scholarly journals University of Kiel Radiocarbon Measurements II

Radiocarbon ◽  
1967 ◽  
Vol 9 ◽  
pp. 257-260
Author(s):  
H. Willkomm ◽  
H. Erlenkeuser
Keyword(s):  
Proportional Counter ◽  
Atmospheric Pressure ◽  
Statistical Error ◽  
Quartz Tube ◽  
Sensitive Volume ◽  
Concrete Wall ◽  
Lead Shield ◽  
Double Ring

Most of the measurements reported here have been obtained with the 4.5-L CO2 counter previously described (Kiel I; Erlenkeuser, 1965). A few samples have been dated with a 3-L proportional counter. The copper counter is surrounded by 28 GM counters in the form of a double ring. The total assembly is shielded by 10 cm of old lead. Neither an inner lead shield between counter and anticoincidence ring nor screening of sensitive volume by a quartz tube-as in the 4.5-L counter-has been used. Background of the small counter is 17.20 cpm or The 0.95 x NBS value is 9.5 cpm at 400 torr. Within statistical error background does not depend on atmospheric pressure. The 3-L counter is placed under a concrete wall, 2.5 m in length and 9.4 m in height.

La pyrolyse de poly(adipate de butylène-1,4)

1977 ◽  
Vol 55 (14) ◽  
pp. 2732-2740 ◽  
Author(s):  
François Messier ◽  
Don C. DeJongh
Keyword(s):  
Adipic Acid ◽  
Atmospheric Pressure ◽  
Quartz Tube ◽  
Heated Zone ◽  
Volatile Products

Poly(1,4-butylene adipate) (1) was pyrolyzed in a porcelain boat placed in a quartz tube heated by a furnace. Volatile products were carried out of the heated zone into traps by a flow of nitrogen. Polyester 1 was pyrolyzed both near the entrance and near the exit of the heated zone, at 500 and 700 °C with and without a vacuum. Adipic acid (2), cyclopentanone (4), and a mixture of mono (5) and diesters (6) of the monomer, dimer, and trimer, were isolated as products of the pyrolyses.The pyrolyses of 1 at 500 °C near the exit of the heated zone at atmospheric pressure gave 14% of 2, 10% of 4, 40% of 5, and 18% of 6; 5 consisted of 26% monoester of monomer and 74% monoester of dimer, whereas 6 consisted of 63% diester of monomer and 37% diester of dimer. At 700 °C, 0.2–0.3 Torr, with 1 near the entrance of the heated zone, the yield of 2 was higher (∼35%), and trimers were found in the monoesters 5 and diesters 6, along with dimers and monomers.

scholarly journals A new imaging technology based on Compton X-ray scattering

2021 ◽  
Vol 28 (5) ◽  
Author(s):  
Ángela Saá Hernández ◽  
Diego González-Díaz ◽  
Pablo Villanueva ◽  
Carlos Azevedo ◽  
Marcos Seoane
Keyword(s):  
Atmospheric Pressure ◽  
Solid Angle ◽  
Photon Counting ◽  
Sensitive Volume ◽  
3D Images ◽  
X Ray ◽  
X Ray Scattering ◽  
Custom Made ◽  
The Rose ◽  
Detector Design

A feasible implementation of a novel X-ray detector for highly energetic X-ray photons with a large solid angle coverage, optimal for the detection of Compton X-ray scattered photons, is described. The device consists of a 20 cm-thick sensitive volume filled with xenon at atmospheric pressure. When the Compton-scattered photons interact with the xenon, the released photoelectrons create clouds of secondary ionization, which are imaged using the electroluminescence produced in a custom-made multi-hole acrylic structure. Photon-by-photon counting can be achieved by processing the resulting image, taken in a continuous readout mode. Based on Geant4 simulations, by considering a realistic detector design and response, it is shown that photon rates up to at least 1011 photons s−1 on-sample (5 µm water-equivalent cell) can be processed, limited by the spatial diffusion of the photoelectrons in the gas. Illustratively, if making use of the Rose criterion and assuming the dose partitioning theorem, it is shown how such a detector would allow obtaining 3D images of 5 µm-size unstained cells in their native environment in about 24 h, with a resolution of 36 nm.

scholarly journals Birmingham University Radiocarbon Dates II

Radiocarbon ◽  
1968 ◽  
Vol 10 (2) ◽  
pp. 200-206 ◽  
Author(s):  
F. W. Shotton ◽  
D. J. Blundell ◽  
R. E. G. Williams
Keyword(s):  
Statistical Analysis ◽  
Standard Deviation ◽  
Proportional Counter ◽  
Half Life ◽  
Background Count ◽  
Radiocarbon Dates ◽  
Double Ring

Measurements have continued with the 6 L counter which has proved reliable at pressures as high as 2.6 atm and as low as 0.3 atm. It has now been enclosed in a double ring of 27 geiger tubes which has reduced the background count to 10 cpm at 2 atm. So far, we have had no success with the 1.5 L Oeschger-type proportional counter. Failure to obtain steady readings is probably due to continued outgassing from the teflon insulation. All insulating parts have now been remanufactured from the same source of teflon as was used in the 6 L counter, and the Oeschger counter is being reassembled.Results are still given without correction for δC13. Errors quoted refer only to the standard deviation calculated from a statistical analysis of count rates and the Libby half-life of 5570 ± 30 yr.

scholarly journals Frankfurt Radiocarbon Dates I

Radiocarbon ◽  
1984 ◽  
Vol 26 (2) ◽  
pp. 185-195 ◽  
Author(s):  
Reiner Protsch ◽  
Bernhard Weninger
Keyword(s):  
Amino Acid ◽  
Proportional Counter ◽  
Radiocarbon Dating ◽  
Radiocarbon Dates ◽  
Lead Shield ◽  
Standard Acid ◽  
Ring Counter ◽  
The University ◽  
Story Building ◽  
Amino Acid Dating

Facilities for radiocarbon dating were established at the University of Frankfurt/Main in the Institute of Anthropology. The Radiocarbon Laboratory provides assistance to the Amino-Acid-Dating Laboratory. This list reports on 14C dates measured up to September 1983.The laboratory is installed in the basement of a three-story building and is equipped with a 2L copper proportional counter filled to 1013 mbar with purified CO2. The counter is protected against cosmic and surrounding radiation by a 3.5 ton lead shield and a copper multiwire anticoincidence ring-counter flushed with purified 90Ar/10CH4. Electronics are of the commercial NIM type. Charcoal and wood samples are treated by standard acid-alkali-acid methods. Bone samples are treated according to the collagen methods described by Berger, Horney, and Libby (1964), Longin (1971), Protsch (1972; 1975), and Protsch and Berger (1973).

Surface-extended x-ray-absorption fine-structure experiments at atmospheric pressure by means of a photocathode proportional counter with monolayer sensitivity

1989 ◽  
Vol 39 (15) ◽  
pp. 10651-10657 ◽  
Author(s):  
G. G. Long ◽  
D. A. Fischer ◽  
J. Kruger ◽  
D. R. Black ◽  
D. K. Tanaka ◽  
...  
Keyword(s):  
Fine Structure ◽  
Proportional Counter ◽  
Atmospheric Pressure ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption
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