BNL, Upton, Long Island, New York, USA
SUNY SB, Stony Brook, New York, USA
SBU, Stony Brook, New York, USA
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
HOM damping is a challenge for high-current SRF linacs possibly generating HOM power at a level of 10 KW per cavity. A rectangular waveguide used as a natural high pass filter is a good option as high power, large spectrum HOM damper. However, its size is too big, causing a big challenge for the cooling and cryogenic system. A reliable, compact HOM damping scheme using a ridged waveguide is being developed to damp high power (> 10 kW), large spectrum HOMs ( up to 40 GHz) that may be generated in the 647 MHz 5-cell eRHIC ERL SRF linac. The size of a ridged waveguide is less than a quarter of the regular waveguide, which alleviates the thermal issue. This paper presents the design of a ridged waveguide and estimated HOM damping results using a ridged waveguide. The thermal or cooling design of the ridged waveguide will also be addressed.
BNL, Upton, Long Island, New York, USA
Fermilab, Batavia, Illinois, USA
Recent developments of the ERL-based design of future high luminosity electron-hadron collider eRHIC focused on balancing technological risks present in the design versus the design cost. As a result a lower risk design has been adopted at moderate cost increase. The modifications include a change of the main linac RF frequency, reduced number of SRF cavity types and modified electron spin transport using a spin rotator. A luminosity-staged approach is being explored with a Nominal design (L ~ 1033 cm-2 s-1) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design (L > 1034 cm-2 s-1) that uses higher electron current and an innovative cooling technique (CeC). The paper describes the recent design modifications, and presents the full status of the eRHIC ERL-based design.
BNL, Upton, Long Island, New York, USA
High current Superconducting Radiofrequency (SRF) 5-cell cavities are essential for the proposed ERL-based electron-ion collider eRHIC in BNL. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the ERL create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in the eRHIC 5-cell cavity with different ERL bunch patterns using both methods. We also discuss possible solutions to reduce this HOM power.
BNL, Upton, Long Island, New York, USA
SUNY SB, Stony Brook, New York, USA
eRHIC project is a future electron-hadron collider proposed at BNL. The proposed electron accelerator will generate up to 20 GeV polarized electrons which will collide with proton beams with energy up to 250 GeV. The proposed collider will deliver electron-nucleon luminosity of 1033- 1034 cm-2 ses−1. A superconducting RF (SRF) 5-cell elliptical cavity will be utilized in electron accelerator. This paper presents a study of higher-order modes (HOM) for this 647 MHz SRF cavity. Different types of HOM modes and their BBU instabilities were investigated for frequencies up to 3.2 GHz. Threshold current values of beam breakup are estimated by GBBU code. Further improvement on this threshold current has been explored and discussed.
SLAC, Menlo Park, California, USA
We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.
