• W. Xu, S.W. Quan, K. Zhao, J. Zhuang
  PKU/IHIP, Beijing

High quality electron beam with low transverse emittance in 3.5‐cell DC‐SC photo‐injector is crucial significance for PKU‐ERL‐FEL facility. In this paper, we analyse the emittance evolution in the 3.5‐cell DC‐SC photo‐injector by simply model with consideration of DC acceleration, RF acceleration and space charge effect. The results are compared with Astra simulation. The matching condition of DC‐gun and Superconducting cavity, which is critical for the final emittance at the exit of the injector, is also presented.

• Z.A. Conway, M. Liepe
  CLASSE, Ithaca, New York

Funding: Work supported by NSF Grant PHY 0131508

The RF power required to phase-stabilize the Cornell University ERL main linac cavities is expected to be driven by microphonic-noise. To reduce the required RF power we are exploring the possibility of active compensation of cavity microphonic noise with the cavities in the Cornell ERL injector cryomodule. The Cornell ERL injector cryomodule houses five elliptical 2-cell SRF cavities developed for the acceleration of a high current (100mA) ultra-low emittance beam and is currently undergoing extensive testing and commissioning. Each of the five cavities is equipped with a blade tuner; each blade tuner integrates 4 piezoelectric actuators and vibration sensors for the active compensation of cavity detuning. This paper presents first results of active frequency-stabilization experiments performed with the Cornell ERL injector cryomodule cavities and their integral blade/piezoelectric fast tuners.

• Z.A. Conway, D.L. Hartill, H. Padamsee, E.N. Smith
  CLASSE, Ithaca, New York

Funding: Work Supported by the NSF and DOE

Superconducting RF cavity quench detection is presently a cumbersome procedure requiring two or more expensive cold tests. One cold test identifies the cell-pair involved via quench field measurements in several 1.3 GHz TM010 pass-band modes. A second test follows with numerous fixed thermometers attached to the culprit cell-pair to identify the particular cell. A third measurement with many localized thermometers is necessary to zoom in on the quench spot. We report here on a far more efficient alternative method which utilizes a few (e.g. 8) oscillating superleak transducers (OST) to detect the He-II second sound wave driven by the defect induced quench. Results characterizing defect location with He-II second sound wave OST detection, powering multiple modes of the 1.3GHz TM010 passband to locate multiple defects, and corroborating measurements with carbon thermometers will be presented.

• D. Meidlinger, E.P. Chojnacki, H. Padamsee
  CLASSE, Ithaca, New York

Funding: National Science Foundation

Diagnosing field-limiting behavior in multi-cell superconducting cavities can be difficult due to the lack of direct local measurements of cavity surface properties. The results of multiple vertical tests on several 5-cell vertically electropolished 1.3GHz superconducting cavities with measurements of cavity surface properties are presented. A combination of oscillating superleak transducer and resistive thermometry data for various accelerating passband modes are used to infer the field-limiting mechanism for several cells of each multi-cell cavity.

• Y. Yamamoto, H. Hayano, E. Kako, S. Noguchi, M. Satoh, T. Shishido, K. Umemori, K. Watanabe
  KEK, Ibaraki
• H. Sakai
  ISSP/SRL, Chiba
• T.X. Zhao
  TIPC, BeiJing

A new vertical test facility for L-band multi-cell cavities has been completed in support of development efforts of ILC (International Linear Collider) and ERL (Energy Recovery Linac) projects at STF (Superconducting rf Test Facility) of KEK. The facility possesses a clean booth for pre-tuning the cavities, four cavity stands to prepare the cavities prior to vertical testing, a half-underground pit which accommodates up to two vertical cryostats which can be pumped and operated separately under a movable iron shield. Vertical testing of the cavities, with a 400 W high-power amplifier and with a temperature-mapping (T-mapping) and additional monitoring systems, is supervised from a control room which overlooks the entire facility. This paper describes the specific details of the facility and results from its initial pilot operation that was conducted in Summer-Fall of 2008.

• Y. Yamamoto, H. Hayano, E. Kako, S. Noguchi, M. Satoh, T. Shishido, K. Umemori, K. Watanabe
  KEK, Ibaraki
• H. Sakai
  ISSP/SRL, Chiba
• T.X. Zhao
  TIPC, BeiJing

A new cavity diagnostic system has been introduced for vertical testing of nine-cell L-band superconducting cavities at KEK-STF. The present system is based on approximately 300 carbon resistors for temperature-mapping (T-mapping), and approximately 40 PIN photo diodes for detecting emission of X-rays. The system can accommodate up to total 600 sensors in needed in the future. While most of the sensors are attached to the cavity exterior in a pre-determined regular pattern, some sensors can be strategically placed at non-regular positions so as to watch the areas which are considered “suspicious” as per the surface inspection done prior to vertical testing. Data from the sensors can be collected every 100 msec. The data can be graphically displayed online and are stored for offline analysis. This paper describes the details of this system, together with results from its initial pilot operation which was done with a nine-cell cavity on loan from FNAL (AES#001). Effectiveness of the combined use of T-mapping and PIN photo diodes in operation of the pi-mode and other pass-band modes in conjunction with surface inspection is discussed.

• T. Tajima, A.S. Bhatty, A. Canabal, P. Chacon, G.V. Eremeev, R.J. Roybal, J.D. Sedillo
  LANL, Los Alamos, New Mexico

Funding: DTRA

A temperature mapping system with 4608 100-ohm Allen-Bradley resistors has been built and tested at LANL. With this temperature mapping system we were able to locate lossy regions in the 1.3 GHz 9-cell SRF cavity due to field emission and direct heating. The results of the temperature mapping have been correlated with the inside surface inspection of the cavity and will be shown together with Q-E curves. A brief description of the mapping system and improvements that have been made in the recent months will also be mentioned in the paper.

• K. Sennyu, H. Hara, K. Kanaoka, M. Matsuoka, T. Yanagisawa
  MHI, Kobe

We report on the activities and achievements at MHI about cavity fabrication for ILC. Some new procedures of cavity fabrication for industrialization are reported.

• F.S. He, J.K. Hao, F. Wang, W. Xu, B.C. Zhang, K. Zhao
  PKU/IHIP, Beijing

Funding: Supported by National Basic Research Program(No. 2002CB713600) and NSFC(No. 10775010).

The 3.5-cell cavity for the PKU DCSC photoinjector requires the main coupler and the pickup be on the same side of the cavity, which will cause crosstalk between them. At room temperature, serious distortion of the RF response is caused. This paper applies a clear understanding of the RF signal; numerical and experimental study shows that the crosstalk will be negligible in superconducting (SC) status. Furthermore, a method to calculater resonant frequency and loaded quality factor from the crosstalk signal is provided

• T. Matsumoto, S. Fukuda, H. Katagiri, S. Michizono, T. Miura, Y. Yano
  KEK, Ibaraki
• Y. Okada
  NETS, Fuchu-shi

Digital low-level rf (LLRF) control system has been installed in many linear accelerators to stabilize the accelerating field. In the digital LLRF system, the rf signal is down-converted into intermediate frequency for sampling at analog-to-digital converter (ADC) and the number of ADC required for vector sum feedback operation is equal to the number of cavity. In order to decrease the number of the ADCs required, a digital LLRF control system using different four intermediate frequencies has been developed at STF (Superconducting RF Test Facility) in KEK. This digital LLRF control system was operated with four superconducting cavities and the rf field stability under feedback operation was estimated. The result of the performance will be reported.

• T. E. Plawski, C. Hovater
  JLAB, Newport News, Virginia

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.

The RF system model based on MATLB has been developed for analyzing the basic characteristics of the LLRF control system being designed for the 12 GeV Energy Upgrade of the CEBAF accelerator. In our model, a typically complex cavity representation is simplified to in-phase and quadrature (I&Q) components. Lorentz Force and microphonic detuning is incorporated as a new quadrature carrier frequency (frequency modulation). Beam is also represented as in-phase and quadrature components and superpositioned with the cavity field vector. Afterward signals pass through two low pass filters, where the cutoff frequency is equal to half of the cavity bandwidth then they are demodulated using the same detuning frequency. Because only baseband I&Q signals are calculated, the simulation process is very fast when compared to other controller-cavity models. During the design process we successfully analyzed gain requirements vs. field stability for different superconducting cavity microphonic backgrounds and Lorentz Force coefficients. Moreover, we were able to evaluate different types of a LLRF structures:GDR* and SEL** as well as klystron power requirements for different cavities and beam loads.

*Generator Driven Resonator
**Self Excited Loop

• K. Yu, S.W. Quan, W. Xu, K. Zhao, F. Zhu, J. Zhuang
  PKU/IHIP, Beijing

The PKU Terahertz facility (PTF) is planned as a compact, high power Terahertz user facility based on the coherent undulator radiation concept and the superconducting radiofrequency technology for the linear accelerator. By utilizing a 3.5-cell DC-SC (DC-Superconducting) photoinjector, the PTF will provide high average power, coherent terahertz radiation with quasi-monochromaticity and wavelength tunable between 400um ~ 1200um, serving as a powerful tool for frontier researches and practical applications in the THz realm. Key components of the 3.5-cell DC-SC photoinjector have been prepared and the beamline is under construction. In this paper, the technical layout of the injector and the conceptual design of the PTF will be presented.

• L. Hagge, J. Bürger, J.A. Dammann, S. Eucker, A. Herz, J. Kreutzkamp, S. Panto, S. Sühl, D. Szepielak, P. Tumidajewicz, N. Welle
  DESY, Hamburg

The DESY Engineering Data Management System, DESY EDMS, is a fully Web-based central information management platform at the European XFEL and the Global Design Effort for the International Linear Collider (ILC GDE). It provides functionality for managing documents and 3D CAD data and for performing configuration and change management. It can control complex information structures and keep track of their dependencies and history, i.e. their evolution over time. Due to its powerful capabilities for automating workflows and controlling information access, the DESY EDMS can coordinate processes and manage authorizations and responsibilities in large and complex organizations, which may include several institutes and industrial partners. Applications of the DESY EDMS range from small-scale document management for work groups, up to managing the complexity of world-wide collaborations during design and construction activities. The poster describes the architecture of the DESY EDMS, introduces some of its use cases and reports lessons learned in developing and operating the system.

• W. Vodel, R. Geithner, R. Neubert, P. Seidel
  FSU Jena, Jena
• A. Peters
  HIT, Heidelberg
• M. Schwickert
  GSI, Darmstadt

Funding: This work was supported in part by the Gesellschaft für Schwerionenforschung Darmstadt, Germany.

We describe an LTS SQUID-based high precision measurement tool for nuclear physics. This device makes use of the Cryogenic Current Comparator (CCC) principle and is able to measure e.g. the absolute intensity of a high energy ion beam extracted from a particle accelerator or the so-called dark current, generated by superconductive RF accelerator cavities at high voltage gradients. The CCC mainly consists of a high performance LTS-DC SQUID system, a special toroidal pick-up coil, and a meander-shaped superconductive magnetic ring structure. The design of the CCC requires a thorough knowledge of several noise contributions to achieve a high current resolution. As the SQUID and the pick-up coil are extremely sensitive to external magnetic fields it is necessary to shield both sufficiently against any disturbing field sources. Theoretical investigations showed that with strong attenuation of external noise sources an improvement of the sensor performance is dependent on the ferromagnetic core material imbedded in the pick-up coil. Several materials were investigated and the temperature- and the frequency dependence measured. The current results will be presented and discussed.