The Lorentz force can dynamically detune pulsed Superconducting RF cavities. Considerable additional RF power can be required to maintain the accelerating gradient if no effort is made to compensate for this detuning. An adaptive feed-forward Lorentz Force Detuning (LFD) compensation algorithm developed at Fermilab is described. Systems based on this approach have been used to successfully reduce LFD from several hundred Hz to several 10s of Hz or better.

/pdf/adaptive-compensation-of-lorentz-force-detuning-in-4sbj0x2p05.pdf

Adaptive compensation of Lorentz force detuning in superconducting RF cavities

Fast, active resonance stabilization has been attempted in several recent accelerator complexes, but has so far been unsuccessful. The next generation of superconducting accelerators will require both precise control of the gradient and active stabilization of the resonance frequency. Advanced techniques are being developed at Fermilab to monitor and correct for cavity detuning using fast piezo electric mechanical tuners. Results from recent cold cavity tests at Fermilab and Cornell University are presented.

Resonance Control for Narrow-Bandwidth, Superconducting RF Applications

The medium energy electron-ion collider (MEIC) being developed at JLAB requires a new ion accelerator complex (IAC). The IAC includes a new linac and a new booster accelerator. The new facility is required for the acceleration of ions from protons to lead for colliding beam experiments with electrons in the EIC storage ring. Originally, we proposed a pulsed linac with a NC frontend up to 5 MeV/u and a SC section for higher energies. The linac is capable of providing 285 MeV protons and ~100 MeV/u lead ions for injection into the IAC booster. A recent cost optimization study of the IAC suggested that lower injection energy into the booster may reduce the overall cost of the project with ~130 MeV protons and ~42 MeV/u lead ions. Stronger space charge effects in the booster caused by lower injection energy will be mitigated by the appropriate booster design. In this paper we discuss both linac options.

Pulsed SC Ion Linac as an Injector to Booster of Electron Ion Collider

SRF cavities are susceptible to detuning by mechanical deformations induced by the Lorentz force and microphonics. Providing the RF overhead required maintaining the accelerating gradient in detuned cavities can increase both the capital and operating costs of superconducting accelerators. Recent work at Fermilab has shown that active vibration control using a piezo actuator can reduce both Lorentz Force detuning and microphonics to the point where negligible RF overhead is required to maintain the accelerating gradient.

Recent progress at fermilab controlling lorentz force detuning and microphonics in superconducting cavities

http://inspirehep.net/record/1482005/files/mopb068.pdf

Pulsed sc ion linac as an injector to booster of electron

Fermilab is developing 325 MHz SRF spoke cavities for the proposed Project X. A compact fast/slow tuner has been developed for final tuning of the resonance frequency of the cavity after cooling down to operating temperature and to compensate microphonics and Lorentz force detuning [2]. The modified tuner design and results of 4.5K tests of the first prototype are presented. The performance of lever tuners for the SSR1 spoke resonator prototype has been measured during recent CW and pulsed tests in the Fermilab SCTF. The tuner met or exceeded all design goals and has been used to successfully: (1) Bring the cold cavity to the operating frequency; (2) Compensate for dynamic Lorentz force detuning; and (3) Compensate for frequency detuning of the cavity due to changes in the He bath pressure.

/pdf/tests-of-a-tuner-for-a-325-mhz-srf-spoke-resonator-dfiwm457za.pdf

R. Pilipenko

Papers

Tests of a tuner for a 325 mhz srf spoke resonator