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Studies of Ion Acceleration from Thin Solid-Density Targets on High-Intensity Lasers

Willis, Christopher Ryan
http://rave.ohiolink.edu/etdc/view?acc_num=osu1467983566

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Physics.
Over the past two decades, a number of experiments have been performed demonstrating the acceleration of ions from the interaction of an intense laser pulse with a thin, solid density target. These ions are accelerated by quasi-static electric fields generated by energetic electrons produced at the front of the target, resulting in ion energies up to tens of MeV. These ions have been widely studied for a variety of potential applications ranging from treatment of cancer to the production of neutrons for advanced radiography techniques. However, realization of these applications will require further optimization of the maximum energy, spectrum, or species of the accelerated ions, which has been a primary focus of research to date. This thesis presents two experiments designed to optimize several characteristics of the accelerated ion beam. The first of these experiments took place on the GHOST laser system at the University of Texas at Austin, and was designed to demonstrate reliable acceleration of deuterium ions, as needed for the most efficient methods of neutron generation from accelerated ions. This experiment leveraged cryogenically cooled targets coated in D2O ice to suppress the protons which typically dominate the accelerated ions, producing as many as 2 x 10^10 deuterium ions per 1 J laser shot, exceeding the proton yield by an average ratio of 5:1. The second major experiment in this work was performed on the Scarlet laser system at The Ohio State University, and studied the accelerated ion energy, yield, and spatial distribution as a function of the target thickness. In principle, the peak energy increases with decreasing target thickness, with the thinnest targets accessing additional acceleration mechanisms which provide favorable scaling with the laser intensity. However, laser prepulse characteristics provide a lower bound for the target thickness, yielding an optimum target thickness for ion acceleration which is dependent on the laser system. This experiment utilized new liquid crystal film targets developed at OSU, which may be formed at variable thicknesses from tens of nanometers to several microns. On this experiment, an optimum ion energy and flux was reached for targets of 600-900 nm, providing a peak proton energy of 24 MeV, and total ion flux of >10^9 protons over 3.4 MeV from 5.5 J of laser energy at an intensity of 1 x 10^20 W/cm^2. The primary ion diagnostics for these two experiments are described in detail, including the analysis techniques needed to extract absolutely calibrated spatial and spectral distributions of the accelerated ions. Additionally, a new technique for target alignment is presented, providing repeatable target alignment on the micron scale. This allows for a repeatable laser intensity on target, allowing improved shot to shot consistency on high intensity experiments. In addition to these two experiments, work on the upgrade and characterization of the 400 TW Scarlet laser is discussed, including several calculations critical to the design and upgrade of the laser system, as well as prepulse characterization needed for experiments on thin targets.
Linn Van Woerkom (Advisor)
Robert Perry (Committee Member)
Richard Furnstahl (Committee Member)
Gregory Lafyatis (Committee Member)
221 p.
Physics
High-intensity; lasers; ion acceleration; High energy density physics; target normal sheath acceleration; protons; ions;

Recommended Citations

Citations

  • Willis, C. R. (2016). Studies of Ion Acceleration from Thin Solid-Density Targets on High-Intensity Lasers [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1467983566

    APA Style (7th edition)

  • Willis, Christopher. Studies of Ion Acceleration from Thin Solid-Density Targets on High-Intensity Lasers. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1467983566.

    MLA Style (8th edition)

  • Willis, Christopher. "Studies of Ion Acceleration from Thin Solid-Density Targets on High-Intensity Lasers." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1467983566

    Chicago Manual of Style (17th edition)

osu1467983566
287
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This open access ETD is published by The Ohio State University and OhioLINK.