Transverse and longitudinal beam dynamics studies at the Fermilab photoinjector (original) (raw)
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2007 IEEE Particle Accelerator Conference (PAC), 2007
Recently we have measured the envelope and the transverse emittance of an 0.85 nC electron beam at the Fermilab A0-Photoinjector facility. The transverse emittance measurement was performed using the multi-slit method. The data have been taken with an unstacked 2.8 ps laser pulse. In this paper we report on these beam measurements and compare the results with the predictions from beam dynamics codes ASTRA and GPT using 3D space charge routines.
First beam measurements at the photo injector test facility at DESY Zeuthen
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2003
The Photo Injector Test facility at DESY Zeuthen (PITZ) was built to develop electron sources for the TESLA Test Facility Free Electron Laser (TTF-FEL) and future linear colliders. The main goal is to study the production of minimum transverse emittance beams with short bunch length at medium charge (~1nC). The facility includes a 1.5 cell L-band cavity with coaxial rf coupler, a solenoid for space charge compensation, a laser capable to generate long pulse trains, an UHV photo cathode exchange system, and different diagnostics tools. Besides an overview of the facility, its main components and their commissioning, this contribution will concentrate on the first measurements at PITZ with photo electrons. This will include measurements of the transverse and longitudinal laser profile, charge and quantum efficiency, momentum and momentum spread, transverse electron beam profiles at different locations and first results on transverse emittance. PACS codes: 29.25 Bx electron sources, 29.27 Fh beam characteristics, 41.60 Cr Free electron Laser, 41.75 Fr electron and positron beam, 41.85 Ew beam profile
Characterization of the electron source at the photo injector test facility at DESY Zeuthen
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2004
The Photo Injector Test Facility at DESY Zeuthen (PITZ) was built to test and optimize electron sources for Free Electron Lasers and future linear colliders. The focus is on the production of intense electron beams with minimum transverse emittance and short bunch length as required for FEL operation. The experimental setup includes a 1.5 cell L-band gun cavity with coaxial RF coupler, a solenoid for space charge compensation, a laser capable to generate long pulse trains with variable temporal and spatial pulse shape, an UHV photo cathode exchange system, and an extensive diagnostics section. This contribution will give an overview on the facility and will mainly discuss the measurements of the electron beam transverse phase space. This will include measurements of the transverse and longitudinal laser profile, beam charge as a function of RF phase, and transverse emittance as a function of different parameters. The corresponding measurements of momentum and momentum spread as well as the RF commissioning results will be summarized. As a first application of the PITZ electron source it will be installed at the TESLA Test Facility Free Electron Laser at DESY Hamburg in autumn 2003. r
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
High brightness electron sources for linac based short-wavelength free-electron lasers are developed and optimized for small transverse projected emittance at the photo-injector test facility at DESY, location Zeuthen (PITZ). A major part of the measurement program at PITZ is dedicated to transverse phase space optimization in order to fulfill the requirements of the European X-ray free-electron laser (European XFEL). A laser-driven RF-gun, treated with a dry-ice sublimation-impulse cleaning technique, a new photocathode laser system allowing short rise and fall times of the flat-top temporal distribution as well as several new diagnostic components have been installed at PITZ in 2008. The electrons generated via the photo-effect at a cesium telluride (Cs 2 Te) cathode are accelerated by a 1.6 cell L-band RF-gun cavity with a maximum accelerating gradient at the cathode of about 60 MV/m. The transverse projected emittance is measured using a single slit scan technique. In the 2008-2009 run period, a detailed characterization of the projected transverse emittance was performed at different operating conditions. Optimizations and measurement results as well as simulation predictions of the transverse projected emittance for bunch charges of 1, 0.5, 0.25 and 0.1 nC are presented and discussed in this paper. The geometric mean of the normalized projected rms emittance in both transverse directions for an electron bunch charge of 1 nC was measured to be 0.8970.01 mm mrad for a 100% rms phase-space distribution.
Experimental characterization of the high-brightness electron photoinjector
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1996
Operational experience of the emittance compensated photoinjector at the Brookhaven Accelerator Test Facility (ATF) is presented in this paper. The photoinjector has demonstrated the stability and reliability required for UV and X-ray FEL applications. The RF gun has been routinely running at more than 100 MV/m peak acceleration field; the laser system of the photoinjector has achieved 2% peak to peak energy stability, 0.5 % point stability and better than 2 ps timing jitter. The highest measured quantum efficiency of the Cu cathode is 0.05%. The electron beam bunch length was measured to be 10 ps using a linac RF phase scan. The normalized rms emittance for a 0.5 nC charge was measured, to be from 1 to 2 mm-mad, which agrees with PARMELA simulations.
Longitudinal bunch shaping of picosecond high-charge MeV electron beams
Physics of Plasmas, 2016
With ever increasing demands for intensities in modern accelerators, the understanding of space-charge effects becomes crucial. Herein are presented measurements of optically shaped picosecond-long electron beams in a superconducting L-band linac over a wide range of charges, from 0.2 nC to 3.4 nC. At low charges, the shape of the electron beam is preserved, while at higher charge densities, modulations on the beam convert to energy modulations. Energy profile measurements using a spectrometer and time profile measurements using a streak camera reveal the dynamics of longitudinal space-charge on MeV-scale electron beams.
The Electron Beam Test Facility (EBTF) is planned for installation in late 2012 at Daresbury Laboratory. An Sband RF photoinjector provides ultrashort, low emittance electron bunches up to 6 MeV. A suite of diagnostics has been designed to fully characterise the bunches. A particular focus has been on producing and measuring bunch lengths less than 100 fs. This can be achieved with a multi-cell standing wave S-band transverse deflecting cavity. Operating such a cavity with low energy electrons provides certain challenges which are discussed in this paper with respect to beam dynamic simulations.
High brightness electron beam emittance evolution measurements in an rf photoinjector
Physical Review Special Topics - Accelerators and Beams, 2008
The new generation of linac injectors driving free electron lasers in the self-amplified stimulated emission (SASE-FEL) regime requires high brightness electron beams to generate radiation in the wavelength range from UV to x rays. The choice of the injector working point and its matching to the linac structure are the key factors to meet this requirement. An emittance compensation scheme presently applied in several photoinjectors worldwide is known as the ''Ferrario'' working point. In spite of its great importance there was, so far, no direct measurement of the beam parameters, such as emittance, transverse envelope, and energy spread, in the region downstream the rf gun and the solenoid of a photoinjector to validate the effectiveness of this approach. In order to fully characterize the beam dynamics with this scheme, an innovative beam diagnostic device, the emittance meter, consisting of a movable emittance measurement system, has been designed and built. With the emittance meter, measurements of the main beam parameters in both transverse phase spaces can be performed in a wide range of positions downstream the photoinjector. These measurements help in tuning the injector to optimize the working point and provide an important benchmark for the validation of simulation codes. We report the results of these measurements in the SPARC photoinjector and, in particular, the first experimental evidence of the double minimum in the emittance oscillation, which provides the optimized matching to the SPARC linac.
Transverse emittance studies of an induction accelerator of heavy ions
Conference Record of the 1991 IEEE Particle Accelerator Conference
achieved in practice. These experiments, in which the current Current amplification of heavy ion beams is an integral was amplified from 4x10 mA to 4x90 mA and the energy feature of the induction linac approach to heavy ion fusion. As increased from 200 keV (the injection value) to 900 keV, were part of the Heavy Ion Fusion Accelerator Research program at accompanied by a growth in the normalised emittance by a LBL we have been studying the evolution of die transverse factor of approximately two. This work has been reported emittance of ion beams while they are undergoing current previously and a review can be found elsewhere in these amplification, achieved by longitudinal bunch compression and proceedings'. acceleration. Experiments are conducted on MBE-4, a four beam Cs + induction linac. The space-charge dominated beams 2. EXPERIMENTS of MBE-4 are focused by electrostatic quadrupoles while they are accelerated tram nominally 200 keV up to-1 MeV by 24 We have identified a number of mechanisms which may accelerating gaps. Initially the beams have currents of typically be responsible for emittance growth in MBE-4 including 4 mA to 10 mA per beam. Early experimental results showed matching errors, rapid longitudinal compression (leading to a a growth of the normalized emittance by a factor of 2 while die change in die space-charge electrostatic-field energy), and nonbeam current was amplified by up to 9 times its initial value, linear field effects (self-fields, image-fields, focus fields). The We will discuss me results of recent experiments in which a last of Uiese mechanisms is particularly troublesome for offmild bunch length compression rate, more typical of that axis beams where the edge of the beam may approach the nonrequired by a fusion driver, has shown that the normalized linear field region of the quadrupoles 2. For die experiments emittance can be maintained at its injection value (0.03 mm-discussed here offsets are minimised by the use of steering mr) during acceleration. elements at die entrance to the linac and by careful alignment of the accelerator. Proper matching of the beam phase-space to 1. INTRODUCTION the lattice of die linac is performed by adjustment of ^'matching section" consisting of eight electrostatic The induction Unac approach to heavy ion driven inertial quadrupoles just downstream of thediode. fusion envisages a design in which multiple beams are Recent experiments have involved the application of an employed at the law energy end of the driver with die beam acceleration schedule which results in a smaller increase in die current undergoing amplification as it is accelerated. Current beam line charge density between injection and full energy. In amplification results both from the increase in panicle velocity order to realise this we have reduced the extent of die applied and also from longitudinal bunch compression. This velocity tilt in the early pps of MBE-4 with the majority of compression is achieved by applying a velocity 'tilt' between die acceleration being provided by waveforms in which die die head and tail of the bunch, provided by tailored voltage voltage does not vary greatly during die passage of die beam waveforms applied at die accelerating gaps. MBE-4 is a four pulse. The reduction in bunch compression in these beam Cs* linac built to investigate longitudinal dynamics experiments means that the beam pulse length is not issues related to this concept. The linac is comprised of a 30 sufficiently short for the final accelerating waveforms to period, electrostatic, AG focusing lattice. Each doublet is completely straddle the beam pulse. Consequently die current followed by an accelerating gap with die exception of every waveforms observed in diese experiments are poorer dian those fifth doublet where the gap is reserved for diagnostic access and obtained in earlier studies, however me focus of these vacuum pumping. Each lattice period (l.p.) is 45.7 cm long experiments is transverse beam dynamics, resulting in a linac of 13.7 metres. Early experiments on MBE-4 concentrated on a In attempting to maintain a matched beam during demonstration of current amplification while maintaining acceleration we scale the strengths of die quadrupoie focusing control of die current profile and correcting for inevitable voltages, Vq, such as to keep diem proportional to die beam acceleration errors', which arose from the difference between lfae-charge density, X, i.e. V Q-\-1 / v, where I and v are ideal accelerating pulser waveforms and those waveforms Ae