The subject of this paper is the design and construction of a new generation of superconducting cavity accelerator measurement and control system. The old system is based on a single digital signal processor (DSP). The new system uses a large programmable array circuit (FPGA) instead, with a multi-gigabit optical link. Both systems now work in parallel in the Free Electron Laser in Hamburg (FLASH). The differences between the systems are shown, based on the measurement results of the working machine. The major advantage of the new system is a bigger area of stability of the machine control loop.

http://iopscience.iop.org/article/10.1088/0957-0233/18/8/010/pdf

FPGA-based implementation of a cavity field controller for FLASH and X-FEL

A review of our today’s understanding of the ultimately broadband photonic Internet is presented. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM. The Polish perspective closes the review. Keywords—Optical networks, Internet, global network, photonic Internet, future Internet, optoelectronic networks.

http://cejsh.icm.edu.pl/cejsh/element/bwmeta1.element.oai-journals-pan-pl-87066/c/oai-journals-pan-pl-87066_full-text_74.pdf

Search for Ultimate Throughput in Ultra-Broadband Photonic Internet

The paper presents a digest of the research results in the domain of accelerator science and technology in Europe, shown during the annual meeting of the EuCARD  European Coordination of Accelerator Research and Development. The conference concerns building of the research infrastructure, including in this advanced photonic and electronic systems for servicing large high energy physics experiments. There are debated a few basic groups of such systems like: measurement  control networks of large geometrical extent, multichannel systems for large amounts of metrological data acquisition, precision photonic networks of reference time, frequency and phase distribution. Keywords: electronics and photonics for high energy physics experiments, free electron laser, distributed measurement and control systems, precise timing dist ribution systems of large space extent, ad vanced electronic systems, integration of hardware and software 1. INTRODUCTION The EUCARD 2011 Annual Conference on the development of the accelerator research infrastructure in Europe was held in Paris on 10-13 May. The venue of the meeting was the IN2P3 institute, a part of the CNRS. Around 150 accelerator researchers participated and 80 papers were presented. The conference covered the following subjects: material engineering  new materials for building accelerator sub-systems, building of research infrastructure for measurements of the mass and oscillations of neutrinos, muon electronics, upgrade of existing accelerators, HL-LHC, HE-LHC, building of new infrastructure of large scale, experiments of new physics, plasma wake field and laser accelerators.

http://cejsh.icm.edu.pl/cejsh/element/bwmeta1.element.oai-journals-pan-pl-87005/c/oai-journals-pan-pl-87005_full-text_57.pdf

Accelerator Infrastructure in Europe EuCARD 2011

Accelerator science and technology is one of a key enablers of the developments in the particle physic, photon physics
and also applications in medicine and industry. The paper presents a digest of the research results in the domain of
accelerator science and technology in Europe, shown during the third annual meeting of the EuCARD – European
Coordination of Accelerator Research and Development. The conference concerns building of the research
infrastructure, including in this advanced photonic and electronic systems for servicing large high energy physics
experiments. There are debated a few basic groups of such systems like: measurement – control networks of large
geometrical extent, multichannel systems for large amounts of metrological data acquisition, precision photonic
networks of reference time, frequency and phase distribution.

/pdf/accelerator-science-and-technology-in-europe-eucard-2012-lcrbefbx24.pdf

Accelerator Science and Technology in Europe EuCARD 2012

The paper presents a digest of chosen technical work results shown by young researchers from different technical universities in this country during the SPIE-IEEE Wilga 2011 symposium on Photonics and Web Engineering. Topical tracks of the symposium embraced, among others, nanomaterials and nanotechnologies for photonics and telecom, sensory and nonlin- ear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonics- electronics co-design, optoelectronic and electronic systems for telecom, astronomy and high energy physics experiments, JET and pi-of-the sky experiments development. The symposium is an annual summary in the development of numerable Ph.D. theses carried out in this country in the area of advanced electronic and photonic systems. It is also an occasion for young researchers to meet together in a large group (under the patronage of IEEE) spanning the whole country with guests from this part of Europe. A digest of Wilga references is presented (1-92).

http://cejsh.icm.edu.pl/cejsh/element/bwmeta1.element.oai-journals-pan-pl-87008/c/oai-journals-pan-pl-87008_full-text_58.pdf

Photonics and Web Engineering 2011

A digital control of superconducting cavities for a linear accelerator is presented. FPGA-based controller, supported by Matlab system, was applied. Electrical model of a resonator was used for design of a control system. Calibration of the signal path is considered. Identification of cavity parameters has been carried out for adaptive control algorithm. Feed-forward and feedback modes were applied in operating the cavities. Required performance has been achieved; i.e. driving on resonance during filling and field stabilization during flattop time, while keeping reasonable level of the power consumption. Representative results of the experiments are presented for different levels of the cavity field gradient.

/pdf/superconducting-cavity-driving-with-fpga-controller-259mxt2ogn.pdf

Superconducting cavity driving with FPGA controller

The Distributed Object Oriented Control System (DOOCS)[1] has been developed at DESY as a control system for FLASH (Freie-Elektronen-LASer in Hamburg)[2]. The DSP based low level RF control system is one of the main subsystems of the linac. Several DOOCS device servers and client applications have been developed to integrate low level RF control into the FLASH control system. The DOOCS approach defines each hardware device as a separate object and this object is represented in a network by a device server, which handles all device functions. A client application can have access the server data using the DOOCS application programming interface (API). A set of generic and specially devoted programs provide the tools for the operators to control the RF system. The RF operation at the linac is being automated by the DOOCS implementation of finite state machine servers.

/pdf/dsp-based-low-level-rf-control-as-an-integrated-part-of-4ox3ukzne6.pdf

Dsp-based low level rf control as an integrated part of doocs control system

The operation of a Free Electron Laser in the X-ray wavelength range is the goal of the international XFEL project. The project critically depends on the linear accelerator component, where radio frequency fields have to be controlled with a very high amplitude and phase precision and under various sources of disturbances. This paper is about finding appropriate dynamical models for this RF system which will be essential for controller design. A physically motivated white box model is compared with a grey box and a black box model that are identified using measurements of an existing Ultraviolet Free Electron Laser VUV-FEL.

Modelling and identification of a free electron laser RF system

The field inside a resonator is proportional to the vector sum of the forward and the reflected wave in front of the power coupler. The cavity field derived from the measured amplitudes and phases of these waves can be used for low level RF (LLRF) control. This approach is required for cavities without field probe but offers also additional diagnostics and possibilities for cross-checks in case a probe is present. A precise field estimate requires a relative calibration of the forward and reflected waves in amplitude and phase. This article introduces a simple online calibration method which is applicable to any resonator that is operated close to steady state. PACS numbers: Inside photoinjectors, electrons are liberated from a cathode (e.g. Cesium Telluride) by means of the photoeffect. In order to keep space charge effects small, the electrons are exposed to a very high field of > 45MV/m in a small volume of the resonator. The electrons are accelerated to a relativistic velocity on a path of the length of only a few centimeters. The RF gun of the FLASH photoinjector is a 1.5 cell normalconducting cavity operated at 1.3GHz. It is designed to operate at high duty cycle with an average heat load of up to 50kW (∼ 200kW/m). This high heat load demands for an optimized placement of cooling channels for the heat-transport. Focussing solenoids put additional space restrictions and led to the decision to build the cavity without RF probe and to measure the forward and the reflected wave with a high precision directional coupler instead. For field stability requirements of 1% in amplitude and 1 ◦ in phase it is not sufficient to stabilize the forward traveling wave alone. An amplitude distortion of 1% is already present if the resonator is detuned by 1% of its half-bandwidth, which is 650Hz for a resonator of half-bandwidth !1/2 = 65kHz. The dependency of the temperature of the resonator (e.g. 20kHz/ ◦ C), would require long term stability of 1 30 ◦ C. Due to the high

https://flash.desy.de/sites2009/site_vuvfel/content/e403/e1642/e1849/e1933/infoboxContent1934/tesla-fel2007-01.pdf

Alexander Brandt

Papers

Superconducting cavity driving with FPGA controller

Dsp-based low level rf control as an integrated part of doocs control system

Modelling and identification of a free electron laser RF system

Field Estimation and Signal Calibration of RF Guns without Field Probe