A Method of Computing Accurate 3D Fields of a Quadrupole Mass Filter and Their Use for Prediction of Filter Behavior

Gibson, John R.; Evans, Kenneth G.; Syed, Sarfaraz U. A. H.; Maher, Simon; Taylor, Stephen

doi:10.1007/s13361-012-0426-7

Cited by 13 publications

(13 citation statements)

References 32 publications

(61 reference statements)

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“…For example, the forces between steady currents and motional electromagnetic induction are identified with the velocity terms in the Weber force formula, while transformer induction is explained through the acceleration terms [13]. Finally, such an approach has potential advantages in a number of fields such as applied electromagnetics [14], and charge particle dynamics [15,16].…”

Section: Resultsmentioning

confidence: 99%

Investigating Electron Beam Deflections by a Long Straight Wire Carrying a Constant Current Using Direct Action, Emission-Based and Field Theory Approaches of Electrodynamics

Smith¹,

Maher²

2017

PIER B

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Abstract-Results are presented for the transverse deflection of an electron beam by a long, straight wire carrying direct current. The experimental deflections are compared with three calculation methods based on the Lorentz force law (field theory) and both the Weber (direct action) and Ritz (emission) force formulae. The Lorentz force calculation is the conventional approach expressed in terms of electric and magnetic field components. By contrast the force formulae of Weber and Ritz do not contain any field vectors relating to E or B. The Weber force is based on direct action whereas the Ritz force expression is based on an emission/ballistic principle and is formulated in terms of a dimensionless constant, λ. The experimental beam deflections are for low speed (non-relativistic) electrons. Good agreement between experiment and theory is demonstrated for each approach. In fact, for the case of an infinitely long wire, all three calculation methods give identical results. Finally, the three approaches are contrasted when applied to the case of high speed electrons.

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Section: Resultsmentioning

confidence: 99%

Investigating Electron Beam Deflections by a Long Straight Wire Carrying a Constant Current Using Direct Action, Emission-Based and Field Theory Approaches of Electrodynamics

Smith¹,

Maher²

2017

PIER B

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“…The complex RF and DC fringe fields at the exit of octopole, the RF fringe fields of the quadrupole and the pressure inside the quadrupole determine the extent of this effect. 22 …”

Section: ■ Results and Discussionmentioning

confidence: 99%

Direct Ion Imaging Approach for Investigation of Ion Dynamics in Multipole Ion Guides

et al. 2015

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A key requirement of electrospray ionization (ESI) and other techniques facilitating ionization at elevated pressures is the efficient transport of free gas-phase ions into the high vacuum region of the mass spectrometer. Radio frequency (RF) multipole ion guides that allow for collisional cooling are one of the most popular means of achieving this. However, their performance is highly dependent on several experimental factors, including pressure and various electrode potentials along the ion path. To experimentally visualize these effects, we have employed a position-sensitive detector at the exit of a quadrupole mass spectrometer (QMS) instrument operated in RF only mode that employs an RF only octopole as a collisional cooling ion guide. This allows the spatial distribution of the ions, and its dependence on experimentally determined conditions, to be directly visualized at the exit of the quadrupole. This investigation provides a detailed insight into the ion dynamics occurring inside multipole ion guides. This knowledge can directly be applied to instrument development and to improve the ion transmission efficiency and, thus, sensitivity. Numerical simulations using custom-developed trajectory simulation software are compared and contrasted with the experimental observations.

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“…In particular, for the solenoid S1 we are able to accurately model the force experienced by the electron beam in a non-uniform (fringing) field. The conventional Maxwell-Lorentz approach relies on the calculation of fields in a continuous system and such an approach is generally complex and computationally intensive [14]. Moreover, Newton's third law is inherently obeyed by Weber's force law and therefore particle momentum and angular momentum are conserved.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Electron Beam Deflections Across a Solenoid Using Weber-Ritz and Maxwell-Lorentz Electrodynamics

Smith¹,

Jjunju²,

Maher³

2015

PIER

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Abstract-The deflection of charged particle beams by electric and/or magnetic fields is invariably based on the field centred approach associated with Maxwell-Lorentz and incorporated into the Lorentz force formula. Here we present an alternative method of calculation based on the force formula of Weber-Ritz and which does not involve, directly, the field entities E and B. In this study we evaluate the deflection of an electron beam by a long solenoid carrying direct current and positioned centrally across the beam. The experiment has some bearing on the Aharonov-Bohm effect in that our calculations indicate that even for very long solenoids the classical force on the beam remains finite. The standard interpretation of the effect is, however, in terms of quantum mechanics and vector potential. Experimental measurements have been made of electron beam deflections by three solenoids, 0.25 m, 0.50 m and 0.75 m long; each solenoid is doubly wound with the same winding density (2600 turns per metre) and carrying the same current of 5.00 A d.c.. Our results indicate that, within the limits of experimental error, both Weber-Ritz and Maxwell-Lorentz theories correlate with measurements for the longer solenoids. However in the case of the shortest solenoid, the lack of uniformity of the magnetic field, leads to significant error in the calculation of beam deflection by the Lorentz force. By contrast in a Weber-Ritz calculation a precise value of beam deflection is obtained by equating the impulse of the non uniform beam force to the vertical momentum change of the electron. This is a fundamentally different approach which uses a statistical summation of forces on the beam in terms of relative velocities between moving electrons and involves a direct computation of the vertical force on the beam due to the circling solenoid current. This method has distinct advantages in terms of economy; that is, it does not involve directly field entities E and B, nor the leakage flux from the solenoid or the vector potential.

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A Method of Computing Accurate 3D Fields of a Quadrupole Mass Filter and Their Use for Prediction of Filter Behavior

Cited by 13 publications

References 32 publications

Investigating Electron Beam Deflections by a Long Straight Wire Carrying a Constant Current Using Direct Action, Emission-Based and Field Theory Approaches of Electrodynamics

Investigating Electron Beam Deflections by a Long Straight Wire Carrying a Constant Current Using Direct Action, Emission-Based and Field Theory Approaches of Electrodynamics

Direct Ion Imaging Approach for Investigation of Ion Dynamics in Multipole Ion Guides

Evaluation of Electron Beam Deflections Across a Solenoid Using Weber-Ritz and Maxwell-Lorentz Electrodynamics

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