Name: 2001 Particle Accelerator Conference
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Created at: Fri Jul 27 23:53:35 -0700 2007
Updated at: Fri Jul 27 23:53:35 -0700 2007
Edit | Back | Add Paper| title: | Beam-plasma interaction experiments at the UCLA Neptune Laboratory |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 5 authors: | | | | | |
| abstract: | We are currently planning several beam-plasma interaction experiments using the high quality 16 MeV electron beam produced by the Neptune 1.625-cell photoinjector and PWT linac. The underdense (n_b > n_0) plasma lens experiment will examine the focusing of a 4 nC beam of 30 psec pulse duration as it passes through a thin 2 cm Ar plasma lens. We are also developing a negative R_56 compressor beamline that will allow us to create ramped sub-picosecond beams of a shape well suited for driving large amplitude plasma wake fields and producing high transformer ratios. Simulations made using the 2-1/2 dimensional particle-in-cell code MAGIC indicate that we could use these ramped beams to produce fields of up to 10 GeV/m in a 10(16) cm(-3) plasma. Ramped beams are also suitable for driving plasma density gradient trapping experiments. When such a beam passes through a region where the plasma density drops suddenly the fast variation of the wake fields traps several pC of plasma electrons in the accelerating portion of the wake field. |
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| title: | Saturation measurements of a visible SASE FEL |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 14 authors: | | | | | | | | | | | | | | |
| abstract: | VISA (visible to infrared SASE amplifier) is an FEL designed to obtain high gain at a radiation wavelength of 800 nm. Large gain is achieved by driving the FEL with the 71 MeV, high brightness beam of the Accelerator Test Facility (ATF) and using a novel, strong focusing, 4 m long undulator with a gap of 6 mm and a period of 1.8 cm. We report measurements of exponential gain, saturation, and spectra of the FEL radiation intensity. (11 References). |
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| title: | Dynamics of a Driver Beam Propagating in an Underdense Plasma with a Downward Density Transition |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 7 authors: | | | | | | | |
| abstract: | When a short electron beam propagates in an underdense plasma (plasma density n_p < beam density n_b) with a downward density transition, it is known that some background plasma electrons are trapped and accelerated by the plasma wakefield[1]. Beam quality of the trapped plasma electrons is severely affected by the wakefield that is generated by the driving electron beam, so dynamics and instabilities of the driver beam are very important. In this paper, we present some simulation results on the self-trapping and driver beam dynamics. |
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| title: | Measuring FEL radiation properties at VISA-FEL |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 25 authors: | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The VISA (Visible to Infrared SASE Amplifier) SASE free electron laser has been successfully operated at the Accelerator Test Facility (ATF) at BNL. High gain and saturation were observed at 840 nm. We describe here the diagnostic system, experimental procedures and data reduction algorithms, as the FEL performance was measured along the length of the undulator. We also discuss selected spectral radiation measurements. (10 References). |
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| title: | Commissioning of the UCLA PEGASUS Photoinjector Laboratory |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 5 authors: | | | | | |
| abstract: | The PEGASUS Photoinjector has been commissioned at UCLA. The Plane Wave Transformer Photoinjector provides a high-brightness 17 MeV beam that will be used for numerous beam-radiation studies. Some of these will include SASE FEL, transition radiation from non-standard surfaces, and monochromatic x-ray production via PXR and Thompson scattering. |
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| title: | Commissioning of the Neptune photoinjector |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 9 authors: | | | | | | | | | |
| abstract: | The status of the RF photoinjector in the Neptune advanced accelerator laboratory is discussed. The components of the photoinjector: the RF gun and booster linac, chicane compressor, and beam diagnostic systems are described. Measurement techniques used to diagnose the short pulse length, high brightness beam are detailed and measurements of emittance and pulse compression are given. The effect of the pulse compressor on transverse emittance is explored. (11 References). |
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| title: | Emittance measurements of the space charge dominated Thomson source photoinjector |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 4 authors: | | | | |
| abstract: | The photocathode rf gun test facility in Livermore National Laboratory's Thomson source is described. The quadrupole scan and slit based emittance measurement techniques are used to measure the emittance of the space charge dominated beam. Experimental results are compared with simulation and theoretical calculations. (10 References). |
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| title: | Ultra high-gradient energy loss by a pulsed electron beam in a plasma |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 9 authors: | | | | | | | | | |
| abstract: | The plasma wake-field mechanism can be used to couple energy at a high rate from a bunched electron beam into a plasma wave. We will present results from the Fermilab A0 facility where a beam with an initial energy of 14 MeV passes through the plasma to emerge with a much broader energy spread, spanning from a low of 3 MeV to a high of over 20 MeV. Over the 8 cm length of the 10(14) cm(-3) plasma, this implies a 140 MeV/m deceleration and 72 MeV/m acceleration gradient. (12 References). |
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| title: | Investigations of electron-beam microbunching and beam coalignment using CTR in a high-gain SASE FEL |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 11 authors: | | | | | | | | | | | |
| abstract: | We recently extended our experiments on z-dependent electron-beam microbunching using coherent transition radiation (CTR) into the high-gain, self-amplified spontaneous emission free-electron laser (FEL) regime. The UV-visible FEL at the Advanced Photon Source was operated at 530 nm and 385 nm using the bunch-compressed photocathode gun electron beam, linac, and 21.6 m of undulator length. The longitudinal microbunching of the electron beam was tracked by inserting a metal foil and a mirror after each of the nine 2.4-m-long undulators. The visible CTR generated by the electron-beam interaction was imaged and analyzed for z-dependent intensity, angular distribution, and spot size. Additionally, the image centroids and structures were used in evaluating the critical electron beam/photon beam overlap issue as a complement to the trajectory data from the beam position monitors. (9 References). |
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| title: | Limitations on Measuring a Transverse Profile of Ultradense Electron Beams with Scintillators |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 5 authors: | | | | | |
| abstract: | As the high-brightness electron beams become denser and reach sub-100 um sizes, a resolution of the transverse profile diagnostics become an important issue. The applicability of the traditional scintillators as the diagnostics for most generic transverse properties of small dense beams is questionable. Recently, a YAG:Ce single crystal was used successfully, but studies indicated the presence of saturation effects. At BNL-ATF (Accelerator Test Facility) we have generated ultra-small beams, and continued an experimental work to further illuminate the nature of YAG:Ce saturation. We have also evaluated alternative diagnostics, such as LuAG:Ce. Imaging properties of various diagnostics were studied, including measurements of emission spectra. |
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| title: | On the IFEL experiment at the UCLA Neptune Lab |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 6 authors: | | | | | | |
| abstract: | We present an inverse free electron laser accelerator proposed for construction at the UCLA Neptune Lab. This experiment will use a 1TW CO/sub 2/ laser to accelerate through two strongly tapered undulators an electron beam from 16 MeV up to 55 MeV. The scheme proposed is the diffraction dominated IFEL interaction. The Raleigh range of the laser beam is about 2 cm, much shorter than the interaction length (the undulator length is 50 cm). In this regime adiabatic capture is possible in the first part of the undulator. In the focus region, we propose a solution to the problem of the dephasing between electrons and photons due to the Guoy phase shift. Ponderomotive effects and implications for tolerances are also studied. (13 References). |
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| title: | Development of an X-Band PWT Photoinjector |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 5 authors: | | | | | |
| abstract: | Development of an X-band Plane-Wave-Transformer (PWT), integrated photoinjector continues. Modifications of the end-cell design in this two-section device allow for simultaneous frequency and phase tuning of the accelerating field, thus preventing deceleration at the drift region that separates the two sections. The Los Alamos version of PARMELA is used to determine the expected performance parameters from the final design. |
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| title: | ORION: An Advanced Accelerator Facility at SLAC |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 13 authors: | | | | | | | | | | | | | |
| abstract: | Extending the center-of-mass energy frontier for high-energy physics depends on the research and development that is conducted now in the area of advanced accelerator physics and technology. In this article, we present the design and beam dynamics simulations for the emittance-compensated, RF photoinjector of the ORION Facility. (4 References). |
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| title: | The free-electron laser collective instability and the development of X-ray FELs |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 1 author: | |
| abstract: | We discuss the physics of collective instabilities in particle beams, and consider one particular case: the free-electron laser (FEL) collective instability. We present a review of the main characteristics of this instability, and its application to the development of Self Amplified Spontaneous Emission (SASE) FELs from the infrared to the X-ray region. (17 References). |
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| title: | Start-to-end simulation for the LCLS X-ray FEL |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 5 authors: | | | | | |
| abstract: | X-ray FELs, such as the LCLS and TESLA FEL, require electron beams with large peak current and very small emittance. The X-ray peak power, temporal and spectral properties, depend significantly on details of the electron beam phase space distribution. The electron beam distribution is determined by many effects, as the emission process at the gun photo-cathode, bunch compression, acceleration and wakefields within the undulator. Although analytical results can give an estimate of the expected performance, the complexity of the electron beam generation, acceleration and compression can only be evaluated using a numerical simulation of all these processes, a start-to-end simulation. In this presentation we discuss the LCLS X-Ray FEL performance estimated by a start-to-end simulation, and we compare the results with those obtained using a simpler model. (19 References). |
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| title: | Transition radiation for uneven, limited surfaces |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 2 authors: | | |
| abstract: | In the most common approach to modeling transition radiation, the annihilation of the incident particle with its image particle at the metallic boundary is calculated. This is valid only for ideal planar boundaries, and is not applicable if the surface is modulated, rough or limited in the transverse dimension. In this paper, we show results obtained by replacing the image current with the induced surface charge and surface distributions. Special problems such as a modulated surface are analytically solved and compared to a numerical simulation. Implications for experimental use of transition radiation-based beam monitors are discussed. (9 References). |
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| title: | Proposal for a IR Waveguide SASE FEL at the PEGASUS Injector |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 3 authors: | | | |
| abstract: | Free Electron Lasers up to the visible regime are dominated by diffraction effects, resulting in a radiation size much larger than the electron beam. Thus the effective field amplitude at the location of the electron beam, driving the FEL process, is reduced. By using a waveguide, the radiation field is confined within a smaller aperture and an enhancement of the FEL performance can be expected. The PEGASUS injector at UCLA will be capable to provide the brilliance needed for an IR SASE FEL. The experiment PERSEUS (Power Enhanced Radiation Source Experiment Using Structures) is proposed to study the physics of a waveguide SASE FEL in a quasi 1D environment, where diffraction effects are strongly reduced as it is the case only for future FELs operating in the VUV and X-ray regime. The expected FEL performance is given by this presentation. |
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| title: | Monitoring and manipulation of sub-picosecond beams |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 1 author: | |
| abstract: | In cutting-edge applications such as advanced accelerators and free-electron lasers, very high brightness beams of duration shorter than a picosecond are required. Further, these applications demand specific types of longitudinal beam profiles, such as pulse trains, and ramped pulses. The production of such types of beams present challenges both in technique, and in the instrumentation required to verify the method employed. The techniques for producing such short beams which have received the most investigation in recent years include chicane compression, and modulation via free-electron laser mechanism and its inverse. We discuss the principles and relevant single particle and collective effects which impact their performance. We review progress in implementing these schemes, as well as newer concepts such as relativistic velocity bunching and use of negative R_56 compressors. We also discussed the challenges in diagnosing these state-of-the-art beam systems. |
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| title: | Chirped-beam two-stage SASE-FEL for high power femtosecond X-ray pulse generation |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 0 authors: | unknown |
| abstract: | We present a method for generating femtosecond duration X-ray pulses using a single-pass free-electron laser (FEL). This method uses an energy-chirped electron beam to produce a frequency-chirped X-ray pulse through self-amplified spontaneous emission (SASE). After the undulator we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse, and therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE-FEL, and consider the performance of the chirped-beam two-stage option for the for the Linac Coherent Light Source (LCLS). |
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