  We present the field-line modeling, design and construction of a prototype
circular-coil tokamak-torsatron hybrid called Proto-CIRCUS. The device has a
major radius R = 16 cm and minor radius a < 5 cm. The six "toroidal field"
coils are planar as in a tokamak, but they are tilted. This, combined with
induced or driven plasma current, is expected to generate rotational transform,
as seen in field-line tracing and equilibrium calculations. The device is
expected to operate at lower plasma current than a tokamak of comparable size
and magnetic field, which might have interesting implications for disruptions
and steady-state operation. Additionally, the toroidal magnetic ripple is less
pronounced than in an equivalent tokamak in which the coils are not tilted. The
tilted coils are interlocked, resulting in a relatively low aspect ratio, and
can be moved, both radially and in tilt angle, between discharges. This
capability will be exploited for detailed comparisons between calculations and
field-line mapping measurements. Such comparisons will reveal whether this
relatively simple concept can generate the expected rotational transform.
