Instabilities of an electron cloud in a Penning trap P. Paasche, C. Angelescu, S. Ananthamurthy, D. Biswas, T. Valenzuela and G. Werth Eur. Phys. J. D, 22 2 (2003) 183-188 Published online: 17 December 2002 DOI: 10.1140/epjd/e2002-00239-3