scholarly journals A Preliminary ion Source Background Study at Lalonde AMS

Radiocarbon ◽  
2019 ◽  
Vol 61 (4) ◽  
pp. 1091-1106
Author(s):  
X-L Zhao ◽  
C A Crann ◽  
S Murseli ◽  
G St-Jean ◽  
W E Kieser ◽  
...  

ABSTRACTObservation of the ion source generated background has been an area of focus during our routine analytical work. It is noted that the results of very-low-ratio samples are dependent upon the particular procedures for measurement using the present-day Cs+ sputter ion sources. When measured without excessive Cs+ fluxes and without interleafing with other higher-ratio samples and references, the accelerator mass spectrometry (AMS) sensitivity can be somewhat improved. In some cases, it appears possible to assess old radiocarbon (14C) samples to beyond the long-standing 60 kyr limit. A number of observational studies are made for the sole purpose of minimizing the final contamination to the rare isotopes that is generated within the ion source.

1998 ◽  
Vol 69 (3) ◽  
pp. 1353-1358 ◽  
Author(s):  
S. H. Sie ◽  
T. R. Niklaus ◽  
G. F. Suter ◽  
F. Bruhn

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 711-716 ◽  
Author(s):  
Christopher Bronk Ramsey ◽  
R. E. M. Hedges

In 14C tracer studies, and when looking for modern contamination in archaeological samples, it is often necessary to measure the 14C concentration of individual chemical fractions. Gas chromatography (GC) is one method that is frequently used for separation of chemical fractions. The gas ion source at the Oxford Radiocarbon Accelerator Unit for accelerator mass spectrometry (AMS) provides the opportunity to measure fractions from a GC instrument directly. Although the first investigations are likely to be 14C tracer studies, such a GC-AMS system could find much wider application. We present results from a pilot study of the peak sensitivity, baseline stability and crosstalk of the accelerator system used in this way. We also discuss the practical considerations in developing a GC-AMS instrument for routine use.


2012 ◽  
Vol 83 (2) ◽  
pp. 02B304 ◽  
Author(s):  
K. F. von Reden ◽  
M. L. Roberts ◽  
J. R. Burton ◽  
S. R. Beaupré

2021 ◽  
Vol 8 ◽  
Author(s):  
Ahsan Habib ◽  
Lei Bi ◽  
Huanhuan Hong ◽  
Luhong Wen

In analytical science, mass spectrometry (MS) is known as a “gold analytical tool” because of its unique character of providing the direct molecular structural information of the relevant analyte molecules. Therefore, MS technique has widely been used in all branches of chemistry along with in proteomics, metabolomics, genomics, lipidomics, environmental monitoring etc. Mass spectrometry-based methods are very much needed for fast and reliable detection and quantification of drugs of abuse and explosives in order to provide fingerprint information for criminal investigation as well as for public security and safety at public places, respectively. Most of the compounds exist as their neutral form in nature except proteins, peptides, nucleic acids that are in ionic forms intrinsically. In MS, ion source is the heart of the MS that is used for ionizing the electrically neutral molecules. Performance of MS in terms of sensitivity and selectivity depends mainly on the efficiency of the ionization source. Accordingly, much attention has been paid to develop efficient ion sources for a wide range of compounds. Unfortunately, none of the commercial ion sources can be used for ionization of different types of compounds. Moreover, in MS, analyte molecules must be released into the gaseous phase and then ionize by using a suitable ion source for detection/quantification. Under these circumstances, fabrication of new ambient ion source and ultrasonic cutter blade-based non-thermal and thermal desorption methods have been taken into account. In this paper, challenges and strategies of mass spectrometry analysis of the drugs of abuse and explosives through fabrication of ambient ionization sources and new desorption methods for non-volatile compounds have been described. We will focus the literature progress mostly in the last decade and present our views for the future study.


2007 ◽  
Author(s):  
Karl von Reden ◽  
Mark Roberts ◽  
Baoxi Han ◽  
Robert Schneider ◽  
John Wills

1998 ◽  
Vol 69 (2) ◽  
pp. 1188-1190 ◽  
Author(s):  
Per Persson ◽  
Kim Freimann ◽  
Ragnar Hellborg ◽  
Kjell Håkansson ◽  
Göran Skog ◽  
...  

The first significant experiment using the technique of accelerator mass spectrometry (AMS) was reported by Alvarez & Cornog in 1939. It was widely thought at the time that tritium , and not 3 He, was stable, and with that in m ind Rutherford had asked Aston to search for hydrogen of mass three in a specially prepared water sample. The result was negative and Rutherford reported this in the last paper he wrote, which was published in Nature a few months before his death in 1937. Alvarez realized that if 3 He, and not tritium , were stable then it should be present in ordinary helium, presumably at a low abundance level. He therefore fed helium into the ion source of the Berkeley 60 inch cyclotron and soon demonstrated the existence of a 24 MeV beam corresponding to mass three and charge two, a unique combination. This identification was confirmed by a measurement of the range of the accelerated particles. Subsequently, Alvarez & Cornog showed that the abundance of 3 He in atmospheric helium was about ten times greater than in well helium, although their absolute abundances were rather lower than the currently accepted values.


Radiocarbon ◽  
2016 ◽  
Vol 58 (2) ◽  
pp. 419-435 ◽  
Author(s):  
C Welte ◽  
L Wacker ◽  
B Hattendorf ◽  
M Christl ◽  
J Koch ◽  
...  

AbstractConventional radiocarbon analysis of carbonate records with accelerator mass spectrometry (AMS) is time consuming and the achievable spatial resolution is limited, because individual samples have to be taken and need to be converted to graphite for the measurement. A new laser ablation (LA) in situ sampling technique for rapid online 14C analyses of carbonate records by AMS is presented. By focusing a 193-nm ArF excimer laser on carbonate samples, carbon dioxide is generated and can directly be introduced into the gas ion source of an AMS. A dedicated LA cell for AMS was constructed in a way that combines rapid gas exchange with the capacity to carry sample specimen with maximum dimensions of 15×2.5×1.5 cm3. With the presented setup, negative carbon ion currents up to 20 µA were achieved. A low 14C background of 0.011±0.002 F14C was observed on 14C-free marble and different standard and reference materials could be well reproduced within errors. The novel technique allows scanning carbonate samples continuously over several cm per hour with achievable measurement precisions of less than 1% for modern samples. This approach allows acquiring highly spatially resolved 14C records at a far higher rate than with any currently available method.


1992 ◽  
Vol 63 (4) ◽  
pp. 2469-2471 ◽  
Author(s):  
R. Höpfl ◽  
T. Bretschneider ◽  
A. Buchler ◽  
Y. Charasse ◽  
W. Ernst ◽  
...  

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