Maximization of Laser Coupling with Cryogenic Targets*

A major obstacle for depositing laser energy to targets in Magnetized Liner Inertial Fusion (MagLIF) is the need to contain the gas with a laser-entrance-hole window (LEH).  With densities of 1.0-1.4 mg/cc at room temperature, previous experiments used a polyimide film of 1.56 µm thickness and 2.2 mm diameter which consumed about 1 kJ of laser energy at the maximum plausible beam spot size of 1.1 mm. 

We will discuss the implementation of cryogenic cooling to enable the use of thinner and wider LEH windows along with a larger beam spots size.  As a result, we dramatically reduced losses while keeping the laser propagation depth within a useful range for MagLIF, and we comfortably exceeded the previously unobtainable laser deposition of 2kJ.

 

* Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. DOE’s National Nuclear Security Administration under contract DE-NA0003525.