Frank Lopez, Hans Herrmann, Ramon Leeper, Steve Batha, John Oertel, Jeffrey Griego, Brian Steinfeld, Paul Polk, Lynne Goodwin, Valerie Fatherley, Thomas Archuleta, Robert Aragonez, Benjamin Pederson, John Celeste, Robin Hibbard, Arthur Carpenter, Jose Hernandez, Jorge Carrera, Hesham Khater, Eric Downing, Nicholas St. Hilaire, Shiva Sitaraman
Fielding the LANL third-generation Gas Cherenkov Detector (GCD-3) at the National Ignition Facility (NIF) revealed an
array of complex engineering challenges. Fielding the GCD-3 Detector in a 3.9 meter re-entrant Well on the NIF Target
Chamber required the development of a specialized detector deployment system named the WellDIM3.9m Diagnostic
Manipulator (WellDIM). The most stringent design requirement entailed a no-load/no-contact condition with the Well, which
dictated that all seismic loads be transferred to the Target Chamber port flange. The WellDIM transports the GCD-3 into the
Well at a distance of 3.9m from Target Chamber Center. The GCD-3 Detector, outfitted with additional shielding to mitigate
higher NIF backgrounds, will serve as a prototype for the future, heavily shielded “Super-GCD”.
The newest Gas Cherenkov Detector (GCD-3) diagnostic has completed its Phase I commissioning/milestone at the
National Ignition Facility (NIF). GCD-3 was fielded for several years at the Omega Laser Facility in its initial
configuration, before being moved to the NIF. Installation at the NIF involved optimization of GCD-3 for the higher
background environment and designing a new insertion carrier assembly. GCD-3 serves as the initial phase towards the
implementation of the “Super GCD” (SGCD) at the NIF. During this phase of development GCD-3 took measurements
from a re-entrant well, 3.9 meters from target chamber center (TCC). Plans to insert GCD-3 within 20 cm of TCC with a
Target and Diagnostic Manipulator (TANDM) will be discussed. Data was collected using a Photomultiplier Tube
(PMT) in combination with a Mach-Zehnder based recording system. These measurements were used to aid in shielding
analysis, validate MCNP models, and fuel design efforts for the SGCD. Findings from the initial data will be covered
extensively, including an in-depth look into sources of background and possible mitigation strategies. Ongoing
development of phase two, the addition of an ultra-high bandwidth Pulse Dilatation Photomultiplier Tube (PD-PMT),
will also be presented.
KEYWORDS: National Ignition Facility, Signal to noise ratio, Digital recording, Sensors, Data transmission, Photodiodes, Diagnostics, Amplifiers, Oscilloscopes, Interference (communication)
This paper covers the performance of a high speed analogue data transmission system. This system uses multiple Mach-
Zehnder optical modulators to transmit and record fusion burn history data for the Gas Cherenkov Detector (GCD) on
the National Ignition Facility. The GCD is designed to measure the burn duration of high energy gamma rays generated
by Deuterium-Tritium (DT) interactions in the NIF. The burn duration of DT fusion can be as short as 10ps and the
optical photons generated in the gas Cherenkov cell are measured using a vacuum photodiode with a FWHM of ~55ps.
A recording system with a 3dB bandwidth of ≥10GHz and a signal to noise ratio of ≥5 for photodiode output voltage of
50mV is presented. The data transmission system uses two or three Mach-Zehnder modulators and an RF amplifier to
transmit data optically. This signal is received and recorded by optical to electrical converts and a high speed digital
oscilloscope placed outside of the NIF Target Bay. Electrical performance metrics covered include signal to noise ratio
(SNR), signal to peak to peak noise ratio, single shot dynamic range, shot to shot dynamic range, system bandwidth,
scattering parameters, are shown. Design considerations such as self-test capabilities, the NIF radiation environment,
upgrade compatibility, Mach-Zehnder (MZ) biasing, maintainability, and operating considerations for the use of MZs are
covered. This data recording system will be used for the future upgrade of the GCD to be used with a Pulse Dilation
PMT, currently under development.
We will describe the installation and wavelength calibration of a multiple monochromatic imager [MMI]1 to be used on mix experiments at National Ignition Facility [NIF]2. The imager works between 8 and 13 keV, has a spatial resolution of 16 micrometers and generates many images each with an energy bandwidth of ~80 eV. The images are recorded either on image plates or on gated x-ray detectors. We will describe: how we aligned the instrument on the bench using visible light, how we checked the alignment and determined the energy range using a k-alpha x-ray source, and how we installed and aligned the instrument to the NIF target chamber.
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