In this paper we study the validity of coupling impedance bench measurements, comparing two of the most commonly used formulas to the result obtained, applying a modified version of Bethe's theory of diffraction to a lumped impedance in a coaxial beam pipe. The equations found provide a quantitative expression for the influence of the wire thickness used in the measurement of the real and imaginary part of the longitudinal impedance. The precision achievable in an actual measurement is therefore discussed. The method presented can also be applied in the presence of distributed impedances as well as to the analysis of transverse impedance measurements.

Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation at high currents. Furthermore, it is difficult to probe their density over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave transmitted over a section of the accelerator and used it to measure the average electron cloud density over a 50 m section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center.

We present a novel method for measuring the energy loss per turn in an electron storage ring. The method involves the accurate measurement of the change in the rotation period of an uncaptured electron bunch using a dual-sweep streak camera. In our opinion, this method is more direct and accurate than other techniques. We present examples of measurements performed at the Advanced Light Source.

We present the results of a study for the design of a fast extraction kicker to be installed in the Accelerator Test Facility ring at KEK. This activity is carried on in the framework of the ATF2 project, which will be built on the KEK Tsukuba campus as an extension of the existing ATF, taking advantage of the world s smallest normalized emittance achieved there. ATF2's primary goal is to operate as a test facility and establish the hardware and beam handling technologies envisaged for the International Linear Collider. In particular, the fast extraction kicker object of the present paper is an important component of the ILC damping rings, since its rise and fall time define the minimum distance between bunches and ultimately the damping rings length itself. Building on the initial results presented at EPAC '06, we report on the present status of the kicker design and define the minimum characteristics for pulsers and other subsystems. In addition to the original scheme with multiple stripline modules producing a total deflection of 5 mrad, we also investigated a scheme with a single kicker module for a reduced deflection of 1 mrad placed inside a closed orbit bump, which takes the electron closer to the extraction septum.

Two-beam accelerators based upon relativistic klystrons (RK's) have been proposed as power sources for future generation electron-positron linear colliders. These drivers are known to suffer from several transverse beam-breakup (BBU) instabilities. A program to study a particular technique (the 'betatron node scheme') of ameliorating the high frequency BBU is under way at LBL. Central to this study are the pillbox RF cavities and RF beam position monitors (BPM's) employed. This paper discusses the design, fabrication, and testing of the RF components. Details of the signal processing and analysis will be presented.

In several cases, coupling synchrotron light into optical fibers can substantially facilitate the use of beam diagnostic instrumentation, that measures longitudinal beam properties by detecting synchrotron radiation. It has been discussed in [1] with some detail, how fiberoptics can bring the light at relatively large distances from the accelerator, where a variety of devices can be used to measure beam properties and parameters. Light carried on a fiber can be easily switched between instruments so that each one of them has 100 percent of the photons available, rather than just a fraction , when simultaneous measurements are not indispensable. From a more general point of view, once synchrotron light is coupled into the fiber, the vast array of techniques and optoelectronic devices, developed by the telecommunication industry becomes available.In this paper we present the results of our experiments at the Advanced Light Source, where we tried to assess the challenges and limitations of the coupling process and determine what level of efficiency one can typically expect to achieve.

We present the initial results of an experimental study of a beam timing monitor based on an optoelectronic technique. This technique uses the electrical signal from a beam position monitor to modulate the amplitude of a train of laser pulses, converting timing jitter into an amplitude jitter. This modulation is then measured with a photodetector and sampled by a fast ADC. This approach has already demonstrated sub-100 fs resolution and promises even better results. Additionally, we are planning to use the technique as a way to extract the maximum possible bandwidth from a BPM, avoiding the dispersion typical of long RF cables. We show our initial results using signals from the Advanced Light Source storage ring.