IEEE NSS MIC RTSD 2023 Conference.

A new detector to muon tomography for glaciers melting monitoring

We present a design project for a muon tomography detector aiming to the monitoring of glacier thickness. The glacier melting process is not completely understood and is considered a hot topic in lieu of the global warming. Muon Tomography is a widely used technique, employed to perform imaging of the inner structure of large objects, as volcanoes, container, and pyramids. This technique takes advantages of the muon flux reaching Earth surface (»70 m-2 s-1 sr-1), produced by the interaction between the primary Cosmic Rays and the atmosphere. The difference between the measured muon flux, with and without a certain object in the field of view, allows to infer the thickness of material (in equivalent water meter) that the muons cross. In case of glaciers, thanks to the different density of ice and rock, a directional flux measurement provides information on both the glacier thickness and the bedrock-ice interface depth.

The goal of our project is the development of a detector able to measure the glacier thickness with short exposure time, and with a real time data taking and processing, in order to perform studies of the seasonal behavior, and the glacier melting trend through the years. The detector will also be operable in open-sky and be replicable. To fulfill all these requirements, the foreseen design of the detector is made by 5 sensitive modules, each of that composed by two layers of bundles of scintillating fibers running along orthogonal directions with respect to each other to reconstruct the three spatial coordinates. Scintillation light produced in the bundles is detected by SiPMs driven by FERS boards (A5202), developed by CAEN s.p.a., that both supply and read the detectors.

Implementation of multi-GHz digital shaper for high-rate nuclear spectroscopy

In recent years, nuclear spectroscopy has benefited from advances in the field of high-speed digital signal processing (DSP), enabling improved detector response and reduced dead time. The trapezoidal shaper, has been widely used for pulse processing in nuclear spectroscopy applications. Trapezoidal allows to fine tune the energy resolution and sustainable rate by selecting the shaping time. The filter is typically implemented in FPGA using a recursive architecture. At the state of art, the recursive implementation of the trapezoidal filter allows to operate no more than 250-300 MHz on modern devices. However, with the advent of very fast detectors such as photomultiplier tubes (PMTs), diamond sensors, and fast silicon photomultipliers (SiPMs), the demand for even higher-speed implementations has grown.

In this paper, we present a novel high-speed implementation of the trapezoidal shaping method that can operate at up to 5 GSPS for trapezoidal filters with a maximum length of 1024 samples and at 2.5 GSPS for filters with a maximum length of 8192 samples. This significant improvement in speed was achieved by parallelizing all digital blocks within the FPGA-based digital pulse processing architecture.

Novel gamma spectroscopy measurements with ASIC front-end electronics

Application Specific Integrated Circuits (ASIC) technology has the great advantage of providing the possibility to produce compact low power consumption devices with a large number of acquisition channels. In this work we want to investigate the capabilities of the CAEN A5202 FERS-5200 board in conjunction with several scintillator detectors. The A5202 board is an all-in-one front end optimized to work in conjunction with SiPM, it has a total of 64 channels, provided by two 32 channels ASIC Citiroc-1A chips. The number of channels can be further expanded by easily connecting more boards together via optical link. Each acquisition line performs the pulse height analysis (PHA), starting with two preamplifiers with different amplification gains. The preamplifiers are followed by an RC-CR2 shaper amplifier with a peaking time ranging from 12.5 ns to 87.5 ns with a 12.5 ns pitch. Finally, the energy of the incoming pulse is evaluated thanks to a peak detector which identifies and stores the maximum value of the shaped signal. The ASIC Citiroc chip is already being employed in cosmic rays measurements, as well as medicine applications like Wearable Positron Emission Tomography. We took measurements with a 6x6x15 mm3 Cerium-doped Lutetium Yttrium Orthosilicate (LYSO(Ce)) paired with a single 6x6 mm2 SiPM and a 22Na radioactive source. The energy resolution of the 511 keV annihilation peak is comparable with what obtained with the same crystal, radioactive source and a charge integration digitizer (CAEN DT5720A). We plan to test further the A5202 capabilities by taking more measurements with other sources and other scintillator crystals like Caesium Iodine (CsI), and Bismuth Germanate (BGO), but also with faster scintillators like Lanthanum Bromide (LaBr3) and Cerium Bromide (CeBr3).

Simplified Firmware Development for Open FPGA Platforms in DAQ Systems using SciCompiler

In the realm of modern trigger and data acquisition (DAQ) systems, the adoption of programmable logic devices underscores the advantages of versatile, reusable mixed-signal platforms, known as open FPGA boards. These boards enable seamless integration of custom processing algorithms into firmware, enhancing their appeal across diverse applications. However, FPGA development languages like VHDL or Verilog for custom logic and readout system development can be daunting. In this presentation, we introduce an innovative approach to simplify firmware development. We present a user-friendly graphical programming interface featuring a catalog of IP cores tailored for nuclear physics applications. This interface allows users to effortlessly connect blocks to implement trigger logic, akin to assembling physical NIM modules. SciCompiler software revolutionizes firmware development, empowering users to create customized readout systems for applications like nuclear spectroscopy, particle imaging, and more. It leverages virtual instruments such as scalers, counters, TDCs, energy filters, and Pulse Shape Discriminators. SciCompiler streamlines processing algorithm implementation and generates essential readout interfaces and libraries for the complete data acquisition chain—from detector to data storage.

This streamlined process is further enhanced through the introduction of the new SciSDK library, which facilitates seamless interfacing with compatible SciCompiler hardware using consistent instructions from virtually any modern programming language. It refocuses development on the application, eliminating the need for deep FPGA programming knowledge. Open FPGA boards, with or without ADCs, cater to diverse needs, ranging from single to 128 channels per module with sampling rates up to 5 GSPS.

Advancements in Multi-Input Readout Systems for Neutron Proportional Counters

Neutron detection is widely used to investigate the structures of materials through elastic scattering techniques, which applies across a diverse range of scientific disciplines, like physics, biology, and materials science. Furthermore, Neutron Spallation Sources and Nuclear Physics laboratories heavily rely on extensive arrays of neutron proportional counters. These detectors have also gained recognition for their utility in nuclear security and Safeguards scenarios, where compactness of the overall system is also an added advantage.

We introduce a 19” rack-mount solution to easily manage 16 position-sensitive neutron proportional counters. The system includes a high voltage power supply to bias independently each detector, a charge sensitive preamplifier specifically designed for 3He/BF3 tubes and a 14-bit 125 MS/s Digital Pulse Processor, featuring 32 independent inputs and a real-time processing algorithm running on a powerful SoC. A dedicated DAQ allows to compute the collected charge, report the interaction time with a precision of 8 ns and reconstruct the axial position of the interaction. It also provides the pulse waveform, in an oscilloscope mode, together with rise time calculation to be used for shape analysis. This system has undergone on-site qualification and it has been proved proficient in conducting neutron spectroscopy, real-time imaging, position reconstruction, time-of-flight measurements, and gamma/neutron discrimination. Multi-input readout systems for proportional counters are in high demand even in specialized applications like Safeguards, where neutron coincidence counting stands as a fundamental technique for non-destructive fuel rod assay. We introduce equipment designed to meet the requirements for both attended and unattended measurements. This range comprises a compact preamplifier/discriminator and a Shift Register/Pulse Train Recorder module, enabling the reconstruction of the multiplicity distribution to identify fissile isotopes.

Evaluation of the Maximum Throughput of ARDESIA-16 with Different Digital Pulse Processors

We present an evaluation of the maximum throughput of ARDESIA-16 at varying Input Count Rates using three different Digital Pulse Processors: XGLab’s DANTE, XIA LLC’s FalconX8, and a modified version of CAEN S.p.A.’s DT5560SE digitizer. We will cover performance metrics such as Output Count Rate and energy resolution, defined as the FWHM of the Mn-Kα peak. These measurements are specifically optimized to achieve a reasonable compromise between a satisfactory energy resolution and a high count rate with low dead time.

The aim of this work is to study the performance of ARDESIA-16 with various Digital Pulse Processors at high input rates in order to cope with the quest for ultra-high-rate detectors required by next-generations synchrotron beamlines.

Development of a SiPM based Detector Array and Data Acquisition System for the Muon Spectrometer ‘Super-MuSR’

Super-MuSR is the first of the next generation of muon spin spectrometers and is currently being built at the ISIS pulsed source, UK. Funded via the ‘Endeavour Programme’, Super-MuSR is a six million pound development which will provide novel muon techniques at transformational counting rates. The expected counting rate is an order of magnitude greater than the existing instrument, exceeding 10^9·counts·hr-1. The improved count rate capability comes from the use of silicon photomultipliers (SiPM) to build a high density detector array and the implementation of a new digital signal processing pipeline. The array will exceed 700 independent detector channels in a barrel geometry, roughly 1 m in length and 0.35 m in diameter. Each SiPM is coupled to a plastic scintillator using wavelength shifting fibers. Encapsulation of the ‘tile’ assembly is required for light collection and optical isolation from the environment. Comparison of encapsulation methods, including spray-coatings are reported. Signal digitisation, processing and streaming are provided by Nuclear Instruments DAQ 121, which uses a Xilinx Zynq® UltraScale+TM ‘system on a chip’ with ADCs capable of 1 GHz sampling. Super-MuSR’s count-rate stability specification, a 0.032% variation, translate into a demanding thermal stability requirement. To hold the array at a fixed temperature a novel temperature control system has been developed. A resistive heater has been embedded inside the readout PCB in a ‘serpentine’ pattern, capable of delivering 400 mW of power, heating the SiPM to ≈45 °C.