Filter cs: Case-Study

Case-Study Case-Study, Coincidence, Trigger, SiPM Case-Study Coincidence Trigger SiPM

Coincidence Trigger

A discrete trigger circuit is a fundamental part of a large detector system used to reduce the readout data rate. The following trigger is based on scintillator bars coupled with SiPM detectors.

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Case-Study Case-Study, Neutron Detector, Large Experiment, ESS Multi Channels Large Experiments R5560 Loki ESS

ESS LoKI SANS: Sci-Compiler for Large Experiments in neutron science

Introduction Loki Experiment is a new instrument at the European Spallation Source (ESS) in Lund, Sweden. It is a high-performance Small Angle Neutron Scattering (SANS) instrument that will provide a unique capability for the study of complex materials and biological systems.

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Case-Study Case-Study, Neutron Detector, Large Experiment, ESS Case-Study Loki ESS Neutron SANS

LOKI Broadband SANS Instrument at ESS

Small angle neutron scattering (SANS) is a technique that is applied across a spectrum of scientific disciplines, with users from chemistry, physics, biology, materials science, engineering and geoscience.

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Case-Study Case-Study, Position Sensitive, Detector, Scintillator, SiPM Case-Study Position Sensitive Detector Scintillator SiPM

Position Sensitive Scintillation Detector

A very simple and inexpensive way to make an incident radiation 2D profile (like a beam profile) is to use a grid of scintillator.

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Case-Study Case-Study, RF, DSP, Signal Processing Case-Study RF DDC NCO CIC CORDIC DSP

Digital Down-Conversion: bringing a carrier to baseband without analog mixers

A large family of measurements does not deliver its information at DC. It arrives riding on a carrier: the free induction decay of an NMR or EPR experiment, the response of a resonant sensor driven at its resonance, the return of a swept optical or acoustic interrogator, the output of an RF front end.

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Case-Study Case-Study, RF, DSP, Signal Processing Case-Study Lock-In RF NCO CORDIC Modulation Low Noise

A lock-in amplifier that lives entirely in the FPGA

A lock-in amplifier is the standard answer to one specific problem: you have a signal you can modulate, and it is far smaller than the noise sitting on top of it.

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Case-Study Case-Study, RF, DSP, Signal Processing Case-Study Goertzel Impedance Spectroscopy RF DSP Resources

Watching a handful of frequencies without paying for an FFT

Electrochemical impedance spectroscopy measures a cell at a dozen or so discrete frequencies. A resonant sensor is interrogated at its resonance and at two points on the skirt.

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Case-Study Case-Study, DSP, Signal Processing, Trigger Case-Study Matched Filter FFT Fast Convolution Trigger SNR

A matched filter at full sampling rate, using fast convolution

If you know the shape of the pulse you are looking for, the filter that maximises the signal-to-noise ratio at the moment of detection is the matched filter: correlate the incoming stream with a time-reversed copy of that shape.

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Case-Study Case-Study, DSP, Signal Processing, Monitoring Case-Study FFT Windowing Spectrum Microphonics Monitoring

Continuous spectral monitoring: finding a line that should not be there

Some of the most useful measurements an instrument makes are not of the thing it was built to measure. A cryostat develops microphonics from a pump that was fine last month.

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Case-Study Case-Study, PSD, Detector, Signal Processing Case-Study Psd Neutron Gamma Scintillator Skewness Kurtosis Statistics

Pulse-shape discrimination from statistical moments, without per-channel calibration

In an organic scintillator, a neutron and a gamma of the same deposited energy produce pulses of the same height. What differs is the shape: the neutron recoil populates triplet states that decay slowly, so its pulse carries a delayed tail the gamma does not have.

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Case-Study Case-Study, Detector, Spectroscopy, Monitoring Case-Study Histogram SiPM Gain Stabilization Spectroscopy Statistics

Closing the gain-stabilisation loop inside the FPGA

A silicon photomultiplier changes its gain by roughly one percent per degree. A photomultiplier tube drifts with supply, with count rate and with its own history.

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Case-Study Case-Study, Multi Channels, Detector, Monitoring Case-Study TM Time Multiplexing Array Detector Diagnostics Statistics

Per-channel health monitoring on an array, out of a single engine

A 16-channel SiPM array, a multi-anode PMT, a strip detector, a segmented drift chamber. They all share a problem that a single-channel instrument does not have: at any moment, some channel is probably misbehaving, and nobody knows which.

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Case-Study Case-Study, Signal Generation, Testing, Detector Case-Study Signal Generation Poisson Spectrum Testing CI Validation

A detector emulator in the FPGA: validating a DAQ chain with no source in the room

Testing a spectroscopy chain properly requires a detector, a source, a licence to hold the source, a room to hold it in, and hours of acquisition to get the statistics.

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Case-Study Case-Study, Signal Generation, Timing, Detector Case-Study Sequencer Pattern Generator ASIC Calibration Timing

Deterministic timing sequences for calibration and ASIC slow control

Most detector systems need a set of digital signals to happen in a precise order, over and over. Configure an ASIC by clocking a shift register with the right chip-select framing.

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Case-Study Case-Study, DSP, Signal Processing, Detector Case-Study Averaging Pump-Probe LIDAR ToF Template SNR

Coherent averaging for repetitive signals, with pile-up thrown away

Whenever a measurement can be repeated on demand, averaging is the cheapest signal-to-noise ratio available. Pump-probe spectroscopy, time-of-flight measurement, LIDAR return profiling, ultrasound, laser-induced breakdown, and the routine business of extracting a detector’s pulse shape all share the same structure: fire something, capture the response, do it again.

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Case-Study Case-Study, Integration, Design Flow Case-Study VHDL Custom HDL GHDL Integration Legacy

Bringing an existing VHDL code base into a graphical design

Most groups that would benefit from a graphical FPGA design tool already have VHDL. Often quite a lot of it: a detector interface written for a previous experiment, a serial protocol nobody wants to re-derive, a filter that took two people three months to get right, an algorithm that is the group’s actual intellectual contribution.

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Case-Study Case-Study, Signal Generation, Testing, DSP Case-Study Noise Pink Noise PRNG Testing Signal Generation Dither

Noise you can specify: choosing the right disturbance for a test

“Add some noise and see if it still works” is one of the most common things said about a signal-processing design, and one of the least precise.

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Case-Study Case-Study, Signal Generation, Testing, Design Flow Case-Study Sequencer Pattern Generator Emulation Test Bench Protocol

Playing the part of hardware you do not have yet

Firmware development almost never starts with all the hardware on the desk. The ADC daughterboard is six weeks out. The ASIC is in fabrication.

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Case-Study Case-Study, Multi Channels, Design Flow, Detector Case-Study Multichannel Sub-Design Hierarchical Design ARRAY COMMON

Drawing the channel once: multichannel sub-designs

Almost every real experiment has more than one channel, and in almost every one of them the channels do the same thing.

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Case-Study Case-Study, Multi Channels, Design Flow, DSP Case-Study TM Time Multiplexing X2730 500 MS/S Concepts

Time multiplexing: what a TM signal is and what a lane means

Every block in the Sci-Compiler library now exists in two versions, and the second one is marked TM. Understanding what that means takes about ten minutes and saves a great deal of confusion, because TM is one mechanism that solves two quite different problems, and the mechanism cannot tell you which of the two you are using it for.

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