Absolute calibration method for laser megajoule neutron yield measurement by activation diagnostics

The areal density (ρR) of cryogenic DT implosions on Omega is inferred by measuring the spectrum of neutrons that elastically scatter off the dense deuterium (D) and tritium (T) fuel. Neutron time-of-flight (nTOF) techniques are used to measure the energy spectrum with high resolution. High signal-to-background data has been recorded on cryogenic DT implosions using a well-collimated 13.4-m line of sight and an nTOF detector with an advanced liquid scintillator compound. An innovative method to analyze the elastically scattered neutron spectra was developed using well-known cross sections of the DT nuclear reactions. The estimated areal densities are consistent with alternative ρR measurements and 1-D simulations.

Section: ρR Measurements Using Backscattered Neutron Yieldsmentioning

confidence: 99%

High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited)

Forrest

Radha

Glebov

et al. 2012

“…Due to its simplicity, this method can be easily transferred to calibrate nTOF systems on other large ICF facilities such as the NIF 4,5,18,19 and LMJ. 20 Review of Scientific Instruments is copyrighted by AIP Publishing LLC (AIP). Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions.…”

Section: Discussionmentioning

confidence: 99%

“…We conclude that the method is well suited to reduce the DD calibration uncertainty of nTOF systems on other large ICF facilities such as the NIF 4,5,18,19 and Laser Megajoule (LMJ). 20 This paper is structured as follows. In Sec.…”

Section: Introductionmentioning

confidence: 99%

A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

Waugh

Rosenberg

Zylstra

et al. 2015

Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition, comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.

“…5 At OMEGA, the MRS is complemented by neutron timeof-flight (nTOF) detectors. 6,7,17 The systematic uncertainty of the nTOF yield data is 5% at OMEGA, 18,9,19 while the systematic uncertainty associated with the OMEGA MRS and the NIF MRS yield is 9% and 4.3%, respectively. Figure 2 shows the determined MRS primary yields produced in gasfilled and cryogenic DT implosions, compared to nTOF primary yields, ranging from Y DT ∼2 × 10 12 to 2 × 10 14 .…”

Section: Mrs Measurements Of the Yield On Omega And The Nifmentioning

confidence: 99%

Measuring the absolute deuterium–tritium neutron yield using the magnetic recoil spectrometer at OMEGA and the NIF

Casey

Frenje

Johnson

et al. 2012

A magnetic recoil spectrometer (MRS) has been installed and extensively used on OMEGA and the National Ignition Facility (NIF) for measurements of the absolute neutron spectrum from inertial confinement fusion implosions. From the neutron spectrum measured with the MRS, many critical implosion parameters are determined including the primary DT neutron yield, the ion temperature, and the down-scattered neutron yield. As the MRS detection efficiency is determined from first principles, the absolute DT neutron yield is obtained without cross-calibration to other techniques. The MRS primary DT neutron measurements at OMEGA and the NIF are shown to be in excellent agreement with previously established yield diagnostics on OMEGA, and with the newly commissioned nuclear activation diagnostics on the NIF.