Ratio Of Beam Size Research Articles

Experimental Demonstration of a Large Transverse Emittance Ratio 11∶1 in the Relativistic Heavy Ion Collider for the Electron-Ion Collider.

The Electron-Ion Collider (EIC), to be constructed at Brookhaven National Laboratory, will collide polarized high-energy electron beams with hadron beams, achieving luminosities of up to 1.0×10^{34} cm^{-2} s^{-1} in the center-of-mass energy range of 20-140GeV. To achieve such high luminosity, the EIC will employ small and flat beams at the interaction point. In the hadron storage ring of the EIC, the ratio of horizontal to vertical emittances is approximately 11∶1. In contrast, in previous or existing hadron colliders, the horizontal and vertical emittances are typically similar or closely matched. At the Relativistic Heavy Ion Collider (RHIC), we experimentally demonstrated a large transverse emittance ratio of 11∶1 with gold ion beams at a particle energy of 100GeV per nucleon, thanks to stochastic cooling and fine decoupling. Furthermore, we demonstrated collisions with flat beams, featuring a transverse beam size ratio of 3∶1 for the first time at the RHIC.

Enhancing earth-to-satellite FSO system spectrum efficiency with adaptive M-ary PSK and SIMO in presence of scintillation and beam wander

In this paper, the performance of the free-space optical (FSO) system from ground-to-satellite is analyzed considering the combined effect of atmospheric turbulence and beam wandering employing M-ary phase-shift keying (MPSK). Key parameters of the vertical connection, such as satellite altitude, zenith angle, and beam size, are investigated. In order to improve the spectrum efficiency, an adaptive transmission approach is applied to ensure efficient channel capacity usage. The procedure depends on changing the modulation order of the MPSK scheme according to the instantaneous channel state and the acceptable bit error rate. Furthermore, a single-input multiple-output (SIMO) system with maximal ratio combining (MRC) diversity is used to mitigate the effects of atmospheric turbulence and beam wandering. Closed-form and asymptotic expressions are presented for the average bit error rate (BER) for a single-input single-output (SISO) and SIMO techniques. Moreover, closed-form expression is deducted for the upper bound bandwidth efficiency. The accuracy of the derived closed-form and asymptotic expressions are verified by adopting appropriate simulation cases and parameters. The results show that the optimal value of the beam size ratio (BSZ) is 1.6. Also, the results prove that the adaptive technique improves spectrum efficiency by more four times the non-adaptive method at the same BER threshold of 10-2. By using a 1×4 SIMO system, the same adapted spectrum efficiency is achieved with a reduction of 4 dB in SNR versus 1×2 SIMO system and 8 dB in SNR versus SISO system. A 1×4 SIMO system achieves a threshold bit error rate of 5 dB reduction in SNR compared to a 1×2 SIMO system and a 10 dB reduction in SNR compared to SISO system.

Transmittance of Multi Gaussian Optical Beams for Uplink Applications in Atmospheric Turbulence

On-axis slant path uplink transmittance (used in short as transmittance throughout the text) for multi Gaussian optical beam in Kolmogorov atmospheric turbulent medium is investigated. It is observed that for both the flat-topped and the annular beams, as the propagation distance, wind speed and the zenith angle increase, the transmittance decreases. The transmittance of flat-topped beams increases when the number of beams, source size or the wavelength increases. For the annular beam, when the outer/inner beam size ratio is kept constant, larger source sizes yield larger transmittance values. Transmittance of the thicker annular beams is found to be larger than the transmittance of the thinner annular beams.

Analytical study on arbitrary waveform generation by MEMS micro mirror arrays

We provide analytical modeling and the detailed procedure that is used in recently proposed arbitrary waveform generation technique by using MEMS digital micro-mirror arrays. We estimate the achievable temporal resolution, repetition rate, modulation index and the rise/fall times of the final waveform as figure of merit in the proposed systems. We show that reducing the diffraction limit via increasing the ratio of beam size to lens focal length (>0.075) and the spatial modulation down to single mirror pitch size (10.8μm), waveforms up to 18GHz repetition rates with >90% modulation index and <100ps rise times are achievable. Theoretical calculations are compared with experimental generation of 120MHz square waves and 160MHz sawtooth waves and obtained good agreement.

Particle size analysis by transmission fluctuation spectrometry in the two-Phase flow irradiated by a rectangular narrow beam

The theory of transmission fluctuation spectrometry (TFS) has been developed as a new method of particle analysis in the two-phase flow. In our earlier publications, a circular beam is used whose intensity is uniform or of a Gaussian profile. In this work, the TFS theory is studied for the case of a rectangular narrow beam. The signal process of the transmission fluctuations is performed in the time and frequency domains and the corresponding analytical expression expressed in terms of the expectancy of the transmission square (ETS) is obtained. In addition, the correlation of the fluctuating transmission signals is studied, expressed in terms of the expectancy of the transmission product (ETP). Numerical calculation shows that the transition function of the transmission fluctuation spectrum is sensitive to both the ratio of beam size to particle size and the shape of the beam cross section.

Numerical modelling of passively Q-switched intracavity Raman lasers

Assuming intracavity photon densities to be of Gaussian spatial distributions, the space-dependent rate equations of passively Q-switched intracavity Raman lasers are deduced for the first time for the pumping beams of Gaussian and top-head spatial distributions, respectively. The new rate equations are normalized and solved numerically to investigate the influences of the normalized initial population inversion density, normalized Raman gain coefficient, saturable absorber parameter, beam size ratio of pump to fundamental laser and loss ratio of the first Stokes to fundamental laser on the pulse parameters of the first Stokes. The results of the Gaussian and top-head pumpings show similar trends despite some discrepancies. The new theories and numerical results will help design passively Q-switched intracavity Raman lasers of high performance.

Random Signal Characteristics of Super Resolution Near Field Structure Read-Only Memory Disc

We report the random pattern signal characteristics of the super resolution near field structure (Super-RENS) disk in a red laser optical system. (Laser wavelength 659 nm, numerical aperture 0.6) We improved the carrier to noise ratio (CNR) characteristics and the low frequency noise by optimizing the layer design and the pit structure, which results in 53 dB CNR at 173 nm pit length. It is equivalent to 50 GB capacity if it is converted by Blu-ray Disc (BD) specification according to the ratio of beam size. We also improved the readout power margin and the stability greatly by introducing the thermal control layer. The eye pattern under phase locked loop (PLL) state could be obtained through equalization adjustment (EQ). Through above improvements, we obtain the bER of 4.6×10-4 at 50 GB level by using partial response maximum likelihood (PRML) method.

Continuous-Wave-Laser versus Pulsed-Laser Excitation for Crossed-Beam Photothermal Detection in Small Volume Applications: Comparative Features

Crossed-beam thermal lens spectrometry can be implemented using continuous-wave- (cw) laser or pulsed-laser excitation. In both cases, the signal depends on the position of the sample with respect to the probe beam waist, the size of the excitation beam, the beamsize ratio into the sample, and the power or energy of the excitation beam. However, due to differences in the rate of formation and relaxation of the thermal lens, both methods exhibit distinct key features. Optimization of the experimental setup and understanding the thermal lens signal are more complicated under cw-laser excitation than with pulsed-laser excitation. Unlike that observed under pulsed excitation, the effect of the excitation beam waist, of the sample size, and of the flow rate are closely related to the effective size of the thermal element and depend on the chopping frequency. Although the intrinsic sensitivities are almost the same, the performance can significantly differ depending on the chopping frequency or pulse repetition rate, which should be high enough to allow fast data collection and efficient signal averaging.

Resist debris formation in electron beam lithography

The resist debris (RD) formation dependence on beam stepping to beam size ratio in electron beam lithography (EBL) is theoretically and experimentally investigated. The theoretically simulated results show a distinct variation in RD formation as the beam stepping to beam size ratio is varied from 0.5 to 2.0. The corresponding experimental results show a very close resemblance with the simulated results. It is further demonstrated that this undesirable phenomenon of RD formation gives another dimension to look at the problem of proximity exposure effect in EBL and can also be well utilized in certain cases.

A theoretical analysis of the laser melt-level monitoring system for the Czochralski crystal growing furnaces

This paper discusses the operating theory of a trigonometrical laser melt-level monitoring system as applied to Czochralski crystal pullers. The surface movement of the silicon melt is modeled with three-dimensional random harmonic waves. The effect of this motion on the spatial distribution of the laser signal is simulated and studied. Means of separating the laser signal from the noise caused by the background radiation from the melt is described. Statistical analysis is used to determine measurement accuracy. It has been found that with a relatively tranquil melt surface, characterized by a small wave amplitude to wavelength ratio and a large wavelength to laser beam size ratio, the laser signal is confined to a limited area, thus can be effectively acquired by a photo detector. The accurate measurement can then be achieved with statistical means. Experimental data generated with water and molten silicon surfaces are in good conformity with the theoretical results.