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5135. Dependence of the radiation spectra from channeled electrons on their energy
Classified abstracts 5128-5138
reaction has been proposed, which appears to be supported by the mass spectrometer measurements. Ilndia) S V Krishna Kumar et al, J Phys D: Appl Phys. 14 18), 1981, LI33-LI35. 33 5128. Stationary striations in a glow discharge. (GB) This letter comments on a conclusion by Landa et al in a recent review paper on moving striations relating to tile theory of stationary striations proposed by the author. I M Chapnik, d Phys D: Appl Phys, 14 18), 1981, LI21 123. 33 5129. Double layer formation in a magnetized laboratory plasma. (GB) Double layers in a current-carrying magnetized argon plasma are studied experimentally. The layer evolves from an unstable anode sheath when the anode voltage has reached a critical value which depends on the neutral gas pressure. The double layer is an oscillating, three-dimensional structure enclosing both axially and radially a plasma at higher potential which is maintained by a low rate of ionization due to the accelerated electrons. Axially accelerated electrons and radially accelerated ions have been detected, but not axially accelerated ions. High frequency is detected on the anode side of the layer. Double layers have also been observed in helium and xenon plasmas. Time independent numerical solutions of Maxwell's equation div D = p in one dinaension including ionization are discussed: they give an upper limit for the anode sheath voltage [before double layer formation) which is too high. but double layer solutions in reasonable agreement with the experiment are obtained. Dag Andersson, d Phys D: Appl Phys, 14 181, 1981. 1403 1418. 33 5130. Test of an electronic distribution model with macroscopic measurements performed on a proton-beam-induced neon plasma containing nitrogen impurities. (GB} A calculation of the medium- and low-energy part of the electronic distribution function is described, together with its indirect comparison to experimental results. The study deals with a plasma created by a proton beam 12 MeV. ~2 I~A cm '1 impinging on a Nc (about 10 torr) target, with N2 impurities. Microwave measurements of electronic density and effective collision frequency agree satisfactorily with calculations using a theoretical distribution function. (France) J Margot et al, J Pllys D: .4ppl Pllys, 14 181, 1981. 1419 1428. 33 5131. lntermolecular potentials from proton spin-lattice relaxation time in H_, Ar and H., N_, gas mixtures. (Canada) Proton spin-lattice relaxation times, T~. have been measured in Hz Ar and H., N2 gas mixtures as a function of density ( 1 0 < p < 7 0 amagat), composition (~ 18 ~5",,). and temperature (300 600 K) with a 30 MHz spin-echo spectrometer using phase sensitive detection. These data together with the T t data obtained by Foster and Rugheimer and by Willmms in these mixtures below 300 K have been analysed using the Bloom-Oppenheim theory. Models for intermolecular potentials to explain the Tj data have been proposed. It is found that the relative anisotropy in the attractive part of the intermolccular potential which fits the T~ data best compares well with that evaluated using polarizability data. (India) Lakshman Pandey and K Lalita Sarkar, Can J Phys. 59 [9). 1981. 1260 1266. 33 5132. Cross sections for the ~"O(l"O,'~Be~.,)-"*Mg reaction and mechanisms of a-rearrangement reactions. (Canada I The ~"O1 ~"O, ~Be~.. I-"*Mg reaction was studied at laboratory beam energy of 53 MeV detecting Z~Mg nuclei in coincidence with :c particles originating from the SBe~, ,2:~ decay. Differential cross sections at 0~,, ~ 90 were found to be approximately 40 pb'sr for the 2"*Mg ground and 1.37 MeV (unresolved) states as well as for the -"*Mg 4.12.4.24. and 5.23 MeV (unresolved)states. A comparison with other :~-rearrangement reactions, leading to the ground and first excited states of final nuclei, shows that tile cross sections for the ~"Olt"O. s Be )"'*Mg reaction are only 1/25 as large as for the z60(t"O.~ZC)-'°Ne reaction and that they are of about equal magnitude as for the ~60(l'O.:~)-'"Si reaction. This suggests that the t6Ol~C'O,SBe)-"~Mg and ~"O(~'O.:O"sSi reactions occur in statistical competition and. consequently, via formation of a more or less equilibrated compound system, while the ~¢'O(tr'O,t"C)Z°Ne reaction is mainly a fast, one-:x-exchange process. Bibiana ~ujec et al, Can d Ph)'s, 59 (9}, 1981, 1233 1240.
33 5133. The level structure of t42Pr deduced from the l'~lPr(n,y)J42Pr reaction. (Canada) A study of the low lying levels of 142pr observed via the n,~lPr(n,,/}n42pr reaction has revealed this nuclide to possess a much more complex structure than previously reported. Acquiring high precision spectra, which readily permitted detection of transitions with intensities greater than 0.01".,,, and employing deconvolution techniques to achieve an effective resolution of I keV, resulted in identification of 455 transitions in the range of excitation energy 0 to 3500 keV. A constant temperature level density model, for which losses due to intensity and resolution effects are included, was used to describe the present results. Computations were undertaken to explore the validity of the assumptions made regarding the primary or secondary nature of the observed transitions. The models used to describe the spacing and intensity distributions in order to account for losses were verified through an examination of the experimental data. In addition, consideration of the degree of E 1 and M I contributions has been included. A high degree of self consistency of all these factors is demonstrated. An examination of the reduced radiative widths strongly suggests the influence of the giant dipole resonance. The precision of the energy measurements permitted the derivation of level energies with an average uncertainty of less than I00 eV. In addition to obtaining a neutron separation energy of 5843.14(10)keV for t'*2Pr, precise values were determined for nuclides ta4Nd, tS6Gd, tS~Gd and 2°~Pb. T J Kennett et al, Can d Phys, 59 (9}, 1981, 1212 1232. 33 5134. Levels in t49Nd studied with the (d,t) reaction. (Canada) The ~5°Nd(d,tlm'~gNd reaction has been studied with 16 MeV deuterons with a vector polarization of ~0.74 from the McMaster University tandem Van de Graaffaccelerator. Measurements were made at I 1 angles from 5.5 to 37.5 using a magnetic spectrograph equipped with photographic emulsions in the focal plane. The measured analysing powers which are well described with standard distorted wave Born approximation calculations, made it possible to give unambiguous assignments for 14 states for which spin information was previously conflicting, incomplete, or lacking. (Norway} L Haugen et al, Can d Phys, 59 (9), 1981, 1183 1193. 33 5135. Dependence of the radiation spectra from channeled electrons on their energy. (USA} Quantum theory of radiation from relativistic electrons in planar channeling has been developed. Analytical expressions have been obtained for the spectral distribution of radiation using a simple model for the planar potential. (USSR) V A Bazylev et al, Rad EJJects, 56 11/2), 1981, 99-104. 33 5136. Radiation from high energy positrons in a potential of crystal planes. (USA} A comparison is made of the radiation spectra of channeled positrons measured at SLAC with theoretical predictions. It is shown that the results obtained can be explained by the effect of the intense radiation accompanying channeling predicted by Kumakhov. (USSR) V A Bazylev et al, Rad Effects, 56 (1/2), 1981, 87-98. 33 5137. Radiation and spin separation of high energy positrons channeled in bent crystals. (USA) The dynamics, radiation and possibilities of the radiation spin separation of positron channeling in bent crystals are studied. It is shown that the channeling of ultra-high energy positrons both in bent and straight Inormal) crystals can serve as an effective source of hard photons. The radiative separation of particles depending on spin orientation with respect to the plane of motion and the radiative polarization can make it possible to obtain, by means of bent crystals, a positron beam with a degree of polarization about 10 to 200~,,. IUSSR) Yu A Bashmakov, Rad Effects, 56 (1/2), 1981, 55~0.
33 5138. Total intensity of Kumakhov radiation of channeled positrons and electrons for high energy particles. (USA) In the wide range of positron or electron energies up to 300-3000 GeV the total intensity of Kumakhov radiation has been calculated by means of classical electrodynamics. In this field the total intensity is proportional to E-'. [West Germany) R Wedell, Rad t~l.]bcts, 56 11/2), 1981, 17-18. 449
reaction has been proposed, which appears to be supported by the mass spectrometer measurements. Ilndia) S V Krishna Kumar et al, J Phys D: Appl Phys. 14 18), 1981, LI33-LI35. 33 5128. Stationary striations in a glow discharge. (GB) This letter comments on a conclusion by Landa et al in a recent review paper on moving striations relating to tile theory of stationary striations proposed by the author. I M Chapnik, d Phys D: Appl Phys, 14 18), 1981, LI21 123. 33 5129. Double layer formation in a magnetized laboratory plasma. (GB) Double layers in a current-carrying magnetized argon plasma are studied experimentally. The layer evolves from an unstable anode sheath when the anode voltage has reached a critical value which depends on the neutral gas pressure. The double layer is an oscillating, three-dimensional structure enclosing both axially and radially a plasma at higher potential which is maintained by a low rate of ionization due to the accelerated electrons. Axially accelerated electrons and radially accelerated ions have been detected, but not axially accelerated ions. High frequency is detected on the anode side of the layer. Double layers have also been observed in helium and xenon plasmas. Time independent numerical solutions of Maxwell's equation div D = p in one dinaension including ionization are discussed: they give an upper limit for the anode sheath voltage [before double layer formation) which is too high. but double layer solutions in reasonable agreement with the experiment are obtained. Dag Andersson, d Phys D: Appl Phys, 14 181, 1981. 1403 1418. 33 5130. Test of an electronic distribution model with macroscopic measurements performed on a proton-beam-induced neon plasma containing nitrogen impurities. (GB} A calculation of the medium- and low-energy part of the electronic distribution function is described, together with its indirect comparison to experimental results. The study deals with a plasma created by a proton beam 12 MeV. ~2 I~A cm '1 impinging on a Nc (about 10 torr) target, with N2 impurities. Microwave measurements of electronic density and effective collision frequency agree satisfactorily with calculations using a theoretical distribution function. (France) J Margot et al, J Pllys D: .4ppl Pllys, 14 181, 1981. 1419 1428. 33 5131. lntermolecular potentials from proton spin-lattice relaxation time in H_, Ar and H., N_, gas mixtures. (Canada) Proton spin-lattice relaxation times, T~. have been measured in Hz Ar and H., N2 gas mixtures as a function of density ( 1 0 < p < 7 0 amagat), composition (~ 18 ~5",,). and temperature (300 600 K) with a 30 MHz spin-echo spectrometer using phase sensitive detection. These data together with the T t data obtained by Foster and Rugheimer and by Willmms in these mixtures below 300 K have been analysed using the Bloom-Oppenheim theory. Models for intermolecular potentials to explain the Tj data have been proposed. It is found that the relative anisotropy in the attractive part of the intermolccular potential which fits the T~ data best compares well with that evaluated using polarizability data. (India) Lakshman Pandey and K Lalita Sarkar, Can J Phys. 59 [9). 1981. 1260 1266. 33 5132. Cross sections for the ~"O(l"O,'~Be~.,)-"*Mg reaction and mechanisms of a-rearrangement reactions. (Canada I The ~"O1 ~"O, ~Be~.. I-"*Mg reaction was studied at laboratory beam energy of 53 MeV detecting Z~Mg nuclei in coincidence with :c particles originating from the SBe~, ,2:~ decay. Differential cross sections at 0~,, ~ 90 were found to be approximately 40 pb'sr for the 2"*Mg ground and 1.37 MeV (unresolved) states as well as for the -"*Mg 4.12.4.24. and 5.23 MeV (unresolved)states. A comparison with other :~-rearrangement reactions, leading to the ground and first excited states of final nuclei, shows that tile cross sections for the ~"Olt"O. s Be )"'*Mg reaction are only 1/25 as large as for the z60(t"O.~ZC)-'°Ne reaction and that they are of about equal magnitude as for the ~60(l'O.:~)-'"Si reaction. This suggests that the t6Ol~C'O,SBe)-"~Mg and ~"O(~'O.:O"sSi reactions occur in statistical competition and. consequently, via formation of a more or less equilibrated compound system, while the ~¢'O(tr'O,t"C)Z°Ne reaction is mainly a fast, one-:x-exchange process. Bibiana ~ujec et al, Can d Ph)'s, 59 (9}, 1981, 1233 1240.
33 5133. The level structure of t42Pr deduced from the l'~lPr(n,y)J42Pr reaction. (Canada) A study of the low lying levels of 142pr observed via the n,~lPr(n,,/}n42pr reaction has revealed this nuclide to possess a much more complex structure than previously reported. Acquiring high precision spectra, which readily permitted detection of transitions with intensities greater than 0.01".,,, and employing deconvolution techniques to achieve an effective resolution of I keV, resulted in identification of 455 transitions in the range of excitation energy 0 to 3500 keV. A constant temperature level density model, for which losses due to intensity and resolution effects are included, was used to describe the present results. Computations were undertaken to explore the validity of the assumptions made regarding the primary or secondary nature of the observed transitions. The models used to describe the spacing and intensity distributions in order to account for losses were verified through an examination of the experimental data. In addition, consideration of the degree of E 1 and M I contributions has been included. A high degree of self consistency of all these factors is demonstrated. An examination of the reduced radiative widths strongly suggests the influence of the giant dipole resonance. The precision of the energy measurements permitted the derivation of level energies with an average uncertainty of less than I00 eV. In addition to obtaining a neutron separation energy of 5843.14(10)keV for t'*2Pr, precise values were determined for nuclides ta4Nd, tS6Gd, tS~Gd and 2°~Pb. T J Kennett et al, Can d Phys, 59 (9}, 1981, 1212 1232. 33 5134. Levels in t49Nd studied with the (d,t) reaction. (Canada) The ~5°Nd(d,tlm'~gNd reaction has been studied with 16 MeV deuterons with a vector polarization of ~0.74 from the McMaster University tandem Van de Graaffaccelerator. Measurements were made at I 1 angles from 5.5 to 37.5 using a magnetic spectrograph equipped with photographic emulsions in the focal plane. The measured analysing powers which are well described with standard distorted wave Born approximation calculations, made it possible to give unambiguous assignments for 14 states for which spin information was previously conflicting, incomplete, or lacking. (Norway} L Haugen et al, Can d Phys, 59 (9), 1981, 1183 1193. 33 5135. Dependence of the radiation spectra from channeled electrons on their energy. (USA} Quantum theory of radiation from relativistic electrons in planar channeling has been developed. Analytical expressions have been obtained for the spectral distribution of radiation using a simple model for the planar potential. (USSR) V A Bazylev et al, Rad EJJects, 56 11/2), 1981, 99-104. 33 5136. Radiation from high energy positrons in a potential of crystal planes. (USA} A comparison is made of the radiation spectra of channeled positrons measured at SLAC with theoretical predictions. It is shown that the results obtained can be explained by the effect of the intense radiation accompanying channeling predicted by Kumakhov. (USSR) V A Bazylev et al, Rad Effects, 56 (1/2), 1981, 87-98. 33 5137. Radiation and spin separation of high energy positrons channeled in bent crystals. (USA) The dynamics, radiation and possibilities of the radiation spin separation of positron channeling in bent crystals are studied. It is shown that the channeling of ultra-high energy positrons both in bent and straight Inormal) crystals can serve as an effective source of hard photons. The radiative separation of particles depending on spin orientation with respect to the plane of motion and the radiative polarization can make it possible to obtain, by means of bent crystals, a positron beam with a degree of polarization about 10 to 200~,,. IUSSR) Yu A Bashmakov, Rad Effects, 56 (1/2), 1981, 55~0.
33 5138. Total intensity of Kumakhov radiation of channeled positrons and electrons for high energy particles. (USA) In the wide range of positron or electron energies up to 300-3000 GeV the total intensity of Kumakhov radiation has been calculated by means of classical electrodynamics. In this field the total intensity is proportional to E-'. [West Germany) R Wedell, Rad t~l.]bcts, 56 11/2), 1981, 17-18. 449