Speaker
Description
The consolidation of the Large Hadron Collider (LHC) beam position monitor (BPM) requires the deployment of about 5000 single-mode radiation-tolerant optical transmitters, working at 10 Gbps during 20 years of operation. While the use of the custom devices being designed at CERN remains the baseline for the project, 8 commercial of the shelf (COTS) optical transceivers have been evaluated as an alternative. This paper presents the results of the full characterization in radiation of these COTS devices, including cumulative effects and single event effects (SEE), evaluated during both data transmission and reception.
Summary (500 words)
The consolidation of the Large Hadron Collider (LHC) beam position monitor (BPM) aims to replace the current BPM system during the Long Shutdown 4 (LS4, i.e. 2032-33). The new BPM system shall reuse the same infrastructure as the current one (i.e. coaxial cables, optical fibres), constraining the digitization of the analogue signals to be performed close to the pick-ups. To cope with the radiation levels expected during High-Luminosity LHC (HL-LHC) operation, the front-end electronics shall be as simple and reliable as possible, whist the back-end will process the incoming raw data. Following this approach, the analogue signals from each BPM will be digitized in the front-end by a 12-bit analogue-to-digital converter (ADC) at 1.25 Gsps. The digitized data will be directly forwarded in parallel through 4 single-mode optical transmitters working at 10 Gbps. These 4 optical signals will be multiplexed over a single optical fibre towards the back-end. This scheme will require about 5000 optical transmitters. While the baseline for the electro-optical interface in the tunnel side remains a single-mode radiation-tolerant dual transmitter named CWDM SM-VTTx developed at CERN by EP-ESE-BE, an alternative option based on commercial of the shelf (COTS) optical transceivers has been evaluated. To validate the feasibility of the alternative option, a radiation test campaign has been carried out in the COmpact MEdical Therapy cyclotron (COMET) at Paul Scherrer Institute (PSI). This cyclotron provides a proton beam that allows to perform radiation tests at component level, with conditions relevant to CERN applications. To maximize the probability of finding a suitable COTS candidate, 8 devices have been selected from 4 different types (SFP+, SFP28, QSFP+ and QSFP28). To obtain the full characterization in radiation of the devices under test (DUTs), cumulative effects and single event effects (SEE) have been evaluated during both data transmission and reception. On one side, cumulative effects have been evaluated through offline analysis. The aim of this test was to evaluate the impact of cumulative effects on the lifetime, optical power of the transmitter and sensitivity of the receiver by comparing measurements before and after irradiation. On the other side, SEE (e.g. single event latch-up (SEL), single event transient (SET), single event upset (SEU)) have been evaluated through online analysis. The aim of this test was to evaluate the impact of SEE on the bit error rate (BER), loss of lock (LOL) and control registers by monitoring the DUT in real-time. Based on the measurements of the online analysis, SEE cross-sections for the different DUTs have been calculated. This paper presents the results of the radiation test performed to COTS optical transceivers and discuss their impact on the reliability of the BPM consolidation project for the LHC, as well as describes the implementation of the radiation test setup.
