EPAC08 - List of Authors (Plum, M. A.)

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Plum, M. A.

Paper	Title	Page
THPC006	Applications of a BPM-based Technique for Measuring Real Space Distributions in the Spallation Neutron Source Ring and Transport Lines	2984
	S. M. Cousineau, T. A. Pelaia, M. A. Plum ORNL, Oak Ridge, Tennessee
	The SNS accumulator ring and associated transport lines are designed to accumulate and transport up to 1.5·10¹⁴ ppp to a liquid mercury target for neutron spallation. Since commissioning, a dedicated effort has been put forth to characterize the lattice and beam dynamics at low intensity. Toward this goal, a BPM-based technique for measuring real space beam distributions at low beam intensities was developed. Recently, this technique has been used to diagnose and localize a strong source of coupling in the lattice, to verify and troubleshoot complementary diagnostics devices, and to provide data for code benchmarking. Other potential applications of this technique include investigations of single particle dynamics and resonances, studies of injection painting techniques, and possibly measurement of quadrupole power supply errors in the ring. In this paper we present the results of applying this technique to various situations in the SNS ring and transport lines, including the first ORBIT benchmarks of the SNS ring and RTBT. T. Pelaia et al, Nucl. Instr. And Methods, in progress.
THPC015	Computational Beam Dynamics Studies for Improving the Ring Injection and Extraction Systems in SNS	3008
	J. A. Holmes, S. M. Cousineau, M. A. Plum, J. G. Wang ORNL, Oak Ridge, Tennessee
	The ring injection and extraction systems must function as designed in order for the Spallation Neutron Source (SNS) to achieve its specified performance. In commissioning and early operations we have encountered problems that have been traced to these systems. We experienced high beam losses in and around the injection dump, the rectification of which has necessitated significant study and development by a multidisciplinary team. The results include a number of enhancements of existing features and the addition of new elements and diagnostics. The problem in the extraction region stems from tilted beam distributions observed in the ring-to-target beam transport line (RTBT) and on the target, thus complicating the control of the beam-on-target distribution. This indicates the inadvertant introdution of x-y beam coupling somewhere upstream of the RTBT. The present paper describes computational studies, using the ORBIT Code, addressed at the detailed understanding and solution of these problems.
THPP073	Performance of the SNS Front End and Warm Linac	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
	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.
THPP085	Status of the SNS Ring Power Ramp Up	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
	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.
THPP086	Diamond Stripper Foil Experience at SNS and PSR	3563
	R. W. Shaw, Y.-J. Chen, R. L. Coleman, D. M. Gardner, C. Luck, A. G. McDermott, M. A. Plum, L. L. Wilson ORNL, Oak Ridge, Tennessee M. J. Borden, T. Spickermann LANL, Los Alamos, New Mexico C. S. Feigerle University of Tennessee, Knoxville, Tennessee
	The SNS is currently operating at about 15% of the 1.4 MW design power, and the diamond stripper foils developed at ORNL continue to perform well. Several corrugated, nanocrystalline diamond stripping foils have been tested at SNS. Beyond about 300 C of injected charge, significant distortion and darkening of the foils is observed. These foils are currently limited in freestanding area to about 17x25 mm due to stress-induced tears in larger foils; this limit positions the residual silicon wafer mounting handle close enough to the circulating beam that additional losses have been observed. The PSR experience with these diamond foils has been promising, with the interesting observation that both the foil current due to secondary emission of electrons and the thermionic foil current are reduced for diamond foils relative to LANL/KEK foils. For comparable thickness foils, losses due to the Ho yield also appear to be higher for diamond. A recent development in our foil preparation has been a change to nano-seeded nucleation from the earlier microcrystal slurry ultrasonic abrasion technique. This has led to a more reproducible and uniform foil morphology with smaller crystallites.