Engineering topics
Jones, D.
Publications and source records attributed to Jones, D..
A high precision calibration of the nonlinear energy response at Daya Bay
A high precision calibration of the nonlinearity in the energy response of the Daya Bay Reactor Neutrino Experiment’s antineutrino detectors is observed. The energy nonlinearity originates from the particle-dependent light yield of the scintillator and charge-dependent electronics response. The nonlinearity model is constrained by γ calibration points from deployed and naturally occurring radioactive sources, the β spectrum from 12 B decays, and a direct measurement of the electronics nonlinearity with a new flash analog-to-digital converter readout system. With this beind said, less than 0.5% uncertainty in the energy nonlinearity calibration is achieved for positrons of kinetic energies greater than 1 MeV.
Measurement of the Electron Antineutrino Oscillation with 1958 Days of Operation at Daya Bay
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Search for a time-varying electron antineutrino signal at Daya Bay
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Performance of a segmented 6 Li-loaded liquid scintillator detector for the PROSPECT experiment
This study describes the design and performance of a 50 liter, two-segment 6 Li-loaded liquid scintillator detector that was designed and operated as prototype for the PROSPECT (Precision Reactor Oscillation and Spectrum) Experiment. The two-segment detector was constructed according to the design specifications of the experiment. It features low-mass optical separators, an integrated source and optical calibration system, and materials that are compatible with the 6 Li-doped scintillator developed by PROSPECT. We demonstrate a high light collection of 850±20 PE/MeV, an energy resolution of σ = 4.0±0.2% at 1 MeV, and efficient pulse-shape discrimination of low dE/dx (electronic recoil) and high dE/dx (nuclear recoil) energy depositions. An effective scintillation attenuation length of 85±3 cm is measured in each segment. The 0.1% by mass concentration of 6 Li in the scintillator results in a measured neutron capture time of τ = 42.8±0.2 μs. The long-term stability of the scintillator is also discussed. Finally, the detector response meets the criteria necessary for achieving the PROSPECT physics goals and demonstrates features that may find application in fast neutron detection.
THE TRANSITION FROM CONSTITUENT INTERCHANGE TO QCD P-TRANSVERSE**4 DOMINANCE AT HIGH TRANSVERSE MOMENTUM
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Cosmogenic neutron production at Daya Bay
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Solvent hold tank sample results for MCU-17-150-152 (July 2017) and MCU-17-153-155 (August 2017): Quarterly report
A trend summary that includes the last two Solvent Hold Tank (SHT) monthly samples is shown; MCU- 17-150-152 (July SHT) and MCU-17-153-155 (August SHT). Since the last SHT sample sent for analysis was the August sample the chemical state of the solvent is best approximated by the chemical analysis of the August SHT sample (MCU-17-153-155). This report mainly focused on the chemical analysis of the August SHT sample. The analysis data from the July SHT sample are presented in the “trend” plots of this report. Analysis of the August SHT sample (MCU-17-153-155) indicated that the modifier (CS-7SB) was 2% below but the extractant (MaxCalix) concentration was at its nominal recommended level (169,000 mg/L and 46,400 mg/L respectively). The suppressor (TiDG) level has decreased since the last measurement taken while the Modular Caustic-Side Solvent Extraction unit (MCU) was operating in January 2017, but has remained steady in the range of 666 (observed in April) to 715 mg/L (observed in the August 2017 sample) since February 2017, well above the minimum recommended level (479 mg/L), but below the nominal level. The “flat” trends observed in the TiDG, MaxCalix, modifier, and Gamma measurement are consistent with the solvent being idle since January 10, 2017. A strong correlation between density and modifier concentration in the solvent continues to be observed in the SHT samples. This analysis confirms the Isopar™L addition to the solvent in January 2017. This analysis also indicates the solvent did not require further additions. Based on the current monthly sample, the levels of TiDG, Isopar™L, MaxCalix, and modifier are sufficient for continuing operation but are expected to decrease with time if the Modular Caustic-Side Solvent Extraction Unit (MCU) returns to processing radioactive liquid waste. Otherwise, the levels of these components will remain steady. A future Isopar™L trimming addition to the solvent is recommended when MCU resumes processing waste. Two unknown impurities related to the modifier (but not sec-butyl phenol: a modifier degradation product observed before) at the 290 and 110 mg/L levels were observed in the August SHT sample by the Gas - Chromatography-Mass Spectrometry (GC-MS) method. They were observed in a second GC-MS re-run with a new column. Their identification can’t be ascertained at this time. No impurities were observed in the Hydrogen Nuclear Magnetic Resonance (HNMR). Another impurity observed in the samples was mercury. Based on the August SHT sample, up to 23 ± 5 micrograms of mercury per mL of solvent was detected (the average of the Cold Vapor-Atomic Adsorption [CV-AA] and X-Ray Fluorescence [XRF] methods). The higher mercury concentration in the solvent (as determined in the last three-monthly samples) is possibly due to either a higher mercury concentration in Salt Batches 8 and 9 (Tank 49H) . The gamma level (~ 2.0E4 dpm/mL) measured in the August SHT samples was one order of magnitude lower than the gamma levels observed in the December 2016 and January 2017 SHT samples. A similar level was observed in the July SHT sample (MCU-SHT-150-152). The gamma level has remained consistently steady since January 10, 2017 when MCU stopped processing radioactive liquid waste. The laboratory will continue to monitor the quality of the solvent in particularly for any new impurities or degradation of the solvent components.
Solvent hold tank sample results for MCU-17-122-124 (March 2017), MCU-17-130-132 (April 2017), MCU-17-133-135 (May 2017), and MCU-17-141-149 (June 2017): Quarterly Report
A trend summary of four Solvent Hold Tank (SHT) monthly samples; MCU-16-122-124 (March 2017), MCU-17-130-132 (April 2017), MCU-17-133-135 (May 2017), and MCU-17-141-149 (June 2017) are reported. Analyses of the June SHT sample (MCU-17-141-149) indicated that the modifier (CS-7SB) and the extractant (MaxCalix) concentrations were slightly below (4% each) their nominal recommended levels (169,000 mg/L and 46,400 mg/L respectively). The suppressor (TiDG) level has decreased since the January 2017 measurement but has remained steady in the range of 666 to 705 mg/L, well above the minimum recommended level (479 mg/L), but below the nominal level. The “flat” trends observed in the TiDG, MaxCalix, modifier, and Gamma measurement are consistent with the solvent being idle since January 10, 2017.
Evolution of the Reactor Antineutrino Flux and Spectrum at Daya Bay
Here, the Daya Bay experiment has observed correlations between reactor core fuel evolution and changes in the reactor antineutrino flux and energy spectrum. Four antineutrino detectors in two experimental halls were used to identify 2.2 million inverse beta decays (IBDs) over 1230 days spanning multiple fuel cycles for each of six 2.9 GW th reactor cores at the Daya Bay and Ling Ao nuclear power plants. Using detector data spanning effective 239 Pu fission fractions F 239 from 0.25 to 0.35, Daya Bay measures an average IBD yield ¯σf of (5.90±0.13)×10 –43 cm 2 /fission and a fuel-dependent variation in the IBD yield, dσ f /dF 239 , of (–1.86±0.18)×10 –43 cm 2 /fission. This observation rejects the hypothesis of a constant antineutrino flux as a function of the 239 Pu fission fraction at 10 standard deviations. The variation in IBD yield is found to be energy dependent, rejecting the hypothesis of a constant antineutrino energy spectrum at 5.1 standard deviations. While measurements of the evolution in the IBD spectrum show general agreement with predictions from recent reactor models, the measured evolution in total IBD yield disagrees with recent predictions at 3.1σ. This discrepancy indicates that an overall deficit in the measured flux with respect to predictions does not result from equal fractional deficits from the primary fission isotopes 235 U, 239 Pu, 238 U, and 241 Pu. Based on measured IBD yield variations, yields of (6.17±0.17) and (4.27±0.26)×10 –43 cm 2 /fission have been determined for the two dominant fission parent isotopes 235 U and 239 Pu. A 7.8% discrepancy between the observed and predicted 235 U yields suggests that this isotope may be the primary contributor to the reactor antineutrino anomaly.
The detection of an extremely bright fast radio burst in a phased array feed survey
We report the detection of an ultra-bright fast radio burst (FRB) from a modest, 3.4-day pilot survey with the Australian Square Kilometre Array Pathfinder. The survey was conducted in a wide-field fly’s-eye configuration using the phased-array-feed technology deployed on the array to instantaneously observe an effective area of 160 deg{sup 2}, and achieve an exposure totaling 13200 deg{sup 2} hr . We constrain the position of FRB 170107 to a region 8{sup ′}×8{sup ′} in size (90% containment) and its fluence to be 58 ± 6 Jy ms. The spectrum of the burst shows a sharp cutoff above 1400 MHz, which could be due to either scintillation or an intrinsic feature of the burst. This confirms the existence of an ultra-bright (>20 Jy ms) population of FRBs.
Measurement of electron antineutrino oscillation based on 1230 days of operation of the Daya Bay experiment
Here, a measurement of electron antineutrino oscillation by the Daya Bay Reactor Neutrino Experiment is described in detail. Six 2.9-GWth nuclear power reactors of the Daya Bay and Ling Ao nuclear power facilities served as intense sources of ¯ν e ’s. Comparison of the ¯ν e rate and energy spectrum measured by antineutrino detectors far from the nuclear reactors (~1500–1950 m) relative to detectors near the reactors (~350–600 m) allowed a precise measurement of ¯ν e disappearance. More than 2.5 million ¯ν e inverse beta-decay interactions were observed, based on the combination of 217 days of operation of six antineutrino detectors (December, 2011–July, 2012) with a subsequent 1013 days using the complete configuration of eight detectors (October, 2012–July, 2015). The ¯ν e rate observed at the far detectors relative to the near detectors showed a significant deficit, R = 0.949 ± 0.002(stat) ± 0.002(syst). The energy dependence of ¯ν e disappearance showed the distinct variation predicted by neutrino oscillation. Analysis using an approximation for the three-flavor oscillation probability yielded the flavor-mixing angle sin 2 2θ 13 = 0.0841 ± 0.0027(stat) ± 0.0019(syst) and the effective neutrino mass-squared difference of |Δm 2 ee | = (2.50 ± 0.06(stat) ± 0.06(syst)) × 10 –3 eV 2 . Analysis using the exact three-flavor probability found Δm 2 32 = (2.45 ± 0.06(stat) ± 0.06(syst)) × 10 –3 eV 2 assuming the normal neutrino mass hierarchy and Δm 2 32 = (–2.56 ± 0.06(stat) ± 0.06(syst)) × 10 –3 eV 2 for the inverted hierarchy.
Q weak : First direct measurement of the proton’s weak charge
The Q weak experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q 2 = 0.025 (GeV/c) 2 . The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well as the method of extracting the weak charge of the proton. Finally, the results from a small subset of the data, that has been published, will also be presented. Furthermore an update will be given of the current status of the data analysis.
A novel comparison of Møller and Compton electron-beam polarimeters
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Implementation of Energy Code Controls Requirements in New Commercial Buildings
This study used a three-step process to evaluate the degree to which high-impact controls requirements included in commercial energy codes are realizing their savings potential. The three-step process included: (1) interviews of commissioning agents; (2) field audits of a sample of commercial buildings to determine how well control measures are being designed, commissioned and correctly implemented; and (3) analysis of the information gathered.
Improved measurement of the reactor antineutrino flux and spectrum at Daya Bay
Here, a new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GW th nuclear reactors and detected by eight antineutrino detectors deployed in two near (560 m and 600 m flux-weighted baselines) and one far (1640 m flux-weighted baseline) underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay (IBD) candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be 0.946 ± 0.020 (0.992 ± 0.021) for the Huber+Mueller (ILL+Vogel) model. A 2.9σ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4$-$6 MeV was found in the measured spectrum, with a local significance of 4.4σ. Finally, a reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.
Solvent Hold Tank Sample Results for MCU-16-991-992-993: July 2016 Monthly sample and MCU-16-1033-1034-1035: July 2016 Superwashed Sample
SRNL received one set of SHT samples (MCU-16-991, MCU-16-992 and MCU-16-993), pulled on 07/13/2016 and another set of SHT samples (MCU-16-1033, MCU-16-1034, and MCU-16-1035) that were pulled on 07/24/2016 after the solvent was superwashed with 300 mM sodium hydroxide for analysis. Samples MCU-16-991, MCU-16-992, and MCU-16-993 were combined into one sample (MCU-16-991-992-993) and samples MCU-16-1033, MCU-16-1034, and MCU-16-1035 were combined into one sample (MCU-16-1033-1034-1035). Of the two composite samples MCU-16-1033-1034-1035 represents the current chemical state of the solvent at MCU. All analytical conclusions are based on the chemical analysis of MCU-16-1033-1034-1035. There were no chemical differences between MCU-16- 991-992-993 and superwashed MCU-16-1033-1034-1035.
The tracking analysis in the Q-weak experiment
Here, the Q-weak experiment at Jefferson Laboratory measured the parity violating asymmetry (A$_{PV}$ ) in elastic electron-proton scattering at small momentum transfer squared (Q$^{2}$=0.025 (G e V/c)$^{2}$), with the aim of extracting the proton’s weak charge ( ${Q^p_W}$ ) to an accuracy of 5 %. As one of the major uncertainty contribution sources to ${Q^p_W}$ , Q$^{2}$ needs to be determined to ~1 % so as to reach the proposed experimental precision. For this purpose, two sets of high resolution tracking chambers were employed in the experiment, to measure tracks before and after the magnetic spectrometer. Data collected by the tracking system were then reconstructed with dedicated software into individual electron trajectories for experimental kinematics determination. The Q-weak kinematics and the analysis scheme for tracking data are briefly described here. The sources that contribute to the uncertainty of Q$^{2}$ are discussed, and the current analysis status is reported.