Seminars by Dr. Christopher K. Allen

(1) An Adaptive Space Charge Algorithm for Three-Dimensional RMS Beam Envelope Simulation: by Dr. Christopher K. Allen (Los Alamos National Laboratory)
on January 20, 2005, 13:30-15:00, at 2goukan 2F Meeting room.; Presentation: [Pdf], [PowerPoint]; Abstract:
We discuss an algorithm for treating the first-order effects of space charge in bunched beam RMS envelope simulation. The envelope simulation is assumed to be of the type employed by TRACE3D or TRANSPORT. Specifically, transfer matrices are used to propagate the Courant-Snyder parameters along the beamline. Thus, to include space charge effects we must determine a transfer matrix representing the dynamics caused by the self electric fields.
We describe how this matrix is computed and, consequently, is employed in the dynamics calculations. Because the space charge matrices depend upon the Courant-Snyder parameters, and the Courant-Snyder parameters in turn depend upon the space charge matrices, we are also faced with some self-consistency issues. To circumvent this problem we present an adaptive technique for applying the space charge matrices that maintains a specified level of accuracy.

(2) Overview of the XAL High-Level Applications Programming Framework: by Dr. Christopher K. Allen (Los Alamos National Laboratory)
on February 18, 2005, 10:30-12:00, at KEKB Controls Building Meeting room.; Presentation: [Pdf], [PowerPoint]; Abstract:
The Spallation Neutron Source (SNS) has been developing a Java based hierarchal framework for application program development. The framework, called XAL, is designed to provide an accelerator physics programming interface to the machine hardware. Use of this framework facilitates implementation of general-purpose applications that can be applied to various parts of the accelerator, and are portable across different machines. As such, the Linac Coherent Light Source (LCLS) at Stanford Linear Accelerator Center (SLAC) has also adopted the XAL framework.
XAL utilizes an XML configuration file for machine hardware and process variables synchronization. Consequently, modifications or introduction of new beamline devices are immediately available for all XAL applications by updating the configuration file. An on-line model is included in this framework for quick beam tracking. Simple interfaces to other external modeling software are also available. Direct scripting interfaces are available for both Python and Matlab, for rapid prototyping uses. Initial applications have been developed and tested with the SNS front end. The overall framework is described, and example applications are shown.

(3) Bunched Beam Envelope Simulation with Space Charge within the SAD Environment: by Dr. Christopher K. Allen (Los Alamos National Laboratory)
on December 7, 2005, 13:30-14:30, at Kaihatsu-to 2nd Floor Meeting room, and
on December 8, 2005, 13:30-15:00, at 2-Gokan 2nd Floor Meeting room.; Presentation: [Pdf], [PowerPoint]; Abstract:
The capability for simulating the envelopes of three-dimensional (bunched) beams has been implemented in the SAD accelerator modeling environment. The simulation technique itself is similar to that of other common envelope codes, such as Trace3D, TRANSPORT, and the XAL online model. Specifically, we follow the second-order statistics of the beam distribution rather than tracking individual particles. If we assume that the beam maintains ellipsoidal symmetry in phase space, we can include the first order effects due to space charge using a semi-analytic model. This is the attractive characteristic of envelope codes, since it greatly reduces computational time. This new feature of SAD is implemented primarily in the SADScript interpreted language, with only a small portion appearing as compiled code. As such, the simulation does run slower than other compiled envelope codes such as TRACE3D or XAL, however, as interpreted code it does have the benefit of being easily modified. We demonstrate use of the new feature and present example simulations of the J-PARC linear accelerator section.

(4) Topics in Software Engineering and RMS Envelope Simulation: by Dr. Christopher K. Allen (Los Alamos National Laboratory)
on March 6, 2007, JAEA, and
on March 7, 2007, 13:30-14:30, at KEKB Meeting room.; Presentation: [Pdf], [PowerPoint]; Abstract:
The XAL accelerator application framework was originally designed with specific architectural goals which are important to recognize in order that future upgrades are consistent with these goals. Consequently software engineering is a very important aspect of XAL development. I will discuss various topics of software engineering in general, and with specific regard to the XAL framework. Also, I will briefly outline the specific enhancements to the XAL online model made during my sabbatical time at J-PARC. Some of this work included adding additional simulation capabilities to the online model, correcting existing ones, and verification. However, much effort was also devoted toward refactoring existing code into a more robust and upgradeable software system consistent with the XAL architecture.

(1) SAD Space Charge Simulation Tutorial: by Dr. Christopher K. Allen on December 9, 2005, at 1goukan 1F Meeting room.; Manual: [Pdf], [Word]; A Manual for SAD RMS Envelope Simulation (December 20 version).; Example Code: ScheffTest.sad [Text]; Example Deck: simdb-LI_L3BT01-nopmq0000.sad [Text]
(The original of this file was prepared by Sako-san, and was modified for the tutorial.); Introduction to SADScript Environment : [Pdf], [Word]; Adding Custom Functions.

(1) J-PARC Trace3D Upgrades: by Dr. Christopher K. Allen on March 2, 2005, at 2goukan 6F Meeting room.; Presentation: [Pdf], [PowerPoint]; The KEK version of Trace3D was improved to include two of three major feature differences in the simulation code inside XAL; namely, arbitrarily oriented beam ellipsoids, and direct evaluation of the elliptic integral instead of the form factor. Another feature of adaptive stepping is also being considered. The comparison with other approaches like the space charge additions to SAD, and J-PARC feature additions to XAL, are discussed as well.

Theory and Technique of Beam Envelope Simulation Simulation of Bunched Particle Beams with Ellipsoidal Symmetry and Linear Space Charge Forces: C.K. Allen et al. (LANL Report) [Pdf]
A Novel Online Simulator for Applications Requiring a Model Reference: C.K. Allen et al. (Icalepcs2003) [Pdf]
A Modular On-Line Simulator for Model Reference Control of Charged Particle Beams: C.K. Allen et al. (Pac2003) [Pdf]
Investigation of Halo Formation in Continuous Beams using Weighted Polynomial Expansions and Perturbational Analysis: C.K. Allen (Linac2000) [Pdf]
Optimal Transport of Low Energy Particle Beams: C.K. Allen et al. (Pac95) [Pdf]
XAL - The SNS Application Programming Infrastructure: J. Galambos et al. (Epac2004) [Pdf]
XAL Application Programming Framework: J. Galambos et al. (Icalepcs2003) [Pdf]