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PS Transverse Feedback Pick-up Amplifier
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The pick-up electrodes
The CODD pick-up electrodes consist of four plates, shaped to obtain
a linear characteristic w.r.t. displacement, and equal inter-electrode
capacitances.
| Aperture | 166x80mm |
| l | 62mm |
| Cel | 70pF | Single plate |
| Cline | 30pF | (Up to feedthrough) |
| Rt | 0.52Ω | (At PU electrodes, high Z) |
| Sx | 174.3mm |
| Sy | 82.3mm |
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| Fig 1: Electrodes |
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The electrodes cover 62mm along the beam direction.
For relatively low frequencies, up to 100MHz or so, the total electrode capacitance
Cel is to be taken as
400pF and is composed of the four PU plates, plus the capacitance
of the short bits of transmission line up to the vacuum feedthroughs.
This yields an open circuit transfer resistance of Rt=l/(cCel)=0.52 Ohms,
where c is the speed of light.
(For higher frequencies, the internal transmission lines can
no longer be considered as lumped capacitors.)
The position of a charged particle beam between the electrodes can be found
by calculating:
where
is the difference of the two horizontal electrode signals, and Σ is the
sum of all of them.
The pick-up dedicated to the transverse feedback system is installed in PS
straight section 98.
A second PU has been added and resides in
straight section 02.
(Both PUs are on the outside of the ring and cannot be seen.)
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Updated: Wednesday, 04-Feb-2009 11:49:16 CET
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