Target diagnostic system for the national ignition facility (invited)

Abstract

A review of recent progress on the design of a diagnostic system proposed for ignition target experiments on the National Ignition Facility (NIF) will be presented. This diagnostic package contains an extensive suite of optical, x ray, gamma ray, and neutron diagnostics that enable measurements of the performance of both direct and indirect driven NIF targets. The philosophy used in designing all of the diagnostics in the set has emphasized redundant and independent measurement of fundamental physical quantities relevant to the operation of the NIF target. A unique feature of these diagnostics is that they are being designed to be capable of operating in the high radiation, electromagnetic pulse, and debris backgrounds expected on the NIF facility. The diagnostic system proposed can be categorized into three broad areas: laser characterization, hohlraum characterization, and capsule performance diagnostics. The operating principles of a representative instrument from each class of diagnostic employed in this package will be summarized and illustrated with data obtained in recent prototype diagnostic tests.

Diagnostics development plan for ZR.

“…This method is almost completely insensitive to target areal density at the point where x-ray imaging techniques fail because of photon absorption [46,[58][59][60]. High spatial resolution and good sensitivity can be achieved using penumbral or annular coded aperture techniques similar to those that were employed in the Nova neutron microscope [61].…”

“…The time history of target thermonuclear emission and the time to peak thermonuclear emission (target bang time) are quantities that depend strongly on the details of target hydrodynamics and plasma conditions and provide a sensitive test for simulations of target behavior [46,47,52,53]. Fusion reaction history diagnostics become practical for neutron yields of 10 10 -10 12 .…”

“…Neutron diagnostics provide essential information on the state of the compressed fuel core in an ICF target [46,47]. The type and accuracy of neutron measurements that are possible for a given experiment depend on the total thermonuclear neutron yield from the target.…”

“…A second basic neutron diagnostic required for initial fuel capsule implosion experiments on ZR is a neutron time-of-flight (TOF) detector system [46,47,50,51]. Neutron TOF measurements of the energy broadening of DD and DT neutrons can determine both the neutron total yield and the fusion burn ion temperature.…”

“…Measurements of fuel areal density <ρr> are essential for characterizing ICF target capsule implosions and are traditionally performed using a number of neutronbased techniques [46,[54][55][56]. One method involves the detection of secondary neutrons produced in reactions in pure deuterium fuel and is useful for <ρr> values below about 20 mg/cm 2 [57].…”