Radiation Tolerant Acquisition System for Beam Loss Monitoring at High–Luminosity LHC

At CERN’s Large Hadron Collider, the strategy for machine protection and the quench prevention of superconductive magnets heavily relies on the Beam Loss Monitoring system. For each turn of the beam train, a large amount of data is acquired from approximately 4000 detectors by 750 digital conversion cards. Within a strict deadline, the readout electronics compare the measured loss radiation with unique per detector thresholds, thus deciding whether the particle beams are permitted to continue circulating or trigger an interlock. In view of the accelerator High-Luminosity upgrade, this protection device needs to be improved in terms of resolution and response speed, enhancing its ability to detect potential hazardous scenarios promptly. Such targets require an entirely renewed electronic front-end that withstands a TID of at least 3 kGy and can be positioned as close as possible to the detection spots. Compared to the currently installed equipment, it will also provide a four times faster sampling rate of 100 kHz. Here, the research activities and the development of such upgrades are reported. They involve the engineering, implementation and validation of a real-time system that digitises the output current of the detectors, forwards the results to a nonradiation area and performs an optimised signal processing, in order to obtain precise and accurate beam loss current measurements. Amongst them, the support for the design and the characterisation of an application-specific integrated circuit is also included, which plays a crucial role in the analogue to digital conversion. A frequency domain analysis of the produced data stream is conducted, demonstrating the advantages of this approach over conventional methods. In this way, a detailed evaluation of the digitiser’s behaviour has been carried out, in response to a wide range of inputs, and appropriate filtering techniques have been identified. Hence, the assembly of an overall system test-bench and the standardised measurement procedures have led to the validation of the readout firmware, the signal treatment chains and the system conversion performance. The devices successfully complied with the design specifications, including the input dynamic range of more than 160 dB and the tolerance to radiation. In addition, the novel processing has provided optimal measurement precisions or, complementary, fast step responses. Finally, the flexibility of the developed instruments allows them to be easily adapted beyond the original scope, such as for medical and technological applications or in other particle accelerators.