Measurement Of Charge Distribution Research Articles

Measurements of fragment mass, charge and kinetic energy distributions in thermal neutron fission of 235U with a back-to-back ΔE- E detector system

A simultaneous measurement of mass ( M), charge ( Z) and kinetic energy ( E k) distributions of fragments in thermal-neutron fission of 235U has been carried out using a back-to-back ΔE- E detector system. A pair of gridded ionization chambers filled with P-5 gas measured the energy losses ΔE 1, ΔE 2 of the complementary fragments in the gas, and the residual fragment energies were measured with a pair of semiconductor detectors. The four-parameter data were analysed to obtain fragment Z-distributions using the mass-momentum conservation relations to obtain M and then using the dependence of ΔE on E/ M and Z. The charge resolution for the light-fragment group was determined at the gas pressures of 44, 150, 270 Torr and the best Z-resolution was obtained at 270 Torr. The data at this latter gas pressure were analysed to obtain the variances σ 2 z of the fragment charge distributions for different E k windows and this was compared with the measured variances σ 2 A of the fragment mass distribution as a function of E k as obtained by twoparameter measurements of the correlated fragment energies. The dependence of the measured variances σ 2 A , σ 2 Z on E k is considered with a view to learning about the degree of neutron-proton correlations in the nucleon exchanges taking place during the mass division in fission, in analogy with that used in the case of heavy-ion deep inelastic collisions (DIC). The variation of σ 2 A σ 2 z with E k observed in the present work, which is somewhat similar to that seen in heavy-ion DIC, implies that the fragment mass division in fission is governed by nucleon-exchange processes, where the degree of neutron-proton correlations is dependent on the total kinetic energy E k. While for very large E k the neutron-proton motion in the exchange processes is found to be uncorrelated, for lower E k values the motion is seen to be correlated. Implications of these results regarding the applicability of fission models such as statistical model are pointed out.

A carbon‐13 NMR study of the ion pair structure of the dibenzo[b,f]pentalene dianion

AbstractThe 1H and 13C NMR chemical shifts of dibenzo[b, f]pentalene and its 5,10‐dimethyl derivative are presented and compared with those of the corresponding dilithium dianions. As probed by the relative 13C NMR chemical shifts, the charge distribution within the dianion system is clearly dependent on the actual ion pair state. This condition is demonstrated by varying the solvent and temperature. The polarization of charge towards the pentalene carbons, i.e. the preferred cation positions, is observed on going to tight ion pair conditions. Further support for this model is gained from 7Li NMR. The limitations of the use of 1H and 13C NMR chemical shifts to measure charge distributions within anion systems are discussed.

Study of position resolution for cathode readout MWPC with measurement of induced charge distribution

A readout technique of multiwire proportional chambers by measurement of charges induced on cathode strips, orthogonal to anode wires, requires an algorithm to relate the measured charge distribution to the avalanche position. With given chamber parameters and under the influence of noise, resolution limits depend on the chosen algorithm. We have studied the position resolution obtained by the centroid method and by the charge-ratio method, both using three consecutive cathode strips. While the centroid method uses a single number, the center of gravity of the measured charges, the charge-ratio method uses the ratios of the charges, Q i−1 / Q i and Q i + 1 / Q i where Q i is the largest. To obtain a given resolution, the charge-ratio method generally allows wider cathode strips and therefore a smaller number of readout channels than the centroid method.

Study of Volume Electric Charge in Radioactive Dielectrics by the Method of “Acoustic Sounding”

The formation of the volume electric charge in dielectrics containing radioactive β-isotope has been theoretically proposed. A method of calculating the value of the charge for both uniform and nonuniform distribution of the isotope in the volume is described. The method of the “acoustic sounding” has been used for the experimental study of charge distribution in the sample of crystalline Y3Al5O12 (90Y) and borosilicate glass (90Sr + 90Y). The results obtained are in good accord with the theoretical evaluations. A conclusion has been drawn to the effect that the measurement of volume charge distribution can be used to study the absorption of β-radiation in a substance and spatial distribution of β-isotope in the material.

Measurement of electrostatic charges and concentration of particles in the freeboard of a fluidized bed

Measurements of electrostatic charges and charge distribution on solid particles were made in the freeboard of a fluidized bed. A Faraday cage was designed and built for this purpose. With 30 to 55 μm glass beads, 30 μm particles predominate in the freeboard with an air velocity of 5.5 cm/s. The charge distribution ranges from less than 10 to more than 60 × 10 −15 C. The mean charge was shown to vary with 1.4 power of the particle diameter. A cylindrical probe, 21 mm i.d. and 56 mm long, was used to determine particle concentration via charge collection.

Charge distributions in hadronic collisions

The distribution of charge versus rapidity is examined in the framework of available parton models for multiparticle production in hadron-hadron collisions. Fragmentation models with a twochain Pomeron contribution (based on the dual topological unitarization scheme) are shown to describe rather well the recently measured data on charge distributions in high energypp and πp collisions (140 GeV/c≦pLAB≦360 GeV/c). Carefully measured charge distributions at still higher energies which will be accessible in the near future offer a possibility of distinguishing between some of the current theoretical approaches.

Measurement of charge distribution in polymer electrets by a new pressure-pulse method

The charge distribution in the thickness direction of 10 to 100 μm thick polymer electrets can be determined with a new method utilizing a <1 ns laser pulse to launch a pressure pulse in the sample. Propagation of the pressure pulse through the film causes electrode currents which yield the charge distribution. The method has been applied to electron-beam charged PETP and FEP samples.

Myonische Atome in Physik, Chemie und Arch�ometrie

A survey is given of properties, formation, and application of muonic atoms in physics, chemistry, and archeometry. In the field of physics the measurement of nuclear charge distributions and vacuum polarization as well as the slowing down of muons in matter are treated in some detail, and in the fields of chemistry and archeometry, non-destructive quantitative chemical analysis of bulk material and, with the help of suitable beam setting, also of selected parts of the specimen.

Electric Fields and Secondary Emission near a Dielectric-Metal Interface

Dielectric surface charge distributions near a metaldielectric interface in vacuum depend upon secondary emission processes in the presence of normal and tangential components of electric field. From measured charge distributions created by exposing a specimen of fluorinated-ethylene-propylene to monoenergetic electron fluxes, it has been possible to calculate potentials and fields on and near the dielectric surface. The effect of normal electric field upon secondaryemission is measured directly and the effect of thetangential field is inferred from the charge distributiondata. The critical point (unity crossover)for secondary emission is shifted by the applicationof fields so that it occurs at much higher primaryenergies than normally. Primary beams having energiesup to 20 keV are used and surface fields are as highas 20 kV/mm.

A Note on the Measurement of Charge Distribution in 4-Propenyl Phenolate Ions with 13C NMR.

A Note on the Measurement of Charge Distribution in 4-Propenyl Phenolate Ions with 13C NMR.

Aerosol particle neutralization to Boltzmann's equilibrium by a.c. corona discharge

Atomization of an aqueous suspension of 0.8 μm polystyrene particles produces highly charged aerosols. The values of the absolute mean charge unit | q| = 31 and the s.d. σ = 4.0 were obtained by charge distribution measurements. In order to neutralize the charges on aerosol particles to the values of | q| = 2.1 and σ = 2.6 given by Boltzmann's equilibrium relationship, a bipolar ion atmosphere was created by a.c. corona discharge between needle point and orifice plate electrodes. Electroneutrality of the ionic cloud was found for one value V 0, of the applied potential V, which depends upon the point-to-plate distance d, and the air velocity through the orifice v. When V < V 0 the sign of the free ion intensity was found to be negative. When V > V 0 the sign was positive. By exposing 0.8 μm aerosol charged particles to a bipolar atmosphere, the residual particle charge reflected the same behaviour as reported above. The electroneutrality was attained for V 0 = 2350 V, d = 2 mm and v = 200 m/sec. For low and higher values of V 0 the aerosol charge assumed a negative or positive value. respectively. The behaviour of the aerosol neutralization with ions created by a.c. corona is similar to the neutralization by α disintegration, where electroneutrality is attained when the source plane-to-aerosol distance corresponds to the Bragg's maximum range in air. As expected, aerosol neutralization was also attained when a bipolar atmosphere was created by two ionizers facing each other, in which the needle electrodes generated d.c. positive and negative corona discharges.

Measurement of charge distribution in electrets

A new nondestructive technique is described which provides information about the distribution of charges in nonpolar electrets. Changes in the equivalent electret voltage are measured during and after the absorption of a short pulse of heat on one side of an otherwise well thermally isolated electret. The total electret charge and its mean position are obtained directly with this technique. The main features of the charge distribution can also be resolved using a deconvolution technique, although it is not yet possible to determine fine details uniquely.

Insulated linear antenna: Theory and experiment. II

Measurements of current and charge distributions and driving−point admittances of insulated monopoles immersed in saline solutions (σ-0, 3.6, and 10, εr-80) are reported when the insulating material is melamine (εr=5.54). These data supplement the previously presented experimental results for air−insulated monopoles. The transmiasion−line−like behavior of the insulated antenna as predicted by the theory is verified experimentally when the ratio of the magnitude of the wave number of the ambient medium to that of the insulating medium is equal to or greater than 3.8.

Measurements of the nuclear charge distribution in the cadmium isotopes

The RMS radii (r2)1/2 of the charge distributions of the even isotopes 110<or=A<or=116 of cadmium have been measured by electron scattering, and the differences delta (r2) for 106<or=A<or=116 by optical isotope shifts. The methods indicate the same trend in delta Jr2) but there is quantitative disagreement.

Equilibrium bipolar charge distribution of aerosols

The equilibrium bipolar charge distribution of aerosols has been measured using monodisperse DOP (di-octyl phthalate) particles of 0.53, 0.55, and 1.17 μm diameter. The measured charge distributions are in good agreement with the Gaussian distributions predicted by Boltzmann's law. Additionally, the ratio of charged and uncharged particles was measured using monodisperse NaCl and methylene blue particles between 0.02 and 0.2 μm diameter. The result was compared with the theories of Bricard, Fuchs, and Natanson as well as with continuum and free molecular theories and values predicted by Boltzmann's law. Best agreement is again obtained for Boltzmann's law. The results indicate that the existing combination rate expressions for ions and particle are not sufficiently exact to account for the experimental results obtained here.

1548. Measurement of equilibrium charge distribution in He + and Be + ion beams : G M Skoromnyy and I E RevutskiyProbl of Atom Science and Technoll, Coll, No 3, Kharkov 1973, 60–65 ( in Russian)

1548. Measurement of equilibrium charge distribution in He + and Be + ion beams : G M Skoromnyy and I E RevutskiyProbl of Atom Science and Technoll, Coll, No 3, Kharkov 1973, 60–65 ( in Russian)

Tangential electric field near a driven cylindrical antenna

A least-squares polynomial-fit representation is obtained for experimentally measured charge distributions on a base-driven monopole antenna immersed in free space and also in a homogeneous dissipative medium. This representation for the charge is then used in evaluating the tangential electric field near the antenna.

Measurement of equilibrium charge distribution with a thick target

Combinations of a position sensitive detector and an electric or a magnetic field are shown to be suitable for measurement of the equilibrium charge distributions of the scattered ions from a thick target.

A method of determining aerosol particle size distribution applying Boltzmann's law

An experimental evaluation was conducted on a method for determination of submicron aerosol particle size distribution. The method utilizes prediction curves based on Boltzmann's charge distribution law and measurements of particle number concentration related to the electrical mobility. The measurements of metallic fumes showed fair agreement with the prediction curves of size distribution. The curves were derived from direct electron microscopic observation of the fumes. For lead fume, the measurement falls within a range of ± 10 per cent of the prediction curve.

Charge Exchange of Fast Iodine Ions in a Dense Jet of Carbon Dioxide

Charge distribution measurements were made with 10-75 MeV iodine ions of various incident charge states traversing either a supersonic CO2-jet of variable density in the range 5 x 1014 to 1.5 x 1017 molecules/cm3 or a target of dilute CO2 with a maximum density of 5 x 1014 molecules/cm3. The equilibrium mean charge ts of the iodine ions in the jet is found to be higher than in the dilute gas. The maximum difference of about one charge unit is observed at 75 MeV. Ihere is no indication for a further increase of Lat gas densities above 5 x 1016 molecules/cm3. Cross sections for electron capture and loss were determined by means of a least-squares-evaluation of non-equilibrium charge distributions. Considerable decrease of the capture cross sections for some lower charge states has proved to be responsible for the increase ?, whereas the loss cross sections do not change measurably with increasing target density.