[Sneap] Charging belts for AN2500

[Ian Vickridge]

Dear SNEAPERS,
 
This is an old question but one that we are now ready to really try and
answer. HVEE no longer supplies belts for the small machines, and refers to
Passaic Rubber. However Passaic Rubber no longer furnish any accelerator
belts either. 
 
As far as I can tell, this means that when the last existing belt becomes
unusable, these small machines will all become useless, in spite of the fact
that there are still quite a number in operation after 30, 40 or perhaps
even 50 years of operation. If a small AN2500 or similar can still provide
the beams necessary for the research that is being done, it seems silly to
have to replace them with a whole brand new accelerator just because there
are no longer any belts : as far as I can tell all of the other components
in these machines can still be replaced and this is still a much cheaper
option than machine replacement. Indeed, in many cases, replacement of the
machine might not be justifiable to funding agencies, whereas continued
maintenance costs for an existing machine may be. We are certainly keen to
eke out some more years from our AN2500  (1965 or so vintage) before finally
trying to get funding to replace it - I guess with a singletron.
 
I would be interested in discussions on :
 
How many of the AN2500 and/or AN2000 machines are still in active service
around the world (including outside the SNEAP community)?
 
Amongst these, how many have teams/teaching/research programs that are
sufficiently dependant on them that there is a strong motivation to solve
the 'belt problem'?
 
What has so far been tried by those who no longer have a spare belt, or are
anticipating soon being in that position? What did the 'old hands' try all
those years ago - and what did they find that worked and what did they find
that didn't work?
 
What really are the options concerning sourcing new belts - even if the cost
is quite high? Is it possible to imagine some kind of joint or cooperative
effort to search for and test various options?
 
If there are any old HVEE belts lying around unused (and who knows .. maybe
unopened and still in their nitrogen-filled plastic bags) what is their
shelf-life likely to be?
 
Over the years I have heard a number of stories - perhaps rumours myths and
legends - about belts : that performance was very batch dependant; that the
Passaic belts, in their brief existence, were rather mechanically fragile
and prone to tearing; that no-one really knows what specific characteristics
make a good belt - it is a 'trial and error' process to find one; that the
machines for making jointless canvas-and-rubber conveyor belts have now all
worn out to the point that they are not worth repairing just for making a
few belts for some old accelerators...
 
I am keen to absorb as much information, culture and experience about Van de
Graaff belts as possible, in the hope of finding some solution to the belt
problem that is looming for these machines - with a personal bias of course
for the small HVEE machines since that is what I want to keep alive as long
as possible.
 
Thanks for sharing your thoughts and experiences
 
Ian Vickridge
Institut des NanoSciences de Paris
SAFIR, sous-sol 24-23, UPMC, Campus Jussieu, et
Campus Boucicaut, 140 rue de Lourmel 75015 Paris
+33 1 44 27 47 10 (phone)
+33 1 44 27 47 11 (fax)
 
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