Austin Yi

Generation of dark-current-free quasi-monoenergetic 1.25 GeV electrons by laser wakefield acceleration

We report electron acceleration to 1.25 GeV by petawatt-laser-driven wakefield acceleration at plasma density 5×1017 cm3. Electron beams are dark-current-free, quasi-monoenergetic, highly collimated (<;1mrad divergence), contain tens of pC and have excellent pointing stability.

Self-injected petawatt laser-driven plasma electron acceleration in 10 17 cm −3 plasma

We report observation of electron self-injection and acceleration in a plasma accelerator driven by the Texas petawatt laser at 1017 cm−3 plasma density, an order of magnitude lower density than previous self-injected laser-plasma accelerators.

Use of 41Ar production to measure ablator areal density in NIF beryllium implosions

For the first time, 41Ar produced by the (n,ϒ) reaction from 40Ar in the beryllium shell of a DT filled Inertial Confinement Fusion capsule has been measured. Ar is co-deposited with beryllium in the sputter deposition of the capsule shell. Combined with a measurement of the neutron yield, the radioactive 41Ar then quantifies the areal density of beryllium during the DT neutron production. The measured 1.15 ± 0.17 × 10+8 atoms of 41Ar are 2.5 times that from the best post-shot calculation, suggesting that the Ar and Be areal densities are correspondingly higher than those calculated. Possible explanations are that (1) the beryllium shell is compressed more than calculated, (2) beryllium has mixed into the cold DT ice, or more likely (3) less beryllium is ablated than calculated. Since only one DT filled beryllium capsule has been fielded at NIF, these results can be confirmed and expanded in the future.