Injection, cooling, and extraction of ions from a very large Paul trap

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" Injection, cooling, and extraction of ions from a very large Paul trap "
A. M. Ghalambor Dezfuli R. Moore

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1113053
Doc. No	:	TLpq193859866
Main Entry	:	A. M. Ghalambor Dezfuli
	:	R. Moore
Title & Author	:	Injection, cooling, and extraction of ions from a very large Paul trap\ A. M. Ghalambor DezfuliR. Moore
College	:	McGill University (Canada)
Date	:	1996
student score	:	1996
Degree	:	Ph.D.
Page No	:	186
Abstract	:	A new system has been developed for in-flight capture of continuous high energy mass separated radioactive ion beams of the ISOLDE type. To test the system, a precision high voltage ion gun based on surface ionization of cesium has also been developed. This gun delivers stable currents to 300 nA at energies to 65 keV with emittances at 50 keV of 1.3 usd\piusd-mm-mrad. The ion collection system is a high-field dc decelerator leading into a very large Paul trap at an elevated potential and employing buffer gas ion cooling. The ring electrode is of internal diameter 120 mm, the end electrodes are separated by 106 mm, and rf amplitudes of up to 10 kV can be applied on the ring. Tests showed that 50% of a 60 keV beam can be injected through the 8 mm hole into a trap at energies of a few tens of eV. Trap performance was analyzed from time-of-flight observations of extracted beam pulses. Extraction included a pulse-down cavity capable of lowering the potential of the extracted ion cloud from 60 kV to zero. Beam pulses of less than 1 usd\mu susd were delivered at energies less than 5 keV to a detector 2 m from the trap with an overall efficiency of about 0.4% of the beam from the ion gun. A thermodynamic model of the ions in the trap, with ion temperatures of 500 K for about usd10\sp4usd ions and of 1000 K for about usd10\sp7usd ions, almost fully accounts for the experimental results, the minor discrepancies between the modeled shape and the observed shape of the detector pulses being attributed to space charge effects in the collected ion clouds. The use of this model to simulate the extracted ion pulses showed the pulses to have a longitudinal emittance of about 5 usd\piusd-eV-usd\mu susd and normalized transverse emittances of about 1 usd\piusd-eVusd\mu s.usd The model also indicates that the extraction system pulled only about 16% of the collected ions out of the trap. Methods are suggested for improving this extraction efficiency and further studies are suggested for improving the incoming ion collection efficiency.
Subject	:	Applied sciences
	:	Electrical engineering
	:	Molecules
	:	Molecules
	:	Pure sciences