F. Sannibale

University of California, Berkeley, Berkeley, California, United States

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Publications (188)141.66 Total impact

  • D. Filippetto · H. Qian · F. Sannibale
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    ABSTRACT: We report on the performances of a Cs2Te photocathode under extreme conditions of high peak time-dependent accelerating fields, continuous wave operations, and MHz pulse extraction with up to 0.3 mA average current. The measurements, performed in a normal conducting cavity, show extended lifetime and robustness, elucidate the main mechanisms for cathode degradation, and set the required system vacuum performance for compatibility with the operations of a high average power X-ray free electron laser user facility, opening the doors to the next generation of MHz-scale ultrafast scientific instruments.
    No preview · Article · Jul 2015 · Applied Physics Letters
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    ABSTRACT: Improvements in brightness and coherent flux of about two orders of magnitude over operational storage ring based light sources are possible using multi bend achromat lattice designs [1]. These improvements can be implemented as upgrades of existing facilities, like the proposed upgrade of the Advanced Light Source, making use of the existing in- frastructure, thereby reducing cost and time needed to reach full scientific productivity on a large number of beamlines. An R&D program funded by internal laboratory funds was started at LBNL to further develop the technologies neces- sary for diffraction-limited storage rings (DLSR). It initially involves five areas, and focuses on the specific needs of soft x-ray facilities: vacuum system/NEG coating of small cham- bers, injection/pulsed magnets, RF systems/bunch lengthen- ing, magnets/radiation production with advanced radiation devices, and beam physics design optimization. Some hard- ware prototypes have been built. The work will expand in the future to demonstrate necessary key technologies at the subsystem level or in beam tests and include new areas like photon beamline optics.
    Full-text · Conference Paper · Jun 2015
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    ABSTRACT: We report on measurements and analysis of a field-emitted electron current in the very-high-frequency (VHF) gun, a room temperature rf gun operating at high field and continuous wave (CW) mode at the Lawrence Berkeley National Laboratory (LBNL). The VHF gun is the core of the Advanced Photo-injector Experiment (APEX) at LBNL, geared toward the development of an injector for driving the next generation of high average power x-ray free electron lasers. High accelerating fields at the cathode are necessary for the high-brightness performance of an electron gun. When coupled with CW operation, such fields can generate a significant amount of field-emitted electrons that can be transported downstream the accelerator forming the so-called ``dark current.'' Elevated levels of a dark current can cause radiation damage, increase the heat load in the downstream cryogenic systems, and ultimately limit the overall performance and reliability of the facility. We performed systematic measurements that allowed us to characterize the field emission from the VHF gun, determine the location of the main emitters, and define an effective strategy to reduce and control the level of dark current at APEX. Furthermore, the energy spectra of isolated sources have been measured. A simple model for energy data analysis was developed that allows one to extract information on the emitter from a single energy distribution measurement.
    No preview · Article · Jan 2015 · Physical Review Special Topics - Accelerators and Beams
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    ABSTRACT: The Advanced Photo-injector EXperiment (APEX) at the Lawrence Berkeley National Laboratory (LBNL), consists in the development of an injector designed to demonstrate the capability of the VHF gun, a normal conducting 186 MHz RF gun operating in CW mode, to deliver the brightness required by X-ray FEL applications at MHz repetition rate. APEX is organized in 3 main phases where different aspects of the required performance are gradually demonstrated. The status and future plans for the project are presented.
    No preview · Article · Jul 2014
  • R. Wells · W. Ghiorso · F. Sannibale · J. Staples · T.M. Huang
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    ABSTRACT: A high repetition rate, MHz, electron source is a key element in future FEL based light sources. The Advanced Photo-injector Experiment (APEX) at Lawrence Berkeley National Laboratory (LBNL) consists of a high repetition rate 186 MHz (VHF-band) CW electron gun, 1 MHz UV laser source, a pulsed 30 MeV linac, and the diagnostic components necessary to quantify the gun's performance. The gun design is based on well-established, conventional RF cavity design, with a couple notable exceptions. The basis for the selection of this technology, novel design features, fabrication techniques and measured cavity performance are presented.
    No preview · Article · Jul 2014
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    ABSTRACT: LCLS-II [1, 2] is a proposal for a high repetition rate (>1 MHz) FEL, based on a CW, superconducting linac. The LCLS-II injector is being optimized by a collaboration from Cornell University, Fermilab, LBNL, and SLAC. There are a number of different possible technical choices for the injector including an rf gun or a high voltage DC gun. In this paper we present the status of the simulations for the injector optimization for an rf gun choice for LCLS-II. A multiob-jective genetic optimizer is implemented for this reason, and optimized solutions for different bunch charges, corresponding to different operating modes, are presented. These operating points are also the initial part of the start-to-end simulations for LCLS-II. Finally, we discuss the trade-offs between compression and brightness conservation in the low energy (<100 MeV) part of the accelerator, as well as the status of sensitivity studies.
    No preview · Article · Jul 2014
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    ABSTRACT: This paper 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 “particles factory”, based on a combination of high duty cycle radio-frequency superconducting electron linacs and of high energy lasers. Conceived to provid eunique 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 is also supposed to be realized in subsequent stages of development depending on the assigned priorities.
    Full-text · Article · Mar 2014 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    ABSTRACT: In this paper we report on start-to-end simulation of a next generation light source based on a high repetition rate free electron laser (FEL) driven by a CW superconducting linac. The simulation integrated the entire system in a seamless start-to-end model, including birth of photoelectrons, transport of electron beam through 600 m of the accelerator beam delivery system, and generation of coherent x-ray radiation in a two-stage self-seeding undulator beam line. The entire simulation used the real number of electrons (̃2 billion electrons/bunch) to capture the details of the physical shot noise without resorting to artificial filtering to suppress numerical noise. The simulation results shed light on several issues including the importance of space-charge effects near the laser heater and the reliability of x-ray radiation power predictions when using a smaller number of simulation particles. The results show that the microbunching instability in the linac can be controlled with 15 keV uncorrelated energy spread induced by a laser heater and demonstrate that high brightness and flux 1 nm x-ray radiation (̃1012 photons/pulse) with fully spatial and temporal coherence is achievable.
    Full-text · Article · Feb 2014 · Physical Review Special Topics - Accelerators and Beams
  • Fernando Sannibale
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    ABSTRACT: High brightness electron sources have been one of the driving forces behind the spectacular results achieved in the last decade by accelerator-based applications. Indeed, X-Ray FELs, with their 10-fold orders of magnitude increase in peak brightness, probably represent the best example of it. New ambitious proposals for X-ray FELs and ERLs, as well as inverse Compton sources for X- or gamma-ray production, are now requiring operation at MHz-GHz repetition rates. In response to that, a number of groups around the world have been actively working in developing high-brightness high-duty cycle electron injectors capable of driving such machines. The high repetition rate requirement cannot be met by the existing low-repetition rate high-brightness injector schemes, and new technologies are under investigation. This paper includes a description of the requirements for such injectors, an overview of the pursued technologies and schemes, a description of the main beam dynamics issues associated with the different choices, and a number of examples of the results obtained so far by the groups active in the field.
    No preview · Article · Feb 2014 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    ABSTRACT: The Advanced Light Source (ALS) at Berkeley Lab has been updated many times and remains as one of the brightest sources for soft x-rays worldwide. However, recent developments in technology, accelerator physics and simulation techniques open the door to much larger future brightness improvements. Similar to proposals at several other 3rd generation sources, this could be achieved by reducing the horizontal emittance with a new ring based on a multi-bend achromat lattice, reusing the existing tunnel, as well as much of the infrastructure and beamlines. After studying candidate lattice designs, development efforts in the last year have concentrated on technology and physics challenges in four main areas: Injection, Vacuum Systems, Magnets and Insertion Devices, as well as main and harmonic RF systems.
    Full-text · Conference Paper · Jan 2014
  • H. Qian · J. Byrd · L. Doolittle · Q. Du · D. Filippetto · G. Huang · F. Sannibale · R. Wells · J. Yang
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    ABSTRACT: High repetition rate photoinjectors, such as APEX at LBNL, are one of the enabling technologies for the next generation MHz class XFELs. Due to the higher repetition rate, a wider bandwidth is available for feedback systems to achieve ultra-stable machine and beam performance. In a first step to improve APEX beam stability, the noise spectra of the APEX laser beam and electron beam are characterized in terms of amplitude and timing. Related feedback systems are also discussed.
    No preview · Article · Jan 2014
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    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 luminosity upgrade.
    Full-text · Article · Dec 2013
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    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.
    Full-text · Article · Jul 2013
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    ABSTRACT: The APEX project at LBNL is developing an electron injector to operate a high repetition rate x-ray FEL. The injector is based on the VHF gun, a high-brightness, highrepetition- rate photocathode electron gun presently under test at LBNL. The design of the injector is particularly critical because it has to take the relatively low energy beam from the VHF gun, accelerate it at more relativistic energies while simultaneously preserving high-brightness and performing longitudinal compression. The present status of the APEX injector design studies is presented.
    No preview · Article · Jan 2013
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    ABSTRACT: The NGLS collaboration is developing design concepts for a multi-beamline soft x-ray FEL array powered by a superconducting linear accelerator, operating with a high bunch repetition rate of approximately 1 MHz. The CW superconducting linear accelerator design is based on developments of TESLA and ILC technology, and is supplied by an injector based on a high-brightness, highrepetition- rate photocathode electron gun. Electron bunches from the linac are distributed by RF deflecting cavities to the array of independently configurable FEL beamlines with nominal bunch rates of ∼100 kHz in each FEL, with uniform pulse spacing, and some FELs capable of operating at the full linac bunch rate. Individual FELs may be configured for different modes of operation, including self-seeded and external-laser-seeded, and each may produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from femtoseconds and shorter, to hundreds of femtoseconds. In this paper we describe current design concepts, and progress in RandD activities.
    No preview · Article · Jan 2013
  • D. Filippetto · L. Doolittle · G. Huang · G. Marcus · H. Qian · F. Sannibale
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    ABSTRACT: The APEX photoinjector has been built and commis- sioned at LBNL. A CW-RF Gun accelerates electron bunches to 750 keV with MHz repetition rate. High quan- tum efficiency photocathodes are being tested with the help of a load lock system, with different work functions. The photocathode drive laser is thus conceived to provide up to 50 nJ per pulse in the UV and 250 nJ per pulse in the green at 1 MHz, with transverse and longitudinal shaping (flat top, 60 ps FWHM). A transfer line of about 12 meters has been designed and optimized to optimize position jitters. Remote control of repetition rate, energy and position have been implemented on the system, together with offline and online diagnostic for beam monitoring. Here we present the laser system setup as well as the first measurements on longitudinal pulse shaping and jitter characterization.
    No preview · Article · Jan 2013
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    ABSTRACT: The planned Next Generation Light Source at LBNL is designed to deliver MHz repetition rate electron beams to an array of free electron lasers. Because of the high beam power approaching one MW in such a facility, effective beam collimation is extremely important to minimize ra- diation damage, prevent quenches of superconducting cav- ities, limit dose rates outside of the accelerator tunnel and prevent equipment damage. We describe the conceptual de- sign of a collimation system, including detailed simulations to verify its effectiveness.
    Full-text · Conference Paper · Jan 2013
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    ABSTRACT: The Next Generation Light Source at LBNL will deliver MHz repetition rate electron beams to an array of free elec- tron lasers. Because of the high beam power approaching one MW in such a facility, effective beam collimation is ex- tremely important to minimize radiation damage, prevent quenches of superconducting cavities, limit dose rates out- side of the accelerator tunnel and prevent equipment dam- age. This paper describes the conceptual design of a colli- mation system, including detailed simulations to verify its effectiveness.
    Full-text · Conference Paper · Jan 2013
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    ABSTRACT: The NGLS collaboration is developing design concepts for a multi-beamline soft X-ray FEL array powered by a superconducting linear accelerator, operating in CW mode, with a high bunch repetition rate of approximately 1 MHz [1]. The superconducting linear accelerator design concept is based on existing TESLA and ILC technology, to be developed for this CW application in a light source. We outline design options and preferred approaches to the linac.
    No preview · Article · Jan 2013
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    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.
    Full-text · Article · Oct 2012 · Review of Modern Physics

Publication Stats

945 Citations
141.66 Total Impact Points

Institutions

  • 2008-2015
    • University of California, Berkeley
      Berkeley, California, United States
  • 2002-2012
    • Lawrence Berkeley National Laboratory
      • Advanced Light Source Facility
      Berkeley, California, United States
  • 1995-2000
    • INFN - Istituto Nazionale di Fisica Nucleare
      Frascati, Latium, Italy