HB2014 - Classification: Beam Dynamics in Linacs

Paper

Title

Page

RMS Emittance Measures for Solenoid Transport and Facitlity for Rare Isotope Beams Front-End Simulations

57

S.M. Lund, G. Pozdeyev, H.T. Ren, Q. Zhao
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Grant No. PHY-1102511.
Measurement of beam phase-space area via rms emittances in solenoid focusing channels with linear x-y coupling is complicated relative to transport channels with decoupled plane focusing. This stems from correlated azimuthal flow of the beam induced by the coupled focusing influencing how the thermal component of the flow should be measured. This is exacerbated when the beam has finite canonical angular momentum – as is the case for beams born in a magnetic field in ECR-type sources. In this study, simple measures of rms emittance for use in solenoid transport for beams with canonical angular momentum are motivated and overviewed. Emphasis is placed on simple to interpret emittance measures which reduce to familiar forms for decoupled plane motion. These emittances are applied in Warp PIC simulations of the near-source region of the FRIB linac front-end. In these simulations, a multi-species heavy-ion dc beam emerging from an ECR source are simulated primarily in transverse slice mode using a realistic lattice description. Emittance growth due to nonlinear applied fields, space-charge, and partial neutralization is analyzed including the influence of net canonical angular momentum.

MOPAB18

An ESS Linac Collimation Study

62

R. Miyamoto, M. Eshraqi
ESS, Lund, Sweden
H.D. Thomsen
ISA, Aarhus, Denmark

The European Spallation Source (ESS) is planned in Lund, Sweden, and will be a neutron source based on a proton linac with an unprecedented 5 MW beam power. Mitigation of beam losses is the most crucial challenge in beam physics for such a high power proton linac and collimation systems are planned in sections of the medium and high energy beam transport (MEBT and HEBT). A preliminary study of the collimation systems was presented in the previous time of this workshop but the linac design went through a significant revision since then. The system to expand the beam for the neutron target, located in the HEBT, was changed from one based on nonlinear magnets to a raster system and this change particularly had a significant impact on the demand on the collimation systems. This paper presents an updated beam dynamics study of the collimation systems for the present layout of the ESS Linac.

MOPAB19

Space-Charge Compensation of Intense Ion Beams by Nonneutral Plasma Columns

67

K. Schulte, M. Droba, O.K. Kester, S. Klaproth, O. Meusel, D. Noll, U. Ratzinger, K. Zerbe
IAP, Frankfurt am Main, Germany
O.K. Kester
GSI, Darmstadt, Germany

Gabor lenses were conceived to focus a passing ion beam using the electrical field of a confined nonneutral plasma column. Beside its application as focusing device, in Gabor lenses space-charge effects can be studied in detail. The influence of the electron distribution on emittance and space-charge dominated ion beams was investigated in beam transport experiments*. In this contribution we want to emphasize one result of these experiments. The measurements indicated a strong contribution of secondary electrons on beam dynamics. Secondary electrons are produced within the transport channel, particularly by interaction of the beam with the surface of the slit-grid emittance scanner. This might lead to an increase of the filling degree and to an improved focusing performance of the lens. Assuming that the loss and production rates within the lens volume and the transport channel determine the equilibrium state of the nonneutral plasma column, the electron cloud was characterized as a function of the external fields and the residual gas pressure in small-scale table top experiments. In this contribution experimental results will be presented in comparison with numerical simulations.
* K. Schulte, “Studies on the focusing performance of a Gabor lens depending on nonneutral plasma properties”, PhD thesis, 2013.

TUO1LR01

Multi-Charge-State Beam Dynamics in FRIB

Q. Zhao
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB) is a new generation national user facility for nuclear science under establishment at the Michigan State University. The cw superconducting driver linac will accelerate all stable isotopes (from protons to uranium) to energies above 200 MeV/u with a beam power of up to 400 kW. To meet the output beam power requirements for ions heavier than xenon, two charge states will be selected from an ECR ion source and accelerated simultaneously in every other rf bucket through RFQ and Segment 1. After the acceleration in Segment 1 up to 20 Mev/u, a charge stripper is used to boost charge states for heavy ions and thus increase the acceleration efficiency for the rest of the linac. Multiple charge states (up to 5 depending on ions) will also be selected after stripper and further accelerated in Segment 2 and Segment 3 in the same rf bucket before delivery to a target. Beam dynamics associated with simultaneous acceleration/transport of multi-charge-state ions in the high power machine will be reported.

Slides TUO1LR01 [2.749 MB]

TUO1LR02

The Design and Beam Dynamics Study for CSNS Linac

H.C. Liu, S. Fu, J. Peng, S. Wang
IHEP, Beijing, People's Republic of China

The China Spallation Neutron Source (CSNS) linac consists of a 50 keV H⁻ ion source, a 3 MeV RFQ, and an 80 MeV alvarez type DTL. It provides an H⁻ beam of 15 mA peak current with a pulsed beam width about 420 μs and a repetition rate of 25 Hz for injection into the following 1.6 GeV rapid-cycling synchrotron (RCS). The transverse and longitudinal beam optics is introduced. The original design scheme is optimized based on the end-to-end simulation. Besides beam dynamics, the commissioning plan for linac is also presented, including the commissioning correlated parameters, beam instrumentation used in commissioning, the goal at different commissioning stages.

Slides TUO1LR02 [6.961 MB]

TUO1LR03

ESS Linac Design and Cost Optimization as Function of Beam Dynamics

M. Eshraqi
ESS, Lund, Sweden

The energy and power of accelerators used for research are growing to meet the demand of experiments. These increases are usually translated to costlier accelerators and bigger facilities. However, proper handling of beam power in the megawatt range requires a robust design that respects the known rules of thumb in accelerator design to limit the losses at a challenging level of less than one part in million. Traditionally cost increases with power and quality of the accelerator and beam. In this paper, using the ESS linac as an example, this tradition is challenged and ways to reduce the cost while neither quality nor power are compromised are presented.

Slides TUO1LR03 [7.327 MB]

WEO3LR01

Beam Setup Conditions and Comparison of Deal and Actual Production Conditions

M.A. Plum, A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
This presentation will review methods for experimental determination of optimal operational set points in a multi-cavity superconducting high power hadron linac. A typical tuning process, including establishing correct acceleration profile and rms bunch size matching, is based on comparisons between measured data and results of simulations from envelope, single and multi-particle models. Presence of significant space charge effects requires simulation and measurement of bunch dynamics in three dimensions to ensure low loss beam transport. This is especially difficult in a superconducting linac where the use of interceptive beam diagnostics is usually restricted because of the risk of SRF cavity surface contamination. The procedures discussed here are based on non-interceptive diagnostics such as beam position monitors and laser wires, and conventional diagnostics devices such as wire scanners and bunch shape monitors installed outside the superconducting linac. The longitudinal Twiss analysis based on the BPM signals will be described. The superconducting SNS linac tuning experience will be used to demonstrate problems and their solution for real world linac tune-up procedures.

Slides WEO3LR01 [7.162 MB]

WEO3LR03

Nonlinear Optimization in High Intensity Superconducting Linac Lattice of CADS

Z.J. Wang, Y. He, S.H. Liu
IMP, Lanzhou, People's Republic of China

With the development of high-energy, high intensity ion linac all over the world, the optimization design of accelerating lattice has become a concern. The China Accelerator Driven System(ADS) superconducting proton linac is used as an example to illustrate the strategies and techniques which we have been developed for the optimization design of ion linac. First, an novel idea, which optimizes the periodic phase advance array directly in both longitudinal and transverse direction, is proposed to design the superconducting acceleration section. The results shown that the new idea can make the lattice design of ion linac easily accord with physics rules. Second, the Particle Swarm Optimiation(PSO) algorithm is utilized to optimize the phase advance array setting automatically. The advantage of utilization of optimiation algorithm is that it can find potential solutions that cannot be found by hand. Addtionally, Multi-goal Optimization technique is used to study the nonlinear properties of lattice. The strategies and techniques are generally-used and can be adopted in the other ion linacs design.

WEO3LR04

Emittance Transfer in Linacs

289

L. Groening, M.T. Maier, C. Xiao
GSI, Darmstadt, Germany
O.K. Kester
IAP, Frankfurt am Main, Germany

Flat beams feature unequal emittances in the horizontal and vertical phase space. Such beams were created successfully in electron machines by applying effective stand-alone solenoid fringe fields in the electron gun. This contribution is an extension of the method to ion beams and on the decoupling capabilities of such a round-to-flat adaptor. The beam line provides a single-knob tool to partition the horizontal and vertical rms emittances, while keeping the product of the two emittances constant as well as the transverse rms Twiss parameters (beta_x;y and alpha_x;y) in both planes. This single knob is the solenoid field strength. The successful commissioning of the set-up with beam will be presented as well.

Slides WEO3LR04 [1.289 MB]

WEO4LR01

New Methods and Concepts for Very High Intensity Beams

P.A.P. Nghiem, N. Chauvin
CEA/DSM/IRFU, France
M. Comunian
INFN/LNL, Legnaro (PD), Italy
C. Oliver
CIEMAT, Madrid, Spain
W. Simeoni
IF-UFRGS, Porto Alegre, Brazil
D. Uriot, M. Valette
CEA/IRFU, Gif-sur-Yvette, France

For very high intensity beams, not only beam power but also space charge is a concern, so that both aspects should be taken into considerations for any analysis. Beam blowup due to space charge forces can be mitigated by bringing closer the focusing and accelerating components, making the beam diagnostic implementation difficult. A clear strategy for beam diagnostic has to be defined. Beam halo is no longer negligible but plays a significant role in the dynamic of the beam and in the particle loss process. Beam optimization must take it into account and beam characterization must describe not only the core part but also the halo one. This paper presents the new concepts and methods for beam analysis, beam diagnostics, beam optimization and beam characterization.

Slides WEO4LR01 [3.342 MB]

WEO4LR02

The Particle-in-Cell Code Bender and Its Application to Non-Relativistic Beam Transport

304

D. Noll, M. Droba, O. Meusel, U. Ratzinger, K. Schulte, C. Wiesner
IAP, Frankfurt am Main, Germany

A new non-relativistic, electrostatic Particle-in-Cell code named bender has been implemented to facilitate the investigation of low-energy beam transport scenarios. In the case of high-intensity beams, space-charge compensation resulting from the accumulation of secondary particles - electrons for positively charged ion beams - is an important effect. It has been shown, that the distribution of compensation electrons can have a significant influence on the beam and lead to an emittance growth. To improve the understanding of the dynamics of the compensation and the resultant self-consistent steady state, ionization of residual gas as well as secondary electron production on surfaces have been implemented and used to study a number of test systems. We will present first results of these compensation studies as well as further applications of the code, among them the chopper section of the future FRANZ facility [1].
* C. Wiesner et al., Experimental Performance of an E×B Chopper System, Proc. of IPAC 2014, THPME015

Slides WEO4LR02 [5.373 MB]

WEO4LR03

Noise and Entropy in Non-Equipartitioned Particle Beams

309

I. Hofmann, O. Boine-Frankenheim
GSI, Darmstadt, Germany
O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany

The numerical noise generated in particle-in-cell simulation of 3D high intensity bunched beams is studied with the TRACEWIN code and compared with the analytical entropy model by Struckmeier. In this model the logarithm of the six-dimensional rms emittance is shown to qualify as rms-based entropy. We confirm the dependence of this growth on the bunch temperature anisotropy as predicted by Struckmeier, but also find modifications not predicted by theory. Our findings are applicable in particular to high current linac simulation, where they can help to estimate noise effects and find an effective balance between the number of simulation particles and the grid resolution. In principle, they can also be generalized to bunches in circular machines.

Slides WEO4LR03 [2.946 MB]

THO2LR01

H⁻ Beam Optics for the Laser Stripping Project

350

T.V. Gorlov, A.V. Aleksandrov, S.M. Cousineau, V.V. Danilov, M.A. Plum
ORNL, Oak Ridge, Tennessee, USA

Successful realization of the laser stripping experiment depends mainly on correct tailoring of H⁻ bunch and laser beam. H⁻ beam preparation is a challenging task that requires to tune up about 10 parameters simultaneously in situ and taking into account life state of accelerator. This makes a huge technological difference compared to the foil stripping method. In this paper we present experience and methods of tuning the H⁻ bunch.

THO2LR02

Beam Dynamics and Experiment of CPHS Linac

355

L. Du, C.T. Du, X. Guan, C.-X. Tang, R. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
TUB, Beijing, People's Republic of China
M.W. Wang
Tsinghua University, Beijing, People's Republic of China

Funding: Work supported by National Natural Science Foundation of China (Major Research Plan Grant No. 91126003 and 11175096)
We present, in this paper, the present beam dynamics simulation results and experiments of the 3 MeV high current proton linac for the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. The beam dynamics simulations of the recent status of the linac have been done, which helps the operation. Facility used for 2D beam profile measurement which is based on the CT algorithm with rotatable multi-wires, is under development. Some other experiments such as beam position measurement will also be introduced below.

Slides THO2LR02 [3.479 MB]

THO2LR03

Beam Halo Control Study on the ADS Superconducting Linac Design at IHEP

F. Yan, H. Geng, C. Meng, S. Pei, J.Y. Tang
IHEP, Beijing, People's Republic of China
Z. Li
SCU, Chengdu, People's Republic of China

The Accelerator Driven sub-critical System (ADS) has an extremely low beam loss rate demand for the driver linac because of the high power intensity needed to be transferred to the target. China ADS project is proposed to build a 15 MW proton linac with final energy of 1.5 GeV and an average beam current of 10 mA. Fulfilling the 1 W/m power losses restriction along the whole linac posed a very high requirement on the stability of the driver linac design. Most of the beam losses in this level associated with the halo particles. In the design stage of China ADS linac, the beam halo are controlled in several aspects according to the halo formation mechanisms. Reasonable designs have been achieved for the China ADS Injector-I with few percentage of normalized rms emittances. Extensive error analysis were carried out to test the stability of the Injector-I design. The design considerations, the results of an optimized design and the beam dynamic simulations including machine errors are introduced and presented in detail.

Slides THO2LR03 [3.023 MB]

THO2LR04

Catalogue of Losses for the Linear IFMIF Prototype Accelerator

360

N. Chauvin, P.A.P. Nghiem
CEA/DSM/IRFU, France
M. Comunian
INFN/LNL, Legnaro (PD), Italy
C. Oliver
CIEMAT, Madrid, Spain
D. Uriot
CEA/IRFU, Gif-sur-Yvette, France

One major activity of the EVEDA (Engineering Validation and Engineering Design Activities) phase of the IFMIF (International Fusion Materials Irradiation Facility) project consists in building, testing and operating, in Japan, a 125 mA/9 MeV deuteron accelerator, called LIPAc, which has been developed in Europe. For the accelerator safety aspects, a precise knowledge of beam loss location and power deposition is crucial, especially for a high intensity, high power accelerator like LIPAc. This paper presents the beam dynamics simulations allowing to estimate beam losses in different situations of the accelerator lifetime: starting from scratch, beam commissioning, tuning or exploration, routine operation, sudden failure. Some results of these studies are given and commented on. Recommendations for hot point protection, beam stop velocity, beam power limitation are given accordingly.

Slides THO2LR04 [2.790 MB]

Paper	Title	Page
MOPAB17	RMS Emittance Measures for Solenoid Transport and Facitlity for Rare Isotope Beams Front-End Simulations	57
	S.M. Lund, G. Pozdeyev, H.T. Ren, Q. Zhao FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Grant No. PHY-1102511. Measurement of beam phase-space area via rms emittances in solenoid focusing channels with linear x-y coupling is complicated relative to transport channels with decoupled plane focusing. This stems from correlated azimuthal flow of the beam induced by the coupled focusing influencing how the thermal component of the flow should be measured. This is exacerbated when the beam has finite canonical angular momentum – as is the case for beams born in a magnetic field in ECR-type sources. In this study, simple measures of rms emittance for use in solenoid transport for beams with canonical angular momentum are motivated and overviewed. Emphasis is placed on simple to interpret emittance measures which reduce to familiar forms for decoupled plane motion. These emittances are applied in Warp PIC simulations of the near-source region of the FRIB linac front-end. In these simulations, a multi-species heavy-ion dc beam emerging from an ECR source are simulated primarily in transverse slice mode using a realistic lattice description. Emittance growth due to nonlinear applied fields, space-charge, and partial neutralization is analyzed including the influence of net canonical angular momentum.

MOPAB18	An ESS Linac Collimation Study	62
	R. Miyamoto, M. Eshraqi ESS, Lund, Sweden H.D. Thomsen ISA, Aarhus, Denmark
	The European Spallation Source (ESS) is planned in Lund, Sweden, and will be a neutron source based on a proton linac with an unprecedented 5 MW beam power. Mitigation of beam losses is the most crucial challenge in beam physics for such a high power proton linac and collimation systems are planned in sections of the medium and high energy beam transport (MEBT and HEBT). A preliminary study of the collimation systems was presented in the previous time of this workshop but the linac design went through a significant revision since then. The system to expand the beam for the neutron target, located in the HEBT, was changed from one based on nonlinear magnets to a raster system and this change particularly had a significant impact on the demand on the collimation systems. This paper presents an updated beam dynamics study of the collimation systems for the present layout of the ESS Linac.

MOPAB19	Space-Charge Compensation of Intense Ion Beams by Nonneutral Plasma Columns	67
	K. Schulte, M. Droba, O.K. Kester, S. Klaproth, O. Meusel, D. Noll, U. Ratzinger, K. Zerbe IAP, Frankfurt am Main, Germany O.K. Kester GSI, Darmstadt, Germany
	Gabor lenses were conceived to focus a passing ion beam using the electrical field of a confined nonneutral plasma column. Beside its application as focusing device, in Gabor lenses space-charge effects can be studied in detail. The influence of the electron distribution on emittance and space-charge dominated ion beams was investigated in beam transport experiments. In this contribution we want to emphasize one result of these experiments. The measurements indicated a strong contribution of secondary electrons on beam dynamics. Secondary electrons are produced within the transport channel, particularly by interaction of the beam with the surface of the slit-grid emittance scanner. This might lead to an increase of the filling degree and to an improved focusing performance of the lens. Assuming that the loss and production rates within the lens volume and the transport channel determine the equilibrium state of the nonneutral plasma column, the electron cloud was characterized as a function of the external fields and the residual gas pressure in small-scale table top experiments. In this contribution experimental results will be presented in comparison with numerical simulations. K. Schulte, “Studies on the focusing performance of a Gabor lens depending on nonneutral plasma properties”, PhD thesis, 2013.

TUO1LR01	Multi-Charge-State Beam Dynamics in FRIB
	Q. Zhao FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The Facility for Rare Isotope Beams (FRIB) is a new generation national user facility for nuclear science under establishment at the Michigan State University. The cw superconducting driver linac will accelerate all stable isotopes (from protons to uranium) to energies above 200 MeV/u with a beam power of up to 400 kW. To meet the output beam power requirements for ions heavier than xenon, two charge states will be selected from an ECR ion source and accelerated simultaneously in every other rf bucket through RFQ and Segment 1. After the acceleration in Segment 1 up to 20 Mev/u, a charge stripper is used to boost charge states for heavy ions and thus increase the acceleration efficiency for the rest of the linac. Multiple charge states (up to 5 depending on ions) will also be selected after stripper and further accelerated in Segment 2 and Segment 3 in the same rf bucket before delivery to a target. Beam dynamics associated with simultaneous acceleration/transport of multi-charge-state ions in the high power machine will be reported.
	Slides TUO1LR01 [2.749 MB]

TUO1LR02	The Design and Beam Dynamics Study for CSNS Linac
	H.C. Liu, S. Fu, J. Peng, S. Wang IHEP, Beijing, People's Republic of China
	The China Spallation Neutron Source (CSNS) linac consists of a 50 keV H⁻ ion source, a 3 MeV RFQ, and an 80 MeV alvarez type DTL. It provides an H⁻ beam of 15 mA peak current with a pulsed beam width about 420 μs and a repetition rate of 25 Hz for injection into the following 1.6 GeV rapid-cycling synchrotron (RCS). The transverse and longitudinal beam optics is introduced. The original design scheme is optimized based on the end-to-end simulation. Besides beam dynamics, the commissioning plan for linac is also presented, including the commissioning correlated parameters, beam instrumentation used in commissioning, the goal at different commissioning stages.
	Slides TUO1LR02 [6.961 MB]

TUO1LR03	ESS Linac Design and Cost Optimization as Function of Beam Dynamics
	M. Eshraqi ESS, Lund, Sweden
	The energy and power of accelerators used for research are growing to meet the demand of experiments. These increases are usually translated to costlier accelerators and bigger facilities. However, proper handling of beam power in the megawatt range requires a robust design that respects the known rules of thumb in accelerator design to limit the losses at a challenging level of less than one part in million. Traditionally cost increases with power and quality of the accelerator and beam. In this paper, using the ESS linac as an example, this tradition is challenged and ways to reduce the cost while neither quality nor power are compromised are presented.
	Slides TUO1LR03 [7.327 MB]

WEO3LR01	Beam Setup Conditions and Comparison of Deal and Actual Production Conditions
	M.A. Plum, A.P. Shishlo ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. This presentation will review methods for experimental determination of optimal operational set points in a multi-cavity superconducting high power hadron linac. A typical tuning process, including establishing correct acceleration profile and rms bunch size matching, is based on comparisons between measured data and results of simulations from envelope, single and multi-particle models. Presence of significant space charge effects requires simulation and measurement of bunch dynamics in three dimensions to ensure low loss beam transport. This is especially difficult in a superconducting linac where the use of interceptive beam diagnostics is usually restricted because of the risk of SRF cavity surface contamination. The procedures discussed here are based on non-interceptive diagnostics such as beam position monitors and laser wires, and conventional diagnostics devices such as wire scanners and bunch shape monitors installed outside the superconducting linac. The longitudinal Twiss analysis based on the BPM signals will be described. The superconducting SNS linac tuning experience will be used to demonstrate problems and their solution for real world linac tune-up procedures.
	Slides WEO3LR01 [7.162 MB]

WEO3LR03	Nonlinear Optimization in High Intensity Superconducting Linac Lattice of CADS
	Z.J. Wang, Y. He, S.H. Liu IMP, Lanzhou, People's Republic of China
	With the development of high-energy, high intensity ion linac all over the world, the optimization design of accelerating lattice has become a concern. The China Accelerator Driven System(ADS) superconducting proton linac is used as an example to illustrate the strategies and techniques which we have been developed for the optimization design of ion linac. First, an novel idea, which optimizes the periodic phase advance array directly in both longitudinal and transverse direction, is proposed to design the superconducting acceleration section. The results shown that the new idea can make the lattice design of ion linac easily accord with physics rules. Second, the Particle Swarm Optimiation(PSO) algorithm is utilized to optimize the phase advance array setting automatically. The advantage of utilization of optimiation algorithm is that it can find potential solutions that cannot be found by hand. Addtionally, Multi-goal Optimization technique is used to study the nonlinear properties of lattice. The strategies and techniques are generally-used and can be adopted in the other ion linacs design.

WEO3LR04	Emittance Transfer in Linacs	289
	L. Groening, M.T. Maier, C. Xiao GSI, Darmstadt, Germany O.K. Kester IAP, Frankfurt am Main, Germany
	Flat beams feature unequal emittances in the horizontal and vertical phase space. Such beams were created successfully in electron machines by applying effective stand-alone solenoid fringe fields in the electron gun. This contribution is an extension of the method to ion beams and on the decoupling capabilities of such a round-to-flat adaptor. The beam line provides a single-knob tool to partition the horizontal and vertical rms emittances, while keeping the product of the two emittances constant as well as the transverse rms Twiss parameters (beta_x;y and alpha_x;y) in both planes. This single knob is the solenoid field strength. The successful commissioning of the set-up with beam will be presented as well.
	Slides WEO3LR04 [1.289 MB]

WEO4LR01	New Methods and Concepts for Very High Intensity Beams
	P.A.P. Nghiem, N. Chauvin CEA/DSM/IRFU, France M. Comunian INFN/LNL, Legnaro (PD), Italy C. Oliver CIEMAT, Madrid, Spain W. Simeoni IF-UFRGS, Porto Alegre, Brazil D. Uriot, M. Valette CEA/IRFU, Gif-sur-Yvette, France
	For very high intensity beams, not only beam power but also space charge is a concern, so that both aspects should be taken into considerations for any analysis. Beam blowup due to space charge forces can be mitigated by bringing closer the focusing and accelerating components, making the beam diagnostic implementation difficult. A clear strategy for beam diagnostic has to be defined. Beam halo is no longer negligible but plays a significant role in the dynamic of the beam and in the particle loss process. Beam optimization must take it into account and beam characterization must describe not only the core part but also the halo one. This paper presents the new concepts and methods for beam analysis, beam diagnostics, beam optimization and beam characterization.
	Slides WEO4LR01 [3.342 MB]

WEO4LR02	The Particle-in-Cell Code Bender and Its Application to Non-Relativistic Beam Transport	304
	D. Noll, M. Droba, O. Meusel, U. Ratzinger, K. Schulte, C. Wiesner IAP, Frankfurt am Main, Germany
	A new non-relativistic, electrostatic Particle-in-Cell code named bender has been implemented to facilitate the investigation of low-energy beam transport scenarios. In the case of high-intensity beams, space-charge compensation resulting from the accumulation of secondary particles - electrons for positively charged ion beams - is an important effect. It has been shown, that the distribution of compensation electrons can have a significant influence on the beam and lead to an emittance growth. To improve the understanding of the dynamics of the compensation and the resultant self-consistent steady state, ionization of residual gas as well as secondary electron production on surfaces have been implemented and used to study a number of test systems. We will present first results of these compensation studies as well as further applications of the code, among them the chopper section of the future FRANZ facility [1]. * C. Wiesner et al., Experimental Performance of an E×B Chopper System, Proc. of IPAC 2014, THPME015
	Slides WEO4LR02 [5.373 MB]

WEO4LR03	Noise and Entropy in Non-Equipartitioned Particle Beams	309
	I. Hofmann, O. Boine-Frankenheim GSI, Darmstadt, Germany O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany
	The numerical noise generated in particle-in-cell simulation of 3D high intensity bunched beams is studied with the TRACEWIN code and compared with the analytical entropy model by Struckmeier. In this model the logarithm of the six-dimensional rms emittance is shown to qualify as rms-based entropy. We confirm the dependence of this growth on the bunch temperature anisotropy as predicted by Struckmeier, but also find modifications not predicted by theory. Our findings are applicable in particular to high current linac simulation, where they can help to estimate noise effects and find an effective balance between the number of simulation particles and the grid resolution. In principle, they can also be generalized to bunches in circular machines.
	Slides WEO4LR03 [2.946 MB]

THO2LR01	H⁻ Beam Optics for the Laser Stripping Project	350
	T.V. Gorlov, A.V. Aleksandrov, S.M. Cousineau, V.V. Danilov, M.A. Plum ORNL, Oak Ridge, Tennessee, USA
	Successful realization of the laser stripping experiment depends mainly on correct tailoring of H⁻ bunch and laser beam. H⁻ beam preparation is a challenging task that requires to tune up about 10 parameters simultaneously in situ and taking into account life state of accelerator. This makes a huge technological difference compared to the foil stripping method. In this paper we present experience and methods of tuning the H⁻ bunch.

THO2LR02	Beam Dynamics and Experiment of CPHS Linac	355
	L. Du, C.T. Du, X. Guan, C.-X. Tang, R. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng TUB, Beijing, People's Republic of China M.W. Wang Tsinghua University, Beijing, People's Republic of China
	Funding: Work supported by National Natural Science Foundation of China (Major Research Plan Grant No. 91126003 and 11175096) We present, in this paper, the present beam dynamics simulation results and experiments of the 3 MeV high current proton linac for the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. The beam dynamics simulations of the recent status of the linac have been done, which helps the operation. Facility used for 2D beam profile measurement which is based on the CT algorithm with rotatable multi-wires, is under development. Some other experiments such as beam position measurement will also be introduced below.
	Slides THO2LR02 [3.479 MB]

THO2LR03	Beam Halo Control Study on the ADS Superconducting Linac Design at IHEP
	F. Yan, H. Geng, C. Meng, S. Pei, J.Y. Tang IHEP, Beijing, People's Republic of China Z. Li SCU, Chengdu, People's Republic of China
	The Accelerator Driven sub-critical System (ADS) has an extremely low beam loss rate demand for the driver linac because of the high power intensity needed to be transferred to the target. China ADS project is proposed to build a 15 MW proton linac with final energy of 1.5 GeV and an average beam current of 10 mA. Fulfilling the 1 W/m power losses restriction along the whole linac posed a very high requirement on the stability of the driver linac design. Most of the beam losses in this level associated with the halo particles. In the design stage of China ADS linac, the beam halo are controlled in several aspects according to the halo formation mechanisms. Reasonable designs have been achieved for the China ADS Injector-I with few percentage of normalized rms emittances. Extensive error analysis were carried out to test the stability of the Injector-I design. The design considerations, the results of an optimized design and the beam dynamic simulations including machine errors are introduced and presented in detail.
	Slides THO2LR03 [3.023 MB]

THO2LR04	Catalogue of Losses for the Linear IFMIF Prototype Accelerator	360
	N. Chauvin, P.A.P. Nghiem CEA/DSM/IRFU, France M. Comunian INFN/LNL, Legnaro (PD), Italy C. Oliver CIEMAT, Madrid, Spain D. Uriot CEA/IRFU, Gif-sur-Yvette, France
	One major activity of the EVEDA (Engineering Validation and Engineering Design Activities) phase of the IFMIF (International Fusion Materials Irradiation Facility) project consists in building, testing and operating, in Japan, a 125 mA/9 MeV deuteron accelerator, called LIPAc, which has been developed in Europe. For the accelerator safety aspects, a precise knowledge of beam loss location and power deposition is crucial, especially for a high intensity, high power accelerator like LIPAc. This paper presents the beam dynamics simulations allowing to estimate beam losses in different situations of the accelerator lifetime: starting from scratch, beam commissioning, tuning or exploration, routine operation, sudden failure. Some results of these studies are given and commented on. Recommendations for hot point protection, beam stop velocity, beam power limitation are given accordingly.
	Slides THO2LR04 [2.790 MB]