Racing sub-femtosecond pulse and relativistic particle in a spark chamber as a new detection tool

Summary form only given. Very recent predictions of near-femtosecond and sub-femtosecond pulses (SFP) brings us close to the experimental observation of these pulses in the near future. SFP are expected to be sub-cycle (e.g. half-cycle) pulses. One of the major issues in this endeavour is how one measures SFPs duration and temporal structure. While one can conceivably think of auto-correlation, "FROG" technique, or across-the-spectrum heterodyne detection, no existing technique was able so far to handle it. We discuss here a radically new approach to the problem. In the proposed arrangement, SFP and a single relativistic particle (e.g. electron or proton) co-propagate or "race" in an spark-like chamber filled with diluted gas and reminiscent, to the extent, to the spark or streamer chambers used in high-energy particles physics.