LIGHT – Laser Ion Generation, Handling and Transport

The LIGHT project makes use of protons (ions) accelerated by means of the PHELIX laser at GSI and investigates their transport, focusing and bunch rotation by conventional ion optics and RF technology. This experiment takes place in a dedicated installation located at the Z6 experimental area of GSI. Learn more about the LIGHT proposal...

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Picture of the target at the time of the laser impact. The laser pulse comes from the right and hits the back of the target. On the other side, the particle beam is visible to the camera.
Laser-ion acceleration in the Target Normal Sheath Acceleration (TNSA) regime

The TNSA mechanism is described in the figure above. The laser pulse coming from the left is focused into the preplasma on the target front side generated by amplified spontaneous emission of the laser system (a). The main pulse interacts with the plasma at the critical surface and accelerates hot electrons into the target material (b). The electrons are transported under a divergence angle through the target, leave the rear side and form a dense electron sheath. The strong electric field of the order of TV/m generated by the charge separation is able to ionize atoms at the rear side (c). They are accelerated over a few μm along the target normal direction. After the acceleration process is over and the target disrupted (~ns), the ions leave the target in a quasi-neutral cloud together with comoving electrons (d). (Image and text courtesy of Dr. Franck Nürnberg)

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Experiment Plan

Proton acceleration by lasers currently reaches energies in the range of 30-60 MeV. It opens new perspectives for future application as novel medium energy accelerators: possibly in the areas of medical treatment, material studies or energy research. The scientific goal of the experiment is to explore several critical interfaces, which are the basis of any future application:

  • de-neutralization of the neutralized particle bunch in a collimation magnetic field,
  • collimation of the broad energy (10-30 MeV) and divergence angle (up to 25 degrees) production spectrum of protons/ions by a pulsed solenoid as first collimator; transport through a drift or focusing channel,
  • RF bunch rotation to complete the de-bunching of the originally sub-ps bunches to ns, and
  • diagnostics of the 6D phase space by means of a sub-ns streak camera and pepper-pot emittance devices.

The experiment planned for 2010-2012 is the first systematic exploration of the interface between laser acceleration (based on "target normal sheath acceleration" - TNSA) and conventional accelerator technology. It combines in a unique and highly efficient way the capabilities of PHELIX as world-class high power (100 TW) laser with the accelerator know-how available at GSI.

References

A. Almomani et al. "Conceptual design report": DOC-2010-Nov-36-1.pdf
B. Zielbauer et al. "LIGHT Update: A laser-based ion-source at Z6" in the 2010 GSI annual report: PNI-PP-16.pdf