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Experiments carried out to fabricate HgxCd(1-x)Te by diffusing mercury into CdTe slices from the vapour, resulted in obtaining slices with a maximum value of x=0.004. Measurements on the diffusion of mercury into such slices, where 0≤x≤0.03, under saturated vapour pressure conditions, resulted in two component profiles, each profile giving two values of D. These results were similar to ones obtained earlier, indicating that the diffusion was rate-limiting. In addition, the diffusivities were found to be independent of x.

In this paper, results published recently on Hg diffusion in the important infrared detector material, Hg0.8Cd0.2Te, and its common substrate material, CdTe, are compared and discussed. As is customary with diffusion studies in II-VI semiconductors, two component profiles were obtained in the majority of cases, each profile giving two values of the diffusivity. The values of D for the mercury diffusion in CdTe were much less than corresponding values in Hg0.8Cd0.2Te diffusion proceeds by volume diffusion followed by short circuit diffusion, whereas in CdTe diffusion is rate limiting volume diffusion involving a slow stream and a fast stream. From pressure dependency measurements, it is proposed that the slow component occurs by an interstitial mechanism at low PHg and a vacancy mechanism at high PHg, whereas in Hg0.8Cd0.2Te the reverse occurs for the fast diffusion component. In CdTe, the slow component increases systematically with etch pit density, whereas in Hg0.8Cd0.2Te, the diffusivity is independent of the quality of the material. From the comparisons, it is seen that there are some common features in the diffusion of Hg in the two materials but there are also some clear and distinct differences.

The diffusion of Hg into CdTe has been studied, under saturated vapour pressure conditions, as a function of time at 300 and 350°C. The Hg concentration profiles showed two components at short and intermediate anneal times reverting to single component at long times, indicating that the diffusion of Hg in CdTe is rate limiting involving two stream diffusion.

The self-diffusion of Cd into Cu doped CdTe is reported as a function of Cu concentration at 523 and 820°C. Some of the diffusion profiles possessed two components and were fitted by a function composed of the sum of two complementary error functions (erfc) whereas others possessed a single component and were fitted by a single erfc. This implied that the diffusion was rate limiting. In addition D Cd increased linearly with [Cu] up to a concentration of 3 × 10 18 atoms cm −3 at both temperatures but at 820°C, D Cd showed a sudden increase at concentrations above this value.

The diffusion of Hg into CdTe under saturated vapour pressure conditions has been studied in the temperature range 160–403°C. Two component profiles were obtained and the diffusion was rate limited giving two values of the diffusivity. All Arrhenius graphs gave two straight lines with an abrupt change of gradient at 275°C, which was probably due to a change in the diffusion mechanism.

In this paper the use of the three standard defect etches for CdTe: Nakagawa's reagent, ferric chloride and Inoue's EAg-1 reagent have been compared and it has been demonstrated, by measuring the etch pit densities (EPD), that Inoue's EAg-1 reagent can be used successfully for making comparisons in CdTe slices which have been given various physical treatments. In addition a graph of the diffusivity of mercury in CdTe, D(Hg), obtained using radiotracer sectioning techniques, versus EPD shows that a tenfold increase (from 4×10 4 to 3×10 5 cm -2 ) in the surface EPD produces an increase of a factor of four in D(Hg)

Measurement of the self-diffusion of Cd in CdTe carried out in an atmosphere of excess Cd and in the temperature range 350–650°C is reported. The diffusion profiles, which were measured using an anodic oxidation sectioning technique, showed two components, a shallow Fickian one and a second, much deeper component which was non-Fickian. When the results for the shallow diffusion component were combined with those reported earlier by Jones and Stewart, an Arrhenius graph was obtained where the diffusion coefficient extended over nearly nine decades in the temperature range 350–920°C. The graph can be represented by the sum of two exponential functions given by the Arrhenius parameters D 01 = 125 cm 2 s −1 , E 1 = 2.55 eV, D 02 = 2.48×10 −8 cm 2 s −1 and E 2 = 1.08 eV,which indicates that at least two diffusion mechanisms were operatin this temperature range. No significant difference was observed in the diffusion coefficients for bulk grown and epitaxially grown material and no significant pressure dependency was observed at 489°C. For the shallow diffusion component, agreement with previously published data is good at temperatures above 625°C, but below this temperature, agreement with the limited amount of data available is poor. This may be due to the higher purity of CdTe used in this study.

The diffusion and solubility of Cu in CdTe single crystal material has been measured in the temperature range 200–400°C using a radiotracer sectioning technique. The diffusivity in this temperature range is given by the Arrhenius relationship: D = 6.65 x 10 -5 (cm 2 s -1 ) exp[-0.57 eV / kT ] and the corresponding surface Cu concentration in the diffused CdTe slices is given by the Arrhenius relationship C 0 = 1.56 x 10 23 (cm -3 ) exp[-0.55 eV / kT ]. The addition of Cd or Te to the capsule did not result in profiles that were significantly different to those given by the above expressions and diffusion probably occurred via a defect of the form (Cu i Cd v )'. The major portion of the activation energy for the diffusion was taken up in the formation of the defect rather than in its migration through the lattice. A much faster diffusion mechanism (≈100 times faster), which did not show any consistent behaviour with temperature, was also observed in the diffusion profiles. Because of this, CdTe will not act as an effective barrier, in the fabrication of Hg x Cd 1− x Te (MCT) infra-red detectors, to prevent Cu diffusing from the substrate through the CdTe buffer layer into the epitaxially grown MCT layer.

The Wolfenstein parameters Dt, Rt and At have been measured in free np elastic scattering with an accuracy of ±0.05 at 220, 325, 425 and 495 MeV in the centre of mass angular range 60° to 160°. The polarisation P has been measured with an accuracy of ±0.015. The I=0 phase shifts differ significantly from theoretical predictions, particularly in the central and spin-orbit combinations of D waves.

The operation of a solar air heating system in a Canadian prairie farm home is described. It is shown that the system provides significant heat in the coldest months, shortens the supplementary heating season, and provides an extra measure of reliability and comfort compared to conventional heating methods. The system employs 26.5 m/sup 2/ of heater on a 250 m/sup 2/ house, uses air for the transfer fluid, rock for heat storage, and a gravity distribution system. Results show that this type of solar air heater can provide a significant amount of the space heating in an environmentally effective manner. >

Process-centred Software Engineering Environments (PSEE) are the most recent generation of environments supporting software development activities. Most of PSEE are based on mechanisms promoting enforcement and automation of process activities. In this kind of mechanisms the process models are prescribed in a detailed and complete way. But the experience shows that supporting processes is more concerned with the flexibility of guidance offered during the process performance than with enforcement of a collection of predefined process models. In this paper, we present a solution to support strategic processes in a PSEE by providing a flexible guidance during process enactment.

Kinematically complete data are presented from the 2 H(n, np)n reaction at 130 MeV The data, in the form of third differential cross sections, cover 40 pairs of final state angles and final state energies ranging from 1 to 100 MeV. The n-n and n-p final state interactions and n-p quasi-free scattering processes are observed in various regions of phase space over a wide range of kinematic conditions. The gross features of the data are reproduced by a simple model based on the simple impulse approximation and the Watson-Migdal model, and a value for the neutron-neutron scattering length, α an = −17.1 ± 0.8 fm, is extracted from one per of angles using this model. The fit to the quasi-free scattering data produced by the simple impulse approximation is unsatisfactory, however, and requires further investigation. No attempt has yet been made to apply more sophisticated three-body models to this higher energy data.

Measurements over an extensive angular range of the D/sub t/ and P parameters in free neutron-proton elastic scattering at laboratory energies of 220, 325, 425, and 495 MeV are reported. Experimental and analytical details are given.

A polarimeter is described having a large solid angle of acceptance and using a carbon analyser combined with 12 multiwire proportional chambers. Its analysing power for protons has been calibrated at TRIUMF with an absolute accuracy reaching ±0.015 ≡ 2% in the angular range 3.5° to 28° laboratory angle and for incident energies between 107 and 462 MeV. A mean analysing power of about 35% and an efficiency of approximately 3% was observed.

The n-p total cross section has been measured in a transmission experiment in which a neutron beam produced by the 2 H(p,n) reaction was incident on a liquid-hydrogen target. Results are presented at 212, 268, 319, 369, 417 and 495 MeV; the overall uncertainties average ±1.9%. The n-p differential elastic cross section between 10° and 180° c.m. was measured at 212, 319, 418 and 493 MeV using the same beam and target. Different techniques were used in two overlapping angular regions, the relative normalisation being fixed by a calibrated monitor of neutron beam intensity. Point-to-point uncertainties in the forward region vary from ±1.4% to ±9.5%, but are generally close to ±2.0%. In the backward region the uncertainties average ±1.5%. Relative normalisation between the two regions has an uncertainty of about ±3% at each energy, and a further normalisation uncertainty of ±1.6% is common to all the data.

A phase-shift analysis is reported incorporating TRIUMF data on np total and differential cross sections and values of Δσ L (pp) and Δσ T (pp), together with all other np data from 120 to 550 MeV and pp data from 120 to 831 MeV. The solutions are unique over these energy ranges. They are compared critically with the predictions of the Paris group.

We have measured the np (nd) elastic scattering cross sections at 25(17) angles in the interval 30°–168° (c.m.), using a neutron beam with a broad spectrum peaked near 130 MeV. At backward angles the outgoing charged particles from a liquid hydrogen (deuterium) target were detected; at forward angles we detected neutrons scattered from a hydrogenated (deuterated) scintillating target. Cross sections have been normalized to the energy dependent solution of the Livermore nucleon-nucleon partial wave analysis, evaluated at 130 MeV. The np measurements represent a marginal improvement on previous work; the nd cross sections show some differences from pd measurements, in agreement with earlier indications at an energy of 152 MeV.

Data on D/sub t/, R/sub t/, A/sub t/, and P lead to unique and accurate np phase shift solutions at 210, 325, 425, and 515 MeV. The I=O, D, and G waves show large systematic deviations from current theoretical models.

New pp measurements of Delta sigma L and Delta sigma T between 200 and 520 MeV disagree with earlier Argonne data, and resolve discrepancies with inelastic data, phase-shift analysis and forward dispersion relations.

A variable energy neutron beam with high polarisation and narrow energy spread has been produced at TRIUMF using the polarised proton beam and a liquid deuterium target. The neutron polarisation has been measured at 237, 343, 445, and 516 MeV incident proton energy by two independent methods. At the lowest energy the neutron polarisation is 73% at 9° laboratory angle. It decreases slowly to 38% at the highest energy.

Measurements of the self diffusion of Cd into the ternary compound In0.67xCd1-xS, where 0

The absolute normalisation of the polarisation in pp elastic scattering at 24 degrees lab has been determined by means of a double-scattering experiment to an accuracy of +or-1.5% at five energies between 200 and 520 MeV.

The transition intensities of 56 Co have been determined using Ge(Li) detectors and uncertainties between previously measured values of different authors clarified.

Results of measurements on the self-diffusion of Cd into CdTe carried out in an atmosphere of excess Cd and in the temperature range 570–920°C are given in this report. CdTe produced by Mining and Chemical Products Limited (MCP) and the University of Durham were used for the measurements. The diffusion profiles obtained using a radiotracer sectioning technique agreed closely with the solution to the diffusion equation which assumes a constant source term for the diffusion. The diffusion coefficients gave a straight line when plotted on an Arrhenius graph and did not show any flattening out at lower temperatures and the best fit through the points gave a value of E = (2.47±0.10) eV and D 0 = (50 × / ÷ 3.0) cm 2 s -1 . When compared with similar measurements reported in the sixties they agree closely with those due to Borsenberger and Stevenson but the agreement is poor when compared with the results due to Whelan and Shaw.

The differences Δσ L ( Δσ T ) between proton-proton total cross sections for parallel and antiparallel longitudinal (transverse) spin states have been measured at six (seven) energies between 200 and 520 MeV. Point-to-point uncertainties vary from ± 0.41 mb to ± 1.21 mb for Δσ L ; for Δσ T they vary from ± 0.33 mb to ± 0.73 mb. Both are subject to additional normalisation uncertainties of about ± 6.7%. Differences from data obtained by other groups are discussed.

States of 9 B and 8 B were studied by measuring differential cross sections for the reactions (p, d) and (p, t) from a 10 B target at E p = 49.5 MeV. Strongly excited states were observed at 0.0, 2.33 and 11.66 MeV in 9 B and at 0.0 and 2.29 MeV in 8 B. The angular distribution of elastic scattering of 49.5 MeV protons from 10 B was also measured and fitted using an optical-model calculation. The distributions of (p, d) and (p, t) cross sections were compared with DWBA predictions and a spin assignment was made for the 2.29 MeV state in 8 B.

Measurements of the Wolfenstein parameter A for the elastic scattering of 48.3 MeV polarized protons from liquid deuterium were made in the angular range 40° to 70° lab. These results together with the previously reported values for D and R are compared with existing impulse-approximation calculations and experimental results at higher energies.

Measurements of the rotation parameter R were made for the elastic scattering of 48.3 MeV polarized protons from liquid deuterium in the angular range 40° to 70° lab.

The angular distribution of the reaction 4 He(p, d) 3 He at 49.5 MeV has been measured over the c.m. angular range of 11°–165°. This angular distribution, together with the angular distributions of the reactions 4 He(p, t)2p, 4 He(p, 3 He)pn, 3 He(p, d)2p at 49.5 MeV and 3 He(p, d)2p at 30.5 MeV reported previously, have been analysed in terms of the plane wave Born approximation, DWBA and diffraction theories.

The depolarization parameter D was measured in the elastic scattering of 48.3 MeV protons from liquid deuterium over an angular range from 40° to 70° lab.

Differential cross-section and polarization measurements on the p- 3 He system at 30 and 50 MeV have been analysed in terms of real phase shifts. It is shown that there is not sufficient data at either energy to define a unique solution.

Cross sections have been measured for the transitions to the ground state and first excited state of 8Be and to the two 2+ levels at 16.63 MeV and 16.93 MeV excitation in the reaction 10B(p, 3He) at Ep = 49.5 MeV. The angular distributions of the cross section were compared with DWBA predictions.

Additional measurements are reported here on the self-diffusion of Cd in CdS which were carried out in an atmosphere of excess Cd vapour in the temperature range 600–1000°C and measured using a radiotracer sectioning method. These results were analysed along with similar results reported by Jones much earlier and the values of D (Cd) reported here are similar to those reported by Jones. When all the values of D (Cd) over the whole temperature range are taken together, they are found to be consistently lower than similar results reported by Shaw and by Woodbury, but the difference with those reported by Shaw is not significant. When plotted on an Arrhenius graph, the results can be divided into two separate straight line sections with different slopes which change at an approximate temperature of 780°C. This behaviour is also similar to that reported by Shaw. In addition, no source dilution occurred during the diffusion anneal and the values of D (Cd) for CdS obtained from two different manufacturers gave similar results.

The p-p total cross-section differences in transverse spin states, ΔσT, have been measured at TRIUMF for incident momenta of 0.662, 0.853, 0.926, 1.037, 1.090 and 1.116 GeV/c. A polarized proton beam and polarized proton target were used, both polarized vertically. Typical beam polarizations were 70% with target polarizations of 65%. The incident beam rate was of the order of 105 protons per second. A six-counter transmission array was used to monitor the transmitted beam in coincidence with an incident beam telescope. Corrections were made for accidental coincidences.

A well known technique for polarizing a proton beam consists by scattering it off some material, typically carbon. The use of such a method has been proposed(1) also for polarizing antiprotons at LEAR, and it is now part of the program of Experiment PS 172. Here we give a brief review of how one can obtain an estimate of the polarization parameter in pC scattering, a description of the beam which has actually been designed, and a first list of the measurements we plan to do with such a beam.

In the beginning of 1980 four letters of intent for experiments at LEAR had been submitted which all proposed to study either pp total cross section or spin effects in pp (elastic) scattering or both. The people who wrote these letters were asked to work together and to submit one proposal covering all the experiments mentioned in the original letter of intent. The proposal resulting from this effort suggests to do a wide range of experiments using a rather complicated set up.

Publisher Summary Using the slow spill time of flight system, data on the elastic scattering of neutrons by deuterons, were taken at seventeen angles in an energy interval between 100 and 150 MeV. Distinct methods were used in two overlapping angular regions. In the first method, between 89.5 and 168 cm, recoil deuterons from a liquid deuterium target were detected, using five counter telescopes simultaneously. In the second method, between 30.5 and 110 cm, data was taken using a scintillating target of deuterated cyclohexane, detecting the scattered neutrons in an array of five scintillation counters. The liquid deuterium target was a vertical cylinder of height 80 mm and diameter 50 mm. The counter telescopes consisted of two thin passing counters and a cylindrical total energy counter. Discrimination between elastically scattered deuterons and protons from the break-up reaction d(n,p)2n was achieved by measuring the particle time of flight and the pulse height recorded in the total energy counter.

Publisher Summary Kinematically, complete data has been obtained from the d(n,np)n reaction over a range of final state angles and a range of incident energies. This chapter discusses a study in which incident neutrons from 50 MeV to 150 MeV were collimated onto a target of liquid deuterium. Two particles, a neutron and proton, were detected in coincidence in the final state at any of the five proton angles and eight neutron angles, defining 40 pairs of the final-state angles. Each event was kinematically determined by measuring the time of flight of the incident neutron, the final state neutron, and the final state proton in addition to the energy of the final state proton. The chapter discusses the analysis of the pairs of angles for which the n–n final-state interaction (FSI) process is optimized using Watson–Migdal theory. It is assumed that the primary interaction produces a distribution proportional to the volume of available phase space.