摘要: developed toprobeunchartedfieldsofnuclear physics,de-livering a variety of heavy ions of elements from hydrogen touranium with energies up to1 GeV/u.The external-target ex-periment (CEE)[4] at the HIRFL-CSR,which is designed tostudy the nuclear matter phase structure at low temperaturesand high baryon densities [5], is currently under development.The design specifications of the CEE include a detectionbeam energy ranging from 0.3 GeV/u to 2.8 GeV/u, a max-imum collisionsystem ofuranium+uranium,andamaximumevent rate of104-s,correspondingtoamaximumbeampar-ticlerate of approximately106.s1[4].As shown inFig.1theCEEdetector consists of adipolemagnet,abeammoni-tor [6-10], a start time detector (T0) [11,12], a time projec-tion chamber(TPC)[13-16],aninner time-of-flightdetector(iTOF)[17,18],multi-wiredriftchambers(MWDCs)[1921],an external time-of-flight detector(eTOF)[22,23],and azero-degree calorimeter (ZDC) [24-26].The beam monitor of the CEE spectrometer is designed tomonitor the beam status and improve the reconstruction res-olutionof theprimaryvertex,whichisotherwisedeterminedby the TPC and MWDCs.The main specifications includea spatial resolution of less than 50μm and a time resolutionof less than 1μs.To achieve these specifications,custom-designed pixel chips named Topmetal-CEEv1[27],which cansimultaneously measure amplitude and time,are deployedin the detector. This approach combines the functions of achargesensor andreadoutapplication-specificintegratedcir-cuit (ASIC).