Pulse Shape Measurements Research Articles

Measurement of scintillation efficiencies and pulse-shapes for nuclear recoils in NaI(Tl) and CaF2(Eu) at low energies for dark matter experiments

Abstract Measurements have been performed with a 2.85 MeV mono-energetic neutron beam of relative scintillation efficiency and pulse-shape for nuclear and electron recoils in NaI(Tl) and CaF2(Eu). Scintillation efficiencies in NaI(Tl) relative to 60 keV gamma events were found to be 27.5±1.8% for Na recoils (recoil energy Erec>4 keV) and 8.6±0.7% for I recoils (Erec>10 keV). Relative scintillation efficiencies in CaF2(Eu) for Ca and F recoils show some evidence for a fall with energy (17% to 8% for F) for 10 keV 〈 t i 〉 of 263±15 ns for Na events (visible energy Evis in the range 2–8 keV and 272±10 ns for I events (2 keV 〈 t i 〉 of 4 keV 〈 t i 〉 for 2 keV

Optical sampling system at 1.5 µm using twophotonabsorption in Si avalanche photodiode

A highly sensitive optical sampling system at 1.5 µm is described, in which an Si avalanche photodiode is used as a two photon absorber for the cross-correlation measurement of optical pulse shapes. The sampling pulse is generated from a passively and actively modelocked external-cavity semiconductor laser with a repetition rate of 10 GHz, and 2 ps temporal resolution is achieved.

Measurements of dead time and characterization of ion counting systems for mass spectrometry

A method for characterization of electron multiplier-based pulse counting systems is presented. Specific attention is paid to measurement of the counting system dead time. The systems discussed here are typically used to measure the abundance of ions passing through a mass spectrometer. A method for the determination of dead time by measurement of at least two isotopic ratios of an element with at least three isotopes is given. This method differs from the “text book” method typically used to measure the dead time. The theoretical basis for the measurements is given and an example of measurements of Ti isotopes by secondary ion mass spectrometry (SIMS) is shown. Dead time measurements on SIMS instruments can be performed in a few hours of machine time. A brief description of the pulse detection and counting circuit and its operation is also given. Guidelines for the proper measurement of pulse shapes and the determination of reasonable settings for electron multiplier gain, preamplifier gain, and discriminator threshold are also discussed.

A new method for ultrashort electron pulse-shape measurement using synchrotron radiation from a bending magnet

A new nondestructive method for measurement of the longitudinal profile of subpicosecond electron bunches is proposed. The method is based on measurement of spectral intensity correlations in synchrotron radiation. Statistical properties of synchrotron radiation produced by a bunch passing the bending magnet are considered. The signal-to-noise ratio is analyzed in terms of the degeneracy parameter. The degeneracy parameter increases approximately as a third power of the wavelength which makes the visible range of synchrotron radiation to be a natural choice for the spectral intensity correlation measurement. An example of the experimental set-up is also described.

Femtosecond continuum interferometer for transient phase and transmission spectroscopy

We measure difference phase spectra (DPS) over the whole visible spectrum by frequency-domain interferometry (FDI), using chirped femtosecond continuum pulses. The effects of the probe-pulse chirp on time-resolved dispersion relations are studied. Because of the correspondence between time and frequency in the chirp, temporal evolution of the optical Kerr response in CS2 is projected into DPS. In addition, it is found that the chirped continuum shows unexpected frequency shifts owing to induced phase modulation even when the continuum has a flat spectrum. The chirp character can be readily obtained from the projected traces, and the potential application to the single-shot pulse-shape measurement by FDI is discussed. It is shown that the delay-time-corrected spectra satisfy the Kramers–Kronig relations if the continuum has a flat spectrum and does not have higher chirp than the linear chirp but that the distortion caused by the induced modulation of the continuum remains unremoved in the corrected spectra.

Enhancing the time resolution of an EBT system via the primary electron pulse shape measurement

Abstract The use of an avalanche photodiode for the direct measurement of the primary electron current pulse of an EBT system is described with reference to the low beam accelerating voltages used in MOS IC testing. Using a known signal as an input to a matched impedance microstrip line, a numerical deconvolution technique has been employed to the signal sampled by finite duration current pulses to evaluate the goodness of the restoration of the original signal. The experimental results show a good agreement of the measured pulse widths with the nominal ones for pulse duration down to 5 ns while, for shorter pulses, some deviations arise due to the different mechanism adopted for the primary electron pulse formation in the blanking unit.

High dynamic range third-order correlation measurement of picosecond laser pulse shapes

A third-order correlation system has been developed, which enables the contrast ratio of high-intensity ultra-short laser pulses to be measured on a single shot, with a dynamic range of better than 108.

Optical properties and synchronously pumped mode-locked 1.73–2.10 μm tunable laser operation of [formula omitted] centers in KCl:Na +:O -2 crystals

Using synchronous pumping with ∽100 ps wide 1.32 μm Nd 3+:YAG laser pulses, we realize mode-locked KCl:Na +:O - 2 (F + 2) AH color center laser operation with nearly transform limited ∽5–10 ps wide pulses throughout a 1.73–2.10 μm tuning range. Pulses shorten continuously with increasing pump power levels. At maximum available pump power (∽2.3 W), average output power up to ∽380 mW is obtained in the peak of the tuning curve at 1.83 μm. Pulse shape and width measurements show that stable mode-locked operation is relatively insensitive towards cavity length detuning.

A complete parametric study of a TEA CO 2 laser of the [formula omitted] type

The complete parametric study of a small scale UV preionized TEA CO 2 laser of the CO 2/H 2 type is presented. The laser gives 10 mJ (TEM 00) and 46 mJ in multimode operation. From energy and pulse shape measurements the pulse output power of 0.2 MW (TEM 00) and 0.9 MW (multimode regime) is deduced. The spectral composition of the TEA CO 2 laser of the CO 2/H 2 type shows simultaneous multiline output in P-branch (00 01→10 00 vibrational band). All experimental measurements were conducted with a nondispersive optical cavity.

Output and discharge characteristics of an X-ray preionized XeCl laser with a large active volume.

The output and discharge characteristics of an x-ray preionized Xe Cl laser with a pulse forming line (PFL), a rail-gap switch (RGS) and a pulse transmission line (PTL) in the excitation circuit are described in detail. It is found that the relatively large inductance of the RGS leads to the efficient energy deposition into the discharge plasmas when the RGS is placed between the PFL and the PTL. The laser system with a low output impedance of 0.26Ω has produced the maximum laser energy of 50 J in an 85-ns pulse (FWHM). The highest electrical efficiency obtained is 3.1%. The discharge stability is also discussed, based on the measurements of laser pulse-shape, laser energy and voltage on the laser electrode.

Wide-energy-range, high-resolution measurements of neutron pulse shapes of polyethylene moderators

We report measurements of the emission time distributions (pulse shapes) as functions of energy for neutrons emerging from two heavily irradiated, ambient-temperature polyethylene moderators in IPNS. A time-focused crystal spectrometer arrangement provided resolution such that instrumental broadening was insignificant; cooling the Ge monochromator to 10 K provided adequate reflectivity in the high energy region. Measurements covered the range 2.5 < E < 1000 meV. We introduce a novel set of functions which fit the pulse shapes over the entire range of energies with four wavelength-independent parameters.

Control and measurement of ultrashort pulse shapes (in amplitude and phase) with femtosecond accuracy

The performances of a tunable femtosecond dye laser are analyzed using accurate correlation techniques. The source is a passively mode-locked dye laser, of which both the frequency and frequency modulation are controlled by one or two intracavity prisms. Interferometric second-order autocorrelations, with a peak-to-background ratio of 8 to 1, are used simultaneously with the conventional intensity autocorrelation and the pulse spectrum to determine the pulse shape. The main advantages of the interferometric autocorrelations are that they provide phase information otherwise not available, and they are more sensitive to the pulse shape than the intensity autocorrelation. The phase sensitivity is demonstrated in an analysis of the Gaussian pulses with a linear frequency modulation. Analytical expressions for the envelopes of the interferometric autocorrelations of typical pulse shapes are provided for quick pulse shape identification. A numerical method is used to analyze the more complex pulse shapes and chirps that can be produced by the laser. A series of examples demonstrates the control of this laser over various pulse shapes and frequency modulations. Pulse broadening or compression by propagation through glass is calculated for the pulse shapes determined from the fittings. Comparisons of autocorrelations and cross correlations calculated for the dispersed pulses, with the actual measurements, demonstrate the accuracy of the fitting procedure. The method of pulse shape determination demonstrated here requires a train of identical pulses. Indeed, it is shown that, for example, a train of unchirped pulses randomly distributed in frequency can have the same interferometric autocorrelation than a single chirped pulse. In the case of the present source, a comparison of the pulse spectrum, with that of the second harmonic, gives an additional proof that pulse-to-pulse fluctuations are negligible.

Measurement and fitting of spectrum and pulse shapes of a liquid methane moderator at IPNS

The absolute intensity, energy spectrum and energy variation of the neutron pulse shape have been measured for the IPNS liquid methane “F” moderator, at 108 K. The spectrum has been corrected for attenuation by aluminum in the beam and has been fitted using a simple parametric description. The pulse shapes have been fitted to a function which is the sum of two decaying exponentials convoluted with a Gaussian. These shapes have been corrected for instrumental resolution, parameterised as a function of neutron wavelength, and compared to the results of Monte Carlo simulations for equivalent moderator geometry. Only four parameters are required to describe the normalised spectrum and, in addition to wavelength dependent time delays, only five wavelength independent parameters are needed to describe the variation of the pulse shape over the entire spectrum.

Application of the HR 400 microchannel plate photomultiplier to study the light pulse shape from fast and slow scintillators by means of the single photon method

The capability of the HR 400 MCP photomultiplier to measure light pulse shaes from scintillators by means of the single photon method was studied. A time resolution of the timing system for single photoelectrons equal to 145 ps at fwhm and a time jitter of the HR 400 photomultiplier equal to 122 ps were measured by means of Cherenkov light produced in the photocathode glass window by γ-rays from a 60Co source. Both techniques of the single photon method, with a common scintillator and with separate ones, were tested during the study. Utilisation of the coincidence of the 625 keV K conversion electrons from a 137Cs source detected in the reference counter with the 31.6 keV K X-rays exciting the scintillator under study was proposed for the separate scintillator technique. This latter technique permits the measurement of light pulse shapes from encapsulated scintillator samples and particularly from black-coated ones to avoid the slowing-down of the light pulse by the light collection process. The application of the method to study light pulse shapes from fast organic scintillators and slow inorganic crystals was tested.

Primary composition of cosmic rays near 1017eV

Measurements of the Cerenkov light pulse shape in cosmic-ray showers of energy approximately 1017-1018 eV are reported. These are interpreted with the aid of detailed computer simulations to give estimates of the mean value and fluctuations in the atmospheric depth of shower maximum. Implications for the primary mass composition and the model of hadronic interactions are discussed briefly.

The vertical component of 1-20 MeV gamma rays at balloon altitudes

view Abstract Citations (72) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The vertical component of 1-20 MeV gamma rays at balloon altitudes Schoenfelder, V. ; Graml, F. ; Penningsfeld, F. -P. Abstract The diffuse cosmic and the vertical atmospheric component of 1-20 MeV gamma rays are determined from the gamma-ray data obtained during a balloon flight of the large-area Compton telescope of the Max-Planck-Institut. It is shown that the basic improvement of this new measurement above previous measurements with a first version of the Compton telescope is based on the fact that for each registered event various additional parameters are determined. Further, by means of the pulse shape measurement of neutron-induced events it is possible to determine most of the undesired background events from the data themselves. Finally, consideration is given to the origin of the diffuse cosmic gamma-ray component, and the results of the atmospheric gamma-ray component are compared with different model calculations. Publication: The Astrophysical Journal Pub Date: August 1980 DOI: 10.1086/158239 Bibcode: 1980ApJ...240..350S Keywords: Balloon Sounding; Cosmic Rays; Gamma Rays; Vertical Distribution; Atmospheric Radiation; Background Radiation; Compton Effect; Diffuse Radiation; Energy Spectra; Extraterrestrial Radiation; Space Radiation full text sources ADS |

Measurement of scintillation pulse shapes by the single-photon technique-an improved method

An instrument employing an improved technique for measurement of scintillation pulse profiles is described. Its advantages over previous instruments are that the pulse profiles and intensities measured for different samples can be compared directly. Its applications to the study of energy transfer in plastic scintillators and the optimisation of scintillator recipes are considered.

Measurements of picosecond pulse shapes for the highly synchronous cw double mode-locked dye laser

Cross-correlation measurements of the cw double mode-locked dye laser are described for two different cases, showing that the two pulse trains are highly synchronized. A direct display of the pulse shape at the longer wavelength resulted for the first case, in which a short primary pulse was generated along with a much longer incompletely mode-locked secondary pulse. For the second case, both pulse trains were completely mode-locked and short. In each case, the jitter between the two pulse trains was less than 1.6 ps and there was zero delay between the two pulses.

Energy transfer in organic systems. XIII. Plastic scintillators

For pt.XII see ibid., vol.11, no.13, p.2301 (1978). Energy transfer has been investigated in polyvinyltoluene (PVT) scintillators containing pyrene p-terphenyl and naphthalene by measurement of scintillation pulse shapes and yields. It is concluded that there is an initial rapid diffusion of the excitation energy with solute molecules, residual monomer and PVT excimer sites acting as competing traps. At later times energy can transfer from residual monomer and PVT excimer traps to the solute either radiatively or via long-range resonance, and the efficiencies of these processes are governed by the absorption characteristics of the solute.

Detailed pulse-shape measurements of a TEA-CO2 laser mode locked by positive germanium

A helical TEA-CO2 laser was mode locked by inserting a positive germanium plate close to the plane mirror of a hemiconfocal type of resonator. Single pulses of the emitted sequence of nanosecond spikes were recorded with high time resolution. Best fitting the experimental curves to a Gaussian and (cosh)−2 time dependence revealed that the temporal pulse shape corresponds with great accuracy to the (cosh)−2 behavior as it is predicted in a theoretical treatment of Haus. Since this theory is dealing primarily with steady-state saturable absorber mode locking, it is also pointed out that it can be applied to the above case.