Study of the energy spectrum and mass composition of primary cosmic rays in the energy range of 10<Superscript>18</Superscript>–10<Superscript>20</Superscript> eV using a balloon setup in antarctica (SPHERE-antarctica project)

An Antarctic balloon experiment for measuring the energy spectrum and elemental composition of cosmic rays in the ultrahigh-energy range (10¹⁸–10²⁰) eV is proposed. Scientific equipment will measure fluorescence caused by an extensive air shower formed in the atmosphere by an ultrahigh energy particle and Cherenkov light of this shower reflected from a snow surface. It is assumed that the balloon will fly in the circumpolar orbit in Antarctica at a height of ~25 km for (2–3) winter (in the Southern Hemisphere)months. For this time, ~3000 events caused by particles with energies above 10¹⁸ eV and (200–300) events caused by particles with energies above 10¹⁹ eV will be detected.     

Development and operation of a balloon-borne telescope for fir imaging, radiometry and spectrometry of the galactic cygnus region

We have designed and built a balloon-borne far-infrared 60 cm telescope equipped with He-cooled filters and a composite silicon bolometer with an NEP of 1.3·10^–14 W/Hz^1/2 for imaging, radiometry and spectroscopy of the Cygnus region at wavelengths up to 330 m. A test flight took place at the CNES balloon station at Aire/Adour, F, on May 8, 1989. The balloon stayed 4_1/2 h at the observation height of 39 km. Tests and results are discussed.     

The LAPEX experiment for observation of the supernova SN 1987A in hard X-rays

Summary The LAPEX payload is described in the configuration that will be launched to observe the supernova SN 1987A. The balloon flight will be performed from Alice Springs (Australia) in April 1989 as a part of a NASA balloon campaign. The experiment will allow simultaneous observations of source and background in order to minimize systematic errors due to background variations. The limiting flux sensitivity of the instrument in the (20÷200) keV energy band is 4·10⁻⁶ ph/(cm²s keV) or ∼2.5 mCrab for a 10⁴ s observation of SN 1987A. The presence of a⁵⁷Co emission line in the SN 1987A photon spectrum could be detected down to an intensity level of ∼8·10⁻⁵ photons/cm²s as at 99.7% confidence level. The high resolution of the event timing (<0.1 ms) will make it possible to detect millisecond pulsations with amplitudes down to ∼4% of the expected average flux from SN 1987A in the (20÷60) keV band. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

Atmospheric gamma rays in the energy region 40–1000 GeV

A large stack of lead-emulsion sandwich detector assembly was flown over Hyderabad, India. High energy gamma rays at the float altitude were unambiguously identified from the cascades they induced, and their energies reliably determined by improved methods. From an analysis of 163 gamma rays of energy ≳ 30 GeV, it is found that the differential energy spectrum is represented by the power lawJ _r (E)= 129·4E ^{−2·62±0·12} photons m⁻² sr⁻¹sec⁻¹ GeV⁻¹ at an effective atmospheric depth of 14·3 g cm⁻²; this is the first reliable balloon measurement of atmospheric gamma rays in the energy range 40–1000 GeV. After correcting for the gamma rays radiated by the primary cosmic ray electrons, the production spectrum of gamma rays, resulting from the collisions of cosmic ray nuclei with air nuclei, at the top of the atmosphere isP _r (E, 0)=8·2 × 10⁻⁴ E^2.60±0.09 photons g⁻¹sr⁻¹sec⁻¹ GeV⁻¹. The atmospheric propagation of the electromagnetic component due to the cascade process is also derived from the gamma ray production spectrum.     

In searches for daemons

A possibility is considered of detecting Planckian particles carrying an electric charge Z≈10 and supposedly forming the dark matter of the Galactic disk, whence they are captured by combined action of the Sun and the Earth into strongly elongated Earth-crossing orbits. The flux of such dark electric matter objects, daemons, at the Earth’s orbit may reach f _⊕≈3×10⁻⁷cm⁻²s⁻¹ at a velocity about 52 km/s. Negatively charged daemons are capable of catalyzing the fusion of light (Z _n<10) nuclei. The rate of capture (and fusion) of nuclei should be particularly high in a metallic phase. A detection system is described that consists of beryllium plates 45 mm thick and 1200 cm² in area coated with a ZnS(Ag) scintillator. It is assumed that the products of the fusion reaction 2⁹Be → ¹⁸O that are ejected in amounts of up to about 10⁴ from the points of daemon entrance and exit would give rise to scintillations with a delay of about 1μs. An exposure of the system for 300 h revealed no event. The reason for the negative result can be (1) too optimistic an estimate of the flux (the inclusion of some factors could lower it by 1.5–3 orders of magnitude) and (2) the poisoning of the catalyst by capture of nuclei with Z _n≥10. The time required for the recovery of the daemon catalytic properties is estimated from the analysis of the energy release in the Sun at no less than 3×10⁻⁷ s. The analysis of the total available data suggests that the daemon flux at the Earth is about 3×10⁻⁸ cm⁻² s⁻¹. The experiments will be continued. From Yadernaya Fizika, Vol. 63, No. 6, 2000, pp. 1112–1117. Original English Text Copyright ? 2000 by Drobyshevski. This article was submitted by the author in English.     

Characterization of Zn<Subscript>2</Subscript>SnO<Subscript>4</Subscript> Thin Films Prepared by RF Magnetron Sputtering

Zn₂SnO₄ (ZTO) is a stable semiconductor in ZnO–SnO₂ system and important transparent conducting oxide (TCO) predominantly used in optoelectronic devices. ZTO thin films were prepared by RF magnetron sputtering using Zn₂SnO₄ ceramic target in this paper. The effects of annealing temperatures and oxygen contents on characterization of ZTO thin films were studied. The results show that ZTO thin films prepared by RF magnetron sputtering are amorphous with an optical band gap of 3.22 eV. After annealing at 650°C in Ar atmosphere for 40 min, ZTO films possess a spinel structure with an optical band gap of 3.62 eV. The atomic force microscope (AFM) data of morphology reveals that the surface roughness of films is about 2 nm. The results of energy dispersive spectrometer (EDS) show that the concentration ratio of Zn to Sn is in the range from 1.44 to 1.57. The results of Hall-effect-measurement system reveal that the resistivity of films varies from 102 to 10–1 Ωcm, carrier concentration is about 10¹⁷ cm^–3, and mobility ranges from 10⁰ to 10¹ cm² v^–1 s^–1.     

The electron-optical system of the LIU-2 induction accelerator

The electron-optical system (EOS) of an induction accelerator for generation of an electron beam with an energy of 2 MeV, a current of 2 kA, an impulse duration of 2 × 10^?7 s, and a geometric output emittance not exceeding the thermal value of it is described. The EOS consists of two parts. The first part is a diode gun with a perveance of 2 × 10^?6 A/B^3/2 and a cathode-anode voltage of 1 MeV. The second part is an accelerating tube with uniform distribution of the same accelerating voltage. A beam is transported at a distance of about 4 m from the cathode and focused on a spot with a diameter of about 1 mm. The compliance tests results of the linear-induction accelerator precisely conform to the calculated design parameters.     

Large-area phoswich balloon experiment for hard-X-ray astronomy

Summary We describe a balloon experiment, currently in the marking, devoted to the observation of celestial X-ray sources. The main features of the X-ray telescope are summarized as follows. It operates in the energy band from 20 to 300 keV. Its energy resolution is about 17% at 60 keV. Under the hypothesis of 10⁴ s of observing time, 3 mbar of residual atmospheric pressure and 3σ of statistical significance, the expected sensitivity of the instrument is 2·10⁻⁶ photons/cm² s keV in the (20÷200) keV energy band, corresponding to about 1 milliCrab. Its high sensitivity allows us to detect both time variability in the flux and cyclotron lines in the spectra of X-ray sources. It has a field of view of 3° FWHM and has the possibility of resolving complex fields by using multipitch modulation collimators. With such a configuration its angular resolution is about 10′. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984.     

Study of spatial characteristics of the incomplete surface discharge in atmospheric-pressure air

Spectra of plasma of the incomplete surface discharge in atmospheric-pressure air were measured. Bands of the systems 2⁺, 1⁺, and 1⁻ of nitrogen were identified. It was shown that periodic excitation at the C ³Π _u nitrogen level results in local equilibrium characterized by a vibrational temperature of 2250 K. For the 1⁺ band system of nitrogen, the structure of rotational transitions was resolved; it was found that the distribution in the 1⁺ band system is significantly nonequilibrium due to the A ³Σ _u ⁺ level metastability. Transverse and longitudinal sections of the plasma band were scanned. It was found that the transverse distribution of the emission intensity has a maximum at a distance of 1 mm from the electrode edge followed by an exponential decay. The plasma band width was ∼5 mm. The longitudinal discharge structure consisted of a system of microchannels (with a characteristic diameter of 0.4 mm) with diffuse overlapping. The average channel density was 10–15 cm⁻¹. It was shown that the spatial distribution of incomplete discharge plasma is characterized by high stability against wide-range variations of discharge electrical characteristics. For example, as the excitation voltage varies within 2–6 kV, the plasma band width changed by no more than 1 mm, and the vibrational temperature varied within 10–12%.     

Stressed Ge:Ga photoconductor with a compact and stable stressing assembly

Sensitive far infrared stressed Ge:Ga photoconductors which have response up to 200μm wavelength have been fabricated and studied to apply them to astronomical and atmospherical observations using balloons and satellites. The stressed Ge:Ga photoconductors have shown very high detectivity, i.e. responsivity of 15 A/W and NEP = 2 × 10⁻¹⁸ W/√Hz when operated at 2 K and at photon fluxes 1.1 × 10⁶ photons/s, and the stable stress operation has been achieved by using the compact stressing mechanism with cone disk springs. The good performance has been confirmed by balloon experiments to detect astronomical CII line at 157.7 μm.     

Two stratospheric superfamilies with <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≈ 10<Superscript>16</Superscript> eV

A comparative analysis of the cosmic ray superfamily STRANA detected by an emulsion chamber aboard the Russian stratospheric balloon and the superfamily JF2af2 detected by an emulsion chamber during a high-altitude flight of the supersonic aircraft Concord (international experiment) is performed. Both events with E ₀ ≈ 10¹⁶ eV are characterized by the pronounced alignment effect and very high transverse momenta of secondary particles.     

Ionic conductivity in Na4ZrSi3O10

A new compound, Na₄ZrSi₃O₁₀, belonging to the ternary system Na₂O-SiO₂-ZrO₂ is presented. Based on X-ray powder methods, it is assigned monoclinic symmetry with the probable group C 2/c. The ionic conductivity was found to be 4 x 10^-3Ω^-1cm^-1 at 300°C and the activation energy for ionic motion is 42 kJ/mol.     

Transport properties of PbSnI4

PbSnI₄ has been prepared from equimolar amounts of PbI₂ and SnI₂. X-ray and DSC measurements show the material to be uniphase in the temperature range 30 to 400°C; it has a tetragonal structure and melts at 379°C. The electrical conductivity is mainly ionic with an ionic transport number greater than 0.99 at 200°C. Conductivity at room temperature is 2.56 × 10⁻⁸ Ω⁻¹ cm⁻¹ while the value at 200°C is 1.25 × 10⁻⁶ Ω⁻¹ cm⁻¹.     

Sub-part-per-billion detection of nitric oxide in air using a thermoelectrically cooled mid-infrared quantum cascade laser spectrometer

Non-cryogenic, laser-absorption spectroscopy in the mid-infrared has wide applications for practical detection of trace gases in the atmosphere. We report measurements of nitric oxide in air with a detection limit less than 1 nmole/mole (<1 ppbv) using a thermoelectrically cooled quantum cascade laser operated in pulsed mode at 5.26 μm and coupled to a 210-m path length multiple-pass absorption cell at reduced pressure (50 Torr). The sensitivity of the system is enhanced by operating under pulsing conditions which reduce the laser line width to 0.010 cm^-1 (300 MHz) HWHM, and by normalizing pulse-to-pulse intensity variations with temporal gating on a single HgCdTe detector. The system is demonstrated by detecting nitric oxide in outside air and comparing results to a conventional tunable diode laser spectrometer sampling from a common inlet. A detection precision of 0.12 ppb Hz^-1/2 is achieved with a liquid-nitrogen-cooled detector. This detection precision corresponds to an absorbance precision of 1×10^-5 Hz^-1/2 or an absorbance precision per unit path length of 5×10^-10 cm^-1 Hz^-1/2. A precision of 0.3 ppb Hz^-1/2 is obtained using a thermoelectrically cooled detector, which allows continuous unattended operation over extended time periods with a totally cryogen-free instrument. Received: 1 May 2002 / Revised version: 6 June 2002 / Published online: 21 August 2002 RID="*" ID="*"Corresponding author. Fax: +1-978/663-4918, E-mail: ddn@aerodyne.com     

Generation of 13.9 µm radiation from CO<Subscript>2</Subscript> by cascade lasing or externally applied CO<Subscript>2</Subscript> laser

13.9 μm radiation from the 10⁰0-01¹0 transition can be obtained from a CO₂ laser by saturating the 00⁰1-10⁰0, 10.6 μm transition with an internally generated q-switched pulse or by the application of an external 10.6 μm pulse. Because of Fermi resonance between the symmetric stretch and the bending modes, decay of population from the 10⁰0 level is fast, and such lasers operate at low power and energies. A theoretical model was developed to study such lasers. The results of the calculations indicate that a large-aperture E-beam-sustained discharge is effective for excitation of the cryogenically cooled gain medium, which uses He rich mixture at low pressure. The system is scalable and capable of generating large powers and energies.     

Leed,aes and photoemission measurements of epitaxially grown GaAs(001), (111)A and (1̄1̄1̄)B surfaces and their behaviour upon cs adsorption

Epitaxially grown GaAs(001), (111) and (1?1?1?) surfaces and their behaviour on Cs adsorption are studied by LEED, AES and photoemission. Upon heat treatment the clean GaAs(001) surface shows all the structures of the As-stabilized to the Ga-stabilized surface. By careful annealing it is also possible to obtain the As-stabilized surface from the Ga-stabilized surface, which must be due to the diffusion of As from the bulk to the surface. The As-stabilized surface can be recovered from the Ga-stabilized surface by treating the surface at 400°C in an AsH₃ atmosphere. The Cs coverage of all these surfaces is linear with the dosage and shows a sharp breakpoint at 5.3 × 10¹⁴ atoms cm^?2. The photoemission reaches a maximum precisely at the dosage of this break point for the GaAs(001) and GaAs(1?1?1?) surface, whereas for the GaAs(111) surface the maximum in the photoemission is reached at a higher dosage of 6.5 × 10¹⁴ atoms cm^?2. The maximum photoemission from all surfaces is in the order of 50μA Im^?1 for white light (T = 2850 K). LEED measurements show that Cs adsorbs as an amorphous layer on these surfaces at room temperature. Heat treatment of the Cs-activated GaAs (001) surface shows a stability region of 4.7 × 10¹⁴ atoms cm^?2 at 260dgC and one of 2.7 × 10¹⁴ atoms cm^?2 at 340°C without any ordering of the Cs atoms. Heat treatment of the Cs-activated GaAs(111) crystal shows a gradual desorption of Cs up to a coverage of 1 × 10¹⁴ atoms cm^?2, which is stable at 360°C and where LEED shows the formation of the GaAs(111) (√7 × √7)Cs structure. Heat treatment of the Cs-activated GaAs(1?1?1?) crystal shows a stability region at 260°C with a coverage of 3.8 × 10¹⁴ atoms cm^?2 with ordering of the Cs atoms in a GaAs(1?1?1?) (4 × 4)Cs structure and at 340°C a further stability region with a coverage of 1 × 10¹⁴ at cm^?2 with the formation of a GaAs(1?1?1?) (√21 × √21)Cs structure. Possible models of the GaAs(1?1?1?) (4 × 4)Cs, GaAs(1?1?1?)(√21 × √21)Cs and GaAs(111) (√7 × √7)Cs structures are given.     

Direct stratospheric measurements of charges and energies of Primary Cosmic Rays in the range of 10<Superscript>13</Superscript> − 10<Superscript>15</Superscript> eV (CROSS Project)

The CROSS (Cosmic Rays Over Spectrum Steepening) experiment is aimed at direct measurements of masses and energies of primary cosmic ray (PCR) nuclei in the range of 10¹³ ? 10¹⁵ eV near the break in the PCR energy spectrum. The experimental equipment includes a balloon ionization spectrometer consisting of X-ray transition radiation generators interlaid with thin-wall proportional chambers.     

Development of a long life, 2 kHz repetition rate X-ray preionizer

A simple and rugged X-ray preionizer system has been developed that is capable of sustained operation at the 2 kHz level with a demonstrated lifetime of2.5× 10⁸ shots and a potential lifetime of >10⁹ shots. At the heart of the system is an advanced form of corona plasma cathode. Cathode wear is minimised by utilising adsorbates from the dielectric surface and not cathode material to form the surface discharge from which the electron beam is extracted. The preionizer chamber background pressure (which is directly proportional to the sticking rate of adsorbates) is found to be of crucial importance in maintaining good cathode emission at high repetition rates. The device emits a rectangular X-ray beam, 5 cm×40 cm, with an X-ray risetime of 20 ns, a FWHM of 60 ns, and a peak energy of 95 keV. Ionization levels of >10⁷ cm^–3 in 1 atm of Ne could be generated after the X-rays had passed through 2 mm of aluminium and 1 mm of steel. Good beam uniformity and reproducibility at 2 kHz were shown to be maintained with the aid of a segmented electrode charge collection chamber. The system should be especially suitable for preionizing lasers containing a strongly electron attaching gas mixture.     

Oxidation of cleaved InAs(1 1 0) surfaces at room temperature: Surface band-bending and ionization energy

The interaction of unexcited, molecular oxygen with cleaved InAs(1 1 0) surfaces was investigated at room temperature by using a Kelvin probe and photoemission spectroscopy excited by HeI radiation. Exposures up to 10⁵ L of O₂, which result in an oxygen uptake up to only a few percent of a monolayer, cause the formation of an inversion layer on the specimen doped p-type and of an accumulation layer on those doped n-type. Between 10⁵ and 10⁸ L of O₂ the Fermi level is found to be pinned at 0.13 eV above the bottom of the conduction band on samples doped p- as well as n-type. This energy position of the Fermi level agrees with the charge- neutrality level of the virtual gap states as calculated by Tersoff. Since the ionization energy remains unchanged up to exposures of 10⁸ L of O₂ it is concluded that the oxygen is incorporated into rather than adsorbed on cleaved InAs surfaces.     

Far-infrared observations of the galactic Cygnus region and Mars with a 60 cm diameter balloon-borne telescope

We have introduced secondary-mirror chopping in our balloon-borne far-infrared 60 cm Ø telescope equipped with He-cooled filters and a composite silicon bolometer with an NEP of 1.3 10^–14 W/Hz^1/2 for imaging, radiometry and spectroscopy of the Cygnus region at the wavelengths 80 m, 130 m and 310 m. The modified system was flown on September 26/27, 1990 with a 380'000m³ hydrogen balloon at the CNES station at Aire/Adour, France. Observations were performed at a platform height of 39 km during 5 hrs. We made successful measurements on the complexes DR21 and S106 of the Cygnus region as well as on Mars at the wavelengths mentioned.