An Attempt to Detect the Neutrino

1935 ◽  
Vol 31 (1) ◽  
pp. 99-107 ◽  
Author(s):  
M. E. Nahmias
Keyword(s):  
High Pressure ◽  
Magnetic Moment ◽  
Ionization Chamber ◽  
Solid Angle ◽  
Total Solid ◽  
Effective Length ◽  
Single Pair ◽  
Wave Mechanics ◽  
Bohr Magneton ◽  
Total Solid Angle

It has been shown by Chadwick and Lee(1), using a high-pressure ionization chamber, that if one neutrino is emitted by each disintegrating Ra E nucleus, then the neutrinos do not produce more than one pair of ions in 150 km. of air at N.T.P. Calculations based on the wave mechanics show that the ionization due to a neutrino having a magnetic moment of one Bohr magneton would be very easily detectable(2), whereas it has peen estimated that if the neutrino has no magnetic moment at all its encounters with nuclei will be as scarce as one in 1016 km. of water(3). I have investigated the matter again, using two Geiger-Müller counters, instead of an ionization chamber. The counters have the advantage of giving a discharge for a single pair of ions(4). The two counters of 15×5cm. were connected in parallel, and filled with air at 76mm. pressure. They were shielded on all sides by 45 mm. of lead. A source of 7 mg. of Ra (D, E, F) was placed at a distance of 11 cm. from the centres of the two counters, so that the total solid angle subtended by the counters at the source was 0·10, expressed as a fraction of the complete sphere. Assuming that both the disintegrating atoms of Ra D and Ra E give one neutrino, then the number of neutrinos crossing the counters per minute is 3·1 × 109. The average effective length of the path in the counter, reduced to N.T.P., is 0·3 cm., so in one min. the total range in air of all the neutrinos crossing the counters is 9·3 × 108 cm.

Toroidally Shaped Hopg Crystals as Strongly Focusing Bragg Reflectors of Characteristic X-Ray Tube Radiation for Edxrf Analysis

1993 ◽  
Vol 37 ◽  
pp. 523-533 ◽  
Author(s):  
B. Beckhoff ◽  
B. Kanngieβer ◽  
J. Scheer ◽  
W. Swoboda ◽  
J. Laursen
Keyword(s):  
Crystal Surface ◽  
Solid Angle ◽  
Bragg Reflection ◽  
Pyrolytic Graphite ◽  
Total Solid ◽  
Bragg Angle ◽  
X Ray ◽  
Spot Area ◽  
Fine Focus ◽  
Total Solid Angle

The characteristic 17.441 keV Mo-Kα tube line yields an exceedingly strong reflection at a Bragg angle of 6.0710 on Highly Oriented Pyrolytic Graphite (IIOPG). Using doubly bent toroidally shaped crystals we were able to concentrate the characteristic radiation from a Mo anode fine focus tube onto a small focal spot area of about 1 mm. FWHM diameter, as was observed by an X-Ray sensitive CCD. The radiation of the Mo anode fine focus tube is emitted at a take-off angle of 60 into a total solid angle with an aperture of 120. About 90 percent of this primary radiation solid angle can be used for the desired Bragg reflection on the designed toroidal crystal surface. This feature ensures the high beam intensity needed for special excitation problems.

The numerical calculation of the scattering correction in γ ray absorption measurements

1932 ◽  
Vol 28 (4) ◽  
pp. 475-489 ◽  
Author(s):  
G. T. P. Tarrant
Keyword(s):  
High Pressure ◽  
Numerical Calculation ◽  
Ionization Chamber ◽  
Solid Angle ◽  
Wave Length ◽  
Method Of Calculation ◽  
Scattering Correction ◽  
Γ Ray ◽  
Experimental Values ◽  
Absorption Measurements

The method of applying the scattering correction in accurate γ ray absorption measurements is discussed, and it is shown that the scattering correction only diminishes, as the solid angle subtended by the chamber at the source is reduced, if the absorber diameter is reduced correspondingly. The method of calculation of the scattering correction in cases in which the absorber is placed very close to the chamber is explained, and the result of the calculation for one particular chamber is shown to be in satisfactory agreement with the experimental values. The scattering correction allows the ionization function of chambers to be determined and an (ionization function)/(wave-length) curve is shown for a steel thick-walled high-pressure ionization chamber.

EM CALORIMETER COMPLEX FOREST FOR THE π0 AND η PHOTO-PRODUCTION EXPERIMENTS AT LNS-SENDAI

2009 ◽  
Vol 24 (11n13) ◽  
pp. 978-981 ◽  
Author(s):  
K. SUZUKI ◽  
H. FUJIMURA ◽  
R. HASHIMOTO ◽  
T. ISHIKAWA ◽  
J. KASAGI ◽  
...  
Keyword(s):  
High Efficiency ◽  
Solid Angle ◽  
Data Acquisition System ◽  
Total Solid ◽  
High Rate ◽  
Lead Glass ◽  
System A ◽  
Total Solid Angle ◽  
Electro Magnetic ◽  
Photo Production

A large solid angle γ-ray detector system, FOREST, has been constructed at LNS-Sendai to study the π0 and η photo-production reactions. The FOREST detector consists of three electro-magnetic calorimeters: pure CsI crystals, Lead/SciFi blocks and Lead Glass Cherenkov counters. It covers about 90% of the total solid angle. A new data acquisition system for the FOREST detector has been developed to handle high rate trigger events with a high efficiency. To investigate performances of FOREST and the DAQ system, a test experiment has been conducted. The π0 and η mesons are clearly observed. A DAQ efficiency of 76% has been obtained at a 2 kHz trigger request.

High-pressure xenon cylindrical ionization chamber with a shielding mesh

1994 ◽  
Author(s):  
Sergey E. Ulin ◽  
Valery V. Dmitrenko ◽  
V. M. Grachev ◽  
O. N. Kondakova ◽  
S. V. Krivov ◽  
...  
Keyword(s):  
High Pressure ◽  
Ionization Chamber ◽  
Cylindrical Ionization Chamber

scholarly journals Supershort avalanche electron beam generation in gases

2008 ◽  
Vol 26 (4) ◽  
pp. 605-617 ◽  
Author(s):  
V.F. Tarasenko ◽  
E.H. Baksht ◽  
A.G. Burachenko ◽  
I.D. Kostyrya ◽  
M.I. Lomaev ◽  
...  
Keyword(s):  
High Pressure ◽  
Electron Beam ◽  
Atmospheric Pressure ◽  
Electron Beams ◽  
Solid Angle ◽  
Generation Mechanism ◽  
Full Width ◽  
Half Maximum ◽  
Electron Beam Pulse ◽  
Supershort Avalanche Electron Beam

AbstractThis paper reports on the properties of a supershort avalanche electron beam generated in the air or other gases under atmospheric pressure and gives the analysis of a generation mechanism of supershort avalanche electron beam, as well as methods of such electron beams registration. It is reported that in the air under the pressure of 1 atm, a supershort (<100 ps) avalanche electron beam is formed in the solid angle more than 2π steradian. The electron beam has been obtained behind a 45 µm thick Al-Be foil in SF6 and Xe under the pressure of 2 atm, and in He, under the pressure of about 15 atm. It is shown that in SF6 under the high pressure (>1 atm) duration (full width at half maximum) of supershort avalanche electron beam pulse is about 150 ps.

scholarly journals Secondary gamma rays excited by the passage of neutrons through matter

1935 ◽  
Vol 150 (871) ◽  
pp. 637-668 ◽  
Keyword(s):  
High Pressure ◽  
Gamma Rays ◽  
Alpha Particle ◽  
Ionization Chamber ◽  
Gamma Ray ◽  
Beta Particle ◽  
Nuclear Excitation ◽  
Ionization Chambers ◽  
Scattering Material ◽  
Pass Through

It is well known that the absorption of neutrons in their passage through matter is due to nuclear collisions, and not appreciably to interaction with extranuclear electrons. A collision of a neutron with a nucleus may result in the scattering of the neutron, or in the disintegration of the nucleus. The experiments of Feather and of Harkins, Gans, and Newson§ have shown that several light elements, C, N, O, F, Ne are disintegrated, the mechanism probably being absorption of the neutron and emission of an alpha particle. Fermi|| has reported that a variety of elements when bombarded by neutrons show the phenomenon of induced radioactivity, emitting beta rays. He suggests that the disintegration process takes place usually by absorption of a neutron and emission of an alpha particle or proton, the resulting nucleus being an unstable radio element, transforming into a stable body by emission of a beta particle. The experiments here to be described show that when neutrons pass through various substances, gamma rays are produced. The origin of this radiation has not definitely been established; nuclear excitation appears to be the most plausible explanation in most cases. 2—Experimental Method The general method consisted in measuring the ionization current produced by a Po + Be source (usually of about 10-15 millicuries) placed above a high pressure ionization chamber, and observing the increased ionization when a block of scattering material was placed immediately above the source. A correction was applied for the diminution of the natural effect caused by the scatterer. The increase in ionization amounted usually to 2-3%, and thus to obtain even a rough measurement of the effect, accurate measurements of the ionization currents were required. For this reason the high pressure ionization chamber was usually used in preference to the counter, since measurements to one part in a thousand are impracticable with the latter. The ionization method has, however, the disadvantage that both gamma rays and neutrons are detected. To distinguish between the two radiations, two similar ionization chambers were used, one containing argon at a pressure of 90 atmospheres, the other hydrogen at about 60 atmospheres. The former is more sensitive to gamma radiation, the latter to neutrons. The ionization chambers were of steel and had cylindrical walls 1 cm thick; the radiations entered through the roofs of the chambers, which were 2·5 cm thick. The inside dimensions were 16 cm high and 12 cm diameter, with a 2-cm diameter central electrode. Collecting potentials of 250-500 volts were used. Measurements were made by a balance method and followed standard practice. From the measurements of ionization currents in argon and hydrogen estimates may be made of the neutron ( n ) and gamma ray (γ) intensities separately. The method by which this is achieved is described in § 11.

Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Giuseppe Vannini ◽  
Stefano Cioncolini ◽  
Giuseppe Del Vescovo ◽  
Massimiliano Rovini
Keyword(s):  
High Pressure ◽  
Preliminary Test ◽  
Labyrinth Seal ◽  
Effective Length ◽  
Single Frequency ◽  
Special Focus ◽  
Test Rig ◽  
Speed Increase ◽  
Gas Market ◽  
Stiffness And Damping

The current centrifugal compressor design for the oil & gas market is more and more challenging, and the presence of many competitors is pushing technology towards both a casing size reduction and a rotational speed increase. The first point is leading to an increase in the number of wheels per rotor (to do the same service), and the second point is forcing to cross two or even three rotor modes (hence a higher control of rotor damping is necessary). The two points together are leading to increase the rotor “flexibility ratio” (defined as the ratio between the maximum continuous speed and the first critical speed at infinite support stiffness according to API standard, and finally the rotordynamic stability is very much challenged. The centrifugal compressor's rotordynamic stability is strongly related to the internal seals' dynamic behavior, and for this reason, the authors' company decided several years ago to develop internally a high pressure seal test rig to measure internal seals stiffness and damping. The rig is now in operation, and in a previous paper the authors described its main capabilities, the applied identification procedures, and the preliminary test results captured for a long labyrinth seal (smooth rotor, straight toothed stator) tested up to 200 bar. This paper is intended to show more data for the same long Laby with special focus on some peculiar test as negative preswirl test, single frequency versus multifrequency test, offset versus centered seal test. The negative preswirl test shows a drastic change in the effective damping (from destabilizing to stabilizing) and provides a support in favor of the selection of swirl reversal devices at seals upstream. The multifrequency excitation test approach (based on the concurrent presence of several frequencies not multiples at each other) is compared with a single frequency excitation providing similar results and thus confirming the soundness of the multiple effects linear superimposition assumption. The effect of a static offset (simulating the real position of a rotor inside an annular seal) is also investigated proving that the relevant impact is negligible within the range of eccentricity explored (10% of seal clearance). Moreover, a pocket damper seal (PDS) with the same nominal diameter, clearance, and effective length has been tested (up to 300 bar) and compared with the Laby. As expected, the PDS shows both a higher effective stiffness and damping at the same test conditions, so the promising results already collected in a previous test campaign which was performed on a smaller scale and lower pressure test rig were mostly confirmed with the only exception for the effective damping crossover frequency which was lower than expected.

The High-Pressure Modification of CePtSn – Synthesis, Structure, and Magnetic Properties

2005 ◽  
Vol 60 (8) ◽  
pp. 821-830 ◽  
Author(s):  
Jan F. Riecken ◽  
Gunter Heymann ◽  
Theresa Soltner ◽  
Rolf-Dieter Hoffmann ◽  
Hubert Huppertz ◽  
...  
Keyword(s):  
High Pressure ◽  
Magnetic Properties ◽  
High Temperature ◽  
Magnetic Moment ◽  
Three Dimensional ◽  
Magnetic Ordering ◽  
Normal Pressure ◽  
Variable Parameters ◽  
X Ray ◽  
Experimental Magnetic Moment

The high-pressure (HP) modification of CePtSn was prepared under multianvil high-pressure (9.2 GPa) high-temperature (1325 K) conditions from the normal-pressure (NP) modification. Both modifications were investigated by powder and single crystal X-ray data: TiNiSi type, Pnma, a = 746.89(9), b = 462.88(4), c = 801.93(7) pm, wR2 = 0.0487, 452 F2 values, 20 variable parameters for NP-CePtSn, and ZrNiAl type, P6̅2m, a = 756.919(5), c = 415.166(4) pm, wR2 = 0.0546, 252 F2 values, 14 variable parameters for HP-CePtSn. Both modifications are built up from platinumcentered trigonal prisms. Together, the platinum and tin atoms form different three-dimensional [PtSn] networks in which the cerium atoms fill channels. The crystal chemistry and chemical bonding of NP- and HP-CePtSn is discussed. Susceptibility measurements of HP-CePtSn indicate Curie-Weiss behavior above 40 K with an experimental magnetic moment of 2.55(1) μB/Ce atom, indicating trivalent cerium. No magnetic ordering could be detected down to 2 K.

Sign in / Sign up

Export Citation Format

Share Document