nhelix - High-energy lasers for plasma physics

Technical contact: Abel Blazevic

The nhelix (nanosecond high-energy laser for heavy ion experiments) laser is a central instrument at the Z6 measuring station. As the first high-energy laser at GSI, it was constructed with the aim of generating plasmas which are then subjected to an examination by the UNILAC ion beam.

The nhelix laser is based on a diode-pumped Nd:YLF frontend operating at a wavelength of 1053 nm. The preamplifier follows the front end. This consists of three amplifier heads: a 9 mm Nd:YLF rod, a 19 mm Nd:glass rod and a 45 mm Nd:glass rod. All amplifier heads are pumped using flash lamps. With the implementation of this amplifier chain, energies of up to 20 J in 7 ns and a repetition rate of one shot every two minutes can be achieved at the output of the preamplifier.

The preamplifier is followed by the main amplifier, which consists of a six-fold pass disk amplifier with a free aperture of 300 mm. The newly designed main amplifier head is equipped with water cooling, which significantly increases the repetition rate compared to an uncooled head - to one shot every 30 minutes. The energy at the end of the main amplifier is up to 120 J in 7 ns with a beam diameter of 85 mm. There is an option to double the laser frequency, allowing energies of up to 60 J at a wavelength of 527 nm.

This laser system has so far produced important results for fusion research in the field of energy loss. It has also made significant contributions to experiments relevant to space travel and astrophysics.

Parameter

Value

Pulse lenght

7 ns

Repetition rate

1 shot per 30 minutes

Energy at 1053 nm

120 J

Energy at 527 nm

60 J

Side view of the nanosecond front end (Powerlight 800, Continuum) and the injection into the amplification beam line. The oscillator is generating pulses with an energy of approximately 150 mJ and a pulse duration of 15 ns (FWHM). A Pockels cell downstreams allows to shaping the pulse to pulse lengths between 4 and 15 ns with a defined rising/falling edge of 3 ns. The pulse frequency for a thermaly stable operation of the oscillator is 10 Hz.

Injection of the two laser beams (Powerlight 4-15 ns, Geola 0.5 ns) into the amplification beam including beam shaping elements and the pockels cell.

View of the optical table containing the double/triple pass amplifiers, spatial filters and laser beam diagnostics.

Top view into the target chamber. The target is placed in the middle of the chamber (bright spot). It can be irradiated by the PHELIX laser (from the top) and/or the nhelix laser (over the mirors from top or down) to heat it to a plasma as well as by a diagnostic beam for laser interferomerty. At the same time, a heavy ion beam (from bottom) can penetrate the target plasma to probe the interaction mechanisms.


Loading...