Prototype of a front-end readout ASIC designed for the Water Cherenkov Detector Array in LHAASO

Guo

et al. 2018

J. Inst.

Self Cite

Time and charge measurements over a large dynamic range from 1 Photo Electron (P.E.) to 4000 P.E. are required for the Water Cherenkov Detector Array (WCDA), which is one of the key components in the Large High Altitude Air Shower Observatory (LHAASO). To simplify the circuit structure of the readout electronics, a front end ASIC was designed. Based on the charge-to-time conversion method, the output pulse width of the ASIC corresponds to the input signal charge information while time information of the input signal is picked off through a discriminator, and thus the time and charge information can be digitized simultaneously using this ASIC and a following Time-to-Digital Converter (TDC). To address the challenge of mismatch among the channels observed in the previous prototype version, this work presents approaches for analyzing the problem and optimizing the circuits. A new version of the ASIC was designed and fabricated in the GLOBALFOUNDRIES 0.35 µm CMOS technology, which integrates 6 channels (corresponding to the readout of the 3 PMTs) in each chip. The test results indicate that the mismatch between the channels is significantly reduced to less than 20% using the proposed approach. The time measurement resolution better than 300 ps is achieved, and the charge measurement resolution is better than 10% at 1 P.E., and 1% at 4000 P.E., which meets the application requirements.

Section: Discussion On the Inconsistencies Among Multiple Channelsmentioning

confidence: 99%

Section: Discussion On the Inconsistencies Among Multiple Channelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

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A multichannel front end ASIC for PMT readout in LHAASO WCDA

Guo

et al. 2018

J. Inst.

Self Cite

“…The requirements on the electronics are: the charge resolution is better than 30% RMS @1 P.E. and 3% RMS @ 4000 P.E., and the time resolution is better than 500 ps RMS over the whole dynamic range [3]. Second, considering the large scale of the WCDA, the Front End Electronics (FEE) modules are placed above water close to the PMTs in order to guarantee good measurement precision.…”

Section: Introductionmentioning

confidence: 99%

Prototype of the Readout Electronics for WCDA in LHAASO

Chu

et al. 2017

IEEE Trans. Nucl. Sci.

In the Large High Altitude Air Shower Observatory (LHAASO), the Water Cherenkov Detector Array (WCDA) is one of the key parts. The WCDA consists of 3600 Photomultiplier Tubes (PMTs) scattered in a 90000 m 2 area, and both high precision time and charge measurements are required over a large dynamic range from 1 to 4000 Photo Electrons (P.E.). To achieve time measurement precision better than 500 ps RMS, high quality clock distribution and automatic phase compensation are needed among the 400 Front End Electronics (FEE) modules. To simplify the readout electronics architecture, clock, data, and commands are transferred simultaneously over 400-meter fibers, while high speed data transfer interface is implemented based on TCP/IP protocol. Design and testing of the readout electronics prototype for WCDA is presented in this paper. Test results indicate that a charge resolution better than 10% RMS @ 1 P.E. and 1% RMS @ 4000 P.E., and a time resolution better than 300 ps RMS are successfully achieved over the whole dynamic range, beyond the application requirement.Index Terms-LHAASO, WCDA, time and charge measurement, large dynamic range, clock distribution and compensation.

“…and 3%@4000 P.E.) and time (required resolution: bin size <1 ns and RMS <0.5 ns) measurements are required over this range [3]. To guarantee a good resolution, the Front End Electronics are placed close to the PMTs.…”

Section: Introductionmentioning

confidence: 99%

Precise Clock Synchronization in the Readout Electronics of WCDA in LHAASO

Chu

et al. 2015

IEEE Trans. Nucl. Sci.

The Water Cherenkov Detector Array (WCDA) is one of the key parts in the Large High Altitude Air Shower Observatory (LHAASO). In the WCDA, 3600 Photomultiplier Tubes (PMTs) and the Front End Electronics (FEEs) are scattered within a m area, while a time measurement resolution better than 0.5 ns is required in the readout electronics. To achieve such time measurement precision, high quality clock distribution and synchronization among the 400 FEEs (each FEE for 9 PMTs readout) is required. To simplify the electronics system architecture, data, commands, and clock are transmitted simultaneously through fibers over a 400-m distance between FEEs and the Clock and Data Transfer Modules (CDTMs). In this article, we propose a new method based on the White Rabbit (WR) to achieve completely automatic clock phase alignment between different FEEs. The original WR is enhanced to overcome the clock delay fluctuations due to ambient temperature variations. This paper presents the general scheme, the design of prototype electronics, and initial test results. These indicate that a clock synchronization precision better than 50 ps is achieved over 1 km fibers, which is well beyond the application requirement.