RF control system for ISAC II superconducting cavities

The TRIUMF ISAC 2 superconducting RF system operates in self-excited, phase locking mode. A mechanical tuner is used to minimize the required RF power. The tuner derives the tuning information from the phase shift around the self-excited loop. Its accuracy is however reduced by phase drift in amplifiers and cables due to thermal effects. The cross product between the amplitude and the phase errors is used to detect this drift. The signal derived from the cross product does not depend on any initial value adjustment. Furthermore, no special adjustment is required and the measurement can be performed online during beam production.

Section: System Equation For Feedback Regulatorsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tuner control in TRIUMF ISAC 2 superconducting RF system

Fong

Laverty

Zheng

2007

“…In one case this has partially been done. At TRIUMF a hybrid analog-digital SEL that utilizes a baseband DSP PID loop was developed [4]. The system also incorporates a PLL-VCO and the system can switch back and forth between the two modes.…”

Section: Conversion To Digital Domainmentioning

confidence: 99%

A digital self excited loop for accelerating cavity field control

Allison

Delayen

Hovater

et al. 2007

We have developed a digital process that emulates an analog oscillator and ultimately a self excited loop (SEL) for field control. The SEL, in its analog form, has been used for many years for accelerating cavity field control. In essence the SEL uses the cavity as a resonant circuit --much like a resonant (tank) circuit is used to build an oscillator. An oscillating resonant circuit can be forced to oscillate at different, but close, frequencies to resonance by applying a phase shift in the feedback path. This allows the circuit to be phased-locked to a master reference, which is crucial for multiple cavity accelerators. For phase and amplitude control the SEL must be forced to the master reference frequency, and feedback provided for in both dimensions. The novelty of this design is in the way digital signal processing (DSP) is structured to emulate an analog system. While the digital signal processing elements are not new, to our knowledge this is the first time that the digital SEL concept has been designed and demonstrated. This paper reports on the progress of the design and implementation of the digital SEL for field control of superconducting accelerating cavities.

“…A new RF control system has been optimized during medium beta SC linac commissioning and initial operation [3]. This experience has allowed us to set specific RF requirements represented in Table 1.…”

Section: Specific Amplifier Parametersmentioning

confidence: 99%

RF amplifier choice for the ISAC superconducting linac

Bylinskii

Fong

et al. 2007

Self Cite

A superconducting linac is being commissioned at TRIUMF as an extension to the existing room temperature accelerator of exotic ions at ISAC. It will increase the isotope final energy from 1.5 to 6.5 MeV/u. Acceleration is accomplished in 40 bulk niobium quarter wave superconducting cavities operating at 106 and 141 MHz. Each cavity is energized from an independent RF amplifier with power rating up to 1 kW cw. Both vacuum tube and solid-state amplifiers were considered as a viable option for the drivers. The paper compares many important parameters of these 2 amplifiers such as reliability, serviceability, capital and maintenance costs, as well as operating characteristics: gain linearity, phase noise, phase drift and others. Test results of prototypes of both types of amplifiers and 1-year operational experience of 20 tube amplifiers are discussed. Based on that the amplifier design recommendations are formulated.