8730506
High current, large aperture, low HOM, single crystal Nb 2.85GHz superconducting cavity
There is an increasing demand for high beam current, high radio-frequency (RF) power S-band cavities in existing and new accelerator projects, such as for a study of future electron-ion collider (eRHIC) and a very brilliant, broadband, teraherz coherent synchrotron radiation source (CRS). To achieve this goal, the RF cavities must be upgraded to a gap voltage of 1.5 MV in a limited space available in the machine with a high gradient superconducting cavity. At the present time there are no cavities and accessories designed to support the high beam currents of up to 10-100 mA and at the same time provide a high gap voltage at such a high S-band frequency. AMAC proposed a high current, large aperture, low HOM, single crystal Nb 2.85 GHz superconducting cavity with high RF power coupler and HOM absorber device.
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.
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>>
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.
123184552
Generation of space-charge waves due to localized perturbations
Generation of various space-charge waves due to localized perturbations on the beam parameters, namely the velocity, density, and current, is reported. Analytical solutions of one-dimensional fluid equations under such perturbations are presented and compared with the experimental results.<<ETX>>
122673118
Coherent synchrotron radiation effects in the electron cooler for RHIC
The Coherent Synchrotron Radiation (CSR) could be a concern in many modern accelerator projects. In the proposed electron-cooling project for the Relativistic Heavy Ion Collider (RHIC), the electron cooler is designed to cool 100 GeV/nucleon bunched ion-beam using 55 MeV electrons. The electron bunch length will be on the order of cm, and the charge per bunch would be around 5-10 nC. We study the CSR effect in this paper.
119298311
Dependence of quantum correlations of twin beams on the pump finesse of an optical parametric oscillator
The dependence of quantum correlations of twin beams on the pump finesse of an optical parametric oscillator is studied via a semi-classical analysis. It is found that the phase-sum correlation of the output signal and idler beams from an optical parametric oscillator operating above threshold depends on the finesse of the pump field when the spurious pump phase noise generated inside the optical cavity and the excess noise of the input pump field are involved in the Langevin equations. The theoretical calculations can explain the previously experimental results quantitatively.
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.
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