Charge Readout Research Articles

Time Projection Chambers instrumented with resistive MicroMegas for the SAND near detector of DUNE

The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino accelerator experiment aiming for precise measurements of the neutrino oscillation parameters. DUNE will include a near detector complex regrouping three different detectors among which SAND (System for on-Axis Neutrino Detection) that will be the only one permanently on the neutrino beam axis in charge of monitoring in detail the emitted neutrino beam and its stability through time, a crucial characteristic to realize accurate oscillation measurements at the percent level. SAND will reuse the superconducting magnet and the electromagnetic calorimeter of the KLOE experiment. We will describe in the following the proposal of using, as inner tracker of SAND, a large 3D matrix of 1.5cm side scintillator cubes (3DST) surrounded by 3 gaseous Time Projection Chambers. This setup allows to realize accurate beam monitoring combining the 3DST unprecedented capability of neutron detection and energy measurement with the high precision momentum resolution for charged particles offered by the TPCs. The proposed TPC design allows to reach spatial resolutions of a few hundreds of micrometers using 1 cm pads by deploying the resistive MicroMegas technology for the charge readout.

Noise-robust classification of single-shot electron spin readouts using a deep neural network

Single-shot readout of charge and spin states by charge sensors such as quantum point contacts and quantum dots are essential technologies for the operation of semiconductor spin qubits. The fidelity of the single-shot readout depends both on experimental conditions such as signal-to-noise ratio, system temperature, and numerical parameters such as threshold values. Accurate charge sensing schemes that are robust under noisy environments are indispensable for developing a scalable fault-tolerant quantum computation architecture. In this study, we present a novel single-shot readout classification method that is robust to noises using a deep neural network (DNN). Importantly, the DNN classifier is automatically configured for spin-up and spin-down traces in any noise environment by tuning the trainable parameters using the datasets of charge transition signals experimentally obtained at a charging line. Moreover, we verify that our DNN classification is robust under noisy environment in comparison to the two conventional classification methods used for charge and spin state measurements in various quantum dot experiments.

Performance of a visible light photon counting imaging detector for weak light intensities

In this study, a visible light photon-counting imaging detector was developed for weak light intensities, such as biofluorescence and photon-counting 3D imaging radars. The proposed visible light photon-counting imaging detector was based on a semitransparent S25 photocathode able of responding to visible light or even near-infrared wavelengths. The detector adopted image charge readout mode through high-resistance Ge layer receiver of electron cloud from the microchannel plate. The performance of the as-obtained visible light photon-counting imaging detector was tested in existing readout electronics and newly designed position-sensitive anodes. The quantum efficiency of the as-prepared detector reached 13.4% (@532 nm) with spatial resolution better than 100 μm. Preliminary imaging results of real objects with commercial lens and detector were also obtained and applied to ultra-weak light detection. In sum, these results look promising for future applications in photon-counting radars and biofluorescence imaging.

A serial-timing multi-channel CMOS charge readout ASIC for X-ray detectors

A serial-timing multi-channel CMOS charge readout ASIC for X-ray detectors

A Highly Linear FPGA-Based TDC and a Low-Power Multichannel Readout ASIC With a Shared SAR ADC for SiPM Detectors

This article presents a low-power highly linear multichannel data acquisition (DAQ) system for silicon photomultiplier (SiPM) readout. A low-input impedance current-mode front-end with a programmable current gain is developed to achieve high-precision charge readout over a large dynamic range. An integrated 10-bit successive-approximation-register (SAR) analog-to-digital converter (ADC) shared by 16 readout channels in a time-multiplexed manner is designed to reduce the overall chip area and power consumption of the SiPM readout. Implementation challenges of field-programmable gate array (FPGA)-based time-to-digital converters (TDCs) including bubble error, zero length bins, interclock region nonlinearity, and chain overflow, are addressed for high accuracy timing measurement. Multichain averaging is developed to improve the TDC linearity. Fabricated in a 180-nm CMOS process, the current-mode 16-channel readout application-specific integrated circuit (ASIC) achieves 3.6% maximum gain nonlinearity over an input dynamic range of 800 pC with dissipating 3.89 mW of power per readout channel, and the ADC achieves an SFDR of 58.34 dB and an SNDR of 51.37 dB at 16 MS/s. Implemented in a Xilinx 28-nm Kintex-7 FPGA, the 32-channel TDC achieves a 15-ps root mean square (RMS) resolution, a differential nonlinearity (DNL) of less than 4 ps, and an integral nonlinearity (INL) of less than 10 ps.

Radio-Frequency Reflectometry in Silicon-Based Quantum Dots

Radio-frequency (rf) reflectometry offers a fast and sensitive method for charge sensing and spin readout in gated quantum dots. We focus in this work on the implementation of rf readout in accumulation-mode gate-defined quantum dots, where the large parasitic capacitance poses a challenge. We describe and test two methods for mitigating the effect of the parasitic capacitance, one by on-chip modifications and a second by off-chip changes. We demonstrate that on-chip modifications enable high-performance charge readout in $\mathrm{Si}$/${\mathrm{Si}}_{x}$${\mathrm{Ge}}_{1\ensuremath{-}x}$ quantum dots, achieving a fidelity of 99.9% for a measurement time of $1\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{s}$.

Characterization with X-rays of a Large-Area GEMPix Detector with Optical Readout for QA in Hadron Therapy

Quality Assurance (QA) in hadron therapy is crucial to ensure safe and accurate dose delivery to patients. This can be achieved with fast, reliable and high-resolution detectors. In this paper, we present a novel solution that combines a triple Gas Electron Multiplier (GEM) and a highly pixelated readout based on a matrix of organic photodiodes fabricated on top of an oxide-based thin-film transistor backplane. The first LaGEMPix prototype with an active area of 60 × 80 mm2 was developed and characterized using low energy X-rays. The detector comprises a drift gap of 3.5 mm, a triple-GEM stack for electron amplification, and a readout featuring 480 × 640 pixels at a 126 µm pitch. Here, we describe the measurements and results in terms of spatial resolution for various experimental configurations. A comparison with GAFCHROMIC® films and the GEMPix detector used in the charge readout mode was performed to better understand the contribution to the spatial resolution from both the electron diffusion and the isotropic emission of photons. The measurements were compared to Monte Carlo simulations, using the FLUKA code. The simulation predictions are in good agreement with the GEMPix results. Future plans with respect to applications in hadron therapy are discussed.

Commissioning of a High Pressure Time Projection Chamber with Optical Readout

The measurements of proton–nucleus scattering and high resolution neutrino–nucleus interaction imaging are key in reducing neutrino oscillation systematic uncertainties in future experiments. A High Pressure Time Projection Chamber (HPTPC) prototype has been constructed and operated at the Royal Holloway University of London and CERN as a first step in the development of a HPTPC that is capable of performing these measurements as part of a future long-baseline neutrino oscillation experiment, such as the Deep Underground Neutrino Experiment. In this paper, we describe the design and operation of the prototype HPTPC with an argon based gas mixture. We report on the successful hybrid charge and optical readout using four CCD cameras of signals from 241Am sources.

A High-Sensitivity Charge Sensor for Silicon Qubits above 1 K.

Recent studies of silicon spin qubits at temperatures above 1 K are encouraging demonstrations that the cooling requirements for solid-state quantum computing can be considerably relaxed. However, qubit readout mechanisms that rely on charge sensing with a single-island single-electron transistor (SISET) quickly lose sensitivity due to thermal broadening of the electron distribution in the reservoirs. Here we exploit the tunneling between two quantized states in a double-island single-electron transistor (SET) to demonstrate a charge sensor with an improvement in the signal-to-noise ratio by an order of magnitude compared to a standard SISET, and a single-shot charge readout fidelity above 99% up to 8 K at a bandwidth greater than 100 kHz. These improvements are consistent with our theoretical modeling of the temperature-dependent current transport for both types of SETs. With minor additional hardware overhead, these sensors can be integrated into existing qubit architectures for a high-fidelity charge readout at few-kelvin temperatures.

RF reflectometry for readout of charge transition in a physically defined p-channel MOS silicon quantum dot

We have embedded a physically defined p-channel MOS silicon quantum dot (QD) device into an impedance transformer RC circuit. To decrease the parasitic capacitance of the device which emerges in MOS devices that have a top gate, we fabricate a new device to reduce the device’s top gate area from 400 to 0.09 μm2. Having a smaller top gate eliminates parasitic capacitance problem preventing the RF signal from reaching QD. We show that we have fabricated a single QD properly, which is essential for RF single-electron transistor technique. We also analyze and improve the impedance matching condition and show that it is possible to perform readout of charge transition at 4.2 K by RF reflectometry. This will enable fast readout of charge and spin states.

Characterisation and suitability of a CdTe detector for strontium 90 assay in groundwater

This paper presents a design of an in-situ detector for monitoring strontium 90 activity in groundwater at nuclear decommissioning sites. Current techniques for monitoring strontium 90 activity are lab-based and are time consuming, expensive and produce secondary waste. To alleviate these problems, a proof-of-concept detector has been developed which will be deployed in-situ, directly into groundwater boreholes. A compact detector was designed, housed in a waterproof casing and its initial performance as a strontium 90 detector in water was examined. A 10 x 10 x 1 mm cadmium telluride detector was paired with a appropriate charge sensitive amplifiers and readout systems to make a 118 x 83 x 40 mm sensor which was submersed in water. A 35.79 MBq collimated strontium 90 source was used to determine that the sensor was capable of counting beta particles from a range of 49.50 mm in water. The detector was held at a reverse bias of 80 V for 290 min, the average counts observed in 5 min intervals went from 1.32×106±1.14×103 to 1.28×106±1.13×103. However, the results presented have established a viable proof-of-concept for an in-situ detector for strontium 90 assay in groundwater.

Study on low noise cryogenic charge readout electronics for liquid xenon time projection chamber

Study on low noise cryogenic charge readout electronics for liquid xenon time projection chamber

Development of Ion Detector Based on Low-Pressure Time Projection Chamber for Accelerator Mass Spectrometry

A new ion identification method for accelerator mass spectrometry on the basis of measuring ion track ranges is proposed. A low pressure time projection chamber (TPC) with charge readout by means of a thick gas electron multiplier (THGEM) was developed for testing this method. Tracks of alpha particles from various radioactive sources were successfully recorded by this TPC. In particular, their track ranges were measured to a high precision of about 2 $$\%$$ . A simulation was performed, and it was shown that track range measurements would permit efficiently separating isobaric boron and beryllium ions (at a level of ten standard deviations). It is expected that this method will be used in the accelerator mass spectrometry facility in Novosibirsk for dating geological objects—in particular, for the geochronology of Cenozoic era.

Charge Noise and Overdrive Errors in Dispersive Readout of Charge, Spin, and Majorana Qubits

Solid-state qubits incorporating quantum dots can be read out by gate reflectometry. Here, we theoretically describe physical mechanisms that render such reflectometry-based readout schemes imperfect. We discuss charge qubits, singlet-triplet spin qubits, and Majorana qubits. In our model, we account for readout errors due to slow charge noise, and due to overdriving, when a too strong probe is causing errors. A key result is that for charge and spin qubits, the readout fidelity saturates at large probe strengths, whereas for Majorana qubits, there is an optimal probe strength which provides a maximized readout fidelity. We also point out the existence of severe readout errors appearing in a resonance-like fashion as the pulse strength is increased, and show that these errors are related to probe-induced multi-photon transitions. Besides providing practical guidelines toward optimized readout, our study might also inspire ways to use gate reflectometry for device characterization.

A distributed readout network ASIC for high-density electrode array targeting at neutrinoless double-beta decay search in a Time Projection Chamber

We present a distributed, self-organizing and fault-tolerant readout network Application Specific Integrated Circuit (ASIC) for the high-density electrode array targeting at neutrinoless double-beta decay search in Time Projection Chamber (TPC). A meter-sized plane tiled by approximately 1×105 single-electrode Topmetal-S sensors with a pitch of 5∼10 mm is utilized to realize charge readout plane in a ton-scale high-pressure gaseous TPC. A sensor network is proposed under the premise of ensuring the tightness and radioactive purity of the high-pressure TPC. As a node of the network, each sensor not only generates and transmits its own data but also forwards the data from its adjacent sensors. Therefore, a Readout and Data-Routing Circuit (RDRC) is integrated into each sensor. To realize the RDRC, a distributed readout network ASIC is fabricated in a 130 nm CMOS Technology. A routing algorithm called Fault-Tolerance XY (FT-XY) is implemented to avoid the faulty sensors from disabling large sections of the network. A single ASIC and a 3 × 3 network have been tested. The test results show that the throughput of the 3 × 3 network reaches 110.52 Mbit/s.

Demonstration of ThGEM-multiwire hybrid charge readout for directional dark matter searches

Sensitivities of current directional dark matter search detectors using gas time projection chambers are now constrained by target mass. A ton-scale gas TPC detector will require large charge readout areas. We present a first demonstration of a novel ThGEM-Multiwire hybrid charge readout technology which combines the robust nature and high gas gain of Thick Gaseous Electron Multipliers with lower capacitive noise of a one-plane multiwire charge readout in SF6 target gas. Measurements performed with this hybrid detector show an ion drift velocity of 138±10 ms−1 in a reduced drift field E/N of 93 ×10−17 Vcm2 with an effective gas gain of 2470±160 in 20 Torr of pure SF6 target gas.

On proportional scintillation in very large liquid xenon detectors

The charge readout of a liquid xenon (LXe) detector via proportional scintillation in the liquid phase was first realized by the Waseda group 40 years ago, but the technical challenges involved were overwhelming. Although the tests were successful, this method was finally discarded and eventually nearly forgotten. Currently, this approach is not considered for large LXe dark matter detectors. Instead, the dual-phase technology was selected despite many limitations and challenges. In two independent studies, two groups from Columbia University and Shanghai Jiao Tong University reevaluated proportional scintillation in the liquid phase. Both studies established the merits for very large LXe detectors, but the Columbia group also encountered apparent limitations, namely the shadowing of the light by the anode wires, and a dependence of the pulse shape on the drift path of the electrons in the anode region. The differences between the two studies, however, are not intrinsic to the technique, but a direct consequence of the chosen geometry. Taking the geometrical differences into account, the results match without ambiguity. They also agree with the original results from the Waseda group.

Charge Detection in an Array of CMOS Quantum Dots

The recent development of arrays of quantum dots in semiconductor nanostructures highlights the progress of quantum devices toward large scale. However, how to realize such arrays on a scalable platform such as silicon is still an open question. One of the main challenge resides in the detection of charges within the array. It is a prerequisite functionality to initialize a desired charge state and readout spins through spin-to-charge conversion mechanisms. In this paper, we use two methods based on either a single-lead charge detector, or a reprogrammable single electron transistor. Thanks to these methods, we study the charge dynamics and sensitivity by performing single shot detection of the charge. Finally, we can probe the charge stability at any node of a linear array and assess the Coulomb disorder in the structure. We find an electrochemical potential fluctuation induced by charge noise comparable to that reported in other silicon quantum dots.

Investigation and improvements of the mechanical structure of cylindrical GEMs for the BESIII experiment

Gas Electron Multipliers (GEMs) can be produced in large foils and molded in different shapes. The possibility to create cylindrical layers has opened the opportunity to use such detector as internal tracker at collider experiments. One crucial item is to have low material budget in the active area, so the supporting structure of anode and cathode must be light. KLOE2 collaboration has built the first Cylindrical GEM detector with honeycomb material with carbon fiber skins produced at high temperature. BESIII is developing an innovative CGEM detector with charge and time readout. Among several innovative features, the mechanical structure was designed to be a sandwich of Rohacell and Kapton, a PMI foam. After the transportation of a first production of the detectors from the construction site in Italy to the Institute of High Energy Physics in Beijing, some malfunctions have been observed in some of them, compatible with GEMs deformation inside the detector. We have performed a detailed study by means of an industrial CT scan available in IHEP laboratory and autopsy to the damaged detectors. In this talk, we will review the construction process, the shipment, the findings of the investigation. A new supporting structure of carbon fiber and honeycomb, assembled at room temperature, has been designed and developed. The thickness of the carbon fiber is small enough to keep the material budget of a single detector layer below 0.5% of a radiation length, while the mechanical robustness results beyond the purpose of a detector for HEP. A first detector with such a mechanical structure has been built and shipped to IHEP, preliminary results from operation (e.g. current stability, discharges, temperature and humidity correlation) of the detectors are also presented in this paper.

Ion detector for Accelerator Mass Spectrometry based on low-pressure TPC with THGEM readout

A new technique for ion identification in Accelerator Mass Spectrometry (AMS) has been proposed by measuring the ion track ranges using a low-pressure TPC. As a proof of principle, a low-pressure TPC with charge readout using a THGEM multiplier was developed. The tracks of alpha particles from various radioactive sources were successfully recorded in the TPC. The track ranges were measured with a high accuracy, reaching the 2% resolution level. Using these results and the SRIM code simulation, it is shown that the isobaric boron and beryllium ions can be effectively separated at ten sigma level. It is expected that this technique will be applied in the AMS facility in Novosibirsk for dating geological objects, in particular for the geochronology of Cenozoic Era.