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Wootton, K. P.

Publications and source records attributed to Wootton, K. P..

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Tapered helical undulator system for high efficiency energy extraction from a high brightness electron beam

In this work we discuss the design choices and construction strategy of the tapered undulator system designed for a high energy extraction efficiency experiment in the ultraviolet region of the electromagnetic spectrum planned for installation at the Argonne National Laboratory Linac Extension Area (LEA) beamline. The undulator is comprised of 4 sections pure permanent magnet Halbach array separated by short break sections, each one of them housing a focusing quadrupole doublet and a phase shifter. The quadrupoles use a novel hybrid design which allows one to vary the gradient and match the beam transversely. Finally, the undulator tapering profile is optimized to maximize the energy conversion efficiency from a 340 MeV 1 kA beam into coherent 257.5 nm radiation taking into account the longitudinal current profile generated by the linac.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Proposed Enhanced Imaging Station in the 6-GeV Booster-to-Storage Ring Transport Line for APS Upgrade

The high charge per micropulse of up to 17 nC in the booster to storage ring transport line (BTS) for APS Upgrade will necessitate changes in the imaging station used to evaluate beam emittance in this key region. The original Chromox screen has recently been replaced by a YAG:Ce single crystal for immediate screen spatial resolution improvement down to <10 µm. However, the optical system also needs an upgrade with lenses and a digital camera to take full advantage of this enhancement. In addition, at the high areal charge densities expected, the YAG:Ce scintillator mechanism will saturate, or quench, leading to images larger than the actual beam size. To circumvent this effect, optical transition radiation (OTR) screens will be implemented. A proposed longer-range goal of a non-intercepting beam-size monitor using optical diffraction radiation techniques during top-up injection will also be addressed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Cumulative material damage from train of ultrafast infrared laser pulses

We developed a systematic experimental method to demonstrate that damage threshold fluence (DTF) for fused silica changes with the number of femtosecond laser (800 nm, $65\pm 5~\text{fs}$ , 10 Hz and 600 Hz) pulses. Based on the experimental data, we were able to develop a model which indicates that the change in DTF varies with the number of shots logarithmically up to a critical value. Above this value, DTF approaches an asymptotic value. Both DTF for a single shot and the asymptotic value as well as the critical value where this happens, are extrinsic parameters dependent on the configuration (repetition rate, pressure and geometry near or at the surface). Here these measurements indicate that the power of this dependence is an intrinsic parameter independent of the configuration.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Flat electron beam sources for DLA accelerators

In this study we discuss the application of the flat beam transform to generate beams suitable for injection into slab-symmetric dielectric laser-driven accelerators (DLAs). A study of the focusing requirements to keep the particles within the tight apertures characterizing these accelerators shows the benefits of employing ultralow beam emittances. The slab geometry of the many dielectric accelerating structures strongly favors the use of flat beams with large ratio between vertical and horizontal emittances. We employ particle tracking simulations to study the application of the flat beam transform for two injector designs, a DC non relativistic photogun and a 1.6 cell S-band RF photoinjector, obtaining in both cases emittance ratios between the horizontal and vertical plane in excess of 100 in agreement with simple analytical estimates. The 4 MeV RF photoinjector study-case can be directly applied to the UCLA Pegasus beamline and shows normalized emittances down to < 3 nm in the vertical dimension for beam charges up to 20 fC, enabling a two-stage DLA experiment.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Observation of 690 MV m -1 Electron Accelerating Gradient with a Laser-Driven Dielectric Microstructure

Acceleration of electrons using laser-driven dielectric microstructures is a promising technology for the miniaturization of particle accelerators. In this work, experimental results are presented of relativistic electron acceleration with 690±100 MVm -1 gradient. This is a record-high accelerating gradient for a dielectric microstructure accelerator, nearly doubling the previous record gradient. To reach higher acceleration gradients the present experiment employs 90 fs duration laser pulses.

43 PARTICLE ACCELERATORS↗