Author: Yuri, Y.
Paper Title Page
MOPPD013 Observation of 2-Component Bunched Beam Signal with Laser Cooling 397
 
  • H. Souda, M. Nakao, A. Noda, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • M. Grieser
    MPI-K, Heidelberg, Germany
  • Z.Q. He
    TUB, Beijing, People's Republic of China
  • K. Ito, H. Okamoto
    HU/AdSM, Higashi-Hiroshima, Japan
  • K. Jimbo
    Kyoto University, Institute for Advanced Energy, Kyoto, Japan
  • Y. Yuri
    JAEA/TARRI, Gunma-ken, Japan
 
  Funding: Work supported by Advanced Compact Accelerator Development Project of MEXT, Global COE program "The Next Generation of Physics, Spun from Universality and Emergence" and Grant-in-Aid for JSPS Fellows.
Longitudinal beam temperature during a laser cooling was measured through bunch length measurement at S-LSR. 40keV 24Mg+ beams were bunched by an RF voltage with a harmonic number of 5 and were cooled by a co-propagating laser with a wavelength of 280nm*. Bunch length was measured by time-domain signal from a pair of parallel-plate electrostatic pickups with a length of 140mm. Injected non-cooled beams gave a bunch length of 2.5m (2-σ) and cooled beam has a 2-component of broad and sharp distribution. Broad distribution had a longitudinal length of 2.2m, which is close to that of initial beam. The length of the sharp distribution shrunk to 0.25m and is considered as a cooled part. Capture efficiency of cooling, which represents the ratio of the particle numbers of cooled part and the total particle number, varies by the change of the detuning of the laser (fixed frequency or scanning). With scanning range of 2GHz, capture efficiency was improved from 66% to 92%, whereas the bunch became longer by 10% with scanning. Approach to improve the number of cooled particle and cut uncooled part** will be applied to attain a strong signal with a low-current beam with a low temperature.
* J. S. Hangst et al., Phys. Rev. Lett. 74, 4432 (1995).
** A. Noda et al., these proceedings.
 
 
MOPPD012 Challenge for More Efficient Transverse Laser Cooling for Beam Crystallization 394
 
  • A. Noda, M. Nakao, H. Souda, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • M. Grieser
    MPI-K, Heidelberg, Germany
  • Z.Q. He
    TUB, Beijing, People's Republic of China
  • K. Ito, H. Okamoto, K. Osaki
    HU/AdSM, Higashi-Hiroshima, Japan
  • K. Jimbo
    Kyoto University, Institute for Advanced Energy, Kyoto, Japan
  • Y. Yuri
    JAEA/TARRI, Gunma-ken, Japan
 
  Funding: Work supported by Advanced Compact Accelerator Development project by MEXT. Also supported by GCOE project at Kyoto University, The next generation of Physics-Spun from Universality and Emergency.
At S-LSR in ICR, Kyoto University, Mg ion beam has been successfully laser cooled both in longitudinal* and transverse** directions. The cooling rate, however, is not strong enough to realize the crystalline beam due to the heating because of intra-beam scattering (IBS) effect. So as to suppress this IBS, reduction of the beam intensity is inevitable, which however, had resulted in poor S/N ratio for observation of the transverse beam size. In the present paper, we would like to describe a new beam scraping scheme, which selects out the beams in the distribution tail of the transverse phase space keeping the beam density in the core part by simultaneous application of multi-dimensional laser cooling and beam scraping. The strategy to reduce the beam intensity and hence beam heating due to IBS by a controlled scraping of the outskirt beam keeping the beam density at core part almost the same, has been searched by combination of the beam experiments and computer simulations.
* M. Tanabe et al., Applied Physics Express 1, 028001 (2008).
** M. Nakao et al., submitted to PRST-AB.
 
 
TUOAA02 Focusing Charged Particle Beams Using Multipole Magnets in a Beam Transport Line 1062
 
  • Y. Yuri, I. Ishibori, T. Ishizaka, S. Okumura, T. Yuyama
    JAEA/TARRI, Gunma-ken, Japan
 
  The intensity distribution of a charged-particle beam is transformed by applying the nonlinear focusing force of a multipole magnet. In this paper, the transformation of the transverse intensity distribution due to the second-order sextupole and third-order octupole focusing force in the beam transport line is explored. As a measure of the distribution transformation induced by the multipole magnets, the beam centroid displacement and the change of the beam size have been analytically derived using the distribution function of the beam. It is numerically verified how the transverse distribution of the beam is transformed by the multipole magnets. As an application of the distribution transformation by nonlinear focusing, a uniform beam can be formed from a Gaussian beam using multipole magnets. The current status and future plan of the experiment on the uniform-beam formation at the cyclotron facility in Japan Atomic Energy Agency will be shown.  
slides icon Slides TUOAA02 [2.032 MB]