Isotropic background cosmic X-rays in the energy range 50–290 KeV

The observations of omnidirectional X-ray flux at the top of the atmosphere have been extended upto 200 KeV using a balloon-borne NaI (Tl) scintillator detector at Hyderabad, India. The omnidirectional flux at 60 KeV is found to be 0·0066±0·0014 photons/cm.² sec. ster. KeV. The X-ray flux in the energy range 50–290 KeV can be adequately represented by the spectrum Ke^?2.2±0.4. New upper limits to the hard X-ray flux from the quiet sun have also been obtained from the same measurement.     

He3 nuclei in the low energy primary cosmic radiation

The flux of He³ nuclei and the ratio He³/(He³+He⁴) in the low energy primary cosmic radiation have been determined using a stack of nuclear emulsions exposed at 3·1 g. cm.^?2 of atmospheric depth from Fort Churchill, Canada, in June 1963. The grain-densityversus residual range method was used to determine the masses of the helium nuclei. Using a sample of 146 helium nuclei whose masses could be identified, the ratio He³/(He³+He⁴) is obtained as 0·14±0·04 for the kinetic energy interval 115–210 MeV per nucleon and 0·43±0·11 for the rigidity interval 0·85–1·05 BV. The differential fluxes of He³ nuclei are determined as 0·017±0·006, 0·045±0·015, and 0·054±0·017 particles/M². Sr. Sec. MeV/nucleon, in the kinetic energy intervals of 117–183, 183–217, and 217–250 MeV/nucleon respectively. These results are compared with those of other investigators. From the results of the present work the amount of matter traversed in space by the primary cosmic ray helium nuclei of energy 115–210 MeV/nucleon is obtained as 4·7±1·8 gm. cm.^?2 of hydrogen.     

Determination of the flux of primary cosmic ray hydrogen and helium nuclei near the geomagnetic equator using nuclear emulsions

Nuclear emulsions exposed to the cosmic radiation over Hyderabad, India, at an altitude of 31·3 km. for six hours, have been used to derermine primary cosmic ray deuteron flux. The flux of deuterons of rigidity ?16·9 GV at the top of the atmosphere is found to be <10 m.^?2 sec.^?1 sterad^?1; this may be compared with the proton fiux of 83±12 m.^?2 sec.^?1 sterad.^?1 in the same rigidity region over Hyderabad.     

Recent observations on cosmic electrons and their consequences on different cosmic ray models and related astrophysical quantities

An experiment has been carried out to study the electron component of the primary cosmic radiation at energies >12 GeV using a hypersensitised nuclear emulsion stack, flown oriented in the east-west plane over Hyderabad, India. The results of this experiment, on the basis of 28 identified electrons of energy above 12 GeV are: (i) the integral flux of electrons above an effective energy of 16 GeV is 0·51±·10 per m.² sec. sr.; (ii) the differential energy spectrum between 12 and 300 GeV can be represented as N(E)dE=12·7 E^?2.1±·2 dE m.^?2 sec.^?1 sr.^?1; and (iii) the fraction of positrons among the total electrons in the energy region 12 to 30 GeV has been discussed. A critical study has been made on the applicability of different cosmic ray models by making use of the observed differential energy spectrum of electrons and the relevant astrophysical parameters associated with the confinement regions. The confinement regions considered are: (i) the universe as a whole, (ii) the super cluster to which our galaxy belongs, (iii) the galactic halo and (iv) the galactic disc. The consequences of the recently postulated universal black body radiation at 3° K. on the cosmic ray models have also been considered. Some of the crucial experiments needed to set more stringent constrains on the models which would then permit meaningful interpretation, are enumerated.     

Determination of the flux of primary cosmic ray hydrogen and helium nuclei near the geomagnetic equator using nuclear emulsions

The flux of helium nuclei of the primary cosmic radiation at the top of the atmosphere has been determined over Hyderabad, India, at a time of high solar activity in the 11-year cycle, namely March 24, 1960. The flux value has been found to be 17·9±1·9 helium nuclei per m.² sec. ster. corresponding to a vertical geomagnetic cut off energy of 7·5 GeV/nucleon. This result when compared with other observations made near the geomagnetic equator shows that the solar modulation effects, if any, at rigidities >16 GV should be ?10% only.     

β-delayed proton decays of81Zr and85Mo

β-delayed proton decays of T_z = 1/2 series nuclei⁸¹Zr and⁸⁵Mo have been studied in detail by using p-γ coincidence measurement. The β-delayed proton spectra populating the first excited states of the daughter nuclei have been obtained. Half-life of⁸¹Zr has been measured tobe5.3s ± 0.5 s and that of⁸⁵Mo 3.2 s ± 0.2 S. By using statistical model calculations and systematic analyses, spins and parities for the ground states of⁸¹Zr and⁸⁵Mo have been tentatively assigned to be 3/2^? and 1/2^?, respectively. Mass excess of⁸¹Zris -58.3 MeV± 0.2 MeV and that of⁸⁵Mo-59.1 MeV ± 0.4 MeV. Combining the measured half-lives with the calculated partial ones yields the branches of β-de-layed proton decay for⁸¹zr and⁸⁵Mo of (1.2 ± 0.2) × 10^-3 and (1.4 ± 0.2) × 10^-3, respectively.     

Ratio of pions to protons and ratio of neutral to charged interacting particles at mountain altitude of 800 gm/cm2

Using a combined set-up of a multiplate cloud chamber, an air Cerenkov counter and a total absorption spectrometer, the ratio of pions to protons not associated with large air showers has been determined to be 0·50 ± ·07 in the energy region 20–40 GeV at an altitude of 800 gm/cm². In the same energy region the ratio of neutral to charged particles is found to be 0·66 ± ·07. From the ratio of neutrons to protons deduced from these measurements (i.e., 0·99 ± ·11), it is concluded that most of the charge excess of nuclear active particles of energies > 20 GeV at mountain altitudes and sea-level is due to pions.     

High energy photons from the Crab nebula due to the universal microwave field

The flux of high energy photons emanating from the Crab nebula due to inverse Compton scattering of the universal microwave photons from the high energy electrons in the nebula has been calculated. This flux is compared with experimentally obtained values at certain energies and also with the flux calculated due to Compton-synchrotron process. The flux of gamma-rays of about 100 MeV due to the scattering of the microwave photons is found to be of the same order as that due to the Compton-synchrotron process.     

β-delayed proton decays of81Zr and85Mo

β-delayed proton decays of T_z = 1/2 series nuclei⁸¹Zr and⁸⁵Mo have been studied in detail by using p-γ coincidence measurement. The β-delayed proton spectra populating the first excited states of the daughter nuclei have been obtained. Half-life of⁸¹Zr has been measured tobe5.3s ± 0.5 s and that of⁸⁵Mo 3.2 s ± 0.2 S. By using statistical model calculations and systematic analyses, spins and parities for the ground states of⁸¹Zr and⁸⁵Mo have been tentatively assigned to be 3/2⁻ and 1/2⁻, respectively. Mass excess of⁸¹Zris -58.3 MeV± 0.2 MeV and that of⁸⁵Mo-59.1 MeV ± 0.4 MeV. Combining the measured half-lives with the calculated partial ones yields the branches of β-de-layed proton decay for⁸¹zr and⁸⁵Mo of (1.2 ± 0.2) × 10^-3 and (1.4 ± 0.2) × 10^-3, respectively.     

Investigations on the multiply charged nuclei of the primary cosmic radiation near the geomagnetic equator using nuclear emulsion

A nuclear emulsion stack was exposed over Hyderabad, India (geomagnetic latitudeλ=7·6° N) under a mean atmospheric depth of 6·8 g./cm.², on 24 March 1960. The relative and absolute intensities of Be and B nuclei and nuclei of charge Z?6 (the S-nuclei) have been determined in this stack. The intensities were extrapolated to the top of the atmosphere using measured fragmentation parameters involved in collisions of cosmic ray nuclei in graphite. The flux values of Be, B and S nuclei at the top of the atmosphere have been determined to be 0·025±0·011, 0·101±0·023 and 1·12±0·10 particles/m.² sec. sr. respectively. The ratios of intensities B/S, Be/S and Be/B have been found to be 0·09±0·02, 0·022±0·008 and 0·25±0·11 respectively. These ratios of intensities have been used (a) to compute the amount of matter traversed by the radiation before reaching the vicinity of the earth as 2·6±0·6 g./cm.², (b) to show that the Fermi mechanism of acceleration of particles is not efficient at these energies (1–10 GeV/n.) in interstellar space and (c) to show that preferential acceleration of H₁-nuclei (Z?20) is not of overwhelming importance. The derived source composition of nuclei of energy ?7·5 GeV/n suggests that N, O, F and H₃-nuclei (Z=10–15) have similar abundances in the universe and in cosmic rays, and that C and H₁-nuclei are overabundant in cosmic rays.     

Atmospheric gamma-rays of 1–200 GeV over Hyderabad

Using a stack of hypersensitized nuclear emulsions, exposed under 10.2 g.cm^?2 of residual atmosphere over Hyderabad, India, gamma-rays of energy > 1 GeV have been studied. It is found that the observed differential energy spectrum can be best represented by two power law spectra, one for energies less than 30 GeV and the other for higher energies but with the same spectral index of 2.6; however the intensities at energies greater than 30 GeV are about three times higher than what would be expected from the extrapolation of the spectrum at lower enerjies. The implication of this observation has been examined. The neutral pion production spectrum over Hyderabad has been derived from the gamma-ray spectrum. Using this information the energy spectrum of atmospheric electrons has been deduced and a comparison made with the observed spectrum below the geomagnetic threshold energy over Hyderabad; therefrom an upper limit of 0.5 particles/(m².sr.sec.) has been deduced for the flux of re-entrant albedo electrons above 2 GeV.     

Cosmic ray nuclei of chargeZ⩾3 during the period of low solar activity

A detailed study of the composition and energy spectra of heavy nuclei of charge Z?3 in the primary cosmic rays has been made during the period of low solar activity, using two stacks of nuclear emulsions exposed in balloon flights from Fort Churchill, Canada, in June 1963. Each of the stacks was composed of 120 nuclear emulsions of three different sensitivities and was exposed at about 3·5 g. cm.^?2 of residual air for about 11.1 hr. Reliable resolution of charges of nuclei from lithium to oxygen was obtained; for heavier nuclei, charge groups were determined. From the analysis of 793 tracks of nuclei with Z?3, results on the following aspects were obtained:

1. The differential energy spectra of L (Z=3–5), M (Z=6–9) and H (Z=10–28) nuclei were measured in the energy intervel 150–600 MeV/nucleon; integral fluxes were obtained for energy >600 MeV/nucleon;
2. The energy dependence of the L/M ratio at the top of the atmosphere was determined; the ratios were obtained as 0·45 ± 0·06 and 0·29 ± 0·03 in the energy intervals of 200–575, and >575 MeV/nucleon respectively;
3. Relative abundances of individual nuclei of Li, Be, B, C, N and O at the top of the atmosphere were determined as 36, 29, 55, 100, 60 and 106 respectively in the energy interval 150–600 MeV/nucleon; corresponding values were also obtained for energy >600 MeV/nucleon.
4. The differential fluxes of multiply charged nuclei measured by us and by other investigators were used to determine the solar modulation between solar maximum to solar minimum. It was found that solar modulation of the fluxes of M and He nuclei were consistent with Rβ dependence and that the modulation parameter Δη between 1965 and 1957 was about 1·1.

The implications of these results are discussed.     

Rigidity spectrum of cosmic ray helium nuclei

An experiment has been carried out using an oriented stack of nuclear emulsions to determine the rigidity spectrum of cosmic ray helium nuclei between 12 and 40 GV, by taking advantage of the variation of the geomagnetic cut-off rigidity in the east-west plane over Hyderabad, India. Altotal of 2433 identified helium nuclei recorded in the stack, has been divided into 8 angular intervals in the east-west plane corresponding to 8 different cut-off rigidities. From this the integral fluxes of helium nuclei at the top of the atmosphere have been obtained for all the 8 rigidity intervals. The vertical flux above an effective threshold rigidity of 16·73 GV has been determined with high statistical accuracy and has a value of 15·0±0·5 helium nuclei (m².sr.sec.)^?1. The rigidity spectrum of these nuclei between 12 and 40 GV can be well represented by a power law of the type N (>R) =1990 R^?1.74±0.11 (m².sr.sec.)^?1 and is the first direct determination so far made in this rigidity region. The differential rigidity spectra of protons, helium nuclei and S-nuclei of the cosmic radiation in the vicinity of the earth at solar minimum (1965) have been constructed with the existing world data and it is found that for rigidities ? 10 GV, the three spectra have, within experimental errors, the same slope of 2·6. The ratio P/He and He/S of the differential fluxes have been studied as a function of rigidity. It is found that for R>2 GV, the ratio P/He has, within experimental errors, a constant value of 6·3; as for the ratio He/S, it seems that the experimental data above a GV is not inconsistent with a constant value of 14 over the entire rigidity interval considered here.     

Spins of the first two excited states in27Mg by an angular correlation technique in the reaction26Mg (d,pγ)27Mg

Proton-gamma-ray angular correlation measurements, employing the ‘method II’ of Litherland and Ferguson, have been made in the reaction²⁶Mg (d, pγ)²⁷Mg, using 1·80 MeV deuteron beam and detecting the outgoing protons at 0° with respect to the beam. Analysis of these measurements leads to spin assignments of 3/2 and 5/2 for the 0·98 and 1·69 MeV excited states of²⁷Mg. The 1·69 MeV second excited state is found to decay almost completely to the ground state.     

Vector magnetic field in solar polar region

By means of ‘deep integration’ observations of a videomagnetograph the vector magnetic field was first systematically measured near the solar south polar region on April 12, 1997 when the Sun was in the minimal phase between the 22nd and 23rd solar cycle. It was found that the polar magnetic field deviated from the normal of solar surface by about 42.2° ± 3.2°, a stronger magnetic element may have smaller inclination, and that within the polar cap above heliolatitude of 50°, the unsigned and net flux densities were 7.8 × 10⁻⁴) T and −3.4×10⁻⁴T, respectively, and consequently, the unsigned and net fluxes were about 5.5 × 10²² and − 2.5 × 10²² Mx. The net magnetic flux, which belongs to the large-scale global magnetic field of the Sun, roughly appmaches the order of the interplanetary magnetic field (IMF) measured at distance of 1 AU. Project supported by the National Natural Science Foundation of China (Grant No. 19791090).     

Flip-chip-type high-T c gradiometer for biomagnetic measurements in unshielded environment

A flip-chip-type gradiometer has been constructed with a 10 mm × 5 mm planar DCSQUID gradiometer fabricated on a SrTiO₃ bicrystal substrate and a flux transformer made from a YBCO*/YBCO/CeO₂/YSZ multilayer on ?50.8 mm Si wafer. The coupling coefficient between the flux transformer and the planar gradiometer is 0.18. The transformer increases effectively the resolution of the gradiometer. A magnetic field gradient resolution of 73 fT.cm^?1Hz^?1/2 in the white region and 596 fT.cm^?1Hz^?1/2 at 1 Hz has been obtained. High quality magnetocardiogram signals have been successfully measured by using this flip-chip-type gradiometer in an unshielded environment.     

Coherence rotation in dissipative reaction19F+51V

Excitation functions of the projectile-like fragments in the dissipative reaction¹⁹F+⁵¹V have been measured at θ₁ = 21.7°, 36.1° and 40.5°. The incident energies are from 102.25 to 109.50 MeV in 250 keV steps. The energy coherence width г and the rotation angular velocities ω of the corresponding dinuclear systems are extracted. The coherence rotation and its importance in the reaction process are discussed.     

IS the ‘8° K’ background radiation universal?

The high energy gamma-ray flux (energy greater than 10¹² eV) resulting from high energy protons interacting with photons of the recently observed sub-millimeter microwave radiation in metagalactic space is calculated. Comparison of the flux of these gamma-rays with experimental observations indicate that the observed sub-millimeter radiation may not be universal.     

Flip-chip-type high-Tc gradiometer for biomagnetic measurements in unshielded environment

A flip-chip-type gradiometer has been constructed with a 10 mm × 5 mm planar DCSQUID gradiometer fabricated on a SrTiO₃ bicrystal substrate and a flux transformer made from a YBCO*/YBCO/CeO₂/YSZ multilayer on ϕ50.8 mm Si wafer. The coupling coefficient between the flux transformer and the planar gradiometer is 0.18. The transformer increases effectively the resolution of the gradiometer. A magnetic field gradient resolution of 73 fT.cm⁻¹Hz^−1/2 in the white region and 596 fT.cm⁻¹Hz^−1/2 at 1 Hz has been obtained. High quality magnetocardiogram signals have been successfully measured by using this flip-chip-type gradiometer in an unshielded environment.     

Gamma radiation from the celestial X-ray source sco X-1

Gamma radiation from the X-ray sources Sco X-1 due to Comptonsynchrotron process is calculated. Comparison with the upper limits set by an experimental survey for sources of gamma-rays with energy greater than 100 MeV has been made and constraints on the size of the source and its magnetic field are discussed. The flux predicted in the energy range 10¹¹–10¹² eV is above the observable lower limit of presentday detectors. An observation of this flux will serve as a test of the synchrotron origin of the X-radiation.