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908 views
05:38 Sep-27-2008
T.J.J.K
Ionization by Radiography

When radiation penetrates a material , depending on energy of radiation electrons are being ejected (Compton,Pairproduction& Photoelectric effect ).

Is this loss a permanent loss & if permanant does the loss of electrons leads to Ionization.

If Ionization happens how does the atom regain the electrons.
( The main process by which the Film is exposed is ejection electron by the radiation as it passes through the lead intensification screen, Does this lead to Ionization of the Intensification screens , Is this Ionization permanent or does it happen?)


 
02:37 Sep-28-2008

N.Kuppusamy

Consultant, NDT Level-III Engineer
Advanced Inspection & Testing (S) Pte Ltd,
Singapore,
Joined Dec 2003
34
Re: Ionization by Radiography Electron loss in the material is not permanent. It immediately acquired the required electrons from the atmosphere and neighboring atom. The atmosphere replenish their lost ions from cosmic radiation.

The lead screen also replenish their electron from atmosphere when the radiant source is removed. This is called reversible reaction.

But the films made of photosensitive chemicals and they undergo photochemical reaction when exposed to photons (electromagnetic radiation).

When a film is exposed, the Silver from Silver Bromide emulsion is reduced to metallic Silver and Bromine remains in electronegative state (actually the AgBr molecule become polarized to Ag+ and Br- . This photochemical reaction is irreversible and cannot replenish its electron deficiency from atmosphere.

The development process reduces the delta Ag+ to metallic Ag and forms the latent image of the object radiographed. This latent image is fixed and unwanted Br- is removed in the fixer solution.

I learn these details 25 years before in my Level-II course.

Now I wonder how the new generation practitioners lacking this fundamental knowledge even after 25 years of advancement in technology.

Regards,
N.Kuppusamy




 
07:40 Sep-29-2008

chris s

Consultant, qc manager
USA,
Joined Apr 2007
9
Re: Ionization by Radiography ----------- Start Original Message -----------
: Electron loss in the material is not permanent. It immediately acquired the required electrons from the atmosphere and neighboring atom. The atmosphere replenish their lost ions from cosmic radiation.
: The lead screen also replenish their electron from atmosphere when the radiant source is removed. This is called reversible reaction.
: But the films made of photosensitive chemicals and they undergo photochemical reaction when exposed to photons (electromagnetic radiation).
: When a film is exposed, the Silver from Silver Bromide emulsion is reduced to metallic Silver and Bromine remains in electronegative state (actually the AgBr molecule become polarized to Ag+ and Br- . This photochemical reaction is irreversible and cannot replenish its electron deficiency from atmosphere.
: The development process reduces the delta Ag+ to metallic Ag and forms the latent image of the object radiographed. This latent image is fixed and unwanted Br- is removed in the fixer solution.
: I learn these details 25 years before in my Level-II course.
: Now I wonder how the new generation practitioners lacking this fundamental knowledge even after 25 years of advancement in technology.
: Regards,
: N.Kuppusamy
------------ End Original Message ------------

Everyone has to start somewhere. Not everyone is as endowed as you sir.


 
09:34 Oct-01-2008

Nick Welland

Other, Quality and NDT
Aben Technical Services,
Australia,
Joined Oct 1999
42
Re: Ionization by Radiography ----------- Start Original Message -----------
: : Electron loss in the material is not permanent. It immediately acquired the required electrons from the atmosphere and neighboring atom. The atmosphere replenish their lost ions from cosmic radiation.
: : The lead screen also replenish their electron from atmosphere when the radiant source is removed. This is called reversible reaction.
: : But the films made of photosensitive chemicals and they undergo photochemical reaction when exposed to photons (electromagnetic radiation).
: : When a film is exposed, the Silver from Silver Bromide emulsion is reduced to metallic Silver and Bromine remains in electronegative state (actually the AgBr molecule become polarized to Ag+ and Br- . This photochemical reaction is irreversible and cannot replenish its electron deficiency from atmosphere.
: : The development process reduces the delta Ag+ to metallic Ag and forms the latent image of the object radiographed. This latent image is fixed and unwanted Br- is removed in the fixer solution.
: : I learn these details 25 years before in my Level-II course.
: : Now I wonder how the new generation practitioners lacking this fundamental knowledge even after 25 years of advancement in technology.
: : Regards,
: : N.Kuppusamy
: Everyone has to start somewhere. Not everyone is as endowed as you sir.
------------ End Original Message ------------

Knowledge is not endowed, it is worked for. The loss of fundamental knowledge is not restricted to our own field; stories abound that some first-year university students are functionally illiterate, which news I find frightening.
I ascribe much of the decline to the philosophy of "teaching to the exam" where the object is to gain a qualification rather than knowledge per se.
We "stand on the shoulders of giants", but it behoves us to ensure that a cadre is educated to carry on!
Regards,
NW


 


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