  Beam emission spectroscopy (BES) is a powerful plasma diagnostic method
especially suited for the measurement of plasma density and its fluctuations.
As such, synthetic BES codes are regularly used to aid the design or
utilization of these diagnostic systems. However, synthetic diagnostics can
also be used to study the method in previously not yet explored operational
conditions. This paper presents such an analysis utilizing the RENATE-OD
synthetic diagnostic code for a hypothetical alkali BES system on the HSX
stellarator. HSX is a device featuring an unusual operating regime in the world
of fusion devices due to the low ion temperature and low plasma density. It was
found that BES shows unusual tendencies in these conditions. The relation
between beam energy and plasma penetration in low-ion-temperature plasma,
together with unique emission features facilitated by low-density plasma, and
the underlying reasons behind these features are explored in this paper.
