The Synchrotron Radiation Research Center (SRRC) as a third generation light source facility began a major machine upgrade project in 1999. This upgrade will double the synchrotron light intensity operating at beam current of up to 500mA. The higher order mode (HOM) effects induced by the accelerating cavities will be eliminated to guarantee spectral performance. The superconducting 500-MHz cavity of the CESR III design has been selected to replace the existing room temperature accelerating cavities. A turbine-based cryogenic plant will enable the operation of the SRF cavity at 4.5K. Commissioning is scheduled for the summer 2003. This report discusses the overall status of the project. The strategy of developing an in-house SRF capability is emphasized, to provide skilled system maintenance and to long-term reliability of the light source.

Superconducting RF project at the synchrotron radiation research center

A longitudinal coupled bunch instability has been observed in the operation of CESR with multiple trains of bunches. The instability threshold is dependent on the number of bunches per train and the spacing between those bunches. The threshold is also sensitive to parameters in the RF system leading to the conclusion that the RF cavities play a significant role in the dynamics. A summary of these observations is presented along with the design and status of a feedback system to stabilize the beams.

/pdf/observation-of-a-longitudinal-coupled-bunch-instability-with-bd7k5wxdbf.pdf

Observation of a longitudinal coupled bunch instability with trains of bunches in CESR

To achieve the desired luminosities and brilliances in future storage rings for colliders and synchrotron light sources, very large beam currents need to be stored in many tightly spaced bunches. A serious limitation of the performances comes then from the conventional coupled bunch instabilities (CBI). Energy oscillations and transverse oscillations are mainly driven by high-Q structures and the resistivity of the vacuum chamber. Control of these multibunch instabilities has become a critical issue and various strategies are considered to push up the instability thresholds: HOM frequency control to avoid the overlap of dangerous modes with beam spectrum, heavy mode damping to reduce the resonant buildup of the fields, Landau damping to destroy the coherence of the beam and lastly strong feedback systems operating either in the frequency or time domains. These different cures and their technological developments are reviewed in this short paper.

/pdf/cures-of-coupled-bunch-instabilities-17cvq9neij.pdf

Cures of coupled bunch instabilities

The superconducting cavities for the CESR III upgrade at Cornell utilize rectangular waveguide iris coupling. Waveguide vacuum windows manufactured by Thomson Tubes have been tested off-line at 500 MHz up to 500 kWCW traveling wave, 130 kWCW full reflection, and on-line attached to an SRF cavity with beam. On and off-line window processing characteristics are presented. This experience has yielded insight regarding window processing in traveling wave and full reflection modes coupled with effects of atmospheric exposure. Designs of future windows targeted for 1 MWCW operation are also presented.

/pdf/tests-and-designs-of-high-power-waveguide-vacuum-windows-at-4asdvzbet7.pdf

Tests and designs of high-power waveguide vacuum windows at cornell

The Taiwan Light Source (TLS) is a third-generation synchrotron light source located at the Synchrotron Radiation Research Center (SRRC) in Taiwan. The TLS is now operating routinely for user experiments, and the highest priorities are increasing user beam time, increasing machine reliability, and improving the stability of the stored electron beam. Many current machine upgrades are intended to improve beam stability: the longitudinal feedback system, orbit feedback systems, radiofrequency-system improvements (better higher-order-mode performance), and utilities upgrades. In addition, a major improvement program to increase the stored beam current is being planned.

/pdf/status-of-the-taiwan-light-source-yb6kmt04dj.pdf

Status of the Taiwan Light Source

After the successful CESR beam test of August 1994 the continued development of a superconducting RF system for the CESR luminosity upgrade is in progress at the Laboratory of Nuclear Studies, Cornell University. The system description as well as recent results are presented.

https://epaper.kek.jp/pac97/papers/pdf/3p021.pdf

Development of superconducting RF for CESR

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Development of superconducting RF for CESR