APELC accessories, such as power and control racks, diagnostics, and calibration loads, these Marx generators are available as user-friendly, turn-key systems.
APELC Marx Generators for Flash X-ray
APELC’s line of Marx Generators are capable of sourcing soft to hard x-ray diodes with energies ranging from 5keV to >2MeV. A sampling of these generators is provided below:
- MG15-3C-940PF: Compact, ~50 Ohm Marx generator capable of delivering 300kV onto a matched load. With many flash X-Ray diodes having operating impedances around 60-70 Ohm, the MG15 is and ideal source for portable flash X-ray systems in the 100-300keV range.
Figure 1 MG15-3C-940PF physical dimensions
Figure 2 MG15-3C-940PF output into 50 ohms at 35kV charge
- MG25-8C-2100PF: This Marx generator was originally designed as a driver for high-power wideband RF sources. However, upon measuring its waveform and impedance, APELC realized that this was an ideal source for more energetic flash X-ray systems. The low impedance and ~80ns pulse-width make it ideal for driving up to 500keV sources that may need a slightly longer exposure compared to the 25-30ns of the MG15-3C-940PF.
- MG40-3C-2700PF: The MG40-3C-2700PF was initially based upon the “Super Saver” Marx pioneered by David Platts of LANL. The Super Saver has been used for decades as a compact source for flash x-ray systems at LANL and other national labs. The APELC MG40 has matured this design to increase lifetime, decrease jitter and add our quick-disconnect output connector as an option to attach an x-ray diode remotely via coaxial cable. The 70 ohm impedance of the MG40, and ~40 ns pulse-width make it ideally suited for sourcing most flash x-ray diodes. Moreover, the peak voltage of 800kV into a matched load and 1:5 dynamic range make it capable of driving diodes with end-point energies from 150 keV to >500 keV.
- Generators for >1MeV: APELC manufactures larger, more energetic Marx generators capable of low source impedances as well as operation up to several MV. One example of this is the MG83-1C-150NF that was originally designed to drive the Vertical EMP System (VEMPS) at Patuxent River Naval Air Station. This generator has a 70 Ohm impedance and can place up to 4 MV onto a matched load, making it ideal for sourcing higher energy flash x-ray systems.
Unique Aspects of APELC Marx Generators for X-Ray Applications
- LOW-JITTER: Nearly all of the generators in APELC’s catalog perform with low-jitter- in some cases as low as <1ns RMS. For applications where the x-ray exposure needs to correspond with a fast event (explosion, chemical reaction, ballistics etc…), low-jitter is critical in ensuring frame alignment with the event being captured.
- EASE OF USE: APELC makes complete turn-key systems that utilize PLC controls and our custom line of quick-disconnect high-voltage connectors. This means that these systems can be easily operated by personnel who are not necessarily familiar with pulsed power and Marx generators. Also, APELC uses compressed dry breath air as a switching medium, and in many cases, as the insulation for the other Marx components. We completely avoid the use of SF6, which is not only a costly gas, but is becoming increasingly difficult to use due to environmental regulations.
- COMPACT: Many of APELC’s Marx Generators utilize unique insulation techniques to ensure a compact form factor. Therefore, these systems can be made portable for ease of mobility in the lab and in fielded applications.
Near-term Future APELC Efforts in Flash X-ray
As well as working on our own X-ray diode technology, APELC has been leveraging a formerly developed technology for use in producing multi-pulse x-ray radiography. The APELC Gatling Marx generator system initially reported on in 2001 is capable of producing multiple pulses from a single 50 Ohm coaxial output with inter-pulse separations as low as 50ns. Moreover, the low-jitter capability of APELC Marxes and trigger systems means that this timing can be completely controlled via a digital delay generator.
Figure 10 Experimental arrangement from APELC 10-pulse adder/Gatling system
Figure 11 9-pulse output waveform from the 10-pulse system (one generator was not being used)
For more information on APELC’s capabilities in support of flash x-ray radiography, see the complete white-paper here.
