In this work we present an innovative all integrated solution, which incorporates on the same chi... more In this work we present an innovative all integrated solution, which incorporates on the same chip both a low-noise low-power charge-sensitive preamplifier and an integrated range booster with second-order effect compensation. The booster is based on a particular Time-to-Amplitude Converter which generates analog signals whose amplitude is directly proportional to the energy of the events that caused saturation (ions, energetic charged particles). In this way a dynamic range from a few keV to more than 800 MeV is obtained.
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2015
The latest experimental results of the multichannel CSP ASIC for TRACE detector are shown. The de... more The latest experimental results of the multichannel CSP ASIC for TRACE detector are shown. The device, submitted to the foundry in the middle of 2014 and received at the end of the same year has been installed on a dedicated pcb and tested using a pulser. The device features four channels specifically designed for hole signals and one channel for electron signals. The power consumption is around 10 mW per channel as required by the specifications of TRACE. The main design goals are low noise and fast rise time. With proper shaping of the signals this device is capable of producing energy spectra with resolution of approximatively 1keV. The rise time of the leading edge of the signals is fast enough to perform pulse-shape analysis of the waveforms. The key feature of this device is the possibility to switch some internal components as desired through an I 2 C bus. In this way some critical parameters, such as bandwidth and gain of the preamplifier, can be adjusted and optimized according to experimental needs.
2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2014
A study of the impedance and noise of an integrated poly-silicon resistor with distributed capaci... more A study of the impedance and noise of an integrated poly-silicon resistor with distributed capacitive coupling to bulk is presented. The system is analyzed by using a closed-form calculus which produces non approximated results. In particular, deviations from ideal conditions are shown when that kind of resistor is used as a continuous-discharge feedback device for charge-sensitive preamplifiers. The effect of using a feedback resistor with capacitive coupling to bulk is an evident deformation of the shape of the signals. An innovative technique is presented, which allows overcoming the problem of the distortions in the CSP output signals. Several n-wells are placed under the resistor and driven with an auxiliary low-impedance divider which minimizes the voltage variations on the plates of the parasitic capacitors. In this way the pulses provided by the charge-sensitive preamplifiers show again a clean R-C exponential-decay shape and are so optimized for signal shaping and adequate for high-resolution spectroscopy.
2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2014
A low-noise wide-bandwidth charge-sensitive micro-probe is being developed, able to capture the c... more A low-noise wide-bandwidth charge-sensitive micro-probe is being developed, able to capture the charge signals of semiconductor detectors. The micro-probe works on a single terminated coaxial cable of whatever length, whose quality is crucial to achieving a good dynamic performance. The cable carries both the power supply (DC signal component) and the event pulses (AC signal component). No power-supply filtering capacitor is required. The micro-probe is particularly compact, consisting of a few devices, including a GΩ surface-mount resistor. Both a discrete-component and an ASIC version are under development. The ASIC version is designed in a 0.35 um 5V CMOS technology and is expected to be fully functional also at cryogenic temperatures. The area occupancy is 0.14 mm 2 bonding pads included. Thanks to such a large degree of integration the micro-probe can be placed very close to the detector electrode and is particularly light, compact and hence suited for hostile environments and for applications where a high radio-purity of the front-end is required, like in rare-decay research in underground laboratories. The rise time of the integrated version, as obtained from experimental results, is with a detector capacitance of 16pF. The energy range is beyond 20 MeV, and the power consumption is ~35 mW per channel. The gain stage includes an innovative low-frequency filtering device to provide a bias point to the system even if there are no constant voltage references such as conventional power rails. To achieve this result, CMOS transistors in underthreshold condition are used in combination with adequate capacitors in order to stabilize the source-to-gate voltage of the current generators. The first chip with various micro-probe versions is being tested.
2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012
A low-noise wide-bandwidth charge-sensitive micro-probe is being developed, able to capture the c... more A low-noise wide-bandwidth charge-sensitive micro-probe is being developed, able to capture the charge signals of semiconductor detectors. The micro-probe works on a single terminated coaxial cable of whatever length, whose quality is crucial to achieving a good dynamic performance. The cable carries both the power supply (DC signal component) and the event pulses (AC signal component). No power-supply filtering capacitor is required. The micro-probe is particularly compact, consisting of a few devices, including a GΩ surface-mount resistor. Both a discrete-component and an ASIC version are under development. The ASIC version is designed in a 0.35 um 5V CMOS technology and is expected to be fully functional also at cryogenic temperatures. The area occupancy is 0.14 mm 2 bonding pads included. Thanks to such a large degree of integration the micro-probe can be placed very close to the detector electrode and is particularly light, compact and hence suited for hostile environments and for applications where a high radio-purity of the front-end is required, like in rare-decay research in underground laboratories. The rise time of the integrated version, as obtained from experimental results, is with a detector capacitance of 16pF. The energy range is beyond 20 MeV, and the power consumption is ~35 mW per channel. The gain stage includes an innovative low-frequency filtering device to provide a bias point to the system even if there are no constant voltage references such as conventional power rails. To achieve this result, CMOS transistors in underthreshold condition are used in combination with adequate capacitors in order to stabilize the source-to-gate voltage of the current generators. The first chip with various micro-probe versions is being tested.
Equivalent Noise Charge Contribution of the √f Parallel Noise in Nuclear Spectroscopic Measurements Using Different Shaping Amplifiers
IEEE Transactions on Nuclear Science
Development of Γ-ray tracking detectors
The next generation of 4π arrays for high-precision γ-ray spectroscopy AGATA will consist of γ-ra... more The next generation of 4π arrays for high-precision γ-ray spectroscopy AGATA will consist of γ-ray tracking detectors. They represent high-fold segmented Ge detectors and a front-end electronics, based on digital signal processing techniques, which allows to extract energy, timing and spatial information on the interactions of a γ-ray in the Ge detector by pulse shape analysis of its signals. Utilizing the information on the positions of the interaction points and the energies released at each point the tracks of the γ-rays in a Ge shell can be reconstructed in three dimensions on the basis of the Compton-scattering formula
2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2012
A low-noise ASIC preamplifier for semiconductor detectors has been built and characterized, which... more A low-noise ASIC preamplifier for semiconductor detectors has been built and characterized, which is able to provide a linear spectroscopic measurement of the detector charge signals even when its output voltage is saturated. The preamplifier works in a conventional mode, i.e. as an active current integrator, when the output signal is below a preset threshold. If the signal is larger the preamplifier operates in a non-standard controlled fast-reset mode, which is effective in providing a linear measurement of the detector signal charge even when the preamplifier works close to or in saturation. The experimental relation between the measurement and the input charge keeps perfectly linear irrespective of the non-linearity of the preamplifier working regime, which yields a dynamic-range boost of more than one order of magnitude.
In a high-resolution spectroscopy system the relatively long exponential decay due to the charge ... more In a high-resolution spectroscopy system the relatively long exponential decay due to the charge preamplifier is customarily canceled in an analogue fashion by means of a PZ (Pole-Zero) stage. The accurateness of such a compensation has a big impact on the energy resolution because it strongly affects the baseline-stability problems. We have automatically and on-line performed such a compensation in a digital way, while maintaining a spectroscopy performance and keeping at minimum both the ADC sampling frequency (thus power consumption) and its resolution (thus cost). This is done through an IIR filter, implemented within a FPGA by a DSP. The so-compensated waveform has, in excellent approximation, an all-pole shape. Starting from such a signal, the minimum-noise filters for energy and/or time measurements are then promptly synthesized and implemented for real time operation through the same DSP.
Classical novae are thermonuclear explosions in stellar binary systems, and important sources of ... more Classical novae are thermonuclear explosions in stellar binary systems, and important sources of 26 Al and 22 Na 1-3. While γ rays from
HEMT input charge preamplifier for nanoseconds processing time applications
NASA STI/Recon Technical Report N, Nov 1, 1993
First experimental characterization of ROTOR: the new switched-current VLSI amplifier for X-ray spectroscopy with silicon drift detectors
IEEE Transactions on Nuclear Science, 2000
ABSTRACT
An Innovative Analog Circuit to Retrieve Energy Information From Signals of Deeply Saturated Preamplifiers Connected to Semiconductor Detectors
IEEE Transactions on Nuclear Science
Recent Developments and Perspectives in Nuclear Structure by γ and Particle Spectroscopy
Toward a Science Campus in Milan, 2018
Advances in nuclear structures studies of neutron-rich systems are presented, focusing on experim... more Advances in nuclear structures studies of neutron-rich systems are presented, focusing on experimental activities based on γ and particle spectroscopy—ideal probes of the multifaceted nature of the atomic nucleus. Emphasis is given to recent highlights obtained in world’s leading laboratories, in Europe and Japan, by large international collaborations in which the Nuclear Physics group of Milano University has played a key role. In particular, experiments are described taking advantage of both stable and radioactive ion beams, as well as intense neutron beams. They require the use of the most advanced detection setups, such as the European array AGATA, based on γ-ray tracking techniques, and also arrays of large size scintillators. Measurements of cross sections of thermonuclear fusion reactions at astrophysically relevant energies, performed by the LUNA collaboration, are also briefly discussed. Finally, research and developments of detectors based on novel scintillators materials are presented, being a significant part of the activity carried out at the Milano Physics Department.
Status of the new AGATA digitizer
Technical details in white paper "DIGI-OPT12: 12-channel 14/16-bit 100/125-MS/s Digitizer wi... more Technical details in white paper "DIGI-OPT12: 12-channel 14/16-bit 100/125-MS/s Digitizer with Optical Output for AGATA/GALILEO", available on request
2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2014
We developed an open-source dia Graphical User Interface for the new "Digi-O 14-bit 100MS/s digit... more We developed an open-source dia Graphical User Interface for the new "Digi-O 14-bit 100MS/s digitizer cards of detectors AG and EUCLIDES. It allows on-the-fly check of c firmware uploading and inspection of all digiti diagnostic tool comprises a simple Arduino-Uno and software scripts developed in the open so environments "Scilab", "Arduino IDE" and " The GUI allows easy writing and reading parameters as well as reading 8 ksamples of dig each digitizer channel. The digitized waveforms statistical data can then be saved in the PC har analysis.
The transitional nuclei 132 Xe and 133 Xe are investigated after multinucleon-transfer (MNT) and ... more The transitional nuclei 132 Xe and 133 Xe are investigated after multinucleon-transfer (MNT) and fusionevaporation reactions. Both nuclei are populated in (i) 136 Xe+ 208 Pb MNT reactions employing the highresolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (ii) in the 136 Xe+ 198 Pt MNT reaction employing the GAMMASPHERE spectrometer in combination with the gas-detector array CHICO, and (iii) as an evaporation residue after a 130 Te(α,xn) 134−xn Xe fusion-evaporation reaction employing the HORUS γ-ray array at the University of Cologne. The high-spin level schemes are considerably extended above the J π = (7 −) and (10 +) isomers in 132 Xe and above the 11/2 − isomer in 133 Xe. The results are compared to the high-spin systematics of the Z = 54 as well as the N = 78 and N = 79 chains. Furthermore, evidence is found for a long-lived (T 1/2 1 µs) isomer in 133 Xe which closes a gap along the N = 79 isotones. Shell-model calculations employing the SN100PN and PQM130 effective interactions reproduce the experimental findings and provide guidance to the interpretation of the observed high-spin features.
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Papers by Alberto Pullia