1,793 research outputs found
Comparison of 35 and 50 {\mu}m thin HPK UFSD after neutron irradiation up to 6*10^15 neq/cm^2
We report results from the testing of 35 {\mu}m thick Ultra-Fast Silicon
Detectors (UFSD produced by Hamamatsu Photonics (HPK), Japan and the comparison
of these new results to data reported before on 50 {\mu}m thick UFSD produced
by HPK. The 35 {\mu}m thick sensors were irradiated with neutrons to fluences
of 0, 1*10^14, 1*10^15, 3*10^15, 6*10^15 neq/cm^2. The sensors were tested
pre-irradiation and post-irradiation with minimum ionizing particles (MIPs)
from a 90Sr \b{eta}-source. The leakage current, capacitance, internal gain and
the timing resolution were measured as a function of bias voltage at -20C and
-27C. The timing resolution was extracted from the time difference with a
second calibrated UFSD in coincidence, using the constant fraction method for
both. Within the fluence range measured, the advantage of the 35 {\mu}m thick
UFSD in timing accuracy, bias voltage and power can be established.Comment: 9 pages, 9 figures, HSTD11 Okinawa. arXiv admin note: text overlap
with arXiv:1707.0496
Charge collection properties of irradiated depleted CMOS pixel test structures
Edge-TCT and charge collection measurements with passive test structures made
in LFoundry 150 nm CMOS process on p-type substrate with initial resistivity of
over 3 kcm are presented. Measurements were made before and after
irradiation with reactor neutrons up to 210
n/cm. Two sets of devices were investigated: unthinned (700
m) with substrate biased through the implant on top and thinned (200
m) with processed and metallised back plane.
Depleted depth was estimated with Edge-TCT and collected charge was measured
with Sr source using an external amplifier with 25 ns shaping time.
Depleted depth at given bias voltage decreased with increasing neutron fluence
but it was still larger than 70 m at 250 V after the highest fluence.
After irradiation much higher collected charge was measured with thinned
detectors with processed back plane although the same depleted depth was
observed with Edge-TCT. Most probable value of collected charge of over 5000
electrons was measured also after irradiation to 210
n/cm. This is sufficient to ensure successful operation of
these detectors at the outer layer of the pixel detector in the ATLAS
experiment at the upgraded HL-LHC
Timing performance of small cell 3D silicon detectors
A silicon 3D detector with a single cell of 50x50 um2 was produced and
evaluated for timing applications. The measurements of time resolution were
performed for 90Sr electrons with dedicated electronics used also for
determining time resolution of Low Gain Avalanche Detectors (LGADs). The
measurements were compared to those with LGADs and also simulations. The
studies showed that the dominant contribution to the timing resolution comes
from the time walk originating from different induced current shapes for hits
over the cell area. This contribution decreases with higher bias voltages,
lower temperatures and smaller cell sizes. It is around 30 ps for a 3D detector
of 50x50 um2 cell at 150 V and -20C, which is comparable to the time walk due
to Landau fluctuations in LGADs. It even improves for inclined tracks and
larger pads composed of multiple cells. A good agreement between measurements
and simulations was obtained, thus validating the simulation results
Field engineering by continuous hole injection in silicon detectors irradiated with neutrons
Abstract The electric field in irradiated silicon diodes was modified by manipulating the occupation of deep levels. This was achieved by continuous injection of holes using light illumination. Effective trapping probabilities and space charge concentrations were measured in this operating mode. The bias voltage needed to establish the electric field in the whole detector volume, charge collection, power consumption and shot noise were investigated. The optimum operation point was found to be independent of irradiation fluence, providing a robust way of operating highly irradiated detectors, even if irradiated in a non-uniform way. PACS: 85.30.De; 29.40.Wk; 29.40.G
Gain Recovery in Heavily Irradiated Low Gain Avalanche Detectors by High Temperature Annealing
Studies of annealing at temperatures up to 450C with LGADs irradiated
with neutrons are described. It was found that the performance of LGADs
irradiated with 1.5e15 n/cm was already improved at 5 minutes of annealing
at 250C. Isochronal annealing for 30 minutes in 50C steps
between 300C and 450C showed that the largest beneficial effect
of annealing is at around 350C. Another set of devices was annealed for
60 minutes at 350C and this annealing significantly increased
V. The effect is equivalent to reducing the effective acceptor
removal constant by a factor of 4. Increase of V is the
consequence of increased effective space charge in the gain layer caused by
formation of electrically active defects or re-activation of interstitial Boron
atoms
Radiation Campaign of HPK Prototype LGAD sensors for the High-Granularity Timing Detector (HGTD)
We report on the results of a radiation campaign with neutrons and protons of
Low Gain Avalanche Detectors (LGAD) produced by Hamamatsu (HPK) as prototypes
for the High-Granularity Timing Detector (HGTD) in ATLAS. Sensors with an
active thickness of 50~m were irradiated in steps of roughly 2 up
to a fluence of . As a function of the
fluence, the collected charge and time resolution of the irradiated sensors
will be reported for operation at
Tests of the Equivalence Principle with Neutral Kaons
We test the Principle of Equivalence for particles and antiparticles, using
CPLEAR data on tagged K0 and K0bar decays into pi^+ pi^-. For the first time,
we search for possible annual, monthly and diurnal modulations of the
observables |eta_{+-}| and phi_{+-}, that could be correlated with variations
in astrophysical potentials. Within the accuracy of CPLEAR, the measured values
of |eta_{+-}| and phi_{+-} are found not to be correlated with changes of the
gravitational potential. We analyze data assuming effective scalar, vector and
tensor interactions, and we conclude that the Principle of Equivalence between
particles and antiparticles holds to a level of 6.5, 4.3 and 1.8 x 10^{-9},
respectively, for scalar, vector and tensor potentials originating from the Sun
with a range much greater than the distance Earth-Sun. We also study
energy-dependent effects that might arise from vector or tensor interactions.
Finally, we compile upper limits on the gravitational coupling difference
between K0 and K0bar as a function of the scalar, vector and tensor interaction
range.Comment: 15 pages latex 2e, five figures, one style file (cernart.csl)
incorporate
The ATLAS SCT grounding and shielding concept and implementation
This paper presents a complete description of Virgo, the French-Italian gravitational wave detector. The detector, built at Cascina, near Pisa (Italy), is a very large Michelson interferometer, with 3 km-long arms. In this paper, following a presentation of the physics requirements, leading to the specifications for the construction of the detector, a detailed description of all its different elements is given. These include civil engineering infrastructures, a huge ultra-high vacuum (UHV) chamber (about 6000 cubic metres), all of the optical components, including high quality mirrors and their seismic isolating suspensions, all of the electronics required to control the interferometer and for signal detection. The expected performances of these different elements are given, leading to an overall sensitivity curve as a function of the incoming gravitational wave frequency. This description represents the detector as built and used in the first data-taking runs. Improvements in different parts have been and continue to be performed, leading to better sensitivities. These will be detailed in a forthcoming paper
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