The Salad Bowl Accelerator
This is a small model of a particle accelerator that can be
used to explain the workings of much larger, research
accelerator such as the Large Hadron Collider at CERN. More background can be found at
royalholloway.ac.uk/PPresources.
Materials:
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ping-pong ball(s)
conductive paint e.g. nickel screening compound (Part# 167-5347) from Farnell
(uk.farnell.com)
plastic salad bowl, needs to be a very good insulator (pyrex / glass is not good)
aluminium (or copper) foil adhesive tape (1-2cm width)
Van de Graaff generator
Electrical leads and crocodile clips
Method:
1. Place one set of metal tape strips forming a
cross over the centre of the bowl (as shown in
picture). Pro tip: cutting rounded ends of the
strips is best to avoid charge leaking from
sharp corners.
2. Place four more strips of metal tape
equidistant around the bowl, but not touching
the centre.
3. Connect the first cross to the top of the Van de
Graaff generator.
4. Connect all other strips to the ground terminal
of the Van de Graaff.
N.B. make sure the high voltage and ground leads don't touch each other. This is
because at high enough voltage there is a current leak through the insulation on the
lead, which stops the accelerator from working.
5. Coat a ping pong ball in conductive paint.
6. Place the coated ball in the bowl and switch on the Van de Graaff.
Safety:
Follow the normal safety procedures for using a Van de Graaff generator and in addition,
avoid touching the strips while they are live. Although the low current means that harmful
shocks are unlikely, it should not be used by people with heart conditions/pacemakers.
For any questions, further advice, or more demos, visit
royalholloway.ac.uk/physics/outreach or email [email protected].