  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
