Measurement Of Nuclides Research Articles

First mass measurement of short-lived nuclides at HIRFL-CSR

Recent commissioning of the HIRFL-CSR has demonstrated its ability to perform direct mass measurement for short-lived nuclides. Projectile fragments produced by the 78Kr ions at 481.88 MeV/u were separated with the new radioactive beam line in Lanzhou (RIBLL2), and injected into and stored in the experimental storage ring (CSRe). By operating the CSRe as an isochronous mass spectrometry, a typical mass resolution around 2.0×10−5 has been achieved. The masses for 63Ge, 65As and 67Se were measured for the first time. The measured masses are compared with theoretical predictions and the location of the proton drip-line for As isotopes is discussed. The implication of the 65As mass in the astrophysical rapid proton capture process has also been addressed.

Enigmatic boulder trains, supraglacial rock avalanches, and the origin of “Darwin's boulders,” Tierra del Fuego

Charles Darwin considered himself to be a geologist and published extensively on many geologic phenomena. He was intrigued with the distribution of erratic boulders and speculated upon their origins. In his accounts of the voyage of the HMS Beagle, Darwin described crystalline boulders of notable size and abundance near Bahia San Sebastian, south of the Strait of Magellan, Tierra del Fuego. Influenced by Charles Lyell’s reflections upon slow, vertical movements of crust, submer gence, and ice rafting to explain drift, Darwin proposed that the boulders of Bahia San Sebastian were ice-rafted. Benefiting from 170 years of subsequent study of the glacial history of Tierra del Fuego, petrography, and terrestrial cosmogenic nuclide measurements, we revisit the origin of “Darwin’s Boulders” at Bahia San Sebastian. We suggest that they, as well as another train of boulders to the west, at Bahia Inutil, represent rock falls of Beagle-type granite from the Cordillera Darwin onto glacial ice flowing into the Bahia Inutil–Bahia San Sebas tian lobe. These supraglacial rock avalanche deposits were subsequently elongated into boulder trains by glacial strain during transport and then deposited upon moraines. The cosmogenic nuclide exposure dates support the correlation of Andean glaciations with the marine oxygen isotope record and the glacial chronologies recently proposed for Tierra del Fuego.

Childhood Leukemia in the Vicinity of Nuclear Power Plants in Germany: Ignorance Is a Curse

The authors noted an increase in the number of cases of leukemia in children younger than 5 years within a 5 km radius of nuclear power stations. Notably, they think that a causal association between raised leukemia incidence and additional radiation exposure through nuclear power stations is implausible. If this conclusion has been clear from the beginning, I don’t understand why the study was conducted in the first place. After the leukemia increase that was found, the usual dose estimate in children now needs to be questioned. And this is where ignorance is a curse. This is part of the highly complex area of biodosimetry and dosage equivalents, a highly technical terrain that neither a psychologist and occupational scientist (Professor Jungermann) nor an epidemiologist and informatics specialist (Dr Kaatsch) is qualified to comment on. The normal, extremely arbitrary dose estimates would need to be subjected to highly complicated tests. Finally, research would need to be conducted into what radiation load exactly an individual resident in the vicinity of a nuclear power plant receives, not only via environmental radiation but also via environmental air and the food chain; how the biological distribution in the body tissues works over time; and which bone seeking radionuclides administer which dosage to a child’s bone marrow. These questions would be worth studying and the computation models prestented by the German Commission on Radiological Protection would be worth verifying, and any insider knows exactly how very arbitrary the presented dose estimates are. What we do not need is a philosophical discourse about risk perception, nor repetitive emphasis on implausible causal associations compared with environmental radiation. What is required is careful checking of the dose estimates presented (allegedly only 1/1000 of environmental radiation). The studies required for this would have to conduct laborious nuclide measurements in the biotope and in the environmental air that the children breathe over the long term. The bone marrow of children who died due to leukemia in the vicinity of nuclear power plants would need to be compared in terms of its radionuclide uptake with that of children elsewhere. For knowledge to be interpreted and integrated, this knowledge has to be gained first of all!

Identification of Time-of-Flight spectra for Isochronous Mass Measurements

The Isochronous Mass Spectrometry (IMS) developed at GSI is a very efficient method for direct mass measurements of short-lived nuclides. By taking a recent IMS experiment as an example, the identification procedure of the Time-of-Flight (TOF) spectrum measured in this experiment is discussed.

LARGE-SCALE MASS MEASUREMENTS OF SHORT-LIVED NUCLIDES WITH THE ISOCHRONOUS MASS SPECTROMETRY AT GSI

Precise mass measurements of short-lived exotic nuclei are very important for the understanding of basic nuclear structure physics and astrophysical nucleosynthesis in nature, as well as for the test and the development of theoretical nuclear mass models. At GSI, the Isochronous Mass Spectrometry (IMS) dedicated to mass measurements of short-lived nuclides was developed. In this contribution, the IMS technique is briefly reviewed. Recently, the first large-scale measurement on the 238 U fission fragment was done successfully. The measured mass values are in excellent agreement with the recent Penning trap data, however, they show a systematical deviation from the values in the latest atomic mass evaluation. Some representative results from this experiment will be presented, including their impact on nuclear structure physics and astrophysical r-process nucleosynthesis.

Glacial dynamics in southernmost South America during Marine Isotope Stage 5e to the Younger Dryas chron: a brief review with a focus on cosmogenic nuclide measurements

AbstractThe timing of major glacial changes between Marine Isotope Stage (MIS) 5e and the Younger Dryas chron (YD) in southern South America is reviewed. Focus is placed on studies that use cosmogenic nuclide measurements. However, other dated records and modelling results are also discussed to provide the broader glacial geological context. Limits on the state of glacial geologic knowledge are examined and suggestions are made as to how some of these can be addressed in future studies. Studies show that on the east side of the Andes at Lago Buenos Aires (45° S) there is evidence indicating that following a MIS 6 glaciation ice was less extensive during MIS 4 than MIS 2. In contrast, on the west side of the Andes in the Chilean Lake District area, MIS 4 ice may have been more extensive than during MIS 2. Although Patagonia experienced an MIS 2 glaciation broadly in phase with that in other areas around the globe, there are differences in glacial histories between areas on millennial timescales. Climate reversals are evident in many records between ca. 17 and 10 ka. The timing of such Lateglacial activity, which included less extensive advances than during the local Last Glacial Maximum (LGM), varies somewhat between areas. This could be due to the relative influence of middle‐ to high‐latitude climatic regimes. At present, chronological uncertainties prevent confident assignment of cosmogenic ages for glacial events at the millennial timescale and defining associated climate variability between different study areas. Copyright © 2008 John Wiley & Sons, Ltd.

Measurement and simulation of the pressure ratio between the two traps of double Penning trap mass spectrometers

Penning traps are ideal tools to perform high-precision mass measurements. For this purpose the cyclotron frequency of the stored charged particles is measured. In case of on-line mass measurements of short-lived nuclides produced at radioactive beam facilities the ions get in general first prepared and cooled by buffer-gas collisions in a preparation trap to reduce their motional amplitudes and are then transported to a precision trap for the cyclotron frequency determination. In modern Penning trap mass spectrometers both traps are placed in the homogeneous region of one superconducting magnet to optimize the transport efficiency. Because the gas pressure inside the precision trap has to be very low in order to minimize the damping of the ion motion caused by collisions with rest gas molecules during the frequency determination, a pumping barrier is installed between both traps. To predict the pressure difference between the two traps in the region of molecular gas flow the motion of each particle can be simulated without consideration of the other particles. Thus, it is possible to calculate the transit probability through a tube of a given geometry. The results are compared with experimentally obtained pressure differences.

Slow regolith degradation without creep determined by cosmogenic nuclide measurements in Arena Valley, Antarctica

Estimates of regolith degradation in the McMurdo Dry Valleys of Antarctica are currently based on indirect evidence and ancient ashes at or near the soil surface that suggest excellent preservation of surfaces. On the other hand, the existing cosmogenic-nuclide surface exposure ages from many parts of the Dry Valleys are younger than the age of surface deposits inferred from stratigraphic relations. This suggests some combination of surface erosion or past ice cover, both of which would reduce the apparent exposure age. This paper quantifies the regolith degradation and/or past ice cover by measuring 10Be and 26Al from a landslide deposit that contains 11.3 Ma volcanic ash. The surface sample yields an apparent exposure age of only 0.4 Ma. However, measurements of the subsurface nuclide concentrations show that the deposit has not been shielded by ice, and that the age of the ash does not conflict with the apparent exposure age when slow degradation of the deposit (2 m Ma −1) is taken into account. Soil creep, which is a common degradational process in a wide variety of environments, is non-existent at this field site, which likely reflects the persistent lack of bio- and cryoturbation.

Atomic mass measurements of short-lived nuclides around the doubly-magic 208Pb

Accurate atomic mass measurements of neutron-deficient and neutron-rich nuclides around the doubly-magic 208Pb and of neutron-rich cesium isotopes were performed with the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The masses of 145,147Cs, 181,183Tl, 186Tl m , 187Tl m , 196Tl m , 205Tl, 197Pb m , 208Pb, 190–197Bi, 209,215,216Bi, 203,205,229Fr, and 214,229,230Ra were determined. The obtained relative mass uncertainty in the range of 2 × 10 −7 to 2 × 10 −8 is not only required for safe identification of isomeric states but also allows mapping the detailed structure of the mass surface. A mass adjustment procedure was carried out and the results included into the Atomic Mass Evaluation. The resulting separation energies are discussed and the mass spectrometric and laser spectroscopic data are examined for possible correlations.

TOF-Bρ mass measurements of very exotic nuclides for astrophysical calculations at the NSCL

Atomic masses play a crucial role in many nuclear astrophysics calculations. The lack of experimental values for relevant exotic nuclides triggered a rapid development of new mass measurement devices around the world. The time-of-flight (TOF) mass measurements offer a complementary technique to the most precise one, Penning trap measurements (Blaum 2006 Phys. Rep. 425 1), the latter being limited by the rate and half-lives of the ions of interest. The NSCL facility provides a well-suited infrastructure for the TOF mass measurements of very exotic nuclei. At this facility, we have recently implemented a TOF-Bρ technique and performed mass measurements of neutron-rich nuclides in the Fe region, important for r-process calculations and for calculations of processes occurring in the crust of accreting neutron stars.

Mass measurements of neutron-deficient radionuclides near the end-point of the rp-process with SHIPTRAP

Direct mass measurements of nuclides near to the supposed end-point region of the astrophysical rp-process were performed at SHIPTRAP, the Penning trap mass spectrometer at GSI Darmstadt. The masses of 24 nuclides were measured with relative uncertainties between 5 . 10-8 and 2 . 10-7 . Three of them, 107Sb , 111I and 112I , were determined experimentally for the first time. The data analysis and mass evaluation are presented in detail.

Quantification of the transient response to base‐level fall in a small mountain catchment: Sierra Nevada, southern Spain

We integrated optically stimulated luminescence dating and 10Be cosmogenic nuclide measurements to quantify short‐to‐medium‐term (102–104 years) catchment dynamics and response to active tectonics. In the 27 km2 Río Torrente catchment, Sierra Nevada, southern Spain, rapid base‐level fall has triggered knickpoint migration up both trunk and tributary channels, resulting in two distinct geomorphic zones: (1) a steep lower catchment with concordant rates of hillslope erosion and channel incision over both short (100 years: 5–8 mm yr−1) and medium (12 ka: 5 ± 1 mm yr−1) timescales and (2) a low‐relief soil‐mantled upland topography with uniformly low bedrock and hillslope erosion rates (0.05 ± 0.02 mm yr−1). The uniformity of erosion in this upland surface indicates that catchment topography was previously in steady state. Rapid river incision below the channel knickpoints has resulted in the development of steep landslide‐dominated hillslopes that are essentially “tracking” the incising channel. The magnitude of base‐level fall required to generate these steep hillslopes is >100 m; at least 50 m of this base‐level fall occurred during the past ∼21 ka. These steep hillslopes are eroding back into the low‐angled upland surface at a much slower rate than the channel knickpoint. Consequently, the trunk channel knickpoint has already reached the catchment headwaters while hillslopes continue to adjust to the new base level, indicating that the channel profile will regain equilibrium form long before hillslopes. Thus hillslopes are the limiting factor for the duration of landscape transience in this small mountain catchment.

A method for optimizing experimental conditions and simulating spectra in the measurement of heavy nuclides in AMS

The sensitivity of accelerator mass spectrometry (AMS) is often limited by interferences from isobars, isotopes and other nuclides. In AMS measurements of heavy nuclides, where a high molecular fragment background can be present, it can be difficult to discriminate the nuclides of interest from the background particles online. In order to solve this problem, a method for optimizing the experimental conditions and simulating spectra in AMS measurements has been developed. Satisfactory agreement has been obtained between calculated and experimental spectra for 26Al, 36Cl, 41Ca and 99Tc measured with the HI-13 AMS system at China Institute of Atomic Energy (CIAE).

Status of the Experimental Program on Mass Measurements of Stored Exotic Nuclei at the FRS-ESR Facility

Schottky Mass Spectrometry (SMS) and Isochronous Mass Spectrometry (IMS) have been successfully applied for direct mass measurements of exotic nuclides at FRS-ESR facility at GSI. Both experimental methods are sensitive to single stored ions and can cover very efficiently a large number of nuclides in one run. Presently, more than 1100 masses of different nuclides have been covered by SMS and IMS in several FRS-ESR experiments whereby about 350 of them have been determined for the first time. In this paper, we present the status of our experimental program and use the experimental mass values to test the predictive power of modern mass models.

Cosmogenic nuclide measurements in southernmost South America and implications for landscape change

We measured in situ 10Be, 26Al and 36Cl on glacial deposits as old as 1.1 Myr in the southernmost part of Patagonia and on northern Tierra del Fuego to understand boulder and moraine and, by inference, landscape changes. Nuclide concentrations indicate that surface boulders have been exposed for far less time than the ages of moraines they sit upon. The moraine ages are themselves constrained by previously obtained 40Ar/ 39Ar ages on interbedded lava flows or U-series and amino acid measurements on related (non-glacial) marine deposits. We suggest that a combination of boulder erosion and their exhumation from the moraine matrix could cause the erratics to have a large age variance and often short exposure histories, despite the fact that some moraine landforms are demonstrably 1 Myr old. We hypothesize that fast or episodic rates of landscape change occurred during glacial times or near the sea during interglacials. Comparison with boulder erosion rates and exhumation histories derived for the middle latitudes of semi-arid Patagonia imply different geomorphic processes operating in southernmost South America. We infer a faster rate of landscape degradation towards the higher latitudes where conditions have been colder and wetter.

Ice height changes in inland East Antarctica determined from cosmogenic nuclide measurements

Ice height changes in inland East Antarctica determined from cosmogenic nuclide measurements

Monte Carlo modelling of a voxel head phantom for in vivo measurement of bone-seeker nuclides

Whole-body counters (WBCs) are used for the assessment of the internal contamination of actinides in the human body. WBCs require adequate calibration procedures that rely on the use of suitable calibration phantoms. A previous study carried out at the ENEA-Radiation Protection Institute was aimed at designing a head calibration phantom in which a heterogeneous distribution of 241Am point sources could satisfactorily approximate an assumed homogeneous contamination throughout the head bones. Suitable correction factors for the WBC detection efficiencies were evaluated with Monte Carlo. The present paper summarises the main aspects and implications of an advanced modelling technique based on a VOXEL approach. The methodology could be extended to other bone-seeker radionuclides.

Cosmogenic nuclide methods for measuring long-term rates of physical erosion and chemical weathering

Understanding the evolution of geochemical and geomorphic systems requires measurements of long-term rates of physical erosion and chemical weathering. Erosion and weathering rates have traditionally been estimated from measurements of sediment and solute fluxes in streams. However, modern sediment and solute fluxes are often decoupled from long-term rates of erosion and weathering, due to storage or re-mobilization of sediment and solutes upstream from the sampling point. Recently, cosmogenic nuclides such as 10Be and 26Al have become important new tools for measuring long-term rates of physical erosion and chemical weathering. Cosmogenic nuclides can be used to infer the total denudation flux (the sum of the rates of physical erosion and chemical weathering) in actively eroding terrain. Here we review recent work showing how this total denudation flux can be partitioned into its physical and chemical components, using the enrichment of insoluble tracers (such as Zr) in regolith relative to parent rock. By combining cosmogenic nuclide measurements with the bulk elemental composition of rock and soil, geochemists can measure rates of physical erosion and chemical weathering over 1000- to 10,000-year time scales.

Investigating the rp-process with the Canadian Penning trap mass spectrometer

The Canadian Penning trap (CPT) mass spectrometer at the Argonne National Laboratory makes precise mass measurements of nuclides with short half-lives. Since the previous ENAM conference, many significant modifications to the apparatus were implemented to improve both the precision and efficiency of measurement, and now more than 60 radioactive isotopes have been measured with half-lives as short as one second and with a precision ( Δm/m) approaching 10-8. The CPT mass measurement program has concentrated so far on nuclides of importance to astrophysics. In particular, measurements have been obtained of isotopes along the rp-process path, in which energy is released from a series of rapid proton-capture reactions. An X-ray burst is one possible site for the rp-process mechanism which involves the accretion of hydrogen and helium from one star onto the surface of its neutron star binary companion. Mass measurements are required as key inputs to network calculations used to describe the rp-process in terms of the abundances of the nuclides produced, the light-curve profile of the X-ray bursts, and the energy produced. This paper will present the precise mass measurements made along the rp-process path with particular emphasis on the “waiting-point” nuclides 68Se and 64Ge.

Recent high-precision mass measurements with the Penning trap spectrometer ISOLTRAP

The Penning trap mass spectrometer ISOLTRAP has to date been used for the determination of close to 300 masses of radionuclides. A relative mass uncertainty of 10-8 can now be reached. Recent highlights were measurements of rp-process nuclides as for instance 72-74Kr or superallowed β emitters like 22Mg, 74Rb and 34Ar. The heaviest nuclides measured so far with ISOLTRAP are neutron-rich radium and francium isotopes. An overview of ISOLTRAP mass measurements and details about the recent experiment on 229-232Ra and 230Fr are presented.