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The Laboratory of Analysis by Nuclear Reaction (LARN) at the University of Namur (Belgium) is equipped with a low background γ-ray detection system. This setup is made of one ton of lead as passive shielding and plastic scintillators as anti-cosmic active shielding that covers a large area around a 3.5 × 3.5 in.2 high purity germanium detector. This setup makes it possible to reduce the background level from two to three orders of magnitude, depending on the energy range of interest. In this work, this polyvalent detection system is described and used to refine the cross-section measurements of the 13C(p,γ)14N nuclear reaction at middle and low energies. The reaction 13C(p,γ)14N plays an important role in the carbon–nitrogen–oxygen cycle and s-process in stellar evolution. In this work, we studied more precisely the 13C(p,γ)14N ground transition (Eγ = 8.06 MeV) for incident energies ranging from 147 to 574.3 keV in the center-of-mass system generated by the 2 MV Tandetron accelerator ALTAÏS installed at the LARN. Our measurements performed both in reverse [i.e., 1H(13C,γ)14N] and direct kinematics are in good agreement with all the data available in the literature, validating our low background detection system. [ABSTRACT FROM AUTHOR]

The performance of current nuclear medicine imaging systems is largely limited by the performance of detectors, and high spatial resolution detectors require high optical yield scintillator arrays. In this work, we simulated and designed for the first time a distributed Bragg reflector (multilayer dielectric film) that covers the entire lutetium yttrium oxyorthosilicate emission spectral band and consists of three 1/4 wavelength (λ/4) primary film systems centered at 420, 500, and 575 nm. In order to achieve ultrahigh reflectivity at the full incidence angle of the scintillator emitting surface, we propose a master optical configuration combining the dielectric film with a metal film/diffuse reflection adhesive. To explain this mechanism, we also simulated the change in reflectivity of the actual inner surface light collection. Experimental results show that a combination of a highly reflective reflector can achieve full-angle high reflectance at the total angle of incidence. We find that the dielectric film does not change the total reflection structure inside the crystal, while the light-blocking layer changes and increases the angular reflection of the dielectric film about the angle. These findings provide important insights into surface treatment as well as the design of scintillation crystal arrays, with far-reaching implications for high spatial resolution optical imaging systems. [ABSTRACT FROM AUTHOR]

A compact online proton spectrometer based on a CMOS plate detector was proposed for the diagnosis of picosecond intense-laser accelerated protons. Inside the CMOS plate detector, a composite structure that composed of a scintillator screen, a fiber optic plate (FOP), and a CMOS sensor was designed to detect the protons safely and efficiently. The scintillator screen converted the incident protons to visible light, which, in turn, was collected by using the FOP and detected by using the CMOS sensor. An additional aluminum housing was designed to decrease the strong electromagnetic pulse (EMP) impact on the electronic readout system from picosecond laser–plasma interaction. This online spectrometer is compact and cost-effective than the system based on the micro-channel plate or scintillator screen in combination with an electron multiplying CCD camera and has better resistance to radiation damage than the system based on a single CMOS sensor. [ABSTRACT FROM AUTHOR]

In this advanced instructional laboratory, students explore complex detection systems and nondestructive assay techniques used in the field of nuclear physics. After setting up and calibrating a neutron detection system, students carry out timing and energy deposition analyses of radiation signals. Through the timing of prompt fission neutron signals, multiplicity counting is used to carry out a special nuclear material (SNM) nondestructive assay. Our experimental setup is comprised of eight trans-stilbene organic scintillation detectors in a well-counter configuration, and measurements are taken on a spontaneous fission source as well as two (α,n) sources. By comparing each source's measured multiplicity distribution, the resulting measurements of the (α,n) sources can be distinguished from that of the spontaneous fission source. Such comparisons prevent the spoofing, i.e., intentional imitation, of a fission source by an (α,n) neutron source. This instructional laboratory is designed for nuclear engineering and physics students interested in organic scintillators, neutron sources, and nonproliferation radiation measurement techniques. [ABSTRACT FROM AUTHOR]

A compact scintillator-based electron–ion Thomson Parabola Spectrometer (ei-TPS) is designed and built up, which is able to measure the spectrum of electron and ion beams simultaneously in the same angular axis and real-time mode. The energy range of electrons is around 0.27–3.8 MeV with a relative energy resolution better than 2.5%, and the energy range of proton is around 0.16–21 MeV with a relative energy resolution better than 4% at the kinetic energy of 1 MeV, which makes it suitable for laser-driven ion acceleration experiments with 100-TW level laser. Detailed mathematical modeling is performed to reveal the dependence of properties, such as energy range and resolution, response, and detection threshold, on various parameters of ei-TPS, which is useful to modify the parameters according to specific requirements of electrons and ions. [ABSTRACT FROM AUTHOR]

The Modulation Transfer Function (MTF) characteristics of radiochromic film (RCF) dosimetry with optical systems were evaluated with an RCF, HD-V2, which is transferred with the line patterns of the resolution test chart. In the evaluation using a GT-X980 flatbed scanner, a high contrast spatial resolution with an MTF of ≥0.8 is limited to about 83.3 μm due to artifacts such as scattering of the HD-V2 transmitted light. To achieve high contrast at higher spatial frequencies, a test bench microdensitometer (TBMD) was developed, and its optical performance, dose equivalent response, and spatial resolution characteristics with MTF were evaluated. The TBMD had a minimum readout focal diameter of 13 μm, and its high contrast spatial resolution with an MTF of ≥0.8 is about 11.9 μm. The result that the optical density error increases with decreasing focal diameter in the TBMD supports our hypothesis that these errors are based on the non-uniformity of the shading and surface roughness of the HD-V2 active layer monomers. [ABSTRACT FROM AUTHOR]

Scintillators are key components in high-energy x-ray detectors for x-ray computed tomography, which are applied in medical diagnosis, nondestructive testing, and security inspection. Scintillators in x-ray imaging are required to have both high spatial resolution and sensitivity; however, a trade-off between spatial resolution and sensitivity exists. To improve the sensitivity of a scintillator, its thickness must be increased; however, spatial resolution deteriorates with increasing thickness. Here, we developed a well-aligned Tb-doped GdAlO3-αAl2O3 phase-separated scintillator fiber (PSSF) with a diameter of 1.25-μm by a micro-pulling-down method. The luminescence, scintillation, and imaging performances of a grown PSSF sample were evaluated. X-ray-induced radioluminescence measurements of the sample showed Tb3+ 4f–4f emissions in the wavelength range of 470–700 nm, and the maximum emission peak was at 550 nm. The contrast transfer function at 10 lp/mm was 82% for both 270 and 500 μm-thick PSSF samples. We calculated the luminescence index, which is the product of the scintillator's light yield and sensitivity, of the samples and compared their values with commercially available conventional CsI:Tl columnar scintillators. The Tb-doped GdAlO3-αAl2O3 PSSF exhibits higher contrast transfer function and luminescence index values at above 60 keV x-ray region compared with the tested conventional scintillators. [ABSTRACT FROM AUTHOR]

Developing a ceramic scintillator operating in a phoswich detector is a feasible way for pulse shape discrimination. A YAG:Ce transparent ceramic scintillator has been synthesized by using the vacuum sintering method. In this work, we present a new phoswich detector mainly developed for the determination of low radioactivity levels. The system was constructed by combining a transparent ceramic scintillator, for the detection of α particles, and a CsI:Tl crystal, for the detection of γ-rays. With the device proposed here, the particle identification in a mixed α–γ field has been achieved with the rise time discrimination method. Furthermore, the figure of merit can also be improved using the phoswich detector. The higher reliability, simplicity, and low cost of the design that combines ceramics and crystals make the YAG ceramic have extremely good application prospects. [ABSTRACT FROM AUTHOR]

The anti-Compton phoswich (ACP) detector, which is composed of multiple scintillators with one photomultiplier tube, takes into account the Compton suppression function and portability, and therefore, a discussion on how to design its shape to improve the performance of the detector has become necessary. Based on an ACP detector using a well-typed LaBr3:Ce/NaI:Tl composite scintillator that has been developed in the laboratory in early work, this study uses GEANT4 to simulate and study the influence of the change in the shape and size of the secondary scintillator on the performance of the detector, such as the Compton suppression ratio, the energy resolution, and the full-energy peak (FEP) loss. In the course of the study, we mainly investigate the variation of the performance of the detector in two ways. First, the inclination angle of the truncated cone is gradually changed to compare its FEP address and Compton suppression ratio. Second, the case of the well-shaped and annular-shaped secondary scintillators is compared, respectively, to find out their impact on energy resolution and FEP address. The final results show that, compared with the ACP detector using a φ75 × 90 mm2 LaBr3:Ce/NaI:Tl cylindrical composite scintillator, a truncated cone-shaped composite scintillator of 0.8 inclination may have an equivalent 137% light yield (137% signal-to-noise ratio), a Compton suppression ratio of 89.62% (at 662 keV), 89.98% FWHM energy resolution, and a volume reduction of 36.74%, which means that the weight of the detector is reduced by 2.107 kg. [ABSTRACT FROM AUTHOR]

To address the problem that the energy response of the plastic scintillator detector is very low in the low energy range, this paper proposes a method to optimize the energy response characteristics by combining the CaWO4 energy compensation layer and the genetic algorithm. First, the energy deposition of X/γ rays in a plastic scintillator with a CaWO4 energy compensation layer is modeled and simulated using MCNP software; then, the thickness and hollow radius of the compensation layer are optimized by using genetic algorithm to run this simulation program. The results show that after adding a CaWO4 compensation layer with a thickness of 45 µm and a hollow radius of 1 cm at the front of the plastic scintillator, its energy response characteristics are consistent in the range of 50 keV to 1.5 MeV, which meets the requirement of IEC 61584:2001 for the energy response coefficient less than ±30%. The maximum deviation of the energy response coefficient at the energy point of 0.662 MeV is reduced from 44% to 13%. [ABSTRACT FROM AUTHOR]

This work presents a novel stereo coded aperture gamma camera based on four detection modules placed within four quadrants. Each module includes 48 × 48 strips of Bi4Ge3O12 scintillators, 24 × 24 pieces of silicon photomultipliers (SiPMs), and a set of data acquisition circuits. All signals from the SiPMs are individually extracted and finally simplified into 144 outputs to calculate the positions and energies of gamma-rays. Two masks of modified uniformly redundant arrays are fixed in the front of the top-right and bottom-left modules and two anti-masks are fixed in the top-left and bottom-right modules to achieve simultaneous imaging without dual measure. Once the projections of radioactive sources are determined, their source-to-detector distances can be estimated by our new multocular ranging algorithm. A series of lab and field experiments, including flood histogram and energy spectrum testing, field-of-view and angular resolution testing, real-time imaging, long-distance imaging, and ranging ability testing, with different radioactive sources, such as 137Cs, 22Na, 241Am, 60Co, 133Ba, and 75Se, have been completed to evaluate the comprehensive ability of the stereo gamma camera. The results show that the stereo gamma camera has a strong ability for the three-dimensional localization of radioactive sources over long distances with a high image sensitivity. So far, the stereo gamma camera has been successfully used in practical nuclear security and safety tasks although the angular resolution and the ranging algorithm robustness should be more optimized in the future. [ABSTRACT FROM AUTHOR]

Temperature dependence of the luminescence characteristics of Lu1.84Y0.16SiO5:Ce (LYSO:Ce) scintillator was investigated under x-ray excitation. The luminescence decay time, light yield, radioluminescence (RL) spectra, spatial resolution, and luminescence homogeneity from 300 to 550 K are experimentally examined with multiple x-ray facilities. The results show that the decay time and light output of the LYSO:Ce scintillator will decrease from 42 to 1.89 ns and from 32 000 to 1120 photons/MeV with a temperature increase from 300 to 550 K, respectively. The RL spectrum experiments demonstrate that the spectrum peak will move from 414 to 426 nm when adjusting the temperature from 300 to 550 K. The spatial resolution experiments show that the spatial resolution is hardly affected and can reach as high as 2.5 lp/mm when increasing the temperature from 300 to 550 K, and the luminescence homogeneity remains unchanged with increase in temperature. The experimental results provide important information for the radiation imaging application of the LYSO:Ce scintillator. [ABSTRACT FROM AUTHOR]

Good specimen quality is a key factor in achieving successful scanning transmission electron microscope analysis. Thin and damage-free specimens are prerequisites for obtaining atomic-resolution imaging. Topological insulator single crystals and thin films in the chalcogenide family such as Sb2Te3 are sensitive to electron and ion beams. It is, therefore, challenging to prepare a lamella suitable for high-resolution imaging from these topological insulator materials using standard focused ion-beam instruments. We have developed a modified method to fabricate thin focused ion-beam (FIB) lamellae with minimal ion-beam damage and artifacts. The technique described in the current study enables the reliable preparation of high-quality transmission electron microscope (TEM) specimens necessary for studying ultra-thin surface regions. We have successfully demonstrated that the careful selection of FIB milling parameters at each stage minimizes the damage layer without the need for post-treatment. [ABSTRACT FROM AUTHOR]

Liquid scintillators provide a fast, single component response. However, they traditionally have a low flashpoint and high vapor pressure. We demonstrate the use of an EJ-309 scintillator (high flashpoint and low vapor pressure variant) to acquire single-shot positron annihilation lifetime spectroscopy spectra using a trap-based positron beam. [ABSTRACT FROM AUTHOR]

This theoretical study is performed to investigate structural, elastic, and electronic properties as well as optical response to incident photons of thallium based chloroperovskite TlXCl3 (X = Ca and Cd) compounds. Both compounds have a stable crystal structure with optimized lattice constants ranging from 5.40 Å to 5.26 Å. The elastic parameters such as elastic constants, bulk modulus, anisotropy factor, Poisson's ratio, and Pugh's ratio are evaluated. Poisson's ratio describes the ductile nature of these materials. The band structure and elemental contribution to different states for all the compounds are analyzed. Materials have a wide bandgap with indirect band nature. Optical parameters such as dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, and optical conductivity are studied in the energy range of 0 eV–30 eV. The comparative results suggest that thallium based compounds are important to be used as scintillating materials and stimulate further experimental investigations of such compounds. [ABSTRACT FROM AUTHOR]

A (Lu,Y)2SiO5:Ce (LYSO) crystal, as a heavy inorganic scintillator, is currently in high demand for various applications in the fields of particle detection. However, its high refractive index (n = 1.83) gives restriction on the measurements of rare events or weak particle flow, where high energy resolution is urgently required for detectors based on the crystal. Utilizing the electron beam lithography technique and the ion beam lithography method, we have successfully prepared a 2.0 × 2.0 mm2 large area two-dimensional photonic crystal (PhC) structure on the LYSO crystal surface. Compared with the plain reference sample, the optical measurements show a 53% enhancement of light extraction for the LYSO nanostructured surface, and the resulted improvement of energy resolution (full width at half maximum) is measured to be 43.8% by gaussian fittings to the energy spectra excited by the 241Am α source. With the advantage of high-resolution patterning, high thermal stability, and firm stickiness on the substrate, the present prescription of the PhC fabrication is still favorable for some special fields (e.g., homeland security and space exploration) though the writing process is extremely time consuming and expensive to use. [ABSTRACT FROM AUTHOR]

Dielectric function spectra of purified thallium bromide crystals grown by the Bridgman method were studied over the photon range of 1.5–5.4 eV at room temperature. In addition, density functional theory (DFT)-based calculations of the electronic band structure were performed. Interband optical transitions associated with the obtained dielectric function were determined using standard critical point analysis. The electronic bands involved in each particular interband transition in the accessed photon energy range were identified within the calculated band structure. [ABSTRACT FROM AUTHOR]

Utilizing the self-assembly method, we have successfully prepared a two-dimensional photonic crystal (PhC) of monolayer SiO2 spheres onto the Bismuth Germinate (Bi4Ge3O12, BGO) crystal and therefore supply another photonic crystal structure with the advantages of low-cost and large-area preparation to improve the light extraction efficiency of scintillator. A light extraction enhancement ratio up to 145.3% as compared the BGO coated by the PhC with the plain reference sample is observed and the underlying mechanism of scintillator light extraction is discussed in detail via a rigorous coupled-wave analysis calculation. The calculated transmission spectra and electric-field distribution exhibit the electric-field eigenmodes confined in SiO2 spheres resonating by the way of whispering gallery modes (WGMs) and becoming leaky modes due to the diffraction effect. Since almost no SiO2 nanospheres over the polystyrene spheres are immersed in preparation, we have demonstrated that the introduction of PhC structures using the SiO2 nanospheres onto the scintillator surface is an effective way to solve the light-trapping problem and therefore the design is very useful to be applied to the particle detection of radiation field. [ABSTRACT FROM AUTHOR]

Surface-enhanced ZnS: Ag quantum dots scintillator has been manufactured by coupling quantum dots and dendritic silver surface-enhanced substrates. Four-fold enhancement of the fluorescence intensity was achieved compare to the undoped quantum dots without surface-enhanced substrates. Two silicon layers of certain thickness were used to prevent quenching of the fluorescence by monitoring the distance between quantum dots and surface-enhanced substrates. The enhancement results show consistence with theories, and larger enhancement factor is possible to be obtained with optimal preparation procedure. This study suggests a new method to achieve high performance quantum dots scintillator beneficial to radiation detection applications. [ABSTRACT FROM AUTHOR]

We present Monte Carlo (MC) simulation results from a study of a compact plastic-scintillator detector suitable for imaging fast neutrons in the 1 – 10 MeV energy range: the miniTimeCube (mTC). Originally designed for antineutrino detection, the mTC consists of 24 MultiChannel Plate (MCP) photodetectors surrounding a 13 cm cube of boron-doped plastic scintillator. Our simulation results show that waveform digitization of 1536 optically sensitive channels surrounding the scintillator should allow for spatiotemporal determination of individual neutron-proton scatters in the detector volume to ∼ 100 picoseconds and ∼5 mm. A Bayesian estimation framework is presented for multiple-scatter reconstruction, and is used to estimate the incoming direction and energy of simulated individual neutrons. Finally, we show how populations of reconstructed neutrons can be used to estimate the direction and energy spectrum of nearby simulated neutron sources. [ABSTRACT FROM AUTHOR]

We present the results of experiments applying a large area tiled array of silicon photomultipliers (SiPM) to gamma ray spectroscopy with 50.8 mm diameter NaI(Tl) and CsI(Tl) scintillators and 25.4 mm diameter CeBr3. These scintillators are many times larger than an individual SiPM, the largest of which are 36 mm2 at present. This work compares two methods of summing 64 SiPMs into a single output signal for use with standard charge integration electronics. The methods are a straightforward passive method, which simply combines all anode and cathodes together, and an active method, which employs high bandwidth op-amps in a summing topology. Comparisons are also made to a high quantum efficiency photomultiplier tube (PMT) for both resolution and pulse shape. Resolution and noise floor are satisfactorily comparable to the PMT from 21 keV to 2614 keV. The passive method provides the most straightforward approach, and slightly better energy resolution than the active method. The active method shows a substantially faster pulse rise time and undistorted fall time compared to the passive method. [ABSTRACT FROM AUTHOR]

This report highlights two different types of cross-talk in the photodetectors of the miniTimeCube neutrino experiment. The miniTimeCube detector has 24 8 × 8-anode Photonis MCP-PMT Planacon XP85012, totalling 1536 individual pixels viewing the 2-liter cube of plastic scintillator. [ABSTRACT FROM AUTHOR]

We review a simple gamma ray spectrometer constructed on a solderless breadboard. The spectrometer's detector consists of a CsI(Tl) scintillator and silicon photomultiplier (SiPM) and its readout is facilitated by an Arduino UNO. The system is low cost and utilizes a minimum of components while still achieving satisfactory charge linearity and noise levels. This instrument can be used in instructional laboratories to introduce both radiation detection and analog signal processing concepts. We also expect it will be of interest to those seeking to introduce gamma spectroscopy to the expanding ecosystem of Arduino hardware. [ABSTRACT FROM AUTHOR]

Colquiriite-type Eu-doped LiCaAlF6 and LiSrAlF6 (Eu:LiCAF and Eu:LiSAF) scintillator single crystals were grown using Al metal as a starting material to improve the Eu dopant segregation. All Eu:LiCAF and Eu:LiSAF single crystals using Al metal (Eu,AlM:LiCAF and Eu,AlM:LiSAF) indicated high transparency and effective segregation coefficients (keff) of Eu2%,AlM1%:LiCAF and Eu2%,AlM1%:LiSAF single crystals were significantly improved to the value of 0.40 and 0.99, respectively. EuF3 starting material reacted with Al metal before colquiriite-type phase was generated. As a result, Eu3+ ion in EuF3 was changed to Eu2+ ion which could be incorporated into Ca2+ and Sr2+ sites easily. [ABSTRACT FROM AUTHOR]

This paper describes the construction of a desktop muon detector, an undergraduate-level physics project that develops machine-shop and electronics-shop technical skills. The desktop muon detector is a self-contained apparatus that employs a plastic scintillator as the detection medium and a silicon photomultiplier for light collection. This detector can be battery powered and is used in conjunction with the provided software. The total cost per detector is approximately $100. We describe physics experiments we have performed, and then suggest several other interesting measurements that are possible, with one or more desktop muon detectors. [ABSTRACT FROM AUTHOR]

A scintillator-based detection system, of the type employed in the popular muon-lifetime instructional lab experiment, is used to measure the muon mass. The photomultiplier pulse pairs produced by the decay of cosmic ray muons into product electrons and positrons within the scintillator are detected by a digitizing oscilloscope and the energies of the product particles are quantified by integrating the area under their associated pulses. The observed distribution of product-particle energies is then compared with Monte Carlo simulated distributions assuming different values of the muon mass mlc2, where the modeling of product-particle energy loss within the scintillator accounts for collisional and radiative effects in a detailed way. Via a least-squares comparison, it is found that the simulated distribution based on a value of mlc2=10565 MeV most closely matches the experimental distribution. [ABSTRACT FROM AUTHOR]

A general approach for obtaining the statistics of a pulse train is developed, where the pulses are space and time dependent, and where the initial distribution of the pulses may be non-uniform. Explicit expressions for the moments up to fourth order, in terms of the moments of the elementary signals constituting the pulse train, are obtained. This is done for elementary signals that are waves. The expressions obtained are totally general as long as the elementary signals are not correlated. In contrast to the standard scintillation index, it may be space and time dependent, in which case it is called the dynamical scintillation index. This allows one to understand how a space-time pulse train approaches stationarity at different positions and times. The scintillation index using both the raw and central moments is defined. For the raw moments, both exact expressions and expansions in 1/N, where N is the number of elementary signals are obtained. For central moments, particularly simple exact expressions are given. [ABSTRACT FROM AUTHOR]

The interaction of vhf 100-1000 kHz underwater sound with the ocean surface is explored. The bistatic forward scatter of 300 kHz sound is measured in a wind driven wave channel. Fluctuations in arrival amplitude are described by the scintillation index (SI) which is a measure of arrival intensity variance. SI initially increases with wind speed but eventually saturates to a value of 0.5 when the root-mean-square (rms) roughness is 0.5 mm. An adjusted scintillation index (SI*) is suggested that accounts for the multiple arrivals and properly saturates to a value of 1. Fluctuations in arrival time do not saturate and increase proportionately to the dominant surface wave component. Forward scattering is modeled at frequencies ranging from 50 to 2000 kHz using the Helmholtz-Kirchhoff integral with surface wave realizations derived from wave gauge data. The amplitude and temporal statistics of the simulated scattering agree well with measured data. Intensity saturation occurs at lower wind speeds for higher frequency sound. Both measured and modeled vhf sound is characterized by many surface arrivals at saturation. Doppler shifts associated with wave motion are expected to vary rapidly for vhf sound however further analysis is required. [ABSTRACT FROM AUTHOR]

A low-cost multi-channel analyzer (MCA) system was developed using a custom-build interface circuit and a PC sound card. The performance of the system was studied using γ-ray spectroscopy measurements with a NaI(Tl) scintillation detector. Our system successfully measured the energy of γ-rays at a rate of 1000 counts per second (cps). [ABSTRACT FROM AUTHOR]

We present measurements of the velocity of electrons, performed with an apparatus using the time-of-flight method, to demonstrate that the speed of light c is the limiting speed for electrons. The results obtained show the applicability of relativity in a regime where nonrelativistic physics predicts velocities exceeding c. The main advantages of the apparatus are the simplicity of its operation and the data analysis. By using electrons from weak radioactive sources the experiment is suitable for the undergraduate laboratory. Furthermore, we show that with electrons from a linear accelerator and the same apparatus, excellent agreement between data and the relativistic expression for the speed of electrons in the keV-MeV energy range is observed. [ABSTRACT FROM AUTHOR]

We describe a compact apparatus for measuring the charge-averaged lifetime of atmospheric muons in plastic scintillator using low-cost, low-power electronics. We present measurements of the stopping rate of atmospheric muons as a function of altitude to demonstrate relativistic time dilation. The apparatus is designed for the advanced undergraduate physics laboratory and is suitable for field measurements. [ABSTRACT FROM AUTHOR]

Presents a simple Monte Carlo algorithm for the simulation of the passage of gamma rays of about 1 MeV in a medium. Visualization of the photon tracks; Proposal of several problems for a layer and a cylinder; Calculation of the energy transferred to electrons in a water cylinder as a function of depth and the line shape of the NaI scintillator. [ABSTRACT FROM AUTHOR]

An acoustical scintillation instrument is described that has been used to measure flow and temperature fluctuations at a hydrothermal vent plume. The vertical buoyancy driven flow together with the root-mean-square temperature fluctuations are obtained for vent structure 8F of the Main Endeavour vent field on the Endeavour segment of the Juan de Fuca Ridge. Long term (71 days) measurements are obtained and an estimate of the heat flux density which is of the order 0.06 MWm-2 is calculated. Measurements also show oscillations in the log-amplitude variance that result from either plume advection or increased entrainment of ambient fluids by the ambient tidal currents, thus demonstrating the need for a long time series measurement of simultaneous horizontal and vertical flow. Future measurements in the Main Endeavour vent field, with possible integration into the NEPTUNE seafloor observatory, will be over extended periods of time so that comparisons of these processes can be made with independent seismic data collected by NOAA/PMEL SOSUS array. [ABSTRACT FROM AUTHOR]