• G. Pöplau, U. van Rienen
  Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock

Precise and fast 3D space-charge calculations for bunches of charged particles are still of growing importance in recent accelerator designs. A widespread approach is the particle-mesh method computing the potential of a bunch in the rest frame by means of Poisson's equation. Whereas an adaptive discretization of a bunch is often required for efficient space charge calculations in practice, such a technique is not implemented in many computer codes. For instance, the FFT Poisson solver that is often applied allows only an equidistant mesh. An adaptive discretization following the particle density is implemented in the GPT tracking code (General Particle Tracer, Pulsar Physics). The disadvantage of this approach is that jumps in the distribution of particles are not taken into account. In this paper we present a new approach to an adaptive discretization which is based on the multigrid technique. The goal is that the error estimator needed for the adaptive distribution of mesh lines can be calculated directly from the multigrid procedure. The algorithm will be investigated for several particle distributions and compared to that adaptive discretization method implemented in GPT.

• A.S. Hofler, P. Evtushenko, F. Marhauser
  JLAB, Newport News, Virginia

Automation of DC photoinjector designs using a genetic algorithm (GA) based optimization is an accepted practice in accelerator physics. Allowing the gun cavity field profile shape to be varied can extend the utility of this optimization methodology to superconducting and normal conducting radio frequency (SRF/RF) gun based injectors. Finding optimal field and cavity geometry configurations can provide guidance for cavity design choices and verify existing designs. We have considered two approaches for varying the electric field profile. The first is to determine the optimal field profile shape that should be used independent of the cavity geometry, and the other is to vary the geometry of the gun cavity structure to produce an optimal field profile. The first method can provide a theoretical optimal and can illuminate where possible gains can be made in field shaping. The second method can produce more realistically achievable designs that can be compared to existing designs. In this paper, we discuss the design and implementation for these two methods for generating field profiles for SRF/RF guns in a GA based injector optimization scheme and provide preliminary results.

• V. Ivanov
  Muons, Inc, Batavia

Many measurements in particle and accelerator physics are limited by the time resolution. This includes particle identification via time-of-flight in major experiments like CDF at Fermilab, Atlas and CMS at the LHC. Large-scale systems could be significantly improved by large-area photo-detectors. The invention of a new method of making MCPs that promises to yield better resolution and be considerably less expensive than current techniques. Two different models for MCP simulations are suggested. Semi-analytical approach is a powerful tool for the design of static image amplifiers. Monte Carlo simulations can be successfully used for large area photo detectors with micron and Pico-second resolution range. Both approaches were implemented in the codes MCPS and MCS. The results of computer modeling are presented. References. 1. V.Ivanov, Z.Insepov, Pico-Second Workshop VII, The Development of Large-Area Pico-second Photo-Devices, Feb. 26-28, 2009; ANL. 2. V.Ivanov. The Code “Micro Channel Plate Simulator”, User’s Guide, Muons, Inc., 2009