In this paper, we present a three-dimensional quasistatic model for high brightness beam dynamics simulation in rf/dc photoinjectors, rf linacs, and similar devices on parallel computers. In this model, electrostatic space-charge forces within a charged particle beam are calculated self-consistently at each time step by solving the three-dimensional Poisson equation in the beam frame and then transforming back to the laboratory frame. When the beam has a large energy spread, it is divided into a number of energy bins or slices so that the space-charge forces are calculated from the contribution of each bin and summed together. Image-charge effects from conducting photocathode are also included efficiently using a shifted-Green function method. For a beam with large aspect ratio, e.g., during emission, an integrated Green function method is used to solve the three-dimensional Poisson equation. Using this model, we studied beam transport in one Linac Coherent Light Sources photoinjector design through the first traveling wave linac with initial misalignment with respect to the accelerating axis.
This is a description of the first tests of the Elliptically Polarizing Undulator (EPU) on the SPEAR storage ring at SSRL. The EPU is the first device of its type; it is capable of producing plane polarized light in the vertical and horizontal, and right and left circularly polarized light in the 500 -1000 eV range. Tests of the EPU were done to characterize its effect on the electron beam in SPEAR. Even at minimum gap, motion of the EPU magnets to vary the polarization of the output radiation caused negligible changes in the tune or the steering of the electron beam, even with no compensation of the steering trim coils. We also measured the polarization of x-rays generated by the EPU using a newly developed multilayer polarimeter built to be efficient in the EPU's energy range. The EPU produces nearly 100% plane and circularly polarized x-rays.Using left and right circularly polarized radiation, we also performed tests of magnetic circular In trsduc tionMagnetic and biological materials that exhibit circular dichroism in x-ray absorption are currently of great research interest and frequently contain metals in the first row transition series. These metals absorb at L-edges in the 500-1000 eV range. Between 300 and 3000 eV, there are no quarter wave plates presently available to Bending magnet sources of circularly polarized radiation have low flux, require separate optical paths for left and right circularly polarized radiation, and are not useful at very high polarization rates. To obtain a higher flux and polarization, various insertion devices have been designed, including several undulators.[I] Of these approaches, we were attracted to the single helical undulator for simplicity and high flux. The result is the elliptically polarizing undulator (EPU).[2] Our design built on a magnet arrangement of Sasaki [3] and the phase tunability concept of our adjustable phase undulator [4] This design, shown in figure 1, comprises two planes of magnets, one above and one below the storage ring's electron beampipe. Each plane consists of two rows of pure NdFeB magnet blocks in the Halbach sinusoidal arrangement [5]. Each of the rows is mounted on slides, and can be moved longitudindly parallel to the electron beam, by +1/2 the undulator period length, h. The EPU is mounted on the SPEAR beamline 5 multiundulator mover; it is one of 5 undulators that can be positioned over the beampipe. The mover can vary the gap between 30 and 200 mm. The EPU has 26 periods; each period is 65 mm long and it generates x-rays in the 500 -1000 eV range when SPEAR is operated at 3 GeV. Performance ResultsWe consider three sets of motions for the magnet rows in each quadrant: Row Phase (+p) (upper left and lower right move one way while upper right and lower left move the other), Jaw Phase (upper left and right one way, lower left and right the other), and Pair Phase (upper and lower left one way, upper and lower right the other). The jaw phase or pair phase motions can be used to tune the strength of the magnetic field and thus the ...
The Heavy Ion Fusion Science Virtual National Laboratory has achieved 60-fold longitudinal pulse compression of ion beams on the Neutralized Drift Compression Experiment (NDCX) [P. K. Roy et al., Phys. Rev. Lett. 95, 234801 (2005)]. To focus a space-charge-dominated charge bunch to sufficiently high intensities for ion-beam-heated warm dense matter and inertial fusion energy studies, simultaneous transverse and longitudinal compression to a coincident focal plane is required. Optimizing the compression under the appropriate constraints can deliver higher intensity per unit length of accelerator to the target, thereby facilitating the creation of more compact and cost-effective ion beam drivers. The experiments utilized a drift region filled with high-density plasma in order to neutralize the space charge and current of an ∼300 keV K+ beam and have separately achieved transverse and longitudinal focusing to a radius <2 mm and pulse duration <5 ns, respectively. Simulation predictions and recent experiments demonstrate that a strong solenoid (Bz<100 kG) placed near the end of the drift region can transversely focus the beam to the longitudinal focal plane. This paper reports on simulation predictions and experimental progress toward realizing simultaneous transverse and longitudinal charge bunch focusing. The proposed NDCX-II facility would capitalize on the insights gained from NDCX simulations and measurements in order to provide a higher-energy (>2 MeV) ion beam user-facility for warm dense matter and inertial fusion energy-relevant target physics experiments.
We present a planar helical undulator designed to produce elliptically polarized light. Helical magnetic fields may be produced by a variety of undulatory with four parallel cassettes of magnets. In our design, all cassettes are mounted in two planes on slides so that they maybe moved parallel to the electron beam. This allows us to produce x-rays of left-or right-handed elliptical or circular polarization as well as horizontal or vertical linear polarization.In model calculations, we have found that by sliding the top pair of rows with respect to the bottom pair, or the left pair with respect to the right pair, we retain the polarization setting but change the magnetic field strength, and hence the x-ray energy. This allows us to select both energy and polarization by independent phase adjustments alone, without changing the gap between the rows. Such a design maybe simpler to construct than an adjustable gap machine. We present calculations that model its operation and its effects on an electron beam.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.