Robin--
I think you are wrong about the nature of Bremsstrahlung.
As I understand, the effect is caused by a charged particle changing its
course--being accelerated--in an electric field. It is not the mass of the
particle but the charge of the stationary particle. Large nuclei have
greater positive charge to deflect an energetic electron. The captured
electrons around a nuclei also pose a integrated electric field much more
diffuse than that associated with a large point charge. Energetic
electrons are not accelerated as much by the diffuse negative charge
presented by cloud of electrons as a stationary "solid" nucleus does.
Slower electrons interact with other electron charge density and are
deflected to produce Bremsstrahlung.
That being said, an energetic proton will also produce Bremsstrahlung
radiation as it is deflected by other heavy, large, positive nuclei.
Bob
-----Original Message-----
From: mix...@bigpond.com
Sent: Friday, March 11, 2016 1:25 PM
To: vortex-l@eskimo.com
Subject: Re: [Vo]: Bremsstrahlung experimental note
In reply to Bob Cook's message of Fri, 11 Mar 2016 09:34:55 -0800:
Hi,
[snip]
The effectiveness of the SS can at stopping any high energy electrons that
cause Bremsstrahlung would depend upon the thickness of the can (or
alumina) and the energy of the incident electrons. I think the loss of
energy per scattering event is proportional to Z ^2 for the nucleus that is
doing the scattering. Al at Z=13 and with Fe at Z=26 the intensity of the
Bremsstrahlung signal would be about a factor of 4 different. The mean
length of the path of an electron is a good parameter to know for any given
substance (basically its density) vs the incident energy of the electron.
Shielding engineering curves provide this information I believe. Iron
being significantly more dense than Al2O3 would be much better at slowing
electrons and thus producing Bremsstrahlung IMHO.
Shielding is based primarily on the electrons of an atom being ionized.
Bremsstrahlung is created when a fast particle interacts with a nucleus.
Most fast electrons impinging on solid matter will create ionization, i.e.
they
get stopped by other electrons. AFAIK Only about 1% get through to the
nucleus
and create Bremsstrahlung. I think that both nuclear charge and number of
nuclei
per unit volume would be important for Bremsstrahlung production. Mass of a
nucleus not so much, because even a single proton is already about 2000
times
more massive than an electron. When it comes to collisions, it makes little
difference whether the nucleus is light or heavy. In short any nucleus is
effectively an "immovable object" as far as an electron is concerned.
BTW if MeV level electrons are stopped by Aluminium foil, then the can would
have to be very thin not to stop them.
Has anyone considered the possibility that some (little) bremsstrahlung
might be
caused by fast protons impacting on heavier nuclei?
Regards,
Robin van Spaandonk
http://rvanspaa.freehostia.com/project.html
