Precise half-life measurement of the 26Si ground state

The β-decay half-life of ²⁶Si was measured with a relative precision of 1.4·10^?3. The measurement yields a value of 2.2283(27) s which is in good agreement with previous measurements but has a precision that is better by a factor of 4. In the same experiment, we have also measured the non-analogue branching ratios and could determine the super-allowed one with a precision of 3%. The experiment was done at the Accelerator Laboratory of the University of Jyväskylä where we used the IGISOL technique with the JYFLTRAP facility to separate pure samples of ²⁶Si.     

A laser sensor of a seismic slope of the Earth surface

A principally new method of the measurement of a seismic slope of the Earth surface is suggested. The method makes it possible to stabilize the position of the laser beam as a highly extended coordinate axis in the metrological support of the precision construction of large-scale physical installations. The method has been tested experimentally: for the first time, low-frequency periodic angular oscillations have been registered with an amplitude of 5 × 10^?7 rad and the noise registration value of 2.5 × 10^?8 rad. The measurements were taken at CERN, during the construction of the spectrometric complex ATLAS.     

Monochromatic neutrinos from the annihilation of fourth-generation massive stable neutrinos in the Sun and in the Earth

The accumulation of relic fourth-generation heavy neutrinos (of mass 50 GeV) in the Earth and the Sun, which is followed by their annihilation, is considered. The most conservative estimates of the fluxes of monochromatic electron, muon, and tau neutrinos and antineutrinos of energy 50 GeV from the annihilation of heavy neutrinos are 4.1×10^?6 cm^?2 s^?1 from Earth’s core and 1.1×10^?7 cm^?2 s^?1 from Sun’s core, whence it follows that an analysis of data from underground neutrino observatories may furnish additional information about the existence of fourth-generation neutrinos. It is shown that, because of kinetic equilibrium between the arrival of cosmic neutrinos and their annihilation, the existence of new U(1) gauge interaction of fourth-generation neutrinos has virtually no effect on the estimates of the annihilation fluxes of electron, muon, and tau neutrinos.     

New measurements with a torsion pendulum during the solar eclipse

During the solar eclipse of 11 July 1991 in Mexico the period of a torsion pendulum was measured in order to reexamine possible anomalies observed in previous experiments of this kind. In our experiment no significant change was found as the relative change in the period associated with the eclipse was less than 2.0×10^–6 (90% confidence). Results were similar to our previous ones made during the eclipse in 1990 in Finland when the Sun was much lower in the horizon. However, two small but distinct shifts were observed in the horizontal position of the pendulum wire which were well correlated with the beginning and the end of the eclipse.     

Untersuchung der Polarisationsebene von Photonen nach Compton-Streuung an polarisierten Elektronen

Two polarization phenomena in Compton scattering by polarized electrons were investigated. In the first experiment, the rotation of the polarization plane of photons passing through magnetized iron and gadolinium was measured. This effect arises from a spin dependence of the Compton forward scattering amplitude. For 228 and 333 keV photons and iron absorbers, the observed rotation angles areφ ₀=(3.90±0.57) ×10^?3 rad · cm^?2 and (4.75±0.58)×10^?3 rad · cm^?2, respectively. Secondly, the orientation of the photon polarization plane after scattering of unpolarized photons by polarized electrons was measured. This experiment tests time reversal invariance in quantum electrodynamics. No dependence of the polarization plane on the direction of the electron spin was found within 2×10^?3.     

Determination of the thermal noise limit in test of weak equivalence principle with a rotating torsion pendulum

Thermal noise is one of the most fundamental limits to the sensitivity in weak equivalence principle test with a rotating torsion pendulum. Velocity damping and internal damping are two of many contributions at the thermal noise, and which one mainly limits the torsion pendulum in low frequency is difficult to be verified by experiment. Based on the conventional method of fast Fourier transform, we propose a developed method to determine the thermal noise limit and then obtain the precise power spectrum density of the pendulum motion signal. The experiment result verifies that the thermal noise is mainly contributed by the internal damping in the fiber in the low frequency torsion pendulum experiment with a high vacuum. Quantitative data analysis shows that the basic noise level in the experiment is about one to two times of the theoretical value of internal damping thermal noise.     

Measurement of the Hydrodynamic Efficiency of Laser Plasma at the “Kanal-2” Installation using Aluminum and Copper Targets

The results of experimental measurements of the hydrodynamic efficiency of laser plasma for aluminum and copper targets are presented. The studies were performed on the “Kanal-2” laser setup system using the ballistic pendulum method. The pressure in the interaction chamber was 10^?4 Torr, the pendulum length was 145 mm, the mass of the pendulum with a target was 7.2 g. At the half-height pulse duration of 2.5 ns, the power density on the target surface was ～10¹³ W/cm². In the case of aluminum target, the hydrodynamic efficiency coefficient increased from 1.5% to 4.5% with increasing laser pulse energy from 5 J to 10 J, whereas it remained at the level of 5% for the copper target.     

The temperature stability of 0.005°C for the concrete floor in the CERN Transfer Tunnel #1 hosting the Precision Laser Inclinometer

To reach a sensitivity level of ~10^–9 rad for the Precision Laser Inclinometer (PLI) for the registration of the Earth surface angular oscillation in the low frequency band of [10^–6 Hz; 1 Hz] the temperature stability of the CERN Transfer Tunnel #1 has been investigated. The daily temperature variation was 0.082°C for the air and 0.005°C for the concrete floor. The last result opened the possibility to observe the Earth surface inclination caused by Moon and Sun if the PLI is thermally stabilized by the massive monolithic concrete floor of the tunnel.     

Resonance shifts in ABMR due to inhomogeneities of the magnetic and rf-fields

On the basis of the non-relativistic time dependent Schrödinger theory shifts of the resonance frequency due to an arbitrary inhomogeneity of the rf-field with respect to amplitude, direction and phase, and shifts due to small inhomogeneities of the magnetic field are considered. A general relation is derived by which one can find the appropriate experimental methods to determine the shifts without a detailed knowledge of the actual line shapes. Usually small effects as shifts due to non-constant field direction or due to neighbouring states are included in the formalism. The results have been used successfully in precision experiments in which frequency shifts of about 10^?2 of the resonance width were eliminated up to a few 10^?5.     

The search for neutrino bursts from core collapse Supernovae at the Baksan Underground Scintillation Telescope

The current status of the experiment on recording neutrino bursts from core collapse stars is presented. The actual observational time T (from June 30, 1980 until December 31, 2009) is 25.58 years. An upper bound of the mean frequency of gravitational collapse in our Galaxy f _col < 0.090 year^?1 at a 90% confidence level. The results of studying single events at the facility in the case of muon inelastic interaction of cosmic rays with the matter of the detector are presented.     

CW EPR, echo-detected EPR, and field-step ELDOR study of molecular motions of nitroxides ino-terphenyl glass: Dynamical transition, dynamical heterogeneity and β-relaxation

Continuous-wave electron paramagnetic resonance (CW EPR), echo-detected (ED) EPR, and field-step electron-electron double resonance (FS ELDOR) were simultaneously applied to study molecular motions of nitroxide spin probes of two different types in glassyo-terphenyl. A strong linear temperature dependence of the overall splitting of the CW EPR lineshape was found for nitroxide Tempone and only a weak one for a phenyl-ring-containing imidasoline nitroxide. The linear temperature dependence of the splitting is explained within the model of harmonic librations. The assessed libration frequency for Tempone is of the order of 3·10¹² rad/s. The observed remarkable difference between the two nitroxides is explained by the different strength of interactions between guest and host molecules and by dynamical heterogeneity of the glass. The nonlinear temperature dependence above 250 K is attributed to the onset of anharmonic motion that is postulated in a number of neutron scattering and Mössbauer spectroscopy studies for molecular glasses and proteins (the so-called dynamical transition). Above 245 K also ED EPR spectra change drastically, which may be explained on the same ground. Magnetization transfer was observed in FS ELDOR for nitroxide Tempone, with a time constant around 10^?5 s. It was found to be almost temperature-independent between 160 K and 265 K and was attributed to the Johari-Goldstein β-relaxation process. For the phenyl-ring-containing imidasoline nitroxide this transfer was not observed, which may be explained again by the dynamical heterogeneity of the glass and by small effectivity of the β-relaxation process in this case.     

精密扭摆研究

本研究旨在提高扭摆精度。扭摆采用大理石——这取自地球的天然材料作摆盘;通过试验,挑选了Q值高、内耗小、剪切模量温度系数接近于零的恒弹性合金丝作为吊丝。特别是,我们把Saxl类型的每周期吸合一次的间断振荡摆回复到小阻尼情况下的自由振荡摆,减少对摆振动的人为干预;增加真空条件,以减少周围环境干扰,延长了阻尼时间;同时在摆盘中央安放多面反射镜环,增加测量点,变一周期仅测一次时间为同一周期测四次以上。这就提供了用计算机求阻尼振荡方程θi=Ae^-t_i/τsin(ωt_i+φ)数值解的条件,不但可直接测得周期T的变化,而且可望计算得振幅A、阻尼时间τ、初相角φ的变化。另外,在光电接收方面也作了一些改进。通过这些措施,我室的精密扭摆对周期的探测精度已比美国Saxl 1964年发表第一篇文章时的扭摆精度提高100倍;比其运转17年,经一再改进的扭摆精度提高10倍。测量有效数字6位至7位,周期相对误差一般达2×10^-6,最佳状况可达8×10^-7,基本达到预期设计要求,为将来探测引力异常,“区分长期间与短期间内频率起伏”提供了可能性。 关键词：     

Precise Underwater Distance Measurement by Dual Acoustic Frequency Combs

Underwater acoustics is of fundamental importance for marine science and technology. However, acoustic waves transmitted by state‐of‐the‐art underwater acoustic systems are not inherently phase locked, which hinders the development of underwater acoustic technology. For example, the precision of underwater distance measurement can only achieve centimeter level. As a versatile tool, optical frequency combs have enabled revolutionary progress in optical metrology and precision measurement. In parallel with optical frequency combs, here, the generation of fully stabilized, underwater acoustic frequency combs is reported, in which equidistant acoustic modes are produced via a hydroacoustic transducer. The precision of each individual acoustic mode is measured to be 10^?9 at 1 s and 10^?12 at 1000 s averaging times. Underwater distance measurements are carried out in an anechoic pool using a dual‐comb scheme. Comparison with reference values shows consistency within 50 µm (7 × 10^?6 in relative). The relatively long‐duration experiments at 7 m distance yield an Allan deviation of 1.8 µm (2.6 × 10^?7 in relative) at 1 s and further 480 nm (6.8 × 10^?8 in relative) at 40 s averaging times. The approach to acoustic frequency comb generation offers a promising and powerful platform for future underwater distance measurement, positioning, and navigation.     

The nEDM experiment at the SNS

The nEDM collaboration proposes to measure the neutron electric dipole moment at the Spallation Neutron Source (Oak Ridge National Laboratory). The nEDM is a clear signature of CP violation. According to the Standard Model the nEDM is very small (～10^?31 e cm), but many theories predict much higher values. In the proposed experiment polarized cold neutrons from the SNS would be trapped in liquid helium at a temperature of about 400 mK. The neutron spin would precess in a very uniform magnetic field (H ～ 30 mG), and the experiment would measure the change in the precession frequency when a very strong electric field (E ～ 50 kV/cm) is applied. Polarized ³He atoms serve as a co-magnetometer. The goal of the experiment is to measure the nEDM with an accuracy of ～9 × 10^?28 e cm, which is more than an order of magnitude better than existing results.     

X-ray-line plasma satellites of ions in solid target plasmas produced by picosecond laser pulse

The X-ray lines of ions in a solid target interacting with picosecond laser pulses of moderate intensity (2×10¹⁷ W/cm²) were measured on the “Neodim” laser facility. X-ray Ly _α emission spectra of hydrogen-like fluorine ions were observed. Satellite lines were also observed, evidencing the presence of intense plasma oscillations. The positions and separation between the satellites allow their assignment to the intense electrostatic oscillations with an amplitude larger than 10⁸ V/cm and a frequency of about 7× 10¹⁴ s^?1 that is noticeably lower than the laser frequency ω_las～1.8×10¹⁵ s^?1. It is suggested that these oscillations may be due to strong plasma turbulence caused by the development of plasma oscillations of the Bernstein-mode type under the action of a strong magnetic field generated in plasma. The experimental results are compared with the calculated spectra of multicharged ions.     

Performance of the far‐IR beamline of the 6 MeV tabletop synchrotron light source

The performance of the far‐infrared (FIR) beamline of the 6 MeV tabletop synchrotron light source MIRRORCLE‐6FIR dedicated to far‐infrared spectroscopy is presented. MIRRORCLE‐6FIR is equipped with a perfectly circular optical system (PhSR) placed around the 1 m‐long circumference electron orbit. To illustrate the facility of this light source, the FIR output as well as its spectra were measured. The optimum optical system was designed by using the ray‐tracing simulation code ZEMAX. The measured FIR intensity with the PhSR in place is about five times higher than that without the PhSR, which is in good agreement with the simulation results. The MIRRORCLE‐6FIR spectral flux is compared with a standard thermal source and is found to be 1000 times greater than that from a typical thermal source at ～15 cm^?1. It is also observed that the MIRRORCLE‐6FIR radiation has a highly coherent nature. The broadband infrared allows the facility to reach the spectral range from 10 cm^?1 to 100 cm^?1. MIRRORCLE‐6FIR, owing to a large beam current, the PhSR mirror system, a large dynamic aperture and small ring energy, can deliver a bright flux of photons in the FIR/THz region useful for broadband spectroscopy.     

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.     

On the Possibility of Testing the Weak Equivalence Principle with Artificial Earth Satellites

In this paper we examine the possibility of testing the equivalence principle, in its weak form, by analyzing the orbital motion of a pair of artificial satellites of different composition moving along orbits of identical shape and size in the gravitational field of the Earth. It turns out that the obtainable level of accuracy is, realistically, of the order of 10^–10 or slightly better. It is limited mainly by the fact that, due to the unavoidable orbital injection errors, it would not be possible to insert the satellites in orbits with exactly the same radius and that such difference could be known only with a finite precision. The present–day level of accuracy, obtained with torsion balance Earth–based measurements and the analysis of the Earth–Moon motion in the gravitational field of the Sun with the Lunar Laser Ranging technique, is of the order of 10^–13. The proposed space–based missions STEP, SCOPE, GG and SEE aim to reach a 10^–15–10^–18 precision level.     

Motion of the spin of particles and nuclei of arbitrary spin in the electric field of crystals

The possibility of verifying the conclusions of quantum theory on the motion of the spin of particles and nuclei of arbitrary spin in an electric field is analyzed. The theory predicts that the planar channeling of particles and nuclei with higher spins (one or more) through straight crystals is accompanied by the rotation of their spin. For some nuclei, the spin-rotation angle per unit length is about 10^?1 rad/cm. For ultrarelativistic nuclei undergoing planar channeling through bent crystals, the spin-rotation angle per unit length is on the order of 1 rad/cm, which makes it possible to verify the validity of the Bargmann-Michel-Telegdi equation for particles and nuclei of higher spins.     

Transient changes in quartz resonators following exposure to pulse ionization

Abstract

This paper is a review of the transient effect of pulse ionization on the resonant frequency and Q of quartz resonators. A number of different samples of both natural and synthetic quartz crystals have been used. Fifth-overtone 5, 32, and 125 MHz thickness shear (AT-cut) crystal units were fabricated and studied using several different oscillator circuits, one of which was designed such that the resistance R_s (αQ ^?1) of the crystal unit at series resonance as well as frequency could be measured after pulse exposure. With the exception of one purposely altered crystal, all the resonators exhibited a negative-transient frequency offset after irradiation which thereafter anneals as a function of t ^?1/2 over nearly four decades of time. The pulse irradiation effect on Q ^?1 is most striking at 5 MHz in natural quartz units, which suffer a thirty-fold increase in acoustic absorption after exposure to 10⁴ rad. The transient increase in the acoustic absorption in natural quartz anneals within 10 seconds to a value somewhat larger than the preirradiation absorption. Theoretical models are described which account for these observations.