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Register a new userWire Scanners for Small Emittance Beam Measurement in Atf
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The wire scanners are used for a measurement of the very small beam size and the emittance in Accelerator Test Facility (ATF). They are installed in the extraction beam line of ATF damping ring. The extracted beam emittance are ex=1.3x10-9 m.rad, ey=1.7x10-11 m.rad with 2x109 electrons/bunch intensity and 1.3GeV energy. The wire scanners scan the beam by a tungsten wire with beam repetition 0.78Hz. The scanning speed is, however, very slow(~500um/sec). Since the extracted beam is quite stable by using the double kicker system, precision of the size measurement is less than 2um for 50 - 150um horizontal beam size and 0.3um for 8 - 16um vertical beam size. The detail of the system and the performance are described.
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After operating as a High Energy Physics electron-positron collider, the Cornell Electron-positron Storage Ring (CESR) has been converted to become a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS). Over the course of several years CESR was adapted for accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Initially some specific topics were targeted for accelerator physic research with the storage ring in this mode, labeled CesrTA. These topics included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud (EC) development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CesrTA occurred over a several year period, described elsewhere. A number of specific instruments were developed for CesrTA. Much of the pre-existing instrumentation was modified to accommodate the scope of these studies and these are described in a companion paper. To complete this research, a number of procedures were developed or modified, often requiring coordinated measurements among different instruments. This paper provides an overview of types of measurements employed for the study of beam dynamics during the operation of CesrTA.
Generally, turn-to-turn power fluctuations of incoherent spontaneous synchrotron radiation in a storage ring depend on the 6D phase-space distribution of the electron bunch. In some cases, if only one parameter of the distribution is unknown, this parameter can be determined from the measured magnitude of these power fluctuations. In this Letter, we report an absolute measurement (no free parameters or calibration) of a small vertical emittance (5--15 nm rms) of a flat beam by this method, under conditions, when it is unresolvable by a conventional synchrotron light beam size monitor.
Next-generation plasma-based accelerators can push electron beams to GeV energies within centimetre distances. The plasma, excited by a driver pulse, is indeed able to sustain huge electric fields that can efficiently accelerate a trailing witness bunch, which was experimentally demonstrated on multiple occasions. Thus, the main focus of the current research is being shifted towards achieving a high quality of the beam after the plasma acceleration. In this letter we present beam-driven plasma wakefield acceleration experiment, where initially preformed high-quality witness beam was accelerated inside the plasma and characterized. In this experiment the witness beam quality after the acceleration was maintained on high level, with $0.2%$ final energy spread and $3.8~mu m$ resulting normalized transverse emittance after the acceleration. In this article, for the first time to our knowledge, the emittance of the PWFA beam was directly measured.
A new laser-wire is being installed in the extraction line of the ATF at KEK. This device aims at demonstrating that laser-wires can be used to measure micrometre scale beam size.
Diagnostics of the beam transverse profile with ever more demanding spatial resolution is required by the progress on novel particle accelerators - such as laser and plasma driven accelerators - and by the stringent beam specifications of the new generation of X-ray facilities. In a linac driven Free-Electron-Laser (FEL), the spatial resolution constraint joins with the further requirement for the diagnostics to be minimally invasive in order to protect radiation sensitive components - such as the undulators - and to preserve the lasing mechanism. As for high resolution measurements of the beam transverse profile in a FEL, wire-scanners (WS) are the top-ranked diagnostics. Nevertheless, conventional WS consisting of a metallic wire (beam-probe) stretched onto a frame (fork) can provide at best a rms spatial resolution at the micrometer scale along with an equivalent surface of impact on the electron beam. In order to improve the spatial resolution of a WS beyond the micrometer scale along with the transparency to the lasing, PSI and FERMI are independently pursuing the technique of the nano-lithography to fabricate a free-standing and sub-micrometer wide WS beam-probe fully integrated into a fork. Free-standing WS with a geometrical resolution of about 250 nm have been successfully tested at SwissFEL where low charge electron beams with a vertical size of 400-500 nm have been characterized. Further experimental tests carried out at SwissFEL at the nominal beam charge of 200 pC confirmed the resilience to the heat-loading of the nano-fabricated WS. In this work, details on the nano-fabrication of free-standing WS as well as results of the electron-beam characterization are presented.
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