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Re: Cloud chambers



I once opened a pressure cooker and saw tracks for over a minute.
Returning to the original question the teacher mentioned using lateen
mantles. I wonder if he used them earlier when it worked. I've found
that with small diffusion CC's other than a very low activity source
will "poison" the chamber. When I've not had a fractional micro Ci.
source, tracks occur only on introduction of the source (fraction of a
second) then one must withdraw the source for several minuses (a
clearing field may speed this up.). As LK (JR) pointed out the chamber
must have minimal leakage, tho as w/ the source a larger chamber is more
forgiving. The Cenco chamber has a small stopper sized hole for the
source, mounted on a needle stuck in a rubber cork. JR makes giant
chambers at correspondingly astronomical prices. Bruce
Denardo purchased one for the Modern Phys. Lab I "run". It is
impressive and additional source(s) are unnecessary at least in a
concrete building. Cosmic ray dendritus may be all we saw. For a time
UCB had an experiment using rather small (~ half the diameter of
Cenco's) Chambers. I took several at the not so recent give away, and
haven't tried one.

bc

p.s. The exploratorium has a gargantuan refrigerated one. There are
usually a number of CR tracks simultaneously *. I wonder if it is one
of JR's

p.p.s. I presume the JHST had this problem ~ > ten years ago, as since
then Th is a no no. I had to got to France to find Th mantles, and they
were phasing them out. I bought all the ones at the back of the rack 55
FF each, ouch.

Must review my video -- I was more interested in the unusual pattern the
drops made in the bottom liquid.


Ludwik Kowalski wrote:

In browsing the Internet I found a question that a physics
teacher asked and the answer provided by Jack Uretsky. This
was not found in in the Phys-L archive; the items are not
dated. I am pasting them for two reasons: (A) to show an
example of misunderstanding (this is not important,
questions are not always asked clearly) and (B) to show
how I understand the operation of a diffusion cloud chamber.

A) Note that the teacher was asking about a diffusion cloud
chamber while Jack's answer referred to an expansion cloud
chamber. Information about commercially available diffusion
cloud chambers can be found at:

<http://www.cloudchambers.com>

That gadget seems to be worth having; like a Geiger
counter a diffusion chamber shows that nuclear processes
are constantly occurring in our environment. Unlike old
expansion chambers they react to charged particles
constantly (rather than only for short intervals after
each expansion).

Question: I am a junior high Science teacher. For the
past two years I have tried to help my students build
cloud chambers. We use small plastic dishes with
black felt on the bottom and a black paper ring around
the inside edge. We use Coleman lantern mantles and
91% isopropyl alcohol. We place this in a Wendy's
salad container along with vermiculite and dry ice.