ICAP2012 - Classification: 06 Beam-Material Interactions

Paper

Title

Page

Low-energy p-He and mu-He Simulation in Geant4

40

Y. Bao
PSI, Villigen, Switzerland

The frictional cooling method is one of the most promising methods on cooling a muon beam. Several frictional cooling schemes have been simulated in Geant4 to be efficient to produce intense muon beams. Frictional cooling works at a low energy range, where the energy loss (momentum transfer) from elastic collision is not negligible. In this paper, the p-He collision process is implemented into Geant4 and the simulation results are compared to the literature data. The cross section is then scaled for mu-He interaction, which will provide more accurate Geant4 simulations at low energies.

Slides MOSCC3 [0.665 MB]

TUSCC3

Undulator Radiation Inside a Dielectric Waveguide

96

A. Kotanjyan, A.A. Saharian
YSU, Yerevan, Armenia

We investigate the radiation from a charge moving along a helix around a dielectric cylinder immersed in a homogeneous medium. We are mainly concerned with the radiation propagating inside the cylinder. The radiation intensity for the modes propagating inside the cylinder is evaluated by the work done by the radiation field on the charge and by evaluating the energy flux through the cross-section of the cylinder. The insertion of a dielectric waveguide provides an additional mechanism for tuning the characteristics of the undulator radiation by choosing the parameters of the waveguide. The radiated energy inside the cylinder is redistributed among the cylinder modes, the corresponding spectrum differs significantly from the homogeneous medium or free-space results. This change is of special interest in the low-frequency range where the distribution of the radiation energy among small number of modes leads to the enhancement of the spectral density for the radiation intensity. The radiation emitted on the waveguide modes propagates inside the cylinder and the waveguide serves as a natural collector for the radiation.

Slides TUSCC3 [0.809 MB]

WEP18

Dynamics of Energy Loss of a Bunch Intersecting a Boundary Between Vacuum and Dielectric in a Waveguide

176

T.Yu. Alekhina, A.V. Tyukhtin
Saint-Petersburg State University, Saint-Petersburg, Russia

Funding: his research was supported by St. Petersburg State University
We analyze radiation of a small bunch crossing a boundary between two dielectrics in a cylindrical waveguide. The total energy of radiation was studied earlier for such problem but dynamics of an energy loss as well as a field structure was not investigated. Meanwhile these questions are of essential interest for the wakefield acceleration technique and for new methods of generation of microwave radiation. Our research is based on original approach used previously for the case of the vacuum-plasma boundary*. The principal difference of presented work consists in generation of Cherenkov radiation in dielectric and so-called Cherenkov-transition radiation in vacuum. Algorithms of computations for the field and the energy loss are founded upon certain transformations of integration path. Comparison of analytical results with numerical ones shows a good coincidence. We consider two instances in detail: the bunch is flying from vacuum into dielectric and from dielectric into vacuum. In both cases we compare the energy losses by transition radiation and by Cherenkov one. Our investigation shows, for example, that energy loss can be negative at certain segments of the bunch trajectory.
* T.Yu. Alekhina and A.V. Tyukhtin, Phys. Rev. E. 83, 066401 (2011)

THAAI1

The Dark Current and Multipacting Capabilities in OPAL: Model, Benchmarks and Applications

201

C. Wang, Z.G. Yin, T.J. Zhang
CIAE, Beijing, People's Republic of China
A. Adelmann
PSI, Villigen, Switzerland

Dark current and multiple electron impacts (multipacting), as for example observed in radio frequency (RF) structures of accelerators, are usually harmful to the equipment and the beam quality. These effects need to be suppressed to guarantee stable operation. Large scale simulations can be used to understand the cause and develop strategies to suppress these phenomena. We extend OPAL, a parallel framework for charged particle optics in accelerator structures and beam lines, with the necessary physics models to efficiently and precise simulate multipacting phenomenas. We added a Fowler-Nordheim field emission model, two secondary electron emission models, developed by Furman-Pivi and Vaughan respectively, as well as efficient 3D boundary geometry handling capabilities. The models and their implementation are carefully benchmark against a non-stationary multipacting theory for the classic parallel plate geometry. A dedicated, parallel plate experiment shows excellent agreement between theory, model/simulations and experiment.

Slides THAAI1 [6.191 MB]

Paper	Title	Page
MOSCC3	Low-energy p-He and mu-He Simulation in Geant4	40
	Y. Bao PSI, Villigen, Switzerland
	The frictional cooling method is one of the most promising methods on cooling a muon beam. Several frictional cooling schemes have been simulated in Geant4 to be efficient to produce intense muon beams. Frictional cooling works at a low energy range, where the energy loss (momentum transfer) from elastic collision is not negligible. In this paper, the p-He collision process is implemented into Geant4 and the simulation results are compared to the literature data. The cross section is then scaled for mu-He interaction, which will provide more accurate Geant4 simulations at low energies.
	Slides MOSCC3 [0.665 MB]

TUSCC3	Undulator Radiation Inside a Dielectric Waveguide	96
	A. Kotanjyan, A.A. Saharian YSU, Yerevan, Armenia
	We investigate the radiation from a charge moving along a helix around a dielectric cylinder immersed in a homogeneous medium. We are mainly concerned with the radiation propagating inside the cylinder. The radiation intensity for the modes propagating inside the cylinder is evaluated by the work done by the radiation field on the charge and by evaluating the energy flux through the cross-section of the cylinder. The insertion of a dielectric waveguide provides an additional mechanism for tuning the characteristics of the undulator radiation by choosing the parameters of the waveguide. The radiated energy inside the cylinder is redistributed among the cylinder modes, the corresponding spectrum differs significantly from the homogeneous medium or free-space results. This change is of special interest in the low-frequency range where the distribution of the radiation energy among small number of modes leads to the enhancement of the spectral density for the radiation intensity. The radiation emitted on the waveguide modes propagates inside the cylinder and the waveguide serves as a natural collector for the radiation.
	Slides TUSCC3 [0.809 MB]

WEP18	Dynamics of Energy Loss of a Bunch Intersecting a Boundary Between Vacuum and Dielectric in a Waveguide	176
	T.Yu. Alekhina, A.V. Tyukhtin Saint-Petersburg State University, Saint-Petersburg, Russia
	Funding: his research was supported by St. Petersburg State University We analyze radiation of a small bunch crossing a boundary between two dielectrics in a cylindrical waveguide. The total energy of radiation was studied earlier for such problem but dynamics of an energy loss as well as a field structure was not investigated. Meanwhile these questions are of essential interest for the wakefield acceleration technique and for new methods of generation of microwave radiation. Our research is based on original approach used previously for the case of the vacuum-plasma boundary. The principal difference of presented work consists in generation of Cherenkov radiation in dielectric and so-called Cherenkov-transition radiation in vacuum. Algorithms of computations for the field and the energy loss are founded upon certain transformations of integration path. Comparison of analytical results with numerical ones shows a good coincidence. We consider two instances in detail: the bunch is flying from vacuum into dielectric and from dielectric into vacuum. In both cases we compare the energy losses by transition radiation and by Cherenkov one. Our investigation shows, for example, that energy loss can be negative at certain segments of the bunch trajectory. T.Yu. Alekhina and A.V. Tyukhtin, Phys. Rev. E. 83, 066401 (2011)

THAAI1	The Dark Current and Multipacting Capabilities in OPAL: Model, Benchmarks and Applications	201
	C. Wang, Z.G. Yin, T.J. Zhang CIAE, Beijing, People's Republic of China A. Adelmann PSI, Villigen, Switzerland
	Dark current and multiple electron impacts (multipacting), as for example observed in radio frequency (RF) structures of accelerators, are usually harmful to the equipment and the beam quality. These effects need to be suppressed to guarantee stable operation. Large scale simulations can be used to understand the cause and develop strategies to suppress these phenomena. We extend OPAL, a parallel framework for charged particle optics in accelerator structures and beam lines, with the necessary physics models to efficiently and precise simulate multipacting phenomenas. We added a Fowler-Nordheim field emission model, two secondary electron emission models, developed by Furman-Pivi and Vaughan respectively, as well as efficient 3D boundary geometry handling capabilities. The models and their implementation are carefully benchmark against a non-stationary multipacting theory for the classic parallel plate geometry. A dedicated, parallel plate experiment shows excellent agreement between theory, model/simulations and experiment.
	Slides THAAI1 [6.191 MB]