I thought the cavities or really 1/4 wavelength lines were neat. Normally
a 1/4 wavelength for 1MHz would be 75 meters long. But the ferrite rings
lowers the propagation velocity a great deal and makes these tuned sections
much shorter. Not only that, by passing DC thru a current loop they can
tune the resonant frequency of the lines. The lines are needed to produce
high voltage RF in the gap to accelerate the charged particles.
73
Bill wa4lav
At 07:31 AM 9/16/2008 -0400, David G4FTC wrote:
> >
> > Neat link. Tetrode-based RF drivers and associated ferrite-loaded
> acceleration cavities are the mainstay of most large proton and heavy ion
> synchrotrons. A brand new machine is being operated at KEK-JAERI in
> Japan, with multiple 500 kW tetrode amplifiers using TH558 devices - very
> large tubes. The CERN PS and PS booster are a pair of synchrotrons that
> provide the particle velocity that then travels into the SPS, their
> super-proton synchrotron. All of these machines have been running for
> years, with some modifications. Being able to sweep frequency rapidly,
> they use DC bias tuning coils on the ferrite cores. The amplifiers have
> either tunable input or broadband design, and the output is directly
> connected to the ferrite-filled resonator via loop(s). In the SPS, they
> use two huge amplifier arrangements, each having 4 combined 125 kW Thales
> (formerly Seimens) tetrodes, type RS2004J, driven by one. With this they
> get about 500 kW of CW power at 200 MHz. These two are combined to
> > get one
> > output even higher power.
> >
> > They also use big Klystrons at CERN in the actual LHC ring, the big one
> we hear about a lot these days.
> >
>
>I noticed the klystons - 48 x 100kw units to produce 4.8MW at 400MHz.
>
>I also noticed the cooling arrangements for the ring - liquid helium to
>maintain the 1.7 Kelvin temperature. If you click on the ring graphic on
>http://lhc.web.cern.ch/lhc/ you will get the real time temperature
>readings for the magnets etc in the ring.
>
>The power supplies are also quite amazing = 18V at 18000 amps at 5mV ripple.
>
>Engineering in the extreme!
>
>
>But the thing which really caught my attention was that the beam energy
>for the operational LHC will be about 1GJ, and that the LHC
>embodies systems to dump the beam in the event of an emergency.
>
>It makes our recent discussions on how best to dump a few hundred Joules
>from a power supply pale into insignificance.
>
>Regards
>
>David G4FTC
>
>
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