1 / 25

Target Material Characterization Apparatus Measurement Technique

Target Material Characterization Apparatus and Measurement Techniques Measurements of Diffusive, Effusive and Electrochemical transport Motivation.

tamara-green
Download Presentation

Target Material Characterization Apparatus Measurement Technique

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Target Material Characterization Apparatusand Measurement TechniquesMeasurements of Diffusive, Effusive and Electrochemical transportMotivation • Direct measurements of the chemical interactions between the RIB species and target / ion source - fundamental limitation of the traditional ISOL technique - isolating the critical phenomena • Provide a matrix for initial investigations into the feasibility of developing new beams: D and ta must be within a reasonable range before investing time and resources • Provide a matrix for direct investigation of new-concept techniques such as electrochemical mass transport and other methods

  2. Target Material Characterization ApparatusMeasurement Technique • Introduce the stable analogue of the RIB species under investigation either as a gas or vapor into sample volume exposed to hot membrane. • Measure the time profile of the permeation and fit to solutions of Fick’s second law determining D ( D>10-9 cm2/s ) • Replace solid membrane with tube long, thin capillary tube with dimensions chosen so that Dcap>>Dsolid. Repeat diffusion measurements extracting ta from flow equations such as the Clausing relation

  3. Target Material Characterization ApparatusMeasurement Technique (con’t) • The permeation constant K=bD can also be measured from the saturation flow-rate. This allows determination of the solubility of the sample gas as a function of sample pressure. • This simplified configuration allows direct measurement of new techniques of mass transport such as: bulk or surface electrochemical (electrolytic) transport, electrochemical suppression (pumping) of unwanted isobars or vapors and the effects of physical or chemical carrier vapors.

  4. Determination of D from the measured time profile - solution to Fick’s second law

  5. Measurements of the diffusion coefficient:fitting the solution to the measured time profile Diffusion of 16O in ZrO2/Y2O3 (xYO=0.1) T=832 C Flow rate (arb. units) Time (min)

  6. T=915 C

  7. Measurement of mean surface adsorption timesta • Replace diffusive membrane with a long narrow capillary channel composed of the target or ion source material under investigation • Select channel dimensions to such that Dtube>> Dbulk and l>>r • Verify geometry using by flowing a mass range of the noble gases • Rapidly fill one side of capillary channel with a sample gas or vapor while monitoring RGA response • Mean surface adsorption times can be related to an effective diffusion coefficient, for example, in the molecular flow range:

  8. Example of surface adsorption time measurement Capillary time f=100 mm l=1 cm for O2 at 1000 C Measured delay time (min) Mean adsorption time (ms)

  9. A tool to investigate new methods of mass transport • Once the material has been characterized in terms of D and ta: the effect of alternative mass transport techniques can be investigated. • For example, the above measurements could be repeated with an electric field applied across the membrane and electrochemical transport investigated. An effective D could then be measured. • To investigate electrochemical surface migration, a potential could be set up along a capillary tube by passing a current through it.

  10. Ionic transport under an electrochemical potential gradient

  11. Conclusions • We have shown that the diffusive measurement technique gives reasonably accurate measurements of D for 16O and 18O in ZrO2/ Y2O3 (x=0.1) over a 400 C temperature range. • The successful diffusion measurements suggest determination of characteristic surface - particle adsorption times should also be readily achieved. • The electrical potential developed across the sample material shows the correct dependence on PO2 as predicted by the Nernst equation. • Repeating the 16O and 18O diffusion measurements with an external electrical potential across the material resulted in a ~103 mass transport enhancement over thermal pure diffusion. • Initial results of the F investigation (one experimental run) suggest fast electrochemical transport of F through ZrO2 / Y2O3. Data suggests Deff > 10-7 cm2/s when an electric field of ~3 V/mm is applied at 1005 C.

  12. Electrochemical transport through YSZ Conclusions • The electrical potential measured across the sample material showed the correct PO2 dependence as predicted by the Nernst equation • Repeating the 16O and 18O measurements with an external electrical potential across the materials resulted in an ~103 flow enhancement over thermal diffusion. The enhancement was increasing with increasing temperature. • Initial results of the F investigation (one experimental run) suggest fast electrochemical transport of F through ZrO2 / Y2O3 (x=0.1). Data suggests Deff> 10-7 cm2/s when an electric field of ~3 V/mm is applied at 1005 C

More Related