54868722
EXPERIMENTAL PROGRESS OF DC-SC PHOTOINJECTOR AT PEKING UNIVERSITY*
Beam loading experiments on DC-SC photoinjector test facility have been finished at 4.4 K. Upon the present experiments, the gradient of 6 MV/m is achieved. The maximum energy gain is 1.1 MeV at 4.4 K. With average beam current of 270 mA, the measured rms emittance is about 5 mm-mrad at the beam energy of 500 keV. Experiments on the test facility has validated that the DC-SC photoinjector is a good choice to provide moderate average current electron beams with low bunch charge and very high repetition rate.
110284812
SVD-BASED METHOD FOR MEASUREMENT OF BEAM PARAMETERS AND FLAG RESOLUTION *
In NSLS II booster to storage ring transport line, the typical beam size in vertical plane is ~60 �� m, which requires very high flag resolution to get good beam parameters measurement. This paper describes a new SVD-based method to measure transverse beam parameters and flag resolution simultaneously with double quads scan. Implementation simulations of the proposed method are performed for a dispersion free region in the NSLS-II booster to storage ring transport line. With this method, it breaks the limitation of beam parameters measurement accuracy due to the flag resolution.
110196583
SHORT PULSE GENERATION BY LASER SLICING AT NSLSII
We discuss an upgrade R&D project for NSLSII to generate sub-pico-second short x-ray pulses using laser slicing. We discuss its basic parameters and present a specific example for a viable design and its performance. Since the installation of the laser slicing system into the storage ring will break the symmetry of the lattice, we demonstrate it is possible to recover the dynamical aperture to the original design goal of the ring. There is a rapid growth of ultrafast user community interested in science using sub-pico-second x-ray pulses. In BNL's Short Pulse Workshop, the discussion from users shows clearly the need for a sub-pico-second pulse source using laser slicing method. In the proposal submitted following this workshop, NSLS team proposed both hard x-ray and soft x-ray beamlines using laser slicing pulses. Hence there is clearly a need to consider the R&D efforts of laser slicing short pulse generation at NSLSII to meet these goals.
55642524
MODULATION OF LOW ENERGY BEAM TO GENERATE PREDEFINED BUNCH TRAINS FOR THE NSLS-II TOP-OFF INJECTION*
The NSLS II linac will produce a bunch train, 80-150 bunches long with 2 ns bunch spacing. Having the ability to tailor the bunch train can lead to the smaller bunch to bunch charge variation in the storage ring. A stripline is planned to integrate into the linac baseline to achieve this tailoring. The stripline must have a fast field rise and fall time to tailor each bunch. The beam dynamics is minimally affected by including the extra space for the stripline. This paper discusses the linac beam dynamics with stripline, and the optimal design of the stripline. A stripline is to be integrated in the linac to match the storage ring uniform bunch charge requirement, which simplifies the gun pulser electronics and looses the edge uniform requirement. It is located at low energy to lower the stripline power supply requirement and limit the dumped electron radiation. By turning off the stripline, the beam dynamics through linac is comparable with the baseline design. More advanced ideas can be explored. If a DC corrector along with the stripline is used, the core bunch trains gets kick from the stripline while the head and the tail of bunch train just gets amore » DC kick. The stripline power supply waveform is a single flat top waveform with fast rise and drop and the pulse length is {approx}200 ns long or 100 bunches, which may be easier from the power supply view point. We are also considering the bunch by bunch charge manipulation to match the storage ring uniform bunch charge distribution requirement. By modulating the flat top waveform at 250 MHz with adjustable amplitude, each the bunch center is either at 45 degree or 135 degree. Only the head or tail of the bunch is trimmed out. Although each bunch center deviation from idea center is very different at low energy, it is gradually minimized with beam energy increase.« less
110104367
OPTICAL DESIGN OF THE ENERGY RECOVERY LINAC FEL AT PEKING UNIVERSITY
Peking University is currently designing an Energy Recovery Linac FEL (PKU-ERL-FEL). The system is consisted of a DC-SC photocathode injector, a superconducting linac which is composed of two nine cell TESLA-type cavities, an undulator and beam transport system. The objectives of the PKU-ERL-FEL are providing infrared FEL and building a test-bed for the study of beam dynamics and accelerator technology for energy recovery. In this paper the main parameters of the PKU-ERL-FEL are described and the optical design for the beam transport of PKU-ERL-FEL is presented. The simulation is carried out using the typical particle tracking codes such as elegant.
55938998
BEAM DIAGNOSTICS USING BPM SIGNALS FROM INJECTED AND STORED BEAMS IN A STORAGE RING
Many modern light sources are operating in top-off injection mode or are being upgraded to top-off injection mode. The storage ring always has the stored beam and injected beam for top-off injection mode. So the BPM data is the mixture of both beam positions and the injected beam position cannot be measured directly. We propose to use dedicated wide band BPM electronics in the NSLS II storage ring to retrieve the injected beam trajectory with the singular value decomposition (SVD) method. The beam position monitor (BPM) has the capability to measure bunch-by-bunch beam position. Similar electronics can be used to measure the bunch-by-bunch beam current which is necessary to get the injection beam position. The measurement precision of current needs to be evaluated since button BPM sum signal has position dependence. The injected beam trajectory can be measured and monitored all the time without dumping the stored beam. We can adjust and optimize the injected beam trajectory to maximize the injection efficiency. We can also measure the storage ring acceptance by mapping the injected beam trajectory.
119770548
ION CHANNELING STUDY OF RADIATION INDUCED DEFECTS IN A BENT SILICON CRYSTAL
Abstract High energy proton channeling (12–120 GeV) and low energy helium ion channeling (1.5–4 MeV) have been used to study the effects of radiation damage induced in silicon by high energy (400 GeV) proton irradiation. It is shown that radiation fluence up to 1017/cm2 does not preclude deflection of high energy charged particle beams in elastically bent silicon crystals. Evidence of macroscopic segregation of residual defects in the strain field of a deformed crystal is demonstrated.
54192336
Proton-proton correlations in central collisions of Ni + Ni at 1.93 A.GeV and the space-time extent of the emission source
Small-angle correlations of proton pairs produced in central Ni+Ni collisions at a beam energy of 1.93 A · GeV are investigated with the FOPI detector system at GSI Darmstadt. Simultaneous comparison of longitudinal and transverse correlation functions with the predictions of the Koonin model allows to unravel the space-time ambiguity of the source extension. The determination of the source rest frame is found essential for the identification of this effect. For the present system, the selection of central events comprising about 8% of the total cross section allows for the isolation of a compact source in momentum space which is centered around the c.m. velocity of the colliding nuclei. Taking into account the strong collective expansion of the participant zone, which introduces a reduction of the extracted source radius of more than 30%, r.m.s. radius and emission time parameters of Rrms=(4.2±1.2) fm and trms=(11+7-5) fm/c are extracted, respectively. In contrast, the analysis of the angle-integrated correlation function mixes the spatial and temporal size of the source and gives an upper limit Rrms=(7.0 ± 0.8) fm of the source radius.
119181798
Radiative E1 decays of X(3872)
Abstract Radiative E1 decay widths of X ( 3872 ) are calculated through the relativistic Salpeter method, with the assumption that X ( 3872 ) is the χ c 1 ( 2 P ) state, which is the radial excited state of χ c 1 ( 1 P ) . We first calculated the E1 decay width of χ c 1 ( 1 P ) . The result is in agreement with experimental data excellently. Then we calculated the width of X ( 3872 ) with the assignment χ c 1 ( 2 P ) . Results are: Γ ( X ( 3872 ) → γ J / ψ ) = 33.0 keV , Γ ( X ( 3872 ) → γ ψ ( 2 S ) ) = 146 keV and Γ ( X ( 3872 ) → γ ψ ( 3770 ) ) = 7.09 keV . The ratio Br ( X ( 3872 ) → γ ψ ( 2 S ) ) / Br ( X ( 3872 ) → γ J / ψ ) = 4.4 agrees with experimental data by BaBar, but is larger than the new up-bound reported by Belle recently. With the same method, we also predicted the decay widths, Γ ( χ b 1 ( 1 P ) ) → γ ϒ ( 1 S ) = 30.0 keV , Γ ( χ b 1 ( 2 P ) ) → γ ϒ ( 1 S ) = 5.65 keV and Γ ( χ b 1 ( 2 P ) ) → γ ϒ ( 2 S ) = 15.8 keV , from which we get the full widths: Γ ( χ b 1 ( 1 P ) ) ∼ 85.7 keV and Γ ( χ b 1 ( 2 P ) ) ∼ 66.5 keV .
16190768
|Delta B|=1 Weak Effective Lagrangian in the Minimal Flavor Violation Supersymmetry
To evaluate the weak decays of b-hadrons, the ∆B = 1 weak effective Lagrangian is the foundation. Any new physics beyond the standard model (SM) would contribute to the effective Lagrangian through the loop integration at the weak scale and evolution from the weak scale down to the hadronic scale. In this work we present a systematic analysis on the effective Lagrangian which mediates hadronic |∆B| = 1 processes in the framework of the minimal flavor violation supersymmetry as well as a numerical evaluation of the Wilson coefficients in the effective theory. PACS numbers: 11.30.Er, 12.15.Ff, 12.60.Jv, 13.10+q.
119253082
Non-photonic electron-hadron correlations and non-photonic electron v2 at STAR/RHIC
Abstract Non-photonic electrons ( p T > 3 GeV / c ) represent the directions of the parent heavy quarks, and their angular correlations with charged hadrons provide a good tool to study the relative contributions from D and B meson decays in p+p collisions, as well as the flavor-dependence of the energy loss mechanism in A+A collisions. We review the disentanglement of charm and bottom contributions to non-photonic electrons in p+p collisions at s = 200 GeV at RHIC. B decay contribution is approximately 50% at the electron transverse momentum of p T > 5 GeV / c from STAR results. Incorporating the energy loss ( R AA ) information of non-photonic electrons, the result indicates a B meson suppression at high p T in heavy ion collisions. We also present non-photonic electron-hadron correlations in d+Au collisions as a baseline reference for the investigation of the heavy quark energy loss in A+A collisions. The interactions between heavy quarks and the QCD medium can lead to a non-zero “elliptic flow” parameter ( v 2 ) of D and B mesons which can be studied through v 2 of non-photonic electrons. Preliminary v 2 measurements for non-photonic electrons are shown to be lower than v 2 of charged hadrons (or K S 0 , Λ ) for 200 GeV Au+Au collisions.