Ultracold Muonium Negative Ion Production

Abstract

A new, efficient method to produce ultracold negative muon ions is proposed. The muonium atom is made up of an antimuon and an electron and is given the chemical symbol Mu. A second electron with binding energy or electron affinity of 0.75 eV makes the Mu- ion, which is in many ways almost identical to the H- ion that is used for charge-exchange injection into most proton particle accelerators. Muonium negative ions were observed in 1987 by interactions of muons with a foil. Using the foil charge-exchange approach, the efficiency of transformation of muons to negative muonium ions has been very low ~10-4. However, by using a hot tungsten or palladium single crystal foil or aerogel treated by cesium deposition, the production efficiency can be improved up to 50%. The process described here has surface muons focused onto a tungsten or palladium single crystal foil or aerogel (that can be heated up to 2000 Celsius) and partially covered by a cesium layer to provide a minimal work function. The negative muon ions can be extracted by a DC electric field and further accelerated by a linac and stripped in a thin foil. Charge exchange with a. dense flow of positive or negative ions is proposed for conversion of slow muonium atoms into positive and negative muonium ions