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Title: Spallation Neutron Source SNS Diamond Stripper Foil Development

Abstract

Diamond stripping foils are under development for the SNS. Freestanding, flat 300 to 500 {micro}g/cm{sup 2} foils as large as 17 x 25 mm{sup 2} have been prepared. These nano-textured polycrystalline foils are grown by microwave plasma-assisted chemical vapor deposition in a corrugated format to maintain their flatness. They are mechanically supported on a single edge by a residual portion of their silicon growth substrate; fine foil supporting wires are not required for diamond foils. Six foils were mounted on the SNS foil changer in early 2006 and have performed well in commissioning experiments at reduced operating power. A diamond foil was used during a recent experiment where 15 {micro}C of protons, approximately 64% of the design value, were stored in the ring. A few diamond foils have been tested at LANSCE/PSR, where one foil was in service for a period of five months (820 C of integrated injected charge) before it was replaced. Diamond foils have also been tested in Japan at KEK (640 keV H{sup -}) where their lifetimes slightly surpassed those of evaporated carbon foils, but fell short of those for Sugai's new hybrid boron carbon (HBC) foils.

Authors:
 [1];  [1];  [1];  [2];  [3];  [4];  [4];  [4]
  1. ORNL
  2. University of Tennessee, Knoxville (UTK)
  3. Los Alamos National Laboratory (LANL)
  4. High Energy Accelerator Research Organization, KEK
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
982100
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: Particle Accelerator Conference 07, Albuquerque, NM, USA, 20070625, 20070629
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 43 PARTICLE ACCELERATORS; ACCELERATORS; BEAM STRIPPERS; BORON; CARBON; CHEMICAL VAPOR DEPOSITION; COMMISSIONING; DESIGN; DIAMONDS; NEUTRON SOURCES; PROTONS; SILICON; SPALLATION; diamond stripper foil

Citation Formats

Shaw, Robert W, Plum, Michael A, Wilson, Leslie L, Feigerle, Charles S., Borden, Michael J., Irie, Y., Sugai, I, and Takagi, A. Spallation Neutron Source SNS Diamond Stripper Foil Development. United States: N. p., 2007. Web.
Shaw, Robert W, Plum, Michael A, Wilson, Leslie L, Feigerle, Charles S., Borden, Michael J., Irie, Y., Sugai, I, & Takagi, A. Spallation Neutron Source SNS Diamond Stripper Foil Development. United States.
Shaw, Robert W, Plum, Michael A, Wilson, Leslie L, Feigerle, Charles S., Borden, Michael J., Irie, Y., Sugai, I, and Takagi, A. 2007. "Spallation Neutron Source SNS Diamond Stripper Foil Development". United States. doi:.
@article{osti_982100,
title = {Spallation Neutron Source SNS Diamond Stripper Foil Development},
author = {Shaw, Robert W and Plum, Michael A and Wilson, Leslie L and Feigerle, Charles S. and Borden, Michael J. and Irie, Y. and Sugai, I and Takagi, A},
abstractNote = {Diamond stripping foils are under development for the SNS. Freestanding, flat 300 to 500 {micro}g/cm{sup 2} foils as large as 17 x 25 mm{sup 2} have been prepared. These nano-textured polycrystalline foils are grown by microwave plasma-assisted chemical vapor deposition in a corrugated format to maintain their flatness. They are mechanically supported on a single edge by a residual portion of their silicon growth substrate; fine foil supporting wires are not required for diamond foils. Six foils were mounted on the SNS foil changer in early 2006 and have performed well in commissioning experiments at reduced operating power. A diamond foil was used during a recent experiment where 15 {micro}C of protons, approximately 64% of the design value, were stored in the ring. A few diamond foils have been tested at LANSCE/PSR, where one foil was in service for a period of five months (820 C of integrated injected charge) before it was replaced. Diamond foils have also been tested in Japan at KEK (640 keV H{sup -}) where their lifetimes slightly surpassed those of evaporated carbon foils, but fell short of those for Sugai's new hybrid boron carbon (HBC) foils.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2007,
month = 1
}

Conference:
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  • The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the $H^0$ excited states created during the $H^-$ charge exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming $H^-$ beam, which circled around to strike the foilmore » bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and describe the improvements we have made to mitigate them.« less
  • The Oak Ridge Spallation Neutron Source comprises a 1 GeV, 1.5 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the H{sup 0} excited states created during the H{sup -} charge-exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming H{sup -} beam, which circled aroundmore » to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and describe the improvements we have made to mitigate them.« less
  • High current and severe restrictions on beam losses, below 1 nA/m, in the designed linac for the National Spallation Neutron Source (NSNS) require clean and fast--with the rise time from 2% to 98% less than 2.5 ns to accommodate a 402.5-MHz beam structure--beam chopping in its front end, at the beam energy 2.5 MeV. The R and D program includes both modification of the existing LANSCE coax-plate chopper to reduce parasitic coupling between adjacent plates, and development of new traveling-wave deflecting structures, in particular, based on a meander line. Using analytical methods and three-dimensional time-domain computer simulations the authors studymore » transient effects in such structures to choose an optimal chopper design.« less
  • For the design of the proposed Spallation Neutron Source (SNS), activation analyses are required to determine the radioactive waste streams, on-line material processing requirements remote handling/maintenance requirements, potential site contamination and background radiation levels. For the conceptual design of the SNS, the activation analyses were carried out using the high-energy transport code HETC96 coupled with MCNP to generate the required nuclide production rates for the ORIHET95 isotope generation code. ORIHET95 utilizes a matrix-exponential method to study the buildup and decay of activities for any system for which the nuclide production rates are known. In this paper, details of the developedmore » methodology adopted for the activation analyses in the conceptual design of the SNS are presented along with some typical results of the analyses.« less