Search

We performed TRIUMF in situ measurements of the levels and kinetics of radiation-induced attenuation (RIA) caused by protons in different bulk optical glasses. Two SCHOTT radiation-hardened glasses (doped with Cerium) and six standard optical glasses (without Cerium) have been characterized. We compared the proton RIA kinetics with those resulting from in situ X-ray irradiations performed at dose and dose rate equivalent to the proton testing ones. The RIA spectra and kinetics are quite comparable in both cases, showing that X-rays can efficiently be used to estimate the RIA caused by protons. To better discuss the differences, we performed Monte Carlo calculations with GEANT4 of the energy deposition coefficient for each glass, according to its composition, and for the different beams. We complete our experimental characterization by comparing our data with those measured by the European Space Agency on the same glasses after $\gamma $ -irradiation. Protons, X-rays and $\gamma $ -rays cause RIA with very close spectral dependences, producing the same defects at similar concentration levels. We also demonstrated that the optimized setup for the in situ RIA characterization of bulk materials is very suitable for measurements under collimated particles beam. [ABSTRACT FROM AUTHOR]

We investigated the potential of a multimode (50- $\mu \text{m}$ core diameter) nitrogen doped silica-based optical fiber for X-rays, protons, and $\gamma $ -rays radiation detection and dosimetry. X-rays results confirm that this N-doped fiber presents a strong radioluminescence (RL) around 550 nm when exposed to radiation. The RL observed from a few centimeter long samples linearly depend on the dose rate at least in the 1-mGy/s–50-Gy/s range. Low dose rate $\gamma $ -ray t ests demonstrate the radiation detection at dose rate as low as $40~\mu $ Gy/s with a 2-m-long fiber sample. This fiber is also associated with an optically stimulated luminescence (OSL) when exposed to a 1064-nm laser light postirradiation. This OSL signature provides shortly after the irradiation a precise estimation of the accumulated dose at least in the 1-Gy–10-kGy range. Under proton exposure, we benchmarked the performances of the N-doped fiber with the ones of a conventional Markus chamber used by the TRIUMF proton-therapy team. This comparison highlights the potential of the small-size N-doped fiber to partially overcome the known limitations of commercial fiber-based dosimeters for medical applications. The obtained results are very promising for the future design of more complex spatially resolved beam monitoring systems. [ABSTRACT FROM AUTHOR]

We discuss upsets in erased floating gate cells, due to large threshold voltage shifts, using statistical distributions collected on a large number of memory cells. The spread in the neutral threshold voltage appears to be too low to quantitatively explain the experimental observations in terms of simple charge loss, at least in SLC devices. The possibility that memories exposed to high energy protons and heavy ions exhibit negative charge transfer between programmed and erased cells is investigated, although the analysis does not provide conclusive support to this hypothesis. [ABSTRACT FROM PUBLISHER]

We investigate the potential of innovative optical fiber bulk materials made by the sol-gel technique for real-time proton beam monitoring. Those types of glass are made of amorphous silica ( a -SiO2) doped with either Copper (Cu) or Cerium (Ce) ions. These optimized materials possess very interesting light emission properties when exposed to protons. For both types of glasses, online monitoring of the strong radiation-induced luminescence (RIL) allows to monitor the time evolution of the proton flux with ms resolution and the cumulated proton fluence can be precisely deduced by integrating the RIL signal. Furthermore, we showed that both samples present optically-stimulated luminescence (OSL) that could be exploited shortly after the end of the irradiation to reconstruct the cumulated fluence too. Preliminary tests presented in this paper have been performed at TRIUMF facility with high energy (30 - 63 MeV) protons at flux and fluences representative of proton therapy treatments. Obtained results demonstrate the potential of the developed optical materials for proton beam monitoring and permits to identify the needs for future experiments on microstructured fibers elaborated from these optical materials. [ABSTRACT FROM PUBLISHER]

The low-energy proton energy spectra of all shielded space environments have the same shape. This shape is easily reproduced in the laboratory by degrading a high-energy proton beam, producing a high-fidelity test environment. We use this test environment to dramatically simplify rate prediction for proton direct ionization effects, allowing the work to be done at high-energy proton facilities, on encapsulated parts, without knowledge of the IC design, and with little or no computer simulations required. Proton direct ionization (PDI) is predicted to significantly contribute to the total error rate under the conditions investigated. Scaling effects are discussed using data from 65-nm, 45-nm, and 32-nm SOI SRAMs. These data also show that grazing-angle protons will dominate the PDI-induced error rate due to their higher effective LET, so PDI hardness assurance methods must account for angular effects to be conservative. We show that this angular dependence can be exploited to quickly assess whether an IC is susceptible to PDI. [ABSTRACT FROM PUBLISHER]

Copyright of Canadian Journal of Physics is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Neutral atoms trapped with modern laser cooling techniques offer the promise of improving several broad classes of weak interaction experiments with radioactive isotopes. For nuclear β decay, demonstrated trap techniques include neutrino momentum measurements from beta-recoil coincidences, along with methods to produce highly polarized samples. These techniques enable experiments to search for non-Standard Model interactions, test whether parity symmetry is maximally violated, search for 2nd-class tensor and other tensor interactions, and search for new sources of time reversal violation. Ongoing efforts at TRIUMF, Berkeley, and Los Alamos will be highlighted. Trap experiments involving fundamental symmetries in atomic physics, such as time-reversal violating electric dipole moments and neutral current weak interactions, will be briefly mentioned. [ABSTRACT FROM AUTHOR]

A novel technique for a high-precision large acceptance determination of the Bragg angle in crystal x-ray spectroscopy is presented and demonstrated. The method exploits visible light beams as fiducials reflected on the x-ray crystal’s surface to ensure exact knowledge of the position on the crystal at which the x rays are reflected, replacing entrance slits, thus making flat crystals suitable for low x-ray fluxes. It can be shown that many error sources arising from uncertainties in the determination of geometrical properties are eliminated in this way. A flat crystal x-ray spectrometer based on this technique has been designed, built, and tested using the most precisely known wavelengths emitted by highly charged ions, namely H- and He-like argon. The result for the 1s2p 1P1→1s2 1S0 w-line of He-like argon exhibits a statistical uncertainty of 3.8 ppm and an estimated systematic error of about 3 ppm, thus becoming the most accurate measurement of the He-like resonance transition in highly charged ions. It is shown that achieving a systematic error of below 1 ppm is feasible with this method. Therefore, our technique should allow reaching total accuracies approaching 1 ppm on transitions of mid-Z highly charged ions, which would provide challenging tests for state-of-the-art theoretical predictions. [ABSTRACT FROM AUTHOR]

Magneto optical traps (MOT) allow the cooling and storing of neutral atoms in a volume of a few cubic millimeters by use of laser beams and a magnetic field. Such devices offer new and exciting opportunities for precision measurements of radioactive isotopes. Here we present experiments performed with a double-MOT system coupled to the on-line separator TISOL at TRIUMF/Vancouver, Canada. For the first time, the Β-decay of free atoms stored in such a device could be observed. We report on coincidence measurements between beta-particles and the argon recoils in the decay of 37K and 38rm{m}}K. The charge state ratios of the recoil-ions were deduced by Time-Of-Flight separation in an acceleration field. The final goal of those investigations is a precision test of the Standard Model by measuring the –nu-correlation parameter a. [ABSTRACT FROM AUTHOR]

The dielectronic recombination resonance (DRR) processes for highly charged krypton ions have been investigated through simultaneously observing the x-ray emission and the ions extracted at the Heidelberg EBIT while slowly scanning the electron beam energy. It was found that at their DR resonance electron energies, the yield of the He-like krypton ions was substantially reduced, whereas that of the Li-like krypton ions was correspondingly increased. At slightly higher electron energies similar features were observed for the Li- and Be-like krypton ions. From the observed ratios of the Li-like/He-like krypton ion currents, we have deduced the dielectronic recombination (DR) strength for the He-like ions, which was found to be in reasonable agreement with theoretical calculations. We have also concluded from the present experiments that the DRR processes can be used to modify the ion charge state distributions and to concentrate the extracted ion currents into particular charge states. This is particularly important for future charge breading experiments with short-lived radioactive isotopes. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]