A compensation circuit for the gain temperature drift of silicon photomultiplier tube

Background Silicon photomultiplier tube(SiPM)has been widely applied in high energy physics experiments.The wide field of view Cherenkov telescope array of Large High Altitude Air Shower Observatory(LHAASO)consists of 12 arrays of SiPMs.Each of the array includes 32*32 pixels.Large Array of imaging atmospheric Cherenkov Telescopes(LACT),the next generation of particle astrophysics experiment,will also adopt SiPM arrays.Purpose LACT will located at a high altitude,leading to a significant operating temperature variation of the SiPM.Since the gain of SiPM is temperature-sensitive,in order to keep it stable,compensation for the gain is necessary by adjusting the bias voltage of SiPM.Methods The compensation circuit provides the bias voltage of SiPM by using a high-voltage output Digital-to-Analog Converter and several high-voltage output amplifiers.To reduce the temperature drift of the gain,the compensation circuit adjust the bias voltage of SiPM according to the operating temperature.Results The compensation circuit supplies SiPM with an adjustable bias voltage from 0 to 80 V,and the adjustment step is 1.22 mV.When the output voltage of the compensation circuit is 64 V,the voltage ripple is 2.59 mV,and the temperature drift is 0.17 mV/℃.In the temperature range from−20 to 30℃,the compensation circuit reduces the gain temperature drift of SiPM to within 2%.

An LDPC coded cooperative MIMO scheme over Rayleigh fading channels with unknown channel state information

This paper describes a coded cooperative multiple-input multiple-output(MIMO) scheme,where structured low-density parity-check(LDPC) codes belonging to a family of repeat-accumulate(RA) codes are employed.The outage probability of the scheme over Rayleigh fading channels is deduced.In an unknown channel state information(CSI) scenario,adaptive transversal filters based on a spatio-temporal recursive least squares(ST-RLS) algorithm are adopted in the destination to realize receive diversity gain.Also,a joint 'Min-Sum' iterative decoding is effectively carried out in the destination.Such a decoding algorithm agrees with the bilayer Tanner graph that can be used to fully characterize two distinct structured LDPC codes employed by the source and relay.Simulation results verify the effectiveness of the adopted filter in the coded cooperative MIMO scheme.Theoretical analysis and numerical simulations show that the LDPC coded cooperative MIMO scheme can well combine cooperation diversity,multi-receive diversity,and channel coding gains,and clearly outperforms coded noncooperation schemes under the same conditions.

CD98-induced CD147 signaling stabilizes the Foxp3 protein to maintain tissue homeostasis

Regulatory T cell(Treg)stability is necessary for the proper control of immune activity and tissue homeostasis.However,it remains unclear whether Treg stability must be continually reinforced or is established during development under physiological conditions.Foxp3 has been characterized as a central mediator of the genetic program that governs Treg stability.Here,we demonstrate that to maintain Foxp3 protein expression,Tregs require cell-to-cell contact,which is mediated by the CD147-CD98 interaction.As Tregs are produced,CD147,which is expressed on their surface,is stimulated by CD98,which is widely expressed in the physiological environment.As a result,CD147’s intracellular domain binds to CDK2 and retains it near the membrane,leading to Foxp3 dephosphorylation and the prevention of Foxp3 degradation.In addition,the optimal distribution of Foxp3+Tregs under both pathological and physiological conditions depends on CD98 expression.Thus,our study provides direct evidence that Foxp3-dependent Treg stability is reinforced in the periphery by the interaction between CD147 and CD98 in the surrounding environment.More importantly,Tregs with high CD147 expression effectively inhibit inflammatory responses and maintain Foxp3 stability,which has guiding significance for the application of Tregs in immunotherapy.

LHAASO KM2A distributed long-distance data transmission

Background The large high-altitude air shower observatory(LHAASO)is being built near Daocheng(4410 m a.s.l.)in the Sichuan province of China.Its main instrument is the one-kilometer square extensive air shower array(KM2A)which will comprise nearly 7000 detectors.The system adopts a distributed architecture where each detector has local front-end electronics for signal digitization and transmission.White Rabbit(WR)is the communication protocol used within KM2A to reach the required 1-ns synchronization accuracy between detectors.Purpose To provide data transport and synchronization over the same network.Methods We have developed a firmware implementation of the TCP/IP protocol in Verilog hardware description language that can be coupled with a WR intellectual property core.Results LHAASO KM2A distributed data and clock synchronization network meets the high requirement of the array for reliable data transmission and clock synchronization.Conclusion The data transmission method based on the TCP/IP protocol suite and WR can be run in Xilinx Spartan6 FPGA with low resource needs,which greatly expand its application field.