A Calorimeter Based on a Resistance Thermometer

A calorimeter based on aluminum alloy was developed to measure bremsstrahlung doses. The absorbed dose is determined using a thin-wire resistance thermometer included in an electrical bridge. It is shown that state-of-the-art instrumentation is capable of measuring average doses of 0.1 Gy (corresponding to a change of 10^?4 K in the sensor's temperature) and over.     

Pulsed interferometric calorimetry

The possibility of using semiconductor single crystals (Si, GaP, etc.) as calorimeters for pulsed heat flux measurements is discussed. The method of laser interferometric thermometry in the reflected light at a wavelength of 1.15 μm makes it possible to detect changes δθ≈2×10⁻⁵ K in the temperature of a 1-mm-thick Si single crystal. The sensitivity of a calorimeter with laser readout is sufficient for detection of the absorbed energy δE≈15 μJ/cm² and is independent of the Si plate thickness. The method for selecting the working point in the resonance curve for achieving maximum sensitivity in detection of pulse fluxes is discussed.     

Radiation damage in soft X-ray microscopy of live mammalian cells

When specimens are observed by soft X-ray microscopy, they always absorb many photons, causing radiation damage at the imaged site. The problems of radiation damage were studied in view of the principle of image formation; absorption contrast, scattering (holography), or phase contrast. In all cases, photons with a wavelength of 1–10 nm interact with the specimen mainly through the photoelectric effect followed by the transfer of energy to the imaging site either directly (absorption imaging) or indirectly (holography or phase contrast). This absorbed energy will cause structural changes to the imaging site. From a review of the literature the absorbed dose is estimated to be as high as 10⁷ Gy when the expected resolution of the specimen (1–10 thick) is 10 nm. This dose is far in excess of the amount required for cells to be able to survive when live mammalian cells are exposed. The levels of radiation effects were extrapolated to the estimated absorbed dose from the reported values for cell survival, chromosome aberrations, and DNA strand breaks with respect to observations on mammalian chromosomes. The extrapolated results show that some damage will occur in every 10 times 10-nm (expected resolution) size unit. Although these studies focused only on the effects on mammalian chromosomes, the present results are more or less common phenomena in the observation of biological specimens. Hence, the results suggest that dynamic observations will be difficult. On the other hand, a time-scale study of the effects of radiation on structural integrity suggests that single-shot imaging with short-pulsed (probably shorter than a few milliseconds) X-rays may be appropriate for the observation of intact live biological specimens in the hydrated condition, before they have deteriorated.     

Use of Large-Area Photodiodes for Improving the Characteristics of an Electromagnetic Calorimeter Based on Lead Tungstate Crystals

It is shown that an increase in the area of photodetectors allows the PHOS electromagnetic calorimeter of the ALICE experiment to operate at room temperature with better spectrometric characteristics. The linearity of the calorimeter response has been investigated in the 1–110 GeV energy range using both Hamamatsu S8664-1010 avalanche photodiodes with a large area (10 × 10 mm²) and arrays of MPPC Hamamatsu S12572-015C silicon photomultipliers with a sensitive area of 6 × 6 mm². The calorimeter based on avalanche photodiodes is linear in the energy range under investigation compared to a calorimeter composed of silicon-photomultiplier arrays.     

A liquid pulsed microwave radiation calorimeter

A wideband calorimeter intended for measuring energies of the pulsed microwave radiation with duration of several nanoseconds to 1 s is described. The calorimeter’s principle of operation is based on measuring the volume increment that results from heating, when the radiation is absorbed by a polar liquid. The energy measurement range is 10 mJ–100 J, the energy-absorption coefficient is >0.9 in a frequency band of 1.6–20 GHz and ～0.99 at frequencies of 4–18 GHz. The measurement error of the absorbed energy in the range 0.2–50 J does not exceed ±4%.     

A Dosimeter for On-line Dose Rate Monitoring Based on a Natural Diamond Detector

The structure and principle of operation of a dosimeter for on-line dose rate monitoring (DOM) are considered. The DOM provides real-time measurements of the absorbed -ray and electron dose rates, monitors relative distributions of radiation fields in radiotherapy facilities, and controls the radiation characteristics of radiotherapeutic equipment during its adjustment, certification, and service. The dosimeter can measure the dose absorbed in a certain period of time. Compared to conventional dosimeters based on air ionization chambers and silicon semiconductor detectors, the DOM has a number of advantages: dose-rate measurement linearity, energy independence of radiation detection in the range of 0.8–20 MeV for -rays and 8–20 MeV for electrons, high sensitivity compared to air ionization chambers, high radiation and thermal stability, and the small size of the device. The detecting element of the dosimeter is manufactured from a tissue equivalent to a biological material. The operating ranges of dose rate measurements are 10^–3–10 Gy/min and 10^–2–10² Gy/min. The DOM measurement error is <2%. Radiation therapy is the dosimeter field of application.     

Potentiometric Detection of Anions Separated by Liquid Chromatography Using a Metallic Silver Wire Electrode

Abstract

A silver metallic wire electrode, coated with AgCl, used for potentiometric detection of inorganic anions in liquid chromatography, is described. The electrode response to the anions was evaluated by both static and flow injection measurements, and results have shown that the electrode exhibits sensitive response to CI^? and SCN^? with a detection limit of 10^?6 M. The electrode was used as a potentiometric detector for the determination of anions following separation by ion chromatography using the eluent containing 5 mM phthalate at pH 4.2. Calibration plots were not linear, but give a useful working range of 5 x10^?5 to 3 x10^?2 M. It also demonstrated to be a useful detector for the detection of anions separated, where the separation of anions was preformed with a C₁₈ column using a 0.1 mM octylammonium salicylate as an ion-paring reagent, by ion-pair chromatography. The determination of chloride in waste water samples were demonstrated by proposed method.

     

Flow of Electric Current Through Lubricated Contacts

A study is made of the passage of current, both DC and AC, through elastohydro-dynamically lubricated contacts using a 4-ball machine running at 175 rpm with 1 in Steel balls. At small applied voltages ～15mV, when there is a coherent oil film, (i.e., when it is not short circuited by metallic contact) it behaves as an ohmic resistance. The resistance of the oil film varies from >10¹ ohms down to 1 ohm. This has important implications for the concept of percentage metallic contact, and for the statistical contact method of assessing oil film thickness.

At high currents (～1 amp.) the current flows by the voltage discharge mechanism. The transition from ohmic resistance to discharge is discussed. Using the resistance of the oil film the lubricating quality of long chain acids in cetane is compared. A brief study is also mode of Fein's temperature correlation.     

Filling the gap of a plasma opening switch with plasma from an electroexploding wire in an external magnetic field

The dynamics of filling the interelectrode gap of a plasma opening switch (POS) using an electroexploding wire with a diameter of 4 μm (tungsten) and 6 μm (carbon) is considered. The wire was connected to coaxial electrodes of the POS perpendicular to the force lines of a longitudinal magnetic field, which was created by an external source. When a current was transmitted through the wire, the longitudinal speed of produced plasma was ≈10⁶ cm/s, and the azimuthal speed was ≈10⁷ cm/s (for tungsten) and ≥1.3 × 10⁷ cm/s (for carbon). As a result, a plasma “washer” was formed and the total quantity of particles in it was determined by the parameters of the wire and the POS gap. This result is the first step in a solution of “the first shot” problem.     

A Direct-Charging Detector for Measuring the Pulse Shape, Absorbed Dose Rate, and γ-Radiation Dose

A method for the calculation and the results of experimental tests of direct-charging detectors of -radiation are described. The current sensitivities to monochromatic -rays with energies of 0.3–10 MeV for three plane detector designs with the thicknesses of the dielectric layers of 0.5 to 2 cm are presented. The sensitivity is a function of energy within this range, and its minimum and maximum values differ by a factor of ten. Therefore, when using direct-charging detectors for measuring the absorbed dose rate and radiation dose, the knowledge of the -radiation spectrum is necessary. The spectrum is unnecessary in radiation pulse-shape measurements. The detector amplitude characteristic is linear for values of the absorbed dose rate of 10¹⁵ rad/s.     

A calorimeter for detecting hadrons with energies of 10–100 GeV

A calorimeter for detecting hadrons in the energy range 10–100 GeV is described. It is used at CERN in the NA58 (COMPASS) experiment aimed at studying the nucleon structure and spectroscopy measurements of charmed particles. The calorimeter is composed of 480 modules with a cross section of 15×15 cm², assembled in a matrix with dimensions of 4.2×3 m² and a central window of area 1.2×0.6 m². In each module are 40 iron and scintillator layers of a total thickness of 4.8 interaction lengths. The energy resolution of the calorimeter for hadrons (pions) and electrons and the spatial resolution, determined on the test beams, are $\frac{{\sigma _\pi (E)}}{{E[GeV]}} = \frac{{59.4 \pm 2.9}}{{\sqrt E }} \oplus (7.6 \pm 0.4)\% ;\frac{{\sigma _e (E)}}{{E[GeV]}} = \frac{{24.6 \pm 0.7}}{{\sqrt E }} \oplus (0.7 \pm 0.4)\% $ , and σ _x,y ≈ 15 mm, respectively. The average value of the e/π ratio that characterizes the amplitude responses of the calorimeter to electrons and pions with equal energies from the above range is 1.2 ± 0.1. This study was performed at the JINR Laboratory for Particle Physics.     

Efficiency of radioluminescence of water under the action of accelerated electrons

The efficiency of radioluminescence (～1.7 × 10^?6) of distilled water has been measured under normal conditions. A beam of accelerated electrons with an energy of up to 230 keV was used to excite the water luminescence. This light was guided through a quartz optical fiber to the photocathode of a photomultiplier. The detecting system was calibrated with a standard ribbon lamp. The dose absorbed in water was recorded with film dosimeters.     

Friction Measurements on a Low Earth Satellite

The coefficient of sliding friction for a number of materials was measured during the flight of Ranger 1 spacecraft. Flat disks of materials of interest were rotated at a speed of 8–14 inches per minute while in contact with 1/8-inch diameter hemispherical riders. Because of the low orbit achieved by Ranger 1, the experiment was exposed to vacuum in the range of 3 × 10^?6 to 8 × 10^?9 mm Hg. For unlubricated metals sliding on metals, the friction coefficient averaged about 0.5; for some combinations of metals, it occasionally exceeded 1.0. Lower values were observed with lubricants of grease or gold-plate and for ceramics sliding against metals. The coefficient of friction was very low, averaging 0.04, for metallic pairs lubricated with molybdenum disulfide and for polytetrafluoroethylene sliding against metals and ceramics. Relatively low friction coefficients were found for metallic materials sliding against unlubricated metallic and ceramic materials when at least one member of the pair was of high hardness. The coefficients observed for unlubricated metal pairs were not inconsistent with the hypothesis that high friction tends to correlate with high mutual solid solubility. In general the coefficients in space and in a laboratory vacuum of 5 × 10^?6 mm Hg were not systematically different. For unlubricated metallic materials, friction in vacuum was higher than in air at shorter running times.     

The Silicon Matrix as a Charge Detector for the ATIC Experiment

The characteristics of the silicon matrix which is the main charge detector in the ATIC balloon experiment are reported. The ATIC spectrometer was designed to measure the elemental composition and energy spectra of primary cosmic rays in an energy range of 10¹⁰to 10¹³eV with individual charge resolution from protons to iron under high albedo conditions from the calorimeter.     

Dynamics of vapor emissions at wire explosion threshold

X-pinch plasmas have been actively studied in the recent years. Numerical simulation of the ramp-up of metallic vapor emissions from wire specimens shows that under impulsive Ohmic heating the wire core invariably reaches a supercritical state before explosion. The heating rate depends sensitively on the local wire resistance, leading to highly variable vapor emission flux along the wire. To examine the vapor emission process, we have visualized nickel wire explosions by means of shock formation in air. In a single explosion as captured by shadowgraphy, there usually appear several shocks with spherical or cylindrical wave front originating from different parts of the wire. Growth of various shock fronts in time is well characterized by a power-law scaling in one form or another. Continuum emission spectra are obtained and calibrated to measure temperature near the explosion threshold. Shock front structures and vapor plume temperature are examined.     

Testing a fiber-optic ionizing-radiation detector

A fiber-optic ionizing-radiation detector is composed of a scintillation sensor, an optical fiber, and a photodetector. Due to the miniature size and the high radiation resistance, the detector is capable of measuring the characteristics of powerful neutron and γ-ray fields with a high spatial resolution. A prototype of the detector has been tested using a ⁶⁰Co γ-ray source with a dose rate as great as 200 R/S. The dynamic range of dose measurements is no less than 10⁵. The detector signal is linearly dependent on the radiation dose rate. The ratio of the useful signal to the background due to radioluminescence of the optical fiber is presented for different types of scintillators.     

The Radiation-Measuring Complex of the СПРУТ-VI System

The radiation-measuring complex of the -VI system is designed to determine the absorbed dose and values of heavy-nuclei fluxes under a program for investigating isolated failures in microcircuits. The complex is composed of active and passive elements. It is used to measure the total absorbed dose and the radiation doses received by exposed microelectronic elements behind shields of <0.3 and >1 g/cm² (across the range of 10^–4–5 Gy), establish a link between isolated failures and the actual radiation environment, detect nuclear fluxes with a charge of Z > 2 and energies of 30–200 MeV/nucleon, and determine the fluence of heavy charged particles across the range of 1 to 10⁵ cm^–2.     

An experimental study of the hadron calorimeter module response to protons and pions with energies of 1–5 GeV

The design of the hadron calorimeter module is discussed. Such modules are expected to be used in the forward calorimeters of the Multi Purpose Detector (MPD) (Dubna, Russia) and Compressed Barionic Matter (CBM) (Darmstadt, Germany) experiments. The module has transverse dimensions of 20 × 20 cm² and is composed of 60 16-mm-thick lead layers interleaved with 4-mm-thick scintillator plates. Light from scintillator plates is captured by wavelength-shifting optical fibers. The module has longitudinal segmentation and consists of 10 sections. Light collected from each section is read out by micropixel photodiodes with a sensitive area of 3 × 3 mm². Test measurements of the energy resolution and linearity of the calorimeter module response in the hadron momentum range of 2–6 GeV/c have been performed. The longitudinal profiles of the hadron shower, obtained in the measurable energy range both for pion and proton beams, are discussed. The measured energy resolution and the linearity of the calorimeter module response at low energies are presented and compared to the data obtained at high energies.     

A Matrix Carbon Detector for Measuring the Energy Flux of a High-Power Beam of Hydrogen Ions

A matrix detector consisting of small calorimeters based on УПВ-1 pyrolytic carbon is described. The detector allows measurements of the spatial distribution of the energy flux of a high-power hydrogen ion beam to be taken over its cross section. Each calorimeter occupies an area of 4 cm², and the area of its working body is 0.25 cm². An unambiguous relation between the heat flux value, the irradiation time, and the calorimeter temperature is established by calculations. The calorimeter measurement error was estimated at ～4%, and the spread of the sensitivity coefficients between the calorimeters was 5–6% (1σ). The detector was used to measure the distribution of the energy flux of hydrogen ions over the cross section of the “scanned” beam 10 cm in diameter from a high-current accelerator of the НГ-12И facility.     

LIU-2 linear induction accelerator

The LIU-2 induction accelerator is described. It is used as an injector for the developed large linear induction accelerator with a maximum electron beam energy of 20 MeV, which is intended for smallangle pulse X-ray tomography. Owing to the good quality and high current of the electron beam (2 kA), the injector is capable of operating as an independent X-ray source with an electron energy of 2 MeV, the beam diameter at the target of <2 mm, and a pulse duration of 200 ns. The total yield of the bremsstrahlung energy is 52.4 J and the fraction of quanta with energies of >1 MeV is ～20% of the total energy yield. The spread of the radiation intensity in the solid angle of 10° is ±5%, and the absorbed dose at a distance of 1 m from the target is 32 × 10^?3 Gy, which allows this source to be used with attenuation of 10³–10⁴ for exposure of available X-ray films. This type of system is characterized by a high transmission capability with a 0.5-mm maximum spatial resolution of X-ray images and can be used in the X-ray imaging technique when carrying out gas-dynamic testing of products with an optical thickness as great as 90 mm of lead equivalent.