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INNOVATION AND SCIENTIFIC FUNDING

Description: This article is an adaptation of the author's testimony before the Committee on Science and Technology of the U.S. House of Representatives regarding his experience of performing successful research projects that were initially rejected for funding.
Date: June 1, 1980
Creator: Muller, Richard A.
Partner: UNT Libraries Government Documents Department

ELECTRON AVALANCHE IN LIQUID XENON

Description: We present detailed measurements of the electron avalanche process in liquid Xenon. The measurements were made by using liquid-Xe-filled proportional chambers with anode diameters of 2.9, 3.5, and 5.0 {approx} to detect 279-keV y rays and measure the photopeak pulse height as a function of applied voltage. The use of uniform pulses of electrons enabled us to discriminate against secondary Townsend processes. We present a table of the first Townsend coefficient a as a function of electric field E; a typical value is {alpha} = (4.5 {+-} 0.3) x 10{sup 4} cm{sup -1} at E = 2 x 10{sup 6} V/cm. The electron avalanche occurs in liquid Xe at electric fields 26 times smaller than would be predicted using measurements made in gaseous Xe and E/{rho} density scaling.
Date: March 1, 1973
Creator: Derenzo, Stephen E.; Mast, Terry S.; Zaklad, Halm & Muller,Richard A.
Partner: UNT Libraries Government Documents Department

INITIAL IMAGES FROM A 24-WIRE LIQUID XENON Y -CAMERA.

Description: A prototype liquid xenon {gamma}-camera has been constructed and preliminary results obtained. The sensitive volume is 7 c x 7 cm in area and 1.5 cm thick. Orthogonal coordinates for each interacting {gamma}-ray are provided by 24 anode wires 5 {micro} in diameter spaced 2.8 mm apart and 24 cathode strips.
Date: December 1, 1972
Creator: Zaklad, Haim; Derenzo, Stephen E.; Muller, Richard A. & Smits,Robert G.
Partner: UNT Libraries Government Documents Department

PARTICLE DETECTORS BASED ON NOBLE LIQUIDS

Description: In order to build a thin particle detector with 10 micron spatial resolution and automatic readout, the avalanche of ionization electrons in high electric fields in liquid argon and liquid xenon has been studied. We present a scheme using an array of points that could be used to make a reliable liquid argon filled detector. The avalanche pulses in liquid xenon have a rise time more than three orders of magnitude faster than that in liquid argon, suggesting that the positive charge carriers are holes, and making possible a detector with a time resolution of better than 100 nanoseconds. A direct observation of hole conduction is described.
Date: September 1, 1970
Creator: Muller, Richard A.; Derenzo, Stephen E.; Smits, Robert G.; Zaklad, Haira & Alvarez, Luis W.
Partner: UNT Libraries Government Documents Department

Radiometer System to Map the Cosmic Background Radiation

Description: We have developed a 33 GHz airborne radiometer system to map large-scale angular variations in the temperature of the 3 K cosmic background radiation. A ferrite circulator switches a room-temperature mixer between two antennas pointing 60{sup o} apart in the sky. In forty minutes of observing, the radiometer can measure the anisotropy of the microwave background with an accuracy of {+-} 1 m{sup o}K rms, or about one part in 3000 of 3 K. The apparatus is flown in a U-2 jet to 20 km altitude where 33 GHz thermal microwave emission from the atmosphere is at a low level. A second radiometer, tuned to 54 GHz near oxygen emission lines, monitors spurious signals from residual atmospheric radiation. The antennas, which have an extremely low side-lobe response of less than -65 dB past 60{sup o}, reject anisotropic radiation from the earth's surface. Periodic interchange of the antenna positions and reversal of the aircraft's flight direction cancel equipment-based imbalances. The system has been operated successfully in U-2 aircraft flown from NASA-Ames at Moffett Field, California.
Date: November 1, 1977
Creator: Gorenstein, Marc V.; Muller, Richard A.; Smoot, George F. & Tyson,J. Anthony
Partner: UNT Libraries Government Documents Department

Cycles in fossil diversity

Description: It is well-known that the diversity of life appears to fluctuate during the course the Phanerozoic, the eon during which hard shells and skeletons left abundant fossils (0-542 Ma). Using Sepkoski's compendium of the first and last stratigraphic appearances of 36380 marine genera, we report a strong 62 {+-} 3 Myr cycle, which is particularly strong in the shorter-lived genera. The five great extinctions enumerated by Raup and Sepkoski may be an aspect of this cycle. Because of the high statistical significance, we also consider contributing environmental factors and possible causes.
Date: October 20, 2004
Creator: Rohde, Robert A. & Muller, Richard A.
Partner: UNT Libraries Government Documents Department

A LIQUID-FILLED PROPORTIONAL COUNTER

Description: We report properties of single-wire proportional chambers and multiple-wire ionization chambers filled with liquid xenon. Proportional multiplication is seen for anode fields > 10{sup 6} volts/cm (anode-cathode voltage> 1 kV for a 3.5-{micro}-diam anode wire). The efficiency for detecting ionizing radiation is {approx} 100%. The time resolution of the chambers is {+-} 10{sup -7} sec. We attained a spatial resolution of {+-} 15 {micro} with a multiwire ionization chamber, considerably better than that of any other real-time particle detector.
Date: June 1, 1971
Creator: Muller, Richard A.; Derenzo, Stephen E.; Smadja, Gerard.; Smith, Dennis B.; Smits, Robert G.; Zaklad, Haim. et al.
Partner: UNT Libraries Government Documents Department

A LIQUID XENON RADIOISOTOPE CAMERA

Description: The increasing availability of short lived gamma and positron emitting isotopes, coupled with the importance of dynamical studies and better imaging, has generated the need for an improved {gamma}-ray camera. The authors discuss a new type of {gamma}-ray camera which makes use of electron avalanches in liquid xenon. A configuration currently under development is shown in Figure 1. The successful operation of a liquid xenon proportional counter was recently reported. The liquid xenon camera promises better spatial resolution and higher counting rate than the existing NaI(Tl) scintillation camera. The spatial resolution for {gamma} rays is in principle limited only by the range of photoelectrons in liquid xenon, which is < 0.2 mm for energies < 1 MeV. A counting rate of 10{sup 6} C/s or more appears possible. As a result of the better resolution and high counting rate capability, the definition of the picture is improved. In addition, the high counting rate capability makes possible dynamic studies which were previously unfeasible. Although they expect the energy resolution with liquid xenon to be superior to that of NaI, the preliminary measurements show 17% FWHM for 279 keV {gamma}'s. Improvements are expected by using better geometry and smoother wire.
Date: February 1, 1972
Creator: Zaklad, Haim.; Derenzo, Stephen E.; Muller, Richard A.; Smadja,Gerard.; Smits, Robert G. & Alvarez, Luis W.
Partner: UNT Libraries Government Documents Department