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Qiang, G.

Publications and source records attributed to Qiang, G..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Monodispersed Spherical Nanoparticles Gd{sub x}Si{sub y}O{sub z}:Eu{sup 3+} for Magnetic Resonance Tomography and Optical Imaging

The melt method is used for synthesizing monodispersed spherical silica nanoparticles Gd{sub x}-Si{sub y}O{sub z}:Eu{sup 3+}. The particle diameter is 450 nm, and the standard deviation does not exceed 5%. The nanoparticles have a line luminescence spectrum with a dominant band at 614 nm. The effect of a constant magnetic field up to 15 T on the intensity and shape of the luminescence spectra of Eu{sup 3+} ions is studied. It is shown that the obtained material has a stable photoluminescence, the intensity of which does not depend on the magnetic field in the entire studied range. The synthesized nanoparticles Gd{sub x}Si{sub y}O{sub z} : Eu{sup 3+} are promising for use as a contrast agent for magnetic resonance tomography and luminescent marker.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Transverse-To-Longitudinal Photocathode Distribution Imaging

In this paper, we present a tunable picosecond-scale bunch train generation technique combining a microlens array (MLA) transverse laser shaper and a transverse-to-longitudinal emittance exchange (EEX) beamline. The modulated beamlet array is formed at the photocathode with the MLA setup. The resulting patterned electron beam is accelerated to 50 MeV and transported to the entrance of the EEX setup. A quadrupole channel is used to adjust the transverse spacing of the beamlet array upstream of the EEX, thereby enabling the generation of a bunch train with tunable separation downstream of the EEX beamline. Additionally, the MLA is mounted on a rotation stage which provides ad- ditional flexibility to produce high-frequency beam density modulation downstream of the EEX. Experimental results obtained at the Argonne Wakefield Accelerator (AWA) facil- ity are presented and compared with numerical simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

A SIMPLE METHOD FOR MEASURING THE ELECTRON-BEAM MAGNETIZATION

There are a number of projects that require magnetized beams, such as electron cooling or aiding in “flat” beam transforms. Here we explore a simple technique to characterize the magnetization, observed through the angular momentum of magnetized beams. These beams are produced through photoemission. The generating drive laser first passes through microlens arrays (fly-eye light condensers) to form a transversely modulated pulse incident on the photocathode surface [1]. The resulting charge distribution is then accelerated from the photocathode. We explore the evolution of the pattern via the relative shearing of the beamlets, providing information about the angular momentum. This method is illustrated through numerical simulations and preliminary measurements carried out at the Argonne Wakefield Accelerator (AWA) facility are presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Microlens Array Laser Transverse Shaping Technique for Photoemission Electron Source

A common issue encountered in photoemission electron sources used in electron accelerators is distortion of the laser spot due to non ideal conditions at all stages of the amplification. Such a laser spot at the cathode may produce asymmetric charged beams that will result in degradation of the beam quality due to space charge at early stages of acceleration and fail to optimally utilize the cathode surface. In this note we study the possibility of using microlens arrays to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes at both Fermilab Accelerator Science \& Technology (FAST) facility and Argonne Wakefield Accelerator (AWA). In particular, we discuss the experimental characterization of the homogeneity and periodic patterned formation at the photocathode. Finally, we compare the experimental results with the paraxial analysis, ray tracing and wavefront propagation software.

43 PARTICLE ACCELERATORS↗