Diffusion of alkali species in porous tungsten substrates used in contact-ionization sources

PDF Version Also Available for Download.

Description

Contact ionization (doped) sources used in current Heavy Ion Fusion (HIF) experiments consist of a porous tungsten substrate doped with an alkali carbonate. During the early stages of the heating cycle (T {approx} 600 C), the carbonate breaks down and releases the alkali atoms that then diffuse through the substrate. At the emitter surface there is a balance between the fast desorption rate of the alkali atoms (mostly as neutrals) and the slower replenishment rate from the substrate by diffusion. Time-resolved measurements of neutral particle evaporation rates at the emitter surface have been used to estimate the effective diffusion coefficient ... continued below

Physical Description

3 pages

Creation Information

Chacon-Golcher, E.; Kwan, J.W. & Morse, E.C. June 1, 2003.

Context

This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this article can be viewed below.

Who

People and organizations associated with either the creation of this article or its content.

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this article. Follow the links below to find similar items on the Digital Library.

Description

Contact ionization (doped) sources used in current Heavy Ion Fusion (HIF) experiments consist of a porous tungsten substrate doped with an alkali carbonate. During the early stages of the heating cycle (T {approx} 600 C), the carbonate breaks down and releases the alkali atoms that then diffuse through the substrate. At the emitter surface there is a balance between the fast desorption rate of the alkali atoms (mostly as neutrals) and the slower replenishment rate from the substrate by diffusion. Time-resolved measurements of neutral particle evaporation rates at the emitter surface have been used to estimate the effective diffusion coefficient (D) that characterizes the migration of alkali species in the substrate. These estimates are consistent with the observed source lifetimes (tens of hrs.) and establish the alkali migration in the bulk as a diffusion-limited process. The measurements suggest that the faster migration rates (D {approx} 10{sup -5}-10{sup -6} cm{sup 2}/s) occur early during the heating cycle when the dominant species are the neutral alkali atoms. At operating temperatures there is a slower migration rate (D {approx} 10{sup -7} cm{sup 2}/s) due to the dominance of ions, which diffuse by a slower surface diffusion process.

Physical Description

3 pages

Notes

INIS; OSTI as DE00815497

Source

  • 2003 Particle Accelerator Conference PAC03, Portland, OR (US), 06/12/2003--06/16/2003

Language

Item Type

Identifier

Unique identifying numbers for this article in the Digital Library or other systems.

  • Report No.: LBNL--52012
  • Report No.: HIFAN 1222
  • Grant Number: AC03-76SF00098
  • Office of Scientific & Technical Information Report Number: 815497
  • Archival Resource Key: ark:/67531/metadc740359

Collections

This article is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this article?

When

Dates and time periods associated with this article.

Creation Date

  • June 1, 2003

Added to The UNT Digital Library

  • Oct. 18, 2015, 6:40 p.m.

Description Last Updated

  • April 4, 2016, 3:06 p.m.

Usage Statistics

When was this article last used?

Yesterday: 0
Past 30 days: 0
Total Uses: 2

Interact With This Article

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

Citations, Rights, Re-Use

Chacon-Golcher, E.; Kwan, J.W. & Morse, E.C. Diffusion of alkali species in porous tungsten substrates used in contact-ionization sources, article, June 1, 2003; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc740359/: accessed December 12, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.