The only real difference between X-Rays and Gamma Rays is the way they are produced.
X-rays are produced electrically in a tube head. Gamma rays are produced by radioactive isotopes such as Iridium and
cobalt.
X-Ray machines require a power source, whereas gamma projectors dont, so gamma is more practical for field work, however
X-Ray machines produce a better quality of radiation usually resulting in better quality radiographs.
X and Gamma rays are identical except the way they are produced, X ray tubes also have a smaller focal spot which accounts for the better picture
x-ray tubes produce a single ray. I believe gamma (IR192) produced 3. making x rays a little cleaner in addition to smaller focal spot.
I think your thinking of cobalt when you quote 3. IR192 has close to 23 as I recall. Apples to apples source size, cobalt will make a better radiograph. Not to many people running around the country side with cobalt. Though given the energy though cleaner, is higher for Co60.
Can't have the natives freaking out because they see half the plant plastered with rad signs.
CWI555 & Hogan,
I'll meet you guys halfway......I'm thinking that Ir-192 has 12 principle gammas and Co-60 has two. I guess when you think about it, a Cobalt source with only a couple of wave lengths would make a better radiograph than Iridium, but like most of you, I only see radiographs made with Cobalt on very thick items which usually gives the image that "fuzzy" look.
~thirdeye~
I have shot with 110ci Co60 on a 20' x 5/8" vessel and it was fuzzy compared to the seams that we used a 150 ci Ir192 source, I have also shot concrete with both and find that cobalt was fuzzier. I believe it is mostly due to the larger focal spot on the cobalt source, I believe the focal spot was three times the size of the iridium source, In one of the seems we shot we found some slag that the cobalt source had completely missed, the AI had us re-shoot the entire vessel with iridium. And if your cobalt camera need rad placards you need a new camera, with 110ci we had a surface reading of 7 mr in a spec 300.
That was why the comments in regards to source size.
i spent a couple of years working with a 100 ci CO60 source. not a lot of fun. we were doing panoramic on a 28' digester with a 4 1/2" wall. some as triple loads due to repairs. I figured you would clear up what i was trying to convey. thanks
An X-ray machine can produce a range of energies, within the range there will be soft (garbage) and hard radiation controlled with filters/screens.
Gamma rays "Average energies" most isotopes emit 2 or more gamma rays (they cannot change). Cobalt 60 emits two gamma rays, with an average level 1.2 mev.
I would guess that some reasons for choosing one over the other depend on the application.
1 A code might dictate one or the other.
2 Thickness range of material being examined.
3 location of inspection area (shop or field).
4 type of flaw in question.
There are many pros and cons to each type.
All that has been said above is absolutely right. However, nobody has said which is the scientific difference between x rays and gamma rays.
The difference is the following:
X rays wave length is from 0.001 to 10 nanometers. Gamma rays wavelength is from 0.000001 (one millionth) to 0.1 nanometers.
One nanometer is one millionth of a millimeter, or to put it in another way, one billionth of a meter (you translate into millionth of an inch)
Giovanni S. Crisi
Sao Paulo - Brazil
Wow! That's pretty deep! Very impressive, no joke.
In light of the previous posts mine could seem trivial, however I was a C3 radiographer and so... heres my two cents.
In practical applications X-ray tubes are not generally used in the field due to the fragile nature of the tubes and the need for a great deal of electrical power for higher Kv tubes for industrial radiography. What you will get with the X-ray over the Gamma source is sensitivity! The absolute best radiographs you will see are in the aero/space industries which will use X-ray in most instances. In my experience the most sensitive I could ever get with Ir-192 was the #5 wire on an "A" penne. I have seen the #1 wire on an X-ray radiograph of a vertical stablizer. Very cool stuff!
As far as Co-60 is concerned on paper it may have a better quality of beam than Ir-192 but you could never convince me of it. As stated before, the applications where you would use Co-60 are in a word "THICK"! The radiographs look fuzzy and the overall image quality is poor. Using a class-I film helps but not much. Usually when you are using Co-60 your looking for gross indications or information only. Time is usually a factor in these situations so class-II film is used more times than not. Co-60 is gorilla radiography IMO, but I have never seen a panoramic with a really long stand off using Co-60. I could imagine the image quality being a little better... I don't know.
Recently, selenium-75 is being actively promoted as an alternative source. It has a lower emissivity(penetrating power) but has good image quality, and is the source of choice with digital radiography. Which I would like to add is really cool! I personally like the Fuji system. As far as image quality it is as close to an actual film image as you can get with current technology.
All that has been said is well and good, very informative.The biggest difference is the portability in most industries and the need of a power source.
With all the variables found in radiography, making the right choice on film type, exposure techniques and processing conditions could produce similar results. Material grades, thickness, location, and geometric limitations play a big part in choosing the type of source to use also.
Iridium 192 vs Cobalt 60, they each have their place. Iridium in the lower thickness range and cobalt in the higher. Cobalt is a hotter source with a larger focal spot, and is best used in material 2" and larger, unless a large source to film distances can be used.
X-ray machines have a wide range of control, and in the most part is a lab type setting. Although there are units that can be mobile and used in the field, most times it would be impractical and more costly to set up for some industries.
Safety controls would be the same for each, with the exception of storage of equipment and licensing. Dependent on the energy levels being used and site conditions the controlled area would be larger with those at the higher energy levels.
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