Showing papers on "Time of flight published in 1974"
TL;DR: In this paper, an analytical technique is presented for determining rotational energy relaxation rates from velocity distributions measured on the axis of the free jet at a fixed distance from the sonic throat, and the agreement with rates obtained by other methods is good.
Abstract: In the free jet generated when a gas is expanded from a reservoir at stagnation temperature T0 and pressure P0 into a vacuum chamber, substantial lags can occur in the conversion of internal energy into directed kinetic energy of the expansion. An analytical technique is presented for determining rotational energy relaxation rates from velocity distributions measured on the axis of the free jet at a fixed distance from the sonic throat. The agreement with rates obtained by other methods is good. Some sample experimental and analytical results for carbon dioxide, oxygen, hydrogen, and methane are presented.
112 citations
TL;DR: In this paper, a straight path beam-modulated time-of-flight mass spectrometer has been constructed, which consists of an ion source, a drift tube and a collector.
Abstract: For pt.I see ibid., vol.6, 785 (1973). A straight path beam-modulated time-of-flight mass spectrometer has been constructed. The instrument consists of an ion source, a drift tube and a collector. The ion source is constructed by combining a conventional ionization chamber with an electron gun structure from a cathode ray tube incorporating an XY deflection system. The ion beam is modulated by applying to the X or Y plates a voltage varying in accordance with a step function. The mathematical analysis of the beam-modulation process has shown that the theoretical resolving power of this instrument should be inversely proportional to the beam plus collector slit width and proportional to the square of the flight path.
71 citations
TL;DR: In this paper, a time-of-flight detection system and apparatus have been developed to obtain photoelectron spectra for electron energies between 0 and 1 eV, which has the advantage of collecting and analyzing photoelectrons of all energies simultaneously and compensating for low signal levels due to low light intensities or small ionization cross sections.
Abstract: A time‐of‐flight detection system and apparatus have been developed to obtain photoelectron spectra for electron energies between 0 and 1 eV. This method has the advantage of collecting and analyzing photoelectrons of all energies simultaneously and therefore compensating for low signal levels due to low light intensities or small ionization cross sections. The collection efficiency and energy resolution are highest for electrons with near zero kinetic energy (≤100 meV). This technique has made it possible to obtain photoelectron spectra with a continuum light source dispersed by a monochromator. It is thus particularly useful for the study of autoionization events. Also presented are calculated potentials in 3‐dimensional rectangular acceleration regions and the effect of initial kinetic energy on space focusing in nonconstant electric fields.
30 citations
TL;DR: In this article, the microwave time-of-flight technique was used to measure the electron drift velocity in n-type GaAs at room temperature, and its advantages and limitations were discussed.
Abstract: The conventional time-of-flight technique for measuring drift velocity in high mobility semiconductors is limited to relatively thick (> 200 μm ) and high resistivity material. The microwave time-of-flight technique described here allows thin (∼ 10 μm ) low resistivity epitaxial layers to be measured with greater accuracy than is afforded by the conventional technique. The new experimental method is applied to the measurement of electron drift velocity in n -type GaAs at room temperature. The method, and its theory, is described in detail and its advantages and limitations are discussed.
28 citations
TL;DR: In this paper, a time-of-flight machine for the velocity analysis of molecular beams is described together with an experimental investigation of systematic errors, and a velocity selecting chopper is used to measure all delay times, including the delay in the beam detector due to the extraction time from the ionizer and the flight time of the ions in the quadrupole mass filter.
Abstract: A time-of-flight machine for the velocity analysis of molecular beams is described together with an experimental investigation of systematic errors. A velocity selecting chopper is used to measure all delay times, including the delay in the beam detector due to the extraction time from the ionizer and the flight time of the ions in the quadrupole mass filter. With the ionizer no memory effects occur at emission currents smaller than 1 mA. Memory effects in the detector chamber due to the direct reflection of beam particles are eliminated.
23 citations
TL;DR: In this article, a time-of-flight spectrometer with ΔE ionization chamber at the end of the flight path allowed complete separation of different elements and isotopes in the region of A ≈ 16 down to energies of 1 MeV/amu.
21 citations
TL;DR: In this article, a heavy ion time-of-flight spectrometer has been brought into operation at the Brookhaven National Laboratory (BNL) MP Tandem-Van-de-Graaff facility.
19 citations
TL;DR: In this paper, a time-of-flight system measuring accelerator beam energies within time intervals of about 10 ms with an absolute accuracy of 1.5:105 has been developed and successfully put into operation.
16 citations
TL;DR: In this paper, the relative cross sections for the production of Lyman-alpha radiation in collisions of atomic metastable hydrogen with molecular hydrogen have been measured at twenty-five velocities between 6*105 and 3*106cms-1.
Abstract: Relative cross sections for the production of Lyman-alpha radiation in collisions of atomic metastable hydrogen with molecular hydrogen have been measured at twenty-five velocities between 6*105 and 3*106cms-1 The measurements were carried out using time of flight techniques in combination with a recently developed target pressure modulation Results for the Lyman-alpha emission cross section exhibit the same velocity dependence as the total destruction cross section (see abstr A78529 of 1973) and are in complete disagreement with earlier measurements of Comes and Wenning (see abstr A7068 of 1970)
14 citations
TL;DR: In this paper, a simple but useful formula describing the effect of electron gun pulse width on the TOF spectra measured in translational spectroscopy experiments is developed, where an approximately monoenergetic pulsed electrostatically focused electron beam traverses a scattering cell filled with a Maxwellian gas.
Abstract: A simple but useful formula describing the effect of electron gun pulse width on the time of flight (TOF) spectra measured in translational spectroscopy experiments is developed. An approximately monoenergetic pulsed electrostatically focused electron beam traverses a scattering cell filled with a Maxwellian gas. Inelastic electron collisions with the gas produce metastable particles, ions, scattered electrons, and photons which then pass through a collimating slit system at right angles to the electron beam. TOF techniques are used to separate the photon signal from the metastable particle signal and to measure the TOF distribution of the metastable species.
8 citations
TL;DR: In this paper, the design and construction of a rotating crystal spectrometer for use with a pulsed neutron source is described, and its performance at wavelengths between 0.5 and 6.2 A has been assessed.
Abstract: The design and construction of a rotating crystal spectrometer for use with a pulsed neutron source is described. The source is the tungsten target of a 33 MeV electron linear accelerator, and at 5 kV mean power the spectrometer performance is equivalent to that of a similar instrument mounted on a nuclear reactor of 4 × 1012 n/cm2 s flux. Future developments will give an order of magnitude overall improvement. This spectrometer has been shown to be useful for studies of dense gases and liquids using an incident neutron wavelength of 2.4 A, and its performance at wavelengths between 0.5 and 6.2 A has been assessed.
TL;DR: In this article, the pulse height defect in semiconductor surface-barrier silicon detectors has been measured for (8−17) MeV 19 F, (4−18) MeVs 27 Al, (7−25) Mev 40 Ca and (6−38) MeVS 58 Ni ions.
TL;DR: In this article, a simple method of measuring the time of flight of charged particles using an alpha particle source, a solid-state detector (SSD) and a channel electron multiplier (CM) is described.
TL;DR: A direct measurement of the mass distribution in the thermal-neutron fission of 235U was made using the single time-of-flight method and particle channeling in the energy detector as mentioned in this paper.
TL;DR: Several time-of-flight properties of an inhomogeneous, oscillatory electric field are described in this paper, which show promise for application in charged particle optical systems, and can be used for particle optical simulations.
TL;DR: In this paper, the angular differential cross sections of (n, charged particles) reactions induced by 14 MeV neutrons are measured using the time of flight of the charged particles.
TL;DR: In this article, a 14 MeV neutron time-of-flight spectrometer having a 7.6 m flight path is described, and an energy resolution of 260 keV for the 14 MeVs neutrons has been obtained at a neutron intensity of 2 × 10 5 n/s.
TL;DR: In this paper, the authors extended previous calculations of the trajectory of ions in a field ion microscope to the situation where the electric field experienced by an ion alters during its time of flight from emitter to screen under the application of a positive voltage pulse applied to the emitter.
Abstract: Previous calculations of the trajectory of ions in a field ion microscope have been extended to the situation where the electric field experienced by an ion alters during its time of flight from emitter to screen under the application of a positive voltage pulse applied to the emitter. The calculations indicate that ion trajectories depend both upon the shape and duration of the pulse, and may lead to errors in aiming in the atom-probe mass spectrometer.
Journal Article•
TL;DR: In this paper, a time-of-flight facility is constructed to investigate photoneutrons in the energy range 5 MeV ≤ En ≤ 200 MeV, where the number of virtual photons to real photons is measured via the photodisintegration of 2H.
TL;DR: In this article, it is shown that such a beam is still suited for neutron time-of-flight spectroscopy, since the true spectrum can be inferred by mathematical decomposition of the measured spectrum.
TL;DR: In this paper, a mechanical time-of-flight (TOF) neutron diffractometer has been constructed and a system of data analysis developed for the study of noncrystalline substances through radial density functions.
01 Jan 1974
TL;DR: In this paper, a double-scintillator spectrometer was developed to measure neutron energy distributions in the range 250 keV to 8 MeV in low-power fast reactor assemblies.
20 Dec 1974
TL;DR: Characteristic features of the TOF (time of flight) neutron diffraction are summarized in this article, where the pulse neutron generator as well as the data acquisition system in the Laboratory of Naclear Science of Tohoku University are described.
Abstract: Characteristic features of the TOF (time of flight) neutron diffraction are summarized. In this method, i) all the reciproal points on the rod passing through the origin in the reciprocal space can be scanned by each burst of white neutrons, ii) it is easy to measure high index reflections at the large scattering angle, iii) each reflection is not affected by the higher-order harmonics, and iv) it is easy to measure the physical properties depending on the neutron wavelength.The pulse neutron generator as well as the data acquisition system in the Laboratory of Naclear Science of Tohoku University is described.The TOF method seems to be very powerful if it is applied to the accurate structure analysis. The data correction methods are discussed. The TOF method is prospective to the study of transient phenomena. In this method one can apply to the crystalline sample an external field pulsed with the same frequency as the neutrons. By using this method, the transient state of the polarization reversal of the ferroelectric NaNO2 has been observed.The magnetically pulsed neutron TOF spectrometer is briefly introduced after a review of the choper history.