Sandia National Laboratories has been operating the Mykonos linear transformer driver (LTD) in a five-cavity configuration since 2014. The machine operates at 1MA output current, 500kV output voltage, with a 10-90% current rise time of 85ns, which enables small scale physics and engineering pulsed power experiments. Mykonos provides hands-on pulsed power experimental training for students and staff along-side senior Sandia scientists in an environment that is more accessible than the Z Facility. Over the years, we have fielded and accumulated a wide variety of optical, x-ray and electrical diagnostics and we are preparing to open this facility to outside users. Here, we are presenting the pulsed power and diagnostic capability of Mykonos as well as some recent experiments that have been performed on the facility. The goal of this publication is to attract researchers across the pulsed power and high energy density (HED) community to collaborate with Sandia on exciting, innovative science and to train the next generation of researchers for the National Nuclear Security Agency (NNSA) and the nation. As such, we have established a Mykonos Academic Access Program (MAAP) as part of ZNetUS to enable academic utilization of the Mykonos Pulsed Power Facility.

Helium or neopentane can be used as surrogate gas fill for deuterium (D2) or deuterium-tritium (DT) in laser-plasma interaction studies. Surrogates are convenient to avoid flammability hazards or the integration of cryogenics in an experiment. To test the degree of equivalency between deuterium and helium, experiments were conducted in the Pecos target chamber at Sandia National Laboratories. Observables such as laser propagation and signatures of laser-plasma instabilities (LPI) were recorded for multiple laser and target configurations. It was found that some observables can differ significantly despite the apparent similarity of the gases with respect to molecular charge and weight. While a qualitative behaviour of the interaction may very well be studied by finding a suitable compromise of laser absorption, electron density, and LPI cross sections, a quantitative investigation of expected values for deuterium fills at high laser intensities is not likely to succeed with surrogate gases.

The Daedalus ultrafast x-ray imager is the latest generation in Sandia's hybrid CMOS detector family. With three frames along an identical line of sight, 1 ns minimum integration time, a higher full well than Icarus, and added features, Daedalus brings exciting new capabilities to diagnostic applications in inertial confinement fusion and high energy density science. In this work, we present measurements of time response, dynamic range, spatial uniformity, pixel cross-talk, and absolute x-ray sensitivity using pulsed optical and x-ray sources. We report a measured 1.5 Me- full well, pixel sensitivity at 9.58 × 10-7 V/e-, and an estimate of spatial uniformity at ∼5% across the sensor array.

The carbon phase diagram is rich with polymorphs which possess very different physical and optical properties ideal for different scientific and engineering applications. An understanding of the dynamically driven phase transitions in carbon is particularly important for applications in inertial confinement fusion, as well as planetary and meteorite impact histories. Experiments on the Z Pulsed Power Facility at Sandia National Laboratories generate dynamically compressed high-pressure states of matter with exceptional uniformity, duration, and size that are ideal for investigations of fundamental material properties. X-ray diffraction (XRD) is an important material physics measurement because it enables direct observation of the strain and compression of the crystal lattice, and it enables the detection and identification of phase transitions. Several unique challenges of dynamic compression experiments on Z prevent using XRD systems typically utilized at other dynamic compression facilities, so novel XRD diagnostics have been designed and implemented. We performed experiments on Z to shock compress carbon (pyrolytic graphite) samples to pressures of 150–320 GPa. The Z-Beamlet Laser generated Mn-Heα (6.2 keV) X-rays to probe the shock-compressed carbon sample, and the new XRD diagnostics measured changes in the diffraction pattern as the carbon transformed into its high-pressure phases. Quantitative analysis of the dynamic XRD patterns in combination with continuum velocimetry information constrained the stability fields and melting of high-pressure carbon polymorphs.

Diagnostics in high energy density physics, shock physics, and related fields are primarily driven by a need to record rapidly time-evolving signals in single-shot events. These measurements are often limited by channel count and signal degradation issues on cable links between the detector and digitizer. We present the Ultrafast Pixel Array Camera (UPAC), a compact and flexible detector readout system with 32 waveform-recording channels at up to 10 Gsample/s and 1.8 GHz analog bandwidth. The compact footprint allows the UPAC to be directly embedded in the detector environment. A key enabling technology is the PSEC4A chip, an eight-channel switch-capacitor array sampling device with up to 1056 samples/channel. The UPAC system includes a high-density input connector that can plug directly into an application-specific detector board, programmable control, and serial readout, with less than 5 W of power consumption in full operation. We present the UPAC design and characterization, including a measured timing resolution of ∼20 ps or better on acquisitions of sub-nanosecond pulses with minimal system calibrations. Example applications of the UPAC are also shown to demonstrate operation of a solid-state streak camera, an ultrafast imaging array, and a neutron time-of-flight spectrometer.

Many experiments at Sandia?s Z Pulsed Power Facility require x - ray backlighting diagnostics to understand experiment performance. Due to limitations in present - day source/detection modalities, most x - ray diagnostics at Z are restricted to photon energies < 20 keV, ultimately limiting the density, amount, and atomic number of targets diagnosable in experiments. These limitations force the use of low - Z materials like Beryllium, and they prevent acquisition of important backlighting data for materials/densities that are opaque to soft x - rays and where background emission from the Z load and transmission lines overwhelm diagnostics. In this LDRD project, we have investigated the design and development of a laser wakefield acceleration platform driven by the Z - Petawatt laser ? a platform that would enable the generation of a pulsed, collimated beam of high energ y x - rays up to 100 keV. Geometrical considerations for implementation on the Z Machine require the use of sacrificial mirrors , which have been tested in offline experiments in the Chama target chamber in building 983. Our results suggest the use of sacrifi cial mirrors would not necessarily inhibit the laser wakefield x - ray process , particularly with the benefits stemming from planned laser upgrades. These conclusions s upport the continuation of laser wakefield source research and the development of the nece ssary infrastructure to deliver the Z - Petawatt laser to the Z center section along the appropriate lines of sight. Ultimately, this new capability will provid e unprecedented view s through dense states of matter , enabling the use of previously incompatible target m aterials/designs, and uncover ing a new set of observables accessible through diffraction and spectroscopy in the hard x - ray regime. These will amplify the data return on precious Z shots and enhanc e Sandia?s ability to investigate fundamental physi cs in support of national security .

Antireflection coatings, containing alternating layers of hafnia (HfO2) and silica (SiO2), were deposited using electron beam (e-beam) evaporation for use in laser operations at 532 nm and 1064 nm in the nanosecond regime. The e-beam evaporation process produces coatings that are porous and therefore absorb water from the ambient environment. Consequently, humidity may affect the spectral performance of the coatings, and the laser damage resistance of the coatings may be affected as well. The purpose of this study was to compare the laser-induced damage thresholds of the antireflection coatings measured in the ambient environment at 0% and 40.5% relative humidity. At 1064 nm, the laserinduced damage thresholds at 0% and 40.5% relative humidity were almost the same. However, at 532 nm, the laserinduced damage thresholds at 40.5% relative humidity were nearly twice as high as those measured at 0% relative humidity. This indicates that humidity can inhibit lower-fluence precursors that would lead to laser damage at 532 nm in the nanosecond regime, thereby improving the durability of the coatings in a humid environment.

We’re happy to report that the full-aperture upgrade project, started in FY18, is now complete and short-pulse target experiments are underway. The table below lists the present performance level of ZPW. Additional laser improvements are in progress to increase the laser energy and pulse contrast along with implementing a correction for achromatic aberrations to reduce the focused spot size and pulse width.

Hybrid CMOS multi-frame imagers with exposure times down to ∼2 ns have made significant impacts in high energy density physics and inertial confinement fusion research. The detector thickness is a key parameter in both detector quantum efficiency and temporal response. The Icarus hybrid CMOS imager has been fabricated with Si detector thicknesses of 8, 25, and 100 µm. The temporal response of imaging sensors with exposure time down to 2 ns has been examined and compared to directly measured photodiode current. The 100-μm thick variant displays extended features related to charge carrier collection and is more susceptible to field collapse. We also demonstrate charge collection time effects on spatial response.

Ultrafast x-ray imagers developed at Sandia National Laboratories are a transformative diagnostic tool in inertial confinement fusion and high energy density physics experiments. The nanosecond time scales on which these devices operate are a regime with little precedent, and applicable characterization procedures are still developing. This paper presents pulsed x-ray characterization of the Icarus imager under a variety of illumination levels and timing modes. Results are presented for linearity of response, absolute sensitivity, variation of response with gate width, and image quality.

Determination of the interacting triton energy spectrum from secondary neutron energy spectroscopy and its application to studies of fuel-pusher mixing will also be discussed.

than the uncertainty (0.2 ± 1.2) nA/cm{sup −2} at 0 °C to (9.39 ± 0.02) μA/cm{sup −2} at 120 °C for D2 at the maximum investigated reverse bias (15 V). The best energy resolution (FWHM at 5.9 keV) was achieved at 5 V reverse bias, at each temperature; 730 eV at 0 °C, 750 eV at 20 °C, 770 eV at 40 °C, and 840 eV at 60 °C. It was found that the parallel white noise was the main source of the photopeak broadening only when the detector operated at 60 °C, at 5 V, 10 V, and 15 V reverse bias and at long shaping times (>5 μs), whereas the sum of the dielectric noise and charge trapping noise was the dominant source of noise for all the other spectra.

Fast x-ray detectors are critical tools in pulsed power and fusion applications, where detector impulse response of a nanosecond or better is often required. Semiconductor detectors can create fast, sensitive devices with extensive operational flexibility. There is typically a trade-off between detector sensitivity and speed, but higher atomic number absorbers can increase hard x-ray absorption without increasing the charge collection time, provided carriers achieve high velocity. This paper presents x-ray pulse characterization conducted at the Advanced Photon Source of x-ray absorption efficiency and temporal impulse response of current-mode semiconductor x-ray detectors composed of Si, GaAs, and CdTe.

Magnetized Liner Inertial Fusion (MagLIF) is a magneto-inertial fusion concept currently being investigated on Sandia's Z facility. In MagLIF an axial magnetic field of 10–30 T is applied to the cold fusion fuel, which is contained in a cm-scale beryllium can, called a liner. The fuel is then heated by a few-kJ, TW-class laser to around 100 eV, The current from the Z machine flows axially through the liner, causing it to implode. The magnetized, laser-heated fuel is compressed and heated to multi-keV temperatures.