Astra Target Area 2

Astra Target Area 2

Target Area 2 (TA2) receives the full beam from the final amplifier of Astra. After compression, the energy on target is on average 500 mJ in 40 fs (a peak power of 12.5 TW). Focused intensities on target can reach a few x 10¹⁹ Wcm^-2.

TA2 has a maximum pulse repetition rate of 2 Hz for continuous operation to avoid heating effects in the compressor gratings. The beam energy into TA2 can be continuously varied down to .01% of the maximum using a waveplate and polarising mirrors and a pair of 10% transmitting mirrors. It can be reduced further to 0.005% for alignment purposes.

TA2 can accommodate a range of focusing geometries, and there is also a suite of plasma diagnostics available to study the laser-target interactions.

In the last couple of years, we have developed a novel dual probe system in TA2 to enable unique ultrafast diagnosis of laser produced plasmas. This comprises of a tuneable probe as well as a short pulse probe with pulse length as short as 10 fs.  The second compressor in the area is used to provide two additional beamlines with energy up to 5mJ and duration of 40fs.These have independent delay lines to adjust the timing up to 60ns after the main laser pulse. At this point, second harmonic probe beams can be generated using non linear crystals, if required.

The tuneable part of the dual probe system is  generated using a commercial optical parametric amplifier system (Topas-White from Light Conversion) with output of order 50mJ with wavelength between 500 and 700nm. The short pulse probe is generated using a hollow fibre pulse compressor (purchased from Imperial College London), which provides pulses with energy up to 1mJ with pulse duration of order 10fs.

The target area has its own control room where experimenters can work away from laser hazards, collect data and monitor the progress of their experiments. There is a suite of laser pulse diagnostics that include an autocorrelator, Spider, Grenouille, spectrometer and energy meters.