JLab, Newport News, Virginia, USA
Cavities for the C75 cryomodule refurbishment program are currently being built, processed, tested and installed in the CEBAF accelerator at Jefferson Lab. They consist of 5-cell, 1497 MHz cavities with waveguide-type power coupler and for higher-order modes. Most of the cavities rf tests in a vertical cryostat at 2.07 K were limited by strong multipacting at accelerating gradients in the range 18 - 23 MV/m. A softer multipacting barrier was sometimes found at 13 - 15 MV/m. An unusual feature of the multipacting was that the barrier often shifted to a lower gradient ~17 MV/m, after multiple quenches at ~20 MV/m. This phenomenon was reproduced in a single-cell cavity of the same shape. The cavity was tested after different amounts of mechanical tuning and residual magnetic field, with no significant impact to the multipacting behavior. This contribution summarizes the experimental results from cavity rf tests, some of which were complemented by additional diagnostic instrumentation. Results from 2D and 3D simulations are also presented, indicating favorable conditions for multipacting at the equator in the range 20 - 29 MV/m.
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
CERN, Meyrin, Switzerland
JLab, Newport News, Virginia, USA
JLab, Newport News, Virginia, USA
GA, San Diego, California, USA
Magnetron has been considered as alternate high-efficiency, low-cost RF sources for linacs and storage rings [1] for national labs and industrial applications. After the demonstration of magnetrons power to drive and combine for a radio frequency cavity at 2450 MHz in CW mode, we have used trim coils adding to a water-cooled magnetron and amplitude modulation feedback to further suppress the side-band noise to -46.7 dBc level. We also demonstrated the phase-locking to an industrial grade cooking magnetron transmitter at 915 MHz with a 75 kW CW power delivered to a water load by using a -26.6 dBc injection signal [2]. The sideband noise from the 3-Phase SCRs DC power supply can be reduced to -16.2 dBc level. Further noise reduction and their power combining scheme using magic-tee and cavity type combiners for higher power application (2x75kW) are to be presented. We intent to use one power station to drive the normal conducting and superconducting RF cavities for the inductrial linac. We also going to demonstarte a vertical SRF cavity test with a high input coupling Q using a 2.45GHz magnetron and comparing with a baseline test result using a solid state amplifier.
[1]. doi:10.18429/JACoW-IPAC2015-WEPWI028.
[2]. doi:10.18429/JACoW-NAPAC2022-WEZD3.