R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, R. P. Doerner, G. De Temmerman, M.J. Baldwin, D. Nishijima Center for Energy Research, University of California at San Diego, USA K. Schmid Max Planck Institut für Plasmaphysik, Garching, Germany A review of the database from controlled codeposition studies Motivation: Trying to make sense of it all Research performed as part of US-EU collaboration on ITER materials

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, 2008 Review: Codeposition of deuterium with carbon Typical values of deuterium codeposition with carbon are in the range of D/C ~ The level of retention decreases slowly for codeposits created above 300°C.

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, 2008 Review: Codeposition of deuterium with carbon Values from tokamak codeposits, although archeological, are consistent with controlled studies database. JET flakes and codeposits (A. Peacock, FED 2000) JT60U dome and inner divertor deposits (Y. Hirohata, JNM 2007 ) TFTR bumper limiter (W. Wampler, J.Vac. Sci. A 1988)

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, 2008 Review: Codeposition of deuterium with beryllium Be codeposition data by Mayer (from ion beam exp.) was contaminated with oxygen and carbon (~15%). Be codeposition data by Causey and Baldwin subsequently showed no systematic dependence with oxygen content, layers also had little carbon content.

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, PISCES-B new Be codeposition data What variables determine the retention in Be codeposited layers ? Large range of possible D/Be values ( ) Some trends can be identified: D/Be decreases with temperature and with deposition rate D/Be increases with particle energy New unpublished data by G. De Temmerman

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, Systematically vary codeposition parameters Suppose the parameters are decoupled: no interdependence From the previous graph: Examine each series of data for which only one parameter is varied, everything else being constant, to determine the dependence of the D/Be ratio on this parameter T: temperature, r d : deposition rate, E n : energy of the incident particles (reflected neutrals from the target), C: constant

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, Influence of the individual parameters Deposition rate Average energy of the incident particles Temperature

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, Parametric dependence of D/Be Empirical equation: Reproduces the influence of the independent parameters on the retention Incident particle energy determines implantation depth Activation energy for desorption from plasma exposed Be ~1800K (R. Doerner FED (2000)183), similar to temperature scaling Dependence on deposition rate is yet to be explained Validity of the equation ?? Fit of De Temmerman data to empirical equation

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, Comparison with literature data Good agreement between literature data from various plasma based devices (not ion beam data) and parametric equation Apparent discrepancies between the different data can be explained by the different experimental conditions, to which the retention is sensitive Good basis for prediction of retention in ITER Markin, J. Nucl. Mater (2000)1094.

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, 2008 Review: Codeposition of deuterium with tungsten Mayer could not detect D in the W codeposits created, his limit of detection was D/W ~ 0.02 (very low deposition rate, kV energy, ion beam) Data by Kawasaki observed blisters in codeposited layers (low deposition rate ~0.001 nm/s, kV energy, D plasma) Data by Doerner (moderate deposition rate ~0.02 nm/s, 100 eV D/Ar plasma)

R. Doerner, ITPA SOL/DIV meeting, Avila, Jan. 7-10, Conclusions Large scatter in deuterium retention levels reported in literature of Be codeposits can be explained by examining the codeposit formation conditions An empirical formula has been developed that can reproduce the D/Be retention levels reported in the literature from various plasma devices ITER must begin to define the operating conditions expected in regions likely to experience codeposition Estimates of the tritium accumulation rate in ITER may become more defensible W codeposition database (although sparse) seems to agree with general trends (decreasing D/W with increasing temperature and decreasing D/W with decreasing incident energy) developed to explain Be codeposition database – subject of ongoing work Note: D/C level increases with decreasing incident energy and temperature dependence exhibits a plateau before decreasing with increasing temperature