Re: relativity labs

[brian whatcott <inet@INTELLISYS.NET>]

There is a product that uses a principle that brings to mind
Bernard's suggestion. Oscilloscope design seeks to reconcile
conflicting objectives (like most products...).
One desires a bright trace, a sensitive deflection amplifier
and a fast maximal timebase speed. (Not to mention solid, versatile
triggering means.)

If one increases the final anode potential, brightness increases
but deflection sensitivity decreases. The result is unsatisfactory
at fast timebase speeds, where the trace repetition rate naturally
declines, so that the trace grows dimmer and dimmer.

The solution used by Tektronix and others, was post deflection
acceleration. If one can deflect the beam at modest electron speeds,
then accelerate the beam through its trajectory to the phosphor screen,
a better brightness.sensitivity product is obtained.

Brian Whatcott

At 22:57 4/2/01 -0700, you wrote:
> I've never done this, but if easily done, I think is a more direct and
> intuitive SR demo.
>
> with a kinescope note that the deflection due to the deflection plates
> field is reduced faster than predicted with increasing anode voltage.
> i.e. the mass of the electrons has increased.  One can easily calc. if
> it should be noticeable (measurable) upon increasing the voltage from
> say 100 v. to a kilo volt.  May be not as the rest mass is ~ 1/2 mev?
> Maybe a typical tube 5BP1 can tolerate 10 kV.  10^4 / 0.55 x 10^6 --- 2
> % ?   color tubes use ~ 20 kV.  but then it's mag.. deflection and the
> intuitive nature is lost   I think telling students mag. and E fields
> are the same (because of SR) doesn't cut it.
>
> bc
>
>
>
> Ben Crowell wrote:
>
> > Does anyone know of any good relativity labs for an
> > introductory course? Jackson refers to a lab with a
> > NaI detector to verify the relativistic energy-
> > momentum relationship, but I haven't yet made the
> > pilgrimage to the closest school that has the
> > journal it's described in. Other possibilities
> > that occur to me include observing pair production
> > by cosmic rays in a cloud chamber, or doing something
> > with GPS (GPS requires general relativity
> > corrections). Ideally I'd like something affordable
> > that could be done hands-on by six lab groups,
> > each with their own equipment, but I realize that's
> > asking a lot.
> >
> > On a related note, has anyone bought and maintained
> > a NaI detector for undergraduate use? Can they
> > be gotten cheap via surplus? Is there
> > cheap ADC/histogramming software and
> > hardware for PC-compatibles?
brian whatcott <inet@intellisys.net>  Altus OK
                Eureka!