A detection system using drift chambers for the SPES4 spectrometer at Laboratoire National Saturne

We describe the “drift chamber” detection setup of SPES4, the 4 GeV/c spectrometer at Laboratoire National Saturne. The particle identification is performed by combining magnetic rigidity selection with energy loss and time of flight measurements. This allows to separate analysed isotopes from Z = 1 to at least Z = 10 up to a rigidity of 4 GeV/c. A charge resolution of ΔZ_rms = 0.1 and a time resolution of Δt_rms = 120 ps for ¹⁸Ne at about 3 GeV/c per Z are easily obtained. Two sets of multiwire drift chambers are used to measure and reconstruct the particle trajectories at the output of the system. A position resolution better than Δx_rms = 160 μm can be achieved in the focal plane. This corresponds to a momentum resolution of Δδ_rms = 0.22 × 10⁻⁴. The performances of SPES4 (Δδ_rms = 2.2 × 10⁻⁴) can then be wholly exploited.     

Precision muon detectors in the TeV region

We present a design study, based on our experience in the construction of the L3 detector at LEP, of a large solid angle muon detector for a high luminosity (> 10³³ cm⁻²/sec) pp collider. It is shown that a resolution of ΔM/M ∼ 1% can be reached for a one TeV particle T→μ⁺μ⁻. Hadron jets can also be measured.     

Structural,dielectric and electrical properties of Al+3-modified PLZT ceramics

Polycrystalline samples of [Pb_0.92(La_1−zAl_z)_0.08][Zr_0.60Ti_0.40]_0.98O₃ (z=0.0, 0.3, 0.6, 0.9, 1.0) were prepared by a high-temperature solid-state reaction technique. Preliminary X-ray study at room temperature shows the formation of single-phase compounds in the tetragonal crystal system. Scanning electron microscopy (SEM) study was employed to observe the microstructure and distributions of grains of the sintered ceramics. Detailed studies of dielectric constant (ϵ) and tangent loss (tanδ) of the compounds as a function of frequency (100 Hz–1 MHz) at different temperature (30–400 °C) show that the compounds have a diffuse ferroelectric phase transition. As we increase z, transition temperature shifts towards higher temperature side. The dc conductivity of the material (as evaluated from the impedance analysis) has been observed to be ∼10⁻⁸ S cm⁻¹ at room temperature (RT) and ∼10⁻⁴ S cm⁻¹ at 550 °C which has indicated a typical semiconductor like behavior with negative temperature coefficient of resistance (NTCR).     

Synthesis and dc conductivity of Nd2/3TiO2.988

The A-site deficient perovskite Nd_2/3TiO_3 − δ was synthesized under an H₂–CO₂ gas mixture. The sample was found to have slight oxygen deficiency of δ∼0.012. The crystal structure was assigned to a double perovskite structure with orthorhombic space group Pmmm, as in the case of La_2/3TiO_3 − δ. Electrical conductivity measurement has also been performed. The temperature dependence of conductivity shows that electronic transport in Nd_2/3TiO_2.988 is well described by Emin–Holstein adiabatic small polaron model. The polaron density extracted from the conductivity measurement is ∼1.96 × 10²⁰ cm^− 3. This result agrees well with nominal polaron density for Nd_2/3TiO_2.988, ∼2.1 × 10²⁰cm^− 3. We have also derived important quantities for transport in Nd_2/3TiO_2.988.     

How to use electrodeless drift chambers in experiments at accelerators

Several types of wide-gap electrodeless drift chambers, including those with dimensions 1×1 m², have been tested at accelerator beams. The chambers work with high efficiency (>99%), good spatial resolution (σ = 0.2−0.4 mm) and good linearity at flux rates up to 2×10⁵ particles⁻¹ per wire in spill, which corresponds to 3×10⁶ particles/s m² on colliders.It is shown that at the proper mode of operation beam intensity oscillations within the range of up to 4×10⁵ particles/spill per wire do not affect the chamber efficiency.     

Development of fast neutron profiling method

We discuss the effects of neutron scattering and γ-ray background in fast neutron imaging and the method to reduce them. As a profiling device, a combination of an imaging plate (IP) and a polypropylene film (CH₂) has been employed in this study. Good profiles were obtained by employing appropriate neutron energy, a CH₂ thickness and geometry for accelerator-based fast neutrons (5–14 MeV). The neutron flux was ∼3.5×10⁴ cm⁻² s⁻¹ in the CH₂–IP position. Furthermore, we are designing the device using a position-sensitive photomultiplier in order to improve the signal-to-noise ratio by obtaining the information of pulse height for particle selection together with position.     

High field kinetics of photocurrent in GaSe amorphous films

The drift mobility of current carriers μ = (2–7)10⁻⁸cm²/V·s and their lifetime τ = 10–17μs have been determined and a cubic dependence of photogeneration charge on electric field has been obtained in the 5×10⁵ to 10⁶V·cm⁻¹ nange from the results of investigation of photocurrent kinetics in GaSe amorphous films.     

Enhancement of nonlinear optical susceptibility of CuPc films by ITO layer

In the present study, the Copper Phthalocyanine (CuPc)/ITO thin film was fabricated using thermal evaporation method. The structural property was analyzed by X-ray diffraction study and confirms that the thin film has been preferentially grown along (200) plane. The atomic force microscope study was carried out on deposited film and quality of thin films is assessed by calculating the roughness of the films. The direct and indirect band gap, linear and nonlinear optical characteristics of grown films were calculated by using UV–Vis–NIR spectrometer studies. The calculated values of the first direct and indirect band gaps (E_g1(d) & E_g1(ind)) are 1.879 and 1.644 eV as a fundamental gap, while the values of second direct and indirect band gap (E_g2(d) & E_g2(ind)) are 1.660 and 1.498 eV as an onset gap for CuPc. The values of nonlinear refractive index (n₂) and third order nonlinear optical susceptibility (χ³) are found to be 5 × 10⁻⁸ and 8 × 10⁻⁹ (theoretical) and 5.2 × 10⁻⁸ and 1.56 × 10⁻⁷ (experimental) respectively. The optical band and third order nonlinear properties suggest that the as-prepared films are may be applied in optoelectronic and nonlinear applications.     

A mercury jet as gas target window for high current beams

A mercury vapour jet is used to seal a 1 cm² aperture between a gas volume (“target chamber”) and the beam-line system. The possible pressure differences and the leakage related to the different target gas pressures have been investigated. Pressure gradients from 10¹ to 10⁻³ mbar and leakages of less than 3×10⁻³ mbar 1/s have been observed. The maximum target pressure was p_T=36 mbar.     

Laser acceleration of particles using resonance inversions of the Cherenkov effect

The possibility of Cherenkov accelerator development for physics experiments in the 10²–10⁶ TeV range is discussed in connection with the realization of some practical schemes of Cherenkov effect inversion using both the transverse homogeneous magnetic field and several Cherenkov waves. The required fields of 10⁻²–10⁵ TV/m can be obtained by double inversion of the Cherenkov effect in conventional and artificial ionic media. Calculations of particle dynamics were made taking into account the Coulomb scattering and radiation losses. The possibility of ∼ 10⁵ T magnetic fields generation by relativistic particle beams is also discussed.     

Space charge limited conduction in bulk Se100 − xSbx chalcogenide glasses

The present paper reports the measurements on space charge limited conduction in bulk glassy Se_100 − xSb_x (x = 2, 4, 6, 8). I–V characteristics have been measured at various fixed temperatures. These characteristics show that, at low electric fields, an ohmic behaviour is observed. However, at high electric fields (E ∼10⁴ V/cm), the current becomes superohmic.At high fields (10⁴ V/cm), current could be fitted to the theory of space charge limited conduction in case of uniform distribution of localized states in the mobility gap of these materials. Using the theory of SCLC for the uniform distribution of the traps, the density of localized states near Fermi level is also calculated. Density of localized states initially increases with Sb concentration till 6 at.% of Sb and then decreases with further increase of Sb. This decrease is explained in terms of average coordination number.     

Indium selenide film formation by the double-source evaporation of indium and selenium

Films of γ-In₂Se₃ are easily obtained by the evaporation of indium and selenium with the supply ratio R = [Se]/[In] above 1.7 and the substrate temperature T_s above 170°C. InSe films are obtained when R ≈ 1.2 and T_s > 100°C. The electrical conductivities of γ-In₂Se₃ and InSe films are about 10⁻¹⁰−10⁻⁷ and 10⁻⁶ S cm⁻¹ respectively. The band gap of γ-In₂Se₃ is estimated to be about 2 eV in this study.The mechanism of film formation is also discussed.     

Trigger system for the TOPAZ detector at TRISTAN,KEK

A trigger system for the TOPAZ detector at the TRISTAN e⁺e⁻ collider has been developed. The system consists of an energy trigger and a track trigger. The track trigger uses track information from the inner drift chamber, the time-of-flight counters and the time projection chamber. A three-dimensional track reconstruction is performed with high-speed logic arrays. The design and the performance are described.     

Secondary particle identification using the relativistic rise in ionization

We report on the data analysis and techniques used to determine particle identification from the relativistic rise in ionization as detected by CRISIS, a 1 × 1 × 3 m³, 192 cell, ionization-sampling drift chamber containing an 80% argon/20% carbon dioxide gas mixture. For 100 GeV/c protons/antiprotons (pions) we obtain an ionization FWHM of 7.6% (7.9%), which compares well with the design value of 7.8%. The separation between the mean ionization values for the protons and pions was determined to be 7.9%. We also present the analysis of particle identification for secondary particles produced by interactions in the bubble chamber. A statistical method for correcting for the overlapping ionization curves from secondary protons/antiprotons and pions is discussed.     

Neutron flux measurements with a Li2B4O7 crystal

The effect of neutron irradiation on a lithium tetraborate (Li₂B₄O₇, LBO) single crystal has been investigated. The crystals of high optical quality are found to be quite stable under high neutron fluence. This study shows that LBO crystals can be used as a proportional counter for neutron fluxes of the order 10⁹ cm⁻² s⁻¹ and higher. The detectors fabricated were found to have a sensitivity of ∼3×10⁻¹⁸ A (nv)⁻¹.     

Phase space compression of muon beams

A phase space compression technique applicable to short-lived particles is proposed. Its specific feature is that it treats each single particle separately by measuring its phase via position sensitive particle detectors and steers it via pulsed electromagnetic deflection. By applying the method to muons, very high quality low energy beams can be obtained. A specific design is presented that should allow to achieve a 50 keV muon beam with 0.1π mm mrad transverse emittance and 10⁴ s⁻¹ intensity. These muons can be further decelerated to ultralow energies so that for example a 50 eV beam with 3π mm mrad and Δp/p = 10⁻³ is obtained. The overall phase space compression compared to the entrance beam exceeds 10¹⁵. With such beams, stopping of muons in atomic beams or on the first atomic layer of a solid can be envisioned. A short list of possible physics applications is given.     

Sonochemical synthesis of Fe-doped Cu3Se2 nanoparticles: Correlation of the strain and electrical properties for optoelectronics applications

This research presents the effect of different concentrations of iron (Fe) as dopants on the physical properties of the copper selenide (Cu₃Se₂) nanoparticle (NPs). The physical properties of the Cu₃Se₂ NPs were investigated using structural, morphological, and optical analysis. The results revealed that the Fe concentrations change the crystallite size (from ∼8 to 44 nm) and strain (from ∼0.0007 to 0.0030). Fe-doped Cu₃Se₂ NPs showed a higher optical energy band gap in comparison to the un-doped sample (1.80 eV). The films prepared by green binder (ethyl cellulose) indicated that the sample with minimum Fe concentration presents the highest carrier concentration (9.56e+18 cm⁻³) and lowest ideality factor (2.02) amounts. The electrical study shows space charge limited current (SCLC) mechanism in Fe-doped Cu₃Se₂ NPs that is not observed in un-doped sample. Using this mechanism, the highest carrier mobility (16.22 cm⁺²V⁻¹s⁻¹) obtained for sample with the lowest amount of Fe concentrations.     

Electroresistance and magnetoresistance in La0.9Ba0.1MnO3 thin films

The electroresistance and magnetoresistance effects have been investigated in La_0.9Ba_0.1MnO₃ epitaxial thin films. Tensile strain caused by substrate mismatch makes the Curie temperature T_C of the film at ∼300 K. The influence of an applied dc-current on the resistance in the absence of a magnetic field was studied. Significant change of the peak resistance at different currents was found. The reduction of the peak resistance reaches ∼27% with an electric current density up to 1.3 × 10⁵ A cm⁻². We also studied colossal magnetoresistance (CMR) effect in the films. Applying a magnetic field of 2 T could lead to a magnetoresistance as large as 42%. The reduction of resistance caused by a current density ∼1.3 × 10⁵ A cm⁻² was found to be equivalent to the CMR effect caused by 1.5 T near T_C. The phenomenon that the resistance in CMR manganites could be easily controlled by the electric current should be of high interest for both fundamental research and practical applications.