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With ever-more demanding requirements for the accurate manufacture of large components, dimensional measuring techniques are becoming progressively more sophisticated. This review describes some of the more recently developed techniques and the state-of-the-art in the more well-known large-scale dimensional metrology methods. In some cases, the techniques are described in detail, or, where relevant specialist review papers exist, these are cited as further reading. The traceability of the measurement data collected is discussed with reference to new international standards that are emerging. In some cases, hybrid measurement techniques are finding specialized applications and these are referred to where appropriate.

GPS location services have benefited the lives of millions. But what if it was possible to perform similar measurements using optical instead of microwave wavelengths? We investigate the potential and challenges of an optical analogue to GPS.

An experiment has been performed to search for the muon- and electron-number non-conserving decay mu+ to e+_gamma. The upper limit for the branching ratio to be GAMMA(mu+ to e+_gamma)/GAMMA(mu+ to e+_nu_nubar) < 1.2e-11 with 90% confidence.

This paper shows how the angular uncertainties can be determined for a rotary-laser automatic theodolite of the type used in (indoor-GPS) iGPS networks. Initially, the fundamental physics of the rotating head device is used to propagate uncertainties using Monte Carlo simulation. This theoretical element of the study shows how the angular uncertainty is affected by internal parameters, the actual values of which are estimated. Experiments are then carried out to determine the actual uncertainty in the azimuth angle. Results are presented that show that uncertainty decreases with sampling duration. Other significant findings are that uncertainty is relatively constant throughout the working volume and that the uncertainty value is not dependent on the size of the reference angle.

A calculation method of estimating instrumental background in high-energy gamma -ray telescopes, using the hadronic Monte Carlo code FLUKA87, is presented. The method is applied to the SAS-2 and EGRET telescope designs and is also used to explore the level of background to be expected for alternative configurations of the proposed GRITS telescope, which adapts the external fuel tank of a Space Shuttle as a gamma -ray telescope with a very large collecting area. The background produced in proton-beam tests of EGRET is much less than the predicted level. This discrepancy appears to be due to the FLUKA87 inability to transport evaporation nucleons. It is predicted that the background in EGRET will be no more than 4-10 % of the extragalactic diffuse gamma radiation. >

The EGRET (Energetic Gamma Ray Experiment Telescope) detector has been calibrated at SLAC (Stanford Linear Accelerator) and, to a lesser degree, at the MIT (Massachusetts Institute of Technology) Bates Linear Accelerator Center. To monitor the photon beams for the calibration, a plastic scintillator block, 5 cm*5 cm in cross section, 15 cm in length, and viewed by a single photomultiplier tube, was used for the entire beam energy range of 15 MeV to 10 GeV. The design operation, and method of analysis of the beam intensity are presented. A mathematical framework has been developed to treat the general case of a beam with multiphoton beam pulses and with a background component. A procedure to deal with the fluctuations of the beam intensity over a data-taking period was also developed. The photon beam monitor is physically sturdy, electronically steady, simple to construct, and easy to operate. Its major merits lie in its sheer simplicity of construction and operation and in the wide energy range it can cover. >

On April 5, 1991, the Space Shuttle Atlantis carried the Compton Gamma Ray Observatory into orbit and the satellite was deployed on April 7. The Energetic Gamma Ray Experiment Telescope (EGRET) instrument was activated on April 15, and the first month of operations was devoted to verification of the instrument performance. Measurements made during that month and in the subsequent sky survey phase have verified that the instrument time resolution, angular resolution, and gamma ray detection efficiency are all within nominal limits. >

The MEGA experiment, which searched for the muon- and electron-number violating decay ${\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\gamma},$ is described. The spectrometer system, the calibrations, the data taking procedures, the data analysis, and the sensitivity of the experiment are discussed. The most stringent upper limit on the branching ratio, $\mathcal{B}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\gamma})l1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ with $90%$ confidence, is derived from a likelihood analysis.

The MEGA experiment is designed to search for the rare decay μ→eγ with a branching ratio sensitivity of ∼5×10−13. Production data have been taken during 1992 and 1993, and the detector is working as expected. Following a complete analysis, the present data set should represent an improvement of 12–15 in sensitivity over the previous limit of μ→eγ.

An absolute interferometric dilatometer is described. It has been designed to measure the linear thermal expansion coefficient of gauge blocks up to 125 mm long. The instrument uses an electrically heated oven to control the temperature of up to 10 gauges at temperatures between about 20 degree(s)C and 37 degree(s)C. A Fizeau interferometer is used to measure the length of the gauges in terms of the wavelengths of frequency stabilized He-Ne lasers using the method of exact fractions. Preliminary results indicate that the target uncertainty of +/- 1 X 10-7 K-1 for the thermal expansion coefficient can be achieved for 100 mm steel gauge blocks.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The main objective of this long term program is the development of the prototype of a space‐based, large area High Resolution Gamma Ray Astrophysics Facility (HR‐GRAF) capable of studying diffuse and point‐like sources of gamma rays in the 1 MeV to 100 GeV energy range with a high angular and energy resolution, and very large sensitivity. The design of the HR‐GRAF will be based on the High Resolution Gamma Ray Telescope (HRGT) developed by the University of Texas at Dallas and University of California, Los Angeles, collaboration for SDIO.The long term studies planned for HR‐GRAF to be flown first either in balloons or free fliers, and eventually in the Space Station are the following:1) Map the galactic gamma radiation with better angular and energy resolution2) Observation of characteristic angular variations in the diffuse gamma rays to identify the primary origin of this radiation as due to discrete structures3) Study of point like sources of MeV and GeV gamma rays 4) Study the structure of the Galacti...

The calibration of the (EGRET) prior to its launch aboard the Compton Gamma Ray Observatory, the continuing calibration after launch, and instrument-performance results based on calibrations and early postlaunch data, are described. Particular attention is given to the effective area, the annular resolution, and the energy resolution.

This study is related to an evaluation of synchrotron radiation for the non-invasive assessment of coronary artery disease in humans. In vivo canine studies are reported for an imaging system developed for use with synchrotron X-ray beams. The probable configuration of an expanded system for pilot human subject studies is described.

Inclusive gamma-ray experiments were carried out in a e(+)e(-) colliding-beam apparatus with NaI(Tl) arrays as detectors. The inclusive gamma-ray spectra, after cosmic-ray background subtraction, are shown as histograms for the decays of the psi(3095) and psi-prime(3684). The psi spectrum has no significant narrow structure, while the psi-prime spectrum shows at least four peaks. Three major radiative decays of the psi-prime(3684) are found, and their respective branching fractions are computed.

X-ray computed tomography (CT) is a widely used method of obtaining cross sectional views of objects. The high intensity, natural collimation, monochromaticity and energy tunability of synchrotron X-ray sources could potentially be used to provide CT images of improved quality. The advantages of these systems would be that images could be produced more rapidly with better spatial resolution and reduced beam artifacts. In addition images, in some cases, could be acquired with elemental sensitivity. As a demonstration of the capability of such a system, CT images were obtained of four slices of an excised pig heart, in which the arteries and cardiac chambers were filled with an iodinated medium. Images were taken with incident X-rays tuned successively to energies just above and below the iodine K edge. Iodine specific images were obtained by logarithmically subtracting the low energy image data from the high energy data and then reconstructing the image. CT imaging using synchrotron radiation may become a convenient and non-destructive method of imaging samples difficult to study by other methods.

A search has been performed for the muon-number--violating decay ..mu -->..e/sup +/e/sup +/e/sup -/. No candidate event has been found, the result yielding an upper limit for the branching ratio of B/sub mu3e/ ..e/sup +/e/sup +/e/sup -/..nu../sub e/nu-bar/sub ..mu../ events, eleven such events were observed. They agree in number and spectra with expectations based on standard electroweak theory.

A search with the Crystal Box detector shows no evidence for the lepton-family-number-nonconserving decays ..mu -->..e..gamma.., ..mu -->..e..gamma gamma.., or ..mu -->..eee. The search provides upper limits for the branching ratios of GAMMA(..mu -->..e..gamma..)/GAMMA(..mu -->..evv-italic-bar) ..e..gamma gamma..)/GAMMA(..mu -->..evv-italic-bar) ..eee)/GAMMA(..mu -->..evv-italic-bar)

A review of techniques used in the production and operation of NaI(Tl) detectors is provided. The scintillation mechanism itself is summarized, and examples of the use of NaI(Tl) detectors is several areas of science and technology are given.

The EGRET telescope, one of the instruments to be carried on NASA's Gamma Ray Observatory, is designed to explore the high-energy portion (20 - 24,000 MeV) of the electromagnetic spectrum. A calibration source of ?-rays over this wide energy range has been used at SLAC, together with an appropriate set of intensity-monitoring instruments, to conduct a calibration of the EGRET telescope over this energy range for the full telescope aperture. The calibration method and an overview of the results are described.

The response of 30 in. diameter NaI(Tl) crystal detectors to electrons in the GeV range is described, and experience acquired in the operation of such detectors in physics experiments is summarized.

A safe and sensitive method of visualizing the coronary arteries is needed. The presently available method of visualization is highly invasive and carries too high a risk and cost. The intensity and tunability of synchrotron X-ray beams provides a new source of X-rays highly suited to the in vivo detection of iodinated contrast agents. The method offers the prospect of non-invasive visualization of the arteries by peripheral venous injection of contrast agent. The studies already conducted and those in preparation for human subjects are reviewed.

The intensity and tunability of synchrotron X-ray beams are highly suited to the non-invasive detection of iodine by K-edge digital subtraction angiography. An imnaging system developed for in vivo canine studies is described. Considerations relating to an expanded system for human subject studies are discussed.

An examination of 3.6\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ${\ensuremath{\mu}}^{+}$ decays yields an improved upper limit for the branching ratio $\frac{\ensuremath{\Gamma}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\gamma})}{\ensuremath{\Gamma}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}{\ensuremath{\nu}}_{e}{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}})}l1.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ with 90% confidence.

A rotating slit system has been designed and tested which can effectively translate a fan-shaped X-ray beam at the same average speed and in the same direction of travel as a patient moving continuously during a line-scan dual-energy medical imaging procedure. The slit has been shown to eliminate the artifacts due to bone in logarithmically subtracted images obtained with monochromatic X-ray beams derived from synchrotron radiation, where one beam is just above and the other just below the K-edge of iodine. Images of iodine-containing phantoms and in vivo canine images after intravenous iodine injection show vessel detail without artifacts due to bone. Corresponding images taken without the rotating slit have severe artifacts.

A double gap of cylindrical proportional chambers has been designed and built for use with a large solid angle, modular NaI(Tl) array (The Crystal Ball). The chambers are constructed of three coaxial foam-epoxy shells, covered with an aluminum-mylar laminate. One of the high voltage cathodes in each chamber has been photo-etched to produce a pattern of stripes and precise position measurements of tracks passing transverse to the chamber axis are found by pulse height analyzing the shaped and amplified induced strip signals. Performance of the chamber using both the strip signals and the sense wire readout is presented. The design of both the signal handling electronics and the digital portions of the systems is discussed.

A search has been performed for the decays μ → eee, μ → e γ , and μ → eγγ with a sensitivity in the branching ratios at the level of 10 −10 . The experiment used a separated, 26 MeV/c μ + beam with an average intensity of 300kHz. A total of 2.2 × 10 11 muon decays were examined for the present result. The detector for the experiment Is the Crystal Box, which consists of a cylindrical drift chamber surrounded by 396 NaI(T1) crystals. A layer of scintillation counters in front of the crystals provided timing for electrons and a veto for photons. The energy resolution for electrons and photons is ≈6% (FWHM). The position resolution of the drift chamber is 350 μm leading to a vertex cut with a rejection of 10 3 for μ → eee. The timing resolution is ≈300 ps from the scintillators and ~1 ns from the crystals. No candidate for μ → eee has been found, yielding an upper limit for the branching ratio of B μ 3e −10 (90% C.L.).

A large aperture, modular NaI(Tl) detector, the Crystal Box, with 396 independent crystal modules is now in operation at LAMPF. Electronics matched to the excellent energy and time resolutions provided by this detector for y rays and electrons has been built and tested, and is described in this paper. Included are base circuit design, photomultiplier (PMT) signal distribution, energy and time measurement, provision of logic signals, and the control of data acquisition and preliminary data processing by a group of small computers.

An array of 45 NaI(Tl) crystals modules, each in 20 in. in length and hexagonal in cross section with six 3 in. sides, has been operated as a detector of 50 MeV γ-rays in a search for the decay μ + →e + γ . The calibration procedure used for this detector and the resolutions achieved in γ-ray energy, time of detection and point of impact on the detector face are described.

Synchrotron radiation provides a new source of X-rays highly-suited to iodine K-edge Digital Subtraction Angiography (DSA). The use of such beams provides maximum sensitivity to intra-arterial iodine and virtually eliminates image contrast due to non-vascular body structures. The intensity of the beams permits short exposure times and allows images to be recorded, in line-scan fashion, in sharp focus despite arterial motions. The sensitivity of this method offers the prospect of visualizing arteries, and in particular the coronary arteries, by peripheral venous injection. The principles of DSA have been demonstrated using phantoms and excised animal hearts, and in vivo studies in animals have begun. The instrumentation developed for this purpose and the results obtained to date are summarized.

A 30-element Si(Li) detector has been fabricated to measure the one-dimensional flux profile of 33 KeV x-rays from a synchrotron radiation beam. The device, which is fabricated from a single 39mm × 15mm silicon wafer, is a linear array of 0.9mm × 7mm elements with a 1mm center-to-center spacing. It is 5mm thick and when operated at room temperature has an average leakage current of 10 nA/element. The x-ray flux in each element is determined by measuring the current with a high quality operational amplifier followed by a current digitizer. This detector is being used to study the use of synchrotron radiation for non-invasive imaging of coronary arteries. The experiment uses the difference in the transmitted flux of a monochromatized x-ray beam above and below the iodine K-edge. Measurements have been made on plastic phantoms and on excised animal hearts with iodinated arteries. The images obtained indicate that a 256-element device with similar properties, but with 0.6mm element spacing, will make a very effective detector for high-speed medical imaging.

Two 30 cm diameter steel drums with four facets rotating at 1800 RPM have produced high-quality digital-subtraction radiographs by alternately blocking and transmitting dual-energy synchrotron X-ray beams. An eight times faster system with 16.5 cm diameter tenfaceted tin-plated aluminum drums rotating at 5760 RPM is presently under construction.

An array of 49 NaI(Tl) modules each 20 inch in depth and 2.5 inch × 2.5 inch in cross section has been constructed and its properties, especially energy resolution, explored for positrons in the range 20 MeV – 18 GeV. A subsequent much larger detector, the Crystal Box, has also been constructed from 396 modules of the same cross section, but mostly 12 inch in depth, and operated as a γ-ray and positron detector in a search for rare muon decays. The calibration procedure used for the Crystal Box and its characteristic resolutions in energy, impact point and time are described.

A large NaI(Tl) spectrometer is expected to play a crucial role in the measurement of the energy spectra from an all-sky survey of high-energy celestial gamma rays on the Gamma Ray Observatory. The crystal size and requirements of space flight have resulted in a novel crystal-packaging and optics combination. The structure of this spectrometer and the operating characteristics determined in a test program using high energy positrons are described.

This paper describes a kinematically complete search for the muon decay ..mu../sup +/..-->..e/sup +/..gamma... The experiment used a magnetic spectrometer outfitted with proportional chambers to measure the positron momentum vector and a large segmented NaI(Tl) array to determine the ..gamma..-ray energy and impact point. The positrons were mostly from normal muon decay while the ..gamma.. rays were mostly from internal and external bremsstrahlung. Approximately 3 x 10/sup 12/ muons were stopped in a 50-mg/cm/sup 2/ polyethylene target. The relative timing between the positron and the ..gamma.. ray was measured with a resolution of 1.9 ns full width at half maximum (FWHM) by the use of a plastic-scintillator hodoscope for the positron and by NaI(Tl) constant-fraction timing for the ..gamma.. ray. The positron energy resolution averaged over all data was 8.8% FWHM, and the ..gamma..-ray energy resolution was 8% FWHM, both at 52.8 MeV. When the ..gamma.. ray is assumed to originate at the same place in the target as the positron, the rms error in the measurement of the angle between the positron and ..gamma..-ray momentum vectors was 37 mrad. The acceptance of the apparatus for ..mu../sup +/..-->..e/sup +/..gamma.. events was (1.75 +- 0.04)%. A maximum-likelihood analysis established a 90%-confidencemore » upper limit for the branching ratio GAMMA(..mu../sup +/..-->..e/sup +/..gamma..)/GAMMA(..mu../sup +/..-->..e..nu nu..) of 1.7 x 10/sup -10/.« less

One of the three co-aligned γ-ray telescopes to be carried into space aboard NASA's Gamma Ray Observatory is the high-energy EGRET telescope. The sensitive range of this instrument extends from 20 to 24000 MeV. A calibration of the EGRET response over its full energy range — including efficiency, angular resolution and energy resolution as a function of γ-ray arrival direction and energy — is an essential precursor to launch. A source of calibration γ-rays was provided by a backscattered laser beam that had been developed earlier at SLAC to provide quasi-monoenergetic 20 GeV γ-rays. In principle, the γ-ray energy in this beam can be reduced by lowering the electron beam energy so that, for example, a 760 MeV electron beam produces a 20 MeV γ-ray beam. The practical problems encountered in extending the operating range of the SLAC beam to low energies are described. The techniques used to monitor the γ-ray beam intensity at ten operating energies are indicated, and an overview of the EGRET calibration procedure is provided.

A precision luminosity monitor is described which has been used successfully in an experimental test of quantum electrodynamics at the 2.6 GeV electron-positron storage ring (SPEAR-I) at the Stanford Linear Accelerator Center. Design considerations and construction details are given, together with a discussion of radiative corrections and an evaluation of the response of the monitor.

A prototye NaI(Tl) detector (the Cluster of 54) of spherical geometry subtending a solid angle of 7.5% of 4? at its center, has recently been assembled and tested. This detector consisted of 54 close-packed but optically isolated NaI(Tl) modules and the associated electronic circuitry. The Cluster of 54 is the predecessor of an almost complete spherical detector, the Crystal Ball, which will cover 94% of 4?. The latter detector is now under construction and is especially designed for the study of ?-rays produced in electron-positron collisions at colliding beam facilities. This article will outline the mechanical, optical, and electronic assembly of the prototype system. Cluster of 54 test data will be presented.

We report the use of a 500 keV Van de Graaff proton accelerator to produce ?-rays in the range 4 - 18 MeV via nuclear reactions for the purpose of calibrating a large NaI(Tl) crystal array. Data analysis indicates an energy calibration to ~ 1% over this range.

Measurements of the cross section for the muon-pair-annihilation reaction e/sup +/e/sup -/ ..-->.. ..mu../sup +/..mu../sup -/, relative to Bhabha scattering at 4/sup 0/, are reported at center-of-mass energies in the range 6.2--7.4 GeV. These measurements provide a fundamental test of quantum electrodynamics (QED) for timelike values of the invariant four-momentum transfer q/sup 2/ as high as 54.8 (GeV/c)/sup 2/, which in this reaction is carried by the photon propagator. The results are in agreement with predictions of QED.

We report measurements of e+e−→e+e−, e+e−→γγ, and e+e−→μ+μ− at angles close to 90°, relative to Bhabha scattering at 3.7°, at a center-of-mass energy equal to 5.2 GeV. The results are found to be consistent with the predictions of quantum electro-dynamics.

This Letter reports a new experimental search for the family-number-nonconserving decay ..mu../sup +/ ..-->.. e/sup +/..gamma... There is no evidence for the presence of this decay mode. The upper limit for the branching ratio is GAMMA(..mu.. ..-->.. e..gamma..)/GAMMA(..mu.. ..-->.. enu anti nu) < 4.9 x 10/sup -11/ (90% C.L.). 13 refs., 3 figs.

The intense synchrotron radiation produced by wiggler magnets at electron storage rings provides a new source of x-rays highly suited to iodine K-edge digital subtraction angiography. The monochromaticity and tunability provide maximum sensitivity to intraarterial iodine and virtually eliminate contrast due to soft tissue and bone. Visualization of arteries, in particular the coronary arteries, by peripheral venous injection is possible. A system design, based on tests already performed, is presented.

A very accurate luminosity monitor for an e + e − storage ring experiment has been built and successfully operated. The systematic error on the measured luminosity is estimated to be approximately 0.6%.

A data-acquisition system is being developed for a large-scale experiment at LAMPF. It will make use of four microprocessors running in parallel to acquire and preprocess data from 432 photomultiplier tubes (PMT) attached to 396 NaI crystals. The microprocessors are LSI-11/23s operating through CAMAC Auxiliary Crate Controllers (ACC). Data acquired by the microprocessors will be collected through a programmable Branch Driver (MBD) which also will read data from 52 scintillators (88 PMTs) and 728 wires comprising a drift chamber. The MBD will transfer data from each event into a PDP-11/44 for further processing and taping. The microprocessors will perform the secondary function of monitoring the calibration of the NaI PMTs. A special trigger circuit allows the system to stack data from a second event while the first is still being processed. Major components of the system were tested in April 1981. Timing measurements from this test are reported.

Silicon lithium-drifted [Si(Li)] detectors 150 mm long, 10 mm wide and 5 mm thick with 300 individual elements have been fabricated as imaging detectors for noninvasive studies of human coronary arteries using 33 keV x-rays from a synchrotron radiation beamline. This detector is an extension of earlier work on 30 mm long devices with initially 30 and later 60 elements. The detector fabrication details are discussed highlighting problems in uniform lithium-ion compensation. The device structure is examined and measurements on the interelement impedances presented. Finally an angiograph of the coronary arteries in an excised pig's heart obtained with this 300-element detector is presented.

The coded aperture, a refinement of the scatter-hole camera, offers a method for the improved measurement of γ-ray direction in γ-ray astronomy. Two prototype coded apertures have been built and tested. The more recent of these has 128 active elements of the heavy scintillator BGO. Results of tests for γ-rays in the range 50 - 500 MeV are reported and future application in space discussed.

A multiwire proportional chamber system is described which has been used successfully in an experiment at the 2.6 GeV electron-positron storage ring (SPEAR) at the Stanford Linear Accelerator Center. Detailed descriptions of the chamber construction and test procedures are given, together with a description of the electronic read-out circuitry. The performance of the system during the experiment is reported and on-line displays of typical events are shown.