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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
REFLECT â Research flight of EURADOS and CRREAT: Intercomparison of various radiation dosimeters onboard aircraft
Aircraft crew are one of the groups of radiation workers which receive the highest annual exposure to ionizing
radiation. Validation of computer codes used routinely for calculation of the exposure due to cosmic radiation
and the observation of nonpredictable changes in the level of the exposure due to solar energetic particles, requires continuous measurements onboard aircraft. Appropriate calibration of suitable instruments is crucial,
however, for the very complex atmospheric radiation field there is no single reference field covering all particles
and energies involved. Further intercomparisons of measurements of different instruments under real flight
conditions are therefore indispensable.
In November 2017, the REFLECT (REsearch FLight of EURADOS and CRREAT) was carried out. With a
payload comprising more than 20 different instruments, REFLECT represents the largest campaign of this type
ever performed. The instruments flown included those already proven for routine dosimetry onboard aircraft
such as the Liulin Si-diode spectrometer and tissue equivalent proportional counters, as well as newly developed
detectors and instruments with the potential to be used for onboard aircraft measurements in the future. This
flight enabled acquisition of dosimetric data under well-defined conditions onboard aircraft and comparison of
new instruments with those routinely used.
As expected, dosimeters routinely used for onboard aircraft dosimetry and for verification of calculated doses
such as a tissue equivalent proportional counter or a silicon detector device like Liulin agreed reasonable with each other as well as with model calculations. Conventional neutron rem counters underestimated neutron
ambient dose equivalent, while extended-range neutron rem counters provided results comparable to routinely
used instruments. Although the responses of some instruments, not primarily intended for the use in a very
complex mixed radiation field such as onboard aircraft, were as somehow expected to be different, the verification of their suitability was one of the objectives of the REFLECT. This campaign comprised a single short
flight. For further testing of instruments, additional flights as well as comparison at appropriate reference fields
are envisaged. The REFLECT provided valuable experience and feedback for validation of calculated aviation
doses
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
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