Cockroft Walton Qu.
entro...@yahoo.com
have more questions than ever. In paricular about the Cockroft Walton
accelerator. The Cockroft Walton (CW) is a votage multiplier,a ladder
of capacitors and diodes or rectifiers. it seems on could just build
that on a circuit board. The device I saw stands about 20 feet
tall,has several legs .So several questions.....Where is the hydrogen
injected..top or bottom?,.....Is the output to the linac from the
large cube on top? What is the function of the three legs and cross
tubes? What is inside of these? I 've so far been unable to get a good
inside anatomy of the CW at fermi,but if anyone is familiar with this
please let me know. Thanks jk
Tom Roberts
> I 've just returned from a great tour of the Fermi Lab and of course
> have more questions than ever. In paricular about the Cockroft Walton
> accelerator. The Cockroft Walton (CW) is a votage multiplier,a ladder
> of capacitors and diodes or rectifiers. it seems on could just build
> that on a circuit board.
No, because surface currents would short out the high voltage. But low
voltage versions of this type of circuit can be built on a circuit
board. For voltages above a kilo-Volt or so one must be careful of
electrostatic discharge, because the air and grime on surfaces can
ionize -- this ionization can quickly become a spark that shorts the
circuit.
> The device I saw stands about 20 feet
> tall,has several legs .So several questions.....Where is the hydrogen
> injected..top or bottom?
There is a glass tube that goes from the HV terminal to the wall. It is
several feet in diameter, and contains the hydrogen input line and the
accelerating column (in which the H- ions come out). The ion source is
inside the HV terminal (which is at -750 kV relative to ground); it
converts the hydrogen into the H- ions which are electrostatically
accelerated between the negative HV and ground.
There is a picture here:
http://www.fnal.gov/pub/inquiring/physics/accelerators/chainaccel.html
The high-voltage generator is on the left (tall and narrow), connected
to the ion source (squarish box held up in the air), and the
accelerating column is on the right headed to the Linac.
> Is the output to the linac from the
> large cube on top?
Yes. That is the HV terminal containing the ion source.
> What is the function of the three legs and cross
> tubes?
The legs support the terminals at the top (where the real work happens).
The legs have those metallic domes at intervals along them to control
the voltage profile along the legs (resistors inside the legs keep it
uniform). I believe the diagonal tubes between the legs of the HV
generator are the voltage multiplier circuit, but am not certain.
> What is inside of these? I 've so far been unable to get a good
> inside anatomy of the CW at fermi,but if anyone is familiar with this
> please let me know.
I don't know the details.
Tom Roberts