From: jtchew@csa3.lbl.gov (Ad absurdum per aspera)
Newsgroups: alt.folklore.urban
Subject: Re: "Microwave in Use"
Date: 19 Nov 1992 14:42 PST
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: world
NNTP-Posting-Host: 128.3.254.198
Summary: What would happen to Schroedinger's cat in the SSC
News-Software: VAX/VMS VNEWS 1.41    

>> So what would happen if you put a paper towel into one of the accelerators?
>> And has anyone ever fried their intestines by standing too close to one?

> I can't speak for Joe's operations

Heh.  Joe's a strategically placed administrative flunky with a technical
background that may impress The Celebrated Man In The Street but is just
short of risible around here.  But anyway...

Accelerator safety is usually concerned with ionizing radiation (x-rays,
prompt and secondary neutrons, and various other particles depending on
energy), and with high voltage and high stored power.  RF is usually
neglected as a risk factor to anyone or anything outside the accelerator,
being contained within conductive waveguides and beamlines.  (Improper
rf supply could cause beam losses with radiation safety implications.)
You could probably stand by the accelerator at full rf power/no beam
with impunity, assuming the interlock system and the safety officer
saw fit to let you do so.  But you wouldn't want to tangle with that
much rf power in free space!  

I honestly don't know what would happen to a paper towel in an accelerator.
The smartass answer is "it'd get sucked up during rough vacuum pumpdown."
For physical scale, we're usually talking about a stainless steel pipe a
few inches in inside diameter in modern synchrotrons and storage rings.
Assuming it stayed in there... well, with many hundreds of kW on tap, 
usually at VHF through UHF, any conductivity it might exhibit would give 
it a short, exciting life.  However, it probably wouldn't burn, since the
insides of an accelerator are at high to ultrahigh vacuum.  Destructive 
distillation -- "Bounty, the coked picker-upper"?  It could conceivably 
just sit there, getting more and more micron-scale holes in it from the 
beam, until eventually it quietly turned to dust and went up the pumps.
Or, depending on beam energy and intensity, not so quietly.  Anybody 
know, offhand, what the interaction cross section is for 20 TeV protons
on wadded-up cellulose?  :)

Some beams are a lot more sensitive to running into things than are 
others.  It stands to reason that, in a machine kept at UHV like a
modern electron storage ring, any junk on any scale that got put into
the beampipe would cause serious performance degradation and loss of
stored beam -- if you're worried about Touschek scattering from a few
random air molecules, for instance, a wadded-up paper towel probably 
won't help your cause any! 

A much simpler experiment, equivalent from an rf standpoint, would be to 
put said towel near a TV station's antenna. Hint:  put the towel in place 
while the station is off the air.  This will increase your chances of
coming down in one piece and in a controlled fashion.  

I don't know if anybody ever fried his guts with high-power microwaves.
But cataracts were one of the first theoretically predicted biological
effects of microwaves and showed up clinically sometimes until the
proper safety procedures (turn the $^&(%*! magnetron off before you sight
down the beamline) were figured out.  A couple of ULs (you knew I'd get
to a UL eventually) are that, in the early days of radar, naval radar
operators would cook eggs by tossing them into the beam, sell beam
exposure to sailors as "VD treatments" or "contraception," etc.  Those
two ULs would seem mutually exclusive, but "No one ever went broke," etc...

People long ago gave up exposing themselves to the particle beam just 
for grins, although it can be done safely if you know what you're doing 
in terms of dose.  (We're all being irradiated all the time, but how,
and at what dose rate and total dose, is of some fiddling significance. :)
A classic experiment was performed at the Bevatron to explain the little
sparklies the early astronauts saw, for example, and particle-beam 
treatments are used widely for medical treatment.

--Joe
"Just another personal opinion from the People's Republic of Berkeley"