| 摘要 |
833,658. Ion sources, particle accelerators. HIGH VOLTAGE ENGINEERING CORPORATION. May 10, 1956 [April 9, 1956], No. 14608/56. Class 39(1). In a negative ion source the negative ions are produced by directing a beam of positive ions into a capillary 2, Fig. 1, into which gas e.g. hydrogen or argon is introduced through a line 16. The negative ions are extracted and accelerated by an electrode 20 and focused by a saddle-field lens produced between electrodes 20 and 4. Electrodes 15, 3 and 20 may act as a lens to produce a cross-over. Electrode 3 serves to repel secondary electrons. The positive ion source 1 consists of an electron emitting spiral filament 8, anode 9, reflector electrode 12 and a focusing coil 11. A gas such as hydrogen or deuterium is introduced through a line 7. A single gas source may be used for both the positive ion source and the capillary. The gas entering the capillary may be cooled or provision may be made for cooling the capillary electrode 15. Electrode 15 may be in two parts, the part facing the positive ion source of molybdenum or beryllium-copper to yield secondary electrons which serve to neutralise the space charge within the positive ion source. The other part of electrode 15 may be of aluminium. Details are given of pumping speeds and relative spacings and dimensions. In pulsed operation both the positive ion source and the gas supply to the capillary may be pulsed. The beam of negative ions produced is diverted through a magnetic analyser to sort out ions of desired momentum. In Fig. 4, the beam of negative ions emerging from source 27 is directed to linear accelerators 28, 33 on belt-type electrostatic accelerators 29, 34, 37 to obtain pulsed beams of variable energy. In the electrostatic accelerators the negative ions may be converted into positive ions by imparting a foil 32. |
