Phase and synchronous detector theory as applied to beam position and intensity measurements
A popular signal processing technique for beam position measurements uses the principle of amplitude-modulation-to-phase-modulation (AM/PM) conversion and phase detection. This technique processes position-sensitive beam-image-current probe-signals into output signals that are proportional to the beam's position. These same probe signals may be summed and processed in a different fashion to provide output signals that are proportional to the peak beam current. This paper derives the transfer functions for the AM/PM beam position and peak beam current processors.
C E~M-POSITION-TRANSFE~ FUNCTIONS USIN CIRCULAR AM-POSITION MONIT
A cylindrical beam-position monitor (BPM) used in many accelerator facilities has four electrodes on which beamimage currents induce bunched-beam signals. These probe-electrode signals are geometrically configured to provide beam-position information about two orthogonal axes. An electronic processor performs a mathematical transfer function (TF) on these BPM-electrode signals to produce output signals whose time-varying amplitude is proportional to the beam's vertical and horizontal position. This paper will compare various beam-position TFs using both pencil beams and will further discuss how diffuse beams interact with some of these TFs. 1 BPM SENSITIVITY BPMs typically have four electrodes on which beam image currents induce bunched-beam signals. These probe signals are initially processed or naturally configured to provide information about the horizontal and vertical axes that describes the beam's position. BPMs may have a variety of cross-sectional shapes, such as circular, rectangular, elliptical, etc. For the circular-cross-section BPM detecting thin beams, sufficient beam position information is contained within Ry . Specifically,
PULSE: a high-repetition-rate linac driver for x-ray FELs
We describe a staged concept for a linac-based freeelectron laser providing coherent tuneable VUV and soft X-ray output with pulse lengths down to 10 fs or less. Use of 1.3 GHz cryomodules operated with CW RF will allow flexible pulse patterns at potentially very high repetition rates up to 1 MHz. We consider the options for FELs that may be included in a facility of this type.