| Paper | Title | Page |
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| TUPC019 | A Retarding Field Detector to Measure the Actual Energy of Electrons Participating in E-cloud Formation in Accelerators | 1086 |
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| Electron cloud related phenomena can cause potentially detrimental effects on beam stability in many planned and under construction accelerators. The possibility to reduce such unwanted phenomena lies on the observation that, machine commissioning does reduce Secondary Electron Yield (SEY). Such SEY reduction (scrubbing) is due to the fact that electrons produced during e-cloud formation hit the accelerator wall, modifying their surface properties. ‘Scrubbing” has been studied only as a function of impinging electron dose but never as a function of the e-cloud electron energy. Simulations predict that the e-cloud is formed by electrons with very low energies (<50 eV). Given the potentially lower scrubbing efficiency for equal dose of very low energy electrons compared to medium energy one, it would be important to measure the actual energy of the electrons forming the cloud in real accelerators. For this reason we decided to construct an optimized retarding Field energy electrometer to be installed in accelerators. Here we will describe what solutions have been adopted during the design phase of such “home made” detector and some laboratory test will be showed and discussed. | ||
| TUPC008 | Beam Diagnostics with IR Light Emitted by Positron at DAΦNE | 1056 |
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Real-time beam diagnostics is mandatory in accelerators and represents one of the most challenging issues of modern storage rings and future FEL's. Recently, compact mid-IR fast uncooled photo-detectors have been used at DAΦNE to monitor single e- bunches using the SINBAD IR beamline installed on the e- ring*. Electron bunches have a FWHM of 150-300 ps and are separated by 2.7 ns**. Detectors performances are then suitable for a compact and low cost bunch-by-bunch longitudinal diagnostic device. To improve the DAΦNE diagnostic a bending magnet SR port on the e+ ring has been set-up with a HV chamber, a gold-coated plane mirror and a ZnSe window. To collect the SR light and focus radiation on IR detectors allowing the diagnostic of e+ a compact optical system has been installed in air after the window. Here we will present the status of the apparatus, the source characteristics, the optical setup and the complete acquisition system. This IR port will allow comparison in the ns time domain between data collected on both rings, and could be also used to improve DAΦNE diagnostics, i.e., identify and characterize bunch instabilities and/or increase the current in the e+ ring.
*M. Cestelli Guidi et al. J. Opt. Soc. Amer. A 22, 2810 (2005). |