92986025
COMMISSIONING OF THE SSRF BOOSTER
The SSRF Booster, designed to accelerate the electrons from 150MeV to 3.5GeV, is a FODO structure synchrotron with 180m circumference and 2Hz repetition rate. The commissioning of the SSRF booster from the LTB transfer line started on Sept. 30th evening, 2007, the first turns of beam in the booster was obtained in 20 hours. With about 60 hours effective commissioning effort, the electrons were accelerated to 3.5GeV on October 5th morning, 2007. And then the first 3.5GeV beam was extracted to BTS transfer line on October 30th, 2007. In this paper, the SSRF booster is introduced and its commissioning results are presented. INTRODUCTION Shanghai Synchrotron Radiation Facility (SSRF) is a 3rd generation light source, which consists of a 150MeV LINAC, a full energy booster synchrotron and a 20-DBA storage ring. It will provide 4nm·rad nature emittance electron beam at 3.5GeV [1][2]. SSRF booster is used to accelerate the electron beam from 150MeV to 3.5GeV. It is composed with 2 super periods, 28 standard FODO cells and 180m circumferences. The curvature radius of dipole is 14.515m, which can reduce the eddy currents effectively during the energy ramping. There are also eight 2.9m straight sections, which used for the installation of injection, extraction and radio frequency systems [3]. BOOSTER PARAMETERS Fig.1 shows layout of one standard booster cell. Fig.2 shows lattice functions in one quarter of the ring. Figure1: Layout of one standard booster cell. Figure 2: Twiss parameters of SSRF booster synchrotron. (One fourth of the ring is shown.). There are two modes, single bunch and multi bunch, designed for booster commissioning, which can satisfy both the accumulative rate and the top-up injection requirements of the storage ring. The main parameters of the booster are shown in Table 1. Table 1: Main Parameters of the Booster Parameters Value Energy range (GeV) 0.15~3.5 Single bunch 2 Current (mA) Multi bunch 15 Repetition rate (Hz) 2 Cell length (m) 6.4286 Length of long straight (m) 2.904 RF frequency (MHz) 499.654 Harmonic number 300 Nature emittance (nm·rad) 104 Tune, νH /νV 8.181/5.229 Natural chromaticity, ξH/ξV -9.91/-7.45 Nature energy spread 7.799×10 Momentum compaction, αP 0.01849 Damping time, τH,V,L (ms) 4.77/4.60/2.26 Longitudinal tune, νs 0.019 Bunch length (mm) 21.4 0 5 10 15 20 25 30 35 40 45 -5 0 5 10 15 20 25 30 s [m] β x ,y [m ] Twiss Parameters 0 5 10 15 20 25 30 35 40 45 0 0.2 0.4 0.6 0.8 1
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>>
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
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.
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.
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>>
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.
119232861
Phase-merging enhanced harmonic generation free-electron laser
Together with one of its variants, the recently proposed phase-merging enhanced harmonic generation (PEHG) free-electron laser (FEL) is systematically studied in this paper. Different from a standard high-gain harmonic generation scheme, a transverse gradient undulator is employed to introduce a phase-merging effect into the transversely dispersed electron beam in PEHG. The analytical theory of the phase-merging effect and the physical mechanism behind the phenomenon are presented. Using a representative set of beam parameters, intensive start-to-end simulations for soft x-ray FEL generation are given to illustrate the performance of PEHG. Moreover, some practical issues that may affect the performance of PEHG are also discussed.
26749894
Compensating the electron beam energy spread by the natural transverse gradient of laser undulator in all-optical x-ray light sources.
All-optical ideas provide a potential to dramatically cut off the size and cost of x-ray light sources to the university-laboratory scale, with the combination of the laser-plasma accelerator and the laser undulator. However, the large longitudinal energy spread of the electron beam from laser-plasma accelerator may hinder the way to high brightness of these all-optical light sources. In this paper, the beam energy spread effect is proposed to be significantly compensated by the natural transverse gradient of a laser undulator when properly transverse-dispersing the electron beam. Theoretical analysis and numerical simulations on conventional laser-Compton scattering sources and high-gain all-optical x-ray free-electron lasers with the electron beams from laser-plasma accelerators are presented.
55611808
Measurement of Short Bunches
In recent years, there has been increasing interest in short electron bunches for different applications such as short wavelength FELs, linear colliders, and advanced accelerators such as laser or plasma wakefield accelerators. One would like to meet various requirements such as high peak current, low momentum spread, high luminosity, small ratio of bunch length to plasma wavelength, and accurate timing. Meanwhile, recent development and advances in RF photoinjectors and various bunching schemes make it possible to generate very short electron bunches. Measuring the longitudinal profile and monitoring bunch length are critical to understand the bunching process and longitudinal beam dynamics, and to commission and operate such short bunch machines. In this paper, several commonly used measurement techniques for subpicosecond bunches and their relative advantages and disadvantages are discussed. As examples, bunch length related measurements at Jefferson lab are presented. At Jefferson Lab, bunch lengths s short as 84 fs have been systematically measured using a zero-phasing technique. A highly sensitive Coherent Synchrotron Radiation (CSR) detector has been developed to noninvasively monitor bunch length for low charge bunches. Phase transfer function measurements provide a means of correcting RF phase drifts and reproducing RF phases to within a couple of tenths ofmore » a degree. The measurement results are in excellent agreement with simulations. A comprehensive bunch length control scheme is presented.« less
18266887
A model of the light curves of Gamma-Ray Bursts
Aims. An extreme Kerr black hole (BH) surrounded by a precessing disk is invoked to explain the light curves of gamma-ray bursts (GRBs) based on the coexistence of the Blandford-Znajek (BZ) and the magnetic coupling (MC) processes. Methods. The overall shape of the light curves and the duration of GRBs are interpreted by the evolution of the halfopening angle of the magnetic flux on the BH horizon, and the complex temporal structures are modulated by the precession and nutation of the jet powered by the BZ process. Results. The time profile of the emission exhibits a fast rise and a slow decay due to the effect of the evolution of the half-opening angle. The light curves of several GRBs are well fitted by this model with only six free parameters.