CPO – Charged Particle Optics

CPO is a general purpose particle optics simulation package, somewhat like SIMION, but based on the Boundary Element Method (BEM) of field calculation.  It is especially suitable for systems requiring space-charge limited cathode emissions or high accuracy field calculations.

• Extremely accurate
• Vast range of capabilities
• Space Charge and Non Space Charge version available

Electric field calculations
Electric field calculations are based on the highly accurate Boundary Element Method (BEM).  BEM computes fields within the 3D volume indirectly from electrode surface charges computed on a surface mesh (thereby avoiding the complexities of 3D volume meshes in FEM).  Accuracy is proven with over 200 benchmark and other examples.

Space-charge limited cathodes/guns
Space-charge limited cathodes and guns are handled where the electric field and space-charge trajectories are mutually dependent, requiring iterative self-consistent solutions. Various types of thermionic and field emission (e.g. Child’s Law and Fowler-Nord-heim) cathode properties are built-in.

Development
Developed continuously since 1974 by one of the leading research groups in electrostatic systems (University of Manchester, UK), CPO contains a vast range of capabilities and options supported by a comprehensive help system and examples. Examples and applications include electrostatic lens and aberration calculations, RF quadrupoles and analysers, guns, dielectrics, and secondary emission effects.

Capabilities:
Electrostatic field solving is done to high accuracy using the Boundary Element Method (BEM) rather than traditional FEM or FDM methods. The BEM has unique advantages and is well-suited to space-charge, cathode problems and nano-structures in the presence of large electrodes. Adaptive surface meshes get smaller where accuracy is critical. The BEM even easily simulates fine meshes and non-enclosed systems. Low-frequency oscillations, such as in a quadrupole, may also be simulated.

Particle trajectories of charged particles are calculated (Bulirsch-Stoer), accurately accounting for space-charge and relativistic effects. Space-charge is handled with iterative convergence tube and mesh methods – accuracy of 1% against theoretical results have been obtained.

Cathode emissions limited by space charge are simulated, including thermionic, field and extended Schottky emissions. Supports Child’s Law/Langmuir, Fowler-Nordheim and Richardson-Dushman relationships, plus user-defined properties. CPO specially handles space-charge effects at the critical cathode region.

Secondary emissions can be generated when a particle hits an electrode. The current multiplication factor and energy/angular distributions of the secondaries are chosen by the user.

Particle scattering and losses due to grid, background gas or secondary emissions are given in the examples included in the scattering version of CPO. Particle-particle scattering inside the beam is possible with the stochastic version. User-defined routines can be written in C++.

Magnetic elements of various types such as solenoids, wire loops and user-defined fields are avilable. Various contour and field plots can be displayed.

Aberration coefficients and lens properties may be calculated directly. An iterative automatic focusing option can find optimum electrode voltages.

Dielectrics calculations now available as a special module!