110815008
Implementation of a DC Bump at the Storage Ring Injection Straight Section
The NSLS II beam injection works with a DC septum, a pulsed septum and four fast kicker magnets. The kicker power supplies each produce a two revolution period pulsed field, 5.2 {micro}s half sine waveform, using {approx}5kA drive voltage. The corresponding close orbit bump amplitude is {approx}15mm. It is desired that the bump is transparent to the users for top-off injection. However, high voltage and short pulse power supplies have challenges to maintain pulse-to-pulse stability and magnet-to-magnet reproducibility. To minimize these issues, we propose implementing a DC local bump on top of the fast bump to reduce the fast kicker strength by a factor of 2/3. This bump uses two storage ring corrector magnets plus one additional magnet at the septum to create a local bump. Additionally, these magnets could provide a DC bump to simulate the septum position effects on the store beam lifetime. This paper presents the detail design of this DC injection bump and related beam dynamics.
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
119066234
NSLS-II Transport Line Progress
The National Synchrotron Light Source II (NSLS-II) is a state-of-the-art 3-GeV third generation light source currently under construction at Brookhaven National Laboratory. The NSLS-II injection system consists of a 200 MeV linac, a 3-GeV booster synchrotron and associated transfer lines. The first part of the Linac to Booster Transport (LBT) line has been installed for linac commissioning. This part includes all components necessary to commission the NSLS-II linac. The second part of this transport line is undergoing installation. Initial results of hardware commissioning will be discussed. The Booster to Storage Ring (BSR) transport line underwent a design review. The first part of the BSR transport line, consisting of all components necessary to commission the booster will be installed in 2012 for booster commissioning. We report on the final design of the BSR line along with the plan to commission the booster.
108968904
LIFETIME MEASUREMENT WITH PSEUDO MOVEABLE SEPTUM IN NSLS X-RAY RING
The National Synchrotron Light Source II (NSLS-II) is a state of the art 3 GeV third generation light source currently under construction at Brookhaven National Laboratory and starts to commission in 2014. The beam injection works with two septa and four fast kicker magnets in an injection section. To improve the injection stability and reproducibility, we plan to implement a slow local bump on top of the fast bump so that the fast kicker strength is reduced. This bump works as a pseudo movable septum. We can also use this 'movable' septum to measure the storage ring beam partial lifetime resulting from the septum edge and possibly increasing the lifetime by moving the stored beam orbit away from the edge. We demonstrate the feasibility of this idea, by implementing DC bump in NSLS X-ray ring. We report the results of beam lifetime measurements as a function of the amplitude of this bumped orbit relative to the septum and the idea of a slow bump that could reduce the fast bump magnet strengths.
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.
122831377
PERFORMANCE OF THE DIAGNOSTICS FOR NSLS-II LINAC COMMISSIONING
The National Synchrotron Light Source II (NSLS-II) is a state of the art 3-GeV third generation light source currently under construction at Brookhaven National Laboratory. The NSLS-II injection system consists of a 200 MeV linac, a 3-GeV booster synchrotron and associated transfer lines. The transfer lines not only provide a means to deliver the beam from one machine to another, they also provide a suite of diagnostics and utilities to measure the properties of the beam to be delivered. In this paper we discuss the suite of diagnostics that will be used to commission the NSLS-II linac and measure the beam properties. The linac to booster transfer line can measure the linac emittance with a three screens measurement or a quadrupole scan. Energy and energy spread are measured in a dispersive section. Total charge and charge uniformity are measured with wall current monitors in the linac and transformers in the transfer line. We show that the performance of the diagnostics in the transfer line will be sufficient to ensure the linac meets its specifications and provides a means of trouble shooting and studying the linac in future operation.
17737818
Non-photonic electron–hadron correlations at STAR
We present STAR's measurements of azimuthal correlations between non-photonic electrons and charged hadrons in p+p, Cu+Cu and Au+Au collisions at GeV. In p+p collisions, from the non-photonic e?h correlation we have extracted the relative B meson semi-leptonic decay contributions to non-photonic electrons up to electron pt ~ 9 GeV/c. In central Cu+Cu and Au+Au collisions where a dense medium is created, we find that the e?h correlation on the away side of the trigger non-photonic electron has been modified in comparison with the expectation from PYTHIA simulations.
20087962
Research on DC-clearing electric field and changes of focusing structure parameters of storage ring
This paper presents DC clearing field to clear ions in vacuum pipe of Hefei ring. It also presents changes of focusing structure parameters caused by the clearing field. It concludes that tune shifts caused by the field are related to real-time closed orbit of the beam. The paper points out that the field asymmetrically distributed along the ring destroys the symmetry of focusing structure and decreases the ring acceptance, which has negative effect to injection and accumulation process in certain condition.
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.
119303730
Annihilation Rate of Heavy 0^{++} P-wave Quarkonium in Relativistic Salpeter Method
Abstract Two-photon and two-gluon annihilation rates of P-wave scalar charmonium and bottomonium up to third radial excited states are estimated in the relativistic Salpeter method. We solved the full Salpeter equation with a well defined relativistic wave function and calculated the transition amplitude using the Mandelstam formalism. Our model dependent estimates for the decay widths: Γ(χc0 → 2γ) = 3.78 keV, Γ(χ′c0 → 2γ) = 3.51 keV, Γ(χb0 → 2γ) = 48.8 eV and Γ(χ′b0 → 2γ) = 50.3 eV. We also give estimates of total widths by the two-gluon decay rates: Γtot(χc0) = 10.3 MeV, Γtot(χ ′ c0) = 9.61 MeV, Γtot(χb0) = 0.887 MeV and Γtot(χ ′ b0) = 0.914 MeV.
121351951
LLRF systems for subharmonic buncher system of BEPCII Linac
The linear accelerator (Linac) completed in 2007 for the upgrading project of the Beijing Electron Positron Collider (BEPCII) provides 1.89 GeV electrons and positrons for the storage rings. BEPCII Linac decides to update the bunching system and adopts two-bunch operation to enhance beam quality and injection rate as its second update phase. Two subharmonic bunchers will be used in this project: one operates at 142.8 MHz and the other operates at 571.2 MHz. Each subharmonic buncher consists of the bunching cavity, power source, LLRF system and other related subsystems. This paper mainly describes the LLRF systems for the subharmonic buncher systems (SHB). (C) 2009 Elsevier B.V. All rights reserved.