Neon lineshift measurements in dense, laser-compressed plasmas

Measurement of shifts in the neon Lyman- alpha , - beta and - gamma lines and the He-like 1s2-1s2p line have been obtained in laser-compressed plasmas at ne approximately 3*1022 cm-3 and Te approximately 300 eV. Calibration of the neon line wavelengths was determined relative to the emission lines of higher Z elements present in the microballoon glass shell. A trend towards larger red shifts in the wavelengths of the lower neon Lyman series members was observed, and the neon He- alpha line was observed to be blue shifted. These trends are shown not to be the result of refractive index corrections to the dispersion of the crystal spectrometer used, and are unlikely to be the result of differential spatial or Doppler effects between the neon and the calibration lines. Assuming that the measured red shift of about 10 mAA for neon Lyman- alpha is an indication of the magnitude of the absolute shift, then the observed shift is an order of magnitude greater than predicted by current plasma polarisation shift theories at the plasma densities and temperatures obtained in the present experiment.