Re: X RAYS

[Bob Sciamanda <trebor@VELOCITY.NET>]

The source is an "X-Ray tube" - a diode in which electrons from a cathode
are accelerated toward, and slam into, a positive anode.  The kinetic
energy of the stopped electrons "is transformed" into radiation by two
major processes:
1.) a broad spectrum of "Bremstrahlung" (braking) radiation and
2.) radiation characteristic of electronic transitions within the atoms of
the anode target (when oncoming electrons eject an electron from an inner
electronic shell).

The operator controls the "on time", the anode potential (kV), and the
electron current (mA) .  The latter is typically controlled by varying the
filament temperature.

The maximum possible X-Ray photon energy is limited by the anode potential
(kV).
The electron current determines the beam intensity.
Overall exposure is a function of all three parameters (kV, mA, and
on-time).
Beam filtering and "spatial shaping" through the interposition of specific
absorbing materials are also an important operator-controlled variables.

Corrections, amplifications, etc are invited.

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: "David Abineri" <dabineri@CHOICE.NET>
To: <PHYS-L@lists.nau.edu>
Sent: Friday, December 29, 2000 08:44 AM
Subject: X RAYS


> While this subject is up, can anyone tell what is used as the source of
> dental (and perhaps other medical) x rays and roughly how is the
> exposure time and intensity controlled?
>
> Thanks,      Dave Abineri
>
>
> --
>  David Abineri   dabineri@choice.net