**Advanced Accelerators: Miniaturizing Accelerators**

**from Kilometers to Meters**

D. Bruhwiler^1^, A. Dragt^2^, S. Habib^3^, T. Katsouleas^4^, K. Ko^5^
(co-PI), W. B.Mori^6^, R. Ryne^7^(co-PI), R. Samulyak^8^, P.
Spentzouris^9^

^1^Tech-X, ^2^U. Maryland, ^3^LANL, ^4^USC, ^5^SLAC, ^6^UCLA, ^7^LBNL,
^8^BNL, ^9^FNAL

Summary

***Advanced accelerator research is aimed at finding new technologies
that can dramatically reduce the size and cost of future high-energy
accelerators. Supercomputing is already playing a dramatic and critical
role in this quest. One of the goals of the SciDAC Accelerator Modeling
Project is to develop code and software that can ultimately be used to
discover the underlying science of new accelerator technology and then
be used to design future high-energy accelerators with a minimum of
capital expenditure on large-scale experiments.***

**1. Introduction**

The long-term future of experimental high-energy physics research using
accelerators depends on the successful development of novel ultra
high-gradient acceleration methods. New acceleration techniques using
lasers and plasmas have already been shown to exhibit gradients and
focusing forces more than 1000 times greater than conventional
technology. The challenge is to control these high-gradient systems and
then to string them together. Such technologies would enable the
development of ultra-compact accelerators. The potential impact on
science, industry, and medicine of placing such compact accelerators in
research organizations, high-tech businesses, and hospitals is
staggering.

Under the Accelerator Modeling SciDAC Project, the Advanced Accelerator
effort has emphasized developing a suite of parallelized
particle-in-cell (PIC) codes, ensuring that all code be reusable and
easily extendable, benchmarking these codes and their underlying
algorithms against each other and against experiments, adding more
realism into the models, and applying them to advanced accelerators as
well as more mainstream problems in accelerator physics, such as the
electron cloud instability. Furthermore, the effort has included running
these codes to plan and interpret experiments and to study the key
physics that needs to be understood before a 100+ GeV collider based on
plasma techniques can be designed and tested. The Advanced Accelerator
effort at the universities has supported PhD students at both UCLA and
USC.

**2. Accomplishments**

In some advanced accelerator concepts a drive beam, either an intense
particle beam or laser pulse, is sent through a uniform plasma. The
space charge or radiation pressure creates a space-charge wake on which
a trailing beam of particles can surf. To model such devices accurately
usually requires following the trajectories of individual plasma
particles. Therefore, the software tools developed fully or partially
under this project, OSIRIS, VORPAL, OOPIC, QuickPIC, and UPIC rely on
the particle-in-cell (PIC) techniques.

Among the major accomplishments are:

[The rapid construction of QuickPIC]{.underline}: The development of
QuickPIC is a success story for the rapid construction of a new code
using reusable parallel code via a SciDAC team approach. The basic
equations and algorithms were developed from a deep understanding of the
underlying physics involved in plasma and/or laser wakefield
acceleration while the code was constructed rapidly using the UPIC
Framework. QuickPIC can completely reproduce the results from previous
algorithms with a factor of 50 to 500 savings in computer resources. It
is being used to study science in regimes not accessible before.

[Rapidly adding realism into the computer models]{.underline}: The large
electromagnetic fields from the intense drive beams can field ionize a
gas forming a plasma. Early SciDAC research using two-dimensional codes
revealed that this self-consistent formation of the plasma from the
drive beam needs to be included in many cases. Via the SciDAC team
approach, ionization models have been added and benchmarked against each
other in the fully three-dimensional PIC codes, VORPAL and OSIRIS.

[The development of UPIC]{.underline}: Using highly optimized legacy
code a modern Framework for writing all types of parallelized PIC codes
including electrostatic, gyrokinetic, electromagnetic, and quasi-static
has been developed. The UPIC Framework has obtained 30% of peak speed on
a single processor and 80% efficiency on well over 1000 processors. It
is used across both the Accelerator and Fusion SciDAC projects.

[Extending the plasma codes to model the electron-cloud
instability:]{.underline} The electron cloud instability is one of the
major obstacles for obtaining the design luminosity in circular
accelerators, storage rings, and damping rings. A set of modules has
been written for QuickPIC that models circular orbits under the
influence of external focusing elements. This new software tool has
already modeled 100,000 km of beam propagation of the CERN SPS machine.
It is a major improvement over previously existing tools for modeling
E-Cloud interactions.

[Applying the suite of codes to discover new accelerator
science]{.underline}: The suite of PIC codes has been used to model the
E-157, E-162, E-164 particle beam accelerator experiments at SLAC and
the laser-plasma experiments at the L'OASIS lab at LBNL. They have also
been used to study key physics issues related the Afterburner concept in
which the energy of an existing beam from an accelerator is doubled with
gradients near 10 GeV/m. An example is shown below where the beam and
plasma density is shown from a three-dimensional simulation for the
afterburner including field ionization.

![](media/image1.jpeg){width="3.0in" height="1.86875in"}

*Figure 1. 3D afterburner simulation results.*

**3. Concluding Remarks**

The field of accelerator physics has greatly benefited by the
integration of codes and expertise that only a program like SciDAC can
offer.

Prof. W.B.Mori

Dept. of Physics & Astronomy and Electrical Eng.

University of California Los Angeles

Los Angeles, CA 90095

Phone: 310-206-0372

E-mail: Mori@physics.ucla.edu