Towards trapped antihydrogen L.V. Jørgensen a, * , G. Andresen b , W. Bertsche c , A. Boston d , P.D. Bowe b , C.L. Cesar e , S. Chapman c , M. Charlton a , J. Fajans c , M.C. Fujiwara f , R. Funakoshi g , D.R. Gill f , J.S. Hangst b , R.S. Hayano g , R. Hydomako h , M.J. Jenkins a , L. Kurchaninov f , N. Madsen a , P. Nolan d , K. Olchanski f , A. Olin f , R.D. Page d , A. Povilus c , F. Robicheaux i , E. Sarid j , D.M. Silveira e , J.W. Storey f , R.I. Thompson h , D.P. van der Werf a , J.S. Wurtele c , Y. Yamazaki k , ALPHA Collaboration a Department of Physics, Swansea University, Swansea SA2 8PP, United Kingdom b Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark c Department of Physics, University of California at Berkeley, Berkeley, CA 94720-7300, USA d Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom e Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972, Brazil f TRIUMF, 4004 Westbrook Mall, Vancouver, Canada BV V6T 2A3 g Department of Physics, University of Tokyo, Tokyo 113-0033, Japan h Department of Physics and Astronomy, University of Calgary, Calgary, Canada AB T2N 1N4 i Department of Physics, Auburn University, Auburn, AL 36849-5311, USA j Department of Physics, NRCN-Nuclear Research Center Negev, Beer Sheva IL-84190, Israel k Atomic Physics Laboratory, RIKEN, Saitama 351-0198, Japan Available online 15 December 2007 Abstract Substantial progress has been made in the last few years in the nascent field of antihydrogen physics. The next big step forward is expected to be the trapping of the formed antihydrogen atoms using a magnetic multipole trap. ALPHA is a new international project that started to take data in 2006 at CERN’s Antiproton Decelerator facility. The primary goal of ALPHA is stable trapping of cold antihydrogen atoms to facilitate measurements of its properties. We discuss the status of the ALPHA project and the prospects for anti- hydrogen trapping. Ó 2008 Published by Elsevier B.V. PACS: 36.10.k; 34.80.Lx; 52.20.Hv Keywords: Antihydrogen; Antiprotons; Positrons; Penning trap; Atom traps; Multipole magnet 1. Introduction Cold antihydrogen was first produced in 2002 by ATHENA [1] at the Antiproton Decelerator (AD) at CERN [2]. The antimatter atoms were made by letting anti- protons and positrons come into close proximity in a nested Penning trap [3]. After formation the antihydrogen was no longer bound by the electric and magnetic fields of the trap regions and the anti-atoms drifted out to the elec- trode wall where they annihilated. This actually formed the basis of the detection in ATHENA where a purpose built annihilation detector monitored the tell-tale signs of an antiproton and a positron annihilating at the same time and in the same position [4]. The ATRAP experiment later made similar observations based on an indirect detection 0168-583X/$ - see front matter Ó 2008 Published by Elsevier B.V. doi:10.1016/j.nimb.2007.12.009 * Corresponding author. Present address: Bat. 545 R-021, CERN – European Laboratory for Particle Physics, CH-1211 Geneva 23, Switzer- land. Tel.: +41 76 487 3214; fax: +41 22 766 9583. E-mail address: lars.varming.jorgensen@cern.ch (L.V. Jørgensen). www.elsevier.com/locate/nimb Available online at www.sciencedirect.com Nuclear Instruments and Methods in Physics Research B 266 (2008) 357–362 NIM B Beam Interactions with Materials & Atoms