In this paper, the iterative learning control (ILC) literature published between 1998 and 2004 is categorized and discussed, extending the earlier reviews presented by two of the authors. The papers includes a general introduction to ILC and a technical description of the methodology. The selected results are reviewed, and the ILC literature is categorized into subcategories within the broader division of application-focused and theory-focused results.

Iterative Learning Control: Brief Survey and Categorization

Review of Charged Particle Dynamics. Beam Optics and Focusing Systems Without Space Charge. Linear Beam Optics with Space Charge. Self-Consistent Theory of Beams. Emittance Variation. Beam Physics Research from 1993 to 2007. Appendices. List of Frequently Used Symbols. Bibliography. Index.

Theory and Design of Charged Particle Beams

Many systems are monitored and evaluated for their behavior using time signals. Additional information about the properties of a time signal can be obtained by representing the time signal by a series of coefficients, based on an analysis function. One example of a signal transformation is the transformation from the time domain to the frequency domain. The oldest and probably best known method for this is the Fourier transform developed in 1807 by Joseph Fourier. An alternative method with some attractive properties is the wavelet transform, first mentioned by Alfred Haar in 1909. Since then a lot of research into wavelets and the wavelet transform is performed. This report gives an overview of the main wavelet theory. In order to understand the wavelet transform better, the Fourier transform is explained in more detail. This report should be considered as an introduction into wavelet theory and its applications. The wavelet applications mentioned include numerical analysis, signal analysis, control applications and the analysis and adjustment of audio signals. The Fourier transform is only able to retrieve the global frequency content of a signal, the time information is lost. This is overcome by the short time Fourier transform (STFT) which calculates the Fourier transform of a windowed part of the signal and shifts the window over the signal. The short time Fourier transform gives the time-frequency content of a signal with a constant frequency and time resolution due to the fixed window length. This is often not the most desired resolution. For low frequencies often a good frequency resolution is required over a good time resolution. For high frequencies, the time resolution is more important. A multi-resolution analysis becomes possible by using wavelet analysis. The continuous wavelet transform is calculated analogous to the Fourier transform, by the convolution between the signal and analysis function. However the trigonometric analysis functions are replaced by a wavelet function. A wavelet is a short oscillating function which contains both the analysis function and the window. Time information is obtained by shifting the wavelet over the signal. The frequencies are changed by contraction and dilatation of the wavelet function. The continuous wavelet transform retrieves the time-frequency content information with an improved resolution compared to the STFT. The discrete wavelet transform (DWT) uses filter banks to perform the wavelet analysis. The discrete wavelet transform decomposes the signal into wavelet coefficients from which the original signal can be reconstructed again. …

/pdf/wavelet-theory-and-applications-a-literature-study-2scp23ylob.pdf

Wavelet theory and applications : a literature study

RF Linear Accelerators

Chemical short-range orders and the induced structural transition in high-entropy alloys

The Spallation Neutron Source (SNS) Superconducting RF (SRF) linear accelerator is operated with a pulsed beam. For the SRF control system to track the repetitive electromagnetic field reference trajectory, both feedback and feedforward controllers have been proposed. The feedback controller is utilized to guarantee the closed loop system stability and the feedforward controller is used to improve the tracking performance for the repetitive reference trajectory and to suppress repetitive disturbances. As the iteration number increases, the feedforward controller decreases the tracking error. Numerical simulations demonstrate that inclusion of the feedforward controller significantly improves the control system performance over its performance with just the feedback controller.

https://epaper.kek.jp/l00/papers/tuc13.pdf

SNS Superconducting RF cavity modeling-iterative learning control

In contrast to a normal conducting RF cavity, a superconducting RF cavity is very susceptible to shifts in its resonance frequency. The main sources of the shift are Lorentz force detuning and microphonics. In a spallation neutron source, to compensate for the frequency shift, a feedforward control is to be applied. In this paper, as an initiative step, a frequency shift observer is proposed which is simple enough to be implemented with a digital signal processor in real time. Simulation results of the proposed frequency shift observer show reliable performance and acceptable computation time for the real time implementation.

/pdf/frequency-shift-observer-for-an-sns-superconducting-rf-4pug6tq04i.pdf

Frequency shift observer for an SNS superconducting RF cavity

Development of the Spallation Neutron Source (SNS) continues, with operations beginning in 2004. The SNS is a 1 GeV machine consisting of a combination normal-conducting and super-conducting linac as well as a ring and target area. The RF control system (RFCS) for the linac has been under development for two years, with the first versions of the individual modules under construction and system integration begun. This paper will discuss this stage of the design and its implementation. In addition, it will report on the module variations required to use similar hardware for both the normal conducting (NC) and superconducting (SRF) portions of the linac.

/pdf/the-sns-linac-rf-control-system-4lu1l43upb.pdf

The SNS linac RF control system

In contrast to a normal conducting RF cavity, a superconducting RF cavity is very susceptible to shifts in its resonance frequency. The main sources of the shift are Lorentz force detuning and microphonics. In SNS, to compensate for the frequency shift, a feedforward control is to be applied. In this paper, as an initiative step, a frequency shift observer is proposed which is simple enough to be implemented with a digital signal processor in real time. Simulation results of the proposed frequency shift observer show reliable performance and acceptable computation time for the real time implementation.

/pdf/frequency-shift-observer-for-sns-superconducting-rf-cavity-394na7cjuu.pdf

Frequency shift observer for SNS superconducting RF cavity.

The SNS linac RF control system (RFCS) is currently in development. A system is being installed in a superconducting test stand at Jefferson Laboratory presently. Two systems will soon be installed at Oak Ridge National Laboratory (ORNL) and more are due to be installed early next year. The RF control system provides field control for the entire SNS linac, including an RFQ and 6 DTL cavities at 402.5 MHz as well as three different types of cavities at of 805 MHz: 4 CCL cavities, 36 medium beta superconducting (SRF) cavities, and 45 high beta superconducting cavities. In addition to field control, it provides cavity resonance control, and incorporates high power protect functions. This paper will discuss the RFCS design to date, with emphasis on the challenges of providing a universal digital system for use on each of the individual cavity types. The RF control system hardware has been designed to minimize the amount of changes for all of the applications. Through software/firmware modification and changing a couple of frequency-dependent filters, the same control system design can be used for all five cavity types. The SNS is the first to utilize SRF cavities for a pulsed high-current proton accelerator, thereby makingmore » RF control especially challenging.« less

SNS LINAC RF control system.

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