Implanted He retention and release from boronized layers
{sup 3}He has been implanted at an energy of 3 keV into amorphous hydrogenated boron-carbon (a-BC) films deposited by RF sputtering onto single crystal Si substrates. The initial composition of the films was analyzed by nuclear-enhanced backscattering spectrometry to be B{sub 2}C with {approximately}20%H and {approximately}10%O. The areal density of the implanted and retained {sup 3}He was measured in situ by a new ion beam analysis technique using the {sup 3}He ({sup 3}He,pp) three-body nuclear reaction. The He trapping or pumping efficiency at room temperature is only 3.4% for low fluence implants and the a-BC layer saturates with He at a fluence of 5 {times} 10{sup 17} He/cm{sup 2}. At this saturation fluence, only 3.1 {times} 10{sup 15} He/cm{sup 2} is retained in the film. Isochronal annealing of the implanted samples reveals a distributed release of implanted He at {approximately}200{degrees}C which corresponds to a trap activation energy of 1.65 {plus minus} 0.25 eV. {sup 3}He was trapped less efficiently at 250{degrees}C than at room temperature and exhibited a saturated retention of 8.6 {times} 10{sup 14} He/cm{sup 2}. These results indicate that wall pumping should play only a minor role in the interpretation of the Textor He-pump experiment carried out earlier this year. The results also show that the unintentional deposition of a-BC, onto He pumping plates could adversely affect the operation of such devices, and should therefore be avoided.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5222316
- Report Number(s):
- SAND-91-2484C; CONF-920311-9; ON: DE92013983
- Resource Relation:
- Conference: 10. international conference on plasma-surface interactions in controlled fusion devices, Monterey, CA (United States), 30 Mar - 3 Apr 1992
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Ma
FIRST WALL
ION IMPLANTATION
HELIUM 3
PUMPING
BORON
FILMS
PUMPED LIMITERS
SPUTTERING
TOKAMAK DEVICES
CLOSED PLASMA DEVICES
ELEMENTS
EVEN-ODD NUCLEI
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
LIMITERS
NUCLEI
SEMIMETALS
STABLE ISOTOPES
THERMONUCLEAR DEVICES
THERMONUCLEAR REACTOR WALLS
700480* - Fusion Technology- Component Development
Materials Studies- (1992-)