Definition of Terms
TERMS USED TO CHARACTERIZE INDIVIDUAL PULSES
Peak Anode Voltage (epy): maximum positive anode voltage, with respect to the cathode.
Peak Inverse Anode Voltage (epx): maximum negative anode voltage, with respect to the cathode.
Peak Forward Anode Current (ib): maximum instantaneous positive anode current.
Peak Inverse Current (Ibx): maximum instantaneous negative anode current.
Pulse Width (tp): current pulse full-width at half-maximum.
Pulse Repetition Rate (prr): average number of pulses/second.
Current Rise Time (tr): time for the forward current to rise from 10% to 90% of its peak value.
Anode Fall Time: time for the forward anode voltage to collapse from 90% to 10% of its maximum value.
Anode Delay Time (tad): time interval between triggering and commutation (commutation is defined below). The precise
reference points for this interval vary with the application.
Anode Delay Time Drift (∆tad): gradual decrease in anode delay time that occurs as the thyratron warms up.
Jitter (tj): pulse-to-pulse variation in anode delay time.
TIME AVERAGED QUANTITIES
DC Average Current (Ib): forward current averaged over one second.
RMS Average Current (Ip): root-mean-square current averaged over one second.
Plate Breakdown Factor (Pb): numerical factor proportional to the power dissipated at the anode, averaged over one
second. Pb = epy x ib x prr.
STRUCTURAL PARTS OF THE THYRATRON
Auxiliary Grid: grid placed between the control grid and cathode in some thyratrons. A small DC current (or a larger pulsed
current) applied between Auxiliary Grid and cathode can be used to control the anode delay time. (Anode delay time is
defined above). Thyratrons with auxiliary girds are called Tetrode Thyratrons.
Reservoir: maintains the gas pressure in the tube at a level which depends on the reservoir heater voltage.
GENERAL TERMINOLOGY
Static (Self) Breakdown Voltage (SBV): applied voltage at which a thyratron will break down spontaneously, without
being triggered.
Commutation: transition from trigger breakdown to full closure of the thyratron.
Recovery Time: time which must elapse after decay of the circuit current before anode voltage can be reapplied to the
thyratron without causing self-breakdown. The maximum possible pulse repetition rate is the inverse of the recovery time.
Grid Bias: negative DC voltage which may be applied to the control grid to speed up recovery.
PERKINELMER [ PERKINELMER OPTOELECTRONICS ]
