  A Lorentz-force hydrophone consists of a thin wire placed inside a magnetic
field. When under the influence of an ultrasound pulse, the wire vibrates and
an electrical signal is induced by the Lorentz force that is proportional to
the pulse amplitude. In this study a compact prototype of such a hydrophone is
introduced and characterized, and the hydrodynamic model previously developed
is refined. It is shown that the wire tension has a negligible effect on the
measurement of pressure. The frequency response of the hydrophone reaches 1 MHz
for wires with a diameter ranging between 70 and 400 \micro m. The hydrophone
exhibits a directional response such that the signal amplitude differs by less
than 3dB as the angle of the incident ultrasound pulse varies from -20$^o$ and
+20$^o$. The linearity of the measured signal is confirmed across the 50 kPa to
10 MPa pressure range, and an excellent resistance to cavitation is observed.
This hydrophone is of interest for high pressure ultrasound measurements
including High Intensity Focused Ultrasound (HIFU) and ultrasonic measurements
in difficult environments.
