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Proportional and drift chambers in applied investigations

Description: Various applications of Multiwire Proportional Chambers (MWPC) to problems in medical imaging of x-rays and $gamma$-rays, technical neutron radiography, x-ray crystallography and x-ray astronomy are reviewed. Various types of drift spaces, gas fillings and solid (boron, plastic, lead) converters for enhancing the detection efficiency of the MWPC to gamma and neutron radiations are discussed. (auth)
Date: June 1, 1975
Creator: Perez-Mendez, V.
Partner: UNT Libraries Government Documents Department

Characteristics of multiwire proportional chambers for positron imaging

Description: Multiwire proportional chambers (MWPC) designed for use in a positron camera for nuclear medicine applications are described. The coordinated of the two anihilation gamma rays are detected in the chamber by their interaction with thin lead converters placed on both faces of each chamber. In order to obtain reasonable efficiencies (10%) the lead converters have been made in a square honeycomb-like structure, which increases the effective surface area and also permits the application of a drift field to extract the electrons into the active area of the MWPC. (auth)
Date: November 1, 1973
Creator: Lim, C.B.; Chu, D.; Kaufman, L.; Perez-Mendez, V. & Sperinde, J.
Partner: UNT Libraries Government Documents Department

Photon detectors with gaseous amplification

Description: Gaseous photon detectors, including very large 4{pi}-devices such as those incorporated in SLD and DELPHI, are finally delivering physics after many years of hard work. Photon detectors are among the most difficult devices used in physics experiments, because they must achieve high efficiency for photon transport and for the detection of single photoelectrons. Among detector builders, there is hardly anybody who did not make mistakes in this area, and who does not have a healthy respect for the problems involved. This point is stressed in this paper, and it is suggested that only a very small operating phase space is available for running gaseous photon detectors in a very large system with good efficiency and few problems. In this paper the authors discuss what was done correctly or incorrectly in first generation photon detectors, and what would be their recommendations for second generation detectors. 56 refs., 11 figs.
Date: August 1, 1996
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

A search for {mu} {yields} e{gamma} at the level of 10{sup {minus}13}

Description: The MEGA -experiment is a search for the decay {mu} {yields} {gamma}, for which the present upper limit for the branching ratio is 4.9 {times} 10{sup {minus}11}. The observation of this decay would indicate the existence of physics outside the standard model of electroweak interactions. The experiment employs highly modular, fast detectors, state-of-the-art electronics, and a staged trigger with on-line filters. The detectors are contained in a 1.5 T solenoidal field produced by a superconducting magnet. Positrons axe confined to the central region and axe measured by a set of thin MWPCs with a designed energy resolution of 350 keV FWHM and angular resolution of 1 deg FWHM. Photons are measured by one of three layers of pair spectrometers in the outer region. The total photon detection efficiency is about 6%; the expected photon energy resolution is 1.7 MeV FWHM and the angular resolution is 10 deg FWHM. The time resolution between the photon and electron is 0.8 ns FWHM. About 10{sup 8} events that passed the on-line inters were recorded during the 1993 run. These data should have a branching ratio sensitivity approximately fifteen times better than the present limit. The measured resolutions are approaching the design values.
Date: July 1, 1994
Creator: Mischke, R. E.; Amann, J. F. & Barlow, D.
Partner: UNT Libraries Government Documents Department

Multiwire proportional chamber for imaging thermal, epicadmium, and fast neutrons

Description: From nuclear science symposium; San Francisco, California, USA (14 Nov 1973). The 25 cm x 25 cm chamber described images thermal and epicadmium neutron beams using two boron-coated conversion screens, and fast neutrons using a single polyethylene converter, Sample images and quantitative attenuation and resolution data are presented, Measurements of neutron attenuation in lucite patterns give good agreement with expected values for thermal, epicadmium, and fast (Pu- Be) beams. The measured mean free energy. This gives good agreement with the experimental data for tracks longer than approx equal 15 mu m (alphas and 160 ions of energies 5.3 to 8.8 MeV and 22 to 42 MeV, respectively). The shorter tracks of fission fragments (90 MeV from /sup 252/Cf) give shorter t/sub p/ values than predicted by the formula above. This is explained by transfer from cylindrical to spherical erosion geometry. (auth)
Date: November 1, 1973
Creator: Velentine, K.; Kaplan, S.; Perez-Mendez, V. & Kaufman, L.
Partner: UNT Libraries Government Documents Department

High efficiency collimator-converters for neutral particle imaging with MWPC

Description: A MWPC with external collimator converter system has been developed specifically for the detection of 0.511 MeV gammas in a positron camera. The design basis is applicable also to the imaging of other gammas and neutrons. The converter consists of honeycomb cells which provide an enhanced area of escape surface as well as restricting the range of conversion electrons to the cell dimensions. (WHK)
Date: December 1, 1975
Creator: Chu, D.; Tam, K.C.; Perez-Mendez, V.; Lim, C.B.; Lambert, D. & Kaplan, S.N.
Partner: UNT Libraries Government Documents Department

Four-deep charge-time and pulse-width scaling discriminator for delay line MWPC's

Description: A discriminator has been developed for digitizing both intercepted total charge and location of electromagnetic shower and particle trajectories in multi- wire proportional chambers read by delay lines. Determination of shower trajectory is aided by video signal integration followed by centroid-locating discrimination. Calibrated run-down of the signal integrating capacitor gives the charge information above a given threshold level. The discriminator is designed to handle up to four shower-induced video signals per event by incorporating steering circuits within the module. Each video signal is examined for time over an adjustable threshold. Video pulses with separation of less than 20 nsec are treated as a single pulse. Counter-logic circuits indicate the number of video signals digitized. These signal processing circuits provide a first level of data sifting which otherwise must be carried out with additional discriminator channels and added complexity in data recognition.
Date: November 1, 1975
Creator: Lee, K.L.; Kirsten, F.A.; Grigorian, A. & Guiragossian, Z.G.T.
Partner: UNT Libraries Government Documents Department

Dissipative model for a two component gas system with friction

Description: For a mixture of small and large component of gases, the large component is treated as an ideal gas. A dissipative model is proposed for the small component, and the thermodynamic characteristics of the gas are derived through a statistical mechanical approach. The model requires for the small component to have a big dimension and its number of particles to be smaller than the large one. Using the associated partition function, the internal energy and the equation of state are calculated. The internal energy does not suffer any deviation from that of the two component ideal gas, but the equation of state deviates from that of the ideal gas for large values of the parameter which characterizes the dissipative model.
Date: February 1, 1994
Creator: Lopez, G.; Murgia, M. & Sosa, M.
Partner: UNT Libraries Government Documents Department

Recent developments in delay line readout of multiwire proportional chambers

Description: From nuclear science symposinm; San Francisco, California, USA (14 Nov 1973). The application of electromagnetic delay line readout methods for determining the track positions of ionizing particles in multiwire proportional chambers is described. Construction techniques for large area chambers, which allow the use of all three planes for track position measurements are given. The construction and characteristics of electromagnetic delay lines optimized for wire chamber readout are discussed. (auth)
Date: November 1, 1973
Creator: Perez-Mendez, V. & Parker, S.I.
Partner: UNT Libraries Government Documents Department

Modular multi-wire readout system for proportional wire chambers

Description: From nuclear science symposium; San Francisco, California, USA (14 Nov 1973). The design features of a data readout system for multiwire proportional chambers are described. The electronic circuitry for this amplifier-per-wire'' system has been designed in modular form to provide ease in system assembly, flexibility, and economy. Fast readout of the hit-pattern data is accomplished by using priority encoder integrated circuits for address generation and bit- parallel transfer of the output data words. About 7000 channels have been implemented using this system and an additional 4000 channels have been ordered. An analysis of cost per channel is given, based on the experience gained thus far. (auth)
Date: November 1, 1973
Creator: Olson, S.R.; Kirsten, F.A.; Binnall, E.P.; Lee, K.L.; Bhandari, N.N. & Nunnally, C.C.
Partner: UNT Libraries Government Documents Department

Capacitive charge division in centroid finding cathode readouts in MWPCs. Revision 1/93

Description: A technique is described in which the centroid of induced charge on cathode strips in a proportional chamber can be determined with reduced differential and integral nonlinearity, without increasing the number of readout channels. It is based on capacitive charge division from intermediate cathode strips to adjacent readout strips, and may be applied to a variety of position readout principles.
Date: October 1, 1987
Creator: Smith, G. C.; Fischer, J. & Radeka, V.
Partner: UNT Libraries Government Documents Department

Laboratory Directed Research & Development program. Annual report to the Department of Energy

Description: This report briefly discusses the following projects coordinated at Brookhaven National Laboratory: investigation of the utility of max-entropy methods for the analysis of powder diffraction data; analysis of structures and interactions of nucleic acids and proteins by small angle x-ray diffraction; relaxographic MRI and functional MRI; very low temperature infra-red laser absorption as a potential analytical tool; state-resolved measurements of H{sub 2} photodesorption: development of laser probes of H{sub 2} for in-situ accelerator measurements; Siberian snake prototype development for RHIC; synthesis and characterization of novel microporous solids; ozone depletion, chemistry and physics of stratospheric aerosols; understanding the molecular basis for the synthesis of plant fatty acids possessing unusual double bond positions; structure determination of outer surface proteins of the Lyme disease spirochete; low mass, low-cost multi-wire proportional chambers for muon systems of collider experiments; theory of self-organized criticality; development of the PCR-SSCP technique for the detection, at the single cell level, of specific genetic changes; feasibility of SPECT in imaging of F-18 FDG accumulation in tumors; visible free electron laser oscillator experiment; study of possible 2 + 2 TeV muon-muon collider; ultraviolet FEL R & D; precision machining using hard x-rays; new directions in in-vivo enzyme mapping: catechol-O-methyltransferase; proposal to develop a high rate muon polarimeter; development of intense, tunable 20-femtosecond laser systems; use of extreme thermophilic bacterium thermatoga maritima as a source of ribosomal components and translation factors for structural studies; and biochemical and structural studies of Chaperon proteins from thermophilic bacteria and other experiments.
Date: December 1, 1995
Creator: Ogeka, G.J. & Romano, A.J.
Partner: UNT Libraries Government Documents Department

A disoriented chiral condensate search at the Fermilab Tevatron

Description: MiniMax (Fermilab T-864) was a small test/experiment at the Tevatron designed to search for disoriented chiral condensates (DCC) in the forward direction. Relativistic quantum field theory treats the vacuum as a medium, with bulk properties characterized by long-range order parameters. This has led to suggestions that regions of {open_quotes}disoriented vacuum{close_quotes} might be formed in high-energy collision processes. In particular, the approximate chiral symmetry of QCD could lead to regions of vacuum which have chiral order parameters disoriented to directions which have non-zero isospin, i.e. disoriented chiral condensates. A signature of DCC is the resulting distribution of the fraction of produced pions which are neutral. The MiniMax detector at the C0 collision region of the Tevatron was a telescope of 24 multi-wire proportional chambers (MWPC`s) with a lead converter behind the eighth MWPC, allowing the detection of charged particles and photon conversions in an acceptance approximately a circle of radius 0.6 in pseudorapidity-azimuthal-angle space, centered on pseudorapidity {eta} {approx} 4. An electromagnetic calorimeter was located behind the MWPC telescope, and hadronic calorimeters and scintillator were located in the upstream anti-proton direction to tag diffractive events.
Date: May 1, 1997
Creator: Convery, M.E.
Partner: UNT Libraries Government Documents Department

Studies of hadron-electron separators for the ZEUS barrel calorimeter

Description: Two possible upgrades, a shower maximum detector and a presampler, designed to improve the low energy electron/hadron separation capabilities of the ZEUS barrel calorimeter are described and test-beam results are reported. The presampler can also be used to correct for energy loss of particles traversing the dead material in front of the calorimeter.
Date: May 25, 1995
Creator: Ambats, I.; Bortz, D. & Connolly, A.
Partner: UNT Libraries Government Documents Department

Utilization of amorphous silicon carbide (a-Si:C:H) as a resistive layer in gas microstrip detectors

Description: Thin semiconducting films of hydrogenated amorphous silicon (a-Si:H) and its carbon alloy (a-Si:C:H) were applied to gas microstrip detectors in order to control gain instabilities due to charges on the substrate. Thin ({approximately}100nm) layers of a-Si:H or p-doped a-Si:C:H were placed either over or under the electrodes using the plasma enhanced chemical vapor deposition (PECVD) technique to provide the substrate with a suitable surface conductivity. By changing the carbon content and boron doping density, the sheet resistance of the a-Si:C:H coating could be successfully controlled in the range of 10{sup 12} {approximately} 10{sup 17} {Omega}/{four_gradient}, and the light sensitivity, which causes the resistivity to vary with ambient light conditions, was minimized. An avalanche gain of 5000 and energy resolution of 20% FWHM were achieved and the gain remained constant over a week of operation. A-Si:C:H film is an attractive alternative to ion-implanted or semiconducting glass due to the wide range of resistivities possible and the feasibility of making deposits over a large area at low cost.
Date: April 1, 1995
Creator: Hong, W.S.; Cho, H.S.; Perez-Mendez, V. & Gong, W.G.
Partner: UNT Libraries Government Documents Department

MWPC with highly segmented cathode pad readout

Description: Experiments being conducted with high energy heavy ion beams at Brookhaven National Laboratory and at CERN have shown the importance of developing position sensitive detectors capable of handling events with high multiplicity in environments of high track density as will also be the case in future high luminosity colliders like SSC and RHIC. In addition, these detectors are required to have a dynamic range wide enough to detect minimum ionizing particles and heavy ions like oxygen or silicon. We present here a description of work being done on a prototype of such a detector at BNL. Results from a similar counter are also presented in this Conference. The ''pad chamber'' is a detector with a cathode area subdivided into a very large number of pixel-like elements such that a charged particle traversing the detector at normal incidence leaves an induced charge on a few localized pads. The pads are interconnected by a resistive strip, and readout amplifiers are connected to the resistive strip at appropriate, carefully determined spacings. The pattern of tracks in a multi-hit event is easily recognized, and a centroid-finding readout system allows position determination to a small fraction of the basic cell size. 5 refs., 9 figs.
Date: January 1, 1989
Creator: Debbe, R.; Fischer, J.; Lissauer, D.; Ludlam, T.; Makowiecki, D.; Radeka, V. et al.
Partner: UNT Libraries Government Documents Department

Performance of a pressurized multiwire proportional chamber for neutron radiography

Description: A study was made of the effect of gas density on resolution and efficiency of a neutron sensitive multiwire proportional chamber. Increasing the density will shorten the reaction products range. A pressure vessel was designed and constructed for 4 atm thereby reducing the range of the reaction products from the neutron converter by a factor of 4, compared to 1 atm. Pressurizing the chamber to 4 atm resulted in a spatial resolution of 1mm under the most favorable operating conditions. For the type of neutron converters used improving the efficiency is limited to a choice of material. Two different materials were tried, gadolinium and boron, with efficiencies of 6.3 and 2.3%, respectively.
Date: June 1, 1979
Creator: Director, B.
Partner: UNT Libraries Government Documents Department