Proposed HighPower Test of the ESS Spoke Cavity
- Slides: 11
Proposed High-Power Test of the ESS Spoke Cavity at the FREIA Facility Vitaliy Goryashko E-mail: vitaliy. goryashko@physics. uu. se
Content Ø Why we need high-power tests of the spoke cavity? Ø Some practical experience Ø Testing of the FREIA high-power source Ø High-power FREIA test stand Ø Proposal for the testing program Ø Summary 2
Why we need high-power tests of the spoke cavity? Ø The spoke LINAC is a low-energy machine and each Me. V is important; Ø Multipacting in cavity coupler is a factor limiting the accelerating gradient; Ø The ESS LINAC is a pulsed machine; Ø Lorentz detuning and mechanical vibrations are expected to be strong; Ø During the pulse the surface resistance can change substantially; Ø The piezo-compensation system has to be tested in a realistic situation. 3
Example of the high-power test: TESLA cavity 4 R. Carcagno et al. Proceedings of SRF 2007, Peking Univ. , Beijing, China
FREIA high-power source 5
Testing of the FREIA high-power source Ø Low-power characterization of all components using VNA; [S] Ø Testing of the preamplifiers on a dummy load; A Ø Testing of the high-power amplifiers on a dummy load; A PA Ø High-power testing of all components, especially the circulators and measurement of their insertion loss; Ø Testing of the high-power amplifiers on a sliding short for different phases of reflection. 6
FREIA test stand 7
Proposed experimental studies on the spoke cavity Ø Perform testing of the cavity coupler; Ø Reach nominal accelerating gradient; Ø Measure Lorentz force detuning of the cavity; Ø Study microphonics; Ø Test the cavity tuner; Ø Implement automatized feed-forward compensation system. 8
Charging the cavity 9
Cavity charging without beam 10
Summary ØThe spoke cavity has never been used in a real operating accelerator; ØThe electroacoustic stability and tuning system of the cavity can be studied only in a high-power test stand; Ø The FREIA group at Uppsala University is building a high-power test stand for studying performance of the ESS spoke cavity; ØThe RF test stand will be able to drive the cavity not only in the selfexcitation mode but also with closed RF loop and fixed frequency; ØThe cavity tuning compensation system will be tested under realistic conditions. 11
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