First Operation of the D0 Run Ⅱ Reconstruction Farm

We report on the first operations of the reconstruction farms for the D0 experiment.Data were read from a tape robot to 50 PC‘s running Linux,processed,spooled to a central disk buffer for merging and then written back to the tape robot.The farms are being used successfully to reconstruct the data as it comes in.Transfer rates well over the 12.5 MB/sec needed for full data rates have been achieved.     

Triggering and guiding of high voltage discharge by using femtosecond laser filaments with different parameters

This paper demonstrates the triggering and guiding of the stationary high voltage (HV) discharges at 5--40 kV by using plasma filaments generated by femtosecond laser pulses in air. A significant reduction of the breakdown voltage threshold due to the pre-ionization of the air gap by laser filamentation is observed. The discharge experiments are performed by using laser pulses with different energy from 15--60 mJ. The electron density of filaments is detected by sonography method. The influence of the electron density of laser filaments on the triggering and guiding HV discharge is experimentally investigated. The results have shown that the behaviour of plasma filaments can strongly affect the efficiency of triggering and guiding HV discharge.     

The BTeV DAQ and Trigger System—Some Throughput,Usability and Fault Tolerance Aspects

As presented at the last CHEP conference,the BTeV triggering and data collection pose a significant challenge in construction and operation,generating 1.5 Terabytes/second of raw data from over 30 million detector channels.We report on facets of the DAQ and trigger farms.We report on the current design of the DAQ,especially its partitioning features to support commissioning of the detector.We are exploring collaborations with computer science groups experienced in fault tolerant and dynamic real-time and embedded systems to develop a system to provide the extreme flexibility and high availability required of the heterogeneous trigger farm(-ten thousand DSPs and commodity processors).We describe directions in the following areas:system modeling and analysis using the Model Integrated Computing approach to assist in the creation of domain-specific modeling,analysis,and program synthesis environments for building complex,large-scale computer-based systems;System Configuration Management to include compileable design specifications for configurable hardware components,schedules,and communication maps. Runtime Environment and Hierarchical Fault Detection/Management-a system-wide infrastructure for rapidly detecting,isolating,filtering,and reporting faults which will be encapsulated in intelligent active entites(agents)to run on DSPs,L2/3 processors,and other supporting processors throughout the system.     

Is the Near-Earth Current Sheet Prior to Reconnection Unstable to Tearing Mode？

The tearing mode instability plays a key role in the triggering process of reconnection. The triggering collisionless tearing mode instability has been theoretically and numerically analyzed by many researchers. However, due to the difficulty in obtaining the observational wave number, it is still unknown whether the tearing mode instability can be excited in an actual plasma sheet prior to reconnection onset. Using the data from four Cluster satellites prior to a magnetospheric reconnection event on 13 September 2002, we utilized the wave telescope technique to obtain the wave number which corresponds to the peak of power spectral density. The wavelength is about 18RE and is consistent with previous theoretic and numerical results. After substituting the wave vector and other necessary parameters of the observed current sheet into the triggering condition of tearing mode instability, we find that the near-Earth current sheet prior to reconnection is unstable to tearing mode.     

Ccontrolling the Transition Between "Higher" and "Lower" State of OB in Coherent Atomic Medium

We present a new experimental demonstration that the threshold points and shape of OB hysteresis curve in a four-level Rb atomic system inside an optical cavity were controllably changed by optical signals.Tuning the triggering optical signal to two different transitions of the atomic system we found that the OB threshold points shift toward different direction and at the same time the shape of the OB curve is also changed.For a given intensity of probe laser the OB system can be reliably inversed from its lower stable state to upper state under the triggering of a suitably tuned optical pulse signal (we named it up-controlling signal).More interesting, the inversed OB state does not drop to its initial lower stable state after the triggering pulse signal has passed, but moves to the upper branch of the initial OB curve and stably stays there until another optical signal tuned on other atomic transition (named down-controlling signal) coming.The result shows that there is the ability of information storage in the OB system.The experiments are reasonably explained with the change of cavity resonant condition resulting from the enhanced third-order nonlinearity in multilevel atomic system owing to atomic coherence.     

Small Stress Change Triggering a Big Earthquake： a Test of the Critical Point Hypothesis for Earthquakes

Whether or not a small stress change can trigger a big earthquake is one of the most important problems related to the critical point hypothesis for earthquakes. We investigate global earthquakes with different focM mechanisms which have different levels of ambient shear stress. This ambient stress level is the stress level required by the earthquakes for their occurrence. Earthquake pairs are studied to see whether the occurrence of the preceding event encourages the occurrence of the succeeding one in terms of the Coulomb stress triggering. It is observed that the stress triggering effect produced by the change of Coulomb failure stress in the same order of magnitudes,about 10-2 MPa, is distinctly different for different focal mechanisms, and thus for different ambient stress levels.For non-strike-slip earthquakes with a relatively low ambient stress level, the triggering effect is more evident,while for strike-slip earthquakes with a relatively high ambient stress level, there is no evident triggering effect.This water level test provides an observational support to the critical point hypothesis for earthquakes.     

POTENTIAL SAFE TERMINATION BY LASER ABLATION OF HIGH Z IMPURITY IN THE HL-1M TOKAMAK

A preliminary experiment for triggering a plasma current quench by high Z impurities has been performed on the HL-1 M tokamak. Using injection of impurity with the higher charge of the nuclei allows us to increase the radiation cooling. It can be a simple and potential approach for decreasing significantly the plasma thermal energy before a disruption and for safe termination of the plasma.     

PULSE ECHO OVERLAP METHOD WITH ALTERNATIVE TRIGGERING AND LIQUID VELOCIMETER

In this paper,the usual pulse echo overlap method for ultrasonic wave velocity measurement isdeveloped to pulse echo overlap method with alternative triggering.The principle of the method liesin that,when the first ultrasonic echo train,being given rise from the first transmitting pulse,is dis-played on an oscilloscope,the oscilloscope is triggered normally and synchronized with the transmittingpulse.But for the next echo train to be displayed,which is given rise from the second transmittingpulse,it will be triggered after a further time delay than that of the first one,which is equal to a roundtrip time of an ultrasonic pulse in the sample.Then the whole procedure is repeated again and againand on the oscilloscope a pattern of overlapped echo trains can be observd.The value of the delaytime can be obtained directly from a digital counter.By changing the scanning rate of the oscilloscopeand adjusting its triggering delay,any part of the overlapped pattern can be observed and studied. Based on this princi     

Parallel signaling-based fast restoration scheme in distributed optical networks

The fast parallel restoration （FPR） scheme is proposed to achieve the fast setup of restoration label switched path （LSP） in the distributed optical networks. The scheme is derived by dividing the whole restoration LSP into several segments of sub-LSP and triggering each sub-LSP along the new route to finish the signaling procedure concurrently, and subsequently merging all sub-LSPs into a whole LSP. The theoretical analysis and simulation results show that the FPR scheme outperforms the other two typical restoration schemes in terms of connection setup time.     

Distributed Simulation of Large Computer Systems

Sequential simulation of large complex physical systems is often regarded as a computationally expensive task.In order to speed-up complex discrete-event simulations,the paradigm of Parallel and Distributed Discrete Event Simulation (PDES) has been introduced since the late 70s.In this paper we‘ll analyze the applicability of PDES to the modeling and analysis of large computer system;such systems are increasingly common in the area of High Energy and Nuclear Physics,because many modern experiments make use of large“compute farms“,Some feasibility tests have been performed on a prototype distributed siumulator.     

Discontinuous event-trigger scheme for global stabilization of state-dependent switching neural networks with communication delay

This paper is concerned with the global stabilization of state-dependent switching neural networks(SDSNNs)viadiscontinuous event-triggered control with network-induced communication delay.Aiming at decreasing triggering times,a discontinuous event-trigger scheme is utilized to determine whether the sampling information is required to be sent outor not.Meanwhile,under the effect of communication delay,the trigger condition and SDSNNs are transformed into twotractable models by designing a fictitious delay function.Then,using the Lyapunov–Krasovskii stability theory,someinequality estimation techniques,and extended reciprocally convex combination method,two sufficient criteria are established for ensuring the global stabilization of the resulting closed-loop SDSNNs,respectively.A unified framework isderived that has the ability to handle the simultaneous existence of the communication delay,the properties of discontinuousevent-trigger scheme,as well as feedback controller design.Additionally,the developed results demonstrate a quantitativerelationship among the event trigger parameter,communication delay,and triggering times.Finally,two numerical examples are presented to illustrate the usefulness of the developed stabilization scheme.     

Tunability of graded negative index-based photonic crystal lenses for fine focusing

Graded negative refractive index-based photonic crystal (PC) lenses are designed by gradually modifying the sizes of air holes along the transverse direction for focusing the incident plane wave. To study the tunability of the graded negative index-based PC, we introduce filling factor A, gradually tune the filling factor, and use the finite-difference and time-domain (FDTD) algorithm for numerical calculation. Our calculation results indicate that the focal length and the spot size increase with A increasing. For the same A value, the focal length of a PC with elliptical air holes is the longest, and those of PC with square and rectangular air holes are the shortest. Moreover, when the focal length is greater than 1 μm, the focal parameters of the PC are highly insensitive to the variation of A. When the focal length is less than 1 μm, the PC lenses have higher transmittances and all well focus with a beam spot size breaking the diffraction limit. This feature possibly makes the graded negative index-based PC lenses have some new applications in optoelectronic systems.     

Practical high-speed light source for decoy-state quantum key distribution

High-speed light source is realized for decoy-state quantum key distribution(QKD) at telecom wavelength of 1.55 μm. By implementing two different electrical pulses together and triggering with 100 MHz pseudorandom number to drive the laser diode, the signal-state and the decoy-state pulses are prepared with identical pulse duration of 25 ps and similar spectral characteristics, avoiding the eavesdropper's attack by temporal and spectral analysis. The intensity fluctuation of the light source is quantified to satisfy the practical decoy-state QKD with random intensity error. The characteristics of the light source are analyzed with a high-speed single-photon detector.     

Subpicosecond pulse compression in nonlinear photonic crystal waveguides based on the formation of high-order optical solitons

We investigate by numerical simulation the compression of subpicosecond pulses in two-dimensional nonlinear photonic crystal (PC) waveguides. The compression originates from the generation of high-order optical solitons through the interplay of the huge group-velocity dispersion and the enhanced self-phase modulation in nonlinear PC waveguides.Both the formation of Bragg grating solitons and gap solitons can lead to efficient pulse compression. The compression factors under different excitation power densities and the optimum length for subpicosecond pulse compression have been determined. As a compressor, the total length of the nonlinear PC waveguide is only ten micrometres and therefore can be easily incorporated into PC integrated circuits.     

Analysis of saturation signal correction of the troposphere lidar

Usually, lidar detection systems are optimized for the measurement of the low intensity signal using the photon counting technique, but this approach results in the nonlinear signal response for the higher intensity signal. The problem is successfully solved by the combination of analog-to-digital （AD） and photon- counting （PC） detection. The optimized processing procedure of the signal combination of AD and PC is described, and the corrected result is analyzed and compared with the results by the dealt-time correction method. In this way, the accuracy of wind and aerosol measurement in the nonlinear range is improved. In addition, the signal-to-noise ratios （SNRs） of the two detection methods of AD and PC are compared in the overall dynamic range of signal for the performance analysis.     

Semiconductor photonic crystal laser

By combing artificial micro–nano structures, photonic crystals(PCs), with traditional semiconductor laser material to realize the dynamic collaborative control of photonic states and confined electrons, the band engineering of the PC has been confirmed. This brings new development space for the semiconductor laser, such as for low threshold and high efficiency.Based on a series of works by Zheng's group, this paper has reviewed kinds of PC lasers including electrical injection PC vertical cavity and lateral cavity surface-emitting lasers, and PC high beam quality lasers, to show that the PC is vital for promoting the continuous improvement of semiconductor laser performance at present and in the future.     

Building an Advanced Computing Environment with SAN Support

The current computing environment of our Computing Center in IHEP uses a SAS (server Attached Storage)architecture,attaching all the storage devices directly to the machines.This kind of storage strategy can‘t meet the requirement of our BEPC II/BESⅢ project properly.Thus we design and implement a SAN-based computing environment,which consists of several computing farms,a three-level storage pool,a set of storage management software and a web-based data management system.The feature of ours system includes cross-platform data sharing,fast data access,high scalability,convenient storage management and data management.     

Negative refraction and subwavelength imaging of a photonic-crystal slab for the frequencies in the third band

Negative refraction and subwavelength imaging properties of a two-dimensional （2D） photonic crystal （PC） slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directions of the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negative refractive-index material. The light radiated from a point source can form a subwavelength image spot through the PC slab. Negative refraction and an effective refractive index of the PC slab n = -1 can be achieved for the incident wave with its incident angle within a certain range.     

Operation and Optimization of a Linux PC farm for Physics Analysis in the ZEUS Experiment

The ZEUS experiment has migrated its reconstruction and analysis farms to a PC-based environment.More than one year of experience has been acquired with successful operation of an analysis farm designed for several hundred users.Specially designed software has been used to proveide fast and reliable access to large amounts of data (30 TB in total),After the ongoing upgrade of the HERA luminosity,higher requirements will arise in terms of data storage capacity and throughput rate,The necessity of a bigger disk cache has led to consideration of solutions based on commodity technology,PC-based file servers are being tested as a cost-effective storage system,In this article we present the hardware and software solutions deplogyed and discuss their performance.scalability and maintenance issues.