|M.Sc Student||Nir Kampel|
|Subject||Towards Nitrogen Recombination X-Ray Laser Using Capillary|
|Department||Department of Physics||Supervisors||Professor Emeritus Ron Amiram|
|Dr. Amnon Fisher|
|Full Thesis text|
In the past two decays capillary discharge z-pinch has been successfully used as a driver for the collisional excitation X-Ray Laser (XRL) in argon at λ=46.9nm. Furthermore, ablative capillary discharge z-pinch has been considered for the recombination XRL using the carbon Balmer-α line at λ=18.2nm. Though amplification was observed, the results did not show high gain and reproducibility as is the case of the argon collisional excitation XRL. In this work we examine experimentally the possibility of realizing the conditions for a nitrogen Balmer-α line recombination XRL at λ=13.4nm. The needed plasma conditions are: initially at least 50% of the nitrogen ions should be fully stripped, i.e. electron temperatures above 140eV. Then the plasma electron temperature should decrease to temperatures below 60eV with an electron density of 5-10·1019cm-3, in order to reduce collisional and photo stimulated excitation into the lower laser level and thus destroying the population inversion. The plasma should cool faster than the three body recombination rate, i.e. faster than 5nsec.
In order to realize these conditions a 5mm diameter 90mm long capillary discharge z-pinch system has been built. To the z-pinch apparatus a pulsed power generator was coupled, which passes through the capillary a peak current of Imax~60kA with a quarter time period of τ¼=70nsec (dI/dt≈0.85kA/nsec). The measured plasma conditions were compared to the needed recombination laser conditions, using filtered XRD and a time integrated free standing transmission grating spectrometer. These measurements show: a lower boundary of 10% of fully stripped nitrogen, implying electron temperature above 100eV. The plasma electron temperature is reduced to temperatures below 60eV, in a time frame faster than 5nsec. Additionally, the electron density was estimated to be 5-10·1019cm-3.
These conditions satisfy the conditions for lasing, except of the needed 50% of the fully stripped nitrogen ions in the pinch. Therefore, these results are promising for realizing a nitrogen based recombination laser using capillary discharge z-pinch. It should be noted that we here only have a lower boundary estimation of the fully stripped abundance, and getting higher abundance needs only higher current.