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| WEPMN002 | Tuner Control in TRIUMF ISAC 2 Superconducting RF System | 2047 |
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| The TRIUMF ISAC 2 superconducting RF system operates on 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 the amplifier due to thermal effects. Cross correlation between the In-phase and the Quadrature-phase errors is used to detect this drift. A Kalman filter is used to combine these information to control the movement of the tuner. | ||
| WEPMN004 | Operation of the SOLEIL RF Systems | 2050 |
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| The 352 MHz RF accelerating systems for the SOLEIL Booster (BO) and Storage Ring (SR) have been commissioned. In the BO, a 5-cell copper cavity of the CERN-LEP type is powered with a 35 kW solid state amplifier. In the SR, the required RF accelerating voltage (up to 4.4 MV) and power (650 kW at full beam current of 500 mA) will be provided by two cryomodules, each containing a pair of superconducting cavities, specifically designed for SOLEIL. The parasitic impedances of the high order modes are strongly attenuated by means of four coaxial couplers, located on the tube connecting the two cavities. The first cryomodule is operational, while the second one, which is being constructed by ACCEL (Germany), will be implemented beginning of 2008. Both cryomodules will be cooled down with liquid helium from a single 350 W liquefier and each cavity is powered with a 190 kW solid state amplifier. With the first cryomodule and two amplifiers in operation, the first year objective of storing 300 mA was successfully achieved. The RF system commissioning and operation results are reported. | ||
| WEPMN005 | The SSRF Booster Cavity System | 2053 |
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| In February 2007 a system consisting out of two 5 cell 500MHz cavities has been delivered to SSRF to accelerate the electrons in their booster ring. The two cavities are controlled by a low level RF system, which forms part of the delivery. The paper will describe the general layout of the booster RF system and the architecture of the low level RF system controlling one amplifier and two cavities. Results of the commissioning phase will be presented and compared with expected and guaranteed values of the system. | ||
| WEPMN006 | Status of the Superconducting CH-structure | 2056 |
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Funding: GSI, BMBF 06F134I, EU 516520-FI6W, RII-CT-2003-506395, EFDA/99-507ERB5005-CT990061 The superconducting CH-structure is the first multi-cell cavity for the acceleration of low and medium energy ions and protons. A superconducting prototype cavity has been built and several cold tests have been performed at the IAP in Frankfurt. After the detection of a field emission centre the cavity will be treated by buffered chemical polishing and high pressure rinsing. Additionally the cavity is being prepared for tests in a horizontal cryostat with slow and fast tuner system. We present the status of these developments and the test results which have been gained recently. |
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| WEPMN007 | Introducing a Homepage for Information Retrieval and Backup of the Ground Vibration Measurements and Mechanical Vibrations of the Superconducting Modules at DESY | 2059 |
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Funding: Work supported by the Commission of the European Communities under the 6th Framework Program Structuring the European Research Area, contract number RIDS-011899. In this paper, we will introduce our homepage (http://vibration.desy.de) which is used for the storage and dissemination of our ground motion measurement data of 20 sites around the world and the XFEL/ILC superconducting module data. This homepage is open to the scientific community and the data can be utilized for planning of future accelerator facilities and design of future prototypes of module vessels containing cold mass. |
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| WEPMN008 | Vibration Stability Studies of a Superconducting Accelerating Module at Room Temperature | 2062 |
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Funding: Work supported by the Commission of the European Communities under the 6th Framework Program Structuring the European Research Area, contract number RIDS-011899. In this presentation, we will report on a comprehensive vibration measurement program of a superconducting accelerating module designed for the European X-ray Free Electron Laser (XFEL), currently planned at DESY, at room temperature. This module is a type III, high gradient module which is also the basis of module design for the International Linear Collider (ILC). We will discuss stability within the vessel, for example, cold mass vs. He Gas Return Pipe (GRP), as well as stability along the length of the module. Results of this study may be used for the design of future XFEL/ILC module prototypes. |
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| WEPMN009 | Vibration Stability Studies of a Superconducting Accelerating Module Quadrupole Operating at 4.5K | 2065 |
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Funding: Work supported by the Commission of the European Communities under the 6th Framework Program Structuring the European Research Area, contract number RIDS-011899. The European X-ray Free Electron Laser (XFEL) and the International Linear Collider (ILC) superconducting accelerating modules, containing a string of Niobium (Nb) cavities and a quadrupole, will operate at 2K. In this paper, we will report on the vibration stability studies of a high gradient XFEL/ILC type III superconducting accelerating module quadrupole operating at 4.5K. Measurements are performed via geophones affixed on the cold mass in both horizontal and vertical directions. This data will be compared with piezoelectric accelerometers for the same module. The goal is to study the stability of the cold quadrupole and to compare the results with room temperature conditions. |
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| WEPMN010 | Linearization of Downconversion for IQ Detection Purposes | 2068 |
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Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 ''Structuring the European Research Area'' program (CARE, contract number RII3-CT-2003-506395).
Measurements of effective Radio Frequency (RF) field parameters (amplitude and phase) are tasks of great importance in high-energy accelerators*. The RF signal is downconverted in frequency to intermediate frequency (IF) but keeping the information about amplitude and phase. The IF signal is then sampled in ADC and processed in digital IQ detector computing the I and Q components**. The downconverter is a nonlinear device thus not only the fundamental frequency but also its harmonics are present and sampled by ADC. For a typical downconverter (used in FLASH LLRF system) the higher order harmonics levels depend on RF signal level and are about 40dBm lower than the fundamental frequency component. These harmonics can produce errors in IQ detector of up to few percent in amplitude and few degree in phase. These errors depends not only on nonlinearity of downconverter but also on the IQ detection scheme*** (IF and sampling rate SR). The paper presents the optimization of the IQ detection scheme (choosing the IF and SR) taking into account the nonlinear characteristics of the downconverter.
*Grelick A. et all:A High-Resolution…, Proc. LINAC 2004,715-718**Grecki M. et all:Estimation of IQ…, Proc. MIXDES 2005,783-788***Simrock S. et all:Considerations…, Proc. EPAC 2006,1462-1464 |
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| WEPMN011 | Multichannel Downconverter for the Next Generation RF Field Control for VUV- and X-Ray Free Electron Lasers | 2071 |
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Funding: We acknowledge financial support by DESY Hamburg and the EUROFEL project. For pump- and probe experiments at VUV- and X-ray free-electron lasers the stability of the electron beam and timing reference must be guaranteed in phase for the injector and bunch compression section within a resolution of 0.01 degree (rms) and in amplitude within 1 10-4 (rms). The performance of the field detection and regulation of the acceleration RF critically influences the phase and amplitude stability. For the RF field control, a multichannel RF downconverter is used to detect the field vectors and control the vectorsum of 32 cavities. In this paper a new design of an 8 channel downconverter is presented. The downconverter frontend consists of a passive rf double balanced mixer input stage, intermediate filters and an integrated 16bit analog-to-digital converter (ADC). The design includes a digital motherboard for data preprocessing and communication with the controller. In addition we characterize the downconverter performance in amplitude and phase jitter, temperature drifts and channel crosstalk in laboratory environment as well as for accelerator operation. |
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| WEPMN012 | Beam Loading Compensation Using Real Time Bunch Charge Information from a Toroid Monitor at FLASH | 2074 |
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Funding: Deutsches Elektronen-Synchrotron - DESY At pulsed linear accelerators, fast proportional rf control compensates beam loading sufficiently for single or a few bunches. In the case of long bunch trains, additional measures have to be taken commonly by adding a compensation signal to the rf drive signals calculated from the predicted beam intensity. In contrast to predictive methods, techniques based on real time beam measurements are sensitive to fast changes of the beam intensity and bunch patterns. At FLASH we apply a beam loading compensation scheme based on toroid monitor signals. This paper presents the compensation scheme, the calibration procedure and the effect on the beam. |
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| WEPMN013 | Testing of 10 MW Multibeam Klystrons for the European X-ray FEL at DESY | 2077 |
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| For the European XFEL project multibeam klystrons, which can produce RF power of 10 MW, at an RF frequency of 1.3 GHz, 1.5ms pulse length and 10Hz repetition rate, were chosen as RF power sources. So far three companies have produced this kind of new klystron. At DESY we installed a new test stand dedicated for testing this new type of RF power source. So far we have tested several tubes from Thales, Toshiba and CPI in our test stand. In this paper we give an overview of the test facilities and we summarize the current test results of the L-band multibeam klystrons (MBK). | ||
| WEPMN016 | Installation and Commissioning of the New 150 kW Plant for the Elettra RF System Upgrade | 2080 |
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| Elettra is the Italian third generation light source in operation in Trieste since 1993. The project of upgrade of the Elettra RF system has become necessary to provide the needed operating margins when all the insertion devices are operational and in view of possible increases in beam current and energy. The first phase of the project regards one of the four plants, which has been upgraded from 60 to 150 kW cw. The power amplifier has been built combining two 80 kW IOTs (inductive output tubes) by means of a switchless combiner. The amplifier and the power plant components have been installed in the second half of year 2006. A coaxial to waveguide transition has been specially designed to interface the coaxial coupler of the cavity to the waveguide power transmission system, taking into account the risks connected to power from the higher order modes excited by the beam in the cavity. After giving an overview of the project, this paper discusses the technical choices adopted, the tests performed during the installation phase and the commissioning of the new system with beam during machine operation. | ||
| WEPMN017 | RF System for the Elettra New Full Energy Booster Injector | 2083 |
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| The Elettra new full energy injector will be based on a 100 MeV linac and a 2.5 GeV booster synchrotron and it will replace the existing 1.2 linac injector. This paper presents the design, construction and the test results of the RF system for the booster synchrotron. The analysis of the foreseen operating scenario is also described. The system must be as simple and reliable as possible, taking into consideration the high availability required for the possible top-up mode of operation. It has also to be consistent with the other upgrades of the facility, as the upgrade of the storage ring RF system. The booster RF system will use a 500 MHz 5-cell copper cavity powered by a 60 kW klystron based power plant. The low level electronics has been in-house developed, starting from the system in operation in the storage ring, increasing the performances and developing the new features required by the use of a five-cell cavity, instead of a single cell one, and by the ramped operation. The commissioning of the new injector is scheduled to start in summer 2007, while the first Elettra operation for users with the new full energy injector is expected for the first quarter of 2008. | ||
| WEPMN018 | High Precision Measurements of Linac Coupled Cells | 2086 |
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Funding: Istituto Nazionale di Fisica Nucleare, Rome, Italy. Italian Ministry of Research. For an assembled structure (module, tank) of a Linac, the single cells, when coupled, loose their individuality and in cooperation contribute to the generation of the structure modes (resonant frequencies) Fm. On the other end these modes are the only measurable quantities. The system of the coupled cells can be modelled, in a narrow frequency band, as a lumped constant circuit. The modes are solution of an equation obtained equating to zero the determinant relevant to the lumped circuit. This is an algebraic equation of the same order as the number N of cells. A plausible question can be posed: is it possible from a manipulation of the measurable quantities (Fm) to draw the lumped circuit parameters, namely coupling constants and single cell resonant frequencies? The answer is positive if a certain degree of symmetry is satisfied. The coefficients of above mentioned equation can be easily related to the measured modes Fm. By varying, by means of tuners, the tune of a single cell of a small unknown amount, any couple of equation coefficient moves on a straight line. Therefore, we have N(N-1) known straight line coefficients which may give the unknowns with extremely high accuracy. |
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| WEPMN020 | Improved Design of the ILC Blade-Tuner for Large Scale Production | 2089 |
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| The ILC superconducting linacs ask for the use of a compact and cost effective tuner design with no interference with the cavity end group area. The integration of the piezo-assisted fast tuning option made the Blade-Tuner, successfully tested at DESY on the superstructures, the most viable candidate to be included into the ILC BCD. In the perspective of large scale production and on the basis of the experience acquired so far, two alternative prototypes have been recently designed and built. They mainly differ for the materials adopted (titanium or stainless steel) and have been optimized to minimize material and construction cost, while fulfilling the reviewed performances required for the high gradient cavity operation up to 35 MV/m or even higher. In this paper we discuss the rationales that brought us to the current solutions, together with a critical comparison of the two systems behavior and cost. | ||
| WEPMN021 | High Pressure Rinsing System Comparison | 2092 |
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| High pressure rinsing (HPR) is a key process for the surface preparation of high field superconducting cavities. A portable apparatus for the water jet characterization, based on the transferred momentum between the water jet and a load cell, has been used in different laboratories. This apparatus allows to collected quantitative parameters that characterize the HPR water jet. In this paper, we present a quantitative comparison of the different water jet produced by various nozzles routinely used in different laboratories for the HPR process | ||
| WEPMN022 | High Gradient Tests of C-band Accelerating System for Japanese XFEL Project | 2095 |
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| The C-band (5712 MHz) choke-mode type accelerating structure will be used for SCSS. Since the C-band accelerator generates higher accelerating gradient than traditional S-band accelerator, it makes the machine size compact and the cost low. In order to confirm the performance of the C-band accelerating system for the 8 GeV XFEL machine, the system including the same accelerating structure and RF system have been installed in the SCSS prototype accelerator. In the prototype machine, four 1.8 m long C-band accelerating structures are used to accelerate electron up to 250 MeV. From November 2005, we have operated the C-band accelerator in the prototype machine with no serious problem. After the RF conditioning, accelerating gradient up to 35 MV/m was achieved. Since a lot of C-band accelerator units, about 70 klystrons and 130 accelerating structures, will be used for 8 GeV XFEL machine, it is necessary to investigate the damage due to the beam operation. Therefore, we plan to observe the inside of the accelerating structure and pulse compressor in early 2007. In this paper, we will report on the achieved performance and the inside observation of the C-band accelerator. | ||
| WEPMN023 | Development of 10 MW L-Band Multi-Beam Klystron (MBK) for European X-FEL Project | 2098 |
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| A 10MW L-band Multi-Beam Klystron (MBK) has been developed and tested by Toshiba, Japan for the European XFEL and a future linear collider projects.? The Toshiba MBK has six low-perveance beams operated at low voltage of 115kV (for 10MW) and six ring-shaped cavities to enable a higher efficiency than a single-beam klystron for a similar power. After the successful acceptance testing at the Toshiba Nasu factory in March 2006, attended by a DESY stuff, the final acceptance test was done at DESY laboratory in June 2006. In these tests, the output power of 10.2MW, more than the design goal (10MW), has been demonstrated at the standard beam voltage of 115kV at the RF pulse length of 1.5ms and the beam pulse of 1.7ms at 10Hz. The efficiency was 66%. The robustness of the tube was also demonstrated by being operated continuously more than 24 hours above 10MW. A horizontal version of the Toshiba MBK is now under construction. | ||
| WEPMN024 | RF Feedback Control Systems of the J-PARC Linac | 2101 |
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| The commissioning of the J-PARC 181MeV proton linac was started from October of 2006. The RF sources of the linac consist of 4 solid-state amplifiers and 20 klystrons. In each RF source, the RF fields are controlled by a digital RF feedback system installed in a compact PCI (cPCI) to realize the accelerating field stability of ±1% in amplitude and ±1 degree in phase. In this paper the performance of the RF feedback control systems will be reported in detail. | ||
| WEPMN026 | Test Operation of Ball-Screw-Type Tuner for Low-Loss High-Gradient Superconducting Cavity in a Cryomodule | 2104 |
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| We are constructing a Superconducting RF Test Facility (STF) at KEK as an R&D for ILC accelerator. In STF, four Low-Loss (LL) type 9-cell cavities will be installed into a cryomodule. We are developing ball-screw-type tuner for these cavities aiming at the accelerating gradient of 45 MV/m. At the end of 2006, we installed one LL 9-cell cavity dressed with the ball-screw tuner into the cryomodule. It will be operated without beam in 2007. This paper describes the results of the first operation of the ball-screw tuner for LL 9-cell cavity in the cryomodule of STF. | ||
| WEPMN027 | Construction of the Baseline SC Cavity System for STF at KEK | 2107 |
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| Construction of STF (Superconducting RF Test Facility) is being carried out at KEK. Four-cavity system including 9-cell baseline cavities (TESLA-type), input couplers and frequency tuners has been developed and will be installed in a 6 m cryomodule. The peculiarity of the STF baseline cavity system is a very stiff design in a jacket and tuner system, which can relax the effect of Lorentz detuning in a pulsed operation. Performance tests of four 9-cell cavities have been carried out repeatedly in a vertical cryostat, and the attained accelerating gradients reached to about 20 MV/m with no field emission in each cavity. High power input couplers with two planar rf windows were fabricated, and the rf processing test with a pulsed klystron was successfully carried out up to 1.0 MW with 1.5 msec and 5 Hz without any troubles. Assembly of the cryomodule including one 9-cell baseline cavity had completed (STF phase 0.5), and the first cool-down test is scheduled in March, 2007. | ||
| WEPMN028 | Development of Digital Low-level RF Control System using Multi-intermediate Frequencies | 2110 |
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| Digital low level rf (LLRF) control system has been developed in Superconducting RF Test Facility (STF) at KEK to carry out the accelerating electric field stability of 0.3% (rms) in amplitude and 0.3 degree (rms) in phase, respectively. In the digital LLRF system, rf probe signal from cavity is down-converted to intermediate frequency (IF) for acquisition at analog-to-digital converter (ADC) and the number of ADCs required is equal to the number of cavities. In order to decrease the number of ADCs, a new digital LLRF control system is under development. In this LLRF system, rf signals are down-converted to different IF and combined. The combined signal is detected with one ADC and I/Q components of each rf signal are calculated with digital signal processing. This paper describes a result of simulation and estimation using cavity simulator based on FPGA board about this new technique. | ||
| WEPMN029 | Status of the Low-Level RF System at KEK-STF | 2113 |
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| RF field stabilities of less than 0.3%, 0.3deg. are required at STF llrf system. In order to satisfy these requirements, digital FB system using a FPGA is adopted. The FB system consists of a FPGA (VirtexIIPro30) with ten 16-bit ADCs and two 14-bit DACs. The rf (1.3 GHz) probe signals are downconverted to the IF (10 MHz) and directly acquired at ADCs. Total 8 cavities will be installed at STF-Phase 1 in 2007 and vector sum control of 8 cavity signals will be carried out. The performance of the FB system is examined with electric cavity simulators prior to the rf operation. | ||
| WEPMN034 | Classification of Eigenmodes in a Side-Coupled Structure According to the Space Group Representations | 2116 |
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The geometric symmetry of an rf structure can be expressed by a group of symmetry operations that keep the configuration unchanged*. In case of a periodic rf structure, the symmetry group is a space group containing translations as well as the other symmetry operations. The eigenmodes in the structure can be classified according to the irreducible representations of the space group of the structure. In this paper, this procedure is described with an example of the side-coupled structure (SCS)**. Since the SCS is symmetric under a screw (rotation followed by a non-primitive translation) and a glide operations, it provides a good example of non-symmorphic space group, that is, the group contains an essential screw or glide operations.
* S. Sakanaka, Phys. Rev. ST Accel. Beams 8, 072002 (2005).** E. A. Knapp, B. C. Knapp, and J. M. Potter, Rev. Sci. Instrum. 39, 979 (1968). |
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| WEPMN036 | High Field Performance in Reduced Cross-sectional X-Band Waveguides Made of Different Materials | 2119 |
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| To study the characteristics of different materials on high-field rf breakdown we designed a simplified waveguide, where the field of 200MV/m is realized at rf power of 100MW. The geometry is transformed from the WR90, where the height and the width are reduced from 10.16 mm to 1mm and from 22.86mm to 14mm, respectively. This paper reports on the high-gradient testing of copper and stainless-steel waveguides. We have observed rf breakdowns by bursts of x-rays, flashes of visible lights and acoustic signals. Frequent breakdowns are observed at about 100MV/m level in copper case and the study on the stainless-steel waveguide will be performed to be compared to that of copper case. | ||
| WEPMN037 | Manufacture and Assembly of the 6 Meter-Long Cryomodules for Superconducting RF Test Facility (STF) at KEK | 2122 |
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| The Superconducting RF Test Facility (STF) has been developed at KEK as an R&D toward ILC (International Linear Collider). Hitachi carried out the fabrication of STF cryostat components and in si-tu assembly of cryomodules cooperated with KEK. Our objective is obtaining the manufacturing experience of long cryostats for superconducting cavities. STF cryomodules are designed on the basis of TESLA design. Those major components are : vacuum vessels, support posts, 80K radiation shields, 5K radiation shields, helium gas return pipe, cryogenic piping, cavity helium vessels, RF input couplers, various measurement equipments and sensors. Two units of 6-meter long cryostat are designed to contain maximum eight 9-cell cavities in total. At the first step of the cryomodules, two different types of cavities and some equipments have been carefully prepared and installed by KEK. This paper briefly presents the structural design of STF cryostat components, cryomodule assembly procedures with specially designed tooling, and a summary for the next step. | ||
| WEPMN038 | Development of the Beam Chopper Timing System for Multi-Turn Injection to the J-PARC RCS | 2125 |
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| Multi-turn injection using charge exchange is employed for the J-PARC Rapid Cycling Synchrotron (RCS). To improve the bunching factor of the beam in the ring, the momentum offset injection scheme is used. In each turn, the bunch trains from the linac are injected into the RF buckets with a momentum offset. The bunch train is called the "intermediate pulse". The intermediate pulses are generated in the low energy section of the linac by the RF chopper and pre-chopper. Since the pulse must be synchronized to the RF voltage in the ring, the timing signals for the choppers are generated by the low-level RF (LLRF) system of the RCS and the signals are sent to the chopper control. The RF chopper and the pre-choppers require different pulse widths. Thanks to the direct digital synthesis (DDS) in the LLRF system, precise zero-cross signals for the reference of the chopper pulses are generated without difficulties. The cable route from the RCS LLRF system to the linac chopper control system is more than one kilometer. Thus, the chopper pulses are sent via optical cables. We developed the chopper timing module. We describe the details of the hardware and the preliminary test results. | ||
| WEPMN039 | Performance of J-PARC Linac RF System | 2128 |
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| High power operation of all the RF systems of J-PARC linac was started for the cavity conditioning in October 2006. Twenty 324-MHz klystrons have powered the accelerating cavities successfully, and the beam commissioning was started in November 2006. The performance of the RF drive and control system will be presented. | ||
| WEPMN040 | MA Cavities for J-PARC with Controlled Q-value by External Inductor | 2131 |
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The original J-PARC RCS cavity design* used cut-cores to control the Q-value. Adjusting the distance between the C-shaped core parts the optimum Q=2 is reached. Because of problems related to the cut-core surfaces, the "hybrid cavity" was introduced, using tanks with uncut cores (Q=0.6) in parallel to tanks with cut cores with a wider gap (Q=4), resulting in total Q=2. This was successfully tested. The manufacturing procedure for cut-cores involves more steps than for uncut cores. To reduce risks for long-term operation, the RCS cavities will be loaded with uncut cores for day-1 operation. With uncut cores (Q=0.6) the maximum beam power is limited. Therefore we introduce a parallel inductor, placed in the push-pull tube amplifier driving the cavity, to adjust the Q-value to 2. Parallel vacuum capacitors shift the resonance near to 1.7 MHz. Each of the 10 cavity systems for RCS, necessary for day-1 operation, is tested for at least 300 hours to detect initial problems before installation into the RCS tunnel. We report the results of cavity performance tests with external inductor, which simulate 25Hz operation and the optimization of the combined system of cavity and amplifier.
* C. Ohmori at. al, "High Field-Gradient Cavity for J-PARC 3 GeV RCS", PAC 2004 |
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| WEPMN041 | Reduction of RF Skin Loss with Thin Foils | 2134 |
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| Reduction of RF power loss caused by skin effect has been studied. Some measurement results on a coaxial cavity with thin foils are described. Application to another type of RF devices will be discussed. | ||
| WEPMN043 | The Modulator Stability System for the BEPCII Klystron | 2137 |
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| The stability of the modulator high voltage output pulse is the important target for the klystron. The stability of the BEPCII modulator is demanded less than 0.15%. To achieve this target, we use thyristor voltage regulator having feedback function to stabilize the DC high voltage of the modulator and the De-Qing circuit to stabilize the charging voltage. This paper describe the modulator stability system and the stabilization measurement . | ||
| WEPMN044 | The Pulsed Power Supply using IGBT Topology for CSNS Injection System Bump Magnet | 2140 |
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| The China Spallation Neutron Source (CSNS) Rapid Cycling Synchrotron(RCS) injection system needs three pulsed power supplies to drive twelve bump magnets. The current of the three pulsed power supplies are 11813A,9706A,8205A. Two of the pulsed power supplies work in controlled method at falling edge. This paper introduces the design of the three pulsed power supplies, the circuit simulation results and the demonstration of power supplies stability. | ||
| WEPMN047 | Electro-polished Cavities Using China Ningxia Large Grain Niobium Material | 2143 |
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| For the International Linear Collider (ILC), superconducting RF cavity technology was chosen. The superconducting cavity is made of polycrystalline niobium material so far. However, the material cost is high and the cavity performance has a rather scatter now. Large grain niobium (LG) cavity is an excellent idea because it simplifies the production process and results in less expensive. JLAB and DESY are pushing the R&D in last two years. KEK also has started to investigate LG. Three cavities with Ichiro shape were made of Chinese large grain niobium (Ningxia). A series of vertical tests has been carried out on several different surfaces treatment procedures by electropolishing. One cavity has reached the high gradient of more than 43 MV/m repeatedly. Other two cavities are still under testing. In this paper, the features of LG on electropolishing will be described with Ningxia large grain niobium material. | ||
| WEPMN048 | Measurement for the Kanthal Alloy Used for Collinear Load and S-band Load Design | 2146 |
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Funding: National Nature Science Foundation No.10675116 No.10375060 We have developed the mathod to determine the permittivity and permeability of Kanthal alloy available. The alloy is coated on the inside walls of disk-loaded cavities,which is used for the collinear load. The collinear load absorbs the remaining rf-power over the last cells of the section while still accelerating the beam. Based on the experimental results of the permittivity and permeability,the computation study of the constant power-loss collinear load has been made by Microwave Studio. The design data about the S-band collinear load are present. |
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| WEPMN050 | Model Cavity Investigations and Calculations on HOM for a X-Band Hybrid Dielectric-Iris-Loaded Accelerating Structure | 2149 |
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Funding: National Nature Science Foundation of China, Grant No.10375060 and No.10675116 Some model cavities have been further developed and investigated for a X-band (f=9.37GHz) hybrid dielectric-iris-loaded accelerating structure based on the calculated results about the effect of the dimension tolerance on the RF properties. The dispersion curve fitted by using the measurement value is consistent with the one calculated. The r/Q values of the dipole modes have been calculated by the Mafia code. The theoretical results show that the r/Q values of dipole modes for the new accelerating structure are lower than those for the iris-load accelerating structure. |
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| WEPMN051 | Coupler Design for X-Band Hybrid Dielectric-Iris-Loaded Accelerator | 2152 |
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Funding: National Nature Science Foundation of China, Grant No.10375060 and No.10675116 The coupler design for X-band hybrid dielectric-iris-loaded accelerator has been studied. Firstly, the S parameters versus the coupler cavity radius, the width and the height of the coupling hole have been simulated by Microwave Studio for the ordinary coupling cavity. We have obtained the primary measurement result of the standing-wave ratio of the coupling cavities being 1.8275. Secondly, the new couplers, which first converts RF from TE to TM mode in a pure metal section and then a tapered transition section is added for high efficiency transmission to the accelerator section, have been calculated for both single and dual coupling ports. The simulated results show that both types are capable to convert the TE 10 mode into TM 01 mode with high efficiency over a relatively wide bandwidth. |
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| WEPMN052 | FPGA - based Control System for Piezoelectric Stacks used for SC Cavity's Fast Tuner | 2155 |
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Funding: We acknowledge the support of the ECRIA under the FP6 program (CARE, contract number RII3-CT-2003-506395), and Polish National Science Council Grant "138/E-370/SPB/6. PR UE/DIE 354/2004-2007" The SC cavities need a fast tuning system, which is able to adjust the shape during the pulse operation. The first attempts were focused on the compensation of the repetitive and periodic distortion. The algorithms were implemented in Matlab and allow compensating only the Lorentz force detuning. However, the previous solution was too slow to be able to compensate the microphonics. The paper presents recent development in the field. The previously worked out algorithms are implemented in the FPGA-based control system. The SIMCON board is used, which allows to perform parallel, deeply pipelined calculation. The new approach allows integrating the algorithm dedicated for cavity shape control with the LLRF system used for vector sum control. Moreover, the new algorithm for on-line detuning calculation which base on the electromechanical model of the cavity is presented. The system is tested with Module Test Stand (MTS) at DESY with the high gradient cavities (37 MV/m). The active elements are the NOLIAC's and PI's multilayer, low voltage piezostacks. The paper will present the first results from these measurements. |
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| WEPMN053 | Test of 700MHz, 1MW Proto-type Klystron for PEFP | 2158 |
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| High power and RF source of 700MHz and 1MW klystron, which has been designed and constructed by Korean Accelerator and Plasma Research Association, has been being tested. To test the primary performance of the klystron, a pulse power supply was used to manipulate a negative high voltage. We are currently reinforcing the protection circuit, and it is going on without much trouble as originally planned. In addition, a baking furnace for the klystron is under fabrication for the ultra high vacuum of better stability. We constructed various infrastructures such as baking furnace for the development of Klystron. | ||
| WEPMN055 | PEFP HOM Coupler Design | 2161 |
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Funding: This work was supported by the 21C Frontier R&D program of Korea Ministry of Science and Technology. A new type of coaxial higher-order mode (HOM) coupler with one hook and two stubs has been designed for PEFP SRF cavities to satisfy the HOM damping requirements of the superconducting RF (SRF) linac of the Proton Engineering Frontier Project (PEFP), and to overcome the notch frequency shift and feed-through tip melting issues. This paper has presents details on the PEFP HOM coupler?s structure, structure optimization, filter characteristics, electro-magnetic field distribution and a coupler installation tool. |
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| WEPMN056 | PEFP Low-beta SRF Cavity Design | 2164 |
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Funding: This work was supported by the 21C Frontier R&D program of Korea Ministry of Science and Technology. An elliptical superconducting RF cavity of 700 MHz with βg=0.42 has been designed for the Linac of Proton Engineering Frontier Project (PEFP). A double-ring stiffening structure is used for a low-beta cavity for a Lorentz force detuning. The results of the electron multipacting analysis of the cavity are presented. A HOM analysis shows that the HOM coupler's Qext is lower than 3·10+5, thus reducing the influence of dangerous modes on the beam instabilities and the HOM-induced power. |
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| WEPMN057 | Development of the PEFP Low Level RF Control System | 2167 |
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Funding: This work is supported by the 21C frontier R&D program in the Ministry of Science and Technology of the Korean government. The RF amplitude and the phase stability requirements of the LLRF system for the PEFP(Proton Engineering Frontier Project) proton linac are within 1% and 1 degree, respectively. As a prototype of the LLRF, a simple digital PI control system based on commercial FPGA board is designed and tested. The main features are a sampling rate of 40 MHz which is four times higher than the down-converted cavity signal frequency, digital in-phase and quadrature detection, pulsed mode operation with the external trigger, and a simple proportional-integral feedback algorithm implemented in a FPGA. The developed system was tested with 3 MeV RFQ and 20 MeV DTL, and satisfied the stability requirements. |
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| WEPMN058 | Analog Components Configuration and Test results for PEFP LLRF system | 2170 |
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Funding: This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government. The PEFP LLRF system for the 3MeV RFQ and 20MeV DTL has been developed. The stability of ±1% in the amplitude and ±1˚ in the phase is required. Therefore, the drift of the analog components should be low to satisfy the requirement. Analog chassis as a prototype of LLRF system is configured and tested. RF components including an IQ modulator, an RF switch, a mixer, phase comparators, RF splitters, RF filters and trip circuit for high VSWR are installed in this chassis. This performs the shift of RF amplitude and phase from IQ signal, down-conversion to 10MHz IF signal, interlock for arc and high VSWR, and RF/clock distribution. The amplitude and phase stability of each component are measured to check the effect on the whole system performance. The detailed configuration and test results are presented. |
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| WEPMN060 | Fabrication of ICHIRO Nine-cell Cavities in PAL for STF of KEK | 2173 |
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Funding: Korea Ministry of Science & Technology Pohang Accelerator Laboratory has studied SRF cavity and set up SRF test laboratory from January 2006. The first activity for SRF research was to develop SRF 3rd harmonic cavity for Pohang Light Source, which was designed, fabricated and tested in 2006. The cryostat are under design. The fabrication of ICHIRO cavity, which is ILC ACD cavity, is PAL's second activity related to SRF. Deep drawing, trimming and welding by electron beam for a 9-cell ICHIRO cavity were done in PAL. The polishing processes for the RF surface including electropolishing were done in KEK under the collaboration between two institutes. This will be tested with real beam in STF-1 of KEK in second half period of 2007. This paper reports the results of fabrication of ICHIRO single- and nine-cell cavities performed in PAL. |
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| WEPMN061 | Design of Cooling System for Resonance Control of the PEFP DTL | 2176 |
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Funding: Supported by the 21st PEFP (KAERI) and MOST in Korea The temperature-controlled cooling water system was designed to obtain the resonance frequency stabilization of the normal conducting drift tube linac (DTL) for the PEFP 100 MeV proton accelerator. The primary sizing of individual closed-loop low conductivity cooling water pumping skids for each DTL system was conducted with a simulation of thermo-hydraulic network model. The temperature control schemes incorporating the process dynamic model of heat exchangers were examined to regulate the input water temperatures into the DTL during the steady state operation. The closed water circuits to achieve system performance and stability for low and full duty operation modes were discussed, and numerical results were also presented. |
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| WEPMN062 | HOM Analysis and Design of its Removal System for SRF 3rd Harmonic RF Cavity in PLS | 2179 |
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Funding: Korea Ministry of Science & Technology Pohang Accelerator Laboratory has prepared to SRF 3rd harmonic cavity to increase beam lifetime and to damp orbit instability by lengthening electron bunch in PLS. The SRF cavity was developed and its vertical test was done already with success. Higher order modes were analyzed to optimize its performance in beam orbit. Most of them are not effective to electron beam, while the others have possibility to impact orbit stability. These harmful HOMs can be removed by HOM absorber installed in beam pipe. This paper reports the HOM analysis and design of its removal system. |
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| WEPMN066 | Progress Towards Development of a Superconducting Traveling Wave Accelerating Structure | 2182 |
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| In the ILC project the required accelerating gradient is higher than 35 MeV/m. For current technology the maximum acceleration gradient in SC structures is limited mainly by the value of the surface RF magnetic field. In order to increase the gradient, the RF magnetic field is distributed homogeneously over the cavity surface (low-loss structure), and coupling to the beam is improved by introducing aperture ?noses? (re-entrant structure). These features allow gradients in excess of 50 MeV/m to be obtained for a singe-cell cavity. Further improvement of the coupling to the beam may be achieved by using a TW SC structure with small phase advance per cell. Calculations show that an additional gradient increase by up to 40% is possible if a p/2 TW SC structure is employed. However, a TW SC structure requires a SC feedback waveguide to return the few GW of circulating RF power from the structure output back to the structure input. We describe a single-cell test TW SC structure with a feedback waveguide. The test cavity is designed to demonstrate the possibility of achieving a significantly higher gradient than existing SC structures. | ||
| WEPMN068 | Design of the Modulator for the CTF3 Tail Clipper Kicker | 2185 |
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| The goal of the present CLIC test facility (CTF3) is to demonstrate the technical feasibility of specific key issues in the CLIC scheme. The extracted beam from the combiner ring (CR), of 35 A in magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX) facility. A Tail Clipper (TC) is required, in the CR to CLEX transfer line, to allow the duration of the extracted beam pulse to be adjusted. It is proposed to use a stripline kicker for the tail clipper, with each of the deflector plates driven to equal but opposite potential. The tail clipper kick must have a fast rise-time, of not more than 5 ns, in order to minimize uncontrolled beam loss and operate at a rate of up to 50 Hz. Several different options are being investigated to meet the demanding specifications for the modulator of the tail clipper. This paper discusses options considered for the fast, high voltage, semiconductor switches and shows results of initial tests on the switches. | ||
| WEPMN069 | Low Power Measurements on an AGS Injection Kicker Magnet | 2188 |
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Funding: Work supported by a contribution from the Canada Foundation for Innovation.
The present AGS injection kickers at A5 location were designed for 1.5 GeV proton injection. Recent high intensity runs have pushed the transfer kinetic energy to 1.94 GeV, but with an imperfect matching in transverse phase space. Space charge forces result in both fast and slow beam size growth and beam loss as the size exceeds the AGS aperture. An increase in the AGS injection energy to 2 GeV with adequate kick strength would greatly reduce the beam losses making it possible to increase the intensity from 70 TP (70 * 1012 protons/s) to 100 TP. R&D studies* have been undertaken by TRIUMF, in collaboration with BNL, to design two new kicker magnets for the AGS A10 location to provide an additional kick of 1.5 mrad to 2 GeV protons. TRIUMF has designed and built a prototype 12.5 Ω transmission line kicker magnet with rise and fall times of 100 ns, 3% to 97% and field uniformity of (±)1% over 85% of the aperture, powered by matched 12.5 Ω pulse-forming lines. This paper describes the results of detailed capacitance and inductance measurements, on the prototype magnet, and compares these with predictions from 2D and 3D electromagnetic simulations.
*L. Ahrens, R. B. Armenta, M. J. Barnes, E. W Blackmore, C. J. Gardner, O. Hadary, G. D. Wait, W. Zhang, "Design Concept for AGS Injection Kicker Upgrade to 2 GeV", PAC 2005, Knoxville Tennessee. |
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| WEPMN070 | High Power Test of an X-band Slotted-Iris Accelerator Structure at NLCTA | 2191 |
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| The CLIC study group at CERN has built two X-band HDS (Hybrid Damped Structure) accelerating structures for high-power testing in NLCTA at SLAC. These accelerating structures are novel with respect to their rf-design and their fabrication technique. The eleven-cell constant impedance structures, one made out of copper and one out of molybdenum, are assembled from clamped high-speed milled quadrants. They feature the same heavy higher-order-mode damping as nominal CLIC structures achieved by slotted irises and radial damping waveguides for each cell. The X-band accelerators are exactly scaled versions of structures tested at 30 GHz in the CLIC test facility, CTF3. The results of the X-band tests are presented and compared to those at 30 GHz to determine frequency scaling, and are compared to the extensive copper data from the NLC structure development program to determine material dependence and make a basic validation of the HDS design. | ||
| WEPMN071 | High RF Power Production for CLIC | 2194 |
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| The CLIC Power Extraction and Transfer Structure (PETS) is a passive microwave device in which bunches of the drive beam interact with the impedance of the periodically loaded waveguide and excite preferentially the synchronous mode. The RF power produced (several hundred MW) is collected at the downstream end of the structure by means of the Power Extractor and delivered to the main linac structure. The PETS geometry is a result of multiple compromises between beam stability and main linac RF power needs. Another requirement is to provide local RF power termination in case of accelerating structure failure (ON/OFF capability). Surface electric and magnetic fields, power extraction method, HOM damping, ON/OFF capability and fabrication technology were all evaluated to provide a reliable design. | ||
| WEPMN072 | Material Selection and Characterization for High Gradient RF Applications | 2197 |
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| The selection of candidate materials for the accelerating cavities of the Compact LInear Collider (CLIC) is carried out in parallel with high power RF testing. The DC breakdown field of copper, copper alloys, refractory metals, titanium and aluminium have been measured with a dedicated setup. Higher maximum fields are obtained for refractory metals and for titanium, which exhibits important damages after conditioning. Fatigue behaviour of copper alloys has been studied for surface and bulk by pulsed laser irradiation and ultrasonic excitation, respectively. The selected copper alloys show consistently higher fatigue resistance than copper in both experiments. RF tests are planned. In order to obtain the best local properties a bi-metallic assembly is being studied for the accelerating structures. The mechanical strength of junctions of molybdenum and copper-zirconium C15000, made either by Hot Isostatic Pressing or explosion bonding was evaluated. The reliability of the results obtained with either technique should be improved. Testing in DC and RF is continued in order to select materials for a bi-metal exhibiting superior properties with respect to the combination C15000-Mo. | ||
| WEPMN073 | A New Klystron Modulator for XFEL based on PSM Technology | 2200 |
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Funding: Supported by DESY contract. Thomson Broadcast & Multimedia has been awarded a contract from DESY to design and build a prototype klystron modulator for the XFEL project. This modulator will be built in pulse step modulator (PSM) technology. This technology will allow to control the pulse form to achieve a maximum flatness of the pulse without tuning any high power components. The modulator will also have a built-in power regulation to prevent voltage flicker of the mains. The paper will give an overview about the principles of the modulator and presents the status of the design. It also shows simulation results about the expected performance. |
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| WEPMN076 | Digital Master Oscillator Results for the ISIS Synchrotron | 2203 |
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| Rutherford Appleton Laboratory in Oxfordshire is home to an 800MeV synchrotron particle accelerator called ISIS. Its main function is to direct a beam of protons into a heavy metal target to produce neutrons for scientists to analyse condensed matter. A second harmonic system is being developed to upgrade the beam current from 200uA to 300uA in order to drive a second target station. This is being achieved by the inclusion of four second harmonic cavities to increase the width of the RF bucket. In the past the six fundamental cavities were driven by an analogue master oscillator but the extra cavities will bring more difficultly in the phasing of the system. This could be more easily and precisely controlled by embedding a Direct Digital Synthesis core into an FPGA chip as the heart of a new digital Master Oscillator. This paper describes the results of the setting up and performance of the prototype instrument and the implications it has for the synchrotron. | ||
| WEPMN077 | Impedance Measurements on a Test Bench Model of the ILC Crab Cavity | 2206 |
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Funding: This work was supported by the EC under the FP6 'Research Infrastructure Action - Structuring the European Research Area' EUROTeV DS Project Contract no.011899, RIDS and PPARC. In order to verify detailed impedance simulations, the modes in an aluminium model of the ILC crab cavity were investigated using a bead-pulling technique as well as a stretched-wire frequency domain measurement. The combination of these techniques allow for a comprehensive study of the modes of interest. For the wire measurement, a transverse alignment system was fabricated and rf components were carefully designed to minimize any potential impedance mismatches. The measurements are compared with direct simulations of the stretched-wire experiments using numerical electromagnetic field codes. High impedance modes of particular relevance to the ILC crab cavity are identified and characterized |
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| WEPMN078 | RF Cavity Development for FFAG Application on ERLP at Daresbury | 2209 |
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| Funding for a non-scaling, Fixed Field Alternating Gradient (FFAG) facility has been approved for installation on the Energy Recovery Linac Prototype (ERLP) at Daresbury. The RF system specification for this project requires the development of a high efficiency, 1.3 GHz, normal conducting accelerating structure, capable of delivering the required accelerating voltage, whilst adhering to stringent space limitations imposed by the extremely compact nature of the FFAG ring. We have optimised a cavity design, providing the necessary acceleration and minimising the RF power requirements to match with commercially available power sources. | ||
| WEPMN079 | Power Coupler for the ILC Crab Cavity | 2212 |
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Funding: This work was supported by the EC under the FP6 "Research Infrasctructure Action - Structuring the European Research Area" EUROTeV DS Project Contract no.011899 RIDS and PPARC. The ILC crab cavity will require the design of an appropriate power coupler. The beamloading in dipole cavities is considerably more variable than accelerating cavities, hence simulations have been performed to establish the required external Q. Simulations of a suitable coupler were then performed and were verified using a normal conducting prototype with variable coupler tips. |
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| WEPMN080 | Development of Circuits and System Models for the Synchronization of the ILC Crab Cavities | 2215 |
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Funding: The Commission of the European Communities under the 6th Framework Programme (Structuring the European Research Area) The UK particle physics and astromony research council. The ILC reference design report (RDR) recommends a 14 mrad crossing angle for the positron and electron beams at the IP. A matched pair of crab cavity systems are required in the beam delivery system to align both bunches at the IP. The use of a multi-cell, 3.9GHz dipole mode superconducting cavity, derived from the Fermilab CKM cavity. Dipole-mode cavities phased for crab rotation are shifted by 90 degrees with respect to similar cavities phased for deflection. Uncorrelated phase errors of 0.086 degrees (equivalent to 61fs) for the two cavity systems, gives an average of 180nm for the relative deflection of the bunch centers. For a horizontal bunch size of 655nm, a deflection of 180nm reduces the ILC luminosity by 2%. The crab cavity systems are to be placed ~28m apart and their synchronization to within 61fs is on the limit of what is presently achievable. This paper describes the design and testing of circuits and control algorithms under development at the Cockcroft Institute in the UK for proof of principle experiments planned on the ERLP at Daresbury and on the ILCTA test beamline at FNAL. Simulation results for measurement and control systems are also given. |
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| WEPMN082 | Global Scattering Matrix Technique Applied to the Calculation of Higher Order Modes for ILC Superconducting Cavities | 2218 |
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| A cascaded scattering matrix approach is used to determine the electromagnetic (e.m.) field in the main ILC cavities. This approach is used to compute higher order e.m. modes in the baseline configuration, and high gradient alternative configurations. We present results on three designs: TESLA, Cornell University's re-entrant and, KEK's "Ichiro". This approach allows realistic experimental errors to be incorporated in the studies in an efficient manner and allows several cavities to be modelled en masse. Simulations are presented on the wake-fields in super-structures and segments of entire modules. Details on trapped eigen-modes and means to avoid them are delineated. The influence of cell misalignments and cavity perturbations on the modes are also presented. | ||
| WEPMN083 | Design of A Direct Power Converter for High Power RF Applications | 2221 |
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| This paper presents practical results from a new type of power supply for high power RF applications for CW operation. The converter is a direct topology, utilising a high frequency resonant link and a high frequency transformer. High operating frequency reduces the transformer and filter size. Soft switching is employed to reduce losses. Two variants of this topology are presented. The first incorporates the high frequency transformer into the resonant circuit. The principle feature of this topology is that parasitic elements associated with all transformers are employed in operation of the converter. However, this requires that the circulating current in the resonant tank flows in the transformer windings. The second topology does not incorporate the transformer into the resonant circuit, therefore requires a smaller transformer. However, the topology will be affected by the parasitic elements of the transformer. Advantages of both these topologies over conventional approaches are discussed. The RF power generated by both topologies is stable and predictable, whilst reduced energy storage in filter components removes the need for crowbar circuits. | ||
| WEPMN085 | The Advanced Photon Source Pulsed Deflecting Cavity RF System | 2224 |
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Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Phase I Advanced Photon Source Deflecting Cavity System for producing short X-ray pulses uses one multi-cell, S-band cavity to apply a deflecting voltage to the stored electron beam ahead of an undulator that supports a beamline utilizing short picosecond X-rays. Two additional multi-cell cavities are then used to cancel out the perturbation and redirect the electron beam along the path of its nominal orbit. The pulsed rf system driving the deflecting cavities is described. Design tradeoffs are discussed with emphasis on topology considerations and digital control loops making use of sampling technology in a manner consistent with the present state of the art. |
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| WEPMN086 | High-Power Tests of a Single-Cell Copper Accelerating Cavity Driven by Two Input Couplers | 2227 |
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Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. High-power tests were conducted on a 350MHz, single-cell copper accelerating cavity driven simultaneously by two H-loop input couplers for the purpose of determining the reliability, performance, and power-handling capability of the cavity and related components, which have routinely operated at 100kW power levels. The test was carried out utilizing the APS 350MHz RF Test Stand, which was modified to split the input rf power into two 1/2-power feeds, each supplying power to a separate H-loop coupler on the cavity. Electromagnetic simulations of the two-coupler feed system were used to determine coupler match, peak cavity fields, and the effect of phasing errors between the coupler feedlines. The test was conducted up to a maximum total rf input power to the cavity of 200kW CW. Test apparatus details and performance data will be presented. |
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| WEPMN087 | Variable CW RF Power Coupler for 345 MHz Superconducting Cavities | 2230 |
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Funding: This work was supported by the U. S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357. This paper reports the development of a 5-10 kW cw variable coupler for 345 MHz spoke-loaded superconducting (SC)cavities. The coupler inserts an 80K copper loop into a 5 cm diameter coupling port on several types of spoke-loaded cavity operating at 2 - 4K. The coupling loop can be moved during operation to vary the coupling over a range of 40 dB. The coupler is designed to facilitate high-pressure water rinsing and low-particulate clean assembly. Design details and operating characteristics are discussed. |
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| WEPMN088 | The IPNS Second Harmonic RF Upgrade | 2233 |
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Funding: This work is supported by the U. S. Department of Energy under contract no. W-31-109-ENG-38. The Intense Pulsed Neutron Source (IPNS) rapid cycling synchrotron (RCS) is used to accelerate protons from 50 MeV to 450 MeV, at a repetition rate of 30 Hz. The original ring design included two identical RF systems, each consisting of an accelerating cavity, cavity bias supply, power amplifiers and low level analog electronics. The original cavities are located 180 degrees apart in the ring, and provide a total peak accelerating voltage of ~21 kV over the 2.21 MHz to 5.14 MHz revolution frequency sweep. A third RF system has been constructed and installed in the RCS. The third RF system is capable of operating at the fundamental revolution frequency for the entire acceleration cycle, providing an additional peak accelerating voltage of up to ~11kV, or at the second harmonic of the revolution frequency for the first ~4 ms of the acceleration cycle, providing an additional peak voltage of up to ~11kV for bunch shape control, resulting in a modest increase in bunch length. We describe here to date, the hardware implementation and operation of the third RF cavity in the second harmonic mode. |
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| WEPMN089 | A General Model of High Gradient Limits | 2236 |
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Funding: Supported by the USDOE / Office of High Energy Physics
Recent experimental work done to develop high gradient, low frequency cavities for muon cooling, has led to a model of rf breakdown and high gradient limits in warm structures. We have recently been extending this model to try to explain some superconducing rf quench mechanisms, as well as DC and dielectric breakdown. The model assumes that the dominant mechanisms in warm metal systems are fractures caused by the the electric tensile stress, and surface micro-topography that is strongly determined by the the cavity design and history*. We describe how these processes can determine all measurable parameters in warm systems. With superconducting systems, these mechanisms also apply, however field emission, impurities and temperature produce a somewhat different picture of quenching and pulsed power processing. We describe the model and some recent extensions and improvements in some detail and a variety of results accelerators and other applications.
* Hassanein et. al. Phys. Rev. STAB, 9, 062001 |
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| WEPMN090 | Recent RF Results from the MuCool Test Area | 2239 |
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Funding: Supported by the USDOE Office of High Energy Physics The MuCool Experiment has been continuing to take data with 805 and 201 MHz cavities in the MuCool Test Area. The system uses rf power sources from the Fermilab Linac. Although the experimental program is primarily aimed at the Muon Ionization Cooling Experiment (MICE), we have been studying the dependence of rf limits on frequency, cavity material, high magnetic fields, gas pressure, coatings, etc. with the general aim of understanding the basic mechanisms involved. The 201 MHz cavity, essentially a prototype for the MICE experiment, was made using cleaning techniques similar to those employed for superconducting cavities and operates at its design field with very little conditioning. |
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| WEPMN091 | Beam Test of a Grid-less Multi-Harmonic Buncher | 2242 |
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Funding: This work was supported by the U. S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC-02-06CH11357. The Argonne Tandem Linear Accelerator System (ATLAS) is the first superconducting heavy-ion linac in the world. Currently ATLAS is being upgraded with the Californium Rare Ion Breeder Upgrade (CARIBU). The latter is a funded project to expand the range of short-lived, neutron-rich rare isotope beams available for nuclear physics research at ATLAS. To avoid beam losses associated with the existing gridded multi-harmonic buncher, we have developed and built a grid-less four-harmonic buncher with fundamental frequency of 12.125 MHz. In this paper, we are going to report the ATLAS beam performance with the new buncher. |
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| WEPMN092 | Capture Cavity II Results at FNAL | 2245 |
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Funding: FRA As part of the research and development towards the International Linear Collider (ILC), several test facilities have been developed at Fermilab. This paper presents the latest LLRF results obtained with Capture Cavity II at these test facilities. The main focus will be on controls and RF operations using the SIMCON based LLRF system. Details about hardware upgrades and overall system performance will be also explained. Finally, design considerations and objectives for the future test facility at the New Muon Laboratory (NML) will be presented. |
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| WEPMN093 | Multipactor Simulations in Superconducting Cavities | 2248 |
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| The multipactor (MP) is a well-known phenomenon. The existence of resonant trajectories can lead to electron avalanche under certain field level and surface conditions. In this paper we describe features of the extension of Analyst software - PT3P code developed for MP simulations in a real 3D RF structures, such as cavities, couplers, RF windows etc. Also we present the results of MP simulations in HOM couplers of TESLA, SNS β=0.61 and β=0.81 and FNAL 3-rd harmonic cavities. We discuss the comparison of simulations with experimental results. | ||
| WEPMN094 | Experience with Capture Cavity II | 2251 |
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Funding: This work supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U. S. DOE. Valuable experience in operating and maintaining superconducting RF cavities in a horizontal test module has been gained with Capture Cavity II. We report on all facets of our experience to date. |
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| WEPMN096 | Status of the 3.9-GHz Superconducting RF Cavity Technology at Fermilab | 2254 |
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Funding: This work supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U. S. DOE. Fermilab is involved in an effort to assemble 3.9 GHz superconducting RF cavities into a four cavity cryomodule for use at the DESY TTF/FLASH facility as a third harmonic structure. The design gradient of these cavities is 14 MV/m limited by thermal heat transfer. This effort involves design, fabrication, intermediate testing, assembly, and eventual delivery of the cryomodule. We report on all facets of this enterprise from design through future plans. Included will be test results of single 9-cell cavities, lessons learned, and current status. |
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| WEPMN097 | A Solid State Marx Generator for TEL2 | 2257 |
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| The solid-state Marx generator modulates the anode of the electron gun to produce the electron beam pulses in the second Tevatron Electron Lens (TEL2). It is capable of driving the 60 pf terminal with 600ns pulses of up to 6 kV with a p.r.r. of 50 kHz. The rise and fall times are 150 ns. Stangenes Industries developed the unit and is working on a second version which will go to higher voltage and have the ability to vary its output in 396 ns intervals over a 5 us pulse. | ||
| WEPMN098 | New HOM Coupler Design for 3.9 GHz Superconducting Cavities at FNAL | 2259 |
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| Last few years Fermilab is developing the superconducting third harmonic section for the FLASH (TTF/DESY) upgrade. The results of vertical tests of 9-cell Nb cavities didn't reached the designed accelerating gradient. The main gradient limitation is multipacting in HOM coupler. In this paper we present the results of vertical tests accompanied with 3D Analyst simulations of multipacting. Also we discuss the RF design of a new HOM couplers. The goal of a new design is to eliminate multipacting and to increase the frequency of second resonance of the HOM. Increasing the frequency will decrease the electric and magnetic fields having the goal to decrease the thermal load on antenna. | ||
| WEPMN099 | Production of 325 MHz Single Spoke Resonators at FNAL | 2262 |
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Funding: US Department of Energy
The High Intensity Neutrino Source (HINS) project represents the current effort at Fermi National Accelerator Laboratory to produce an 8-GeV proton linac based on about 400 independently phased superconducting resonators. Eighteen β=0.21 single spoke resonators, operating at 325 MHz, comprise the first stage of the linac cold section. We are presenting the production status of the first two of these resonators and the performance of the tuning mechanism prototype. In particular, we will report on the construction phases, the pre-weld tuning process and the comparison of low power RF measurements with calculations made using Microwave Studio*.
* CST MICROWAVE STUDIO (CST MWS), http://www.cst.com/ |
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| WEPMN100 | RF Design and Processing of a Power Coupler for Third Harmonic Superconducting Cavities | 2265 |
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Funding: U. S. Department of Energy The FLASH user facility providing free electron laser radiation is built based on the TTF project at DESY. Fermilab has the responsibility for the design and processing of a third harmonic, 3.9 GHz, superconducting cavity which is powered via a coaxial power coupler. Six power couplers have been manufactured at CPI after successful design of the power coupler including RF simulation, multipacting calculation, and thermal analysis. The power couplers are being tested and processed with high pulsed power in an elaborate test stand at Fermilab now. This paper presents the RF design and processing work of the power coupler. |
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| WEPMN101 | Coupling Interaction Between the Power Coupler and the Third Harmonic Superconducting Cavity | 2268 |
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Funding: U. S. Department of Energy Fermilab has developed a third harmonic superconducting cavity operating at the frequency of 3.9 GHz to improve the beam performance for the FLASH user facility at DESY. It is interesting to investigate the coupling interaction between the SRF cavity and the power coupler with or without beam loading. The coupling of the power coupler to the cavity needs to be determined to minimize the power consumption and guarantee the best performance for a given beam current. In this paper, we build and analyze an equivalent circuit model containing a series of lumped elements to represent the resonant system. An analytic solution of the required power from the generator as a function of the system parameters has also been given based on a vector diagram. |
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| WEPMN102 | A 96 Channel Receiver for the ILCTA LLRF System at Fermilab | 2271 |
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| The present configuration of an ILC Main Linac RF station has 26 nine cell cavities driven from one klystron. With the addition of waveguide power coupler monitors, 96 RF signals will be downconverted and processed. A downconverter chassis is being developed that contains 12 eight channel analog modules and a single upconverter module. This chassis will first be deployed for testing a cryomodule composed of eight cavities located at New Muon Laboratory (NML) - Fermilab. Critical parts of the design for LLRF applications are identified and a detailed description of the circuit with various characteristic measurements is presented. The board is composed of an input band-pass filter centered at 1.3GHz, followed by a mixer, which downconverts the cavity probe signal to a proposed 13 MHz intermediate frequency. Cables with 8 channels per connector and good isolation between channels are being used to interconnect each downconverter module with a digital board. As mixers and power splitters are the most sensitive parts for noise, nonlinearities and cross-talk issues, special attention is given to these parts in the design of the LO port multiplication and distribution. | ||
| WEPMN103 | Mechanical Stability Study of Capture Cavity II at Fermilab | 2274 |
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Problematic resonant conditions at both 18 Hz and 180 Hz were encountered and identified early during the commissioning of Capture Cavity II (CC2) at Fermilab. CC2 consists of an external vacuum vessel and a superconducting high gradient (close to 25 MV/m) 9-cell 1.3 GHz niobium cavity, transported from DESY for use in the A0 Photoinjector at Fermilab. An ANSYS modal finite element analysis (FEA) was performed in order to isolate the source of the resonance and directed the effort towards stabilization. A novel idea was implemented, by using a fast piezoelectric tuner to excite (or shake) the cavity at different frequencies (from 10 Hz to 200 Hz) as a low-range sweep for analysis purposes. Both warm (300 K) and cold (1.8 K) accelerometer measurements at the cavity were taken as the resonant 'fix' was applied. FEA results, cultural and technical noise investigation, and stabilization techniques are discussed.
Operated by Universities Research Association, Inc., under Contract No. DE-AC02-76CH03000 with the U. S. Department of Energy#mcgee@fnal.gov |
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| WEPMN104 | Mechanical Stability Study of Type IV Cryomodule (ILC Prototype) | 2277 |
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An ANSYS modal and harmonic finite element analysis (FEA) was performed in order to investigate cryomodule design mechanical stability for the proposed International Linear Collider (ILC). The current cryomodule, designated Type IV or T4CM, closely follows the Type III TESLA Test Facility (TTF) version used at DESY, with the exception of a proposed location of the superconducting (SC) quadrupole at the center. This analysis considered the stringent stability criteria established for the ILC, where vertical motion for the SC quad is limited to the micron range, at a few Hz. Model validation was achieved through Type II cryomodule vibration measurement studies performed at DESY. The effect of support location, support stiffness and other important parameters were considered in a parametric sensitivity study. FEA results, fast motion investigations and stabilization techniques are discussed.
Operated by Universities Research Association, Inc., under Contract No. DE-AC02-76CH03000 with the U. S. Department of Energy#mcgee@fnal.gov |
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| WEPMN105 | Fast Thermometry for Superconducting RF Cavity Testing | 2280 |
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Funding: Work supported by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy. Fast readout of strategically placed low heat capacity thermometry can provide valuable information of Superconducting RF (SRF) cavity performance. Such a system has proven very effective for the development and testing of new cavity designs. Recently, several RTDs were installed in key regions of interest on a new 9 cell 3.9 GHz SRF cavity with integrated HOM design at FNAL. A data acquisition system was developed to read out these sensors with enough time and temperature resolution to measure temperature changes on the cavity due to heat generated from multipacting or quenching within power pulses. The design and performance of this fast thermometry system will be discussed along with results from tests of the 9 cell 3.9GHz SRF cavity. |
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| WEPMN106 | Design and Commissioning of Fermilab's Vertical Test Stand for ILC SRF Cavities | 2283 |
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Funding: Operated by Universities Research Association, Inc. for the U. S. Department of Energy under contract DE-AC02-76CH03000 As part of a program to improve cavity performance reproducibility for the ILC, Fermilab is developing a facility for vertical testing of SRF cavities. It operates at a nominal temperature of 2K, using an existing cryoplant that can supply LHe in excess of 20g/sec and provides steady-state bath pumping capacity of 125W at 2K. The below-grade cryostat consists of a 4.9m long vacuum vessel and 4.5m long LHe vessel. The cryostat is equipped with external and internal magnetic shielding to reduce the ambient magnetic field to <10mG. Internal fixed and external movable radiation shielding ensures that radiation levels from heavily field-emitting cavities remain low. In the event that radiation levels exceed allowable limits, an integrated personnel safety system consisting of RF switches, interlocks, and area radiation monitors disables RF power to the cavity. In anticipation of increased throughput requirements that may be met with additional test stand installations, sub-systems have been designed to be easily upgradeable or to already meet these anticipated needs. Detailed facility designs, performance during system commissioning, and results from initial cavity tests are presented. |
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| WEPMN107 | RF and Data Acquisition Systems for Fermilab's ILC SRF Cavity Vertical Test Stand | 2286 |
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Funding: Operated by Universities Research Association, Inc. for the U. S. Department of Energy under contract DE-AC02-76CH03000 Fermilab is developing a facility for vertical testing of SRF cavities as part of a program to improve cavity performance reproducibility for the ILC. The RF system for this facility, using the classic combination of oscillator, phase detector/mixer, and loop amplifier to detect the resonant cavity frequency and lock onto the cavity, is based on the proven production cavity test systems used at Jefferson Lab for CEBAF and SNS cavity testing. The design approach is modular in nature, using commercial-off-the-shelf (COTS) components. This yields a system that can be easily debugged and modified, and with ready availability of spares. Data acquisition and control is provided by a PXI-based hardware platform in conjunction with software developed in the LabView programming environment. This software provides for amplitude and phase adjustment of incident RF power, and measures all relevant cavity power levels, cavity thermal environment parameters, as well as field emission-produced radiation. It also calculates the various cavity performance parameters and their associated errors. Performance during system commissioning and initial cavity tests will be presented. |
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| WEPMN108 | A Technique for Monitoring Fast Tuner Piezoactuator Preload Forces for Superconducting RF Cavities | 2289 |
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Funding: Work supported by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy.
The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities*. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant preload force on the piezo stack in the range of 10 to 50% of its specified blocking force. Determining the preload force during cooldown, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. This paper will address the design and testing of piezo actuator preload sensor technology. Results from measurements of preload sensors installed on the tuner of the DESY Capture Cavity II tested at Fermilab will be presented. These results include measurements during cooldown, warm-up, and cavity tuning along with dynamic Lorentz force compensation.
* M. Liepe et al," Dynamic Lorentz Force Compensation with a Fast Piezoelectric Tuner" PAC2001 |
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| WEPMN110 | Fabrication and Test of the First Normal-Conducting Crossbar H-type Accelerating Cavity at Fermilab for HINS | 2292 |
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Funding: This work was supported by the U. S. Department of Energy under contract number DE-AC02-76CH03000 The proposed High Intensity Neutrino Source at Fermilab is based on an 8 GeV linear proton accelerator which consists of a normal-conducting and a superconducting section. The normal-conducting (warm) section is composed of an ion source, a radio frequency quadrupole, a medium energy beam transport and 16 normal-conducting crossbar H-type cavities that accelerate the beam from 2.5 MeV to 10 MeV (from β=0.0744 to β=0.1422). These warm cavities are separated by superconducting solenoids enclosed in individual cryostats. Beyond 10 MeV, the design uses superconducting spoke resonators to accelerate the beam up to 8 GeV. In this paper, we illustrate the completion of the first normal-conducting crossbar h-type cavity (β=0.0744) explaining in detail the mechanical engineering aspects related to the machining and brazing processes. The radio-frequency measurements and tuning performed at Fermilab on the resonator and the comparisons with the former simulations are also discussed. |
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| WEPMN111 | 3.9 GHz Superconducting Accelerating 9-cell Cavity Vertical Test Results | 2295 |
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| The 3rd harmonic 3.9GHz accelerating cavity was proposed to improve beam performances of the FLASH (TTF/DESY) facility. In the frame of collaboration Fermilab will provide DESY with a cryomodule containing a string of four cavities. In addition, a second cryomodule with one cavity will be fabricated for installation in the Fermilab photo-injector, which will be upgraded for the ILC accelerator test facility. The first results of vertical tests of 9-cell Nb cavities didn?t reached the designed accelerating gradient. The main problem is multipactoring in HOM couplers, which leads to quenching and overheating of the HOM couplers. New HOM couplers with improved design integarated to next 9-cell cavities. In this paper we present all results of vertical tests. | ||
| WEPMN112 | Multichannel Vector Field Control Module for LLRF Control of Superconducting Cavities | 2298 |
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| The field control of multiple superconducting RF cavities with a single Klystron, such as the proposed RF scheme for the ILC, requires high density (number of RF channels) signal processing hardware so that vector control may be implemented with minimum group delay. The MFC (Multichannel Field Control) module is a 33-channel, FPGA based downconversion and signal processing board in a single VXI slot, with 4 channels of high speed DAC outputs. An LO input of upto 1.6 GHz can be divided down to provide 8 clock signals through a clock distribution chip. A 32-bit, 400MHz floating point DSP provides additional computational capability for calibration and implementation of more complex control algorithms. Both the FPGA and DSP have external SDRAM memory for diagnostic data and nonvolatile Flash memory for program and configuration storage. Multiple high speed serial transceivers on the front panel and the backplane bus allow a flexible architecture for inter-module real time data exchanges. An interface CPLD supports the VXI bus protocol for communication to a Slot0 CPU, with Ethernet connections for remote in system programming of the FPGA and DSP as well as for data acquisition. | ||
| WEPMN113 | A High Voltage Hard Switch Modulator for the International Linear Collider | 2301 |
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| Under the U. S. DOE SBIR program, Diversified Technologies, Inc. (DTI) is developing a modulator to supply 135 kV, 165A, 1.5 ms pulses for the International Linear Collider. The hard-switch modulator, using DTI?s solid-state switches, will accommodate the long pulse-length required by the L-band (1.3 GHz) klystrons. To achieve required pulse flatness (0.5% at 5 Hz) without a large capacitor bank, a bouncer circuit is used to compensate the voltage droop. An LC ringer, switched separately from the main HV capacitor bank, is employed. The main storage capacitor is charged by a 185 kW DTI inverter driving a four-stage voltage multiplier. The bouncer capacitor is charged by a commercial high voltage supply. A multi-stage, high voltage switch connects the main capacitor to the load during the linear portion of the bouncer ringing transient. The inverter transformers, multiplier, bouncer inductor, capacitor, high voltage switches, main capacitor bank (90kJ), and voltage and current diagnostic probes are completely housed in oil-filled tanks. This paper describes the structure and operating theory of this switching system, and reports on its construction and initial testing. | ||
| WEPMN114 | Modular Multiple Frequency RF Amplifier | 2304 |
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| The construction and support of a wide range of RF amplifiers are significant cost components in the operation of the research community's accelerator facilities. This situation exists because amplifiers have been designed for a single application, often by multiple vendors, and therefore have very little commonality in their design, construction, and control interfaces for remote operation. To address these shortcomings, Diversified Technologies, Inc. (DTI) is developing a versatile and cost effective, modular RF amplifier design that can be employed across a wide range of RF amplifier requirements. Regardless of frequency or power, amplifiers built on this model feature commonality of design, controls system, and spares. A marriage of solid-state RF driver, power conditioning and control circuitry with high power Vacuum Electronic Device (VED) power amplifiers provide the ultimate in modular, cost-effective, and re-configurable RF power sources. In this paper, DTI will describe the modular RFA amplifier's topology and operating theory, and progress to date in the development of a prototype. | ||
| WEPMN115 | Results of the ALS Booster Ring RF System Upgrade for Top-Off Mode of Operation | 2307 |
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Funding: Supported by the U. S. Department of Energy under Contract No. DE-AC03-76SF00098. ALS, one of the first third generation synchrotron light sources which has been operating since 1992 at Berkeley Lab has been upgraded from its present operation scenario of injecting the 1.5GeV electron beam from the Booster ring into the Storage ring every 8 hours where it is accelerated to the final energy of 1.9GeV to full energy (1.9GeV) injection from the Booster ring into the Storage ring every 3 seconds for filling and every 30-35 seconds for Top-Off mode. Additionally the beam current has been increased from the time averaged value of 250mA to 500mA to increase the brightness. In this paper we will present the results of the new ALS injector RF system set-up for Top-Off mode of operation, the final design and operational results of the Booster RF power source and control system upgrades. |
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| WEPMN116 | Plans for Precision RF Controls for FERMI@ELETTRA | 2310 |
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| FERMI@ELETTRA is a 4th generation light source under construction at Sincrotrone Trieste. It will be operated as a seeded FEL driven by a warm S-band linac presently serving as the injector for the ELETTRA storage ring. Operation as an FEL driver places much more stringent specifications on control of the amplititude and phase of the RF stations than in its present operation. This paper describes a conceptual design of an upgrade to the RF controls to achieve these specifications. The system consists of a stabilized distribution of the master oscillator signal providing a reference to local digital RF controllers . The RF reference distribution system takes advantage of recent breakthroughs in optical techniques where stabilized fiber lasers are used to provide a very accurate control of RF phases over long distances. The RF controller is based on recent improvements on modern digital systems, using a 14-bit high speed digitizer in combination with an FPGA and high speed DAC. This paper also presents experimental results of early tests performed as a feasibility study of the system. | ||
| WEPMN118 | Mechanical Design and Analysis of a 200 MHz, Bolt-together RFQ for the Accelerator Driven Neutron Source | 2313 |
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Funding: This work was supported by the U. S. Dept. of Energy under Contract No. DE-AC02-05CH11231 and by the Dept. of Homeland Security's Domestic Nuclear Detection Office under Award No. HSHQPB-05-X-00033. A high-yield neutron source to screen sea-land cargo containers for shielded Special Nuclear Materials (SNM) has been designed at LBNL. The Accelerator-Driven Neutron Source (ADNS) utilizes the D(d,n)3He reaction to produce a forward directed neutron beam. Key components are a high-current radio-frequency quadrupole (RFQ) accelerator and a high-power neutron production target capable of delivering a neutron flux of >107 n/(cm2 s) at a distance of 2.5 m. The mechanical design and analysis of the four-module, bolt-together RFQ will be presented here. Operating at 200 MHz, the 5.1 m long RFQ will accelerate a 40 mA deuteron beam to 6 MeV. At a 5% duty factor, the time-average d+ beam current on target is 1.5 mA. Each of the 1.27 m long RFQ modules will consist of four solid OFHC copper vanes. A specially designed 3-D O-ring will be used to provide vacuum sealing between both the vanes and the modules. RF connections are made by means of canted coil spring contacts. Quadrupole mode stabilization is obtained with a series of 60 water-cooled pi-mode rods. A set of 80 evenly spaced fixed slug tuners is used for final frequency adjustment and local field perturbation correction. |
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| WEPMN119 | Equilibrium Theory of an Intense Elliptic Beam for High-Power Ribbon-Beam Klystron Applications | 2316 |
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Funding: Research supported by US Department of Energy, Office of High-Energy Physics, Grant No. DE-FG02-95ER40919 and Air Force Office of Scientific Research, Grant No. FA9550-06-1-0269. A concept for a high-power ribbon-beam klystron (RBK) employing a novel large-aspect ratio elliptic electron beam instead of a conventional circular electron beam is presented. Both cold-fluid and kinetic equilibrium theories are developed and applied in the design of the elliptic electron beam for the RBK. A small-signal theory is developed and applied in the design of the beam tunnel and the input, idler and output cavities. The electron gun and beam matching is being studied. Design results of a 10 MW 1.3 GHz RBK for the International Linear Collider (ILC) and of a 50 MW 22 GHz RBK for high-gradient research will be discussed. |
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| WEPMN120 | Photonic Band Gap Higher Order Mode Coupler for the International Linear Collider | 2319 |
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Funding: Research supported by US Department of Energy, Office of High-Energy Physics, Grant No. DE-FG02-95ER40919 and Air Force Office of Scientific Research, Grant No. FA9550-06-1-0269. A photonic band gap (PBG) higher-order-mode (HOM) coupler is proposed as an Alternative Configuration Design (ACD) for the HOM coupler for the International Linear Collider (ILC). The PBG HOM coupler uses a two-dimensional triangular PBG structure with good axial symmetry. Simulation studies of a PBG HOM coupler show that it maintains the operating mode at 1.3 GHz with . While a PBG HOM coupler provides superior damping for all the higher order modes in principle, detailed studies of the effectiveness of HOM damping are being carried out, and results will be discussed. |