• H. Higaki, H. Okamoto
  HU/AdSM, Higashi-Hiroshima
• Y. Enomoto, C.H. Kim, N. Kuroda, Y. Matsuda, H.A. Torii, Y. Yamazaki
  The University of Tokyo, Institute of Physics, Tokyo
• H. Hori
  MPQ, Garching, Munich
• H. Imao, Y. Kanai, A. Mohri, Y. Nagata
  RIKEN, Wako, Saitama
• K. Kira
  Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima
• K. Michishio
  Tokyo University of Science, Tokyo

In Antiproton Decelerator (AD) at CERN, unique low energy antiproton beams of 5.6 MeV have been delivered for physics experiments. Furthermore, the RFQ decelerator (RFQD) dedicated for Atomic Spectroscopy And Collisions Using Slow Antiprotons (ASACUSA) collaboration enables the use of 100 keV pulsed antiproton beams for experiments. What is more, Mono-energetic Ultra Slow Antiproton Source for High-precision Investigations (MUSASHI) in ASACUSA can produce antiproton beams with the energy of 100 ~ 1000 eV. Since the successful extraction of 250 eV antiproton beams reported in 2005, continuous improvements on beam quality and equipments have been conducted. Here, the basic properties of a tank circuit attached to MUSASHI trap are reported. Signals from a tank circuit provide information on the trapped antiprotons, as Shottky signals do for high energy beams in accelerators. In fact, it is known that this kind of trap-based beams are physically equivalent with those in a FODO lattice. Monitoring the tank circuit signals will be useful for on-line handling of the low energy antiproton beams from MUSASHI.

• N. Kuroda, Y. Enomoto, H. Imao, C.H. Kim, Y. Matsuda, H.A. Torii, Y. Yamazaki
  The University of Tokyo, Institute of Physics, Tokyo
• H. Higaki
  HU/AdSM, Higashi-Hiroshima
• H. Hori
  MPQ, Garching, Munich
• Y. Kanai, A. Mohri, Y. Nagata
  RIKEN, Wako, Saitama
• K. Kira
  Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima
• K. Michishio
  Tokyo University of Science, Tokyo
• H. Saitoh
  University of Tokyo, Chiba
• M. Shibata
  KEK, Tsukuba

The ASACUSA collaboration at CERN has been developed a unique Mono-energetic Ulta-Slow Antiproton beam Source for High-precision Investigation (MUSASHI) for collision studies between antiproton and atoms at very low energy region, which also used as an intense ultra-low energy antiproton source for the synthesis of antihydrogen atoms in order to test CPT symmetry. MUSASHI consists of a multi-ring electrode trap housed in a bore surrounded by a superconducting solenoid, which works with a sequential combination of the CERN Antiproton Decelerator and the Radio-Frequency Quadrupole Decelerator. GM-type refrigerators were used to cool the solenoid and also the bore at 4K to avoid losses of antiprotons with residual gasses. Up to 1.8 millions of antiprotons per one AD cycle were successfully trapped and cooled. MUSASHI achieved to accumulate more than 12 millions of cold antiprotons by stacking several AD shots. Such cooled antiprotons were extracted as 150 or 250eV beams with various bunch lengths from 2 micoroseconds to 30 seconds long, whose energy width was the order of sub-eV. The beam intensity was enhanced by a radial compression technique for the trapped antiproton cloud.