DUV-VEL Brookhaven National Laboratory has established an initiative in FEL science and technology which includes the Deep Ultra-Violet Free Electron Laser (DUV-FEL) experiment. The DUV-FEL will be used as a test-bed for experiments to utilize the UV radiation it produces, and serve as model for extending its principles to much shorter wavelengths (x-rays). It is a single pass device to avoid the wavelength limitations imposed by oscillator optics. It is configured as a sub-harmonically seeded High Gain Harmonic Generator (HGHG) to improve coherence and pulse control as contrasted with other schemes that start up from noise. In this process UV light from a solid state laser (Titanium:Sapphire with conventional harmonic generation) is used to illuminate the cathode of an RF photo-injector. This generates an intense electron bunch that is accelerated by an electron linac. The electrons then pass through a short magnetic wiggler where they are coupled with light split off from the laser. The resulting energy modulation is then converted to spatial modulation (micro-bunching) in a dispersive section. A longer wiggler is then used to generate FEL radiation at harmonics of the initial seed laser. This process produces radiation with optical properties and stability that are controlled by the original seed laser (pulse length, bandwidth, coherence). This approach has been successfully demonstrated at BNL in the IR region, converting 10 micron wavelength seed radiation to 5 micron wavelength FEL radiation. In its initial configuration the DUV-FEL will allow operation at wavelengths down to 200 nm at pulse lengths below a picosecond. Planned enhancements can extend this performance to wavelengths the order of 50 nm and pulse lengths as short as 10 femtoseconds. One way to view the DUV-FEL is essentially as a harmonic generation and amplification system for a solid-state laser. Whatever you can produce in the laser can in principle be carried through to the FEL output. This includes its stability as well as programmed pulse formats that can be used to make the FEL a chirped pulse amplification system, potentially yielding pulses shorter that 10 femtoseconds at wavelengths below 100 nm with energies up to a milli-joule. These properties should prove valuable to experimental users of the DUV-FEL. The other obvious feature of the facility is that pump-probe multicolor experiments should be readily possible with excellent timing jitter if the alternate colors can be derived from the facility laser. It should be noted that the tuning agility of the FEL depends on the tuning of the seed laser. The bandwidth of the Ti:Sapp is sufficient for small tuning ranges with relative ease, but broadly tunable operation will depend on enhancing its capabilities over the present system. http://www.stanford.edu/group/fel/center/ovrview.htm Overview of the Stanford Picosecond FEL Center The Stanford FEL facility has been serving users since 1986. The Center has grown and matured considerably since then, but the goal has always been to provide the highest-quality beam possible for use as a scientific tool. The data presented here will show the exceptional quality and stability of our FEL beam, and the ease with which it can be adjusted to suit user requirements. The physical infrastructure has also been expanded to provide users with the laboratory space and support they need. To provide experimenters with precise and stable beams, we have installed feedback loops to control the optical pulse wavelength and amplitude. Variations in wavelength can be reduced to
less than 1 part in 10,000 rms, a small fraction of the transform-limited linewidth. Amplitude variations are reduced to less than 2% rms. The micropulse width can be varied to suit the experiment. Pulse lengths from 700 fs to 3 ps have been delivered to users. Since the beam is transform-limited the spectral width varies accordingly. A real-time diagnostic display in every lab room shows the pulse length, spectrum, power, beam position and pointing, all of which are critical for crossed-beam nonlinear optics experiments. There are 10 experimental rooms at the Stanford Center, each provided with an optical bench and some basic electronics. In addition, the Center has a picosecond dye laser and a sub-picosecond Ti:Sapphire laser which are synchronized to the FEL, a Fourier Transform Infrared Spectrometer and a multi-beam microscope. These facilities, along with a biological sample preparation lab and a modest pool of electronics and optics, greatly reduce the time required for experimenters to gather useful data. Center Facilities Real-Time FEL Diagnostics and User Control Spectrum, autocorrelation, power, pointing data are displayed in every FEL room. Users can control the wavelength (within limits) and diagnostics display from their rooms. Generic Pump-Probe Setup pre-assembled in FEL 2 Optics and data acquisition are provided; users need only provide the sample and do final alignment. Ti:Sapphire laser synchronized to FEL Spectra-Physics Tsunami produces 80 fs, 13 nj pulses tunable from 700 nm to 1000 nm. An amplifier for the Ti:Sapphire laser has been installed. This produces 120 fs pulses with 150 microjoules energy at a 5 khz rate with wavelength tunable from 730 nm to 840 nm. Dye laser synchronized to FEL Nd:YLF CW synchronously-pumped dye laser produces 3 ps, 1.5 nj pulses from 575 to 635 nm. With optional cavity dumper, the system produces 8 ps, 20 nj pulses at up to a 4 MHz repetition rate. A three-stage dye amplifier allows for 3 ps, 1 mj pulses at a 10 Hz rate. Fourier Transform Infrared Spectrometer (Bruker IFS-66v/s FTIR) with resolution from.1 cm -1 and a range from 20 cm -1 to 7500 cm -1 is available for sample analysis. The optical path can be evacuated. The FTIR has step-scan capability for time resolution down to 20 ns, or for lock-in detection The FTIR has an infrared microscope with 15x and 36x magnification. The FEL beam can be delivered to the sample chamber. Multi-beam microscope Biomedical laboratory for sample preparation
Electronics pool for data acquisition and signal processing Operational Parameters of the Stanford FEL Mid-IR (STI) Far-IR (Firefly) Wavelength 3-15 microns 15-65 microns Micropulse Width 0.7-3 ps 2-10 ps Micropulse Repetition Rate 84.6 ns 84.6 ns Macropulse Width 5 ms 5 ms Macropulse Repetition Rate 20 Hz 20 Hz Micropulse Energy 2 microjoule 1 microjoule Average Power 2 W 1 W Spectral Bandwidth Transform-Limited Transform- Limited Gaussian Gaussian Spectral Stability 0.01 % rms 0.01 % rms Amplitude Stability < 2 % rms < 2 % rms Annual Operations 2000 hours ---------- ---- For simple discussion of FEL and how it works: http://www.fel.eng.osakau.ac.jp/english/felp1_e.html http://www.rijnh.nl/n4/n3/f1234.htm The IR User Facility FELIX The user facility provides continuously tunable radiation in the spectra range of 40-2500 cm -1 (4-250 µ m), at peak powers ranging up to 100 MW in (sub)picosecond pulses, and is being used for scientific research in (bio-) medicine, (bio-)chemistry and (bio-)physics. Layout of the user facility Nine user stations are available. Five user stations are located in the central hall. Four of these cover a floor space of 4x5 m 2 each, one covers 8x5 m 2. The layout of the user hall is shown in the figure, which also shows the location of the control room and office space available to users. The transport system delivering the FELIX radiation runs through the centre of this figure.
Each booth in the hall consists of a section that can be made dark, with an opaque roof at 3.5 m height, and an open section with walls of 2 m height. The two sections are separated by a curtain. Unshielded laser beams may only be used in the closed section, which covers roughly half the floor space available per booth. Each booth can be accessed through a magnet-key operated door. Besides FELIX, also other radiation sources present in the booth will be incorporated in an interlock system connected to this door. A labyrinth separates the door and the experimental set-up. US 1: regular user station. US 2: this user station contains an FTICR which is operated by the inhouse user group Molecular Dynamics, the University of Florida (Gainsville, USA) and the National High Field Magnet Laboratory (Tallahassee, USA). Photo FTICR in US 2 US 3: regular user station. It also houses an Oxford Instruments 16T DC super-conducting magnet.photo US 3 Photo 16 T magnet US 4: the non-linear optics lab. There are two separate systems in this user station, the long wavelength pump probe and the photon echo/transient grating/pump probe set-up. These two set-ups are in basic construction the same; however as they are used in different wavelength ranges they have distinct features.pump-probe setup US 5: contains two Ti:Sapphire laser systems that are synchronized to the FEL. One of the systems is used to pump two OPG/OPA systems
(specifications: see below). These lasers can be used for (two-color) experiments in user stations 1-7. An additional area is available in the basement of the user hall: US 6: occupied by the in-house user group Molecular Dynamics. US 7: occupied by the in-house user group Molecular Dynamics. US 8: houses the 45 Tesla pulsed magnet. Photo pulsed magnet US 9: regular user station. Photo: user experiment Basic provisions in user stations Standard utilities like one- and three-phase mains voltage, cooling water, pressurized air, and dry nitrogen gas are provided. A network of tubes has been installed for this. An additional tube is used to supply less common gases, for instance carbon dioxide. An exhaust line for removal of laser gases or vacuum pump outlets is available. Another line provides a 'roughing' vacuum. The booths are furnished with an optical table of typically 1.2x2.4 m 2 size. Some basic mounting hardware (lenses, mirrors, mirror holders, etc.) are available, as well as a set of standard tools and other accessories. For experiments requiring rather extensive set-ups or specialised equipment, users may have to rely on their own resources. (see Ancillary Equipment) Power and spectrum of the radiation is measured on-line in a diagnostic station operated by the FELIX team. This station is located in between the basic FEL equipment and the user stations. Characteristics of the FELIX output which are critical for a certain experiment may have to be measured independently at the user station in question. During operation, the user interacts with the control room through an intercom system. A set of coaxial cables is used for transfer of signals from the FELIX control room to the booths, for instance trigger signals. A serial gate (RS232) and an ethernet cable with TCP/IP protocol are available for transfer of measured data to the users 'home-base' computer, via surfnet. The users have the possibility to adjust a number of FELIX parameters, the most important ones being the wavelength and spectrum. Ancillary equipment available to users (for more details: (berden@rijnh.nl)) Synchronized to FELIX: External lasers: - (Doubled) Nd:YAG : 10 Hz, 50 mj, 100 ps. (jitter <5 ps rms)
- Doubled Nd:YLF : 10Hz, 4 µs -long burst @ 250 MHz, 5 µj, 7 ps. (jitter <2 ps rms) - Ti:Sapphire laser: 100 MHz, 10 fs (oscillator); 1 khz (or e.g. 10 Hz), 30 fs (amplifier) - Ti:sapphire laser system including OPG/OPA stages running in two modes: Other: a. λ = 250-400 nm, >30 µj @ 300 nm, 1 khz, 3 ps, BW < 15 cm -1 b. λ = 3-18 µm, > 10 µj @ 3 µm - 1 µj @ 18µm, 1 khz, 300 fs - CO 2 laser, <8 W, CW or pulsed ( >60 µs, <5 khz) Detectors: - MCT's: wavel. range 3-24 µm, BW 10 MHz, LN 2 -cooled - Ge:Ga: wavel. range 10-200 µm, BW 40 MHz, Liquid He cooled. - pyrodetectors: wavel. range 0.5-1000 µm, BW 3 MHz - Joule meters: threshold 10 µj, integral over macropulse - CCD camera: LN 2 -cooled - pyro array: 256 element, 0.1 * 1 mm 2, integral over macropulse Spectrometers: Grating spectrometers: - Bentham: F.L.= 0.3 m, wavel. range: vis + 3-80 µm - Jarrell-Ash: F.L.= 0.5 m, wavel. range: vis + near-ir Fourier-transform spectrometer: - Nicolet: range 50-7000 cm -1, resolution 0.1 cm -1 Oscilloscopes Digital Storage Oscilloscopes: - 9 bits, 5 Gs/s (Tektronix TDS 3052 and 3054), BW 500 MHz - 8 bits, 100 Ms/s (LeCroy 9310), 2.5 Gs/s (LeCroy 9361) single shot,
BW 300 MHz - 10 bits, 100Ms/s, BW 150 MHz (LeCroy 9430) Sampling scope: - Tektronix, CSA803, 20GHz-BW sampling head, jitter w.r.t. FELIX ( 10ps) Cryostats: - Optistat (CF1204) dynamic-flow cryostat (Oxford Instr.), 4-300 K - Microstat 'cold-finger' flow cryostat (Oxford Instr.), 5-300 K - Bath cryostat (Oxford Instr.) with 14 T superconducting coil magnet Pulsed magnet facility: B < 40 T, upto 10 T sweep during FELIX pulse, equipped with a flow cryostat 20-300 K, max. sample size: < 4 mm wavelength range: 4.5-20 µm Pump-probe, transient grating and photon echo setup: Enclosures: Purgeable, vacuum-tight box for control of experimental environment. Dimensions: 60 * 70 * 34 cm 3 General infrastructure available to users Small modifications or repair of user equipment will be done by the Rijnhuizen Technical Division. This involves access to the mechanical workshop, the electrical/electronical engineering department, and the chemistry department. A small workshop in the user area can be used for repairs by users or FELIX personnel. Liability and safety Users are liable for the infrastructure of the experimental station and the equipment that is made available to them by the facility. The facility reserves the right to charge the user for loss or damages, other than resulting from normal use. For its part, the facility accepts liability for damages to user equipment resulting from culpable actions or negligence by facility personnel and/or malfunctioning of facility equipment. Users are amenable to the safety regulations in force at the facility and subject to directions by the facility manager.
http://www.jlab.org/fel/feldescrip.html Consumables The facility reserves the right to charge the user for consumables, e.g. cryogenic liquids, provided by the facility. Transportation, accommodation and subsistence Only in exceptional cases, and after a motivated, written request has been received, the facility management may decide to bear (part of) the expenses for transportation, accommodation and subsistence. For 'first-time' researchers from the EU- and associated countries (except the Netherlands), support for travel and subsistence is available under the EU-programme 'Transnational access to research infrastructure'. At request, the facility is most willing to help in making the necessary arrangments for travel and accommodation. Free-Electron Laser Program Photo of the Jefferson Lab Free Electron Laser building. The laser is on a lower floor, with laboratories located on an upper level. We are in the process of commissioning an upgrade to our FEL facility, and expect to be lasing again in 2003.
The first FEL, the IR-Demo whose commissioning was completed in August '99, ran as a user facility in Oct. '99, Feb. '00, July '00, Oct. '00, Feb. '01, June '01, Aug. '01, and Oct. '01 providing about 3000 hours of user beam to ~30 groups. Schematic of the original JLab FEL with its photoinjected, superconducting rf linac with energy recovery. Average Power 1720 watts Wavelength range 3-6.2 microns Specifications of the original JLab FEL. Micropulse energy up to 70 microjoules Pulse length 0.5-1.7 ps PRF 74.85, 37.425, 18.7 MHz Bandwidth 0.3-2% Amplitude jitter <10% p-p Polarization >6000:1 Transverse mode < 2x diffraction limit Beam diameter at lab 1.5-3.5 cm The FEL upgrade will enable operation in a wider wavelength range,
namely from 0.25 microns in the ultraviolet, to 15 microns and with average powers up to 10,000 watts and more rapid tunability. In the upgraded machine (see schematic above), the energy will be increased from 40 MeV to 160 MeV by the addition of 2 superconducting linac modules, the average beam current will be increased from 5 to 10 ma, while the extraction efficiency will be increased by a factor of 2 through the use of an optical klystron. A separate optical cavity and wiggler will be used for the ultraviolet region. Additional plans call for the installation of a superconducting compact storage ring to provide synchrotron radiation with light pulses synchronized with those from the FEL. Plan of the laboratories on the upper level of the free-electron laser building with the proposed addition of a synchrotron radiation source.
Center for Terahertz Science and Technology, U. California Santa Barbara http://sbfel3.ucsb.edu/ctst/ http://sbfel3.ucsb.edu/ctst/ Neil Calder, SLAC: (650) 926-8707, neil.calder@slac.stanford.edu German and U.S. laboratories to collaborate on X-ray free-electron lasers The Deutsches-Elektronen-Synchrotron (DESY), Germany's leading particle physics and synchrotron radiation laboratory, and the U.S. Department of Energy's Stanford Linear Accelerator Center (SLAC) signed a laboratory-to-laboratory Memorandum of Understanding on Nov. 1 to establish a unique international collaboration for the development of X-ray free-electron lasers. The collaboration will spur a giant leap forward for synchrotron radiation research. Both facilities will generate X-ray pulses 10 billion times brighter and a thousandfold shorter in duration than existing sources. Scientists can use these ultrabrilliant beams to explore previously inaccessible dynamics in chemistry, biology and materials science, as well as in nanoscale phenomena and atomic and plasma physics. "We are all excited by the colossal discovery potential of X-ray free-electron lasers," said SLAC Director Jonathan Dorfan. "International collaboration is the most efficient, responsible and cost-effective way of building world-class science facilities. There is already dynamic collaboration between SLAC, DESY and the KEK laboratory in Japan on research and development for a future high-energy physics linear collider. Today's agreement establishes stronger bonds between international centers of excellence."
Albrecht Wagner, chairman of the DESY board of directors, said he is "delighted by this collaboration. Both projects will be enriched and accelerated by the first-class personnel and accumulated expertise at both laboratories." DESY and SLAC are world-leading laboratories in the development and operation of electron accelerators for research in high-energy physics and in the many fields of science that make use of synchrotron radiation. Both institutions are committed to exploring the extraordinary scientific capabilities that X-ray free-electron lasers will offer and are advanced in the planning for two facilities -- the Linac Coherent Light Source (LCLS) at SLAC and the TESLA X-ray Free-Electron Laser (TESLA-XFEL) at DESY. The LCLS project engineering and design has been authorized by the Department of Energy, and the facility is scheduled to become operational in 2008. The TESLA-XFEL is expected to be operational in 2011. The agreement sets the framework for practical collaboration between DESY and SLAC on the many technical challenges to be faced in fully exploiting the capabilities of X-ray freeelectron lasers. This collaboration will be based on exchange of personnel and equipment and open interchange of research results, know-how and data. "These machines can be used to observe atoms in the process of forming or breaking bonds in molecules -- in effect, freeze-frame photography of molecular formation," said John Galayda, head of the SLAC X-ray free-electron laser project. Both DESY and SLAC already are working on short-wavelength linear-accelerator-driven light sources that provide a preview of the extraordinary capabilities of LCLS and TESLA- XFEL. The TESLA Test Facility (TTF) at DESY is the shortest wavelength free-electron laser in the world, and the Sub-Picosecond Pulse Source (SPPS) being developed at SLAC will match its performance. The TTF and SPPS offer a combination of peak brightness and short pulse duration far beyond any other sources in the world today. The agreement between DESY and SLAC gives a green light for immediate collaboration on research at TTF and SPPS. This initial work will provide valuable preliminary information and solutions to the technical challenges of the future LCLS and TESLA-XFEL.