The lower limit of the device size is determined by anti-proton handling issues and fission reaction requirements, such as the structure used to contain and direct the blast.
[4][5] As the antimatter must remain away from ordinary matter until the desired moment of the explosion, the central pellet must be isolated from the surrounding hollow sphere of 100 grams of thermonuclear fuel.
Annihilation reactions, which would start soon after the Penning trap is destroyed, is to provide the energy to begin the nuclear fusion in the thermonuclear fuel.
In both cases the electromagnetic pulse effect and the radioactive fallout are substantially lower than that of a conventional fission or Teller–Ulam device of the same yield, approximately 1 kt.
For missions with longer periods of higher efficiency but with lower thrust, such as outer-planet probes, a combination of microfission and fusion might be preferred because it would reduce the total fuel mass.
Antiproton-driven ICF is a speculative concept, and the handling of antiprotons and their required injection precision—temporally and spatially—will present significant technical challenges.
A record for antimatter storage of just over 1000 seconds, performed in the CERN facility, during 2011, was at the time a monumental leap from the millisecond timescales that previously were achievable.
The anti-matter trap (Mark 1 version) at Penn State University has the capacity for the storage of 10 billion for a period of approximately 168 hours.