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Re: [Amps] Tetrode amplifiers at LHC

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Subject: Re: [Amps] Tetrode amplifiers at LHC
From: David G4FTC <>
Date: Tue, 16 Sep 2008 11:31:08 +0000
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> 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 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.


David G4FTC 

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