Serial Powering Research Articles

Ongoing studies for the control system of a serially powered ATLAS pixel detector at the HL-LHC

In terms of the phase-2 upgrade of the ATLAS detector, the entire inner tracker (ITk) of ATLAS will be replaced. This includes the pixel detector and the corresponding detector control system (DCS). The current baseline is a serial powering scheme of the detector modules. Therefore a new detector control system is being developed with emphasis on the supervision of serially powered modules. Previous chips had been designed to test the radiation hardness of the technology and the implementation of the modified I2C as well as the implementation of the logic of the CAN protocol. This included tests with triple redundant registers. The described chip is focusing on the implementation in a serial powering scheme. It was designed for laboratory tests, aiming for the proof of principle. The concept of the DCS for ATLAS pixel after the phase-2 upgrade is presented as well as the status of development including tests with the prototype ASIC.

ATLAS strip tracker stavelets

The engineering challenges related to the supply of electrical power to future large scale detector systems are well documented. Two options remain under active study in our community, namely serial powering and the use of DC-DC converters. Whilst clearly different in detail, both have the potential to increase the efficiency of the powering system.The ATLAS Upgrade Strip Tracker Community has constructed two demonstrator stavelets using the ABCN-25 ASIC, each comprising four silicon strip detector modules. The first stavelet is serially powered, using shunt transistors integrated into the ABCN-25 chip to maintain the required operating voltage given a constant supply current, and the second stavelet uses STV-10 DC-DC converters provided by the CERN group. Although the detailed test programme shall continue at CERN, results from stavelet tests made at RAL are presented here.

Progress and Advances in Serial Powering of Silicon Modules for the ATLAS Tracker Upgrade

It is expected that at SLHC the number of detector channels in the ATLAS Semiconductor Tracker will increase by a factor 10, to cope with the increased luminosity. Currently every detector module has its own power cable, known as independent powering (IP). In the upgrade, this arrangement will no longer be tenable, due to cable volume and power losses. The serial powering alternative scheme, in which supermodules, with many readout hybrids, are connected in a serially powered chain, has been proposed and actively pursued over the last few years by the ATLAS Tracker Upgrade Community. This scheme presents some benefits, including simplicity, lower mass and reduced power losses. On the other hand, grounding, shielding and data transmission schemes are modified with respect to the conventional arrangement. Custom components specifically for serial powering have been produced, including the ABCN-25 readout ASICs and the SPI serial powering regulation ASIC, both in 250 nm CMOS, a dedicated programmable current source and power protection elements. In this paper the latest measurements from testing of the new custom electronics are presented and future plans are outlined.

Progress and advances in Serial Powering of silicon modules for the ATLAS Tracker Upgrade

Future detector systems will face technical difficulties with the supply of electrical power to a multitude of sub-detectors. The Serial Powering (SP) scheme is an elegant solution which leads to a great reduction in cable mass, whilst increasing efficiency and reducing cost. In recent years, substantial developments in SP have been made by the ATLAS Tracker Upgrade Community. Initial demonstrator modules and supermodules (known as Staves) used the ABCD chip, with shunt regulators made from discrete components. Continuous development of the SP architecture has led to shunt regulation within the latest ABCN-25 ASICs themselves. From a system point of view, studies of protection schemes and current sources have advanced greatly. We report recent progress, including first results from a serially powered Stavelet using the ABCN-25 chip.

Towards minimum material trackers for high energy physics experiments at upgraded luminosities

Abstract Reducing material in silicon trackers is of major importance for a good detector performance overall, and poses a big challenge in the development of the detectors. To match the low material desirable for trackers in High Energy Physics experiments at upgraded luminosities, special techniques have to be developed to address the main sources of material, i.e. mechanical structure and services, and to prevent new significant contributions to the detector material coming for instance from larger Front-End chips. In this framework three methods are developed to reduce the material added by services and electronics: (1) serial powering, (2) light weight aluminum flex cables and Through Silicon Vias, and (3) thin Front-End chips. The methods are presented in this paper using the upgrades of the ATLAS pixel detector as an example of application.

Switched capacitor DC-DC converter ASICs for the upgraded LHC trackers

The High Luminosity Upgrade of the ATLAS Inner Tracker puts demanding requirements on the powering system of the silicon strip detector modules due to 10-fold increase of the channel count compared to the existing SemiConductor Tracker. Therefore, new solutions for the powering scheme must be elaborated. Currently two possible approaches, the serial powering and the parallel powering scheme using the DC-DC conversion technique, are under development. This paper describes two switched capacitor DC-DC converters designed in a 130 nm technology. For the optimized step-down converter, foreseen for the parallel powering scheme, power efficiency of 97% has been achieved, while for the charge pump, designed for the serial powering scheme, power efficiency of 85% has been achieved.

A serial powering scheme for the ATLAS pixel detector at sLHC

Powering concepts, such as serial powering and DC-DC conversion, are in development for the silicon trackers at sLHC to achieve an efficient power distribution with a minimum volume of cables. This paper will describe the serial powering scheme developed for the upgraded ATLAS pixel detector, with focus on the scheme architecture and on the main components involved: the Shunt-LDO regulator and the protection scheme. Issues connected to system aspects will be discussed, and the advantages in terms of material reduction provided by the proposed serial powering scheme will be presented.

Serial Powering of Silicon Strip Modules for the ATLAS Tracker Upgrade

Serial Powering is a powering solution to the issues of costs, difficulties and inefficiencies associated with the cabling of large detector systems. This powering option is being actively pursued by the ATLAS Tracker upgrade community. Demonstrator supermodules have been produced using the ABCD chip from the present ATLAS SCT together with serial powering circuitry built from commercial components. Two six modules stave systems have been built, and construction of a third stave consisting of thirty modules has been designed and construction is in progress. Recent results from these supermodules have been discussed. New ASICs have been designed that include elements of the serial powering scheme, and studies of system issues are ongoing. These developments and their application to the next demonstrator supermodule will be outlined.

Serial powering of silicon strip detectors at SLHC

Serial powering is a technique to power a large numbers of detector modules using a single power cable and a constant current source. Module power is derived using local shunt regulators. Serial powering is of great interest for large-scale silicon tracking detectors for particle physics with many thousands of densely packed detector modules. We have been operating six ATLAS Semiconductor Tracker (SCT) modules using both serial powering and conventional independent powering. The modules operated stably with no indication of any extra noise sources. We present selected results and discuss the system aspects of serial powering.

Concept, realization and characterization of serially powered pixel modules (Serial Powering)

We prove and demonstrate here for the example of the large-scale pixel detector of ATLAS that Serial Powering of pixel modules is a viable alternative and that has been devised and implemented for ATLAS pixel modules using dedicated on-chip voltage regulators and modified flex hybrid circuits. The equivalent of a pixel ladder consisting of six serially powered pixel modules with about 0.3 Mpixels has been built and the performance with respect to noise and threshold stability and operation failures has been studied. We believe that Serial Powering in general will be necessary for future large-scale tracking detectors.

Serial powering: Proof of principle demonstration of a scheme for the operation of a large pixel detector at the LHC

Large detectors in high-energy physics experiments are mostly built from many identical individual building blocks, called modules, which possess individual parts of the services. The modules are usually also powered by parallel power lines such that they can be individually operated. The main disadvantage of such a parallel powering scheme is the vast amount of necessary power cables which constitutes also a large amount of material in the path of the particles to be detected. For the LHC experiments already now this is a major problem for the optimal performance of the detectors and it has become evident, that for an upgrade programme alternative powering schemes must be investigated. We prove and demonstrate here for the example of the large scale pixel detector of ATLAS that Serial Powering of pixel modules is a viable alternative. A powering scheme using dedicated voltage regulators and modified flex hybrid circuits has been devised and implemented for ATLAS pixel modules. The modules have been intensively tested in the lab and in test beams and have been compared to those powered in parallel with respect to noise and threshold stability performance. Finally, the equivalent of a pixel ladder consisting of six serially powered pixel modules with about 0.3 Mpixels has been built and the performance with respect to operation failures has been studied.

Serial powering of pixel modules

Modern pixel detectors for the next generation of high-energy collider experiments like LHC use readout electronics in deep sub-micron technology. Chips in this technology need a low supply voltage of 2–2.5 V alongside high current consumption to achieve the desired performance. The high supply current leads to significant voltage drops in the long and low mass supply cables so that voltage fluctuations at the chips are induced, when the supply current changes. This problem scales with the number of modules when connected in parallel to the power supplies. An alternative powering scheme connects several modules in series resulting in a higher supply voltage but a lower current consumption of the chain and therefore a much lower voltage drop in the cables. In addition the amount of cables needed to supply the detector is vastly reduced. The concept and features of serial powering are presented and studies of the implementation of this technology as an alternative for the ATLAS pixel detector are shown. In particular, it is shown that the potential risk of powering in series can be addressed and eliminated.