Final Deflecting Cavity Design
Deflecting Cavity Animations
Prototype Cavity
Final Deflecting Cavity Design
Deflecting Cavity Animations
Prototype Cavity
In order to do time-resolved measurements of the current profile of the compressed bunches produced by the photoinjector and dogleg compressor, a 9-cell standing wave deflecting mode cavity has recently been constructed and installed at the Neptune laboratory.
The cavity design was developed in collaboration with INFL Frascatti Laboratory in Italy as a tool for experimental verification of beam shaping. Transverse mode deflection is a diagnostic method which imposes upon the beam a time-dependent transverse momentum kick that is proportional to longitudinal position within the bunch. The beam's distribution in the longitudinal phase space is thereby deflected transversely so that it can be observed on a simple profile monitor downstream. This is illustrated by the following cartoon.
The RF input power, at a design frequency of 9.59616 GHz, is produced by frequency multiplying the drive laser oscillator signal and amplifying it with an X-Band klystron, producing 1 microsec RF pulses with a peak power of 50 kW. For more information on the X-Band RF system for this experiment visit the X-Band RF System Page.
Field measurements of the deflecting cavity were carried out using the bead-pull technique and a network analyzer.
The plot above shows the square root of the measured frequency shift as a function of position along the cavity. The positive-going peaks are proportional to the magnetic field magnitude and the negative-going peaks are proportional to the electric field magnitude on-axis. The plot in (b) shows the resonance of the pi-mode measured in (a) at room temperature.