Abstract
Pyroelectric crystal has spontaneous polarization so that the surface of the crystal is charged. The surface charge is compensated by the electron or ion in the air. The variation of the temperature of the pyroelectric crystal yields the residual compensating charge that generates the high-voltage field. This leads to make a compact radiation source. Several studies of the radiation source using the pyroelectric crystal showed the emission of the electron, ion, x ray, and neutron. However, it is not clear for the parameters in order to control the emission of the radiations. In this study, the electron current from the pyroelectric surface to the ground was measured with the parameters of the pressure and the temperature ramp rate that is the rate of the temperature variation to the time. A single crystal of LiTaO3 (10 mm X 10 mm X 5 mmt) was fixed on a copper plate. The surface of the crystal faced to another copper plate at intervals of about 4.8 mm. The copper plate was connected to the picoammeter (Keithley 6485). The electron current was measured with the pressure of 15-25 Pa and the maximum temperature ramp rate of 2.0 K/s. The pulsed electron current was observed with the current of about 100 uA and the duration of about 1 ms. This is explained as follows. The compensating charge appears at the surface of the pyroelectric crystal by varying the temperature and the surface charge generates the high voltage. When the voltage exceeds a breakdown voltage at a pressure, the surface charge is discharged as the pulsed current. For the pressure, the number of the pulse increased as the pressure increased because the breakdown voltage become low as the pressure increases at the pressure around 20 Pa. For the temperature ramp rate, in proportion as the rate increases the number of the pulse increased because the surface charge appeared increases.
