172134161
INSTALLATION AND COMMISSIONING OF THE 100 MeV PREINJECTOR LINAC OF THE NEW ELETTRA INJECTOR
A new full energy injector has been installed and commissioned at ELETTRA, the Italian Synchrotron Light Source facility in Trieste. It consists of a 100 MeV pre-injector linac followed by a 2.5 GeV booster Synchrotron, that fills the Elettra Storage Ring with 2.0 GeV and 2.4 GeV electrons. Here a complete description of the preinjector linac and a first evaluation of its performance will be presented and discussed. INTRODUCTION AND MILESTONES The new ELETTRA full energy injector, consisting of a 100 MeV pre-injector linac and a 2.5 GeV booster synchrotron, has been successful commissioned and routinely providing electrons for the storage ring for users operations since 3 of March 2008 [1]. The new pre-injector linac can fill the booster in two operating modes: • single bunch mode (SB), with one booster RF bucket (@500 MHz) filled; • multibuch mode (MB), with up to 75 buckets filled. The main parameters of the machine are summarized in Table 1, showing the designed and achieved performance. One of the most important requirements of the new injection system is to guarantee the operation in top-up mode, keeping constant the ELETTRA stored current. This in general implies machine reliability and an adequate safety margin for the operating levels of the main components. For this reasons the pre-injector layout foresees a second RF power station, now under assembly, with a spare klystron that guarantees the machine operation in case of fault of the main RF plant. This will have a noticeably effect on the down time of the machine. The installation of the pre-injector started at the end of June ’07 with co-occupancy of the building and putting in place the two main accelerating sections. The whole machine installation, the first RF plant, the WG circuits and the ancillary systems, was completed in late August. Two weeks were spent for RF conditioning of the accelerating structures (Aug. 24Sept. 6), pushing the klystron peak power up to 38-40 MW for 3.5 μsec pulse width at 10 Hz pulse repetition rate (prr). The first electrons from the gun were extracted on September 7 (multi bunch mode) and a week later we transported the first accelerated beam to the exit of the second accelerating section, measuring 90 MeV beam energy (September 15). Then the machine was operated up to Sept. 24 to explore its performance and for beam optimization. With a quite moderate level of power from the klystron, (≈ 36 MW), we have obtained a beam energy in excess of 115 MeV, with 100 mA current in 100 nsec pulse width. The overall transmission efficiency (Gun-Linac exit) was better than 60% and a first estimation of beam energy spread was less than 1 MeV @ 115 MeV. After these preliminary tests, from September 25, the machine was set at 110 MeV, 20 mA, 100 nsec, to allow, the starting of booster commissioning. Table 1: Preinjector main beam parameters
45940461
STATUS OF THE FERMI @ ELETTRA PHOTOINJECTOR
The new FERMI@Elettra photoinjector is presently undergoing high-power testing and characterization at MAXlab in Lund, Sweden. This effort is a collaboration between Sincrotrone Trieste, MAX-lab and UCLA. The 1.6-cell RF gun cavity and the focusing solenoid were successfully designed and built by the Particle Beam Physics Laboratory at UCLA, delivered to Sincrotrone Trieste at the beginning of 2008, and installed in the linac tunnel at MAX-lab. Use of the MAX-lab facility will allow the FERMI project to progress significantly with the photoinjector while waiting for the completion of the new linac building extension at Sincrotrone Trieste. We report here on the high-power conditioning of the RF cavity and the first beam tests. STATUS OF THE FERMI@ELETTRA PHOTOINJECTOR∗ M. Trovò† , L. Badano, S. Biedron, D. Castronovo, F. Cianciosi, P. Craievich, M.D. Danailov, G. D’Auria, M. Ferianis, S.V. Milton, G. Penco, L. Pivetta, L. Rumiz, D. Wang, Sincrotrone Trieste, Trieste, Italy M. Eriksson, D.Kumbaro, F. Lindau, MAX-lab, Lunds Universitet, Lund, Sweden H. Badakov, A. Fukasawa, B. O’Shea, J. Rosenzweig, UCLA Department of Physics and Astronomy, Los Angeles, CA 90095
124623797
HESYRL 200 MeV linac single bunch energy spectrum measurement
The HESYRL 200-MeV electron linac was completed in December 1987, and has been running well. A careful study of the single-bunch energy spectrum for the linac was done. The measurement shows that the energy spread of the linac is +or-0.4%. The energy spectrum is quite stable and repeatable, and the resolution and accuracy are found to be satisfactory.<<ETX>>
55356715
PROGRESS OF THE eRHIC ELECTRON RING DESIGN
Over the past year, a baseline design of the electron ring for the eRHIC hadron-lepton collider has been developed. This site-specific design is based on the understanding of the existing RHIC machine performance and its possible upgrades. The design includes a full energy polarized electron beam injector to ensure operational reliability and to provide high integrated luminosity. The electron ring energy range is 5 to 10 GeV. The electron beam emittance, the electron beam path length, and the interaction region optics have to be adjustable over wide ranges depending on the ion species and energy for collisions. We describe the design features and expected machine performance. The results of recent beam polarization and beam-beam studies are also discussed.
120931097
Stripline beam position monitor for the MIT-Bates South Hall Ring
The MIT-Bates South Hall Ring (SHR) is an electron storage ring currently being commissioned. It is designed to operate at an RF frequency of 2856 MHz with all of the 1812 buckets filled and a circulating current of 80 mA or greater. This leads to a small charge per bunch and the requirement for beam position monitors. Since there will be 31 such monitors in the vacuum system, it is important to suppress trapped modes which may excite coupled bunch instabilities. The stripline monitor built for the SHR is a stainless steel structure, designed to be manufactured using standard machining techniques and commercial feedthroughs. With proper 50 Ohm matching and a geometry derived from insight from MAFIA calculations, the monitor was constructed having a nearly flat RF response up through 10 GHz over the range of measurement. The stripline electronics allows the measurements with 0.1 mm resolution, maintains orbital harmonics information past the 10th harmonic, and operates over a dynamic range of 1 mA to greater than 80 mA of beam current.<<ETX>>
55429266
STUDY OF THE ENERGY CHIRP EFFECTS ON SEEDED FEL SCHEMES AT SDUV-FEL
In this paper, theoretical and simulation study of the energy chirp effects on the HGHG and EEHG schemes are present. It is found that the central wavelength and output bandwidth of EEHG can be nearly immune to the beam energy chirp by properly setting the strengths of the chicanes. Experimental studies for both these two schemes have been carried out at the SDUV-FEL to demonstrate the theoretical predictions.
109205409
A design and performance analysis tool for superconducting RF systems
Superconducting RF systems are usually operated with continuous RF power or with RF pulse lengths exceeding 1 ms to maximize the overall wall plug power efficiency. Typical examples are CEBAF at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) and the TESLA Test Facility at DESY. The long pulses allow for effective application of feedback to stabilize the accelerating field in presence of microphonics, Lorentz force detuning, and fluctuations of the beam current. In this paper we describe a set of tools to be used with MATLAB and SIMULINK, which allow to analyse the quality of field regulation for a given design. The tools include models for the cavities, the RF power source, the beam, sources of field perturbations, and the RF feedback system. The RF control relevant electrical and mechanical characteristics of the cavity are described in form of time-varying state space models. The power source is modelled as a current generator and includes saturation characteristics and noise. An arbitrary time structure can be imposed on the beam current to reflect a macro-pulse structure and bunch charge fluctuations. For RF feedback several schemes can be selected: Traditional amplitude and phase control as well as I/Q control. The choices for the feedback controller include analog or digital approaches and various choices of frequency response. Feed forward can be added to further suppress repetitive errors. The results of a performance analysis of the CEBAF and the TESLA Linac RF system using these tools are presented.
119275688
Recoiling Supermassive Black Holes in Spin-flip Radio Galaxies
Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q {approx}> 0.3 with a minimum possible value q{sub min} {approx_equal} 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s{sup -1} in the direction within an angle {approx}< 40 Degree-Sign relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity andmore » apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to 'dust-poor' active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.« less
119432190
Semileptonic decay Lambda(c) ---> Lambda l+ nu from QCD light-cone sum rules
We present the study of the semileptonic decay \Lambda_c to \Lambda\ell^+\nu by using the light-cone sum rule approach. Distribution amplitudes (DAs) for the \Lambda baryon are discussed to the leading order conformal spin, and QCD sum rule estimate for the corresponding parameters is presented. The form factors describing the decay are calculated and used to predict the decay width and the decay asymmetry parameter \alpha. With the inclusion of twist-3 contributions the calculated decay width \Gamma=(7.2+/-2.0)X10^{-14} GeV as well as asymmetry \alpha=-(0.88+/-0.03) is found in good agreement with the experimental data, while there are appreciable deviations from experiment values when the higher twist contributions are included.
125862664
Dynamical Breaking of Supersymmetry and Its Restoration at High Temperatures
The dynamical breaking of the supersymmetric Higgs model is discussed without adding the Fayet—Iliopoulos term to the Lagrangian. It is shown, in terms of the Nambu—Jona-Lasinio mechanism, that the supersymmetry breaking can be realized dynamically in the supersymmetric Higgs model. The supersymmetry behavior at finite temperatures is also investigated and it is shown that the supersymmetry broken dynamically at zero temperature can be restored at finite temperatures.
125041691
The Start-to-End Simulation of Electron Beam in the RHIC E-cooling Facility (L-band option) with PARMELA
The electron cooling facility has been proposed as a way to reduced the ion beam emittance and energy spread for the RHIC (Relativistic Heavy Ion Collider) to significantly enhance the luminosity. In a high energy electron cooling facilities like the one for RHIC, since the very higher beam quality is needed for the sufficient cooling rate, the traditional way to produce, accelerate and focus beam are hardly applicable. The new solutions include photo-injector for producing the high charge electron bunch with very low emittance, superconducting linac cavities for high current operations, strong cooler solenoid and beam transport to achieve specific beam parameters and make energyrecovery, etc. A start-to-end simulation has been performed with L-band (1.3GHz) gun and linac (TESLA cavity) to demonstrate the feasibility of such an unprecedented cooling facility from the beam production and transport point of view. The main results are, totally revised gun performance considering the crucial heating and RF power issues; workable scheme for merging high/low energy beam into linac with small bending angle dipole, septum magnet and rotation cavity; magnetized beam simulations, beam stretching and compressing, etc. It shows first time that such a design, with high charge beam, magnetized cathode, L-band super-conducting cavities and long transport lines, is feasible from the single bunch particle tracking point of view. The next step is to include real cooler solenoid sections (under design in the Magnet Division). The coherent synchrotron radiation effects is investigated in a separate study.