Experimental study of the radiation emitted by 180-GeV/c electrons and positrons volume-reflected in a bent crystal

The radiation emitted by 180-GeV/c volume-reflected electrons and positrons impinging on a bent crystal has been measured by the H8RD22 Collaboration on the H8 beamline at the CERN SPS. A dedicated spectrometer has been developed to measure high-energy photon spectra (up to similar to 100 GeV) under volume reflection: photon and charged particle beams have been separated by a bending magnet and leptons were detected and tagged by microstrip silicon detectors and a Pb-scintillator sampling calorimeter. A comparison between the experimental and analytical data for the amorphous and volume-reflection cases is presented and the differences are discussed

High-efficiency deflection of high energy protons due to channeling along the (110) axis of a bent silicon crystal

A deflection efficiency of about 61% was observed for 400 GeV/c protons due to channeling, most strongly along the 〈110〉 axis of a bent silicon crystal. It is comparable with the deflection efficiency in planar channeling and considerably larger than in the case of the 〈111〉 axis. The measured probability of inelastic nuclear interactions of protons in channeling along the 〈110〉 axis is only about 10% of its amorphous level whereas in channeling along the (110) planes it is about 25%. High efficiency deflection and small beam losses make this axial orientation of a silicon crystal a useful tool for the beam steering of high energy charged particles

Crystal undulator experiment at IHEP

Accelerator-based sources of hard-photon radiation are a rapidly developing field. Coherent radiation of a particle beam in an undulator is a popular choice. The crystalline undulators with periodically deformed crystallographic planes offer electromagnetic fields of the order of 1000 T and could provide a period L in the sub-millimeter range. In this way, a hundred-fold gain in the energy of emitted photons would be reached, as compared to a usual undulator. The first real construction of a crystal channeling undulator was recently proposed and realised by the present collaboration. After the sine-like deformation of crystal was proven in X-ray tests, four undulators were tested for channeling in a beam of 70-GeV protons. It was observed in the experiment that the crystal cross-section is efficiently channeling high energy particles, similarly to usual crystal deflectors. The experimentally established transparence for channeling of high energy particles allows one to start a direct experiment on photon production from a positron beam in the crystalline undulator. Details of commissioning of the experimental setup in the first run with 3 GeV positron beam are presented

Observation of strong leakage reduction in crystal assisted collimation of the SPS beam

In ideal two-stage collimation systems, the secondary collimator–absorber should have its length sufficient to exclude practically the exit of halo particles with large impact parameters. In the UA9 experiments on the crystal assisted collimation of the SPS beam a 60 cm long tungsten bar is used as a secondary collimator–absorber which is insufficient for the full absorption of the halo protons. Multi-turn simulation studies of the collimation allowed to select the position for the beam loss monitor downstream the collimation area where the contribution of particles deflected by the crystal in channeling regime but emerging from the secondary collimator–absorber is considerably reduced. This allowed observation of a strong leakage reduction of halo protons from the SPS beam collimation area, thereby approaching the case with an ideal absorber

Observation of channeling for 6500 GeV/c protons in the crystal assisted collimation setup for LHC

Two high-accuracy goniometers equipped with two bent silicon crystals were installed in the betatron cleaning insertion of the CERN Large Hadron Collider (LHC) during its long shutdown. First beam tests were recently performed at the LHC with 450 GeV/c and 6500 GeV/c stored proton beams to investigate the feasibility of beam halo collimation assisted by bent crystals. For the first time channeling of 6500 GeV/c protons was observed in a particle accelerator. A strong reduction of beam losses due to nuclear inelastic interactions in the aligned crystal in comparison with its amorphous orientation was detected. The loss reduction value was about 24. Thus, the results show that deflection of particles by a bent crystal due to channeling is effective for this record particle energy

Multiple volume reflections of high-energy protons in a sequence of bent silicon crystals assisted by volume capture

Multiple volume reflections of the 400 GeV/c proton beam by the sequence of fourteen bent silicon strips has been studied at the CERN SPS. The sequence is close to be parallel that is the spread of the strip orientation angles is much smaller than their bend angle and eleven strips working coherently in the regime of volume reflections deflected the beam by 110 mu rad with the efficiency 88%, which is significantly larger than the estimation based on independent reflections. The mechanism giving the efficiency increase has been studied by simulation. It appears that many particles volume captured in one of the strips take part in volume reflections in the subsequent ones. Such a crystal multi reflector can be successfully used as a primary collimator for the beam halo collimation of high-energy accelerators

First observation of multiple volume reflection by different planes in one bent silicon crystal for high-energy protons

Multiple volume reflection by different planes in a bent silicon crystal with its axis orientation close to the beam direction was observed for the first time for 400 GeV/c protons at the CERN SPS. The proton beam was deflected to the side opposite to the crystal bend by an angle of about 67 urad, which is five times larger than in a single volume reflection by the (110) bent planes. The registered efficiency of one side deflection was about 84%. It was shown that multiple volume reflection transforms to a single volume reflection when the orientation angle of the axis relative to the beam direction is increased

计划与市场相结合的金融调控机制初探

本文试图通过对计划与市场这两种经济调节手段的研究，探索 金融领域中英立两者有机结合。金融调控机制的途径．文章先从。 究计划与市场的涵义及两者的关系人手，探讨金融调控中运用这两 种手段的必要性与可能性，再从计划与市场的最佳结合方式看眼， 找出金融调控中计划与市场有机结合的难点与重点，继两结合分析 我国中央银行现行调控手段的弊端，深入详尽地探讨难点的解决办 法，重点提出培育金融市场机制和完善信贷计划手段的对策，最后 沿着这一思路，进行建立我国计划与市场有机结合的金融调控机制 的构想。 全文共分四个部分．＿ 第一部分通过对计划，市场所下定义，明确两者都去经济调节 手段，并非相互...学位：经济学硕士院系专业：经济学院财政金融系_金融学(含保险学)学号：YL00012