  A low-emittance, high-intensity atomic beam of muonium ($\mathrm{M}=\mu^+ +
\mathrm{e}^-$) using superfluid helium as muon-to-muonium converter is being
developed at the Paul Scherrer Institute (PSI). This beam could advance laser
spectroscopy of muonium and allow the first atomic interferometry experiments
for the direct observation of the M gravitational interaction. In this paper,
we describe the development of compact detection schemes which resulted in the
background-suppressed observation of atomic muonium in vacuum, and can be
adapted for cryogenic measurements. Using these setups, we compared the
emission characteristics of various muonium production targets using low
momentum ($p_{\mu} = 11$-$13~$MeV/c) muons, and observed muonium emission from
zeolite targets into vacuum for the first time. For a specific laser-ablated
aerogel target, we determined a muon-to-vacuum-muonium conversion efficiency of
$7.23 \pm 0.05 \text{(stat)} ^{+1.06}_{-0.76}\text{(sys)}\,\text{%}$, assuming
thermal emission of muonium. Moreover, we investigated muonium-helium
collisions and from it we determined an upper temperature limit of 0.3 K for
the superfluid helium converter.
