| Paper | Title | Page |
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| TUPD26 | Cavity-based Beam Diagnostics at ELSA | 362 |
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Funding: Funded by DFG SFB/TR 16 Online monitoring of the intensity and position of an electron beam of a few hundred pA in the experiment beamlines at the ELSA facility is enabled by a system of resonant cavities. The position signal extracted from the resonators amounts to about 10-19 W for 0.1 mm displacement at a beam current of 400 pA. It is separated from noise by phase-sensitive detection in a lock-in amplifier. The beam's position is obtained with a precision of one tenth of a millimeter, the signal strength being normalized by a beam current measurement with an uncertainty of a few pA. Via frequency mixing, the cavity signal of 1.5 GHz is converted down to a frequency below 100 kHz in order to be accepted by the amplifier, requiring a local oscillator stabilized by a feedback loop to 10-6 precision. Details of the measurement system are presented. |
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