MOP2WB —  WG-B   (18-Jun-18   16:00—18:00)
Chair: P.A.P. Nghiem, IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
Paper Title Page
MOP2WB01 60 mA Beam Study in J-PARC Linac -1
  • Y. Liu
    KEK/JAEA, Ibaraki-Ken, Japan
  • A. Miura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • T. Miyao
    KEK, Ibaraki, Japan
  • M. Otani, T. Shibata
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  Upgrade of Linac peak current from 50 mA to 60 mA is one of the keys to the next power upgrade in J-PARC. Beam studies with 60 mA were carried out in July and December, 2017, for the challenging issues such as investigation of beam property from the ion source, halo behavior throughout the LEBT, RFQ and MEBT1, emittance/Twiss measurement at MEBT1, beam emittance control, etc. Expected/unexpected problems, intermediate results and preparation for the next trials were introduced in this paper.  
slides icon Slides MOP2WB01 [12.952 MB]  
MOP2WB02 Simulation and Measurement Campaigns for Characterization and Performance Improvement of the CERN Heavy Ion Linac3 -1
  • G. Bellodi, S. Benedetti, D. Küchler, F.J.C. Wenander
    CERN, Geneva, Switzerland
  • V. Toivanen
    GANIL, Caen, France
  In the framework of the LHC Injector Upgrade programme (LIU), several activities have been carried out to improve the GTS-LHC ion source and Linac3 performance (Linac3 providing the charged heavy ion beams for CERN exper-iments). A restudy of the beam dynamics and transport through the linac was initiated, through a campaign of systematic machine measurements and parallel beam simulations, generalising techniques developed for beam characterization during Linac4 commissioning. The work here presented will review the most relevant findings and lessons learnt in the process.  
slides icon Slides MOP2WB02 [17.512 MB]  
MOP2WB03 Emittance Growth and Beam Losses in LANSCE Linear Accelerator -1
  • Y.K. Batygin, R.W. Garnett, L. Rybarcyk
    LANL, Los Alamos, New Mexico, USA
  Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
The LANSCE Accelerator facility currently utilizes four 800 MeV H beams and one 100 MeV proton beam. Multi-beam operation requires careful control of accelerator tune to minimize beam losses. The most powerful 80 kW H beam is accumulated in the Proton Storage Ring and is extracted to the Lujan Neutron Scattering Center facility for production of moderated neutrons with meV-keV energy. Another H beam is delivered to the Weapon Neutron Research facility to create un-moderated neutrons in the keV - MeV energy range. The third H beam is shared between the Proton Radiography Facility and the Ultra-Cold Neutron facility. The 23 kW proton beam is used for isotope production in the fields of medicine, nuclear physics, national security, environmental science and industry. Minimization of beam losses in the linac is achieved due to careful tuning of the beam in each section of the accelerator facility, imposing restrictions on amplitudes and phases of RF sections, control of H beam stripping, and optimization of ion sources operation. This paper summarizes experimental results in accelerator operations and categorizes various sources of emittance growth and beam losses.
slides icon Slides MOP2WB03 [4.570 MB]  
The Beam Dynamics Design of CW RFQ for Chinese ADS  
  • W.P. Dou, Y. He, H. Jia, S.H. Liu, C. Wang, Z.J. Wang
    IMP/CAS, Lanzhou, People's Republic of China
  A superconducting proton linear accelerator for Chinese ADS have been proposed by IMP CAS. The preliminary beam dynamics design is finished. The RFQ is designed to be operated at CW mode will accelerate 10 mA proton from 35 keV to 2.1 MeV. The acceleration rate of RFQ is 95.2% with the length of 4.5 meters. The 99.9 % longitudinal emittance at the RFQ exit is optimized to 4.98 and 0.18 times of the longitudinal acceptance of downstream superconducting accelerator. These goals of RFQ beam dynamic studies usually are minimize the vane length, beam loss and emittance growth. But the 99.9 % longitudinal emittance of RFQ is proposed as the new and key optimization goal to reduce the possibility of downstream beam loss for the RFQ which is in the front of superconducting linear accelerator. The 99.9 % longitudinal emittance is optimised at the cost of RFQ transmission rate though three steps. First, the optimised longitudinal phase space is got by the long and stable shaper section. Second, Smaller longitudinal acceptance is adopted to make particle loss in low energy section. third, the shrink of longitudinal acceptance is optimised to get lower 99.9% longitudinal emittance.  
slides icon Slides MOP2WB04 [4.448 MB]  
Analysis of Envelope Perturbations in High-Intensity Beams Using Generalized Courant-Snyder Formulation  
  • M. Chung
    UNIST, Ulsan, Republic of Korea
  • H. Qin
    PPPL, Princeton, New Jersey, USA
  Funding: This research was supported by the National Research Foundation of Korea (Grant No. NRF-2017M1A7A1A02016413).
Analysis of the small-amplitude perturbations around the matched beam envelope has been used as a basic theoretical framework to characterize the high-intensity beam transport. The beam stability properties in periodic quadrupole and solenoid channels have been analyzed by many authors in terms of that framework. In general, the linearized perturbed envelope equations are coupled. Therefore, application of the conventional Courant-Snyder theory to this problem has not been straightforward. In this work, we adopt the recently developed generalized Courant-Snyder formulation, and revisit the spectral and structural stability properties of the envelope perturbations. The generalized Courant-Snyder invariant of the envelope perturbations is identified, and its physical interpretation will be given. Since the generalized Courant-Snyder formulation can be easily extended to three-dimensional cases, we also investigate the three-dimensional envelope instability by means of the generalized Courant-Snyder formulation.
slides icon Slides MOP2WB05 [6.945 MB]