radiography101
Please log in to view forum, once you signed up please leave a message on the shout out thread for your first post. Introduce yourself and let yourself known to the group state your name and section for your user name use your first name so we can identify you as a RT student. For alumni you can post on the alumni section.
Members that has not yet posted a single post 30days after they are a member will be remove from the group. keep this forum alive for all RadTechs!!
Log in

I forgot my password

Latest topics
» Anniversary of the Discovery of X-Ray
by Admin Sat Nov 05, 2011 10:51 am

» First time members click here to join the fun
by Samjaypineda Fri Nov 04, 2011 10:40 pm

» RADICAL:THE COMIC SERIES
by muyco Tue Aug 16, 2011 1:35 pm

» EdmefoWkes
by Guest Tue Aug 02, 2011 4:52 am

» RT Day with other RT School ( s)
by Polon PearL Thu Jul 07, 2011 9:16 pm

Who is online?
In total there are 2 users online :: 0 Registered, 0 Hidden and 2 Guests

None

[ View the whole list ]


Most users ever online was 41 on Tue Oct 22, 2013 8:58 am
Poll

what is your thought for e-learning

50% 50% [ 4 ]
38% 38% [ 3 ]
13% 13% [ 1 ]

Total Votes : 8


X-ray Tubes

Go down

X-ray Tubes

Post by Joshua on Tue Sep 08, 2009 4:12 pm

X-rays tubes

Any high-speed electron
that strikes a metal target might release an x-ray. However x-ray
tubes were developed
1. to increase the efficiency of production
2. to provide control over the type of x-rays that emerge.




Early X-ray tubes were gas discharge tubes made essentially for
producing
cathode rays. They consisted of a partially evacuated glass bulb containing two electrodes. This was commonly known as a Crooke’s tube. By connecting a voltage across the electrodes, the gas became ionised. Positive ions were then attracted to the cathode and upon striking it, imparted their energy to it, causing electrons to escape. These electrons, in the form of a beam of cathode rays, bombard the glass walls of the tube and produce X-rays. Such tubes produced only soft X-rays of low energy.

An early improvement in the x-ray tube was the introduction of a curved cathode to focus the beam of electrons on a metal target (of high atomic number), called the anode. This type generates harder rays of shorter wavelengths and of greater energy than those produced by the original Crookes tube.

The next great improvement was made in 1913 by the American physicist William David Coolidge.



He designed an x-ray tube, which incorporated a number of improvements.

1. It contained a heated filament to release electrons from the cathode (by a process called
thermionic emission).
2. It contained a cooling system to remove unwanted heat from the target.

3. It was more highly evacuated. The Coolidge tube greatly increased the efficiency of x-ray production. It also offered
independent control of the
intensity and penetrating power of x-rays. Most of the x-ray tubes in present-day usage are modified Coolidge tubes.

How x-ray tubes control the quality of x-rays released

1. If the filament current is increased, more heat is released, therefore more electrons are released and so more electrons travel to the target. Consequently, more x-rays are released, and so the intensity of the x-ray beam is increased.

2. If the voltage between cathode and anode is increased, the electrons are accelerated to higher speeds and so have greater energy when they hit the target. Consequently when their energy is converted to a
photon of radiation, the photon has greater energy (E = hf). A higher energy photon corresponds to a higher frequency of radiation and so to a more penetrating x-ray. The intensity of the x-rays refers to the energy passing through unit area per
second.
The ability of x-rays to penetrate matter is related to their frequency.
avatar
Joshua

Posts : 9
Join date : 2009-08-19
Age : 40

Back to top Go down

Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum