86
Aluminum
Nitride Radio Frequency Windows--Sienna
Technologies, Inc., 19501 144th Avenue, NE, Suite F-500, Woodinville, WA
98072-4423;
425-485-7272, www.siennatech.com
Dr.
Ender Savrun, Principal Investigator, ender.savrun@siennatech.com
Dr.
Canan Savrun, Business Official, canan.savrun@siennatech.com
DOE
Grant No. DE-FG02-03ER83774
Amount:
$750,000
New window materials that can handle multi-megawatt
radio frequency (RF) powers are needed to increase the reliability of RF windows
for linear particle accelerators. Aluminum
nitride would be an excellent window material due to its high thermal
conductivity, high dielectric strength, low secondary electron emission, and
high mechanical strength, if its dielectric loss (loss tangent) could be
controlled and/or reduced. This
project will develop technology for optimizing aluminum nitride for the RF
window application. In particular, the
effects of starting powder type and purity, porosity, grain size, and yttria
additive concentration on the thermal conductivity and microwave dielectric
properties (dielectric constant and loss tangent) of aluminum nitride will be
investigated. Phase
I identified the variables that control dielectric loss and thermal conductivity
of aluminum nitride. The presence of
certain impurities in the starting powders, and the type and concentration of
the second phase (added as a sintering aid), were found to be responsible for
controlling the dielectric loss and thermal conductivity.
Phase II will determine the sintering aid concentration and associated
processing variables that minimize dielectric loss without significantly
reducing thermal conductivity. The
material's thermal and dielectric properties will be fully characterized to help
the RF window design. Thermetically
sealed prototype windows will be prepared by newly developed metallization
techniques. Cold and hot tests will
be performed to demonstrate the windows’ power handling capabilities.
Commercial
Applications and Other Benefits as
described by awardee: Almost
every medium-to-high vacuum electron device would benefit from the low loss,
high thermal conductivity aluminum nitride ceramics.
Applications include Klystrons and gyrotrons that supply microwave energy
to improve the performance of chemical processes and materials processing;
Klystrons for direct broadcast satellites; gyrotrons for magnetic fusion based
on electron cyclotron heating; and microwave communications.