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Title |
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| MOPP017 |
A Kicker Driver Exploiting Drift Step Recovery Diodes for the International Linear Collider
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589 |
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- F. O. Arntz, M. P.J. Gaudreau, A. Kardo-Sysoev, M. K. Kempkes, A. Krasnykh
Diversified Technologies, Inc., Bedford, Massachusetts
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Diversified Technologies, Inc. (DTI) is developing a driver for a kicker strip-line deflector which inserts and extracts charge bunches to and from the electron and positron damping rings of the International Linear Collider. The kicker driver must drive a 50 Ω terminated TEM deflector blade at 10 kV with 2 ns flat-topped pulses, which according to the ILC pulsing protocol, bursts pulses at a 3 MHz rate within one-millisecond bursts occurring at a 5 Hz rate. The driver must also effectively absorb high-order mode signals emerging from the deflector. In this paper, DTI will describe current progress utilizing a combination of high voltage DSRDs (Drift Step Recovery Diodes) and high voltage MOSFETs. The MOSFET array switch, without the DSRDs, is itself suitable for many accelerator systems with 10 – 100 ns kicker requirements. DTI has designed and demonstrated the key elements of a solid state kicker driver which both meets the ILC requirements, is suitable for a wide range of kicker driver applications. Full scale development and test are exptected to occur in Phase II of this DOE SBIR effort, with a full scale demonstration scheduled in 2009.
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| MOPP065 |
Microwave Transmission Measurement of the Electron Cloud Density in the Positron Ring of PEP-II
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694 |
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- M. T.F. Pivi, A. Krasnykh
SLAC, Menlo Park, California
- J. M. Byrd, S. De Santis, K. G. Sonnad
LBNL, Berkeley, California
- F. Caspers, T. Kroyer, F. Roncarolo
CERN, Geneva
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Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave which is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solenoid magnets to control the electrons.
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| WEPP041 |
High-current Effects in the PEP-II Storage Rings
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2611 |
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- U. Wienands, W. X. Cheng, W. S. Colocho, S. DeBarger, F.-J. Decker, S. Ecklund, A. S. Fisher, D. Kharakh, A. Krasnykh, A. Novokhatski, M. K. Sullivan
SLAC, Menlo Park, California
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High beam currents, 2A(HER) & 3A(LER), in PEP-II has been a challenge for the vacuum system. For the ~1 cm long bunches peak currents reach 50 A. Thus modest impedances can give rise to voltage spikes and discharges. A weakness was uncovered during Run 6: rf seals at the "flex flanges" that join the HER arc dipole and quadrupole chambers became a source of an increasing number of HER beam aborts. Vacuum activity was seen and thermal sensors on these flanges saw temperature spikes. Inspection of the seals found arcing and melting, prompting us to replace all of these seals with an improved design using Inconel instead of GlidCop fingers. We believe the GlidCop fingers do not maintain elasticity and hence can not follow chamber motion due to thermal effects. The Run 7 startup confirmed the success of this repair. However, high bunch current in the LER caused breakdown in a LER kicker. This limited the LER bunch current to about 1 mA. Inspection revealed damage to one of the recently added Macor pins that help support the electrodes. Failure analysis revealed heating of the pin & post-facto modeling shows high fields coming from a combination of HOM impedance and high peak currents.
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