Automation of variable low-energy positron beam experiments

By exploiting the special BIOS interrupt (INT 1CH) of PC in conjunction wit h a compatible high-voltage controller card and menu-driven control program , we report here the automation of variable low-energy posit ron beam exper iments. The beam experiment consists of monitoring the Doppler broadening l ineshape parameters corresponding to the annihilation 511 keV gamma-ray at various positron beam implantation energies. The variation and monitoring o f the sample high voltage, which determines positron beam energy, is carrie d out using a controller add-on card coupled to a 0-30 kV high-voltage unit . The design features of this controller card are discussed. This controlle r card is housed in a PC, which also houses a multichannel analyser (MCA) c ard. The MCA stores the Doppler energy spectrum of the annihilation gamma-r ay. The interactive control program, written in Turbo C, carries out the as signed tasks. The design features of the automation and results are present ed. (C) 2000 Elsevier Science B.V. All rights reserved,