APAC 2007 - List of Keywords (impedance)

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impedance

Paper	Title	Other Keywords	Page
MOOPMA05	R&D on Vacuum Components for High-Current Accelerators	electron, vacuum, positron, radiation	41
	Y. Suetsugu, H. Hisamatsu, K.-I. Kanazawa, K. Shibata, M. Shirai KEK, Ibaraki
	In anticipation of coming high current accelerators era, R&D on various vacuum components has been carried out at KEK. Copper beam ducts with ante-chambers were designed to deal with the intense synchrotron radiation (SR) power density emitted from the high current beam. The ante-chamber structure is also effective to reduce photoelectrons around positron beam, which is helpful to suppress the electron cloud instability (ECI). A comb-type RF-shield was developed to reduce the beam impedance and improve the thermal strength compared to the conventional finger-type one, and applied to bellows chambers and gate valves. The connection flange with the same cross section to the beam duct was also developed in parallel. Novel structure of a movable mask (collimator) was recently proposed, which had lower impedance compared to the conventional one, and now the test model was under fabrication. The beam ducts, the bellows chambers, and the gate valves have been installed in the KEK B-factory (KEKB) positron ring for several years. The performance of these components has been studied during beam operation, and the promising results have been obtained.
	Slides

TUPMA016	Computation of Wakefields and Impedances for the PETRA III Longitudinal Feedback Cavity	feedback, simulation, scattering, kicker	124
	A. K. Bandyopadhyay, A. Joestingmeier, A. S. Omar Otto-Von-Guericke University, Magdeburg K. Balewski, R. Wanzenberg DESY, Hamburg
	At DESY the existing PETRA II storage ring will be converted into a 3rd generation synchrotron radiation source, called PETRA III. The total beam current is limited by coupled bunch instabilities, which are mainly driven by the parasitic modes of the RF cavities. It is planned to use longitudinal and transverse feedback systems to achieve the design current of 100 mA. Eight single cell feedback cavities will be installed into the PETRA III ring to damp the coupled bunch longitudinal phase oscillations. It is important to know the contribution of the feedback cavity to the impedance budget of PETRA III. In this article, the wake and impedance computation results, using the loss and kick parameters, will be reported. The computer codes MAFIA and Microwave Studio have been used to compute the electromagnetic fields.

WEPMA002	A Large Area Scanning Magnet For Homogeneous Irradiation of Targets	power-supply, controls, dipole, ion	339
	A. Mandal, R. Kumar, G. Rodrigues, S. K. Suman IUAC, New Delhi
	The scanner is an important tool for accelerator based material science research. For high energy (~100 MeV) ion beam scanner has to be magnetic one. Major problem faced with magnetic scanner is its high inductance which causes large impedance to the a.c. power supply used to energise the magnet. We have designed a magnetic scanner keeping attention to minimise its inductance. The scanner is composed of two independent H-type dipole magnets which are fed by saw tooth pulses. It can scan over an area of 25 mm x 25mm at a distance of 1 metre. The power supplies for this scanner have also been designed. These are bipolar, wideband, high speed amplifirs that can reproduce complex waveform without any distotion. The ratings are 60V, 50A operating at 50Hz for x-scanner and 5V,70A at 0.2Hz for y-scanner. Design and performance of the scanner magnet and power supplies will be presented.

WEPMA035	Degradation of the Beam passing through Idle Coupled Cavities	linac, proton, coupling, injection	369
	Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken S. Machida STFC/RAL/ASTeC, Chilton, Didcot, Oxon
	Effects of wake fields on high intensity proton beam are studied, when it passes through idle coupled cavities. There is the same number of frequencies as the number of gaps that consist on the coupled cavity. Since cavities are designed for the accelerated beam, the shunt impedance for each mode is different from the designed value, when the beam is not accelerated. This change of shunt impedances reduces the detuning effect for the reduction of beam degradation.

WEPMA037	Beam Coupling Impedance Studies of the CSNS Ring	kicker, coupling, space-charge, extraction	372
	N. Wang, Q. Qin IHEP Beijing, Beijing
	The China Spallation Neutron Source (CSNS) is a high intensity proton accelerator with an injection energy of 80 MeV. The knowledge of impedance in the vacuum chamber is necessary for optimizing the accelerator performance. In this paper, the longitudinal and transverse coupling impedances of the CSNS Rapid Cycling Synchrotron (RCS) are estimated.

WEPMA038	A Study on the Applicability of Landau Cavity to the 1.2 GeV Booster Synchrotron at Tohoku University	synchrotron, injection, booster, target	375
	F. Hinode, K. Akiyama, K. Kasamsook, M. Kawai, A. Kurihara, T. Muto, K. Nanbu, Y. Shibasaki, S. Takahashi, T. Tanaka, M. Yasuda Tohoku University, School of Scinece, Sendai
	In these years, a 1.2 GeV Stretcher-Booster (STB) ring at Laboratory of Nuclear Science, Tohoku University, has been mainly operated in the booster-storage mode in which the high energy gamma-ray beam generated via bremsstrahlung from internal target wire has been utilized for experiments of nuclear physics. Beam energy injected from linac is not high enough (150 or 200 MeV), so that radiation damping time is much long. Although the injector linac provides sufficient beam current without beam stacking, circulating beam current decays rapidly due to instabilities before the beam reaches the top energy. One of the main causes in the beam current limitation is supposed to be strong coupled bunch instability due to the cavity HOM. In order to suppress the instability, applicability of a third-harmonic Landau cavity has been studied for the STB. The 1.5 GHz Landau cavity was already manufactured and installed in the ring. Beam commissioning will be started soon. We are also planning to introduce a longitudinal feedback into the STB. We will report the present status of the STB in this conference.

WEPMA049	Design of a Stripline Kicker for Tune Measurement in SESAME Storage Ring	storage-ring, betatron, synchrotron, kicker	390
	S. Varnasseri SESAME, Amman
	Traveling wave electrodes are commonly used in synchrtorn light sources as a tool for both excitation and beam sensing for tune measurement. Noraml longitudinally symmetric stripline has a posivie sine wave response in the frequency domain. An exponentially taperd stripline has a constant coupling impedance versus frequency and better frequency response. In this paper the design of stripline kicker for the purpose of tune measurement in the SESAME storage ring is reported.

WEPMA051	Development of Wide Band FCT System for Booster Synchrotron of Indus-1 & 2	pick-up, booster, synchrotron, coupling	396
	P. Pareek, R. S. Shinde, K. Singh RRCAT, Indore (M. P.)
	A high precision & non-destructive type of wide band FCT for the measurements of electron current has been developed. This monitoring system is composed of slow & fast FCTs, NiZnCo ferrite toroidal cores, pick up coils, electromagnetic shields & pulse amplifiers. A wide band FCT (rise time 60 ns & decay 1 ms) required for measurement of Electron beam intensity & turn-to-turn observation & stored current accumulation during 1 us pulse injection into Booster Synchrotron. Single FCT can't measure e beam current & turn-by-turn observation from 60 ns to 1 ms. Therefore, we designed & developed two FCTs housed in a single box. The spacing between them is optimized so that coupling between them will not affect pulse shape. The FCT consists of two NiZn ferrite ring cores separable into two pieces for easy setting around ceramic beam duct. A beam intensity of pulse (100 ns ~1 us) beam is monitored by fast rise Current monitor (~ 60 ns)& turn/stored currents monitored by slow FCT (~ 1 us to 1 ms). A wide band FCT showed fast rise & slow decay, high sensitivity (0.050V/mA), linearity within 1 % & good S/N ratio. This paper focuses on FCT designs, construction & their pulse response

WEPMA110	Development of 100 kW RF Amplifier for Superconducting Cyclotron at VECC	power-supply, cyclotron, higher-order-mode, controls	476
	S. S. Som, M. B. Banerjee, D. S.B. Bhattacharyay, S. B. Biswas, P. G. Gangopadhyay, A. Mandal, S. K. Manna, A. K. Mukherjee, S. P. Pal, J. S.P. Prasad, P. R. Raj, M. S. Saha, S. Saha, S. Seth, K. V. krishnaiah DAE/VECC, Calcutta
	High power rf amplifiers (3 nos.) have been developed at our centre for feeding power to three nos. of coaxial rf cavities of the k500 Superconducting Cyclotron. Each of this amplifier can supply output power of 100 kW (max.) at 50 Ω impedance within the frequency range of 9 MHz to 27 MHz. The amplifier, based on Eimac 4CW 150,000E water-cooled tetrode, is tuned by moving the sliding short of the coaxial cavity within the said frequency range. An inductive coupling loop is inserted along one side of the coaxial cavity through the sliding short and is matching the output impedance of 50 ohm. The four identical Bridge-T network in the grid of the final amplifier are driven with equal power levels of up to 150 watts. The amplifier is operated in Class-AB mode with power gain of 22 dB. A PC-based stepper motor controlled sliding short movement system have been done. The frequency response of the input circuit of the amplifier has been measured using Vector Network Analyzer and the result is very satisfactory.

WEPMA133	Evaluation of External Q Using Kroll-Yu Method With Microwaves Studio	resonance, coupling, proton, superconductivity	503
	A. S. Dhavale, K. C. Mittal BARC, Mumbai
	Design and development of superconducting cavity has been taken up as a part of Accelerator Driven Subcritical project(ADSS). An input coupler is designed for the same using Kroll-Yu method. The evaluation procedure is optimized and the method has been successfully implemented for the evaluation high external Q. The validity of the Kroll-Yu method is tested with the external Q calculations by P. Balleyguier method for the Benchmark cavtity which is a pillbox cavity of diameter ~200 mm, length ~150 mm with semi-rigid coaxial line*. It is found that the careful choice of data points provides accurate results over wide range. N. M.Kroll, D. U.L. Yu, "Computer determination of the external Q and resonant frequency of waveguide loadaed cavities", SLAC-PUB-5171, Jan1990(A) A. S.Dhavale and K. C.Mittal,"Evaluation of external Q of the superconducting cavity using Kroll-Yu method", Review Of Scientific Instruments 77, 06610¹ (2006)* P. Balleyguier, "A straightforward method for cavity external Q computation", Particle Accelerators, Vol.57, P.113-127, 1997

WEPMA143	High-Power, Low-Loss, Radial Rf Power Dividers/Combiners	insertion, coupling, simulation, controls	520
	A. Jain, A. Gupta, P. R. Hannurkar, D. Sharma RRCAT, Indore (M. P.)
	A 20 kW Solid State Power Amplifier (SSPA) at 352 MHz development is in progress at RRCAT. This design uses radial splitting and combining architecture in which the signal is divided into a number of individual parts. Each individual part is then amplified by a respective amplifier of 200 W. The outputs of the amplifiers are then combined into a single output that achieves final output power of the order of 1.5 kW to 4 kW. As a part of this system, two high power combiners have been designed and developed. One is 8 way with output ports opposite to input port. Second one is 16 way with radial output ports. Both of these designs are compact with 20 cm diameter of outer radial disk. Input ports are N connector, while output port is 15/8” rigid coaxial line. Measured performance of these two designs shows insertion loss of 0.6 dB and input VSWR of 1.09. Radial architecture uses in-phase, non-resonant radial transmission line structures.

WEPMA144	High Power Microwave Generation From Coaxial Virtual Cathode Oscillator	cathode, electron, plasma, space-charge	523
	A. Roy, RM. Menon, S. Mitra, K. C. Mittal, J. Mondal, D. D. Praveen Kumar, A. S. Sharma BARC, Mumbai
	A coaxial virtual cathode oscillator (VIRCATOR) has been designed to generate Relativistic Electron Beams and High Power Microwaves. Coaxial virtual cathode oscillators are known for better efficiency compared to the axial virtual cathode oscillators. This Coaxial VIRCATOR has been designed for the KALI-5000 (1MeV, 60kA, 100 ns) pulse power system. Provision for a large anode cathode gap has been kept to avoid the prepulse effect during the electron beam generation from the KALI-5000 system. Experimental studies are carried out to generate and characterize Relativistic Electron Beams and High Power Microwaves. Relativistic Electron Beams are generated by the Coaxial Explosively emitted graphite cathodes. Electron beam voltage has been measured by a copper sulphate voltage divider and beam current by a B-dot probe. High Power Microwaves are detected by the glow of neon lamps placed closed to the output window.

THYMA01	Kickers for Injection and Extraction in Damping, Combiner and Storage Rings	kicker, injection, extraction, damping	539
	F. Marcellini INFN/LNF, Frascati (Roma)
	Injection and extraction kickers play a fundamental role in all the projects of new major accelerators at present under study. The feasibility of these accelerators depends also on the possibility to realize kickers based on unconventional design and new technologies. This paper describes the R&D carried out at LNF on two different types of deflecting devices. The first are the kickers for the Damping Ring (DR) of the International Linear Collider (ILC) and the Storage Rings (SR) of colliders like DAFNE. They require very low impedance, good field uniformity in a wide region around the beam axis and very short pulse duration for limiting the length and consequently the cost of the DR and for reducing the perturbation of the stored bunches in SRs. The tests made on stripline prototypes, fast high voltage pulsers and vacuum feedthroughs are presented. The second are the RF kickers for the CLIC Test Facility 3 (CTF3) for which an original SW structure has been designed and realized for the Delay Loop (DL) while a more conventional TW deflector allows the multiplication of bunch current and frequency in the Combiner Ring (CR). Results of their performances are described.
	Slides

THPMA032	Active Filter for Harmonic Mitigation for Magnet Power Supplies of INDUS-II	power-supply, controls, resonance, feedback	671
	Y. P. Singh, S. Kotaiah, A. C. Thakurta RRCAT, Indore (M. P.)
	Power supplies used for powering of magnets in INDUS-I and INDUS-II uses different type of power converters including SMPS and thyristorised power converters. Though considerations are given to keep the harmonic loading on a.c. mains low while designing these power supplies and selecting a suitable power converter for the required power, still they give a significant amount of harmonic loading on a.c. mains. In all the high power d.c. power supplies, wide variation in operating point leads to a considerable amount of reactive power generation and harmonic loading on ac mains. In this work a study has been performed to know the variation of reactive power with time on some of the d.c. power supplies of INDUS-II. Various options to improve the power factor has been studied and their advantages & limitations for accelerator magnet power supplies has been highlighted. A combined system of a shunt passive and small rated series active filter has been proposed. The compensation principle is described and filtering characteristics are discussed in detail. A scale down prototype of proposed series active filter has been developed in lab and experimental results produced.

THPMA046	Study and Comparison of Reactive Power Compensation Schemes for Air-Core Transformer in ELV-type DC Accelerators	simulation, electron, synchrotron, vacuum	688
	M. Borage, S. Kotaiah, S. R. Tiwari RRCAT, Indore (M. P.)
	The ELV-type electron accelerators are widely used in industrial and research applications. The scheme for generating high voltage in these machines is based on air-core transformer, which has large leakage inductance and small magnetizing inductance. To minimize the reactive power loading on the inverter feeding the primary winding, suitable compensation scheme must be employed. Conventional compensation scheme using shunt capacitor and a series inductor however can minimize the reactive power only at one particular loading condition. Also the compensating inductor becomes heavy and bulky. In this paper, the results of studies done to investigate suitability of various compensation networks are presented. Following desirable features are looked for: (1) Near-unity power factor operation under all loading conditions. (2) Nearly load independent output voltage. (3) Minimum additional reactive components. (4) Elimination of compensating inductor. Characteristics of compensation networks are studied and compared using simulation software PSpice wherein with the proposed method, normalized results suitable for comparison are directly obtained.

THPMA067	Stability Analysis of a Klystron-Modulator for PAL XFEL	klystron, electron, linac, free-electron-laser	729
	J.-S. Oh, C. W. Chung, S. D. Jang, S. J. Kwon, Y. G. Son, J.-H. Suh PAL, Pohang, Kyungbuk I. S. Ko, W. Namkung POSTECH, Pohang, Kyungbuk
	The PAL (Pohang Accelerator Laboratory) is persuading to construct a SASE-XFEL facility (PAL XFEL). The stable electron beam is essential for the single-pass free electron laser facility. The beam stability is governed by an accelerating RF field, of which fluctuation is mainly caused by the modulation of klystron voltage pulses. Therefore, it is directly determined by the charging stability of a modulator that uses an inverter charging system. The stable charging power supply can be realized by a stable probing and correct manipulating of a charging signal, a fine control of charging current, low noise environment, etc. This paper shows the detail analysis of the stability dependency of a klystron-modulator on the related parameters.

THPMA070	Characterisation of Amorphous Magnetic Material with Multiple Pulse Excitation	induction, linac, power-supply	732
	A. S. Sharma, S. Acharya, K. V. Nagesh BARC, Mumbai U. Kumar, G. R. Nagabhushana IISC, Bangalore
	An experimental investigation for the understanding of magnetic core saturation behaviour under pulse excitation is presented in this paper. The effect of repetitive shots, after resetting, on the magnetic properties of toroidal amorphous core of size 160/240/25 mm is reported. This study is made using 20kV, 20, and 200ns square pulse source, to realize the various steps which an amorphous core undergoes on saturation as well as corresponding changes in magnetic parameters viz. magnetization force, total flux swing and relative permeability. The most significant effect of pulsing is seen at higher values of operating flux, compared to lower flux regimes. Effects of number of turns and input power level to the core are also shown in this paper. It has been shown that the total energy required to saturate the core in multiple pulses is less if peak input is smaller than that in case of higher peak pulse excitation. Keyword: amorphous core, multiple pulses, effect of turns, pulse excitation