| Triton ETD
is a world class leader in the design and manufacture of state-of-the-art
hydrogen thyratrons for a broad spectrum of high power switching applications.
Thyratrons were developed to make high-performance radars and high-energy
particle accelerators practical. They are now also the switch of choice
for many CO2, EXCIMER and metal vapor lasers. Triton thyratrons perform
reliably in numerous medical, industrial and scientific environments.
The thyratron is an electronic, repetitive "on" switch used
to generate trains of high energy, accurately timed and precisely
spaced pulses. Features include high voltage hold-off capability,
high efficiency, the ability to be triggered by low level pulses and
reliable performance over a wide range of operating voltages. The
thyratron offers robust construction and is tolerant to fault conditions
without failure.
Triton's unique, high quality and cost effective designs, ranging
from miniature airborne radar to megawatt average, super power system
devices, are the result of more than 50 years of experience in continuous
Electron Technology Division tube production.
Theory of Operation
In its simplest form, the thyratron contains an anode, control
grid, thermionic cathode and a ceramic or glass envelope filled
with a low pressure gas, typically hydrogen or deuterium (see figure
Thyratron-1). The control grid is constructed so that the cathode
is completely shielded from the electrostatic field of the anode.
Due to this tight mechanical baffling, high voltage can be applied
to the anode without current flow in an unbiased, quiescent state,
producing an open switch. Voltage hold-off is accomplished in the
anode-grid gap by optimum design of the spacing distance (D) and
neutral gas pressure (P), to concurrently satisfy the conflicting
criteria of wide spacing to prevent field emission and the narrow
gaps required to prevent long path discharge of' Paschen Law"
(PxD product) high voltage breakdown (see figure Thyratron-2).
A positive signal applied to the control grid ionizes the gas in
the cathode-grid region. Electrons are then accelerated by the anode
field, causing the entire tube volume to become ionized (conductive)
by collision of the accelerated particles with neutral gas molecules.
The tube then becomes a closed switch after a few tens of nanoseconds
commutation time. Conduction current is determined by the external
circuit.
During conduction, a sheath is formed around the grid to prevent
any subsequent voltage applied to the grid from penetrating into
the main body of the discharge, causing the grid to lose control
once the discharge is initiated.
The thyratron returns to the non-conducting (open) state only
after anode voltage has been removed from the tube and sufficient
time (tens of microseconds) has elapsed for the charge density to
decay to a low value. Recovery is accomplished by diffusion of the
ionized particles to the grid wall, where recombination/gas neutralization
takes place.
Performance
Metal-ceramic construction thyratrons are rated at I to 100 KV,
can switch at rates up to 500 KA/ps, 20 to 20 KA at average powers
to 1.0 MW. On-state loss is low at 50 to 300 V tube drop. Timing
is precise with typically 2 ns jitter. Typical application circuits
are shown in figures Thyratron- 3a and 3b.
Cooling
The majority of applications require only natural convection or
forced air cooling. Oil immersion is recommended for low profile,
low inductance designs for hold-off voltages greater than 50 KV,
and for very high average power applications.
Product availability is subject to change without notice. For
current pricing and availability, please contact
your local Richardson sales office.
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