Laser Ion Acceleration from the Interaction of Ultra-Intense laser Pulse with thi foils

Thesis/Dissertation · Fri Mar 12 00:00:00 EST 2004

DOI:https://doi.org/10.2172/15009814· OSTI ID:15009814

Allen, Matthew Mark ^[1]

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1. Univ. of California, Berkeley, CA (United States)

The discovery that ultra-intense laser pulses (I > 10¹⁸ W/cm²) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 10¹⁸ W/cm²), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U_p = ([1 + Iλ²/1.3 x 10¹⁸]^1/2 - 1) m_oc², where Iλ² is the irradiance in Wμm²/cm² and m_oc² is the electron rest mass.At laser irradiance of Iλ² ~ 10¹⁸ Wμm²/cm², the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 15009814
• Report Number(s): UCRL-TH-203170; TRN: US0406629
• Resource Relation: Other Information: TH: Thesis (Ph.D.); Submitted to the Univ. of California, Berkeley, CA (US); PBD: 12 Mar 2004
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
22 GENERAL STUDIES OF NUCLEAR REACTORS
ACCELERATION
ELECTRIC FIELDS
ELECTRONS
ELECTROSTATICS
HYDROCARBONS
LASER TARGETS
LASERS
PROTON BEAMS
PROTONS
REST MASS
TARGETS