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D-T gamma-to-neutron branching ratio determined from inertial confinement fusion plasmasa)
a)Paper NI3 6, Bull. Am. Phys. Soc. 56, 186 (2011).
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Image of FIG. 1.
FIG. 1.

Schematic cutaway view of (a) GCD and (b) GRH fielded at OMEGA. GCD is inserted into an OMEGA TIM (10 in. manipulator) and placed at 20 cm from TCC. As a prototype to NIF GRH-6m, GRH is attached to the outside of the OMEGA chamber. GRH converter front distance is 187 cm from TCC.

Image of FIG. 2.
FIG. 2.

Time history of D-T fusion γ-rays measured from (a) GCD, where shot 54 449 was taken at 100 psia of CO2 and shot 54 474 was taken without gas, (b) GRH, where shot 58 162 was taken at SF6 87 psia and shot 58 158 was taken without gas. Absolute time bases are arbitrary.

Image of FIG. 3.
FIG. 3.

Time-integrated and normalized (a) GCD and (b) GRH γ-ray signals () as a function of absolute neutron yield, obtained from 22 OMEGA shots. increases linearly with neutron yield, indicating constant gamma-to-neutron branching ratio.

Image of FIG. 4.
FIG. 4.

(a) Comparison of geant4 simulation and GCD measurement at HIγS, where fixed 16.86 MeV 1 cm diameter γ-ray beam and varied CO2 pressure up to 100 psia are used. (b) Comparison of accept simulation and GRH measurement at HIγS, where 4.4 MeV γ-ray beam was injected to GRH front at center on axis and SF6 pressure was varied up to 220 psia.

Image of FIG. 5.
FIG. 5.

D-T branching ratios determined from GCD (blue) and from GRH (red) are in agreement. After a weighted average, a D-T branching ratio of (4.3 ± 1.8) × 10−5 is obtained from absolute calibration method.

Image of FIG. 6.
FIG. 6.

GCD reaction histories from (a) September 2010 and (b) May 2011, where top curves (blue) show D-3He γ-ray signals normalized by proton yields and bottom curves (red) show D-T γ-ray signals normalized by neutron yields. D-T γ/n branching ratio is determined to be (0.31 ± 0.08) of the D-3He γ/p branching ratio from the average of two show days.

Image of FIG. 7.
FIG. 7.

A schematic drawing of puck experiment at OMEGA (puck used: Si, Cu, Al, and C).

Image of FIG. 8.
FIG. 8.

Simultaneous measurement of D-T fusion γ-rays and 14.1 MeV neutron-induced Si γ-rays.

Image of FIG. 9.
FIG. 9.

Simulated Si n-γ spectrum using MCNP (red curve on the left) and simulated GCD response using accept (black curve on the right).

Image of FIG. 10.
FIG. 10.

D-T branching ratios obtained from cryogenic D-T fuel in CH capsules (blue) and D-T glass capsules (red) are compared to the D-T branching ratio of CH capsules (green), showing that no clear temperature dependency on D-T branching ratio within error bars.

Image of FIG. 11.
FIG. 11.

D-T branching ratio determined from ICF implosion studies is compared to earlier beam-target measurements. Branching ratios shown in the left figure include γ0 and γ1 emissions, while only γ0 is considered in the right figure. The energy band of present ICF data has been extended relative to Ref. 1 by glass and cryo implosions.


Generic image for table
Table I.

Summary of D-T branching ratios determined by two methods.

Generic image for table
Table II.

D-T branching ratio inferred with various puck materials.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: D-T gamma-to-neutron branching ratio determined from inertial confinement fusion plasmasa)