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A new technique that uses inertial confinement implosions for measuring low-energy nuclear reactions important to nuclear astrophysics is described. Simultaneous measurements of n–D and n–T elastic scattering at 14.1 MeV using deuterium–tritium gas-filled capsules provide a proof of principle for this technique. Measurements have been made of D(d,p)T (dd) and T(t,2n)[superscript 4]He (tt) reaction yields relative to the D(t,n)[superscript]He (dt) reaction yield for deuterium–tritium mixtures with fT/fD between 0.62 and 0.75 and for a wide range of ion temperatures to test our understanding of the implosion processes. Measurements of the shape of the neutron spectrum from the T(t,2n)[superscript 4]He reaction have been made for each of these target configurations., National Laser User’s Facility (Grant NA0000877), United States. Dept. of Energy (Grant DE-FG52-09NA29553), University of Rochester. Fusion Science Center (Rochester Subaward 415023-G, UR Account 5-24431), University of Rochester. Laboratory for Laser Energetics (Grant 412160-001G), Lawrence Livermore National Laboratory (Grants B580243 and DE-AC52-07NA27344)

The ablator couples energy between the driver and fusion fuel in inertial confinement fusion (ICF). Because of its low opacity, high solid density, and material properties, beryllium has long been considered an ideal ablator for ICF ignition experiments at the National Ignition Facility. We report here the first indirect drive Be implosions driven with shaped laser pulses and diagnosed with fusion yield at the OMEGA laser. The results show good performance with an average DD neutron yield of ~2 × 10[superscript 9] at a convergence ratio of R[subscript 0]/R ~ 10 and little impact due to the growth of hydrodynamic instabilities and mix. In addition, the effect of adding an inner liner of W between the Be and DD is demonstrated., United States. Dept. of Energy (Lawrence Livermore National Laboratory Contract DE-AC52-07NA27344)

Monoenergetic-proton radiographs of laser-generated, high-Mach-number plasma jets colliding at various angles shed light on the structures and dynamics of these collisions. The observations compare favorably with results from 2D hydrodynamic simulations of multistream plasma jets, and also with results from an analytic treatment of electron flow and magnetic field advection. In collisions of two noncollinear jets, the observed flow structure is similar to the analytic model’s prediction of a characteristic feature with a narrow structure pointing in one direction and a much thicker one pointing in the opposite direction. Spontaneous magnetic fields, largely azimuthal around the colliding jets and generated by the well-known ∇T[subscript e] × ∇n[subscript e] Biermann battery effect near the periphery of the laser spots, are demonstrated to be “frozen in” the plasma (due to high magnetic Reynolds number Re[subscript M] ~ 5 × 10[superscript 4]) and advected along the jet streamlines of the electron flow. These studies provide novel insight into the interactions and dynamics of colliding plasma jets., United States. Dept. of Energy (University of Rochester. Laboratory for Laser Energetics. National Laser User’s Facility DE-FG52-07NA28 059), United States. Dept. of Energy (University of Rochester. Laboratory for Laser Energetics. National Laser User’s Facility DE-FG03-03SF22691), Lawrence Livermore National Laboratory (B543881), Lawrence Livermore National Laboratory (LDRD-08-ER-062), University of Rochester. Laboratory for Laser Energetics (414090-G), University of Rochester. Fusion Science Center (412761-G)

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Cataloged from student submitted PDF version of thesis., Includes bibliographical references (p. 139-148)., A novel neutron spectrometer, called the Magnetic Recoil Spectrometer (MRS), was designed, built, and implemented on the OMEGA laser facility and the National Ignition Facility (NIF) to measure the neutron spectra from inertial confinement fusion (ICF) implosions. Using the MRS, the down-scattered neutron (DSn) spectrum has been used to infer the areal density ([rho]R) of ICF implosions for the first time. The DSn technique is essential for diagnosing high [rho]R (>180mg/cm²) cryogenic deuterium-tritium (DT) implosions, where most other methods fail. The MRS has helped to guide the cryogenic campaign toward the highest [rho]Rs ever achieved at OMEGA. In addition, the MRS is currently being used to diagnose the DSn spectrum from cryogenic implosions at the NIF during the beginning phases of the National Ignition Campaign (NIC). MRS data have already been essential for tuning these implosions to the highest [rho]Rs ever achieved in an ICF implosion (>1 g/cm²), and thus for guiding the NIC toward the realization of thermonuclear ignition. The first measurements of the T(t,2n)⁴He (TT) neutron spectrum in DT implosions at OMEGA have also been conducted using the MRS. The TT-neutron (TTn) spectrum was measured at low reactant central-mass energies of ~23 keV. The results from these measurements indicate that the TT reaction proceeds primarily through the direct three-body reaction channel, which is in contrast to the results obtained in higher energy accelerator experiments. Measurements of the TTn and DD proton yields were also conducted and compared to the DT neutron yield in DT implosions. From these measurements, it is concluded that the DD yield is anomalously low and the TTn yield is anomalously high, relative to the DT yield. These results have been explained by a stratification of the fuel in the core of an ICF implosion., by Daniel Thomas Casey., Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Cataloged from student submitted PDF version of thesis., Includes bibliographical references (p. 139-148)., A novel neutron spectrometer, called the Magnetic Recoil Spectrometer (MRS), was designed, built, and implemented on the OMEGA laser facility and the National Ignition Facility (NIF) to measure the neutron spectra from inertial confinement fusion (ICF) implosions. Using the MRS, the down-scattered neutron (DSn) spectrum has been used to infer the areal density ([rho]R) of ICF implosions for the first time. The DSn technique is essential for diagnosing high [rho]R (>180mg/cm²) cryogenic deuterium-tritium (DT) implosions, where most other methods fail. The MRS has helped to guide the cryogenic campaign toward the highest [rho]Rs ever achieved at OMEGA. In addition, the MRS is currently being used to diagnose the DSn spectrum from cryogenic implosions at the NIF during the beginning phases of the National Ignition Campaign (NIC). MRS data have already been essential for tuning these implosions to the highest [rho]Rs ever achieved in an ICF implosion (>1 g/cm²), and thus for guiding the NIC toward the realization of thermonuclear ignition. The first measurements of the T(t,2n)⁴He (TT) neutron spectrum in DT implosions at OMEGA have also been conducted using the MRS. The TT-neutron (TTn) spectrum was measured at low reactant central-mass energies of ~23 keV. The results from these measurements indicate that the TT reaction proceeds primarily through the direct three-body reaction channel, which is in contrast to the results obtained in higher energy accelerator experiments. Measurements of the TTn and DD proton yields were also conducted and compared to the DT neutron yield in DT implosions. From these measurements, it is concluded that the DD yield is anomalously low and the TTn yield is anomalously high, relative to the DT yield. These results have been explained by a stratification of the fuel in the core of an ICF implosion., by Daniel Thomas Casey., Ph.D.

The deuterium-tritium (D-T) γ-to-neutron branching ratio [[superscript 3]H(d,γ)[superscript 5]He/[superscript 3]H(d,n)[superscript 4]He] was determined under inertial confinement fusion (ICF) conditions, where the center-of-mass energy of 14–24 keV is lower than that in previous accelerator-based experiments. A D-T branching ratio value of (4.2 ± 2.0) × 10[superscript −5] was determined by averaging the results of two methods: (1) a direct measurement of ICF D-T γ-ray and neutron emissions using absolutely calibrated detectors, and (2) a separate cross-calibration against the D-[superscript 3]He γ-to-proton branching ratio [[superscript 3]He(d,γ)[superscript 5]Li/[superscript 3]He(d,p)[superscript 4]He]. Neutron-induced backgrounds were significantly reduced as compared to traditional beam-target accelerator-based experiments due to the short pulse nature of ICF implosions and the use of gas Cherenkov γ-ray detectors with fast temporal responses and inherent energy thresholds. These measurements of the D-T branching ratio in an ICF environment test several theoretical assumptions about the nature of A = 5 systems, including the dominance of the 3/2[superscript +] resonance at low energies, the presence of the broad first excited state of [superscript 5]He in the spectra, and the charge-symmetric nature of the capture processes in the mirror systems [superscript 5]He and [superscript 5]Li., National Laser User’s Facility (United States. Dept. of Energy.) (Grant number DE-FG03-03SF2269), University of Rochester. Fusion Science Center (United States. Dept. of Energy.) (Grant. Number DE-FC02-04ER54789)

Ignition implosions on the National Ignition Facility [ J. D. Lindl et al. Phys. Plasmas 11 339 (2004)] are underway with the goal of compressing deuterium-tritium fuel to a sufficiently high areal density (ρR) to sustain a self-propagating burn wave required for fusion power gain greater than unity. These implosions are driven with a very carefully tailored sequence of four shock waves that must be timed to very high precision to keep the fuel entropy and adiabat low and ρR high. The first series of precision tuning experiments on the National Ignition Facility, which use optical diagnostics to directly measure the strength and timing of all four shocks inside a hohlraum-driven, cryogenic liquid-deuterium-filled capsule interior have now been performed. The results of these experiments are presented demonstrating a significant decrease in adiabat over previously untuned implosions. The impact of the improved shock timing is confirmed in related deuterium-tritium layered capsule implosions, which show the highest fuel compression (ρR~1.0 g/cm[superscript 2]) measured to date, exceeding the previous record [ V. Goncharov et al. Phys. Rev. Lett. 104 165001 (2010)] by more than a factor of 3. The experiments also clearly reveal an issue with the 4th shock velocity, which is observed to be 20% slower than predictions from numerical simulation., Lawrence Livermore National Laboratory (Contract No. DE-AC52-07NA27344)

Ignition implosions on the National Ignition Facility [ J. D. Lindl et al. Phys. Plasmas 11 339 (2004)] are underway with the goal of compressing deuterium-tritium fuel to a sufficiently high areal density (ρR) to sustain a self-propagating burn wave required for fusion power gain greater than unity. These implosions are driven with a very carefully tailored sequence of four shock waves that must be timed to very high precision to keep the fuel entropy and adiabat low and ρR high. The first series of precision tuning experiments on the National Ignition Facility, which use optical diagnostics to directly measure the strength and timing of all four shocks inside a hohlraum-driven, cryogenic liquid-deuterium-filled capsule interior have now been performed. The results of these experiments are presented demonstrating a significant decrease in adiabat over previously untuned implosions. The impact of the improved shock timing is confirmed in related deuterium-tritium layered capsule implosions, which show the highest fuel compression (ρR~1.0 g/cm[superscript 2]) measured to date, exceeding the previous record [ V. Goncharov et al. Phys. Rev. Lett. 104 165001 (2010)] by more than a factor of 3. The experiments also clearly reveal an issue with the 4th shock velocity, which is observed to be 20% slower than predictions from numerical simulation., Lawrence Livermore National Laboratory (Contract No. DE-AC52-07NA27344)

The National Ignition Facility has been used to compress deuterium-tritium to an average areal density of ~1.0±0.1 g cm[superscript -2], which is 67% of the ignition requirement. These conditions were obtained using 192 laser beams with total energy of 1–1.6 MJ and peak power up to 420 TW to create a hohlraum drive with a shaped power profile, peaking at a soft x-ray radiation temperature of 275–300 eV. This pulse delivered a series of shocks that compressed a capsule containing cryogenic deuterium-tritium to a radius of 25–35 μm. Neutron images of the implosion were used to estimate a fuel density of 500–800 g cm[superscript -3]., Lawrence Livermore National Laboratory (Contract No. DE-AC52-07NA27344)

For the first time the differential cross section for the elastic neutron-triton (n-[superscript 3]H) and neutron-deuteron (n-[superscript 2]H) scattering at 14.1 MeV has been measured by using an inertial confinement fusion facility. In these experiments, which were carried out by simultaneously measuring elastically scattered [superscript 3]H and [superscript 2]H ions from a deuterium-tritium gas-filled inertial confinement fusion capsule implosion, the differential cross section for the elastic n-[superscript 3]H scattering was obtained with significantly higher accuracy than achieved in previous accelerator experiments. The results compare well with calculations that combine the resonating-group method with an ab initio no-core shell model, which demonstrate that recent advances in ab initio theory can provide an accurate description of light-ion reactions., United States. Dept. of Energy (Grant No. NA0000877), University of Rochester. Fusion Science Center (Rochester Subaward PO No. 415023-G, UR Account No. 5-24431), United States. Dept. of Energy (Grant No. DE-FG03-03SF22691), University of Rochester. Laboratory for Laser Energetics (Grant No. 412160-001G), Lawrence Livermore National Laboratory (Grant No. B504974), United States. Dept. of Energy (Grant No. DE-AC52-06NA27279)

Measurements of the neutron spectrum from the T(t,2n)[superscript 4]He (tt) reaction have been conducted using inertial confinement fusion implosions at the OMEGA laser facility. In these experiments, deuterium-tritium (DT) gas-filled capsules were imploded to study the tt reaction in thermonuclear plasmas at low reactant center-of-mass (c.m.) energies. In contrast to accelerator experiments at higher c.m. energies (above 100 keV), these results indicate a negligible n+[superscript 5]He reaction channel at a c.m. energy of 23 keV., United States. Dept. of Energy (grant no. DE-FG52-09NA29553), National Laser User’s Facility (grant no. NA0000877), University of Rochester. Fusion Science Center (subaward PO no. 415023-G, UR acct. no. 5-24431), University of Rochester. Laboratory for Laser Energetics (grant no. 412160-001G), Lawrence Livermore National Laboratory (grant nos. B580243 and DE-AC52-07NA27344)

Measurements of the D(d,p)T (dd) and T(t,2n)[superscript 4]He (tt) reaction yields have been compared with those of the D(t,n)[superscript 4]He (dt) reaction yield, using deuterium-tritium gas-filled inertial confinement fusion capsule implosions. In these experiments, carried out on the OMEGA laser, absolute spectral measurements of dd protons and tt neutrons were obtained. From these measurements, it was concluded that the dd yield is anomalously low and the tt yield is anomalously high relative to the dt yield, an observation that we conjecture to be caused by a stratification of the fuel in the implosion core. This effect may be present in ignition experiments planned on the National Ignition Facility., University of Rochester. Fusion Science Center (412761-G), University of Rochester. Laboratory for Laser Energetics (414090-G), Lawrence Livermore National Laboratory (B580243), United States. Dept. of Energy (DE-NA0000877), United States. Dept. of Energy (DE-FG52-09NA29553)

For the first time the differential cross section for the elastic neutron-triton (n-[superscript 3]H) and neutron-deuteron (n-[superscript 2]H) scattering at 14.1 MeV has been measured by using an inertial confinement fusion facility. In these experiments, which were carried out by simultaneously measuring elastically scattered [superscript 3]H and [superscript 2]H ions from a deuterium-tritium gas-filled inertial confinement fusion capsule implosion, the differential cross section for the elastic n-[superscript 3]H scattering was obtained with significantly higher accuracy than achieved in previous accelerator experiments. The results compare well with calculations that combine the resonating-group method with an ab initio no-core shell model, which demonstrate that recent advances in ab initio theory can provide an accurate description of light-ion reactions., United States. Dept. of Energy (Grant No. NA0000877), University of Rochester. Fusion Science Center (Rochester Subaward PO No. 415023-G, UR Account No. 5-24431), United States. Dept. of Energy (Grant No. DE-FG03-03SF22691), University of Rochester. Laboratory for Laser Energetics (Grant No. 412160-001G), Lawrence Livermore National Laboratory (Grant No. B504974), United States. Dept. of Energy (Grant No. DE-AC52-06NA27279)

The performance of triple-picket deuterium-tritium cryogenic target designs on the OMEGA Laser System [T.R. Boehly et al., Opt. Commun. 133, 495 (1997)] is reported. These designs facilitate control of shock heating in low-adiabat inertial confinement fusion targets. Areal densities up to 300 mg=cm[superscript 2] (the highest ever measured in cryogenic deuterium-tritium implosions) are inferred in the experiments with an implosion velocity ~3×10[superscript 7] cm=s driven at peak laser intensities of 8×10[superscript 14] W=cm[superscript 2]. Extension of these designs to ignition on the National Ignition Facility [J. A. Paisner et al., Laser FocusWorld 30, 75 (1994)] is presented., United States. Office of Inertial Confinement Fusion (Cooperative Agreement No. DE-FC52-08NA28302), University of Rochester, New York State Energy Research and Development Authority