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| MOP015 | Linac Design for the FERMI Project | linac, controls, gun, electron | 61 | ||
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FERMI is a fourth generation light source under construction at Sincrotrone Trieste. This is based upon the conversion of the existing injector linac to a 1.2 GeV machine suitable to drive a seeded FEL. The linac will require significant improvements and the addition of several new accelerating modules. Important parameters are pulse to pulse energy stability and the jitter of the e-bunch time of arrival. This paper will cover the baseline design of the machine, as well as experimental results and the proposed technical solutions for the more critical sub-systems.
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| MOP028 | Creation of Peaks in the Energy Spectrum of Laser-Produced Ions by Phase Rotation | proton, target, ion, acceleration | 97 | ||
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Efficient acceleration of ions with use of very high electromagnetic field created by a high power laser has been paid attention because of its attainable very high acceleration gradient. Its intensity, however, has exponentially decreases according to the increase of its energy, which causes essential difficulty for its real application. For the quality improvement of laser-produced ions in their energy spreads, a scheme to apply an additional RF electric field synchronous to the pulse laser, called “Phase Rotation”,* has been applied to the ions produced from the thin foil target 3 and 5 mm, in thickness by irradiation of focused Ti:Sapphire laser with the wave length of 800 nm after optimization of the ion production process with use of real time observation of ion energy by TOF measurement.** Energy peaks with the spread of 7 % have been created in the energy spectrum at the positions depending on the relative phase between the pulse laser and the RF electric field. Possible application of “Phase Rotated” laser-produced ion beam is also to be discussed.
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* A. Noda et al., Laser Physics, Vol. 16, No.4, pp.647-653(2006). |
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| MOP029 | Laser Beat-Wave Microbunching of Relativistic Electron Beam in the THz Range | electron, undulator, plasma, radiation | 100 | ||
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Laser-driven plasma accelerators have recently demonstrated a ~1GeV energy gain of self-trapped electrons in a several-centimeter-long plasma channel. Potential staging of such devices will require external injection of an electron beam prebunched on the scale of 1-10 THz into a plasma accelerating structure or plasma LINAC. Seeded FEL/IFEL techniques can be used for modulation of the electron beam longitudinally on the radiation wavelength. However a seed source in this spectral range is not available. At the UCLA Neptune Laboratory a Laser Beat-Wave (LBW) microbunching experiment has begun. Interaction of the electron beam and the LBW results in ponderomotive acceleration and energy modulation on the THz scale. This stage is followed by a ballistic drift of the electrons, where the gained energy modulation transfers to the beam current modulation. Then the beam is sent into a 33-cm long undulator, where a coherent start-up of THz radiation takes place providing efficient bunching of the whole beam. The performance of LBW bunching is simulated and analyzed using 3D FEL code for the parameters of an existing photoinjector and two-wavelength TW CO2 laser system.
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| MOP036 | Status of the PAL-XFEL Project | electron, undulator, linac, radiation | 118 | ||
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PAL-XFEL, the new X-ray FEL machine that is going to be built at Pohang Accelerator Laboratory, is under intensive design study. The electron beam energy will be 3.7 ~ 4.0 GeV and the target wavelength will be 0.3 nm. The results as well as the strategy and the difficulties in the PAL-XFEL design are presented in this paper.
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| MOP037 | Applications of Time-of-Flight Measurements at FLASH | electron, linac, vacuum, undulator | 121 | ||
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As a prototype of the XFEL, VUV-FEL has been build and commissioned at DESY by an international collaboration. It is a linear electron accelerator with an undulator arrangement to produce laser pulses by the 'Self-Amplified Spontaneous Emission' (SASE) process. To generate the laser pulses, electron bunches are compressed in longitudinal direction to reach the necessary peak current of about 2.5 kA. To control the compression process a number of 'Phase Monitors' are installed at the accelerator. They measure the time of the bunch passages. Differences of the bunch passage times at different linac locations yield the 'Time-Of-Flight' (TOF) between these locations. The system is installed with regard to the planned installation of a further RF module operating at the third harmonic RF frequency. This 'third harmonic cavity' is required to optimize the longitudinal bunch charge distribution. Its effect is examined by the TOF measurements. The paper presents the Phase Monitor system to measure the TOF at VUV-FEL. The principle is shown, the determination of 'on-crest'-phases is demonstrated and first measurements of the momentum compaction coefficients, R56 and T566, are discussed.
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| TU2002 | Laser-Based Heavy Ion Production | ion, plasma, rfq, target | 219 | ||
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We have focused on high brightness of induced plasma in Laser Ion Source (LIS) to provide intense highly charged ions efficiently. To take the advantage of the intrinsic density of the laser plasma, Direct Plasma Injection Scheme (DPIS) has been developed. The induced laser plasma has initial expanding velocity and can be delivered directly to the RFQ. Extraction electrodes and focusing devices in LEBT are not needed. Since 2004, a newly designed RFQ has been used to verify the capability of the new ion production scheme. We succeeded to accelerate 60 m A of Carbon beam and 60 mA of Aluminium beam. We have also tried to understand plasma properties of various species by measuring charge states distributions and time structures, and are now ready to accelerate heavier species. Currently Silver 15+ beam is planned to be accelerated. In the conference, design strategies and detailed techniques for the DPIS will be described based on the measured plasma properties of various elements and new findings obtained from recent acceleration experiments. The durability and the reproducibility will be also explained.
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| TUP008 | The Low Emittance Photoinjector in Tsinghua University | emittance, cathode, gun, electron | 259 | ||
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A photocathode rf gun system is under developing in Tsinghua University for Thomson scattering. The microwave properties and the high power processing of this rf gun were finished. The UV laser system can provide a 266nm laser pulse with 1~10ps and 200μJ photo energy per pulse. The beam experiments are under way. This paper gives a general description of this photocathode rf gun and its preparation.
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| TUP009 | First Operation of the FLASH Machine Protection System with Long Bunch Trains | undulator, beam-losses, linac, radiation | 262 | ||
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The linac-based free electron laser facility FLASH at DESY Hamburg is designed to transport an electron beam with an average power of more than 50 kW. To avoid serious damage to accelerator components, a fast active machine protection system (MPS) stops the production of new bunches if hazardous machine conditions are detected. This paper gives an overview of the MPS topology and its subsystems. Furthermore, we present results from the commissioning of the fast beam interlock system that has for the first time allowed to operate the accelerator with macropulses of up to 600 bunches.
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| TUP038 | Status of the Sparc Photoinjector | emittance, gun, electron, cathode | 333 | ||
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The SPARC Project is starting the commissioning of its photo-injector. RF gun, RF sources, RF network and control, power supplies, emittance meter, beam diagnostics and control to measure the RF gun beam have been installed. The photocathode drive laser has been characterized in terms of pulse shape and quality. We will report also about first tests made on RF gun and on the emittance meter device. Additional R&D on X-band and S-band structures for velocity bunching are in progress, as well as studies on new photocathode materials . We will also discuss studies on solenoid field defects, beam based alignments and exotic electron bunch production via blow-out of short laser pulses.
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| TUP045 | Photothermal Cathode Measurements at the Advanced Photon Source | cathode, gun, klystron, electron | 349 | ||
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The Advanced Photon Source (APS) ballistic bunch compression (BBC) injector presently uses an M-type thermionic dispenser cathode as a photocathode. This “photothermal” cathode offers substantial advantages over conventional metal photocathodes, including easy replacement and easy cleaning via the cathode’s built-in heater. We present the results of quantum efficiency measurements as a function of cathode heater power, laser pulse energy, and applied rf field strength.
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| TUP049 | Metal-Based Photocathodes For High-Brightness RF Photoinjectors | cathode, gun, vacuum, target | 358 | ||
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Advanced high brightness RF gun injectors require photocathodes with fast response, high quantum efficiency and good surface uniformity. Metal films deposited by various techniques on the gun back wall could satisfy these requirements. Two new deposition techniques have been recently proposed, i.e. pulsed laser ablation and vacuum arc. Several samples of various materials have been deposited by the two techniques: The emission performance and morphological changes induced on the cathode surface by laser beam are compared and discussed.
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| TUP059 | Photoinjector Production of a Flat Beam with Transverse Emittance Ratio of 100 | emittance, quadrupole, simulation, electron | 382 | ||
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The generation of a flat electron beam directly from a photoinjector is an attractive alternative to the electron damping ring as envisioned for linear colliders. It also has potential applications to light sources such as the generation of ultrashort x-ray pulses or Smith-Purcell free electron lasers. In this paper, we report on the experimental generation of a flat beam with a measured transverse emittance ratio of 100±20 for a bunch charge of ≅0.5~nC*. The experimental data, obtained at the Fermilab/NICADD Photoinjector Laboratory, are compared with numerical simulations and the expected scaling laws. Possible improvement of the experiment along with application for such a flat beams are discussed
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* P. Piot, Y.-E. Sun and K.-J. Kim, Phys. Rev. ST Accel. Beams 9, 031001 (2006) |
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| TUP062 | Experimental Optimization of TTF2 RF Photoinjector for Emittance Damping | emittance, booster, gun, damping | 391 | ||
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To get lasing and saturation at FEL facilities, we should generate high quality electron beams with a low emittance, a high peak current, and a low energy spread. Generally, the RF photoinjector is a key component to generate such a high quality beams. During DESY TESLA Test Facility (TTF) phase 2 commissioning, we optimized our L-band RF photoinjector and bunch compressor by comparing measurement results and simulation ones. In this paper, we describe our optimization experiences to get about 1.1 mm.mrad transverse normalized emittance for 1.0 nC single bunch charge and 4.4 ps RMS bunch length from TTF phase 2 RF photoinjector.
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| WE1003 | The TTF/VUV-FEL (FLASH) as the Prototype for the European XFEL Project | linac, electron, free-electron-laser, radiation | 486 | ||
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The European X-ray Free-Electron Laser Facility (XFEL) is going to be built in an international collaboration at the Deutsches Elektronen-Synchrotron (DESY), Germany. The Technical Design Report was published recently. The official project start will be before end of this year. The new facility will offer photon beams at wavelengths as short as 1 Angstroem with highest peak brilliance being more than 100 million times higher than present day synchrotron radiation sources. The radiation has a high degree of transverse coherence and the pulse duration is reduced from ~100 picoseconds down to the ~10 femtosecond time domain. The overall layout of the XFEL will be described. This includes the envisaged operation parameters for the linear accelerator using superconducting TESLA technology. The complete design is based on the actually operated VUV Free-Electron Laser at DESY. Experience with the operation during first long user runs will be described in detail. Many of the different subsystems of the XFEL could be tested. Specially developed electron beam diagnostics was commissioned. A summary of the status of the XFEL preparation work will be given.
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| TH2002 | Timing and Synchronization in Large-Scale Linear Accelerators | diagnostics, radiation, electron, linac | 536 | ||
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New coherent light sources are based on large scale linear accelerator; the adopted single pass acceleration scheme allows the preservation of bunch 6D phase space leading to ultra short (<100fsFWHM) and ultra bright (average Brilliance = 1024 (1) ph/sec/mm2/mrad2/0.1%bw) pulses of coherent radiation in the DUV-x-ray regions. Femto-second lasers are deeply integrated in the electron bunch and photon pulse generation, in diagnostic set-ups and in time resolved experiments: the timing may be as low as 10% of pulse duration. The requirements on the stability of RF acceleration call for distribution of ultra-stable and ultra-low phase noise reference signal for the Low Level RF feedback loops. A non reversible breakthrough into the adoption of optical and O/E techniques is on-going which is taking advantage on five order of magnitude reduction in the period of the carrier. Being the current limit represented by the carrier-envelope stabilization techniques, sub-fs jitters have been demonstrated in the laboratory; the preservation of laboratory levels of jitters and stability over the whole accelerator premises is the next step. On-going efforts and results let us be optimistic.
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Interim Report of the Scientific and Technical Issues (XFEL-STI) Working Group ona European XFEL facility in Hamburg, January 11, 2005. |
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| TH2004 | Nuclear Photo-Science and Applications with Thomson-Radiated Extreme X-Ray (T-REX) Sources | electron, scattering, photon, brightness | 546 | ||
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The Thomson scattering of picosecond and femtosecond duration laser pulses off of low emittance electron beams is an effective method of producing mono-chromatic, MeV-range gamma-rays with unprecedented peak brightness. With peak brightness at 1 MeV > 15 orders of magnitude beyond 3rd generation synchrotrons, these sources open the possibility for a host of new nuclear applications based on photons. In this presentation an overview of the requisite photo-gun, short pulse laser and linear accelerator technologies required for production of high brightness gamma-rays will be presented. Potential applications of these unique sources of radiation will be discussed with particular emphasis given to the excitation and use of nuclear resonance fluorescence (NRF) for isotope detection and imaging of special nuclear materials of importance to homeland security.
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| TH3001 | Photoinjectors R&D for Future Light Sources and Linear Colliders | gun, electron, emittance, cathode | 549 | ||
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Linac-driven light sources and linear proposed colliders require high brightness electron beams. In addition to the small emittances and high peak currents, linear colliders also require spin-polarization and possibly the generation of asymmetric beam in the two transverse degree-of-freedom. Other applications (e.g. high power free-electron lasers) call for high duty cycle and/or angular-momentum-dominated electron beams (electron cooling). We review on-going R&D programs aiming at the production of electron beams satisfying these various requirements. We especially discuss R&D on photoemission electron sources (especially based on radio-frequency gun) along with the possible use of emittance manipulation techniques.
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| THP003 | Integrated Optical Timing and RF Reference Distribution System for Large-Scale Linear Accelerators | feedback, electron, linac, controls | 565 | ||
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Highly-stable timing and RF reference distribution systems are required to meet the tight specifications in large scale accelerators for next generation light sources. In this paper, we present an approach based on the distribution of an optical pulse train from a mode-locked laser via timing stabilized fiber links. The timing information is contained in the precise repetition rate of the optical pulse train (~50 MHz), so RF can be extracted at end stations with a stability on the order of 10 fs. Less timing critical signals such as ADC clocks and trigger signals can be transmitted through the same stabilized fiber using a modulated cw laser operating at a different wavelength with sub-ps stability. As multiple wavelengths can propagate without interference through the fiber, it is also possible to integrate data communication in such a fiber system. This paper will review the timing system requirements and present a conceptual layout of an optical timing and reference frequency distribution system based on work done at MIT and DESY for the XFEL.
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| THP007 | Timing Distribution in Accelerators via Stabilized Optical Fiber Links | controls, feedback, pick-up, linac | 577 | ||
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We present progress on fiber-optic based systems for highly stable distribution of timing signals for accelerators. This system has application for linac-based sources of ultrafast radiation which require sub-100 fsec synchronization or for very large accelerators such as the linear collider. The system is based on optical fiber links that are stabilized with an optical interferometer with RF and timing signals distributed as modulations on the optical carrier. We present measurements of the stability of this link over distances of several hundred meters and discuss issues for testing the link over 10 km.
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| THP024 | Development of Ultra-fast Silicon Switches and their Applications on Active X-Band, High-Power RF Compression Systems | simulation, coupling, plasma, resonance | 619 | ||
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In this paper, we present the recent results of our research on the ultra-high power fast silicon RF switch and its application on active X-Band RF pulse compression systems. This switch is composed of a group of PIN diodes on a high purity silicon wafer inserted into a cylindrical waveguide operating in the TE 01 mode. Switching is performed by injecting carriers into the bulk silicon through a high current pulse. A switch module is composed of the silicon switch, a circular waveguide T with the silicon switch at the center port and a movable short at the other end of silicon switch. The module can tune the S-matrix of on and off states to desired value. Our current design uses a CMOS compatible process and the fabrication is accomplished at SNF (Stanford Nanofabrication Facility). The switch has achieved <300ns on time with ~3% loss on the wafer. The RF energy is stored in a room-temperature, high-Q 400 ns delay line; it is then extracted out of the line in a short time using the switch. The pulse compression system has a achieved a gain of 7, which is the ratio between output and input power. Power handling capability of the switch is estimated at the level of 10MW.
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| THP065 | High-Gradient Generation in Dielectric-Loaded Wakefield Structures | electron, simulation, gun, klystron | 731 | ||
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Dielectric loaded wakefield structures have potential to be used as high gradient accelerator components. Using the high current drive beam at the Argonne Wakefield Accelerator Facility, we employed cylindrical dielectric loaded wakefield structures to generate accelerating fields of up to 43 MV/m at 14 GHz. Short electron bunches (13 ps FWHM) of up to 86 nC are used to drive these fields, either as single bunches or as bunch trains. One of these structures consists of a 23 mm long cylindrical ceramic tube (cordierite) with a dielectric constant of 4.76, and inner diameter of 10 mm, inserted into a cylindrical copper waveguide. This standing-wave structure has a field probe near the outer edge of the dielectric to sample the RF fields generated by the electron bunches. The signal is sent to a mixer circuit, where the 14 GHz signal is down converted to 5 GHz and then sent to an oscilloscope. A similar structure, with smaller inner diameter and an operating frequency of 9 GHz, is ready for initial tests. Its accelerating fields will be twice as high as the fields in the 14 GHz structure, for the same bunch charge.
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| THP072 | Fabrication and Low-Power Measurements of the J-PARC 50-mA RFQ Prototype | rfq, linac, vacuum, pick-up | 749 | ||
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In the Japan Proton Accelerator Research Complex (J-PARC) project, the beam commissioning of the H- linac will be started with a 30mA peak current. A 30mA type RFQ, which is developed for the former Japan Hadorn Facility (JHF) project, is used for the day-1 operation. However, it is required to accomplish the peak current of 50mA as soon as possible. For this purpose, we have developed an RFQ for the 50mA peak current, which is a four vane type RFQ and resonant frequency of which is 324MHz, same as the 30mA RFQ. In the R&D of this RFQ, we have adopted laser welding to join oxygen free copper blocks to be a cavity structure. The heat load of the laser welding can be more localized than that of the brazing, and the copper is not annealed, therefore, we think, it is possible to obtain more mechanical accuracy. We have developed a longitudinally 1/3 prototype cavity of the J-PARC 50mA RFQ. In this cavity, the distortion of the vane tips is measured to be less than 30 micro-meters, and the field uniformity of within 1% is obtained in a low power measurement after tuning. In this paper, we discuss about the fabrication and the low power measurement of this prototype cavity.
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| THP083 | Generation of Ellipsoidal Beam Through 3-D Pulse Shaping of a Photoinjector Drive Laser | simulation, emittance, electron, gun | 776 | ||
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Due to the linear space-charge force, an ellipsoidal beam is expected to have much smaller emittance in comparison with beams of other geometries, which is critical for many accelerator applications. Up to now, no practical way of generating such beams is available. In this paper we present a few schemes for 3-D laser pulse shaping that can be used to generate ellipsoidal laser pulses that in turn can be applied for generating ellipsoidal electron bunches from a photoinjector. Our simulations show that 3D laser pulse shaping can be realized through laser phase tailoring in combination with properly designed refractive and diffractive optics. Performance of an electron beam generated from such shaped laser pulses is compared with that of the ideal flat-topped and Gaussian electron bunches by numerical simulation, showing improvement in both beam dynamics and performance.
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| THP094 | GeV Laser Wakefield Acceleration and Injection Control at LOASIS | electron, plasma, simulation, injection | 806 | ||
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Experiments at the LOASIS laboratory of LBNL have demonstrated production of GeV electron beams with low energy spread and divergence from laser wakefield acceleration. The pondermotive force of a 40 TW laser pulse guided by a 3 cm capillary discharge plasma density channel drove an intense plasma wave (wakefield), producing acceleration gradients on the order of 50 GV/m. Electrons were trapped from the background plasma and accelerated. Beam energy was increased from 100 to 1000 MeV*, compared to earlier experiments**, by using a longer guiding channel at low density, demonstrating the anticipated scaling to higher beam energies. Particle simulations are used to understand the trapping and acceleration mechanisms. Other experiments and simulations are also underway to control injection of particles into the wake, and hence improve beam quality and stability further. Recent experimental and simulation results from channel guided laser acceleration, and initial injection results, will be presented.
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*W. P. Leemans et al, submitted. |
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| FR2001 | Targets and Ion Sources Development at ISAC-TRIUMF | target, ion, ion-source, proton | 823 | ||
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The ISAC facility is operational since 1998, we utilize the proton beam from the TRIUMF H- cyclotron to produce the radioactive ion beams (RIB) via the isotopic separation on line (ISOL) method. The ISAC facility is designed to accommodate 100 μA proton beam at 500 MeV. Since beginning operation irradiation currents have progressively increased from initial values of ~ 1 μA to present levels of up to 75 μA on refractory metal foil targets and recently equally on composite carbide targets. Beyond the 50 μA limit the target has to be cooled. A new target equipped with fins has been developed that can sustain proton beam up to 100 μA. The RIB intensities depend not only on the target but also on the ability to produce ion beam. The ion sources design for on-line applications are extremely important because of the close contact with the target. They must sustain high radiation field and operate in a large gas pressure range. In order to produce a larger range of beam we are looking at other types, ECR, FEBIAD, negative and the laser ion sources. Report on the recent progress accomplished during the past years will be made.
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