Charged Particle Generator

High energy, high current proton beams are currently used in many areas of technology and research, and continue finding applications in even more areas. Reliability of such beam sources have been a major problem in the commercial viability of the same, especially in fields where reliability is key such as accelerator driven sub-critical reactors. STFC’s new charged particle generator provides a reliable solution, the use of which allows the shift of nuclear fuels to safer ones like thorium.





Charged particle beam generators, especially proton beam generators, are well known and used in many areas of science and technology. Nevertheless, the stability and reliability of high energy, high current proton beam generators are an issue and an improvement in this technology would benefit many industries, especially accelerator driven sub-critical reactors. For instance, Thorium based reactors propose the use of a plutonium core to generate neutrons rather than safer accelerating technologies due to its current state of development. The replacement of such plutonium cores would greatly enhance safety as well as security risks, because the accelerator may be switched off thus stopping the sub-critical reaction and the lack of plutonium in the whole process removes the risk of proliferation.

This technology provides a stable and reliable method of generating composite protons beams using multiple generator units (at least two). Each of the ‘n’ units uses an ion source like H- to generation ion beams, which after an initial acceleration is stripped of its electrons to generate a proton beam. These individual proton beams are again accelerated and then merged optically into a composite proton beam on entry to a beamline. This beamline is then fired into a spallation target to generate neutrons. The neutrons thus generated will convert Thorium, which in itself is non-fissile but fertile, into fissile uranium with hardly any production of Plutonium. 

The plurality of generator units and therefore proton beams offers flexibility and reliability. The n number of individual pulsed beams may be merged into a single channel or sequentially to obtain a repetition rate of n. The system may be over-worked with n+1 generators followed by a chopper to allow only n beams to form a composite. This would compensate for failure of one of the other beams or when one of them is temporarily pulled out for servicing. Even without overworking, the system may be adjusted in the event of a generator failure by a factor of (n-1)/n to preserve the composite beam as well as its repetition rate. Adjusting by a factor of n/(n-1) would allow higher beam current without filling in the missing pulses. A combination of both may be used to increase both repetition rate and beam current.

The flexibility of this method lies in the variety and combination of both ion sources and accelerators that can be employed. More than one ion source many be adopted by the generator units thus permitting a backup ion source. Accelerators can vary from LINACs, Cyclotrons, and Synchrotrons to Fixed-Field Accelerating Gradient accelerators. These accelerators may be used in combination such as a LINAC for H- acceleration followed by an FFAG for proton beam acceleration after stripping. Two stage FFAGs may also be used; either stacked on top of one another or arranged concentrically if the radii are different.

Lastly, an added advantage of such accelerator driven sub-critical reactors is the ability to feedback part of the energy generated in the reactor to power the ion beam generator.



  • The method involves using a negative hydrogen ion source to generate negative hydrogen ion beams, and stripping the negative hydrogen ions to create proton beams.

  • The proton beams are pulsed, and the proton beams are merged such that proton pulses are interleaved, where the proton pulses in the proton beams have common repetition rate.



  • The method enables providing a stable and reliable composite high-energy, high-current proton beam.

  • Permits utilization of nuclear fuel such as thorium, so that radioactive waste produced is far shorter-lived, thus easing disposal problem.

  • The reaction scheme of thorium produces almost no plutonium.

  • The thorium found in earth's crust does not require costly enrichment, so that pure thorium fuel rods can be used and converted to a thorium/uranium mixture as spallation occurs.



  • Nuclear Reactors (Thorium)

  • Particle Accelerators

Patent Information:
For Information, Contact:
Elizabeth Bain
IP Manager
STFC Innovations
+44 (0) 1925 60 3680
04.e. Nuclear Fission/Nuclear Fusion