107346282
Progress on the high-current 704 MHz superconducting RF cavity at BNL
The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups and results for the copper prototype. The progress with the niobium cavity fabrication will also be described.
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.
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.
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.
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.
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
1190941
Higher moments of net proton multiplicity distributions at RHIC.
We report the first measurements of the kurtosis (κ), skewness (S), and variance (σ2) of net-proton multiplicity (Np-Np) distributions at midrapidity for Au+Au collisions at square root of s(NN)=19.6, 62.4, and 200 GeV corresponding to baryon chemical potentials (μB) between 200 and 20 MeV. Our measurements of the products κσ2 and Sσ, which can be related to theoretical calculations sensitive to baryon number susceptibilities and long-range correlations, are constant as functions of collision centrality. We compare these products with results from lattice QCD and various models without a critical point and study the square root of s(NN) dependence of κσ2. From the measurements at the three beam energies, we find no evidence for a critical point in the QCD phase diagram for μB below 200 MeV.
118838150
Recent Heavy Flavor Results at RHIC
We summarize the recent experimental results of heavy favor physics from the Relativistic Heavy Ion Collider (RHIC) in Brookhaven National Lab (BNL) at Long Island, New York, USA.We will discuss the directly reconstructed open charm mesons as well as electrons from heavy favor hadron decays. The charm and bottom quark production cross-sections have also been measured. We will also discuss JPsi and Upsilon states in p+p and heavy ion collisions. The studies described here were carried out and reported by the STAR and PHENIX collaborations at RHIC.
118658801
Note on a noncritical holographic model with a magnetic field
We consider a noncritical holographic model constructed from an intersecting brane configuration D4 root D4-D4 with an external magnetic field. We investigate the influences of this magnetic field on strongly coupled dynamics by the gauge/gravity correspondence.
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.
53453694
Extended phase space thermodynamics for third-order Lovelock black holes in diverse dimensions
Treating the cosmological constant as thermodynamic pressure and its conjugate as thermodynamic volume, we investigate the critical behavior of the third-order Lovelock black holes in diverse dimensions. For black hole horizons with different normalized sectional curvature $$k=0,\pm 1$$k=0,±1, the corresponding critical behaviors differ drastically. For $$k=0$$k=0, there is no critical point in the extended thermodynamic phase space. For $$k=-1$$k=-1, there is a single critical point in any dimension $$d\ge 7$$d≥7, and for $$k=+1$$k=+1, there is a single critical point in $$7$$7 dimensions and two critical points in 8, 9, 10, 11 dimensions. We studied the corresponding phase structures in all possible cases.