We have searched in niobium and tungsten for fractionally charged particles with effective nuclear charge Z = 7V+y (where TV = 0,1,2,3, . . .). In addition, we have looked for fractionally charged particles with Z concentration limits are reported.j-and y in the same materials. No positive signal was observed, and PACS numbers: 14.80. Dq, The reported observation 1 of fractional charge on superconducting niobium spheres has stimulated much experimental 2,3 and theoretical 4,5 work in the past few years. Aside from Ref. 1, the experiments that search in niobium 2 all assumed that the fractionally charged particles (FCP) will diffuse out of the sample as a positive ion when the sample is heated. The efficiency of this diffusion process is difficult to estimate. The effects observed by the authors of Ref. 1 could imply the existence of fractional charges (modulo \e) at a concentration level of 2xlO~1 8 /Nb atom, and possibly that the fractional charge is transferred from tungsten during annealing of the niobium sample. Since most of the residual charges observed corresponded to + \e (rather than -}e) a fractionally charged particle with an effective nuclear charge of Z = TV 4-y (where 7V = 0, 1,2,3,. . .) is more likely than those with Z = N+\. We define the quantity Z as the charge that would remain on the FCP if all of the atomic electrons were removed.We have performed an experimental search to test this hypothesis, and report the initial results in this Letter. Our technique is sensitive to FCP with Z = JV+| (7V = 0,1,2,3, . . .) which would form negative ions of charge -y, as well as FCP with Z = y or y which would form negative ions of charge -y. A detailed paper describing the apparatus and technique will be published elsewhere.The method we employed involves four steps (see Fig. 1): (a) extraction of the FCP from the host sample and formation of a negative ion (see below); (b) acceleration of negative FCP and stripping of an electron in a tandem electrostatic accelerator; (c) deflection of the (now positively charged) FCP in a transverse electric field; and (d) measurement of the kinetic energy in a particular detector. The acceleration and deflection of nonrelativistic charged particles from rest in purely electrostatic fields yields trajectories which are mass independent (stray magnetic fields and relativistic effects limit our sensitivity to FCP with mass > 200 MeV/c 2 ). The efficiency for the transmission of particles through the accelerator to a particular final charge state is primarily determined by the stripping efficiency, which drops off for masses greater than several hundred GeV/c 2 . The transmission efficiencies and mass independence of trajectories were determined by use of integrally charged ion beams (1 GeV/c 2 < m < 200 GeV/c 2 ) from both the FCP source and a conventional sputter ion source.The charge measurement results from steps (c) and (d).Step (c) selects ions with the desired ratio of kinetic energy to charge (the "electric rigidity") to an FCP sputter source , charge exchange cana...

Short- and long-term side effects following the treatment of cancer with radiation are strongly related to the amount of dose deposited to the healthy tissue surrounding the tumor. The characterization of the radiation field outside the planned target volume is the first step for estimating health risks, such as developing a secondary radioinduced malignancy. In ion and high-energy photon treatments, the major contribution to the dose deposited in the far-out-of-field region is given by neutrons, which are produced by nuclear interaction of the primary radiation with the beam line components and the patient's body. Measurements of the secondary neutron field and its contribution to the absorbed dose and equivalent dose for different radiotherapy technologies are presented in this work. An anthropomorphic RANDO phantom was irradiated with a treatment plan designed for a simulated 5 × 2 × 5 cm³ cancer volume located in the center of the head. The experiment was repeated with 25 MV IMRT (intensity modulated radiation therapy) photons and charged particles (protons and carbon ions) delivered with both passive modulation and spot scanning in different facilities. The measurements were performed with active (silicon-scintillation) and passive (bubble, thermoluminescence ⁶LiF:Mg, Ti (TLD-600) and ⁷LiF:Mg, Ti (TLD-700)) detectors to investigate the production of neutral particles both inside and outside the phantom. These techniques provided the whole energy spectrum (E ≤ 20 MeV) and corresponding absorbed dose and dose equivalent of photo neutrons produced by x-rays, the fluence of thermal neutrons for all irradiation types and the absorbed dose deposited by neutrons with 0.8 < E < 10 MeV during the treatment with scanned carbon ions. The highest yield of thermal neutrons is observed for photons and, among ions, for passively modulated beams. For the treatment with high-energy x-rays, the contribution of secondary neutrons to the dose equivalent is of the same order of magnitude as the primary radiation. In carbon therapy delivered with raster scanning, the absorbed dose deposited by neutrons in the energy region between 0.8 and 10 MeV is almost two orders of magnitude lower than charged fragments. We conclude that, within the energy range explored in this experimental work, the out-of-field dose from secondary neutrons is lowest for ions delivered by scanning, followed by passive modulation, and finally by high-energy IMRT photons.

This paper presents the absorbed dose and dose equivalent rate measurements achieved with the DOSimetry TElescope (DOSTEL) during the two Matroshka (MTR) experiment campaigns in /2005 (MTR-1) and 2007/2008. The comparison between the inside (MTR-2B) and outside (MTR-1) mission has shown that the shielding thickness provided by the International Space Station (ISS) spacecraft hull has a minor effect on the radiation exposure caused by Galactic Cosmic Rays (GCR). The exposure varies with the solar modulation of the GCR, too. Particles from Earth's radiation belts are effectively shielded by the spacecraft hull, and thus the contribution to the radiation exposure is lower for the inside measurement during MTR-2B. While the MTR-DOSTEL absorbed dose rate shows a good agreement with passive detectors of the MTR experiment for the MTR-2B mission phase, the MTR-1 absorbed dose rates from MTR-DOSTEL measurements are much lower than those obtained by a nearby passive detector. Observed discrepancies between the MTR-DOSTEL measurements and the passive detectors located nearby could be explained by the additional exposure to an enhanced flux of electrons trapped between L-parameter 2.5 and 3.5 caused by solar storms in July 2004.

The radiation environment encountered in space differs in nature from that on Earth, consisting mostly of highly energetic ions from protons up to iron, resulting in radiation levels far exceeding the ones present on Earth for occupational radiation workers. Since the beginning of the space era, the radiation exposure during space missions has been monitored with various active and passive radiation instruments. Also onboard the International Space Station (ISS), a number of area monitoring devices provide data related to the spatial and temporal variation of the radiation field in and outside the ISS. The aim of the DOSIS (2009DOSIS ( -2011 and the DOSIS 3D (2012-ongoing) experiments was and is to measure the radiation environment within the European Columbus Laboratory of the ISS. These measurements are, on the one hand, performed with passive radiation detectors mounted at 11 locations within Columbus for the determination of the spatial distribution of the radiation field parameters and, on the other, with two active radiation detectors mounted at a fixed position inside Columbus for the determination of the temporal variation of the radiation field parameters. Data measured with passive radiation detectors showed that the absorbed dose values inside the Columbus Laboratory follow a pattern, based on the local shielding configuration of the radiation detectors, with minimum dose values observed in the year 2010 of 195-270 lGy/day and maximum values observed in the year 2012 with values ranging from 260 to 360 lGy/day. The absorbed dose is modulated by (a) the variation in solar activity and (b) the changes in ISS altitude.

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