Pulse Shape Measurements Research Articles

Position dependent measurement of single event transient voltage pulse shapes under heavy ion irradiation

A CMOS inverter in 90 nm CMOS bulk technology was exposed to heavy ion radiation (Au-197) at a micro-beam facility. The targeted inverter occupies an area of 6×3 µm2. The resulting single event transient (SET) voltage pulses at the output were measured using an on-chip analogue sense amplifier. The output of the amplifier was recorded with a 15 GHz real-time oscilloscope. Depending on the location of the ion hits strongly different pulse shapes were observed.

Measuring the dependence of the decay curve on the electron energy deposit in NaI(Tl)

We report on the first measurement of the decay times of NaI(Tl) as a function of the deposited electron energy. It has been suggested that the decay curve depends on the ionization density, which is correlated with the electron energy deposit in the scintillator. The ionization creates excitation states, which can decay radiatively and non-radiatively through a number of competing processes. As a result, the rate at which the excitation decays depends on the ionization density. A measurement of the decay curve as a function of the ionization density will allow us to probe the kinetic rates of the competing processes. The Scintillator Light Yield Non-proportionality Characterization Instrument (SLYNCI) measures the electron response of scintillators utilizing fast sampling ADCs to digitize the raw signals from the detectors, and so can provide a measurement of the light pulse shape from the scintillator. Using data collected with the SLYNCI instrument, the intrinsic scintillation profile is extracted on an event-by-event basis by deconvolving the raw signal with the impulse response of the system. Scintillation profiles with the same electron energy deposit are summed to obtain decay curves as a function of the deposited electron energy. The decay time constants are obtained by fitting the decay curves with a two-component exponential decay. While a slight dependence of the decay time constants on the electron energy deposit is observed, the results are not statistically significant.

Performance of the ATLAS Forward Calorimeters in First LHC Data

The ATLAS Forward Calorimeters (FCal) cover the very forward region of 3.1 < |η| < 4.9 and are hence designed to operate in a very high rate environment. This paper discusses the design of the FCal and presents studies of its performance in beam test data and LHC collision data. Measurements of the signal pulse shape, and the distribution of reconstructed cell energies are presented and compared with the expectation from simulations. A measurement of the location of the FCal is also performed in the data by studying the average deposited energy as a function of transverse distance to the beam axis.

Pulse shape measurements using single shot-frequency resolved optical gating for high energy (80 J) short pulse (600 fs) laser

Relevant to laser based electron/ion accelerations, a single shot second harmonic generation frequency resolved optical gating (FROG) system has been developed to characterize laser pulses (80 J, ∼600 fs) incident on and transmitted through nanofoil targets, employing relay imaging, spatial filter, and partially coated glass substrates to reduce spatial nonuniformity and B-integral. The device can be completely aligned without using a pulsed laser source. Variations of incident pulse shape were measured from durations of 613 fs (nearly symmetric shape) to 571 fs (asymmetric shape with pre- or postpulse). The FROG measurements are consistent with independent spectral and autocorrelation measurements.

Digital signal processing application to 252Cf(sf) reaction products spectroscopy

The emission of prompt fission neutrons in spontaneous fission of 252Cf was studied by the application of digital data processing for the first time. The study was aimed at comparing the obtained results with those from the pioneering work of Budtz-Jorgensen and Knitter. By using a twin Frisch grid ionization chamber for fission fragment detection and a neutron scintillator (NE213) for the detection of neutrons, a total of about 107 neutron coincidences were registered. The fission-fragment kinetic energies were measured using a fast (80 MHz) waveform digitizer that provided 10-bit amplitude resolution. Standard analog NIM modules were used for neutron time-of-flight and pulse shape measurements. A time-to-digital converter (TDC) with 1-ns resolution and a pair of gated charge-to-digital converters with 12-bit amplitude resolution were also used. The fission fragment signals were analyzed by means of digital signal processing algorithms. Data on prompt fission neutron energies were obtained by using a time-of-flight (TOF) spectrum unfolding procedure applicable to list-mode data.

Nonadiabatic nondegenerate excitation by optical near-field and its application to optical pulse-shape measurement

Using DCM dye grains and light of different wavelengths generated by two CW laser diodes that oscillate in the near-infrared wavelength region, visible light emission from dye grains due to near-infrared excitation based on a nonadiabatic, nondegenerate excitation process was observed for the first time. Unlike sum-frequency generation with nonlinear polarization, the difference in polarization angles of the two beams did not affect the emitted light intensity. Optical sampling based on this nonadiabatic, nondegenerate excitation principle was demonstrated for the first time. The optical pulse shape in the wavelength band of λ=1250–1350 nm, which is close to the wavelength range used for optical fiber communications, was measured with a temporal resolution of 0.8–1.1 ps.

Microfluidic structures for flow cytometric analysis of hydrodynamically focussed blood cells fabricated by ultraprecision micromachining

We present three-dimensional microfluidic structures with integrated optical fibers, mirrors and electrodes for flow cytometric analysis of blood cells. Ultraprecision milling technique was used to fabricate different flow cells featuring single-stage and two-stage cascaded hydrodynamic focusing of particles by a sheath flow. Two dimensional focussing of the sample fluid was proven by fluorescence imaging in horizontal and vertical directions and found to agree satisfactorily with finite element calculations. Focussing of the sample stream down to 5 microm at a particle velocity of 3 m s(-1) is accessible while maintaining stable operation for sample flow rates of up to 20 microL min(-1). In addition to fluorescence imaging, the micro-flow cells were characterised by measurements of pulse shapes and pulse height distributions of monodisperse microspheres. We demonstrated practical use of the microstructures for cell differentiation employing light scatter to distinguish platelets and red blood cells. Furthermore, T-helper lymphocytes labelled by monoclonal antibodies were identified by measuring side scatter and fluorescence.

Exploratory Research on the Development of Novel ${\rm Ce}^{3+}$-Activated Phosphate Glass Scintillators

We report the discovery of a new family of Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -activated phosphate glass scintillators that can be formed either with or without the addition of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> Li, for neutron or X-ray/gamma-ray radiation detection, respectively. Trivalent cerium can be efficiently introduced into these phosphate glasses in surprisingly high concentrations in the form of anhydrous cerium tri-chloride. Additionally, these glasses can be melted and poured at the relatively low temperatures of 1000-1050degC (i.e., substantially lower than silicate glasses), and to retain the cerium in the trivalent state it is not necessary to maintain highly reducing conditions during the synthesis process. The family of alkaline-earth-alkali phosphate glasses investigated here represents a system with two dissimilar cations - thereby offering a large range of potential compositional variations, substitutions, and combinations. In order to alter the scintillator characteristics, we have explored part of that compositional space by studying Ca-Na, Ca-Li, Ca-Cs, Ca-Rb, Ca-K and Ca-Ba-Na phosphate glasses, as well as various co-doping and post-synthesis thermal processing schemes. A series of experiments under X-ray, gamma-ray, and neutron excitations was carried out. The broad, peaking at about 354 nm, UV scintillation of these glasses is well suited for applications that use common photomultipliers with bi-alkali photo-cathodes. Pulse shape measurements show that the primary component of the scintillation in most of these glasses corresponds to 75-90% of the emitted photons, and it decays with a time constant of 30 to 40 ns, which classifies these materials as reasonably fast scintillators. Although the gamma-induced light yield of these new scintillating phosphate glasses is, thus far, only about 30% of that of commercial GS20 silicate glass, due to the generally faster scintillation, the initial amplitude of the scintillation pulse of these glasses is close to that of the above-mentioned GS20 scintillator.

Double beta decay of 48Ca studied by CaF2(Eu) scintillators

We report the new limit on the half-life of neutrino-less double beta decay(0νββ) of 48Ca. In order to achieve the background free measurement, measurement of pulse shape was essential. We have observed no event in the Qββ-value region. We set the new limit on 0νββ half-life as T0νββ1/2 > 40 × 1022 year.

極端紫外単一アト秒パルス光の波形・位相同時測定

極端紫外単一アト秒パルス光の波形・位相同時測定

Beam distortion detection technique for picosecond ultrasonics

Beam distortion detection (BDD) technique was successfully used for the detection of picosecond longitudinal and shear acoustic pulses in micrometric metallic layers. It is optimised for the measurement of the displacement pulse shape. In this communication the application of BDD for the evaluation of displacement acoustic echoes in 250 nm tungsten film is presented. The reflectivity term has been removed from photoacoustic signal by the introduction of reference channel in the differential photodetection. The result of test experiment with W film has shown promising ability of BDD technique for the surface displacement detection without interferometry and deflectometry.

Averaging of Replicated Pulses for Enhanced-Dynamic-Range Single-Shot Measurement of Nanosecond Optical Pulses

Measuring optical pulse shapes beyond the dynamic range of oscilloscopes is achieved by temporal pulse stacking in a low-loss, passive, fiber-optic network. Optical pulses are averaged with their time-delayed replicas without introducing additional noise or jitter, allowing for high-contrast pulse-shape measurements of single-shot events. A dynamic-range enhancement of 3 bits is experimentally demonstrated and compared with conventional multishot averaging. This technique can be extended to yield an increase of up to 7 bits of additional dynamic range over nominal oscilloscope performance.

Cerium-doped mixed-alkali rare-earth double-phosphate scintillators for thermal neutron detection

Previous measurements of the scintillation properties of members of the single-alkali, rare-earth double-phosphate family have demonstrated high light output and fast decay times when exposed to ionizing radiation. Because of the ease with which the alkali constituents (Li, Na, K, Rb, Cs) of the crystal matrix may be interchanged (e.g. K 2CsLu(PO 4) 2 and CsLi 2Lu(PO 4) 2), the rare-earth double-phosphate family of scintillators provides an ideal system for the study of matrix effects on scintillation efficiency and kinetics. New members of the rare-earth double-phosphate family have been synthesized by high-temperature flux growth. These new samples, represented by the general formula (A,B) 3Lu(PO 4) 2:Ce where A and B are alkali elements, incorporate lithium as one of the components and varying levels of Ce doping. Characteristics important to gamma-ray and thermal neutron excitation are calculated for three model systems which incorporate total lithium-ion substitution. Light output, scintillation decay times, and photoluminescence measurements for the most promising of the samples to date are reported. Future work includes (1) synthesis of mixed-alkali scandium and yttrium double-phosphates in which Li ions are substitutional in the structure with varying lithium-ion content up to and including total lithium–ion substitution on the alkali ion site and (2) measurements of light output and pulse shape using thermal neutron excitation.

Measurements of femtosecond pulse temporal profile by means of a Michelson interferometer with a Schottky junction

We introduce a new method for femtosecond pulse shape measurement. The interference of two pulses is employed rather than the second-harmonic generation (SHG). Usually, the measurements of the femtosecond pulse is realized by an interferometer in combination with a nonlinear optical material, while the measurement that we describe is realized by means of a Michelson interferometer with a Schottky junction. Only a metal-semiconductor junction (Schottky junction) is needed, and neither the nonlinear optical material nor a photodetector is included. The two-photon absorption arises when the light is strong enough, while there is only a one-photon absorption when the light is weak. And the calculations are in good agreement with the experimental results. In principle, the new technique could be used for the measuring of pulses with any duration and with very low power. Unlike the SHG scheme, in the new method the quality of optics, mechanics, and other elements of the scheme are not essential, and the measurement is easily realized, but the results are quite precise and very sensitive to the light.

Pulse shape measurement by a non-collinear third-order correlation technique

A third-order correlator suitable for detailed shape measurements of picosecond laser pulses has been developed. The working principle in both the single shot and the scanning mode is based on detection of the phase-matched difference frequency non-collinear generated signal in a non-linear crystal. This third-order OPA correlator was applied for the characterization of the specifically shaped picosecond laser pulses from the MBI CPA Nd: glass laser system.

First limits on nuclear recoil events from the ZEPLIN I galactic dark matter detector

We report first results from the ZEPLIN I dark matter detector, based on measurement of scintillation pulse shapes in a liquid xenon target of 3.2 kg fiducial mass. Neutron calibration shows nuclear recoil pulses to have a time constant ≅ 0.5 that of gamma and beta background events. The detector is located in the 2800 mwe depth UK Boulby Mine, and is surrounded by a liquid scintillator Compton veto and passive lead shielding. Three runs totaling 293 kg d fiducial exposure yielded data consistent with a single population of background pulses, with no significant low energy population of shorter pulses. From the 90% confidence limit on the latter a limit is derived on the spin-independent WIMP-nucleon cross-section versus particle mass with a minimum at 1.1 × 10 −6 pb.

Measurement of eV-Region Pulse Shapes of Neutrons from the KENS Thermal Neutron Source by a Neutron Resonance Absorption Method

The eV-region pulse data of neutrons emitted from a moderator at a pulsed neutron source are important for scattering experiments using eV region neutrons. Therefore, we measured the pulse data of neutrons from the H2O thermal moderator at KENS, using a neutron resonance absorption spectrometer (N-RAS) because it can give the pulse information due to the fact that it includes pulse shape information in a form of convolution with the resonance spectrum. We also performed a simulation calculation for the pulse shapes. It was found that the pulse widths obtained experimentally were proportional to E−0:48, which result is almost equal to those of the simulation, and there existed little difference in widths compared with those evaluated by using the slowing down theorem in an infinite medium having mass number 1.

Measurement of eV-Region Pulse Shapes of Neutrons from the KENS Thermal Neutron Source by a Neutron Resonance Absorption Method

The eV-region pulse data of neutrons emitted from a moderator at a pulsed neutron source are important for scattering experiments using eV region neutrons. Therefore, we measured the pulse data of neutrons from the H2O thermal moderator at KENS, using a neutron resonance absorption spectrometer (N-RAS) because it can give the pulse information due to the fact that it includes pulse shape information in a form of convolution with the resonance spectrum. We also performed a simulation calculation for the pulse shapes. It was found that the pulse widths obtained experimentally were proportional to E−0:48, which result is almost equal to those of the simulation, and there existed little difference in widths compared with those evaluated by using the slowing down theorem in an infinite medium having mass number 1.

A simple method for the determination of the structure of ultrashort relativistic electron bunches

In this paper we propose a new method for measurements of the longitudinal profile of 100 fs electron bunches for X-ray Free Electron Lasers (XFELs). The method is simply the combination of two well-known techniques, which where not previously combined to our knowledge. We use seed 10-ps 1047 nm quantum laser to produce exact optical replica of ultrafast electron bunches. The replica is generated in an apparatus which consists of an input undulator (energy modulator), and the short output undulator (radiator) separated by a dispersion section. The radiation in the output undulator is excited by the electron bunch modulated at the optical wavelength and rapidly reaches 100 MW-level peak power. We then use the now-standard method of ultrashort laser pulse-shape measurement, a tandem combination of autocorrelator and spectrum (FROG—frequency resolved optical gating). The FROG trace of the optical replica of electron bunch gives accurate and rapid electron bunch shape measurements in a way similar to a femtosecond oscilloscope. Real-time single-shot measurements of the electron bunch structure could provide significant information about physical mechanisms responsible for generation ultrashort electron bunches in bunch compressors. The big advantage of proposed technique is that it can be used to determine the slice energy spread and emittance in multishot measurements. It is possible to measure bunch structure completely, that is to measure current, energy spread and transverse emittance as a function of time. We illustrate with numerical examples the potential of the proposed method for electron beam diagnostics at the European XFEL.

Quasiparticle dynamics in a tantalum superconducting tunnel junction photon detector studied using phonon pulses

We have used non-equilibrium phonon pulses to mimic X-ray photon absorption in a high quality Ta superconducting tunnel junction at 20 mK. From pulse shape measurements the charge output and decay time were determined. Values obtained were in good agreement with those obtained by photo-absorption after allowance for loss due to flux trapping. Results obtained for the quasiparticle loss rate due to Abrikosov vortices (fluxoids) were compared with the trapping model of Golubov and Houwman. Comparison of Ta and Nb results suggest that at very low temperatures fluxoid trapping may result in enhanced tunnelling rather than extra loss. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)