The Dark Matter Time Projection Chamber ( DMTPC ) collaboration is developing low-pressure gas TPC detectors for measuring WIMP-nucleon interactions .
Optical readout with CCD cameras allows for the detection for the daily modulation in the direction of the dark matter wind , while several charge readout channels allow for the measurement of additional recoil properties .
In this article , we show that the addition of the charge readout analysis to the CCD allows us too obtain a statistics-limited 90 % C.L .
upper limit on the e ^ { - } rejection factor of 5.6 \times 10 ^ { -6 } for recoils with energies between 40 and 200 keV _ { \mathrm { ee } } .
In addition , requiring coincidence between charge signals and light in the CCD reduces CCD-specific backgrounds by more than two orders of magnitude .