U.S. patent application number 12/699456 was filed with the patent office on 2011-02-03 for trace sampling.
This patent application is currently assigned to L-3 Communications CyTerra Corporation. Invention is credited to Edward E.A. Bromberg, Paul Crabb, David H. Fine, C. Andrew Helm, Ravi Konduri, Daniel O'Donnell.
Application Number | 20110024626 12/699456 |
Document ID | / |
Family ID | 37595732 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110024626 |
Kind Code |
A1 |
O'Donnell; Daniel ; et
al. |
February 3, 2011 |
TRACE SAMPLING
Abstract
A trace sampling detection system includes a gathering device
configured to gather particles through a handle-bar, a gate and an
air-stream gatherer. The handle-bar includes collection holes
positioned to be adjacent to a user's hand when the user grips the
handle-bar, and is configured to dislodge and capture particles
from the user's hand when the user grips and moves the handle-bar.
The gate includes a series of collection holes, is positioned to be
adjacent to the user's clothing when the user traverses the gate,
and is configured to dislodge and capture particles from the user's
clothing in response to pressure applied from the user. The
air-stream gatherer includes an outward vent and an in-drawing
vent, and is positioned to enable objects, such as the user's feet,
to be placed between the outward and in-drawing vents. The air
stream is configured to dislodge and capture particles from
objects, such as the user's feet, that block the air-stream between
the vents. A collection tube is configured to deposit gathered
particles from the gathering device onto a portion of a sample
media. A carousel wheel that includes the sample media is
configured to rotate the sample wheel such that the portion of the
sample media including the gathered particles is presented to an
exothermic decomposition detector that detects, through an infrared
sensor, the decomposition of the gathered particles.
Inventors: |
O'Donnell; Daniel; (Orlando,
FL) ; Bromberg; Edward E.A.; (Orlando, FL) ;
Crabb; Paul; (Orlando, FL) ; Konduri; Ravi;
(Waltham, MA) ; Helm; C. Andrew; (Oviedo, FL)
; Fine; David H.; (Orlando, FL) |
Correspondence
Address: |
FISH & RICHARDSON P.C. (DC)
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
L-3 Communications CyTerra
Corporation
Orlando
FL
|
Family ID: |
37595732 |
Appl. No.: |
12/699456 |
Filed: |
February 3, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11425313 |
Jun 20, 2006 |
7666356 |
|
|
12699456 |
|
|
|
|
60691778 |
Jun 20, 2005 |
|
|
|
60700039 |
Jul 18, 2005 |
|
|
|
60702616 |
Jul 27, 2005 |
|
|
|
60743083 |
Dec 29, 2005 |
|
|
|
60743402 |
Mar 3, 2006 |
|
|
|
Current U.S.
Class: |
250/338.1 ;
73/28.01 |
Current CPC
Class: |
G01N 2001/028 20130101;
G01N 33/0057 20130101; G01N 2001/024 20130101; G01N 1/2214
20130101 |
Class at
Publication: |
250/338.1 ;
73/28.01 |
International
Class: |
G01J 5/00 20060101
G01J005/00; G01N 37/00 20060101 G01N037/00 |
Claims
1. A trace sampling detection system comprising: a gathering device
configured to gather particles through each of: a handle-bar
including collection holes positioned to be adjacent to a user's
hand when the user grips the handle bar, wherein the handle-bar is
configured to release particles in response to a grip and motion of
the user, a gate including a series of collection holes positioned
to be adjacent to the user's clothing when the user traverses the
gate, wherein the gate is configured to release particles in
response to pressure applied from the user, an air-stream gatherer
including an outward vent and an in-drawing vent positioned to
enable objects to be placed between the outward and in-drawing
vents, wherein the air-stream is configured to release particles
from objects that block the air-stream between the outward and
in-drawing vent; a collection tube configured to deposit gathered
particles from the gathering device onto a portion of a sample
media; a carousel wheel that includes the sample media and is
configured to rotate the sample wheel such that the portion of the
sample media including the gathered particles is presented to an
exothermic decomposition detector; and an exothermic decomposition
detector configured to detect, through an infrared sensor, the
decomposition of the gathered particles.
2. The system of claim 1 wherein the collection holes are
tapered.
3. The system of claim 1 wherein the collection holes have edges
configured to scrape a surface that contacts the edges.
4. The system of claim 1 wherein the handle-bar is configured to
move in a radial motion.
5. The system of claim 1 wherein the handle-bar includes a
conductivity sensor configured to detect the presence of skin.
6. The system of claim 1 wherein the gate is shaped with a curve
that is designed to conform to the shape of part of a human
body.
7. The system of claim 1 wherein the gate will swing out only when
the handle-bar is moved.
8. The system of claim 7 wherein the movement of the gate presents
a path for the user to traverse.
9. The system of claim 1 wherein the gathering device is configured
to gather particles concurrently from the handle-bar, gate, and the
air-stream gatherer.
10. The system of claim 1 wherein the analyzing system is
configured to detect particles other than explosive particles.
11. The system of claim 1 further comprising a blower to create the
vacuum in the collection holes and the in-drawing vent.
12. A trace sampling detection system comprising: a gathering
device configured to gather particles through two or more of: a
handle-bar including collection holes positioned to be adjacent to
a user's hand when the user grips the handle bar, a gate including
a series of collection holes positioned to be adjacent to the
user's clothing when the user traverses the gate, an air-stream
gatherer including an outward vent and an in-drawing vent
positioned to enable objects to be placed between the outward and
in-drawing vents; and an analyzing device configured to analyze
gathered particles from the gathering device for properties that
are indicative of the presence of particles of explosive
materials.
13. The system of claim 12 wherein the collection holes are
tapered.
14. The system of claim 12 wherein the collection holes have edges
configured to scrape a surface that contacts the edges.
15. The system of claim 12 wherein the handle-bar is configured to
move in a radial motion.
16. The system of claim 12 wherein the handle-bar includes a
conductivity sensor configured to detect the presence of skin.
17. The system of claim 12 wherein the gate will swing out only
when the handle-bar is moved.
18. The system of claim 12 wherein the movement of the gate
presents a path for the user to traverse.
19. The system of claim 12 wherein either the gate or the
handle-bar employs less resistance to movement for slow movements
than for quick movements.
20. The system of claim 12 wherein the gathering device is
configured to gather particles concurrently from two or more of the
handle-bar, gate, and the air-stream gatherer.
21. The system of claim 12 wherein the analyzing system is
configured to detect particles other than explosive particles.
22. A method of trace sampling detection comprising: gathering
particles through two or more of: a handle-bar including collection
holes positioned to be adjacent to a user's hand when the user
grips the handle bar, a gate including a series of collection holes
positioned to be adjacent to the user's clothing when the user
traverses the gate, an air-stream gatherer including an outward
vent and an in-drawing vent positioned to enable objects to be
placed between the outward and in-drawing vents; and analyzing the
gathered particles for properties that are indicative of the
presence of particles of explosive materials.
23. A trace sampling detection system, comprising a gathering
device configured to gather particles through one or more
collection holes; an impact collector configured to deposit
gathered particles onto a portion of a sample media; a carousel
wheel which includes the sample media wherein the carousel wheel is
configured to rotate the sample wheel such that the portion of the
sample media including the deposited gathered particles is
presented to an exothermic decomposition detector; an exothermic
decomposition detector configured to detect, through an infrared
sensor, decomposition of heated materials.
24. The system of claim 23 wherein the carousel wheel is configured
to heat the sample media resistively.
25. The system of claim 24 wherein the sample media is configured
to be resistively heated by running a current through the sample
media.
26. The system of claim 23 wherein the sample media is configured
such that the same portion of the sample media may be reused
through multiple exposures to the impact collector and the
exothermic decomposition detector.
27. The system of claim 23 wherein the exothermic decomposition
detector is configured to heat the sample media radiatively.
28. The system of claim 23 wherein the carousel wheel is configured
to direct the sample media through a reel-to-reel mechanism.
29. A transportation mechanism for a trace sampling particle
detection system which includes a gathering device, an impact
collector configured to deposit gathered particles, and an
exothermic decomposition detector configured to detect
decomposition of a deposited material, the transportation mechanism
comprising: a carousel wheel which includes a sample media
configured to accept a deposit of material from the impact
collector, wherein the carousel wheel is configured to rotate the
sample wheel such that the portion of the sample media including
the deposited gathered particles is presented to the exothermic
decomposition detector.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of and claims
priority to U.S. patent application Ser. No. 11/425,313, filed Jun.
20, 2006, and titled "Trace Sampling" which claims priority from
U.S. Provisional Application Nos. 60/691,778, filed Jun. 20, 2005,
and titled "Simplified Trace Sampling of People For Explosives";
60/700,039, filed Jul. 18, 2005, and titled "Simplified Trace
Sampling of People For Explosives"; 60/702,616, filed Jul. 27,
2005, and titled "Trace Explosives Detector Based Upon Detecting
Exothermic Decomposition"; 60/743,083, filed Dec. 29, 2005, and
titled "Energetic Material Detector For Explosive Trace Detection";
and 60/743,402, filed Mar. 3, 2006, and titled "Energetic Material
Detector For Explosive Trace Detection." Each of these applications
is incorporated by reference.
TECHNICAL FIELD
[0002] This disclosure relates to trace sampling to detect
materials such as explosives.
BACKGROUND
[0003] In order to detect the presence of a material, such as
explosives, particles of the material may be collected and
analyzed.
SUMMARY
[0004] In one general aspect, a trace sampling detection system
includes a gathering device configured to gather particles through
each of several components. A handle-bar includes collection holes
positioned to be adjacent to a user's hand when the user grips the
handle-bar. The handle-bar is configured to dislodge and capture
particles from the user's hand when the user grips and moves the
handle-bar. A gate including a series of collection holes is
positioned to be adjacent to the user's clothing when the user
traverses the gate. The gate is configured to dislodge and capture
particles from the user's clothing in response to pressure applied
from the user. An air-stream gatherer including an outward vent and
an in-drawing vent is positioned to enable objects, such as the
user's feet, to be placed between the outward and in-drawing vents.
The air-stream is configured to dislodge and capture particles from
objects, such as the user's feet, that block the air-stream between
the outward and in-drawing vent. A collection tube is configured to
deposit gathered particles from the gathering device onto a portion
of a sample media. A carousel wheel that includes the sample media
is configured to rotate the sample wheel such that the portion of
the sample media including the gathered particles is presented to
an exothermic decomposition detector. An exothermic decomposition
detector is configured to detect, through an infrared sensor, the
decomposition of the gathered particles.
[0005] Implementations may include one or more of the following
features. For instance, the collection holes may be tapered, and
may have sharp edges configured to scrape a surface that contacts
them.
[0006] The handle-bar may be configured to move in a radial motion.
The handle-bar may include a conductivity sensor configured to
detect the presence of skin. The conductivity sensor may be
configured to determine if two hands are being used to grip the
handle-bar.
[0007] Also, the gate may be shaped with a curve that is designed
to conform to the shape of part of a human body. The gate may swing
out only when the handle-bar is moved. The movement of the gate, or
the concurrent movement of the gate and of the handle-bar, may
present a path for the user to traverse. Either the gate or the
handle-bar, or both, may employ less resistance to movement for
slow movements than for quick movements.
[0008] The analyzing system may be configured to detect particles
other than explosive particles.
[0009] The system may also include a blower to create the vacuum in
the collection holes and the in-drawing vent, and the air pressure
for the outward vent. One blower may be used for the collection
holes in the handle-bar and the gate, and the in-drawing vent, and
a second blower may be used for the outward vent.
[0010] In another general aspect, a trace sample detection system
includes a gathering device configured to gather particles through
at least two or more of a handle-bar, a gate, and an air-stream
gatherer. The handle-bar includes collection holes positioned to be
adjacent to a user's hand when the user grips the handle-bar, and
the gate includes a series of collection holes positioned to be
adjacent to the user's clothing when the user traverses the gate.
The air-stream gatherer includes an outward vent and an in-drawing
vent positioned to enable objects to be placed between the outward
and in-drawing vents. An analyzing device is configured to analyze
gathered particles from the gathering device for properties that
are indicative of the presence of particles of explosive
materials.
[0011] Implementations may include one or more of the features
noted above.
[0012] In another general aspect, trace sampling detection includes
gathering particles through two or more of a handle-bar, a gate and
an air-stream gatherer, and analyzing the gathered particles for
properties that are indicative of the presence of particles of
explosive materials.
[0013] In another general aspect, a trace sampling detection system
includes a gathering device configured to gather particles through
one or more collection holes and an impact collector configured to
deposit gathered particles onto a portion of a sample media. The
system also includes a carousel wheel including the sample media.
The carousel wheel is configured to rotate the sample wheel such
that the portion of the sample media including the deposited
gathered particles is presented to an exothermic decomposition
detector. The system further includes an exothermic decomposition
detector configured to detect, through an infrared sensor,
decomposition of heated materials.
[0014] Implementations may include one or more of the following
features. For instance the carousel wheel may be configured to heat
the sample media resistively. The sample media may be configured to
be resistively heated by running a current through the sample
media. The sample media may be configured such that the same
portion of the sample media may be reused through multiple
exposures to the impact collector and the exothermic decomposition
detector. The exothermic decomposition detector may be configured
to heat the sample media radiatively. The carousel wheel may be
replaced with a reel-to-reel mechanism.
[0015] In a further general aspect, a transportation mechanism for
a particle detection system that includes a gathering device, an
impact collector configured to deposit gathered particles, and an
exothermic decomposition detector configured to detect
decomposition of a deposited material includes a carousel wheel
including a sample media configured to accept a deposit of material
from the impact collector. The carousel wheel is configured to
rotate the sample wheel such that the portion of the sample media
including the deposited gathered particles is presented to the
exothermic decomposition detector.
[0016] The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other features
and advantages will be apparent from the description and drawings,
and from the claims.
DESCRIPTION OF DRAWINGS
[0017] FIGS. 1A, 1B, and 1C illustrate views of an exemplary
collection device for collecting samples of material.
[0018] FIG. 2 illustrates an exemplary hand sampler.
[0019] FIG. 3 illustrates an exemplary impact collector.
[0020] FIGS. 4A and 4B illustrate a top and side view of an
exemplary collector and detection system.
[0021] FIGS. 5A and 5B illustrate data results of particle
detection.
[0022] FIG. 6 illustrates a method of detecting particles.
[0023] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0024] People who handle or work with explosives, drugs, or other
materials typically become contaminated with trace residue of the
materials. For example, explosive particles may remain on the hands
following manufacturing and/or handling of a bomb or explosive
material, and some of these particles are may be transferred to the
person's clothing, such as the front pockets and the fly area of
the person's pants. Such trace residue may also be transferred onto
items such as wallets, spectacles, keys, purses, and door handles,
and serves to re-contaminate the hands, even when they are washed
and the person changes clothing.
[0025] In order to thwart sample collection methods such as
pressing a button or ticket, or atmospheric testing, a contaminated
person may take precautions, such as washing of the hands
immediately prior to entering a security checkpoint. Sampling
material from multiple locations on an individual's body while
applying a shearing force to release particles increases the
difficulty of thwarting such detection attempts.
[0026] Sampling techniques described in this document will work in
a variety of situations and locations. For example, the sampling
techniques may be employed with train and aircraft passengers, as
well as at other location where it is necessary to prevent the
transport of explosives or other materials, or to determine if
someone has handled explosives or other materials. The trace
sampling technologies are not limited by many temperature extremes,
and can be installed in a broad range of operational environments,
indoor or outdoor.
[0027] Although the following discussion is directed to explosive
detection, other particles may be detected. Specifically, the
system and methods discussed below may be used to gather, collect,
and detect hazardous chemicals, illicit drugs, chemical and/or
biological warfare agents, or other materials that may leave trace
particles. Further, although the following discussion is directed
towards people, many of the techniques described below could be
used to detect other objects with minimal adjustment. For example,
luggage on a conveyer belt could be sent through a similar
turnstile system with minor modifications to the samplers.
[0028] Referring to FIGS. 1A-1C, a collection device 100 includes
material collection mechanisms in an explosive trace sampling and
detection turnstile system. The collection device 100 includes
pedestals 105 and 106, an entrance 107, an exit 109, a hand sampler
110, a torso or waist sampler 120, and a shoe sampler 130 with
sampling techniques directed to each corresponding area of the
body.
[0029] In the device 100, passengers traverse a passage which is
defined by the pedestals 105 and 106. The passage includes an
entrance 107, a walkthrough space including the samplers 110-130,
and an exit 109. In various implementations, the entrance 107 or
exit 109 is presented by the motion of the hand and torso samplers
110 and 120. Each of the samplers 110-130 includes collection holes
which draw in materials such as explosive particles for analysis.
Each of the samplers 110-130 may also include an associated
movement or action designed to increase the number of particles
that will be gathered. With sufficient pressure and shear force,
explosive particles will be extracted from the hand, torso, or shoe
areas. In particular, the hand and torso samplers 110 and 120
dislodge and collect samples of material through contact, and the
shoe sampler employs a directional air stream to dislodge particles
from pants, cuffs, and shoes, and push the particles to the shoe
sampler 130.
[0030] The collection device 100 may be integrated into a
small-profile walkthrough turnstile, as shown in FIGS. 1A-1C. As a
passenger passes through the turnstile, the collection device 100
automatically screens a passenger's hands, torso, and feet for
trace explosives.
[0031] In the implementation shown, the passenger pushes the hand
sampler 110 down to unlock the turnstile gate that includes the
torso sampler 120. When the passenger grasps the hand sampler 110
at grips 115, suction in the interior of tube 117 dislodges
particles on the passenger's hands and draws the particles in
through the collection holes on the grips 115 of the hand sampler
110. In one implementation, the hand-sampler 110 may move in two
motions. Specifically, in the first motion, the handle-bar may
traverse 30-90.degree. of a circumference of a circle vertically
downward from the position shown in order to rotate the surface
area of the grips 115 with respect to the surface area of the
hand(s) pushing down. In the second motion, the handle-sampler 110
may traverse 60-90.degree. of a circumference of a circle
horizontally from the position shown. The first and second motions
may occur concurrently or separately.
[0032] As the passenger moves through the turnstile, the torso
sampler 120 brushes against the waist/torso area of the passenger,
and suction in the interior of tube 125 dislodges particles from
the passenger's waist and draws the particles in through the
collection holes 127 of the waist sampler 125. In one
implementation, the torso sampler 120 traverses 60-90.degree. of a
circumference of a circle horizontally outward from the position
shown, similar to the hand sampler 110. The combination of the
movement of the hand and torso samplers 120 present the entrance
107 which enables the passenger to traverse the collection device
100.
[0033] While the passenger moves and/or traverses the hand and
torso samplers 110 and 120, the shoe sampler 130 directs a stream
of air from an outlet port 134 (shown in FIG. 1B) to an inlet port
135. Specifically, the stream of air moves towards the passenger's
shoe/pant cuff area to dislodge particles and, with the dislodge
particles, is drawn into the shoe sampler 130 through the inlet
port 135. The hand sampler 110 and torso sampler 120 may both be
locked closed and only unlock when certain conditions are met. In
one implementation, the outlet port 134 is on the right pedestal
106, while the inlet port 135 is on the left pedestal 105. The air
streams from the samples 110-130 are joined inside the pedestal 105
through "Y" type connections so as to enable the three samplers
110-130 to impact on the sample media simultaneously as described
with respect to FIG. 3.
[0034] The collection device 100 may include a pressure switch on
the floor just before the entrance to the turnstile, or a proximity
sensor at the entrance to detect the presence of the passenger. A
detected presence may control system components, such as, for
example, the status of a blower, or the locking or unlocking of the
hand and torso samplers 110 and 120.
[0035] Components of the system may be constructed using a variety
of materials, such as, but not limited to, aluminum, steel, glass,
plastic or composite. Metals such as aluminum or steel may
interfere with the operation of standard walk-through metal
detectors if they are in close proximity to the collection device
100. Composite or plastic materials may be used to avoid such
interference.
[0036] In one implementation, the target sample rate is about 360
passengers per hour through the system, corresponding to 6
passengers per minute. This rate is determined by three main
factors. One factor is the time taken takes by the passenger to
pass through the turnstile.
[0037] The second factor is the analysis time, which includes the
time required to transport the sample to the analyzer, the time
required for analysis of the material, and the time required to
calculate results using the data produced by the analyzer. In some
implementations, the analysis functions may be operated in a
pipelined manner such that, for example, a first sample is analyzed
while a second sample is being collected and transported to the
analyzer.
[0038] The final controlling factor is one of choreography. For
example, if the turnstile is capable of accepting a passenger every
five seconds, to maximize efficiency, the passengers need to
present themselves to the turnstile in that amount of time.
[0039] Referring particularly to FIGS. 1B and 1C, internal
components of the collection device 100 include a blower 155
operating in a vacuum mode, a multi-area trace particle sampling
and transport mechanism 160, a collection system 165, a detection
unit or detector 170, retractable wheels 180, a computer system
185, a power supply 190, a carousel wheel 195, and a detection unit
197. Other implementations of the collection device 100 may include
other components, such as, for example, a boarding pass reader, a
wireless link unit, or a system controller including a TCP/IP
interface to an airport security network.
[0040] The blower 155 provides the necessary vacuum to operate the
samplers 110-130 and may be on continuously during operation of the
collection device 100, or may include a "standby" mode in which the
blower is turned on when activated by the operator, or when a
passenger sensor senses a passenger approaching or entering the
turnstile. The specific type of blower 155 may be selected
depending on desired parameters such as required output, power
consumption, or noise level. The blower 155 may be a high quality
regenerative blower, such as, for example, the Gast Regenair Model
R3105-12. In one implementation, a second blower is used to
generate the air flow for the shoe sampler 130.
[0041] The multi-area trace particle sampling and transport
mechanism 160 is enabled by efficiently transporting trace
explosives particles down tubing to a collection system 165 without
significant loss to the interior walls of the piping. Small
particles of explosives are known to be unusually "sticky," as the
explosive crystals are often coated in oils, waxes or polymers. One
way to prevent the particles from sticking (or at least to reduce
the number of particles that stick) is to minimize the number of
particles that reach the interior surfaces. This may be
accomplished through design parameters such as, for example,
maintaining proper velocity (e.g., greater than 10 m/s) within the
transport piping, using gentle bend radii (e.g., greater than 8
times the diameter of the pipe), and having inlet holes that that
are sized to create a vacuum effect. Additionally, inside surfaces
should be smooth and free of abrupt transitions. In one
implementation employing the above parameters, particles ranging in
size from 5 to 300 microns may be entrained in a flow with a
Reynolds Number between 10,000 and 50,000, with near 100% transport
efficiency.
[0042] The collection system 165 is used to gather transported
material particles so that the material may be analyzed by the
detector 170. Various collector systems 165, such as a carousel
wheel or reel-to-reel ribbon system, which has multiple sample
media collection stations or portions, may be used. In the
collection system 165, the material is gathered on a sample media
that is presented to the detector 170 for analysis. During
gathering, the collection system 165 may be sealed against the
collection material.
[0043] One implementation employs contamination controlling
software that controls positioning of the sample media such that,
if a given station or portion of the sample media is deemed
contaminated, that station or portion is skipped until cleaning or
replacement of the sample media. Depending on implementation, the
sample media needs to be replaced or cleaned at different intervals
(e.g., daily or monthly).
[0044] As noted above, the collection device 100 also includes
retractable wheels 180, a computer system 185, and a power supply
190. The retractable wheels 180 are used to simplify transportation
of the turnstile 175. The wheels may be raised (i.e., retracted
into the walls of the device) by use of one of several mechanisms,
such as a jackscrew, a cam-lever, or a hex-bolt.
[0045] The computer system 185 may include a single CPU or multiple
computers. In an implementation including two CPUs, one CPU is
directed to controlling the turnstile system 100, and the second
CPU is directed to analyzing data. Included in the computer system
185 are application specific boards such as an I/O (input/output)
digital controller with an integral A/D (analog/digital) and D/A
(digital/analog) converter such as devices manufactured by National
Instruments. A monitor and keyboard may be included to accept user
input or for service and maintenance. In one implementation, a
small LCD VGA monitor with either a touchscreen or a keyboard is
permanently connected to the computer system 185 and placed behind
an access panel.
[0046] To enable compatibility with various supplied voltages, the
line voltage may be converted by the power supply 190 to feed DC
components. In one implementation, the power supply 190 operates to
convert 110/220 VAC, 50/60 Hz to the required output(s). A small
UPS (uninterrupted power supply) may be included to enable
completion of any sampling or analysis in progress if a power
failure occurs, as well as to enable a clean shut down of the
computer system 185 in the event of a power failure.
[0047] The collection device 100 may further include a carousel
wheel 195 and detection unit 197. The carousel wheel 195 includes a
sample media configured to hold the sample material as described
with respect to FIG. 4A. The detection unit 197 analyzes the sample
material on the sample media as described with respect to FIG.
4B.
[0048] Referring to FIG. 2, an exemplary hand sampler 110 includes
collection holes 210 and hole contours 220. The hand sampler 110
may be used in the device 100 of FIGS. 1A-1C. In the hand sampler
110, trace sampling of hand(s) occurs as the passenger moves the
handle-bar on the hand sampler 110.
[0049] The hand sampler 110 has a right and left hand section which
may each include collection holes 210 to vacuum the hand during the
sampling process. In certain implementations, each of the two
sections also may have a conductivity meter to determine that the
passenger is using both hands to hold the hand sampler, and that
the passenger is not wearing gloves. Since it is desired to have
some wiping motion to create sheer and pressure forces between the
handle-bar and the hand of the passenger, the design is such that
the passenger needs to push the handle-bar down, in a motion
similar to that typically used, for example, to unlock the brakes
of luggage carts at airports. The handle-bar may move downward
along an arcuate path, such that the handle-bar rotates with
respect to a downward pressing hand. Both the mechanical motion of
pushing the handle-bar down and a conductivity meter reading
indicative of skin may be required to unlock the hand sampler 110
and torso sampler 120 allowing them to rotate and thus allowing the
passenger to pass through the collection device 100.
[0050] Air and particles suspended in the air are drawn in for
collection and detection through the collection holes 210. As
explosive particles may be wedged in rough surfaces (e.g., skin or
clothing), the hand sampler 110 is designed to place a pressure and
shear force on a passenger's hands concurrent with the intake of
dislodged sample material. The hole contours 220 are shaped to
ensure an appropriate pressure and sheer force is generated locally
around the collection holes 210. In one implementation, the hole
contours 220 are flared or "V" shaped such that the effective
collection area is larger than the diameters of the collection
holes. The edges of the hole contours 220 or collection holes 210
may be sharp, abrupt, or otherwise shaped to facilitate a scraping
movement. As with all three samplers 110-130, the number of
collection holes 210 on the hand sampler 110 is a design feature
and may vary depending on desired characteristics. In particular,
more or larger collection holes 210 increases the amount of
gathered material for analysis while also increasing the size and
power requirements of the blower(s).
[0051] As particles are dislodged, they are vacuumed into the
system. A hand-release mechanism on the gate is designed to ensure
contact with the finger tips, and the downward pressure applied to
the hand bar optimizes the sampling conditions. Optionally, a
protective panel above the hand bar houses a UV sterilizer 172 as
shown in FIG. 1C, and also serves to ensure that the bar may only
be pushed with the hand, and not with the elbow or a handheld
item.
[0052] One particular implementation includes a 6 mm inner-diameter
hole at the end of the hand sampler 110 to develop at least a 10
m/s linear gas velocity inside the hand sampler 110. The sampling
section has collection holes 210 which may be angled at 45.degree.
to the direction of flow for each hand. Depending on
implementation, the grip may be operated with one or both hands.
Each collection hole 210 is at the apex of approximately 1 cm wide
and 1 cm long V-shaped hole contour 220. Each hole has about 1.5 mm
inner-diameter, with the velocity at the hole being 105 to 110 m/s,
and the linear velocity in the pipe being 10 to 15 msec. The flow
in the pipe is turbulent with a Reynolds number of from 15,000 to
22,000.
[0053] Trace sampling of the waist/pocket area occurs as passenger
pushes the torso sampler 120 open with the body. The torso sampler
120 may be locked until movement or a conductivity reading of the
hand sampler 110 triggers unlocking. As shown, the torso sampler
120 includes an oval shaped gathering tube and a planar surface.
Other implementations of the torso sampler 120 may employ different
shapes. For example, the gathering tube may be a "U" shaped, and
the surface may be curved or otherwise formed to conform to the
shape of a body. The torso sampler may include a series of
collection holes that are the same or similar to the collection
holes 210 on the hand sampler 110. The torso sampler 120 uses
close-coupled vacuuming of the clothing surface while applying a
shear force. This is achieved by having the passenger push against
a swinging tubular door, with the vertical tube section of the door
being designed to come into close contact with the body so as to
sample the region between mid torso and thighs.
[0054] As with the hand sampler 110, particles that are in the path
of the collection holes 210 will be mechanically dislodged by the
shear force and applied pressure of the lip edges, and then sucked
into the collection holes. As the passenger moves past the gate,
the vertical part of the tube scrubs the torso from the center of
the body to the side, covering about 25% of the total torso surface
area.
[0055] In one particular implementation, the vertical section of
the torso sampler 110 is 50 cm tall, with 18 collection holes. Each
collection hole 210 is 1.5 mm in diameter and located at intervals
of 1 cm, with a 0.2 cm rounded lip on each V. Each orifice is at
the apex of a 1 cm wide and 1 cm long V-shaped indent. The flow
velocity at each orifice is between 59 and 110 msec. This is
sufficient to entrain particles in the 5 to 200 micron size range,
without entraining larger particles and hairs. The linear velocity
inside the pipe is 10 to 28 m/s. As with the hand sampler, the flow
inside the 1 inch diameter pipe is turbulent with a Reynolds number
in the 14,000 to 41,000 range.
[0056] Both the hand and torso samplers 110 and 120 may be spring
loaded to place a resistance of about a few pounds against the
passenger. If a passenger moves past the samplers 110-130 too
quickly, an insufficient sample may be collected. Optionally, speed
of a passenger may be slowed by designing a resistance system that
increases exponentially with speed. In particular, a hydraulic or
pneumatic resistance system may be included to provide low
resistance with slow movement and high resistance with quick
movement. Further, the torso sampler 120 may include a
significantly higher resistance than the hand sampler 110 at any
speed to encourage use of the passenger's torso, rather than the
passenger's hands, to push the gate.
[0057] In the shoe sampler 130, trace sampling of the shoes and
pant cuffs occurs while the passenger stands at the turnstile
entrance and begins to pass through the gate. The sampling is
conducted by gathering particles from an air stream that is blown
out of one or more holes (e.g., the outlet port 134) on one side of
the turnstile passage and sucked in through one or more other holes
(e.g., the inlet port 135) on the other side of the turnstile
passage. In one implementation, an air-knife less than 1 cm in
width and 15 cm in height, with a flow rate of 4 liters per sec
(Us) is used to dislodge particles from shoes, boots and pant
cuffs, as the passenger walks through the turnstile. The air-knife
has benefits over a "puff" based blowing system, in that the
gathering ability is continuous and less susceptible to missing
areas of passengers. The particles are drawn into the air and then
sucked into a vacuum-line at a flow of 6.5 l/s by means of 4
sampling ports of 6 mm inner-diameter. Tapered lower sidewalls of
the turnstile minimize the distance between the air-knife and the
shoes/pant cuffs, and the distance to the sampling inlet. The air
jet and intake ports are positioned to maximize particle collection
efficiency.
[0058] Once the passenger has completely passed the collection
device 100, the hand sampler 110 and torso sampler 120 return to
the original start position. Spring loading that is dampened to
insure that these two components do not slam shut may be included.
After completion of the sampling, the collection device 100
analyzes the sample and may present the results to the operator as
either "Clear" or "Alarm."
[0059] The previous descriptions provide exemplary implementation
of a detection system 100 including a hand sampler 110, a
waist/torso sample 120, and a shoe sampler 130. Other
implementations may include different features, such as a pressure
sensor to detect performance-limiting hole blockage and to
automatically prompt a cleaning cycle upon detection of such
blockage. Also, sensors (e.g., optical sensors) may be employed to
detect passengers climbing, crawling, or otherwise avoiding the
samplers. Further, a camera may be included that may take pictures
of all passengers or only passengers that test positive for certain
materials.
[0060] Referring to FIG. 3, an impact collector 300 combines the
air streams of the three samplers into a single air-stream from
which particles are collected onto a sample media 320. There is a
critical flow to avoid particles falling out of the airflow and
onto the tubing walls. One implication of particles falling out of
the sample stream is a loss of sample that leads to a false
negative. Another implication is one of carry over. Specifically,
if a particle falls out of the sample stream, it has the potential
of showing up in later samples leading to a false positive. Because
of such implications, after every positive sampling, there may be a
clearing purge cycle, where the system is run without additional
sample material.
[0061] In the impact collector 300, the end of the sample tube may
be close coupled to the sample media 320. The sample media may be
constructed out of a variety of materials, such as, for example,
Teflon, stainless steel mesh, carbon fiber, or a deactivated glass
wool pad. If resistive heating is being employed, the sample media
320 may need to be conductive. If radiative heating is being
employed, conductivity of the sample media 320 is not required.
[0062] In the impact collector 300, the air and explosive vapors
divide according to the ratio of the bypass flow to the collector
flow. Typical collector flows are between 0 and 10 percent of the
total flow. Particles, however, are not able to make the
180.degree. turn 310 and thus impact upon the sample media 320. In
order to keep the piping of the turnstile clean, valves may be
placed downstream of the collection system and kept closed except
during the sampling time.
[0063] In one particular implementation, the internal
inner-diameter of the impact collector 300 is about 1.5 cm. The
outer ring is about 3 cm in diameter. If the sample media 320
rotates, the impact collector 300 itself needs to clear the sample
media 320. The impact collector 300 may need to seal against the
portion of the sample media 320 at the outer ring with the inner
tube being from about 0.2-2.0 cm away from the sample media 320. An
O-ring may be included on the outer tube to form a seal. In come
cases, slight leakage may be acceptable. Depending on
implementation, either the impact collector 300 is lowered to form
the seal, or the sample media 320 itself is raised to form the
seal.
[0064] Referring to FIG. 4A, a top view of a collection system 400
includes the impact collector 300 and sample media 320 of FIG. 3,
and a detection unit 430. In the collection system 400, the impact
collector 300 is used to deposit the gathered material onto the
sample media 320. The media moving mechanism moves the sample media
320 such that the sample media including the deposited material
moves from a region adjacent to the impact collector to a region
within the detection unit 430. The deposited material is than
analyzed for traces of specific material.
[0065] Referring to FIG. 4B, a side view of a collection system 400
includes a media moving mechanism 440, a heating controller 450,
and contacts 460. The discussion below refers to two specific
implementations directed to resistive and radiative heating
exothermic decomposition (with resistive heating shown in FIG. 4B),
but other methods of initiating thermal decomposition may also be
used. In particular, elevating the temperature of a particle by
using electromagnetic radiation, lasers, the convection of heat via
warm air to the particle, or the conduction of heat to the particle
would be sufficient for causing thermal decomposition.
[0066] The particular collection system 400 to be used may be based
on factors such as a desired period between maintenance sessions,
ease of maintenance, or cost. FIG. 4 illustrates an implementation
involving a carousel wheel 410 with a reusable discreet sample
media 320. Other implementations, such as a "reel-to-reel" system
with a one time or reusable sample media 320, also may be used.
Such a reel-to-reel mechanism may be more costly to build and more
difficult to maintain (e.g., by replacing the worn sample media
320) than the carousel mechanism of 400. Because the reel-to-reel
mechanism could hold more sample media, the time between
replacements would be greater than for the carousel
implementation.
[0067] In the illustrated implementation having a carousel wheel
410, the sample media 320 is within the carousel wheel 410 and
includes either a series of discreet collecting areas or a
continuous collecting area. In a series of steps, the collection
system 400 gathers collected material onto an area of the sample
media 320 and then rotates to a detection unit 430 to enable the
deposited material to be analyzed by a detection unit to detect the
presence of particles of materials.
[0068] According to various implementations employing the carousel
wheel, a first station is the impact collector 300, which may seal
to the carousel wheel 410. The term "station" refers to specific
locations or degrees of rotation of the carousel wheel 410. The
position of stations may be determined by the position of holes
along the circumference at angular positions of the carousel wheel
410. After particles are deposited with the impact collector 300 to
an area of the sample media 320, the carousel wheel 410 rotates to
the second station, which is the detection unit 430.
Characteristics of the detection unit 430 depend on the detection
unit employed. If the detection unit is a thermal desorber, the
detection unit may clamp over the gathered material which is
vaporized.
[0069] The actual detection unit chosen may vary based on desired
characteristics, such as complexity, cost, or sensitivity. Various
detection units may be employed, such as an ion mobility detector
(IMS), gas chromatography coupled with a chemiluminescence detector
(GC-CL), a thermal desorber, a resistive heating exothermic
decomposition detector, or a radiative heating exothermic
decomposition detector.
[0070] A media moving mechanism 440 is employed to rotate the
sample media 320, and in the implementation discussed above, the
carousel wheel 410. For a high degree of positional accuracy, a
stepper motor may be employed. As a stepper motor is expensive and
requires specialized electronics to control, a simpler alternative
that may be used is a unidirectional or bidirectional DC motor. An
LED optical sensor may be used to determine and control the
position of the media moving mechanism 440. Maintenance of the
carousel wheel 410 may be conducted through an automatic disc
loading and unloading station to extend the time between routine
replacement of the sample media to, for example, one month.
[0071] In one implementation that includes a resistive heating
exothermic decomposition detector (discussed below), the sample
media 320 area is three cm.sup.2 and includes two contacts 460
which are placed at opposite ends of the sample media 320. The
contacts 460 may be shaped in various ways, such as, for example,
raised metallic bumps (e.g., like a contact for a battery), rods,
or plates. A spring loaded contact may be used to complete the
connection. The sample media 320 may be designed with upper and
lower halves. In one assembly method, the two halves are separated,
the sample media 320 is installed on the bottom half, and the top
half is attached on top of the sample media 320 forming a sandwich.
In one implementation, for each portion of the sample media 320,
one of the contacts 460 is in the form of an electrode which is
tied to a single common connection point (not shown), and the other
contact 460 is a unique connection (as shown in FIG. 4B). In such
an implementation, the common connection point is constantly
connected to the power supply, and only one unique connection is
connected at a time to enable only one portion to be resistively
heated. The sample media may include holes for the optical sensors
(or LED sensor as discussed above with respect to the carousel
wheel 410 implementation).
[0072] Residual material, such as oils, may contaminate or mask
later measurements, or may shorten the life of a reusable sample
media 320. By heating the sample media 320 to a higher temperature
than that required to trigger decomposition of energetic material,
such residual material may be burned off. Optionally, a high
temperature bake out at temperatures in excess of 300.degree. C.
may be conducted at the second station or a separate third station
in order to thermally decompose remaining particles. A bake out at
a third station may be particularly useful in implementations
without resistive or radiative heating, such as an IMS or GC-CL
system with thermal vaporization.
[0073] In one implementation, the real-time temperature of the
sample media 320 is measured through a pyrometer, and such
measurement is a part of a feedback loop to enable the temperature
to be actively controlled. The pyrometer may be included in the
detection unit 430 or the heating controller 450. During heating,
there is slight expansion of the sample media 320. In order to
prevent distortion, the design is such that there is a slight
tension on the sample media 320.
[0074] Detecting trace amounts of explosives remains a challenging
task and often suffers from poor sensitivity to minute amounts of
explosives and low throughput. These issues can be addressed by
relying on the rapid kinetics and thermodynamics associated with
the thermal decomposition of explosives. Although most molecules
decompose endothermically when heated in an atmosphere deprived of
oxygen, an explosive compound decomposes exothermically releasing
heat to the environment. The released heat is immediately
transferred to the molecules surrounding the decomposing
explosives, which results in a localized increase in temperature
that provides a measurable indicator of an explosive compound.
[0075] Specifically, explosive compounds decompose exothermically
(they release heat to the surroundings) when heated anaerobically.
If the mass of the explosives is large enough, the temperature
rises, which accelerates the reaction rate even further, releasing
additional heat, and culminating in a runaway thermal explosion.
For sub-critical masses, the material is consumed before it
explodes as heat is lost to the surroundings. Nevertheless, even
for these sub-critical cases, the temperature rises above its
surroundings before decaying back to the ambient.
[0076] A resistive heating exothermic decomposition detector senses
the thermal energy released during exothermic decomposition, which
is a thermodynamic property unique to energetic materials. This
feature makes it possible to detect explosives, including
nitro-organics and nitro-salts, peroxides, perchlorates, and gun
powder, as well as homemade explosives of as yet unknown
composition.
[0077] The heat released from small amounts of explosives during
decomposition may be detected by using the IR detection array to
detect the thermal signature resulting from this process. The
camera is configured to detect heat in the mid-wave infrared
(MWIR), 3 to 5 micron wavelength, or long-wave infrared (LWIR), 8
to 12 micron wavelength, regions to observe the temperature of the
environment surrounding an explosive particle. Thermal imaging
cameras employing detection in the MWIR region benefit from
superior resolution and contrast while those detecting in the LWIR
region offer enhanced sensitivity to smaller temperature
fluctuations and are less affected by atmospheric conditions (e.g.,
LWIR radiation can be transmitted through mist and smoke).
[0078] For trace explosive decomposition, the inherently small
particle sizes complicate the detection process. For an explosive
compound undergoing anaerobic thermal decomposition, the heat
released is expected to be equivalent to about a 100.degree. C.
temperature rise in a 200.degree. C. environment within a five to
five hundred millisecond time frame, depending upon the type of
explosive, its mass, the heating rate and the rate of heat loss. In
some cases, the time frame is 5 to 30 milliseconds. If all of the
exothermic energy produced by the decomposition of the explosive
occupied one instantaneous field of view (IFOV) of the IR detection
array, this would be easily detectable, since most MWIR/LWIR
cameras have sensitivities near 0.05.degree. C. However, trace
amounts of explosive particles emitting this heat weigh as little
as a few nanograms and their emitted energy would only occupy a
region 0.1 to 0.01 millimeters in diameter. Since the IFOV per
pixel of a typical camera lens is about two millimeters in diameter
at close range (approximately one foot away from the source), the
released energy from a trace explosive is undetectable across the
IFOV area. In this case, the temperature rise has been diluted
across the entire IFOV and appears as a temperature increase as
small as 0.003.degree. C. for a nanogram-size particle.
[0079] In order to detect localized heat signatures, the IR
detection array is appropriately configured to record fast,
microscopic reactions. Because of these constraints, the camera has
a macro (close-up) lens capable of achieving an IFOV of less than
between 50 and 150 microns in diameter per pixel. In addition, the
resolution of the camera is sufficient to provide numerous
individual pixels which act as their own individual heat detectors
and serve to increase the sensitivity of the detection of energetic
particles. For example, doubling the resolution of a thermal
imaging camera leads to a .times.4 to .times.8 lowering of the
lower detection limit of this method. Using a camera with a
sensitivity of 0.05.degree. C., a trace explosive decomposition
could be easily detected with a signal to noise somewhere between
100 and 200 (with a signal to noise of 40 as the video threshold
for the human eye). A final technical challenge arises due to the
speed of the thermal decomposition process. If the camera
integration time between frames is long relative to the energy
release, the energy is time averaged and may not be captured by the
camera. For example, for a five to ten millisecond reaction and
using a 60 Hz (16 ms) imaging rate, the observed energy released
from an energetic particle is reduced by less than a factor of 3.
This yields a signal to noise ratio somewhere between 40 and
80.
[0080] In one implementation, the IR detector array is a long wave
infra red detector (LWIR) that is sensitive in the 7.5 to 14 micron
range. The detector is equipped with a focusing lens in order to
resolve pixels down to about 50 microns. The refresh rate of the
system is 60 Hz. The detector is a 320.times.240 array with 76,800
pixels. The sensitivity of each pixel is specified as 0.05.degree.
C., which facilitates sensitivity at the mid-picogram level. Since
the particle mass is inversely proportional to the third power of
the pixel size, the sensitivity can be enhanced by using a more
powerful focusing lens.
[0081] Analytical interpretation of the results is possible by
examining the temperature of individual pixels or the average of
several pixels as a function of time. Results may demonstrate that
a particle's rapid increase in temperature exceed that of the
sample media 320. This feature can be used in algorithms to
automatically detect the presence of explosives. In particular,
each energetic compound has a quantifiable and positive heat of
decomposition (H) and a quantifiable activation energy (E). H
impacts the total heat that is released and E the rate of heat
release. These two properties interact in such a way that a
detector may distinguish classes of explosives and/or the chemical
composition.
[0082] Automatic algorithm based target recognition is used to
track multiple pixels simultaneously and to automatically recognize
the unique characteristics of explosives. Simple enhancements
include subtraction of the varying background temperature, and
displaying the differential so as to better visualize the peak
maximum. Local maxima in a temperature versus time plot are
indicative of the presence of explosives and are mathematically
defined as points at which the time rate of change of the
temperature equals zero (i.e., dT/dt=0). However, both local maxima
due to the fluctuating temperature of the sample media 320 may also
be present. To correct for these artifacts, the sample media 320
temperature may be subtracted from the temperature recorded at
various points.
[0083] Specifically, in one implementation, the analysis of the
sample collected on the sample media 320 may be performed by
heating the collection area from ambient to about 300.degree. C. in
one to two seconds. This heating may be performed in front of the
IR detection array (included in the detection unit 430) one
implementation of which includes 320.times.240 pixels focused on
the sample area. Each pixel may view about 100 .mu.m square for a
total viewing area of about 2.5.times.1.5 cm. When the sample media
320 is rotated to the second station, which includes the detection
unit 430, heating is performed resistively with about 10 amps at 2
volts.
[0084] In a radiative heating implementation, a flash lamp is
included in the heating controller. The heating controller 450 and
the detection unit 430 may optionally be on the same side of the
sample media 320. The flash lamp delivers the necessary activation
energy for initiating decomposition of residual explosive
particles.
[0085] The previous description provides exemplary implementations
of a collection system 400 and a detection system 450. Other
implementations may include different features, such as a checking
solution injected onto the sample media 320 on an infrequent but
scheduled basis to test the ability of the system to successfully
detect particles of a material. This mechanism may include a
reservoir, that needs to be replaced monthly, and may include
either the LEE miniature variable volume pump model number
LPVX0502600B, (see www.theleeco.com) or a small KNF model UNMP830
(see www.knf.com) or similar pump and a LEE solenoid valve similar
to LEE model number INKX051440AA.
[0086] FIG. 5A shows data results 500 of exothermic decomposition
detection. In particular, a picture is shown of a sample media with
a decomposing material at four different instances of time.
Specifically, data results 500 for the energetic detection of a
particle of smokeless powder using a 60 Hz frame rate are shown.
Element (a) shows an initial IR image at frame 110 with a
relatively cool particle and filament. Next, element (b) shows an
IR image at frame 389 showing elevated temperatures around the
particle just prior to explosion. Next, element (c) shows an IR
image at frame 390 showing the particle explosion. Finally, element
(d) shows an IR image at frame 391 showing elevated gas
temperatures resulting from the particle explosion.
[0087] Referring to FIG. 5B, data results 550 for the same
decomposition are shown from the perspective of a pixel viewing the
smokeless powder and a pixel viewing the sample media across time.
In the results, the four instances of time from the results 500 of
FIG. 5A are marked. Specifically, a two-dimensional plot of the
thermal signature of one pixel near a smokeless pellet and one
pixel on the sample media is shown.
[0088] Referring to FIG. 6, a method for detecting particles
includes gathering the particles from one or more locations,
depositing the gathered particles onto a sample media, rotating the
sample media to a detection system, and analyzing the gathered
particles with the detection system.
[0089] Particles are gathered through collection holes (610). As
shown in FIG. 1, the collection holes may be distributed across a
handle-bar, torso gate, a shoe blower, or other devices. The
particles may be gathered through multiple devices concurrently. In
one implementation, a passenger pulls down a handle-bar which
unlocks a gate that may be pushed with the passenger's torso, all
while an air-knife blows particles from the passenger's shoes and
cuffs. In particular, friction, pressure, and sheer force are
produced by the resistance of the handle-bar, torso gate, and
air-stream, which releases dislodged particles for gathering.
[0090] The gathered particles are then deposited onto the sample
media (620). If gathered from multiple locations, the particles may
first be combined into a single stream of particles, and then the
single stream may be deposited onto the sample media as shown in
FIG. 2. In one implementation, the sample media is reusable and may
be moved after a deposition such that a different portion of the
sample media is presented for the next deposition.
[0091] The gathered particles are presented to a detection unit
(630). If the sample media is within a carousel wheel, the carousel
wheel is rotated to present the portion of the sample media which
includes the gathered particles to the detection unit. In one
implementation, after each deposition, the carousel wheel is
rotated, and after a number of decompositions, a portion of the
sample media is reused.
[0092] The gathered particles are analyzed (640) by the detection
unit. Either the carousel wheel or the detection unit may heat or
radiate the gathered particles to spur decomposition. In one
implementation, a current is driven through the sample media to
resistively heat the gathered particles while an IR detection array
monitors particle decomposition.
[0093] The previous description provides exemplary implementations
of a method for detecting particles. Other implementations may
include different steps, such as, for example, a cleaning cycle may
be run after every deposition or analysis. The cleaning cycle may
include heating and/or running an air-stream through part or all of
the sample media.
* * * * *
References