The development of high resolution coordinate detectors for the DEUTRON facility
The DEUTERON internal target facility at the VEPP-3 storage ring at BINP is intended for the experiments on interaction of electrons and positrons with proton and deuteron. The experiment requires high resolution tracking detectors which can provide the energy and angles of scattered electron. The prototype detector with a sensitive area of 160x40 mm² was built and proved to be operational. It consists of three cascades of gaseous electron multiplier (GEM), the readout structure and detector electronics. Readout structure has 640 channels which reside evenly on two layers skewed by 30 degrees. Electronics of the detector includes APC128 ASICs, Altera Cyclone III FPGA, 100 MBit ethernet. In the APC128 ASIC each channel has a separate analog pipeline consisting of 32 cells which are cyclically switched by a global clock synchronized to the bunch crossing rate (~4 MHz). At the trigger input channels of APC128 are electronically disconnected from the readout structure, and the stored charges of the pipeline capacitors are serially transferred through analog multiplexer into 14bit ADC. Finally FPGA sends UDP packets with digitized measurements to PC over ethernet. For the needs of DEUTRON experiment the expected resolution of less than 100 μm and thickness ~0.15% of radiation length are considered to be quite satisfactory. At the conference the latest results will be presented, including tests with radioactive sources and at the extracted beam installation at the VEPP-4M collider.