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Digital light processing three-dimensional (3D) printing technique is a powerful tool to rapidly manufacture plastic scintillators of almost any shape or geometric features. In our previous study, the main properties of light output and transmission were analyzed. However, a more detailed study of the other properties is required to develop 3D printed plastic scintillators with expectable and reproducible properties. The 3D printed plastic scintillator displayed an average decay time constants of 15.6 ns, intrinsic energy resolution of 13.2%, and intrinsic detection efficiency of 6.81% for 477 keV Compton electrons from the 137Cs γ-ray source. The 3D printed plastic scintillator showed a similar decay time and intrinsic detection efficiency as that of a commercial plastic scintillator BC408. Furthermore, the presented estimates for the properties showed good agreement with the analyzed data.

A simple and economic scintillator kit in combination with a computer-based oscilloscope was used to develop a learning experience, comprised of a set of activities to introduce students in an interactive way to the physics of gamma-ray detection. The proposal for secondary school and university students is built by means of frequent on-the-fly formative assessment to collect difficulties of students and ways to overcome them. Internal decays of Lutetium–yttrium oxyorthosilicate (LYSO) crystals already present in the scintillator kit are used as sources of gamma rays, so no external sources were needed. In addition, the use of LYSO crystals offers a reason to discuss coincidence measurements, because of the inherent beta background present in the internal decay, which can be at least partially removed with coincidence measurements. The goal of the learning experience is to experience how gamma-ray detection is actually done, discussing the physics involved, motivated by the current frontline research on the detection of gamma-ray bursts.

LHAASO is planning to enhance its sensitivity at energies around 100 GeV by utilize MCP staffed 20” PMT in the Water Cherekove Detector Array. The effective area for gamma ray detection will reach to 1800 m2 and differential sensitivity to 0.2 CU at 50 GeV. It will be the very useful survey detection for transient phenomena at 50 GeV in the northern sky. LHAASO is expected to play an important role in the multimessenger observation with the upgrading.

Europium-doped TlSr2I5 (TSI), a new high light yield scintillator for gamma-ray detection, has been grown by the vertical Bridgman method. A 12mm and 16mm diameter boules of TSI is grown in a two-zone vertical furnaces. Samples extracted from the grown boule have been characterized for their scintillation properties. Energy resolution of < 3% (FWHM) at 662 keV and a gamma-ray light yield of approximately 54,000 Ph/MeV have been obtained. Decay times of 395 ns (89%) and 2.0 microseconds (11%) have been measured.

A simple scintillator kit developed by Ian Bearden [1] was used to prepare a learning experience on gamma ray detection for secondary students. The goal is to offer an opportunity to collect gamma spectra, analyse data and understand how coincidence measurements are useful in space physics and in many other applications.

In article number 2001882, Pavao Andričević, László Forró, and co‐workers introduce the ‘oriented crystal‒crystal intergrowth’ method, yielding solution‐grown MAPbBr(3) crystals with volume and mass of over 1000 cm(3) and 3 kg. Its increased size, equipped with carbon electrodes, is utilized for sensitive gamma ray detection of a (60)Co source at the dose rate up to 2.3 Gy h(−1) at ambient conditions. [Image: see text]

Glenn Knoll was one of the leaders in the field of radiation detection and measurements and shaped this field through his outstanding scientific and technical contributions, as a teacher, his personality, and his textbook. His Radiation Detection and Measurement book guided me in my studies and is now the textbook in my classes in the Department of Nuclear Engineering at UC Berkeley. In the spirit of Glenn, I will provide an overview of our activities at the Berkeley Applied Nuclear Physics program reflecting some of the breadth of radiation detection technologies and their applications ranging from fundamental studies in physics to biomedical imaging and to nuclear security. I will conclude with a discussion of our Berkeley Radwatch and Resilient Communities activities as a result of the events at the Dai-ichi nuclear power plant in Fukushima, Japan more than 4 years ago.

The development of autonomous measuring systems for radioactivity in the ma- rine environment is today of important scientific priority for the marine sciences and especially for the Operational Oceanography. This paper concentrates on the improvement and application of an existing Nal-based gamma ray detection system for radioactivity measurements in seawater. The set up of the system will be described together with the appropriate calibrations in the laboratory. The operation of the system in the Aegean Sea provides the monitoring efficiency at 1461 keV by intercalibration with an appropriate salinity sensor mounted close to the Nal-detector. The gross counting rate was found constant within the statistical uncertainty of the measurements, during dry periods. The artificial radioactivity (137Cs) in the North Aegean Sea was increased, however, up to seven times after strong rainfall, compared to the mean radiation level as given in literature. This increment remains only for a short period of time (~2 days), due to strong advection processes of the water masses during strong rainfall.

Directional detection plays an important role in the search for rogue or illicit radioactive sources but is often complicated by Poisson statistics, large distances, and various sources of noise. A currently used directional detection method involves extracting the angular information of a source’s location from a cluster of detectors in a set geometry. Traditional algorithms designed to process detected data typically involve performing a least squares assessment against a database prepopulated with detector responses of known source locations. These algorithms perform best when the standoff distance is like that available in the prepopulated database; they lose accuracy when distances and environments of measurements are not well represented in the database. Analysis of highly variable and noisy data can often benefit from the robustness of machine learning, which has been implemented in applications such as isotope identification and radium mapping. This work aims to investigate the utility of machine learning algorithms capable of analyzing data with large amounts of statistical variability to improve directional location capabilities for large area source searches. Preliminary results with a fully connected residual neural network include the successful source location for simulated search scenarios to within 1 degree in 24% of trials. The same simulated data analyzed using traditional methods resulted in 1 degree location for 11% of trials. The traditional and neural network algorithms were compared in terms of error and accuracy as well performance as a function of distance for a simulated dataset of source searches. Results indicate that more robust algorithms, such as the implemented neural network, can improve system-inherent accuracy and over all directional capabilities.

SrF2 ve SrF2:xCe3+ (x=0.5 mol %, 0.6282 g -10 mol %, 12.5630 g) nanoparçacıklar kimyasal birlikte çöktürme yöntemiyle sentezlenmiştir. Katkısız ve seryum katkılı nanoparçacıkların yapısal ve optik özellikleri X-Işını Difraktometresi (XRD), Yüksek Çözünürlüklü Geçirimli Elektron Mikroskobu (HRTEM) ve Fotolüminesans Spektrofotometre (PL) ile karakterize edilmiştir. Sentezlenen nanoparçacıkların otalama parçacık boyutları, Debye-Scherer eşitliği kullanılarak, X-Işını kırınım desenlerindeki piklerin genişlemesinden belirlenmiştir. Hesaplanan ortalama parçacık boyutları 30 nm - 52 nm aralığında değişmektedir. Sentezlenen tüm nanoparçacıkların uyarma ve emisyon piklerinin dalga boyları sırasıyla 232 nm ve 464 nm’dir. Disk şekline sahip iri ve hacimli nanokompozit sintilatör malzemelerin üretiminde sentezlenen SrF2 and SrF2: %1 Ce3+ nanoparçacıklar fosfor dolgu malzemesi olarak, epoksi reçine ise matriks malzemesi olarak kullanılmıştır. Üretilen iri ve hacimli nanokompozit sintilatör malzemelerinin enerji spektrumları Am-241, Cs-137 ve Co-60 nokta kaynakları kullanılarak elde edilmiştir. Elde edilen spektrumlar incelendiğinde üretilen nanokompozit sintilatör malzemelerin, gama ışını dedeksiyonunun yanı sıra, gelen gama ışınının enerjisini ayırabilecek potansiyelde olduğunu göstermektedir. SrF2 and SrF2:xCe3+ (x=0.5%-10%) nanoparticles were synthesized using chemical co-precipitation method. Structural and optical properties of the undoped and cerium doped nanoparticles were characterized with X-Ray Diffraction (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), and Photoluminescence (PL) measurements. Average sizes of the synthesized nanoparticles were determined from the broadening of X-Ray Diffraction peaks using Debye-Scherer equation. Estimated values were ranging between 30 nm-52 nm. All synthesized nanoparticles show photoluminescence characteristics with an excitation and emission peaks centered at 232 nm and 464 nm, respectively. Disc shaped bulk nanocomposite scintillators were also fabricated using synthesized SrF2 and SrF2:1% Ce3+ nanoparticles as phosphor fillers and epoxy resin as matrix material. Energy spectrums of bulk nanocomposite scintillators were collected using Am-241, Cs-137, and Co-60 point sources. Gamma ray energy responses of the fabricated scintillator materials revealed the fact that these nanocomposites have a potential for the detection of gamma rays and energy discrimination of the radioactive sources.

Quality and performance of a detection system are the crucial parameters in all nuclear physics experiments. This system serves as a source of all signals and noises to be processed. Better performance, higher amplification and lower noises occurrence simplify subsequent signal analysis. In the field of Mossbauer spectroscopy, the spectrum quality and Mossbauer effect are crucial parameters which are affected especially by the quality of the detection system. These parameters were evaluated for different types of a detection setup. Finally an improvement of the spectrum quality by 15% and Mossbauer effect by 7% has been achieved for the natural iron reference absorber measurement in comparison with previous version of the detection system. K e y w o r d s: gamma ray detection, signal processing, Mossbauer spectroscopy, Mossbauer spectrum

As one of the important targets of the DArk Matter Particle Explorer (DAMPE), the GeV gamma- ray observations of DAMPE with good angular resolution, high energy resolution and high back- ground rejection facilitate the search of fine structures in the spectra of gamma-ray sources. In this work we summarize the performance of DAMPE for gamma-ray detection using simulation data, including the effective area, angular resolution and energy resolution.

In this paper, we propose the fast and efficient detection method using the continuous measurement technique for the gamma-ray signal acquisition. This method is improved than the conventional method for the getting information of the radiation distribution. First, we implement the stereo radiation detection system using gamma-ray sensors and the motion controller. We apply continuous measurement technique to the gamma-ray detector and conduct gamma-ray irradiation test for the comparison of detection techniques. The results show that the continuous measurement technique has the high efficient performance than the conventional method.Key Words : Fast gamma detector, Scintillation detector, Gamma-ray detection, Gamma Imager†Corresponding Author : Dept. of Nuclear convergence Techcnology Development, Korea Atomic Energy Research Institute, Korea.E-mail: yghwang@kaeri.re.kr*Dept. of Nuclear convergence Techcnology Development, Korea Atomic Energy Research Institute, Korea.Received : July 31, 2014; Accepted : August 26, 2014

We proposed a new method to determine the activity of each nuclide in a mixture of Cs-134, Cs-137 and Sr/Y-90. The point of this new measurement method is simultaneous counting between beta and gamma ray detection. We assembled a setup that employs plastic and NaI(Tl) scintillation detectors for beta- and gamma-ray detection, respectively. The obtained result shows that discrimination of Cs-134 and Cs-137 was successfully achieved. Radioactivity determined by measurement was in agreement with one prepared as a mixture. The results show that the method can be adapted to measure the radioactivity of samples contaminated by the accident at the Fukushima Daiichi Nuclear Power Plant.

Due to its exceptional properties, 3He proportional counters are the golden standard for neutron detection, particularly in homeland security applications where large area detectors are deployed. However, in recent years 3He has become severely scarce, which led to a tremendous price increase and acquisition restrictions of this material. Motivated by this, the development of 3He-free solutions became a priority. In a previous work, we have established a novel concept for neutron detection: a proportional counter with boron carbide (B 4 C) fine powder suspended in the proportional gas, forming a neutron sensitive aerosol that relies on the 10B neutron capture reaction. Computer simulations and prototype exposure to a cold neutron beam yielded favorable results, validating the detection concept, which may also be applied to hard x-ray and gamma ray detection by using fine particles made of a heavy element, such as Bi or Au. In this work we study the effect of the presence of B 4 C microparticles in the charge gain and energy resolution of a proportional counter filled with Ar-CH4 (90%–10%), by irradiation with x-rays from a 55Fe source. For the same applied voltage, an average gain loss by a factor of 36% and energy resolution (FWHM) increase by 15% (absolute value) was observed with the inclusion of B 4 C microparticles. Intrinsic energy resolution was calculated, obtaining 15% for pure P10 operation and 32% in the presence of the microparticles. While the gain drop is recoverable by increasing anode voltage, energy resolution degradation may be a drawback in low energy applications, were energy resolution is favored over detection efficiency.

We describe experiments for the undergraduate laboratory that use a high-resolution gamma detector to measure radiation in environmental samples. The experiments are designed to instruct the students in the quantitative analysis of gamma spectra and secular equilibrium. Experiments include the radioactive dating of Brazil nuts, determining radioisotope concentrations in natural samples, and measurement of the 235U abundance in uranium rich rocks.

As safety and security systems of shipping logistics are reinforced all over the world, ubiquitous technology-based core technology for safety and security is developing to build the system of logistics security. It is feared that the logistics security system of Korea has a possibility to technically depend on developed countries in the futures. Because the essential skills and equipment to retain security of logistics are not developed. It is urgent to introduce a logistics security system that fully integrates the entire logistics segment in the future. Thus, the necessity of developing the portable radiation detector which can detect gamma-ray nuclide is increasing for reinforcing safety and security systems. In this paper, a research suggests the implementation of portable radiation detector platform using Cortex-A8.

The possibility has been investigated of determining, using graydar (Gamma RAY Detection And Ranging)approach, the in-depth partial-density profile of some substance absorbed in a dense medium. Analyticalalgorithms have been derived for retrieving the in-depth profile of the partial density of the absorbed substanceon the basis of the conjecturally known in-depth profile of the extinction of the absorbing medium and theexperimentallydeterminablegraydarprofile. TheretrievalerrorunderthePoissonnoiseconditionshasalsobeenestimated analytically. The simulations performed of the Poisson-noise effect concern the case of soil moisture.The results obtained confirm the validity of the derived retrieval algorithms and error estimates and show thatthesoilmoistureprofilemaybeaccuratelydeterminedtodepthsof50cm,dependingonthedry-soilbulkdensity,thesensingphotonflux,andthemeasurementtime.PACSnumbers:07.85.

This paper describes a study of background estimation in Modular X- and Gamma ray Sensor (MXGS) onboard ESA's Atmosphere-Space Interactions Monitor (ASIM) mission, using Geant4 simulations and Spenvis packages for particle flux generations.

This paper measures the sample to sample variation in the light yield proportionality of NaI(Tl), and so explores whether this is an invariant characteristic of the material or whether it depends on the chemical and physical properties of the tested samples. We report on the electron response of nine crystals of NaI(Tl), differing in shape, volume, age, manufacturer and quality. The proportionality has been measured at the SLYNCI facility in the energy range between 3.5 to 460 keV. We observe that while samples produced by the same manufacturer at approximately the same time have virtually identical electron response curves, there are significant sample to sample variations among crystals produced by different manufacturers or at different times. In an effort to correlate changes in the electron response with details of the scintillation mechanism, we characterized other scintillation properties, including the gamma response and the x-ray excited emission spectra and decay times, for the nine crystals. While sample to sample differences in these crystals were observed, we have been unable to identify the underlying fundamental mechanisms that are responsible for these differences.

A transportable and robust gamma ray detection system (GISPI) was employed to determine the concentrations of naturally occurring radionuclides on various beaches in and around Saldanha Bay, located on the West Coast of South Africa. Several mathematical techniques were applied to obtain GIS overlay that could be used to investigate various geophysical phenomenon. The results demonstrated direct relationships between radionuclide concentrations, grain size of beach sediment and the intensity of wave action. The element concentrations were used to make deductions on the origin of some of the beach sand. The article finally draws conclusions on coastal and beach formation processes, based on the results of the distribution of various radionuclides.

Some examples of space-borne applications that require improvements in detector technology compared with conventional Si and Ge designs are described. Properties of compound semiconductors are noted, and a range of different detector developments are briefly reviewed. Material fabrication improvements for several compound semiconductors have resulted in near Fano-limited performance.

The detection of high-energy γ-ray sources is vitally important to national security for numerous reasons, particularly nuclear materials smuggling interdiction and threat detection. This article presents two methods of detecting and locating a concealed nuclear γ-ray source by analyzing detector data of emissions that have been modulated with a coded mask. The advantages of each method, derived from a simulation study and experimental data, are discussed. Energetic γ-rays readily penetrate moderate amounts of shielding material and can be detected at distances of many meters. Coded masks are spatial configurations of shielding material (e.g., small squares formed from plates of lead or tungsten) placed in front of a detector array to modulate the radiation distribution. A coded mask system provides improved detection through an increased signal-to-noise ratio. In a search scenario it is impossible to obtain a comparison background run without the presence of a potential concealed source. The developed an...

Currently we are investigating the inclusion of organotin compounds in new polystyrene scintillator materials to improve full gamma-ray energy sensitivity. Accurate calibration of the relative light yield from the newly developed scintillators is crucial to assess merits of compounds and chemical processes used in the scintillators' development. The full energy gamma-ray peak in a measured gamma-ray spectrum is commonly used in calibrating the relative light yield. However, the Compton continuum in the newly developed plastic scintillators is measured with much better efficiency and statistics and is found to be the best spectral feature that can be exploited for expeditious calibration of the relative light yield. In this study, we present a spectral gain matching of measured and simulated spectra, using a spectrum rebinning technique, to determine the Compton edge in a measured Compton continuum for accurate relative light yield calibration. The Compton edges determined using this technique were found to be within 1.2% of their theoretical estimates.

Nuclear-weapon-material detection via gamma-ray sensing is routinely applied, for example, in monitoring cross-border traffic. Natural or deliberate shielding both attenuates and distorts the shape of the gamma-ray spectra of specific radionuclides, thereby making such routine applications challenging. We develop a Lagrange multiplier (LM) test for shielding. A strong advantage of the LM test is that it only requires fitting a much simpler model that assumes no shielding. We show that, under the null hypothesis and some mild regularity conditions and as the detection time increases, LM test statistic for (composite) shielding is asymptotically Chi-square with the degree of freedom equal to the presumed number of shielding materials. We also derive the local power of the LM test. Extensive simulation studies suggest that the test is robust to the number and nature of the intervening materials, which owes to the fact that common intervening materials have broadly similar attenuation functions., Comment: Published in at http://dx.doi.org/10.1214/13-AOAS704 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Observations of strong flux of low-energy neutrons were made by $^{3}\mathrm{He}$ counters during thunderstorms [Gurevich et al (Phys. Rev. Lett. 108, 125001, 2012)]. How the unprecedented enhancements were produced remains elusive. To better elucidate the mechanism, a simulation study of surrounding material impacts on measurement by $^{3}\mathrm{He}$ counters was performed with GEANT4. It was found that unlike previously thought, a $^3\mathrm{He}$ counter had a small sensitivity to high-energy gamma rays because of inelastic interaction with its cathode-tube materials (Al or stainless steel). A $^{3}\mathrm{He}$ counter with the intrinsic small sensitivity, if surrounded by thick materials, would largely detect thunderstorm-related gamma rays rather than those neutrons produced via photonuclear reaction in the atmosphere. On the other hand, the counter, if surrounded by thin materials and located away from a gamma-ray source, would observe neutron signals with little gamma-ray contamination. Compared with the Gurevich measurement, the present work allows us to deduce that the enhancements are attributable to gamma rays, if their observatory was very close to or inside a gamma-ray emitting region in thunderclouds., Comment: Accepted for publication in Astroparticle Physics.29 Pages, 9 figures

The solution to the scatter problem remains a major technical challenge in gamma ray imaging. This paper presents a modelization of apparent images formed by scattered photons at various energies. It may be used either to generate a series of realistic multi-energy images or be included in an image enhancement procedure. The application to SPECT is discussed.

Several articles have been reviewed on the scintillation response of NaI(Tl). Those publications which report results obtained with radioactive sources either dispersed throughout the NaI(Tl)-lattice or located inside the wells of NaI(Tl)-crystals match within a /spl plusmn/0.9% standard deviation of a linear scintillation response between 3 MeV and 3 keV. Several authors who plated their sources outside the crystals measured nonlinear responses of NaT(TI) with up to /spl plusmn/7% of standard deviations between 700 and 4.5 keV. The presented analysis suggests that the observed nonlinearity is not an intrinsic effect of NaI(TI) but could be caused, at least partly, by effects occurring at the radiation entrance surfaces of the crystals.

International audience; Prompt secondary radiations such as gamma rays and protons can be used for ion-range monitoring during ion therapy either on an energy-slice basis or on a pencil-beam basis. We present a review of the ongoing activities in terms of detector developments, imaging, experimental and theoretical physics issues concerning the correlation between the physical dose and hadronic processes

Summary form only given. A hybrid coded imaging and detection system developed at the U.S. Naval Research Laboratory (NRL) was used for active interrogation measurements with pulsed bremsstrahlung at the Hermes-III facility at Sandia National Laboratories. This work follows previous experiments performed in 2011 and explores different targets and system conditions to the previous work. Unique detection and imaging of fissionable compared to nonfissionable material will be discussed.

We investigated the feasibility of long-drift-time CdZnTe (CZT) gamma-ray detectors, fabricated from CZT material produced by Redlen Technologies. CZT crystals with cross-section areas of 5 5 mm2 and 6 6 mm2 and thicknesses of 20-, 30-, 40-, and 50-mm were configured as 3D position-sensitive drift detectors and were read out using a front-end ASIC. By correcting the electron charge losses caused by defects in the crystals, we demonstrated high performance for relatively thick detectors fabricated from unselected CZT material. VC 2016 AIP Publishing LLC.

We have recently evaluated the quality of γ -ray angular distributions that can be extracted in particle-gamma coincidence measurements using the CHIMERA detector at LNS. γ -rays have been detected using the CsI(Tl) detectors of the spherical part of the CHIMERA array. Very clean γ -rays angular distributions were extracted in reactions induced by different stable beams impinging on 12 C thin targets. The results evidenced an effect of projectile spin flip on the γ -rays angular distributions. γ -particle coincidence measurements were also performed in reactions induced by neutron rich exotic beams produced through in-flight fragmentation at LNS. In recent experiments also the Farcos array was used to improve energy and angular resolution measurements of the detected charged particles. Results obtained with both stable and radioactive beams are reported.

Lessons learned by basic scientists in the study of experimental nuclear physics can often go unnoticed by cyclotron operator’s intent on meeting a demanding schedule of tracer production. Prompt neutrons and gammas are the signature that the desired reaction is occurring, providing a robust measure of the expected yield.

Inhomogeneity effect on full energy peak (FEP) efficiency in a soil sample was determined using the Monte Carlo simulation technique. The dependence of the FEP efficiency on the homogeneity in the soil was obtained for some particular photon energies ranging from 60 keV to 2 MeV and, as a result, the corresponding correction factors were obtained. This effect was more significant at lower energies and for higher inhomogeneity rates.

Radionuclide emissions from nuclear contraband challenge both detection and measurement technologies to capture and record each event. The development of a sequential Bayesian processor incorporating both the physics of gamma-ray emissions and the measurement of photon energies offers a physics-based approach to attack this challenging problem. It is shown that a "physics-based" structure can be used to develop an effective detection technique, but also motivates the implementation of this approach using particle filters to enhance and extract the required information. The resulting processor is applied to feasibility data obtained from a controlled proof-of-concept experiment.

Weakly interacting massive particles (WIMPs) can be captured by heavenly objects, like the Sun. Under the process of being captured by the Sun, they will build up a population of WIMPs around it, that will eventually sink to the core of the Sun. It has been argued with simpler estimates before that this halo of WIMPs around the Sun could be a strong enough gamma ray source to be a detectable signature for WIMP dark matter. We here revisit the problem using detailed Monte Carlo simulations and detailed composition and structure information about the Sun to estimate the size of the gamma ray flux. Compared to earlier estimates, we find that the gamma ray flux from WIMP annihilations in the Sun halo would be negligible and no current or planned detectors would even be able to detect this flux., Comment: 5 pages, 1 figure. To appear in the proceedings of the Identification of Dark Matter conference (IDM 2008), Stockholm, Sweden, 18-22 August, 2008

Recent developments in detector technologies applicable to low-energy gamma-ray detection are reviewed. Emphasis is given on the silicon technologies now being developed around particle physics laboratories. They are expected to lay basis for new generation low-energy cosmic gamma-ray detectors.

A simple setup for measuring the amount of potassium in foods is described. A 3-in. NaI detector is used to measure samples that are 3000 cm3 in size. With moderate shielding, the potassium content can be measured down to a detection limit of a few parts per 10 000.

Microcalorimeter detectors based on transition-edge sensors coupled to a bulk absorber are an emerging technology for hard X-ray and soft gamma-ray measurements. Monte Carlo simulations codes, like GEANT4, can be a valuable tool for evaluating detector design ideas, interpreting measured data, and predicting detector performance. We report on initial attempts to reproduce measured microcalorimeter data with GEANT4 simulations.

The present status and understanding of the "spectral sequence" of blazars is discussed in the perspective of the upcoming GLAST launch. The vast improvement in sensitivity will allow to i) determine more objectively the "average" gamma-ray properties of classes objects ii) probe more deeply the ratio between accretion power and jet power in different systems., 3 pages, 4 figures. Proceedings of the First GLAST Symposium, to be published

Gamma‐ray pulsars are among the best targets for the Large Area Telescope (LAT) aboard the GLAST mission. The higher sensitivity, time and energy resolution of the LAT will provide data of fundamental importance to understand the physics of these fascinating objects. Powerful tools for studying the LAT capabilities for pulsar science are the simulation programs developed within the GLAST Collaboration. Thanks to these simulations it is possible to produce a detailed distribution of gamma‐ray photons in energy and phase that can be folded through the LAT Instrument Response Functions (IRFs). Here we present some of the main interesting results from the simulations developed to study the discovery potential of the LAT. In particular we will focus on the capability of the LAT to discover new radio‐loud gamma‐ray pulsars, on the discrimination between Polar Cap and Outer Gap models, and on the LAT pulsar sensitivity.

The Advanced Compton Telescope (ACT), NASA’s next major step in gamma‐ray astronomy, will probe the fires where chemical elements are formed by enabling high‐resolution spectroscopy of nuclear emission from supernova explosions. During the past several years, our collaboration has been undertaking a NASA mission concept study for ACT. This study was designed to (1) transform the key scientific objectives into specific instrument requirements, (2) to identify the most promising technologies to meet those requirements, and (3) to design a viable mission concept for this instrument. We will present the results of this study, including scientific goals, instrument design, and mission requirements.

The Minimal Spanning Tree (MST) algorithm is a graph‐theoretical method of finding clusters in a given set of points. We apply MST to gamma‐ray bidimensional images and associate possible sources with the regions where photons’ arrival directions clusterize. Additional filters to select clusters are included to reduce spurious detections. We present some applications to simulated GLAST data.