Conventional Readout Electronics Research Articles

Time-Variant Front-End Read-Out Electronics for High-Data-Rate Detectors

The foreseen incremental luminosity for near-future high-energy physics experiments demands evolution for the read-out electronics in terms of event data-rate. However, the filtering necessary to reject noise and meet the signal-to-noise-ratio requirements imposes a restriction on the operational speed of the conventional read-out electronics. The stringent trade-off between signal-to-noise-ratio and the event data-rate originates from the time-invariant behavior of the conventional systems. In this paper, the cases of time-variant systems are addressed, studying a benchmark with the RC-CR shaping function used in time-over-threshold methods. It was demonstrated that the time-variant systems enable a higher data-rate for the given noise performance. Moreover, taking advantage of time-variant systems, the proposed rising-edge method enables further data-rate enhancement with respect to the traditional time-over-threshold technique by reading the data from the rising edge of the analog output waveform. A comparison between the conventional time-invariant time-over-threshold technique, its time-variant equivalent and rising-edge method confirms the better performance of the latter one in terms of data-rate enhancement for a target noise performance. Moreover, design challenges for time-variant systems are briefly discussed, considering the ATLAS Monitored Drift Tube detector as a design case.

The prototype design of integrated base for PMT with pulse digitalization and readout electronics

High-speed pulse digitalization is critical for modern physics experiments with photomultiplier tubes (PMTs). This prototype design integrates the high-speed analogue to digital converter (ADC) for pulse digitalization, high voltage generator, high-speed buffer, synchronized clock, PoE (Power over Ethernet) power management and ZYNQ SoC (System on Chip) in a compact base which can be mounted with the PMT directly. There is only one category 5 Gigabit Ethernet cable needed for power, data and synchronized timing. This integrated design can be used to replace the conventional readout electronics system with PMTs which use the discrete or integrated pulse shaping circuit and FADC boards based on NIM or VME system. In the applications of several PMTs are used, or in the system where thousands of PMTs are deployed, this prototype design of integrated base for PMT has advantages to simplify the tremendous long distance analogue cables and high voltage cables. This paper presents the mechanical and hardware design, challenges and software design, the ENOB (effective number of bits) of ADC and the TCP data throughput of the Gigabit Ethernet will also be discussed. A scintillator neutron detector mounted with PMTs is connected to this prototype and spectrum analysis with the 137Cs γ source is performed to verify the system function; the preliminary results are also illustrated.

Novel Stable and Reliable Readout Electronics for HTS rf SQUID

Conventional readout electronics for radio-frequency SQUIDs exhibit long-term instabilities due to a temperature-dependent frequency drift of their voltage controlled oscillator. A novel electronics with a quartz-controlled synthesizer was developed to solve this problem. The frequency can be adjusted from 450 to 900 MHz with 2 ppm frequency stability, the amplitude range covers more than 60 dB. An adjustable phase shifter for demodulation is implemented to compensate for variable cable length. The total amplification is about 100 dB. The electronics with touchpanel and remote USB control is commercially available with up to three preamplifier units. Because thermal drift is eliminated, it is well suited for outdoor applications, e.g. in geophysics.

Superconducting single photon detectors integrated with single flux quantum readout circuits in a cryocooler

We report the operation of superconducting single photon detectors (SSPDs) with integrated readout electronics based on a single-flux-quantum (SFQ) circuit. The SSPDs were connected to a SFQ readout circuit without bias tee in a cryocooler system, and detection efficiencies (DEs) were measured to verify their correct operation. The DE curves matched well with those measured by conventional readout electronics, and the maximum bias current for normal operation was increased. In addition, we confirmed that the SFQ circuit correctly merged the input signals from two SSPDs. SSPDs with a SFQ readout circuit demonstrated a favorable timing jitter of 50 ps.

Highly integrated front-end electronics for spaceborne fluxgate sensors

Scientific instruments for challenging and cost-optimized space missions have to reduce their resource requirements while keeping the high performance levels of conventional instruments. In this context the development of an instrument front-end ASIC (0.35 µm CMOS from austriamicrosystems) for magnetic field sensors based on the fluxgate principle was undertaken. It is based on the combination of the conventional readout electronics of a fluxgate magnetometer with the control loop of a sigma-delta modulator for a direct digitization of the magnetic field. The analogue part is based on a modified 2–2 cascaded sigma-delta modulator. The digital part includes a primary (128 Hz output) and secondary decimation filter (2, 4, 8,…, 64 Hz output) as well as a serial synchronous interface. The chip area is 20 mm2 and the total power consumption is 60 mW. It has been demonstrated that the overall functionality and performance of the magnetometer front-end ASIC (MFA) is sufficient for scientific applications in space. Noise performance (SNR of 89 dB with a bandwidth of 30 Hz) and offset stability (< 5 pT °C−1 MFA temperature, < ±0.2 nT within 250 h) are very satisfying and the linear gain drift of 60 ppm °C−1 is acceptable. Only a cross-tone phenomenon must be avoided in future designs even though it is possible to mitigate the effect to a level that is tolerable. The MFA stays within its parameters up to 170 krad of total ionizing dose and it keeps full functionality up to more than 300 krad. The threshold for latch-ups is 14 MeV cm2 mg−1.

Non-constant bias current for dc SQUID operation

The in-phase current noise of the two junctions leads to additional 1/ f noise in dc SQUIDs, which is reduced by the well-known bias reversal technique (ac bias reversal). In this paper, a new idea for dc SQUID operation with ac bias reversal non-constant bias current is described. In most conventional readout electronics with constant dc bias, the dc SQUID is connected to the preamplifier by means of a transformer in order to enhance the SQUID voltage signal and thus reduce the preamplifier noise contribution. We analyse this case in ac bias condition and find that the current through the SQUID is not constant after the bias reversal. In order to solve this problem, we derived the differential equation governing the network and solved it for a constant current through the SQUID. The transient of the applied bias current is chosen to satisfy this differential equation. The time constant of the transient does not depend on the dynamic resistance of the SQUID. The bias reversal frequency could be increased without introducing additional noise to the SQUID.

Sensitivity enhancement of Quantum Design dc superconducting quantum interference devices in two-stage configuration

The energy sensitivity of a direct current (dc) superconducting quantum interference device (SQUID) can be improved if it is operated in a two-stage configuration. Employing this technique, a commercial dc SQUID system was modified and made competitive with other sensors especially designed for very low noise applications. We report the noise measurements performed in the temperature range 4.2 K–25 mK. At 4.2 K, the coupled energy sensitivity obtained with the two-stage dc SQUID was approximately ten times better than with a conventional readout electronics. The noise energy decreases linearly until approximately 300 mK, in good agreement with theoretical previsions. At lower temperature the hot-electron effect produces a saturation and the best energy sensitivity measured with open input coil is 35 ℏ.

A scanning SQUID microscope for samples at room temperature

We report on the development of a scanning SQUID microscope for measurements of samples at room temperature. A thin film niobium DC-SQUID is used with conventional read-out electronics. It is placed above the thin bottom window of a fiberglass cryostat, allowing us to realize a distance of about 75 /spl mu/m between SQUID and sample. The evaporation rate for the liquid helium was about 0.3 1/h. Because the effective SQUID area can easily be brought below 10 /spl mu/m/sup 2/, the obtainable spatial resolution of such a scanning SQUID microscope is limited mainly by the distance between SQUID and sample. The sample is moved under the cryostat with a computer controlled XY-stage. Provisions are made for quick sample changes which are important for the practical application of such a device.

Study of the first stage of PbSe growth on Se-terminated CaF2 surface

Heterostructures of IV–VI compounds, such as epitaxial films of PbSe grown on Si(111) via a CaF2 layer, have been the object of increasing scientific interest in the last few years because of their detection properties. A monolithic integration of the I-R detection functions is possible on an Si conventional read-out electronics. The high mismatch and the difference of the thermal expansion coefficients between Si and PbSe require the use of a buffer layer of CaF2. The CaF2/Si(111) interface has been widely studied but PbSe/CaF2 belongs to a group of interfaces which has been rarely studied. Annealing of the CaF2 surface under Se flux in the range 200–600°C shows the incorporation of Se into the CaF2 surface at a temperature higher than the growth temperature. The Se incorporation increases the stability of the CaF2 surface, avoids its oxidation and creates nucleation sites for PbSe. The optimization of the subsequent buffer layer is a key problem in the growth process. On a Se-terminated CaF2 surface, the first stage of the PbSe nucleation has been studied by AES, RHEED, XPS and AFM.

Conventional readout electronics for superheated superconducting grains — First experimental results

Complete analysis of the electronics for a superheated superconducting grains detector is presented. The designed electronics readout is presented as a good tool to understand grains transiting signals. First experimental results for very small grains, less than 8 μm size, and transiting time evaluation are presented.