| Paper | Title | Page |
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| THPO022 | Risk Assessment of the Chopper Dipole Kicker Magnets for the MedAustron Facility | 3388 |
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| The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research. Different types of kicker magnets will be used in the facility, including fast beam chopper dipoles: these allow the beam to be switched on and off for routine operational reasons or in case of emergency. One of the main requirements for the beam chopper system is reliability. A criticality analysis, to chart the probability of failure modes against the severity of their consequences of the fault, has been carried out for the chopper dipole system. This “Failure Mode, Effects, and Criticality Analysis” (FMECA), has been used to highlight failure modes with relatively high probability and severity of consequences: conservative ratings of critical components and appropriate redundancy, together with measurements and interlocks, have been used to reduce the probability and criticality of faults. This paper presents the results of the FMECA. | ||
| THPO023 | Ageing of Airix Accelerating Units | 3391 |
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| Airix is a linear accelerator producing a 60ns, 2kA, 19MeV electron beam. It has been operated in a single shot mode by the “Commissariat à l’Energie Atomique et aux Energies Alternatives” (CEA) for flash X-ray radiography purposes for 10 years. Its modular architecture increases the beam energy by quarter of a megavolt step: each cell delivers a 75ns impulsion of 250kV amplitude. Our aim is to guarantee a minimum lifetime for the cells and their pulse driver. To achieve it, we are operating a test-bed at a moderately low repetition rate (a couple of pulses per minute) for tens of thousands of pulses. Afterwards, we will run a series of both non-destructive and destructive analysis to identify the most stressed parts, and, if necessary, the means of increasing the cell lifetime. This paper describes the test-bed: a pair of cells and its driver, and the first results of these ageing tests. | ||
| THPO024 | Development of a Non-Linear Kicker System to Facilitate a New Injection Scheme for the BESSY II Storage Ring | 3394 |
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Top-Up injections without noticeable motion of the stored beam is a challenge. The common method of beam accumulation with a local bump formed by four independent pulsed dipole kicker magnets usually causes beam oscillations. The matching of the four independent kicker systems regarding pulse jitters and shapes is technologically limited. Afterward the beam excitation was reduced more when two kicker magnets on each side of the septum were powered in series by one pulser unit. An even more promising approach is to adopt an alternative injection method deploying a single non-linear kicker magnet with zero Bx,y-field in the center and an off-axis maximum, By, which is horizontally displaced by 10-12 mm. There the injected beam gets kicked and looses half of its transverse momentum. Such a magnet was designed and built as a short in-vacuum magnet with a small vertical gap height. For first beam tests the kicker was placed in the second straight section after the injection point, and the 1.5 μs pulse was designed to deflect the 1.72 GeV beam by 1 mrad. In this paper, the calculations of the magnetic fields, the mechanical design as well as the electrical pulser circuit are described.
*New injection scheme using a pulsed quadrupole magnet in electron storage rings, Kentaro Harada, PHYSICAL REVIEW SPECIAL TOPICS - AB 10, 123501 (2007) |
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| THPO027 | Novel Switching Power Supply utilizing SiC-JFET and its Potential for the Digital Accelerator | 3400 |
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Funding: Japan Science and Technology Agency New induction synchrotron system using an induction cell has been developed and constructed at KEK*. We refer to the accelerator using the induction acceleration system combined with digitally controlled PWM power supply as "Digital Accelerator". In that system, the switching power supply is one of the key devices which realize digital acceleration. The requirements of the switching power supply are high voltage (2 kV) and high repetition frequency (1 MHz). In the present system, we used series connected MOSFETs as the switching device and obtained successful operation. However, series connection gives large complexity and less reliability. Among the various switching devices, a SiC-JFET is the promising candidates that substitute existing silicon MOSFET because it has ultrafast switching speed and voltage blocking capability**. Therefore, we have started to develop new device in collaboration with device manufacturers. Switching and heat removal performance of the newly developed SiC-JFET and a future plan will be presented at the conference. * T. Iwashita et al., “KEK Digital Accelerator”, Phys. Rev. ST-AB, published in 2011. ** K. Ise et al., IEEE Trans. Plasma Sci., pp. 730-736 (2011). |
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| THPO028 | Upgrade Design of the Bump System in the J-PARC 3-GeV RCS | 3403 |
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| The 3-GeV RCS aims at providing at least 300 kW output beam power with the injection beam at 181 MeV. In the second stage, the upgrade of the LINAC beam energy to 400 MeV was funded and started in March 2009. This plan will be completed in 2012. Consequently, the 3-GeV RCS will aim at 1 MW beam power. The injection bump system of the RCS is composed of the shift bump-magnets, the horizontal paint bump-magnets and the vertical paint magnets. | ||
| THPO029 | Microwave Beating Generated by a Dual Beam Accelerator | 3406 |
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Funding: National University of Defense Technology As high power microwave (HPM) technologies gradually matured, the technologies for enhancing the output capacity of HPMs are becoming more and more attractive. However, limited by physics and technology, the approaches for enhancing the output capacity with a single HPM source have encountered difficulties. An alternative method for enhancing the output capacity of HPM sources is the coupling output of dual channel HPM sources. However, if the microwave sources have some coupling with each other, they maybe inter modulate with each other, and the phase-locking of the HPM sources may occur. In order to make sure that the beat waves are generating on the right way, a waveguide diplexer is introduced. Each channel has disjoint pass frequency band, and dual-channel HPM sources are isolated. As the dual-channel electron beams are driven by one accelerator, the HPM sources are expected to have a better match with the accelerator, and even higher microwave power is possible. In the high power experiments, the radiated powers of the beat waves are measured to be about 4.3 GW, 40 ns, the frequencies are about 9.41 GHz and 9.59 GHz. Correspondence: Guolin Li, College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China. Email: nudt-liguolin@hotmail.com |
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| THPO032 | Preliminary Design of an Inductive Adder for CLIC Damping Rings | 3409 |
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| The Compact Linear Collider (CLIC) study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC damping rings will produce ultra-low emittance, with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse power modulators for the damping rings kickers must provide extremely flat, high-voltage pulses: specifications call for a 160 ns duration flattop of 12.5 kV, 250 A, with a combined ripple and droop of not more than ±0.02 %. A solid-state modulator, the inductive adder, is a very promising approach to meeting the demanding specifications; this topology allows the use of both digital and analogue modulation. To effectively use modulation techniques to achieve such low ripple and droop requires an in-depth knowledge of the behaviour of the solid-state switching components and their gate drivers, as well as a good understanding of the overall circuit behaviour. This paper describes the initial design of the inductive adder. | ||
| THPO033 | Calculation of Metallization Resistivity and Thickness for MedAustron Kicker Systems | 3412 |
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| The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research. Different types of kicker magnets will be used in the facility. The kicker magnets are outside machine vacuum: each kicker magnet has a ceramic beam chamber whose inner surface is metallized. The resistivity and thickness of the metallization are chosen such that the induced eddy currents, resulting from the pulsed kicker magnetic field, do not unduly affect the rise/fall times or homogeneity of the magnetic field. A comparison of an analytical calculation and measurement is reported for the effect of metallization of the ceramic beam chamber of an existing kicker system at CERN. For a MedAustron kicker the result of an analytical calculation is compared with predictions from electromagnetic simulations: conclusions concerning the metallization of the ceramic beam chambers, for the MedAustron kicker magnets, are presented. | ||
| THPO034 | Optimization of a Dual One-turn Coils Kicker Magnet System | 3415 |
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| Optimization of a dual one-turn coils configuration for fast kicker magnet system is presented in this report. Emphasis has been made on the: 1) optimization of various possible coils arrangement restricted by the existing available hardware; and 2) synchronization between pulsed currents delivering on the respective upper and lower coils. In the consideration of coils arrangement, good field region is utilized as the guiding parameter while adjusting fixture gap between the coils. As for coil currents timing optimization, fast rise-time and pulse shape preservation are used for practical implementation purpose. Both numerical analysis and experimental data will be presented and discussed. | ||
| THPO035 | Computer Investigation of Efficiency Enhancement in Coaxial Gyrotron Backward Wave Oscillators | 3418 |
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The gyrotron backward wave oscillator (gyro-BWO) is a high frequency (HF) powerful oscillator for cm and mm wavelengths*,**,***.Gyro-oscillators are possible devices for accelerators techniques. For efficiency enhancement in gyro-devices we suggest profiling of guiding magnetic field Hg(z) at longitudinal direction z by special law, namely Hg(z)=Hg0*(1+alfa*(z/L)*f(z/L))**0.5 where Hg0 is amplitude of homogenous guiding magnetic field, alfa is non-homogeneity amplitude, L is waveguide length and function f(z/L))is similarly to the shape (envelope) of longitudinal distribution of HF electrical field E(z) in gyro-device along longitudinal coordinate z. For investigated gyro-BWO f(z/L)=(cos(pi*z/2L))**m, f(0)=1, f(L)=0, L=60cm, m=6 and pi=3.14. We obtained enhancing of gyro-BWO’s efficiency from 11% (homogenous distribution of guiding magnetic field) up to 32% (non-homogenous one) due to profiling of magnetic field under conditions above.
* A.V.Gaponov et al., Izv. VUZov(USSR), Radiofizika 10(9), 10, 1967. ** V.Khoruzhiy et al., Phys. J.of Ukraine 49(2), 126, 2004. *** V.Khoruzhiy et al., Phys. J.of Ukraine 50(11), 1230, 2005. |
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| THPO036 | Final Layout and Test Results of the Disconnect Switch for ALS Storage Ring RF System Power Supply | 3421 |
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Funding: Work supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Science and Engineering Division, of the Department of Energy under contract No. DE-AC02-05CH11231. ALS is the 1.9 GeV third generation synchrotron light source which has been operating since 1993 at Berkeley National Lab. The new RF system, which is now under construction will use two TH 2161B 300kW klystrons to power two single cell RF cavities. In the new design the existing conventional crow-bar klystron protection system will be replaced with the fast disconnect switch. The switch consist 24 high voltage IGBTs connected in series, equipped with static and dynamic balancing systems. The main advantage of using this new technology is faster action and virtually no stress for the components of the high voltage power supply. This paper will show the final lay-out and the test results of the production unit. |
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| THPS048 | Design of Electrostatic Septa and Fast Deflector for MedAustron | 3532 |
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| For the MedAustron facility, under construction in Wiener Neustadt, three electric field deflectors are developed in collaboration with CERN. A fast deflector is used in the Low Energy Beam Transfer line to chop the beam. The chopped beam is swept onto a Faraday cup for measurement purposes and to stop beam being sent towards the synchrotron. Electrostatic septa are used for the multi turn injection of protons and ions as well as for the slow extraction from the synchrotron. Novel design features for MedAustron include an inversed cathode/anode support and high voltage feedthroughs rated at 150 kV. The possibility for a higher voltage will significantly improve the conditioning process of the septa surfaces. This paper describes the requirements of these devices as well as the mechanical design and strategies adopted for their power supplies. | ||