Experimental test of the nonlinearity of the characteristics of the piezoelectric transducer of the phase modulator of a fiber ring interferometer at small sinusoidal deformations

We show that the level of the second harmonic of sinusoidal modulation resulting from the non-linearity of the characteristics of piezoelectric transducer does not exceed0.005–0.0005% for deformations ranging from10−8 to10−6. The influence of the nonlinearity of the characteristics of a piezoelectric transducer used as a modulator of the optical length of the loop of a fiber ring interferometer on the accuracy parameters of the latter is analyzed. It is shown that the given level of the second harmonic does not lead to a significant shift of the zero of the interference of counterpropagating waves at the interferometer output. Institute of Applied Physics, Russian Academy of Sciences; Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 2, pp. 198–200, February 1999.     

Atom interferometry measurement of the electric polarizability of lithium

Using an atom interferometer, we have measured the static electric polarizability of ⁷Li α=(24.33 ±0.16)×10^-30 m³ = 164.2±1.1 atomic units with a 0.66% uncertainty. Our experiment, which is similar to an experiment done on sodium in 1995 by Pritchard and co-workers, consists in applying an electric field on one of the two interfering beams and measuring the resulting phase-shift. With respect to Pritchard's experiment, we have made several improvements which are described in detail in this paper: the capacitor design is such that the electric field can be calculated analytically; the phase sensitivity of our interferometer is substantially better, near 16 mrad/ ; finally our interferometer is species selective so that impurities present in our atomic beam (other alkali atoms or lithium dimers) do not perturb our measurement. The extreme sensitivity of atom interferometry is well illustrated by our experiment: our measurement amounts to measuring a slight increase Δv of the atom velocity v when it enters the electric field region and our present sensitivity is sufficient to detect a variation Δv/v ≈6 ×10^-13.     

A new type of quantum interferometer for gravitational wave detection

We present an orientational quantum interferometer sensitive to gravitational waves that is based on orienting quantum objects like molecules, atoms, or nuclei in space. The detection principle is based on inducing non-sphericity to the corresponding wave functions by light-pulses. In the field of a gravitational wave these objects then possess spectra that depend on their orientation in space. In our measurement scheme we investigate the adiabatic influence of a monochromatic gravitational wave over a quarter gravitational wave period and compare the corresponding frequencies at instances with maximal and vanishing gravitational wave elongation. We therefore explore the effect over a quarter gravitational wave period (or wavelength) and the resulting frequency shift scales with the binding energy of the system times the amplitude of the gravitational wave. In particular, a gravitational wave with amplitude h = 10⁻²³ will induce a frequency shift of the order of 110 μHz for an atom interferometer based on a 91-fold charged uranium ion.     

Modification of nanostructured states in ion-implanted platinum

The formation of nanostructures in subsurface volumes of Pt as a result of the implantation of Ar⁺ ions (E = 30 keV, F = 10¹⁶−10¹⁸ cm⁻²) was studied by the method of field ion microscopy. This phenomenon was observed at distances not less than 60 nm from the irradiated surface of the metal (at F = 10¹⁸ cm⁻²). It was established that the optimum regime for obtaining nanocrystalline structures in subsurface volumes of ion-implanted platinum is irradiation to F = 10¹⁷ cm⁻² (E = 30 keV, j = 200 μA cm⁻²). In such a regime, the formation of nanoblock structures is observed at distances not less than 20 nm from the irradiated surface, rather than the formation of vacancy pores.     

Development of an atom gravimeter and status of the 10-meter atom interferometer for precision gravity measurement

Experimental realizations of cold ⁸⁵Rb atom interferometers in Wuhan are reviewed in this paper. The application of atom interferometers in local gravity measurement are reported. The resolutions of gravity measurement are 2.0 × 10⁻⁷g for 1 s and 4.5 × 10⁻⁹g for 1,888 s. The absolute g value was derived with a difference of 1.6 × 10⁻⁷g compared to the gravity reference value. The tidal phenomenon was observed by continuously monitoring the local gravity over 123 h. A 10-meter atom interferometer designed for precision gravity measurement and the equivalence principle test is under construction, the latest status is reported for the first time.     

Laser interferometry of acoustic fields generated by high-current electron beams in solids

We have developed a method for detecting acoustic fields in solids irradiated with dense electron beams. The method is based on laser Michelson interferometry. The electron source is a high-current DZhIN electron accelerator. The detection system features a short baseline Michelson interferometer located inside the experimental chamber with the sample, a stabilized initial beam pathlength difference within the interferometer, high temporal resolution, an analog-to-digital converter with output to a personal computer, and a program for reducing the interferometer data. We can measure both long pulses with minimum displacements of 10⁻¹⁰ m and durations of 10⁻⁸ sec, and flexure waves with large-amplitude displacements of 10⁻⁵ m and oscillation periods of 10⁻³ sec. We present results from studies of flexure waves in thin plates and rods of copper, silicon, alkali-halide crystals, quartz glasses, and D16T aluminum alloy irradiated by nanosecond high-density electron beams. Institute of High-Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 82–92, November, 1997.     

Phase-coherent comparison of two optical frequency standards over 146 km using a telecommunication fiber link

We have explored the performance of two “dark fibers” of a commercial telecommunication fiber link for a remote comparison of optical clocks. The two fibers, linking the Leibniz University of Hanover (LUH) with the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, are connected in Hanover to form a total fiber length of 146 km. At PTB the performance of an optical frequency standard operating at 456 THz was imprinted to a cw transfer laser at 194 THz, and its frequency was transmitted over the fiber. In order to detect and compensate phase noise related to the optical fiber link we have built a low-noise optical fiber interferometer and investigated noise sources that affect the overall performance of the optical link. The frequency stability at the remote end has been measured using the clock laser of PTB’s Yb⁺ frequency standard operating at 344 THz. We show that the frequency of a frequency-stabilized fiber laser can be transmitted over a total fiber length of 146 km with a relative frequency uncertainty below 1×10⁻¹⁹, and short term frequency instability given by the fractional Allan deviation of σ _y (τ)=3.3×10⁻¹⁵/(τ/s).     

Probing for new physics and detecting non-linear vacuum QED effects using gravitational wave interferometer antennas

Low energy non-linear QED effects in vacuum have been predicted since 1936 and have been subject of research for many decades. Two main schemes have been proposed for such a ‘first’ detection: measurements of ellipticity acquired by a linearly polarized beam of light passing through a magnetic field and direct light–light scattering. The study of the propagation of light through an external field can also be used to probe for new physics such as the existence of axion-like particles and millicharged particles. Their existence in nature would cause the index of refraction of vacuum to be different from unity in the presence of an external field and dependent of the polarization direction of the propagating light. The major achievement of reaching the project sensitivities in gravitational wave interferometers such as LIGO and VIRGO has opened the possibility of using such instruments for the detection of QED corrections in electrodynamics and for probing new physics at very low energies. We show that it is possible to distinguish between various scenarios of new physics in the hypothetical case of detecting unexpected values. Considering the design sensitivity in the strain of the near future VIRGO+ interferometer leads to a variable dipole magnet configuration such that B ² D≥13000 T² m  for a ‘first’ vacuum non-linear QED detection.     

Massive spin-momentum entanglement measured in an atomic beam spin echo experiment

In this paper we present an experiment performed with an atomic beam spin echo interferometer, in which massive intraparticle entanglement is demonstrated. In the longitudinal Stern-Gerlach arrangement the nuclear spin and linear momentum of ³He particles are inextricably linked, such that the overall system state cannot be written as the tensor product of the corresponding Hilbert spaces. The measured data show maximal entanglement between ℋ _I and ℋ _p . This hybrid system of one quantum and one classical degree of freedom is a textbook example of entanglement between discrete and continuous observables.     

Nonequilibrium motion of a metal surface exposed to submicrosecond laser pulses

The results of experimental studies and theoretical analysis of the displacement of a metal mirror surface upon heating by submicrosecond laser pulses (t ₀ = 15 × 10⁻⁹ s) are reported. The dynamics of the surface displacement in the irradiation zone was monitored by a Michelson interferometer with photoelectron count of fringes. A substantial delay of the motion of the exposed surface relative to a heating pulse was observed in experiments. It is shown that under thermal perturbations with high temperature gradients corresponding to large optical absorption coefficients, the contribution of nonequilibrium processes to the thermomechanical response of metals becomes decisive even for a submicrosecond duration of heating. The allowance for nonequilibrium processes in theoretical analysis leads to the generalized Duhamel law with thermal memory, which can be used for describing the observed effect correctly. The resultant characteristic time of a transient process (∼(2–6) × 10⁻⁸ s) considerably exceeds the available estimates of the phonon-phonon interaction time and is due to the effect of nonequilibrium processes on the scale of structural elements, which is considerably larger than the atomic scale.     

Production of medical radioisotopes with high specific activity in?photonuclear reactions with γ-beams of high intensity and?large brilliance

We study the production of radioisotopes for nuclear medicine in (γ,xn+yp) photonuclear reactions or (γ,γ′) photoexcitation reactions with high-flux [(10¹³–10¹⁵)γ/s], small diameter ∼(100 μm)² and small bandwidth (ΔE/E≈10⁻³–10⁻⁴) γ beams produced by Compton back-scattering of laser light from relativistic brilliant electron beams. We compare them to (ion,xn+yp) reactions with (ion = p,d,α) from particle accelerators like cyclotrons and (n,γ) or (n,f) reactions from nuclear reactors. For photonuclear reactions with a narrow γ-beam the energy deposition in the target can be managed by using a stack of thin target foils or wires, hence avoiding direct stopping of the Compton and pair electrons (positrons). However, for ions with a strong atomic stopping only a fraction of less than 10⁻² leads to nuclear reactions resulting in a target heating, which is at least 10⁵ times larger per produced radioactive ion and often limits the achievable activity. In photonuclear reactions the well defined initial excitation energy of the compound nucleus leads to a small number of reaction channels and enables new combinations of target isotope and final radioisotope. The narrow bandwidth γ excitation may make use of the fine structure of the Pygmy Dipole Resonance (PDR) or fluctuations in γ-width leading to increased cross sections. Within a rather short period compared to the isotopic half-life, a target area of the order of (100 μm)² can be highly transmuted, resulting in a very high specific activity. (γ,γ′) isomer production via specially selected γ cascades allows to produce high specific activity in multiple excitations, where no back-pumping of the isomer to the ground state occurs. We discuss in detail many specific radioisotopes for diagnostics and therapy applications. Photonuclear reactions with γ-beams allow to produce certain radioisotopes, e.g. ⁴⁷Sc, ⁴⁴Ti, ⁶⁷Cu, ¹⁰³Pd, ^117m Sn, ¹⁶⁹Er, ^195m Pt or ²²⁵Ac, with higher specific activity and/or more economically than with classical methods. This will open the door for completely new clinical applications of radioisotopes. For example ^195m Pt could be used to verify the patient’s response to chemotherapy with platinum compounds before a complete treatment is performed. Also innovative isotopes like ⁴⁷Sc, ⁶⁷Cu and ²²⁵Ac could be produced for the first time in sufficient quantities for large-scale application in targeted radionuclide therapy.     

Laser produced plasma: A pumping source for cadmium photo-ionization laser

We report laser oscillations in Cd II on 4d ⁹5s ^{2 2} D _5/2 − 4d ¹⁰5p ² P _3/2 transition at 441.6 nm using laser produced tungsten plasma as a pumping source. Mach Zehnder interferometer is used to measure electron density. Design and working of the crossed heat pipe used in the studies is discussed.     

Metastable rare gas atoms scattered by nano- and micro-slit transmission gratings

The transmission of metastable argon atoms through nano-slit or micro-slit gratings is studied by use of time of flight and angular analysis. This transmission departs from the simple geometric one essentially by two ways: (i) the elastic or diagonal part of the van der Waals (vW) interaction with the solid causes an angular narrowing of the emerging beam; (ii) the off-diagonal vW interaction induces the exothermal fine structure transition ³ P ₀↦³ P ₂ (ΔE = 175 meV) leading to large scattering angles; the resulting angular distribution is very sensitive to the roughness of the surface in the direction of the depth. An extension of these experiments to transversally coherent beams is proposed. It should be considered as a first step towards a new type of interferometer in which the inelastic diffraction makes the gratings work as beam splitters or mirrors. Received 6 July 2001 and Received in final form 17 September 2001     

Gravity waves accompanying supernova explosions

Gravitational radiation arising during the formation of a protoneutron star is studied. Here it is mainly large-scale nonuniformities that develop inside the star. The entropy and density profiles of such nonuniformities resemble the “mushroom cloud” of a nuclear explosion. A bubble of hot neutron matter floats to the surface of the star, like the “mushroom cloud” of an explosion in the earth’s atmosphere. Depending on the symmetry of the problem, from two to six bubbles can float upward at the same time. The characteristic masses of such bubbles are 0.01M _⊗ and the radial velocities reach ∼0.1c. The energy radiated in the form of gravitational waves in one cycle of bubbles floating to the surface is ∼10⁻² M _⊗ c ²−10⁻¹⁰ M _⊗ c ². Such cycles occur repeatedly as the neutron star cools. This phase can last up to seconds. The total energy radiated in the form of gravitational radiation can reach 10⁻¹ M _⊗ c ². Pis’ma Zh. éksp. Teor. Fiz. 64, No. 12, 817–822 (25 December 1996)     

Subthreshold ϕ-meson production and medium effects in proton-nucleus reactions

Within the spectral function approach, we study the direct production and decay via the dikaon (dimuon) channel of ϕ mesons in the interactions of 2.4-and 2.7-GeV protons with light and medium target nuclei. It is shown that the K ⁺ K ⁻ (μ⁺ μ⁻) invariant-mass distribution consists of the two components, which correspond to the ϕ decay “outside” and “inside” the target nucleus. The first (narrow) component has the free ϕ width, while the second (broad) component is distorted by the nuclear matter owing to resonance-nucleon scattering and a possible in-medium modification of the kaons and ρ meson at finite baryon density. The relative strength of the “inside” and “outside” components is analyzed in different scenarios for the ϕ width and momentum cut. It is demonstrated that the width of the resulting dimuon invariant-mass distribution on medium nuclei is larger than the free ϕ width by a factor of about 2 if the total ϕ in-medium width is used and the respective cutoff for the ϕ three-momentum is applied, whereas the resulting dikaon invariant-mass distribution has an insignificant sensitivity to the ϕ in-medium properties owing to the strong absorption of the K ⁻ in the surrounding nuclear matter. On the other hand, because of the distortion of the K ⁺ and K ⁻ on their way out of the target nucleus mainly due to the hadronic kaon potentials, the latter distribution is broadened and shifted to higher invariant masses, which means that the measurement of such broadening would give additional evidence for the modification of the kaon and antikaon properties in the nuclear medium. The text was submitted by the author in English.     

Noise spectrum of the 140-GHz gyrotron designed for controlled thermonuclear fusion installations

A method for measurement of gyrotron amplitude noise using the Mach-Zehnder interferometer as a rejection filter, the measurement facility, and results of testing a 140-GHz industrial high-power gyrotron are discussed. The method improved the sensitivity by two orders of magnitude over that of the direct detection method. The experimental relative power spectral density in a frequency range of 50–250 MHz from the line center is 7 × 10⁻²⁰–5 × 10⁻¹⁹ 1/Hz.     

Anharmonic force constants of GaSb from the measured third order elastic constants at 300°K

The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The constants at 300°K, in units of 10¹¹ N.m.⁻², are C_l11 = ™ 4 ·75 ± 0·06 C₁₄₄ = + 0·50 ± 0·25 C₁₁₃ = ™ 3 ·08 ± 0·02 C₁₆₆ = ™ 2·16 ± 0·13 C₁₂₃ = ™ 0 ·44 ± 0·29 C₄₅₆ = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based on modified Keating’s model. The constants are (in units of 10¹¹ N.m⁻²)γ=− 2·406;δ=0·407;ε=−0·222.     

The Szekeres Swiss Cheese model and the CMB observations

This paper presents the application of the Szekeres Swiss Cheese model to the analysis of observations of the cosmic microwave background (CMB) radiation. The impact of inhomogeneous matter distribution on the CMB observations is in most cases studied within the linear perturbations of the Friedmann model. However, since the density contrast and the Weyl curvature within the cosmic structures are large, this issue is worth studying using another approach. The Szekeres model is an inhomogeneous, non-symmetrical and exact solution of the Einstein equations. In this model, light propagation and matter evolution can be exactly calculated, without such approximations as small amplitude of the density contrast. This allows to examine in more realistic manner the contribution of the light propagation effect to the measured CMB temperature fluctuations. The results of such analysis show that small-scale, non-linear inhomogeneities induce, via Rees-Sciama effect, temperature fluctuations of amplitude 10⁻⁷–10⁻⁵ on angular scale ϑ < 0.24° (ℓ > 750). This is still much smaller than the measured temperature fluctuations on this angular scale. However, local and uncompensated inhomogeneities can induce temperature fluctuations of amplitude as large as 10⁻³, and thus can be responsible the low multipoles anomalies observed in the angular CMB power spectrum.     

Growth velocity and the topography of Ni-Zn binary alloy electrodeposits

We show that the electrodeposition of Ni-Zn alloys at the lowest growth velocities, v < 0.5μm/s, exclusively proceeds from an abnormal co-deposition phenomenon. The growth process in this v region greatly depends on the initial [Co²⁺] concentration of the film deposition bath. A theoretical approach of this process including the role of the saturation surface roughness of the alloy, , leads to an estimation of the transport properties of the ad-atoms involved during the deposit formation. Their surface diffusion coefficient varying between 1.76×10^-10 and 2.40×10^-8 cm^-2/s exhibits a minimal value, D _s = 2.10×10^-10 cm^-2/s located between v = 0.17 and 0.35μm/s. The spatial scaling analysis of the local roughness, σ, examined according to the power-law σ≈L ^α reveals that the resulting roughness exponents concurs with the Kardar-Parisi-Zhang dynamics including the restricted surface diffusion. Two main v regions leads to different fractal textural features of the alloy film surface. Below 0.10 μm/s, the roughness exponent obtained is α≈ 0.6, depicting a limited ad-atom mobility. Over v = 0.30μm/s, this exponent stabilises at α≈ 0.82, indicating an increase of the surface diffusion. Received 16 August 2000 and Received in final form 20 June 2001     

Table-top kHz hard X-ray source with ultrashort pulse duration for time-resolved X-ray diffraction

The interaction of ultrashort laser pulses with solid state targets is studied concerning the production of short X-ray pulses with photon energies up to about 10 keV. The influence of various parameters such as pulse energy, repetition rate of the laser system, focusing conditions, the application of prepulses, and the chirp of the laser pulses on the efficiency of this highly nonlinear process is examined. In order to increase the X-ray flux, the laser pulse energy is increased by a 2nd multipass amplifier from 750 μJ to 5 mJ. By applying up to 4 mJ of the pulse energy a X-ray flux of 4×10¹⁰ Fe K _α photons/s or 2.75×10¹⁰ Cu K _α photons/s are generated. The energy conversion efficiency is therefore calculated to η _Fe≈1.4×10⁻⁵ and η _Cu≈1.0×10⁻⁵. The X-ray source size is determined to 15×25 μm². By focusing the produced X-rays using a toroidally bent crystal a quasi-monochromatic X-ray point source with a diameter of 56 μm×70μm is produced containing ≈10⁴ Fe K _α1 photons/s which permits the investigation of lattice dynamics on a picosecond or even sub-picosecond time scale. The lattice movement of a GaAs(111) crystal is shown as a typical application.