MUSASHI --- "Monoenergetic Ultra Slow Antiproton Source for High-precision Investigations"

Making ultra-slow antiproton beams with RFQD and MUSASHI at CERN AD.

The preparation of large samples of antiprotons at extremely low energy is an important step on the road to synthesizing antihydrogen (pe+) and antiprotonic atoms (pA+).

The CERN Antiproton Decelerator (AD) decelerates antiprotons with GeV-scale kinetic energy to 5.3 MeV, and re-ejects them every 90-120 sec in 100 ns long pulses, containing some 3 x 10^7 particles. This beam energy is, however, still far above the 10 keV range at which antiprotons can readily be captured and cooled in electromagnetic traps.

We replaced ordinary simple degrader foils to reduce antiproton energy by a Radio Frequency Quadrupole Decelerator (RFQD). This substantial decelerator, 4 meters in length, reduced the 5.3 MeV AD beam energy between 10 and 120 keV. Some (5--9) x 10^6 antiprotons within a single shot fulfilled the phase condition necessary for acceptance and deceleration by the RFQD, the remainder being transmitted without deceleration. We expected that the reduced antiproton energy would allow a much larger number of the emerging antiprotons to be captured in a trap placed after the RFQD than is normally the case for simple degrader foils. For these experiments we used a multiring trap (MRT) comprised of several ring electrodes lying perpendicular to the beam and on the axis of a superconducting solenoid at 10 K.

Antiproton trap

Antiprotons from the RFQD were trapped and cooled in this electro-magnetic trap.

  • liquid helium free Superconducting solenoid
  • Multi-Ring electrode Trap (MRT)

Ultra-Slow antiproton beam transport line

After the cooling, antiprotons were extracted from the trap and transported to experimental chambers via this transport beam line.

  • differential pumping system
  • elctrostatic lens


  • N. Kuroda, H. A. Torii, Y. Nagata, M. Shibata, Y. Enomoto, H. Imao, Y. Kanai, M. Hori, H. Saitoh, H. Higaki, A. Mohri, K. Fujii, C. H. Kim, Y. Matsuda, K. Michishio, Y. Nagashima, M. Ohtsuka, K. Tanaka, and Y. Yamazaki.
    Phys. Rev. ST Accel. Beams, 15(2)024702, Feb. 2012
    "Development of a monoenergetic ultraslow antiproton beam source for high-precision investigation. "
  • N. Kuroda, H.A. Torii, M. Shibata, Y. Nagata, D. Barna, M. Hori, D. Horváth, A. Mohri, J. Eades, K. Komaki, and Y. Yamazaki.
    "Radial compression of an antiproton cloud for production of intense antiproton beams"
    Phys. Rev. Lett., 100(20):203402, May 2008.
  • N. Kuroda, H.A. Torii, K. Yoshiki Franzen, Z. Wang, S. Yoneda, M. Inoue, M. Hori, B. Juhász, D. Horváth, H. Higaki, A. Mohri, J. Eades, K. Komaki, and Y. Yamazaki.
    "Confinement of a Large Number of Antiprotons and Production of an Ultraslow Antiproton Beam"
    Phys. Rev. Lett., 94(2):023401, January 2005.
  • H. Higaki, N. Kuroda, K. Yoshiki Franzen, Z. Wang, M. Hori, A. Mohri, K. Komaki, and Y. Yamazaki.
    "Radial compression of protons and H3+ ions in the multiring trap: for the production of ultra low energy antiproton beams"
    Phys. Rev. E, 70(2):026501, August 2004.
  • K. Yoshiki Franzen, N. Kuroda, H.A. Torii, M. Hori, Z. Wang, H. Higaki, S. Yoneda, B. Juhász, D. Horváth, A. Mohri, K. Komaki, and Y. Yamazaki.
    "Transport beam line for ultraslow monoenergetic antiprotons."
    Rev.Sci.Instrum., 74(7):3305, July 2003.
  • H. Higaki, N. Kuroda, T. Ichioka, K. Yoshiki Franzen, Z. Wang, K. Komaki, and Y. Yamazaki.
    "Electron cooling of high-energy protons in a multiring trap with a tank circuit monitoring the electron-plasma oscillations."
    Phys.Rev.E, 65(4):046410, April 2002.
  • Y. Yamazaki.
    "Production of ultra slow antiprotons, its application to atomic collisions and atomic spectroscopy - ASACUSA project"
    Nucl.Instrum.Methods Phys.Res.B, 154:174, June 1999.