Paper 
Title 
Page 
TUPWA034 
On the Choice of Linac Parameters for Minimal Beam Losses 
1787 

 M. Eshraqi
ESS, Lund, Sweden
 J.M. Lagniel
GANIL, Caen, France



In high intensity linear accelerators, the tune spreads induced by the spacecharge forces in the radial and longitudinal planes are key parameters for halo formation and beam losses. For matched beams they are the parameters governing the number of resonances (including coupling resonances) which affect the beam and determine the respective sizes of the stable and halo areas in phase space. The number and strength of the resonances excited in mismatched beams leading to even higher amplitude halos are also directly linked to the tune spreads. In this paper, the equations making the link between the basic linac parameters (rf frequency, zerocurrent phase advances, beam intensity and emittances) and the tune spreads are given. A first analysis of the way these linac parameters can be chosen to minimize the tune spreads is presented. The parameters of ESS linac are used for this study.



TUPWO046 
The ESS Linac Simulator: A First Benchmark with TraceWin 
1970 

 E. Laface, M. Eshraqi, R. Miyamoto
ESS, Lund, Sweden



The ESS Linac Simulator, ELS, will be the core of the online model used in the normal operations of the ESS linac. ESS Linac Simulator will operate through the eXtensible Accelerator Language, XAL, in order to provide an effective interface capable to simulate and predict the beam dynamics of the accelerator. The ELS is capable of simulating the dynamics of the beam envelope in both transverse and longitudinal planes in real time. In order to validate the effectiveness of the physics implemented, the ELS calculations are here benchmarked with TraceWin: the simulation code used for the design of the accelerator.



WEPEA040 
Space Charge and Cavity Modeling for the ESS Linac Simulator 
2588 

 E. Laface, M. Eshraqi, R. Miyamoto
ESS, Lund, Sweden



The proton linac of the European Spallation Source will operate at unprecedented beam power of 5 MW. Such power requires a precise modeling of the beam dynamics in order to protect its components from losses. The high peak current of 62.5 mA produces a space charge force that dominates the dynamics at low energy, while the high gradient required to accelerate up to 2 GeV in the 500 m of linac length is challenging for the dynamics in the RF cavities. This paper presents modelings of the space charge force and RF cavities used in the ESS Linac Simulator. The simulator is under development as part of the XAL online model, and it will be adopted for the ESS linac operations.



THPWO072 
Design Options of the ESS Linac 
3921 

 M. Eshraqi, H. Danared, D.P. McGinnis
ESS, Lund, Sweden



The European Spallation Source, ESS, uses a linear accelerator to deliver the high intensity proton beam to the target station. The nominal average beam power is 5~MW with a peak beam power at target of 125~MW. During last year the ESS linac was costed, and to meet the budget a few modifications were introduced to the linac design, namely the final energy was decreased from 2.5~GeV to 2.0~GeV and the beam current was increased accordingly to compensate the lower final energy. As a result the linac is designed to meet the cost objective by taking a higher risk. This paper focuses on the new design options, beam dynamics requirements of the design and finally on the beam dynamics performance of the linac.


