Akademik Veri Yönetim Sistemi
ADIM Fizik Günleri–I, Afyonkarahisar, Türkiye, 21 - 22 Mayıs 2010, ss.88, (Özet Bildiri)
The time of flight mass spectrometer (TOFMS) has become
widely used for the structural analysis of organic and inorganic molecules
because of several characteristic advantages. These advantages include the fact
that TOFMS devices can rapidly acquire an entire mass spectrum over wide mass
range. It is especially suitable for measuring mass spectra of pulsed laser
ionization techniques. All ions generated by a short laser pulse can be used
for generating mass signal and this makes TOFMS a high sensetivity mass
detection device. Major advantage is that there is no theoretical upper mass
limit for the TOFMS which is an essential feature for dedection of large
molecules. Besides the advantages mentioned above, the TOFMS is relatively
inexpensive and simple device. The development high order focusing methods has
made TOFMS a special technique working with a significant high resolution.
Mathematically modeling the time of flight of ions in a
TOFMS device is relatively simple since only static electric fields inside the
system is applied. However, modelling of motion of ions inside the ionization
region have been simulated using software called SIMION 8.0 to obtain
statistical result which can be used to evaluat various methods to improve the
performance of TOFMS. The SIMION program has a performance to calculate the
electric field with given dimensions and shapes of the electrodes used in set-up.
The Mathematica 7.0 program has also been used to obtain optimal TOFMS lens
voltages to compose space focusing condition.
We have designed and constructed a homemade two-field TOFMS
system and its ion optics for the mass separation analysis of samples in
connection with a pulsed laser system. This instrument collects positive ions
to produce spectra for each particle in mass spectra. We are interested in the
resolution which can be improved by increasing the acceleration voltage to
minimize the initial energy spread problem in the ionization region. However,
in practice the acceleration voltage can not be increased infinitely.
In the TOFMS experiment, the time of flight signal of the
ions were obtained using a pulsed laser system via multiphoton ionization
technique and dedected using microchannel plate (MCP) detector and measured
using a 600 MHz digitial oscilloscope (Lecroy Inc). Mass spectra were typically
recorded averaging signal over 100 laser shotsand recorded in a binary format
oscilloscope to manipulate later. The experimental and theorical improvement
for TOFMS have been presented in this poster presentation.