We have been developing a novel radiation-tolerant n+-in-p silicon microstrip sensor for very high radiation environments, aiming for application in the high luminosity large hadron collider. The ...sensors are fabricated in 6in., p-type, float-zone wafers, where large-area strip sensor designs are laid out together with a number of miniature sensors. Radiation tolerance has been studied with ATLAS07 sensors and with independent structures. The ATLAS07 design was developed into new ATLAS12 designs. The ATLAS12A large-area sensor is made towards an axial strip sensor and the ATLAS12M towards a stereo strip sensor. New features to the ATLAS12 sensors are two dicing lines: standard edge space of 910μm and slim edge space of 450μm, a gated punch-through protection structure, and connection of orphan strips in a triangular corner of stereo strips. We report the design of the ATLAS12 layouts and initial measurements of the leakage current after dicing and the resistivity of the wafers.
The ATLAS group has evaluated the charge collection in silicon microstrip sensors irradiated up to a fluence of 1×1016neq/cm2, exceeding the maximum of 1.6×1015neq/cm2 expected for the strip tracker ...during the high luminosity LHC (HL-LHC) period including a safety factor of 2. The ATLAS12, n+-on-p type sensor, which is fabricated by Hamamatsu Photonics (HPK) on float zone (FZ) substrates, is the latest barrel sensor prototype. The charge collection from the irradiated 1×1cm2 barrel test sensors has been evaluated systematically using penetrating β-rays and an Alibava readout system. The data obtained at different measurement sites are compared with each other and with the results obtained from the previous ATLAS07 design. The results are very consistent, in particular, when the deposit charge is normalized by the sensor's active thickness derived from the edge transient current technique (edge-TCT) measurements. The measurements obtained using β-rays are verified to be consistent with the measurements using an electron beam. The edge-TCT is also effective for evaluating the field profiles across the depth. The differences between the irradiated ATLAS07 and ATLAS12 samples have been examined along with the differences among the samples irradiated with different radiation sources: neutrons, protons, and pions. The studies of the bulk properties of the devices show that the devices can yield a sufficiently large signal for the expected fluence range in the HL-LHC, thereby acting as precision tracking sensors.
Detectors planned for use at the Large Hadron Collider will operate in a radiation field produced by beam collisions. To predict the radiation damage to the components of the detectors, prototype ...devices are irradiated at test beam facilities that reproduce the radiation conditions expected. The profile of the test beam and the fluence applied per unit time must be known. Techniques such as thin metal foil activation and radiographic image analysis have been used to measure these; however, some of these techniques do not operate in real time, have low sensitivity, or have large uncertainties. We have developed a technique to monitor in real time the beam profile and fluence using an array of p-i-np-i-n semiconductor diodes whose forward voltage is linear with fluence over the fluence regime relevant to, for example, tracking in the LHC Upgrade era. We have demonstrated this technique in the 800 MeV proton beam at the LANSCE facility of Los Alamos National Laboratory.
Detailed studies of full-size ATLAS12 sensors Hommels, L.B.A.; Baca, M.; Broughton, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2016, Letnik:
831
Journal Article
Recenzirano
Odprti dostop
The “ATLAS ITk Strip Sensor Collaboration” R&D group has developed a second iteration of single-sided n+-in-p type micro-strip sensors for use in the tracker upgrade of the ATLAS experiment at the ...High-Luminosity (HL) LHC. The full size sensors measure approximately 97×97mm2 and are designed for tolerance against the 1.1×1015neq/cm2 fluence expected at the HL-LHC. Each sensor has 4 columns of 1280 individual 23.9mm long channels, arranged at 74.5μm pitch. Four batches comprising 120 sensors produced by Hamamatsu Photonics were evaluated for their mechanical, and electrical bulk and strip characteristics. Optical microscopy measurements were performed to obtain the sensor surface profile. Leakage current and bulk capacitance properties were measured for each individual sensor. For sample strips across the sensor batches, the inter-strip capacitance and resistance as well as properties of the punch-through protection structure were measured. A multi-channel probecard was used to measure leakage current, coupling capacitance and bias resistance for each individual channel of 100 sensors in three batches. The compiled results for 120 unirradiated sensors are presented in this paper, including summary results for almost 500,000 strips probed. Results on the reverse bias voltage dependence of various parameters and frequency dependence of tested capacitances are included for validation of the experimental methods used. Comparing results with specified values, almost all sensors fall well within specification.
A radiation hard n+-in-p micro-strip sensor for the use in the Upgrade of the strip tracker of the ATLAS experiment at the High Luminosity Large Hadron Collider (HL-LHC) has been developed by the ...“ATLAS ITk Strip Sensor collaboration” and produced by Hamamatsu Photonics.
Surface properties of different types of end-cap and barrel miniature sensors of the latest sensor design ATLAS12 have been studied before and after irradiation. The tested barrel sensors vary in “punch-through protection” (PTP) structure, and the end-cap sensors, whose stereo-strips differ in fan geometry, in strip pitch and in edge strip ganging options. Sensors have been irradiated with proton fluences of up to 1×1016 neq/cm2, by reactor neutron fluence of 1×1015 neq/cm2 and by gamma rays from 60Co up to dose of 1MGy. The main goal of the present study is to characterize the leakage current for micro-discharge breakdown voltage estimation, the inter-strip resistance and capacitance, the bias resistance and the effectiveness of PTP structures as a function of bias voltage and fluence. It has been verified that the ATLAS12 sensors have high breakdown voltage well above the operational voltage which implies that different geometries of sensors do not influence their stability. The inter-strip isolation is a strong function of irradiation fluence, however the sensor performance is acceptable in the expected range for HL-LHC. New gated PTP structure exhibits low PTP onset voltage and sharp cut-off of effective resistance even at the highest tested radiation fluence. The inter-strip capacitance complies with the technical specification required before irradiation and no radiation-induced degradation was observed. A summary of ATLAS12 sensors tests is presented including a comparison of results from different irradiation sites. The measured characteristics are compared with the previous prototype of the sensor design, ATLAS07.
•Surface study verified high radiation resistance of developed n-in-p strip sensors.•Sensors have high breakdown voltage before and after irradiation.•Inter-strip capacitance is sufficiently low and does not change with irradiation.•Primary factor of inter-strip resistance decrease is total ionizing dose.•New gated PTP doubles current flowing into bias rail without onset voltage increase.
The upgrade to the High-Luminosity LHC foreseen in about ten years represents a great challenge for the ATLAS inner tracker and the silicon strip sensors in the forward region. Several strip sensor ...designs were developed by the ATLAS collaboration and fabricated by Hamamatsu in order to maintain enough performance in terms of charge collection efficiency and its uniformity throughout the active region. Of particular attention, in the case of a stereo-strip sensor, is the area near the sensor edge where shorter strips were ganged to the complete ones. In this work the electrical and charge collection test results on irradiated miniature sensors with forward geometry are presented. Results from charge collection efficiency measurements show that at the maximum expected fluence, the collected charge is roughly halved with respect to the one obtained prior to irradiation. Laser measurements show a good signal uniformity over the sensor. Ganged strips have a similar efficiency as standard strips.
A proposal to fabricate large area strip sensors with integrated, or embedded, pitch adapters is presented for the End-cap part of the Inner Tracker in the ATLAS experiment. To implement the embedded ...pitch adapters, a second metal layer is used in the sensor fabrication, for signal routing to the ASICs. Sensors with different embedded pitch adapters have been fabricated in order to optimize the design and technology. Inter-strip capacitance, noise, pick-up, cross-talk, signal efficiency, and fabrication yield have been taken into account in their design and fabrication. Inter-strip capacitance tests taking into account all channel neighbors reveal the important differences between the various designs considered. These tests have been correlated with noise figures obtained in full assembled modules, showing that the tests performed on the bare sensors are a valid tool to estimate the final noise in the full module. The full modules have been subjected to test beam experiments in order to evaluate the incidence of cross-talk, pick-up, and signal loss. The detailed analysis shows no indication of cross-talk or pick-up as no additional hits can be observed in any channel not being hit by the beam above 170mV threshold, and the signal in those channels is always below 1% of the signal recorded in the channel being hit, above 100mV threshold. First results on irradiated mini-sensors with embedded pitch adapters do not show any change in the interstrip capacitance measurements with only the first neighbors connected.
A
bstract
We report the measured transverse momentum (
p
T
) spectra of primary charged particles from pp, p-Pb and Pb-Pb collisions at a center-of-mass energy
s
N
N
=
5.02
TeV in the kinematic range ...of 0
.
15
< p
T
<
50 GeV/
c
and |
η
|
<
0
.
8. A significant improvement of systematic uncertainties motivated the reanalysis of data in pp and Pb-Pb collisions at
s
N
N
=
2.76
TeV, as well as in p-Pb collisions at
s
N
N
=
5.02
TeV, which is also presented. Spectra from Pb-Pb collisions are presented in nine centrality intervals and are compared to a reference spectrum from pp collisions scaled by the number of binary nucleon-nucleon collisions. For central collisions, the
p
T
spectra are suppressed by more than a factor of 7 around 6–7 GeV/
c
with a significant reduction in suppression towards higher momenta up to 30 GeV/
c
. The nuclear modification factor
R
pPb
, constructed from the pp and p-Pb spectra measured at the same collision energy, is consistent with unity above 8 GeV/
c
. While the spectra in both pp and Pb-Pb collisions are substantially harder at
s
N
N
=
5.02
TeV compared to 2.76 TeV, the nuclear modification factors show no significant collision energy dependence. The obtained results should provide further constraints on the parton energy loss calculations to determine the transport properties of the hot and dense QCD matter.
PDF
