Measurement of areal density in the ablators of inertial-confinement-fusion capsules via detection of ablator (n, n′γ) gamma-ray emission

We report the first gamma-ray-based measurements of the areal density of ablators in inertial-confinement-fusion capsule implosions. The measurements, made at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], used observations of gamma rays arising from inelastic scattering of 14.1-MeV deuterium-tritium (DT) neutrons on 12C nuclei in the compressed plastic ablators. The emission of 12C(n,n′γ) gamma rays from the capsules is detected using the Gamma Reaction History instrument [H. W. Herrmann et al., J. Phys.: Conf. Ser. 244, 032047 (2010)] operating at OMEGA. From the ratio of a capsule's 12C(n,n′γ) emission to the emission from the same processes in an in situ reference graphite “puck” of known mass and geometry [N. M. Hoffman et al., in IFSA 2011 proceedings (submitted)], we determine the time-averaged areal density of 12C in the capsule's compressed ablator. Measured values of total ablator areal density for thirteen imploded capsules, in the range 23 ± 10 to 58 ± 14 mg/cm2, are comp...

[1]  J. M. Mack,et al.  Diagnosing inertial confinement fusion gamma ray physics (invited). , 2010, The Review of scientific instruments.

[2]  P. B. Radha,et al.  Study of direct-drive, deuterium–tritium gas-filled plastic capsule implosions using nuclear diagnostics at OMEGA , 2001 .

[3]  Frederick J. Wysocki,et al.  The effects of laser absorption on direct-drive capsule experiments at OMEGA , 2012 .

[4]  Samuel A. Letzring,et al.  Initial performance results of the OMEGA laser system , 1997 .

[5]  T. C. Sangster,et al.  Prototypes of National Ignition Facility neutron time-of-flight detectors tested on OMEGA , 2004 .

[6]  Edward I. Moses,et al.  The National Ignition Facility: enabling fusion ignition for the 21st century , 2004 .

[7]  Ramon Joe Leeper,et al.  Probing high areal-density cryogenic deuterium-tritium implosions using downscattered neutron spectra measured by the magnetic recoil spectrometera) , 2010 .

[8]  Edward I. Moses,et al.  Special Topic: Plans for the National Ignition Campaign (NIC) on the National Ignition Facility (NIF): On the threshold of initiating ignition experimentsa) , 2011 .

[9]  S. S. Medley,et al.  Gamma ray diagnostics of high temperature magnetically confined fusion plasmas , 2006 .

[10]  Robert B Webster,et al.  Knudsen layer reduction of fusion reactivity. , 2012, Physical review letters.

[11]  G. Dimonte.  Spanwise homogeneous buoyancy-drag model for Rayleigh–Taylor mixing and experimental evaluation , 2000 .

[12]  J Edwards,et al.  Generalized measurable ignition criterion for inertial confinement fusion. , 2010, Physical review letters.

[13]  D. Wilson,et al.  Using gamma-ray emission to measure areal density of inertial confinement fusion capsules. , 2010, The Review of scientific instruments.

[14]  J. Lindl,et al.  Inertial Confinement Fusion: The Quest for Ignition and Energy Gain Using Indirect Drive , 1998 .

[15]  Barry E. Schwartz,et al.  Spectrometry of charged particles from inertial-confinement-fusion plasmas , 2003 .

[16]  Brian Spears,et al.  Influence and measurement of mass ablation in ICF implosions , 2007 .

[17]  Z. A. Ali,et al.  ICF gamma-ray reaction history diagnostics , 2010 .

[18]  P. B. Radha,et al.  Nuclear measurements of fuel-shell mix in inertial confinement fusion implosions at OMEGAa) , 2007 .

[19]  J. A. Frenje,et al.  First measurements of the absolute neutron spectrum using the magnetic recoil spectrometer at OMEGA (invited). , 2008, The Review of scientific instruments.

[20]  Lee Allen Bernstein,et al.  Determination of the deuterium-tritium branching ratio based on inertial confinement fusion implosions , 2012 .

[21]  Mohammad W. Ahmed,et al.  Research opportunities at the upgraded HIγS facility , 2007 .

[22]  Lee Allen Bernstein,et al.  D-T gamma-to-neutron branching ratio determined from inertial confinement fusion plasmasa) , 2012 .