98 research outputs found
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Working group II report: Production and dynamics of high brightness beams
This paper summarizes the main discussions of the Working Group on the Production and Dynamics of High Brightness Beams. The following topics are covered in this paper. Proposed new electron sources and needed research on existing sources is covered. The discussions on issues relating to the description of phase space on non-thermalized electron beam distributions and the theoretical modeling on non-thermalized electron beam distributions is presented. Finally, the present status of the theoretical modeling of beam transport in bends is given
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Electron beamline design for the Los Alamos National Laboratory 1 kW FEL
This paper describes the electron beam simulations for a 1 kW average power FEL. The experiment utilizes the existing AFEL accelerator. An expected 6% total efficiency of electron beam power to optical power gives 17 kW of electron beam power for 1 kW of optical power. A constraint on the beamline design is that the FEL electron beamline and optical components must fit on the existing AFEL 6 ft. high by 10 ft. long optical table. The components include electron beam diagnostics, a 2 meter long wiggler, bending magnets, and optical feedback components. The electron beam design point is 300 A peak current, 17 MeV energy, 7.5 {pi} mm-mrad effective normalized rms emittance and 6 nC micropulse charge. The electron beamline will have greater than 99% transmission. The wiggler will have weak (natural) two plane focusing to maintain the electron beam size in the long wiggler. The beamline after the wiggler has to transport a beam with a 14 to 18 MeV energy spread and an average energy of 16 MeV
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High-brightness photoemitter development for electron accelerator injectors
Free-electron-laser (FEL) oscillators require a train of high-brightness bunches. Conventional subharmonic bunchers are currently used with rf linacs to generate pulse trains, but the resulting dilution of the transverse phase space and lower beam brightness are unacceptable for high-performance FELs. Recent developments suggest that photoemitters of high quantum efficiency combined with rapid acceleration can produce pulse trains of higher brightness than has been achieved before
MHD equilibrium properties of tokamak fusion reactor designs
The equilibrium properties of several Tokamak Reactor Designs are analyzed and compared for varying pressure and current profiles using the Princeton Equilibrium Code. It is found that the UWMAK configuration has a broader range of equilibria than the Princeton Reference Design configuration, but that the safety factor on axis is less than unity for peaked current distributions. The Argonne Experimental Power Reactor has a satisfactory range of equilibria, but a means of limiting or diverting the plasma has not yet been proposed, and this may substantially change the results obtained. (auth
Measurements of differential production cross sections for a Z boson in association with jets in pp collisions at root s=8 TeV
Peer reviewe
Charged-particle nuclear modification factors in PbPb and pPb collisions at √=sNN=5.02 TeV
The spectra of charged particles produced within the pseudorapidity window
|η| < 1 at √
sNN = 5.02 TeV are measured using 404 µb
−1 of PbPb and 27.4 pb−1 of pp data
collected by the CMS detector at the LHC in 2015. The spectra are presented over the
transverse momentum ranges spanning 0.5 < pT < 400 GeV in pp and 0.7 < pT < 400 GeV
in PbPb collisions. The corresponding nuclear modification factor, RAA, is measured in
bins of collision centrality. The RAA in the 5% most central collisions shows a maximal
suppression by a factor of 7–8 in the pT region of 6–9 GeV. This dip is followed by an increase,
which continues up to the highest pT measured, and approaches unity in the vicinity
of pT = 200 GeV. The RAA is compared to theoretical predictions and earlier experimental
results at lower collision energies. The newly measured pp spectrum is combined with the
pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear
modification factor, RpA, up to 120 GeV. For pT > 20 GeV, RpA exhibits weak momentum
dependence and shows a moderate enhancement above unity
Simulation of a regenerative MW FEL amplifier
Both oscillator and regenerative amplifier configurations are being studied to optimize the design
of a MW-class FEL. The regenerative amplifier uses a longer undulator and relies on higher
extraction efficiency to achieve high average power, whereas the oscillator is a more compact
overall design requiring the transport of the high energy electron beam around bends for energy
recovery. Using parameters extrapolated from the I kW LANL regenerative amplifier, simulations
study the feasibility of achieving I MW average power.Los Alamos National Laborator
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Short wavelength FELS
The generation of coherent ultraviolet and shorter wavelength light is presently limited to synchrotron sources. The recent progress in the development of brighter electron beams enables the use of much lower energy electron rf linacs to reach short-wavelengths than previously considered possible. This paper will summarize the present results obtained with synchrotron sources, review proposed short- wavelength FEL designs and then present a new design which is capable of over an order of magnitude higher power to the extreme ultraviolet. 17 refs., 10 figs
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High-brightness electron injectors
Free-electron laser (FEL) oscillators and synchrotron light sources require pulse trains of high peak brightness and, in some applications, high-average power. Recent developments in the technology of photoemissive and thermionic electron sources in rf cavities for electron-linac injector applications offer promising advances over conventional electron injectors. Reduced emittance growth in high peak-current electron injectors may be achieved by using high field strengths and by linearizing the radial component of the cavity electric field at the expense of lower shunt impedance
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Progress in photoinjectors for linacs
Several programs have started which are based on the photoinjector as the electron source. Some reasons for using a laser to produce an electron beam are improved beam brightness, high-charge single-bunch pulses (>50 nC), and several high-current pulses closely spaced in time. This presentation will cover present and planned activities in photoinjector development. Topics will include materials, gun designs, and present experimental results. 21 refs
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