Alan Prosser

The versatile link, a common project for super-LHC

A common project to develop a bi-directional, radiation tolerant, high speed (4.8 Gb/s) optical link for future high energy physics experiments is described. Due to be completed in 2012, it targets the upgrade programs of detectors installed at CERNs Large Hadron Collider (LHC). The development of radiation and magnetic field tolerant opto-electronic devices, fibre and connectors is described. Both Single-Mode and Multi-Mode versions of the system operating respectively at 850 nm and 1310 nm wavelength are proposed. First results at component and system level are presented, based mostly on commercially available devices.

The Versatile Link common project: feasibility report

The Versatile Link is a bi-directional digital optical data link operating at rates up to 4.8 Gbit/s and featuring radiation-resistant low-power and low-mass front-end components. The system is being developed in multimode or singlemode versions operating at 850 nm or 1310 nm wavelength respectively. It has serial data interfaces and is protocol-agnostic, but is targeted to operate in tandem with the GigaBit Transceiver (GBT) serializer/deserializer chip being designed at CERN. This paper gives an overview of the project status three and a half years after its launch. It describes the challenges encountered and highlights the solutions proposed at the system as well as the component level. It concludes with a positive feasibility assesment and an outlook for future project development directions.

CAPTAN: A hardware architecture for integrated data acquisition, control, and analysis for detector development

The Electronic Systems Engineering Department of the Computing Division at the Fermi National Accelerator Laboratory has developed a data acquisition system flexible and powerful enough to meet the needs of a variety of high energy physics applications. The system described in this paper is called CAPTAN (Compact And Programmable daTa Acquisition Node) and its architecture and capabilities are presented in detail here.

A software solution for the control, acquisition, and storage of CAPTAN network topologies

The Electronic Systems Engineering department of the Computing Division at the Fermi National Accelerator Laboratory is developing a data acquisition system that is flexible and powerful enough to meet the demands of pixel and strip detectors for high energy physics applications, but also capable of far broader application utility. To facilitate data acquisition and processing as well as system configuration and control, a stacked system was devised with support for gigabit Ethernet networking. The individual unit within the system is known as a Compact And Programmable daTa Acquisition Node, or CAPTAN. The platform’s flexibility is achieved through the ability to stack specialized boards, both vertically and horizontally, to create an integrated system that can be optimized for each user and application. The CAPTAN’s main interface is via the Universal Datagram Protocol of the Internet Protocol (UDP/IP). The software solution presented in this paper is at the other end of the UDP/IP interface, and must orchestrate communications. The software must take a modular approach to its command library to give the user a unique and extensible vocabulary with which to communicate with ever advancing readout chip technologies and varying configurations of the specialized boards within a CAPTAN. The software must also handle multiple CAPTANs, each producing gigabits of data per second, thus the solution presented here provides an option to employ distributed computing for CAPTAN network topologies involving large amounts of data.

The Gigabit Link Interface Board (GLIB) ecosystem

The Gigabit Link Interface Board (GLIB) project is an FPGA-based platform for users of high-speed optical links in high energy physics experiments. The major hardware component of the platform is the GLIB Advanced Mezzanine Card (AMC). Additionally to the AMC, auxiliary components are developed that enhance GLIB platforms I/O bandwidth and compatibility with legacy and future triggering and/or data acquisition interfaces. This article focuses on the development of the auxiliary components that together with the GLIB AMC offer a complete solution for beam/irradiation tests of detector modules and evaluation of optical links.

The VCSEL-based array optical transmitter (ATx) development towards 120-Gbps link for collider detector: development update

A compact radiation-tolerant array optical transmitter module (ATx) is developed to provide data transmission up to 10Gbps per channel with 12 parallel channels for collider detector applications. The ATx integrates a Vertical Cavity Surface-Emitting Laser (VCSEL) array and driver circuitry for electrical to optical conversion, an edge warp substrate for the electrical interface and a micro-lens array for the optical interface. This paper reports the continuing development of the ATx custom package. A simple, high-accuracy and reliable active-alignment method for the optical coupling is introduced. The radiation-resistance of the optoelectronic components is evaluated and the inclusion of a custom-designed array driver is discussed.

Free-Space optical interconnects for cable-less readout in particle physics detectors

Particle physics detectors utilize readout data links requiring a complicated network of copper wires or optical fibers. Upgrades to such detectors may require additional bandwidth to be provisioned with limited space available to route new cables or fibers. In contrast, free-space optical interconnects will offer cable-less readout, thereby resulting in significant reductions of material and labor to install and manage the cables. A collaborative effort between Fermilab and Vega Wave Systems is pursuing the development of a unique free-space optical link design that utilizes the transparency of silicon at wavelengths including 1310 nm and multiple wavelengths used in standard telecommunications applications such as coarse wavelength division multiplexing (CWDM). The first step in the pursuit of that design is a proof that the concept may be viable. To that end, experiments have been performed to characterize the bit error rate performance of a prototype link over a free-space optical path and through doped silicon at multi-gigabit rates. These experiments have demonstrated that operation within acceptable bit error rates is possible using single and multiple wavelength transmission arrangements.

Testbeam and laboratory characterization of CMS 3D pixel sensors

The pixel detector is the innermost tracking device in CMS, reconstructing interaction vertices and charged particle trajectories. The sensors located in the innermost layers of the pixel detector must be upgraded for the ten-fold increase in luminosity expected at the High-Luminosity LHC (HL-LHC). As a possible replacement for planar sensors, 3D silicon technology is under consideration due to its good performance after high radiation fluence. In this paper, we report on pre- and post- irradiation measurements of CMS 3D pixel sensors with different electrode configurations from different vendors. The effects of irradiation on electrical properties, charge collection efficiency, and position resolution are discussed. Measurements of various test structures for monitoring the fabrication process and studying the bulk and surface properties of silicon sensors, such as MOS capacitors, planar and gate-controlled diodes are also presented.

The 120Gbps VCSEL Array Based Optical Transmitter (ATx) development for the High-Luminosity LHC (HL-LHC) experiments

The integration of a Verticle Cavity Surface-Emitting Laser (VCSEL) array and a driving Application-Specific Integrated Circuit (ASIC) in a custom optical array transmitter module (ATx) for operation in the detector front-end is constructed, assembled and tested. The ATx provides 12 parallel channels with each channel operating at 10 Gbps. The optical transmitter eye diagram passes the eye mask and the bit-error rate (BER) less than 10(-12) transmission is achieved at 10 Gbps/ch. The overall insertion loss including the radiation induced attenuation is sufficiently low to meet the proposed link budget requirement.

Evaluation of emerging parallel optical link technology for high energy physics

Modern particle detectors utilize optical fiber links to deliver event data to upstream trigger and data processing systems. Future detector systems can benefit from the development of dense arrangements of high speed optical links emerging from industry advancements in transceiver technology. Supporting data transfers of up to 120 Gbps in each direction, optical engines permit assembly of the optical transceivers in close proximity to ASICs and FPGAs. Test results of some of these parallel components will be presented including the development of pluggable FPGA Mezzanine Cards equipped with optical engines to provide to collaborators on the Versatile Link Common Project for the HI-LHC at CERN.