Laboratory photo-ionized plasma David Yanuka

Introduction  Photo-ionized plasmas are common in astrophysical environments  Typically near strong sources of X-ray  Absorption spectra from these plasmas contain wealth of information

What can be learned from the recorded spectra?  Material  Distance  Velocity  Degree of ionization  Temperature  Pressure  Density

Disadvantages of studying astrophysical plasmas  Complex interpretation models which include unknown parameters:  Geometry of the system  Gas composition  Density distribution  Photon energy distribution of the driving X-ray flux  Multi element plasmas – overlapping of spectral lines

Difficulties in study of laboratory plasmas  In astrophysical photo-ionized plasmas the radiation field is more dominant than collisions  In laboratory plasmas collisions are dominant  To overcome this need strong X-ray radiation source  Z facility in Sandia produces 1-2 MJ of X-ray energy with a pulse duration of ~6 ns

Z pinch

Experimental setup  Current of 20 MA  Power of ~135 TW  BB radiation ~200 eV  Duration of ~7.5 ns  Height of 2 cm  Diameter of 0.2 cm  Gas-cell at 6 cm  Assumed temperature of eV

Opacity

Bound-bound opacity

Line shape

Photon energy resolved transmission

Finding best fit to experimental results

Ionization parameter

Finding temperature

Summary  A method of extracting the charge state of plasma from absorption spectra has been introduced  Simulation was used to find best match of charge distribution to color and brightness temperatures  Temperature was used to calculate the ionization parameter