Signal and background considerations for the MRSt on the National Ignition Facility (NIF)

Plasma Phys. Control. Fusion

2020

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The field of nuclear diagnostics for Inertial Confinement Fusion (ICF) is broadly reviewed from its beginning in the seventies to present day. During this time, the sophistication of the ICF facilities and the suite of nuclear diagnostics have substantially evolved, generally a consequence of the efforts and experience gained on previous facilities. As the fusion yields have increased several orders of magnitude during these years, the quality of the nuclear-fusion-product measurements has improved significantly, facilitating an increased level of understanding about the physics governing the nuclear phase of an ICF implosion. The field of ICF has now entered an era where the fusion yields are high enough for nuclear measurements to provide spatial, temporal and spectral information, which have proven indispensable to understanding the performance of an ICF implosion. At the same time, the requirements on the nuclear diagnostics have also become more stringent. To put these measurements into context, this review starts by providing some historical remarks about the field of ICF and the role of nuclear diagnostics, followed by a brief overview of the basic physics that characterize the nuclear phase and performance of an ICF implosion. A technical discussion is subsequently presented of the neutron, gamma-ray, charged-particle and radiochemistry diagnostics that are, or have been, routinely used in the field of ICF. This discussion is followed by an elaboration of the current view of the next-generation nuclear diagnostics. Since the seventies, the overall progress made in the areas of nuclear diagnostics and scientific understanding of an ICF implosion has been enormous, and with the implementation of new high-fusion-yield facilities world-wide, the nextgeneration nuclear diagnostics will play an even more important role for decades to come.

Section: Next-generation Nuclear Diagnosticsmentioning

confidence: 99%

Nuclear diagnostics for Inertial Confinement Fusion (ICF) plasmas

Plasma Phys. Control. Fusion

2020

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“…In these simulations, the MRSt was operated in high-resolution mode, i.e., configuration #1 (Table I), generating about 9500, 41 200, and 790 000 signal protons at the CsI photocathode for the three implosions. According to Wink et al, 15 each proton generates ∼1 secondary electron in the CsI photocathode. See text for additional details.…”

Section: Simulated Mrst Performancementioning

confidence: 99%

“…The details of how the MRSt data will be recorded are still being defined. Additionally, an understanding of the pulse-dilation-drift-tube response to the signal protons (or deuterons in case of a CD 2 foil) and background, mainly consisting of neutrons and γ-rays, is discussed by Wink et al, 15 who also discuss the signal-to-background (S/B) required for successful implementation of the MRSt on the NIF.…”

Section: Simulated Mrst Performancementioning

confidence: 99%

The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF)

Review of Scientific Instruments

Hilsabeck

Wink

et al. 2016

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The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (T), yield (Y), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate data with a time resolution of ∼20 ps and energy resolution of ∼100 keV for total neutron yields above ∼10. At lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ∼20 ps.

“…6 These diagnostics are crucial to the facility; however, in order to assess how the fuel assembly and nuclear burn evolve during the implosion, time-resolved neutron measurements are the key. The MRSt [7][8][9] is being designed as the first instrument for time-resolved measurements of these parameters.…”

Section: Introductionmentioning

confidence: 99%

Implementation of the foil-on-hohlraum technique for the magnetic recoil spectrometer for time-resolved neutron measurements at the National Ignition Facility

Parker

Review of Scientific Instruments

Johnson

et al. 2018

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The next-generation Magnetic Recoil Spectrometer, called MRSt, will provide time-resolved measurements of the deuterium-tritium-neutron spectrum from inertial confinement fusion implosions at the National Ignition Facility. These measurements will provide critical information about the time evolution of the fuel assembly, hot-spot formation, and nuclear burn. The absolute neutron spectrum in the energy range of 12-16 MeV will be measured with high accuracy (∼5%), unprecedented energy resolution (∼100 keV) and, for the first time ever, time resolution (∼20 ps). Crucial to the design of the system is a CD conversion foil for the production of recoil deuterons positioned as close to the implosion as possible. The foil-on-hohlraum technique has been demonstrated by placing a 1-mmdiameter, 40-µm-thick CD foil on the hohlraum diagnostic band along the line-of-sight of the current time-integrated MRS system, which measured the recoil deuterons. In addition to providing validation of the foil-on-hohlraum technique for the MRSt design, substantial improvement of the MRS energy resolution has been demonstrated.