Note: Descriptions are shown in the official language in which they were submitted.
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1. Pield of the Invention
This invention relates to systems for the detection
of explosives and other controlled substances such as drugs
r narcotics. ~:ore particularly, the present invention
relates to an integrated system consisting of a sampling
chamber, a detection system, and a data processing system
for the detection of the vapor and/or particulate emissions
o explosives and controlled substances in a non-invasive
ner .
2. Discussion of the Prior Art
In recent years there has been a steady increase in
the illegal use of explosives 2s well as an increase in the
transportation of contraband substances such as drugs or
narcutics. It is impossible to detect the existence or
prevent all of the cases of bombings and drug smuggling going
on; however, it is possible to detect explosives and
contraband substances in particular areas where high
visibility and/or vulnerability exists such as in airports or
airplanes. There are numerous ways in which an individual
can place drugs or explosives on an airplane, and even more
places an individual can hide the drugs or explosives once on
the airplane. The illegal substances can be brought on the
alrplane by a knowing or unknowing individual by concealing
the substance on his/her person or by placing the substances
n baggage to be placed in the cargo section of the aircraft.
The methods for detecting substances such as
explosives and drugs or narcotics have been studied for many
years, and various techniques have been developed ~hich range
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from e~plosives/drug sniffing dogs to highly sophisticated
vapor detection devices. Basically, the detection of the
aforementioned substances is accomplished in one of two ways;
namely, non-vapor detection and vapor detection. Non-vapor
detection methods include x-ray detection, gamma-ray
detection, neutron activation detection and nuclear magnetic
resonance detection. These methods of detection are more
applicable to ~he detection of the various substances when
the substances are concealled and are carried or associated
with non-living items such as baggage to be carried onto an
aircraft in that the detection techniques might pose a threat
to living items. Vapor detection methods include electron
capture detection, gas chromatography detection, mass
spectroscopy detection, plasma chromatography detection,
bio-sensor detection and laser photoacoustic detection.
These methods of detection are more applicable to the
detection of substances that are concealled and associated
with living items such as those that can be carried by
individuals including the residuals left on the individual
who handled the various substances. All of the above methods
are presently utilized, including explosive and drug sniffing
dogs.
Today, there are many private and government
research studies devoted to the development of systems and
methods for the detection of explosives and drugs or
narcotics. With the advances in explosives technology, such
as the advent of the plastique explosives, which can be
disguised as common items, it is becoming increasingly
difficult to detect these substances. The problems that must
be overcome in the detection of these substances as well as
3 others, include low vapor pressure of the particular vapors
escaping from the particular substance, the search time and
the throughput of the various systems, the low concentration
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of the vapor or particulate emissions from the particular
subst~nce, isolation of the particular substance with a high
degree of reliability, and maintaining the integrity of the
systems environment. -
There is numerous prior art dealing with the
technology of explosive and drug detection devices. The
article "Air Flow Studies For Personnel Explosi~e Screening
Portals" authored by R. L . Schellenbaum of Scandia National
Labs which was published in 1987 as part of the Carnahan
Conference on Securities Technology in Atlanta, Georgia (July
15, 1987) discloses a study on various types of integrated
systems for the detection of contraband explosives. ~he study
outlined a three step process, which includes the collection
of vapor, preconcentration,-and detection, for the capture
and detection of the vapors eminating from explosive
substances. The article discloses various types of
collection devices for cGllecting the sample. Various portal
configurations and air flow mechanics within each of the
portals were studied to see which one provided the best
sample. The Atmos-Tech Air Shower Portal, a Modified
Atmos-Tech Portal and a Cylindrical Portal were used in the
study with various air flow configurations. The study
concluded that downward, semi-laminar flow over the body
cross-sectional area combined with a vacuum flow collection
funnel of approximately twelve inches in diameter placed
bëneath the grating in the floor of the portal was the best
way to collect the explosives vapor or particulate emissions
from an individual passing through the portal.
~ or the detection part of the study, various
detection devices were used including the *Phemto-Chem 100 Ion
3 Mobility ~pectrometer in combination with a preconcentrator
developed by Ion Track Instruments Inc. The ion mobility
spectrometer is a plasma chromatograph which uses an
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atmospheric ion-molecule reactor that produces charged
molecules which can be analyzed by ion mobility. The
preconcentrator comprises a motor-driven~ metal screen disc
rotated within a cast metal casing. The screen adsorbs the
vapor and is then heated for desorption of the vapor. This
adsorption-desorption process is the necessary
preconcentration step which is used to increase the vapor or
particulate concentration in the collected air sample.
The major problem encountered in the use of the
portal detection systems in the study was maintaining the
integrity of the sample air volume. In maintaining the
integrity of the s~mple air volume, it is necessary to
prevent the sample air volume to be contaminated with the
am~ient environment at the s-ame time trying to maintain a
steady flow of traffic through the portal, which is essential
to efficient operation of any type of screening system in
which heavy traffic is common place. The aforementioned -~
article suggests that the integrity of the sample air volume
was not maint,ined in portals without doors. If ambient
drafts were present, such as those from air conditioners or
just the flow of pedestrian traffic, a reduction of ten
percent in detection was encountered. The addition of doors
on the portals effected a rise in the detection rate;
however, it produced unacceptable pedestrian traffic problems -
which would not meet the requirements for high throughputs
required by airports.
In the patent art, there are a group of references
which disclose various methods and devices for detecting
contraband substances, including both drugs and explosives.
These references are all directed to the detection of ~ -
3 contraband substances within a container or luggage, and not
those carried on a person. U.S. Patent 4,580,440 and U.S. ;-
Patent 4,718,268 both assigned to British Aerospace Public
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Company Limited disclose a method and apparatus for detecting
contraband substances sealed in freight type cargo,
sasically~ the method consists of sealing the cargo in a
container, agitating the cargo in order to shake off the
vapor or particulate matter eminating from the cargo into the
surrounding atmosphere, sampling the atmosphere, heating the
collected s2mple and analyzing the sample utilizins gas
chromatography. U.S. Patent 4,202,200 assigned to Pye
Limited discloses an apparatus for detecting explosive
substances in closed containers. Basically, objects such as
luggase are passed through a controlled axis tunnel wherein
the objects are swept by circulating air flows, and then the
air sample is collected and analyzed. It is also suggested
that if a larger tunnel is constructed, people as well as
objects can be passed through it. The aforementioned
inventions provide a means and method for detecting
contraband substances by using vapor sampling; however, none
of the inventions provide or suggest the use of a
preconcentrator means for increasing the sensitivity and
selectivity of the detection means. Additional patent
references which disclose similar type systems are U.S.
Patent 3,998,101 and U.S. Patent 4,111,049.
There are numerous patent references in the testing
and monitoring art which disclose a concentration step which
includes the filtration or absorption of the molecules of
interest over time. After a predetermined period of
exposure, the filtering/absorption media is removed and
desorbed with heat~ while a new filter/absorption media is
placed in the air stream. U.S. Patent 3,768,302 assigned to
Barringer Research Limited discloses a system used in the
3 geological testing area and in which the system receives an
air stream containing particulates. The sample undergoes a
concentration step which includes passing the air sarnple over
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two paths with adsorbing/desorbing steps, and finally
analyzed. U.S. Patent 4,056~968 assigned to the same
assignee as the above patent also discloSes a Syste~ which is
also used in the geological testing area. In this invention,
the concentrated molecules could be desorbed from a moving
tape as well as from a moving disk. U.S. Patent 4,775,484
discloses a rotating filter media ~hich is used to absorb
particulate material during one stage of its rotati~n, and
which is purged or cleaned at a separate and second stage of
its rotation. U.S. Patent 4,127,395 also discloses a common
absorption/desorption circuit uslng a pair of absorbent
media, wherein one of the pair is absorbing, while the other
is desorhing. U.S. Patent 3,925,022, U.S. Patent 3,997,297 -~ -
and U.S. Patent 3,410,663 al~ disclose absorption/desorption -
type devices. All of the aforementioned devices disclose
systems for the abso-ption and subsequent desorption of
particulate or vapor matter; however, none disclose a portal
type sampling chiamber.
The present invention is directed to a system for
the detection of e~plosives, chemical agents and other
controlled substances such as drugs or narcotics by detecting
their vapor and/or particulate emissions. The system
co~prises a sampling chamber, a vapor or particulate
concentrator and analyzer, and a control and data processing
system. The system is particularly useful in field
environments, such as airports, where it can be used to
detect the aforementioned substances on an individual or in
3 the baggage of the individual. The system meets the
requirement to detect the aforementioned substances in a
non-invasive manner at any required level, and to do it so
quickly that the free passage of people and baggage is not
unduly interrupted.
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The sampling chamber is a portal with internal
1 dimensions of appro~imately siY. feet in length, seven feet
in height and three feet in ~idth. The dimensions of the
portal are such as to allow an average sized indiviaual as
~ell as a wheel chair bound individual to easily pass
through. The portal is desisned in such a way as to have an
internal air flow sweep over an individual walking or passing
through the portal at a normal walking pace, and at the same
time have the air sample swept from the individual contain a
meaningful concentration of vapors or particulate matter to
be analyzed. To accomplish this, the sampling chamber or
portal is designed with a unique geometry and contains air
guides or jets for providing an air flow which effectively
isolates the internal air volume from the ambient environment
while efficiently sweeping the individual passing through the
portal. The air volume or sample inside the portal is
collected through a sampling port located within the ceiling
section of the portal. The air sample is then transported to
the sample collector and preconcentrator (SCAP).
The sampling chamber or portal is capable of
collecting and delivering to the SCAP vapor or particulate
matter when they are present in as low a concentration as
several parts per trillion of ambient air. The SCAP, through
a series of steps of decreasing sample volume and increasing
sample concentration, delivers a concentrated sample to a
fàst response chemical analyzer which may be either a gas
chromatograph/electron capture detector or an ion mobility
spectrometer or both. The principle of operation of the SCAP
is one of adsorbing the sample onto a selected substrate
with subsequent selective thermal desorption. This process
3 is repeated through a series of steps of decreasing sample
volume and increasing sample concentration. Upon completion
of the preconcentration steps, the purified sample material
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is analyzed by the aforementioned devices wherein the
l analysis consists of identifying the various materials and
determining the amount of material present.
The total system and all system processeS are
controlled by a control system which comprises a digital
computer and associated software. The system is configured
and controlled to make all required measurements and prepare
the results in a usable and inte11igible format. The control
system controls the collection of vapors, the
preconcentration and analysis steps, and the data analysis
and data formatting. In addition, the computer continuously
performs self diagnostics and self calibration procedures on
the total system and alerts the user to any potential
problems.
~ The system for the detection of e~:plosives and
other controlled materials of the present invention provides
for the efficient detection of explosives, chemical agents or
other controlled materials such as drugs or narcotics by
detecting the vapor and/or particulate emissions from these
substances. The vapor or particulate emissions can come from
substances concealled on the individual, the individuals
baggage, or from a residue left on an individual who handled
the particular substance. The present invention provides a
system with a high degree of sensitivity and selectivity.to a
wide range of substances. The high degree of sensitivity and
25 selectivity is accomplished by employing a system which -
utilizes the combination of a unique geometry portal with
aerodynamics that prevent the cross-contamination of air
within the portal with that of the ambient environment and a
multi-stage preconcentrator that decreases sample volume
3 while maximizing sample concentration thereby allowing much
larger sample volumes to be taken as well as much shorter
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sample collection times. The system provides a high
1 reliability rate which is accomplished by utilizing the
computer control system for automatic calibration and self
diagnostic procedures. In addition, the system provides a
high degree of versatility in that by changing the
programming of the computer, a wide range of explosives,
controlled chemical agents, and drugs and narcotics which
have differing physical and chemical properties can be
detected. Having the total system under software control
provides a more versatile system and one that is easily
reconfigurable.
The present invention has a ~lde variety of
applications where a high throughput of people is required.
In airports, the detection o~ explosives and controlled
substances is of paramount importance due to the rise in
terrorist attacks and drug smuggling. The present invention
allows for the fast and reliable detection of the
aforementioned substances in a non-invasive manner in a
variety of field environment such as in airports. The system
of the present invention is applicable where the detection of
concealled substances is absolutely required.
. .
For the purpose of illustrating the invention,
th~ere is shown the drawings the forms which are presently
preferred; however, it should be understood that the
invention is not necessarily limited to the precise
arrangements and instrumentalities here shown.
Figure 1 is a sectional side view of the sampling
3 chamber of the present invention;
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Fi~ure 2 is a sectional end view of the sampling
l chamber of the presen~ invention taken along section lines
2-2' in Figure l;
Figure 3 is a top viet~ of -the sampling chamber of
the present invention;
Figure 4 is an end vie~J of the sampling chamber of
the present invention;
Figure 5 is a ciasrammatic representation of the
flow of air within the sampling chamber of the present
invention;
Figure 6 is a diasra~matic sectional view of the
internal/external air boundary that eAists at the end of the
sampling chamber of the present invention;
Figure 7 is a diagrammatic block diagram of the
sample collector and preconcentrator of the present
invention~
Figure 8 is a diaqrammatic block diagram of the . .
sample collector and preconcentrator of the present invention
with a three filter configuration; ~.
Figure ~ is a plane view of the three filter : :
configuration of the primary preconcentrator of the present
invention. -lOB
Figure lOA/is a diagrammatic representation of the
multi-port valve used in the present invention;
Figure 1~ is a diagrammatic diagram of the portable
25 sample collector of the present invention; - .
Figure llB is a diagrammatic representation of the
luggage sampling means of the present invention;
Figure 12 is a block diagram of the control and
data processing system of the present invention; ~;:
3 Figure 13 is a flow chart of the computer program
used in the present invention: and
Figure 14 is a time chart indicating the various
time durations of the processes associated with the screening
process.
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The e~plosive detection screening system of the
present inve~tion is designed to detect explosives, chemical
agentS or other controll~d materials such as drugs or
narcotics by detecting their vapor or particulate emissions.
These substances are assumed to be concealled on individuals
or in their baggage in airports or in other high
vulnerability, high visibility environments. It is necessary
to detect these substances in a non-invasive manner at any
required level, and to do it so cuickly that the ~ree Dassage
of people and baggage is not unduly interrupted. The system
is an integrated system comprising a sampling chamber, a
vapor and/or particulate concentrator and analyzer and a
control data processing system.
The sampling chamber is a portal in which
internally generated air flows sweep the vapor znc/or
particulate emissions eminatins from an individual or object
passing through the chamber to a collection area. The
sampling chamber is designed in such a way as to capture a
high enough concentration of emissions so as to be able to
detect the presence of the aforementioned substances with a
high degree of reliability and dependability. The internal
volume of air is recirculated with a small amount being
removed at the sampling time. At the sampling time, an
external air pump or fan draws a sample of the collected air
volume into a sample collector and preconcentrator (SCAP).
The sampling chamber is capable of collecting and
delivering to the SCAP, vapors when they are in as low a
concentration as several parts per trillion of ambient air. `
3 The SCAP, through a series of steps of decreasing sample `
volume and increasing sample concentration, delivers a
concentrated sample to a fast response chemical analyzer
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which may be either a gas chromatograph/electron capture
l detector ox an ion mobility spectrometer or both. Using this
multi-stage concentratiOn process of adsorption and
desorption, much larger sample volumes can be processed with
high degrees of sensitivity and selectivity. The data
collected is then assimilated and analyze~ by a digital
computer which is part of the control s~stem which operates
and controls the total system.
The control system is a control and data processing ~-
system of which the primary requirement is to reDort the
presence of, and if required, the level of a speci'ied
substance. The system must be capable of distinsuishing
between background levels of a substance and alarm levels.
The system also controls the operation of the entire system
by automatic control metho*s which is run by a microprocessor
or digital computer. The control system is easily
reprogrammed to detect various substances because of
modularized programming techniques.
.
The sampling chamber for people is a portal that is
designed in such a way that as a person walks throush this
chamber, at a normal walking pace, an internal air flow
carries a sample of vapors and/or particulate matter from
them to a sampling port where it will be collected for
analysis. There are three major design requirements that the -
chamber was designed to meet. First, the sampling chamber
must gather a meaningful sample of the environment
surrounding a person or object passing through the chamber.
3 In considering a solution to the problem posed by the first
design requirement, it is necessary to consider that the
sampling chamber must be large enough 'or an average size
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individual to comfortably pass through the chamber;
l therefore, there is a considerable volume of air located
within the chamber resulting in possibly only several parts
vapor or particulate emission per trillion parts of air or
possibly even less. The solution to this problem of dilution
is to design the chamber long enough so the individual or
object passing through the chamber remains in the chamber for
a duration of time so as a meaningful sample of the
environment can be gathered. Second, for the purposes o'
sensitivity, selectivity and preventing cross-contamination
of the sample to be analyzed, the sample to be collected must
be isolated as much as possible from the ambient enviro~ent.
In considering a solution to the problem posed by the second
design requirement, it is necessary to once again consider
the problem of dilution caused by having a larger chamber.
Since there already exists a dilution problem, the chamber
must be designed with a unique geometry and in'ernal
aerodynamics so as to prevent further dilution and
contamination by the mixing of internal air with the ambient
air to the greatest extent possible. The third design
requirement is that the sample must be gathered in as
complete form as possible in as short as time as possible.
In considering a solution to the problem posed by the third
design requirement, it is necessary to consider the problems
and solutions considered above and find a balance between
them. The time an individual or object spends in passing
through the chamber must be long enough so as to gather a
meaningful sample, but not long enough to cause unduly long
- pedestrian traffic delays. Secondly, since there is a
dilution problem, the chamber was designed in a unique way
3 so as to prevent cross-contamination with the ambient
environment, and this unique design must not prevent the -
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normal flow of traffic; ther~fore, the aerodYnamics discussed
l in the solution to the second problem must be such that the
meaningful sample is gathered quickly.
Referring to ~igures 1 an~ 2, there is shown a
s~ctional side view and end view or the sampling chamber 100
or portal. The sampling chamber 100 has a rectangular
geometry having internal dimensions of app_oximately six feet
in lensth, seven ~eet in height, and three feet in ~idth.
These dimensions allow an average size individual, walking at
an normal walking pace to remain in the chamber 100 for
approximately two to three seconds which is enough .ime to
gather the aforementioned meaningful s~r.ple. The rectangular
chamber 100 has two ~7alls 102a and 102b, 7hich run the le~gth
of the chamber 100, a floor ~04, a convergent or conically
shaped ceiling 106 the importance of which will be discussed
15 subsequently and a roof 107. In order to maintain the ;
uninhibited flow of pedestrian trafric through the chamber
100, no doors and only two walls, 102a znd 102b, were used.
Hand rails 108a and 108b attached to walls 102a and 102b
respectively are provided to aid individuals in passing
through the chamber 100 quickly and safely. The floor 104 of
the chamber 100 is not a necessary component, and in other
con~igurations it is not utilized. The chamber lO0 can be
constructed utilizing a variety of materials including
aluminum and plas ics; however, clear materials such as
*plexiglass or ~iberglass is pre~erred 80 individuals passing
through the chamber 100 can be observed. In addition, a
video camera 109 may be utilized to capture an image of the
individual passing through the chamber 100 which will be
electronically stored along with the collected data.
3 The sampling chamber 100 operates on an air
recirculat~ng principle and the only air removed from the
internal recirculating volume is a comparatively small amount
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leaving by sampling port 118a. The internal air volume is
1 circulated through internal air flow guides or jets and is
collected by collection duct 110 which is a 16" x 20" x 6"
rectangular duct connected to the center Oc the conical
ceiling 106 and which empties into the space created between
the ceiling 106 and the roof 107. ~his results in a large
volume of controlled recirculating air flow cap2ble of
delivering a vapor and/or particulate sample from anywhere in
the chamber 100 to the sampling port 118a in approY.imately
one second.
The conical ceiling 106 aids in the collection of
the sample volume by creating an inverted funnel for the air
sample flow which serves to concentrate a larger volume of
air across a smaller cross section for sampling purposes. A
dynamic low pressure zone is created in the region of the
collection duct 110 when the air is drawn through the
collection duct 110 into the ceiling plenum by four eAhaust
fans two of which are sho~n in Figure 2 as 114, and 114a. In
each corner of the chamber 100, there are six inch diameter
end columns 112a-d. Each of the four end columns 112a-d are
mounted vertically in the chamber 100 and run from the floor
104 to the ceiling 106. Each column 112a-d has six slots of
one foot in length and a half inch in width 113a-d as shown
in Figure 3, which is a top view of the chamber 100, with
inch and a half internal guide vanes (not shown) for
directing the air flow at a forty-five degree angle towards
the center of the chamber 100 as shown by arrows 115a-d in
Figure 3. The air flow through the columns 112a-d is
provided by four independent fans, two of which are shown in
Figure 2 as fans 114 and 114a. The four fans are mounted in
3 the chamber 100 above the conical ceiling 106 and below the
outer roof 107. Each fan is connected to one of the end
columns 112a-d and provide 1000 CFM of air to each column
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112a-d resulting in an air velocity of 17m/sec, in the
1 directions indicated by arro~s llSa-d, from the guide vanes
of the columns 112a-d as shown in Figure 3. The suction side
of the fans are open to a com~on plenum located in the same
space that the fans occupy. In addition to these inwardly
directed vertical air jets 113a-d there are two upwardly
directed air guides 117a and 117h or jets located in side air
flow pipes 116a and 116b which are mounted along the floor
104 and against walls 102a and 102b. The side flow pipes
116a and 116b are connected to end columns 112a-d and receive
air rrom them; In each side flow pipe 116a and 116b there
are twelve inch by half inch air slots 117a and 117b located
in the center of each pipe and directed towards the center of
the chamber at a forty-five degree angle as shown in Figure
4. The air velocity of the air leaving side flow pipes 116a
and 116b is lSm/sec in the direction indicated by arrows ll9a
and ll9b. The combined effect of the air flow created by the
end columns 112a-d and the side flow pipes 116a and 116b is a
dynamic high pressure region created in the center region of
chamber 100. ~he recirculating fans which draw air through
collection duct 110 create a dynamic low pressure zone within
chamber 100, which creates a net air flow up towards the
collection duct 110. This air flow is the flow that sweeps
individuals or objects passing through the chamber. The
effect of the high pressure region and the low pressure
region created by the exhausting air sample through conical
ceiling 106 and into the collection duct 110 i.s a balance of
atmospheric conditions which results in very little external
air entering or leaving the chamber 100. Basically, the high
pressure region inhibits air from entering the chamber 100.
3 The majority of the moving air mass goes through the
collection duct 110 and to the common plenum where it will
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once again be used by the fGur fans to recirculate the
l internal volume of the chamber lO0. ~ portion of the
recirculated air is collected through a sampling port 118a,
which is the open end of a stainless steel pipe 118 which is
used to transport a selected sa~,ple from the cha~er lO0 to
the second stage of operation; namely, the preconcentration
stage which shall be discussed subsecuently.
The four end columns 112a-d and the two side air
flow pipes 116a and 116 represent one embodiment for
delivering the air supplied by the four independent fans as
separate and directional air jet streams. The fans can be
connected to various types of air ducts or plenums with guide
vanes or nozzles to form the e~iting air into jet streams.
In addition, partioned hollow walls also with guide vanes or
nozzles can be used as an alternate approach for forming the
air from the fans into separate and directional air jet
streams. The manner in which the air flow is supplied to the
guide means and the manner in which the jet streams are
formed is not critical; however, the specific directions of
the jets streams are. It is important that the proper angle
and orientation of the jet streams be maintained so as to
provide a net fiow of air capable of sweeping an individual
or object passing through said sampling chamber means lO0
while maintaining the integrity of the volume of air within
the sampling chamber means 100.
~ Referring now to Figure 5, the volume of air 120
enclosed by the dashed lines indicates the total volume of
air moving towards the collection duct 110 and sampling port
118a shown in Figure 2. The upward flow of air starts at
approximately one foot in from the perimeter of the chamber
3 floor 104. Ihis figure indicates the net upward flow of air,
and does not intend to exclude other air currents present in
the chamber, because other currents are present; however,
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their direction is not upward. As can be seen in Figure 5,
the effect of the generated internal air flows and the shape
of the ceiling 106 shown in Pigure 2 tends to focus or
concentrate the large volume of air flo~7ing up~7ards to a
smaller, but more concentrated volume of air. Arrows 122a-c,
124a-c and 126a-c indicate the velocities of the air mass at
different stages in the flo~7. In the lo~7er to middle
regions, the air flo~7 is 2-3 m/sec, and as the air mass
approaches the low pressure region, the velocity increases
to 4-5 m/sec.
Turning to Figure 6, a diagrammatic side view of the
chamber 100 is shown. The region indicated by the dotted
lines 128 and 130 indicate the region in which
cross-contamination of the internal air volume with the
ambient environment occurs. As indicated by arro~s 132a-c,
air from the surrounding environment enters the chamber 100
at approximately 0.5 m/sec. The air from the outside
environment is drawn in by the aerodynamics created by the
internal air flow. This air flow into the chamber 100
results in one half of the internal air to be exchanged with
the outside air in approximately 30 seconds. Since the
collection time take approximately one second, the cross-
contamination is minimal. The only way to maintain absolute
integrity of the internal air volume is to provide rotating -
doors with a seal, and this however, would result in
uAdesirable time delays.
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The sample collector and preconcentrator (SCAP) is
3 used as part of the overall system to enchance overall system
sensitivity and selectivity. In general terms, the SCAP must
simply discard, in a multi-step process, non-required
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132~
molecules of air while not losing the targeted molecules of
interes~. In the sample collection and preconcentration
step, the targeted materials are adsorbed onto a selected
substrate, and then selectively desorbed. This process is
repeated through a series of steps which decrease sample
volume and increase sample concentration.
As illustrated in Figure 7, the SCAP 200 is
supplied with sample air by pipe 118 which e~tends to the
sampling chamber 100. During sampling periods 2 high suction
fan 202 draws the sample volume through the sampling port
118a. The fan 202 is connected to pipe 118 on the suction
side with the discharge side connected to a vent or exhaust
system to the ambient environment.
The first stage of the concentration process
involves the primary preconcentrator 201 which consists
essentially of a rotating filtering means 204. The air
sample drawn from the sampling chamber 100 is drawn through
filtering means 204. The filtering means 204 consists of two
interconnected filtering elements 206 and 208. The filtering
elements 206 and 208 are wire screens which hold an adsorbing
material. Each filtering element 206 and 208 may be rotated
through either of two positions. Position 1 is in line with
pipe 118 and position 2 is in line with a secondary
preconcentrator 203. The positions of the filtering elements
206 and 208 are changed by a control system which in this
embodiment is a hydraulic actuation system 210 which is
connected to filtering means 204 by shaft 212 which lifts
movable platform 211 to move each of the filter elements into
a sealed connection at position 1 and at position 2. A
preconcentrator control unit 214 is also connected to
3 filtering means 204 by shaft 216. The hydraulic actuation
system 210 is comprised of a hydraulic control unit 210a and
a hydraulic pump 210b and is operable to lower and raise
holding elements 205 and 207, into the unlocked and ~ :
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-20- 1329~
locked positions respectively. When it is time to rotate the
1 filters 206 and 208 hydraulic actuation system 210 lowers
holding elements 207 and 205 .hich engage filter ele~ents 206
and 208 respectively. Upon engaaement o. the filter elements
206 and 208 preconcentrator control u~it 214, whlch is a
computer controlled stepp~r motor is operable to rotate
filtering elements 206 and 208 between positior.s 1 and 2 via
shaft 216. The control of the hydraulic actuation system 210
and the preconcentrator control unit 214 is acco~plished via
the control system ~hich will be fully e~:plained in
subsequent paragraphs.
In a second embodiment the filtering means 204
consists of three interconnected fil ering elements 206, 208 ~ -
and 209 as shown in Figure 8; Filter element 209 like filter
elements 206 and 208 is a wire screen which holds the
15 adsorbing material. Each filtering element 206, 208 ar.d 209 -
may be rotated through either of three positions. Position 1
is in line with pipe 118, position 2 is in line with a
secondary preconcentrator 203 and position 3 is exactly
in between position 1 and position 2. Figure 9 shows a plane
view of the three filter elements 206, 208, and 209 spaced
120 degrees apart on movable platform 211. The positions of
the filtering elements 206 208 and 209 are changed by a
control system which in this embodiment is a hydraulic ~-
actuation system 210 which is connected to filtering means
204 by shaft 212 which lifts movable platform 211 to move
each of the filter elements into a sealed connection at
position 1, into a sealed connection at position 2 and at
position 3. The hydraulic actuation system 210 is comprised
of a hydraulic control unit 210a and a hydraulic pump 210b
-3 and is operable t:o lower and raise holding elements 205, 207
and 215 into the unlocked and locked positions respectively.
When it is time to rotate the filters 206, 208 and 209,
hydraulic actuation system 210 lowers holding elements 207,
205 and 215 which engage filter elements 206, 208 and 209,
~ .
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~329~9,~
-21-
respectively. Upon engagement of the filter elements 206,
l 208 and 209, preconcentration control unit 214, which is a
computer controlled stepper motor, is operablé to rotate
filtering elements 206, 208 and 209 between positions 1, 2
and 3 via shaft 216.
Xeferring now to Figure 7, the two filter process
is described. During a sampling period which is controlled
by the control system, fan 202 draws the sample îrom the
chamber lO0 and through filter element 206 which is position ~ -
1. Filter element 206 collects the vapor and/or pa-ticulate
matter contained in the air sample on an aasor_tion
substrate. The filter element 206 comprises an adsorber that
is selected to have enhanced adsorption for the target
materials and lessor adsorption for any contaminants. When
the air sample passes through the filter element 206
containing the adsorber, the adsorber pre erentially selects
a sample of the target materials, and other contaminants are
passed on to be vented or exhausted by fan 202. Upon
completion of the sampling period, and adsorption of the
target materials onto filter element 206, filter element 206
is switched to position 2 by the preconcentrator control unit
214 and raised into a locked position by the hydraulic
actuation system 210 so the desorption of the target
materials can occur.
In the desorption process, a stream of pure gas is -~
passed over the adsorber containing the target materials and
any remaining contaminants. The pure gas, which is usually -
an inert gas, is supplied from a gas supply 218 and
transported to position 2 of filter means 204 by gas line
220. This pure gas flow is much smaller then the volume of
3 air used in the sampling chamber 100. The temperature of the
ads~rber is raised in a controlled fashion by the control
system, illustrated in Figure 12. The temperature of the ~ -
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-- -22-
~L32~
filter being desorbed is raised by either a heat e~:changer
1 213 or by the temperature of the pure gas from source 218.
If the temperature of the filter being àesorbed is raised
utilizing the pure gas, then the gas flow is diverted to a
heating element (not shown) where it is raised to the proper
temperature. When the desorption temperature for the target
material is reached, the temperature is held constant and the
pure gas flow is quickly switched to the desorption stage in
the concentration process. The heated gas then absorbs the
target materials and carries them on to the next stage. The
gas flow containing the target materials is routed to the
secondary preconcentrator 203 or interface unit via gas line
222. As the desorption process is rapid, only a small volume
of gas is transferred which Eesults in the next stage
receiving the target materials in a concentrated form.
The primary concentration of the target materials
is a continuous two step process because of the two filter
elements 206 and 208 both contain adsorbing subs'rates. When
filter element 206 is adsorbing the target materials, filter
element 208 is in the desorption process. Upon completion of
the desorption of the target materials from element 208, the
adsorbing material of element 208 is purified from materials
and contaminants and thus ready to be used as the adsorber in
position 1. While a pair of rotating filter elements is
illustrated in Figure 7, it would also be possible to use
single use strip media which traverses from the absorbing
station to the desorbing station, or to hold the position of
the filters fixed and alternate the sample and purge air
streams to absorb and desorb the target materials.
Referring to Figure 8, the three filter process is
3 now described. In a second embodiment for the primary
preconcentrator 201, a third filter element 209 is added,
thus making the primary concentration of the target materials
' ,'
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-23~ 132~
a continuous three step process, because the three filter
l elements 206, 208 and 209 all contain adsorbing substrates.
When fiLter element 206 is adsorbing the target m~terials,
filter element 208 is in the desorption process, and filter
element 209 is be added to provide for a thermal cleansing of
any vapors or particulates which may remain after the
desorption process. l~hen a particular filter element is in
position 3, the pure gas supplied from gas supply means 218
is routed to position 3 of filter means 204 by gas line 220.
The gas flow further sweeps the particular filter element in
an attempt to further purify the adsorbing materi~l from
contaminants. The exiting gas with contaminants is exhausted -~
to the ambient environment. A valve 217 is located in line
with gas line 220 and is operable to switch the gas flow from
position 2 to position 3 and vise versa.
The treatment of particulates and gaseous materials
is slightly different at the first step of the concentration -~
process. The particulates may be small particles or droplets ~ -
of the tarqet material itself or small particulates or
droplets attached to dust particles or other vapor droplets.
For particulates, the first stage is a filter or screen having
selective adsorption characteristics in the path of the
sample air flow from the sampling chamber 100. The
particulates are physically trapped or adsorbed on this
filter, and then the filter, or a portion of it, it
physically transferred to a heated chamber and rapidly heated
to a temperature that is sufficient to vaporize without -
decomposing the target particulates. A small quantity of
heated pure carrier gas is admitted to the chamber to carry
the now vaporized material to the next stage of the process.
3 As stated previously, the heated gas can be used for
supplying the heat for vaporization.
,
-24- ~2~4
It is usually the-case that the filter used in the
1 sampling air flow for particulate materials is also the
absorber for gaseous materials and therefore, as is show~ in
Figure 7 a single primary preconcentrator 207 can be used to
capture both particulate materials and gaseous materials. It
lS necessary to sample target materials as pariiculates
because certain target materials may have too low a vapor
pressure at room temperature to be sampled as gas or vapor.
In addition, it is possible that the target material itself
has a tendency to be present in the sample volume as an
adsorbate on particulate material independent of vapor
pressure considerations.
In the subsequent stages of concentration the
selectable adsorbers are fixed and confined to metallic
tubes. The sample and purge carrier gas flows are
manipulated by switching valves which are under computer
control. Referring once again to Figure 7, the primary
preconcentrator 201 is connected to the interface 203 by gas
flow line 222. The interface 203, contains a secondary
preconcentrator 224 and a multiport valve system 226. The
purpose of the multi-port valve system 226 is for switching
between the gas supply line 230 which is supplied by gas
supply 228, the preconcentrator 224 adsorption tubes, the gas
flow line 222 from the primary preconcentrator 201 and the
gas flow line 232 to the chemical analyzers 234 and 236.
Basically, the multi-port valve system 226 is a switching
network. The secondary preconcentrator 224 is a series of
adsorption tubes. The multi-port valve system 226 is driven
by an interface control unit 238 which is simply a stepper
motor to rotate the valves in the multiport valve system 226
3 when commanded to do so by the computer. The interface 203
represents a generic block of secondary preconcentrators, and
-25- 132~
thus one can cascade a series of multiport valve systems and
i adsorption tubes in an attempt to further purify the sample
to be analyzed.
The adsorber tubes are very rapidly heated to and
held at the selected predetermined temperature by heating the
surroun~ing metallic tube. This is usually done by passing a
controlled electrical current through the tube and using the
tube itself as the heating element. In the case of 12rser
adsorbent containing tubes, for the heating times of tens, to
a very few hundreds of milliseconds, this current may be
several hundred amperes. The temperature maybe measured by
brazing a tiny, very low mass thermocouple or thermister to
the tube. The thermocouple must be small enough so as ~ot to
affect the tube in any manner and it must be capable of - -
responding rapidly. The thermocouple feeds the measured
temperature to the computer of the control system wherein the
computer controls the amount of current flowing through the
tubes. Basically, the computer forms the digital closure of -
an analog control loop. The computer is used to monitor and
control the temperature because the proper thermal program
for the desired target materials or material is critical.
The size of the tubes is decreased in steps to reflect the
decrease in volume of gas containing the samples and may
eventually reach the internal size of a capillary gas
chromatograph column~
, The multiport valve system 226 is a switching
network with multiple ports as the name suggests. In one
embodiment of the present invention, the multiport valve
system 226 is a 6-port valve. Figures lOA and 10~ represent
the two positions that the 6-port valve 226 can occupy. The
3 interface control unit 238, is a stepper motor, and is -
operable to switch the 6-port valve 226 between the two
positions. In either position, only pairs of ports are
,.
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26 ~32~
.
:. , connected. In position l, illustrated in Figure lOB, ports 1
1 and 2, 3 and 4, and 5 and 6 are connected, and in position 2,
ilLustrated in Figure lOA, ports 2 and 3, 4 and 5, and 6 and
1 are connected. Position 2 places the adsorb-desorb tube
248 in the load position. The gas flow line 222 shown in
~igure 7 carries the gas containing ~he target material and
some contaminants into port 1 indicated at 242 in Figure lOA
of valve 226 wherein the gas automatically flows through an
internal passageway 244 to port 6, indicated at 2~6 in Figure
lOA. Connected between port 6 and port 3 is an external
adsorption/desorption tube 248 in which the gas containing
the target material and some minor contaminants pass through.
The adsorbing material inside the tube 248 is specifically
targeted for the target material; therefore, the carrier gas
and the contaminants flow through the tube 248 to port 3,
indicated at 250 while the target material is adscrbed within
the tube. The carrier gas and contaminants flow from port 3
indicated at 250 in Fisure lOA to port 2 indicated at 252 in
Figure lOA through internal passageway 254, and is vented to
the external atmosphere through exhaust line 256. Pure
carrier gas supplied from gas supply 228 shown in Figure 7 is
fed into port 4 indicated at 258 via line 230. The pure
carrier gas automatically flows from port 4 indicated at 258
to port 5 indicated at 260 via internal passageway 262~ The
carrier gas then flows from port 5, indicated at 260 to
eIther of the chemical analyzers 234 or 236 via line 264.
The analyzers 234, 236 require a continuous gas flow to
remain operational. The use of multiport valve systems
allows pure carrier to be fed gas continuously to the
analyzers 234, 236, even when the adsorb/desorb tube 248 is
3 in the adsorb cycle.
At the end of the adsorption cycle, the computer of
the control system then automatically switches the 6-port
~ . . . .. . . .
`` 132~91~
:` -27-
valve 226 into position 1 which is the desorb mode as shown
in ~igure lOs. Port 1, indicated at 242 in Figure lOB still
receives gas from the primary concentrator 201 via line 230;
however, the gas flows from port 1, indicated at 242 to port
2, indicated at 252 via internal passageway 268 and is vented
to the atmosphere via exhaust line 256. Port 4, indicated at
258 is injected with pure carrier gas from supply 228 via
line 230 which flo~7s to port 3, indicated at 250 via internal
passageway 270. As stated before, port 3, indicated at 250
and port 6, indicated at 246 are connected via an e~ternal
adsorption/desorption tube 248; however, in this position,
the carrier gas is flowing through the tube 248 in the
opposite direction. Therefore, when the tube 248 is heated to
desorption temperature, the gas will sweep the desorbed
target material and czrry it to port 6, indicated at 246 free
of atmospheric contaminants. From pGrt 6, indicated at 246,
the target material flows to port 5, indicated at 260, via
internal passageway 272 and to the chemical analyzers 234 and
236 via line 264.
The external adsorption/desorption tube 248 is
electrically insulated from the valve body and contains a
selected quantity of the adsorbing material which has the .
best characteristics for adsorbing the target material. High
current connections are made to the ends of this tube 248
and are shown in Figures lOA and lOB as electric lines 280
a~d 282. Lines 280 and 282 are connected on the other end to ~ ~ .
a controlled current source 281. A thermocouple 283 is shown
attached to tube 248 in Figures lOA and lOB. This
thermocouple 283 as stated previously, is used to raise the
temperature of the tube 248 so as to achieve the proper .
3 temperatures for desorption. The gas sample which contains
the target material, contaminants and excess gas, passes
through the tube 248 and because it is cold, and the adsorber
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: . :
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-28- 132~
material has been selected to be a strong adsorber for the
1 target- material, most of the sample will be adsorbed at the
end of the tube 248 near port 6. The contaminants are less
strongly adsorbed and thus any adsorption of them will be
throughout the length of the tube 248. Also, because the
contaminants are not strongly adsorbed a larger portion of
them will pass through the tube to the exhaust vent 256 and
be discarded.
A desirable property of thermal deso-ption of
gases or vapors on solid or liquid substrates is that the
process can be highly thermally sensitive and thermally
dependent~ At a specified temperature the amcunt of any
material desorbed is related to its physical and chemical
propexties and the physical and chemical properties of the
adsorbing material. It is possible to choose adsorbing
materials such that the contaminating materials are desorbed
at a workable lower temperature than the target materials.
Careful thermal programming allows one to use these
properties. An example is to heat the desorber tube 248 in a
controlled fashion with the valve 226 in position 2. The
contaminants such as water vapor etc. are not strongly
adsorbed and â low temperature will cause â major portion of
them to leave the adsorber and pass out of the system through
the vent. At the same time, the target materials will not be
desorbed and will remain at the end of the adsorber tube 248
adjacent port 6. If the position of the rotor in the 6-por).-
valve is now changed to the 1 position, two important changes
are made. The adsorber tube is now connected to the next -
stage in the sequence and the pure carrier gas flows through
the adsorber tube in the opposite direction to the previous -
3 gas flow direction. A rapid controlled increase in
temperature will now cause the sample to be desorbed in a
short period of time. This results in a sample which has
been purified by the previously described adsorption and
:'
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: .~ ' .,
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2 ~
-29-
.. ..
desorption process passing to the ne~t stage in the process,
1 contained in the minimum of pure carrier gas. Thus the
sample has been twice purified of contaminant5 and
concentrated in a much reduced volume o pure inert carrier
gas.
The next step in the purification and concentration
process may be another 6-port valve with a smaller diameter
desorption tube. The final desorption tube should match in
diameter the size of the column in one of the analyzers, such
as analyzers 234, which is a gas chromatograph. If this is
done, it results in ideal sample injection into the gas
chromatograph. In fact, it is possible by careful design and
construction to have the desorber tube the same internal
diameter as a capillary gas chromatograph column. It is
possible to use the tube connecting two 6-port valves as a
desorber tube for purification and concentration purposes.
It may be packed with adsorber and fitted with heating and
temperature measuring equipment such as electrical ;
connections and thermocouples.
The adsorbent material used in the various staqes
of concentration of the target materials may be selected from
a group of materials commonly used for vapor sampling
including *Texax and *Carbotrap. There are other adsorbing
materials that can be used with the present invention
depending on the particular materials that are to be detected
25- and isolated.
The SCAP also 200 contains an attachment for a
portable sampling device 2g2 which is shown in Figure llA.
The connection is a pipe 223 which is connected to pipe 118
shown in Figure 7 or 8 through valve 221. The pipe 118
3 may be stainless steel, aluminum or even ABS plastic.
Basically, the portable sampling device is a hand
held wand which when valve 299 closes off the chamber
100 and valve 221 is opened end of pipe 118 and fan -
*Trade mark
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-3.
- _30_ ~32~
202 draws an air sample, the wand 2g2 is capable of drawing
1 vapor and/or particulate emissions from a specific area on an
individual or object. The wand 292 is used to sample an
individual intensively when the results from the pass through
the chamber 100 are inconclusive.
A second use for the hand held wand 292 ~ould be to
dra~ vapor and/or particulate emissions from baggage that is
going to be stored in the cargo hold of the airplane. The
system including the hand held wand 292 has proven very
effective as a means of detecting explosive vapors in
packages and baggage. In tests ~Iherein the hand held wand
292 has been held against cardboard box pac~ages znd various
types of luggage, positive indentifications of low levels of
explosive vapors, equivalent to approximately a third of a
stick of dynamite, are made. In addition, the hand held wand
292 can be attached to a sampling box 294 as shown in Figure
llB that is placed over luggage to enhance the efficiency of
detection and provides a means to automate baggage screening
by including a conveyor belt 298. The wand 292 is attached
to sampling box 294 through connection means 296.
The analysis of the purified target material
consists of identifying the materials and of determining the
amounts present. Because the original concentrations were so
low with respect to many other common ambient materials it is
possible for there to be, even under the best of purification -
and concentration systems, some remaining impurities of
materials with similar characteristics to the target
3 materials. Thus the analysis system must be capable of
separating the target material response from the response due
to interfering materials.
-31- 1 3 2 9 ~r 9 4
Two forms of analysis systems are used either
1 separately or in combination, These systems are an ion
mobility spectrometer (IMS) ~36 based analysis system and a
gas chromatograph (GC) 234 based sysiem. The final detector
for the GC 234 is usually a electron capture detector
(ECD) but the IMS 236 can also be used as the detector if
desired. Depending on the the application, a photo
ioniæation detector or a nitrogen-phosphorus detector or some
other detector may be also used following this. The GC 234
may be of the "packed column" type or the capillary column
type. Both analyzers 234 and 236 can be used separately or
in a combined fashion. Valve 235 is used to direct the
collected and purified sample to either or both of the
analyzers. -
Whatever analysis system is used the analysis must -
be completed in a time that is short enough that the free
flow of people, luggage and baggage is not unduly inhibited.
This also implies that the time for the concentration and
purification process is short as well.
If all the valves in the system are motor driven or
solenoid driven valves, the flow directions timings and
magnitude may be controlled and varied. The time and
temperature parameters are controlled and variable. Thus the ~;
physical characteristics of the complete system may be
adjusted to detect a wide range of target materials and the
sensitivities may be adjusted to accommodate a wide range of
threats as perceived by the authorities using the system.
All the process involved in the collection and
concentration as well as the final analysis of the collected
material is controlled by the computer of the control and
-3 data processing system and will by fully explained in the
following section.
-32- 1~2~9~
i
The primary requirement for the control and data
procesSing system of the screening sys-tem is that it reports
the presence of, and if required, the level of specified
substances. This means that the equipment must be configured
and controlled to make the required measurement and it also
means that the result must be presented to the user in a
usable form. The subject or target materials may be present
in varying amounts in the environment of the system and
therefore, the system must be capable of distinguishing
between this background level and an alarm level. It may
also be a requirement to report on this backsround level.
A secondary requirement for the control and data
processing system of the integrated system is self
diagnostics, as there may be considerable time between
alarms, the control and data processing system must be
capable of performing confidence checks that are satisfactory
to the operator on demand. There must also be routine self
checks and calibration procedures performed on the total
system by the control and data processing system.
Basically, this ensures that the test results, wAether
positive or negative, must be believable.
A third requirement for the control and data
processing system is ease of reconfiguration and versatility.
Th`e range of target materials may be changed from time to
time, and the system must be capable of varying its internal
operation parameters under program control to detect these
materials. ~t is desirable that the rigor of the
measurement in terms of time constraints and number and types
-3 of substances detected be alterable in an expeditious fashion
at any time. The user's requirements in terms of level of
~ 3 2 ~
threat and types of materials may quickly change and the
1 equipment must respond to these changing needs.
The final requirement for the control and data
processing system is that the parameters and operations of
the sampling chamber and the SCAP must be m,onitored and
controlled. This means that all internal timings,
temperatures and mechanical components must be controllable
by the control and data processing system.
Tne primary method of achieving these requirements -
is to put the total system under the control of a stored
program digital computer. This computer through a series of
modularized software routines performs the data analysis and
presents the results in the required form to the ùser. The
computer ~hrough another series of modularized software
routines continuously performs self diagnostics and self
calibration procedures on the total system, and alerts the
user to any potential problems. The computer through still
another set of modularized software routines controls all the
processes of the total system and shall be more fully
explained in subsequent paragraphs.
One primary benefit of this system of control is
reliability. By themselves the components are rugged and
reliable and not prone to failure. However, any system made
up of many items is subject to drifts due to ambient changes
and-time. By having all components under program control and
by arranging for a known input to the system such as a
controlled injection of target material or target simulant,
there can be a calibration and self-diagnostic program. The
function of this program is to calibrate the entire system
and determine and store the required time, temperature etc.
3 parameters. If these parameters are not within specified
limits for any reason, the program can alert the user.
Guided by a service program the user response can range from
'
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-34~
immediate shutdown to scheduling service at a later date, to
simpl~ noting the circumstanceS By use of a modem this
information can be easily transmitted to any~here in the
world. The other aspect of reliability in a system of this
type is that the user must kno~t that the system is reliable.
Hopefully there will be very long periods of time bet~!een
actual alarm events. However, if there is a calibraiion and
self diagnostic program and associated hardware for realistic
sample injection, the user can generate, at anytime, an
actual/simulated alarm event as a confidence check -
The second primary benefit of this system of
control is versatility. It is advantageous for the system to
have the capability of detecting a ~ide range of e~plosives,
a range of controlled che~lical agents, drugs, and narcotics
etc. All these materials have differing physical ~nd
chemical properties. These properties give rise to a set of
internal parameters for optimum detec,ion. However ,hese
parameters will be less than optimum for some other
materials. ~ut, if these parameters are all controllable and
easily changed such as by simply reading in or activating a
different program in the computer memory, then the user can
effectively change the system to meet what is considered to
be the threat at that time without making any hardware
changes.
Referring now to Figure 12, there is shown a block
diagram representation of the control and data processing
system 300 and its associated peripheral elements. The
digital computer 302 or processor is an AT type personal
computer running at lOMHz and has a standard video display ~-
terminal 304. The computer 302 is responsible for process
-3 control, data acquisition, data analysis and display of
results. In addition, as mentioned previously, the computer
302 also contains software routines for self diagnostics and
~.
-35- 1~2~
self calibration procedures. The computer 302 receives power
from the power distribution unit 306 as does the sampling
chamber 100, the hydraulic pump 210b which supplies hydraulic
pressure for the hydraulic control unit 210a, and the process
control unit 308. The process and control unit 308 under the
control of the computer 302 interfaces and provides the
necesSary signals to run the hydraulic control unit 210a, the
preconcentrator control unit 214 and the interface control
unit 238.
The process and control unit 308 is a standard
interface unit between computer 302 and the various
actuato~s. The hydraulic control unit 210a controls a
hydraulic piston which travels up and do~n to unlock and lock
the filter elements 206 and 208 of the primary
preconcentrator 201, as sho~n in Figure 7, so they can be
rotated from position 1 to position 2 as described in the
previous section. Under software control, the process
control unit 308 outputs com~ands to a two-way solenoid, not
shown, which engages or disengages the hydraulic piston. The
preconcentrator control unit 214 is a stepper motor which
rotates the filter elements 206 and 208 after they are no
longer locked in place by the hydraulic control unit 210a.
The stepper motor is run under soft~are control. The
interface control unit 238 is also a stepper motor, and it is
used to rotate the multi-port valve 226, used in the
sëcondary preconcentrator 203, from position 1 to position 2
and vise versa. Data from the analyzers 234 and 236 is
brought directly into the computer 302 for processing. Data
from the gas chromatograph/ECD system 234 is taken into the
computer 302 as a varying frequency, and data from the IMS
3 system 236 is taken into the computer 302 as a varying analog
voltage. The data input to the computer 302 is correlated by
-36- ~32~9~ -
processor 302 to the process control module 308 which
generateS the necessary inte~rupts for processor 302 so the
data can be input at the proper time intervals.
The computer 302 has an internal clock ~hich
provides the reference clock for all timing se~uences.
Therefore, because all the valves and mechanical motions are -~
being actuated by the computer, all gas and sample flows in
the equipment are controllable with respect to the time of
actuation. The re ative sequencing and timing of actuations
are simply steps in a stored program in the memory of the
computer. In addition, all the temperatures in the equipment
are read into the computer and all heating functions are
actuated by the computer. Therefore, all the temperatures
and their magnitudes at any time and rate of change with
respect to time are under program control. The data output
from the ECD 234 and the Il~1S 236 are processed as necessary
and the required information is extracted and displayed by
the same computer.
Figure 13 is a flow chart 400 showing the overall
process control as accomplished by the control and data
processing systems and run by the computer 302. ~lock 402 of
flow cAart 400 is simply the starting point or entry into the
entire soft~are package. The Run Diagnostics block 404
represents the block of software that is responsible for self
diagnostics and self calibration. The Sample Air block 406
represents the block of code that causes the air sample drawn
from the sampling port of the sampling chamber to be drawn
into the SCAP. The Release Filters block 408 represents the
block of software that is responsible for the control of the
hydraulic control unit. The Rotate Filters block 410 - ~-
-3 represents the block of software responsible for the control
of the preconcentrator control unit. The Lock Filters block
412 represents the block of software that is responsible for
132g~
the control of the hydraulic control unit in that it commands
l the unit to lock the filter elements in the holding means.
The Desorb Va~or bloc~ 414 represents the block of soft~are
that is responsible for the controlling of the heating means
and the flow of pure gas in the desorption process. The
Rotate ~lultiport Valve block 416 represents the block of
soft~are that is responsible for controlling the multiport
valve of the secondary preconcentrator so that the
concentrated sample is properly routed to the analyzers. The
Acquire Data block 418 represents the block of software that
is responsible for the acquisition of data from the analyzers
and the subsequent analysis and display of the resultant
data. The software is a cyclic process and following step
418, returns to sampling ste~ 406 and continues until
stopped. As stated previously, the software routine is
modularized and therefore can be easily changed, updated,
removed or added on to.
There are t~o schemes that exist for the screening
process. The sequential scheme requires approximately 14.0
seconds to complete one screening cycle and the concurrent
scheme requires approximately 3.6 seconds to complete one
screening cycle. Both schemes are implemented using the flow
chart 400 illustrated in Figure 13; however, as the name
implies, the concurrent scheme involves performing certain of
the operations involved in the screening process in an
overlapping or multi-tasking environment. Basically, in the
concurrent scheme, the software routines are run in a
foreground/background scenario in a true interrupt mode. In
- this type of scenario the mechanical operations can be run in
background while the analysis and data processing can be run
3 in foreground. Figure 13 is a general representation of the
software and should not be construed as a timing diagram.
Ta~le 1 given below illustrates the required steps and
associated times involved in the screening procedure
utilizing the sequential scheme. -
'
~ _3~_ 1 32~4~
1 SA~PLE COLL~CTION 5.0 seconds
PRI~RY CONC~NTRATION STAGE 3.0 seconds
SECOND~RY CONCE~TR~TION STAGE 2.0 seconds
5 AN~LysIs 3.0 seconds
DATA PROCESSING/REPORTI~IG 1.0 seconds
TOTAL SCREEI~ING TI~lE 14.0 seconds
Table 1
Referring now to Figure 14, a se~uence diagram 500
or timing chart is given in order to illustrate the various -
time parameters for each given in the concurrent sampling
scheme. Each time bar is comprised of five boxes indicating
the various steps in the process. Box 502 represents the air
sampling step time, box 504 represents the time for the
mechanical steps involved in the collection of the sample,
box 506 represents the time associated for injecting the
concentrated sample into the chemical analyzers, and box 510
represents the analysis time. Since it takes approximately
2.5 seconds to pass through the portal, two people can pass
through in 5.0 seconds, and thus the timing chart 500 is
shown for two people. To calculate the total time for a
single person; which is approximately 3.6 seconds, the total
time for the first two people to be screened, which is 14.4
seconds, has subtracted from it the time for sampling and ~ - -
collecting the sample from the next two people, which is
approximately 7.2 seconds, resulting in a time of ~
approximately 7.2 seconds for two people and 3.6 seconds for - ~-
30 a single person. As indicated in chart 500, the concurrent -
scheme overlaps in the sampling and collection periods. The
three remaining time lines are identical numerals with
-
: .. ',
.. .
. .
_39- ~32~
prime, double prime and triple primes added. It is important
1 to note that if an alarm indicating a particular substrate
does go off, it is necessary to send the two people thxouqh
individually, thus ta~;ing appro~imately 14.0 seconds as
indicated in the previous paragraph.
Although shown and described in what is believed to
be the most practical and preferred embodiments, it is
apparent that departures from specific methods and designs
described and shown will suggest themselves to those skilled
in the art and may be used without departing from the spirit
and scope of the invention. The present invention is not
restricted to the pariicular constructions described and
illustrated, but should be constructed to cohere of all
modifications that may fall within the scope of the appended
claims`
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