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simulation

     
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TUZH103 Electron Cloud Experiments, Simulation and Cure electron, feedback, quadrupole, dipole 89
 
  • H. Fukuma
    KEK, Ibaraki
  A large number of electrons called electron clouds have been observed both in positron and hadron accelerators. Possible sources of the electron clouds are photoelectrons generated by synchrotron radiation, electrons produced by beam hitting vacuum components, electrons multiplied by beam induced multipacting, electrons created by ionization of residual gasses and so on. The electron clouds produce various effects such as pressure rise, heat load on a cold chamber wall, beam induced multipacting, betatron tune shifts, coupled bunch instability and beam size blow-up which often limit the performance of the accelerators. Many experimental and theoretical studies on the electron clouds have been carried out and their results have contributed to the improvement of performance of existing accelerators and design of future accelerators. This talk reviews experiments, simulations and cures of the electron cloud effects in positron and hadron accelerators.  
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TUPMA016 Computation of Wakefields and Impedances for the PETRA III Longitudinal Feedback Cavity feedback, impedance, 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.  
 
TUPMA038 Start-up of an FEL Oscillator from Shot Noise electron, radiation, undulator, free-electron-laser 163
 
  • V. Kumar, S. Krishnagopal
    RRCAT, Indore (M. P.)
  • W. M. Fawley
    LBNL, Berkeley, California
  In free-electron laser (FEL) oscillators, as in self-amplified spontaneous emission (SASE) FELs, the build-up of intra-cavity power starts from shot noise resulting from the discreteness of charge in the electron bunch. It is important to do the start-up analysis for the build-up of intracavity power in order to fix the macropulse width from the electron accelerator such that the system reaches saturation. In this paper, we show that one can use the time-dependent oscillator code GINGER [1] to perform this anlysis. we present results of this analysis for the parameters of the Compact Ultrafast TErahertz FEL (CUTE-FEL) [2] being built at RRCAT.

1. W. Fawley, 'A user Manual for GINGER and Its Post-Processor XPLOTGIN}},LBNL-49625-Rev. I' ed., Lawrence Berkley National Laboratory (2004).2. S. Krishnagopal et al., Proceedings of FEL conference (2006) 496.

 
 
TUPMA039 Comparison of Codes for Smith-Purcell FEL electron, free-electron-laser, plasma, laser 166
 
  • V. Kumar
    RRCAT, Indore (M. P.)
  • K.-J. Kim
    ANL, Argonne, Illinois
  • D. Li
    ILT, Suita, Osaka
  Smith-Purcell FELs using low energy electron beam are being seen as attractive option for a compact source of coherent Terahertz ratiation. Recently, Kumar and Kim [1] have performed numerical simulation of Smith-Purcell free-electron lasers (SP-FELs) based on a computer code using Maxwell-Lorent equations. Li et al. [2], and Dounhue et al. [3] have performed calculations using PIC codes. In this paper, we present a comparision of these methods and compare results obtained using different codes.

1. V. Kumar et al., Phys. Rev. E 73, 026501 (2006). 2. D. Li et al., Phys. Rev. ST Accel. Beams 9, 040701 (2006). 3. J. T. Donohue et al., Phys. Rev. ST Accel. Beams 9, 060701 (2006).

 
 
TUPMA042 Beam Parameters of the SCSS Prototype Accelerator Designed by PARMELA and Comparison with Measured Values electron, emittance, gun, cathode 169
 
  • T. Hara, H. Kitamura, T. Shintake, K. Togawa
    RIKEN Spring-8 Harima, Hyogo
  • H. Tanaka
    JASRI/SPring-8, Hyogo-ken
  • T. Tanikawa
    University of Hyogo, Hyogo
  The 250 MeV prototype facility of the SCSS X-FEL project was constructed in the Octorber 2005 and the machine commissioning was started in May 2006. One month later, we have succeeded in confirming the amplification of the synchrotron radiation. The electron beam parameters, such as peak current and emittance, have been designed and estimated using PARMELA. In contrast to other X-FEL projects, the SCSS injector uses a thermionic pulsed electron gun [1]. Compared with RF photocathode guns, the thermionic gun is stable and easy to handle. Its peak current, however, is smaller, and the compression of the electron bunch is necessary at early stage of the low beam energy injector. In this report, we compare the simulation and measured values, such as a bunch length and projected emittance, on the SCSS prototype accelerator. The measured beam parameters, after the bunch compression procedure and emittance degradation due to space charge, show fairly good agreement with the simulation.

[1] K. Togawa, et al., “Emittance Measurement on the CeB6 Electron Gun for the SPring-8 Compact SASE Source”, Proceedings of the 2004 FEL Conference, (2004)351-354, URL: http://www. JACoW.org.

 
 
TUPMA049 Development of an Injector to Generate a Very Short Bunch for a Super Coherent Terahertz Light Source Project gun, cathode, sextupole, emittance 178
 
  • T. Tanaka, K. Akiyama, H. Hama, F. Hinode, K. Kasamsook, M. Kawai, T. Muto, K. Nanbu, M. Yasuda
    Tohoku University, School of Scinece, Sendai
  • N. Kumagai, H. Tanaka
    JASRI/SPring-8, Hyogo-ken
  A project to develop a coherent Terahertz (THz) light source is in progress at Laboratory of Nuclear Science, Tohoku University. The coherent synchrotron light in the THz region is emitted from electron bunches with a very short bunch less than 100 fs (rms) generated by a thermionic RF gun and a sophisticated bunch compressor. As an injector of this ring, we have developed an independently tunable cells (ITC) RF gun and a magnetic bunch compressor. The longitudinal phase space extracted from the ITC-RF gun can be manipulated by feeding RF microwave to cells independently. To generate a short bunch with a significant bunch charge, a magnetic compressor is used downstream from the gun. Two kinds of bunch compressors have been studied. From simulation of an injector, we have got a very short bunch length about 42 fs (rms). A prototype of the gun has been manufactured. Results of low power tests of the gun will be presented.  
 
TUPMA052 Study on Compact DC Electron Gun using Single Crystal Cathode of LaB6 cathode, gun, emittance, electron 181
 
  • K. Kasamsook, K. Akiyama, H. Hama, F. Hinode, M. Kawai, T. Muto, K. Nanbu, T. Tanaka, M. Yasuda
    Tohoku University, School of Scinece, Sendai
  A novel, compact DC gun has been designed and is currently on a test bed at LNS. Applying 50 kV high voltage for the gun, it is expected to supply a high brightness beam of which the beam current of 300 mA and the variable pulse duration from 1 to 5 ?sec. In addition, a floating bias voltage can be applied between the cathode and the wehnelt to manipulate electric field near cathode surface. In order to produce lower emittance beam, the thermionic cathode should have very much higher current density and the size of that should be very small. Consequently we have chosen single crystal LaB6 as the thermionic cathode, which can provide higher current density with good homogeneity electron emission. The design parameters and initial operating experience of the DC gun are discussed. This DC gun will be used for free electron lasers such as backward-wave oscillator, advanced accelerator researches and other experiments. Results of numerical calculations show good distribution of macroparticles in the phase space, which results from optimization of the bias voltage. A normalized rms emittance at the exit of the gun is expected to be less than 1 ? mm mrad.  
 
TUPMA066 Energy Equalization by using S-band and X-band Accelerator Modules linac, positron, klystron, acceleration 205
 
  • K. Yokoyama, T. Kamitani
    KEK, Ibaraki
  To reduce the beam loss and to restrict the expanse of the bunch length of the positron beam from the KEKB injector, the energy spread of ±0.25% or less is required for the beam transport line of the KEKB ring. Generally, the positron beam has a large energy spread because the original bunch length is large and all positrons do not see the same accelerating filed. Thus, an energy compression system which consists of six rectangular magnets and two 2-m S-band accelerating structures is implemented at the end of the linac but it has a demerit that the beam bunch is lengthened. We propose a new method to suppress the energy spread without enlarging the bunch length. This method utilizes the superimposed acceleration of the S-band modules and X-band modules.  
 
TUPMA070 Progress of RFQ Accelerator at Peking University rfq, ion, ion-source, linac 214
 
  • Z. Y. Guo, J.-E. Chen, J. X. Fang, S. L. Gao, J. F. Guo, W. G. Li, Y. R. Lu, S. X. Peng, Z. Z. Song, Z. Wang, X. Q. Yan, J. X. Yu, M. L. Yu, C. Zhang, K. Zhu
    PKU/IHIP, Beijing
  The progress of two RFQ accelerators at Peking University is presented: one is Separated Function RFQ (SFRFQ), which separates the focusing and acceleration of traditional RFQ to get higher acceleration efficiency. The first prototype of the SFRFQ is designed to accelerate O+ from 1MeV to 1.5MeV and used as a postaccelerator for ISR RFQ-1000 (Integral Split Ring) [1]. The other is high current deuteron 201.25MHz RFQ, it will accelerate 50mA D+ beam to 2MeV with a duty cycle of 10%. The design study of SFRFQ and high current Deuteron RFQ accelerator are outlined.  
 
TUPMA097 Characteristics of the Magnetic Channel in the Yoke Hole of K-500 Superconducting Cyclotron cyclotron, ion, extraction, beam-transport 241
 
  • J. Pradhan, R. K. Bhandari, S. Bhattacharya, U. Bhunia, J. Debnath, M. K. Dey, A. Dutta, C. Mallik, Z. A. Naser, S. Paul
    DAE/VECC, Calcutta
  The detail magnetic field measurement of K-500 superconducting cyclotron has been carried out. The last magnetic channel of the extraction system placed in the yoke hole of the cyclotron before external beam line is active, unlike others, which are all passive. This channel comprises a coil and a special shaped iron to produce both quadrupole and dipole field for focussing and radially aligning the different ion species coming out from the cyclotron, with the external beam transport line. The magnetic field inside the channel along with the outside stray field has been measured for different channel currents as well as main magnet excitations. A 3-D model of the full magnet is constructed using magneto- static code RADIA [2] to simulate the yoke field. This paper reports the comparative study of measured and calculated field and studies the trajectories for the representative ions through the stray field calculated from the model. The later being used to locate the starting point (or matching point) for the external beam transport line  
 
TUPMA108 Benchmarking of Multiparticle Phase Scan and Acceptance Scan Techniques for the SNS DTL linac, target, beam-losses, space-charge 253
 
  • D.-O. Jeon
    ORNL, Oak Ridge, Tennessee
  For a high intensity linac such as SNS Drift Tube Linac, it matters to accurately determine the rf set-point of the tank rf field to minimize beam mismatch and potential beam loss. Two techniques were benchmarked which are multiparticle phase scan and acceptance scan techniques. Excellent agreement was obtained between the set-points obtained from the two techniques. The analysis of both techniques are based on multiparticle tracking using the Parmila code.

*SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

 
 
TUPMA115 Simulations of Non-uniform High Density Electronegative Plasma for Optimization of H- ions and their Extraction plasma, ion, electron, ion-source 265
 
  • A . Kumar, S. Kotaiah
    RRCAT, Indore (M. P.)
  • V. K. Senecha
    KEK, Ibaraki
  Numerical simulations of radio frequency multi-cusp volume type H- ion source have been performed under non-uniform electronegative plasma equilibrium conditions in order to understand the physics of formation of various ion species (H+, H-, e- etc.) and for optimization of H- ion formation and extraction. Coupled momentum balance equations along with continuity equations were solved in a cylindrical geometry to obtain the density profile of various ion species. The relevant cross-section data available in the literature as a function of temperature has been used in the computation. The hydrodynamic model of plasma in equilibrium with background neutral gas has been used. Low degree of ionization ( ~1%) has been assumed. The collision less sheath formation, penetration of electric and magnetic field and power requirement to sustain the plasma has been worked out numerically. An effort has been made to give a self-consistent numerical scheme for the solution of inductively coupled plasma (ICP) in equilibrium, and the results obtained have been presented  
 
WEYMA02 India-based Neutrino Observatory - Present Status site, electron, target, controls 290
 
  • V. M. Datar
    BARC, Mumbai
  The current status of the India based Neutrino Observatory (INO) project is summarized. The two major physics goals are (a) unambiguous demonstration of neutrino oscillation and a more precise measurement of the associated neutrino parameters and (b) to search for matter effects in neutrino oscillation, using the charge identification capability of the magnetized iron calorimeter, which would help determine the signs of one pair of mass differences. The status of the 1 m3 prototype iron calorimetric detector, the design of the 50 kton magnet, the experience with resistive plate chambers used for tracking the charged particles produced in neutrino-iron interactions and the planned electronics and data acquisition system will be presented.  
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WEC3MA01 Experimental Verification of Halo Formation Mechanism of the SNS Front End optics, emittance, linac, beam-losses 333
 
  • D.-O. Jeon
    ORNL, Oak Ridge, Tennessee
  A new halo formation mechanism predicted by the simulation study was confirmed through a series of emittance measurement during the SNS Linac commissioning. The rms emittance and beam tail were greatly suppressed by the cure of transverse optics change. Detailed analisys and comparison of emittance measurement and simulation are presented here.

*SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

 
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WEPMA030 The Bunch Lengthening due to Electron Cloud in Positron Storage Ring electron, positron, storage-ring, damping 366
 
  • Y. D. Liu
    IHEP Beijing, Beijing
  The electron cloud generates not only the transverse wake field but also the longitudinal wake field. The mechanism of the bunch lengthening due to longitudinal wake produced by the electron cloud in the positron storage ring is analyzed. The longitudinal field, which depends on the density of the electron cloud in the storage ring, arises from the accumulation of the electrons near to the center of the bunch during the bunch passage. Based on the longitudinal wake field, tracking method is used to simulate variation of the bunch longitudinal profile in different electron cloud density. According to simulation, the longitudinal action on the bunch from electron cloud is the similar as the potential-well distortion to shift the bunch distribution and give a rise to the bunch deformation. The result has been used to the simulation for BEPCII.  
 
WEPMA039 Effect of Magnetic Field Coupling On INDUS-2 Quadrupole Magnets quadrupole, coupling, dipole, multipole 378
 
  • G. Sinha, A. Kumar, A. Mishra, G. Singh
    RRCAT, Indore (M. P.)
  The distances between the magnets in the Indus-2, are small and as a result, the magnetic field of one magnet may affect the fields of the adjacent magnets. Therefore, it is important to find out the effect of mutual coupling between magnets in the actual condition in the ring and the ways to overcome this problem. In this paper, we will discuss how the field quality of Quadrupole magnets (QPM) in the ring is affected when accompanied by various corrector dipole magnets (CDM)(vertical and horizontal) and sextupole magnets (SPM). Variation of integrated quadrupole strength in presence of CDM is measured at various field excitations and also by varying the distance between the magnets using a rotating coil. Experimental results are compared with the results obtained from 3D simulations. Possibilities of studying the interference effect by scanning the field by a Hall probe, is explored. Dependence of field interference on the distance between magnets, pole gap and the steel length are studied. Effects of the adjacent magnets on the higher order multipole of QPM are also examined.  
 
WEPMA045 Study of Space Charge Compensation In LEBT space-charge, proton, quadrupole, rfq 384
 
  • S. C.L. Srivastava, T. Basak, R. Pande, S. Roy, P. Singh, V. L.SR. sista
    BARC, Mumbai
  A 20 MeV, 30 mA CW proton accelerator is being built in BARC which consists of 50 keV ECR ion-source, LEBT, 3 MeV RFQ, MEBT and 20 MeV DTL. In designing low energy beam transport (LEBT) line, which matches the beam from ion-source to RFQ, the expansion of the proton beam is a severe problem. As the energy of the beam is only 50 keV, coulomb repulsion is enormous and for minimization of this repulsion, space charge compensation is done. In this process, a gas is introduced in the beam pipe, which gets ionized by the beam. The produced electrons are trapped in the beam potential and reduce the repulsive space charge forces. To simulate the beam dynamics part, a PIC code is written, which allows beam of different distributions like KV, Parabolic, and Waterbag. This is an electrostatic code, which can also take care of external magnetic fields. A Monte Carlo collision scheme is being implemented for the ionization of the background gas. In this paper, we are presenting the simulation of space charge compensation of the 30 mA proton beam at 50 keV.

e-mail: shashics@barc.gov.in

 
 
WEPMA112 Thermal Simulations of a Photocathode R. F. Gun gun, vacuum, laser, electron 482
 
  • B. Biswas, S. Krishnagopal, A. Kumar, S. Lal, K. K. Pant
    RRCAT, Indore (M. P.)
  We are developing a photocathode linac, which uses a 2856 MHz r.f. gun, with a copper cathode driven by a 102 MHz, 266 nm laser at inclined incidence. The laser photocathode r.f. gun is a 1.6 cell BNL/SLAC/UCLA type III r.f. gun. In this paper we present the dynamic thermal cooling simulations to calculate the structural deformations and consequent frequency drift of the gun. We have done a complete r.f.-thermal-structural-r.f finite-element analysis (FEA) of the gun in that order, using ANSYS/MULTIPHYSICS. We find that with the present coolant channel design the gun can operate at up to 2 Hz without any significant change in resonant frequency and field balance.  
 
WEPMA120 Development of the Digital RF Control System for the PEFP Proton Accelerator feedback, controls, proton, beam-loading 488
 
  • H. S. Kim, Y.-S. Cho, I.-S. Hong, H.-J. Kwon, K. T. Seol, Y.-G. Song
    KAERI, Daejon
  The low level RF system is under development for the PEFP Proton Accelerator. The RF amplitude and phase stability requirements of the LLRF system are ±1% and ±1°, 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. The control logic is implemented in the Xilinx FPGA by using VHDL coding and the application program based on the VxWorks and VME platform is also developed. In this paper, the detailed design study and the test results of the prototype LLRF system are presented.  
 
WEPMA123 Comparative Analysis of Blade Tuner Optimization Options for the ILC superconducting-RF, vacuum, electron 494
 
  • C. Pagani, N. Panzeri
    INFN/LASA, Segrate (MI)
  Following the successful experience of the blade tuner concept for superconducting cavities, a full parametric analysis has been performed for ILC cost optimization. Different design details have been reconsidered and optimized on the basis of their impact on the ILC requirements and on production costs. Two different designs have been then developed for two options of fabrication material: titanium or stainless steel. The realization of two prototypes, one for each type, has been recently launched for the designs qualification and comparison. In this paper we discuss the optimization rationales and the expected differences in cost and tuner integration and performances. Cold tests on cavities will be at the basis of the final choice for the ILC.  
 
WEPMA135 Mechanical Analysis and Design of the PEFP Low Beta Cavity controls, superconducting-RF, linac, radiation 506
 
  • S. An, Y.-S. Cho, B. H. Choi
    KAERI, Daejon
  Proton Engineering Frontier Project (PEFP) Linac employs the superconducting RF cavity of β=0.42 to accelerate the proton beam with repetition rate of 60 Hz. In order to control the Lorentz force detuning effect, a stiffening structure with double rings and cones is designed for PEFP low beta cavities. This stiffening structure can reduce Lorentz force detuning coefficient to be lower than 1 Hz/(MV/m)2. The cavity’s mechanical modes are calculated by using ANSYS 2-D model and 3-D model. The calculation results demonstrate that PEFP Low Beta Cavity has no dangerous mechanical modes for 60 Hz pulse repetition. The mechanical stability of the SRF cavity is analyzed under the atmosphere pressure after being pumped down and under the helium liquid pressure after being cooled down.

*This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government.

 
 
WEPMA137 Design and Simulation of Multibeam Klystron Cavity klystron, coupling, linac, vacuum 509
 
  • A. K. Tiwari, R. K. Arora, P. R. Hannurkar
    RRCAT, Indore (M. P.)
  The klystron amplifier is capable of providing maximum power per unit length. A number of klystrons may be paralleled to get more power output and increased redundancy but phase matching at output remains a troublesome part of any such arrangement. Multibeam klystron provides a solution where all the beams are accelerated through a common voltage and interaction takes place in a common structure namely multibeam cavity so the problem of phase matching no longer exists. The advantage of MBK is low perveance for individual beams and hence higher efficiency. The design and simulation of a multibeam klystron cavity with four beams is presented using electromagnetic code Microwave Studio. R/Q at frequency 350MHz is optimized. The cavity simulated is to be used in 350 MHz, 250 kW CW klystron. This klystron will be used for 100 MeV proton Linac for Spallation Neutron source (SNS). Important Simulation results are described.  
 
WEPMA140 Development of C-band Multi Beam Sub-booster Klystron klystron, electron, gun, cathode 514
 
  • M. Yoshida, S. Fukuda
    KEK, Ibaraki
  • V. E. Teryaev
    BINP SB RAS, Novosibirsk
  A C-band small multi beam klystron (MBK) has been under development. It is designed for the sub-booster klystron which is required to drive multiple 50 MW C-band klystrons for the SuperKEKB injector upgrade plan. The designed output power is over 100 kW in case of the applied voltage of 25 kV which is suitable for the existing pulse modulator for the S-band sub-booster klystron. At this operating condition, the designed micro-perveances of the total and the each beamlet are 2.0 and 0.25 respectively. The design overview will be presented.  
 
WEPMA143 High-Power, Low-Loss, Radial Rf Power Dividers/Combiners impedance, insertion, coupling, 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.  
 
WEPMA145 Development of A 35 Kw Power Amplifier At 350 Mhz For RFQ Accelerator Based Neutron Generator power-supply, controls, rfq, cathode 526
 
  • M. M. Pande, V. K. Handu, N. R. Patel, V. Rao, A. Soni
    BARC, Mumbai
  • K. R. Shinde
    New Affiliation Request Pending, -TBS-
  A Radio Frequency Quadrupole (RFQ) based 14 MeV Neutron generator is being developed at BARC, as a part of its ADSS program. It is estimated that RF power of about 70 KW is required in RFQ to accelerate 1mA deuterium beam up to 400 KeV. Hence two RF systems, feeding power of about 35 KW at each of the two ports of the accelerator, are being developed. Each RF system employs a 100 W solid state driver, 1500 W intermediate power amplifier (IPA) using EIMAC 8938, and a high power amplifier (HPA) using TH571B. Solid state driver has been tested to 100 W. The IPA has been tested to 100 W in grounded grid configuration and with half wavelength strip line output circuit. The HPA cavity with tube is installed and being analyzed at low power. The 6 1/8 inch, 50 Ω coaxial transmission line has been simulated in Microwave Studio for analyzing RF parameters. The anode power supply (12KV/10 Amp) of HPA has been tested and installed. A spark gap based crowbar circuit for anode is under construction. For HPA the thyristor based safeguard circuit for screen grid, a ramping filament control circuit (0 to 8 Volts in 5 minutes) and an overall control-interlock system has also been developed.  
 
THYMA05 Low-level RF Control System Design and Architecture feedback, controls, klystron, linac 559
 
  • L. R. Doolittle
    LBNL, Berkeley, California
  Low-level RF (LLRF) control hardware and its embedded programming plays a pivotal role in the performance of an accelerator. Modern designs implement most of the signal processing in the digital domain. This reduces the size and cost of the hardware, but places the burden of proper operation on the programming. FPGAs (field programmable gate arrays) and communications-grade ADCs and DACs enable sub-microsecond group delay for the LLRF controller feedback signal. Ancient concepts of the virtue of simplicity are easy to apply to the hardware, but more of a challenge in the context of programming. Digital signal processing, combined with dedicated hardware, can control and maintain cavity phase (relative to an absolute reference) unaffected by drift or 1/f noise of any long cables or active components. Developing and testing that programming is a very real challenge. This paper discusses approaches and techniques to make LLRF systems meet their goals in upcoming accelerators.  
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THC2MA03 Design of L-band Superconducting Cavity for the Energy Recovery Linacs damping, quadrupole, dipole, linac 570
 
  • K. Umemori, T. Furuya, S. Sakanaka, T. Suwada, T. Takahashi
    KEK, Ibaraki
  • H. Sakai, K. Shinoe
    ISSP/SRL, Chiba
  • M. Sawamura
    JAEA/ERL, Ibaraki
  The ERL project in Japan has been started with the cooperation of?KEK, JAEA, ISSP and other SR institutes. For the ERL, superconducting cavities are key components to achieve high energy, high current and low-emittance electron beams. One challenging task, required for the cavity, is a strong damping of the higher-order-modes (HOMs), since they could cause the beam-breakup instabilities and the significant heat load on the cryomodule. We are proceeding with the cavity design, which is optimized for ERLs, with concentrating our attention on HOM damping. A large diameter beam-pipe with microwave absorber is adopted as HOM damping scheme. It can extract the HOM power effectively. We have also investigated optimization of the cavity shape for further suppression of the HOMs. In this report, our cavity design and its HOM characteristics are presented.  
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THPMA033 Digital Power Supply Development at the PLS power-supply, controls, booster, feedback 674
 
  • K. M. Ha, J. H. Kim
    PAL, Pohang, Kyungbuk
  Digital power supply controller using the Digital Signal Processor (DSP) and Field Programmable Gate Array (FPGA) has been developed over the year at the Pohang Light Source (PLS). Recently, full digital power supply controller has been completed and tested. A new digital controller is designed as 3U euro-standard size and provides overall performance of the power supplies stability better than 5 ppm short-term stability (< 1 min) and 25 ppm long-term stability (< 12 hours). The digital controller made use of the digital PID current controller with one-pole digital filter and feed-forward voltage ripple compensation control algorithms. By implementation of the digital controller, it is capable of high step resolution (150 ps) Digital Pulse Width Modulation (DPWM) for FET or IGBT switch drivers and high resolution (18-bit, 400 kSPS) analog to digital converter (ADC) for current and voltage signal measurements. In this paper the hardware and software structure of the developed digital controller and experimental results of digital power supply are described.

Pohang Accelerator Laboratory, Pohang, 790-784, Korea* This works supported by the Ministry of Science and Technology, Korea.

 
 
THPMA046 Study and Comparison of Reactive Power Compensation Schemes for Air-Core Transformer in ELV-type DC Accelerators electron, synchrotron, vacuum, impedance 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.  
 
THPMA061 Numerical study of field errors due to mechanical tolerances in superconducting miniundulators undulator, linac, microtron, synchrotron 711
 
  • C. Diao, H. O. Moser
    SSLS, Singapore
  Based on a wire model, analytical formulae are derived to describe the spatial distribution of the magnetic field as determined by the parameters of the undulator including positional and orientational errors. Semi-analytical numerical simulations are performed to estimate the tolerance of the errors required for a satisfactory function of the supramini, including the effects of systematic errors (pitch, yaw and roll errors) and random errors of the wire position. The effects of these errors on the quality of the field are then graphically analyzed to show the RMS spread of the functions.  
 
THPMA071 Study of Insulation Coordination in the Presence of Multiple Dielectric Materials pulsed-power, accumulation 735
 
  • S. Mitra, D. P. Chakravarthy, K. V. Nagesh, D. D. Praveen Kumar, A. K. Ray, A. S. Sharma
    BARC, Mumbai
  Use of various dielectric materials for insulation is inevitable in high voltage systems. Choosing a particular insulating material (solid, liquid, and gas) depends on various factors like the nature of the system, insulation level required, dielectric strength and thermal & mechanical stress handling capability of the material. Besides the surface break down strength of two material interfaces plays important role in the high voltage design considerations of the system. This paper critically analyses the field stress in high voltage points in presence of multiple dielectric media, in particular on the existing system of Kilo Ampere Linear Injector (KALI – 5000) system. In this paper, local field enhancement phenomenon due to presence of different solid and liquid dielectrics is evaluated. Mathematical derivations of the percentage increment of field, at the critical point, due to presence of hybrid dielectric materials, are calculated for planar, spherical and cylindrical geometry of the high voltage elements. 2-D simulations of the same to support the mathematical calculations are done using MAXWELL SV software.  
 
THPMA073 Artificial Neural Network Calculates Backward Wave Oscillator Parameters Reliably For Pulsed Accelerators electron, plasma, controls, radiation 738
 
  • A. Gokhale
    Terna Collage of Engineering, Navi Mumbai
  • B. P. Dubey
    Bhabha Atomic Research Center, Computer Division, Mumbai
  • A. S. Sharma
    BARC, Mumbai
  A method of quickly and accurately getting the dispersion curves for a slow wave structure filled with plasma is investigated. A universal dispersion equation is derived by utilizing the field theory and expressing the slow wave structure's profile in a finite Fourier series. In principle simulation program takes nearly 6 to 8 hours to generate a single result. A trained Artificial Neural Network, used in this study, calculates the BWO dispersion curve in a fraction of a second accurately and reliably.  
 
THPMA123 Analysis and Evaluation of Gamma and Neutron Dosimetry from 48 MeV 7Li on Natural Cu and its Dose Simulation with MCNP radiation, target, ion, heavy-ion 815
 
  • R. G. Sonkawade, P. K. Kumar, S. P. Lochab, B. S. Singh
    IUAC, New Delhi
  • R. V. Kolekar
    Bhabha Atomic Research Centre, Mumbai
  Neutron and gamma angular radiation dose was measured from 48MeV, 7Li ion beam incident on natural thick copper target. Experiment is simulated keeping in view the health physics importance for monitoring the radiation environment in the charged particle accelerator. The neutron dose observed in the forward direction is slightly more compared to the lateral direction. Fast neutron dose was observed by using the 1mm polyethylene radiator in front of the CR-39 detectors and the thermal neutrons were observed using the Lithium Borate radiator. Neutron Spectra is observed using the BC501, with the Time of Flight experimental arrangement. The gamma dosimetry is done using the TLD and the active survey meters, gamma energy of the same reaction is also monitored in the same setup with the HPGe-detector. From the observed gamma spectrum, and the PACE calculation, the possible reactions were identified and correlated with the observed spectrum and the dose results. The neutron and gamma angular dose distribution observed will be discussed, as well an attempt is being made to simulate the same with MCNP and PACE simulation codes.  
 
THPMA130 Introduction of EPICS in VEC & SCC Control Systems controls, power-supply, monitoring, cryogenics 827
 
  • T. Bhattacharjee, S. Bandyopadhyay, R. B. Bhole, Chaddha, N. Chaddha, A. De, Kundu, K. C. Kundu, J. Misra, S. Pal, A. Roy, B. Sarkar
    DAE/VECC, Calcutta
  As a part of computerization of the VEC and SCC Control System, using a standard open-source software tool for designing distributed control system named as EPICS (Experimental Physics and Industrial Control System), several IOCs' (I/O controller) have been developed to control and monitor the Main Magnet Power Supply (MPS), Beam line MPS, Deflector PS, Beam line instruments and LCW (Low Conductivity Water) system. The device layer of IOC, responsible for communication with MPS distributed among several multi-drop networks (RS485) ensures reliable and fast response while setting several MPS simultaneously. Process parameters e.g. water level, temperature and conductivity in different subsystems are measured using standard industrial sensors. An IOC has been developed for acquiring process data form sensors using Modbus-TCP based distributed DAQ modules on Windows platform. An IOC is being developed for affecting the necessary control for conditioning of the electrostatic deflector with facility for supervisory intervention. Application of EPICS in sub-systems will lead towards a unified distributed control architecture for auto beam tunning of the machines.