The Experts below are selected from a list of 100437 Experts worldwide ranked by ideXlab platform
C Pellegrini - One of the best experts on this subject based on the ideXlab platform.
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multicolor operation and spectral control in a gain modulated x ray free electron laser
Physical Review Letters, 2013Co-Authors: Agostino Marinelli, Alberto Lutman, Yuantao Ding, J Krzywinski, H D Nuhn, Yiping Feng, R Coffee, C PellegriniAbstract:We show that the spectral properties of a self-amplified spontaneous emission x-ray free-electron laser can be controlled by modulating the gain in magnetic undulators, thus producing one or several spectral Lines within a single few femtosecond pulse. By varying the magnetic field along the undulator and the electron beam Transport Line, the system we demonstrate can tailor the x-ray spectrum to optimally meet numerous experimental requirements for multicolor operation.
P Scampoli - One of the best experts on this subject based on the ideXlab platform.
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a system for onLine beam emittance measurements and proton beam characterization
Journal of Instrumentation, 2018Co-Authors: Konrad Pawel Nesteruk, M Auger, S Braccini, A Ereditato, P Scampoli, Tommaso Stefano CarzanigaAbstract:A system for onLine measurement of the transverse beam emittance was developed. It is named 4PrOBeaM (4-Profiler OnLine Beam Emittance Measurement) and was conceived to measure the emittance in a fast and efficient way using the multiple beam profiler method. The core of the system is constituted by four consecutive UniBEaM profilers, which are based on silica fibers passing across the beam. The 4PrOBeaM system was deployed for characterization studies of the 18 MeV proton beam produced by the IBA Cyclone 18 MeV cyclotron at Bern University Hospital (Inselspital). The machine serves daily radioisotope production and multi-disciplinary research, which is carried out with a specifically conceived Beam Transport Line (BTL). The transverse RMS beam emittance of the cyclotron was measured as a function of several machine parameters, such as the magnetic field, RF peak voltage, and azimuthal angle of the stripper. The beam emittance was also measured using the method based on the quadrupole strength variation. The results obtained with both techniques were compared and a good agreement was found. In order to characterize the longitudinal dynamics, the proton energy distribution was measured. For this purpose, a method was developed based on aluminum absorbers of different thicknesses, a UniBEaM detector, and a Faraday cup. The results were an input for a simulation of the BTL developed in the MAD-X software. This tool allows machine parameters to be tuned onLine and the beam characteristics to be optimized for specific applications.
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low current performance of the bern medical cyclotron down to the pa range
Measurement Science and Technology, 2015Co-Authors: M Auger, S Braccini, A Ereditato, Konrad Pawel Nesteruk, P ScampoliAbstract:A medical cyclotron accelerating H− ions to 18 MeV is in operation at the Bern University Hospital (Inselspital). It is the commercial IBA 18/18 cyclotron equipped with a specifically conceived 6 m long external beam Line ending in a separate bunker. This feature is unique for a hospital-based facility and makes it possible to conduct routine radioisotope production for PET diagnostics in parallel with multidisciplinary research activities, among which are novel particle detectors, radiation biophysics, radioprotection, radiochemistry and radiopharmacy developments. Several of these activities, such as radiobiology experiments for example, require low current beams down to the pA range, while medical cyclotrons are designed for high current operation above 10 μA. In this paper, we present the first results on the low current performance of a PET medical cyclotron obtained by ion source, radio-frequency and main coil tuning. With this method, stable beam currents down to () pA were obtained and measured with a high-sensitivity Faraday cup located at the end of the beam Transport Line.
Alessandro Flacco - One of the best experts on this subject based on the ideXlab platform.
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Demonstration of relativistic electron beam focusing by a laser-plasma lens
Nature Communications, 2015Co-Authors: Cédric Thaury, Emilien Guillaume, Andreas Döpp, Rémi Lehe, Agustin Lifschitz, Kim Ta Phuoc, Julien Gautier, Jean-philippe Goddet, Amar Tafzi, Alessandro FlaccoAbstract:Laser-plasma technology promises a drastic reduction of the size of high-energy electron accelerators. It could make free-electron lasers available to a broad scientific community and push further the limits of electron accelerators for high-energy physics. Furthermore, the unique femtosecond nature of the source makes it a promising tool for the study of ultrafast phenomena. However, applications are hindered by the lack of suitable lens to Transport this kind of high-current electron beams mainly due to their divergence. Here we show that this issue can be solved by using a laser-plasma lens in which the field gradients are five order of magnitude larger than in conventional optics. We demonstrate a reduction of the divergence by nearly a factor of three, which should allow for an efficient coupling of the beam with a conventional beam Transport Line.
W Blokland - One of the best experts on this subject based on the ideXlab platform.
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active beam position stabilization of pulsed lasers for long distance ion profile diagnostics at the spallation neutron source sns
Optics Express, 2011Co-Authors: Robert A Hardin, A Aleksandrov, Cary D Long, W BloklandAbstract:A high peak-power Q-switched laser has been used to monitor the ion beam profiles in the superconducting linac at the Spallation Neutron Source (SNS). The laser beam suffers from position drift due to movement, vibration, or thermal effects on the optical components in the 250-meter long laser beam Transport Line. We have designed, bench-tested, and implemented a beam position stabilization system by using an Ethernet CMOS camera, computer image processing and analysis, and a piezo-driven mirror platform. The system can respond at frequencies up to 30 Hz with a high position detection accuracy. With the beam stabilization system, we have achieved a laser beam pointing stability within a range of 2 μrad (horizontal) to 4 μrad (vertical), corresponding to beam drifts of only 0.5 mm × 1 mm at the furthest measurement station located 250 meters away from the light source.
L Prost - One of the best experts on this subject based on the ideXlab platform.
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low emittance growth in a low energy beam Transport Line with un neutralized section
Physical review accelerators and beams, 2018Co-Authors: L Prost, J P Carneiro, A ShemyakinAbstract:In a low energy beam Transport Line (LEBT), the emittance growth due to the beam's space charge is typically suppressed by way of neutralization from either electrons or ions, which originate from ionization of the background gas. In cases where the beam is chopped, the neutralization pattern usually changes throughout the beginning of the pulse, causing the Twiss parameters to differ significantly from their steady state values, which, in turn, may result in beam losses downstream. For a modest beam perveance, there is an alternative solution, in which the beam is kept un-neutralized in the portion of the LEBT that contains the chopper. The emittance can be nearly preserved if the transition to the un-neutralized section occurs where the beam exhibits low transverse tails. This report introduces the rationale for the proposed scheme and formulates the physical arguments for it as well as its limitations. An experimental realization of the scheme was carried out at Fermilab's PIP2IT where low beam emittance dilution was demonstrated for a 5 mA, 30 keV ${\mathrm{H}}^{\ensuremath{-}}$ beam.
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experimental demonstration of relativistic electron cooling
Physical Review Letters, 2006Co-Authors: S Nagaitsev, L Prost, D Broemmelsiek, Alexey Burov, Kermit Carlson, Consolato Gattuso, Thomas K Kroc, Stanley Pruss, Mary Sutherland, Charles W SchmidtAbstract:We report on an experimental demonstration of electron cooling of high-energy antiprotons circulating in a storage ring. In our experiments, electron cooling, a well-established method at low energies (< 500 MeV/nucleon), was carried out in a new region of beam parameters, requiring a multi-MeV dc electron beam and an unusual beam Transport Line. In this letter we present the results of the longitudinal cooling force measurements and compare them with theoretical predictions.
