Total flight width

If the various contributions to power consumption are carefully examined, it can be seen that a substantial portion is consumed in the clearance between the flight tip and the barrel see, for instance, Eq. 8.71(d). The power consumption in the clearance is inversely proportional to the radial clearance and directly proportional to the total flight width pw. However, the viscosity in the clearance will generally be lower than the viscosity in the channel since the polymer melt is pseudo-plastic. Figure 8.25 shows how the ratio of power consumption in the clearance to the total power consumption Z, depends on the ratio of flight width w to channel width plus flight width W + w for a polymer with a power law index n = 0.5. 

These distributions are the major origins of the poor resolution observed using simple linear TOF instrumentation. Resolution (R) for a TOF mass spectrometer is dependent on peak width (At) and the total flight time (t) ... 

The power consumption in the clearance is directly proportional to the number of parallel flights, the local viscosity, and the flight width, and is inversely proportional to the radial clearance. It will be shown later that a substantial portion (in some cases 50% or more) of the total power consumption is consumed in the clearance. Therefore, the geometry of the flight clearance becomes an important geometrical variable when It comes to minimizing power consumption. 

With these equations, the effect of various geometrical variables can be determined. Figure 8.15 shows the total axial melting length as a function of the helix angle at various values of the flight width. 

Total volume of liquid in extraction section Width of channel perpendicular to screw flights in screw extruder... 

The drift time as calculated by means of Eq. 4.7 is not fully identical to the total time-of-flight. Obviously, the time needed for acceleration of the ions has to be added. Furthermore, a short period of time Iq may be attributed to the laser pulse width and the process of desorption/ionization, which is typically in the order of a few nanoseconds. Thus, the total time-of-flight itotai is given by... 

TOFSIMS analyses were performed on a Kratos PRISM instrument. It was equipped with a reflectron-type time-of-flight mass analyzer and a pulsed 25 kV liquid metal ion source of monoisotopic 69Ga ions with a minimum beam size of 500 A. Positive and negative spectra were obtained at a primary energy of 25 keV, a pulse width of 10-50 ns, and a total integrated ion dose of about 10" ions/cm2. This is well below the generally accepted upper limit of 5 x 1012 ions/cm2 for static SIMS conditions in the analysis of organic materials [12], The mass resolution at mass 50 amu varied from M/AM= 1000 at 50 ns pulse width to about 2500 at 10 ns pulse width. 

Spectrum acquisition rates are a major concern in high-speed GC-MS where total separation times in seconds and peak widths typically less than 200 ms are common. The separation conditions are relatively easy to achieve with short, wide bore, open tubular columns operated at low pressures [131-136]. The ion source of the mass spectrometer provides the vacuum source for the column. Time-of-flight mass analyzers are most suitable for these applications. Time-of-flight mass spectrometers in production are capable of recording up to 500 full-mass spectra per second based on averaging 10 transient spectra per single spectrum [135-138]. At present, this is a unique... 

For a time-of-flight diffractometer the three major contributions to the Q-resolution are due to the geometrical uncertainty in angle, A6, the uncertainty in flight path, AL, and the uncertainty in time-of-flight, At, leading to the following expression for the total combined resolution width ... 

At Waterloo, Gough, Miller, and Scoles have generated a molecular beam of N20 N20. A diode laser beam was then scanned over the V3 mode to produce N20(001) N20(000). [The notation (vx,V2,V3) labels the vibrational levels involving the chemical bonds of N2O.] They reported the lifetime of this vibrationally excited complex to be in the range 10 to 10 s. The upper limit was established from the time of flight from the place of irradiation to the detector, and the lower limit was obtained by assuming that the total width of the diffuse absorption bond was due to predissociation. 

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