Regular Article

Compression of a mixed antiproton and electron non-neutral plasma to high densities

¹ Politecnico of Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
² INFN Milano, via Celoria 16, 20133 Milano, Italy
³ Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria
⁴ Department of Mechanical and Industrial Engineering, University of Brescia, via Branze 38, 25123 Brescia, Italy
⁵ INFN Pavia, via Bassi 6, 27100 Pavia, Italy
⁶ Department of Physics, University of Trento, via Sommarive 14, 38123 Povo, Trento, Italy
⁷ TIFPA/INFN Trento, via Sommarive 14, 38123 Povo, Trento, Italy
⁸ Department of Science, University of Insubria, Via Valleggio 11, 22100 Como, Italy
⁹ Department of Physics, University of Genova, via Dodecaneso 33, 16146 Genova, Italy
¹⁰ INFN Genova, via Dodecaneso 33, 16146 Genova, Italy
¹¹ Department of Physics, University of Milano, via Celoria 16, 20133 Milano, Italy
¹² Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany
¹³ Laboratoire Aimé Cotton, Université Paris-Sud, ENS Cachan, CNRS, Université Paris-Saclay, 91405 Orsay Cedex, France
¹⁴ Kirchhoff-Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
¹⁵ Physics Department, CERN, 1211 Geneva 23, Switzerland
¹⁶ Department of Physics, University of Oslo, Sem Sælandsvei 24, 0371 Oslo, Norway
¹⁷ Institute of Nuclear Physics, CNRS/IN2p3, University of Lyon 1, 69622 Villeurbanne, France
¹⁸ Institute for Nuclear Research of the Russian Academy of Science, Moscow 117312, Russia
¹⁹ Joint Institute for Nuclear Research, 141980 Dubna, Russia
²⁰ INFN Padova, via Marzolo 8, 35131 Padova, Italy
²¹ Czech Technical University in Prague, Břehová 7, 11519 Prague 1, Czech Republic
²² University of Bologna, Viale Berti Pichat 6/2, 40126 Bologna, Italy
²³ Department of Physics, University of Pavia, via Bassi 6, 27100 Pavia, Italy
²⁴ The Research Council of Norway, P.O. Box 564, 1327 Lysaker, Norway
²⁵ Department of Physics, Heidelberg University, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
²⁶ Department of Civil Engineering, University of Brescia, via Branze 43, 25123 Brescia, Italy

^a e-mail: daniel.krasnicky@ge.infn.it

Received: 28 September 2017
Received in final form: 17 January 2018
Published online: 30 April 2018

Abstract

We describe a multi-step “rotating wall” compression of a mixed cold antiproton–electron non-neutral plasma in a 4.46 T Penning–Malmberg trap developed in the context of the AEḡIS experiment at CERN. Such traps are routinely used for the preparation of cold antiprotons suitable for antihydrogen production. A tenfold antiproton radius compression has been achieved, with a minimum antiproton radius of only 0.17 mm. We describe the experimental conditions necessary to perform such a compression: minimizing the tails of the electron density distribution is paramount to ensure that the antiproton density distribution follows that of the electrons. Such electron density tails are remnants of rotating wall compression and in many cases can remain unnoticed. We observe that the compression dynamics for a pure electron plasma behaves the same way as that of a mixed antiproton and electron plasma. Thanks to this optimized compression method and the high single shot antiproton catching efficiency, we observe for the first time cold and dense non-neutral antiproton plasmas with particle densities n ≥ 10¹³ m⁻³, which pave the way for an efficient pulsed antihydrogen production in AEḡIS.