3,620 research outputs found
Bias dependence and bistability of radiation defects in silicon
Influence of bias on effective dopant concentration in neutron and pion irradiated diodes has been measured. Detailed studies of annealing of the bias-induced damagehave revealed three components, with introduction rates from 0.005 to 0.008 cm andannealing time constants ranging from 5 to 1000 hours at 20C. Variation of annealing temperatures yielded activation energies around 1 eV for all the three components. Bistable behavior of radiation damage under bias has been observed and its activation and annealingstudied. The bistable damage was associated to the fastest annealing component of bias-induced damage.Using the parameterization obtained, a prediction for ATLAS SCT operation was made.Bias-induced damage is shown to require an additional 80 V to fully deplete detectors at the end of LHC operation
Radiation detection properties of 4H-SiC Schottky diodes irradiated up to 10(16) n/cm(2) by 1 MeV neutrons
We report the results of an experimental study on the radiation hardness of 4H-SiC diodes used as alpha-particle detectors with 1 MeV neutrons up to a fluence of 8 x 10(15) n/cm(2). As the irradiation level approaches the range 10(15) n/cm(2), the material behaves as intrinsic due to a very high compensation effect and the diodes are still able to detect with a reasonable good Charge Collection Efficiency (CCE = 80%).For fluences > 10(15) n/cm(2) CCE decreases monotonically to approximate to 20 % at the highest fluence. Heavily irradiated SiC diodes have been studied, by means of Photo Induced Current Transien
Precision planar drift chambers and cradle for the TWIST muon decay spectrometer
To measure the muon decay parameters with high accuracy, we require an array
of precision drift detector layers whose relative position is known with very
high accuracy. This article describes the design, construction and performance
of these detectors in the TWIST (TRIUMF Weak Interaction Symmetry Test)
spectrometer.Comment: 44 pages, 16 Postscript figures, LaTeX2e, uses Elsevier class
elsart.cls, package graphicx, submitted to Nuclear Instruments & Methods in
Physics Researc
Radiation Hardness of Thin Low Gain Avalanche Detectors
Low Gain Avalanche Detectors (LGAD) are based on a n++-p+-p-p++ structure
where an appropriate doping of the multiplication layer (p+) leads to high
enough electric fields for impact ionization. Gain factors of few tens in
charge significantly improve the resolution of timing measurements,
particularly for thin detectors, where the timing performance was shown to be
limited by Landau fluctuations. The main obstacle for their operation is the
decrease of gain with irradiation, attributed to effective acceptor removal in
the gain layer. Sets of thin sensors were produced by two different producers
on different substrates, with different gain layer doping profiles and
thicknesses (45, 50 and 80 um). Their performance in terms of gain/collected
charge and leakage current was compared before and after irradiation with
neutrons and pions up to the equivalent fluences of 5e15 cm-2. Transient
Current Technique and charge collection measurements with LHC speed electronics
were employed to characterize the detectors. The thin LGAD sensors were shown
to perform much better than sensors of standard thickness (~300 um) and offer
larger charge collection with respect to detectors without gain layer for
fluences <2e15 cm-2. Larger initial gain prolongs the beneficial performance of
LGADs. Pions were found to be more damaging than neutrons at the same
equivalent fluence, while no significant difference was found between different
producers. At very high fluences and bias voltages the gain appears due to deep
acceptors in the bulk, hence also in thin standard detectors
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
Fast Polycrystalline-CdTe Detectors for LHC Luminosity Measurements
Beam diagnostics in future high-energy accelerators will require long lived instrumentation in highly hostile radiation environments. A research program aiming at individuating new solutions and testing them under extreme operational conditions has been launched at CERN in the framework of developments for the LHC instrumentation. Its outcome might be used in future accelerator projects, in industry or in physics applications. The detectors which will be adopted for the LHC luminosity monitoring and optimization will be installed close to or inside copper absorbers specifically designed for radiation protection of the accelerator magnetic elements in the interaction regions. These detectors will have to withstand extreme radiation levels and their long-term operation has to be assured without requiring human intervention. Polycrystalline-CdTe detectors have demonstrated their radiation hardness against extreme doses of X-ray exposure in the LEP collider and are considered as good candidates for LHC luminosity monitoring applications. After recalling a series of measurements obtained on CdTe samples exposed to different sources to study their time response and sensitivity we present results on their performance after irradiation at doses of 10^16 neutrons/cm^2. This is a preliminary step in the program intended to test the samples during and after irradiation up to levels of 10^18 neutrons/cm^2 and 10^16 protons/cm^2 comparable to those anticipated at the detector locations over ten years of operation of the accelerator
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
- âŠ