<s>
Muon	O
tomography	B-Algorithm
or	O
muography	B-Algorithm
is	O
a	O
technique	O
that	O
uses	O
cosmic	O
ray	O
muons	O
to	O
generate	O
three-dimensional	O
images	O
of	O
volumes	O
using	O
information	O
contained	O
in	O
the	O
Coulomb	O
scattering	O
of	O
the	O
muons	O
.	O
</s>
<s>
Since	O
muons	O
are	O
much	O
more	O
deeply	O
penetrating	O
than	O
X-rays	B-Library
,	O
muon	O
tomography	B-Algorithm
can	O
be	O
used	O
to	O
image	O
through	O
much	O
thicker	O
material	O
than	O
x-ray	B-Library
based	O
tomography	B-Algorithm
such	O
as	O
CT	O
scanning	O
.	O
</s>
<s>
The	O
muon	O
flux	B-General_Concept
at	O
the	O
Earth	O
's	O
surface	O
is	O
such	O
that	O
a	O
single	O
muon	O
passes	O
through	O
an	O
area	O
the	O
size	O
of	O
a	O
human	O
hand	O
per	O
second	O
.	O
</s>
<s>
Since	O
its	O
development	O
in	O
the	O
1950s	O
,	O
muon	O
tomography	B-Algorithm
has	O
taken	O
many	O
forms	O
,	O
the	O
most	O
important	O
of	O
which	O
are	O
muon	O
transmission	O
radiography	O
and	O
muon	O
scattering	O
tomography	B-Algorithm
.	O
</s>
<s>
Muography	B-Algorithm
uses	O
muons	O
by	O
tracking	O
the	O
number	O
of	O
muons	O
that	O
pass	O
through	O
the	O
target	O
volume	O
to	O
determine	O
the	O
density	O
of	O
the	O
inaccessible	O
internal	O
structure	O
.	O
</s>
<s>
Muography	B-Algorithm
is	O
a	O
technique	O
similar	O
in	O
principle	O
to	O
radiography	O
(	O
imaging	O
with	O
X-rays	B-Library
)	O
but	O
capable	O
of	O
surveying	O
much	O
larger	O
objects	O
.	O
</s>
<s>
Muon	O
tomography	B-Algorithm
imagers	O
are	O
under	O
development	O
for	O
the	O
purposes	O
of	O
detecting	O
nuclear	O
material	O
in	O
road	O
transport	O
vehicles	O
and	O
cargo	O
containers	O
for	O
the	O
purposes	O
of	O
non-proliferation	O
.	O
</s>
<s>
Another	O
application	O
is	O
the	O
usage	O
of	O
muon	O
tomography	B-Algorithm
to	O
monitor	O
potential	O
underground	O
sites	O
used	O
for	O
carbon	O
sequestration	O
.	O
</s>
<s>
The	O
term	O
muon	O
tomography	B-Algorithm
is	O
based	O
on	O
the	O
word	O
"	O
tomography	B-Algorithm
"	O
,	O
a	O
word	O
produced	O
by	O
combining	O
Ancient	O
Greek	O
tomos	O
"	O
cut	O
"	O
and	O
graphe	O
"	O
drawing.	O
"	O
</s>
<s>
Some	O
authors	O
hence	O
see	O
this	O
modality	O
as	O
a	O
subset	O
of	O
muography	B-Algorithm
.	O
</s>
<s>
Muography	B-Algorithm
was	O
named	O
by	O
Hiroyuki	O
K	O
.	O
M	O
.	O
Tanaka	O
.	O
</s>
<s>
There	O
are	O
two	O
explanations	O
for	O
the	O
origin	O
of	O
the	O
word	O
"	O
muography	B-Algorithm
"	O
:	O
(	O
A	O
)	O
a	O
combination	O
of	O
the	O
elementary	O
particle	O
muon	O
and	O
Greek	O
γραφή	O
(	O
graphé	O
)	O
"	O
drawing	O
,	O
"	O
together	O
suggesting	O
the	O
meaning	O
"	O
drawing	O
with	O
muons	O
"	O
;	O
and	O
(	O
B	O
)	O
a	O
shortened	O
combination	O
of	O
"	O
muon	O
"	O
and	O
"	O
radiography.	O
"	O
</s>
<s>
Although	O
these	O
techniques	O
are	O
related	O
,	O
they	O
differ	O
in	O
that	O
radiography	O
uses	O
X-rays	B-Library
to	O
image	O
the	O
inside	O
of	O
objects	O
on	O
the	O
scale	O
of	O
meters	O
,	O
while	O
muography	B-Algorithm
uses	O
muons	O
to	O
image	O
the	O
inside	O
of	O
objects	O
on	O
the	O
scale	O
of	O
hectometers	O
to	O
kilometers	O
.	O
</s>
<s>
Tanaka	O
and	O
Niwa	O
’s	O
pioneering	O
work	O
created	O
film	O
muography	B-Algorithm
,	O
which	O
uses	O
nuclear	B-Algorithm
emulsion	I-Algorithm
.	O
</s>
<s>
Exposures	O
of	O
nuclear	B-Algorithm
emulsions	I-Algorithm
were	O
taken	O
in	O
the	O
direction	O
of	O
the	O
volcano	O
and	O
then	O
analyzed	O
with	O
a	O
newly	O
invented	O
scanning	O
microscope	O
,	O
custom	O
built	O
for	O
the	O
purpose	O
of	O
identifying	O
particle	O
tracks	O
more	O
efficiently	O
.	O
</s>
<s>
Film	O
muography	B-Algorithm
enabled	O
them	O
to	O
obtain	O
the	O
first	O
interior	O
imaging	O
of	O
an	O
active	O
volcano	O
in	O
2007	O
,	O
revealing	O
the	O
structure	O
of	O
the	O
magma	B-General_Concept
pathway	O
of	O
Asama	O
volcano	O
.	O
</s>
<s>
In	O
1968	O
,	O
the	O
group	O
of	O
Alvarez	O
used	O
spark	B-Algorithm
chambers	I-Algorithm
with	O
a	O
digital	O
read	O
out	O
for	O
their	O
Pyramid	O
experiment	O
.	O
</s>
<s>
Tracking	O
data	O
from	O
the	O
apparatus	O
was	O
onto	O
magnetic	O
tape	O
in	O
the	O
Belzoni	O
Chamber	O
,	O
then	O
the	O
data	O
were	O
analyzed	O
by	O
the	O
IBM	B-Device
1130	I-Device
computer	O
,	O
and	O
later	O
by	O
the	O
CDC	B-Device
6600	I-Device
computer	O
located	O
at	O
Ein	O
Shams	O
University	O
and	O
Lawrence	O
Radiation	O
Laboratory	O
,	O
respectively	O
.	O
</s>
<s>
Real-time	O
muography	B-Algorithm
requires	O
muon	O
sensors	O
to	O
convert	O
the	O
muon	O
's	O
kinetic	O
energy	O
into	O
a	O
number	O
of	O
electrons	O
in	O
order	O
to	O
process	O
muon	O
events	O
as	O
electronic	O
data	O
rather	O
than	O
as	O
chemical	O
changes	O
on	O
film	O
.	O
</s>
<s>
Electronic	O
tracking	O
data	O
can	O
be	O
processed	O
almost	O
instantly	O
with	O
an	O
adequate	O
computer	O
processor	O
;	O
in	O
contrast	O
,	O
film	O
muography	B-Algorithm
data	O
have	O
to	O
be	O
developed	O
before	O
the	O
muon	O
tracks	O
can	O
be	O
observed	O
.	O
</s>
<s>
Real-time	O
tracking	O
of	O
muon	O
trajectories	O
produce	O
real-time	O
muograms	O
that	O
would	O
be	O
difficult	O
or	O
impossible	O
to	O
obtain	O
with	O
film	O
muography	B-Algorithm
.	O
</s>
<s>
The	O
MicroMegas	B-Algorithm
detector	I-Algorithm
has	O
a	O
positioning	O
resolution	O
of	O
0.3mm	O
,	O
an	O
order	O
of	O
magnitude	O
higher	O
than	O
that	O
of	O
the	O
scintillator-based	O
apparatus	O
(	O
10mm	O
)	O
,	O
and	O
thus	O
has	O
a	O
capability	O
to	O
create	O
better	O
angular	O
resolution	O
for	O
muograms	O
.	O
</s>
<s>
Muons	O
have	O
been	O
used	O
to	O
image	O
magma	B-General_Concept
chambers	O
to	O
predict	O
volcanic	O
eruptions	O
.	O
</s>
<s>
reported	O
using	O
tomographic	B-Algorithm
methods	O
to	O
track	O
the	O
passage	O
of	O
cosmic	O
rays	O
muons	O
through	O
cesium	O
iodide	O
crystals	O
for	O
quality	O
control	O
purposes	O
.	O
</s>
<s>
The	O
Mu-Ray	O
project	O
has	O
been	O
using	O
muography	B-Algorithm
to	O
image	O
Vesuvius	O
,	O
famous	O
for	O
its	O
eruption	O
of	O
79	O
AD	O
,	O
which	O
destroyed	O
local	O
settlements	O
including	O
Pompeii	O
and	O
Herculaneum	O
.	O
</s>
<s>
The	O
ASTRI	O
SST-2M	O
Project	O
is	O
using	O
muography	B-Algorithm
to	O
generate	O
the	O
internal	O
images	O
of	O
the	O
magma	B-General_Concept
pathways	O
of	O
Etna	O
volcano	O
.	O
</s>
<s>
Monitoring	O
the	O
magma	B-General_Concept
flows	O
with	O
muography	B-Algorithm
may	O
help	O
to	O
predict	O
the	O
direction	O
from	O
which	O
lava	B-Application
from	O
future	O
eruptions	O
may	O
emit	O
.	O
</s>
<s>
From	O
August	O
2017	O
to	O
October	O
2019	O
,	O
time	O
sequential	O
muography	B-Algorithm
imaging	O
of	O
the	O
Etna	O
edifice	O
was	O
conducted	O
to	O
study	O
differences	O
in	O
density	O
levels	O
which	O
would	O
indicate	O
interior	O
volcanic	O
activities	O
.	O
</s>
<s>
The	O
apparatuses	O
use	O
nuclear	B-Algorithm
emulsions	I-Algorithm
to	O
collect	O
data	O
near	O
Stromboli	O
volcano	O
.	O
</s>
<s>
Recent	O
emulsion	O
scanning	O
improvements	O
developed	O
during	O
the	O
course	O
of	O
the	O
Oscillation	O
Project	O
with	O
Emulsion	O
tRacking	O
Apparatus	O
(	O
OPERA	O
experiment	O
)	O
led	O
to	O
film	O
muography	B-Algorithm
.	O
</s>
<s>
Unlike	O
other	O
muography	B-Algorithm
particle	O
trackers	O
,	O
nuclear	B-Algorithm
emulsion	I-Algorithm
can	O
acquire	O
high	O
angular	O
resolution	O
without	O
electricity	O
.	O
</s>
<s>
Over	O
a	O
period	O
of	O
5	O
months	O
in	O
2019	O
,	O
an	O
experiment	O
using	O
nuclear	B-Algorithm
emulsion	I-Algorithm
muography	B-Algorithm
was	O
done	O
at	O
Stromboli	O
volcano	O
.	O
</s>
<s>
Muography	B-Algorithm
has	O
been	O
applied	O
to	O
groundwater	O
and	O
saturation	O
level	O
monitoring	O
for	O
bedrock	O
in	O
a	O
landslide	O
area	O
as	O
a	O
response	O
to	O
major	O
rainfall	O
events	O
.	O
</s>
<s>
The	O
applicability	O
of	O
muography	B-Algorithm
to	O
glacier	O
studies	O
was	O
first	O
demonstrated	O
with	O
a	O
survey	O
of	O
the	O
top	O
portion	O
of	O
Aletch	O
glacier	O
located	O
in	O
the	O
Central	O
European	O
Alps	O
.	O
</s>
<s>
In	O
2017	O
,	O
a	O
Japanese/Swiss	O
collaboration	O
conducted	O
a	O
larger	O
scale	O
muography	B-Algorithm
imaging	O
experiment	O
based	O
at	O
Eiger	O
Glacier	O
to	O
determine	O
the	O
bedrock	O
geometry	O
beneath	O
active	O
glaciers	O
in	O
the	O
steep	O
alpine	O
environment	O
of	O
the	O
Jungfrau	O
region	O
in	O
Switzerland	O
.	O
</s>
<s>
Muography	B-Algorithm
has	O
been	O
used	O
to	O
map	O
the	O
inside	O
of	O
big	O
civil	O
engineering	O
structures	O
,	O
such	O
as	O
dams	O
,	O
and	O
their	O
surroundings	O
for	O
safety	O
and	O
risk	O
prevention	O
purposes	O
.	O
</s>
<s>
Muography	B-Algorithm
imaging	O
was	O
applied	O
to	O
the	O
identification	O
of	O
hidden	O
construction	O
shafts	O
located	O
above	O
the	O
Alfreton	O
Old	O
Tunnel	O
(	O
constructed	O
in	O
1862	O
)	O
in	O
the	O
UK	O
.	O
</s>
<s>
Muography	B-Algorithm
was	O
applied	O
to	O
investigating	O
the	O
conditions	O
of	O
nuclear	O
reactors	O
damaged	O
by	O
the	O
Fukushima	O
nuclear	O
disaster	O
,	O
and	O
helped	O
to	O
confirm	O
its	O
state	O
of	O
near-complete	O
meltdown	O
.	O
</s>
<s>
Tomographic	B-Algorithm
techniques	O
can	O
be	O
effective	O
for	O
non-invasive	O
nuclear	O
waste	O
characterization	O
and	O
for	O
nuclear	O
material	O
accountancy	O
of	O
spent	O
fuel	O
inside	O
dry	O
storage	O
containers	O
.	O
</s>
<s>
Homogeneity	B-General_Concept
of	O
the	O
waste	O
needs	O
characterization	O
(	O
i.e.	O
</s>
<s>
sludge	O
in	O
tanks	O
,	O
in-homogeneities	O
in	O
cemented	O
waste	O
,	O
etc	O
.	O
</s>
<s>
Muon	O
Tomography	B-Algorithm
can	O
be	O
useful	O
to	O
assess	O
the	O
characterization	O
of	O
waste	O
,	O
radiation	O
cooling	O
,	O
and	O
condition	O
of	O
the	O
waste	O
container	O
.	O
</s>
<s>
On	O
March	O
11	O
,	O
2011	O
,	O
a	O
9.0-magnitude	O
earthquake	O
,	O
followed	O
by	O
a	O
tsunami	B-Application
,	O
caused	O
an	O
ongoing	O
nuclear	O
crisis	O
at	O
the	O
Fukushima	O
Daiichi	O
power	O
plant	O
.	O
</s>
<s>
A	O
few	O
months	O
of	O
measurements	O
with	O
muon	O
tomography	B-Algorithm
,	O
will	O
show	O
the	O
distribution	O
of	O
the	O
reactor	O
core	O
.	O
</s>
<s>
Industrial	O
muography	B-Algorithm
has	O
found	O
an	O
application	O
in	O
reactor	O
inspection	O
.	O
</s>
<s>
It	O
was	O
used	O
to	O
locate	O
the	O
nuclear	O
fuel	O
in	O
the	O
Fukushima	O
Daiichi	O
nuclear	O
power	O
plant	O
,	O
which	O
was	O
damaged	O
by	O
the	O
2011	O
Tōhoku	O
earthquake	O
and	O
tsunami	B-Application
.	O
</s>
<s>
Tools	O
such	O
as	O
muon	O
tomography	B-Algorithm
can	O
help	O
to	O
stop	O
the	O
spread	O
of	O
nuclear	O
material	O
before	O
it	O
is	O
armed	O
into	O
a	O
weapon	O
.	O
</s>
<s>
Muon	O
tomography	B-Algorithm
can	O
be	O
used	O
for	O
treaty	O
verification	O
due	O
to	O
many	O
important	O
factors	O
.	O
</s>
<s>
Cosmic	O
rays	O
are	O
much	O
more	O
penetrating	O
than	O
gamma	O
or	O
x-rays	B-Library
.	O
</s>
<s>
In	O
2015	O
,	O
35	O
years	O
after	O
Alvarez	O
’s	O
experiment	O
,	O
the	O
ScanPyramids	O
Project	O
,	O
which	O
is	O
composed	O
of	O
an	O
international	O
team	O
of	O
scientists	O
from	O
Egypt	O
,	O
France	O
,	O
Canada	O
,	O
and	O
Japan	O
,	O
has	O
started	O
using	O
muography	B-Algorithm
and	O
thermography	B-Algorithm
imaging	O
to	O
survey	O
the	O
Giza	O
pyramid	O
complex	O
.	O
</s>
<s>
The	O
3rd	O
largest	O
pyramid	O
in	O
the	O
world	O
,	O
the	O
Pyramid	O
of	O
the	O
Sun	O
,	O
situated	O
near	O
Mexico	O
City	O
in	O
the	O
ancient	O
city	O
of	O
Teotihuacan	O
was	O
surveyed	O
with	O
muography	B-Algorithm
.	O
</s>
<s>
In	O
2020	O
,	O
the	O
US	O
National	O
Science	O
Foundation	O
awarded	O
a	O
US-Mexico	O
international	O
group	O
a	O
grant	O
for	O
muography	B-Algorithm
to	O
investigate	O
El	O
Castillo	O
,	O
the	O
largest	O
pyramid	O
in	O
Chichen	O
Itza	O
.	O
</s>
<s>
A	O
three-dimensional	O
muography	B-Algorithm
experiment	O
was	O
done	O
in	O
the	O
underground	O
tunnels	O
of	O
Mt	O
Echia	O
(	O
in	O
Naples	O
,	O
Italy	O
)	O
with	O
2	O
muon	O
detectors	O
,	O
MU-RAY	O
and	O
MIMA	O
,	O
which	O
successfully	O
imaged	O
2	O
known	O
cavities	O
and	O
discovered	O
one	O
unknown	O
cavity	O
.	O
</s>
<s>
Yuanyuan	O
Liu	O
of	O
the	O
Beijing	O
Normal	O
University	O
and	O
her	O
group	O
showed	O
the	O
feasibility	O
of	O
muography	B-Algorithm
to	O
image	O
the	O
underground	O
chamber	O
of	O
the	O
first	O
emperor	O
of	O
China	O
.	O
</s>
<s>
Muography	B-Algorithm
may	O
potentially	O
be	O
implemented	O
to	O
image	O
extraterrestrial	O
objects	O
such	O
as	O
the	O
geology	O
of	O
Mars	O
.	O
</s>
<s>
It	O
has	O
been	O
calculated	O
that	O
the	O
atmosphere	O
of	O
Mars	O
is	O
sufficient	O
to	O
produce	O
a	O
horizontal	O
muon	O
flux	B-General_Concept
for	O
practical	O
muography	B-Algorithm
,	O
roughly	O
equivalent	O
to	O
the	O
Earth	O
’s	O
muon	O
flux	B-General_Concept
.	O
</s>
<s>
In	O
the	O
future	O
,	O
it	O
may	O
be	O
viable	O
to	O
include	O
a	O
high-resolution	O
muography	B-Algorithm
apparatus	O
in	O
a	O
future	O
space	O
mission	O
to	O
Mars	O
,	O
for	O
instance	O
inside	O
a	O
Mars	O
rover	O
.	O
</s>
<s>
The	O
“	O
NASA	O
Innovative	O
Advanced	O
Concepts	O
(	O
NIAC	O
)	O
program	O
”	O
is	O
now	O
in	O
the	O
process	O
of	O
assessing	O
whether	O
muography	B-Algorithm
may	O
be	O
used	O
for	O
imaging	O
the	O
density	O
structures	O
of	O
small	O
solar	O
system	O
bodies	O
(	O
SSBs	O
)	O
.	O
</s>
<s>
While	O
the	O
SSBs	O
tend	O
to	O
generate	O
lower	O
muon	O
flux	B-General_Concept
than	O
the	O
Earth	O
's	O
atmosphere	O
,	O
some	O
are	O
sufficient	O
to	O
allow	O
for	O
muography	B-Algorithm
of	O
objects	O
ranging	O
from	O
1km	O
or	O
less	O
in	O
diameter	O
.	O
</s>
<s>
The	O
program	O
includes	O
calculating	O
the	O
muon	O
flux	B-General_Concept
for	O
each	O
potential	O
target	O
,	O
creating	O
imaging	O
simulations	O
and	O
considering	O
the	O
engineering	O
challenges	O
of	O
building	O
a	O
more	O
lightweight	O
,	O
compact	O
apparatus	O
appropriate	O
for	O
such	O
a	O
mission	O
.	O
</s>
<s>
In	O
undersea	O
muography	B-Algorithm
,	O
time-dependent	O
mass	O
movements	O
consisting	O
of	O
or	O
within	O
targeted	O
gigantic	O
fluid	O
bodies	O
and	O
submerged	O
solid	O
material	O
bodies	O
can	O
be	O
more	O
precisely	O
imaged	O
than	O
with	O
land-based	O
muography	B-Algorithm
.	O
</s>
<s>
Time-dependent	O
fluctuations	O
of	O
the	O
muon	O
flux	B-General_Concept
due	O
to	O
atmospheric	O
pressure	O
variations	O
are	O
suppressed	O
when	O
muography	B-Algorithm
is	O
conducted	O
under	O
the	O
seafloor	O
by	O
the	O
“	O
inverse	O
barometric	O
effect	O
(	O
IBE	O
)	O
”	O
of	O
seawater	O
.	O
</s>
<s>
It	O
has	O
been	O
proposed	O
to	O
use	O
muography	B-Algorithm
as	O
a	O
monitoring	O
tool	O
for	O
CCS	O
.	O
</s>
<s>
In	O
2018	O
,	O
a	O
2	O
month	O
study	O
supported	O
the	O
feasibility	O
of	O
CCS	O
muography	B-Algorithm
monitoring	O
.	O
</s>
<s>
Muon	O
scattering	O
tomography	B-Algorithm
was	O
first	O
proposed	O
by	O
Chris	O
Morris	O
and	O
his	O
group	O
at	O
Los	O
Alamos	O
National	O
Laboratory	O
(	O
LANL	O
)	O
.	O
</s>
<s>
With	O
muon	O
scattering	O
tomography	B-Algorithm
,	O
both	O
incoming	O
and	O
outgoing	O
trajectories	O
for	O
each	O
particle	O
are	O
reconstructed	O
.	O
</s>
<s>
This	O
results	O
in	O
an	O
angular	O
distribution	O
that	O
is	O
Gaussian	B-Application
in	O
shape	O
with	O
tails	O
from	O
large	O
angle	O
single	O
and	O
plural	O
scattering	O
.	O
</s>
<s>
Multiple	O
scattering	O
can	O
be	O
defined	O
as	O
when	O
the	O
thickness	O
increases	O
and	O
the	O
number	O
of	O
interactions	O
become	O
high	O
the	O
angular	O
dispersion	O
can	O
be	O
modelled	O
as	O
Gaussian	B-Application
.	O
</s>
<s>
The	O
Image	O
can	O
then	O
be	O
reconstructed	O
by	O
use	O
of	O
GEANT4	B-Application
.	O
</s>
<s>
The	O
incident	O
flux	B-General_Concept
projected	O
to	O
the	O
core	O
location	O
was	O
used	O
to	O
normalize	O
transmission	O
radiography	O
(	O
attenuation	O
method	O
)	O
.	O
</s>
<s>
From	O
here	O
the	O
calculations	O
are	O
normalized	O
for	O
the	O
zenith	O
angle	O
of	O
the	O
flux	B-General_Concept
.	O
</s>
<s>
Despite	O
the	O
various	O
benefits	O
of	O
using	O
cosmic	O
ray	O
muons	O
for	O
imaging	O
large	O
and	O
dense	O
objects	O
,	O
i.e.	O
,	O
spent	O
nuclear	O
fuel	O
casks	O
and	O
nuclear	O
reactors	O
,	O
their	O
wide	O
applications	O
are	O
often	O
limited	O
by	O
the	O
naturally	O
low	O
muon	O
flux	B-General_Concept
at	O
sea	O
level	O
,	O
approximately	O
10,000	O
m−2min−1	O
.	O
</s>
<s>
To	O
measure	O
cosmic	O
ray	O
muon	O
momentum	O
in	O
the	O
field	O
,	O
a	O
fieldable	O
muon	O
spectrometer	O
using	O
multi-layer	O
pressurized	O
gas	O
Cherenkov	O
radiators	O
has	O
been	O
developed	O
and	O
the	O
muon	O
spectrometer-tomography	O
shows	O
improved	O
muon	O
scattering	O
tomography	B-Algorithm
resolutions	O
.	O
</s>
<s>
Mu-CAT	O
is	O
a	O
technique	O
which	O
combines	O
multiple	O
projected	O
muographic	O
images	O
to	O
create	O
a	O
3D	O
muography	B-Algorithm
image	O
.	O
</s>
<s>
While	O
medical	O
CAT	O
scanners	O
use	O
a	O
rotating	O
X-ray	B-Library
generator	O
around	O
the	O
target	O
object	O
,	O
Mu-CAT	O
uses	O
multiple	O
detectors	O
around	O
the	O
target	O
object	O
and	O
naturally	O
occurring	O
muons	O
as	O
probes	O
.	O
</s>
<s>
Either	O
the	O
tomographic	B-Algorithm
reconstruction	I-Algorithm
technique	O
or	O
the	O
inverse	O
problem	O
is	O
applied	O
to	O
these	O
data	O
from	O
the	O
Mu-CAT	O
observations	O
to	O
reconstruct	O
3d	O
images	O
.	O
</s>
<s>
Mu-CAT	O
revealed	O
the	O
three-dimensional	O
position	O
of	O
a	O
fractured	O
zone	O
below	O
the	O
crater	O
floor	O
of	O
an	O
active	O
volcano	O
related	O
to	O
a	O
past	O
eruption	O
that	O
had	O
caused	O
a	O
large	O
pyroclastic	O
and	O
lava	B-Application
flow	O
on	O
its	O
northern	O
slope	O
.	O
</s>
<s>
The	O
Cosmic	O
Ray	O
Inspection	O
and	O
Passive	O
Tomography	B-Algorithm
(	O
CRIPT	O
)	O
detector	O
is	O
a	O
Canadian	O
muon	O
tomography	B-Algorithm
project	O
which	O
tracks	O
muon	O
scattering	O
events	O
while	O
simultaneously	O
estimating	O
the	O
muon	O
momentum	O
.	O
</s>
<s>
The	O
majority	O
of	O
the	O
detector	O
mass	O
is	O
located	O
in	O
the	O
muon	O
momentum	O
spectrometer	O
which	O
is	O
a	O
feature	O
unique	O
to	O
CRIPT	O
regarding	O
muon	O
tomography	B-Algorithm
.	O
</s>
<s>
The	O
CRIPT	O
detector	O
is	O
presently	O
examining	O
the	O
limitations	O
on	O
detection	O
time	O
for	O
border	O
security	O
applications	O
,	O
limitations	O
on	O
muon	O
tomography	B-Algorithm
image	O
resolution	O
,	O
nuclear	O
waste	O
stockpile	O
verification	O
,	O
and	O
space	O
weather	O
observation	O
through	O
muon	O
detection	O
.	O
</s>
<s>
There	O
are	O
several	O
different	O
kinds	O
of	O
muon	O
sensors	O
used	O
in	O
muography	B-Algorithm
apparatuses	O
:	O
plastic	O
scintillators	O
,	O
nuclear	B-Algorithm
emulsions	I-Algorithm
,	O
or	O
gaseous	B-Algorithm
ionization	I-Algorithm
detectors	I-Algorithm
.	O
</s>
<s>
There	O
are	O
several	O
advantages	O
that	O
muography	B-Algorithm
has	O
over	O
traditional	O
geophysical	O
surveys	O
.	O
</s>
<s>
This	O
abundant	O
muon	O
flux	B-General_Concept
is	O
nearly	O
constant	O
,	O
therefore	O
muography	B-Algorithm
can	O
be	O
used	O
worldwide	O
.	O
</s>
<s>
Second	O
,	O
because	O
of	O
the	O
high-contrast	O
resolution	O
of	O
muography	B-Algorithm
,	O
a	O
small	O
void	O
of	O
less	O
than	O
0.001	O
%	O
of	O
the	O
entire	O
volume	O
can	O
be	O
distinguished	O
.	O
</s>
<s>
In	O
the	O
field	O
of	O
muography	B-Algorithm
,	O
the	O
transmission	O
coefficient	O
is	O
defined	O
as	O
the	O
ratio	O
of	O
the	O
transmission	O
through	O
the	O
object	O
over	O
the	O
incident	O
muon	O
flux	B-General_Concept
.	O
</s>
<s>
By	O
applying	O
the	O
muon	O
's	O
range	O
through	O
matter	O
to	O
the	O
open-sky	O
muon	O
energy	O
spectrum	O
,	O
the	O
value	O
of	O
the	O
fraction	O
of	O
incident	O
muon	O
flux	B-General_Concept
that	O
is	O
transmitted	O
through	O
the	O
object	O
can	O
be	O
analytically	O
derived	O
.	O
</s>
<s>
The	O
phenomenon	O
that	O
muography	B-Algorithm
cannot	O
differentiate	O
density	O
variations	O
is	O
called	O
the	O
"	O
Volume	O
Effects.	O
"	O
</s>
<s>
Volume	O
Effects	O
happen	O
when	O
a	O
large	O
amount	O
of	O
low	O
density	O
materials	O
and	O
a	O
thin	O
layer	O
of	O
high	O
density	O
materials	O
cause	O
the	O
same	O
attenuation	O
in	O
muon	O
flux	B-General_Concept
.	O
</s>
