Trapping in irradiated p-on-n silicon sensors at fluences anticipated at the HL-LHC outer tracker

The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 $\mu$m thick n-type silicon sensors are irradiated with protons of different energies to fluences of up to $3 \cdot 10^{15}$ neq/cm$^2$. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggests an improved tracker performance over initial expectations

Compete to Play: Trade-Off with Social Contact in Long-Tailed Macaques (<i>Macaca fascicularis</i>)

<div><p>Many animal species engage in various forms of solitary object play, but this activity seems to be of particular importance in primates. If playing objects constitute a valuable resource, and access to such objects is limited, a competitive context may arise. We inserted a unique toy within a mini-colony of long-tailed macaque (<i>Macaca fascicularis</i>) and compared their behaviors to sessions without playing object. An automatic color-based 3D video device was used to track the positions of each animal and the toy, and this data was categorized into 5 exclusive behaviors (resting, locomotion, foraging, social contact and object play). As expected, the delay to first access to the object reflected the hierarchy of the colony, indicating that a competition took place to own this unique resource of entertainment. In addition, we found that the amount of object play was not correlated with social or foraging behavior, suggesting independent motivational mechanisms. Conversely, object playing time was negatively correlated with idling time, thus indicating its relation to pastime activities. Interestingly, the amount of social contacts in the group was significantly reduced by the heightened competitive context, suggesting that competitors are more likely to be perceived as potential threat requiring caution, as shown in humans. Experimental manipulation of competitive contexts in primates reveals common mental processes involved in social judgment, and shows that access to valuable resources can be a sufficient cause for variations in group cohesion.</p></div

Hierarchy estimated from access to toys.

<p>Mean delay between toy introduction in the home cage and first toy interaction event lasting>10 s with M1 presence (left panel, n = 11) and absence (right panel, n = 18) in the group. * indicate significant pairwise differences (Wilcoxon rank sum test p<0.05). M1 designate the most dominant monkey and M4 the most subordinate monkey as established through the classical water access test (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115965#s2" target="_blank">Materials and Methods</a>).</p

Intra-individual correlations between rate of object play and: (A) rate of social contact R = 0.13 p>0.05, (B) rate of foraging R = 0.08 p>0.05, (C) rate of resting R = −0.31 p<0.01, (D) rate of locomotion R = −0.32 p<0.01.

<p>All scores arcsine transformed. Symbols correspond to mean rate of a given behavior on a given day for a given monkey (M1-4: ▿, □, ◊, ○ respectively).</p

Impact of novel object introduction on monkeys' social and non-social activities (A) Radar plot of 5 mutually-exclusive individual activities of the mini-colony during recording sessions with (n = 18) or without (n = 17) prior introduction of a single toy (average and s.e.m.).

<p>(B) Distance to closest peer when a monkey was playing with the object or performing another activity (except social contact). All recording sessions with objects were used (n = 28). *** indicate significant differences (Wilcoxon rank sum test p<0.001).</p

Impact of low-dose electron irradiation on n+p silicon strip sensors

The response of n+p silicon strip sensors to electrons from a 90Sr source was measured using a multi-channel read-out system with 25 ns sampling time. The measurements were performed over a period of several weeks, during which the operating conditions were varied. The sensors were fabricated by Hamamatsu Photonics on 200 μm thick float-zone and magnetic-Czochralski silicon. Their pitch was 80 μm, and both p-stop and p-spray isolation of the n+ strips were studied. The electrons from the 90Sr source were collimated to a spot with a full-width-at-half-maximum of 2 mm at the sensor surface, and the dose rate in the SiO2 at the maximum was about 50 Gy(SiO2)/d. After only a few hours of making measurements, significant changes in charge collection and charge sharing were observed. Annealing studies, with temperatures up to 80 °C and annealing times of 18 h showed that the changes can only be partially annealed. The observations can be qualitatively explained by the increase of the positive oxide-charge density due to the ionization of the SiO2 by the radiation from the β source. TCAD simulations of the electric field in the sensor for different oxide-charge densities and different boundary conditions at the sensor surface support this explanation. The relevance of the measurements for the design of n+p strip sensors is discussed

Trapping in proton irradiated p(+)-n-n(+) silicon sensors at fluences anticipated at the HL-LHC outer tracker

The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 μm thick n-type silicon sensors are irradiated with protons of 15 2 different energies to fluences of up to 3 · 10 neq/cm . Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggest an improved tracker performance over initial expectations