A. N. Verentchikov, B. N. Kozlov, M. I. Yavor, A. S. Trufanov, D. V. Nikitina
Institute for Analytical Instrumentation
RAS, Saint-Petersburg
To combine a multiple-reflection time-of-flight mass spectrometer
(MR-TOF-MS) with continuous mode ion sources such as those of electrospray
type, it has been proposed to accumulate ions in a trap in the intervals
be-tween rare accelerator pulses. The ion accumulation scheme offered in
the present paper consists of a gas-filled segmental quadrupole with radio-frequency
entrainment and axial emission. The paper presents the necessary calculations
for the ion trap and analysis of processes of ion capture, collisional cooling,
and pulsed emission. Experimental studies of the storage trap have shown
almost complete transformation of a continuous ion beam into a pulsed one
and the possibility of long-time (for up to a few seconds) ion holding. Satisfactory
beam pa-rameters are achieved at sufficient cooling (defined by the dwell
time and pressure in the trap, 5 ms∙mTorr), low gas pressure collisions,
and at a low trap load (below 100 000 charges). The combination of these
two require-ments limits the total beam current at which the ion flux can
be converted into minimum width pulses to 3 nA.