Radiation damage effects in channeling applications

Use of a bent single crystal to split off a small fraction of an incident high energy (400 to 800 GeV) particle beam has been demonstrated. The question which remains to be answered is: Will radiation damage effects deteriorate crystal performance in too short a time for practical application. Single Si crystals exposed to 10/sup 17/ high energy protons per cm/sup 2/ have been examined previously using low energy (1.5 to 3.0 MeV) helium ion backscattering. The amount of radiation damage indicated by this low penetration technique was very small. This paper reports verification that such an exposed crystal still channels high energy particles. Furthermore, results using helium ion backscattering following an irradiation to 10/sup 18//cm/sup 2/ predict no deterioration in channeling performance

Thoron detection with an active Radon exposure meter - first results.

For state-of-the-art discrimination of Radon and Thoron several measurement techniques can be used, such as active sampling, electrostatic collection, delayed coincidence method, and alpha-particle-spectroscopy. However, most of the devices available are bulky and show high power consumption, rendering them unfeasible for personal exposition monitoring. Based on a Radon exposure meter previously realized at the Helmholtz Center Munich (HMGU), a new electronic prototype for Radon/Thoron monitoring is currently being developed, which features small size and weight. Operating with pin-diode detectors, the low-power passive-sampling device can be used for continuous concentration measurements, employing alpha-particle-spectroscopy and coincidence event registration to distinguish decays originating either from Radon or Thoron isotopes and their decay products. In open geometry, preliminary calibration measurements suggest that one count per hour is produced by a 11 Bq m(-3) Radon atmosphere or by a 15 Bq m(-3) Thoron atmosphere. Future efforts will concentrate on measurements in mixed Radon/Thoron atmospheres

Simulation and calibration of an active neutron dosemeter.

Here the latest development stages of the HMGU active neutron dosemeter are presented. This work includes the comparison of the dosemeter's response function, calculated with Geant4, and the measurements in monoenergetic neutron fields at the Physikalisch Technische Bundesanstalt in Braunschweig, Germany. These results were used to match the response function and the count-to-dose conversion factors of the dosemeter to the H-p(10) personal dose equivalent

Electronic neutron dosimeter in high-energy neutron fields.

In neutron fields including neutron energies above 20 MeV a conventional neutron dosimeter is not suitable for measurements of neutron personal dose equivalent, Hp(10), over the whole energy range. Therefore, for such fields an electronic neutron dosimeter has been developed recently at Helmholtz Zentrum München (HMGU). In general, neutron dose measurements performed with this dosimeter at neutron energies below 2 MeV show an accuracy of about 30% [1]. Here we report the use of this dosimeter at the CERN-EU high-energy Reference Field (CERF) facility in Geneva, Switzerland. At this facility the available neutron fields include neutrons with energies below, but also above 20 MeV. In the present paper, personal dose equivalent (Hp(10)) values obtained with the ELectronic neutron DOsimeter (ELDO) are compared to neutron personal dose equivalent (Hp(10)) values obtained with the HMGU extended-range Bonner Sphere Spectrometer, and to reference values from FLUKA Monte Carlo simulations provided by CERF. It is shown that for continuous neutron spectra as those at CERF behind concrete shielding or secondary neutrons from cosmic rays, the dosimeter results are satisfactory for radiation protection purposes. However, in neutron fields including neutrons above about 7 MeV, where the major neutron dose contribution is from neutrons between 10 keV and several MeV (like those at CERF behind iron shielding), the doses provided by ELDO might be too small and care must be taken in interpreting the results