| Paper |
Title |
Page |
| MOPP091 |
Upgrade of Input Power Coupling System for the SNS RFQ
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763 |
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- Y. W. Kang, A. V. Aleksandrov, P. E. Gibson, T. W. Hardek, C. Luck, R. C. Peglow, A. V. Vassioutchenko
ORNL, Oak Ridge, Tennessee
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A RF input power coupler system has been developed for upgrade of input coupling to the RFQ in the SNS linac front-end. The design employs two coaxial loop couplers for 402.5 MHz operation. Two couplers are used in parallel to power the accelerating structure with up to 800 kW total peak power at 8% duty cycle. Each coupler loop has a coaxial ceramic window that is connected to each output of a magic-T waveguide hybrid splitter through a coaxial to waveguide transition. The coaxial loop couplers have been designed, manufactured, and high power processed. This paper presents the following: RF and mechanical designs of the couplers and system, procedure and result of high power RF conditioning, and test and operation results of the upgraded system.
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| THPC036 |
Model Based Orbit Correction in a Diagnostics Deficient Region
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3056 |
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- A. P. Shishlo, A. V. Aleksandrov
ORNL, Oak Ridge, Tennessee
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A method is presented for an orbit correction in a region where the number of beam position monitors is much less than the number of possible trajectory distortions points (quads). The method was developed for the Coupled Cavities Linac (CCL) part of the Spallation Neutron Source (SNS) linac. The orbit correction is very important in this region to minimize losses and activation, but the usual orbit correction method did not work here. The new method is based on a usage of a realistic online model. The parameters of the model were defined by multidimensional fitting procedure with a substantial array of measured trajectories in CCL. The procedure of parameters finding, model, and results are discussed.
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| THPP044 |
Experience with the SNS SC Linac
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3461 |
| |
- Y. Zhang, A. V. Aleksandrov, C. K. Allen, I. E. Campisi, S. M. Cousineau, V. V. Danilov, J. Galambos, J. A. Holmes, D.-O. Jeon, S.-H. Kim, T. A. Pelaia, A. P. Shishlo
ORNL, Oak Ridge, Tennessee
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The SNS SC linac (SCL) is designed to deliver 1 GeV, up to 1.56 MW pulsed H- beams for neutron production. Beam commissioning of the SNS accelerator systems completed in June 2006 with the maximum linac output beam energy approximately 952 MeV. In 2007, we successfully tuned the SCL for 1 GeV beams during a test run, and the SNS linac achieved its design energy for the first time. During the linac tune-up, phase scan signature matching, drifting beam measurement as well as linac RF cavity phase scaling was applied. In this paper, we will introduce the experiences with the SCL, and we will also briefly discuss beam parameter measurements.
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| THPP073 |
Performance of the SNS Front End and Warm Linac
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3530 |
| |
- A. V. Aleksandrov, C. K. Allen, S. M. Cousineau, V. V. Danilov, J. Galambos, J. A. Holmes, D.-O. Jeon, T. A. Pelaia, M. A. Plum, A. P. Shishlo, M. P. Stockli, Y. Zhang
ORNL, Oak Ridge, Tennessee
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The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60 Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5 MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006 and beam power is being gradually ramped up toward the design goal. Operational experience with the injector and linac will be presented including chopper performance, longitudinal beam dynamics study, and the results of a beam loss study.
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| THPP074 |
Optimal Design of a High Current MEBT with Chopper
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3533 |
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- A. V. Aleksandrov
ORNL, Oak Ridge, Tennessee
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Many existing and proposed projects require a certain temporal structure imposed on the beam pulse, e.g., creating gaps for low-loss extraction from a circular accelerator. Usually it is achieved using chopper systems. In order to reduce average beam power on the target and simplify kicker requirements chopper system is located in a lower energy part of the accelerator, typically in the medium energy transport line (MEBT) between the RFQ and the linac. Many of the MEBT layouts, proposed and in use, look very much alike and try to achieve a compromise between two opposing requirements of providing strong transverse focusing and sufficiently long empty drifts for the kickers. As a result, both requirements are not fully satisfied leading to space charge induced emittance increase and very challenging technical specifications for the kicker and its power supply. These difficulties quickly increase with the beam current. We propose a different MEBT layout, which does not compromise quality of beam transport and allows space for a kicker with any reasonable parameters. A generic design of a 5.5m long MEBT transporting 100mA with emittance increase of less than 5% is shown as an example.
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| THPP085 |
Status of the SNS Ring Power Ramp Up
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3560 |
| |
- M. A. Plum, A. V. Aleksandrov, C. K. Allen, S. M. Cousineau, V. V. Danilov, J. Galambos, J. A. Holmes, D.-O. Jeon, T. A. Pelaia, A. P. Shishlo, Y. Zhang
ORNL, Oak Ridge, Tennessee
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Beam was first circulated in the SNS ring in January 2006. Since that time we have been working to raise the beam power to the design value of 1.4 MW. In general the power ramp up has been proceeding very well, but several issues have been uncovered. Examples include poor transmission of the waste beams in the injection dump beam line, cross-plane coupling in the ring to target beam transport line, and higher-than-expected peak densities in the ring to target transport. In this paper we will discuss these issues and present an overall status of the ring and the transport beam lines.
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