  In the DeeMe experiment, approximately $70\ \mathrm{GHz/mm^{2}}$
prompt-charged particles will hit the multi-wire proportional chambers (MWPCs)
before signal electrons come. To avoid the space charge effect, we developed
fast HV-switching MWPCs in order to control the gas gain dynamically. All four
of the MWPCs were manufactured. Last year, the circuit of readout amplifiers is
slightly modified to further improve the efficiency of the detector, and we
also started to investigate other possible choices of the gas mixture. In this
article, the development of the detectors and results of performance tests will
be presented.
