A new sequence for the MQMAS/HETCOR experiment

Two-dimensional (2D) multiple quantum MAS (magic angle spinning) spectroscopy has been combined with cross-polarisation to obtain a heteronuclear correlation spectrum between a quadrupolar spin-3/2 and a spin-1/2 nucleus. The advantage over the conventional correlation experiment is the increased resolution obtained in the multiple quantum dimension. Pure absorption 2D spectra can be obtained by implementing a zero quantum filter between the evolution of multiple quanta and the subsequent cross-polarisation step. The current experiment shows a considerable improvement in sensitivity compared to a previously introduced sequence.     

一个新颖的白光干涉实验的开发与研究

开发了一个获得白光条纹的新实验.把劳埃镜干涉和光栅衍射结合起来,有可能使白光源产生的不同颜色的条纹彼此重合,从而能观察到清晰的黑白条纹.讨论了有关的实验原理、装置和方法,介绍了主要的实验关键并提供了相应的测量数据.     

介绍一套新体系的物理实验教材

介绍由中国科学技术大学霍剑青、吴泳华等主编，高等教育出版社出版的《大学物理实验》教材，该教材分为四册，对应新实验体系的四级物理实验。     

A sixteen-channel multiplexing upgrade for single channel receivers

With the increasing interest in phased arrays in magnetic resonance imaging, imaging system receivers capable of acquiring larger number of parallel signals are needed. Suggested techniques for rapid imaging propose the use of arrays with as many as 128 elements. While simply duplicating the number of receiver chains as needed is a viable technique, it quickly becomes both cumbersome and expensive.Time domain multiplexing offers an alternative solution to this problem. By using RF multiplexing switches, a single receiver can be upgraded to an array receiver capable of multi-channel data acquisition giving users array capability. Additionally, it can be used to dramatically increase acquisition capability of multiple receiver systems.This paper reports results from a multiplexing system upgrade, which converts a single channel standard clinical imaging system to a 16-channel array system. The upgrade includes both the RF multiplexing front-end and an external data acquisition system with image processing capability. Issues concerning the implementation of high channel-count multiplexers are also discussed.     

A fast muon trigger for the PHENIX forward spectrometer upgrade

The PHENIX forward upgrade adds nosecone calorimeters and level-1 trigger (LVL-1) detectors to the muon forward spectrometers. The muon detector will trigger on high pT muons from W decay and reject background. This will enable study of quark and anti-quark polarizations in the proton. The upgrade will add momentum and timing information to the present muon trigger. Signals from 3 Resistive Plate Chambers (RPCs) will provide momentum and timing information for the LVL-1 trigger. Each RPC carries a plane with coarse structure to establish a space point for timing and one with radial cathode strips for azimuthal resolution. Timing resolution of ≈ 2 ns rejects beam-related backgrounds and tracking from RPCs minimizes muons from hadron decays. RPC information is sent by optical. bers to LVL-1 trigger processors. A discussion of physics measurements possible, layout of the upgrade and details of RPC design and tests are given below. for the PHENIX collaboration Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

A new FPGA-based trigger/DAQ system for the MTV experiment at TRIUMF

A new FPGA based data acquisition (DAQ) and trigger combined system is developed for the MTV experiment (Mott Polarimetry for T-Violation Experiment). The MTV experiment measures backward Mott scattering events by detecting the incident and scattered tracks using a drift chamber. For the backward scattering probability is as small as less than 0.1%, efficient triggering system is required to select the desired events. An intelligent Level-2 trigger system reading hitting pattern together with its digital readout system are built in a custom FPGA system. In this paper, design overview and results from performance tests are described.     

KARMEN: Neutrino oscillation limits and new results with the upgrade

The neutrino experiment KARMEN is situated at the beam stop neutrino source ISIS which provides ν_μ's, ν_e's and from the π⁺−μ⁺-decay at rest. The oscillation channels ν_{μ → νe} and are investigated with a 56 t liquid scintillation calorimeter. No evidence for oscillations could be found with KARMEN, resulting in 90% CL exclusion limits of sin²(2Θ) < 8.5 · 10⁻³ ( ) and sin²(2Θ) < 4.0 · 10⁻² (ν_μ → ν_e) for Δm² > 100 eV². In 1996, the experiment has been upgraded by an additional veto counting system with a total coverage of 300 m². The new system allows the identification of cosmic muons in the vicinity of the detector. Vetoing these muons suppresses energetic neutrons from deep inelastic scattering of muons as well as from μ-capture by a factor of 40. Up to 1996, these neutrons represented the main background for oscillation search. The experimental sensitivity for will be significantly enhanced towards sin²(2Θ) 1.0 · 10⁻³ after a further measuring period of 2–3 years.     

A new comparison between experiment and theory for the X-ray K absorption edge of nickel

New structure has been resolved in the X-ray K absorption edge of nickel. There is rough qualitative agreement between our spectrum and the calculations of Nagel et al., for which the presence of the core hole is neglected in the computation of the final state wave function. However, the two lowest energy experimental peaks are significantly shifted to lower energies relative to the corresponding theoretical peaks. In addition, the theoretical spectrum is much sharper than the experimental curve even after accounting for instrumental broadening and broadening due to the natural width of the K level, indicating that hot electron broadening effects strongly influence the final ejected electron states.     

基于机器视觉的ROV水下管线自动跟踪方法

针对混浊水下管线检测过程中由于光学图像成像不清而难以实现自动跟踪的问题,提出一种基于机器视觉和声纳图像处理的水下管线自动跟踪方法。鉴于声纳图像噪声大的问题,该方法采用Gabor滤波器增强管线特征,然后通过二值化,以及Canny边缘提取管线轮廓,最后通过霍夫变换得到管线的几何特征。为了提高管线提取的效率,采用卡尔曼滤波对管线走向和位置进行预测。通过ROV实验,结果表明,该方法能够减少图像搜索的面积,减少处理时间,成功地提取出管线特征。该方法应用于混浊水下管线跟踪是可行的、有效的。     

Energy weighting for the upgrade of the CMS HCAL

In these simulation studies an energy weighting method is applied to the signals of the CMS hadronic calorimeter readout with a longitudinal segmentation for a possible future upgrade. Tabulated weighting factors are used to compensate for the different response of hadronic and electromagnetic energy depositions of simulated pion showers in the hadronic calorimeter. The weighting improves the relative energy resolution: $$ (\sigma _E /E)^2 = \left[ {((92.2 \pm 0.6)\% /\sqrt E )^2 + ((6.5 \pm 0.1)\% )^2 } \right] $$ (before weighting), $$ (\sigma _{E,weight} /E)^2 = \left[ {((85.4 \pm 0.5)\% /\sqrt E )^2 + ((4.4 \pm 0.1)\% )^2 } \right] $$ (after weighting), where E in the square root has units of GeV.     

A new test of the equivalence principle: a null phase-delay experiment

The Einstein Equivalence Principle (EEP) provides the fundamental basis for any metric theory of gravity, such as general relativity. It implies that the only observable effects of gravitation are those mediated by the spacetime metric. Therefore, at the origin of a local freely falling frame there should be no observable effects of gravity. Null redshift tests provide an interesting way to test this prediction. In this test, the frequencies of two oscillators of a different type are compared at the same location in a gravitational field as the field is varied. Any variation in the frequency would signal a violation of the EEP. Here we shall propose a new test of the EEP called a null phase-delay experiment, in which the phase-delay of a signal propagated over a coil of optical fiber is monitored as the gravitational field at the coil is varied. An interesting test of the EEP in the solar gravitational field can be performed in the laboratory under carefully controlled conditions. With presently available technology, such an experiment could provide a 0.01% test.This essay received the third award from the Gravity Research Foundation, 1993-Ed.     

Design of the readout electronics for the DAMPE Silicon Tracker detector

The Silicon Tracker (STK) is one of the detectors of the DAMPE satellite used to measure the incidence direction of high energy cosmic rays. It consists of 6 X-Y double layers of silicon micro-strip detectors with 73728 readout channels. It is a great challenge to read out the channels and process the huge volume of data in the harsh environment of space. 1152 Application Specific Integrated Circuits (ASIC) and 384 ADCs are used to read out the detector channels. 192 Tracker Front-end Hybrid (TFH) modules and 8 identical Tracker Readout Board (TRB) modules are designed to control and digitalize the front signals. In this paper, the design of the readout electronics for the STK and its performance are presented in detail.     

Measurement of and the dipion contribution to the muon anomaly with the KLOE detector

We have measured the cross section σ(e⁺e⁻→π⁺π⁻γ(γ)) at DAΦNE, the Frascati -factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb⁻¹. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two-pion states in the mass range 0.592<M_ππ<0.975 GeV. For the latter we find Δ^ππa_μ=(387.2±0.5_stat±2.4_exp±2.3_th)×10⁻¹⁰.     

模拟海市蜃楼实验的配液新方案

分析了配制传统模拟海市蜃楼溶液的方法的不足,提出了新的配制溶液的方案,推导出了所配制的溶液浓度梯度随高度的分布公式,从而使实验过程中配液的时间大大缩短,实验现象更加明显,提高了实验的成功率.     

Background studies for the A4 experiment

Backward angle measurements with the A4 setup at Mainz have been performed and are ongoing. Differently as with the forward measurements severe background issues had to be faced, due to ??-events generated by the ?? ⁰ decay. Hardware upgrades as well as data analysis improvements were needed. For the latest a detailed study of the background by means of Monte Carlo simulations has been undertaken. Its major features together with the basic ansaetze of the ??-background handling are presented in this contribution.     

Investigations of the new generation pixel detectors for ALICE experiment at LHC

We present the results from testing Monolithic Active Pixel Sensors of the detector ALPIDE (ALICE Pixel Detector). The purpose of these tests was to measure the pixel threshold and noise distributions in each of the four sectors of the detector, as well as the analysis of the hit maps produced by different radioactive sources.