Search

In the late 1930s, a team of physicists from the National Bureau of Standards (now the National Institute of Standards and Technology) published eight papers on the investigation of cosmic rays in the atmosphere. Payloads launched with weather balloons, also known as radiosondes, were equipped with sensors to measure temperature, relative humidity, pressure, and radiation dose. A battery-operated telemetry system was used to continuously transmit at 60 MHz to a base station. They measured the radiation dose profiles of cosmic radiation in the atmosphere up to 21 km. Calibration of the Geiger-Müller counters with a standard radium source allowed them to calculate a radiation dose rate at an altitude corresponding to 10 kPa that was 180 times the dose rate near sea level in Washington, DC. Ascents in Washington, DC (latitude 39 degrees) and Lima, Peru (near equator) allowed them to demonstrate the effects of Earth's magnetic field on incident galactic cosmic rays; the dose rate in Peru was only half that in Washington, DC. [ABSTRACT FROM AUTHOR]

Ionizing radiation is one of the main risks affecting healthcare workers and patients worldwide. Special attention has to be paid to medical staff in the vicinity of radiological equipment or patients undergoing radioisotope procedures. To measure radiation values, traditional area meters are strategically placed in hospitals and personal dosimeters are worn by workers. However, important drawbacks inherent to these systems in terms of cost, detection precision, real time data processing, flexibility, and so on, have been detected and carefully detailed. To overcome these inconveniences, a low cost, open-source, portable radiation measurement system is proposed. The goal is to deploy devices integrating a commercial Geiger-Muller (GM) detector to capture radiation doses in real time and to wirelessly dispatch them to a remote database where the radiation values are stored. Medical staff will be able to check the accumulated doses first hand, as well as other statistics related to radiation by means of a smartphone application. Finally, the device is certified by an accredited calibration center, to later validate the entire system in a hospital environment. [ABSTRACT FROM AUTHOR]

A computerized tomography (CT) system using a 0.1μCi Sr-90 beta source, Geiger counter, and low density foam samples was developed. A simple algorithm was used to construct images from the data collected with the beta CT scanner. The beta CT system is analogous to X-ray CT as both types of radiation are sensitive to density variations. This system offers a platform for learning opportunities in an undergraduate laboratory, covering topics such as image reconstruction algorithms, radiation exposure, and the energy dependence of absorption. [ABSTRACT FROM AUTHOR]

This paper describes the development of an instrument for radiological monitoring, identified as Gamma Alarm (GAMAL01). The instrument monitors the increment of radiation count rate and produces an alarm signal, when the count rate becomes superior to a fixed threshold value. The threshold is fixed to assure that the signal emission will start when the value of the radiation count rate may cause a non acceptable radiological exposition of the personnel, according to the radiological safety regulations existing in the country. Following the signal the personnel must be evacuated from the affected place. The instrument consists of two sections, an analogical section and a digital one. [ABSTRACT FROM AUTHOR]

Operating systems interface between hardware and the user, random numbers are useful for security and simulation, and file systems form the program access to them in a modern operating system. Blending these items into a remotely accessed infrastructure forms the basis for supporting operating systems projects. This work describes the hardware, software, and communication infrastructure to support student projects by sharing remote hardware to acquire background radiations events with a Geiger counter, transforming those events into random numbers, and providing those numbers through a custom file system. Collectively, the hardware and software provide an inexpensive remote laboratory experience for computing students. [ABSTRACT FROM AUTHOR]

The article discusses the effect of radiation. An overview of the process of radiation is presented. The chemical effects of radiation are attributed to their capacity to break up certain chemical configurations. The author reveals that radiation damage can be detected using instruments like electroscope and Geiger counter, and the main problem is the disposal of radio active wastes. The impact of atomic warfare are enumerated including the total disorganization of communications and civic life resulting from a single explosion and the panic caused by its threat. Due to this, the author emphasized that radiation creates symptoms which can be counteracted by known treatments and it does not mean a sudden death. Civilian defense organization to protect the population is recommended.

Microfabricated radiation detectors can be used to provide first alert information about presence of harmful radiation. This paper describes a micromachined gamma detector that operates in the Geiger–Muller (G–M) regime. Gamma rays eject photoelectrons from the cathode material through the photoelectric effect and/or Compton scattering, which in turn ionize the Ar fill-gas providing a current pulse. The detector utilizes cathode stacks that are micromachined from stainless steel #304 foil. Micromachined glass fingers with thin-film anode metal traces are positioned transversely through aligned perforations in the stacked cathodes. This orthogonal array of anodes and cathodes effectively distinguishes electron avalanche regions from drift regions despite the miniaturization, thereby reducing the likelihood of spurious discharges. Overall, the detector diameter and height are 9 and 2.5 mm, respectively. Detector performance is characterized using a 99- $\mu $ Ci 137Cs source placed at a distance of 3 cm from the detector. In an integration time of 10 min at an applied voltage of 630 V, a source:background ratio of 89:1 is achieved—a fivefold improvement over the previously reported micromachined devices operating in the G–M regime. This architecture also reduces the typical charge per discharge to 6.6 pC, allowing the estimated dead time between detection events to be $\sim 1 \mu $ s. [2014-0333] [ABSTRACT FROM PUBLISHER]

The term 'thermal flux' implies a Maxwellian distribution of velocity and energy corresponding to the most probable velocity of 2200 m s at 293.4 K. In order to measure the thermal neutron flux density, the foil activation method was used. Thermal neutron flux determination in paraffin phantom by counting the emitted rays of indium foils with two different detectors (Geiger-Muller counter and NaI(Tl)) was the aim of this project. The relative differences of the outcome of the experiments were between 2.5% and 5%. The final results were compared with MCNP4C outputs and the best agreement was generated using NaI(Tl) by a minimum discrepancy of about 0.6% for the foil placed 8.5 cm from the neutron source. [ABSTRACT FROM AUTHOR]

We study the effects of post-selection measurements on both the non-classicality of the state of a mechanical oscillator and the entanglement between two mechanical systems that are part of a distributed optomechanical network. We address the cases of both Gaussian and non- Gaussian measurements, identifying in which cases simple photon counting and Geiger-like measurements are effective in distilling a strongly non-classical mechanical state and enhancing the purely mechanical entanglement between two elements of the network. [ABSTRACT FROM AUTHOR]

Objective: To determine correction factors for the variation in volume of radiopharmaceuticals in containers of different geometries, comparing the influence of such factors on the determination of 99mTc and 123I activity with two types of calibrators - one with ionization chamber and another with Geiger-Müller (G-M) detector -; and to evaluate calibrators performance in the measurement of 99mTc and 123I activities. Materials and Methods: Eight calibrators, 10R glass vials, 3 and 5 mL plastic syringes and 99mTc and 123I solutions were utilized. The correction factors were determined with basis on practical measurements of the variation in the calibrators' response according to the volume of radionuclide solution in the glass vials. The performance was evaluated according to the acceptance criterion of ±10% accuracy required by the Brazilian standard. Results: The variation of the calibrators' response according to the variation in radionuclide volume was reasonably greater in the calibrator with G-M detector. It was also greater for 123I than for 99mTc. Conclusion: The results confirm that the calibrators' response depends on the radionuclide volume contained in the vials. Such dependence is more critical for the calibrators equipped with G-M detector and for 123I as compared with 99mTc. Keywords: Radionuclides calibrator; Nuclear medicine; Activity; Tc-99m; I-123. [ABSTRACT FROM AUTHOR]

In 1924, Walther Bothe and Hans Geiger applied a coincidence method to the study of Compton scattering with Geiger needle counters. Their experiment confirmed the existence of radiation quanta and established the validity of conservation principles in elementary processes. At the end of the 1920s, Bothe and Werner Kolhörster coupled the coincidence technique with the new Geiger-Müller counter to study cosmic rays, marking the start of cosmic-ray research as a branch of physics. The coincidence method was further refined by Bruno Rossi, who developed a vacuum-tube device capable of registering the simultaneous occurrence of electrical pulses from any number of counters with a tenfold improvement in time resolution. The electronic coincidence circuit bearing Rossi's name was instrumental in his research on the corpuscular nature and the properties of cosmic radiation during the early 1930s, a period characterized by a lively debate between Millikan and followers of the corpuscular interpretation. The Rossi coincidence circuit was also at the core of the counter-controlled cloud chamber developed by Patrick Blackett and Giuseppe Occhialini, and became one of the important ingredients of particle and nuclear physics. During the late 1930s and 1940s, coincidences, anti-coincidences and delayed coincidences played a crucial role in a series of experiments on the decay of the muon, which inaugurated the current era of particle physics. [ABSTRACT FROM AUTHOR]

The article offers information on "Research technologies - Forschungstechnologien. 94. Jahrestagung der Deutschen Gesellschaft für Geschichte der Medizin, Naturwissenschaft und Technik," a conference about research technologies that took place in Stuttgart, Germany from September 23-25, 2011. Topics discussed included how the Geiger-Müller counter radiation detector was developed, how doctors are medicating mental patients, and the different types of chromatographic analysis.

The linearity of response and spatial uniformity of response characteristics of two commercially available single-photon avalanche photodiode (SPAD) detection systems were experimentally investigated using a dedicated characterization facility that measures these parameters. Both SPAD detection systems are shown to exhibit a nonlinear response. Moreover, the responsivity of both SPAD systems is shown to be spatially nonuniform and the degree of nonuniformity depends on the single-photon detection probability setting of these systems. The experimentally observed spatial uniformity of response behavior of these detectors is explained in terms of the spatial nonuniformity in the breakdown voltage Vb across the active area of the device. The experimentally observed linearity of response characteristics of these detectors at high count rates can be explained in terms of “pulse collisions.” However, the origin of the experimentally observed linearity of response characteristics of the same detectors at low count rates is currently unknown. [ABSTRACT FROM PUBLISHER]

An effective method to analyze the origin of primary dark counts is presented for single-photon-detection avalanche photodiodes (APDs) operated in the gated Geiger modes. It is revealed that a band-to-band tunneling model reproduces the experimental data very well for GaInAs/InP single-photon-detection APDs, while a phonon-assisted tunneling model fails. Therefore, we concluded that primary dark counts are dominated by the band-to-band tunneling for the GaInAs/InP single-photon-detection APDs. Then, we calculate the dark count probability and the detection efficiency by modeling the band-to-band tunneling. It is found that the ratio of the dark count probability to the detection efficiency is reduced by decreasing the impurity concentration of the multiplication region and of the p-type window. [ABSTRACT FROM PUBLISHER]

This paper reports on a multichannel radiation detection platform enabled with nanoparticles that is capable of detecting and discriminating all types of radiation emitted from fissionable bomb making materials. Typical Geiger counters are limited to detecting only beta and gamma radiation. The microGeiger counter reported here detects all species of radiation including beta particles, gamma/X rays, alpha particles, and neutrons. The multispecies detecting micro-Geiger counter contains a hermetically sealed and electrically biased fill gas. Impinging radiation interacts with tailored nanoparticles to release secondary charged particles that ionize the fill gas. The ionized particles collect on respectively biased electrodes resulting in a characteristic electrical pulse. Pulse height spectroscopy and radiation energy binning techniques can then be used to analyze the pulses to determine the specific radiation isotope. The ideal voltage range of operation for energy discrimination was found to be in the proportional region at 1000 Vdc. In this region, specific pulse heights for different radiation species resulted. The amplification region strength which determines the device sensitivity to radiation energy can be tuned with the electrode separation distance. An electrode separation of 0.8 mm produced a count rate of 530 cpm for a 90Sr beta source when compared to an off-the-shelf Geiger counter which produced 1500 cpm. Count rates as high as 15300 were observed for the same radiation source with electrodes spaced closer than 0.5 mm. By using a novel microinjection ceramic molding and silver paste metallizing process, the batch fabrication of essentially disposable devices can be achieved. [ABSTRACT FROM AUTHOR]

To assess the performance of radionuclide calibrators in 55 Brazilian nuclear medicine services in the measurement of 99Tcm radiopharmaceutical activity. Proficiency tests were applied to data sets with 63 results originated from the comparison program developed by Laboratório Nacional de Metrologia das Radiações Ionizantes of Instituto de Radioproteção e Dosimetria. MATERIALS AND METHODS: The calibrators' performance was evaluated in compliance with the acceptance criterion of ±10% accuracy required by the Brazilian standards and also the criteria established by the ISO/IEC Guide 43-1, and classified as either "acceptable" or "non-acceptable". The samples of 99Tcm utilized in the comparison were supplied by some of the participants and calibrated at Laboratório Nacional de Metrologia das Radiações Ionizantes for determining the activity reference value. RESULTS: The present study utilizing 99Tcm has shown that 82.5% of the calibrators were considered as acceptable according to the Brazilian standards, while by the criteria established by ISO/IEC 43-1, 81.0% were considered as acceptable. On the other hand, radionuclide calibrators with Geiger-Müller detectors presented unsatisfactory performance when compared with calibrators with ionization chambers. CONCLUSION: The performance evaluation based on the ISO/IEC 43-1 criteria, which are applied to analytical laboratories, in spite of being more restrictive, has demonstrated to be quite consistent with the accuracy criterion established by the Brazilian standard. [ABSTRACT FROM AUTHOR]

Abstract: A benchmark experiment has been performed during the 2005–2007 campaigns of JET in order to validate the rigorous two-step (R2S) and direct one-step (D1S) methods for the prediction of shutdown dose rates in full 3D geometry. Dose rate levels calculated using D1S and R2S methods have been compared with experimental data collected before and during off-operational periods and at the end of the last JET campaigns. Measurements have been carried out in two irradiation positions: in-vessel with high sensitivity thermoluminescent detectors and ex-vessel with an active detector of Geiger–Mueller type. Satisfying agreement between calculations and measurements has been obtained in in-vessel position, whereas both methods underestimate the experimental quantity in the external one. [Copyright &y& Elsevier]

Avalanche photodiodes (APDs) operating in Geiger mode can detect weak optical signals at high speed. The implementation of APD systems in a CMOS technology makes it possible to integrate the photodetector and its peripheral circuits on the same chip. In this paper, we have fabricated APDs of different sizes and their driving circuits in a commercial 0.18-µm CMOS technology. The APDs are theoretically analyzed, measured, and the results are interpreted. Excellent breakdown performance is measured for the 10 and 20 pm APDs at 10.2 V. The APD system is compared to the previous implementations in standard CMOS. Our APD has a 5.5% peak probability of detection of a photon at an excess bias of 2 V, and a 30 ns dead time, which is better than the previously reported results. [ABSTRACT FROM AUTHOR]

The present paper deals With the marking of the moth Phyllocnistis labyrinthella with p32. Laboratory experiments were carried out with the intention of determining the concentration of the phosphoric acid most suitable. The highest radioactivity of the moth was obtained with solution containing 100 μC of p32 per ml. In this experiment the moths acquire an activity of 100000 cpm, which makes it possible to register the moth at a distance of 1/2 m. The released, activated moths in the field were recovered by means of the Geiger counter. [ABSTRACT FROM AUTHOR]

The cyclotron is the most widely used particle accelerator for producing medically important radio nuclides. Many medical centers in India have installed compact medical cyclotrons for on-site production of short-lived positron-emitting radio nuclides such as 18F, 13N, and 11C. A mandatory requirement for cyclotron installation is radiation control permit from Atomic Energy Regulatory Board. Cyclotron radiation survey is an integral part of the overall radiation safety in the cyclotron facility. Radiation surveillance in and around a newly installed cyclotron was performed using ionization chamber counter and Geiger Muller counter before, during and after operating the cyclotron. The readings were recorded at various locations where a high radiation field was expected. The results were recorded, tabulated and analyzed. The highest exposure level (0.93 µSv) was found at the back wall of the radiochemistry lab facing the cyclotron vault. Reason for the high exposure of 0.93 µSv/h: Synthesis of 18F-Fluoro-Deoxy-Glucose (18F-FDG) was going in the synthesis module and activity (18F) was present in the synthesis module when reading was taken. All other values were found to be below the recommended levels of exposure. [ABSTRACT FROM AUTHOR]

This article explores the characteristics of artificial glass. It identifies the properties that were obtained through standard gemological testing: hydrostatic, polariscope reaction, and ultraviolet (UV) fluorescence. It notes that no radioactivity was detected with a Geiger counter and microscopic examination revealed no inclusions. It notes that the spectrum of the light yellow state showed only a very slight increase in absorption toward the blue region and that the spectrum of the dark bluish gray state revealed a broad absorption.

In this brief, an integrated avalanche photodiode-active pixel sensor (APD-APS) for "daylight to subtwilight" imaging has been demonstrated. Excellent logarithmic response of the APS was demonstrated by images taken with a 64 × 64 pixel array. Image degradation occurred when the APD was operated in sub-Geiger avalanche mode. Analysis of the APD current revealed that leakage from parasitic diodes obscured the internal avalanche gain. The parasitics will be shown to impede fabricating of useful APD-APS circuits and advanced isolation techniques must be employed to operate in avalanche mode. [ABSTRACT FROM AUTHOR]