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Accelerator design and simulation codes

Some of the accelerator design and simulation codes supported by LMY Technology are: (1) TStep, a simulation code that tracks charged particles through accelerators and beam line transport elements. (2) RFQGen is a collection of codes used to design (RFQ) Radio Frequency Quadrupole accelerators. 

TStep

 TStep is an electron-linac particle-dynamics code. It is a versatile multi-particle code that transforms the beam, represented by a collection of particles, through a user-specified linac and/or transport system. It includes options for 2-D and 3-D space-charge calculations. TStep integrates the particle trajectories through the fields. This approach is especially important for electrons where some of the approximations used by other codes (e.g. the “drift-kick” method commonly used for low-energy protons) would not hold. TStep works equally well for electrons, positrons, ions, or mixtures of different species. TStep can read field distributions generated by either Fish for rf problems or Poisson for magnet problems and electrostatic problems. 

RFQGen, an RFQ Design and Simulation Code

  

The RFQGen distribution contains a number of codes used to design RFQs and simulate their beam performance. The utility codes Curli and RFQuick generate an input file for RFQGen that designs the RFQ and simulates its performance with beam. The code RFQgraf is a post processor that displays the results of the simulation performed by RFQGen.  A good description of the RFQ physics can be found in Thomas P. Wangler, RF Linear Accelerators, Wiley & Sons, Inc. (1998).
Curli calculates current limits for linacs.

The critical area in an RFQ is near the end of the gentle buncher which typically occurs at an energy approximately 10 times the input energy of the RFQ.   Curli calculates the current limits for this area and writes a file named RFQ.def that is subsequently used by RFQuick to explore the RFQ parameter space. 

RFQuick explores the RFQ parameter space.

This program displays a dialog window containing proposed accelerator design parameters. The user can edit the entries as desired and click on “Update Results” to fill in the pull-down scrolling table near the bottom of the screen.  After highlighting the line having the desired shaper energy the user then clicks on the button “Write RFQGen Input File Using Selected Shaper Energy” to create the file RFQ.in4 RFQ.in4 is the input file for RFQGen. This file can be edited using a text editor giving the user almost complete freedom over the design of the RFQ.  The user is also free to generate the input file with a text editor without using of Curli and RFQuick.  The RFQGen User Guide contains a complete listing and description of the keywords used to specify the input data.  The Setup program adds a Windows filename extension association to launch RFQGen automatically when the user double-clicks on a file having the .in4 extension. 

RFQGen designs the RFQ cells.

Program RFQGen designs the cells of the RFQ, including radial matching sections on both ends of the structure. The code can modify the cell geometry slightly to produce the accelerating and focusing forces assumed by the two-term potential function. 

RFQGen allows the use of LEBT and MEBT transport sections.

These beam-line sections consist of one or more common transport elements described in the RFQGen Users Guide. The LEBT (Low Energy Beam Transport) comes before the RFQ while the MEBT (Medium energy Beam Transport) follows the RFQ. 

RFQGen performs the beam dynamics calculations.

RFQGen generates the detailed RFQ design and transports multi-particle bunches through the accelerator. The simulation includes space charge effects as well as the effects of image charges and higher order multipole field components arising from the use of circular vane tips.   

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