Broad band impedance measurements on the electron storage ring ELETTRA

Abstract

In the design of the vacuum chamber of a storage ring, special care has to be taken to keep the impedance as low as possible, in order to not degrade the quality of the circulating beam. Since the start of the commissioning of the Italian synchrotron light source ELETTRA in 1993, several low gap insertion vacuum chambers with internal aperture of 14 mm have been installed into the storage ring. Monitoring of their individual impedances and effects has been carried out with measurements on the electron beam after each new installation. The subsequent evolutions of the total longitudinal and transverse impedances are presented in this paper. Furthermore, in contradiction with the foreseen single-bunch effect, noticeable excitations of particular narrow band longitudinal coupled multibunch instabilities as a function of the position of the blades of the vertical scraper have been observed. In order to achieve a deeper insight of the phenomenon, an exhaustive characterization of both the longitudinal and transverse impedances of the scraper has been carried out.

Coupling impedance of an in-vacuum undulator: Measurement, simulation, and analytical estimation

“…The simulated results by CST PARTICLE STUDIO and the GDFIDL code are green triangles and blue squares, respectively. The solid line is the analytical calculation performed using formulas (10) and (7).…”

“…The measurement technique has been developed and realized first at Budker Institute of Nuclear Physics [8]. Later, similar techniques were used at APS [9], ELETTRA [10], and ESRF [11]. The method is based on the fact that an off-axis beam passing through the vacuum chamber section with a nonzero transverse impedance is deflected by the wakefields.…”

<title>Synchronization of ELETTRA storage-ring light sources with an ultrafast CR:LISAF laser</title>

“…Typical electron energies are ranging form 2 to 2.4GeV, with a maximum average current of 33OmA. SB mode is used mostly during Machine Physics studies as, with a single bucket filled, collective effects are avoided and more accurate measurements are possible [7]. Four-bunch mode is used by the SR-FEL, at I GeV, and by the Users canying out "time resolved" experiments, mostly at 2GeV as the photon beam is brighter.…”

Review of the longitudinal impedance budget of the ELETTRA storage ring

“…The measurement of k || for the ELETTRA storage ring is presented in this paper. Since the energy loss of equation 1 changes by varying the beam charge, an indirect method to measure k || is to take the closed orbit at a reference beam current I 0 and measuring the horizontal BPMs readings deviation in the dispersive region of the storage ring versus the beam current [1]:…”

“…Its contribution comes from both its shape and material as well as from its discontinuities such as holes, steps and tapers. In reference [1] impedance budget measurements on the ELETTRA storage ring is extensively handled. Recently the Libera electron [2] device was used to upgrade the original Beam Position Monitor (BPM) detectors.…”