Ewart W. Blackmore

Improved capabilities for proton and neutron irradiations at TRIUMF

Improvements have been made at TRIUMF to permit higher proton intensities of up to 10/sup 10/ cm/sup -2/s/sup -1/ over the energy range 20-500 MeV. This improved capability enables the study of displacement damage effects that require higher fluence irradiations. In addition, a high energy neutron irradiation capability has been developed for terrestrial cosmic ray soft error rate (SER) characterization of integrated circuits. The neutron beam characteristics of this facility are similar to those currently available at the Los Alamos National Laboratory WNR test facility. SER data measured on several SRAMs using the TRIUMF neutron beam are in good agreement with the results obtained on the same devices using the WNR facility. The TRIUMF neutron beam also contains thermal neutrons that can be easily removed by a sheet of cadmium. The ability to choose whether thermal neurons are present is a useful attribute not possible at the WNR.

Operation of the TRIUMF (20-500 MeV) proton irradiation facility

The TRIUMF proton irradiation facility can cover an energy range from below 20 MeV to 500 MeV using two extracted proton beam lines which operate into the same experimental area. The range of proton intensities is ideal for single event effect testing and high enough for some radiation damage testing of components. Neutrons, pions and higher intensity protons are also available at TRIUMF.

Muon-Induced Single Event Upsets in Deep-Submicron Technology

Experimental data are presented that show low-energy muons are able to cause single event upsets in 65 nm, 45 nm, and 40 nm CMOS SRAMs. Energy deposition measurements using a surface barrier detector are presented to characterize the kinetic energy spectra produced by the M20B surface muon beam at TRIUMF. A Geant4 application is used to simulate the beam and estimate the energy spectra incident on the memories. Results indicate that the sensitivity to this mechanism will increase for scaled technologies.

LET spectra of proton energy levels from 50 to 500 MeV and their effectiveness for single event effects characterization of microelectronics

The effective linear energy transfer of heavy nuclear recoils (Z/spl ges/3) produced by proton interactions in silicon are calculated for incident proton energies of 50, 100, 200, and 500 MeV. The LAHET intranuclear cascade and evaporation code is used to obtain the energy spectra of the nuclear recoils and a Monte Carlo code is then used to follow these recoils as they stop in silicon. The total LET spectra at an observation layer located at a depth of 100 microns in the silicon is calculated. The effectiveness of each proton energy level for single event effects screening of microelectronics is evaluated.

Radiation Effects of Protons on Samarium-Cobalt Permanent Magnets

At TRIUMF the use of samarium-cobalt permanent magnet quadrupoles as the first element in a secondary channel has been studied as a means of increasing the solid angle acceptance of the channel. The high remanent induction Br and high coercive force Hc of rareearth cobalt (REC) can be utilized to produce a high-gradient quadrupole field in an extremely compact magnet. Although many properties of REC material have been measured, little is known about the effect of charged particle radiation on the magnetic behaviour. As the TRIUMF application requires the magnets to operate in a high radiation environment it was considered essential to study this effect. This paper describes the results of exposing samples of samarium-cobalt and other permanent magnet materials to a beam of protons.

High gradient magnetic separation of cells on the basis of expression levels of cell surface antigens.

The possibility of separating cells on the basis of levels of antigen expression was explored in a model system using fixed erythrocytes and high gradient magnetic separation (HGMS). Fixed human erythrocytes were labelled to varying degrees with tetrameric monoclonal antibody complexes specific for both dextran and glycophorin A-M. The cells were then mixed and incubated with dextran iron particles prior to magnetic separation. The small size of the dextran iron particles (less than 0.2 microns) resulted in quantitative magnetic labelling of cells as shown using fluoresceinated anti-dextran antibodies and flow cytometry. The relationships between the initial percentage of labelled cells, cell recovery, non-specific entrapment of unlabelled cells, the purity of the removed fraction, the degree of antigen expression and separation conditions (flow rate and field strength) were determined and used to establish separation conditions that allowed recovery of cells that differ only in the degree of antibody labelling.

The Effect of High-Z Materials on Proton-Induced Charge Collection

Charge collection measurements reveal that the presence of high-Z materials increases proton-induced charge collection cross sections for high charge collection events. The mechanism for this effect is proton-induced fission events as shown through validated Monte Carlo simulations. These fission fragments are emitted isotropically in contrast to high-LET secondary particles from proton-silicon interactions which tend to be forward directed.

A detector to search for K+ → π+ νν

Abstract The detector built for experiment 787 to measure the decay K + → π + ν ν at Brookhaven National Laboratory is describe

Outcomes of Proton Radiation Therapy for Peripapillary Choroidal Melanoma at the BC Cancer Agency

PURPOSEnTo report toxicity, local control, enucleation, and survival rates for patients with peripapillary choroidal melanoma treated with proton therapy in Canada.nnnMETHODS AND MATERIALSnWe performed a retrospective analysis of patients with peripapillary choroidal melanoma (≤ 2 mm from optic disc) treated between 1995 and 2007 at the only Canadian proton therapy facility. A prospective database was updated for follow-up information from a chart review. Descriptive and actuarial data are presented.nnnRESULTSnIn total, 59 patients were treated. The median age was 59 years. According to the 2010 American Joint Committee on Cancer TNM classification, there were 20 T1 tumors (34%), 28 T2 tumors (48%), and 11 T3 tumors (19%). The median tumor diameter was 11.4 mm, and the median thickness was 3.5 mm. Median follow-up was 63 months. Nineteen patients received 54 cobalt gray equivalents (CGE) and forty patients received 60 CGE, each in 4 fractions. The 5-year actuarial local control rate was 91% (T1, 100%; T2, 93%; and T3, 59%) (p = 0.038). There was a suggestive relationship between local control and dose. The local control rate was 97% with 60 CGE and 83% with 54 CGE (p = 0.106). The metastasis-free survival rate was 82% and related to T stage (T1, 94%; T2, 84%; and T3, 47%) (p < 0.001). Twelve patients died, including eleven with metastases. The 5-year actuarial rate of neovascular glaucoma was 31% (23% for T1-T2 and 68% for T3, p < 0.001), and that of enucleation was 0% for T1, 14% for T2, and 72% for T3 (p < 0.001). Radiation retinopathy (74%) and optic neuropathy (64%) were common within-field effects.nnnCONCLUSIONSnProton therapy provides excellent local control with acceptable toxicity while conserving the globe in 80% of cases. These results are consistent with other single-institution series using proton radiotherapy, and toxicity rates were acceptable. T3 tumors carry a higher rate of both local recurrence and metastasis.

Enhanced Proton and Neutron Induced Degradation and Its Impact on Hardness Assurance Testing

It is shown that protons and neutrons can induce enhanced degradation in power MOSFETs, including both trench and planar geometry devices. Specifically, large shifts in current-voltage characteristics can be observed at extremely low proton total dose levels (as low as ~ 2 rad(SiO2)). These shifts can induce significant increases in device ldquooffrdquo state leakage current. Neutron irradiations show similar degradation at equivalent fluence levels, even though neutrons do not deposit dose due to direct ionization. These data suggest that the mechanism responsible for the enhanced degradation is a microdose effect associated with secondary particles produced through nuclear interactions between protons and neutrons and the materials in integrated circuits. The secondary particles deposit enough charge in the gate oxide to induce a parasitic drain to source leakage path in the transistor. Although the results are demonstrated here for only trench and planar geometry power MOSFETs, microdose effects can impact the radiation response of other integrated circuit types. Hardness assurances issues implications are discussed.