Vertical Bump Effect at PHOBOS in Run-4

In the gold operation of RHIC Run 2004, the experiment back ground of PHOBOS had limited the beam intensity, and hence the luminosity. This background was caused by the pressure rise at the beam rebucketing. In this note, the effect of the vertical orbit bump at the PHOBOS on the rebucketing pressure rise is reviewed. If proven effective, then it may be applied to the Run 2005 copper operation for luminosity improvement.