A new method for high-energy pulsed Gamma measurement within intense background x-rays

The accelerator-generating 6.13 MeV pulsed Gamma by 19F（p, αγ）160 reaction usually synchronizes with an intense bremsstrahlung x-ray which has a maximum energy of 1 MeV. This paper proposes a new method, named the scattering and absorbing method, to diagnose the 6.13 MeV Gamma. This method includes two parts： the detector and a scatterer placed in front of the detector. The detector converts the Gamma to electrons and then collects the electrons by a scintillator. In order to restrain the interference of the low-energy background, the scintillator collects the electrons at a small angle. The scintillator is wrapped with electro-absorbing material to absorb the low-energy electrons generated by background x-rays. The theoretical sensitivity ratio of 6.13 MeV Gamma to 1 MeV x-rays is greater than 150. The scatterer is a pretreatment tool to scatter some background x-rays away from the radial beam before they enter the detector. By varying the length, the scatterer can reduce the background x-rays to an acceptable level for the detector.

Design aspect of a novel L-shaped pulsed column for liquid–liquid extraction applications: Energy consumption and the characteristics velocity concept

This article deals with the evaluation of the consumption of energy for a steady state solvent extraction in a novel L-shaped pulsed sieve-plate column, which is highly required for design and optimization of the periodic flow processes for industrial applications. In this regard, a comprehensive evaluation on the energy consumption in case of a pulsed flow for three different chemical systems is conducted and besides the influence of pulsation intensity, the effect of geometrical parameters including the plate spacing and the plate free area is investigated as well. Moreover, the concept of characteristic velocity models at flooding points is evaluated with respect to the variation of pressure drop along the column at different operational conditions.

Effect of air breakdown on microwave pulse energy transmission

The energy transmission of the long microwave pulse for the frequency of 2.45 GHz and 5.8 GHz is studied by using the electron fluid model, where the rate coefficients are deduced from the Boltzmann equation solver named BOLSIG＋. The breakdown thresholds for different air pressures and incident pulse parameters are predicted, which show good agreement with the experimental data. Below the breakdown threshold, the transmitted pulse energy is proportional to the square of the incident electric field amplitude. When the incident electric field amplitude higher than the breakdown threshold increases,the transmitted pulse energy decreases monotonously at a high air pressure, while at a low air pressure it first decreases and then increases. We also compare the pulse energy transmission for the frequency of 2.45 GHz with the case of 5.8 GHz.

Effects of pulse energy ratios on plasma characteristics of dual-pulse fiber-optic laser-induced breakdown spectroscopy

Laser-induced plasmas of dual-pulse fiber-optic laser-induced breakdown spectroscopy with different pulse energy ratios are studied by using the optical emission spectroscopy(OES)and fast imaging.The energy of the two laser pulses is independently adjusted within 0–30 m J with the total energy fixed at 30 m J.The inter-pulse delay remains 450 ns constantly.As the energy share of the first pulse increases,a similar bimodal variation trend of line intensities is observed.The two peaks are obtained at the point where the first pulse is half or twice of the second one,and the maximum spectral enhancement is at the first peak.The bimodal variation trend is induced by the change in the dominated mechanism of dual-pulse excitation with the trough between the two peaks caused by the weak coupling between the two mechanisms.By increasing the first pulse energy,there is a transition from the ablation enhancement dominance near the first peak to the plasma reheating dominance near the second peak.The calculations of plasma temperature and electron number density are consistent with the bimodal trend,which have the values of 17024.47 K,2.75×10^(17)cm;and 12215.93 K,1.17×10^(17)cm;at a time delay of 550 ns.In addition,the difference between the two peaks decreases with time delay.With the increase in the first pulse energy share,the plasma morphology undergoes a transformation from hemispherical to shiny-dot and to oblate-cylinder structure during the second laser irradiation from the recorded images by using an intensified charge-coupled device(ICCD)camera.Correspondingly,the peak expansion distance of the plasma front first decreases significantly from 1.99 mm in the single-pulse case to 1.34 mm at 12/18(dominated by ablation enhancement)and then increases slightly with increasing the plasma reheating effect.The variations in plasma dynamics verify that the change of pulse energy ratios leads to a transformation in the dual-pulse excitation mechanism.

Energy Scaling of Terahertz Pulses Produced through Difference Frequency Generation

We study the energy scaling of terahertz (THz) emission through difference frequency generation of near-infrared pulses, and demonstrate that Gigawatt few-cycle THz transients at the central frequency of 30 THz are produced from GaSe crystal pumped by two pulses at 1.65 and 1.95 micrometers, with the high quantum yield of 28%. Our analysis indicates that the high yield of DFG originates from the largely reduced group velocity mismatch as the long-wavelength pumping pulses are employed.

Effect of water temperature on pulse duration and energy of stimulated Brillouin scattering

The water temperature has a strong effect on the kinematic viscosity, which is inversely proportional to the phonon lifetime and the gain coefficient. The higher the temperature is, the smaller the kinematic viscosity is, and the larger the phonon lifetime is. At a low pump power and a short focal length, we can derive a single-peak stimulated Brillouin scattering （SBS） pulse. The duration of this single-peak SBS pulse depends mainly on the phonon lifetime of water. With the increase of the water temperature, the duration of such a single-peak SBS pulse will become longer, and the SBS energy will become higher for the gain coefficient, which is related to the phonon lifetime. Therefore, varying the medium temperature can lead to the changes of SBS pulse duration and SBS energy.

Seismic Reliability Assessment of Inelastic SDOF Systems Subjected to Near-Fault Ground Motions Considering Pulse Occurrence

The ground motions in the orientation corresponding to the strongest pulse energy impose more serious demand on structures than that of ordinary ground motions.Moreover,not all near-fault ground motion records present distinct pulses in the velocity time histories.In this paper,the parameterized stochastic model of near-fault ground motion with the strongest energy and pulse occurrence probability is suggested,and the Monte Carlo simulation(MSC)and subset simulation are utilized to calculate the first excursion probability of inelastic single-degree-of-freedom(SDOF)systems subjected to these types of near-fault ground motion models,respectively.Firstly,the influences of variation of stochastic pulse model parameters on structural dynamic reliability with different fundamental periods are explored.It is demonstrated that the variation of pulse period,peak ground velocity and pulse waveform number have significant effects on structural reliability and should not be ignored in reliability analysis.Then,subset simulation is verified to be unbiased and more efficient for computing small reliable probabilities of structures compared to MCS.Finally,the reliable probabilities of the SDOF systems with different fundamental periods subjected to impulsive,non-pulse ground motions and the ground motions with pulse occurrence probability are performed,separately.It is indicated that the ground motion model with the pulse occurrence probability can give a rational estimate on structural reliability.The impulsive and ordinary ground motion models may overestimate and underestimate the reliability of structures with fundamental period much less than the mean pulse period of earthquake ground motions.

A 37 mJ,100 Hz,high energy single frequency oscillator

Ways on energy enhancement for single frequency oscillator are reported in this paper.By quantitative analysis on gain and loss coefficients for each cavity mode with inserted etalons,a 37 mJ,100 Hz high energy single-frequency Nd:YAG oscillator is obtained.The pulse energy is promoted by enhancement of nearly 7 times for a single frequency oscillator reported.The result proves that this method does help for energy enhancement.It has attractive potential for high energy single frequency oscillator design,especially on condition of intensive side pumped or long cavity laser,where strong competitors exist and are hard to be suppressed.

Influences of finite gain bandwidth on pulse propagation in parabolic fiber amplifiers with distributed gain profiles

The evolutions of the pulses propagating in decreasing and increasing gain distributed fiber amplifiers with finite gain bandwidths are investigated by simulations with the nonlinear SchrSdinger equation. The results show that the parabolic pulse propagations in both the decreasing and the increasing gain amplifiers are restricted by the finite gain bandwidth. For a given input pulse, by choosing a small initial gain coefficient and gain variation rate, the whole gain for the pulse amplification limited by the gain bandwidth may be higher, which is helpful for the enhancement of the output linearly chirped pulse energy. Compared to the decreasing gain distributed fiber amplifier, the increasing gain distributed amplifier may be more conducive to suppress the pulse spectral broadening and increase the critical amplifier length for achieving a larger output linearly chirped pulse energy.

QUANTITATIVE ANALYSIS ON CHANGES OF HEPATIC HEMODYNAMICS AFTER TRANSCUTANEOUS ELECTRIC PULSE STIMULATION OF LOCAL POINTS BY USING COLOR DOPPLER ULTRASOUND DIAGNOSTIC APPARATUS

Objective: To evaluate the effect of transcutaneous electric pulse stimulation (TEPS) on hepatic blood flow and parenchymal microcirculation in patients with fatty liver. Methods: A total of 31 fatty liver volunteer patients were observed in this study. Changes of color Doppler energy (CDE) images before and after TEPS of local points nearby the liver were recorded by using color Doppler ultrasound diagnostic apparatus (ACUSON 128XP/10C). Sum of color pixel area (SCPA), average of color value (ACV) and SCPA×ACV (integral) of the hepatic flow images were analyzed by an image processing system, single blind method and paired t-test. Programmed TEPS (0.5- 150 Hz / 2 000 Hz , 10- 25 V ) was applied to the right Qimen (期门 LR 14)-Jingmen (京门 GB 25), Fuai (腹哀 SP 16)-Ganshu (肝俞 BL 18) respectively for 15 min. Results: Compared with basic values of pretreatment, SCPA, ACV and SCPA×ACV increased significantly (t=2.71, P<0.02; t=3.42, P<0.01; and t=8.15, P<0.001) after TEPS, meaning improvement of hepatic blood flow supply. Conclusion: TEPS of acupoints near the liver can improve hepatic blood flow and hepatic parenchymal microcirculation in patients with fatty liver.

A Novel TiO_2 Combined Pulsed Diaphragm Discharge System for Phenol Degradation

A synergistic photocatalysis combined pulsed diaphragm discharge（PDD）system with TiO_2 nanofilm deposited on the surface of quartz diaphragm is developed for the first time for phenol degradation in an aqueous solution.It is observed that the decomposition efficiency of phenol in the TiO_2 combined PDD system is higher than that of the single PDD system under the same conditions,indicating a successful collaboration between the photocatalysis and the plasma decomposition in the present system.Analysis of the solution＇s pH value confirms this collaboration and further reveals that the photocatalytic enhancement effect of phenol degradation is strong at a relatively low supplied voltage.The present TiO_2 combined PDD system exhibits improved efficiencies of pollutant degradation and energy utilization,suggesting a good candidate for wastewater treatment.

A study of the strong pulses detected from PSR B0656+14 using the Urumqi 25-m radio telescope at 1540 MHz

We report on the properties of strong pulses from PSR B0656＋14 by analyzing the data obtained using the Urumqi 25-m radio telescope at 1540 MHz from August 2007 to September 2010.In 44 h of observational data,a total of 67 pulses with signal-to-noise ratios above a 5σthreshold were detected.The peak flux densities of these pulses are 58 to 194 times that of the average profile,and their pulse energies are 3 to 68 times that of the average pulse.These pulses are clustered around phases about 5-ahead of the peak of the average profile.Compared with the width of the average profile,they are relatively narrow,with the full widths at half-maximum ranging from 0.28 ° to 1.78 °.The distribution of pulse-energies follows a lognormal distribution.These sporadic strong pulses detected from PSR B0656＋14 have different characteristics from both typical giant pulses and its regular pulses.

High-energy and high-peak-power GHz burst-mode all-fiber laser with a uniform envelope and tunable intra-burst pulses

We report a Yb-doped all-fiber laser system generating burst-mode pulses with high energy and high peak power at a GHz intra-burst repetition rate.To acquire the uniform burst envelope,a double-pre-compensation structure with an arbitrary waveform laser diode driver and an acoustic optical modulator is utilized for the first time.The synchronous pumping is utilized for the system to reduce the burst repetition rate to 100 Hz and suppress the amplified spontaneous emission effect.By adjusting the gain of every stage,uniform envelopes with different output energies can be easily obtained.The intra-burst repetition rate can be tuned from 0.5 to 10 GHz actively modulated by an electro-optic modulator.Optimized by timing control of eight channels of analog signal and amplified by seven stages of Yb-doped fiber amplifier,the pulse energy achieves 13.3 mJ at 0.5 ns intra-burst pulse duration,and the maximum peak power reaches approximately3.6 MW at 48 ps intra-burst pulse duration.To the best of our knowledge,for reported burst-mode all-fiber lasers,this is a record for output energy and peak power with nanosecond-level burst duration,and the widest tuning range of the intra-burst repetition rate.In particular,this flexibly tunable burst-mode laser system can be directly applied to generate high-power frequency-tunable microwaves.

Exploration and determination of the principles of rotary-percussive underground slimhole drilling

A possibility of the efficient use of rotary percussive drilling to provide drilling smaller diameter holes(40–70 mm) both in mining and prospecting is disclosed herein. A new construction designed for the nipple thread connection is described. The relative amplitude variation, change of power pulse time and energy in their propagation throughout the drilling tool are determined. A possibility of the efficient power pulse transfer along the drill string to the rock destruction tools with new nipple connections which allow automating the make-up and breakout system of drill pipe was supported by experiments.

Two-micron all-fiberized passively mode-locked fiber lasers with high-energy nanosecond pulse

We report on mode-locked thulium-doped fiber lasers with high-energy nanosecond pulses,relying on the transmission in a semiconductor saturable absorber(SESA)and a carbon nanotube(CNTs-PVA)film separately.A section of an SMF-MMF-SMF structure multimode interferometer with a transmission peak wavelength of^2003 nm was used as a wavelength selector to fix the laser wavelength.When the SESA acted as a saturable absorber(SA),the mode-locked fiber laser had a maximum output power of^461 mW with a pulse energy of^0.14µJ and a pulse duration of^9.14 ns.In a CNT-film-based mode-locked fiber laser,stable mode-locked pulses with the maximum output power of^46 mW,pulse energy of^26.8 nJ and pulse duration of^9.3 ns were obtained.To the best of our knowledge,our experiments demonstrated the first 2µm region‘real’SA-based dissipative soliton resonance with the highest mode-locked pulse energy from a‘real’SA-based all-fiberized resonator.

A Modified Code Domain Transmitted Reference UWB System

Based on the research on time domain and frequency domain transmitted reference Impulse Radio Ultra-WideBand (IR-UWB) system, this paper studies the optimization design for code domain transmitted reference IR-UWB system, and proposes a modified code domain transmitted reference IR-UWB system. The Bit Error Rate (BER) expressions for the modified system model in the condition of Additive White Gaussian Noise (AWGN) and multipath fading are deduced respectively. In addition, the performances of the modified system and the other three transmitted reference IR-UWB systems are simulated and compared. Theoretical analysis and simulation results show that the performance of the modified system is superior to the other three systems.

2.1 μm,high-energy dissipative soliton resonance from a holmium-doped fiber laser system

We propose a 2.1μm high-energy dissipative soliton resonant(DSR)fiber laser system based on a mode-locked seed laser and dual-stage amplifiers.In the seed laser,the nonlinear amplifying loop mirror technique is employed to realize mode-locking.The utilization of an in-band pump scheme and long gain fiber enables effectively exciting 2.1μm pulses.A section of ultra-high numerical aperture fiber(UHNAF)with normal dispersion and high nonlinearity and an output coupler with a large coupling ratio are used to achieve a high-energy DSR system.By optimizing the UHNAF length to55 m,a 2103.7 nm,88.1 nJ DSR laser with a 3-dB spectral bandwidth of 0.48 nm and a pulse width of 17.1 ns is obtained under a proper intracavity polarization state and pump power.The output power and conversion efficiency are 0.233W and 4.57%,respectively,both an order of magnitude higher than those of previously reported holmium-doped DSR seed lasers.Thanks to the high output power and nanosecond pulse width of the seed laser,the average power of the DSR laser is linearly scaled up to 50.4 W via a dual-stage master oscillator power amplifier system.The 3-dB spectral bandwidth broadens slightly to 0.52 nm,and no distortion occurs in the amplified pulse waveform.The corresponding pulse energy reaches 19.1μJ,which is the highest pulse energy in a holmium-doped mode-locked fiber laser system to the best of our knowledge.Such a 2.1μm,high-energy DSR laser with relatively wide pulse width has prospective applications in mid-infrared nonlinear frequency conversion.

Simulation studies on laser pulse stability for Dalian coherent light source

Dalian Coherent Light Source will use a 300 MeV LINAC to produce fully coherent photon pulses in the wavelength range between 150–50 nm by high gain harmonic generation free electron laser（FEL） scheme. To generate stable FEL pulses, a stringent tolerance budget is required for the LINAC output parameters, such as the mean beam energy stability, electron bunch arrival time jitter, peak current variation and the transverse beam position ofset. In order to provide guidance for the design of the Dalian Coherent Light Source, in this paper, the sensitivity of FEL pulse energy fluctuation to various error sources of the electron bunch was performed using intensive start-to-end FEL simulations.

Generation of 100 nJ pulse,1 W average power at 2μm from an intermode beating mode-locked all-fiber laser

We report on the investigation of intermode beating mode-locked(IBML)pulse generation in a simple all-fiber Tm^3+-doped double clad fiber laser(TDFL).This IBML TDFL is implemented by matching longitudinal-mode frequency between 793 nm laser and TDFL without extra mode locker.The central wavelength of 1983 nm,the fundamental pulse frequency of 9.6 MHz and the signal-to-noise ratio(SNR)of>50 dB are achieved in this IBML TDFL.With laser cavity optimization,the IBML TDFL can finally generate an average output power of 1.03 W with corresponding pulse energy of 107 nJ.These results can provide an easily accessible way to develop compact large-energy,highpower TDFLs.

Analysis and simulation of a coupled-cavity pulse compressor

An equivalent circuit model is built for a coupled-resonator pulse compressor. Based on the circuit, the general second order differential equation is derived and converted into the first order equation to save computing time. In order to analyze the transient response and optimize parameters for the pulse compressor, we have developed a simulation code. In addition, we have also designed a three-cavity pulse compressor to get the maximum energy multiplication factor. The size of the cavities and coupling apertures is determined by HFSS.