—. —

Chapter Ill TAGGANT RESEARCH REVIEW —. .——

Chapter 111.–TAGGANT RESEARCH REVIEW

**** **** *.*0 **** 9*** **** **** ***0 *0** **** **0 *****9 51 Taggant Development History ● **** **** **** 900* **4* *a **a********** 51 Identification Taggants...... 51 Predetonation Only...... 52 Radiological Tracers...... 52 Chemical Assay...... 53 Physical Taggants ...... 53 Summary...... 56 Detection Taggants...... 56 Vapor Taggants...... 57 Summary...... 58 Detection Taggant Sensor Systems...... 59 untagged Detectoin ● **** a*** **** **** e.** a*** **** *e* be********* 62 Vapor Detection...... 62 Differential Contrast Radiography ...... 63 Excitation lnduced Emissions...... 64 Summary...... 65 Current BAFT/Aerospace Tagget ● **** 65 Program Status ... , ...... 65 Projected Schedule...... 68 Implementation Philosophy...... , ...... 69 Identification Taggant Surviaval Teasting ● **0* **** **m* **09 *b** **em **0** 70 Boosters, Military ...... , ...... 71 Black and Smokeless Powders ...... 72 Detonators and Detonating Cord ...... 72 Summary...... 72 Chapter Ill TAGGANT RESEARCH REVIEW

INTRODUCTION

TAGGANT DEVELOPMENT HISTORY

The idea of adding material to explosives to Identification Taggants enhance the predetonation detection and the postdetonation identification of explosives has Ideas for tagging materials to be used for been considered by various military and civil- identification of the source of explosives used ian agencies for at least 15 years. Some of the in criminal bombings and bombing attempts suggested material, such as radioactive iso- can be generally grouped into the following topes, would perform both functions, some four classes: could only perform one. A number of the con- 1. addition of materials that would not sur- cepts which have been proposed during that vive the detonation, but which would pro- time are briefly described in the following sub- vide information if a bomb were recov- sect ions. ered undetonated;

51 52 ● Taggants in Explosives

2. addition of materials that would physical- not legally usable in New York. This data is not ly survive the detonation and be recov- helpful to police in tracking bombers but does ered intact; assist in control of legal uses of dynamite 3. addition of materials to the explosives within New York. that would be detected in an assay of the The English apparently use a method some- debris; and what better than the date-shift code in that the 4. addition of radioactive isotopes. identifying code consists of colored threads within the explosives. The threads do not sur- Predetonation Only vive the detonation, but the information con- Since 1970, the date, shift, manufacturer, tent is not lost by discarding the cartridge, as is and product have been printed on the car- the case with the date-shift code; it may not be tridge of cap-sensitive high explosives. The possible, however, to encode sufficient infor- manufacturer keeps records, by that date-shift mation for U.S. needs by that method. code, and can tell to whom each batch of ma- terial was sold; distributors also are required to Radiological Tracers keep records of sale. It is possible, from the Addition of small amounts of radioactive date-shift code, to compile a list of last legal isotopes to explosives during the manufactur- purchasers of explosives from a lot with the ing process is particularly attractive as it pro- same date-shift code. I n fact, BATF maintains vides a mechanism for both identification of a National Explosives Tracing Center, whose the materials from the postdetona- function is to coordinate that activity. A typi- tion debris and a simple detection mechanism. cal trace would start with the recovery of an There are a large number of radioisotopes, so undetonated bomb by a BATF special agent. an identification scheme could certainly be de- He would call into the tracing center with the veloped that would provide sufficient unique information, and the data would be forwarded code species. to the manufacturer who would provide the list of consumers or distributors; if explosives The two primary objections to this often- from that lot were sold to a distributor or dis- proposed solution are public reaction and tributors, they would be contacted for a list of safety. Given the present widespread antipathy retail purchasers. to anything involving radioactivity, it is doubt- ful if the public would accept such a solution, The date-shift code information has proven even if there were no safety hazards. useful in investigations of criminal bombings, although its utility is Iimited to instances Two potential safety hazards exist, one hav- where the explosive is recovered before deto- ing to do with sensitization of the explosive nation, or in some cases, where a low-order materials, and the other with the effects of detonation does not destroy the cartridge. In low-level radiation. Addition of foreign materi- addition, the information is only on cap-sensi- als to explosives poses a potential sensitivity tive high explosives, and on the packages of hazard. However, the amount of radioisotopes detonators, black powder, and detonating required would be far smalIer than the mate- cord. No trace data is available for other ex- rial necessary for other tagging mechanisms, plosive material, such as smokeless powder, in- so explosive sensitization would probably be dividual detonators, or even cap-sensitive high no more of a problem than with other types of explosives that have been removed from the taggants. cartridge. The hazards of low-level exposure to radia- Smaller amounts of information are given by tion are not well-defined; the current trend is other systems that do not survive the detona- toward severe limitation of exposure. Thou- tion. For instance, all dynamite legally coming sands of people come into direct contact with into New York must be red. I f dynamite is re- explosives every day at the manufacturers, dis- covered that is not red, it indicates a purchase tributors, and users level, so a large number of Ch. 111—Taggant Research Review . 53

people would have some exposure. Primary ethanol solutions. By using several rare earths concern would be at the manufacturing level, and by varying concentrations, a sufficient where workers would have more continuous number of unique codes could be constructed. exposure than, for instance, a user. Aside from The taggants were recovered from the debris the adverse psychological effect the use of with ethanol-dampened cotton swabs. The tracers might have on such workers, and the swabs were then assayed in the laboratory by possible long-term effects of low-level expo- ion-exchange methods; analysis was accom- sure, there would be a large cost impact due to plished by X-ray excited optical luminescence the need for specially trained personnel, as techniques. welI as storage, handling, and decontaminat- ing equipment. If it were necessary for the Drawbacks to the Ames taggants included Nuclear Regulatory Commission to control the sensitization of the explosives by the ethanol shipment of the explosives and to license and carrier, a high background level, particularly otherwise supervise all explosive users, addi- for detonations taking place near or on the tional major costs and inconvenience would ground, and a rather specialized laboratory occur. procedure necessary for the taggant assay and identification. A final drawback is that reading of the in- formation encoded in the postdetonation de- Physical Taggants bris would be a fairly complicated laboratory procedure involving sample preparation, radia- This class of taggants is designed to survive tion counting, and radioisotope identification. the detonation in its original physical form, to Only a limited number of laboratories in the be separated from the debris, and to be de- country have the trained personnel and facili- coded, either in the field or in the laboratory. ties; police forensic laboratories are not Several types of materials have been sug- among them. gested. Physical taggants must meet the same requirements as the chemical taggants, how- Chemical Assay ever, in addition to physical survival, so the number of serious candidates is somewhat lim- A number of approaches have been pro- ited. Three taggants remain promising candi- posed that have in common the addition of dates. chemicals to the explosives that would be re- covered from the postdetonation debris and be 3M COLOR-CODED TAGGANT identified by a laboratory assay of the debris. More research has been conducted with the While the number of chemical materials is al- 3M identification taggant than with any other. most limitless, a successful chemical taggant It is the baseline taggant proposed by BATF for must have the following properties: implementation if a taggant program is legis- ● inertness, lated, and is the taggant used for the OTA cost, ● nonsensitization of the explosives, safety, and utility analyses. ● not present in background material, The taggant consists of an irregular chip of ● able to survive the detonation, thermosetting melamine alkyd, approximately ● long-term stability, 0.12 mm thick and about 0.40 mm in its great- ● not a health hazard, and est dimension. Figure 6 shows the eight-layer ● sufficient variation must be possible to construction; variation of the sequence colors form a large number of unique codes. provides the necessary library of codes. A total The chemical taggant with which the great- of approximately 6 million unique codes is est amount of research has been conducted available, when al Iowances are made for cer- was developed by the Ames Laboratories in the tain forbidden adjacencies (colors too difficult early 1970’s, I n this method, rare earths were to distinguish) and other restrictions. One face added to explosives as oxides or as nitrates in of the taggant visably fluoresces when illumi- 54 . Taggants in Explosives

Figure 6.—3M Color-Coded Identification Taggants

. . . 4 --- I . “ : . 3 -. Im

-. r ., -. - -4 Ch. 111—Taggant Research Review ● 55

nated with black Iight (366 nanometers) as an fluoresces in the visible range when illumi- aid in recovery, either in the field or labora- nated by shortwave radiation (254 tory. The other face contains iron powder, al- nanometers) and magnetic particles, both of lowing the taggant to be picked up by a which assist in the recovery process. magnet, another recovery aid. Due to the limited number of rare-earth I n theory, the taggant can be recovered from compounds available, and the fact that the in- the debris by use of a magnet and a black , dividual components are not ordered like the read in the field by a low-power microscope, 3M taggant layers, the Iibrary of possible codes and traced through the BATF tracing center. I n is only approximately 3,000, even with three fact, laboratory separation may be needed in distinct spotting phosphors. Use of different most bombings; the recovery and laboratory concentrations or pairing of two different tag- procedures are quite simple, however, and can gants to form a unique species can significant- be performed in the field with little equipment ly increase the library, with approximately and train i ng. 600,000 codes available for the paired taggant variation. Several variations of the basic concept have been tried, some including a polyethylene en- A significant number of compatibility tests capsulant and some including SIightly different have been conducted with the taggant, as have chemical and physical properties of the indi- a small number of survivability-recoverability vidual layers. The safety, survivability, utility, tests. Due to the ceramic nature of the taggant, and cost aspects are discussed in great detail it is extremely survivable and does not ther- elsewhere in this report. mally degrade in high-energy explosives (such WESTINGHOUSE CERAMIC TAGGANT as boosters), as does the 3M taggant. In addi- tion, since the rare-earth doping is homoge- The Westinghouse taggant consists of a mix- neous throughout the material, the full code ture of rare-earth compounds, bound together can be read from even a small recovered tag- into a ceramic-1ike particle, whose appearance gant chip. The Westinghouse taggant is ex- is similar to a grain of sand, and whose largest tremely gritty, and has been shown to sensitize dimension is approximately 0.2 mm. Each of explosives if not encapsulated in a polyethyl- the rare-earth compounds fluoresces at a char- ene coating. acteristic wavelength when illuminated by ul- traviolet radiation (325 nanometers). A scan- No additional effort is currently underway ning monochronometer is used to read the with the Westinghouse taggant, due to a West- wavelength of the various rare-earth com- inghouse concern over liability should some pounds, and thus to identify the taggant code. taggant not be fully encapsulated and thus The 10 rare earths that have been evaluated, cause sensitization of an explosive material. and their characteristic emission wavelengths, From the limited data available, it would ap- are: pear that the Westinghouse taggant shows in- teresting potential, particularly due to its high Nanometers survival rate, although solutions must be Strontium chlorophosphate. europium 447 Yttrium vanadate thulium. 476 sought to ensure 100-percent encapsulation. I n Yttrium phosphate cerium, terbium 546 addition, some further limitations are imposed Yttrium vanadate erblum 555 by the relatively small code library available Yttrium vanadate: dysprosium 575 and by the rather complex laboratory identifi- Yttrium vanadate: samarium 608-648 cation procedure required. Yttrium vanadate: europlum 618 Yttrium oxy sulfide europlum 626 CURIE POINT TAGGANT Strontium fluoroborate. europlum, samarium 687 The Curie point taggant consists of a collec- Strontium fluoroborate europlum 375 tion of five distinct ferrites, packaged with an As in the 3M taggant, the Westinghouse tag- ultraviolet sensitive spotting phosphor in a gant incorporates a spotting phosphor which binder of potassium silicate. Ferrites exhibit 56 ● Taggants in Explosives

the property that their ferromagnetism disap- Detect ion Taggants pears when the temperature of the ferrite is raised above a specific temperature, desig- Four general types of detection tagging ap- nated the Curie point temperature. identifica- proaches are described in the literature, in- tion of a particular taggant is thus accom- CI uding: plished by placing the recovered taggant in a 1. radioisotopes, temperature-controlled chamber and record- 2. vapors, ing the magnetism as a function of tempera- 3. electromagnetic (E/M) taggants, and ture. 4. activation of nonradioactive isotopes

Radioisotopes for use as detection taggants Approximately 50 ferrites have been identi- possess the same drawbacks as they do for use fied whose Curie point falls in a laboratory as identification taggants; the above discus- practical temperature range. The 50 ferrites, sion need not be repeated here. used in combinations of s at a time, yield a li- brary of approximately 2 million unique spe- Electromagnetic taggants incorporated into cies. a detonator, such as the passive harmonic ra- dar taggant investigated by the Aerospace As the taggants are ceramics, their surviva- Corp., offer the possibility of detection at a bility in high-energy explosives, such as boost- distance with a relatively low rate of false ers, should be good. Very preliminary tests alarms. All of the concepts so far proposed, have demonstrated the survivability of the tag- however, can be easily defeated by wrapping gant in boosters and high-power commercial explosives in metal foi1. I n addition, inclusion explosives such as Power Primer. of such devices would probably have a signifi- cant effect on the procedures used to manu- The Curie point taggants share the potential facture detonators, on detonator cost, and sig- sensitization problem of the Westinghouse nificant false alarms could be caused by com- taggants, and must therefore be encapsulated mon diodes from radios, calculators, and other with 100-percent certainty. The Curie point electronic instruments. taggants have another serious drawback: mag- A variation of the idea of electromagnetic netic separation from powdery materials such taggants has been proposed, called detonator as gunpowders and powdery dynamite would deactivation. In this concept, a reed switch is be an obvious simple countermeasure. connected in series with a detonator bridge wire. illumination of the detonator by a switch- able electromagnetic source would cause the Summary reed to open. A number of methods are possi- The 3M taggant, which has been the most ble to ensure that the reed could not be subse- thoroughly researched identification taggant, quently closed. The advantages of the concept appears to be the most viable candidate, al- are twofold: though the Westinghouse taggant exhibits a ● the necessary illuminator could probably good deal of promise at this early stage of de- be made quite inexpensively, allowing it velopment. The other candidates exhibit tech- to be used to protect far more targets than nical, cost, countermeasure, or public accept- would be possible with other detector ance problems, or require elaborate laboratory concepts; and separation and analysis to yield the identifica- ● the deactivator process is passive — no op- tion code. However, as other sections of this erator is necessary. report make clear, the 3M taggant is not yet fully developed or tested, and could not be Disadvantages include the fact that deacti- generally used unless and until several remain- vation rather than detection of bombs would ing problems are resolved. offer no help in finding the would-be criminal Ch. 111—Taggant Research Review . 57

bombers; significant (and possibly costly) im- Vapor Taggants pacts on current processes of manufacturing vapor taggants have received the bulk of detonators; and the risk of accidentally deacti- the research on detection taggants. vapor tag- vating detonators, resulting in their failure for gants share the common taggant requirements normal use. No research beyond initial concep- of stabiIity, inertness, compatibility with ex- tualization has been conducted for this con- plosives, and absence from normal materials. cept. In addition, they must have a vapor pressure An interesting taggant concept has been sug- sufficient to produce enough molecules to be gested by the Franklin Institute, based on the sensed, but not so high that a large initial mass idea of using Moss bauer active isotopes as tag- would be required to ensure continued opera- gants. The technique involves the addition of tion when placed in explosives that have a nonradioactive trace taggants to explosives, shelf-life of several years. They must have a followed by the gamma ray excitation of the relatively steady molecuIe emission rate over a Mossbauer isotopes and the measurement of 5- to 10-year shelf-life, must not produce an en- the characteristic absorption spectrum of vironmental hazard, and must not readily ad- those taggant isotopes. The Mossbauer effect here to surfaces with which they are likely to has been measured in numerous common ele- come into contact. ments, including iron, tin, and nickel. In a Several hundred different vapor sources Mossbauer isotope, gamma rays, whose energy have been considered, with almost 200 having corresponds to the transition energy between been investigated in the laboratory. Avenues nuclear levels, may be resonantly absorbed of approach have included the use of dispro- upon excitation, producing a sharp absorption portionating salts, the direct adsorption of spectrum characteristic not simply of the vapor taggants into the elastomeric plug mate- Mossbauer element, but of the chemical com- rial of detonators, and the microencapsulation pound of the element. This effect is due to the of taggant materials. small perturbations of the nuclear levels by the surrounding electrons. For use as a taggant, a DISPROPORTIONATING SALTS chemical compound not found in nature or A number of the salts of weak acids and used in industry would be manufactured. Due bases, such as boron trifluoride adduct com- to the low excitation level required, little pounds, disproportionate or separate into two shielding of the source wouId be necessary. or more constituent parts, some of which sub- limate at room temperatures, theoretically Mossbauer taggants are simply a concept at providing a possible stable vapor emission this stage, however, so little judgment can be source. Tests conducted by the Aerospace made of its practicality, cost, or safety in ex- Corp. indicated that no compounds investi- plosives An Aerospace Corp, analysis ques- gated had the proper balance of vapor pres- tions the practicality of the technique. A sig- sure, emission rate, desired Iifetime, and pro- nificant I imitation to the use of the Moss bauer jected detection limit by a sensor to allow the and other activation techniques is that they use of a sufficiently small amount of taggant cannot be used to search people, due to the ac- material. It is possible to control the emission tivation radiation rate of a high vapor pressure salt by the use of a microencapsulation membrane; use of such A number of other activation taggant tech- a membrane allows the consideration of a niques have been suggested, including the dop- large number of more easily handled liquid ing of explosives with material that would en- taggants, however, as described below. hance the effectiveness of X-ray or similar de- vices These concepts al I lack specificity, how- ELASTOMERIC ADSORPTION OF ever, and could cause the X-ray to be triggered VAPOR TAGGANTS by many common items, resulting in an unac- The adsorption of the vapor detection mat e- ceptable faIse a I arm rate rial directly into the elastomer used to fabri-

61-401 0 - 80 - 5 58 ● Taggants in Explosives

cate the end plug of detonators offers a num- sive, easy to use with the candidate taggant ber of advantages, including removal of the materials, compatible with the explosive mate- necessity for additional steps or changes in the rials, and form membranes that account for detonator fabrication process. Research has only 10 to 20 percent of the microencapsu- therefore been conducted to evaluate the ef- Iated taggant weight. Figure 7 shows a photo- fectiveness of various elastomer/taggant pairs. graph of a canadidate microencapsulated vapor Taggants evaluated include sulfur hexafluo- detection taggant, with a needle to indicate ride, and hologenated alkanes, amines, aero- relative size. batics, esters, and ketones. A number of com- binations appear feasible, although useful life- Emission rate studies are currently under- times may be shorter than the 5-year minimum way with a number of membrane materials. desirable. A more severe limitation, however, Early tests were very encouraging; a number of is that the elastomerically adsorbed taggants more recent test results show variations in would be useful only on detonators, and pos- emission rate from lot to lot and as a function sibly with detonating cord. None of these tag- of ambient relative humidity and temperature. gants appears to be as successful as other can- Tests have not yet started on long-term emis- didates when microencapsulated for use with sion behavior, especially in the presence of ex- other explosive materials. Use of separate tag- plosives. Tests have only recently started on gants for detonators for other explosives the compatibility of explosive materials with would lead to the development of two sensors either the taggant vapors or the membrane ma- or to the requirement for dual-mode sensing in terials. a single sensor, an unnecessary sensor develop- ment constraint. Summary MICROENCAPSULATED VAPOR TAGGANTS Although a wide range of detection taggant Approximately 180 vapor materials have materials have been proposed, the need for been screened in the laboratory as candidate long life, stability, specificity, and absence of microencapsulated vapor taggants. In addi- easy countermeasures has caused the bulk of tion, several hundred other materials were re- these to be rejected, at least given the current jected after a thorough analytical review. Five state-of-the-art. The most promising concept is candidate perfluorinated cycloalkane com- the microencapsulation of perfluorinated cy- pounds have been extensively tested, and have cloalkane compounds, although the direct ad- successfulIy completed barrier penetration, sorption of taggants into the detonator plug mutagen, toxicity, and atmospheric impact elastomer appears promising for that applica- testing. The five candidate vapor taggants and tion. A number of preliminary tests have been their chemical properties are shown in table conducted with five candidate taggants; com- 16. patibility testing has just been initiated. Deto- A parallel research effort has been under- nator deactivation is a possible alternate ap- way to find an appropriate microcapsuIe mate- proach, although little research has been ac- rial. The optimum material would be inexpen- compl i shed.

Table 16.–Candidate Vapor Taggant Properties

Empirical Molecular Boiling point Melting point Specific Vapor pressure Chemical name Abbreviation formula weight “c “c gravity (300° K = 27° C) Perfluoro-1 1-2-dlmethyl-cyclobutane PDCB C, F,, 300 45 -32 1.67 390 Perfluoromethylcy clohexane ., PMCH C, F,, 350 76 -37 1.79 106 Perfluoro-1,3 3-dimethylcyclohexane PDCH C, F,, 400 101-2 -70 185 35

Perfluorodecalln PFD C 0F,8 462 141-2 0 193 6.6 Perfluorohexylsulf sulfur-pentafluonde L-4412 CSFI,SF, 446 118 -31 1.89 195

SOURCE The Aerospace Corp Photo credtt Aerospace Corp

Detect ion Taggant Sensor Systems prior to insertion of the air into the sensor. If the vapor taggant is present, an alarm indica- tion is registered; if none is present, then the The development of a system to detect the item passes through with no delay. A detailed emitted vapors is proceeding in parallel with procedure has not been developed to deal with the development of vapor-emitting detection alarms, but the procedure would probably in- taggants. A schematic block diagram for the clude a recycle through the sensor to eliminate operation of such a system is shown in figure 8. the chance of an equipment transient being re- Air, from the vicinity of the item being in- sponsible, followed by a suspected bomb dis- spected, is collected and delivered to a sensor, posal procedure if the alarm persists. after first being conditioned. The sample col- lector can simply consist of a gust of air for in- Work is progressing on three candidate de- spection of boarding passengers, or can in- tection sensors. Very little effort has been ex- clude a small pressure pulse to a piece of pended by the Aerospace Corp. on the other checked baggage to introduce more of the air elements of the system, although some prelimi- from the interior of the baggage into the air nary design identification work has taken sample stream. For some of the concepts the place on the air sampling process and on meth- free oxygen and water vapor must be removed ods of enhancing the original sample. A U.S. 60 ● Taggants in Explosives

Figure 8.— Detection Taggant Sensor System time so that one can turn-on, or gate, the de- Block Diagram tector to respond only to a specific molecular species or group of species such as the taggant Sample vapors. collector The taggant molecules being considered all have long drift times and are easily separated Air from common gasses in the IMS. Additional sampler specificity is gained by the toughness of the taggants; most other large molecules fragment Sampler in processing through the detector. conditioner IMS devices have been commercially avail- able for approximatelys years, with about sO currently in use for various applications. Tests sensor have been run with a commercial IMS unit at airports to examine ambient air for the pres- Alarm No Alarm ence of molecules in the critical drift time re- gion; no molecules which would have triggered a false alarm were detected. Calibrator Inspection While the laboratory tests are promising, it is not possible to extrapolate to estimates of IMS SOURCE: Office of Technology Assessment. performance in the field, in a real-life envi- ronment, when maintained by normal airport maintenance people, and when using an inter- Customs Service device has been tested, for in- nal calibration source. stance, which exerts a gentle force on baggage, causing an exhalation of the baggage interior CECD can be conceptually viewed as an IMS air into the sampling network. device without a drift tube. It simply consists of the conditioner and reaction chamber; the The three candidate detection sensors are, in decrease in current in the reaction chamber is order of increasing complexity and cost, the a sign that the taggant molecules are present continuous electron capture detector (CECD), and have been ionized. As described, CECD the ion mobility spectrometer (lMS), and the would have less specificity than IMS, and mass spectrometer (MS). Figure 9 shows a sche- would probably be triggered by a wider range matic diagram of the operation of IMS. Gas is of interference sources. The key to the device introduced from the sampling device into the is in the conditioning chamber; the chamber is conditioner. After the free oxygen and water a catalytic reactor that contains hydrogen gas vapor are removed, the sampled gas molecules and palladium metal plated onto a number 5A are drawn into the ionization region where molecular sieve and operating at 1400 C. The many molecular species, including the taggant reactor removes oxygen and water vapor, frac- molecules if present, form negatively charged tures some other potential interference ions. The negative ions are then gathered and sources, while still others are removed by injected into a drift tube where an electric reduction or combustion. The number of mole- field causes them to flow against a counter- cules that will survive the conditioning cham- flowing drift gas stream. By virtue of the ion ber is limited, but the taggants may well not be molecule reactions between the negative ions the only survivors of the passive screening and the neutral drift gas molecules, the ions process. are separated into spatial clumps of like spe- cies. Each species, depending on the strength CECD devices have been used as a labora- of the ion-molecule interaction, traverses the tory instrument by the Brookhaven National length of the drift tube in a different length of Laboratory for the past several years. A bread- Ch. 111—Taggant Research Review . 61

Figure 9.— Cutaway View of the Phemto”Chem 100 Sensor Cell in the Ion Mobility Spectrometer

ALL GAS ● SAMPLE AND GAS FLOWS DRIFT GAS 80% CARRIER 200/0 SAMPLE ●

; : 7 ml ol d SAMPLE INLET 7=-7! .—=’) : -L .—. —————— -— ~-MoL=E : DRIFT REGION — — NIr2x. AZ—= + - ‘ REKJON R EG IOy< : FAST IONIZER ELEcTROMEl ‘ER Ni-63 AMPLIFIER 100 ml Vol

IMS HOUSING AND HEATER

DRIFT GAS 100-3000 ml/min

SOURCE David Williams BATF board device was recently shown to be quite The time required to develop instruments of successful in detecting vapor-tagged dummy this type is a pertinent subject for discussion, blasting caps in baggage on a conveyer belt. even assuming that the technical problems can be solved. The milestones in a development The MS is a standard laboratory instrument, process include: easily capable of resolving the taggant mole- cuIes from other species. Current MSS, how- ● demonstration of technical feasibility, ever, are usualIy expensive, relatively sensitive ● generation of specifications for a proto- laboratory instruments. The challenge is to de- type, sign and develop a low-cost, field-usable in- ● prototype development, strument that will detect taggant molecules in ● generation of specifications for the instru- a parts-per-tril I ion concentration level. ment, ● pilot production of the instrument, and The limited laboratory testing of detection ● ful l-scale production. sensors that has taken place has demonstrated that the technology exists for sensors which None of the detection sensor concepts has could detect the taggant vapors. These tests yet passed the technical feasibility demonstra- have not yet demonstrated, however, the abili- tion milestone. The only time estimate which ty of the instruments to distinguish between has been made is an extremely optimistic es- the taggant materials and similar materials timate of 14 months from demonstration of which may exist in the environment or may be technical feasibility to completion of a proto- deliberately introduced into the environment type. The estimate assumed no technical, con- as a countermeasure. It has also not been dem- tractual, or other problems, and may well be onstrated that any of the instruments can suc- off by a factor of two. Given the fact that these cessfully detect the taggants in the required instruments would be produced in quantity (up parts-per-tri I I ion concentration level under to several thousand), must be self-calibrating, field-use conditions. maintained by routine maintenance people, 62 ● Taggants in Explosives

and detect at the state-of-the-art parts-per- effective; the operating costs and false alarm trillion level, it is unlikely that production rates would be negligible while the detection could be underway in less than 5 years. rate would ensure essentially no successful penetration of the sensor system. If the instruments can be developed to per- form as desired, however, they should be quite

UNTAGGED DETECTION

Three general methods have been explored ors, and boosters. A detection device would for detecting explosives that do not have de- thus have to be able to detect a significant va- tection taggants added. These include vapor riety of vapors (and thus either be quite slow or detection of the characteristic vapors present expensive) or it would be subject to a high rate in the explosives, the use of differential con- of false alarms if it could be triggered by the trast radiography, and the use of excitation in- spectrum of materials that would be spanned duced emissions. Some of the specific tech- by the vapors from the common explosive ma- niques investigated are briefly discussed terials. below. A second significant problem is the amount of vapor actually available for detection. Vapor Detection While the equilibrium concentrations of the vapors are high enough to ensure detection, A great deal of research effort has been ex- the actual amount of vapor present will be sig- pended in the field of detection of the charac- nificantly degraded by the container that con- teristic vapors emitted by explosives. Table 17 tains the explosive, particularly if an effort is shows the physical properties of the vapor made to create a vapor barrier. The explosive phase of a number of explosive materials, vapors do not have the properties of penetra- while table 18 shows some of the methods tion and nonadsorption of the vapor taggant used to detect the explosive vapors. ’ Much of materials discussed in the previous section. the effort has been concerned with character- Concentration of the vapors could help alle- izing the vapors that are present in explosives, viate this problem, but that might cause suffi- looking for vapors common to a number of ex- cient concentration of ambient interference plosive materials, and quantifying the prob- molecules to generate a high false alarm rate. lems of vapor detection. While the equilibrium concentrations of the vapors shown in table 17 These defects must be balanced against the major advantage that detection of the charac- are within the detection capabilities of much teristic vapors of explosives has over the detec- of the instrumentation depicted in table 18, several problems limit the utility of vapor de- tion of taggant vapors —only those explosives tection. that have been tagged can be detected if the sensors are designed to look for the vapor tag- One of the primary problems is the lack of a gant. common vapor in the various explosive mate- rials. Either nitroglycerine or EGDN is often As shown in table 18, a large number of present in dynamites, and in smokeless pow- physical principles have been used to detect ders, but neither are present in the other ex- the vapors. The most successful, however, are plosive materials used in criminal bombings, the ionization mechanisms exploited for detec- tion of taggant vapors. Continued research is such as gels, slurries, black powder, detonat- primarily devoted to these sensors. ‘From “Explosive Vapor Detection Instrumentation, ” by j R Hobbs, prtnted In the Proceedings of the 1979 Electro Profes- Animal detection deserves a specific com- sional Program, New York, April 1979 ment. Although less sensitive than the other Ch. 111—Taggant Research Review . 63

Table 17.–Vapor Pressures of Selected Explosives

Vapor pressure Composition Mole fraction Compound Molecular weight Temperature 0 C mm Hg gm/cm3 (V. P./76O) EGDN–ethylene glycol dmltrate 152 25 2,8 X 10-2 23 x 107 37 ppm NG–nitroglycerine. 227 25 2,4 X 1O-s 29 x 10-10 32 ppb PETN–pentaerythrltol tetranltraie’ ., . . 316 25 54 x 10”6 9.2 X 10 II 7 ppb AN–ammonium nitrate 80 25 5.0 x 10”6 2.2 x 1011 7 ppb DNT–dinitrotluene ,. 182 25 1 4 x 10”4 1,4 x 109 184 ppb TNT–2, 4, 6,-trinitrotoluene. ~ 227 25 30 x 10”6 37 x 10”11 4 ppb RDX 222 25 1.4 x 109 1.7 x 1014 2 ppt

SOURCE J R Hobbs Explosive Vapor Dection Instrumentations`

Table 18.–Explosive Vapor Detection Techniques

Optical Ionization Animals Other Infrared Electron capture Bioluminescence Plezoelectnc Ultraviolet Dogs Thermoionic Microwave Gerbils Condensation nuclei Gas chromatography/ Enzymes Laser- raman mass spectrometry Two-photon absorption Plasma chromatography Chemiluminescence Laser optoacoustical

SOURCE J R Hobbs Explosive Vapor Detection Instrumentations sensors (by orders of magnitude), animals have density. Most dynamites have a specific gravi- some potential advantages. If small animals ty of approximately 1.6; booster materials and such as rats and gerbils can successfulIy detect military explosives are SIightly higher (up to explosive vapors, then the cost of an animal 1,8); gunpowders have a bulk density of less backup system would be quite small. Dogs are than 1.0. more expensive to train and work with, but The current imaging systems at airports are have the advantage of being used for other law operator-monitored and therefore dependent enforcement work such as patrols. on the ability of the poorly trained operator to Differential Contrast Radiography discriminate small density differences. Most recent research has been concerned with auto-

Differential contrast radiography takes ad- mating the radiographic scanning systems. vantage of the fact that different materials at- Due to the wide span in density of explosive tenuate the strength of a source to a different materials, and the large density overlap be- degree, depending primarily on density and tween explosives and other materials, it is atomic number. Common clinical X-rays and necessary to include other means of discrim- the imaging X-ray detectors used to screen ination in the detection algorithm. Shape is the hand baggage at airports work on this princi- other discriminant currently used. The pattern ple. Similar devices have been fabricated using recognition algorithm in a computer reacts gamma radiation and neutrons as the beam when the proper density and shape pattern are source. This method is quite effective for de- detected. Such a system is sensitive to orienta- tecting materials whose density is significantly tion, arrangement, and shape of the high explo- greater than other materials in the environ- sive as well as to the mass of the high explo- ment, such as a steel gun (specific gravity of sive. The breadboard laboratory models so far 7.8) in a briefcase containing books or clothes developed can incorporate only a limited (specific gravity less than 1,0), but is much less number of shape-density combinations and are effective in detecting smaller differences in able to detect only certain shapes of C-4 explo- 64 “ Taggants in Explosives

sive and certain shapes of dynamite bombs. duced radiation whose energy may be a func- While they could detect a 2-lb C-4 charge tion of the element itself or of the specific shaped like a package of butter, they would compound, due to the interaction of the orbit- not detect the same charge shaped as a sphere, al electrons with the nuclear material. The cylinder, pancake, or sausage, or even another Mossbauer isotope taggants described in the explosive of slightly different density shaped previous section were an example. Several in the butter package shape. As the devices methods of utilizing induced emissions have scan from only one axis, a 2-inch-thick slab been investigated for detection of explosives, with a specific gravity of 0.5 looks much Iike a including the use of thermal neutrons, X-ray l-inch-thick slab of density 1.0. Such a lack of fIuorescence, and nuclear magnetic reso- specificity not only generates high false nance. alarms, but explosives arranged in an unusual shape would not be detected. The thermal neutron detection concept uti- Two avenues of approach are being pursued lizes the capture of thermal neutrons by nitro- to try and alleviate the discrimination specific- gen with the subsequent prompt emission of a ity problem. The first is to use more than one 10.8 MeV gamma ray. Explosives are rich in ni- energy level for the radiation source. Each trogen and should be easily detected in an un- type of material has a different opacity to dif- shielded suitcase, but so are a large number of ferent radiation energies. If more than one en- other materials, such as wool, orlon, nylon, ergy source is used to illuminate the object, and leather. Coupling the system to a pattern then additional information about the material recognition computer might be sufficient to is gained. Some recent work indicates substan- discriminate between a solid block of explo- tial gains in information are possible using two sives and a couple of orlon sweaters (although carefully chosen energy levels. test results were marginal), but discrimination between these sweaters and a bomb in which The second approach is to illuminate the single dynamite sticks are connected by deto- package along more than one scanning direc- nating cord, for instance, would be extremely tion. The information gained can help generate difficult. Processing times for this concept are a better idea of both the package shape and its also rather long for efficient transport of bag- density. In a technique called tomography, the gage. images formed by scanning from several direc- tions are computer processed and used to gen- Nuclear magnetic resonance (NMR) is a erate a three-dimensional image of the pack- technique with considerably greater specifici- age in the computer. Any two-dimensional pro- ty. In NMR detection, an applied radio fre- jection can then be generated as well as an ac- quency magnetic field, with the correct fre- curate density value. This image can be com- quency, induces energy level transitions in hy- pared to all possible conformations of com- drogen, with the subseq~ent prompt reradia- mon explosive materials by the computer, tion of energy in a manner specific to the yielding a much higher probability of detec- chemical compound containing the hydrogen. tion as well as a lower false alarm rate. Aero- A sensor, tuned to receive the signals that space Corp. is currently sponsoring research on would be emitted by the hydrogen in various dual-energy tomography, which would com- explosive materials, could theoretically detect bine the additional information available from any type of explosive, even when present in both multiple directional scans and multiple small quantities. A major problem with the energy scans. utilization of this technique for explosive detection would be the fact that metal inter- Excitation-Induced Emissions feres with the NMR performance, thus shield- ing the explosive. The unit would also have to Many materials absorb radiation of a specif- be quite large (and thus expensive); the magnet ic wavelength and subsequently emit an in- for an NMR unit large enough to scan a suit- Ch, 111—Taggant Research Review . 65

case would weigh several tons. Another prob- suggested, and extremely Iimited testing has lem is the rather slow response cycle time. been conducted on some of them. All of the untagged detector concepts contain signif- icant problems in terms of adaptation to field Summary use. Instrumentation for many of the concepts A number of techniques have been de- would be large and expensive; many are easily scribed for the detection of untagged explo- countermeasure and none, with the except ion sives. Preliminary testing has been accom- of the vapor detection devices, could be used plished on most of the techniques discussed; to screen passengers. few concepts have progressed as far as the studies on detecting vapor taggants, with the Granting the many problems in nontagged exception of the use of animals to detect the detection, there may still be a significant po- characteristic vapors of explosive materials. tential payoff. If an explosive detection instru- Some explosive detection devices are currently ment or technique could be fielded, it could on the market, although their performance is detect all explosives, not just those to which not satisfactory. Other techniques have been taggants had been added.

CURRENT BATF/AEROSPACE TAGGANT PROGRAM

I n 1976, the Aerospace Corp. was designated and to demonstrate their use in explosive ma- by BATF as the system technical manager of terials. Details of the taggant and sensor devel- the taggant program. Prior milestones leading opment programs were given above; the status to the current taggant program development of the compatibiIity testing program is de- effort were: tailed in chapter IV; the status of survivability and recovery testing is reviewed in the follow- 1973.–Joint establishment by BATF and ing section and in appendix C; some details of FAA of an ad hoc committee on explo- the analysis and pilot testing status are re- sives seeding. viewed in chapter V. This information is briefly 1973.–Formation of the Advisory Commit- summarized below, as is a description of the tee on Explosives Tagging chaired by BATF implementation philosophy. BATF for coordination of Federal agen- cies involved with tagging and the control of the illegal use of explosives. Program Status 1973.–Lawrence Livermore Laboratory study to determine feasibility of identifi- The status of the taggant development ef- cation tagging with Aerospace Corp. act- fort is summarized in table 19 for identifica- ing as the program technical manager and tion taggants and in table 20 for detection tag- LEAA as sponsor. gants. In the tables, “Technical feasibility” 1976.–National Implementation Model refers to a demonstration or analysis which in- and Pilot Test Plan for Identification Tag- dicates the concept is feasible, “Technical ging developed by the Aerospace Corp. read i ness ” refers to a demonstration or anal- u rider contract to the Bureau of Mines, ysis that the concept will work in the manner 1977.–Aerospace Corp. designated the suggested, and “Practical readiness” indicates system technical manager for the tagging that the full spectrum of analyses and tests has program by BATF. been completed which shows that the concept is ready for full-scale implementation. Since 1977, Aerospace has been engaged in an ongoing program of analysis and testing to The ability of the 3M Co, to produce the develop identification and detection taggants color-coded taggants has been demonstrated, 66 ● Taggants in Explosives

Table 19.–ldentification Taggant Program Status

Accomplished I Planned or required Technical feasibility Technical readiness Practical readiness 1 Technical feasibility Technical readiness Practical readiness Color-coded taggant development I ● Initial survivability ● Pilot production ● Leadyime study ● Tooling-up period/ compatibility compatibility testing testing Optimize hues ● Environmental im- pact assessment ● Health impact assessment Cap-sensitive packaged explosives (dynamite, water gels, slurries, and emulsions) ● Initial compatibihty ● Online tagging ● Pilot test produc- Comprehensive ● Comprehensive sur- ● Analysis/optimiza- testing demonstrated tion-level tagging compatibility testing vivability testing tion of approach ● Initial survivability ● Tagging methods ● Record/tracing Long-term compati- testing selected/evaluated methods demon- bility ● Manufacturing strated process reviewed and practicality assessed Black powders ● Initial compatibility ● Online tagging ● Some ballistics Comprehensive com- ● Comprehenswe sur- ● Ballistics testing testing ● Additional compati- testing patibility testing vivability testing ● Online tagged sur- ● Hand-mix survwa- bility (electrosta- vivability testing bility testing tic) testing Long-term segre- ● Manufacturing ● Transport/vibration gation process reviewed segregation testing ● Long-term compati- and practicality bility assessed Cast boosters I ● ● Initial compatibility ● Online tagging Solution of problem Comprehensive sur- ● Pilot testing, produc- testing ● Tagging methods posed by reactivity vivability testing tion-level tagging ● Initial survivability selected/evaluated (and presumed in- ● Long-term compatt- testing compatibility) with bility I ● ● Manufacturing Composition B Comprehensive sur- process reviewed Comprehensive com- vivability testing and practicahty patibility testing ● Record/tracing assessed Recovery testing methods demonstrated I ● Analysis/optimiza- tion of approach Detonating cord 1 ● Taggants added by 0 Recovery testing ● Tagging station Comprehensive sur- hand, initial development vivability/compati - surwvability demon- ● Online tagging bility testing strated ● Pilot testing ● Manufacturing process studied and tagging practicabil- ity assessed Smokeless powders ● Hand-mix surviva- Solution of problem ● Evaluation testing Ballistics testing bility testing I posed by reactivity of sequential lots Pilot testing (and presumed in- ● Production hazard compatibility) with and acceptance Herco” powder testing I ● Compatibility and ● Comprehensive sur- hazards analysis vivability testing . Compatibility and ● Online tagging acceptance testing Detonators I — I Full range 01 tests and process evaluation required

SOURCE Office of Technology Assessment Ch. 111—Taggant Research Review ● 67

Table 20.–Detection Taggant Program Status

Accomplished I Planned or required Technical Practical I Technical feasibility readiness readiness 1 Technical feasibility Technical readiness Practical readiness Microcapsule development I Production and eval- 10 Intial compatibility studies ● Pilot production of capsules ● Competitive award /leadtime uation of test batches 10 Complete health and atmos- studies ● Health and atmospheric I pheric Impact assessment ● Development and testing 1 Impact assessment 0 I Taggant selection of production ● Full-scale production capability Dynamite, slurries, and water gels ● Compatibility testing — initiated Black powder ● Compatibility testing — initated Cast Boosters I ● Compatlblllty testing — — initiated The full range of analyses and tests detailed for identification taggants must be accomplished Smokeless powder for the detection taggants, with the exception of postdetonation surivability ● Compatibility testing— — and recovery testing initiated I Detonating cord I — — — I Detonators I ● Compatibility testing I Initiated I Continuous electron capture detector I — ● ● Successful bread- — Instrument character- ● Design prototype Prototype field test board demonstration I ization (in process) ● Fab and lab test ● Prototype design changes ● Instrument charac- 10 Calibration (in process) evaluation ● Final production drawings terization (initiated) ● Aerospace lab test ● Production pilot release ● Callbration system ● Production pilot complete (initiated) ● Field support function setup ● Training and field test IMS detector I ● Initial feasibility Demonstration ● Design prototype ● Prototype design changes studies (Imminent) ● Fab and lab test ● Production drawings I prototype ● Manufacture and checkout ● Aerospace lab test engineering Prototype field test ● Production pilot release / ● I Production pilot complete ● I Support functions setup ● I Training and field test MS detector I ● High-cost laboratory 10 Development and bread- Prototype design, ● Prototype design changes system testing I board demonstration fabrication, and test ● Production drawings ● Development and to be completed ● Manufacture and checkout breadboard demon- I engineering stration—in process I Production pilot release I Production pilot complete I Support functions setup I Training and field test SOURCE Off Ice of Technology Assessment although some hue and color code optimiza- in detail, this initial testing has revealed ap- tion remains, as well as construction of a facili- parent incompatibilities between the 3M tag- ty to produce the taggants. Initial compatibili- gant and one type of smokeless powder and ty and survival testing has been completed for also between the 3M taggant and one cast the cap-sensitive high explosives, as has pilot booster material. If and when these presump- production of tagged explosives and activation tions of incompatibility are removed, compre- of the tracing network. As chapter IV describes hensive compatibility and survivability testing 68 . Taggants in Explosives

must then be completed and decisions made fort; the estimate is shown in table 21. This on implementation levels before readiness is schedule does not take into account, however, demonstrated. A similar level of testing and the need for additional compatibility and sur- analysis has been accomplished for black pow- vivability recovery tests, particularly the res- der, while significantly less has been accom- olution of the current smokeless powder and plished for smokeless powder and cast boost- booster material reactivity issues, and the need ers. One of the key remaining booster issues is for the evaluation of long-term effects of tag- the recoverability of the taggants when gants on explosive material safety and per- pressed into large pellets (survivability has formance. These efforts would probably add been demonstrated). Methods of approach at least 1 year, and possibly more, to the devel- have been explored for tagging detonators and opment time. It is unlikely that the effort to detonating cord, but little testing has oc- demonstrate the use of identification taggants curred. in cap-sensitive high explosives, the type of ex- plosives with which the research effort has pro- The significant accomplishments in identifi- gressed farthest, could be completed prior to cation taggant compatibility testing which early 1981. The research on identification tag- have so far occurred have been made possible gants in detonators, including pilot-plant tool- by cooperation between the Aerospace Corp. up and testing, would not likely be finished and the explosives and gunpowder industries. before late 1983; the research on other explo- Unfortunately, this working arrangement has sive materials would probably fall between broken down in the past few months, and the these dates. These estimates assume a success- industry has, for a number of reasons, with- ful completion of each development stage. drawn its cooperation. The result of this Technical problems may occur that add sub- change in the prior working relationship has stantially to the estimate delays; continued been a significant delay in the program, par- lack of industry participation could make pilot ticularly with regard to compatibility testing of testing impossible; even resolution of contrac- the detection taggants. The results of these de- tual problems could add months of delay. lays, together with an originally planned lag of approximately 1‘A years between the identifi- cation and detection taggant development ef- forts, are evident in the current status of the Table 21 ,–Revised Schedule Estimates for the detection taggant development program, Identification Tagging Program shown in table 20. Aerospace preliminary Program element estimated completion date a Development of candidate detection tag- Identification taggants gants is continuing. Taggants have only recent- Color-coded taggant Early 1983 ly been added to explosive materials for com- Cap-sensitive packaged explosives ., Early 1980 patibility testing and process evaluation. As Black powders. ., ., Cast boosters ., ., ., Mid-1981 described previously, development of three Detonating cord ... ., ., ., ., Mid-1980 candidate sensors is also continuing, with lab- Smokeless powders ., Mid-1983 oratory-type tests showing prom i sing resuIts. Detonator ., . ., ., ., Late 1983 Detection taggants Mlcrocapsule development ., Mid-1981 Cap-sensitive packaged explosives. ., Mid-1981 Projected Schedule Black powder Not critical Cast boosters ., . 7 As a result of withdrawal of industry coop- Smokeless powder, ... Late 1981 eration, technical problems which have oc- Detonating cord ., ., Not critical ? curred, and the uncertainty of funding for out- Blastlng caps-micocapsules. ., CECD ., ., Mid-1982 year efforts, a firm schedule for the remaining IMS detector. ., ., Late 1981 development effort is not available. An esti- MS detector ., ., . ., Mid-1982 mate was made by Aerospace of the revised a Estimated by Aerospace October 1979 schedule for the remaining development ef - SOURCE Office of Technology Assessment Ch. 111—Taggant Research Review ● 69

3M has indicated that it would need a lead- sives containing detection taggants could time of at Ieast 22 months after receipt of a probably not be underway until mid-1 982, with firm order before substantial quantities of tag- sometime in 1984 a more reasonable estimate. gants could be delivered. It is unlikely that a As indicated previously, the estimated de- firm order would be given before resolution of velopment schedule for the detection taggant all technical problems, including uncertainties sensors is extremely optimistic; a more realistic regarding long-term effects. If a mid-1 983 date estimate would be that production of the sen- is assumed for resolution of al I identification sors couId be underway by late 1984. taggant efficacy and compatibility questions, then explosives tagged with the 3M identifica- In summary, by early 1985 it is possible that tion taggant could be in full-scale production all explosives manufactured could be tagged by late 1985. with both identification and detection tag- gants, and that detection taggant sensors A decision could be made to implement tag- could be in fulI production. This schedule is ging as soon as all technical uncertainties are realizable only if no major development prob- resolved for some portion of the explosive ma- lems occur and a taggant program is mandated terials, such as cap-sensitive explosives. Under by legislation, those circumstances, 3M could receive firm orders by early 1981 and tagged explosives could therefore be in full-scale production as Implementation Philosophy early as 1983, BATF has publicly stated’ that it feels tag- The detection taggant development has gants should be included only in those explo- lagged that of identification taggants; the sive materials that constitute a present or ex- development cycle may be shorter, however, pected threat of use by criminal bombers. due both to the learning experience of the They feel that explosive materials that do not identification taggant tests and to the fact that constitute a threat could be excluded. Among no survivability demonstration is necessary. the materials which BATF considers appropri- The Aerospace Corp. estimates are probably ate for exclusion are: quite optimistic, however, for development and test times of both the detection taggant 1. explosives manufactured for U.S. Govern- and the detection sensors, Few compatibility ment agencies other than the military tests have yet been conducted. These tests, (e.g., National Aeronautics and Space Ad- particularly the effects of long-term storage, ministrate ion); military explosives are spe- will take at least 2 years. No specific taggant or cificalIy excluded in S.333; encapsulation method has been chosen. Pilot- 2. special fireworks such as used for 4th of plant production of the taggant is likely to July displays; take a considerable time, as the manufacturing 3, industrial tools such as explosive bolts, processes are complex and the reagents used switches, and air bag in flaters; quite reactive. It is unlikely that solving the 4. blasting agents. It is the BATF intention to technical problems and constructing proper fa- tag the boosters and detonators normally ciIities for the large-scale production of detec- used to initiate the blasting agents. The tion taggants can be accomplished in a signifi- explosives industry maintains that if cap- cantly shorter period than that required for the sensitive explosives are tagged but blast- identification taggants. Assuming completion ing agents are not, the use of ANFO by of the compatibility tests, pilot-plant testing of bombers will increase, and BATF will then detection taggants in the explosive materials could be accomplished by early 1983, and assuming 22 months from that time to the Proposed Guidelines for Exemptions to the Requirements for availability of production quantities of detec- Tagging Explosive Materials Bureau of AIcohol, Tobacco, and tion taggants, full-scale production of explo- Firearms, June 7, 1978 70 ● Taggants in Explosives

wish to tag ANFO. See chapters 1, 11, and team has concentrated on taggant research for VI for a discussion of this issue; and cap-sensitive high explosives (dynamites, gels, 5. explosives which are raw materials used in emulsions, slurries), boosters, detonating cord, a fabrication process, such as the black black and smokeless powders directly con- powder used infuzes. sumed by the public (primarily for handload- ing), and detonators. Blasting agents would not In addition to the categories eligible for ex- be directly tagged; rather the detonators and emption, certain types of explosive materials boosters normally used to initiate the blasting are currently exempted from regulation, and agents would be tagged. are viewed by BATF as inappropriate for tag- ging, including: A strict interpretation of S. 333, at least in the opinion of the Institute of Makers of Ex- 1. explosives used in medicine; plosives, would not allow the Secretary of the 2. fireworks soId to the public; Treasury to exempt explosives simply because 3. propellant-activated industrial devices, they do not constitute a significant threat. such as nail guns; and Resolution of this issue may be facilitated by 4. fixed small arms ammunition. more specific wording in the final proposed Given that philosophy, the BAT F/Aerospace legislation.

IDENTIFICATION TAGGANT SURVIVAL TESTING

The 3M identification taggant would have to muddy or covered the taggants with a layer of survive the detonation of the explosive and be water, severely decreasing the efficiency of the recoverable from the postdetonation debris to magnetic pickup. be useful in identifying the source of the ex- The survival test results for cap-sensitive plosive. It is useful to separate the survival and high explosives, under the varying conditions, recovery discussions. Recovery of taggants un- are gathered in table 22. That table includes all der real-life conditions is discussed in detail in the survival tests conducted by Aerospace with chapter I I and in appendix C. Survival of the taggant is briefly reviewed here. uniformly tagged explosives. Earlier tests, in which the explosive stick was split down the To assess the survivability of taggants in ex- center and salted, are not realistic and are not plosives, the tests should be carried out so that discussed here. Some of the tests used unen- recovery is maximized. ideally, tests would capsulated taggants (so indicated on the take place on a large concrete pad or in a very table); as no difference was observed, they are large bunker with steel or concrete walls and lumped together in the discussion. floor. Unfortunately, few of the survivability tests carried out by the Aerospace Corp. were Aging time was another variable tested, with done under conditions that enhanced recov- the material being aged up to 6 months before ery. A majority of the tests were carried out in testing; again, no effect was observed and all a 4-ft-diameter steel-walled chamber. For all the tests are lumped together. but the lowest power explosives, the taggants Given the diversity of test sites and condi- either shattered upon impact or flowed plasti- tions, it is difficult to assess each test. How- cally due to the large impact pressure pulse ever, several trends appear clear: (estimated by Aerospace to be between 10 and 40 kilobars (kb)). Many of the other tests were 1, Under optimum recovery conditions, carried out in a chamber with a cracked rock using small explosive charges, many hun- floor, or in the open on a dirt and cinder floor. dreds of taggants survive, even for Power I n several cases rain made the open area quite Primer, the most powerful cap-sensitive Ch. 111—Taggant Research Review . 71

Table 22.–3M Identification Taggant Survival Testing

Detonation pressure Number of Tags recovered Explosive K bars Explosive weight, lb Test site tests (averaqe) Independent K -10-40 1/2 4-ft diameter steel chamber 2 1,000 Coalite 8S 30-40 1/2 4-ft diameter steel chamber 10 1,000 10 (part of composite 25-lb charge) Open air, dirt, cinder floor 1 180 Gel coal -25-40 3/4 4-ft diameter steel chamber 7 75 10 10-ft cube concrete chamber, rock floor 1 4 Gel power A-2 -40 1 4-ft diameter steel chamber 8 115 10 10-ft cube concrete chamber, rock floor 1 10 12x 20x 8 ft concrete bunker 3 1,450 (unencapsulated) 600/o Extra 50 ‘/2 4-ft diameter steel chamber 9 1,160 5 (Part of composite 25-lb charge) Open air, dirt, cinder floor 1 58 Tovex 800 70 ‘/2 12x 20x 8 ft concrete bunker 6 1,390 (unencapsulated) 400/o giant gelatin 75 ‘/2 4-ft diameter steel chamber 5 16 (some tests with encapsulated, some unencapsulated) ‘/2 12x 20x 8 ft concrete bunker 6 545 Specially sensitized emulsion 100 ‘/2 4-ft diameter steel chamber 12 620 Power Primer 135 1/2 4-ft diameter steel chamber 11 16 1/2 12x 20x 8 ft concrete bunker 13 510 (unencapsulated) 1 4-ft diameter steel chamber 6 3 1 500 x 100 ft concrete pad 6 530 10 (part of composite 25-lb charge) Open air, dirt, cinder floor 1 4 25 Open air, muddy, cinder floor 1 0 25 500 x 100 ft concrete pad, rainy day 1 26

SOURCE Office of Technology Assessment

commercial explosive (excluding boost- Boosters, Military Exp osives ers). 2. As the size of the charge increases, the Commercial boosters are normally made percent of surviving taggants decreases from cast TNT or TNT-based explosives. These sharply, particuIarly for the most power- explosives have higher detonation pressures ful explosives, Under optimum condi- than even the most powerful cap-sensitive tions, however, dozens of taggants still commercial explosives (180-200 kb v. 135 kb). survive; even under rainy conditions 26 Calculations by the Aerospace Corp. show that taggants were recovered from the 25-lb taggants will be raised above 4000 C, their de- Power Primer tests. composition temperature, by booster explo- 3. Confinement sharply decreases survival, sives. Testing showed fewer than two taggants even under optimum recovery conditions. recovered per pound of booster, even for tests Only one test has been conducted with ex- conducted under ideal conditions on a large plosives confined in a pipe bomb (see concrete pad. The Aerospace solution to the chapter I I discussion); in that test scores problem is to press the individual taggants and of taggants were recovered from 60 Per- polyethylene into a large pellet (one-fourth cent Extra Dynamite. When that result is inch). Tests show that approximately 65 tag- compared to the chamber survival tests gants survive in a pound booster when pelle- (in which over 1,000 taggants were recov- tized into a one quarter-inch-diameter pellet. ered from 60 Percent Extra) it appears Iike- Initial recovery tests indicate that the taggants Iy that considerably fewer taggants would from boosters can be recovered, but far too survive in pipe born b detonations using few tests have been completed to allow a de- one of the more powerful explosives. finitive judgment. 72 ● Taggants in Explosives

Military explosives are generally at least as Detonators and Detonating Cord energetic as boosters, presenting even more se- vere survival problems for the taggants. Due to Only the most rudimentary tests have been the survival issue , the excessive cost of tagging conducted of the survival of identification tag- military explos ives and their low frequency of gants when placed on a detonator and none use in criminal bombings, BATF does not pIan conducted with detonating cord. As the tag- to include military tary explosives in the taggant gants are placed outside of the explosive in program. both cases, sufficient taggants should survive to enable a positive trace to be made. How likely the taggants are to be recovered in real- world s ituat ions, however, cannot be ascer- Black and Smokeless Powders tained without testing. Black and smokeless powders are much less energetic than the least energetic dynamite. Summary Gunpowders are normally used as fillers for pipe bombs, however, so the effect of confine- In summary, the 3M identification taggants ment is expected to be considerable, Tests with survive the detonation of cap-sensitive high ex- both black and smokeless powders were con- plosives in large numbers for small charges ducted in a 20-ft semicircular chamber having which are unconfined. Survival decreases as steel walls but a sand floor. Due to the poor the charge size increases, but sufficient tag- recovery conditions, only 2 to 3 dozen tag- gants should survive even a large charge of the gants were recovered for the black powder most energetic commercial explosive. The ef- bombs, and from O to 3 for the smokeless pow- fect of confinement significantly reduces tag- der. When black powder bombs were deto- gant survival, but taggants can probably sur- nated under near ideal recovery conditions, vive pipe bombs filled with low-energy explo- using the 8 ‘ x 12 ‘ x 20 ‘ bunker, an average sives and gunpowder; their survival in pipe of 1,100 taggants survived 1 lb of the FFFg bombs filled with higher energy explosives is powder. No ideal recovery tests have been uncertain. Individual taggants do not survive conducted with smokeless powders, but the booster detonation but pellets made from the one pipe bomb test with explosives gives an in- taggants do. Taggants wou Id probably survive dication that scores to hundreds of taggants the explosion of detonators and detonating should survive. cord, but there is little or no test data.