Jeffrey Schweitzer

University of Connecticut | UConn · Department of Physics

The fusion reaction C12(C12,p)Na23 has been studied from E=2.00 to 4.00 MeV by particle spectroscopy. The data reveal broad resonances above E=3.00 MeV and are compatible with previously reported resonance structure around E=2.1 MeV. The data were limited at low energies by low count rates as well as possible background contributions. This experime...

The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Some of the perlite may have compacted over time, compromising the thermal performance and also the structural integrity of the tanks. Neutrons can readily penetrate through the 1.75 cm outer steel shell and throu...

The current gamma-ray/neutron instrumentation development effort at NASA Goddard Space Flight Center aims to extend the use of active pulsed neutron interrogation techniques to probe the subsurface elemental composition of planetary bodies in situ. Previous NASA planetary science missions, that used neutron and/or gamma-ray spectroscopy instruments...

This paper describes the Probing In situ with Neutron and Gamma rays (PING) instrument, that can measure the subsurface elemental composition in situ for any rocky body in the solar system without the need for digging into the surface. PING consists of a Pulsed Neutron Generator (PNG), a gamma ray spectrometer and neutron detectors. Subsurface elem...

Nonlinear time series analysis, though a powerful tool, has not been used widely in astronomy and astrophysics because the principle requirements that the data be sampled uniformly and continuous are rarely met. Kepler Space Telescope variable-star light curves satisfy these and almost all other requirements. These data have allowed a more systemat...

The Probing In situ with Neutrons and Gamma rays (PING) instrument is capable of performing detailed bulk geochemical analysis in situ 30-50 cm into the subsurface of planetary bodies without the need to take a soil sample. Neutrons emitted by the pulsed neutron generator (PNG) interact with the nuclei in the soil, causing the nuclei to emit gamma...

The Probing In situ with Neutrons and Gamma rays (PING) instrument, with its PNG and gamma and neutron spectrometers, is a promising technology for measuring the bulk elemental composition of the subsurface of any rocky body in the solar system.

The Advanced Energetic Pair Telescope (AdEPT) will explore the universe in the medium-energy range from about 5 MeV to greater than 200 MeV via gamma-ray pair production. AdEPT will provide high angular resolution observations and for the first time high polarization sensitivity over this essentially unexplored energy range. The NASA/GSFC quasi-mon...

One year of continuous Kepler Space Telescope data for the central object of planetary nebula NGC 6826 (KIC 12071221) were analyzed. KIC 12071221 has long-cadence light curves with stochastic brightness variations and broadband power spectra. The exception is a one-month long period during which variability was detected with a period of 14.8 hr. In...

The Probing In situ with Neutrons and Gamma rays (PING) instrument (formerly named PNG-GRAND) [I] experiment is an innovative application of the active neutron-gamma ray technology successfully used in oil field well logging and mineral exploration on Earth over many decades. The objective of our active neutron-gamma ray technology program at NASA...

The current state of knowledge of cement hydration mechanisms is reviewed, including the origin of the period of slow reaction in alite and cement, the nature of the acceleration period, the role of calcium sulfate in modifying the reaction rate of tricalcium aluminate, the interactions of silicates and aluminates, and the kinetics of the decelerat...

We describe the development of an instrument capable of detailed in situ bulk geochemical analysis of the surface of planets, moons, asteroids, and comets. This instrument technology uses a pulsed neutron generator to excite the solid materials of a planet and measures the resulting neutron and gamma-ray emission with its detector system. These tim...

This paper describes the testing of a prototype active neutron/ gamma ray instrument for use in planetary science space applications. The Probing In situ with Neutrons and Gamma rays (PING) instrument can measure the full bulk elemental composition of a planet's surface over a 1 m2 area and down to 30 – 50 cm depth without the need to drill into th...

The only main source of elemental composition information for carbonaceous (spectral type C or C-type) asteroids is from their optical, near-infrared and infrared properties, which include their spectral reflectance characteristics, albedo, polarization, and the comparison of optical spectroscopy with meteorite groups corresponding to asteroids of...

The Probing in situ with Neutrons and Gamma rays (PING) instrument uses a pulsed neutron generator and neutron and gamma-ray detectors to measure the surface and subsurface elemental composition of planetary bodies without the need for drilling.

It is important for planetary sciences to find a gamma-ray spectrometer that is compact, light and provides good energy resolution in an energy range that varies from ∼ 30 keV to 10 MeV. Pixelated CdZnTe detector is a good candidate for this application due to its small volume, light weight and it has demonstrated good energy resolution below ∼2–3...

The current gamma ray/neutron instrumentation development effort at NASA Goddard Space Flight Center¿s Astrochemistry Laboratory aims to extend the use of neutron interrogation techniques, using a 14 MeV Pulsed Neutron Generator (PNG) combined with neutron and gamma ray detectors, to probe the surface and subsurface of planetary bodies in situ with...

We will present test data demonstrating the in situ bulk elementary composition measurement capabilities of the Pulsed Neutron Generator-Gamma Ray And Neutron Detector (PNG-GRAND) planetary geochemistry instrument.

A unique outdoor gamma ray and neutron instrumentation development test facility has been constructed at NASA's Goddard Space Flight Center for evaluating in situ gamma ray and neutron instrumentation designed for future planetary missions in a controlled environment.

The fusion reactions ^12C(^12C,p)^23Na and ^12C(^12C,alpha)^20Ne are the relevant nuclear processes in the carbon burning phase of stellar evolution. The stellar mass required to ignite carbon depends on the fusion reaction rates at the Gamow energy. The measurement of carbon burning reaction rates near the Gamow energy has been limited by hydrogen...

The cross section of 12C+12C fusion reactions determines the conditions reactions determines the conditions of carbon ignition in stars. The presence of structures, which are likely to extend to low energies, makes the extrapolation of data collected at high energy to the stellar energy difficult and potentially inaccurate, so a direct measurement...

The setting and development of strength of Portland cement concrete depends upon the reaction of water with various phases in the Portland cement. Nuclear resonance reaction analysis (NRRA) involving the (1)H((15)N,alpha,gamma)(12)C reaction has been applied to measure the hydrogen depth profile in the few 100 nm thick surface layer that controls t...

Nuclear resonance reaction analysis (NRRA) has been applied to measure the nanoscale distribution of hydrogen with depth in the hydration of cementitious phases. This has provided a better understanding of the mechanisms and kinetics of cement hydration during the induction period that is critical to improved concrete technology. NRRA was also appl...

A nonlinear time series analysis is performed on light intensity data for the variable DB white dwarf PG 1351+489. The data were collected during the XCov12 campaign of the Whole Earth Telescope. Two data sets integrated to 30 and 10 s, taken at different times during the campaign, were analyzed. The power spectrum of PG 1351+489 is broadband, with...

The set of fusion reactions play a critical role in several astrophysical processes. In a recent experiment, the fusion reactions have been studied at to 4.75 MeV by γ‐ray spectroscopy using a C target of ultra‐low hydrogen contamination. The deduced astrophysical factor exhibits previously unknown resonances at in particular a strong and narrow re...

Embrittlement of high-strength steel is known to be caused by hydrogen penetration into the network of the metal. However, the penetration mechanism of hydrogen into the steel is still under discussion, as it is not so easy to detect and measure the hydrogen in steels. In this paper, relatively large commercial cold drawn pearlitic steel wires have...

The fusion reactions 12C(12C,alpha)20Ne and 12C(12C,p)23Na have been studied from E=2.10 to 4.75 MeV by gamma-ray spectroscopy using a C target with ultralow hydrogen contamination. The deduced astrophysical S(E)* factor exhibits new resonances at E< or =3.0 MeV, in particular, a strong resonance at E=2.14 MeV, which lies at the high-energy tail of...

Comparison among several tests for measuring fly ash pozzolanicity has been made in this study. Indirect tests based on measurement engineering properties of mortar or concrete may be not useful for understanding these mechanisms because of the additional factors of aggregate and cement properties. Direct tests which concern only fly ash could be a...

A combined pulsed neutron/gamma-ray system can be used on planetary surfaces to provide valuable geochemical analysis of surface materials to depths of ~1 m. We describe experimental results that demonstrate the capabilities of such a system.

Nonlinear projective noise reduction is one way to extend the useful frequency range in the power spectra of quasiperiodic stellar light curves. This method can also be used to estimate the time scale of the turbulent contribution. The neighborhood which yields the best noise reduction results in phase space is a reflection of the phase-space scale...

Arsenic is an extremely toxic metal, which poses a significant problem in many mining environments. Arsenic contamination is also a major problem in ground and surface waters. A feasibility study was conducted to determine if neutron-activation analysis is a practical method of measuring in situ arsenic levels. The response of hypothetical well-log...

We have investigated the low-energy states of 11N by the resonant elastic-scattering method in inverse kinematics using a 10C beam and a (CH2)n target at the CYCLONE facility at Louvain-la-Neuve. Recoil protons were detected at laboratory angles θlab=5.2°-18.3° in a ΔE-E detector system. The absolute 10C+p elastic cross-section data were analyzed i...

Unattended and remote detection systems find applications in space exploration, telemedicine, teleforensics, homeland security and nuclear non-proliferation programs. The National Institute of Justice (NIJ) and the National Aeronautics and Space Administration’s (NASA) Goddard Space Flight Center (GSFC) have teamed up to explore the use of NASA dev...

A pulsed neutron/gamma-ray detection system for use on rovers to survey the elemental concentrations of Martian and Lunar surface and subsurface materials is evaluated. A robotic survey system combining a pulsed neutron generator (PNG) and detectors (gamma ray and neutron) can measure the major constituents to a depth of about 30 cm. Scanning mode...

There have been recent reports of evidence for low-dimensional chaos in a number of semiregular variables, RS Cyg among them (ApJ, 2004, 613, Issue 1, pp. 532-547). The data analyzed for RS Cyg in that study was its photometric light curve, sampled at 10-day intervals, that was 15 cycles long (6,255) days. We analyze a daily-averaged light curve fr...

Orbital and in situ measurements of characteristic gamma-ray and neutron emission spectra are used in geochemical explorations of condensed bodies in our solar system. Orbital studies measure the characteristic gamma-ray emissions produced by the natural radioactive elements K, Th, and U, and the secondary cosmic-ray induced gamma-ray and neutron e...

A pulsed neutron gamma-ray system (PNGS) can be used to determine the subsurface planetary geochemistry on rover missions to Mars and other planetary bodies. These data can be used to unravel the history of formation of biogenic materials, characterize the climate, explore the geology and characterize the radiation environment. We have performed fe...

The light curve of DB white dwarf PG 1351+489 has a broadband power spectrum. Nonlinear time series analysis using time-delay phase space reconstruction is one way to deal with such nonlinear signals. However, the utility of this method is greatly diminished by noise. For PG 1351+489 or any variable whose trajectory in phase space lies on an identi...

A nonlinear time series analysis was conducted of 100 years of daily AAVSO intensity data for SS Cygni. Poincare section return times for the phase space portrait, obtained using the time delay method, indicate a possible periodicity of 52 years in the time between successive outburst maxima. Recurrence plot analysis shows that the minima of the cu...

Nuclear instrumentation techniques have been widely accepted into well logging for mineral resources, oil, and gas. This article reviews the applicability of neutron and gamma scattering processes to the analysis of subsurface geological formations. Related topics included in the review are absorption rates of thermal neutrons, natural gamma radioa...

The National Institute of Justice (NIJ) and the National Aeronautics and Space Administration's (NASA) Goddard Space Flight Center (GSFC) have teamed up to explore the use of NASA developed technologies to help criminal justice agencies and professionals investigate crimes. The objective of the program is to produce instruments and communication ne...

We have studied the resonant elastic scattering reaction 18Ne+p in reverse kinematics, by using the intense (4 × 106 pps) 18Ne radioactive beam at the Centre de Recherches du Cyclotron RIB facility at Louvain-la-Neuve. The recoil protons were detected at 20 different angles in the LEDA segmented silicon detector. The resulting elastic scattering cr...

Tricalcium silicate is the major constituent of Portland cement, and the kinetics of its hydration is a major topic in concrete technology. Nuclear resonance reaction analysis using 15N has been applied to measure the evolution of the hydrogen profile. During the first few hours, the induction period, the hydrogen diffusion is controlled by a 10–20...

A nonlinear time series analysis is performed on light intensity data for variable DB white dwarf PG 1351+489. The data were collected and reduced using a spectral window by the WET during its xCov12 campaign. Two data sets were analyzed: one integrated to 30 s and the other to 10 s. The latter was obtained by Antonio Kanaan (of the Brazilian Natio...

The second excited state (Jπ=1/2+, l=0) of the proton-rich nucleus 19Na has been observed for the first time using the elastic scattering reaction 1H(18Ne,1H)18Ne. An intense (4×106pps) 18Ne radioactive beam was produced at the CRC-RIB facility at Louvain-la-Neuve to bombard a polyethylene target. The recoil protons were detected at 20 different an...

The National Institute of Justice (NIJ) and the National Aeronautics and Space Administration's (NASAs) Goddard Space Flight Center (GSFC) have teamed up to explore the use of NASA developed technologies to help criminal justice agencies and professionals solve crimes. The objective of the program is to produce instruments and communication network...

A full nonlinear time series analysis was conducted of 100 years of AAVSO data for SS Cygni. The missing gaps in the data were bridged by linear interpolation. Both magnitude and intensity data, F(Lambda ), where F(Lambda ) = 10 {- (0.4 (visual magnitude) + 8.43)}, were analyzed. The magnitude data gave results consistent with noise in all steps of...

A full nonlinear time series analysis was conducted of 100 years of visual observations from the American Association of Variable Star Observers (AAVSO) International Database for the cataclysmic variable SS Cygni. Intensity was obtained from the AAVSO magnitude data using: F(L)=10{-(0.4(visual magnitude)+8.43)}. Intensity is a "better" dynamical v...

Daily sunspot number data for the northern and southern solar hemispheres from 22 cycle maximum to the current cycle 23 maximum are analyzed using nonlinear time series methods in an effort to identify chaotic behavior on short time scales as indicated by the recent helioseismic observations. We find that separate analyses of north and south solar...

Velocity shear at the solar tachocline with a period of 16 months has recently been detected. This kind of behavior is predicted even in the simplest 1-D dynamo models when they are operating in a chaotic regime. Sunspot numbers, as a manifestation of solar activity driven by a dynamo, should also reflect such chaotic behavior. We look at daily sun...

Nuclear resonance reaction analysis has been applied for the first time to measure the development of the hydrogen depth profile in the early stages of hydration of tricalcium silicate using the 1H(15N,αγ)12C reaction. The surface layer had an H concentration and thickness consistent with a few unit cells (1.1 nm) of tobermorite-like material. The...

Nuclear Resonance Reaction Analysis (NRRA) has been applied for the first time to measure the development of the hydrogen depth profile in the early stages of hydration of tricalcium silicate, the major constituent of Portland cement. To obtain the best spatial resolution, it is necessary to have good beam energy resolution. Three regions were obse...

The ratio of thermoluminescence and scintillation light outputs of Ce : Lu2SiO5 (LSO) was measured as a function of gamma-ray dose. Together, they account for only a fraction of the predicted electron—hole pairs. Electron traps saturate rapidly, and their concentration is at least two orders of magnitude less than that of cerium.

Room temperature semiconductors introduce some exciting potential for use in instruments designed for planetary measurements. It is important, however, to consider carefully the different types of measurement environments. In some cases room temperature semiconductors provide significant advantages over scintillators, while in some cases scintillat...

The X-ray/gamma-ray spectrometer (XGRS) instrument onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft will map asteroid 433 Eros in the 0.2 keV to 10 MeV energy region. Measurements of the discrete line X-ray and gamma-ray emissions in this energy domain can be used to obtain both qualitative and quantitative elemental composition maps of...

Gamma-ray spectra provide useful data in the study of the development of planets. Measurements made on landers overcome many of the limitations of orbital measurements, especially for solar-system bodies where atmospheres interfere with obtaining orbital data. Elemental compositions can be inferred from the spectra, produced by neutron interactions...

Atomic excitation and ionization processes affect the shape of yield curves of narrow nuclear resonances obtained with high beam energy resolution. Yield curves for the narrow resonances in the 21Ne+p reaction at Ep=126, 272 and 291 keV and for the Ep=309 keV resonance in 23Na+p were measured with very low target densities (i.e., with thin targets...

Solid neon samples at 8+/-2 K and under vapor pressure were used to measure yield curves of the 272-keV nuclear resonance in the 21Ne(p,γ)22Na reaction. The Doppler broadening of the narrow resonance due to target atom motion was determined with very good beam energy resolution. The average kinetic energy of single neon atoms in the solid due to th...

The difficulty of using a gas target in nuclear experiments makes it advantageous to devise a method for implanting gaseous elements into thin foils. Noble gases are known to be stable when implanted into metals. Such targets are particularly useful for studies involving RNBs; e.g. the hot pp chain with ^7Be beams. We have produced and tested impla...

The motion of the target nuclei in the surface of a solid affects the shape of yield curves of narrow nuclear resonances. We measured yield curves for the 272 keV resonance in 21Ne(p,γ)22Na with frozen neon. The in-situ preparation of the targets and the measurements were carried out under UHV conditions. The targets were cooled by a He evaporation...

The crystal structure of Lu₂(SiO₄)O:Ce (“LSO”) has two trivalent cation sites which may be occupied by Ce³⁺ to form luminescence centers. Previous investigations revealed the existence of two distinct sets of Ce³⁺ excitation and emission spectra and suggested that the differences in the spectra are due to...

We identify the chemical elements and element ratios that should be analyzed to address many of the issues identified by the Committee on Planetary and Lunar Exploration (COMPLEX). We determined that most of these issues require two sensitive instruments to analyze the necessary complement of elements. In addition, it is useful in many cases to use...

Nuclear resonant reaction analysis techniques for hydrogen depth profiling in solid materials typically have used 15N ion beams at 6.40 MeV and 19F ion beams at 6.42 MeV, which require a tandem accelerator. We report a new technique using an18O ion beam at a resonance energy of 2.70 MeV, which requires only a single stage accelerator. Improved valu...

A pulsed DT neutron generator system, similar to that used in commercial well logging, offers the possibility of performing accurate elemental analyses to depths of tens of centimeters in a few seconds with the probe on the body's surface. Through time-phased measurements of the gamma-ray spectrum synchronized with the neutron pulses, concentration...

A cryogenic target system has been built to study yield curves of narrow nuclear resonances. The crucial part of the UHV set-up is a liquid helium cooled sample holder mounted on a goniometer, allowing the use of gas and solid targets in the temperature range 10–600 K. Particle detectors and γ-ray detectors can be installed in close geometry to the...

Detectors that will be used for planetary missions must have their responses calibrated in a reproducible manner. In addition, it is important to characterize a detector system at uneven portions of its life cycle, for example after exposure to different amounts of radiation. A calibration and response characterization facility has been constructed...

The absolute light yield of cerium doped lutetium oxyorthosilicate Lu₂SiO₅:Ce³⁺ (LSO:Ce) scintillation crystals is presented. From 60 keV to above 1 MeV the light output increases linearly with the gamma-ray energy and is about 67% of that of NaI(Tl⁺). However, a nonlinear response is observed for X-ray e...

Photostimulated luminescence (PSL) and thermoluminescence (TL) from five Lu_2(1-x/)Cesub 2x/(SiO₄)O (LSO) crystals with different light outputs is reported. Optical irradiation into the Ce³⁺ absorption bands causes the appearance of a broad absorption band near 280 nn which is ascribed to Ce⁴⁺. In addition...

The scintillation decay of cerium-doped gadolinium oxyorthosilicate Gd₂(SiO₄)O:Ce is lengthened by the energy transfer from Gd to Ce. To investigate the role of the Gd in the scintillation processes, the Gd was partially replaced by optically inactive rare earth elements, Y and Lu, and the effective transfer rates from Gd to C...

The origins of two decay constants in the scintillation decay of cerium-doped gadolinium oxyorthosilicate (Gd2(SiO4)O:Ce) are investigated using UV light. We find that build-ups and long decay components observed with gamma-ray excitation are due to non-radiative energy transfer from Gd to Ce. The transfer rate from Gd to Ce increases as the Ce con...

The absolute light yield of cerium doped lutetium oxyorthosilicate Lu[sub 2]SiO[sub 5]:Ce[sup 3+] (LSO:Ce) scintillation crystals is presented. From 60 keV to above 1 MeV the light output increases linearly with the gamma-ray energy and is about 67% of that of NaI(Tl[sup +]). However, a non-linear response is observed for X-ray energies between 5 a...

Detectors that will be used for planetary missions must have their responses calibrated in a reproducible manner. A calibration facility is being constructed at Schlumberger-Doll Research for gamma and x ray detectors. With this facility the detector response can be determined in an invariant and reproducible fashion. Initial use of the facility is...

The luminescence decays of Gd2(SiO4)O:Ce obtained by exciting two Gd3+ absorption lines show a build-up and a long decay component, suggesting that the origin of two slow decay components observed in the gamma-ray excited decay is caused by the energy transfer from Gd to Ce.

Various parameters relevant to the design of a small scale PET scanner were studied both experimentally and by computer simulation. LSO (cerium-doped lutetium oxyorthosilicate) was compared with EGO, using a position sensitive PMT (PSPMT). (Compared to EGO, LSO has 8 times faster decay time, 4 times the scintillation light output, but 14% lower att...

A new scintillation crystal, cerium doped lutetium oxyorthosilicate (LSO), is discussed. It has light intensity which is 75% of NaI(Tl), scintillation decay time of 12 ns (30%) and 42 ns (70%), effective Z of 66, and density of 7.4 g/cm³. The fast decay time and scintillation light output of LSO are superior to those of bismuth germanate...

A gamma-ray spectrometer based on a germanium detector is used to obtain elemental concentration logs in three zones of the German Continental Deep Drilling Project pilot hole, with a primary goal of obtaining logs of elements that could not be obtained by commercial logging measurements. Delayed activation measurements provide elemental logs of Na...

Lutetium oxyorthosilicate Lu[sub 2](SiO[sub 4])O has two crystallographically independent lutetium sites. When it is doped with Ce, the dopant Ce is assumed to occupy two different sites and thus the existence of two activation centers (called Ce1 and Ce2) was proposed. UV and gamma-ray excited spectra clearly indicate that two activation centers e...

Two types of excitation and emission spectra with ultraviolet excitation are shown at 11 K for Lu_2(SiO_4)O:Ce (LSO). Since there are two crystallographically independent lutetium sites in LSO, the existence of two Ce activation centers (two-activation-center model) is proposed. The existence of two different decay time constants of the order of te...

id="ab1">Single crystals of three Ce-doped rare earth oxyorthosilicates, Ln2(SiO4)O where Ln =Y, Gd, or Lu, were grown by the Czochralski technique. The formation of defects was strongly influenced by the crystal growth conditions for Ln = Gd but high quality boules for Ln = Y and Lu were grown under a variety of conditions. The luminescence proper...