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G.H. Hoffstaetter,
I.V. Bazarov,
D.H. Bilderback,
J. Codner,
B. Dunham,
D. Dale,
K. Finkelstein,
M. Forster,
S. Greenwald,
S.M. Gruner,
Y. Li, M. Liepe,
C. Mayes,
D. Sagan,
C.K. Sinclair,
C. Song,
A. Temnykh,
M. Tigner,
Y. Xie
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ABSTRACT: The status of plans for an energy-recovery linac (ERL) X-ray facility at Cornell University are described. Cornell currently operates the Cornell high energy synchrotron source (CHESS) at the CESR ring. The ERL is planned to be an extension to that ring by a 5-GeV superconducting c.w. linac. The very small electron-beam emittances would produce an X-ray source that is considerably better than any existing storage-ring light source. The ERL design that is presented has to allow for non-destructive transport of these small emittances. It includes up to 18 X-ray beamlines for specific areas of research that are currently being defined by an international community. Special attention is given to reuse of many of the existing ring components. Here it is described which subjects are being investigated or will have to be studied at Cornell to prepare for the construction of this new hard X-ray source; references to other contributions to this conference (PAC07) demonstrate this effort. This project illustrates how existing storage rings could be upgraded as ERL light sources with vastly improved beam qualities and with limited dark time for X-ray users. The presented list of research topics shows R&D issues for any such upgrade project.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: Cornell is building a 1.3 GHz Injector Cryomodule for an ERL prototype. The cryomodule consists of five two-cell niobium cavities, each cavity having two coaxial input couplers. Cavity and coupler pairs require acceptance testing at high power prior to assembly in the injector cryomodule. A liquid nitrogen cryostat for testing the couplers at high power has been built and the first input coupler test is complete. In addition, a Horizontal Test Cryostat (HTC) is being built to test input coupler pairs and cavities as a set. The first HTC test is scheduled for summer 2007. Details for instrumentation of the Coupler Test Cryostat (CTC) and HTC are presented.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: Cornell University is developing and fabricating a SRF injector cryomodule for the acceleration of the high current (100 iriA) beam in the Cornell ERL prototype and ERL light source. Major challenges include emittance preservation of the low energy, ultra low emittance beam, cw cavity operation, and strong HOM damping with efficient HOM power extraction. Prototypes have been completed for the 2-cell niobium cavity with helium vessel, coaxial blade tuner with piezo fine tuners, twin high power input couplers, and beam line HOM absorbers loaded with fer- rites and ceramics. Axial symmetry of HOM absorbers, together with two symmetrically placed input couplers per cavity, avoids transverse on-axis fields, which would cause emittance growth. A one-cavity cryostat has been designed following concepts of the TTF cryostat, and is presently under fabrication and assembly. The cryostat design has been optimized for precise cavity alignment, good magnetic shielding, and high dynamic cryogenic loads from the RF cavities, input couplers, and HOM loads. In this paper we report on the status of the assembly and first test of the one-cavity test cryostat.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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R.L. Geng,
P. Barnes,
B. Clasby,
J. Kaminski, M. Liepe,
V. Medjidzade,
D. Meidlinger,
H. Padamsee,
J. Sears,
V.D. Shemelin,
N. Sherwood,
M. Tigner
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ABSTRACT: Six 1300 MHz superconducting niobium 2-cell cavities are manufactured in-house for the prototype of the Cornell ERL injector to boost the energy of a high current, low emittance beam produced by a DC gun. Designed for high current beam acceleration, these cavities have new characteristics as compared to previously developed low-current cavities such as those for TTF Precision manufacture is emphasized for a better straightness of the cavity axis so as to avoid unwanted emittance dilution. We present the manufacturing, processing and vertical test performance of these cavities. We also present the impact of new cavity characteristics to the cavity performance as learnt from vertical tests.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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G.H. Hoffstaetter,
I.V. Bazarov,
S. Belomestnykh,
D.H. Bilderback,
M.G. Billing,
J.S.-H. Choi,
Z. Greenwald,
S.M. Gruner,
Y. Li, M. Liepe,
H. Padamsee,
D. Sagan,
C.K. Sinclair,
K.W. Smolenski,
C. Song,
R.M. Talman,
M. Tigner
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ABSTRACT: We describe the status of plans to build an Energy-Recovery Linac (ERL) X-ray facility at Cornell University. This 5 GeV ERL is an upgrade of the CESR ring that currently powers the Cornell High Energy Synchrotron Source (CHESS) [1]. Due to its very small electron-beam emittances, it would dramatically improve the capabilities of the light source and result in X-ray beams orders of magnitude better than any existing storage-ring light source. The emittances are based upon simulations for currents that are competitive with ring-based sources [2, 4]. The ERL design that is presented has to allow for non-destructive trans port of these small emittances. The design includes a series of X-ray beamlines for specific areas of research. As an upgrade of the existing storage ring, special attention is given to reuse of many of the existing ring components. Bunch compression, tolerances for emittance growth, simulations of the beam-breakup instability and methods of increasing its threshold current are mentioned. This planned upgrade illustrates how other existing storage rings could be upgraded as ERL light sources with vastly improved beam qualities.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: Five 1300 MHz superconducting niobium cavities are to be used for the injector of Cornell ERL prototype. The beam power requirement (100 kW each cavity CW) and the need to minimize emittance dilution due to the cavity structure have important impacts to the design and fabrication of these cavities. We plan to use Conflat stainless-steel flanges brazed to niobium tubes. Two copper prototype cavities have been built and measured. Parts for the first niobium cavity have been manufactured. In this report, we will present the progress of the prototyping copper as well as niobium cavities.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: The Cornell ERL Prototype injector will accelerate bunches from an electron source to an energy of several MeV, while preserving the ultra-low emittance of the beam. The injector linac will be based on superconducting RF technology with five 2-cell RF cavities operated in cw mode. The beam tubes on one side of the cavities have been enlarged to propagate Higher-Order-Mode power from the cavities to broadband RF ring-absorbers located at 80 K between the cavities. The axial symmetry of these ferrite based absorbers, together with two symmetrically placed input couplers per cavity, avoids transverse on-axis fields, which would cause emittance growth. Each cavity is surrounded by a LHe vessel and equipped with a frequency tuner. The cryomodule provides the support and alignment for the cavity string, the 80 K cooling of the ferrite loads, and the 2K LHe cryogenic system for the high cw heat load of the cavities. In this paper we give an overview of the ERL injector cryomodule design.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: The Energy Recovery LINAC (ERL) being developed at Cornell should be an excellent source for Inelastic X-ray Scattering (IXS) because it will permit long undulators to operate at high efficiency generating unprecedented spectral flux (photons/second/meV) and brilliance. We discuss several advantages of the ERL for IXS experimentation.
Journal of Physics and Chemistry of Solids - J PHYS CHEM SOLIDS. 01/2005; 66(12):2310-2312.
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ABSTRACT: For the ERL injector, superconducting cavities are needed to deliver to the beam a 100 kWCW RF power. With a beam current of 100...33 mA, gap voltage of 1...3 MV, the coupler must have an external g-factor in the range of 4.6×10<sup>4</sup>...4.1×10<sup>5</sup>. The cavity shape and coupler design presented provide the possibility of working in the range of parameters without substantial transverse kick to the beam and HOM-losses in the system. In order to preserve field flatness while the dipole mode is driven out, the 2-cell cavity has a protruding iris between the cell and the larger beam pipe. A twin-coaxial coupler has high coupling but low kick because of its symmetry. Calculation and optimization of the coupler-cavity system are performed with a 2D SLANS and 3D Microwave Studio<sup>®</sup> codes.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: A conceptual design of the input coupler for superconducting injector cavities of Cornell/JLab ERL project is presented. The injector cavities are two-cell structures operating at 1300 MHz in CW mode. The coupler has a symmetric design to accommodate requirements for small transverse kick, high RF power delivery to the cavity, and high input coupling value. Therefore it consists of two identical antenna type couplers symmetrically attached to a beam pipe of the cavity. Each coupler delivers 50 kW of CW RF power to the beam. The coupler has a variable coupling. Q<sub>ext</sub> should be varied from 4.6 × 10<sup>4</sup> to 4.1 × 10<sup>5</sup>. The symmetric design of the coupler dramatically reduces the transverse kick, a critical requirement for the ERL project. Estimates of the influence of coupler induced fields on beam dynamics are given.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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H. Padamsee,
B. Barstow,
I. Bazarov,
S. Belomestnykh, M. Liepe,
R.L. Geng,
V. Shemelin,
C. Sinclair,
K. Smolenski,
M. Tigner,
V. Veserevich
[show abstract]
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ABSTRACT: The Laboratory for Elementary-Particle Physics, Cornell University, in collaboration with Jefferson Lab is exploring the potential of a Synchrotron Radiation User Facility based on a multi-GeV, low emittance, Energy-Recovery Linac (ERL) with a 100 mA CW beam. The ERL injector will accelerate bunches from the electron source from 0.5 MeV to 5 MeV with minimal emittance growth. The injector and main linac of the ERL will be based on superconducting RF technology to provide CW operation. There will be one cryomodule with five 1300 MHz 2-cell cavities, each providing one MV of acceleration, corresponding to an accelerating field of about 4.3 MV/m in CW operation. Besides standard features such as an integrated helium vessel and mechanical tuner, each cavity has two input couplers, symmetrically placed on the beam pipe to cancel kicks due to coupler fields. For a 100 mA maximum injected beam current, each coupler must deliver 50 kW of beam power leading to a Qext of 4.6 × 10<sup>4</sup> for matched beam loading conditions. Antenna- and loop-based HOM couplers can disturb beam emittance through kicks. We plan to avoid the use of such couplers. Following the strategy for B-factory SRF cavities, the beam pipe aperture has been enlarged on one side to propagate all higher order modes out to symmetric ferrite beam pipe loads. These are positioned outside the helium vessel and cooled to liquid nitrogen temperature. Ferrite properties at 77 K have been measured and the corresponding damping evaluated. To explore the full capabilities of the injector, energy gains up to 3 MV per cavity will be considered at lower beam currents. For this flexibility, the input coupling needs to be adjustable by a factor of 9.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: Cornell University, in collaboration with Jefferson Laboratory, has proposed the construction of a prototype energy-recovery linac (ERL) to study the energy recovery concept with high current, low emittance beams. The beam with a current of up to 100 mA will excite significant higher-order-mode (HOM) power in the superconducting (s.c.) RF cavities with frequencies up to 100 GHz. Strong damping of the HOMs is essential for beam stability and to reduce the HOM losses to a few hundred Watts per meter. To achieve this demanding goal we plan to place RF absorbing material in the beam tubes between the cavities in the linac. However, this will require operating the HOM absorbers at temperatures below 80 K to simplify the thermal transition to the cavities at 2 K with low static losses to 2 K. One possible material candidate is ferrite, as it is used at room temperature in the HOM absorbers in the s.c. CESR cavities. In this paper we present experiments performed to study the RF absorption properties of ferrite at cryogenic temperatures in the frequency range from 1 GHz to 15 GHz. First results are shown and the resulting HOM damping is evaluated and discussed.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: Cornell is testing superconducting cavities for many different purposes: system development for CESR, supporting technology transfer of CESR SRF systems to storage ring light sources around the world, collaboration with the world-wide TESLA project, collaboration with Muon Collider/Neutrino Factory projects, developing an Energy Recovery Linac (ERL) based synchrotron light source in collaboration with TJNAF, and basic cavity R&D in the areas of high Q, high field Q-slope and field emission. For this Cornell has upgraded its preparation and test facilities and now has the capabilities to test s.c. cavities with frequencies between 200 MHz and 3 GHz. Three radiation-shielded test pits have been built. The largest pit has a size of 2.4 m diameter by 4.4 meter deep. In addition to the existing RF test system at 500 MHz, 1.3 GHz and 1.5 GHz, a 200 MHz low power (2 kW) RF test system has been completed. The high-power 1.3 GHz test system as well as the cavity preparation facility are presently being upgraded to incorporate TESLA 9-cell cavities. A new 1000 sq. ft. clean room is in operation for improved cavity preparation.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: The RF system of the Cornell Electron Storage Ring (CESR) consists of four superconducting (s.c.) 500 MHz cavities. For a charm-tau upgrade (CESR-c) we plan to drive two cavities by one klystron and to operate some cavities in passive mode. During the previous high energy run the RF system performance was not significantly affected by microphonic cavity detuning, since the cavities were operated under strong beam loading with a low loaded quality factor of 2 · 10<sup>5</sup>. However, in low energy CESR-c operation with increased loaded Q-factor the RF system becomes less tolerant to microphonics, especially when two cavities are driven by one klystron. In order to address this potential problem we have studied microphonics in the CESR cavities in detail. Significant improvements have been achieved by reducing major contributions to the detuning. For further improvements we plan to study the performance of an active microphonics compensation scheme, which is based on a fast piezoelectric-driven frequency tuner.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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[show abstract]
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ABSTRACT: Cornell University, in collaboration with Jefferson Laboratory, has proposed the construction of a prototype energy-recovery linac (ERL) to study the energy recovery concept with high current, low emittance beams. The ERL will require the operation of superconducting cavities in two extreme regimes. In the injector a multi-mA beam is accelerated to several MeV energy. The resulting high beam loading in the superconducting cavities requires a strong coupling of the fundamental mode coupler and a high power transfer. The dominating sources of field perturbation in the injector cavities are beam transients and beam current fluctuations. In the main linac the decelerated recirculated beam cancels the beam loading of the accelerated beam. Accordingly these cavities are operated at a high external quality factor to minimize the RF power requirements. Microphonic cavity detuning and path length fluctuations significantly increase the RF power demands. In this paper an overview of the prototype RF system is given and the RF power demands and field stability requirements are discussed in detail.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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G.H. Hoffstaetter,
B. Barstow,
I.V. Bazarov,
S. Belomestnykh,
D. Bilderback,
S. Gruner, M. Liepe,
H. Padamsee,
D. Sagan,
V. Shemelin,
C. Sinclair,
R. Talman,
M. Tigner,
V. Veshcherevich,
G.A. Krafft,
L. Merminga
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ABSTRACT: Synchrotron light sources based on Energy Recovery Linacs (ERLs) show promise to deliver X-ray beams with both brilliance and X-ray pulse duration far superior to the values that can be achieved with storage ring technology. Cornell University, in collaboration with Jefferson Laboratory, has proposed the construction of a prototype ERL. This 100MeV, 100mA CW superconducting electron accelerator will be used to study and resolve the many accelerator physics and technology issues of this type of machine. These studies are essential before ERLs can be confidently proposed for large-scale applications such as synchrotron light sources. Key issues include the generation of high average current, high brightness electron beams; acceleration and transport of these beams while preserving their brightness; adequate damping of higher order modes (HOMs) to assure beam stability; removal of large amounts of HOM power from the cryogenic environment; stable RF control of cavities operating at very high external Q; reduction of beam losses to very low levels; and the development of precision non-intercepting diagnostics to allow beam setup, control and characterization. Our prototype design allows us to address these and other issues over a broad range of parameter space. This design, along with recent progress on understanding these issues, will be presented.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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J. Sekutowicz,
C. Albrecht,
V. Ayvazyan,
R. Bandelmann,
T. Buttner,
P. Castro,
S. Choroba,
J. Eschke,
B. Faatz,
A. Gossel, [......], M. Liepe,
M. Huening,
M. Ferrario,
E. Plawski,
C. Pagani,
N. Baboi,
H. Chen,
H. Wenhui,
C. Tang,
S. Zheng
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ABSTRACT: After three years of preparation, two superstructures, each made of two superconducting 7-cell weakly coupled subunits, have been installed in the TESLA Test Facility linac (TTF) for the cold- and beam test. The energy stability, the HOMs damping, the frequency and the field adjustment methods were tested. The measured results confirmed expectation on the superstructure performance and proved that alternative layout for the 800 GeV upgrade of the TESLA collider, as it was proposed in TDR, is feasible. We report on the test and give here an overview of its results which are commented in more detail elsewhere in these Proceedings.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: Recent progress in developing digital low-level RF con- trols for accelerators has made digital systems an option of choice. At Cornell we are presently working on two projects: upgrading the RF controls of the Cornell Electron Storage Ring (CESR) for charm-tau operation (CESR-c) and developing a new low-level RF system for the proposed Cornell energy-recovery linac (ERL). The present CESR RF control design is based on classic analog amplitude and phase feedback loops. In order to address the required flexibility of the RF control system in the CESR-c upgrade and to implement a true vector sum control we have designed and built a new digital control system. The main features of the new controller are high sampling rates, high computation power and very low la- tency. The digital control hardware consists out of a pow- erful VME processing board with a Xilinx FPGA, an Ana- log Devices digital signal processor (DSP) and memory. A daughter board is equipped with four fast analog-todigital converters (up to 65 MHz sampling rate) and two digital- toanalog converters (up to 50 MHz update rate). The first set of new electronics will be used in the CESR RF system. However, the described digital control hardware can also be used for the Cornell ERL as it was designed to meet its challenging field stability requirements (see (1) ).
01/2003; 5:3347-3349.
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V. Ayvazyan,
N. Baboi,
I. Bohnet,
R. Brinkmann,
M. Castellano,
P. Castro,
L. Catani,
S. Choroba,
A. Cianchi,
M. Dohlus, [......],
R. Wanzenberg,
T. Weiland,
H. Weise,
M. Wendt,
T. Wilhein,
I. Will,
K. Wittenburg,
S. Wolff,
M.V. Yurkov,
K. Zapfe
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ABSTRACT: We present experimental evidence that the free-electron laser at the TESLA Test Facility has reached the maximum power gain
of 107 in the vacuum ultraviolet (VUV) region at wavelengths between 80 and 120 nm. At saturation the FEL emits short pulses with
GW peak power and a high degree of transverse coherence. The radiation pulse length can be adjusted between 30 fs and 100
fs. Radiation spectra and fluctuation properties agree with the theory of high gain, single-pass free-electron lasers starting
from shot noise.
The European Physical Journal D 06/2002; 20(1):149-156. · 1.48 Impact Factor
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V Ayvazyan,
N Baboi,
I Bohnet,
R Brinkmann,
M Castellano,
P Castro,
L Catani,
S Choroba,
A Cianchi,
M Dohlus, [......],
V Verzilov,
R Wanzenberg,
T Weiland,
H Weise,
M Wendt,
I Will,
S Wolff,
K Wittenburg,
M V Yurkov,
K Zapfe
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ABSTRACT: Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring of the bunch charge distribution. A complete characterization of the linear and nonlinear modes of the SASE FEL operation was performed. At saturation the FEL produces ultrashort pulses (30-100 fs FWHM) with a peak radiation power in the GW level and with full transverse coherence. The wavelength was tuned in the range of 95-105 nm.
Physical Review Letters 04/2002; 88(10):104802. · 7.37 Impact Factor
