How the Detonator plays a "Significant" role in the ability of an X-Ray operator to detect an Improvised Explosive Device (IED) threat. Part 1

When you think of security x-ray systems and the detection of the IED threat most people think about automatic explosives detection software. Trying to detect the explosive with x-ray has become a huge market and has made billions of dollars for the industry. There are just a "few" problems with the idea of explosive detection with x-ray.

1. It does not work so great and to try and increase the accuracy you have to have a OMG expensive Computed Tomography (CT) x-ray system. Even when you have a CT system it can still miss detecting the explosive and also create many false alarms.
2. It only detects organic based explosives' and does not detect inorganic explosives. This is kind of a "HUGE" problem because the bad guys tend to use inorganic explosives vs organic.
3. Not everybody and to be honest the majority of security checkpoints worldwide cannot afford these OMG expensive CT x-ray systems. Most people are using single and double generator x-rays which have a much poorer explosive detection capability and a very high false alarm rate vs the CT systems. You are talking about $300,000.00 US Dollars for a CT system whereas a single view x-ray would only be around $20-30,000.00. Unless you have a massive budget, you are going to be using a much lower cost x-ray.
4. No matter if the x-ray detects the explosive, you still must rely on the x-ray operator to make the call and have that item sent to a more intensive process to try and determine "IF" it is an explosive. This can only be done by doing a visually inspection of the item or also use an Explosives' Trace Detection (ETD) technology.

I am a certified Explosive Ordnance Disposal (EOD) Technician and have been teaching both Bomb Technicians and Security Screeners on how to detect a IED threat in x-ray for many years. The process Bomb Techs use is very different vs what a checkpoint x-ray operator uses, and this is because Bomb Techs use an x-ray technology that provides significantly better image quality vs a checkpoint x-ray. The other huge difference is Bomb Techs do not use Color Imaging (aka Materials discrimination) and only use Black and white. The Bomb Techs also do not have any software that automatically detects the explosive and they rely solely on their ability to identify the IED components in the x-ray image.

When I train these two groups, I can tell you that Bomb Technicians are much better at identifying IED's in an x-ray image vs a security checkpoint x-ray operator. The question you need to ask is "WHY" are Bomb Techs so much better when they do not have color imaging nor software that automatically detects explosives? How can Bomb Techs who only use a black and white image outperform a trained x-ray operator using a $300,000.00 CT x-ray?

The answer is actually pretty simple and is because bomb techs are trained differently vs how checkpoint x-ray operators are trained. Bomb Techs are trained to know what IED's use as far as their components. They do not focus on trying to detect the explosive and focus on detecting the IED components. Bomb Techs are very well versed in looking at an x-ray and picking out items that can be part of a IED firing train. They never look at an x-ray image and try and determine "what" could potentially be the explosive. Bomb Techs only determine where the explosive might be located "after" they have identified the parts and pieces of the IED firing system. Bomb Techs determine where the explosive main charge is once they locate the component that can set off the explosives'. That item is the DETONATOR and when they locate that item they can determine in a black and white image where the explosive main charge is positioned.

It is my experience that when Bomb Techs look at a x-ray image they can very quickly pick out the IED components and that includes the detonator. When I do x-ray interpretation training with them and a student says "That is the explosive" I ask them why they think that is the explosive in a black and white image. They always respond "because I can see the detonator inside of that area". Thier ability to pick out a detonator in a complex background is pretty impressive but the reality is that they can do this because of HOW THEY ARE TRAINED. They are trained to know what a detonator looks like in x-ray and also know what the key identification features of a detonator are.

Placement of the Detonator into the explosive

Detonators or also known as Blasting Caps are used to initiate (set off) High Explosives (have a burn rate over the speed of sound). Detonators have to have a high explosive at the end because they need to have enough power to provide enough Heat, Shock, and friction to set of the explosive. This High explosives in the detonator is very important and requires the end of the detonator to be imbedded in the explosive material and have 360-degree contact. The detonator also has to be inserted at one end of the explosives' material to felicitate the propagation of the explosive wave. What I just explained is where I see many TIP images get it totally wrong and you will see detonators not inserted into the explosive (next to it, etc.) or they are not inserted on the end of the explosive material.

The above image are just some examples of what I see all of the time in TIP IED libraries. This is because whoever is making the library is lazy and does not understand how IEDs are put together. There are many other things also wrong with the above IED's but the Detonator not being inserted into the explosive main charge is the main point I want you to see. These IED's will not detonate the main charge if it is a high explosives'.

The above image shows you how the detonator must be inserted into one end of the explosive to once it goes off it will spread the reaction through all of the explosive material and not cause a Low order. A Low Order is when the explosive only partially is set off and most of it does not explode. this is typically because the detonator was inserted incorrectly.

Types of Detonators and internal components

Detonators can be 1st broken down into two main categories and each category can have many subcategories depending on how the detonators were manufactured.

Category A: Commercially manufactured Detonators

Category A Subcategory 1: Electrically initiated Detonators

• Bridge wire instantaneous (Aluminum and Copper Shell)
• Bridge wire Delay (Aluminum and Copper Shell)
• Fusehead instantaneous (Aluminum and Copper Shell)
• Fusehead Delay (Aluminum and Copper Shell)

Category A Subcategory 2: Nonelectric Detonators

• Time or safety fuse initiated nonelectrical detonators.
• Shock tube or Nonel initiated nonelectrical detonators.

Category B: Improvised or homemade Detonators

Category A Commercial Detonators

The learn how these are made the best place to start looking is for the patents for these products. these patents will provide you very detailed descriptions of the internal components of each type of detonator. Once you know this information you will have a really good idea on what they should look like in a -ray image.

Patent Electrical Bridge wire delay Detonator: US2999460A - Electric blasting cap - Google Patents

The commercial bridge wire detonator is one of the more common types on the market along with the Fusehead type detonators. The internal components have some similarities but depending on the type (Delay or instantaneous) there can be many variations with the internal components. How well these are seen in x-ray is dependent on if you are using a checkpoint security x-ray or a Bomb Technician Portable x-ray. The checkpoint x-ray systems (even CT) have poor resolution (lp/mm) and most of the internal components in a detonator cannot be seen and will pixelate. However, there are some key identification features that you can see with these systems.

In the above image we see a side by side of a patent diagram of a bridge wire delay detonator compared to a checkpoint x-ray of a real bridge wire delay detonator from Dyno Nobel. This one might seem odd to most people because the blue area inside of the Dyno Nobel detonator x-ray is not something most people know about. This is actually one-way manufactures encase the delay element and primer charges in a metal sleeve whereas others will use a plastic sleeve. If the Manufacture uses metal or plastic to sleeve the delay and primer charges will play a significant role in what a -ray operator will see in the x-ray image. This type of detonator is not typically taught to x-ray screeners and the reason is people just do not know how detonators are made. Even Bomb Technicians who are supposed to be the experts are NOT experts on the internal make up of detonators and blasting caps. This lack of in-depth understanding is why the training thus far is very limited and, in some cases, incorrect.

In the above you can see that the dyno Nobel delay detonator is uses a steel sleeve to protect the delay element and primer charge. steel in a checkpoint x-ray will show up in the color blue. The base charges (typically PETN but can use RDX) are organic explosives' and will show up in an aluminum shell in the color orange. The plastics they use in the detonators are very low density and will typically not be seen in an x-ray image from a checkpoint x-ray.

In the above image we are looking at the same Dyno Nobel Detonators but from a checkpoint x-ray system that has better quality detector boards. This provides a better lp/mm and improves the overall image quality and also decreases the bad pixelation we saw in the first image. While this is a much better image, we can still see that all of the items that are actually inside of the Dyno Nobel detonator cannot be imaged by checkpoint x-ray systems. (CT image quality is typically worse).

What we can see is what is important and also what we should be teaching x-ray operators to be looking for. So, when we look at this image, we have to know what we are looking at so you can detail to the x-ray operator what it is they are seeing and will see when looking for a detonator type threat.

1. We clearly see 2 duplex wires going into the detonator and this is common to all detonators. These wires are typically in the 20-21 AWG and DO NOT look anything like the wires that are common in a person's personal belongings (laptop power cord, USB cables, etc.). This is another thing you do not see being taught to x-ray operators when looking for a IED type threat in an x-ray image.
2. As the 2 wires go into the detonator, they are very aligned to each other, and this is caused by the plug they are passing through. This is also very common to all electrical detonators.
3. At the end of the 2 wires are can actually see the bridge wire which will have a small dark area. They will use different metals, but most are very dense (like tungsten or gold). You will get a semi glowing black area around these bridge wires.
4. We can see that the tube is made from aluminum and that is the green outline you see in the x-ray image. If this was a copper shell it would be blue in color and the internal components harder to see.
5. We can see the steel sleeve showing up in a very distinctive blue color.
6. At the end of the detonator, we can see the base charge (PETN) showing up in an orange color because it is an organic based explosive.

The other type of bridge wire detonator is the instantaneous detonator, and this one will not have a delay element inside of the shell. in the below image we are showing you the M6 electrical instantaneous detonator and all of the internal components. When you compare this to the delay detonator you can see that there are some common parts that are exactly the same used in both detonators.

When we look at this detonator in a checkpoint x-ray, we can see a very distinctive difference between the Dyno Nobel steel sleeve delay detonator.

As you can see in the above images of a M6 instantaneous Bridge Wire Detonator the Lead Azide/Lead Styphnate shows up in a Black color right after where the 2 wires end at the Bridgewire. You can also see the PETN (Organic/Orange) base charge. Because this is an aluminum shell (most common) you are able to see the base charge color. If this were a Copper shell Detonator you would not be able to see the color orange. You can also see that the 2 wires are inserted about halfway into the aluminum shell. Where the wires go into the Detonator, they will use a Plug Assembly, and this can be made from a plastic or rubber type material but typically cannot be seen in checkpoint security x-ray systems. However, with a Bomb Technician/Disposal portable x-ray you can make out the Plug assembly and even the crimps in the aluminum shell that holds it in place.

Fuse Head Electrical Detonators

The next type of detonator and the more common used worldwide is the fuzehead detonator. These detonators use a pyrotechnic type of electrically initiated matchhead to set off the detonator. These fuzeheads are similar to a fireworks electrical match but are more powerful and look a little different in x-ray. The tip of the fuzehead will be much darker than what a fireworks style e-match will look in x-ray. On the outside they look just like any other electrical detonator but internally the fuzehead will give you a second BLACK dot just before where the lead azide/lead styphnate is located. Some people even refer to these as "Snake eyes" because of the 2 black areas inside of the detonator.

The Fusehead style of detonator can come in an instantaneous and delay version just like the bridgewire electrical detonators. The delay element portions are the same version that are used with the bridgewire detonators. Some can have a plastic or metal metal sleeve around the delay element. the plastic sleeves do not show up very well in a checkpoint x-ray, but the metal sleeves will and have the same blue color you saw in the bridgewire detonator.

In the below image you can see the difference between a standard fireworks e-match and a fuzehead used in an electrical detonator. the pyrotechnic material at the tip of the e-match is a much lighter color vs the fuzehead. The e-match does have a dark spot, but this is the lead at the base and not the actual pyrotechnic material at the tip.

What you will see in INERT training aides are companies using e-matches to try and simulate a fuzehead detonator. This is not accurate as you now know based on how they are actually constructed. E-matches are used in homemade detonators and was a favorite of ISIS but they are not the same as a fuzehead when x-rayed. We will look at improvised detonators in part 2 of this series.

This concludes Part 1 of Detonator Detection