A kind of thick GEM-like gaseous electron multiplier （THGEM）, which is mechanically an expansion of the GEM with its various dimensions being enlarged, is studied. The leak current of THGEM plates is measured. The effective gain and energy resolution of a single THGEM are studied with a source of 55Fe, and the effective gain of the single THGEM versus the electric field strength in the induction region is investigated. The results show that the leak current of THGEM plates is less than 200 pA. In an atmospheric-pressure standard gas mixture, 8×103 effective gain and about 32% energy resolution can be reached for the single-THGEM detector.
The THGEM detector without and with a CsI has been tested successfully. The optimal parameters of THGEM have been determined from eight samples. The UV photoelectric effect of the CsI photocathode is observed. The changing tendency related to the extraction efficiency （εextr） versus the extraction electric field is measured, and several electric fields influencing the anode current are adjusted to adapt to the THGEM detector with a reflective CsI photocathode.
A test system is developed for the BESIII ETOF/MRPC beam tests of data acquisition, environment monitoring and automatic control. The software framework is based on the CAMAC bus, VME bus and Serial Port,which are responsible for communications with the detectors. The monitor system works well in the beam test.
The endcap of time-of-flight （ETOF） detector in BES （Beijing Spectrometer） III is planned to be upgraded by using multi-gap resistive plate chambers （MRPCs） and the designed time resolution of the MRPCs is around 50 ps. Thus a time-zero （TO） detector needs to be built to offer a high quality reference time for the MRPCs beam test. So a TO detector is built using plastic scintillator tiles （BC420） to couple with four fast phototubes （PMTs, Hamamatsu H6533）. The timing properties of the detector is studied by using a cosmic ray test and factors related to the time resolution, such as plastic scintillator size, readout mode and angle effects, are discussed. TO detector timing resolutions of -41-62 ps are achieved, which means that the TO detector can be used in the MRPC beam test.
