Beam Position Detection of a Short Electron Bunch in Presence of a Longer and More Intense Proton Bunch for the AWAKE Experiment
75
E. Senes, R. Corsini, W. Farabolini, A. Gilardi, M. Krupa, T. Lefèvre, S. Mazzoni, M. Wendt
CERN, Meyrin, Switzerland
P. Burrows, C. Pakuza
JAI, Oxford, United Kingdom
P. Burrows, C. Pakuza
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
W. Farabolini
CEA-DRF-IRFU, France
The AWAKE experiment studies the acceleration of electrons to multi-GeV levels driven by the plasma wakefield generated by an ultra-relativistic and high intensity proton bunch. The proton beam, being considerably more intense than the co-propagating electron bunch, perturbs the measurement of the electron beam position achieved via standard techniques. This contribution shows that the electrons position monitoring is possible by frequency discrimination, exploiting the large bunch length difference between the electron and proton beams. Simulations and a beam measurement hint, the measurement has to be carried out in a frequency regime of a few tens of GHz, which is far beyond the spectrum produced by the 1ns long (4 σ Gaussian) proton bunch. As operating a conventional Beam Position Monitor (BPM) in this frequency range is problematic, an innovative approach based on the emission of coherent Cherenkov Diffraction Radiation (ChDR) in dielectrics is being studied. After describing the monitor concept and design, we will report about the results achieved with a prototype system at the CERN electron facility CLEAR.
Two-Dimensional Beam Size Measurements with X-Ray Heterodyne Near Field Speckles
176
M. Siano, L. Teruzzi
Università degli Studi di Milano, Milano, Italy
D. Butti, A. Goetz, T. Lefèvre, S. Mazzoni, G. Trad
CERN, Meyrin, Switzerland
U. Iriso, A.A. Nosych, E. Solano, L. Torino
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
B. Paroli, M.A.C. Potenza
Universita’ degli Studi di Milano & INFN, Milano, Italy
We report on 2D beam size measurements with a novel interferometric technique named Heterodyne Near Field Speckles, capable of resolving few-micrometer beam sizes. It relies on the interference between the weak spherical waves scattered by a colloidal suspension and the intense transilluminating X-ray beam. Fourier analysis of the resulting speckles enables full 2D coherence mapping of the incoming radiation, from which the beam sizes along the two orthogonal directions are retrieved. We show experimental results obtained with 12.4 keV X-rays at the NCD-SWEET undulator beamline at ALBA, where the vertical beam size has been changed between 5 and 15 micrometers by varying the beam coupling. The results agree well with the estimated beam sizes from the pinhole calculations. Finally, we discuss recent investigations on alternative targets aimed at improving the signal-to-noise ratio of the technique.
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