Benchmark studies of induced radioactivity produced in LHC materials, Part I: Specific activities

Samples of materials which will be used in the LHC machine for shielding and construction components were irradiated in the stray radiation field of the CERN-EU high-energy reference field facility. After irradiation, the specific activities induced in the various samples were analysed with a high-precision gamma spectrometer at various cooling times, allowing identification of isotopes with a wide range of half-lives. Furthermore, the irradiation experiment was simulated in detail with the FLUKA Monte Carlo code. A comparison of measured and calculated specific activities shows good agreement, supporting the use of FLUKA for estimating the level of induced activity in the LHC.     

Correction of phase distortion in spatial heterodyne spectroscopy

The detailed analysis of measured interferograms generally requires phase correction. Phase-shift correction methods are commonly used and well documented for conventional Fourier-transform spectroscopy. However, measured interferograms can show additional phase errors, depending on the optical path difference and signal frequency, which we call phase distortion. In spatial heterodyne spectroscopy they can be caused, for instance, by optical defects or image distortions, making them a characteristic of the individual spectrometer. They can generally be corrected without significant loss of the signal-to-noise ratio. We present a technique to measure phase distortion by using a measured example interferogram. We also describe a technique to correct for phase distortion and test its performance by using a simulation with a near-UV solar spectrum. We find that for our measured example interferogram the phase distortion is small and nearly frequency independent. Furthermore, we show that the presented phase-correction technique is especially effective for apodized interferograms.     

Averaged particle dose conversion coefficients in air crew dosimetry

The MCNPX Monte Carlo code was used to calculate energy-dependent fluence-to-effective dose conversion coefficients for neutrons, protons, electrons, photons, charged pions and muons. The FLUKA Monte Carlo code was used to calculate the spectral particle fluences of secondary cosmic rays for different altitudes, and for different combinations of solar modulation and vertical cut-off rigidity parameters. The energy-averaged fluence-to-dose conversion coefficients were obtained by folding the particle fluence spectra with the conversion coefficients for effective dose and ambient dose equivalent. They show a slight dependence on altitude, solar activity and location in the geomagnetic field.     

Robust monolithic ultraviolet interferometer for the SHIMMER instrument on STPSat-1

We describe the design, fabrication, and testing of a monolithic interferometer consisting entirely of optically contacted fused-silica optical elements that are assembled, adjusted, and permanently bonded in place. The interferometer is part of a spatial heterodyne spectrometer (SHS) [SHIMMER (Spatial Heterodyne Imager for Mesospheric Radicals)] that will be used for near-ultraviolet high-spectral-resolution limb imaging of OH solar resonance fluorescence from low Earth orbit aboard the satellite STPSat-1 scheduled for launch in 2006. The stability of the monolith coupled with the relaxed tolerances on optical quality and alignment inherent to SHS make this new instrument extremely robust and especially attractive for applications in harsh environments.     

A p47-phox pseudogene carries the most common mutation causing p47-phox- deficient chronic granulomatous disease

The predominant genetic defect causing p47-phox-deficient chronic granulomatous disease (A47 degrees CGD) is a GT deletion (DeltaGT) at the beginning of exon 2. No explanation exists to account for the high incidence of this single mutation causing a rare disease in an unrelated, racially diverse population. In each of 34 consecutive unrelated normal individuals, both the normal and mutant DeltaGT sequences were present in genomic DNA, suggesting that a p47-phox related sequence carrying DeltaGT exists in the normal population. Screening of genomic bacteriophage and YAC libraries identified 13 p47-phox bacteriophage and 19 YAC clones. The GT deletion was found in 11 bacteriophage and 15 YAC clones. Only 5 exonic and 33 intronic differences distinguished all DeltaGT clones from all wild-type clones. The most striking differences were a 30-bp deletion in intron 1 and a 20-bp duplication in intron 2. These results provide good evidence for the existence of at least one highly homologous p47-phox pseudogene containing the DeltaGT mutation. The p47-phox gene and pseudogene(s) colocalize to chromosome 7q11.23. This close linkage, together with the presence within each gene of multiple recombination hot spots, suggests that the predominance of the DeltaGT mutation in A47 degrees CGD is caused by recombination events between the wild-type gene and the pseudogene(s).     

Induced radioactivity in and around high-energy particle accelerators

Particle accelerators and their surroundings are locations of residual radioactivity production that is induced by the interaction of high-energy particles with matter. This paper gives an overview of the principles of activation caused at proton accelerators, which are the main machines operated at Conseil Européen pour la Recherche Nucléaire. It describes the parameters defining radio-nuclide production caused by beam losses. The second part of the paper concentrates on the analytic calculation of activation and the Monte Carlo approach as it is implemented in the FLUKA code. Techniques used to obtain, on the one hand, estimates of radioactivity in Becquerel and, on the other hand, residual dose rates caused by the activated material are discussed. The last part of the paper focuses on experiments that allow for benchmarking FLUKA activation calculations and on simulations used to predict activation in and around high-energy proton machines. In that respect, the paper addresses the residual dose rate that will be induced by proton-proton collisions at an energy of two times 7 TeV in and around the Compact Muon Solenoid (CMS) detector. Besides activation of solid materials, the air activation expected in the CMS cavern caused by this beam operation is also discussed.