110532551
Status of high current R&D Energy Recovery LINAC at Brookhaven National Laboratory
An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under construction at Brookhaven National Laboratory (BNL) for testing of concepts relevant for high-energy coherent electron cooling and electron-ion colliders. One of the goals is to demonstrate an electron beam with high charge per bunch ({approx} 5 nC) and low normalized emittance ({approx} 5 mm-mrad) at an energy of 20 MeV. Flexible lattice of ERL loop provides a test-bed for investigating issues of transverse and longitudinal instabilities, and diagnostics for intense CW e-beam. The superconducting 703 MHz RF photoinjector is considered as an electron source for such a facility. We will start with a straight pass (gun - 5 cell cavity - beam stop) test for the SRF Gun performance studies. Later, we will install and test a novel injection line concept for emittance preservation in a lower energy merger. In this paper we present the status and our plans for construction and commissioning of this facility.
55660748
HOM identification by bead pulling in the Brookhaven ERL cavity
Abstract Exploratory measurements of the Brookhaven Energy Recovery Linac (ERL) cavity at superconducting temperature produced a long list of high order modes (HOMs). The niobium 5-cell cavity is terminated at each end with HOM ferrite dampers that successfully reduce the Q -factors to levels required to avoid beam break up (BBU) instabilities. However, a number of un-damped resonances with Q ≥10 6 were found at 4 K and their mode identification forms the focus of this paper. The approach taken here consists of bead pulling on a copper (Cu) replica of the ERL cavity with dampers involving various network analyzer measurements. Several different S 21 transmission measurements are used, including those taken from the fundamental input coupler to the pick-up probe across the cavity, others between beam-position monitor probes in the beam tubes, and also between probes placed into the cells. The bead pull technique suitable for HOM identification with a metallic needle or dielectric bead is detailed. This paper presents the results for HOMs in the first two dipole bands, the un-damped modes in the first quadrupole band, and the identification of several high- Q modes beyond.
106990919
Multipacting in a grooved choke joint at SRF gun for BNL ERL prototype
The 703 MHz superconducting gun for BNL ERL prototype was tested at JLab with and without choke-joint and cathode stalk. Without choke-joint and cathode stalk, the gradient reached was 25 MV/m with Q{sup 0} {approx} 6E9. The gun cathode insertion port is equipped with a grooved choke joint for multipacting suppression. We carried out tests with choke-joint and cathode stalk. The test results show that there are at least two barriers at about 3.5 MV/m and 5 MV/m. We considered several possibilities and finally found that fine details of the grooved shape are important for multipacting suppression. A triangular groove with round crest may cause strong multipacting in the choke-joint at 3.5 MV/m, 5 MV/m and 10 MV/m. This paper presents the primary test results of the gun and discusses the multipacting analysis in the choke-joint. It also suggests possible solutions for the gun and multipacting suppressing for a similar structure.
56445385
Design, simulation and conditioning of the fundamental power couplers for BNL SRF gun
The 704 MHz SRF gun for the BNL Energy Recovery Linac (ERL) prototype uses two fundamental power couplers (FPCs) to deliver up to 1 MW of CW RF power to the half-cell cavity. To prepare the couplers for high-power RF service and process multipacting, the FPCs should be conditioned prior to installation into the gun cryomodule. A room-temperature test stand was configured for conditioning FPCs in full reflection regime with varied phase of the reflecting wave. The FPCs have been conditioned up to 250 kW in pulse mode and 125 kW in CW mode. The multipacting simulations were carried out with Track3P code developed at SLAC. The simulations matched the experimental results very well. This paper presents the FPC RF and thermal design, multipacting simulations and conditioning of the BNL gun FPCs.
119109044
High-energy high-luminosity electron-ion collider eRHIC
Joanne Beebe-Wang, Sergey Belomestnykh, Michael M. Blaskiewicz, Rama Calaga, XiangyunChang, Alexei Fedotov, David Gassner, Harald Hahn, Ping He, William Jackson, Animesh Jain,Elliott C.Johnson, Dmitry Kayran, Jorg Kewisch, Yun Luo, George Mahler, Gary McIntyre, WuzhengMeng, Michiko Minty, Brett Parker, Alexander Pikin, Vadim Ptitsyn, Triveni Rao, Thomas Roser, JohnSkaritka, Brian Sheehy, Steven Tepikian, Yatming Than, Dejan Trbojevic, Nicholaos Tsoupas, JosephTuozzolo, Gang Wang, Qiong Wu, Wencan Xu, and Anatoly Zelenski
54678014
High Current SRF Cavity Design for SPL and eRHIC
A high current five-cell Nb superconducting cavity, called BNL3 cavity, was optimized and designed for the SPL and eRHIC. For the fundamental mode, the optimization process aimed at maximizing the R/Q of the fundamental mode and the geometry factor G under an acceptable RF field ratio level of B{sub peak}/E{sub acc} and E{sub peak}/E{sub acc}. For higher order modes, the optimization is to lower (R/Q)Q{sub ext} for dipole and quadrupole modes to suppress the beam-break-up (BBU). To extract the HOM power out of the cavity, the BNL3 cavity employs a larger beam pipe, allowing the propagation of HOMs, but not the fundamental mode. Six HOM couplers (three at each end) are used to extract large HOM power. To avoid the cross-talk between cavities, tapers are employed between the cavities. This paper presents the design of the BNL3 cavity, end groups and BBU simulation results.
119106935
Applying Bayesian neural networks to event reconstruction in reactor neutrino experiments
A toy detector has been designed to simulate central detectors in reactor neutrino experiments in the paper. The electron samples from the Monte-Carlo simulation of the toy detector have been reconstructed by the method of Bayesian neural networks (BNNs) and the standard algorithm, a maximum likelihood method (MLD), respectively. The result of the event reconstruction using BNN has been compared with the one using MLD. Compared to MLD, the uncertainties of the electron vertex are not improved, but the energy resolutions are significantly improved using BNN. And the improvement is more obvious for the high energy electrons than the low energy ones.
118418619
Novel rotating hairy black hole in (2+1)-dimensions
We present some novel rotating hairy black hole metric in (2 + 1) dimensions, which is an exact solution to the field equations of the Einstein-scalar-AdS theory with a non-minimal coupling. The scalar potential is determined by the metric ansatz and consistency of the field equations and cannot be prescribed arbitrarily. In the simplified, critical case, the scalar potential contains two independent constant parameters, which are respectively related to the mass and angular momentum of the black hole in a particular way. As long as the angular momentum does not vanish, the metric can have zero, one or two horizons. The case with no horizon is physically uninteresting because of the curvature singularity lying at the origin. We identify the necessary conditions for at least one horizon to be present in the solution, which imposes some bound on the mass-angular momentum ratio. For some particular choice of parameters our solution degenerates into some previously known black hole solutions.
124762878
Results of R&D on a new construction technique for W/ScFi Calorimeters
We report on results of an R&D program to develop new, simple and cost effective techniques to build compact sampling calorimeters utilizing tungsten powder and scintillating fibers. Such calorimeter detectors are under consideration for experiments at the planned Electron Ion Collider and the future upgrade of the STAR experiment at RHIC (BNL). In the first year of this R&D project we built two prototypes of very compact electromagnetic calorimeters and tested them at FNAL test beam T1018 in January 2012. Details of the construction technique, results of the test run and future plan will be presented.
117043294
Three dimensional rotating hairy black holes, asymptotics and thermodynamics
A rotating hairy black hole solution is found in gravity minimally coupled to a self-interacting real scalar field in three spacetime dimensions. Then we discuss analytically the horizon structure and find an analogue of the famous Kerr bound in (2+1) dimensions because of the existence of black hole horizons. We present the asymptotic symmetries and find the same symmetry group (i.e. the conformal group) and central charge as in pure gravity. Based on the asymptotic behavior, the mass and angular momentum are presented by the Regge-Teitelboim approach. Other thermodynamic quantities are also obtained and the first law of black hole thermodynamics and Smarr relation are checked. In addition, we also investigate the local thermodynamic stability and find the existence of Hawking-Page phase transition in the rotating hairy black hole.
17939294
Yang-Type Monopoles In 5 Dimensional Curved Space-Time
Motivated by Gibbons and Townsend's recent work, we construct Yang-Type monopoles in maximally symmetric space-time. We then analyze the dependence of horizon structure of the space-times around the 5-dimensional monopoles on the relative strength of gravitations to Yang-Mills interactions. We also analyze the stability of the monopoles against tensor type perturbations on metrics.