Speaker
Description
The low-voltage supply chain for the High Granularity Calorimeter (HGCAL) Phase-2 upgrade of CMS powers the front-end electronics of 620m2 of silicon sensors and 370m2 of SiPM-on-Scintillating tiles. This chain consists of Low-Voltage Power Supplies custom-developed by CMS to operate in the experimental cavern, that power bPOL12V-based DCDC converters located inside the experiment, and custom low-dropout linear regulators as Point-Of-Load regulation. This work presents the design details, the electrical characteristics and the system integration challenges. Experimental tests are presented to evaluate the static and transient performance of the full powering chain and its impact on the front-end modules.
Summary (500 words)
The High Granularity Calorimeter (HGCAL) upgrade of the CMS experiment will replace the existing ECAL and HCAL calorimeter endcaps in the High Luminosity phase of the Large Hadron Collider (HL-LHC). HGCAL is a 47-layer sampling calorimeter, with 620 m2 of silicon sensors in the Electromagnetic section (CE-E) and high-radiation regions of the Hadronic section (CE-H), and 370 m2 of SiPM-on-Scintillating tiles in the low-radiation region of CE-H. Furthermore, the modules are equipped with ASICs for data and trigger readout (HGCROC), clock distribution (RAFAEL), data and trigger transmission, and slow control (ECON, lpGBT, and VTRX+).
Given the demanding power requirements and low operating voltage of the ASICs, a point-of-load regulation at 1.2V is required to ensure that all the devices are correctly supplied, regardless of the sensor’s activity and throughout the lifetime of the detector. For this reason, custom low-dropout linear regulators have been added to the modules, which are supplied by 1.5V from DCDC mezzanines based on bPOL12V chips. In turn, the DCDC mezzanines are supplied by 10V lines from Low-Voltage Power Supplies (LVPS) that are located in the experimental cavern of CMS. These LVPS are custom developed for CMS to be able to operate under 32Gy of total ionizing dose, 2E11 high-energy hadrons/cm2 and a stray magnetic field of up to 120mT.
The racks allocation for the HGCAL in the experimental cavern of CMS and the expected required power yield a full utilization of the available space to install the LVPS. Furthermore, given the circular structure and segmentation of the detector, the length of the path from the LVPS to the edge of each layer needs to be optimised to prevent excessively long wires that could exceed the voltage and power budget. In addition, the on-detector system integration including the read-out chain, grounding and return paths, power sequencing and bias voltage supply, impose the grouping requirements for the low voltage power distribution. This, in turn, constraints the mapping and allocation between the LVPS and front-end electronics. When the tight mechanical integration requirements are combined with the stringent electrical and system integration requirements, an optimisation need arises with a multidisciplinary approach.
In order to satisfy the aforementioned system-architecture optimisation, a careful design of the power distribution network for each part of the detector was carried out. Each case was evaluated and designed to fit into the power budget of each LVPS, satisfy the turn-on transient requirements and reduce the in-rush currents while fitting in the overall mechanical constraints of CMS. This work presents the design details, the electrical characteristics and the system integration constraints. Furthermore, experimental tests are presented to evaluate the DC and transient performance of the full powering chain and its impact on the front-end modules.
