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Hatarik, R

Publications and source records attributed to Hatarik, R.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Achieving 280 Gbar hot spot pressure in DT-layered CH capsule implosions at the National Ignition Facility

We are reporting on a series of indirect-drive 0.9-scale CH capsule implosions (inner radius = 840 μm) fielded in low gas-fill (0.6 mg/cm 3 ) hohlraums of 6.72 mm diameter at the National Ignition Facility. Thanks to the 11%-reduction of the capsule size at a given hohlraum diameter compared to previously tested full-scale capsules, we achieved good hot spot symmetry control near 33% cone-fraction and without the need to invoke cross beam energy transfer. As a result, we achieved a hot spot pressure of 280 ± 40 Gbar, which is the highest pressure demonstrated in layered DT implosions with CH capsules to date. Pushing this design to higher velocity resulted in a reduction of neutron yield. Highly resolved capsule simulations suggest that higher Au M-shell preheat resulted in an increase in Atwood number at the ablator–ice interface, which leads to increased fuel-ablator instability and mixing. The results reported here provide important scaling information for next-generation CH designs.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Neutron Time-of-Flight Measurements of Charged-Particle Energy Loss in Inertial Confinement Fusion Plasmas

Neutron spectra from secondary 3 H(d,n)α reactions produced by an implosion of a deuterium-gas capsule at the National Ignition Facility have been measured with order-of-magnitude improvements in statistics and resolution over past experiments. Furthermore, these new data and their sensitivity to the energy loss of fast tritons emitted from thermal 2 H(d,p) 3 H reactions enable the first statistically significant investigation of charged-particle stopping via the emitted neutron spectrum. Radiation-hydrodynamic simulations, constrained to match a number of observables from the implosion, were used to predict the neutron spectra while employing two different energy loss models. This analysis represents the first test of stopping models under inertial confinement fusion conditions, covering plasma temperatures of k B T ≈ 1–4 keV and particle densities of n ≈ (12–2) × 10 24 cm –3 . Under these conditions, we find significant deviations of our data from a theory employing classical collisions whereas the theory including quantum diffraction agrees with our data.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Diagnosing residual motion via the x-ray self emission from indirectly driven inertial confinement implosions

In an indirectly driven implosion, non-radial translational motion of the compressed fusion capsule is a signature of residual kinetic energy not coupled into the compressional heating of the target. A reduction in compression reduces the peak pressure and nuclear performance of the implosion. Measuring and reducing the residual motion of the implosion is therefore necessary to improve performance and isolate other effects that degrade performance. Using the gated x-ray diagnostic, the x-ray Bremsstrahlung emission from the compressed capsule is spatially and temporally resolved at x-ray energies of >8.7 keV, allowing for measurements of the residual velocity. Here details of the x-ray velocity measurement and fitting routine will be discussed and measurements will be compared to the velocities inferred from the neutron time of flight detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Photon strength and the low-energy enhancement

Several measurements in medium mass nuclei have reported a low-energy enhancement in the photon strength function. Although, much effort has been invested in unraveling the mysteries of this effect, its physical origin is still not conclusively understood. Here, a completely model-independent experimental approach to investigate the existence of this enhancement is presented. The experiment was designed to study statistical feeding from the quasi-continuum (below the neutron separation energy) to individual low-lying discrete levels in {sup 95}Mo produced in the (d, p) reaction. A key aspect to successfully study gamma decay from the region of high-level density is the detection and extraction of correlated particle-gamma-gamma events which was accomplished using an array of Clover HPGe detectors and large area annular silicon detectors. The entrance channel excitation energy into the residual nucleus produced in the reaction was inferred from the detected proton energies in the silicon detectors. Gating on gamma-transitions originating from low-lying discrete levels specifies the state fed by statistical gamma-rays. Any particle-gamma-gamma event in combination with specific energy sum requirements ensures a clean and unambiguous determination of the initial and final state of the observed gamma rays. With these requirements the statistical feeding to individual discrete levels is extracted on an event-by-event basis. The results are presented and compared to {sup 95}Mo photon strength function data measured at the University of Oslo.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗