Multi-detector System Research Articles

Transverse velocity scaling in197Au+197Aufragmentation

Invariant transverse-velocity spectra of intermediate-mass fragments were measured with the 4π multidetector system INDRA for collisions of 197Au on 197Au at incident energies between 40 and 150 MeV per nucleon. Their scaling properties as a function of incident energy and atomic number Z are used to distinguish and characterize the emissions in (i) peripheral collisions at the projectile and target rapidities, and in (ii) central and (iii) peripheral collisions near midrapidity. The importance of dynamical effects is evident in all three cases and their origin is discussed.Received 22 April 2002DOI:https://doi.org/10.1103/PhysRevC.66.064606©2002 American Physical Society

Fractionation and characterization of a conjugate between a polymeric drug-carrier and the antitumor drug camptothecin.

A conjugate between the antitumor drug camptothecin and the polymeric drug-carrier poly[N-(2-hydroxypropyl)methacrylamide] was synthesized and fractionated. The conjugate samples, both fractionated and unfractionated, were characterized with a multi-detector SEC system using three on-line detectors: a multi-angle light scattering photometer, a viscometer, and a refractometer. The used mobile phase (DMF + 0.01 M LiBr + 0.05 M CH(3)COOH) derives from previous experience with similar conjugates. Narrow molar mass distribution fractions of the conjugate obtained by means of a semipreparative LC system were used to derive the coefficients of the Mark-Houwink-Sakurada relationship and to check the universal calibration of the SEC system. This study has demonstrated that the conjugate elutes according to the hydrodynamic volume. Thus, a conventional SEC method that uses only an on-line refractometer detector, commercially available narrow standards, and the universal calibration is adequate for the characterization of the molar mass distribution. Also the size and the conformation of the conjugate were studied by means of the gyration radius-molar mass power law.

The CELSIUS/WASA Detector Facility

The 4π multidetector system for investigation of η-meson rare decays at the Uppsala CELSIUS storage ring is presented. A detailed description of the design, and achieved performance parameters is given.

Proposal for a multi-detector system for residual stress measurements

Abstract The scheme of a multi-detector system dedicated to full strain tensor measurements by neutron diffraction is suggested. The proposed system can considerably shorten measurement time in comparison with the conventional one-detector system and simplify the measurement procedure. A “ring” of detectors disposed along the circumference of a diffraction cone which can simultaneously scan different parts of the diffraction cone is suggested. The detectors constituting the “ring” measure strain in different directions, with the number of directions equal to the number of detectors. The instrument has maximum advantage for the measurement of the full strain tensor when the gauge volume is small and fine collimation (∼0.2°) is used to provide spatial resolution in the horizontal and vertical direction. The experiments carried out using the one-dimensional position sensitive detector showed the feasibility of the proposed multi-detector system.

Radiometric sand mud characterisation in the Rhine–Meuse Estuary: Part B. In situ mapping

Traditionally, obtaining accurate spatial information about the textural composition of heterogeneous aquatic sediments requires extensive sediment sampling. To avoid a costly and time-consuming operation, a new in situ technique has been investigated. This technique characterises sediment components by the activity concentrations of natural radionuclides. In situ activity concentrations are continuously measured with the Multi-Detector system for Underwater Sediment Activity (MEDUSA), a detector trailed over the bottom by a towing vessel, containing a highly sensitive gamma-ray BGO-detector, a water-depth sensor and a microphone. From the collected γ-ray spectra, the activity concentrations of 40K, 238U and 232Th are derived. During two separate field surveys of 5 days each, MEDUSA was applied to the Hollandsch Diep and Haringvliet, two fresh water basins, each approximately 20 km long and 2–3 km wide in the Rhine–Meuse Estuary, the Netherlands. In part A of this paper (this issue), it has been illustrated how the radiometric fingerprint of sand and mud in the area was determined. This fingerprint was then used to calculate the sand-mud ratio from the 238U and 232Th activity concentrations of about 25,000 MEDUSA data points. The interpolated sand-mud distribution of the top layer of the aquatic sediment shows a distinct correlation with bathymetry: the deeper channels are mud-rich, whereas the shallow zones are predominantly sandy. In general, the mud content decreases in the seaward direction. This corroborates well with the morphological development of the area in which the deposition of mud is highest near the rivers' outflow in the east. The absolute total random error in the sand map varies between 6% and 18%, where the largest errors are caused principally by spatial variability of the sediment composition. At present, the radiometric results underestimate the mud content by 10–30% due to a higher water content of sediment with high mud contents (>60%). The simultaneously recorded friction sound levels provide qualitative information with respect to the sediment composition. Sandy areas show a higher sound level than muddy areas; with the sound and sand map showing a striking similarity.

Investigation of surface topography using a multidetector system in a SEM

The backscattered electron (BSE) signal is widely used for examination of surface topography in a scanning electron microscope (SEM). For detection of this signal both the standard configuration of two detectors as well as a multidetector system are employed. In the BSE mode, the sum of signals becomes less dependent on the surface inclination whereas the difference signal becomes proportional to the local surface tilt angle. One can see, that the signal from the two-detector system is influenced by an artefact. A successful combination of several independent detector signals to improve the topographical image has been proposed. For an investigation of the topographic mode in SEM, six p–i–n diodes of small surface area were placed opposite to each other. The digital BSE signal processing system enabled realization of different algorithms of mixing signals coming from several detectors. Some ways for eliminating the artefacts were proposed. For example, a method to form images without a shadow effect was used. It is useful for distinguishing between artefacts and real features. Moreover, the experimental results indicate that the real topography of a specimen can be obtained if the specimen is rotated. The aim of this work was to use a multidetector system and to develop models to allow the data to be interpreted.

Test and analysis of hadronic interaction models with KASCADE event rates

Based on the KASCADE multi-detector system with its large hadron calorimeter and using the CORSIKA simulation program with the implemented high-energy hadronic interaction models QGSJET, VENUS, DPMJET, SIBYLL, and HDPM, a method for the test of models by comparing event rates is described. Preliminary results show differences of the model predictions both among each other and when confronted with measurements. The rates are strongly influenced by the inelastic cross sections and the elasticity, especially by the contribution of diffractive dissociation. The discrepancy to measurements at primary energies below ⋍ 3 · 10 13 eV can be reduced by increasing the non-diffractive inelastic cross section.

Specific Interactions of Organic Substances in Size-Exclusion Chromatography

Size-exclusion experiments of alcohols, mono- and dicarboxylic acids, aromatic acids, and amino acids were conducted. Two columns with different gel packings (TSK HW 50 S and TSK G2000SW) were used to determine the influence of the gel core structure on the elution volume of organic substances. Neither for the polymer based gel nor for the silica based gel specific interactions, especially hydrophobic interactions, could be neglected. For both alcohols and monocarboxylic acids the elution volume increased with an increasing number of carbon atoms. It was found that aromatic compounds interacted strongly with both gels. Whereas alcohols were not affected by differences in ionic strength between sample and eluent, the elution volume of carboxylic acids was strongly influenced. In combination with a multidetector system (UV absorption, fluorescence, dissolved organic carbon, electrical conductivity) changes in the chromatographic behavior of these compounds due to differences in ionic strength between sample...

Onset of midvelocity emissions in symmetric heavy ion reactions

Experimental data obtained with the $4\ensuremath{\pi}$ multidetector system INDRA are used to study midvelocity emissions of light charged particles (LCP) and intermediate mass fragments for peripheral and semicentral collisions of Xe and Sn at energies between 25 and 50 MeV/nucleon. The analysis is performed as a function of incident energy and of impact parameter, defined through the total transverse energy of LCP. The onset of midvelocity emissions is found to be close to 25 MeV/nucleon. Evaporative processes are also identified and are found to be sensitive to the impact parameter but show, for a given impact parameter, little dependence on the incident energy. A chemical analysis of the midvelocity component is performed. Compared to the evaporative process, midvelocity matter is found to be more neutron rich. Results are compared with the predictions of a dynamical model (CHIMERA). The general trends are well reproduced but some interesting differences are observed, notably in the amount of relative energy dissipation, showing that midvelocity emissions could be sensitive to the finer details of the interaction.

Helical SPECT using axially truncated data

In this study, use of a helical orbit in performing a long object SPECT scan with parallel, cone, fan, rotated fan, varying focal-length cone, divergent, and astigmatic collimators is proposed. Sufficient-data scanning helical orbits for these collimation geometries are developed. Both a single-detector system and a multi-detector system are considered. In order to verify the authors' orbit design requirement, the iterative ML-EM algorithm is used to reconstruct images of a long Defrise phantom. The phantom height is five times the height of the detectors. Computer simulations are performed and exact reconstructions are obtained. The proposed sufficient helical orbit pitch will facilitate performing whole body SPECT and PET scans that demand an exact reconstruction.

Electron–ion correlation in divalent liquid metals by diffraction method

The structure factor of liquid Zn has newly been obtained by neutron diffraction above melting temperature with sufficient accuracy by a powder diffractometer with multi-detector system, HERMES, which is installed at T1-3 beam line in JRR-3M. The observed structure factor of liquid Zn has a very clear profile in the low Q region less than Q=4.5 Å −1 and connected with the structural data obtained previously. The structure factor of liquid Zn by X-ray diffraction has an asymmetric peak profile, while that by neutron diffraction does not. There has been detected a small but clear difference around the first peak region. Electron-ion correlation function and electron charge distribution around an ion have been obtained. The relation between the liquid structure and the electron charge distribution around an ion for liquid Zn will be discussed as compared with the simple liquid metals.

A multi-detector system for a triple-axis spectrometer

Until now there have been only a few attempts to use many scattering angles simultaneously in triple-axis spectrometry with neutrons. We present a novel Multi-Analyzer Detector (MAD) unit for a Triple-Axis Spectrometer (TAS) set up at the Forschungsreaktor München (FRM). The layout is based on the principle of monochromatic defocusing. Up to 61 analyzers are mounted around the sample in the constant final energy mode. This arrangement supplies the flexibility of a TAS with a multi-channel analyzer capacity similar to a Time-of-Flight Spectrometer. The gain in measurement time can be more than an order of magnitude.

The New Neutron Powder Diffractometer with a Multi-Detector System for High-Efficiency and High-Resolution Measurements

We describe a multipurpose neutron powder diffractometer for high-efficiency and high-resolution measurements, HERMES, which has been installed at the JRR-3M reactor in Japan Atomic Energy Research Institute. To obtain high-quality data for a short counting time, or with a small sample amount, HERMES has a multi-detector system which consists of 150 3He neutron detectors and simple window type collimation. The best resolution is Δ2θ of 18' and Δd/d of 3 ×10-3, where 2θ and d are scattering-angle and d-spacing, respectively. The duration of an ordinary powder diffraction experiment is 1–5 h under the present conditions in JRR-3M. Some typical results of powder diffraction experiments and performance are given in this paper. We also show a result of 2D intensity mapping of magnetic diffuse scattering from a single crystal of a spin glass material.

Blood flow distribution in the normal human preterm brain.

Disturbances in cerebral blood flow (CBF) are a major factor in the etiology and pathogenesis of cerebral damage in the neonate. As most animals are more mature at birth than man, extrapolation from animal studies to the human is questionable. Therefore, we have measured regional CBF (rCBF) in preterm infants. rCBF flow was measured in 12 normotensive and normoxic preterm infants [mean birth weight 915 g (range 550 to 2680 g), mean gestational age 27.7 wk (25 to 32 wk)]. All infants had a normal cerebral ultrasound examination. rCBF was measured using a mobile brain dedicated fast-rotating four-head multidetector system specially designed for neonatal studies. The tracer was 99mTc-labeled D,L-hexamethylpropylenamine oxime in a dose of 4 Mbq/kg. rCBF of the subcortical white matter was 0.53 (0.48-0.58) of the global CBF. After correction for scattered radiation, the estimate of rCBF to the white matter was reduced to 0.39 (0.36-0.42). The flow to the basal ganglia was 2.33 (2.08-2.59) times the global CBF. After correction for partial volume effect, the cortical flow was higher than the flow to the basal ganglia and highest in the frontotemporal cortex (motor cortex). The flow to the cerebellum was of the same magnitude as the flow to the basal ganglia, but with a significantly higher variation. rCBF in 12 preterm infants showed a flow distribution similar to flow in other newborn mammals. The gray-white matter contrast, however, was greater. This new information, combined with existing data showing low global CBF, suggests that blood flow to the white matter in the preterm human neonate is extremely low.

HERMES, the high-efficiency multipurpose powder diffractometer

We have constructed the high-efficiency and medium-resolution powder diffractometer with multi-detector system, HERMES, at JRR-3M reactor at JAERI. A typical counting duration and the best resolution are 2–5 h and 0.3% of Δd/ d, respectively. We have obtained satisfactory results in crystal and magnetic structure refinement, and diffuse scattering measurements on a single crystal. The instrumental details and experimental performance are presented.

Effects of detector sensitivity on image quality in multidetector SPECT

The common imaging practice of each detector on a multidetector SPECT imaging system to acquire only a fraction of the total number of projections in a 360/spl deg/ projection set introduces the possibility of imbalances in system response which can cause artifacts and changes in image quality. Here we evaluate the effect of variations in detector sensitivity caused by differences in the position of the photopeak window, window width, and different collimators on reconstructed image quality. Analytical simulations of cardiac phantom geometries and experimental measurements with Data Spectrum's Cardiac and Deluxe SPECT phantoms on a three detector SPECT imaging system were used in the evaluation. The relative efficiency of one of three detectors was changed over a series of values between 100 and 0%, while the efficiency of the remaining two detectors was maintained at 100%. The results show that decreased activity and geometric distortions occur along directions perpendicular to the projections with altered sensitivity. The degree of distortion and decrease of activity depends on the geometry of the activity distribution and the reduction in sensitivity. The relative count ratios in the regions with decreased activity varied over a range of 1.0 to 0.59 as the detector sensitivity is decreased from 100 to 0% of the full energy window. Variations in detector sensitivity can degrade spatial resolution and uniformity and create artifacts in reconstructed tomographic slices.

CHICSi — a 3π multi-detector system for studying heavy ion interactions inside a storage ring

CHICSi — a 3π multi-detector system is presented. The setup consists of 576 ultra high vacuum compatible telescopes to study intermediate energy heavy ion as well as proton induced collisions at storage rings operating in slow ramping mode. Primary it will be installed at the gas-jet target station of the CELSIUS facility at The Svedberg Laboratory in Uppsala.

Neutron cross-talk in a multi-detector system

Two 2 m × 2 m “walls” were built for experiments with two neutrons in the final state. Each wall consists of 25 rectangular cells filled with NE-213 liquid scintillator. The close-packed design of the array makes cross-talk an inevitable contributor to distortion of measurements with this system. For E n ≤ 25 MeV almost all the detection efficiency comes from n-p scattering, and the simple two-body kinematics can be used as the basis for identifying cross-talk events. A Monte-Carlo code was developed to simulate the detection process. We found that most cross-talk events could be distinguished from real two-neutron events. A test experiment for comparison with the code was performed with neutrons from the 7Li(p, n) 7Be reaction at E p = 30 MeV. With this reaction all two-detector coincidences are cross-talk events. Consistency between the experimental data and the simulation results was obtained.

Initial evaluation of123I-5-I-R91150, a selective 5-HT2A ligand for single-photon emission tomography, in healthy human subjects

The mapping of 5-HT2 receptors in the brain using functional imaging techniques has been limited by a relative lack of selective radioligands. Iodine-123 labelled 4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]-5-iodo-2-methoxybenzamide (123I-5-I-R91150 or123I-R93274) is a new ligand for single-photon emission tomography (SPET), with high affinity and selectivity for 5-HT2A receptors. This study reports on preliminary123I-5-I-R91150 SPET, wholebody and blood distribution findings in five healthy human volunteers. Maximal brain uptake was approximately 2% of total body counts at 180 min post injection (p.i.). Dynamic SPET sequences were acquired with the brain-dedicated, single-slice multi-detector system SEM-810 over 200 min p.i. Early peak uptake (at 5 min p.i.) was seen in the cerebellum, a region free from 5HT2A receptors. In contrast, radioligand binding in the frontal cortex increased steadily over time, up to a peak at approximately 100–120 min p.i. Frontal cortex-cerebellum activity ratios reached values of 1.4, and remained stable from approximately 100 min p.i. onwards. Multi-slice SPET sequences showed a pattern of regional variation of binding compatible with the autoradiographic data on the distribution of 5-HT2A receptors in (cerebral cortex>striatum>cerebellum). These findings suggest that123I-5-I-R91150 may be used for the imaging of 5-HT2A receptors in the living human brain with SPET.

Dynamical effects and intermediate mass fragment production in peripheral and semicentral collisions of Xe+Sn at 50 MeV/nucleon

Experimental data obtained with the 4{pi} multidetector system INDRA are used to study the light charged particle (LCP, Z{le}2) and intermediate mass fragment (IMF, Z{ge}3) production in peripheral and semicentral collisions of Xe and Sn at 50 MeV/nucleon. It is found that a sizable fraction of the detected LCP`s and IMF`s originates from the midvelocity region. These fragments can be seen to come either from a prompt (preequilibrium) mechanism or from a slower but dynamically influenced emission process. The relative magnitude of the dynamically influenced emission relative to the isotropic statistical evaporation is presented as a function of the transverse energy of light particles, used as an impact parameter selector. The results are compared to dynamical models with which a good agreement is obtained. {copyright} {ital 1997} {ital The American Physical Society}