Showing papers in "Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment in 1986"

A new type of X-ray area detector utilizing laser stimulated luminescence

Abstract: A conceptually new integrating area (250 mm×200 mm or larger) detector system, originally developed for diagnostic radiography, has been used for synchrotron radiation experiments. In this detector system, an X-ray image is temporarily stored as a distribution of F-centers in a photostimulable phosphor (BaFBr:Eu 2+ ) screen. The stored image is read out by measuring the intensity of fluorescence ( λ ∼390 nm) stimulated by a HeNe laser beam scanned over the surface of the screen. The detector has 100% detective quantum efficiency for 8–17 keV X-rays, a spatial resolution better than 0.2 mm (fwhm) in both directions, a dynamic range of 1:10 5 and no counting rate limitation. Diffraction patterns from muscle and a protein crystal were recorded in several tens times less exposure than that of high-sensitivity X-ray films.

Data appraisal, evaluation and display for synchrotron radiation experiments: Hardware and software

Abstract: The hardware and software of the data appraisal, evaluation and display systems used for synchrotron radiation experiments at the EMBL Outstation on the storage ring DORIS are described. The system is based on CAMAC hardware and modular software and has been extensively used for a variety of applications in EXAFS and small angle scattering and diffraction.

SHADOW: A synchrotron radiation ray tracing program

Abstract: We present the new ray-tracing program SHADOW. The program was written specifically for the XUV optics range, but is now completely general. Its capabilites are discussed in terms of the physical basis on which the program is built, with particular emphasis on the synchrotron radiation applications.

Brightness, coherence and propagation characteristics of synchrotron radiation

Abstract: A formalism is presented by means of which the propagation and imaging characteristics of synchrotron radiation can be studied, taking into account the effects of diffraction, electron beam emittance, and the transverse and longitudinal extent of the source. An important quantity in this approach is the Wigner distribution of the electric fields, which can be interpreted as a phase-space distribution of photon flux, and thus can be identified with the brightness. When integrated over the angular variables, the brightness becomes the intensity distribution in the spatial variables and when integrated over the spatial variables, it becomes the intensity distribution in angular variables. The brightness so defined transforms through a general optical medium in exactly the same way as in the case of a collection of geometric rays. Finally, the brightness of different electrons adds in a simple way. Optical characteristics of various synchrotron radiation sources — bending magnets, wigglers and undulators — are analyzed using this formalism.

An analysis of self-amplified spontaneous emission

Abstract: The following analysis develops a classical theory of how a signal evolves from the initial incoherent spontaneous emission in long undulators. The theory is based on the coupled Klimontovich-Maxwell equations. Formulas for the radiated power, spectral characteristics and electron correlations are derived. The saturation due to nonlinear effects is studied using a quasilinear extension of the theory. The results agree reasonably well with the recent Livermore experiment in the microwave range. Performance of a possible high-gain free electron laser in a short-wavelength region is evaluated.

A soft X-ray monochromator for the MAX synchrotron radiation facility

Abstract: A high resolution soft X-ray monochromator for the 550 MeV MAX storage ring is described. The instrument combines a plane elliptical premirror collecting a large (10 mrad) horizontal angle of radiation and a modified version of the well-known SX-700 plane grating monochromator (PGM). The modification consists of changing the original ellipsoidal focussing mirror to a plane elliptical mirror. Thereby the horizontal and vertical focussing are decoupled and good imaging properties are obtained irrespective of the large horizontal acceptance angle. The MAX-PGM will be part of an experimental station for photoelectron, photoabsorption and photon stimulated ion desorption spectroscopy.

Models for a three-parameter analysis of neutron signal correlation measurements for fissile material assay

Abstract: For the nondestructive assay of Pu-containing fuel, interpretation models are derived to obtain its spontaneous fission rate or its Pu-mass equivalent. The factorial moments of the frequency distribution of neutron signal multiplets in signal and randomly triggered time intervals are used as measurement results.

Projectile fragments isotopic separation: Application to the lise spectrometer at GANIL

Abstract: The isotopic separation of intermediate-energy (30 to 100 MeV per nucleon) heavy-ion projectile fragments is theoretically and experimentally investigated. Physical separation of nuclides is achieved through magnetic analysis (AZ sensitivity) and differential stopping-power effects (Z−2 sensitivity). Depending on the specific case, a complete mass and charge separation may be achieved or a few nuclides may be selected simultaneously. The projectile fragments isotopic separation method described allows us to obtain an experimental mass separation AΔA ≈ 100. Simple formulae are given to determine the optimum factors for the best separation and transmission of the device. First applications to the spectroscopy of exotic nuclei lead to the new observation of the beta decay of 37P at GANIL and 15B at CERN.

In-flight capture of ions into a penning trap

Abstract: A bunched beam of alkali ions with a pulse length of about 10 μs and an energy of 1 KeV has been retarded electrostatically and captured in flight into a Penning trap. A trapping efficiency of up to 70% has been determined. Subsequently the cyclotron resonance was induced. In the case of K a line width of the resonance of 4 Hz was measured at a resonance frequency of 2.3 MHz. This enables mass determinations of unstable nuclei produced at on-line mass separators with an accuracy in the sub-ppm region.

X-ray absorption in dispersive mode: A new spectrometer and a data acquisition system for fast kinetics

Abstract: The photodiode array provided a position sensitive detector for powerful X-ray sources. Then the development of the energy dispersive scheme for the X-ray absorption experiments became realistic. The data acquisition system and elements of optics are discussed. Experiments in transmission mode and in total reflection mode illustrate the dramatic gain in data acquisition time as well as advantages dealing with the focussing optics.

Design of a portable large spectral range grazing incidence instrument

Abstract: A design of a small size grazing incidence instrument is presented, which offers large spectral range and high resolution without sacrificing luminosity. The instrument is particularly suited for use at synchrotron radiation sources since it can be conveniently attached to existing experiment chambers. The basic idea of the design is the use of fixed mounted gratings of diffent radii and groove densities and a big two-dimensional position sensitive detector mounted on a x-y angle table. The design is discussed in some detail and performance is presented. © 1986.

A transient analysis of a bunched beam free electron laser

Abstract: We studied the problem of the bunched beam operation of a free electron laser. Assuming the electron beam to be initially monoenergetic, the Maxwell-Vlasov equations describing the system reduce to a third order partial differential equation for the envelope of the emitted light. The Green function corresponding to an arbitrary shape of the electron bunch, which describes the transient behavior of the system, is obtained. We use Green's function to discuss the start-up problem as well as the power output and the power spectrum of self-amplified spontaneous emission.

Elliptically polarized synchrotron radiation source with crossed and retarded magnetic fields

Abstract: A method which enables us to obtain any kind of elliptically polarized synchrotron radiation from relativistic electrons by use of crossed and retarded magnetic fields is proposed. This method can be actualized as a new type of multipole wiggler or undulator. As a preliminary study of this device the spatial distribution of magnetic field in the combination of two magnet arrays whose fields are mutually perpendicular and have some phase retardation is investigated. It is expected that this device would be very useful in the polarization modulation spectroscopy where two orthogonal linearity or circularly polarized synchrotron radiations are needed.

Progress in semiconductor drift detectors

Abstract: Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements.

Review of wire chamber aging

Abstract: This paper makes an overview of the wire chamber aging problems as a function of various chamber design parameters. It emphasizes the chemistry point of view and many examples are drawn from the plasma chemistry field as a guidance for a possible effort in the wire chamber field. The paper emphasizes the necessity of tuning of variables, the importance of purity of the wire chamber environment as well as it provides a practical list of presently known recommendations. In addition, several models of the wire chamber aging are qualitatively discussed. The paper is based on a summary talk given at the Wire Chamber Aging Workshop held at LBL, Berkeley on January 16–17, 1986. Presented also at Wire Chamber Conference, Vienna, February 25–28, 1986.

Charged particles identification with a CsI(Tl) scintillator

Abstract: A CsI(Tl) scintillator with two light decay components is used to detect and identify p, d, t, 3 He and α particles with a low energy threshold. Besides, the addition of a thin plastic scintillator in front of the CsI(Tl) crystal allows charge identification for ions with Z up to 19.

The high energy plane grating monochromators at BESSY

Abstract: Two plane grating grazing incidence monochromators based on the author's solution of the plane grating focussing term are described. The instruments continuously cover the soft X-ray spectral range up to 2 keV. Source size limited spectral resolution can be obtained when the influence of the too high tangent error of the present focussing mirror is eliminated through aperture reduction. Higher orders can be suppressed by varying the cutoff angle at the plane premirror. The stray light content of the spectrum is very low and allows an edge-jump of 1:2.5 at the silicon K-edge.

State-of-the-art efficiency determination for a Si(Li) X-ray detector in the 3–40 keV energy range

Abstract: Emission data for radionuclide X-ray intensity standards are revised, and an extensive set of standards is used to determine a very precise efficiency curve between 3 and 40 keV energy for a Si(Li) detector. The curve is compared to predictions of a physical model; it is used to assess the internal consistency of the standard set and to determine the minimum subset of standards necessary to maintain the accuracy afforded by the entire set. The curve is fully consistent with the detector's properties as measured by independent experiments, provided that a surface layer of ice is invoked, as was recently suggested by Cohen. The efficiency values that it generates have accuracy under 1% in the 5–30 keV region. The need for new work on radionuclide standards in the 1–5 keV region is discussed.

Three-dimensional simulations of free electron laser physics

Abstract: A computer code has been developed to simulate three-dimensional free electron laser physics. A mathematical formulation of the FEL equations is presented, and the numerical solution of the problem is described. Sample results from the computer code are discussed.

The Stanford Mark III infrared free electron laser

Abstract: We have built and operated a compact infrared free electron laser using a conventional linear accelerator and a broadband optical cavity. The gain was measured to be 28% and saturation was obtained with a 2.5 μs macropulse. The laser was tuned from 3.1 to 2.6 μm by changing the undulator gap. Coherent spontaneous radiation at the fifth and seventh harmonics was seen.

Nonlinear response of Si detectors for low-Z ions

Abstract: We report measurements of the relative mean pulse height produced by 1H, 4He, 7Li and 16O ions in Si surface barrier detectors. The data are anomalous in that the pulse height for different ions of the same energy (after window and nonionizing losses are subtracted) increases with atomic number, contrary to observations for fission fragments. A simple model invoking a stopping power dependence of the energy required to create an electron-hole pair is consistent with all experimental data, suggesting that the response of Si detectors is nonlinear with particle energy.

Design and performance of a UHV compatible soft X-ray double crystal monochromator at the proton factory

Abstract: The design and performance of an ultrahigh vacuum compatible soft X-ray double crystal monochromator at the Photon Factory in operation is described. This is a compact version of the JUMBO at SSRL with some improved mechanisms. Ge(111), InSb(111), α-quartz (10 1 0), beryl (10 1 0 and GGG(211) were tested as monochromatizing elements with regard to the resolution, intensity and radiation damage.

A positron camera for industrial application

Abstract: A positron camera for application to flow tracing and measurement in mechanical subjects is described. It is based on two 300 × 600 mm 2 hybrid multiwire detectors; the cathodes are in the form of lead strips plated onto printed-circuit board, and delay lines are used to determine the location of photon interactions. Measurements of the positron detection efficiency (30 Hz μCi −1 for a centred unshielded source), the maximum data logging rate (3 kHz) and the spatial resolving power (point source response = 5.7 mmfwhm) are presented and discussed, and results from initial demonstration experiments are shown.

Angular distribution of undulator power for an arbitrary deflection parameter K

Abstract: A calculation of the angular distribution of power generated from an undulator, integrated over all frequencies, is presented. The result, valid for any arbitrary value of the deflection parameter K, reduces to the known expressions in the cases K ..-->.. infinity and K ..-->.. 0.

New electronically black neutron detectors

Abstract: Two neutron detectors are described that can function in a continuous radiation background. Both detectors identify neutrons by recording a proton recoil pulse followed by a characteristic capture pulse. This peculiar signature indicates that the neutron has lost all its energy in the scintillator. Resolutions and efficiencies have been measured for both detectors.

The Topaz Time Projection Chamber

Abstract: A Time Projection Chamber (TPC) is under construction for the TOPAZ e + e − experiment at TRISTAN. The dimension of the TPC is 260 cm in diameter and 300 cm in axial length. Fin-type fine field cages are set inside GFRP insulator cylinders which also serve as the pressure container. The sector is made of multilayer G10 boards for better electric and thermal isolation. The cathode pads are substantially larger in area than those of the PEP4-TPC and having zigzag-shaped boundary. These serve to maintain high spatial resolution with fewer number of pad channels. Signals are amplified by low noise preamplifiers and shaping amplifiers, and, stored and digitized by FASTBUS based CCD-digitizers. Digitized information is preprocessed and sent to VAX 11/780 at a rate 2 MHz per 32 bit word. Nitrogen LASER beam will be used extensively with the LASER beacon system for calibration. Test results on production prototypes are also reported.

A plastic multidetector for light nuclei identification at GANIL

Abstract: A multidetector consisting of 96 plastic scintillators is now in operation at GANIL. It can identify in charge all fast light nuclei emitted between 3° and 30°.

The ion guide isotope separator on-line, IGISOL

Abstract: A new ISOL method, the IGISOL (Ion Guide Isotope Separator On-Line), permits thermalized primary recoil ions produced in nuclear reactions to be run directly through a mass separator without a conventional ion source. It allows a fast (≳ 100 μs) separation of various radioactive isotopes of both volatile and nonvolatile elements. The overall separation efficiencies measured for heavy nuclides produced in light ion induced reactions are up to 10%. The shortest-lived activity identified in an on-line separation is the 182 μs isomeric state of 207Bi.

Applications of fiber technique in the X-ray region

Abstract: The fiber technique has been applied to X-rays by the use of a thin capillary of glass. The critical angles for total reflection have been measured and compared with calculated values from a simple theory. The ability of bending the X-ray beam within the fiber has been demonstrated.

A plane-grating monochromator for 2 eV ≤ hv ≤ 150 eV

Abstract: Design and performance of a plane-grating monochromator at UVSOR facility are described. Two monochromators of the present design have been constructed and are used for optical and photoelectron spectroscopy of solids.