arXiv subjects

Gary S. Varner

Publications and source records attributed to Gary S. Varner.

8 recordsLinked to original sources

arXiv2024

GRAPH -- An readout ASIC for large MCP based detectors

We present a programmable 16 channel, mixed signal, low power readout ASIC, having the project historically named Gigasample Recorder of Analog waveforms from a PHotodetector (GRAPH). It is designed to read large aperture single photon imaging detectors using micro channel plates for charge multiplication, and measuring the detector's response on crossed strips anodes to extrapolate the incoming photon position. Each channel consists of a fast, low power and low noise charge sensitive amplifier, which provides a myriad of coarse and fine programmable options for gain and shaping settings. Further, the amplified signal is recorded using, to our knowledge novel, the Hybrid Universal sampLing Architecture (HULA), a mixed signal double buffer memory, that enables concurrent waveform recording, and selected event digitized data extraction. The sampling frequency is freely adjustable between few~kHz up to 125~MHz, while the chip's internal digital memory holds a history 2048 samples for each channel, with a digital headroom of 12 bits. An optimized region of interest sample-read algorithm allows to extract the information just around the event pulse peak, while selecting the next event, thus substantially reducing the operational dead time. The chip is designed in 130~$n$m TSMC CMOS technology, and its power consumption is around 47~$m$W per channel.

physics.ins-det↗

arXiv2022

STOPGAP -- a Time-of-Flight Extension for the Belle II TOP Barrel PID System as a Demonstrator for CMOS Fast Timing Sensors

The Belle II barrel region is instrumented with the Time of Propagation (TOP) particle identification system based on sixteen fused-silica bars arranged around the interaction point acting as Cherenkov radiator. Due to the mechanical design of the TOP system these quartz bars do not overlap, but leave a gap of around 2cm between them. This leads to around 6% of all tracks in the nominal TOP acceptance region to escape without traversing any of the quartz bars and thus not giving any usable particle identification information from the TOP system and an additional 3% of tracks being degraded due to edge effects. We propose a possible solution to remedy these gaps in the TOP acceptance in the form of a Supplemental TOP GAP instrumentation (STOPGAP) that covers the dead area between adjacent quartz bars with fast silicon detectors to directly measure the time-of-flight of traversing particles for particle identification purposes. Modern, fast timing silicon sensors and readouts can offer sufficient time resolution for the task at hand, so that STOPGAP modules could be built compact enough to fit into the limited space available in the area of interest between the Belle II central drift chamber (CDC) and the TOP system. In this article, we present a simulation study demonstrating the feasibility of a silicon time-of-flight system based on its reconstruction performance in $Υ(4S)\rightarrow B\bar{B}$ events simulated using the Belle II simulation and reconstruction software. We discuss the performance requirements for possible sensor technologies and demonstrate that such a project could be realised with novel, fast monolithic CMOS sensors that are expected to reach MIP timing resolutions of down to 50ps. Additionally, we discuss the use of fast timing layers at lower radii for track triggering as well as particle identification at low momenta <1GeV/c.

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arXiv2019

LAB4D: A Low Power, Multi-GSa/s, Transient Digitizer with Sampling Timebase Trimming Capabilities

The LAB4D is a new application-specific integrated circuit (ASIC) of the Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR) family, for use in direct wideband radio frequency digitization such as is used in ultrahigh energy neutrino and cosmic ray astrophysics. The LAB4D is a single channel switched-capacitor array (SCA) 12-bit sampler with integrated analog-to-digital converters (ADC), developed in the TSMC 0.25um process. The LAB4D, operating at 3.2GSa/s, contains 4096 total samples arranged in 32 windows, for a total record length of 1280ns. The 3dB bandwidth is approximately 1.3GHz, with a directly-coupled 50ohm input. This represents a factor of 16 increase in the sample depth and an increase in analog bandwidth and sampling depth in comparison to the previous generation LAB3 digitizer. Individually addressable windows allow for sampling and digitization to occur simultaneously, leading to nearly deadtime-free readout for kHz readout rates. All biases and current references are generated via internal digital-to-analog converters (DACs), resulting in a stand-alone digitizer with no additional support circuitry. In addition, the LAB4D contains sample cell timebase trimming capabilities, reducing the intrinsic sample-to-sample time variance to less than 5ps; an improvement of about 80%. This allows the LAB4D to be used in precision timing applications with minimal post-hoc calibration.

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arXiv2008

Sub-10ps Monolithic and Low-power Photodetector Readout

Recent advances in photon detectors have resulted in high-density imaging arrays that offer many performance and cost advantages. In particular, the excellent transit time spread of certain devices show promise to provide tangible benefits in applications such as Positron Emission Tomography (PET). Meanwhile, high-density, high-performance readout techniques have not kept on pace for exploiting these developments. Photodetector readout for next generation high event rate particle identification and time-resolved PET requires a highly-integrated, low-power, and cost-effective readout technique. We propose fast waveform sampling as a method that meets these criteria and demonstrate that sub-10ps resolution can be obtained for an existing device.

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arXiv2008

The first version Buffered Large Analog Bandwidth (BLAB1) ASIC for high luminosity collider and extensive radio neutrino detectors

Future detectors for high luminosity particle identification and ultra high energy neutrino observation would benefit from a digitizer capable of recording sensor elements with high analog bandwidth and large record depth, in a cost-effective, compact and low-power way. A first version of the Buffered Large Analog Bandwidth (BLAB1) ASIC has been designed based upon the lessons learned from the development of the Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR) ASIC. While this LABRADOR ASIC has been very successful and forms the basis of a generation of new, large-scale radio neutrino detectors, its limited sampling depth is a major drawback. A prototype has been designed and fabricated with 65k deep sampling at multi-GSa/s operation. We present test results and directions for future evolution of this sampling technique.

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arXiv2007

A Monolithic Time Stretcher for Precision Time Recording

Identifying light mesons which contain only up/down quarks (pions) from those containing a strange quark (kaons) over the typical meter length scales of a particle physics detector requires instrumentation capable of measuring flight times with a resolution on the order of 20ps. In the last few years a large number of inexpensive, multi-channel Time-to-Digital Converter (TDC) chips have become available. These devices typically have timing resolution performance in the hundreds of ps regime. A technique is presented that is a monolithic version of ``time stretcher'' solution adopted for the Belle Time-Of-Flight system to address this gap between resolution need and intrinsic multi-hit TDC performance.

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arXiv2006

The Modern FPGA as Discriminator, TDC and ADC

Recent generations of Field Programmable Gate Arrays (FPGAs) have become indispensible tools for complex state machine control and signal processing, and now routinely incorporate CPU cores to allow execution of user software code. At the same time, their exceptional performance permits low-power implementation of functionality previously the exclusive domain of dedicated analog electronics. Specific examples presented here use FPGAs as discriminator, time-to-digital (TDC) and analog-to-digital converter (ADC). All three cases are examples of instrumentation for current or future astroparticle experiments.

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arXiv2005

Evaluation of Giga-bit Ethernet Instrumentation for SalSA Electronics Readout (GEISER)

An instrumentation prototype for acquiring high-speed transient data from an array of high bandwidth antennas is presented. Multi-kilometer cable runs complicate acquisition of such large bandwidth radio signals from an extensive antenna array. Solutions using analog fiber optic links are being explored, though are very expensive. We propose an inexpensive solution that allows for individual operation of each antenna element, operating at potentially high local self-trigger rates. Digitized data packets are transmitted to the surface via commercially available Giga-bit Ethernet hardware. Events are then reconstructed on a computer farm by sorting the received packets using standard networking gear, eliminating the need for custom, very high-speed trigger hardware. Such a system is completely scalable and leverages the hugh capital investment made by the telecommunications industry. Test results from a demonstration prototype are presented.

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