ZEBRA
The Zebra pulsed-power generator is driven by the discharge of a Marx capacitor bank with 150kJ of energy that delivers a 1MA peak current pulse with a rise time of 90ns or a 0.6MA peak current with a rise time of 250ns. A load current multiplier option increases the peak current up to 1.6MA. The Zebra experimental chamber sits atop a vertical transmission line that has 16 diagnostics ports, equally spaced at 22.5 degrees, with alternating diameters of 3” and 2”. Diagnostics ports can be used for fielding core as well as user provided diagnostics. Core diagnostics include a bolometer and PCDs and XRDs for radiation energy and power measurements, four-color optical laser shadowgraphy and interferometry, Faraday rotation diagnostics, x-ray pinhole cameras, and visible and x-ray spectroscopy. Zebra can be used with several type of loads including a variety of wire-arrays, gas puffs, and customized rod and coil loads. The latter produce magnetic fields in the 1MG to 4MG range in a volume of 10mm3 for over 30ns. Wire array implosions radiate a bright broadband x-ray flux with up to 20kJ of x-ray energy in a 12-25 ns time interval. In addition, the 50TW Leopard laser beam can be coupled to Zebra experiments. Leopard in long-pulse mode delivers 30J in 0.8ns and in short-pulse 15J in 0.35ps. Coupled Zebra-Leopard shots create opportunities to investigate magnetized plasma physics in MegaGauss-range magnetic fields as well as the fundamental physics of magnetized inertial fusion energy.
Diagnostics Summary
The suite of core diagnostics available at Zebra includes four-color optical laser diagnostics for multi-frame shadowgraphy, interferometry and Faraday rotation; diffraction grating and crystal spectrometers for visible, UV and x-ray spectroscopy; and neutron detectors and diagnostics. In addition, customized diagnostics for specific applications will be considered and discussed with the user.
The detail of core diagnostics and instrumentation follows:
B-dots: Load and Stack B-dots are used for current measurement detectors on the Zebra pulsed-power machine, specifically for current pulse diagnostics, and for the triggering of other diagnostics. Three load B-dots and two stack B-dots are emplyed on each zebra shot.
XRD: X-Ray Detectors (XRDs) for the measurement of x-ray radiation yields from the Zebra pulsed-power machine.
PCD: Filtered X-ray and photoconductive diodes.
Bolometers: Ni bolometer for measuring the energy of x-ray flux. Two Bolometers can be set up concurrently on the Zebra pulsed-power machine.
MCP detector: Micro-channel Plates for time-gated diagnostics such as x-ray spectrometer and pinhole imaging.
Spectrometers: Time-integrated spectroscopy measurements can be performed on Zebra experiments. Measurements are made with a time-integrating, axially resolved, x-ray spectrometer equipped with KAP or quartz crystals, as well as with the cylindrical/conical Von Hamos spectrometer with mica crystals for the keV spectral range, and an X-ray conical focusing spectrometer with a mica crystal.
Pinhole cameras: Time-integrated pinhole camera with MCP for two spectral ranges, namely, E1>1 keV and E2>3.2 keV are available.
Laser diagnostics: Two-frame shadowgraphy system including several laser wavelengths (1064, 532, 266 nm, 150ps, 60-300 mJ), four CCD cameras, and two laptops for data acquisition. A UV laser system for shadowgraphy and interferometry, including a laser (266nm, 150 ps) and three UV CCD cameras are also available.
Additional laser diagnostic capabilities include interferometry with Mach-Zehnder and differential interferometers, Faraday rotation and Schlieren diagnostics at 532 nm with 4 CCD cameras, and two laptops for data acquisition. Optical grating spectrometer with an ICCD camera is available.
Bubble detectors: BTI bubble detectors for fast and thermal neutron detection.
Scintillation Detectors: Scintillation PMT BC-400 detectors for neutron and gamma detection.
Gamma detectors: NaI detectors for detection of gamma rays.
CCD and ICCD Cameras: Optical, time-gated CCD cameras.
Streak Cameras: Optical streak cameras.
Oscilloscopes: A collection of 6 scopes is available that are used for various diagnostics measurements for experiments on Zebra and Leopard, along with computers for data collection and storage.
Delay Generators: 8 delay generators are used around the facility on various diagnostics and lasers for triggering, timing and synchronization purposes.
Power supplies: high-voltage (1KV-5KV range) power supplies are available for diagnostics.
Other: multiple gate valves, two fast-valve setups and a wide variety of screen boxes, pulsers, numerous low-voltage power supplies and various test equipment are available to support all diagnostics.
Zebra-Leopard coupled shots
The Leopard laser is a high-power, hybrid Ti:Sapphire/Nd:glass laser system that can be operated in long (30J, 0.8ns) or short (15J, 0.35ps) pulse modes delivering up to 1019W/cm2 on target with a bandwidth of 5nm. A vertical laser beam access has been installed in the Zebra target chamber to bring in the Leopard laser beam to support coupled Zebra pulsed power and Leopard laser experiments. The short-pulse Leopard laser beam is transported to the Zebra vacuum chamber through the Optical Switching Apparatus, i.e., an evacuated beam line. This apparatus focuses the short pulse Leopard beam with an Off-Axis Parabolic (OAP) mirror. The long pulse is transported to Zebra through a different optical path and focused on target with lenses. The refractive optics can focus the laser beam within a region of about 5cm in diameter around the center of the Zebra target chamber. The Zebra generator is synchronized with lasers for coupled shots and diagnostics. Examples of Zebra-Leopard coupled shots include using Leopard to drive a source of backlit photons for Zebra experiments as well as studying magnetized plasmas in MegaGauss-range magnetic fields.