Dr. Robert Meger, Head of the Charged Particle Physics Branch,
Plasma Physics Division at the Naval Research Laboratory (NRL),
delivered a seminar on March 1 summarizing the current status
of the development of the plasma mirror.
The plasma mirror, called Agile
Mirror, is a multipurpose, microwave beam director. It has advantages
over existing director technology including size, weight and
cost, but especially electronic steering, wide bandwidth operation,
and high-power capability, Dr. Meger explained.
"Because a plasma mirror
is electronically steerable with no moving parts, it possesses
the ability to move very fast from one point to another,"
Dr. Meger said.
Agile Mirror consists of a smooth
plasma sheet formed in a low-pressure chamber by a gas discharge,
Dr. Meger said. The present laboratory system measures 60 centimeters
x 60 centimeters x 1 centimeter thick. The plasma acts just like
a conducting metal sheet to the microwaves. It is possible to
turn the plasma mirror on and off repeatedly and very rapidly
(less than 10 microseconds) and change the orientation of the
mirror in between pulses. Multiple high-power microwave sources
with the same or different frequencies could use a single Agile
Mirror beam director, in sequence or simultaneously.
"Its beauty is that it could
allow a radar system to follow many targets simultaneously while
continuing to search for more," Dr. Meger said.
Agile Mirror is being developed
at NRL's Plasma Physics Division in collaboration with the Radar
Division.
Dr. Meger explained that radar
redirection (crucial for finding targets) originally depended
on moving antennas mechanically. This limited response time.
A substantial improvement in response time was achieved with
phased arrays, which are used on Aegis cruisers.
Phased array radar, which is
steered electronically by changing the relative phase of individual
elements in the array, is costly and has frequency limitations.
Broadband frequency capability is important because a target
invisible in one frequency may be readily visible in another,
Dr. Meger explained.
Agile Mirror differs significantly
because it separates the beam generator from the means of electronically
directing the high-frequency microwaves to a target. This allows
use of multiple or broadband high-power microwave sources with
a single mirror.
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