K. Elmgren

SAUNA : a system for automatic sampling, processing, and analysis of radioactive xenon

Abstract A system for automatic sampling, processing, and analysis of atmospheric radioxenon has been developed. From an air sample of about 7 m 3 collected during 12 h , 0.5 cm 3 of xenon is extracted, and the atmospheric activities from the four xenon isotopes 133 Xe , 135 Xe , 131m Xe , and 133m Xe are determined with a beta–gamma coincidence technique. The collection is performed using activated charcoal and molecular sieves at ambient temperature. The sample preparation and quantification are performed using preparative gas chromatography. The system was tested under routine conditions for a 5-month period, with average minimum detectable concentrations below 1 mBq / m 3 for all four isotopes.

Nucleon-induced reactions at intermediate energies: New data at 96 MeV and theoretical status

Double-differential cross sections for light charged particle production (up to A=4) were measured in 96 MeV neutron-induced reactions, at the TSL Laboratory Cyclotron in Uppsala (Sweden). Measurements for three targets, Fe, Pb, and U, were performed using two independent devices, SCANDAL and MEDLEY. The data were recorded with low-energy thresholds and for a wide angular range (20 deg. -160 deg. ). The normalization procedure used to extract the cross sections is based on the np elastic scattering reaction that we measured and for which we present experimental results. A good control of the systematic uncertainties affecting the results is achieved. Calculations using the exciton model are reported. Two different theoretical approaches proposed to improve its predictive power regarding the complex particle emission are tested. The capabilities of each approach is illustrated by comparison with the 96 MeV data that we measured, and with other experimental results available in the literature.

Light‐Ion Production in the Interaction of 96 MeV Neutrons with Silicon

Double-differential cross sections for light-ion (p, d, t, He and α) production in oxygen, induced by 96 MeV neutrons are reported. Energy spectra are measured at eight laboratory angles from 20◦ to 160◦ in steps of 20◦. Procedures for data taking and data reduction are presented. Deduced energydifferential and production cross sections are reported. Experimental cross ∗Corresponding author, Tel. +46 18 471 6850, Fax. +46 18 471 3853, E-mail: stephan.pomp@tsl.uu.se

Elastic neutron scattering at 96 MeV from {sup 12}C and {sup 208}Pb

A facility for detection of scattered neutrons in the energy interval 50-130 MeV, SCANDAL, has recently been installed at the 20-180 MeV neutron beam line of the The Svedberg Laboratory, Uppsala. Elastic neutron scattering from {sup 12}C and {sup 208}Pb has been studied at 96 MeV in the 10 deg. -70 deg. interval. The achieved energy resolution, 3.7 MeV, is about an order of magnitude better than for any previous experiment above 65 MeV incident energy. The present experiment represents the highest neutron energy where the ground state has been resolved from the first excited state in neutron scattering. A novel method for normalization of the absolute scale of the cross section has been used. The estimated normalization uncertainty, 3%, is unprecedented for a neutron-induced differential cross section measurement on a nuclear target. The results are compared with modern optical model predictions based on phenomenology or microscopic nuclear theory.

Elastic neutron scattering at 96 MeV

A facility for detection of scattered neutrons in the energy interval 50–130 MeV, SCANDAL (SCAttered Nucleon Detection AssembLy), has recently been installed at the 20 – 180‐MeV neutron beam line of The Svedberg Laboratory, Uppsala. Elastic neutron scattering from 12C, 16O, 56Fe, 89Y, and 208Pb has been studied at 96 MeV in the 10 – 70° interval. The results from 12C and 208Pb have recently been published,6 while the data from 16O, 56Fe, and 89Y are under analysis. The achieved energy resolution, 3.7 MeV, is about an order of magnitude better than for any previous experiment above 65 MeV incident energy. The present experiment represents the highest neutron energy where the ground state has been resolved from the first excited state in neutron scattering. A novel method for normalization of the absolute scale of the cross section has been used. The estimated normalization uncertainty, 3%, is unprecedented for a neutron‐induced differential cross section measurement on a nuclear target. The results are com...

Experimental Double-Differential Light-Ion Production Cross Sections for Silicon at 95 MeV Neutrons

The importance of cosmic radiation effects in aircraft electronics has recently been highlighted. At commercial flight altitudes, as well as at sea level, the most important particle radiation is due to neutrons, created in the atmosphere by spallation of nitrogen and oxygen nuclei, induced by cosmic-ray protons. When, e.g., an electronic memory circuit is exposed to neutron radiation, charged particles can be produced in a nuclear reaction. The charge released by ionization can cause a flip of the memory content in a bit, which is called a single-event upset (SEU). A similar logic error in one of the storage registers of a microprocessor may trigger an unanticipated loop that cannot be escaped without turning the unit off. To get a deeper understanding of these phenomena, more detailed cross section information on neutron-induced charged-particle production at intermediate energies is needed. To this end, double-differential cross sections of inclusive light-ion production in silicon, induced by 95 MeV neutrons, have been measured. The experiment was performed using the MEDLEY setup, which consists of eight three-element particle telescopes, covering the angular range 20° – 160°. The charged particles were identified using ΔE – ΔE – E techniques. By using an active target, consisting of a 300 μm thick Si detector, the energy loss in the target itself could be measured and corrected for.

Cross Section Data and Kerma Coefficients at 95 MeV Neutrons for Medical Applications

Motivated by the need of data on neutron-induced reactions with biologically relevant materials, e.g., carbon and oxygen, we have constructed and installed the MEDLEY detector array at the neutron beam facility of the The Svedberg Laboratory in Uppsala. The central detection elements of MEDLEY are three-detector telescopes, consisting of two silicon detectors and a Csl crystal. To cover wide energy and angle ranges, we have mounted eight such telescopes at 20° intervals. We have used ΔE − ΔE − E techniques to obtain good particle identification for protons, deuterons, tritons, 3He and α particles over an energy range from a few MeV up to 100 MeV. To define the detector solid angle, plastic scintillators were employed to serve as active collimators. We have up to now measured double-differential cross sections of inclusive light-ion production induced by 95 MeV neutrons on carbon and oxygen. From these data production cross sections, as well as partial kerma coefficients, are being determined. We have found that especially the proton kerma coefficient for carbon is substantially larger than that of a recent evaluation, leading to a larger total kerma coefficient. The obtained data supports a trend observed for similar data at lower energies.

SCANDAL - A Facility for Elastic Neutron Scattering Studies in the 50–130 MeV Range

Recently, a large number of applications involving high-energy (> 20 MeV) neutrons have become important. Examples are development of spallation sources, transmutation of nuclear waste, fast-neutron cancer therapy, as well as dose effects for airflight personnel and electronics failures due to cosmic-ray neutrons. Elastic neutron scattering plays a key role for the understanding of all these areas. The most important reason is that it allows a determination of the optical potential, which plays a decisive role in every microscopic calculation including neutrons in either the entrance or exit channel. In addition, the elastic cross section is also the largest of the individual partial cross sections contributing to the total cross section. A facility for detection of scattered neutrons in the energy interval 50–130 MeV, SCANDAL (SCAttered Nucleon Detection AssembLy), has recently been installed at the 20–180 MeV neutron beam facility of the The Svedberg Laboratory, Uppsala. It is primarily intended for studies of elastic neutron scattering, but can be used for the (n,p) t and (n,d) reaction experiments as well. The performance of the spectrometer is illustrated in measurements of the (n,p) and (n,n) reactions on 1H and 12 C at 96 MeV.

Neutron-Proton Scattering at Intermediate Energies - Recent, New and Future Measurements

A programme to investigate the neutron-proton scattering differential cross section at intermediate energies is active at the The Svedberg Laboratory, Uppsala, Sweden. Up to now, measurements of back angle differential np scattering cross sections have been undertaken at 96 MeV and 162 MeV. These high-precision data are well described by partial-wave analyses of other data sets over a wide angular range, but deviate at the most backward angles. However, they agree well in shape over the full angular range with another recent high-quality measurement from PSI. These results have large consequences for measurements of nuclear data for applications, because back angle np scattering is used as a primary standard. A new setup, SCANDAL (SCAttered Nucleon detection AssembLy), has been developed and installed for measurements aiming at clarifying the situation at back angles, as well as for forward-angle experiments, resulting in a complete angular distribution.