The buncher develops a 14-kV peak amplitude across the resonator gap and is energized in 3 ms-long pulses at rates up to more » 24 Hz.
These bunches, which circulate at a 2.8-MHz frequency, are longitudinally confined by an rf electric field produced at that frequency by a ferrite-loaded coaxial quarter-wave resonator driven by a unique low-impedance rf amplifier. The Proton Storage Ring (PSR) now under construction at Los Alamos National Laboratory is a device designed to accept a proton beam from the 800-MeV linear accelerator (LAMPF) and accumulate the protons to provide short, extremely high intensity bursts that drive a high-flux pulsed-neutron source. For the stacking cavity, operating at 4.45 MHz, Z/n < 1 ohm. For the ISABELLE accelerating cavity, operating at 235.5 KHz, Z/n must be less than 10 ohms. The maximum allowable impedance at any frequency, f, is given in the form Z/n where n = f/f/sub rotation/. more » For ISABELLE a method has been designed for building a network into the cavity accelerating gaps which will satisfy the impedance criteria to at least 1300 MHz. At low frequencies, up to 10 to 20 MHz, the low impedance requirement for the cavities can be satisfied by designing the driving power amplifiers with a very low output impedance. These impedances are due to the resistive wall effect and any deviation from a smooth vacuum chamber such as at pick-up electrodes, vacuum pump stations, rf cavities, etc. This is necessary to prevent the excitation of longitudinal instabilities. This can be corrected by elevating the heater line on DC, but that can cause problems with preamp tubes operating NOT as cathode followers, since their cathodes are one or two volts above ground.In a storage ring, where beam lifetime is measured in hours, it is necessary to keep the longitudinal impedance, as seen by the beam, very low, even into the gigahertz region. Since in most guitar amps, the heaters are ground referenced, and the cathode is above ground by whatever value the circuit sets it to, you get differential. The various spec sheets show 100 to 180 volts as maximum differential: This means some of the current tubes don't meet old manufacturers specs. I've edited my earlier post, as I discovered by looking this up, that the actual value of 100 volts is actually within spec. This potential should not normally exceed 100 volts except in the case of tubes specifically designed for this, like a rectifier and the many tubes designed for ac/dc circuits."Įxceeding this maximum value can cause premature tube failure through something called "cathode stripping", which means the chemical coating on the cathode can arc or burn off, and it's remnants cause shorts or failures within the tube.
According to the Radiotron Designers Handbook: "It's generally desirable to avoid a large potential difference between heater and cathode. Heater cathode differential in a typical cathode follower can usually run from 20 to 100 volts or so. You can make a cathode follower have gain (they don't sound very good), but here's the skinny: A cathode follower is usually fed by 200 to 300 volts on it's plate, and biased to put a given voltage at the cathode, and it acts as a unity gain buffer. The AC signal floats on the DC value of the cathode. The signal really has nothing to do with this issue. You are correct, the output is in phase with the input.