A detailed study on this peak using the DSS spectrum was carried out in ROBIN RF Operated Beam source in India for Negative Ion research test stand The appearance of the peak is due to hydrogen bearing negative impurity ions ID: 927086
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Slide1
FIP-P3/47
In this work we reported the appearance of the Doppler shift peak in the vicinity of the un shifted peak
.
A detailed study on this peak using the DSS spectrum was carried out in ROBIN (RF Operated Beam source in India for Negative Ion research) test stand.
The appearance of the peak is due to hydrogen bearing negative impurity ions
T
he formation of OH- ion an ion-molecule interaction of H
-
and H
2
0 seem to be most probable formation mechanism.
Estimates of impurity content have been made using intensity ratio of fast hydrogen peak and hydrogen peak originating from the negative ion impurity.
The extracted current of hydrogen neutrals originating from these impurities was typically about 3% of the total current from the main species :j°(H
+
) + j°(H
-
) + j°(H).
To obtain this value, the beam fractions for the species originated from the dissociation of OH- ion and also extracted H- ion are estimated.
Balmer
-alpha excitation cross-section at low energies (< 2
keV
) were reviewed and recommended from Phelps et al are used.
The species fractions due to impurity showed a dependency on the source pressure and input RF power and hence influence the H- species. It is concluded that a systematic study on the behaviour of this impurity is required for controlling and maintenance of the ion source.