An ion collision cell is fabricated by four semi-circular profile elements, all of which are attach to the same reference plate. Consequently, all four elements remain aligned to the same reference plate. The four elements form a semi-circular channel with a semi-circular quad electrodes. The quad electrodes receive electrical potential to form the field required to focus and maintain the ions at the center of the channel. semi-circular insulators are provided on all sides of the channel so as to seal the channel over its length from the interior of the mass spectrometer.