Los Alamos National Laboratory

Los Alamos National Laboratory

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Relativistic Laser-Matter Interactions

Enabling the next generation of intense particle accelerators


  • Juan Fernandez
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Short-pulse ion acceleration

The Trident facility is a world-class performer in the area of ion acceleration from laser-solid target interactions.

Trident has demonstrated over 100 MeV protons at intensities of 8x1020 W/cm2 with efficiencies approaching 5%. These intense relativistic interactions can be diagnosed using a suite of instruments:

  • The proton beam is easily diagnosed using the Radiochromic Film (RCF) Imaging Spectroscopy technique, where the beam is captured on a stack of RCF and deconvolved into spectral and spatial data.
  • Heavier ions are diagnosed using Thomson Parabolas (TPs) loaded with either CR39 nuclear track detector or Image Plates (IPs). The TPs allow one to differentiate between ion charge and mass with energy, thus enabling a full picture of the ion acceleration in a single shot. This diagnostic led to the discovery of monoenergetic carbon beams at Trident.

Laser spot profile

Understanding the conditions for acceleration are important, and one initial condition affecting beam quality most is the laser spot profile.

Trident has two main diagnostics for determining spot size quality:

  1. On the short-pulse system, a suite of laser diagnostics that measure the laser beam far-field, near-field, spectrum, pulse duration, and phase front simultaneously
  2. In the North Target Chamber (NTC), an x-ray pinhole camera with 8-10 X imaging of x-rays above 1 keV, and a 1-micron imaging Backscatter Focusing Diagnostic (BFD)

Both of these systems give a very good indication of the beam quality on target and an image of the x-ray emitting area corresponding to the area on the front surface responsible for making the hot electrons for the ion acceleration.

Related images

A proton beam

A proton beam of greater than 50 MeV from the same Mo target with 96J on target producing an intensity of ~5x1019 W/cm2, rivaling the NOVA Petawatt in proton energy at five times less laser energy and intensity.

The TRIDENT Short-pulse laser shooting a Mo target foil (center) for Proton and X-ray production.

The Trident short-pulse laser shooting a Mo target foil (center) for proton and x-ray production. The x-ray pinhole camera is on the left and the stack of RCF is on the right. In the foreground (left) is a mesh used for x-ray characterization.

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