-
R.A. Rimmer,
R. Bundy,
G. Cheng,
G. Ciovati,
E.F. Daly,
R. Getz,
J. Henry, W.R. Hicks,
P. Kneisel,
S. Manning,
R. Manus,
F. Marhauser,
K. Smith,
M. Stirbet,
L. Turlington,
L. Vogel,
H. Wang,
K.M. Wilson
[show abstract]
[hide abstract]
ABSTRACT: We describe the activities underway at JLab to develop new CW cryomodules capable of transporting up to Ampere-levels of beam currents for use in ERLs and FELs. Goals include an efficient cell shape, high packing factor for efficient real-estate gradient and very strong HOM damping to push BBU thresholds up by two or more orders of magnitude compared to existing designs. Cavity shape, HOM damping and ancillary components are optimized for this application. Designs are being developed for low-frequency (750 MHz), Ampere-class compact FELs and for high-frequency (1.5 GHz), 100 mA configurations. These designs and concepts can easily be scaled to other frequencies. We present the results of conceptual design studies, simulations and prototype measurements. These modules are being developed for the next generation ERL based high power FELs but may be useful for other applications such as high energy light sources, electron cooling, electron-ion colliders, industrial processing etc.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
-
[show abstract]
[hide abstract]
ABSTRACT: We describe the concepts and developments underway at JLab as part of the program to develop a new CW cryomodule capable of transporting Ampere-level beam currents in a compact FEL. Requirements include real-estate gradient of at least 10 MV/m and very strong HOM damping to push BBU thresholds up by two or more orders of magnitude compared to existing designs. Cavity shape, HOM damping, power couplers, tuners etc. are being designed and optimized for this application. Cavity considerations include a large iris for beam halo, low-RF losses, HOM frequencies and Q’s, low peak surface fields, field flatness and microphonics. Module considerations include high packing factor, low static heat leak, image current heating of beam-line components, cost and maintainability. This module is being developed for the next generation ERL based high power FELs but may be useful for other applications such as electron cooling, electron-ion colliders, industrial processing etc.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
-
[show abstract]
[hide abstract]
ABSTRACT: The new tuner design for the 12 GeV Upgrade SRF cavities consists of a coarse mechanical tuner and a fine piezoelectric tuner. The mechanism provides a 30: 1 mechanical advantage, is pre-loaded at room temperature and tunes the cavities in tension only. All of the components are located in the insulating vacuum space and attached to the helium vessel, including the motor, harmonic drive and piezoelectric actuators. The requirements and detailed design are presented. Measurements of range and resolution of the coarse tuner are presented and discussed.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
-
E.F. Daly,
I.E. Campisi,
J. Henry, W.R. Hicks,
J. Hogan,
P. Kneisel,
D. Machie,
C.E. Reece,
T. Rothgeb,
J. Sekutowicz,
K. Smith,
T. Whitlatch,
K.M. Wilson,
M. Wiseman
[show abstract]
[hide abstract]
ABSTRACT: In order to provide a higher performance building block cryomodule for the CEBAF 12 GeV upgrade, modifications have been made to the design of the Upgrade Cryomodule. The prototype cryomodule will be completed in 2004 and be installed for operation in CEBAF. Design changes enable the use of higher gradient cavities to achieve greater than 100 MV per cryomodule while not exceeding the budgeted cryogenic load of 300 W during steady-state operation. They also include refinements based on experience gained during the construction of the first generation upgraded cryomodules as well as the prototype cryomodule for the Spallation Neutron Source. Two cavity designs will be used in the prototype, one optimized for E<sub>peak</sub>/E<sub>acc</sub> ratio, and the other optimized for minimum cryogenic load. The input waveguides, thermal shield and piping have been redesigned to accommodate the higher expected heat loads. The vacuum connections consist of niobium-titanium flanges, aluminum-magnesium seals and stainless steel clamps to provide reliable UHV sealing. The cavity tuner features one cold motor and two piezoelectric actuators to provide coarse and fine tuning respectively.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
-
R A Rimmer,
G Ciovati,
E F Daly,
T Elliott, W R Hicks,
J Henry,
P Kneisel,
S Manning,
R Manus,
J Preble,
M Stirbet,
K Smith,
L Turlington,
L Vogel,
H Wang,
K M Wilson,
G Wu
[show abstract]
[hide abstract]
ABSTRACT: For the next generation of compact high-power FELs a new cryomodule is required that is capable of accelerating up to Ampere levels of beam current. Challenges include strong HOM damping, high HOM power and high fundamental-mode power (in operating scenarios without full energy recovery). For efficient use of space a high real-estate gradient is desirable and for economic operation good fundamental-mode efficiency is important. The technology must also be robust and should be based on well-proven and reliable technologies. For Ampere-class levels of beam current both halo interception and beam break-up (BBU) are important considerations. These factors tend to drive the designs to lower frequencies where the apertures are larger and the transverse impedances are lower. To achieve these goals we propose to use a compact waveguide-damped multi-cell cavity packaged in an SNS-style cryomodule.
-
R A Rimmer,
R Bundy,
G Cheng,
G Ciovati,
W Clemens,
E F Daly,
J Henry, W R Hicks,
P Kneisel,
S Manning,
R Manus,
F Marhauser,
J Preble,
C Reece,
K Smith,
M Stirbet,
L Turlington,
H Wang,
K M Wilson
[show abstract]
[hide abstract]
ABSTRACT: Fourth generation light sources hold the prospect of unprecedented brightness and optical beam quality for a wide range of scientific applications. Many of the proposed new facilities will rely on large superconducting radio frequency (SRF) based linacs to provide high energy, low emittance CW electron beams. For high average power applications there is a growing acceptance of energy recovery linac (ERL) technology as the way to support large recirculating currents with modest RF power requirements. CW SRF and high current ERLs are two core competencies at Jefferson Lab. JLab has designed and built a number of CW cryomodules of several different types starting with the original CEBAF design, with variations for higher current in the two generations of JLab's free-electron laser (FEL), through two intermediate prototypes to the final high-performance module for the 12 GeV upgrade. Each of these represent fully engineered and tested configurations with a variety of specifications that could be considered for possible use in fourth generation light sources. Furthermore JLab has been actively pursuing advanced concepts for high-current high-efficiency cryomodules for next generation ERL based FEL's. These existing and proposed designs span the range from about 1mA single-pass to over 100 mA energy recovered current capability. Specialized configurations also exist for high-current non-energy recovered sections such as the injector region where very high RF power is required. We discuss the performance parameters of these existing and proposed designs and their suitability to different classes of fourth generation light sources.
-
[show abstract]
[hide abstract]
ABSTRACT: During initial testing of the prototype cavities incorporated into the developmental cryomodule Renascence severe thermal stability issues were encountered during CW operation. Additional diagnostic instrumentation was added. This enabled identification of an unanticipated thermal impedance between the HOM coupler probe feedthrough assembly and the cavity beamtube. Subsequent detailed FE analysis successfully modeled the situation and indicated the need for alternate cooling path for the couplers on those cavities. HOM damping was measured to be adequate employing only two of the four HOM couplers. The two pickup probes on the couplers at the input power coupler side of each cavity were removed, the remaining HOM probe feedthroughs were heat stationed to two-phase helium supply piping, and a novel heat sink was added to station both the inner and outer conductors of the remaining HOM rf cables. The characterization measurements, analysis, modifications, and resulting performance are presented.
-
R A Rimmer,
R Bundy,
G Cheng,
G Ciovati,
E F Daly,
R Getz,
J Henry, W R Hicks,
P Kneisel,
S Manning,
R Manus,
F Marhauser,
K Smith,
M Stirbet,
L Turlington,
L Vogel,
H Wang,
K M Wilson
[show abstract]
[hide abstract]
ABSTRACT: We describe the activities underway at JLab to develop new CW cryomodules capable of transporting up to Ampere-levels of beam currents for use in ERLs and FELs. Goals include an efficient cell shape, high packing factor for efficient real-estate gradient and very strong HOM damping to push BBU thresholds up by two or more orders of magnitude compared to existing designs. Cavity shape, HOM damping and ancillary components are optimized for this application. Designs are being developed for low-frequency (750 MHz), Ampere-class compact FELs and for high-frequency (1.5 GHz), 100 mA configurations. These designs and concepts can easily be scaled to other frequencies. We present the results of conceptual design studies, simulations and prototype measurements. These modules are being developed for the next generation ERL based high power FELs but may be useful for other applications such as high energy light sources, electron cooling, electron-ion colliders, industrial processing etc.
-
E F Daly,
I E Campisi,
J Henry, W R Hicks,
J Hogan,
P Kneisel,
D Machie,
C E Reece,
T Rothgeb,
J Sekutowicz,
K Smith,
T Whitlatch,
K M Wilson,
M Wiseman
[show abstract]
[hide abstract]
ABSTRACT: In order to provide a higher performance building block cryomodule for the CEBAF 12 GeV upgrade, modifications have been made to the design of the Upgrade Cryomodule. The prototype cryomodule will be completed in 2004 and be installed for operation in CEBAF. Design changes enable the use of higher gradient cavities to achieve greater than 100 MV per cryomodule while not exceeding the budgeted cryogenic load of 300 W during steady-state operation. They also include refinements based on experience gained during the construction of the first generation upgraded cryomodules as well as the prototype cryomodule for the Spallation Neutron Source. Two cavity designs will be used in the prototype, one optimized for E peak /E acc ratio, and the other optimized for minimum cryogenic load. The input waveguides, thermal shield and piping have been redesigned to accommodate the higher expected heat loads. The vacuum connections consist of niobium-titanium flanges, aluminum-magnesium seals and stainless steel clamps to provide reliable UHV sealing. The cavity tuner features one cold motor and two piezoelectric actuators to provide coarse and fine tuning respectively.
