Volume H/sup -/ generation with the SITEX source in the VITEX reflex mode without cesium
The ORNL SITEX (Surface Ionization with Transverse Extraction) Negative ion source utilizes a reflex discharge operating in a 1300-G magnetic field to generate H/sup -/ or D/sup -/ ions on a cesiated converter placed directly behind and adjacent to the 100-V/20-A discharge column. We have recently operated a newly assembled source, without cesium, in the VITEX (Volume Ionization with Transverse Extraction) mode to see how many volume H/sup -/ ions could be produced. The total gas flow during the test was held constant at approx.1.6 torr/L.s/sup -1/. This flow would correspond to an arc-chamber pressure of 10 mtorr for a 500/sup 0/C chamber temperature. In this volume-production mode, the converter was in its usual position; the separation was less than 0.1 mm from arc to converter. Variation of the converter voltage up to -200 V at full output had no appreciable effect on the maximum output current. This is sharp contrast to the SITEX mode, in which the maximum current increases by a factor of about 5 with converter voltage - the optimum value being dependent upon electrode spacing and magnetic field. H/sup -/ beam output of 80 mA, 17.5 keV, and 760 ms has been achieved. This corresponds to 32 mA/cm/sup 2/ (2.5-cm/sup 2/ extraction aperture) and was extracted with 45 mA of electrons giving extracted electron to H/sup -/ ion ratio of 0.6. All extracted electrons were recovered at 2.5 keV on the source electron recovery system and none were accelerated with the beam. Long-pulse operation of I/sub H-/ = 55 mA, I/sub electron R/ = 35 mA, tua = 4 s, V/sub accel/ = 17.5 kV, and j/sub H- = 22 mA/cm/sup 2/ has also achieved. 15 refs., 3 figs.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5918888
- Report Number(s):
- ORNL/TM-9753; ON: DE86007877
- Country of Publication:
- United States
- Language:
- English
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