[show abstract][hide abstract] ABSTRACT: Since the last EPAC2000 Conference, both the peak and integrated luminosity of the e+e- collider DAΦNE, Italian Φ–factory, have grown by an order of magnitude. In this paper we describe the steps that have led to the luminosity increase and discuss our plans for further
[show abstract][hide abstract] ABSTRACT: This report describes the scientific aims and potentials as well as the
preliminary technical design of IRIDE, an innovative tool for
multi-disciplinary investigations in a wide field of scientific, technological
and industrial applications. IRIDE will be a high intensity 'particle factory',
based on a combination of a high duty cycle radio-frequency superconducting
electron linac and of high energy lasers. Conceived to provide unique research
possibilities for particle physics, for condensed matter physics, chemistry and
material science, for structural biology and industrial applications, IRIDE
will open completely new research possibilities and advance our knowledge in
many branches of science and technology. IRIDE will contribute to open new
avenues of discoveries and to address most important riddles: What does matter
consist of? What is the structure of proteins that have a fundamental role in
life processes? What can we learn from protein structure to improve the
treatment of diseases and to design more efficient drugs? But also how does an
electronic chip behave under the effect of radiations? How can the heat flow in
a large heat exchanger be optimized? The scientific potential of IRIDE is far
reaching and justifies the construction of such a large facility in Italy in
synergy with the national research institutes and companies and in the
framework of the European and international research. It will impact also on
R&D work for ILC, FEL, and will be complementarity to other large scale
accelerator projects. IRIDE is also intended to be realized in subsequent
stages of development depending on the assigned priorities.
[show abstract][hide abstract] ABSTRACT: The Advanced Photoinjector Experiment (APEX) at the Lawrence Berkeley
National Laboratory is dedicated to the development of a high-brightness
high-repetition rate (MHz-class) electron injector for x-ray
free-electron laser (FEL) and other applications where high repetition
rates and high brightness are simultaneously required. The injector is
based on a new concept rf gun utilizing a normal-conducting (NC) cavity
resonating in the VHF band at 186 MHz, and operating in continuous wave
(cw) mode in conjunction with high quantum efficiency photocathodes
capable of delivering the required charge at MHz repetition rates with
available laser technology. The APEX activities are staged in three
phases. In phase 0, the NC cw gun is built and tested to demonstrate the
major milestones to validate the gun design and performance. Also,
starting in phase 0 and continuing in phase I, different photocathodes
are tested at the gun energy and at full repetition rate for validating
candidate materials to operate in a high-repetition rate FEL. In phase
II, a room-temperature pulsed linac is added for accelerating the beam
at several tens of MeV to reduce space charge effects and allow the
measurement of the brightness of the beam from the gun when integrated
in an injector scheme. The installation of the phase 0 beam line and the
commissioning of the VHF gun are completed, phase I components are under
fabrication, and initial design and specification of components and
layout for phase II are under way. This paper presents the phase 0
commissioning results with emphasis on the experimental milestones that
have successfully demonstrated the APEX gun capability of operating at
the required performance.
Review of Modern Physics 10/2012; 15(10):103501. · 44.98 Impact Factor
[show abstract][hide abstract] ABSTRACT: We report on on-going studies of a superconducting CW linac driver intended to support a high repetition rate FEL
operating in the soft x-rays spectrum. We present a pointdesign for a 1.8 GeV machine tuned for 300 pC bunches and delivering low-emittance, low-energy spread beams as needed for the SASE and seeded beamlines.
[show abstract][hide abstract] ABSTRACT: Requirements and challenges for high-brightness electron injectors operating in a high-repetition-rate X-ray FEL are described. Schemes presently under development or study are reviewed, and their advantages and limitations are compared. Beam dynamics and engineering/technological aspects are addressed, with a particular emphasis placed on how the high-repetition-rate requirement impacts the choice of cathodes and of gun/accelerator technologies, and on how those choices consequently impact beam dynamics.
Journal of Modern Optics 09/2011; 58(16):1419-1437. · 1.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: An upgrade project is under way to further improve the brightness of the Advanced Light Source at Berkeley Lab by reducing its horizontal emittance from 6.3 to 2.2 nm (effective emittance in the straights from 6.4 to 2.5 nm). This will result in a brightness increase by a factor of three for bend magnet beamlines and at least a factor of two for insertion device beamlines and will keep the ALS competitive with newer sources. This paper presents an overview of the upgrade project with emphasis on the nonlinear beam dynamics simulations. It also discusses in a more general way the techniques used at LBNL for finding optimum lattices (e.g. the ones with maximum brightness) and optimizing the particle dynamics, thereby increasing beam lifetime and stability.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2011; 649(1):25-29. · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: The development of undulator technologies capable of generating sub-cm undulator periods is assuming an increasing importance in X-ray free electron laser (FEL) applications. Indeed, such devices jointly with the high brightness electron beams already demonstrated at operating facilities would allow for lower energy, more compact electron linacs with a beneficial impact on the size and cost of X-ray FEL facilities.A novel design super-conducting undulator is being developed at the Lawrence Berkeley National Laboratory (LBNL) with the potential of sub-cm periods with reasonably large undulator parameter and gap. The potential and capability of such undulator technology need to be experimentally demonstrated.In this paper, the possibility of constructing an infrared FEL by combining the new undulator with the high brightness beam from the APEX injector facility at LBNL is investigated.Calculations show that the resulting FEL, when operated in self-amplified-spontaneous-emission mode, is expected to deliver a saturated power of almost a MW within a ∼4m undulator length, in a single-spike of coherent radiation at ∼2μm wavelength.It will be also shown that the small-period of the undulator associated with the relatively low energy of the APEX beam, forces the FEL to operate in a regime with unusual and interesting characteristics. The alternative option of laser seeding the FEL is also briefly examined, showing the potential to reduce the saturation length even further.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2011; 660(1):138-146. · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Next Generation Light Source (NGLS) is a design concept, under development at LBNL, for a 10beamline xray FEL array powered by a superconducting linear accelerator of ~2 GeV, operating with a 1 MHz bunch repetition rate. The CW superconducting linear accelerator is supplied by a high-brightness, high-repetition-rate photocathode electron gun. Beam is distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz, with even pulse spacing. Individual FELs may be configured for EEHG, HGHG, SASE, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format ranging from sub-femtoseconds to hundreds of femtoseconds.
[show abstract][hide abstract] ABSTRACT: The fabrication and installation at the Lawrence Berkeley National Laboratory of a high-brightness high-repetition rate photo-gun, based on a normal conducting 187 MHz (VHF) RF cavity operating in CW mode, is in an advanced phase. The cavity will generate an electric field at the cathode plane of ~ 20 MV/m to accelerate the electron bunches up to ~ 750 keV, with peak current, energy spread and transverse emittance suitable for FEL and ERL applications. The gun vacuum system has been designed for achieving pressures compatible with the use of "delicate" high quantum efficiency semiconductor cathodes to generate up to a nC bunches at MHz repetition rate with present laser technology. Several photo-cathode/laser systems are under consideration, and in particular photo-cathodes based on K 2 CsSb are being developed for the gun and have already achieved a QE of 8% at 532 nm wavelength, or close to 20% including the Schottky barrier lowering. The cathode will be operated by a μJ fiber laser in conjunction with refractive transverse beam shaping to create a flat top transverse profile, as well as a birefringent pulse stacker to create a flat top temporal profile. The present status and the plan for future activities are presented.
[show abstract][hide abstract] ABSTRACT: With the scientific successes of the soft X-ray FLASH facility in Germany and the recent spectacular commissioning of the Linac Coherent Light Source at SLAC, free electron lasers are poised to take center stage as the premier source of tunable, intense, coherent photons of either ultra-short time resolution or ultra-fine spectral resolution, from the far infrared to the hard X-ray regime. This paper examines the state of the art in FEL performance and the underlying enabling technologies. It evaluates the state of readiness of the three basic machine architectures—SASE FELs, seeded FELs, and FEL oscillators—for the major X-ray science user facilities on the 5–10 years time scale and examines the challenges that lie ahead for FELs to achieve their full potential throughout the entire spectral range. In soft and hard X-rays, high longitudinal coherence, in addition to full transverse coherence, will be the key performance upgrade; ideas using laser-based or self-seeding or oscillators can be expected to be qualitatively superior to today's SASE sources. Short pulses, from femtoseconds to attoseconds, can be realistically envisioned. With high repetition rate electron sources coupled to superconducting radiofrequency linear accelerators, unprecedented average beam brightness will be possible and many users would be served simultaneously by a single accelerator complex.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2010; · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: Several recent reports have identified the scientific requirements for a future soft X-ray light source [1, 2, 3, 4, 5], and a high-repetition-rate free-electron laser (FEL) facility responsive to them is being studied at Lawrence Berkeley National Laboratory (LBNL) . The facility is based on a continuous-wave (CW) superconducting linear accelerator with beam supplied by a high-brightness, high-repetition-rate photocathode electron gun operating in CW mode, and on an array of FELs to which the accelerated beam is distributed, each operating at high repetition rate and with even pulse spacing. Dependent on the experimental requirements, the individualFELs may be configured for either self-amplified spontaneous emission (SASE), seeded highgain harmonic generation (HGHG), echo-enabled harmonic generation (EEHG), or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format ranging from sub-femtoseconds to hundreds of femtoseconds. This new light source would serve a broad community of scientists in many areas of research, similar to existing utilization of storage ring based light sources. To reduce technical risks and constructioncosts, accelerator research, development, and design studies at LBNL target the most critical components and systems of the facility. We are developing a high-repetition-rate low-emittance electron gun, high quantum efficiency photocathodes, and have embarked on design and optimization of the electron beam accelerator, FEL switchyard, and array of FELs. We continue our work on precision timing and synchronization systems critical for time-resolved experiments using pump-probe techniques.
[show abstract][hide abstract] ABSTRACT: A new bunch cleaning system has been designed and is currently in operation in the storage ring of the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. The new system provides for high bunch purity, arbitrary filling patterns, and is compatible with the various ALS user operation modes. Design details and performance results of the new system will be described.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2009; · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: At the Lawrence Berkeley National Laboratory, a high-brightness high-repetition rate photo-injector is under fabrication. The scheme is based on a normal conducting 187 MHz RF cavity operating in CW mode and capable of generating an electric field at the cathode plane of ~ 20 MV/m. The electron bunches will be accelerated to ~ 750 keV with peak current, energy spread and transverse emittance suitable for FEL and ERL applications. At the same time, the presence of a vacuum load-lock mechanism jointly with a vacuum system designed to operate in the 10 picoTorr range, will make of this injector a flexible cathode test facility. In particular, it will allow to use "delicate" high quantum efficiency cathodes to generate nC bunches at MHz repetition rate with present laser technology. Construction status and future plans are presented.
[show abstract][hide abstract] ABSTRACT: Storage ring lattice design is a highly constrained multiobjective optimization problem. The objectives can include lattice functions or derived quantities like emittance, brightness, or luminosity while simultaneously fulfilling constraints such as linear stability of the lattice. In this paper we explore the use of multiobjective genetic algorithms (MOGA) to find globally optimized lattice settings in a storage ring. Using the Advanced Light Source (ALS) for illustration, three examples of MOGA are shown and analyzed—(i) using three fit parameters to optimize the straight section betatron function and the natural emittance, (ii) using three fit parameters to optimize the photon brightness of bending magnet and insertion device source points in the lattice and (iii) a six parameter fit creating alternating high and low horizontal betatron functions in subsequent straight sections while still minimizing the natural emittance. Making use of one of the main benefits of MOGA, we also study the trade-offs in the optimization objectives between sets of optimal solutions.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment - NUCL INSTRUM METH PHYS RES A. 01/2009; 609(1):50-57.
[show abstract][hide abstract] ABSTRACT: The upgrade of the Advanced Light Source to enable top-off operation has been ongoing for the last four years. Activities over the last year have centered around radiation safety aspects, culminating in a systematic proof that top-off operation is equally safe as decaying beam operation, followed by commissioning and full user operations. Top-off operation at the ALS provides a very large increase in time-averaged brightness to ALS users (by about a factor of 10) as well as improvements in beam stability. The fol-lowing sections provide an overview of the radiation safety rationale, commissioning results, as well as experience in user operations.
[show abstract][hide abstract] ABSTRACT: IKNO (Innovation and KNOwledge) is a proposal for a multi-user facility based on an electron storage ring optimized for the generation of coherent synchrotron radiation (CSR) in the terahertz frequency range, and of broadband incoherent synchrotron radiation ranging from the IR to the VUV. IKNO can be operated in an ultra-stable CSR mode with photon flux in the terahertz frequency region up to nine orders of magnitude higher than in existing third-generation light sources. Simultaneously to the CSR operation, broadband incoherent synchrotron radiation up to VUV frequencies is available at the beamline ports. The main characteristics of the IKNO storage and its performance in terms of CSR and incoherent synchrotron radiation are described in this paper. The proposed location for the infrastructure facility is Sardinia, Italy.
[show abstract][hide abstract] ABSTRACT: Currently proposed energy recovery linac and high average power free electron laser projects require electron beam sources that can generate up to bunch charges with less than 1 mm mrad normalized emittance at high repetition rates (greater than ). Proposed sources are based around either high voltage DC or microwave RF guns, each with its particular set of technological limits and system complications. We propose an approach for a gun fully based on mature RF and mechanical technology that greatly diminishes many of such complications. The concepts for such a source as well as the present RF and mechanical design are described. Simulations that demonstrate the beam quality preservation and transport capability of an injector scheme based on such a gun are also presented.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 10/2008; · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and successfully tested a simple scheme based on this principle that allows for the absolute measurement of the rms bunch length. A description of the method and the experimental results are presented.
Physical Review Special Topics - Accelerators and Beams 09/2008; 30. · 1.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: The traditional process of designing and tuning the magnetic lattice of a particle storage ring lattice to produce certain desired properties is not straightforward. Often solutions are found through trial and error and it is not clear that the solutions are close to optimal. This can be a very unsatisfying process. In this paper we take a step back and look at the general stability limits of the lattice. We employ a technique we call GLASS (GLobal scan of All Stable Settings) that allows us to rapidly scan and find all possible stable modes and then characterize their associated properties. In this paper we illustrate how the GLASS technique gives a global and comprehensive vision of the capabilities of the lattice. In a sense, GLASS functions as a lattice observatory clearly displaying all possibilities. The power of the GLASS technique is that it is fast and comprehensive. There is no fitting involved. It gives the lattice designer clear guidance as to where to look for interesting operational points. We demonstrate the technique by applying it to two existing storage ring lattices—the triple bend achromat of the Advanced Light Source and the double bend achromat of CAMD. We show that, using GLASS, we have uncovered many interesting and in some cases previously unknown stability regions.
Review of Modern Physics 01/2008; 11(2). · 44.98 Impact Factor