Abstract
The transmission of silicon crystals irradiated by 24 GeV/c protons and reactor neutrons has been measured for photon energies,
E
γ
, between 0.95 and 1.3 eV. From the transmission data the ...absorption coefficient
α
is calculated, and from
α
(
E
γ
) the fluence dependence of the band-gap energy,
E
gap
, and the energy of transverse optical phonons,
E
ph
, determined. It is found that within the experimental uncertainties of about 1 meV neither
E
gap
nor
E
ph
depend on fluence up to the maximum fluence of 1 × 10
17
cm
−2
of the measurements. The value of
E
gap
agrees within about 1 meV with the generally accepted value, if an exciton-binding energy of 15 meV is assumed. A similar agreement is found for
E
ph
. For the extraction of
E
gap
and
E
ph
the second derivative of
α
(
E
γ
)
smoothed with a Gaussian kernel has been used.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
3.
SiPM understanding using simple Geiger-breakdown simulations Klanner, R.; Schwandt, J.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
20/May , Volume:
1062
Journal Article
Peer reviewed
Open access
The results of a 1-D Monte-Carlo program, which simulates the avalanche multiplication in diodes with depths of the order of 1μm based on the method proposed in Ref.Windischhofer and Riegler (2023), ...are presented. The aim of the study is to achieve a deeper understanding of silicon photo-multipliers. It is found that for a given over-voltage, OV, the maximum of the discharge current is reached at the breakdown voltage, Ubd, and that the avalanche stops when the voltage drops to approximately Ubd−OV. This is completely different to the generally accepted understanding of SiPMs, that the discharge stops at about Ubd. Simulated characteristics of the avalanche breakdown, like the time dependence of the avalanche current, over-voltage dependence of the Geiger-breakdown probability and the gain for photons and dark counts, are presented and compared to experimental findings.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract The exclusive photoproduction reactions γp → J/ψ(1S)p and γp → ψ(2S)p have been measured at an ep centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated ...luminosity of 373 pb −1. The measurement was made in the kinematic range 30 < W < 180 GeV, Q 2 < 1 GeV2 and |t| < 1 GeV2, where W is the photon-proton centre-of-mass energy, Q 2 is the photon virtuality and t is the squared four-momentum transfer at the proton vertex. The decay channels used were J/ψ(1S) → μ + μ − , ψ(2S) → μ + μ − and ψ(2S) → J/ψ(1S)π + π − with subsequent decay J/ψ(1S) → μ + μ − . The ratio of the production cross sections, R = σ ψ(2S) /σ J/ψ(1S), has been measured as a function of W and |t| and compared to previous data in photoproduction and deep inelastic scattering and with predictions of QCD-inspired models of exclusive vector-meson production, which are in reasonable agreement with the data.
A method is proposed for determining the electric field in highly-irradiated silicon pad diodes using admittance-frequency (Y−f), and current measurements (I). The method is applied to Y−f and I data ...from square n+p diodes of 25 mm2 area irradiated by 24 GeV/c protons to four 1 MeV neutron equivalent fluences between 3×1015 cm−2 and 13×1015 cm−2. The measurement conditions were: Reverse voltages between 1 V and 1000 V, frequencies between 100 Hz and 2 MHz and temperatures of −20 °C and −30 °C. The position dependence of the electric field is parameterised by a linear dependence at the two sides of the diode, and a constant in the centre. The parameters as a function of voltage, temperature and irradiation fluence are determined by fits of the model to the data. For voltages below about 300 V all data are well described by the model, and the results for the electric field agrees with expectations: Depleted high-field regions towards the two faces and a constant low electric field in the centre, with values which agrees with the field in an ohmic resistor with approximately the intrinsic resistivity of silicon. For conditions at which the low field region disappears and the diode is fully depleted, the method fails. This happens around 300 V for the lowest irradiation fluence at −30 °C, and at higher voltages for higher fluences and lower temperatures. In the conclusions the successes and problems of the method are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
6.
On the weighting field of irradiated silicon detectors Schwandt, J.; Klanner, R.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2019, Volume:
942
Journal Article
Peer reviewed
Open access
The understanding of the weighting field of irradiated silicon sensors is essential for calculating the response of silicon detectors in the radiation environment at accelerators like at the CERN ...LHC. Using 1-D calculations of non-irradiated pad sensors and 1-D TCAD (Technology Computer-Aided Design) simulations of pad sensors before and after irradiation, it is shown that the time-dependence of the weighting field is related to the resistivity of low field regions with ohmic behaviour in the sensor. A simple formula is derived, which relates the time constant of the time-dependent weighting field, τ, with the resistivity and the extension of the low-field region for pad detectors. As the resistivity of irradiated silicon increases with fluence and finally reaches the intrinsic resistivity, τ becomes much larger than the charge-collection time and the weighting field becomes essentially independent of time. The TCAD simulations show that the transition from a time-dependent to a time-independent weighting field occurs at a neutron-equivalent fluence of ≈5×1012 cm−2 for a 200μm thick pad diode operated at 40 V and −20°C. It is therefore concluded that the use of a time-independent weighting field calculated with the same method as for a fully-depleted non-irradiated sensor is also appropriate for the simulation of highly irradiated silicon sensors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Electro-optical imaging of electric fields in silicon sensors Klanner, R.; Vauth, A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2021, Volume:
995
Journal Article
Peer reviewed
Open access
A conceptual set-up for measuring the electric field in silicon detectors by electro-optical imaging is proposed. It is based on the Franz–Keldysh effect which describes the electric field dependence ...of the absorption of light with an energy close to the band gap in semiconductors. Using published data for silicon, a measurement accuracy of 1 to 4kV/cm is estimated. The set-up is intended for determining the electric field in radiation-damaged silicon detectors as a function of irradiation fluence and particle type, temperature and bias voltage. The overall concept and the individual components of the set-up are presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Charge multiplication (CM) in p+n epitaxial silicon pad diodes of 75, 100 and 150μm thickness at high voltages after proton irradiation with 1MeV neutron equivalent fluences in the order of 1016cm−2 ...was studied as an option to overcome the strong trapping of charge carriers in the innermost tracking region of future Super-LHC detectors. Charge collection efficiency (CCE) measurements using the Transient Current Technique (TCT) with radiation of different penetration (670, 830, 1060nm laser light and α-particles with optional absorbers) were used to locate the CM region close to the p+-implantation. The dependence of CM on material, thickness of the epitaxial layer, annealing and temperature was studied. The collected charge in the CM regime was found to be proportional to the deposited charge, uniform over the diode area and stable over a period of several days. Randomly occurring micro-discharges at high voltages turned out to be the largest challenge for operation of the diodes in the CM regime. Although at high voltages an increase of the TCT baseline noise was observed, the signal-to-noise ratio was found to improve due to CM for laser light. Possible effects on the charge spectra measured with laser light due to statistical fluctuations in the CM process were not observed. In contrast, the relative width of the spectra increased in the case of α-particles, probably due to varying charge deposited in the CM region.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
For experiments at the European X-Ray Free-Electron Laser (XFEL) the Adaptive Gain Integrating Pixel Detector (AGIPD) is under development. The particular requirements include a high dynamic range of ...0, 1 to more than 10 super(4) photons of 12.4 keV per pixel within an XFEL pulse of less than 100 fs duration, and a radiation tolerance for doses up to 1 GGy for 3 years of operation. AGIPD is a hybrid-pixel detector system with a total of 1024 x 1024 pixels of size 200 mu m x 200 mu m. AGIPD will use 16 p super(+)n-silicon sensors of 500 mu m thickness. The nominal operating voltage is 500V, however, for special applications operation close to 1000V should be possible. Experimental data on the X-ray-dose dependence of the oxide-charge density and of the surface-current density have been implemented in the SYNOPSYS TCAD simulation program in order to optimize the design of the pixel and guard-ring layout. The methodology of the sensor design, the optimization of the most relevant parameters, and the optimized layout are described. Finally, the simulated performance, in particular the breakdown voltage, dark current and interpixel capacitance as function of the X-ray dose are presented.
Within the framework of the CALICE collaboration, our group has characterized Silicon Photomultipliers (SiPMs) from various producers, in order to enhance the single cell performances of a highly ...granular analog hadron calorimeter, with particular emphasis on improving the linearity of the response, ensuring environmental stability, calibration portability and reducing the parameters spread among the different channels. As an outcome, new plastic scintillator tiles coupled to KETEK PM1125 SMD SiPM have been commissioned, characterized and mounted on calorimeter modules: details and results of the characterization procedure, together with the performances of the new tile and SiPM design will be discussed. The radiation tolerance to X-rays of KETEK PM1125 is also under investigation. The amount and type of damage caused by irradiation of the devices exposed to 3 kGy and 20 MGy doses will be presented.
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