| Paper | Title | Page |
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| TPPT054 | CW Operation of the TTF-III Input Coupler | 3292 |
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| Many newly proposed light sources, operating in the CW regime, are based on superconducting TESLA technology. Since this was originally developed for pulsed, 1-% duty-factor operation, it is important to determine the limitations of the TESLA cryomodule and its components when operated CW. Among the critical components is the RF input coupler. Two tests have been performed to determine the average power limit of the TTF-III system. First, room temperature tests up to 4 kW were performed at the Forschungszentrum Rossendorf. These permitted the calibration of computer codes developed to calculate the temperature distribution in the coupler. The programs then were used to make predictions for the (normal) cold operation of the coupler. At BESSY, the coupler test stand was assembled inside the HoBiCaT horizontal cryostat test facility to operate the coupler in an environment close to that of a real accelerator. The results of the two tests are presented here. | ||
| TPPT089 | Commissioning and Operations Results of the Industry-Produced CESR-Type SRF Cryomodules | 4233 |
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Funding: Work is partially supported by the National Science Foundation. Upon signing a technology transfer agreement with Cornell University, ACCEL began producing turn-key 500 MHz superconducting cavity systems. Four such cryomodules have been delivered, commissioned and installed in accelerators for operation to date. Two more cryomodules are scheduled for testing in early 2005. One of them will be put in operation at Canadian Light Source (CLS); the other will serve as a spare at Taiwan Light Source (TLS). The commissioning results and operational experience with the cryomodules in CESR, CLS and TLS are presented. |
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| TPPT094 | Design of the CW Cornell ERL Injector Cryomodule | 4290 |
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Funding: This work is supported by Cornell University. 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 LN 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. |
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| WPAT038 | Instability of the RF Control Loop in the Presence of a High-Q Passive Superconducting Cavity | 2553 |
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Funding: Work is supported by the National Science Foundation. An instability of the active RF cavity field control loop was observed during experiments with beam-driven (passive) superconducting cavities in CESR when the cavity external Q factor was raised to a value above 1x107. A computer model was developed and further experiments have been performed to study this instability and find a way to cure it. The results of simulations are presented alongside the experimental results. |
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| WPAT039 | Experience with the New Digital RF Control System at the CESR Storage Ring | 2592 |
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Funding: This work is supported by NSF. A new digital control system has been developed, providing great flexibility, high computational power and low latency for a wide range of control and data acquisition applications. This system is now installed in the CESR storage ring and stabilizes the vector sum field of two of the superconducting CESR 500 MHz cavities and the output power from the driving klystron. The installed control system includes in-house developed digital and RF hardware, very fast feedback and feedforward control, a state machine for automatic start-up and trip recovery, cw and pulsed mode operation, fast quench detection, and cavity frequency control. Several months of continuous operation have proven high reliability of the system. The achieved field stability surpasses requirements. |
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| WPAT040 | Pushing the Limits: RF Field Control at High Loaded Q | 2642 |
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Funding: This work is supported by Cornell University. The superconducting cavities in an Energy-Recovery-Linac will be operated with a high loaded Q of several 1E7, possible up to 1E8. Not only has no prior control system ever stabilized the RF field in a linac cavity with such high loaded Q, but also highest field stability in amplitude and phase is required at this high loaded Q. Because of a resulting bandwidth of the cavity of only a few Hz, this presents a significant challenge: the field in the cavity extremely sensitive to any perturbation of the cavity resonance frequency due to microphonics and Lorentz force detuning. To prove that the RF field in a high loaded Q cavity can be stabilized, and that Cornell's newly developed digital control system is able to achieve this, the system was connected to a high loaded Q cavity at the JLab IR-FEL. Excellent cw field stability – about 2·10-4 rms in relative amplitude and 0.03 deg rms in phase - was achieved at a loaded Q of 2.1·107 and 1.4E8, setting a new record in high loaded Q operation of a linac cavity. Piezo tuner based cavity frequency control proved to be very effective in keeping the cavity on resonance and allowed reliable to ramp up to high gradients in less than 1 second. |
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| RPPT026 | Status of a Plan for an ERL Extension to CESR | 1928 |
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Funding: Cornell University. 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). 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. The ERL design that is presented has to allow for non-destructive transport 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. Options of bunch compression are discussed, tolerances for emittance growth are specified, and simulations of the beam-breakup instability and methods of increasing its threshold current are shown. This planned upgrade illustrates how other existing storage rings could be upgraded as ERL light sources with vastly improved beam qualities. |