111152253
Multipacting simulation and test results of BNL 704 MHz SRF gun
The BNL 704MHz SRF gun has a grooved choke joint to support the photo-cathode. Due to the distortion of grooves at the choke joint during the BCP for the choke joint, several multipacting barriers showed up when it was tested with Nb cathode stalk at JLab. We built a setup to use the spare large grain SRF cavity to test and condition the multipacting at BNL with various power sources up to 50kW. The test is carried out in three stages: testing the cavity performance without cathode, testing the cavity with the Nb cathode stalk that was used at Jlab, and testing the cavity with a copper cathode stalk that is based on the design for the SRF gun. This paper summarizes the results of multipacting simulation, and presents the large grain cavity test setup and the test results.
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.
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.
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.
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
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.
118561275
Test of the prototype of electron detector for LHAASO project using cosmic rays
LHAASO project is to be built in south-west China, which use an array of 5137 election detectors for the measurement of the incident electrons arriving at the detector plane. For the quality control of the big quantity of electron detectors, a cosmic ray hodoscope with two-dimensional spacial sensitivity and good time resolution has been developed. The ?rst prototype of electron detector is tested with the hodoscope and the performance of the detector is validated to be consistent with the design.
119246945
Charged black hole with a scalar hair in (2+1) dimensions
We obtain and analyze an exact solution to Einstein-Maxwell-scalar theory in (2+1) dimensions, in which the scalar field couples to gravity in a nonminimal way, and it also couples to itself with the self-interacting potential solely determined by the metric ansatz. A negative cosmological constant naturally emerges as a constant term in the scalar potential. The metric is static and circularly symmetric and contains a curvature singularity at the origin. The conditions for the metric to contain 0, 1 and 2 horizons are identified, and the effects of the scalar and electric charges on the size of the black hole radius are discussed. Under proper choices of parameters, the metric degenerates into some previously known solutions in (2 + 1)-dimensional gravity.
119245563
FIVE-DIMENSIONAL VACUUM EINSTEIN SPACETIMES IN C-METRIC LIKE COORDINATES
A five-dimensional Einstein spacetime with (non)vanishing cosmological constant is analyzed in detail. The metric is in close analogy with the four-dimensional massless uncharged C-metric in many aspects. The coordinate system, horizons and causal structures, relations to standard form of de Sitter, anti de Sitter and Minkowski vacua are investigated. After a boost and Kaluza–Klein reduction, we get an exact solution of four-dimensional Einstein–Maxwell–Liouville theory which reduces to a solution to Einstein–Liouville theory in the limit of zero boost velocity and to that of Einstein–Maxwell–dilaton theory in the case of zero cosmological constant.
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.
197490176
Membrane in M5-branes Background
In this paper, we investigate the properties of membrane in the M5-branes background. Through solving the classical equations of motion of membrane, we can understand the classical dynamics of membrane in this background.