  While information exists on high energy negative particle channeling there
has been little study of the challenges of negative particle bending and
channeling collimation. Partly this is because negative dechanneling lengths
are relatively much shorter. Electrons are not particularly useful for
investigating negative particle channeling effects because their material
interactions are dominated by channeling radiation. Another important factor is
that the current central challenge in channeling collimation is the
proton-proton Large Hadron Collider (LHC) where both beams are positive. On the
other hand in the future the collimation question might reemerge for
electron-positron or muon colliders. Dechanneling lengths increase at higher
energies so that part of the negative particle experimental challenge
diminishes. In the article different approaches to determining negative
dechanneling lengths are reviewed. The more complicated case for axial
channeling is also discussed. Muon channeling as a tool to investigate
dechanneling is also discussed. While it is now possible to study muon
channeling it will probably not illuminate the study of negative dechanneling.
