NON-INTERCEPTING DIAGNOSTIC FOR HIGH BRIGHTNESS ELECTRON BEAMS USING OPTICAL DIFFRACTION RADIATION INTERFERENCE (ODRI) A. Cianchi #1,2, M. Castellano 3, L. Catani 2, E. Chiadroni 3, G. Gatti 3, K. Honkavaara 4, G. Kube 4 1 University of Rome Tor Vergata v. della Ricerca Scientifica 1, Rome, Italy 2 INFN- Roma Tor Vergata, v. della Ricerca Scientifica 1, Rome, Italy 3 INFN LNF, v. E. Fermi 40, Frascati (RM), Italy 4 DESY, Notkestrasse 85, Hamburg, Germany IX International Symposium RREPS - 11 Outlook Importance of not intercepting diagnostic Optical Diffraction Radiation vs Optical Diffraction Radiation Interference Non collinear apertures Experimental setup Results Horizontal polarization High Brightness Machines [A/(m-rad) 2 ] V. Balandin, N. Golubeva High density power beam can substantially damage or destroy a foil or a wire scanner Possible alternatives are multishots devices Wire scanner (intercepting) Laser wire Optical Diffraction Radiation (ODR) The charge goes into the hole without touching the screen The electromagnetic field of the moving charge interacts with the metallic screen No power is deposited on the screen The angular distribution of the emerging radiation is affected by the beam transverse size, the angular spread and the position inside the slit Rectangular slit P. Karataev et al., Beam-Size Measurement with Optical Diffraction Radiation at KEK Accelerator Test Facility, Phys. Rev. Lett. 93, (2004) Background noise E. Chiadroni et al., Non-intercepting electron beam transverse diagnostics with optical diffraction radiation at the DESY FLASH facility NIM B 266 (2008) 37893796 Mainly Synchrotron radiation, both directly coming for bending magnets and reflected from the vacuum chamber walls Two slits geometry (ODRI) Optical Diffraction Radiation Interference (ODRI) Collinear slits Point like beams with different angular spread Possible confusion between the contribution of the angular spread and the beam dimension Non collinear slits The 50 m offset between the slits is enough to avoid mixing between the contributions of angular spread and beam size Approximations and formulas Perfect metal Filter bandwidth negligible Beam energy spread negligible Beam Gaussian both in y and y Slit parallelism correction (M. Castellano, E. Chiadroni, A. Cianchi, Phase control effects in optical diffraction radiation from a slit, Nuclear Instruments and Methods in Physics Research A 614 (2010) 163168) Numerical code FLASH FLASH is an excellent linac for this experiment: High energy up to 1 GeV Large number of bunches (up to 30) with high charge (up to 1 nC) Frequency repetition 5 Hz Long collaboration history Optical System (1) High Sensitivity Hamamatsu Camera High quantum efficiency Air Cooling -55C Long exposure time up to 2 hours Interferential filter at 800 nm Interferential filter at 450 nm Glenn-Thompson polarizer Achromat Lens with f=500 mm for DR angular distribution Lens with f=250 mm for beam imaging Hamamatsu CCD camera Experimental Setup (1) Mirror Lenses Actuator Interferential filters Polarizer Camera holder center -25 um -50 um -75 um -100 um -125 um -150 um Angular distribution center +25 um +50 um +75 um +100 um +125 um +175 um Angular distribution (2) Two different spots OTR beam 784 m 904 m ODRI beam 82 m 94 m, A divergence of about 320 rad can be estimated from a quadrupole-scan emittance measurement carried out under the same experimental conditions RMS Beam Size ( m) 8278 RMS angular spread ( rad) Displacement in respect to the second slit ( m) Misalignment between two slits ( m) Hardware evolution New design in the mover Old screen holderNew screen holder Experimental Setup (2) Mirror Lenses with one apochromatic lens Interferential filter 2 polarizers Different wavelength 800 nm550 nm Horizontal polarization Vertical Horizontal X polarization 550 nm800 nm Scan with the 1 mm slit 0.5 m slit out off center about -70 m 1 mm slit move range from -66 m to +200 m To improve Horizontal polarization features not fully understood A control of the all known parameters is mandatory in order to make precise measurements An analytic formula would be better than a MonteCarlo code Conclusion ODRI is in developing ODRI dramatically reduce or eliminate the problem of background Asymmetric configuration resolves parameters ambiguities New measurements are foreseen to make a totally non intercepting emittance measurement Thank you for your attention Formulas Multiple fit Importance of side peaks All data