Pulsed x-rays

Depending on conditions XTVI can use both stationary, mobile or small-size pulse X-ray units like RUP-150/300, RUP-120, "Arina-02". The tests of unit showed effective operation of XTVI in conjunction with program-controlled pulse X-ray units RAP-90, RAP-160, RAP-300, developed in Introscopy Institute. 

J.S. Wark, R.R. Whitlock, A. Hauer, J.E. Swain, and P.J. Solone, Short-Pulse X-Ray Diffraction from Laser-Shocked Crystals, in Shock Waves in Condensed Matter 1987 (edited by S.C. Schmidt and N.C. Holmes), Amsterdam, 1988, pp. 781-786, Elsevier Science. 

The first—and central— point in this discussion concerns the pulsed X-ray source. The shortest time scales involved when chemical bonds are formed or broken are of the order of a few femtoseconds. An ideal X-ray source should thus be capable of providing pulses of this duration. Unfortunately, generating them represents a heavy technological problem. The best one can do at present is to use a pulsed synchrotron X-ray source (Fig. 2). Electrons are rapidly circulating in its storage ring at speeds close to the speed of light. X-rays are spontaneously... 

Another application is for X-ray security machines. Here, the contrast between different materials is large, so the X-ray intensity is less high, but a high acceleration voltage is needed, as the penetration depth should be large. Thus a number of pulsed X-ray devices have been made, following the early work of Zhou et al. [59 62]. 

The TRAPI was developed by Matsuoka and co-workers " and has been used to determine the rate constants of about a dozen IM reactions at atmospheric pressure. As a first approximation, the TRAPI experiment might be described as an atmospheric pressure version of the PHPMS with initial ionization caused by a pulsed X-ray source. The X-rays cause relatively even ionization throughout the 6.4-cm ion source volume by penetrating through thin sections of the ion source walls formed by 25- im thick molybdenum foil. A 16-pm ion-sampling aperture is located at the center of one of these thin walls. The ions that pass through this aperture are measured by an associated mass spectrometer as a function of time after the X-ray pulse. 

Chen LX, Jennings G, Liu T, Gosztola DJ, Hessler JP, Scaltrito DV, Meyer GJ (2002) Rapid excited-state structural reorganization captured by pulsed X-rays. J Am Chem Soc 124 10861-10867... 

Irradiation Source. One to two rad electron or x-ray pulses are required to produce 6 to 12 nAf e aq. We use 1 Msec, pulses of 16 m.e.v. tungsten x-rays generated with an ARCO electron accelerator. The pulse must, however, be introduced in a time short compared to the measured half-lives. Any similarly pulsed x-ray beam of 150 to 200 k.e.v. would serve equally well since there is no rigid requirement of uniform irradia-... 

The hydrated electron may well find use in analytical chemistry laboratories. Not only have we shown that e aq is a valuable species for measuring submicromolar concentrations of its scavengers, but we have also demonstrated that satisfactory results may be obtained by very feeble x-ray pulses. While we irradiated our samples with 16 m.e.v. electrons or x-rays from a linear accelerator, an inexpensive pulsed x-ray unit of 150-200 k.e.v., capable of delivering 1 to 2 r/pulse, should serve equally well. Furthermore only minimal shielding is required under these conditions, thereby greatly facilitating manipulations needed for carrying out routine analyses. 

Aside from the first instant of the interaction of the laser with the matter, the X-ray radiation self-emitted from laser-produced plasmas provides an efficient diagnostic of processes that occur within such plasmas. Over the past ten years, the advent of short-duration laser systems and the progress made in the development of short-pulse X-ray sources have led to such systems being applied to multidisciplinary fields in order to probe matter. 

In this study, in order to better understand the fundamentals of the laser-cluster interaction, we have carried out systematic investigations of the properties of X-ray radiation from high-density and high-temperature cluster plasma created by the action of superintense laser irradiation. The interrelationship between the X-ray radiation properties and ion kinetic energies has been examined for the first time via simultaneous measurements of X-ray radiation spectra and ion energy spectra. The time scale and mechanism of the X-ray emission process are discussed here based on a time-dependent plasma kinetics model. Moreover, in order to demonstrate the practical capabilities of the X-rays thus produced, pulse X-ray diffraction from an Si crystal using this source has been examined. 

Using laser-induced X-ray pulses from solid targets, ultrafast time-resolved X-ray diffraction experiments have been performed extensively and new phenomena such as ultrafast melting have been demonstrated [26,27]. In the present study, in order to demonstrate the practical capabilities of the X-rays thus produced, the pulse X-ray diffraction obtained from a Si crystal with this source is examined [28]. 

Fukuda Y, Akahane Y, Aoyama M, Inoue N, Ueda H, Nakai Y, Tsuji K, Yamakawa K, Hironaka Y, Kishimura H, Morishita H, Kondo K, Nakamura KG (2004b) Relativistic laser plasma from micron-sized argon clusters as a debris-free X-ray source for pulse X-ray diffraction. Appl. Phys. Lett. 85 5099-5101... 

Abstract We review the basic theoretical formulation for pulsed X-ray scattering on nonstationary molecular states. Relevant time scales are discussed for coherent as well as incoherent X-ray pulses. The general formalism is applied to a nonstationary diatomic molecule in order to highlight the relation between the signal and the time-dependent quantum distribution of intemuclear positions. Finally, a few experimental results are briefly discussed. 

An alternative track which has been pursued recently is time-resolved X-ray diffraction. An important goal is to improve the time resolution such that direct observation of the dynamics of the chemical bond is possible, corresponding to the observation of the time-dependent distribution of atomic positions. Pulsed X-rays are, e.g., obtained from synchrotron radiation or plasma sources. The temporal duration of these pulses is currently in the range of 100 ps-100 fs [4], Very recently, the first free-electron laser has produced short 100-10 fs coherent and highly intense bursts of X-rays [4—6]. 

In this section, we review the derivation of the scattering signal from a pulsed X-ray field on a time-dependent molecular system. The key quantity of interest is the differential signal strength dS/dQ, which we define as the total number of scattered photons arriving at the detector per solid angle. Various derivations of dS/dQ exist in the literature based on perturbation or response theory [14, 15, 19]. In the... 

Fig. 17. Gated viewing recordings of a small lead object using short-pulse X-ray bursts passing through water layers of different thicknesses. In the lower part of the figure time-integrated representations are shown clearly demonstrating the loss of contrast for thicker samples (From Ref. [70]).

The lifetime of the photo-induced state in a given material dictates the instruments required for the determination of its structure. The smaller is the lifetime of such a species, the more chalienging the experiment becomes. These instmmental challenges are divisible into four categories steady-state methods (t > min), pseudo-steady-state methods (ms < Tq < min), and stroboscopic methods using a pulsed X-ray source generated by means of either a mechanical chopper (/as instrumental requirements as a function of time. 

A pulsed X-ray source is therefore required to study all processes driven by light with a sub-millisecond photo-active lifetime. If one is to realise the structural perturbations that result from the technologically important high-speed electrical and optical properties described in the second section, one needs an experimental method that provides access to structures enduring ms to ps. 

Hydrated Electron and Thermoluminescent Dosimetry of Pulsed X-ray Beams... 

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