1. High
power
microwave
beam-­‐spli3er
Ta$ana
Yugay1,2,
Thierry
Dubroca2,
Eden
Steven2,
Stephen
Hill2,3
1. Simmons
College
2.
Na$onal
High
Magne$c
Field
Laboratory
3.
Florida
State
University
Funding:
NSF-­‐MRI
CHE-­‐1229170,
NSF
DMR-­‐1157490,
State
of
Florida
Introduc9on
Component
Characteriza9on
Methods
Dynamic
nuclear
polariza$on
is
the
process
of
irradia$ng
a
sample
with
microwaves
to
increase
its
nuclear
resonance
lines’
intensity.
A
quasi-­‐op$cal
setup
is
used
to
guide
microwaves
from
a
395
GHz
gyrotron
source
to
the
sample.
Transmission
losses
of
the
quasi-­‐
op$cal
components
were
evaluated.
Addi$onally,
a
beam-­‐spliWer
was
designed
and
fabricated
to
simultaneously
run
two
dynamic
nuclear
polariza$on
experiments
in
parallel.
Beam-­‐spli3er
Fabrica9on
Methods
Le@:
an
airbrush
was
used
to
spray
solu$on
of
polymer
and
silver
par$cles
onto
various
substrates
such
as
polyethylene
(middle)
and
quartz
(right).
Beam-­‐spli3er
Characteriza9on
Results
Conclusion
Out
of
the
six
beam-­‐spliWers
created
by
two
different
methods
(spray-­‐coa$ng
and
evapora$on)
on
three
different
substrates,
only
the
beam-­‐spli3er
created
by
evapora9ng
a
thin
layer
of
silver
onto
a
1
mm
thick
quartz
was
able
to
sustain
microwave
beam
powers
up
to
50
wa3.
There
are
therefore
four
requirements
to
making
a
successful
high
power
microwave
beam-­‐spliWer:
Component
Characteriza9on
Results
• 3D
horn:
compared
transmission
with
and
without
the
horn
• Cu
horn:
compared
transmission
with
and
without
horn
• Shu3er:
compared
transmission
with
open
and
without
shuWer
• Back-­‐to-­‐back
horn:
compared
transmission
at
entrance
and
exit
• Mirrors:
Measured
reflec$on
• Grid:
Measured
transmission
from
0°
to
90°
rota$on.
Le@:
beam-­‐spliWer,
made
with
silver
sprayed
onto
film,
melted
at
3
waWs
of
microwave
power
from
a
395
GHz
gyrotron.
Middle:
150
μm
thick
quartz
with
evaporated
silver
damaged
by
a
20
waW
microwave
beam.
Right:
no
observable
damages
were
made
to
a
1
mm
thick
quartz
with
evaporated
silver,
up
to
the
maximum
source
power
of
50
waW.
Op9cal
Component
Transmission
3D
Horn
33%
Cu
Horn
38%
Open
ShuWer
99%
Back-­‐to-­‐back
Horn
92%
Sample
Low
Power
High
Power
Polyethylene
film
✔
✔
Quartz
✔
✔
Polyethylene
+
spray-­‐coated
silver
✔
✗
Polyethylene
+
deposited
silver
✔
✗
150
μm
quartz
+
spray-­‐coated
silver
✔
✗
150
μm
quartz
+
deposited
silver
✔
✗
1
mm
quartz
+
deposited
silver
(20
nm)
✔
✔
395
GHz
gyrotron
600
MHz
NMR
magnet
References:
1.
Overhauser
A.,
Phys.
Rev.
92,
2
(1953);
2.
Griffin
R.
et
al.,
PCCP
12,
5737
(2010);
3.
Ung
B.
et
al.,
Op$cs
Express.
20,
5
(2012).
COPPER
HORN
3D
HORN
PYROMETER
BEAM
BACK-­‐TO-­‐BACK
HORN
GRID
SHUTTER
FLAT
MIRROR
CURVED
MIRROR
BEAM
SPLITTER
POLARIZER
#1
GYROTRON
EXPERIMENT
1
EXPERIMENT
2
• Gyrotron:
395
GHz
beam
source
• Polarizer
#1:
filters
out
beam
of
wrong
polariza$on
• Beam-­‐spli3er:
splits
beam
in
two
• Curved
Mirror:
converges
and
propagates
beam
• Flat
Mirror:
changes
beam
direc$on
• Shu3er:
on/off
beam
switch
• Back-­‐to-­‐back
Horn:
Gaussian
beam
filter
0
20
40
60
80
100
120
0
20
40
60
80
100
120
140
160
Measured
Transmission
(mW)
Distance
(mm)
0
50
100
150
200
250
0
10
20
30
40
50
60
70
80
90
100
Measured
Transmission
(mW)
Angle
Rotated
(Degrees)
Measured
Malus
Law
Where
beam
diameter
=
3D
horn
diameter
100%
transmission
Transmission
plot
of
microwave
power
as
a
func$on
of
distance
between
source
and
3D
horn
(blue
dots).
Linear
regression
model
(solid
black).
Transmission
plot
of
microwave
power
as
a
func$on
of
rota$on
angle
of
a
polariza$on
grid
(blue
dots).
Malus
Law
model
overlayed
(solid
orange).
Le@:
a
deposi$on
chamber
was
used
to
deposit
silver
par$cles
onto
quartz.
Middle:
high
homogeneity
silver
deposi$on
on
quartz
substrate.
Mounted
beam-­‐spliWer
in
quasi-­‐op$cal
bench
with
airflow
cooling
(bo3om
right).
1. A
substrate
transparent
to
microwaves,
yet
thick
(i.e.
strong)
enough
to
mechanically
handle
thermal
stress.
2. A
metal
layer
of
high
thickness
homogeneity,
ensuring
the
beams’
shape
remains
unchanged.
3. Silver
layer
of
high
conduc9vity,
ensuring
minimal
heat
absorp$on
(minimizes
thermal
stress).
4. A
cooling
source,
to
reduce
thermal
stress
on
the
substrate
caused
by
microwave
hea$ng
of
the
metal
layer.