GEM Operation in Negative Ion Drift Gas Mixtures

The first operation of GEM gas gain elements in negative ion gas mixtures is reported. Gains up to several thousand were obtained from single-stage GEMs in carbon disulfide vapor at low pressure, and in mixtures of carbon disulfide with Argon and Helium, some near 1 bar total pressure.Comment: 7 pages, 3 figure

Search for axion-like particles from the sun in an underground negative-ion TPC

Axion-like particles produced in the sun with masses in the keV range have been proposed to explain several long-standing anomalies in astrophysical X-ray observations. The gravitationally bound massive axions could be observed decaying to two X-ray photons in an instrumented underground detector volume. We propose to use a 1.5m(3) Negative-Ion TPC instrumented with GEM/Micromegas pad readout to perform a sensitive search for keV range axions. The sensitivity of the proposed experiment will be five orders of magnitude below existing limits after one year of running