Accelerated Simulation Study of Space Charge Effects in Quadrupole Ion Traps Using GPU Techniques

Abstract

Space charge effects play important roles in the performance of various types of mass analyzers. Simulation of space charge effects is often limited by the computation capability. In this study, we evaluate the method of using graphics processing unit (GPU) to accelerate ion trajectory simulation. Simulation using GPU has been compared with multi-core central processing unit (CPU), and an acceleration of about 390 times have been obtained using a single computer for simulation of up to 10 5 ions in quadrupole ion traps. Characteristics of trapped ions can be investigated at detailed levels within a reasonable simulation time. Space charge effects on the trapping capacities of linear and 3D ion traps, ion cloud shapes, ion motion frequency shift, mass spectrum peak coalescence effects between two ion clouds of close m/z are studied with the ion trajectory simulation using GPU.

Reducing Space Charge Effects in a Linear Ion Trap by Rhombic Ion Excitation and Ejection

“…The rest of the trapped ions would form an ion cloud with an ion spatial distribution in both x-and y-directions following the Boltzmann distribution under thermal equilibrium [9,16,41,42]. Therefore, excited ions would penetrate through the ion cloud many times before ejection, and the Coulombic force (or relative distance) between the ion cloud and an excited ion changes with time or the momentary position of the excited ion [10,17,19].…”

“…Under the pseudo-potential approximation (with the Mathieu equation coefficient q < 0.4) and with controlled number of ions [9,10], an ion cloud trapped in a quadrupole ion trap would have a Gaussian distribution in the direction of the quadrupole electric field. According to the ion distribution model proposed by Guo et al [37], the electric field generated by the ion cloud within a linear ion trap has an expression of…”

“…Compared with beam-type mass analyzers (such as time-of-flight [5] quadrupole rods), an ion trap typically traps a large amount of ions [6][7][8] (thousands to millions of ions) and an ion cloud is formed in its center [9]. The density and volume of the ion cloud increase as the number of ions increases [10,11]. With the presence of a large population of ions, ion-ion Coulomb interactions, namely space charge effects, would alter ion motion frequencies in an ion trap [12][13][14].…”

“…With the presence of a large population of ions, ion-ion Coulomb interactions, namely space charge effects, would alter ion motion frequencies in an ion trap [12][13][14]. During a conventional dipolar ion excitation process for either collision induced dissociation (CID) [8,15] or ion massselective ejection, space charge could also result in delayed ion ejection [16], peak covalence, and nonlinear resonance of excited ions, which is similar to high-order field effects [10,[17][18][19][20][21][22][23]. As a result, space charge effects degrade MS performances in terms of dynamic range, mass accuracy, and resolving power [4,[24][25][26][27][28][29][30][31][32][33].…”

GPU Assisted Simulation Study of Ion–Ion Reactions within Quadrupole Ion Traps

“…Then, the theoretical model was integrated into the ion trajectory simulation program developed in our lab earlier [27,33,34]. Since the simulation of ion-ion interaction is a time-consuming process, GPU parallel computation techniques were applied to accelerate the simulation process.…”