Xiangming Sun

A Low-Noise CMOS Pixel Direct Charge Sensor, Topmetal-II-

We report the design and characterization of a CMOS pixel direct charge sensor, Topmetal-II-, fabricated in a standard 0.35µm CMOS Integrated Circuit process. The sensor utilizes exposed metal patches on top of each pixel to directly collect charge. Each pixel contains a low-noise charge-sensitive preamplier to establish the analog signal and a discriminator with tunable threshold to generate hits. The analog signal from each pixel is accessible through time-shared multiplexing over the entire array. Hits are read out digitally through a column-based priority logic structure. Tests show that the sensor achieved a < 15 e analog noise and a 200 e = minimum threshold for digital readout per pixel. The sensor is capable of detecting both electrons and ions drifting in gas. These characteristics enable its use as the charge readout device in future Time Projection Chambers without gaseous gain mechanism, which has unique advantages in low background and low rate-density experiments.

Optical data transmission ASICs for the high-luminosity LHC (HL-LHC) experiments

We present the design and test results of two optical data transmission ASICs for the High-Luminosity LHC (HL-LHC) experiments. These ASICs include a two-channel serializer (LOCs2) and a single-channel Vertical Cavity Surface Emitting Laser (VCSEL) driver (LOCld1V2). Both ASICs are fabricated in a commercial 0.25-μm Silicon-on-Sapphire (SoS) CMOS technology and operate at a data rate up to 8 Gbps per channel. The power consumption of LOCs2 and LOCld1V2 are 1.25 W and 0.27 W at 8-Gbps data rate, respectively. LOCld1V2 has been verified meeting the radiation-tolerance requirements for HL-LHC experiments.

The clock and control system for the ATLAS Liquid Argon Calorimeter Phase-I upgrade

A Liquid-argon Trigger Digitizer Board (LTDB) is being developed to upgrade the ATLAS Liquid Argon Calorimeter Phase-I trigger electronics. The LTDB located at the front end needs to obtain the clock signals and be configured and monitored remotely from the back end. A clock and control system is being developed for the LTDB and the major functions of the system have been evaluated. The design and evaluation of the clock and control system are presented in this paper.

Mid-board miniature dual channel optical transmitter MTx and transceiver MTRx

We report the development of a mid-board, TOSA and ROSA based miniature dual channel optical transmitter (MTx) and a transceiver (MTRx). The design transmission data rate is 5.12 Gbps per channel and receiving data rate 4.8 Gbps. MTx and MTRx are only 6 mm tall and are electrically and optically pluggable. Although the fiber TOSA/ROSA coupling is through a custom latch, the fiber uses the standard LC ferrule, flange and spring. Light coupling is ensured by the TOSA and ROSA with the LC coupling mechanism. With the dual channel serializer LOCx2 sits under MTx, one achieves high data transmission with a small PCB footprint, and enjoys the reliability of the hermetically packaged TOSA. MTx and MTRx are designed for detector front-end readout of the ATLAS Liquid Argon Calorimeter (LAr) trigger upgrade.

A low-power, low-latency, dual-channel serializer ASIC for detector front-end readout

In this paper, we present a dual-channel serializer ASIC, LOCx2, and its pin-compatible backup, LOCx2-130, for detector front-end readout. LOCx2 is fabricated in a 0.25-um Silicon-on-Sapphire CMOS process and each channel operates at 5.12 Gbps, while LOCx2-130 is fabricated in a 130-nm bulk CMOS process and each channel operates at 4.8 Gbps. The power consumption and the transmission latency are 900 mW and 27 ns for LOCx2 and the corresponding simulation result of LOCx2-130 are 386 mW and 38 ns, respectively.

A Low-Noise CMOS Pixel Direct Charge Sensor Topmetal-IIa for Low Background and Low Rate- Density Experiments

We present the design and characterization of a CMOS pixel direct charge sensor, Topmetal-IIa, fabricated in a standard 0.35µm CMOS process. The sensor features a 45 × 216 pixel array with a 40µm pixel pitch which collects and measures external charge directly through exposed metal electrodes in the topmost metal layer. Each pixel contains a low-noise charge-sensitive preamplifier to establish the analog signal, which is read out through time-shared multiplexing over the entire array. Compared to the earlier Topmetal-II- chip, the analog readout noise of Topmetal-IIa is reduced by 10.8% from 13.9e- to 12.4e-, and the DC voltage variation noise is reduced by 21% from 1.2mV down to 0.946mV. The sensor is capable of detecting both electrons and ions drifting in gas. These characteristics enable its use as the charge readout device in future Time Projection Chambers without gaseous gain mechanism, which has unique advantages in low background and low rate-density experiments.

An asynchronous data-driven readout prototype for CEPC vertex detector

The Circular Electron Positron Collider (CEPC) is proposed as a Higgs boson and/or Z boson factory for high-precision measurements on the Higgs boson. The precision of secondary vertex impact parameter plays an important role in such measurements which typically rely on flavor-tagging. Thus silicon CMOS Pixel Sensors (CPS) are the most promising technology candidate for a CEPC vertex detector, which can most likely feature a high position resolution, a low power consumption and a fast readout simultaneously. For the R&D of the CEPC vertex detector, we have developed a prototype MIC4 in the Towerjazz 180 nm CMOS Image Sensor (CIS) process. We have proposed and implemented a new architecture of asynchronous zero-suppression data-driven readout inside the matrix combined with a binary front-end inside the pixel. The matrix contains 128 rows and 64 columns with a small pixel pitch of 25 μm. The readout architecture has implemented the traditional OR-gate chain inside a super pixel combined with a priority arb...

A highly pixelated CdZnTe detector based on Topmetal-II– sensor

Topmetal-II– is a low noise CMOS pixel direct charge sensor with a pitch of 83 μm. CdZnTe is an excellent semiconductor material for radiation detection. The combination of CdZnTe and the sensor makes it possible to build a detector with high spatial resolution. In our experiments, an epoxy adhesive is used as the conductive medium to connect the sensor and cadmium zinc telluride (CdZnTe). The diffusion coefficient and charge efficiency of electrons are measured at a low bias voltage of −2 V, and the image of a single alpha particle is clear with a reasonable spatial resolution. A detector with such a structure has the potential to be applied in X-ray imaging systems with further improvements of the sensor.